Feel free to correct me or add more info on this guide, trying to help others as much as I can in eradicating these nasties so the more accuracy and advice, the better. Please, if you have info to help update parts of this guide, comment or shoot me a dm! I have put placeholders for info I just can't find enough reliable anecdotes on as "**NEED INFO**", so look out for that on the data table if you know a bit about this!
I know this guide is massive, (sorry! haha) bio major here and I just did like four 7-10 pg research papers a few weeks back so I ended up getting into that writing mode when I started citing sources here.
I've had a prolonged and terrible experience with multidrug-resistant camallanus parasites, and during this time I had to look up and research by myself many things about them. Unfortunately most of this info was not localized in one place, or was based on experience rather than backed by scientific studies, so I would like to share my findings here with both these factors to assist anyone else struggling with these particularly nasty parasites, and educate other fish owners with more useful information than just "hey, try this random drug!".
Camallanus is a genus of internal parasitic roundworms (nematodes) in which nine species exist. Species doesn't matter hugely if it's alive and actively infecting your fish, because only two kinds infect fish this rapidly and are found in the aquarium trade; C. cotti and C. lacustris, C. cotti being the most common. Moravec and Justine (2006) state that in aquarium fish cultures, this nematode may be found in Europe, North America (Canada specifically), South America (Brazil specifically), the West Indies (Puerto Rico), and Australia. It is in all these countries the parasite is frequently imported with exotic fish from Asia, especially Singapore. This was the case with my fish, as my parasite problems started after I bought an adult Gardner's Killifish from the pet store, from which the vast majority of this species is bred in Singapore. Bettas are another common species found with this parasite, and the fancier varieties all come from Singapore. Camallanus is extremely common among guppies, which seem to have an affinity for the nematode. Guppies are bred worldwide, but this statement from a fishkeeping magazine article on guppies pretty much summarizes why many new guppy owners may find themselves dealing with this parasite; "stock from a retailer will generally have been bred on fish farms in South-East Asia or from Sri Lanka" (Practical Fishkeeping, 2016).
Interestingly enough, all 3 species are in the same order; Cyprinodontiformes, which includes labyrinth fishes, livebearers, and killifish. However, I can confirm without doubt (along with the many other studies that exist) that it can most definitely infect fish outside this order, as one of my Peacock Gudgeons (Order Gobiiformes) came down with the worms. But it does seem to be more infectious towards Cyprinodontiformes in particular. In my tank I had a roughly equal population ratio of gudgeons to killifish, and all fish were of similar size and age. During the 2+ months dealing with this, all but 2 of my killies got worms, while only one gudgeon caught them. Additionally, none of my otocinclus catfish appeared to have been infected. I suspect fish with highly specialized intestines like this may be immune to Camallanus, as the structure is simply too different to figure out or even thrive in.
Life Cycles
Camallanus have two methods of reproduction. The first involves using live microscopic invertebrates like cyclops, tubifex worms, copepods, or daphnia as a secondary host for larvae, which are eventually killed and/or eaten by a fish (also known as heteroxeny). In most aquarium infections, species that reproduce through heteroxeny alone are quite rare because this is highly inefficient as far as parasites go, and rarely infects more than one fish, making this strategy far less infective (Levsen and Jakobsen, 2002). According to Levsen and Jakobsen (2002), species that can reproduce via both methods are pressured to spread through live larvae rather than heteroxeny in aquariums, as the parasite can face up to several generations in copepod-free tanks, or experience a bottleneck due to a low availability of copepod hosts. Generally the only way you'd get a strain like this would be if your fish has been fed aquatic invertebrates that were live or weren't freeze-dried/processed in a method that removes any and all possible germs/parasites, and again, infections from this is rare even then. I've seen forum posts before where people state Camallanus is spreading by using their mystery snails or ramshorns, or even shrimp as an intermediate host, but this is impossible for 2 reasons. 1: because the infected fish would have to eat the large inverts, and 2: in general snails and other large inverts are MUCH too big to be a useful host for heteroxeny. Camallanus infects copepods and other small hosts by wiggling around as a microscopic larvae on the substrate, which is then eaten by the hungry, miniscule invertebrates that can SEE it. They are far to small to be seen and targeted by larger invertebrates, and if they are by chance then they will just be digested by the far stronger stomach acids of a large host. It's simply not realistic. Just because you have any type of invert in the tank does not mean that Camallanus can use it as a host and spread through it, because only the tiny, insectlike "feeder" invertebrates can be hosts for it.
The other method of infection spreads live larvae into the water column (also known as monoxeny). I've seen people say both that they spread live larvae in the water, or drop eggs into the substrate (more often about eggs), but most people have heard about these nematodes from little to no research or anecdotes from others, so I'll clear up the confusion here. Don't bother to worry and read what people write about Camallanus eggs, because if more than one of your fish has come down this parasite then this is a 99.9% confirmation that you have a species that reproduces via monoxeny (LIVE LARVAE, and NOT EGGS), and is most likely C. cotti. Untergasser's Handbook of Fish Diseases (1989) makes this distinction the most clear and well-understood:
"Most Camallanus species reproduce by means of an intermediate host . . . These bring the larval worms into the aquarium, but the probability of infection even with live food from ponds is extremely small. The species Camallanus lacustris and C. cotti, probably from Asia, can multiply in an aquarium because they produce live larvae. They do not need an intermediate host for at least several generations." (Untergasser, pg. 106).
These species are the ones that are going to spread in your aquarium, and a lot of people talk about eggs but this is literally not what happens biologically with highly infectious C. cotti, because those species do not need to reproduce with intermediate hosts and eggs. This concern with eggs likely stems from a misunderstanding as the majority of anti-parasitic fish meds mention eggs, however these meds are also intended to treat multiple species/genus of parasites, some of which do produce eggs. What lands on the substrate instead of eggs are larvae, and as Rogowski et al. (2020) describes, the life cycle from gut larvae to adult worms takes about 30 days.
Reproduction and Attachment
After this, mature females emerge from the vent and live larvae are deposited to the substrate, where " they can survive for up to 3 wks" (p. 8). These larvae are produced in the ovoviviparous (eggs hatch in the mother and are born live, like garter snakes) female, and released motile and able to directly infect fish or copepods immediately after birth. After feeding and maturing in the gut of their host, they become sexually mature and latch onto the tissue of the host's gut using a ridged or spiked sclerotized structure specific to predatory nematodes, known as the Buccal Capsule. The Buccal Capsule functions as a "mouth" for parasitic worms, which don't have a fully developed oral structure. The Buccal Capsule does not fully sclerotize (harden) until the worm becomes sexually mature (Levsen and Berland, 2002). After attachment, the worms feed on the blood and tissue fluid of their host, giving them their red color (Rogowski et al., 2020). As soon as you see adult worms coming out a fish's anus, consider the rest in the tank infected.
Microscopic view of Camallanus cotti. Image 5. Cross-section view of the buccal capsule attached to the intestinal wall of the rectum. 6. Anterior (head-facing) ventral (underside) view of an adult female C. cotti. 7. Mouth of adult female Camallanus, with fully sclerotized ridges of buccal capsule visible, front view. 8. Buccal capsule of mature female Camallanus, side view. The three prongs show a lateral view of a chitinous structure that functions like lips for Camallanidae, called tridents (Hetherington, 1922). Menezes et al., 2006 (see works cited for full entry).
These worms infect two parts of the body; the females cling to the inside of the rectum or intestinal lining and stick out as a red thread about 2 or more mm out of the fish, spreading eggs or larvae. They go in and out of the anus of the fish, and I've only ever seen a maximum of 2-3 females in a fish at a time, but more severe infections could have more. Females are the hardest to kill. When they are removed, because they bite into the intestines to stay anchored they can end up tearing out tissue, leading to bacterial infections or necrotic tissue. This is more often the cause of death than the worms themselves.
Not visible from the outside are the male Camallanus, which I have read somewhere (but can't seem to find the source; virtually no articles mention the location of the males in their host for some reason) live in the intestines somewhere. Males are much smaller than females, with a smaller buccal capsule (Menezes et al., 2006). From what I can tell, males are FAR easier to kill than females (I had fish ejecting small, lighter-colored worms after some treatments, but the red female worms sticking out the anus would not die, so I assume these were either male or younger worms). An orally administered strongish anthelmintic (will get to this later, but basically this is the class of drug that all treatments of Camallanus- with the exception of a few- have as an active ingredient) will wipe out the male population in one go generally.
Please note that these worms, depending of the species of the infected, take a while to kill their host. This does not mean you should leave it, but for robust fish at least they can easily survive for at least 2 months with adult worms sticking out. Or they did in my case. I haven't lost a fish yet just using mostly ineffective treatments. However, the longer you wait the larger the risk you run of bacterial infections after the parasite is removed, as the buccal capsule damages the tissues and mucous membrane of the host's intestines.
The nastiest part about Camallanus, apart from their resistance to many commonly used drugs to treat them, is the fact that they can take up to a month or more to become visible, and by then it's too late. I had a single fish with active Camallanus floating in a container that escaped into the tank (with no prior exposure to the nematode) at some point that night, and though I immediately removed it, weeks later a fish in that same tank had an infection of adult worms.
Cited:
Hetherington, D.C. 1922. Comparative studies on certain features of nematodes and their significance. In: Illinois Biological Monographs (Forbes, S.A., Trelease, W., Ward, H.B., eds.), Vol. VIII. University of Illinois, IL, p. 35. https://core.ac.uk/download/pdf/4833064.pdf
Levsen, A., Berland, B. 2002. The development and morphogenesis of Camallanus cotti Fujita, 1927 (Nematoda: Camallanidae), with notes on its phylogeny and definitive host range. Systematic Parasitology, 53: 29-37. https://doi.org/10.1023/A:1019955917509
Levsen, A., Jakobsen, P.J. 2002. Selection pressure towards monoxeny in Camallanus cotti (Nematoda, Camallanidae) facing an intermediate host bottleneck situation. Parasitology, 124(6): 625-629. https://doi.org/10.1017/S0031182002001610
Menzes, R.C., Tortelly, R., Tortelly-Neto, R., Noronha, D., Pinto, R.M. 2006. Camallanus cotti Fujita, 1927 (Nematoda, Camallanoidea) in ornamental aquarium fishes: pathology and morphology. Mem Inst Oswaldo Cruz, 101(6):683-687. https://doi.org/10.1590/S0074-02762006000600018
Rogowski, E.L.B., Alst, A.D.V., Travis, J., Reznick, D.N., Coulson, T., Bassar, R.D. 2020. Novel parasite invasion leads to rapid demographic compensation and recovery in an experimental population of guppies. PNAS, 117(36): 22580-22589. https://doi.org/10.1073/pnas.2006227117
Rundle, J. (Article Writer unknown, Rundle was interviewed for article). The Guppy: First loves never die [Internet]. UK. Practical Fishkeeping; 2016 June [cited 2021 Jan 8]. Available from https://www.practicalfishkeeping.co.uk/features/the-guppy-first-loves-never-die/
Untergasser, D., trans. Hirschhorn, H.H. 1989. Handbook of fish diseases. Beptune City, NJ: TFH Publications. Link.
All but a couple of the deworming medications for Camallanus that are available or recommended are a class of drugs known as anthelmintics. Anthelmintics used to treat fish most often work on these worms by paralyzing them so they can be passed out through the anus. Some people say certain (weaker) drugs can kill adult female worms at higher doses but I would say this is a mistaken assumption based off seeing the internal male worms dying, and would not recommend it. I kept trying more and more meds with the first fish out of sheer desperation and they ended up killing her (and this was with fenbendazole, a dewormer with one of the largest safety margins out there). Some anthelmintics DO kill nematode worms, but most are not safe for fish or have an extremely low margin of safety (ie: Ivermectin). The (safe) drugs are not easily metabolized by the bodies of fish, so when ingested the drug will pass through the GI tract and out the anus, where it makes contact with the worms and paralyzes them.
Resistance
In North America at least, Camallanus worms are apparently so frequently treated with the most commonly-recommended medications (fenbendazole and levamisole) that most are completely resistant to them (I have no official research articles on this as this topic is, unfortunately, highly understudied). Though I can only find anecdotes from fellow aquarists to confirm this, I can confirm 100% that in my case the worms I encountered were resistant, because I treated my fish with multiple meds, both normally and with much larger-than-recommended doses, as well as administered both orally and externally, and for longer periods of time*. Neither Fenbendazole or Levamisole worked.
*Note that you shouldn't do this unless your fish are extremely robust like my killifish and peacock gudgeons. If it's not working, don't keep pushing because from what I've found, chances are more will not help. Also note that the less stress you can put on your fish during treatment, the longer they will last. I found my killifish all became stressed and very pale when they were isolated in containers in the tank. Due to this I chose to just let them stay in the tank because it was probably all infected anyways. However I only have a 20G so for others this might not be a good idea. But less stress is very important because it lets your fish survive for much longer and reduces the chances of the fish dying from intestinal damage later when the nematodes are finally removed.
While few parasitic nematodes, and especially Camallanus, have been studied for resistance, other related Helminths (parasitic worms) have been, and their resistance towards Anthelmintics has grown much like antibacterial resistance has to antibiotics. As Abongwa et al. (2017) states, "The repeated and improper use of currently available anthelmintics has led to the development of resistance in numerous veterinary parasite species worldwide", and as a result of the mechanism of action for the majority of drugs in this class being similar, resistance to one mechanism is likely to work on multiple drugs, also known as side resistance. Additionally, according to Abongwa, the development of resistance can be rapid as some parasites were found to be resistant to the livestock dewormer thiabendazole only 3 years after the drug's release. The strategies parasitic worms use to develop resistance to dewormers are the exact same that bacteria use to resist antibiotics; mutation or deletion of genes, modifying the receptor target of the drug to decrease affinity, decreasing or removing the enzymes that catalyze reactions with the drug, and more (Abongwa et al., 2017).
Cited:
Abongwa, M., Martin, R.J., Robertson, A.P. 2017. A brief review on the mode of action of antinematodal drugs. Acta veterinaria, 67(2): 137–152. https://doi.org/10.1515/acve-2017-0013
What works?
The best treatment I know of that can be used on Camallanus, is used rarely enough (and virtually never in NA because you can only get it from the UK or EU) that the chances of resistance is virtually none, and is highly effective against nematodes in specific, and safe to treat fish with, is Nematol by Sera, the active ingredient of which is Emamectin Benzoate, a common pesticide for parasitic nematodes in plant roots. This medication, as a pesticide, is much more effective on the worms and actually fully kills or paralyzes worms (it can be hard to tell which when they're hanging out). Best of all, it's not just a general dewormer but a nematode-specific killer. The largest downside is the difficulty in obtaining it. If you ordered from a German ebay vet while in Canada in mid-November like I did, it might take over 2 months to randomly show up at your house squashed and with an $18 customs fee.
ALSO: NEVER GIVE UP TRYING, no matter how many drugs these worms might be resisting, they cannot possibly be resistant to every one out there, because some treatments are WAY less common than others!! Keep using new drugs until one happens to work!! I believe in you, and your fish do too. Give them a good, long happy life and don't let these shitty worms win!!!
Data Table Notes:
Here is a table of medications that may or may not work on Camallanus, and their various pros and cons. This is based on my experience and observations which may not be the same case for everyone, and some I have not tried, but read about other peoples' experiences or knowledge on forums posts, or found studies on. Certain info is not confirmed to be entirely accurate or known (ie: effectiveness on males) because of how little studies exist on Camallanus treatment, so this info is based on accounts and statements by aquarists in forum posts I've come across in the past. If certain info is not mentioned (ie: whether it's safe for inverts), this means it's the same as the other entries, and the opposite of mentioned info (ie: if it's mentioned one drug isn't safe for inverts, others where this isn't mentioned means safe for inverts).
Note that Anthelmintics NOT mentioned in this table I have already looked into and found to be unsafe for aquatic life and fish, or are NOT EFFECTIVE FOR INTERNAL ROUNDWORM PARASITES, and therefore should definitely NOT be used in the treatment of Camallanus, or in aquariums at all. Some are for external parasites only (ie: Metronidazole) or just ineffective against Camallanus (ie: Praziquental). See a list of these other drugs and their effectiveness here. Also note some drugs (Ivermectin, other livestock dewormers safe for fish) may not obviously label the main ingredient on the front, but it is very easy to obtain this information with a quick google search as they are likely legally obliged to provide it (search "medicine name" active ingredient). Any medicines with a form of copper in them should not be used in the presence of invertebrates period. Goat dewormers are, for the most part, unsafe for fish. Also note that vast amounts of so-called "medicine" that are sold on online vendors like amazon are herbal snake oil bs that will do NOTHING to help your fish. Onion oil and thistle extract does not cure Camallanus. Beware of this.
Also, it is possible that given time and a robust biology, a fish can overcome Camallanus on its own, however reinfection chances are extremely high. I could not kill female worms with Levamisole alone, yet one of my fish at some point suddenly had no more adult females sticking out its vent. I suspect this was because the tissue the worm was attached to eventually necrotized, causing it to fall off. Or it might have just not inherited resistance. Weeks later this fish is still active and healthy, so it was likely able to overcome any possible secondary infections from the removal, or perhaps the worm(s) just weren't very well attached to begin with.
Effectiveness on larvae/eggs isn't included in this as I have no way of confirming it. Regardless, every treatment for Camallanus recommends to dose again after 3 weeks when any intermediate-host-generation worms would have hatched or reached the limit of their lifespan on the substrate, or when any still-infected fish would have almost mature worms. So even if it doesn't work, it doesn't matter because you just kill off the worms after they've possibly "hatched" or infected but before they've sexually matured and can spread more.
One very useful source I found that actually tested multiple medications in laboratory conditions on C. cotti is this info sheet. Unfortunately, the original pdf is in German but since the google patent had a transcript in english for it I decided to make a translated version of the pdf myself for easier reading: https://drive.google.com/file/d/1iRXxfYtRXzUz9OaEFGHB2qzbeWjhTO3e/view?usp=sharing
Cited:
Mehlhorn, H., Schmal, G., Schmidt, J. Use of avermectin with derivation of epi-methylamino group (emamectin) or epi-acetylamino group (eprinomectin) and/or salts, for treatment of fish against parasites, nematode, Acanthocephala or Crustacea. Alpha-Biocare GmbH Patent no. DE102007002872A1. Available at: https://patents.google.com/patent/DE102007002872A1/en (Accessed: 8 Jan 2021)
Data Tables:
Anthelmintics:
[1] On Fenbendazole safety margins: In much higher quantities than recommended in the water column, this can have a detrimental effect to fish. I doubt anyone does/will try the same thing I did, but be aware that a large amount of this in a smallish amount of water causes a great deal of stress on the body of a fish and can cause them to stop eating and eventually die in less than a week. This is probably true of any anthelmintic or fish meds, so don't repeat my mistakes and kill an innocent fish; don't put a large, unknown quantity of meds into a container with your fish, no matter how desperate you are.
[2] On Fenbendazole administration: Easiest to come by as most vets have it, it was what my vet recommended at well. It's one of the weaker Anthelmintics. Apparently only effective orally, however I was told by my vet to add it to the water. I did both and neither worked well.
[3] On Levamisole safety margins: The LC50 (lethal concentration) for fish is 250 mg/L (0.94 g/Gal) for 24 h in the water. I have yet to find a lethal dose for oral administration, fish seem to be able to easily tolerate food soaked in large quantities of this med, even having eaten it before the food has come into contact with the tank water.
[4] On Levamisole administration: I didn't find adding it to the water worked very well, but adding a small amount of water to the powder to make a pastelike substance then dipping food in it wiped the internal worms out greatly at least. Note that this med dissolves very easily in water so for oral administration to be effective you want your fish eating it almost the second it hits the water, or even before. My fish are aggressive and will attack my hands and the medicinal dropper I use so this method worked well for me as they ate it rapidly.
[5] Collymore, C., Watral, V., White, J.R., Colvin, M., Rasmussen, S., Tolwani, R.J., Kent, M.L. 2014. Tolerance and efficacy of emamectin benzoate and ivermectin for the treatment of Pseudocapillaria tomentosa in laboratory zebrafish (Danio rerio). Zebrafish, 11(5): 490-497. https://dx.doi.org/10.1089%2Fzeb.2014.1021
This study and multiple treatment reports online confirm a low safety margin for this drug. It can easily cause neurological issues with fish and it is hard to calculate dosage as it's not made for aquarium use and the paste often sold for horses can result in unexpectedly high concentrations in food, causing deaths.
[6] Easily found as a paste for deworming horses on amazon, but this is not a "pure" form and thus it may be very difficult to accurately calculate a safe dosage. Additionally, a paste form will come with additional chemicals/additives which may have unexpected or negative side effects towards aquatic life. Non-paste forms of ivermectin are not nearly as easy to find and may have to be ordered from a pharmaceutical or industrial chemicals vendor.
[7] Flubendazole and Mebendazole have extremely similar molecular structures, and belong to the same "family" of drugs in the anthelmintics class, known as Benzimidazoles. The Benzimidazoles group includes Thiabendazole, Fenbendazole, Flubendazole, Mebendazole, Febantel, Netobimin, and many more types of livestock dewormers. If your worm strain is resistant to one type of "-dazole" it's highly likely it's resistant to others, if not all in that group. The only difference between Mebendazole and Flubendazole is that Flubendazole has a fluoride attached at the end of a benzene ring.
Flubendazole
Mebendazole
Fenbendazole
Non-Anthelmintic Dewormers:
[1*] On obtaining Piperazine: Most small animal vets should have or be able to obtain this, but this is more an "experimental" treatment for Camallanus as it's rarely recommended so less flexible vets may not be willing to prescribe it. I was told by my vet that it is weaker than fenbendazole, however this might not be the case with nematodes. I do not consider it an "official" treatment either, not only because it is so rarely recommended but because few accounts exist on whether or not it works well. It is, however, a different class of drug and therefore may possibly have a more useful effect on your strain of nematodes than anthelmintics.
[2*] Source (look at section on piperazine)
[3*] Because this is the only fish medication that uses this salt as an active ingredient. Emamectin Benzoate is the benzoate salt of the anthelmintic Abamectin, or the 4'-deoxy-4'-epi-Methylamino Derivative of Avermectin B1.
[4*] Eprinomectin is the 4'-deoxy-4'-epi-Acetylamino Derivative of Avermectin B1.
[5*] https://drive.google.com/file/d/1iRXxfYtRXzUz9OaEFGHB2qzbeWjhTO3e/view?usp=sharing
[6*] With a quick google search I found you can get massive quantities of it intended for cattle use in the US, but this likely isn't made to dissolve in aquarium water or be safe for fish. The patent guide also mentions the methods you can/must use to make the ingredient water-soluble, so if you are able to access these tools and materials it's certainly possible. It's also possible that the cattle varieties are in fact water-soluble and fish-safe, but you would have to perform multiple tests or calculations to confirm this without risking the lives of your fish.
How do you know for sure Camallanus has been killed, or what does it look like when Camallanus is dying from an effective or semi-effective medication?
Here are some images I took of my fish (Fundulopanchax nigerianus, males) after dosing with Nematol (Emamectin Benzoate). Nematol completely killed and removed all mature male and female Camallanus nematodes 48h after dosing. Previously visible and moving red female worms were nowhere to be seen after this period of time. An effective nematocidal fish medication should take care of the parasites within 48 h. and no longer. If your fish still have worms after this time period, either your dosing was too weak or the parasite is resistant (more likely the case).
Worms (white lines just before anal fin) being ejected from anus, ~18h after dosing Nematol. Presumably male or young worms found in the intestines rather than vent; I noticed these types of worms have a pale yellowish color, when ejected at least, rather than the red females. This type of ejection of small internal worms was also observed, with a nearly identical appearance, when fish were orally fed Levamisole. I would call this \"Stage 1\" of treatment, with at least a portion of the population of worms being removed.
Treatment of C. cotti with Nematol (Emamectin Benzoate), ~24h. after first and only dose. Female nematode is hanging out vent of fish. During this time, movement of worms in and out of anus was not observed (during both Fenbendazole and Levamisole treatments, movement of females entering and leaving of anus never ceased). Blood pulsing through the worm was also visible, however worm was hanging out far far more than usual, and not motile otherwise. Within 12 h. after this, the female worms disappeared entirely, presumably ejected. I call this \"Stage 2\", and this stage guarantees your fish will be cured, because the most resistant and difficult to kill mature females are removed from the fish for good. After this all that needs to be removed are the remaining worms, and then recovery.
Worm ejection, 5 days after initial treatment. White color clearly indicates dead status of worm, which was presumably still attached by the buccal capsule somewhere in the body until its eventual ejection. I would call this \"stage 3\", or the final stage of worm removal from the intestines of your fish. They repel the last few dead worms out. After this stage, bacterial infections may be a risk.
[1] Lumaret, J. P., Errouissi, F., Floate, K., Römbke, J., Wardhaugh, K. 2012. A review on the toxicity and non-target effects of macrocyclic lactones in terrestrial and aquatic environments. Current Pharmaceutical Biotechnology. 13(6): 1004-1060. https://doi.org/10.2174/138920112800399257
[2] Abongwa, M., Martin, R.J., Robertson, A.P. 2017. A brief review on the mode of action of antinematodal drugs. Acta veterinaria, 67(2): 137–152. https://doi.org/10.1515/acve-2017-0013
There's a lot more to be written about and revised here but I've been working on this guide for several days now in a reddit draft and I want to post it now as this type of research can be exhausting, no matter how passionate you are about it. Probably few people will even read this anyways because it's such a niche topic and I wrote like a bajillion words that can be a huge ass pain to sift through, buut... I learned a lot, I found it interesting and incredibly informative, so I sincerely hope it can help others too. I included as much as came to my mind and will add more to fill in the blanks but yea... I think it really covers just about everything endoparasite-related with fish and it's a lot more comprehensive than the majority of research articles out there, while still being long, detailed, and researched enough to be trustworthy and helpful (I hope). So for anyone struggling with nematodes out there... good job finding this guide, it shows you care a hell of a lot about your fish. You got this, you'll cure them, I'm proud of you. Good luck.
submitted by Shelilla to Aquariums [link] [comments] I know this guide is massive, (sorry! haha) bio major here and I just did like four 7-10 pg research papers a few weeks back so I ended up getting into that writing mode when I started citing sources here.
I've had a prolonged and terrible experience with multidrug-resistant camallanus parasites, and during this time I had to look up and research by myself many things about them. Unfortunately most of this info was not localized in one place, or was based on experience rather than backed by scientific studies, so I would like to share my findings here with both these factors to assist anyone else struggling with these particularly nasty parasites, and educate other fish owners with more useful information than just "hey, try this random drug!".
Part 1: The Biology of Camallanus
General Info and TheoriesCamallanus is a genus of internal parasitic roundworms (nematodes) in which nine species exist. Species doesn't matter hugely if it's alive and actively infecting your fish, because only two kinds infect fish this rapidly and are found in the aquarium trade; C. cotti and C. lacustris, C. cotti being the most common. Moravec and Justine (2006) state that in aquarium fish cultures, this nematode may be found in Europe, North America (Canada specifically), South America (Brazil specifically), the West Indies (Puerto Rico), and Australia. It is in all these countries the parasite is frequently imported with exotic fish from Asia, especially Singapore. This was the case with my fish, as my parasite problems started after I bought an adult Gardner's Killifish from the pet store, from which the vast majority of this species is bred in Singapore. Bettas are another common species found with this parasite, and the fancier varieties all come from Singapore. Camallanus is extremely common among guppies, which seem to have an affinity for the nematode. Guppies are bred worldwide, but this statement from a fishkeeping magazine article on guppies pretty much summarizes why many new guppy owners may find themselves dealing with this parasite; "stock from a retailer will generally have been bred on fish farms in South-East Asia or from Sri Lanka" (Practical Fishkeeping, 2016).
Interestingly enough, all 3 species are in the same order; Cyprinodontiformes, which includes labyrinth fishes, livebearers, and killifish. However, I can confirm without doubt (along with the many other studies that exist) that it can most definitely infect fish outside this order, as one of my Peacock Gudgeons (Order Gobiiformes) came down with the worms. But it does seem to be more infectious towards Cyprinodontiformes in particular. In my tank I had a roughly equal population ratio of gudgeons to killifish, and all fish were of similar size and age. During the 2+ months dealing with this, all but 2 of my killies got worms, while only one gudgeon caught them. Additionally, none of my otocinclus catfish appeared to have been infected. I suspect fish with highly specialized intestines like this may be immune to Camallanus, as the structure is simply too different to figure out or even thrive in.
Life Cycles
Camallanus have two methods of reproduction. The first involves using live microscopic invertebrates like cyclops, tubifex worms, copepods, or daphnia as a secondary host for larvae, which are eventually killed and/or eaten by a fish (also known as heteroxeny). In most aquarium infections, species that reproduce through heteroxeny alone are quite rare because this is highly inefficient as far as parasites go, and rarely infects more than one fish, making this strategy far less infective (Levsen and Jakobsen, 2002). According to Levsen and Jakobsen (2002), species that can reproduce via both methods are pressured to spread through live larvae rather than heteroxeny in aquariums, as the parasite can face up to several generations in copepod-free tanks, or experience a bottleneck due to a low availability of copepod hosts. Generally the only way you'd get a strain like this would be if your fish has been fed aquatic invertebrates that were live or weren't freeze-dried/processed in a method that removes any and all possible germs/parasites, and again, infections from this is rare even then. I've seen forum posts before where people state Camallanus is spreading by using their mystery snails or ramshorns, or even shrimp as an intermediate host, but this is impossible for 2 reasons. 1: because the infected fish would have to eat the large inverts, and 2: in general snails and other large inverts are MUCH too big to be a useful host for heteroxeny. Camallanus infects copepods and other small hosts by wiggling around as a microscopic larvae on the substrate, which is then eaten by the hungry, miniscule invertebrates that can SEE it. They are far to small to be seen and targeted by larger invertebrates, and if they are by chance then they will just be digested by the far stronger stomach acids of a large host. It's simply not realistic. Just because you have any type of invert in the tank does not mean that Camallanus can use it as a host and spread through it, because only the tiny, insectlike "feeder" invertebrates can be hosts for it.
The other method of infection spreads live larvae into the water column (also known as monoxeny). I've seen people say both that they spread live larvae in the water, or drop eggs into the substrate (more often about eggs), but most people have heard about these nematodes from little to no research or anecdotes from others, so I'll clear up the confusion here. Don't bother to worry and read what people write about Camallanus eggs, because if more than one of your fish has come down this parasite then this is a 99.9% confirmation that you have a species that reproduces via monoxeny (LIVE LARVAE, and NOT EGGS), and is most likely C. cotti. Untergasser's Handbook of Fish Diseases (1989) makes this distinction the most clear and well-understood:
"Most Camallanus species reproduce by means of an intermediate host . . . These bring the larval worms into the aquarium, but the probability of infection even with live food from ponds is extremely small. The species Camallanus lacustris and C. cotti, probably from Asia, can multiply in an aquarium because they produce live larvae. They do not need an intermediate host for at least several generations." (Untergasser, pg. 106).
These species are the ones that are going to spread in your aquarium, and a lot of people talk about eggs but this is literally not what happens biologically with highly infectious C. cotti, because those species do not need to reproduce with intermediate hosts and eggs. This concern with eggs likely stems from a misunderstanding as the majority of anti-parasitic fish meds mention eggs, however these meds are also intended to treat multiple species/genus of parasites, some of which do produce eggs. What lands on the substrate instead of eggs are larvae, and as Rogowski et al. (2020) describes, the life cycle from gut larvae to adult worms takes about 30 days.
Reproduction and Attachment
After this, mature females emerge from the vent and live larvae are deposited to the substrate, where " they can survive for up to 3 wks" (p. 8). These larvae are produced in the ovoviviparous (eggs hatch in the mother and are born live, like garter snakes) female, and released motile and able to directly infect fish or copepods immediately after birth. After feeding and maturing in the gut of their host, they become sexually mature and latch onto the tissue of the host's gut using a ridged or spiked sclerotized structure specific to predatory nematodes, known as the Buccal Capsule. The Buccal Capsule functions as a "mouth" for parasitic worms, which don't have a fully developed oral structure. The Buccal Capsule does not fully sclerotize (harden) until the worm becomes sexually mature (Levsen and Berland, 2002). After attachment, the worms feed on the blood and tissue fluid of their host, giving them their red color (Rogowski et al., 2020). As soon as you see adult worms coming out a fish's anus, consider the rest in the tank infected.
Microscopic view of Camallanus cotti. Image 5. Cross-section view of the buccal capsule attached to the intestinal wall of the rectum. 6. Anterior (head-facing) ventral (underside) view of an adult female C. cotti. 7. Mouth of adult female Camallanus, with fully sclerotized ridges of buccal capsule visible, front view. 8. Buccal capsule of mature female Camallanus, side view. The three prongs show a lateral view of a chitinous structure that functions like lips for Camallanidae, called tridents (Hetherington, 1922). Menezes et al., 2006 (see works cited for full entry).
These worms infect two parts of the body; the females cling to the inside of the rectum or intestinal lining and stick out as a red thread about 2 or more mm out of the fish, spreading eggs or larvae. They go in and out of the anus of the fish, and I've only ever seen a maximum of 2-3 females in a fish at a time, but more severe infections could have more. Females are the hardest to kill. When they are removed, because they bite into the intestines to stay anchored they can end up tearing out tissue, leading to bacterial infections or necrotic tissue. This is more often the cause of death than the worms themselves.
Not visible from the outside are the male Camallanus, which I have read somewhere (but can't seem to find the source; virtually no articles mention the location of the males in their host for some reason) live in the intestines somewhere. Males are much smaller than females, with a smaller buccal capsule (Menezes et al., 2006). From what I can tell, males are FAR easier to kill than females (I had fish ejecting small, lighter-colored worms after some treatments, but the red female worms sticking out the anus would not die, so I assume these were either male or younger worms). An orally administered strongish anthelmintic (will get to this later, but basically this is the class of drug that all treatments of Camallanus- with the exception of a few- have as an active ingredient) will wipe out the male population in one go generally.
Please note that these worms, depending of the species of the infected, take a while to kill their host. This does not mean you should leave it, but for robust fish at least they can easily survive for at least 2 months with adult worms sticking out. Or they did in my case. I haven't lost a fish yet just using mostly ineffective treatments. However, the longer you wait the larger the risk you run of bacterial infections after the parasite is removed, as the buccal capsule damages the tissues and mucous membrane of the host's intestines.
The nastiest part about Camallanus, apart from their resistance to many commonly used drugs to treat them, is the fact that they can take up to a month or more to become visible, and by then it's too late. I had a single fish with active Camallanus floating in a container that escaped into the tank (with no prior exposure to the nematode) at some point that night, and though I immediately removed it, weeks later a fish in that same tank had an infection of adult worms.
Cited:
Hetherington, D.C. 1922. Comparative studies on certain features of nematodes and their significance. In: Illinois Biological Monographs (Forbes, S.A., Trelease, W., Ward, H.B., eds.), Vol. VIII. University of Illinois, IL, p. 35. https://core.ac.uk/download/pdf/4833064.pdf
Levsen, A., Berland, B. 2002. The development and morphogenesis of Camallanus cotti Fujita, 1927 (Nematoda: Camallanidae), with notes on its phylogeny and definitive host range. Systematic Parasitology, 53: 29-37. https://doi.org/10.1023/A:1019955917509
Levsen, A., Jakobsen, P.J. 2002. Selection pressure towards monoxeny in Camallanus cotti (Nematoda, Camallanidae) facing an intermediate host bottleneck situation. Parasitology, 124(6): 625-629. https://doi.org/10.1017/S0031182002001610
Menzes, R.C., Tortelly, R., Tortelly-Neto, R., Noronha, D., Pinto, R.M. 2006. Camallanus cotti Fujita, 1927 (Nematoda, Camallanoidea) in ornamental aquarium fishes: pathology and morphology. Mem Inst Oswaldo Cruz, 101(6):683-687. https://doi.org/10.1590/S0074-02762006000600018
Rogowski, E.L.B., Alst, A.D.V., Travis, J., Reznick, D.N., Coulson, T., Bassar, R.D. 2020. Novel parasite invasion leads to rapid demographic compensation and recovery in an experimental population of guppies. PNAS, 117(36): 22580-22589. https://doi.org/10.1073/pnas.2006227117
Rundle, J. (Article Writer unknown, Rundle was interviewed for article). The Guppy: First loves never die [Internet]. UK. Practical Fishkeeping; 2016 June [cited 2021 Jan 8]. Available from https://www.practicalfishkeeping.co.uk/features/the-guppy-first-loves-never-die/
Untergasser, D., trans. Hirschhorn, H.H. 1989. Handbook of fish diseases. Beptune City, NJ: TFH Publications. Link.
Part 2: Drugs and Treatment
General InfoAll but a couple of the deworming medications for Camallanus that are available or recommended are a class of drugs known as anthelmintics. Anthelmintics used to treat fish most often work on these worms by paralyzing them so they can be passed out through the anus. Some people say certain (weaker) drugs can kill adult female worms at higher doses but I would say this is a mistaken assumption based off seeing the internal male worms dying, and would not recommend it. I kept trying more and more meds with the first fish out of sheer desperation and they ended up killing her (and this was with fenbendazole, a dewormer with one of the largest safety margins out there). Some anthelmintics DO kill nematode worms, but most are not safe for fish or have an extremely low margin of safety (ie: Ivermectin). The (safe) drugs are not easily metabolized by the bodies of fish, so when ingested the drug will pass through the GI tract and out the anus, where it makes contact with the worms and paralyzes them.
Resistance
In North America at least, Camallanus worms are apparently so frequently treated with the most commonly-recommended medications (fenbendazole and levamisole) that most are completely resistant to them (I have no official research articles on this as this topic is, unfortunately, highly understudied). Though I can only find anecdotes from fellow aquarists to confirm this, I can confirm 100% that in my case the worms I encountered were resistant, because I treated my fish with multiple meds, both normally and with much larger-than-recommended doses, as well as administered both orally and externally, and for longer periods of time*. Neither Fenbendazole or Levamisole worked.
*Note that you shouldn't do this unless your fish are extremely robust like my killifish and peacock gudgeons. If it's not working, don't keep pushing because from what I've found, chances are more will not help. Also note that the less stress you can put on your fish during treatment, the longer they will last. I found my killifish all became stressed and very pale when they were isolated in containers in the tank. Due to this I chose to just let them stay in the tank because it was probably all infected anyways. However I only have a 20G so for others this might not be a good idea. But less stress is very important because it lets your fish survive for much longer and reduces the chances of the fish dying from intestinal damage later when the nematodes are finally removed.
While few parasitic nematodes, and especially Camallanus, have been studied for resistance, other related Helminths (parasitic worms) have been, and their resistance towards Anthelmintics has grown much like antibacterial resistance has to antibiotics. As Abongwa et al. (2017) states, "The repeated and improper use of currently available anthelmintics has led to the development of resistance in numerous veterinary parasite species worldwide", and as a result of the mechanism of action for the majority of drugs in this class being similar, resistance to one mechanism is likely to work on multiple drugs, also known as side resistance. Additionally, according to Abongwa, the development of resistance can be rapid as some parasites were found to be resistant to the livestock dewormer thiabendazole only 3 years after the drug's release. The strategies parasitic worms use to develop resistance to dewormers are the exact same that bacteria use to resist antibiotics; mutation or deletion of genes, modifying the receptor target of the drug to decrease affinity, decreasing or removing the enzymes that catalyze reactions with the drug, and more (Abongwa et al., 2017).
Cited:
Abongwa, M., Martin, R.J., Robertson, A.P. 2017. A brief review on the mode of action of antinematodal drugs. Acta veterinaria, 67(2): 137–152. https://doi.org/10.1515/acve-2017-0013
What works?
The best treatment I know of that can be used on Camallanus, is used rarely enough (and virtually never in NA because you can only get it from the UK or EU) that the chances of resistance is virtually none, and is highly effective against nematodes in specific, and safe to treat fish with, is Nematol by Sera, the active ingredient of which is Emamectin Benzoate, a common pesticide for parasitic nematodes in plant roots. This medication, as a pesticide, is much more effective on the worms and actually fully kills or paralyzes worms (it can be hard to tell which when they're hanging out). Best of all, it's not just a general dewormer but a nematode-specific killer. The largest downside is the difficulty in obtaining it. If you ordered from a German ebay vet while in Canada in mid-November like I did, it might take over 2 months to randomly show up at your house squashed and with an $18 customs fee.
ALSO: NEVER GIVE UP TRYING, no matter how many drugs these worms might be resisting, they cannot possibly be resistant to every one out there, because some treatments are WAY less common than others!! Keep using new drugs until one happens to work!! I believe in you, and your fish do too. Give them a good, long happy life and don't let these shitty worms win!!!
Data Table Notes:
Here is a table of medications that may or may not work on Camallanus, and their various pros and cons. This is based on my experience and observations which may not be the same case for everyone, and some I have not tried, but read about other peoples' experiences or knowledge on forums posts, or found studies on. Certain info is not confirmed to be entirely accurate or known (ie: effectiveness on males) because of how little studies exist on Camallanus treatment, so this info is based on accounts and statements by aquarists in forum posts I've come across in the past. If certain info is not mentioned (ie: whether it's safe for inverts), this means it's the same as the other entries, and the opposite of mentioned info (ie: if it's mentioned one drug isn't safe for inverts, others where this isn't mentioned means safe for inverts).
Note that Anthelmintics NOT mentioned in this table I have already looked into and found to be unsafe for aquatic life and fish, or are NOT EFFECTIVE FOR INTERNAL ROUNDWORM PARASITES, and therefore should definitely NOT be used in the treatment of Camallanus, or in aquariums at all. Some are for external parasites only (ie: Metronidazole) or just ineffective against Camallanus (ie: Praziquental). See a list of these other drugs and their effectiveness here. Also note some drugs (Ivermectin, other livestock dewormers safe for fish) may not obviously label the main ingredient on the front, but it is very easy to obtain this information with a quick google search as they are likely legally obliged to provide it (search "medicine name" active ingredient). Any medicines with a form of copper in them should not be used in the presence of invertebrates period. Goat dewormers are, for the most part, unsafe for fish. Also note that vast amounts of so-called "medicine" that are sold on online vendors like amazon are herbal snake oil bs that will do NOTHING to help your fish. Onion oil and thistle extract does not cure Camallanus. Beware of this.
Also, it is possible that given time and a robust biology, a fish can overcome Camallanus on its own, however reinfection chances are extremely high. I could not kill female worms with Levamisole alone, yet one of my fish at some point suddenly had no more adult females sticking out its vent. I suspect this was because the tissue the worm was attached to eventually necrotized, causing it to fall off. Or it might have just not inherited resistance. Weeks later this fish is still active and healthy, so it was likely able to overcome any possible secondary infections from the removal, or perhaps the worm(s) just weren't very well attached to begin with.
Effectiveness on larvae/eggs isn't included in this as I have no way of confirming it. Regardless, every treatment for Camallanus recommends to dose again after 3 weeks when any intermediate-host-generation worms would have hatched or reached the limit of their lifespan on the substrate, or when any still-infected fish would have almost mature worms. So even if it doesn't work, it doesn't matter because you just kill off the worms after they've possibly "hatched" or infected but before they've sexually matured and can spread more.
One very useful source I found that actually tested multiple medications in laboratory conditions on C. cotti is this info sheet. Unfortunately, the original pdf is in German but since the google patent had a transcript in english for it I decided to make a translated version of the pdf myself for easier reading: https://drive.google.com/file/d/1iRXxfYtRXzUz9OaEFGHB2qzbeWjhTO3e/view?usp=sharing
Cited:
Mehlhorn, H., Schmal, G., Schmidt, J. Use of avermectin with derivation of epi-methylamino group (emamectin) or epi-acetylamino group (eprinomectin) and/or salts, for treatment of fish against parasites, nematode, Acanthocephala or Crustacea. Alpha-Biocare GmbH Patent no. DE102007002872A1. Available at: https://patents.google.com/patent/DE102007002872A1/en (Accessed: 8 Jan 2021)
Data Tables:
Anthelmintics:
| Drug Name & Family | Kills or Removes Male Worms/Younger Worms? | Kills or Removes Adult Female Worms? | Easy to Obtain? | Safety Margins | Best Administered | Resistance Common? |
|---|---|---|---|---|---|---|
| Fenbendazole (Common Dog/Cat dewormer). Benzimidazole family. | Not IME | Not IME | Very easy | High [1] | Orally [2] | Common resistance and side resistance |
| Levamisole (Fish and Bird dewormer).Imidazothiazole family. | Yes IME | Not IME | Moderately; banned from vet use in Canada, but can be found here | High [3] | Orally [4] most effective, water column may or may not work | Common resistance |
| Ivermectin (Horse dewormer). Avermectin family. | Yes, may not kill entire population [5] | Yes | Easy to moderate; depends on form [6] | Low [5] | Orally | Resistance can occur but far less common as it's rarely used for fish |
| Flubendazole. Benzimidazole family. | Side Resistance likely if resisting a "-dazole" medication[7] | |||||
| Mebendazole. Benzimidazole family. | Side Resistance likely if resisting a "-dazole" medication [7] | |||||
| And more, virtually all the same medications and far more difficult to find and dose than the ones listed above... |
[2] On Fenbendazole administration: Easiest to come by as most vets have it, it was what my vet recommended at well. It's one of the weaker Anthelmintics. Apparently only effective orally, however I was told by my vet to add it to the water. I did both and neither worked well.
[3] On Levamisole safety margins: The LC50 (lethal concentration) for fish is 250 mg/L (0.94 g/Gal) for 24 h in the water. I have yet to find a lethal dose for oral administration, fish seem to be able to easily tolerate food soaked in large quantities of this med, even having eaten it before the food has come into contact with the tank water.
[4] On Levamisole administration: I didn't find adding it to the water worked very well, but adding a small amount of water to the powder to make a pastelike substance then dipping food in it wiped the internal worms out greatly at least. Note that this med dissolves very easily in water so for oral administration to be effective you want your fish eating it almost the second it hits the water, or even before. My fish are aggressive and will attack my hands and the medicinal dropper I use so this method worked well for me as they ate it rapidly.
[5] Collymore, C., Watral, V., White, J.R., Colvin, M., Rasmussen, S., Tolwani, R.J., Kent, M.L. 2014. Tolerance and efficacy of emamectin benzoate and ivermectin for the treatment of Pseudocapillaria tomentosa in laboratory zebrafish (Danio rerio). Zebrafish, 11(5): 490-497. https://dx.doi.org/10.1089%2Fzeb.2014.1021
This study and multiple treatment reports online confirm a low safety margin for this drug. It can easily cause neurological issues with fish and it is hard to calculate dosage as it's not made for aquarium use and the paste often sold for horses can result in unexpectedly high concentrations in food, causing deaths.
[6] Easily found as a paste for deworming horses on amazon, but this is not a "pure" form and thus it may be very difficult to accurately calculate a safe dosage. Additionally, a paste form will come with additional chemicals/additives which may have unexpected or negative side effects towards aquatic life. Non-paste forms of ivermectin are not nearly as easy to find and may have to be ordered from a pharmaceutical or industrial chemicals vendor.
[7] Flubendazole and Mebendazole have extremely similar molecular structures, and belong to the same "family" of drugs in the anthelmintics class, known as Benzimidazoles. The Benzimidazoles group includes Thiabendazole, Fenbendazole, Flubendazole, Mebendazole, Febantel, Netobimin, and many more types of livestock dewormers. If your worm strain is resistant to one type of "-dazole" it's highly likely it's resistant to others, if not all in that group. The only difference between Mebendazole and Flubendazole is that Flubendazole has a fluoride attached at the end of a benzene ring.
Flubendazole
Mebendazole
Fenbendazole
Non-Anthelmintic Dewormers:
| Drug Name & Family | Kills or Removes Male Worms/Younger Worms? | Kills or Removes Adult Female Worms? | Easy to Obtain? | Safety Margins | Best Administered | Resistance Common? |
|---|---|---|---|---|---|---|
| Piperazine (Chicken dewormer). Piperazine family. Same drug class as Viagra | Very to Moderately easy [1*] | Orally; apparently 25 mg/10 g of food is recommended [2*] | Resistance possible or may just be too weak for majority of cases | |||
| Emamectin Benzoate (AKA Nematol [3*]). Avermectin family of Macrocyclic Lactones. | Yes | Yes | Easy in UK/EU through Amazon, also on the shelf in pet stores. Must be ordered internationally for NA, make take months to arrive due to customs. | High, both orally and in the water column; well tolerated by fish. [3, cited above] | In the water column is recommended by Sera, but in study [3, cited above] it was given orally, so both are possible and effective. | Resistance HIGHLY UNLIKELY in North America, and probably also rare in UK/EU as it's not used very commonly. |
| Eprinomectin. (Cattle dewormer). [4*] Avermectin family of Macrocyclic Lactones. | Yes [5*] | Yes [5*] | Easy if you're a chemist, might be impossible for anyone else [6*] | High, both orally and in the water column [5*] | Both orally and in the water column is effective | Resistance extremely unlikely, I've only ever found mention of this med's use in that German patent, shocking it's not more well-known. |
[2*] Source (look at section on piperazine)
[3*] Because this is the only fish medication that uses this salt as an active ingredient. Emamectin Benzoate is the benzoate salt of the anthelmintic Abamectin, or the 4'-deoxy-4'-epi-Methylamino Derivative of Avermectin B1.
[4*] Eprinomectin is the 4'-deoxy-4'-epi-Acetylamino Derivative of Avermectin B1.
[5*] https://drive.google.com/file/d/1iRXxfYtRXzUz9OaEFGHB2qzbeWjhTO3e/view?usp=sharing
[6*] With a quick google search I found you can get massive quantities of it intended for cattle use in the US, but this likely isn't made to dissolve in aquarium water or be safe for fish. The patent guide also mentions the methods you can/must use to make the ingredient water-soluble, so if you are able to access these tools and materials it's certainly possible. It's also possible that the cattle varieties are in fact water-soluble and fish-safe, but you would have to perform multiple tests or calculations to confirm this without risking the lives of your fish.
How do you know for sure Camallanus has been killed, or what does it look like when Camallanus is dying from an effective or semi-effective medication?
Here are some images I took of my fish (Fundulopanchax nigerianus, males) after dosing with Nematol (Emamectin Benzoate). Nematol completely killed and removed all mature male and female Camallanus nematodes 48h after dosing. Previously visible and moving red female worms were nowhere to be seen after this period of time. An effective nematocidal fish medication should take care of the parasites within 48 h. and no longer. If your fish still have worms after this time period, either your dosing was too weak or the parasite is resistant (more likely the case).
Worms (white lines just before anal fin) being ejected from anus, ~18h after dosing Nematol. Presumably male or young worms found in the intestines rather than vent; I noticed these types of worms have a pale yellowish color, when ejected at least, rather than the red females. This type of ejection of small internal worms was also observed, with a nearly identical appearance, when fish were orally fed Levamisole. I would call this \"Stage 1\" of treatment, with at least a portion of the population of worms being removed.
Treatment of C. cotti with Nematol (Emamectin Benzoate), ~24h. after first and only dose. Female nematode is hanging out vent of fish. During this time, movement of worms in and out of anus was not observed (during both Fenbendazole and Levamisole treatments, movement of females entering and leaving of anus never ceased). Blood pulsing through the worm was also visible, however worm was hanging out far far more than usual, and not motile otherwise. Within 12 h. after this, the female worms disappeared entirely, presumably ejected. I call this \"Stage 2\", and this stage guarantees your fish will be cured, because the most resistant and difficult to kill mature females are removed from the fish for good. After this all that needs to be removed are the remaining worms, and then recovery.
Worm ejection, 5 days after initial treatment. White color clearly indicates dead status of worm, which was presumably still attached by the buccal capsule somewhere in the body until its eventual ejection. I would call this \"stage 3\", or the final stage of worm removal from the intestines of your fish. They repel the last few dead worms out. After this stage, bacterial infections may be a risk.
Conclusion
Anthelmintics/Anti-parasite drugs that are relatively new or so little known about them apart from that they treat for nematodes that more studies need to be performed to find out effectiveness and toxicity towards aquatic life:- Tetrahydropyrimidines, according to study [1] causes spastic paralysis of worms as an effective class of nematocidal drugs, and according to this patent, fish are some of the safest patients for the drugs. However too little info is known and to my knowledge there are currently no existing veterinary medications which use these drugs as an active ingredient, making them nearly impossible to come by. A snippet of info on a compound that includes a tetrahydropyrimidine in the formula stated that lethal concentration occurred for danios after 4 days in a concentration of less than 100 mg/L (>0.4 g/Gal). However this isn't much to go off of nor does it tell us much about the use of it on nematodes.
- Abamectin/Avermectin B1, apparently the benzoate salt that is derived from this make emamectin benzoate. Commonly used to treat livestock. According to study [1] it's also used in fish farms to treat fish lice, however I've found multiple articles (1, 2, 3) which conflict with this info and have found it to be highly toxic towards danios, so unless it's used in microscopic quantities at fish farms or commercial fish are more tolerant, they probably don't use the same form of it that these other studies have, nor the same kind used as an insecticide for crops.
- Spiroindoles, this is a lesser known class of drug but the only patent of it available for veterinary use I found in study [2] (derquantel) is highly toxic to aquatic life so I would stay away from this class entirely, especially since you cannot obtain this class without having other aquatic-toxic compounds mixed in
- Organophosphates, Carbamates, Synthetic Pyrethroids, not all are for nematodes specifically but all 3 are veterinary anti-parisitic drug classes that should not be used, because according to this website on parasites, all have proven to be highly toxic towards aquatic life.
- Artemisinin, a wormwood compound which apparently shows anti-parasitic activity but is toxic to fish regardless (category 1 aquatic toxicity = the highest toxicity level towards aquatic life).
[1] Lumaret, J. P., Errouissi, F., Floate, K., Römbke, J., Wardhaugh, K. 2012. A review on the toxicity and non-target effects of macrocyclic lactones in terrestrial and aquatic environments. Current Pharmaceutical Biotechnology. 13(6): 1004-1060. https://doi.org/10.2174/138920112800399257
[2] Abongwa, M., Martin, R.J., Robertson, A.P. 2017. A brief review on the mode of action of antinematodal drugs. Acta veterinaria, 67(2): 137–152. https://doi.org/10.1515/acve-2017-0013
There's a lot more to be written about and revised here but I've been working on this guide for several days now in a reddit draft and I want to post it now as this type of research can be exhausting, no matter how passionate you are about it. Probably few people will even read this anyways because it's such a niche topic and I wrote like a bajillion words that can be a huge ass pain to sift through, buut... I learned a lot, I found it interesting and incredibly informative, so I sincerely hope it can help others too. I included as much as came to my mind and will add more to fill in the blanks but yea... I think it really covers just about everything endoparasite-related with fish and it's a lot more comprehensive than the majority of research articles out there, while still being long, detailed, and researched enough to be trustworthy and helpful (I hope). So for anyone struggling with nematodes out there... good job finding this guide, it shows you care a hell of a lot about your fish. You got this, you'll cure them, I'm proud of you. Good luck.
