This is my first posting to the forum so I apologize if I am overlooking a comment that was similar to mine.
For details on my background, check out my bio at Arizona Exotic Animal Hospital
(See webpage "About" and then select "Kevin Wright"). I may be familiar to some of you who have read the book I co-authored, Amphibian Medicine and Captive Husbandry.
I started out 20 years ago approaching frog parasites (and dendrobatid frog parasites in particular) with the approach that any parasite was a bad parasite. Lots of work has shown the huge parasite population found in healthy newly captured dendrobatids (and what happens following collection). In the past decade (and even since I wrote the book) I have concluded that failure to find a parasite in a dart frog is simply failure to look hard enough and often enough, and that the cost of achieving this "negative" state was often detrimental to the frogs with poor reproduction, poor body conditions, and outbreaks of random illnesses occuring that I could only attribute to the stress of treating asymptomatic frogs for parasites I perceived to be a problem but that may not have actually been problems in and of themselves. Since that time, papers have come out demonstrating that fenbendazole is not benign and causes immunosuppression and liver changes even at levels lower than have been advocated as benign and appropriate for prophylactic management of nematodes. When I stopped being so aggressive and just monitored fecals for existing levels of parasites and only treating where I saw frogs that were unthrifty and had white blood cells and red blood cells in their feces, along with parasites, I experienced a much more healthy frog population with fewer incidents of random deaths. In fact, I know of dendrobatids with high levels of various nematode parasites, flagellated parasites, and even amoebas, that lived long lives with good bodyweight and successful reproduction and recruitment/survival of offspring.
That said, there are some parasites I always worry about. Certain nematodes (Rhabdias and Strongyloides), coccidia, and Cryptosporidium are all parasites that I feel can be devastating if introduced to a collection or, if already present, aren't managed appropriately. Cryptosporidium is currently in a nebulous area but given the problems seen in reptiles, I certainly think Crypto-positive animals should be identified and managed to prevent spread to other animals & enclosures. Coccidia is often effectively treated with a few doses of ponazuril. Rhabdias and Strongyloides can be managed, but not eliminated, with a variety of anthelmintics including pyrantel palmoate, ivermectin, levamisole, and fenbendazole.
I know this opinion may not be a popular one but it is one derived from 20 years of experience with captive amphibians including several years managing a large captive collection of amphibians at the Philadelphia Zoo. It is amazing how many "parasite infections" turn out to truly be poor nutrition, poor husbandry, or underlying diseases such as ranavirus, toxicoses, or other problems.
I assess a collection's overall health, recommend regular fecal parasite examinations (fresh are best, generally observed within a few hours of deposition; if older, I recommend splitting a fecal and looking at some by direct wet mount and some preserved in polyvinyl alcohol and sending to a lab for identification of protozoa/cysts) to assess what is really going on in the collection, and coming up with a targeted preventive medicine program based on the species, the fecal fauna identified, and the morbidity & mortality of the collection.
As far as "clean tanks", there is no way to guarantee you are not bringing in a nasty with live plants (or, as appears to be the case with ranavirus, live food). A healthy vivarium with a low level of frogs, thriving plants, and good sanitation is somewhat self-policing except for things like Rhabdias, Strongyloides, and coccidia (including Cryptosporidium). You may run levamisole through a system to try and wipe out larval nematodes but Rhabdias can become free-living generation and persist in the soil without frogs! Look at your frogs before you put them in a new tank so you know what is going in there.
My final comment is to always look at the level of vitamin A in your diet as so many outbreaks of illness are now tied in to hypovitaminosis A!
Kevin Wright, DVM
Arizona Exotic Animal Hospital
744 N Center Street
Mesa, AZ 85201
Arizona Exotic Animal Hospital