Protozoa in Poison Dart Frogs (Dendrobatidae): Clinical Assessment and Identification

Poison dart frogs (Dendrobatidae) are small, brightly colored frogs indigenous to the neotropics. In the wild, two genera are vulnerable to extinction, yet in captivity increasing numbers of dendrobatids are maintained. Despite the great interest in these frogs, there is little published information available on their health. Clinical assessment of the protozoa from wild-caught and captive-bred dendrobatids was based on examination of approximately 300 direct fecal samples from a colony of frogs. Intestinal protozoa were observed in 26% of all colony frogs. In different groups, the prevalences were as follows: sick frogs, 50%; quarantined frogs, 35%; healthy frogs, 25%; and exiting frogs, 15%. The densities of infection were usually light or moderate for all protozoa (opalinid, ciliate, and flagellate trophozoites and opalinid and coccidian cysts). Most of the intestinal protozoa appeared to be commensals rather than parasites and are not routinely treated. The use of therapeutic agents may be indicated, however, to regain homeostasis in frogs following stressful events such as capture, shipping, or illness. Protozoa were identified in detail from black and green poison dart frogs (Dendrobates auratus) and strawberry poison dart frogs (Dendrobates pumilio), "research frogs" wild caught in Central America especially for this purpose. The 69 research frogs were euthanized and necropsied. Protozoans in the large intestine and blood were photographed and preserved for identification using light microscopy and scanning and transmission electron microscopy. All research frogs had a dense protozoan fauna in their large intestine. Organisms included the opalinid Zelleriella sp., the ciliate Nyctotheroides sp., and retortamonad, trichomonad, and diplomonad flagellates; these flagellates are reported from dendrobatids for the first time. Prevalence of infection was not significantly different in D. auratus euthanized within a day of capture and in frogs subsequently maintained in captivity. Nyctotheroides sp. was not seen in D. pumilio, and Zelleriella sp. was significantly less prevalent in D. pumilio than in D. auratus. Trypanosoma sp. was present in the blood of D. auratus.