Anthelmintic treatment to eradicate cutaneous capillariasis in a colony of South African clawed frogs (Xenopus laevis).

The nematode Capillaria xenopodis (Pseudocapillaroides xenopi), a skin parasite of South African clawed frogs (Xenopus laevis), is quite common in laboratory animal facilities. It causes serious skin changes and may further lead to wasting and death of affected frogs. Various treatment protocols, using the anthelmintics ivermectin and levamisole, were successively tested for practicability of elimination of the parasite from a colony of clawed frogs. Nematodes were reduced below diagnostic levels by various methods of application of ivermectin (orally or by injection into the dorsal lymph sac, twice at intervals of 10 to 14 days). However, nematodes were found again in the treated animals 1 to 3 months later. Treatment by use of ivermectin-medicated tank water is not feasible due to its low water solubility. Elimination of the parasite was reliably achieved by use of levamisole-medicated tank water. Relapses were not seen during the 18-month posttreatment observation period. Levamisole concentration was 12 mg/L of water, with 4.17, 5.00, or 6.25 L of tank water/frog, and 50, 60, or 75 mg of levamisole available/frog, for at least 4 days, with treatments repeated after 10 to 14 days. Results were reproducible in two trials each with five tanks containing, in turn, four or five frogs each. A treatment trial carried out with a group of 20 adult frogs exposed to 12 mg of levamisole/L of tank water, but with only 2.5 L of tank water/frog (i.e., only 30 mg of levamisole available/animal), was not effective in eradicating the parasites. Not only the drug concentration, but also the amount of drug available per animal seems to be of importance. In contrast to thiabendazole, which is often reported in literature as treatment for cutaneous capillariasis, negative side effects were not observed with use of levamisole.