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Increased mortality was observed in a single colony of 50 Xenopus laevis. The frogs were used as oocyte donors in developmental biology studies. Necropsy findings included dermal erythema and petechiation consistent with red leg syndrome; dermal ulcerations and white, filamentous growths on the skin were consistent with Saprolegnia sp. Microscopic evaluation of the skin and fungus revealed an astigmatid mite similar to those of the genus Rhizoglyphus. The mite was also found in the water and the biological filter of the tanks housing the frogs. This mite is considered not to be a parasite of X. laevis; instead, it feeds off moss, fungi, and detritus. Subsequent evaluation of the sphagnum moss used for shipping the frogs from the supplier revealed the same mite in the moss. Our hypothesis is that the mite was introduced into the tank with the shipment of new frogs in sphagnum moss. The mites lived within the biological filter, and were only found after the growth of Saprolegnia sp. attracted the mites to the frogs. Laboratory animal care and veterinary personnel should consider non-pathogenic species of mites in the differential diagnosis of acariasis in Xenopus frogs.

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.

Xenopus laevis, the South African clawed frog or toad, is a member of the family Pipidae. Now in high demand for research purposes, they are available commercially. Its reported lifespan is up to fifteen years. Investigators and caretakers are frustrated when commercially obtained, young frogs (four years or younger), not subjected to any studies, "waste" and die. The wasting syndrome is characterized by anorexia, color change, and "flaky skin." Often the first sign of this syndrome is the presence of large fragments of "flakes" of desquamated epithelium in the water. At necropsy, these frogs are thin and have rough skin instead of smooth slimy skin. Histologic examination reveals tortuous intraepithelial cavities or tunnels that contain nematodes, and associated mild to moderate granulomatous inflammation. Nematodes are also found in the kidneys of some of these frogs, usually in Bowman's space, wrapped around the glomerulus. The cutaneous capillarid nematode is identified as Pseudocapillaroides xenopi. Successful treatment with ivermectin and thiabendizole has been reported. The renal glomerular nematode has not been identified.

Significant morbidity and mortality of South African clawed frogs, Xenopus laevis, can be caused by parasitism of the epidermis by a capillarid nematode. These worms produce an erosive dermatitis that is complicated by infection with gram-negative microorganisms. The nematode apparently has a direct life cycle that can be completed within the epidermis of the frog. These characteristics are suggested by the lack of an intermediate host and failure to detect visceral migration. Another unique feature of the parasite was the presence of larvated eggs, in utero. Some have named the parasite Capillaria xenopodis, whereas others called it Pseudocapillaroides xenopi to distinguish it form the typical members of the genus Capillaria.