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Introduced species can arrive into new territories with parasites; however, these species are expected to face lower parasite richness than in their original regions. Both introduced hosts and parasites can affect native fauna. Since their release into the wild in Chile following laboratory use, Xenopus laevis Daudin, 1802 has widely spread throughout central Chile. The only pathogen described on the host is the fungus Batrachochytrium dendrobatidis Longcore, Pessier, Nichols, 1999; thus, this is the first parasitological study of this species in Chile. In 10 localities in central Chile, 179 specimens of X. laevis were captured and examined for parasites in the gastrointestinal tube, cavities, lungs, liver, and skin. Only nine specimens of the genus Contracaecum Railliet, Henry, 1912 were found in six specimens of X. laevis from a private dam in La Patagua. It is likely that these parasites originated from species of native birds. This is the first record of Contracaecum sp. in Chilean amphibians.

The African clawed frog Xenopus laevis (Anura: Pipidae) is host to more than 25 parasite genera encompassing most of the parasitic invertebrate groups. Protopolystoma xenopodis Price, 1943 (Monogenea: Polystomatidae) is one of two monogeneans infecting X. laevis. This study focussed on the external morphology of different developmental stages using scanning electron microscopy, histology and light microscopy. Eggs are released continuously and are washed out when the frog urinates. After successful development, an active swimming oncomiracidium leaves the egg capsule and locates a potential post-metamorphic clawed frog. The oncomiracidium migrates to the kidney where it attaches and starts to feed on blood. The parasite then migrates to the urinary bladder where it reaches maturity. Eggs are fusiform, about 300 μm long, with a smooth surface and are operculated. Oncomiracidia are elongated and cylindrical in shape, with an oval posterior cup-shaped haptor that bears a total of 20 sclerites; 16 marginal hooklets used for attachment to the kidney of the host and two pairs of hamulus primordia. Cilia from the 64 ciliated cells enable the oncomiracidium to swim for up to 24 h when the cilia subsequently curl up, become non-functional and are shed from the body. The tegument between the ciliated cells bears a series of sensory papillae. The body of the mature parasite is elongated and pyriform and possesses an opisthaptor armed with three pairs of suckers and two pairs of falciform hooks to ensure a firm grip on the flexible internal surface of the urinary bladder., (© M. Theunissen et al., published by EDP Sciences, 2014.)

A postmortem evaluation of a domestically bred, adult, female Xenopus laevis revealed the presence of a urinary bladder protozoan consistent with Trichodina xenopodus. T. xenopodus is considered an incidental finding, as its presence in the urinary bladder in frogs has not been correlated with disease or with urinary bladder epithelial lesions. Trichodina spp. are ciliated protozoa known to colonize many species of amphibians and fish. These protozoa frequently inhabit the skin and gills, but may also be present in the urinary bladder of infected animals. Their presence on the skin and gills in low numbers is not related to disease; however, large numbers may indicate poor water quality and overcrowding.

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.

Naive, full-sibling juveniles of Xenopus laevis laevis were exposed to 10, 30, or 50 larvae of the monogenean Protopolystoma xenopodis from an isolate known to produce relatively low adult establishment (typically less than 25% prevalence) in hosts of the same pedigree. Postlarval survival (worms per host) 7 days postinfection (PI), timing from the end of a 10-day infection window, was significantly related and proportional (approximately 31%) to infection dose. Establishment of newly mature adults 90 days PI was low (0-3 worms/host) and unrelated to infection dose. Results confirm that postlarval mortality is severe in primary infections, and that surviving adult infrapopulations appear to be regulated to a very low level (most often 1 worm/ host), even at relatively high larval infection pressures. This density-dependent process could involve direct antagonistic parasite-parasite interactions or indirect interference mediated by parasite-induced host defenses.

Specimens of the freshwater snail Bulinus tropicus (Krauss, 1848) collected in the Free State, South Africa shed cercariae with an oral collar bearing 27 spines. Tadpoles of the African clawed toad Xenopus laevis laevis Daudin, 1802 collected from the same waters harbored metacercariae with a similar collar of spines. Adults were obtained after feeding infected tadpoles to laboratory-reared reed cormorants, Phalacrocorax africanus (Gmelin, 1789). The parasite was identified as Petasiger variospinosus (Odhner, 1910), the life cycle was experimentally completed, and stages described by the use of light and scanning electron microscopy.

Viable Cryptosporidium serpentis oocysts originating from 6 captive snakes were gastrically delivered to 12 Cryptosporidium-free African clawed frogs and 9 tadpoles and 3 recently metamorphosed adults of Cryptosporidium-free wood frogs. On days 7 and 14 postinoculation, no life-cycle stage of Cryptosporidium was observed in any of the histological sections of stomach, jejunum, ileum, cloaca, and cecum. However, viable inoculum-derived C. serpentis oocysts were recovered from the water in which the amphibians were kept. Amphibians may disseminate C. serpentis oocysts in the natural habitat.

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.

The strigeoid metacercaria Diplostomulum xenopi is commonly found in the pericardial cavity of Xenopus laevis laevis. This paper provides the first description of the adult obtained from the intestine of an experimental host, the darter, Anhinga melanogaster. Natural cercarial infections were found in specimens of the freshwater snail Bulinus tropicus collected from dams in the Free State. South Africa. The life cycle was experimentally completed and all stages were described by light and scanning electron microscopy.

A recent report suggested that an isolate of Cryptosporidium parvum had established infections in fish, amphibians, and reptiles and raises concern that animals other than mammals might be a potential source of waterborne Cryptosporidium oocysts. To test this possibility, viable C. parvum oocysts, infectious for neonatal BALB/c mice, were delivered by gastric intubation to bluegill sunfish, poison-dart frogs, African clawed frogs, bearded dragon lizards, and corn snakes. Histological sections of the stomach, jejunum, ileum, and cloaca prepared from tissues collected on days 7 and 14 postinoculation (PI) were negative for Cryptosporidium developmental stages. However, inoculum-derived oocysts were detectable by fluorescein-labeled monoclonal antibody in feces of inoculated animals from day 1 to day 12 PI in fish and frogs, and up to day 14 PI in lizards. Snakes did not defecate for 14 days PI. Impression smears taken at necropsy on days 7 and 14 PI revealed C. parvum oocysts in the lumen of the cloaca of 2 fish and 1 lizard on day 7 PI only. Because tissue stages of the pathogen were not found, it appears that C. parvum was not heterologously transmitted to lower vertebrates. Under certain circumstances, however, such as after the ingestion of C. parvum-infected prey, lower vertebrates may disseminate C. parvum oocysts in the environment.

The possibility exists that paratenic hosts play a role in the life cycle of various Dracunculus species. In the present study, we established that tadpoles of 2 genera of frogs (Xenopus and Rana) were capable of ingesting copepods infected with third-stage larvae (L3) of Dracunculus insignis. Once ingested, the L3s migrated from the gut to the somatic tissues of the tadpoles. In Xenopus, the dracunculid larvae persisted through the metamorphosis of the tadpoles into adult frogs. These observations confirm the concept that paratenic hosts, such as tadpoles or frogs, may be important means of transporting infective larvae of Dracunculus species up the food chain and facilitate transmission to the definitive hosts.