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Bacterial Infection of Embryos

Symptoms: Embryos disintegrate due to a bacterial infection.

Treatment: Maintaining embryos in gentamicin (100 µg/mL) from fertilization to stage 41, when they are free-swimming, is effective at killing bacterial pathogens. Also, it is essential to keep the embryos at a low density, because a high density can spread infection from a few dying embryos, and to quickly remove any unfertilized eggs or dead embryos. In fact, at high density, embryos are susceptible to bacterial infection and death despite gentamicin. Refer to Raising Frogs and Tadpoles for information on tadpole raising and density. The embryos should look very sparse in the dish.



Caused by an acid-fast bacilli of the genus Mycobacterium. Many mycobacterial species have been found to cause infection in amphibians, including M. marinum, M. chelonae, and M. xenopi. The causative agent in X. tropicalis colonies recently has been proven, through molecular and phenotypic characterization, to be M. ulcerans-like and named M. liflandii. M. ulcerans is a water-borne pathogen endemic to tropical regions of Africa, Australia, Central America, and Eastern Asia that causes dermal-epidermal ulcerations in humans. In some colonies M. liflandii strain KT1 is most closely related, although not identical, to M. ulcerans by molecular analysis and has the growth characteristics of M. ulcerans. However, since the bacteria is related to M. ulcerans, a known human pathogen, it is recommended that personnel wear protective eyewear and gloves when handling the frogs. Using aggressive quarantine, we have not seen mycobacteriosis in our Yale colony. As there is no treatment and the bacteria may be dormant, healthy frogs and constant vigilance is key.

Chytridiomycosis (Batrachochytrium dendrobatidis)

Chytrid pathogen of amphibian skin. Refer to the following paper for information on Signs and Treatment.

*Parker, John M.; Mikaelian, Igor; Hahn, Nina; Diggs, Helen E. Clinical diagnosis and treatment of epidermal chytridiomycosis in African clawed frogs (Xenopus tropicalis). Comparative Medicine. June, 2002. 52 (3): 265-268.

Incidental Findings

Intestinal parasites found upon gross examination and not believed to be the causative agent of death or illness (Fig. 5,6).


Intestinal Ciliated Protozoan:

contributed by Kristin Trott and John Parker