Reptiles and Amphibians Q&A 08
This is one of a group of approximately 100 African clawed frogs used in biomedical research that experienced a sudden mortality following a single feeding of thawed, frozen salmon brought into the laboratory by an animal caretaker who had caught the fish.
All of the dead and dying frogs shared identical gross lesions consisting of full-thickness cutaneous ulcerations. The mucous integument that surrounded each ulcer was raised and erythematous. Gross necropsy and histopathologic findings were minimal, consisting only of ulceration and mild mononuclear leukocytic infiltration of the denuded skeletal muscle.
| Question | Answer | Article | |
| What is your tentative diagnosis? | Aeromoniasis, although similar lesions are seen in other Gram-negative infections. |
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| What tests would you perform to confirm your diagnosis? | Microbiological culture, particularly one that is carried out on specimens subcultured in thioglycholate broth and incubated at 30°C and at a reduced oxygen atmosphere. |
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| What is the prognosis? | The prognosis is poor to guarded because of the virulent pathogenicity of many Gram-negative microorganisms in amphibians. |
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| How would you treat the remaining frogs? | Frogs exposed to this frog and other sick frogs should be isolated and kept in uncrowded treatment tanks. An appropriate bacteriocidal antibiotic, determined by sensitivity testing, should be administered by the intramuscular or oral route; alternatively, enrofloxacin has been shown recently to be effective when added to the tank water in which the frogs under treatment are being kept. |
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| What control measures should be instituted to prevent a repetition of this problem? | Outbreaks such as this one can usually be avoided by adhering to strict quarantine, enhancing sanitary and other hygienic practices, and controlling the food sources. In this instance, the aetiologic agent responsible for the outbreak was Aeromonas salmonicida, a common pathogen of salmonid fishes (salmon and trout). |
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