Inconsistent efficacy of water-soluble amphotericin B for the treatment of Macrorhabdus ornithogaster in a budgerigar (Melopsittacus undulatus) aviary

Objective To assess the efficacy of a commercially available in-water amphotericin B treatment for Macrorhabdus ornithogaster. Design Clinical treatment trial. Methods Faecal shedding of 16 naturally infected budgerigars (Melopsittacus undulatus) was monitored while they were being treated using in-water amphotericin B, as per the manufacturer's instructions, for 10 days. Any birds that remained positive after 10 days received a further 10 day course of treatment. All birds were rechecked 16 days after the end of the second treatment period. Results At the conclusion of treatment, 11 birds had stopped shedding M. ornithogaster, and 5 birds were still shedding. Sixteen days after the conclusion of the second treatment period, four birds that were negative after 10 days of treatment were shedding again, and two of the birds that were treated for 20 days were shedding. In addition, one bird from each treatment group died after treatment and before follow-up testing. Conclusion These findings represent a 36% treatment failure, suggesting that treatment with the commercially available, water-soluble amphotericin B has inconsistent efficacy against M. ornithogaster in some budgerigars in Australia and is not effective for eliminating it from budgerigar aviaries.