In August 1997, another outbreak of botulism occurred in fish-eating birds. Again, sick and dead tilapia were observed at the same time. The suspect parasite is found worldwide and infects more than 100 species of marine fish in North America alone. In wild fish, the number of parasites per fish is typically very low, and they do not usually die from the infestation. When present at levels as high as those detected in tilapia from the Salton Sea, the parasite impairs respiratory function and can suffocate the fish.
Diagnosis is based on finding the attached feeding stage of the parasite present in gill scrapings.
Since the life cycle of Amyloodinium can be completed in less than one week at high temperatures and in high saline conditions, like those currently present at the Salton Sea, it is expected that massive and lethal infestations can develop rapidly. Now that the parasite is present in the Salton Sea, and is able to reproduce without control, persistent, chronic die-offs of fish may be expected to continue, the scientists said. The connection between this parasite, other bacterial infections in fish and the occurrence of botulism in fish-eating birds is still under investigation. Along with environmental stressors and other disease-causing agents identified in fish and birds, Amyloodinium represents another threat to the overall health of the Salton Sea ecosystem.