Most types of cyanobacteria that produce neurotoxins occur in marine environments, where they can cause red tides. A few species are found in freshwater around the world, and they sometimes kill dogs, cattle and other animals that drink from or swim in contaminated water bodies.
“One of the biggest unresolved issues is why there seems not to have been collateral mortality,” said Chris Thouless, head of research at Save the Elephants, an organization based in Kenya. “That is one of the reasons we originally said this was not a probable explanation, because other animals didn’t seem to be dying.”
Elephants account for the majority of wildlife in the area, but cattle are also found there, Dr. Thouless said. He has not been able to verify, however, whether cattle drink from the same bodies of water used by elephants.
That said, he added, “While no suggested cause is a perfect fit