Abstract

Eastern equine encephalitis virus (EEEV) is an arbovirus that causes disease in horses, humans, and a wide variety of avian species. Morbidity and mortality from EEE outbreaks have occurred in captively held birds including species in the orders Gruidae and Icteridae. Disease-related mortality and pathology appear to be highly species specific. Whooping cranes and emu appear to be particularly susceptible, while a colony of African penguins experienced morbidity but little mortality.

In the summer of 2014, the Virginia Zoo experienced acute mortality in four southern cassowaries (Casuarius casuarius) over a two-week period. The birds affected included three 27-day-old chicks and their 23-year-old dam. Two of the chicks were found dead with no premonitory signs; the other two birds showed signs of dyspnea, mental obtundation, weakness, lethargy, and anorexia. Both birds died shortly after initiation of intensive medical care. Clinicopathologic changes included leukocytosis, hyperuricemia, and elevated liver enzymes indicative of systemic inflammation. Plasma protein electrophoresis revealed elevated beta globulins indicative of acute inflammation.

On postmortem examination, coelomitis and diarrhea were observed. Common histopathologic abnormalities were encephalitis, vasculitis, hepatitis, nephritis, and splenitis. The diagnosis of EEEV was confirmed through the detection of viral RNA via PCR assay in the brain tissue of these cases. The EEEV in southern cassowary has never been fully described and has different pathologic characteristics than those observed in other species. Vaccination of susceptible birds is recommended with a killed polyvalent equine product. Mosquito control should also be implemented to help prevent disease.