Serologic evidence for the presence in Pteropus bats of a paramyxovirus related to equine morbillivirus.

Dispatches 239 Two outbreaks of a previously unknown disease in horses and humans occurred in Queensland in 1994. The outbreaks occurred within 1 month of each other in Brisbane and Mackay, which are approximately 1000 km apart. In the Brisbane incident, 21 horses were infected of which 14 died or were euthanized after severe clinical signs of an acute respiratory disease. Two human cases were in patients with less well defined clinical signs; one patient died (1,2). In the Mackay incident two horses became seriously ill and died, and one person also died (3). Although it is now known that the two outbreaks occurred in August and September 1994, knowledge of the Mackay outbreak did not occur until late 1995 when the infected person died of a relapsing encephalitis. The name equine morbillivirus (EMV) has been proposed for a paramyxovirus isolated from four of the Brisbane horses and the first patient who died (2). In both locations, the index case appears to have been in a mare in late pregnancy, on pasture. The mode of transmission to other horses and to humans is unknown. In spite of intensive investigations, no connection has been established between the two incidents. At both locations, initial serologic studies of in-contact horses and humans failed to show evidence of neutralizing antibody, and it was concluded that infection by contact is uncommon. A subsequent statewide serologic survey of 2,411 horses has also shown no evidence of infection (4). At present, only seven horses have had antibody, and all were involved in the Brisbane outbreak. To evaluate the theory that EMV originated from a wildlife source, a trapping program was initiated, focusing on the location of the index cases, first in Brisbane and later in Mackay when the details of that incident became known. A total of 5,264 sera from 46 species were tested, none of which showed any evidence of antibody. Further information from the Mackay cases enabled us to think more logically about a possible reservoir host. Although virus was not isolated from the two horses, it was possible to amplify part of the EMV matrix protein gene by PCR. A comparison of the sequence of this PCR product with PCR product from the Brisbane cases showed that they were identical, indicating a common source of origin (5). In our consideration of possible reservoir hosts, the following criteria were applied to prioritize species for investigation: …