Genetic characterization of rabies field isolates from Venezuela.

Twenty samples from cases of rabies in humans and domestic animals diagnosed in Venezuela between 1990 and 1994 and one sample from a vampire bat collected in 1976 were characterized by reactivity to monoclonal antibodies against the viral nucleoprotein and by patterns of nucleotide substitution in the nucleoprotein gene. Three antigenic variants were found: 1, 3, and 5. Antigenic variant 1 included all samples from dogs and humans infected by contact with rabid dogs. Unique substitutions permitted identification of two separate outbreaks of dog rabies in the Maracaibo Depression and Los Llanos region and in the Andean region of Venezuela. Samples from the vampire bat and two head of cattle were characterized as antigenic variant 3 and showed a nucleotide sequence homology of 96 to 98% to each other and to samples of vampire bat-associated rabies throughout Latin America. Ten of the remaining 12 samples were characterized as antigenic variant 5. Genetic studies indicated that 11 of these samples formed a highly homologous and distinctive group but were closely related to samples of vampire bat-associated rabies. The 12th sample of variant 5 (from a cat) showed only 78 to 80% genetic homology to samples of rabies associated with vampire bats. The application of antigenic and genetic typing to rabies surveillance in Latin America is essential to improve control programs. Recognition of the source of outbreaks of dog rabies and identification of wildlife species maintaining sylvatic cycles of rabies transmission permit better utilization of public health resources.

Antigenic analysis of rabies-virus isolates from Latin America and the Caribbean.

A total of 288 rabies-virus samples from 17 Latin American and Caribbean countries were reacted with an array of monoclonal antibodies. Identification of eight distinct antigenic variants among these samples permitted epidemiologic studies of the geographic distribution of different concentrations of rabies in the region and of the animal species serving as maintenance sources for rabies within a concentrated area. Two variants were broadly distributed and associated with enzootic disease in dogs and vampire bats. All isolates from cases of human rabies contained one of these two variants. Two variants had a limited distribution: an outbreak in Brazil, primarily affecting dogs and believed to be maintained by dog-to-dog transmission, and nine cases of rabies in cattle in Venezuela, animal reservoir unknown. A reservoir of rabies in insectivorous bats was identified and the associated variant was found in a rabid domestic cat. The remaining three rabies variants were found in single isolates only, but due to inference from antigenic-typing data from North American samples, were believed to be maintained by reservoirs of rabies in hoary bats, foxes, and skunks.

A second Dr(a-) proposita with anti-Dra and a family with the Dr(a-) phenotype in two generations.

An Israeli Jewish woman who originated from the Uzbekskaya SSR in the south of the Soviet Union, had anti-Dra in her serum and her red cells were Dr(a-) as were those of three of her four children. All Dr(a-) red cells had weakened expression of their Cra, Tca, Esa, IFC, and other Cromer-related antigens. It is suggested that the Dr(a-) phenotype may result from inheritance of a dominant inhibitor gene, although a relatively common recessive allele of Dra was not excluded. Anti-Dra was inhibited by serums from the Dr(a+), but not the Dr(a-), members of the family.