Vampire Bat Populations Research Articles

Genetic characterization of Rabies virus isolated from cattle between 1997 and 2002 in an epizootic area in the state of São Paulo, Brazil

The biogeographical history of rabies can be reconstructed using molecular data. This work describes the genetic characterization of the Rabies virus variant that circulates in the Desmodus rotundus (vampire bat) population in an epizootic area and is transmitted to herbivorous livestock. The N and G genes of this virus were sequenced, and the phylogenetic trees generated were topologically concordant. Three genetic clusters were identified in the epizootic area and were designated RD1, RD2 and RD3. The results show that the origins of the epizootics in areas RD1 and RD2 were different and that the epizootic in area RD3 was the result of expansion of that in area RD2. The two genes analyzed are conserved, and their identities, which are greater than 98%, were maintained over time and space. The genetic sequences in this study were compared with others retrieved from GenBank, and the high identity of the N and G genes was also shown to be maintained over time and space. The results suggest that the D. rotundus lineages of the Rabies virus from the Atlantic coast of South America are highly conserved.

Áreas propícias para o ataque de morcegos hematófagos Desmodus rotundus em bovinos na região de São João da Boa Vista, Estado de São Paulo

Baseada em estudos anteriores, a Coordenadoria de Defesa Agropecuária da Secretaria da Agricultura e Abastecimento do Estado de São Paulo (CDA) vinha realizando nas regiões administrativas onde é feita a vigilância da raiva em herbívoros o controle de populações de Desmodus rotundus em áreas próximas aos principais rios. A descoberta de abrigos e de animais mordidos pelos morcegos vampiros em outras áreas, além das áreas estabelecidas de risco levaram a questionamentos dos métodos em vigência. Isso estimulou a elaboração de um modelo descritivo para analisar áreas de risco para o ataque espoliativo de morcegos hematófagos em bovinos na região de São João da Boa Vista, estado de São Paulo. Para tanto, foram utilizadas imagens de satélite, parâmetros de estudos anteriores sobre o comportamento dos morcegos vampiros, dados da CDA e da Fundação Instituto Brasileiro de Geografia e Estatística (IBGE). Todas as informações foram agrupadas em um banco de dados e integradas em um Sistema de Informação Geográfica. Contraditoriamente ao que se pensava, observou-se que áreas próximas aos principais rios da região das cidades de Aguaí, Casa Branca, Santa Cruz das Palmeiras e Tambaú não deveriam ser consideradas de risco para o ataque dos morcegos hematófagos em bovinos. Isso sugere que é necessária uma reavaliação dos métodos adotados para o controle das populações da espécie e enfermidade em questão.

Molecular Diversity of Rabies Viruses Associated with Bats in Mexico and Other Countries of the Americas

Bat rabies and its transmission to humans and other species in Mexico were investigated. Eighty-nine samples obtained from rabid livestock, cats, dogs, and humans in Mexico were studied by antigenic typing and partial sequence analysis. Samples were further compared with enzootic rabies associated with different species of bats in the Americas. Patterns of nucleotide variation allowed the definition of at least 20 monophyletic clusters associated with 9 or more different bat species. Several lineages associated with distinctive antigenic patterns were found in rabies viruses related to rabies in vampire bats in Mexico. Vampire bat rabies virus lineages associated with antigenic variant 3 are widely spread from Mexico to South America, suggesting these lineages as the most likely ancestors of vampire bat rabies and the ones that have been moved by vampire bat populations throughout the Americas. Rabies viruses related to Lasiurus cinereus, Histiotus montanus, and some other not yet identified species of the genus Lasiurus were found circulating in Mexico. Long-range dissemination patterns of rabies are not necessarily associated with migratory bat species, as in the case of rabies in Desmodus rotundus and Histiotus montanus. Human rabies was associated with vampire bat transmission in most cases, and in one case, rabies transmission from free-tailed bats was inferred. The occurrence of rabies spillover from bats to domestic animals was also demonstrated. Genetic typing of rabies viruses allowed us to distinguish trends of disease dissemination and to address, in a preliminary fashion, aspects of the complex evolution of rabies viruses in different host-reservoir species.

Geographical Distribution of Vampire Bat-related Cattle Rabies in Brazil

Seventy-seven rabies virus (RV) isolates originating from Brazilian cattle were genetically characterized. Partial nucleoprotein gene sequences of these isolates were phylogenetically and geographically analyzed. Cattle isolates, which clustered with the vampire bat-related RV group, were further subdivided into nine genetic subgroups. These subgroups were distributed widely in lowland regions, with some subgroups separated from each other by mountain ranges. In addition, separation of the groups in mountainous regions was correlated with altitude. These results indicate that cattle rabies is derived from several regionally-defined variants, which suggests that its geographical distribution is related to that of the vampire bat population.

Outbreak of aggressions and transmission of rabies in human beings by vampire bats in northeastern Brazil.

Outbreaks of attacks upon human beings by vampire bats seems to be a common phenomenon in several regions of Latin America, but the occurrence of rabies infection among humans bled by vampires, is relatively low. In the present study, two outbreaks of human rabies transmitted by common vampire bats (Desmodus rotundus) are described from Bahia State, Northeastern Brazil, in 1991 and 1992. The first was recorded in Aporá where 308 people were bled by vampires bats and three of these die from this zoonosis. The 2nd outbreak occurred in Conde where only five people were bled by vampires, and two deaths by rabies were registered. Our data suggest that rabies transmitted by bats basically depends on the presence of virus in the vampire bat population and not on the number of humans bled by them.

Relative population densities and predation of the common vampire bat ( Desmodus rotundus) in natural and cattle-raising areas in north-east Argentina

Studies were carried out to determine the relative population density and predation of the common vampire bat ( Desmodus rotundus) in both natural and cattle-raising ecosystems in north-east Argentina. Relative censuses with nets were used to study the population density, while predation was estimated by direct observation. In the cattle-raising ecosystem, the vampire bat population is almost two times larger than in the natural ecosystem. The vampire preys on cattle, horses, pigs, sheep and poultry in proportion to the availability of these domestic species. The capture in both ecosystems of a larger proportion of males confirms that each sex has different patterns of activity and suggests the existence of division of work.

Vampire bat-transmitted rabies in cattle.

A short history of bovine paralytic rabies in the Americas is given. Based on information from the Animal Health Yearbook--a cooperative publication of the Food and Agriculture Organization (FAO), the World Health Organization (WHO), and the International Office of Epizootics (OIE)--a comparison is made of the epidemiology of the disease in 1968, 1978, and 1985. An important reduction in the number of cases of rabies was observed in some countries (Bolivia, Brazil, Guatemala, Mexico, Nicaragua, and Panama), mainly as a result of the use of effective vaccines that are now available and of the application of new technology to reduce the vampire bat population, the vector of the disease in cattle. The trials performed in Argentina and Mexico in the 1960s and 1970s provide enough evidence that many vaccines will protect cattle against bovine paralytic rabies. Results of these trials are presented.

Biology, ecology, and control of the vampire bat.

The importance of the vampire bat as a vector of rabies and its taxonomy, anatomic characteristics, distribution, feeding habits, behavior, and habitat are described. Also described are studies of methods of reducing vampire bat populations. Anticoagulants such as diphenadione and warfarin were shown to be effective in reducing vampire bat populations. These substances were used in different ways: application of the compound to the skin of captured vampires and then the release of the animals to contaminate the rest of the colony; treatment of vampire niches; topical treatment of vampire bites; and systemic treatment of cattle by administration of the anticoagulant intraruminally or intramuscularly. All these methods were shown to be effective and can be used to reduce vampire populations and to decrease the risk of transmission of rabies in enzootic areas.