RESUMO
A study of the epidemiology of bluetongue viruses is in progress with the collaboration of 11 Central American and Caribbean countries. To date, over 200 bluetongue virus isolates have been obtained from cattle and sheep in sentinel groups distributed in the participating countries. Bluetongue serotypes identified include 1, 3, 6, and 12, virus types not previously recorded in the Western Hemisphere. Although the clinical impact of bluetongue virus infections in this hyperendemic environment appears to be minimal, the ubiquity of infection causes restrictions on the export of ruminant livestock and germ plasm. The stability of the Caribbean region ecosystem and the long-range implications of the interface with the northern temperate bluetongue virus ecosystem are reviewed.
Assuntos
Bluetongue/epidemiologia , Doenças dos Bovinos/epidemiologia , Doenças dos Ovinos/epidemiologia , Clima Tropical , Animais , Bovinos , América do Norte/epidemiologia , Ovinos , América do Sul/epidemiologiaRESUMO
There is recent evidence of bluetongue (BT) and epizootic haemorrhagic disease (EHD) virus infection of cattle in the American tropics, including BT group reactive antibody in Colombian cattle. These observations prompted a study to determine serologically the specific BT and EHD virus types present, and time of infection and to collect Culicoides spp. as potential vectors. A prospective study of BT and EHD virus infection was done on two farms in the Colombian department of Antioquia. Sequential sampling of young cattle indicated acquisition of neutralizing antibody to BT virus serotypes 12, 14 and 17, and EHD virus serotypes 1 and 2. Insect captures showed a high association of Culicoides insignis with infected cattle.
Assuntos
Vírus Bluetongue/classificação , Bluetongue/microbiologia , Doenças dos Bovinos/microbiologia , Infecções por Reoviridae/veterinária , Reoviridae/classificação , Animais , Anticorpos Antivirais/análise , Bluetongue/epidemiologia , Vírus Bluetongue/imunologia , Bovinos , Doenças dos Bovinos/epidemiologia , Ceratopogonidae , Colômbia , Cervos , Feminino , Insetos Vetores , Testes de Neutralização , Testes de Precipitina , Reoviridae/imunologia , Infecções por Reoviridae/epidemiologia , Infecções por Reoviridae/microbiologia , Sorotipagem , OvinosRESUMO
The ability of Simulium mexicanum and Simulium metallicum to serve as biological or mechanical vectors of an enzootic and an epizootic strain of Venezuelan equine encephalitis (VEE) virus was examined. Guinea pigs were inoculated with the epizootic Cordoba strain or the enzootic RPVP407 strain of VEE virus. Wild-caught adult Simuliidae were fed on the viremic guinea pigs and the virus content of groups of flies was determined at daily intervals post-engorgement to test for viral replication. Flies were refed on suckling mice at greater than or equal to 8 days post-engorgement to test for biological transmission. Other flies were interrupted while feeding on viremic guinea pigs and refed on suckling mice to test for mechanical transmission. Neither S. mexicanum nor S. metallicum appear to be efficient vectors of either strain of VEE virus, although occasional mechanical transmission was obtained. Titers of virus in flies decreased rapidly after engorgement and from 3-12 days post-engorgement virus was detected only in 5%-25% of both species of flies. Although earlier field evidence implicated both S. mexicanum and S. metallicum as vectors of epizootic VEE, we conclude that it is highly unlikely that they play an important role as vectors of the virus in nature.
Assuntos
Encefalomielite Equina/transmissão , Encefalomielite Equina Venezuelana/transmissão , Simuliidae/microbiologia , Animais , Colômbia , Vírus da Encefalite Equina Venezuelana/fisiologia , Encefalomielite Equina Venezuelana/microbiologia , Comportamento Alimentar , Cobaias , Masculino , Camundongos , Simuliidae/fisiologiaRESUMO
Recent evidence of bluetongue (BT) virus infection of livestock in scattered localities in the neotropics prompted a serologic survey of cattle in Colombia and Costa Rica. In Costa Rica 48.1% of 1435 bovine animals had BT virus antibody in the agar gel precipitation test (AGPT). In Colombia 51.8% of 635 cattle were AGPT-positive for BT virus. Antibody prevalence ranged from over 50% in the lowlands to 0% in Costa Rica and 19% in Colombian cattle above 2000 m altitude. Neutralization tests indicated that Costa Rican cattle had been exposed to BT virus types 6, 12, 14 and 17.
Assuntos
Anticorpos Antivirais/análise , Vírus Bluetongue/imunologia , Bluetongue/epidemiologia , Doenças dos Bovinos/epidemiologia , Reoviridae/imunologia , Altitude , Animais , Bovinos , Colômbia , Costa Rica , Imunodifusão , Testes de Neutralização , OvinosRESUMO
Bluetongue virus (BTV) group antibodies are widely distributed in Costa Rica and Northern Colombia; prevalence is highest at lowest altitudes. Clinical evidence of bluetongue (BT) infection in cattle is not seen. Evidence exists of the circulation of BTV serotypes 6 and 14 in Costa Rica and BTV serotype 12, 14 and 17 in Northern Colombia in the period 1981-1983. Culicoides insignis is implicated as a probable vector in Colombia.
Assuntos
Bluetongue/epidemiologia , Doenças dos Bovinos/epidemiologia , Animais , Anticorpos Antivirais/análise , Bluetongue/microbiologia , Vírus Bluetongue/imunologia , Bovinos , Doenças dos Bovinos/microbiologia , Ceratopogonidae/microbiologia , Colômbia , Costa Rica , Insetos Vetores/microbiologia , OvinosRESUMO
We investigated the effects of chlorocholine chloride (CCC), a plant growth regulator, and cyclophosphamide (CP), a known immunosuppressant, on the ability of deer mice (Peromyscus maniculatus) to resist challenge with a sublethal dose of Venezuelan equine encephalitis virus ( VEEV ). The toxicants were continuously delivered in low doses in the feed; CP at 20 mg/kg body wt/day and CCC at 1, 10, 20 or 40 mg/kg body wt/day. Mice were inoculated with 3 X 10(4) plaque forming units (pfu) of VEEV after eating experimental feed for 23 days. Mice were bled daily for 7 days and at selected intervals from 8 to 63 days post inoculation (PI) for viremia and antibody titer determinations. CP treatment increased the duration of viremia and significantly (P less than or equal to 0.05) decreased mean viremia titers. Antibody titers were significantly (P less than or equal to 0.05) depressed in CP-treated mice compared to controls. CP treatment increased mortality. CCC had no effect on viremia duration or titer except when given in doses of 1 mg/kg body wt/day when it significantly (P less than or equal to 0.05) decreased mean viremia titers compared to controls. Early antibody responses were increased by CCC treatment except in the 10 mg/kg body wt/day treatment group in which titers were decreased. By 30 days PI antibody titers of CCC-treated mice were no different from controls.