RESUMEN
Anaplasma marginale (A. marginale) is an obligate intracellular bacterium that infects bovine erythrocytes causing extravascular hemolysis and anemia. In the present work, we combine SYTO16 labeling of parasitized cells with the statistical power of flow cytometry to study the evolution of erythrocyte infection during bovine anaplasmosis.
Asunto(s)
Anaplasma marginale , Anaplasmosis/diagnóstico , Anaplasmosis/microbiología , Enfermedades de los Bovinos/diagnóstico , Eritrocitos/microbiología , Citometría de Flujo , Anaplasmosis/sangre , Anemia/sangre , Anemia/etiología , Animales , Bovinos , Enfermedades de los Bovinos/sangre , Enfermedades de los Bovinos/microbiología , Índices de Eritrocitos , Citometría de Flujo/métodos , Masculino , Reproducibilidad de los ResultadosRESUMEN
An indirect enzyme-linked immunosorbent assay (ELISA) for Brucella abortus antibodies detection in bovine milk and serum samples was validated. The assay use B. abortus smooth lipopolysaccharide as antigen, immobilized on a polystyrene matrix; milk diluted 1:2 or serum diluted 1:50, in a buffer containing divalent cation chelating agents EDTA and EGTA (ethyleneglycol-bis-aminoether-N,N,N',N'-tetraacetic acid) to reduce non-specific reactions; and a mouse monoclonal antibody specific for an epitope of bovine IgG1, conjugated with horseradish peroxidase. A total of 2646 sera and 2119 milk samples from cows older than 24 months were obtained from 12 brucellosis-free herds for at least the previous 5 years. Milk samples were obtained in parallel with serum samples. The remaining 527 serum samples were from dry cows. All cattle were vaccinated with B. abortus strain 19 between 3-10 months of age. Five hundred and fifty-two milk samples and 562 serum samples were obtained from 6 infected herds with abortions where B. abortus was isolated at least once no more than 6 months before sampling. The complement-fixation test (CFT) on serum samples was considered the gold standard. Serum samples were also tested with the official screening test: the buffered plate antigen (BPA) test. The cut-off point was determined using receiver-operating characteristic (ROC) analysis. For milk samples, it was fixed at 36 percent positivity (PP) giving a sensitivity of 99.6% with a 95% confidence interval (CI) of 98.6-99.9%. The specificity was 99.1% (CI 98.9-99.4%). For serum samples, the cut-off was fixed at 53 PP giving a sensitivity of 99.6% (CI 98.6-99.9%) and a specificity 98.6% (CI 98-99%). The BPA test showed a relative sensitivity of 99.6% (CI 98.6-99.9%) and a relative specificity of 98.6% (CI 98.1-99%). Our results indicate that the indirect ELISA is a highly sensitive and specific test and can be adapted to process a large number of samples.
Asunto(s)
Brucella abortus/aislamiento & purificación , Brucelosis Bovina/diagnóstico , Industria Lechera , Ensayo de Inmunoadsorción Enzimática/veterinaria , Leche/química , Animales , Argentina , Bovinos , Pruebas de Fijación del Complemento/veterinaria , Interpretación Estadística de Datos , Ensayo de Inmunoadsorción Enzimática/métodos , Femenino , Inmunoglobulina G/análisis , Inmunoglobulina G/sangre , Pruebas Serológicas/métodosRESUMEN
The prevalence of Babesia bovis antibodies was estimated by using an ELISA (98% sensitivity and 95% specificity). Sera were obtained from 165 calves (mean age and standard deviation: 9.7 +/- 2.7 months) from an area in Argentina known to be unfavourable for the development of the vector tick, Boophilus microplus. The area comprised about 300,000 ha used for cattle breeding. The cattle population of 55,000 included 12,000 cattle under 1 year of age. Cattle were maintained mainly on natural grasses in communal lands. The true prevalence of antibodies to Babesia bovis was 12.2% with a confidence interval of 7.6% to 18.2%, and an inoculation rate (h; daily probability of infection) of 0.0004. This confidence interval has its lower boundary in the area of endemic stability due to low h of Babesia bovis by the vector tick and the upper limit in the area of endemic instability. This type of analysis could help to decide the implementation of preventive measures (e.g. vaccination) rationally, even in remote areas (such as the one of the present study) with an extensive cattle industry.
Asunto(s)
Anticuerpos Antiprotozoarios/sangre , Babesia bovis/inmunología , Babesiosis/epidemiología , Babesiosis/prevención & control , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/prevención & control , Animales , Anticuerpos Antiprotozoarios/inmunología , Argentina/epidemiología , Cruzamiento , Bovinos , Estudios Transversales , Brotes de Enfermedades/veterinaria , Vectores de Enfermedades , Prevalencia , Enfermedades por Picaduras de Garrapatas/epidemiología , Enfermedades por Picaduras de Garrapatas/inmunología , Enfermedades por Picaduras de Garrapatas/veterinariaRESUMEN
A live, frozen experimental vaccine containing Babesia bovis and Babesia bigemina multiplied in vitro was stored in liquid nitrogen after simultaneous cryopreservation using glycerol as cryoprotectant. The viability of the vaccine was tested by inoculating (subcutaneously) three groups of seven steers each, 2, 12 and 24 h after thawing at 40 degrees C and dilution to obtain a dose of 2 x 10(7) of each organism. All vaccinated cattle developed detectable parasitaemia in thin and/or thick blood smears. No statistically significant differences in the prepatent period were detected amongst the cattle groups (analysis of variance). This prepatent period was 12.3 days for B. bovis and 8.4 days for B. bigemina. Vaccinal organisms derived from in vitro culture systems may replace antigens obtained from in vivo culture to produce vaccine against cattle babesiosis.
Asunto(s)
Babesia bovis/inmunología , Babesia/inmunología , Babesiosis/inmunología , Enfermedades de los Bovinos , Criopreservación , Vacunas Antiprotozoos , Animales , Babesiosis/prevención & control , Bovinos , Crioprotectores , Glicerol , MasculinoRESUMEN
Nine splenectomised calves were infested with dissimilar numbers of adult Boophilus microplus ticks 72 h after collection as engorged nymphs from three non splenectomised calves with different levels of Anaplasma marginale rickettsaemia. Successful transmission of A. marginale appeared to be more dependent on the level of rickettsaemia of the donor calves than on the number of ticks attaching to the splenectomised calves, since infection was transmitted only when the rickettsaemia was 0.3% or greater. Field transmission would thus depend on the rate of tick migration amongst susceptible hosts and the rickettsaemia level of cattle on which the ticks fed previously.
Asunto(s)
Anaplasma/aislamiento & purificación , Anaplasmosis/transmisión , Vectores Arácnidos/microbiología , Bacteriemia/transmisión , Enfermedades de los Bovinos/transmisión , Infestaciones por Garrapatas/veterinaria , Garrapatas/microbiología , Animales , Bovinos , Enfermedades de los Bovinos/parasitología , Femenino , Masculino , Ninfa/microbiología , Esplenectomía/veterinaria , Infestaciones por Garrapatas/parasitologíaRESUMEN
Three trials were performed to test the infectivity of a vaccinal and a pathogenic strain of Babesia bovis for the tick Boophilus microplus. The progeny of engorged female ticks fed on calves inoculated with the pathogenic strain were able to transmit the infection to splenectomised calves (measured by the presence of the parasite in their blood and seroconversion), whereas the progeny of engorged females fed on calves inoculated with the vaccinal strain did not transmit the organisms. These results appear to show that this strain of Babesia bovis would not be transmitted by ticks under natural conditions. This is a considerable advantage since the organisms used in the vaccine would not be able to establish foci in the field although they would be able to confer a long-lasting immunity.
Asunto(s)
Vectores Arácnidos/parasitología , Babesia bovis/patogenicidad , Vacunas Antiprotozoos , Garrapatas/parasitología , Animales , Babesia bovis/inmunología , Babesiosis/prevención & control , Babesiosis/transmisión , Bovinos , Enfermedades de los Bovinos/prevención & control , Enfermedades de los Bovinos/transmisión , Femenino , Masculino , Pase Seriado , Vacunación/veterinariaRESUMEN
Attenuated Babesia bigemina were multiplied in vivo and in vitro to vaccinate two groups (Groups 2 and 3) of Holstein Friesian heifers. Another group (Group 1) of heifers was vaccinated twice with purified soluble antigens obtained from the supernatant of in vitro culture combined with saponin. All these heifers plus controls (Group 4) were inoculated with heterologous pathogenic B. bigemina 5 months later. Heifers vaccinated with live organisms (Group 2 and 3) were able to stand the challenge without specific treatment whereas the opposite occurred in heifers vaccinated with soluble antigens (Group 1) and controls (Group 4). Antibody titres were higher in heifers inoculated with soluble antigens than in heifers inoculated with live B. bigemina multiplied in vivo, indicating that antibody titres may not be a proper indicator of protection. In vitro culture of this protozoan is probably a better source of live antigens for vaccine production than in vivo culture. These kind of immunogens can fill the gap until improved vaccines are available.