Current trends in bovine abortion in Argentina / Tendências atuais do aborto bovino na Argentina

Bovine abortion is an important cause of significant economic losses in beef and dairy herds. This syndrome is usually difficult to diagnose. The aim of this study was to characterize bovine abortion causes in Argentina by standard diagnosis procedures (histology, bacterial and viral isolation) and other diagnostic tests like direct fluorescent antibody test (DFAT), fetal serology, immunohistochemistry (IHC), and PCR, showing their specific advantages and limitations. Necropsies were performed in 150 aborted bovine fetuses submitted to the diagnostic laboratories of Instituto Nacional de Tecnología Agropecuaria (INTA) Balcarce, Argentina. Etiological diagnosis was confirmed in 78 fetuses (52% of the cases). Most causes of abortion were of infectious origin, being Neospora caninum (14.67%), Campylobacter fetus sp. (9.33%), Leptospira spp. (7.33%) and Brucella abortus (6.65%) the main microorganisms identified. Bovine viral diarrhea virus (BVDV) and bovine herpes virus (BHV) were diagnosed in 2 (1.33%) and 3 (2%) cases, respectively. This study showed a better characterization of bovine abortion compared with previous researches done on this topic.(AU)

O aborto bovino é uma causa importante de perdas econômicas significativas em rebanhos bovinos e leiteiros. Esta síndrome é geralmente difícil de diagnosticar. O objetivo deste estudo foi caracterizar o aborto bovino na Argentina por procedimentos diagnósticos de rotina (histologia, isolamento viral e bacteriana) e outros testes diagnósticos como ensaio directo de anticorpos fluorescentes (DFAT), sorologia fetal, imuno-histoquica (IHC), e PCR; mostrando suas vantagens e limitações específicas. As necropsias foram realizadas em 150 fetos bovinos abortados submetidos aos laboratórios de diagnóstico do Instituto Nacional de Tecnologia Agropecuária (INTA) de Balcarce, na Argentina. O diagnóstico etiológico foi confirmado em 78 fetos (52% dos casos). A maioria das causas de aborto foram de origem infecciosa, sendo Neospora caninum (14,67%), Campylobacter fetus sp. (9,33%), Leptospira spp. (7,33%) e Brucella abortus (6,65%) os principais microrganismos identificados. O vírus da diarréia viral bovina (BVDV) e o herpesvírus bovino (BHV) foram diagnosticados em 2 (1,33%) e 3 (2%) casos, respectivamente. Este estudo mostrou uma melhor caracterização do aborto bovino em comparação com pesquisas anteriores feita sobre este tema.(AU)

Evaluación y comparación de pruebas serológicas para la detección de la neosporosis bovina en Argentina / Evaluation and comparison of serological methods for the detection of bovine neosporosis in Argentina

Neospora caninum is a protozoan parasite that causes abortion and important economic losses in cattle worldwide. The accurate diagnosis of neosporosis is essential for management and control measures. The aims of this study were: i) to evaluate the performance of an in-house enzyme-linked immunosorbent assay based on the 38 kDa native antigen (p38-ELISA) to diagnose bovine neosporosis in Argentina using a well- characterized local sera panel from experimentally infected and naturally exposed cattle and ii) to compare the diagnostic performance and agreement of three N. caninum serological tests: p38-ELISA, indirect fluorescence antibody test (IFAT) and immunoblotting (IB) using the same sera panel. Serum samples testing either positive or negative by IFAT and IB were considered "Relative Standards of Comparison" (RSC) and used for p38-ELISA evaluation. Receiver operating characteristics analysis revealed that p38-ELISA was highly accurate (area under the curve= 0.982) according to RSC with a cut-off index of 0.0905. Relative sensitivity and specificity of p38-ELISA were 97.8 % and 99.5 %, respectively and agreement between RSC and p38-ELISA was almost perfect (k= 0.97). The evaluation and performance comparison of serological tests were performed according to the definition of gold standard based on the decision of the "majority of tests". All tests displayed high sensitivity and specificity values (greater than 95 %); and excellent agreement. This study describes the accurate performance of p38-ELISA evaluated locally and the highly accurate diagnostic performance of the studied tests for the detection of anti-N. caninum antibodies in cattle from Argentina.

Neospora caninum es un parásito protozoo responsable de abortos y pérdidas económicas en bovinos. La realización de un diagnóstico serológico preciso y con resultados comparables obtenidos por diferentes pruebas contribuye al manejo de este problema y a encarar medidas de control. Los objetivos del presente trabajo fueron los siguientes: 1) evaluar en Argentina una prueba de enzimoinmunoensayo in-house con el antígeno nativo de 38 kDa de N. caninum (ELISA-p38) para el diagnóstico de la neosporosis bovina, utilizando un panel de sueros locales bien caracterizados, procedentes de bovinos infectados de modo experimental o naturalmente expuestos; 2) comparar el desempeño y establecer el nivel de concordancia de tres pruebas serológicas para la detección de N. caninum, ELISA-p38, inmunofluorescencia indirecta (IFI) e inmunoblot (IB), con el mismo panel de sueros. Los sueros que resultaron positivos o negativos a IFI e IB fueron considerados como estándares relativos de comparación (ERC) para evaluar la prueba de ELISA-p38. El análisis de característica operativa del receptor determinó que la prueba de ELISA-p38 fue altamente precisa (área bajo la curva= 0,982) usando el punto de corte 0,0905. La sensibilidad y especificidad relativa del ELISA-p38 fue 97,8 % y 99,5 %, respectivamente, con una concordancia casi perfecta (k= 0,97) respecto del ERC. La comparación del desempeño de las pruebas se realizó usando como gold standard el criterio de la decisión de la "mayoría de las pruebas". Las pruebas exhibieron altos valores de sensibilidad y especificidad (mayores del 95 %) y excelente concordancia. Este trabajo describe un buen desempeño de la prueba de ELISA-p38 evaluada localmente y adecuada performance diagnóstica de las pruebas serológicas analizadas para la detección de anticuerpos anti N. caninum en bovinos de Argentina.

Neosporosis epidémica y endémica: descripción de dos eventos en bovinos para cría / Endemic and epidemic bovine neosporosis: description of two events in beef cattle

El objetivo de este trabajo es describir dos eventos producidos en la provincia de Buenos Aires en los cuales Neospora caninum estuvo asociado a la ocurrencia de abortos en bovinos de cría para carne. En uno de ellos se registraron 11 abortos en 57 vaquillonas durante 45 días, en este evento fue 5 veces más probable que una vaquillona que sufrió un aborto fuera seropositiva a N. caninum que una que no lo sufrió (odds ratio [OR] = 4,9 IC 1,2­19,9) (p<0,05). En el otro evento se registraron 14 abortos en 140 vacas, y no se observó asociación significativa entre los abortos y la seropositividad frente a N. caninum OR = 0,69 (0,06­7,31) (p>0,05). Se analizaron dos fetos de cada evento: estos resultaron negativos a otros patógenos de la reproducción, aunque presentaron anticuerpos específicos y lesiones histopatológicas compatibles con infecciones por N. caninum. Estos resultados sugieren dos posibles modalidades de presentación de abortos en bovinos causados por N. caninum: una epidémica, como la del primer evento aquí referido, y una endémica, como la del segundo

The aim of this study was to describe two events in which Neospora caninum was involved in bovine abortions in beef cattle. In the first event, 11 abortions in 57 heifers were recorded in 45 days. One aborted heifer was 5 times more likely to be seropositive than a non-aborted heifer (OR=4.9; IC 1.2­19.9) (p<0.05). In the second event, no association between serological results and abortions were observed (OR= 0,69; 0,06­7,31) (p>0.05). Neither antibodies nor isolation of other pathogens were achieved in any case. On the contrary, antibodies and pathognomonic histopathological lesions were observed in the four fetuses from both cases. Interestingly, the findings in the first event suggest the epidemic behavior of the disease. In contrast, in the second event it appears that few abortions were due to N. caninum, suggesting the presence of endemic neosporosis

Concomitant infection of Neospora caninum and Bovine Herpesvirus type 5 in spontaneous bovine abortions / Infecção simultânea de Neospora caninum e Herpesvirus bovino tipo 5 em casos espontâneos de aborto bovino

Bovine Herpesvirus type 5 (BoHV-5) has not been conclusively demonstrated to cause bovine abortion. Brain lesions produced by Neospora caninum and Bovine Herpesvirus type 1 (BoHV-1) exhibit common features. Therefore, careful microscopic evaluation and additional diagnostic procedures are required to achieve an accurate final etiological diagnosis. The aim of the present work was to investigate the occurrence of infections due to BoHV-1, BoHV-5 and N. caninum in 68 cases of spontaneous bovine abortions which showed microscopic lesions in the fetal central nervous system. This study allowed the identification of 4 (5.9%) fetuses with dual infection by BoHV-5 and N. caninum and 33 (48.5%) cases in which N. caninum was the sole pathogen identified. All cases were negative to BoHV-1. The results of this study provide evidence that dual infection by BoHV-5 and N. caninum occur during pregnancy in cattle; however, the role of BoHV-5 as a primary cause of bovine abortion needs further research. Molecular diagnosis of BoHV-5 and N. caninum confirmed the importance of applying complementary assays to improve the sensitivity of diagnosing bovine abortion.

Não está demonstrado até ao momento, que o Herpesvírus bovino tipo 5 (BoHV-5) seja um agente causal de aborto bovino. Uma vez que as lesões cerebrais tanto de Neospora caninum como de Herpesvírus bovino tipo 1(BoHV-1) têm características similares, é necessária uma avaliação microscópica cuidadosa, bem como exames laboratoriais adicionais, para obter um diagnóstico final preciso. O objetivo do presente trabalho foi investigar a presença de infeções por BoHV-1, BoHV-5 e N. caninum em 68 casos de aborto espontâneo, nos quais se verificaram lesões microscópicas no sistema nervoso central. Foram encontrados 4 (5,9%) fetos com infeção simultânea de BoHV-5 e N. caninum e 33 (48,5%) casos com infeção exclusiva de N. caninum. Todos os casos foram negativos a BoHV-1. Os resultados deste estudo demonstram que a infeção dual por BoHV-5 y N. caninum está presente durante a gestçao dos bovinos. Apesar disso, o papel de BoHV-5 como agente primário causal de aborto, carece de mais investigaçao. O diagnóstico molecular de BoHV-5 e N. caninum confirmou a importância de se aplicar ensaios complementares para melhorar a sensibilidade do diagnóstico de aborto bovino.

Fate of Neospora-seropositive animals: an opinion

Neospora caninum es un protozoo que causa abortos en los bovinos produciendo importantes pérdidas económicas en todo el mundo. Existe evidencia reciente que demuestra que los bovinos infectados en forma crónica desarrollan mecanismos inmunes de protección contra el aborto causado por N. caninum. Por otro lado, la existencia de otras pérdidas económicas distintas del aborto es aún tema de controversia. Aunque la eliminación de bovinos seropositivos a la enfermedad a sido recomendado como medida de control sanitaria, un rodeo libre de infección no está exento de sufrir una exposición postnatal y "tormentas" de abortos. La utilización de una vacuna inactivada disminuye la tasa de abortos; sin embargo los anticuerpos vacunales no pueden ser diferenciados de aquellos producidos por infecciones naturales. Considerando que los anticuerpos maternos desaparecen a los 6 meses de vida, la serología de terneras de reemplazo antes del servicio y la vacunación podría ser una posible estrategia de control. Este artículo discute las estrategias de control para limitar la difusión de la neosporosis en bovinos y brinda posibles líneas de investigación.

Neospora caninum is an abortive protozoon in cattle, which causes severe economic losses worldwide. Chronically infected cattle however develop immune responses protecting against further Neospora induced abortions. Controversy about losses other than abortion in Neospora-infected cattle still exists. Although, culling of seropositive animals has been recommended as a strategy for reducing economic losses due to N. caninum, there is no guarantee of escaping postnatal infection and abortion storms by having a "Neospora-sterile herd". An inactivated vaccine has been demonstrated to reduce abortion rates. Antibodies generated by natural infection can not presently be differentiated from those induced by vaccination; however, since maternal antibodies disappear by 6 months in calves born to vaccinated heifers, a test-and cull strategy could be performed in replacement heifers before breeding and vaccination. This review article discusses control strategies for Neospora-infection in cattle, and provides suggestions for further research.