Retrospective study of bovine neonatal mortality: cases reported from INTA Balcarce, Argentina / Estudio retrospectivo de mortalidad neonatal bovina: Casos hallados en INTA-Balcarce, Argentina

A retrospective study was performed on 169 beef and dairy calves aged from 1 to 7 days old submitted to the Diagnostic Laboratories at INTA Balcarce, Argentina. Bacterial culture was performed for aerobic and microaerophilic organisms. Samples from spleen and lymph nodes, and peripheral blood mononuclear cells were also cultured for viral isolation on cell culture. Bovine rotavirus was detected by direct-ELISA. Multiple tissue samples were fixed in 10% formalin, routinely processed and stained with hematoxylin and eosin for microscopic examination. Etiological diagnosis was made in 70 of the 169 calves. Infectious agents were identified in 49 cases, the most common being Escherichia coli. When the histopathological examination was performed in cases with undetermined diagnosis, it was noted that 44 specimens had histological lesions, which suggested the presence of an infectious agent. In order to characterize the causes of bovine neonatal mortality, the protocols and methodology should be improved in further works.

Se realizó un estudio restrospectivo en 169 terneros muertos 1 a 7 días después del nacimiento pertenecientes a rodeos para carne y leche, remitidos a los Laboratorios de Diagnóstico del INTA Balcarce, Argentina. Para detectar organismos aeróbicos y microaerófilos se realizó el cultivo bacteriano. Para el aislamiento viral sobre cultivo celular, se recolectaron muestras de bazo, ganglios linfáticos y sangre periférica. El rotavirus bovino fue identificado por ELISA directo. Se efectuó el examen microscópico de diferentes tejidos, los cuales fueron fijados en formol al 10%, procesados y teñidos con hematoxilina y eosina. Se obtuvo un diagnóstico etiológico en 70 de los 169 terneros. Se identificaron agentes infecciosos en 49 casos, siendo el más común Escherichia coli. En los casos con diagnóstico indeterminado, el examen histopatológico realizado determinó que 44 especímenes poseían lesiones compatibles con la presencia de agentes infecciosos. Es necesario mejorar los protocolos y las metodologías de trabajo a los fines de caracterizar las causas de mortalidad neonatal en bovinos.

Neosporosis bovina: conceptos generales, inmunidad y perspectivas para la vacunación / Bovine neosporosis: general concepts, immunity and perspectives for vaccination

Neospora caninum es agente causal de aborto en bovinos de regiones ganaderas de todo el mundo. Su ciclo de vida es heteroxeno siendo el perro (Canis familiaris) y el coyote (Canis latrans) los hospedadores definitivos reconocidos hasta el presente. La infección transplacentaria es un eficiente mecanismo de transmisión de la enfermedad pero existe evidencia que demuestra la transmisión postnatal en los bovinos. Debido a las pérdidas económicas que causa la neosporosis, diversas técnicas diagnósticas han sido desarrolladas. La fisiopatología del aborto causado por N. caninum no ha sido completamente esclarecida. La modulación del sistema inmune por efecto de la preñez ocasiona un período de susceptibilidad al aborto por N. caninum. Aunque la resistencia al parásito ha sido asociada con una respuesta de linfocitos T tipo 1, dicha respuesta inmune es incompatible con una preñez exitosa. Sin embargo, los mecanismos inmunes presentes en animales crónicamente infectados protegen del aborto ante una segunda exposición al protozoo. La comprensión de esa respuesta inmune adquirida constituye un desafío para el desarrollo de inmunógenos. Este trabajo menciona conceptos generales de la neosporosis bovina haciendo énfasis en los mecanismos inmunes y las perspectivas para la vacunación.

Neospora caninum causes abortions in cattle worldwide. The Neospora-cycle of life is heteroxenous. Dogs (Canis familiaris) and coyotes (Canis latrans) are the definitive hosts known at present. Although, transplacental infection is an efficiently mode of transmission in cattle; there are also experimental and field data that prove horizontal transmission. Several techniques are available for diagnosis since neosporosis is recognized as a disease that causes economic losses in cattle. The mechanisms that produce the abortion are not completely understood. The immunomodulation observed during the pregnancy, is associated with a susceptible period where Neospora-abortion can occur. Resistance to the parasite is dependent on T helper cell 1 cytokine responses. This has important repercussions for pregnant female bovine because strong T helper cell 1 cytokine responses are incompatible with successful pregnancy. However, it was demonstrated that chronically infected cows develop immune mechanisms against the abortion caused by a second Neospora-exposure. The comprehension of those mechanisms is needed for the formulation of Neospora-vaccines that prevent bovine neosporosis. General concepts about neosporosis with emphasis in the immune response and perspectives for vaccination are mentioned in the present review.

Humoral immune response to infectious agents in aborted bovine fetuses in Argentina

The purpose of this study was to characterize the exposure of bovine aborted fetuses from beef and dairy herds of the humid pampas of Argentina to different infectious agents by the evaluation of fetal fluid antibodies. Presence of fetal antibodies to bovine viral diarrhea virus genotype 1 (BVDV-1), bovine herpes virus type 1 (BHV-1), Leptospira interrogans, Brucella abortus, and Neospora caninum was determined. Of the 95 fetuses processed, 66 came from 49 beef herds and 29 from 12 dairy herds. The average gestational age of the aborted fetuses was 7.1 months. Antibodies to the mentioned agents were detected in 65 of the 95 fetal fluids (68.4

). In addition, antibodies to more than one infectious agent were detected in 32 fetuses (33.7

), suggesting fetal exposure to multiple antigens during gestation. There were antibodies to BVDV-1, BHV-1, N. caninum and Leptospira interrogans in 43 (45.2

) and 5 (5.2

) specimens, respectively. Antibodies to B. abortus were not detected in any of the fetal fluids. The results of this study provide information on the determination of antibodies in fluids from bovine aborted fetuses exposed to different infectious agents in the region.