Resumen: Leucosis Bovina Enzoótica es la principal virosis que afecta al ganado lechero en Uruguay. La infección subclínica causa disfunciones importantes del sistema inmune impactando directamente en la salud animal. El objetivo de este estudio fue evaluar si la respuesta inmune humoral de vaquillonas holando serológicamente positivas al virus de la leucosis bovina (BLV) es afectada frente a la inmunización a campo con una vacuna clostridial. Se realizó el seguimiento de la respuesta inmune humoral posvacunación durante 12 meses de un grupo de animales serológicamente positivos (n=29) y otro serológicamente negativos a BLV(n=19). Los animales recibieron tres dosis de una vacuna comercial contra Clostridios (días 0, 30, 173) y se extrajeron muestras de sangre los días 0, 30, 60, 90, 180 y 365 luego de la primovacunación. Se cuantificaron anticuerpos totales mediante ensayo inmunoabsorbente ligado a enzimas (ELISAs) contra las toxinas alfa, beta y épsilon del C. perfringens y anticuerpos neutralizantes mediante Seroneutralización (SN) in vitro para la toxina épsilon. Los resultados evidenciaron una baja respuesta de anticuerpos neutralizantes contra la toxina épsilon utilizando la técnica de SN in vitro lo cual no se correlacionó con los resultados obtenidos en el ELISA comercial. La respuesta de anticuerpos totales utilizando ELISA comerciales fue variable según el toxoide evaluado. No se evidenciaron diferencias significativas en la concentración de anticuerpos contra Clostridium perfringens entre animales seropositivos y seronegativos a BLV. La utilidad de los test de ELISA comerciales para analizar la respuesta a la vacunación contra clostridiosis, debe ser discutida y analizada a partir de los resultados encontrados en este ensayo.

Summary: Enzootic bovine leukosis is the main virosis that affects dairy cattle in Uruguay. The subclinical infection causes importants dysfunctions in the immune system impacting directly in the animal health. The aim of this study was to evaluate the immune response of Holstein heifers with positive serology against Leukosis bovine virus (BLV) when they were ordinary immunized against Clostridium perfringens. It was evaluated a seropositive group to BLV animals (n=29) and other seronegative group (n=19) during twelve months. The animals recived three immunizations with a commercial polyvalent vaccine against several Clostridios (days 0, 30, 173). Blood samples were taken in days 0, 30, 60, 90, 180 y 360 post vaccination and then the humoral immune response was analyzed through the use of the ELISA technique to quantify total antibodies against C. perfringens toxins alfa, beta and épsilon. Besides it was in vitro analyzed the amount of neutralizing antibodies against epsilon toxin using the reference technique, seroneutralization. The results demonstrated a low response of neutralizing antibodies to epsilon toxin by SN technique showing no correlation with the results obtained by the commercial ELISA kit. Total antibodies response evaluated using commercial ELISA Kit was variable according to the studied toxoid. No significant differences were found in the immune response against Clostridium perfringens vaccination between BLV seropositive and seronegative animals using the techniques mentioned. The commercial ELISA kit use to analyze the response to vaccination against Clostridiosis, must be discussed and analyzed according to the results of this work.

Clostridium perfringens é um habitante normal da microbiota intestinal de frangos, sendo um agente potencialmente patogênico, causador de enterite necrótica e colangio-hepatite. A concentração inibitória mínima (CIM) de sete drogas utilizadas na terapêutica, como agentes promotores de crescimento ou na prevenção de coccidiose foi determinada pelo método de diluição em ágar para 55 estirpes de C. perfringens isoladas do intestino de frangos de corte. Todas as estirpes revelaram alta sensibilidade à penicilina, avilamicina, narasin e monensina, apenas 7,3% demonstraram CIM intermediário para lincomicina e 89.1% foram consideradas sensíveis. Para tetraciclina e bacitracina, 41,8% e 47.3% das amostras, respectivamente, foram consideradas resistentes.

Clostridium perfringens is a normal inhabitant of the intestinal tract of chickens as well as a potential pathogen that causes necrotic enteritis and colangio hepatitis. The minimum inhibitory concentration (MIC) of seven different compounds used for therapy, growth promotion or prevention of coccidiosis was determined by agar dilution method for 55 C. perfringens strains isolated from the intestines of broiler chickens. All strains showed high susceptibility to penicillin, avilamycin, monensin and narasin. Only 7.3% of the strains showed an intermediated sensitivity to lincomycin, and 49 (89.1%) were considered susceptible. For tetracycline and bacitracin, 41.8% and 47.3% of strains, respectively, were considered resistant.