Seropositivity rates as predictors of Neospora caninum congenital transmission in cattle

MIQUEO, E.; CRUZ, M.S.; MOORE, D.P.; CAMPERO, L.M.

La Plata

Congreso; XXXIV Reunión Anual de la Sociedad Argentina de Protozoología (SAP).; 2023

SAP

This study aimed to determine how the level of antibodies to N. caninum in dairy cows correlated with the occurrence of congenital transmission measured by ELISA. The study involved 59 cow/calf pairs from a dairy herd (n= 400) from Mar y Sierras Basin, Argentina. Serum samples from cows were obtained 9 days prepartum, along with samples from their calves at birth (pre-colostrum), 7, 14, and 63 days post-birth. A commercial ELISA kit was used for N. caninum antibodies detection (Neospora Civtest, HIPRA) and values were computed as relative index percent (RIPC). Seropositive cows (n= 17/59) exhibited a higher abortion likelihood. The vertical transmission rate was 88.2% (15/17). Two N. caninum seropositive cows gave birth to seronegative calves which maintained their serostatus throughout the study. Interestingly, among seropositive cows, there was a distinctive difference in RIPC values, where higher values were associated with successful vertical transmission (69.8 vs. 7.8; p= 0.01). In addition, calves congenitally infected also had higher RIPC values compared to calves that seroconverted postnatally (32 vs 17.4; p= 0.02). Of the 44 seronegative calves at birth, 37 sustained negative serostatus throughout the study. However, seven seronegative calves seroconverted in one of the subsequent sampled intervals to then drop to undetectable levels in ulterior sampling (r= -0.61; p= 0.003). Colostrum samples from their mothers were negative by ELISA, which leads to the suspicion that these calves might have been fed from a colostrum bank positive to N. caninum. This work demonstrates a substantial transplacental transmission associated with higher RICP in seropositive cows, and limited N. caninum exposure during the artificial rearing. Results shed light on two factors: higher antibody concentration (here expressed as RIPC) correlated with congenital transmission in both mothers and calves and the absence of horizontal transmission during the dairy calf rearing stage.