<i>Neospora caninum</i> and <i>Toxoplasma gondii</i> infections and their relationship with reproductive losses in farmed red deer (<i>Cervus elaphus</i>)

Abstract

The aims of the present study were to determine the <i>Neospora caninum</i> and <i>Toxoplasma gondii</i> seropositivity rates in farmed red deer hinds from Argentina and their relationship with reproductive losses. Over a 2-year period, 449 hinds from 4 commercial farms were serologically tested at late gestation for <i>N. caninum</i> and <i>T. gondii</i> by IFAT. During the first year, a sequential serological analysis was carried out at 3 different time points to analyze antibody dynamics from mating until the end of the gestation period. Fetal and postnatal mortality rates were estimated by 3 successive ultrasound scannings (us) annually and a breeding control carried out after the calving period. Ultrasound fetal measurements were used to estimate conception date and gestational age of abortions. The seropositivity rate for <i>N. caninum</i> was 25.5% (37/145) for the yearlings and 34.2% (104/304) for the adults, while for <i>T. gondii</i> was 64.3% (93/145) and 78.3% (238/304), respectively. Abortions detected at us1 and us2 were 13/21 (61.9%) with a range of gestational age of 30-87 days, while abortions detected at us3 were 8/21 (38.1%) with a range of gestational age of 49-209 days. The fetal mortality rate was 4% and 5.8%, while the postnatal mortality rate was 18.8% and 4.1% of 101 yearlings and 294 adult pregnant hinds, respectively. Most seropositive hinds to both protozoans showed a stable antibody titer pattern from mating to the end of gestation, and a lower proportion developed an increase in titers suggesting infection recrudescence. Seroconversion during the gestational period was demonstrated in 6 and 50 hinds for <i>N. caninum</i> and <i>T. gondii</i>, respectively. Hinds with fetal mortality were more likely to be seropositive to <i>N. caninum</i> (OR = 3.1) or have <i>N. caninum</i> titers ≥400 (OR = 27.4) than hinds that weaned a fawn. No statistical associations were detected for <i>T. gondii</i> seropositivity and reproductive losses. The pregnancy rate was not affected by <i>N. caninum</i> or <i>T. gondii</i> infection, while the serological evidence of <i>N. caninum</i> causing postnatal mortality was marginal. Based on serological evidence, <i>N. caninum</i> would be a potential abortigenic agent in red deer hinds.