Factors associated with seroprevalence of Neospora caninum in dairy cattle in southeastern Brazil.

Neosporosis is an infectious disease caused by Neospora caninum, an obligate intracellular cyst-forming protozoan considered a major cause of miscarriage in dairy cattle in many parts of the world. This cross-sectional study evaluated the relationship between reproductive abnormalities and seropositivity to N. caninum in 1,204 dairy cows from 40 farms located in the state of Minas Gerais, southeastern Brazil. Producers were interviewed, and blood samples were collected to perform indirect immunofluorescence tests (IFAT 1:200). Association between reproductive abnormalities and seropositivity in cattle was evaluated with generalized estimating equations. The true herd-level seroprevalence of N. caninum was 95 % (83.3-99.1), while the individual-level true seroprevalence was 21.6 % (19.2-24.2). Several reproductive abnormalities were significantly associated with seropositivity to N. caninum: occurrence of repeated estrus (p=0.02; OR=3.84; 95 % CI=1.239-11.893), repeated miscarriages (p=0.001; OR=2.54; 95 % CI=1.423-5.402), and temporary anestrus (p=0.001; OR=3.44; 95 % CI=1.976-5.994). Furthermore, loose dogs (p=0.041; OR=2.20; 95 % CI=1.033-4.672) when fed raw meat (p=0.001; OR=1.91; 95 % CI=1.443-2.519) are risk factors for N. caninum infection. We observed that seropositivity to N. caninum in cattle increases risk of miscarriage by almost twice throughout the reproductive life of cows (p=0.004; OR=1.978; 95 % CI=1.249-3.131). Serologic evidence in this study indicates that N. caninum infection is widely distributed among dairy herds and significantly associated with reproductive disorders, especially miscarriage, repeated estrus, and temporary anestrus.