Risk factors related to Toxoplasma gondii seroprevalence in indoor-housed Dutch dairy goats

•Binary mixture analysis is useful for analyzing serological data.•The multispecies T. gondii ELISA shows good discriminatory power with goat sera.•T. gondii infection is present in indoor housed Dutch dairy goats.•The number of cats at the farm is strongly associated with farm prevalence.

Toxoplasma gondii can cause disease in goats, but also has impact on human health through food-borne transmission. Our aims were to determine the seroprevalence of T. gondii infection in indoor-housed Dutch dairy goats and to identify the risk factors related to T. gondii seroprevalence. Fifty-two out of ninety approached farmers with indoor-kept goats (58%) participated by answering a standardized questionnaire and contributing 32 goat blood samples each. Serum samples were tested for T. gondii SAG1 antibodies by ELISA and results showed that the frequency distribution of the log10-transformed OD-values fitted well with a binary mixture of a shifted gamma and a shifted reflected gamma distribution. The overall animal seroprevalence was 13.3% (95% CI: 11.7-14.9%), and at least one seropositive animal was found on 61.5% (95% CI: 48.3-74.7%) of the farms. To evaluate potential risk factors on herd level, three modeling strategies (Poisson, negative binomial and zero-inflated) were compared. The negative binomial model fitted the data best with the number of cats (1-4 cats: IR: 2.6, 95% CI: 1.1-6.5; > = 5 cats: IR: 14.2, 95% CI: 3.9-51.1) and mean animal age (IR: 1.5, 95% CI: 1.1-2.1) related to herd positivity. In conclusion, the ELISA test was 100% sensitive and specific based on binary mixture analysis. T. gondii infection is prevalent in indoor housed Dutch dairy goats but at a lower overall animal level seroprevalence than outdoor farmed goats in other European countries, and cat exposure is an important risk factor.