Demography of Q fever seroprevalence in sheep and goats in The Netherlands in 2008

At the end of 2007, the first year of what later turned out to be one of the largest Q fever outbreaks in the world with ultimately almost 3500 human patients notified in three years time, dairy goats were suspected to be the possible cause. However, current information on the Q fever prevalence in small ruminants in The Netherlands was lacking. A serological survey, using an indirect ELISA, was carried out in 15,186 sheep and goats in The Netherlands in 2008. In total, 2.4% (95% CI: 2.2-2.7) of the sheep and 7.8% (95% CI: 6.9-8.8) of the goats was seropositive for antibodies against Coxiella burnetii. In 14.5% (95% CI: 12.5-16.5) of the sheep flocks and 17.9% (95% CI: 14.2-21.5) of the goat herds at least one seropositive animal was found. In sheep flocks with at least one seropositive sheep, the within herd seroprevalence was 14.8% (95% CI: 12.6-17.0). In goat herds with at least one seropositive goat, the within herd seroprevalence was 29.0% (95% CI: 24.6-33.3). The seropositive sheep were equally distributed across the country. The seroprevalence in goats in the south-eastern part of The Netherlands, the area where most of the human Q fever cases were notified, was significantly higher than the seroprevalence in goats in the rest of The Netherlands. Dairy sheep and dairy goats had a significantly higher chance of being seropositive than non-dairy sheep and goats. During pregnancy and in the periparturient period, small ruminants tested significantly more often seropositive than in the early- or non-pregnant period. The seroprevalence as well as the true prevalence among small ruminants in The Netherlands were lower than prevalences reported elsewhere. The seroprevalence among sheep was also lower than reported in an earlier Dutch study in 1987. The Q fever seroprevalence was highest in pregnant and periparturient dairy goats in the south-eastern part of The Netherlands, which coincides with the region with the highest human incidence of Q fever.