A study using an ELISA and a real-time PCR assay based on the detection of the repetitive transposon-like gene of Coxiella burnetii revealed that infection with the bacterium was widespread among Dutch dairy herds, with antibodies detected in bulk tank milk (BTM) from 268 of 341 herds (78.6 per cent) and bacterial DNA detected in 193 of 341 herds (56.6 per cent). The BTM samples were taken in November and December 2007. Serological and molecular studies in young and adult cattle selected from 100 herds showed that antibodies were present in the blood of 470 of 2936 (16.0 per cent) lactating cows but only in 19 of 1831 (1.0 per cent) young animals. Bacterial DNA was detected in the milk of 254 of 2925 (8.7 per cent) lactating cows; bacterial DNA was not detected in any of the faecal samples obtained from youngstock. The blood and milk samples were taken from the cattle in the period January to April 2008.

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We describe the paratuberculosis management practices applied in dairy herds in the Netherlands. The findings from paratuberculosis seronegative and seropositive herds were compared to discover possible risk factors. In total, 370 randomly selected herds with > or =20 dairy cows were surveyed. A questionnaire was used to collect data on current and previous paratuberculosis management practices. All cattle aged > or =3 years were serologically tested for paratuberculosis using an enzyme-linked immunosorbent assay. Herds with >33 tested cattle, of which only one was seropositive, were excluded to reduce the risk of including false-positive herds in the analysis. A comparison of the management data of the seronegative herds (n = 166) and the seropositive herds (n = 143) showed that in both groups important management measures for the prevention of paratuberculosis, such as calving in a cleaned calving area, removing the calf immediately after birth, and feeding paratuberculosis non-suspect roughage to calves, were used only rarely. However, such measures should be regarded as the critical first step to control the disease and/or reduce its prevalence. Using univariable analysis, four factors were statistically different between seronegative and seropositive herds: herd size, cows with clinical signs of paratuberculosis, prompt selling of clinically diseased cattle and feeding milk replacer. Using a multivariable logistic regression model, only herd size was a significantly different factor. These results indicate that most of the paratuberculosis preventive management measures were executed on these Dutch dairy farms only to a limited extent.

Coxiella burnetii infections are mostly subclinical in cattle, but can occasionally be associated with abortion. In the present study, 100 aborted fetuses or stillborn calves that were submitted for postmortem examination between September 2007 and March 2008 were examined for infection with C burnetii. Samples of both pooled fetal tissues and placental cotyledon were tested using a real-time PCR assay. In addition, the sections of placental cotyledon were examined using immunohistochemistry (IHC). The IHC of four placentas was positive. The PCR results of the IHC-positive placentas were high positive (HP); the PCR results of the organs of these four fetuses and calves varied from low positive (LP) to HP. The four IHC-positive fetuses had a gestation length of seven to nine months. All four placentas had histological signs of inflammation, but only one of four placentas had gross pathological signs of inflammation possibly due to a concomitant infection with Bacillus licheniformis. Five other IHC-negative placentas had (high) positive PCR results; the PCR results of the organs of these fetuses were LP or negative. The present study indicates that C burnetii infections are detected in a limited percentage of aborted fetuses and stillborn calves by IHC. To assess the importance of placentas with PCR-positive and IHC-negative test results, more research is needed.