Use of competition ELISA for monitoring of West Nile virus infections in horses in Germany.

West Nile virus (WNV) is a mosquito-borne viral pathogen of global importance and is considered to be the most widespread flavivirus in the World. Horses, as dead-end hosts, can be infected by bridge mosquito vectors and undergo either subclinical infections or develop severe neurological diseases. The aim of this study was to detect WNV specific antibodies in horses in Germany as an indicator for an endemic circulation of WNV. Sera from more than 5,000 horses (primarily fallen stock animals) were collected in eight different federal states of Germany from 2010 to 2012. Sera were screened by a competitive ELISA and positive reactions were verified by an indirect IgM ELISA and/or by virus neutralization tests (VNT) for WNV and Tick-borne encephalitis virus (TBEV) in order to exclude cross-reacting antibody reactions. In essence WNV specific antibodies could not be detected in any of the horse sera. Not surprisingly, a small number of sera contained antibodies against TBEV. It is noteworthy that equine sera were often collected from horse carcasses and therefore were of poor quality. Nonetheless, these sera were still suitable for WNV ELISA testing, i.e., they did not produce a high background reaction which is a frequently observed phenomenon. According to these data there is no evidence for indigenous WNV infections in horses in Germany at present.

Improving the sensitivity of the IBR-gE ELISA for testing IBR marker vaccinated cows from bulk milk.

The low sensitivity of the IBR-gE ELISA compared to other diagnostic ELISA tests for IBR is a major disadvantage of IBR control programmes based on IBR marker vaccination. Therefore the IBR-gE ELISA is not generally recommended for testing pooled or bulk milk samples.The aim of this study was to determine the performance of a commercially available kit for concentrating and purifying antibodies in milk in order to improve the sensitivity of detecting IBR-gE antibody positive cows from pooled and bulk milk samples. A single IBR-gE positive cow is likely to remain undetected in a pool of 49 negative milk samples without concentration. By contrast, the bulk milk concentration procedure improved sensitivity from 5.4% to 75.7% in a positive herd. Milk samples with a high or moderate positive signal are more likely to be detected after pool milk concentration compared to weak positive samples. Whereas a follow up study involving a monthly testing of bulk milk samples from three marker vaccinated IBR-gE negative herds over a period of seven months yielded negative results each month, bulk milk from a herd containing <5% IBR-gE positive cows always detected positive after concentration. Although the milk concentration procedure had no impact on specificity, it significantly enhanced the sensitivity of the detection of IBR-gE positive milk in pooled and bulk milk samples. After further evaluation this procedure could allow a cost efficient and reliable method of monitoring IBR marker-vaccinated herds for IBR-gE antibodies.

Prevalence of Coxiella burnetii in clinically healthy German sheep flocks.

BACKGROUND: Current epidemiological data on the situation of Coxiella (C.) burnetii infections in sheep are missing, making risk assessment and the implementation of counteractive measures difficult. Using the German state of Thuringia as a model example, the estimated sero-, and antigen prevalence of C. burnetii (10% and 25%, respectively) was assessed at flock level in 39/252 randomly selected clinically healthy sheep flocks with more than 100 ewes and unknown abortion rate. RESULTS: The CHECKIT™ Q-fever Test Kit identified 11 (28%) antibody positive herds, whereas real-time PCR revealed the presence of C. burnetii DNA in 2 (5%) of the flocks. Multiple-locus variable number of tandem repeats analysis of 9 isolates obtained from one flock revealed identical profiles. All isolates contained the plasmid QpH1. CONCLUSIONS: The results demonstrate that C. burnetii is present in clinically inconspicuous sheep flocks and sporadic flare-ups do occur as the notifications to the German animal disease reporting system show. Although C. burnetii infections are not a primary veterinary concern due to the lack of significant clinical impact on animal health (with the exception of goats), the eminent zoonotic risk for humans should not be underestimated. Therefore, strategies combining the interests of public and veterinary public health should include monitoring of flocks, the identification and culling of shedders as well as the administration of protective vaccines.