Bovine viral diarrhoea virus (BVDV) infection of cattle causes a diverse range of clinical outcomes from being asymptomatic, or a transient mild disease, to producing severe cases of acute disease leading to death. Four groups of calves were challenged with a type 1 BVDV strain, originating from a severe outbreak of BVDV in England, to study the effect of viral dose and immunosuppression on the viral replication and transmission of BVDV. Three groups received increasing amounts of virus: Group A received 102.55TCID50/ml, group B 105.25TCID50/ml and group C 106.7TCID 50/ml. A fourth group (D) was inoculated with a medium dose (105.25TCID50/ml) and concomitantly treated with dexamethasone (DMS) to assess the effects of chemically induced immunosuppression. Naïve calves were added as sentinel animals to assess virus transmission. The outcome of infection was dose dependent with animals given a higher dose developing severe disease and more pronounced viral replication. Despite virus being shed by the low-dose infection group, BVD was not transmitted to sentinel calves. Administration of dexamethasone (DMS) resulted in more severe clinical signs, prolonged viraemia and virus shedding. Using PCR techniques, viral RNA was detected in blood, several weeks after the limit of infectious virus recovery. Finally, a recently developed strand-specific RT-PCR detected negative strand viral RNA, indicative of actively replicating virus, in blood samples from convalescent animals, as late as 85 days post inoculation. This detection of long term replicating virus may indicate the way in which the virus persists and/or is reintroduced within herds.
Neosporosis caused by Neospora caninum, paratuberculosis (or Johne's disease) caused by Mycobacterium avium subspecies paratuberculosis (MAp), and Q fever caused by Coxiella burnetii are three infectious cattle diseases that have significant health and economic impacts (Woldehiwet 2004, Haddad and others 2005, McKenna and others 2006). Whereas Neospora and Q fever in cattle are mostly associated with reproductive disorders, such as abortion (Woldehiwet 2004, Dubey and others 2007), MAp causes chronic enteritis and progressive weight loss (Tiwari and others 2006). Q fever, moreover, is a zoonotic disease. For MAp, a possible relationship has been suggested with Crohn's disease in humans, although this remains controversial (over and others 2011). in Belgium, a cross-sectional serological survey of cattle, the winter screening, is carried out during the housing period in winter every year. This winter screening provides an ideal opportunity for the simultaneous monitoring and surveillance of several infectious diseases in the Belgian cattle population. As no recent seroprevalence data were available for N caninum, MAp or Q fever at the regional or national level in Belgium, it was decided to test for those diseases during the winter screening conducted between November 2009 and February 2010. For this survey, a total of 1100 cattle herds were selected for sampling by simple random sampling using the
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.