The Regional Veterinary Laboratories (RVLs) have detected Schmallenberg virus (SBV) in reports of milk drop syndrome in dairy herds this summer.
According to an RVL report published yesterday (Wednesday, September 25), a “high rate” of seropositivity to SBV has been found in samples submitted from some of these herds to the laboratories.
In the SBV-seropositive cows, clinical signs have included milk drop, diarrhoea, pyrexia (raised body temperature) and apparent pregnancy loss, although not all clinical signs were present in all affected animals.
The RVLs stated that there has been a “more recent re-emergence of the virus” but it added that “care must be taken in interpreting single serology results as alone they are not diagnostic for SBV”.
However, in some of these herds the virus itself has been detected or very recent infection has been diagnosed using paired serology tests around the same time the clinical signs occurred, suggesting that SBV was responsible.
Animal keepers should be vigilant for the clinical signs described and consult their veterinary practitioner for advice if they are seen.
Schmallenberg virus
In Autumn 2011, cows with fever, diarrhoea, and drop in milk yield were observed near the German town of Schmallenberg.
Blood samples revealed the presence of a novel virus which was named Schmallenberg virus.
The first Irish case of SBV was confirmed in Cork in late 2012 in a calf. Subsequently, an outbreak of congenital Schmallenberg disease occurred in the south and south east of Ireland in late 2012/early 2013.
In cattle, SBV is associated with fever, milk drop, diarrhoea, as well as abortion and deformed foetuses.
In sheep and goats, it is known to cause abortion and deformed lambs. The congenital deformities which occur include torticollis (twisted neck), arthrogryposis (limbs bent and locked), shortened lower jaws and hydranencephaly (abnormalities with excess fluid in the brain).
The critical period for the development of congenital deformities is when infections occurs between 28-56 days in sheep and 62-170 days in cattle.