What can Akabane disease teach us about other arboviral diseases

Viruses of the Simbu serogroup cause lesions to foetuses that are seen at birth and that correlate with the stage of pregnancy at which the dam first contracts the virus. The Simbu serogroup comprises arboviruses known to cause outbreaks of abnormal parturitions in domestic ruminants; these abnormalities include abortion, stillbirth, and congenitally deformed neonates. Simbu serogroup members include: Akabane virus (AKAV), Aino virus, Cache Valley virus, and Schmallenberg virus. Lately, dairy herds calf malformations have been observed in Europe, where there have been reports of clinical manifestations such as diarrhoea, fever, and reduced milk yield in adult lactating cows. The Israeli dairy cattle industry has experienced 2 major episodes of abnormal parturitions that resulted from 2 arboviral Simbu serogroup episodes, which occurred 35 years apart. A wave of apparently newly introduced AKAV was noted from the beginning of January 2012. Investigations carried out throughout the period of late Summer 2011 to early Winter 2012, associated the Israeli AKAV strain with central nervous system manifestations in lactating cows. A lack of clinical/epidemiological 'uniformity' among the AKAV infections was noted during these investigations. Here we describe and discuss the clinical and spatial distribution differences found among the 3 above-mentioned outbreaks. Comparable features in the clinical presentation, spatial distribution, and target‑animal issues relating to Akabane disease are discussed.