Serological and clinical evidence of a teratogenic Simbu serogroup virus infection of cattle in Israel, 2001-2003.

During the last 35 years, two major outbreaks of Akabane virus (AKAV) infection were recorded in cattle in Israel in 1969/1970 and 2002/2003. Congenital malformations of calves characterised by the appearance of an arthrogryposis and hydranencephaly syndrome first appeared in Israel in 1969. Based on epidemiological, clinical, pathological, histopathological and serological data, this syndrome was strongly correlated with seroreactivity to AKAV, a member of the Bunyaviridae, Simbu serogroup. In February 2002, the first cases of 'blind newborn calves' (BNC) were observed on farms located in the northern valleys of Israel. Microtitre serum neutralisation (SN) tests of serum from malformed calves and their dams were conducted using Akabane and Aino viruses (AINOV). The first SN test was performed at the reference laboratory of the Clinical Virology Section, Kyushu Research Station, National Institute of Animal Health, Kagoshima, Japan. The clear-cut findings of seroreactivity to AKAV by cattle located in the affected zone, in contrast to negative findings in cattle from unaffected farms (87% and 3.7%, respectively) was indicative of AKAV infection. In contrast, seroreactivity to Aino virus was relatively low in both affected and non-affected areas during the 2002 outbreak. In order to establish Israeli laboratory standards for Simbu serogroup diagnosis, 57 serum samples tested by the Japanese laboratory were retested by SN in Israel. An almost complete homology (96.5%) was found between the two SN panels of sera (kappa = 0.92). SN and ELISA kits enabled the surveillance of this arbovirus epidemic in the second consecutive year (2003). Moreover, AKAV was identified in trapped midges by hemi-nested PCR and real-time PCR. With these techniques, the geographical limits of the BNC epidemic that appeared in some areas of Israel was identified for the first time and was recorded in the Arava Rift Valley, 400 km south of the epicentre of the 2002 outbreak. The reintroduction of AKAV into this region, together with some evidence of AINOV activity and epidemics of bluetongue (BT) in the southern parts of Europe and the eastern Mediterranean, and renewed outbreaks of West Nile virus infection in Israel, Italy and southern France, are all evidence of the potential spread of arbovirus activity into southern Europe from the Mediterranean Basin.