Bovine ephemeral fever in a dairy cattle herd in the Jordan Valley

Abstract

BOVINE ephemeral fever (BEF), caused by the BEF virus (family Rhabdoviridae, genus Ephemerovirus), is a short-term inflammatory disease which affects cattle (Uren and others 1992). The BEF virus life cycle is maintained through a vectorhost system, probably involving mosquitoes and cattle (Walker and Boreham 1976). The viral agent has been isolated from various species of midges and mosquitoes, which probably act as vectors (Mellor 1996, Venter and others 2003). However, there is no evidence to suggest which vector species can transmit the BEF virus. BEF is spread by movement of the host or by vectors (St George 1988, Murray 1997). It is most likely that windborne carriage of infected insects over large distances is responsible for the spread of BEF in various countries (Newton and Wheatley 1970, St George 1988). It is becoming increasingly apparent that BEF occurs as a direct result of disruption of the normal functioning of the physiological and immunological systems of the host (Uren and others 1992). The clinical signs and pathological changes are a reflection of the effect of the growth of the virus and the host’s response (Burgess and Spradbrow 1977). Significant economic losses in dairy cattle herds may result from morbidity, reduced milk production (Newton and Wheatley 1970, Theodoridis and others 1973, Davis and others 1984, Wenbin and others 1991, Nandi and Negi 1999, Yeruham and others 2002), an increase in somatic cell count (Yeruham and others 2003), abortions (Wenbin and others 1991, Nandi and Negi 1999, Yeruham and others 2003) and mortality (Newton and Wheatley 1970, Uren and others 1989, Yeruham and others 2003). However, there is little information on whether the fertility of dairy cattle is affected, particularly under a subtropical climate. This short communication describes the morbidity, mortality and reproductive failure caused by outbreaks of BEF in a high-yielding dairy cattle herd in the Jordan Valley in Israel in 1999 and 2001. Field observations were carried out during 1999 and 2001, at the Gilgal kibbutz , which is located in the Jordan Valley (32°00′N, 35°26′E). This is a part of the Rift Valley and forms a part of the leeside dry lands east of the hill region; it belongs to the Irano-Turanian zoogeographical zone. The region is semiarid with a mean annual precipitation of 189 mm. BEF outbreaks had occurred in a Holstein-Israeli dairy herd comprising 480 animals with an average of 200 lactating cows. The lactating cows were divided into three groups, heifers, first calvers and cows; dry cows and heifers were kept in separate sheds. The herd was kept under a zero-grazing management system, and each lactating cow produced an average milk yield of 10,200 kg/year. The herd was visited twice weekly by the attending veterinarian, and morbidity, mortality, fertility, number of abortions, milk production and somatic cell counts were recorded by computerised dairy management systems. Oestrus was detected by pedometers and visually, three times daily, and the cows in heat were inseminated artificially every morning. The conception rate was then compared with data from the same herd during the three years before the 1999 BEF outbreak (1996 to 1998), and the year after the 2001 outbreak (2002). Cases of BEF were diagnosed clinically. Viruses were isolated from cattle which had severe disease incursions at Veterinary Record (2005) 156, 284-286