Clinical signs and pathology shown by British sheep and cattle infected with bluetongue virus serotype 8 derived from the 2006 outbreak in northern Europen

Abstract

Four poll Dorset sheep and four Holstein-Friesian cattle were infected with the northern European strain of bluetongue virus (BTV), BTV-8, to assess its pathogenicity in UK breeds. The time course of infection was monitored in both species by using real-time reverse transcriptase-PCR (RT-PCR), conventional RT-PCR and serology. Two of the sheep developed severe clinical signs that would have been fatal in the field; the other two were moderately and mildly ill, respectively. The cattle were clinically unaffected, but had high levels of viral RNA in their bloodstream. Real-time RT-PCR detected viral RNA as early as one day after infection in the cattle and three days after infection in the sheep. Antibodies against BTV were detected by six days after infection in the sheep and eight days after infection in the cattle. Postmortem examinations revealed pathology in the cattle that was more severe than suggested by the mild clinical signs, but the pathological and clinical findings in the sheep were more consistent.

Transplacental infection in goats experimentally infected with a European strain of bluetongue virus serotype 8

“…This second increase in body temperature coincided with an increase in BTV RNA levels in the blood of the animals between 7-13 dpi. A similar close relationship between the level of viral RNA in the blood and the occurrence of fever and clinical signs has previously been reported in experimentally infected sheep and cattle, although it has been pointed out that this correlation is not always clear cut (Darpel et al, 2007).…”

Experimental reproduction of bluetongue virus serotype 8 clinical disease in calves

“…The day after the infection the calves had pyrexia, a sign which has been already observed in previous experimental infection with BTV (Odeó n et al, 1997; Darpel et al, 2007). Probably related to the high levels of viraemia of the following days, we measured a slight increase in body temperature between 7 and 10 days P.I.…”

“…Many experimental inoculation studies have been conducted to characterize BTV pathogenesis in cattle, including a variety of serotypes, animals of different ages and various methods of inoculation. At present, only one study has been published with BTV-8 experimental infected sheep and cattle, where the latter did not show obvious clinical manifestations of the disease, although the necropsy revealed a generalized lymphadenopathy and, only in one cattle, petechial haemorrhages on several organs (Darpel et al, 2007).…”

Bluetongue in Europe: past, present and future

“…Infection with BTV can result in a wide range of clinical signs or can be entirely sub-clinical. The majority of infected animals develop no detectable clinical signs (Anon 2005) but, in others, signs may include fever, depression, lameness, oedema of the lips, tongue and head, conjunctivitis, coronitis, excessive salivation, nasal discharge, hyperaemia and pain at muco-cutaneous junctions such as the gums and vulva, and death (Darpel et al 2007). In pregnant animals abortion may also occur.…”