Abstract
Serum samples of 749 sheep from 75 sheep flocks in Norway, i.e. 361 lambs (6 to 7 months old) and 388 adults (>1.5 year), were analysed for antibodies to Ehrlichia equi. Ten animals from each flock were examined. Seropositive animals were found along the coast of southern Norway from Vestfold to Sør-Trøndelag (as far north as 63°38'N). Seropositive sheep were not found in southeast, east or northern Norway. Thirty-two flocks were seropositive, although tick-borne fever had only been diagnosed earlier in half of these. In 78% of the seropositive flocks, more than 80% of the sheep were seropositive. A total of 35.7 % and 36.3 % of lambs and adults were found seropositive, respectively. However, the overall seroprevalence among animals that had been grazing on Ixodes pastures were 0.80 for the lambs and 0.84 for the adults. Mean antibody titres (± SD) (log10) in seropositive lambs and adults were 2.59 (± 0.449) and 2.70 (± 0.481), respectively. No significant differences in either seroprevalence or mean antibody titre between sheep of different ages were obtained in this study. Based on antibodies 94% of sheep flocks on Ixodes pastures were infected with a granulocytic Ehrlichia infection. The association between seropositive flocks and Ixodes infested pasture shows a very high degree of agreement (p < 0.00001). The present study indicates that granulocytic Ehrlichia infection in sheep is underdiagnosed in Norway.
Highlights
The most common tick-borne disease in domestic animals in Norway is tick-borne fever (TBF), caused by Ehrlichia phagocytophila, and transmitted by the tick Ixodes ricinus (Øverås 1972, Stuen 1997)
TBF may cause abortion in ewes and temporary infertility in rams (Woldehiwet & Scott 1993), but the main consequence of an E. phagocytophila infection in sheep is the ensuing immunosuppresion that leads to secondary infections, such as Staphylococcus aureus pyaemia and Pasteurella hemolytica septicaemia (Brodie et al 1986, Stuen 1996)
TBF has for decades been considered as an important disease in lambs in certain areas along the coast of southern Norway (Stuen 1998)
Summary
The most common tick-borne disease in domestic animals in Norway is tick-borne fever (TBF), caused by Ehrlichia phagocytophila, and transmitted by the tick Ixodes ricinus (Øverås 1972, Stuen 1997). TBF may cause abortion in ewes and temporary infertility in rams (Woldehiwet & Scott 1993), but the main consequence of an E. phagocytophila infection in sheep is the ensuing immunosuppresion that leads to secondary infections, such as Staphylococcus aureus pyaemia and Pasteurella hemolytica (trehalosi) septicaemia (Brodie et al 1986, Stuen 1996). TBF has for decades been considered as an important disease in lambs in certain areas along the coast of southern Norway (Stuen 1998). The purpose of the present study was to investigate the distribution of E. phagocytophila infection in sheep in different areas of Norway, especially in areas with a distribution of I. ricinus
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