Abstract
Tick-borne fever (TBF) is caused by the rickettsia Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila) and is a common disease in sheep in areas of Norway infested by Ixodes ricinus ticks. TBF can cause both direct and indirect losses to sheep kept on tick-infested pastures. In the present work we studied a sheep flock of 26 ewes and 50 lambs on pasture from May until September. No cases of TBF had earlier been observed on this pasture. Blood samples from lambs with a reduced weekly weight gain were collected and analysed for A. phagocytophilum infection by blood smear examination. In addition, at the end of the study, sera from all lambs were analysed by an indirect fluorescent antibody assay (IFA) to determine the antibody titre to E. equi. No clinical signs of tick-borne infections were observed, except in one lamb. However, 30 (60%) of the lambs grazing on this pasture became infected with A. phagocytophilum, and the infected lambs had a reduced weight gain (mean) of 3.8 kg compared with the uninfected lambs. The present study indicates that A. phagocytophilum infection may be widespread and contribute to considerable productivity losses even on pastures with no apparent tick infestation.
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Artursson, K., Gunnarsson, A., Wikström, U.-B. and Olsson Engvall, E. 1999. A serological and clinical follow-up in horses with confirmed equine granulocytic ehrlichiosis. Equine Vet. J. 31: 473-477.
Brodie, T.A., Holmes, P.H. and Urquhart, G.M. 1986. Some aspects of tick-borne diseases of British sheep. Vet. Rec. 118: 415-418.
Brodie, T.A., Holmes, P.H. and Urquhart, G.M. 1988. Prophylactic use of long-acting tetracycline against tick-borne fever (Cytoecetes phagocytophila) in sheep. Vet. Rec. 122: 43-44.
Dumler, J.S., Asanovich, K.M., Bakken, J.S., Richter, P., Kimsey, R. and Madigan, J.E. 1995. Serologic cross-reaction among Ehrlichia equi, Ehrlichia phagocytophila and human granulocytic Ehrlichia. J. Clin. Microbiol. 33: 1098-1103.
Hunt, J. 1986. Pour-on licks ticks and swells fell margins. Farmers Weekly 25: 24.
MacLeod, J. and Gordon, W.S. 1933. Studies in tick borne fever of sheep. 1. Transmission by the tick-Ixodes ricinus with a description of the disease produced. Parasitology 25: 273-283.
Kingsbury, P.A. 1965. Relationship between egg counts and worm burdens of young sheep. Vet. Rec. 77: 900-901.
McKenna, P.B. 1981. The diagnostic value and interpretation of faecal egg counts in sheep. NZ Vet. J. 29: 129-132.
Nicholson,W.L., Comer, L.A., Sumner, J.W., Gingrich-Baker, C., Coughlin, R.T., Magnarelli, L.A., Olson, J.G. and Childs, J.E. 1997. An indirect immunofluorescence assay using a cell culture-derived antigen for detection of antibodies to the agent of human granulocytic ehrlichiosis. J. Clin. Microbiol. 35: 1510-1516.
Scott, G.R. 1991. Tick-borne infections. In: Diseases of Sheep, 2nd edn.,W.B.Martin and I.D. Aitken (eds), pp. 327-336. Blackwell Scientific Publications, Oxford, UK.
Stuen, S. 1993. Tick-borne fever in lambs of different ages. Acta Vet. Scand. 34: 45-52.
Stuen, S. 1997. The distribution of tick-borne fever (TBF) in Norway. Norsk Vet. Tidssk. 109: 83-87 (in Norwegian).
Stuen, S. and Artursson, K. 2000. Effects of the dose of Ehrlichia phagocytophila on the severity of experimental infections in lambs. Vet. Rec. 146: 669-672.
Stuen, S. and Bergström, K. 2001. Serological investigation of granulocytic Ehrlichia infection in sheep in Norway. Acta Vet. Scand. 42: 331-338.
Stuen, S. and Kjølleberg, K. 2000. An investigation of lamb deaths on tick pastures in Norway. In: Proceedings of the Third International Conference on Ticks and Tick-borne pathogens: Into the 21st Century, M. Kazimirová, M. Labuda and P.A. Nuttall (eds), pp. 111-115. Slovak Academy of Sciences, Bratislava, Slovakia.
Stuen, S., Hardeng, F. and Larsen, H.J. 1992. Resistance to tick-borne fever in young lambs. Res. Vet. Sci. 52: 211-216.
Stuen, S., Artursson, K. and Olsson Engvall, E. 1998a. Experimental infection of lambs with an equine granulocytic Ehrlichia species resembling the agent that causes human granulocytic ehrlichiosis (HGE). Acta Vet. Scand. 39: 491-497.
Stuen, S., Olsson Engvall, E. and Artursson, K. 1998b. Persistence of Ehrlichia phagocytophila in lambs in relation to clinical parameters and antibody responses. Vet. Rec. 143: 553-555.
Stuen, S., Van de Pol, I., Bergström, K. and Schouls, L.M. 2002. Identification of Anaplasma phagocytophila (formerly Ehrlichia phagocytophila) variants in blood from sheep in Norway. J. Clin. Microbiol. 40: 3192-3197.
Trodahl, S. 1998. Sheep as a domestic animal. In: Saueboka 2nd edn., pp. 11-27. A/S Landbruksforlaget, Oslo, Norway (in Norwegian).
Urquhart, G.M., Armour, J., Duncan, J.L., Dunn, A.M. and Jennings, F.W. 1987. Veterinary Parasitology, pp. 269-272. Longman, Harlow, Essex, UK.
Øverås, J., Ulvund, M.J., Waldeland, H. et al. 1985. Sheep losses and their causes. Norsk Vet. Tidsskr. 97: 469-475 (in Norwegian).
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Stuen, S., Bergström, K. & Palmér, E. Reduced Weight Gain Due to Subclinical Anaplasma phagocytophilum (Formerly Ehrlichia phagocytophila) Infection. Exp Appl Acarol 28, 209–215 (2002). https://doi.org/10.1023/A:1025350517733
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DOI: https://doi.org/10.1023/A:1025350517733