Abstract
The epidemiology of toxoplasmosis in sheep was studied during a period of 31/2 to 6 years in 4 flocks in which abortions from the infection previously had occurred.
The epidemiological pattern indicated that a heavy contamination of the environment may persist for about 2 years. Even in flocks with an apparently normal reproductive performance, toxoplasmosis may cause barrenness, abortion or delivery of dead lambs in 1–2 % of the breeding ewes.
The prevalence of infected sheep increased with the age. The incidence of infection was significantly lower in 6–12 months old lambs than in mature ewes.
The incidence of infection was higher on lowland pastures than on mountain pastures in not populated areas. On lowland pastures the incidence of infection was lower during the summer than during the winter. kw|Keywords|k]toxoplasma infection; k]epidemiology; k]sheep {fn1|This work was supported by grants from the Norwegian Research Council for Science and for the Humanities.}
Sammendrag
Epidemiologiske undersøkelser ble foretatt i løpet av 31/2 til 6 år i 4 saueflokker hvor det tidligere hadde forekommet toxoplasma-abort.
Det epidemiologiske mønster tydet på at en sterk kontaminering av miljøet kan ha en varighet på omkring 2 år. Selv i flokker hvor reproduksjonen tilsynelatende var normal, viste det seg at toxoplasmose kunne resultere i infertilitet, abort, eller dødfødte lam hos 1–2 % av søyene.
Forekomsten av infiserte sauer øket med al deren. Infeksjonshyp- pigheten var signifikant lavere hos 6–12 måneder garnie lam enn hos voksne sauer.
Infeksjonshyppigheten var høyere på lavlandsbeite enn på fjell- beite. På lavlandsbeite var hyppigheten lavere om sommeren enn om vinteren.
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