Abstract
A total of 407 swine bred in south-eastern Norway have been tested for the presence of Toxoplasma gondii antibodies in serum by use of the dye-test, and diaphragm muscle from all sero-positive and some sero-negative swine has been tested for the presence of mouse-infective cysts. The prevalence of antibodies was as low as 10.1 %. The prevalence increased with the weight of the swine, but apparently with a decline after passing a weight of 140 kg. Only dye-test titres up to 50 were found. The prevalence of dye-test positive swine was higher in small herds (< 300 swine p.a.) than in larger ones (> 300 swine p.a.). The prevalence of herds with dye-test positive swine in the region surrounding the Oslo-fjord was higher in the coastal than in the inland zone. The incidence of infection was the same during the summer-autumn period as during the winter-spring period. Toxoplasma was recovered from the diaphragm muscle of about % of the dyeπtest positive swine. Parasites were isolated from some pigs with a dye-test titre of 4, and from all the pigs with a titre of 50. Toxoplasma was not isolated from dye-test negative swine. The epidemiological and food-hygienic significance of porcine toxoplasmosis in Norway is discussed according to the present results.