Pulmonary pathology in rabbits infected with the Baling and Koyan strains of Schistosoma malayensis.

Two distinct strains of Schistosoma malayensis exist in Malaysia (designated the Baling and Koyan strains). Both these strains show intraspecific variations in pathology (Greer et al, 1988). To evaluate the differences in the pulmonary pathology resulting from infections of the two different strains of Malaysian schistosome, a total of 20 experimental rabbits were infected, 10 each with cercariae of the Koyan strains. Pathological changes were studied over a period of 28 weeks. Granulomas in the lung occurring as a result of infection with the Baling strain were compared with those caused by infection with the Koyan strain. Although both strains produced parenchymatous and alveolar lesions, granulomas caused by the Baling strain of Malaysian schistosome were more numerous and larger (when comparing mean diameter as well as area of granuloma, p < 0.05). In addition, pulmonary vascular hypertensive changes were present in Baling strain infected rabbits. These comprised of pulmonary arteriolar endothelial swelling and damage, intimal elastosis and medial hypertrophy. Angiitis and pulmonary periphlebitis were also noted occasionally. In contrast, Koyan strain infection resulted in fewer and smaller granulomas. Pulmonary vascular changes were minimal.