Two groups of three rabbits each were infected with 250 cercariae of the Baling and Koyan strain of Schistosoma malayensis. Changes induced by both strains included periportal hepatocellular necrosis and fibrosis. Vascular changes such as portal phlebitis and thrombophlebitis and varying degrees of pericholangitis were also present. Amyloid deposition was noted. A comparative study of the changes induced in rabbits by S. malayensis, S. mekongi and S. japonicum showed that the hepatic lesions induced by the Baling strain of S. malayensis were similar to that induced by S. japonicum, and were more severe than that induced by S. mekongi or the Koyan strain.
Schistosoma malayensis Sp N is a putative new species of schistosome discovered in Peninsular Malaysia in 1973. This paper comprises the first report on the detailed gastrointestinal pathology present in rabbits infected with strains of the parasite. Two different strains of schistosome--the Baling and Koyan strains--from two different ecosystems were used to infect inbred rabbits and the resulting pathophysiology was studied. Our results showed that the Baling strain of S. malayensis was more virulent than the Koyan strain and produced nodular, segmental circumferential lesions and large bilharziomas measuring 1-7 cm in diameter in the distal jejunum, ileum and the ileo-caecal junction. The findings indicate that the Baling strain of S. malayensis was more pathogenic for rabbits as compared with the Koyan strain--in relation to the gross pathology of the gut and the tissue egg load. Earlier reports have shown that rabbits infected with S. japonicum induces significant intestinal lesions in rabbits (Cheever et al, 1980 a,b) but these animals are refractory to infection with S. mekongi (Byram and Lichtenberg, 1980). Our studies show that the two strains of S. malayensis adapted well in rabbits. It is also established that in rabbits, the virulence of the Baling strain of S. malayensis is greater than that of S. mekongi and approximates that of S. japonicum.