Schistosomiasis Mansoni in the Chimpanzee: Parasitologic, Clinical, Serologic, Pathologic and Radiologic Observations


Studies conducted in splenectomized and intact chimpanzees (Pan satyrus) indicated that this primate is susceptible to experimental infections with Schistosoma mansoni. After a prepatent period of six to seven weeks, viable eggs appeared in the stools. The pattern of egg production remained relatively constant and sustained for the duration of the experiment. At necropsy, active and well-developed adult schistosomes were found in the distal branches of the mesenteries. Although most of the eggs were recovered in the large intestine and in the liver, viable eggs were also found in the lungs, the pancreas, the kidneys, the small intestine, the urinary bladder and the spleen. In the heavily infected chimpanzees, there was an elevation in temperature between the sixth and ninth week after exposure, anoxia, diarrhea with mucus and frank hemorrhage, and a transient marked decrease in activity and responsiveness. These symptoms were followed approximately three weeks later by transient hepatomegaly and ascites. A lymphocytic leukocytosis accompanied the first appearance of eggs in the feces and the onset of clinical symptoms. Pathologic and radiologic observations revealed changes resembling human pipestem fibrosis in a heavily infected animal, and portocaval anastomoses around the lower esophagus and diaphragm. Most of the eggs in the gut were in the mucosal layer.

The course of antibody production as measured by the slide flocculation test using as antigens somatic extracts of eggs and cercariae and metabolic products of adult worms followed a pattern similar to that observed previously in mice, rabbits, monkeys and humans. Cutaneous reactivity was successfully transferred from an infected chimpanzee and from infected humans to uninfected rhesus monkeys. Reagenic antibodies, which were largely destroyed by heating the serum, were demonstrated approximately three months after exposure and persisted throughout the duration of the experiment. To the authors' knowledge this is the first time that antischistosome reagenic antibodies have been detected in humans and chimpanzees and successfully transferred to rhesus monkeys.

The pattern of egg output in the feces, the distribution of eggs in various organs, the clinical course, the pathological effects and the serological response of schistosomiasis in chimpanzees followed a course similar to that which had been observed in men.

Author Notes

Department of Medical Zoology, Walter Reed Army Institute of Research, Washington, D. C.

Department of Pathology, Peter Bent Brigham Hospital, Harvard Medical School, Boston, Massachusetts.