Genetic analysis of Enterobius vermicularis isolated from a chimpanzee with lethal hemorrhagic colitis and pathology of the associated lesions

Human pinworms, Enterobius vermicularis, are normally recognized as minor pathogens. However, a fatal case of human pinworm infection has been reported in a nonhuman primate, a zoo reared chimpanzee. Here, we histopathologically examined the lesions in tissues from the deceased chimpanzee and genetically characterized the isolated worms to investigate the pathogenicity and determine the phylogeny. We identified ulcers deep in the submucosa where many parasites were found to have invaded the lamina propria mucosa or submucous tissue. An inflammatory reaction consisting mainly of neutrophils and lymphocytes but not eosinophils was observed around the parasites, and intense hemorrhage in the lamina propria was confirmed. The parasites were morphologically similar to E. vermicularis based on the shape of the copulatory spicules. Mitochondrial cytochrome c oxidase subunit 1 gene products were amplified from worm DNA by PCR and were genetically identified as E. vermicularis based on > 98.7 % similarity of partial sequences. Phylogenetic analysis revealed that the sequences clustered together with other chimpanzee E. vermicularis isolates in a group which has been referred to as type C and which differs from human isolates (type A). The samples were negative for bacterial pathogens and Entamoeba histolytica indicating that E. vermicularis could be pathogenic in chimpanzees. Phylogenetic clustering of the isolates indicated that the parasite may be host specific.