Study of Baylisascaris procyonis larva migrans : Pathological and parasitological analysis and development of serological diagnosis.

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Larva migrans caused by the common raccoon ascarid, Baylisascaris procyonis, is a zoonotic disease of critical importance in North America. We encountered the first proven outbreak of this disease in Japan in domestic rabbits in a small wildlife park. In this park, raccoons had been kept for 9 years, and one raccoon was donated to the park by a pet owner 8 weeks prior to the occurrence of an outbreak in rabbits. Circumstantial evidence indicates that the donated raccoon is the likely source of this outbreak. Also, we investigated the details of the central nervous lesion in the rabbits affected with B.procyonis larva migrans in Japan. In this study, we demonstrated ascarid larvae in only eight out of 23 animals diagnosed as B.procyonis larva migrans. Since it is not always possible to detect the larvae, the possibility of B.procyonis larva migrans must be given serious consideration to the characteristic lesions. Also, B.procyonis causes a severe retinal lesion in humans. The lesion is termed as diffuse unilateral subacute neuroretinitis (DUSN). To understand the pathogenesis of B.procyonis in gerbils, we inoculated the embryonated eggs of B.procyonis into Mongolian gerbils, and monitored their fundi with an ophthalmoscope. Histopathological examination revealed perivasculitis in the optic disk region, inflammatory proliferation of the pigment cells, and vitreitis in most cases. These findings were similar to those in human cases of DUSN, suggesting that gerbils might be a useful model for understanding the pathogenesis of B.procyonis infection in humans.