Neuropathological Observation of Rabbits (Oryctolagus cuniculus) Affected with Raccoon Roundworm (Baylisascaris procyonis) Larva Migrans in Japan

Abstract

ABSTRACT. Larvae of the raccoon roundworm, Baylisascaris procyonis (B. procyonis) are a known cause of cerebrospinal larva migrans in animals and humans. The present paper described details of the central nervous lesion in the rabbits (Oryctolagus cuniculus) affected with B. procyonis larva migrans in Japan. Clinically affected animals showed neurological signs including circling, torticollis, tremor of head, or ataxic gait. The most characteristic pathological alterations were large malacic lesions associated with an activated astroglial proliferation which was seen at the corpus medullare in the cerebellum including the cerebellar peduncle. Moreover, focal malacic lesions with perivascular cuffing and infiltration by lymphocytes and heterophiles were scattered everywhere throughout the brain. In these lesions or normal-appearing areas away from obvious lesions, ascarid larvae, about a maximum 65-75 µm in diameter, were recognized. Other prominent features were minute lesions (we call them migration tract-like lesions) composed of lymphocytes, hemosiderin-laden macrophages and reactive astrocytes scattering throughout the cerebrum. 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 described above.

Update on Baylisascariasis, a Highly Pathogenic Zoonotic Infection

“…In Germany alone, over 100,000 raccoons exist in the wild, with a prevalence of B. procyonis of 71% (1,88). Starting in 1977, an astonishing number of more than 20,000 raccoons were introduced as pets into Japan (77,89); many of these animals escaped, and raccoons became established in the wild. Following past importations and spread within the system, infected raccoons were recently documented throughout the wildlife parks of China (78).…”

“…However, it is doubtful such approaches would be justified in most cases in light of the present availability of good serologic methods (1, 4, 6, 7). Pathology studies of experimental animal models and natural cases have shown that the cerebrum, cerebellum, brain stem, and spinal cord can all be affected by the migration of larvae (1,89,90,100). Hemorrhagic and malacic migration tracks were seen throughout the brains of primates experimentally infected with B. procyonis and were directly associated with migrating larvae (90).…”

Encephalitozoonosis in rabbits

“…Parasitic infections causing neurological sings in rabbits include cerebral larva migrans of nematodes and toxoplasmosis Furuoka et al 2003). Baylisascaris infections are not uncommon in rabbits in the USA (Deeb and Di Giacomo 1994).…”

Parasitic helminths from feral raccoons (Procyon lotor) in Japan

“…Thus, no raccoon roundworms have been found in the 2244 free-ranging raccoons examined to date. However, the prevalence of roundworms in captive raccoons in Japanese zoos is very high, and outbreak of the fatal neurological larva migrans caused by roundworms in captive mammals has occurred in zoos (Miyashita, 1993;Furuoka et al, 2003;Sato et al, 2002Sato et al, , 2003Sato et al, , 2005b. It is not uncommon for taxa parasites to occur in free ranging raccoons in Japan: T. tanuki and Porrocaecum sp.…”