Differences of larval development and pathological changes in permissive and nonpermissive rodent hosts for Angiostrongylus cantonensis infection.

Angiostrongylus cantonensis is a neurotrophic and pulmonary parasite which causes severe neuropathological damages by invading and developing in the central nervous system (CNS). Nonpermissive host with A. cantonensis infection appeared to have more serious neurologic symptoms, and there is still not much knowledge about the host-parasite interrelationship in different hosts. We investigated and compared the larval size, recovery rate, distribution, and the severity of pathologic injuries in the CNS of both permissive host (e.g., rats) and nonpermissive hosts (e.g., mice). In present study, mice infected with A. cantonensis showed higher worm recovery rate in late-stage infection and smaller size of intracranial larvae as compared to the infected rats. Intracranial larvae mainly aggregated on cerebral surface of infected rats but on surface of cerebellum and brainstem in mice. Hemorrhage and tissue edema on brain surface caused by worm migration appeared earlier and severer in infected mice than in rats. Neuropathological examination revealed that injuries induced by A. cantonensis in brain parenchyma included hemorrhage, vascular dilatation, focal necrosis with neuronal loss, and infiltration of inflammatory cells. In the comparison of these pathological changes in rats and mice, infected mice suffered more serious injuries and provoked more intense inflammatory response as compared to infected rats. All these morphological evidences indicate that larval development was retardant in the CNS of nonpermissive host, and nonpermissive host experienced more serious pathological injuries than permissive host. It implies that the difference in innate immune response to parasite infection attribute to host specificity.