Capillaria hepatica infection in rodents from Anning Prefecture of Yunnan Province and experimental research on host animals

OBJECTIVE: To investigate the prevalence of Capillaria hepatica in rodents from Anning Prefecture, Yunnan, and observe the susceptibility of C. hepatica to SD rats and KM mice. METHODS: Rodents were trapped in a cultivated filed of Wenquan Town, Annning from March 2010 to March 2012. The species of rodents were identified. The liver was examined and a microscopic examination of tissue was performed by the tissue press technique for the presence of the typical bipolar eggs, adults or larval stages. The prevalence of C. hepatica in rodents was calculated. C. hepatica eggs were collected and cultured in vitro. Each SD rat or KM mouse was orally infected with approximately 1 000 C. hepatica eggs. The control groups with 4 SD rats or 4 KM mice received only normal saline. The experimental animals were euthanized at the 30th and 80th day post infection. Collected liver samples were processed for gross pathological and histological section examination. RESULTS: A total of 115 rodents were captured and examined. C. hepatica eggs were found in 26 (22.6%) rodents. There was no significant difference in the prevalence between female (22.5%, 18/80) and males (22.9%, 26/115) (P > 0.05). The highest prevalence was found in Rattus norvegicus (10/11). Pathologi cal findings showed numerous white-yellow small nodules ranged from 0.1-0.2 cm in diameter. Under light microscope, C. hepatica eggs were ovoid [(50-65) microm x (25-30) microm]. At the 30th day post-infection, there were several adult worms and their eggs delimited by a fibrous capsule, and septal fibrosis formations occurred in the liver of SD rat. No worm or eggs were found in the mouse liver, but the liver presented inflammatory cell infiltration. At the 80th day post-infection, live worms disappeared from the focal lesions in the liver of SD rat, being replaced by partially calcified worm debris. Mature worms and eggs were seen in the KM mouse liver, however, septal fibrosis was absent. CONCLUSION: This study has documented a high prevalence of C. hepaticum in R. norvegicus from Anning Prefecture. SD rat and KM mouse are the susceptible hosts of C. hepatica.