Molecular prevalence of zoonotic nematode parasite Calodium hepaticum in household rat population in Chennai city, India.

Calodium hepaticum (syn. Capillaria hepatica) is a zoonotic nematode parasite occurring commonly in the liver of rats, which act as primary reservoir hosts. In the present study, 55 household rats in Chennai, Tamil Nadu, India, were trapped and screened for C. hepaticum infection in the liver. All the collected rat liver samples were subjected to macroscopic examination. Rat liver samples with yellowish-white patch lesions were confirmed for the presence of bi-operculate and ellipsoidal shape eggs by parasitological and histopathological examination. A parasite-specific semi-nested PCR was developed to amplify the partial 18S rRNA gene of C. hepaticum. The limit of detection of the semi-nested PCR was 15 aM. All the liver samples were screened by the semi-nested PCR. Of the 55 rat liver samples screened by semi-nested PCR, 21 were positive for C. hepaticum, indicating a prevalence of 38.18 %. Phylogenetic analysis confirmed that the 18S rRNA gene sequence belonged to C. hepaticum. This report is the first molecular confirmation of C. hepaticum in rats in India. This study highlights the high level of prevalence of C. hepaticum in the household rat population and the risk of zoonotic transmission of hepatic calodiosis to human beings living in close proximity to infected rats.