Food-borne parasitic zoonoses in India: Review of recent reports of human infections

For many protozoan and helminth parasites, the environmental routes of transmission, involving food, soil and water are particularly significant. Their capacity to produce large number of transmissive stages capable of long period of survival in the environment increases their potential for threat to both animals and man. This review focuses on the current status of the more well-known food-borne zoonoses with emphasis on the human component. It also puts in perspective the existence of human foci of some other infections which, till recently, were regarded as rare or even non-existent in India despite the presence of their animal reservoirs and epidemiological factors favourable for their transmission. For a more composite picture, one has to take into account the reports of human infections which, of late, are becoming increasingly available. Advent of better detection methods such as imaging techniques as well as recent advances in immunology and molecular biology have also contributed to this trend. Of the plant-borne trematodes, while fasciolopsiosis and gastrodiscoidosis have been sporadically reported, human fasciolosis is also surfacing. Cystic echinococcosis has been found lodged in a variety of organs and tissues. Records of sparganosis involving vital organs have also come up. Less often encountered nematode infections like gnathostomosis, dracunculosis and trichinosis find mention. Among food- (and water-) borne protozoan zoonoses, cryptosporidiosis, giardiosis, sarcocystosis and toxoplasmosis have been dealt with in the context of recent Indian reports.