Natural History of Cryptosporidial Infection in a Birth Cohort in a South Indian Semi Urban Slum

Abstract

Cryptosporidium spp. is a protozoan parasite and is a leading cause of parasitic diarrhoea in children under the age of 5 years, especially among those living in developing countries. Early exposure to cryptosporidial infections is believed to have significant ill effects on the physical and cognitive development of children. A majority of the studies on cryptosporidiosis so far have aimed at understanding the clinical course of Cryptosporidium associated diarrhoea and few have looked at infection in the absence of clinical symptoms. There is also a lack of longitudinal data that can help understand the natural history of cryptosporidial infection, the risk factors that influence the acquisition of infection, and the protection conferred by natural infection in children living in endemic settings. In this birth cohort, recruited between April 2009 and May 2010, a total of 497 new born were enrolled from four adjacent semi-urban slum areas in Vellore, India, where earlier studies have shown cryptosporidiosis to be endemic. Children were then followed up twice weekly, until they attained the age of three years, and diarrhoeal and other illnesses were documented. Stool samples were collected fortnightly and also during diarrhoeal episodes. These samples were tested for the presence of Cryptosporidium spp. by PCR. Anthropometric measurements from children were obtained every month. Samples of blood were collected at 6-monthly intervals and were tested for the presence of Cryptosporidium IgG by ELISA. Baseline demographic and birth details were obtained at the time of recruitment and data on breast feeding and household hygiene were obtained at regular intervals. Of 497 children, 410 (82.5%) completed the three year follow-up period. The results of this study provide valuable insights into the epidemiology of cryptosporidiosis in settings with poor environmental, sanitary conditions and close human-animal contact and can be used to design targeted disease control measures in such settings.