Transmission of Cryptosporidium spp. among human and animal local contact networks in sub-Saharan Africa: a multi-country study.

INTRODUCTION: Cryptosporidiosis has been identified as one of the major causes of diarrhoea and diarrhoea-associated deaths in young children in sub-Saharan Africa. This study traces back Cryptosporidium positive children to their human and animal contacts to identify transmission networks. METHODS: Stool samples were collected from children below five years with diarrhoea in Gabon, Ghana, Madagascar and Tanzania. Cryptosporidium positive and negative initial cases (IC) were followed to the community, where stool samples from households, neighbours and animal contacts were obtained. Samples were screened for Cryptosporidium spp. by immunochromatographic tests and by sequencing the 18S rRNA gene and further subtyped at the 60 kDa glycoprotein gene (gp60). Transmission clusters were identified and risk ratios (RR) calculated. RESULTS: In total, 1,363 paediatric ICs, 184 (13%) were diagnosed with Cryptosporidium spp. One hundred eight contact networks were sampled from Cryptosporidium positive and 68 from negative ICs. Identical gp60 subtypes were detected amongst two or more contacts in 39 (36%) of the networks from positive ICs and in one (1%) from negative ICs. In comparison to Cryptosporidium negative ICs, positive ICs had an increased risk of having Cryptosporidium positive household members (RR = 3.6; 95%-confidence interval (CI): 1.7-7.5) or positive neighbouring children (RR = 2.9; 95%-CI: 1.6-5.1), but no increased risk of having positive animals (RR = 1.2; 95%-CI: 0.8-1.9) in their contact network. CONCLUSION: Cryptosporidiosis in rural sub-Saharan Africa is characterized by infection clusters among human contacts, to which zoonotic transmission appears to contribute only marginally.