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Cryptosporidia are mainly transmitted from child to child. The close coexistence with farm animals is not of great importance, contrary to what has been assumed so far. This is the conclusion reached by a research group of the Bernhard Nocht Institute for Tropical Medicine. The Infection Epidemiology Group, led by Daniel Eibach and Ralf Krumkamp, has carried out the largest study on cryptosporidia to date and recently published its work in the journal Clinical Infectious Deseases.
Diarrhoeal diseases are still one of the major causes of child mortality in developing countries. Most of them are caused by rotaviruses, immediately followed by so-called cryptosporidia. In South Asia and sub-Saharan Africa alone, the parasite is responsible for 200,000 deaths per year in children under two years of age. It is also associated with secondary diseases in more than 7 million children in these regions.
The research group led by Daniel Eibach and Ralf Krumkamp conducted extensive studies on transmission mechanisms in the four African countries Gabon, Ghana, Tanzania and Madagascar. They took stool samples from children in study hospitals to examine them for cryptosporidia. Cryptosporidium-positive and also -negative children were traced back to their communities. Here they collected stool samples from household members and from neighbouring households. They also included samples from pets. The researchers then examined these samples for cryptosporidia. If the results were positive, they identified specific gene sequences, compared them with each other and reconstructed transmission paths. In this way, the research group identified transmission chains and determined the risk of infection through household contact, contact in the neighbourhood or contact with animals.
The authors found that neighbouring children under five years of age showed the highest risk of cryptosporidia transmission. The infection is mainly passed from child to child. The zoonotic transmission through animals played a minor role, said Ralf Krumkamp: "This is important information for containing the spread of cryptosporidia in rural sub-Saharan Africa and also in other regions: The problem is not so much the close coexistence of humans and animals. What is more important is good sanitation, clean water and hygiene."
So far there is no vaccine or specific medication against cryptosporidia. Apart from severe diarrhoea, an illness can lead to growth retardation and disabilities and thus put a lasting strain on a child's development.