October 27, 2023

expert comment on Cryptosporidium infections

Scientists react to a spike in Cryptosporidium infections in the UK. 

Prof Paul Hunter, Professor of Health protection, UEA, said:  

“Cryptosporidium is a protozoan parasite, of which two species predominantly cause disease in humans. C. parvum infections affect many different mammal species but its main host is cattle. C. hominis mainly only infects humans.

“Cryptosporidium causes diarrhoea which usually lasts longer than other causes and can lead to significant weight loss in some. Most infections are in children, but cryptosporidiosis can occur in people of all ages. Most people recover eventually with or without treatment, though some go onto have more prolonged symptoms or suffer relapses of diarrhoea for some weeks.

“In low income countries it can be very severe in malnourished children and is a leading cause of death in children under 2 years, but not in Europe. In immune suppressed people such as those living with AIDS it can also be severe and occasionally fatal. There is no vaccine for human use and drug treatment can reduce the duration of diarrhoea but doesn’t reliably cure the infection.

“Outbreaks of Cryptosporidium infection have been associated with drinking water contaminated by human sewage or animal manure. Outbreaks have also been linked to swimming pools, unpasteurised milk, foods especially salads. The infection has also caused outbreaks in child care settings.

“The current wave of infection is mainly due to C. hominis, the predominantly human infection. Many cases of C. hominis, but not C. parvum are linked to recent foreign travel, especially to Spain and also swimming pools. Ireland has also seen an increase of infections this year.

“The big question with the current surge in infections is what is driving the current wave of infection. Are cases are up because C. hominis has been virtually absent since soon after the start of the pandemic and this is an example of the “immunity gap” which was talked about a lot last year for flu and RSV? Or is this due to increased exposure, perhaps linked to overseas travel and swimming pools. There has very recently been a big drinking water outbreak in Spain, but not in an area close to the Med. I suspect that infections were up because of the immunity gap but that then increased contamination of swimming pools which in turn led to more infections and the cycle continues.”

Declared interests

Prof Paul Hunter: I have just finished a grant funded by the European Union INTERREG programme on Cryptosporidium infections in cattle.