Cyclospora cayetanensis (PCR)

A tropical parasite, imported through contaminated food (raspberries, basil). Causes prolonged diarrhoea in cycles.

How Cyclospora cayetanensis lives

Cyclospora cayetanensis is a single-celled organism for which only humans are so far known as hosts. Oocysts are excreted in the stool and are not infectious at first: outside the body, in warmth and humidity, they must mature over days to weeks. That is why people hardly ever catch it directly from others, but rather through water, fruit, salad or herbs that have been irrigated or washed with contaminated water. In regions where the pathogen is widespread, infections cluster in certain seasons, such as the rainy season. Once swallowed, the pathogens penetrate the cells of the small intestinal lining and multiply there.

How Cyclospora affects the lining of the small intestine

In the affected sections of the small intestine the lining becomes inflamed, the villi flatten, and the crypts from which new gut cells grow become enlarged. The absorptive surface therefore becomes smaller: in investigations, the absorption of fat and certain sugars was reduced. This explains the watery diarrhoea, loss of appetite and weight loss. Because the pathogens keep multiplying inside the cells over several generations, the course can drag on for weeks, with phases of improvement followed by renewed diarrhoea.

What happens when Cyclospora multiplies heavily?

With a weakened immune system, for example with advanced HIV infection, infections last longer and are more severe, and the pathogens can also affect the bile ducts. In individual case reports, inflammation of the gallbladder, reactive joint inflammation and nerve inflammation have also been described after a Cyclospora infection – consequences of an immune reaction that extends beyond the gut. In people who live in areas where it is common, repeated infections were often milder or symptom-free in studies, which suggests partial immunity.

The interpretation is given in your report.