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Microsporidia common in China – in humans, farm animals and water

December 07 2018

About 90% of human cases of microsporidiosis are caused by Enterocytozoon bieneusi, which was first described in AIDS in 1995. Microsporidia are opportunistic obligate intracellular fungi, with one of the smallest fungal genomes at ~6Mb.  Of the 1300–1500 formally described species of microsporidia within 187 genera, four cause almost all human disease: E. bieneusi and three Encephalitozoon species (E. cuniculi, E. intestinalis, and E. hellem).

Microsporidiosis comprises many different clinical syndromes including both chronic and acute diarrhoea (worse in AIDS and immunocompromised patients), malabsorption, respiratory infection, acalculous cholecystitis and keratitis.

In a recent review of ~100 papers from China, Sha-Sha Wang and colleagues from Yangling, Shaanxi Province and Zhengzhou, Henan province, show than E. bieneusi is common in China, in most localities studied. Detection rates in children with diarrhoea ranged from 1% in Wuhan to 23% in Changchun.  In HIV positive patients, detection rates varied from 4% to 12%.

E. bieneusi is also commonly found in cattle (and water buffalo and Yaks), in sheep, goats and pigs, as well as many domestic animals such as dogs, cats,  rabbits chickens and ducks. It is no surprise therefore that E. bieneusi is commonly found in water. Combined detection rates in sewage, drinking water and rivers vary from 32% to 100%. They found 361 different genotypes based on ITS sequences including novel genotypes, some apparently restricted to certain hosts.

The only medication effective for microsporidiosis is fumagillin (a secondary metabolite of Aspergillus fumigatus) is unfortunately to toxic to administer as therapy. So no useful treatment exists currently for microsporidiosis

References

Prevalence and genotypes of Enterocytozoon bieneusi in China. Wang SS, Wang RJ, Fan XC, Liu TL, Zhang LX, Zhao GH. Acta Trop. 2018 Jul;183:142-152.