Emerging protozoal pathogens in India: How prepared are we to face the threat?

Emerging protozoal pathogens have become a major threat to human health. The number of protozoal pathogens causing human disease has been on the rise since the last two to three decades. Significant increase in the number of immunocompromised people, increase in international travel, deforestation, and widespread urban dwellings are some of the factors contributing to this changing epidemiology of protozoal diseases. Apart from Naegleria and Acanthamoeba, other free-living amoebae like Balamuthia and Sappinia are being reported to cause meningoencephalitis in humans. Plasmodium knowlesi, a zoonotic malarial parasite, has become a major cause of human malaria in Southeast Asia. Trypanosoma evansi and Trypanosoma lewisi, which normally infect horses and rodents respectively, have been reported to cause human trypanosomiasis in India. Balantidium coli is emerging as an important cause of dysentery especially in the immunocompromised population. In India, where a significant proportion of population lives in close proximity to cattle and pigs, B. coli can emerge as a significant pathogen in cases of dysentery, especially in the immunocompromised population. Babesia microti has become an important cause of transfusion transmitted babesiosis (TTB) in countries like the United States. As Babesia can be misdiagnosed as Plasmodium and blood transfusion is becoming common in India, it is necessary to develop diagnostic tests to rule out this pathogen in blood donors. Increased awareness among clinicians, pathologists, and microbiologists along with other factors like constant surveillance, improved diagnostic tests, and a high index of suspicion are important to detect and properly treat such emerging protozoal pathogens in humans.