Balantidiasis

Epidemiology

 

The parasite is mainly spread fecal-orally through the contamination of food and water. Pigs, higher primates, rodents, sheep, and horses are all reservoirs, but the main reservoir relevant to humans is pig. In areas where humans are in close contact with pigs, there are higher rates of infection since the parasite is found in 20-100% of pigs in various populations. It can also be spread person to person, but that is not the main mode of transmission. It lives in the lumen of the intestine and carriers can be asymptomatic, yet still infectious. There is no vector since the parasite, in its cyst form, directly infects individuals that consume contaminated water or food containing it. The incubation period is not known, but it can be up to several days. In addition, the cysts can remain viable in the environment for months.

In terms of distribution, it is known to be found worldwide. It can be found as far north as Sweden, Finland, and Northern Russian, but it is more prevalent in tropical or subtropical regions. There are frequent reports in Central and South America as well as the Philippines, Papua New Guinea, Central Asia, and some Pacific Islands. This infection is not very common and prevalence is usually estimated at less than 1%. However, in areas where people live in close contact to pigs, such as Papua New Guinea, infection rates among swine herders and slaughterhouse workers are as high as 28%.

The occurrence of Balantidiasis in western countries is very rare, while in Islamic countries, where pigs are considered untouchable, the incidence is essentially nonexistent, except for Iran. The reports in Iran could possibly be explained by the contamination of soil and water due to the presence of wild boars in rural areas.