It is possible to acquire parasites in developed countries. However they are usually less common than in developing countries partly because of the temperate climate and better hygiene and infrastructure, including sanitation system and food inspection. However, some parasitic diseases are still endemic in developed countries. It is important to note that this post concern mainly parasites present in the United States as it is easier to obtain public data from this country. These parasites can still be present in other developed countries as they are usually present worldwide.
Trichomonas vaginalis, responsible for the sexually transmitted disease trichomoniasis, is the most common protozoan parasites in developed countries. For instance, the Centers for Disease Control and Prevention estimate that 1.1 million new cases of infection occur each year only in the United States. Prevention by wearing a condom during sexual intercourse is important, as men are mostly asymptomatic.
Toxoplasma gondii is though to infect half the population of the world, but is asymptomatic for healthy individuals. For instance, the Centers for Disease Control and Prevention estimate that more than 60 million people are chronically infected with this parasite. It is mainly transmitted by contact or ingestion of food or soil contaminated with cat’s faeces. As such, changing the cat’s litter box can also cause this infection. Newly acquired infection is a great concern for pregnant women as it can cause disease or even death for the unborn child. Furthermore, it can cause a severe disease for people having compromised immune system.
Cryptosporidiosis, a gastrointestinal illness caused by the parasite Cryptosporidium, is a frequent waterborne disease acquired from recreational waters, as it can be resistant to chlorine treatments, or from ingestion of untreated water. It is actually one of the leading causes of waterborne disease in the United States.
Giardiasis, caused by Giardia intestinalis, is also frequent in developed countries, especially in the United States. It occurs more often in the summer where outdoors activities, such as backpacking and travelling in the wilderness, are more common. Drinking untreated water, for instance from lakes or rivers, is considered as a transmission mode for this parasite.
Hookworms, including the parasite Necator americanus in the United States and the less frequent parasite Ancyclostoma duodenale in Europe, are transmitted by contact with contaminated soil. These parasitic diseases are seen occasionally in developed countries and are more frequent in children from economically challenged rural areas.
Foodborne parasitic diseases can also be found in developed countries, but are now less frequent because of the strict regulation in the food industry. They include trichinosis caused by Trichinella spiralis and present in undercooked pork and the parasite Taenia acquired from the ingestion of undercooked or raw pork or beef. Few non-endemic infection cases can also be linked to the ingestion of contaminated imported food, such as the trematode Clonorchis sinensis, also known as the Chinese liver fluke, present in raw or undercooked imported fish from Asia.
Rare infections, such as Acanthamoeba keratitis linked to the misuse of contact lens can also occur in developed countries. The extremely rare and almost always fatal primary amoebic meningoencephalitis caused by Naegleria fowleri has also been observed in the United States. Actually, 133 cases have been reported in this country in the last 50 years, representing almost half of the global reported cases. This disease is caused by the passage of contaminated water from warm fresh sources through the nose.
It is noteworthy that some parasites, such as Leishmania, are not considered to be endemic in developed countries. However, they are able to infect and cause opportunistic diseases in people with compromised immune system, such as AIDS patients.
Sources: Centers for Disease Control and Prevention, World Health Organization