The hatching period of protozoa is longer than in the case of bacterial and viral infections. Therefore, it is very difficult to associate changes in the functioning of the organism with the carrier of the intestinal protozoa. In this post, we describe the most common unicellular parasites of the gastrointestinal tract.

Cyclospora cayetanensis

Cyclospora cayetanensis is a coccidial parasite causing acute diarrhoea. The parasite causes histopathological changes in the upper part of the small intestine. Diarrhoea may be self-limiting in immunocompetent, immune-responding individuals, but it may also be prolonged and last for weeks. The disease is very severe in immunocompromised people, especially HIV-positive patients.

Clinical symptoms: mild nausea, abdominal cramps, anorexia, watery diarrhoea, flatulence.

Giardia Lamblia

Giardia lamblia is flagellate that lives in the duodenal and jejunum epithelium of humans and most mammals. The mechanism of the spread of parasites is the faecal-oral route. Infection is initiated by the ingestion of cysts. The transfer of cysts is often facilitated by environmental contamination of food and water. Therefore, infection with G. lamblia occurs through the consumption of contaminated and undercooked vegetables and fruit, as well as through interpersonal contacts like oral-anal sexual practices. Infection with Giardia spp. can lead to both asymptomatic carriage and symptomatic disease – ranging from mild diarrhoea to even severe malabsorption syndrome.

Clinical symptoms: watery diarrhoea alternating with constipation and fatty stools, emaciation, physical underdevelopment, fatigue, malaise, flatulence, abdominal pain and digestive disorders.

Entamoeba histolytica

Entamoeba histolytica is the etiological cause of amoebic colitis. Patients infected with E.histolytica produce non-invasive trophozoites and invasive cysts in the stools. By dividing in the large intestine, trophozoites lead to extensive necrosis as a result of attachment to the host cells. Sexual transmission of trophozoite may occur, resulting in cutaneous amoebiasis. The cysts themselves, on the other hand, are most often transmitted by flies, cockroaches and asymptomatic vectors.

Clinical symptoms are most often associated with localized destruction of the colon tissue: abdominal pain, cramps, and colitis with diarrhoea. The severe form of the disease is manifested by numerous bloody stools throughout the day. In patients with parenteral amoebiasis, there are parenteral symptoms, such as fever, chills, and leukocytosis. The liver is mainly affected, which is associated with the removal of trophozoites passing through this organ from the blood.

Cryptosporidium spp.

Cryptosporidium spp. are parasitic protozoa that live in the brush border of the intestinal epithelium. Coccidia, by attaching to the surface of cells, replicate through a series of processes leading to the production of new invasive oocysts. Mature oocysts can spread through the host’s gastrointestinal tract leading to the invasion of new cells, or they can be excreted into the environment. The most common infectious species in humans are C. hominis and C. parvum. The spreading mechanism consists of the faecal-oral and oral-anal routes. In immunocompetent patients, the disease is usually mild, manifested by inflammation of the small intestine and colon accompanied by watery diarrhoea without blood. However, in immunocompromised patients, infection is manifested by frequent stools (> 50) per day and a loss of large amounts of fluid.

Clinical symptoms: diarrhoea.

Blastocystis hominis

Blastocystis hominis is an anaerobic protozoan sporadically living in the gastrointestinal tract. The mechanism of the spread of these parasites is the faecal-oral and alimentary pathways. The factor contributing to infection is travelling to countries with low sanitary and hygienic standards. The clinical picture of patients is very diverse – from asymptomatic to gastrointestinal disorders.

Clinical symptoms: chronic, less frequently acute diarrhoea, weight loss, headaches.

Dientamoeba fragilis

Dientamoeba fragilis are pathogenic parasites that colonize the cecum and upper colon. The spreading mechanism consists of the faecal-oral and oral-anal routes. Most infections with Dientamoeba fragilis are asymptomatic, although some patients may develop a symptomatic disease with abdominal discomfort, flatulence, recurrent diarrhoea, anorexia and weight loss.

Clinical symptoms: diarrhoea and abdominal pain.

The genXone offer includes a molecular Real-Time PCR test identifying all the above-mentioned intestinal protozoa, as well as a panel diagnosing viral, bacterial and protozoal infection.