The Sporozoa’s group of protozoan parasites are characterized by their inability to move anymore when they reach their mature form. Here are some of the commonly known parasites from this group.
Plasmodium species are responsible for malaria, the most common parasitic disease in the world infecting approximately 200 million and killing about half a million people per year according to the World Health Organization. It is transmitted by the bite of an infected female Anopheles mosquito. The parasite then migrates to the liver and ultimately infects red blood cells. This disease is widespread in a broad band of areas around the equator with the majority of the cases and the reported death in Sub-Saharan Africa, mostly in children. A wide range of symptoms can occur depending of the involved species and the severity of the infection. It can range from mild non-specific symptoms, such as fever, chills, headaches and weakness to severe and potentially fatal symptoms, such as central nervous system infection, renal failure, respiratory distress and severe anemia. Diagnosis is made by visualisation of the parasite in blood smear from the infected patient. Different anti-parasitic treatments can be used depending of the patient, the severity of the symptoms and the species involved. However, treatment is now complicated with the emergence of parasites resistant to the drugs in some countries, especially in Asia. Total recovery can be expected for patients with milder symptoms, but death occur in up to 20% of the severe infection cases, despite the treatment. Chronic infection is also possible with this parasite. Although there is no vaccine available yet for parasitic disease, a drug commonly called Malarone can be taken by people travelling to endemic countries in order to avoid being infected.
Almost half the population of the world is thought to carry the parasite Toxoplasma gondii. As such, it is one of the most common human infections worldwide. However, the vast majority of these people are asymptomatic with the exception of a mild flu-like illness occurring within the first weeks after the primary infection. However, new primary infection can be severe and even fatal for people with compromised immune system, such as AIDS carrier, and pregnant women as well as their unborn child. It is a known cause of miscarriage and stillborn child. Children infected during pregnancy can develop symptoms, such as vision loss, mental disability and seizures, later in life. Furthermore, asymptomatic toxoplasmosis can be reactivated when the immune system become compromised. People with compromised immune system present usually severe symptoms, such as confusion, fever, headaches, nausea, poor coordination and seizures. Known definitive hosts of this parasite are mainly felid, such as cats. It can be transmitted to humans by eating undercooked meat from infected animals, contaminated food or water with cat faeces, changing the cat’s litter box, blood transfusion, organ transplantation or vertically from the mother to the unborn child. Different methods are available to diagnose toxoplasmosis. However, the method of choice is usually the detection of antibodies against the parasite, but it is problematic to distinguish between past and newly acquired infection. DNA from the parasite can also be detected in the amniotic fluid of newly infected pregnant women to detect potential infection in the unborn child. Toxoplasmosis is usually treated while symptoms are present, but the parasite still remains present inside its host. Different treatments are available for pregnant women, depending if the infection is detected or not in the unborn child. Finally, children born with congenital toxoplasmosis are usually treated throughout their entire first year of life.
The Sporozoa’s also include the coccidian parasites Cyclospora cayetanensis, Cryptosporidium species and Cystoisospora belli. These parasites caused the respective intestinal illnesses cyclosporiasis, cryptosporidiosis and cystoisosporiasis. They are acquired by the ingestion of contaminated food or water with faeces from infected individuals. Cryptosporidium is also a frequent waterborne disease acquired from recreational waters. They are present worldwide, but mainly in tropical and subtropical regions. Healthy individuals are usually asymptomatic or present mild gastrointestinal symptoms. However, people with compromised immune system can be affected with severe gastrointestinal symptoms, such as extreme diarrhoea and vomiting. These parasites are diagnosed using cysts visualisation from faeces samples under the microscope. However, as cysts may not be constantly present in the faeces, samples from several days are usually necessary in order to obtain a positive diagnosis. These diseases can be cured without treatment or are easily treatable with anti-parasitic drugs, but relapses are common for people with compromised immune system. Furthermore, hydration is indicated for patients with more severe symptoms. They are also usually easily preventable by good hygiene, such as hand washing.
Sources: Centers for Disease Control and Prevention, World Health Organization