Some, however, can cause severe disease in humans. Read more: Health check: the low-down on 'worms' and how to get rid of them. Faecal-oral transmission , where parasites found in the stool of one person end up being swallowed by another person, is the most common mode of transmission of parasitic protozoa and helminths.
The initial symptoms tend to be gastrointestinal symptoms like diarrhoea. When parasites invade the red blood cells or organs, the consequences can become more serious.
The protozoa giardia, for example, has a classic two-stage life cycle. In the first stage, called trophozoite, the parasite swims around and consumes nutrients from the small bowel. In the second stage it develops into a non-moving cyst. Cysts excreted in faeces can contaminate the water supply, and ingesting contaminated food or water results in transmission. Close human to human contact and unsanitary living conditions can promote transmission. Symptoms of giardia can include severe or chronic diarrhoea, abdominal cramps, fatigue, weakness and weight loss.
Other important protozoa are the plasmodium species. Plasmodium develop in mosquitoes, and infected mosquitoes transmit the parasite to humans by biting them.
Plasmodium destroys red blood cells which impacts organ function and causes a disease in humans known as malaria. Malaria causes the most deaths of all parasitic diseases.
Contaminated water and food are most commonly responsible for transmission. The protozoan can also be transmitted through human contact with infected animals or their feces. In the United States, outbreaks of cryptosporidiosis generally occur through contamination of the public water supply or contaminated water at water parks, swimming pools, and day-care centers.
The risk is greatest in areas with poor sanitation, making the disease more common in developing countries. Signs and symptoms include watery diarrhea, nausea, vomiting, cramps, fever, dehydration, and weight loss.
The illness is generally self-limiting within a month. Diagnosis involves direct examination of stool samples, often over multiple days.
Acid fast staining is often used. Enzyme immunoassays and molecular analysis PCR are available. The first line of treatment is typically oral rehydration therapy. Medications are sometimes used to treat the diarrhea.
The broad-range anti-parasitic drug nitazoxanide can be used to treat cryptosporidiosis. Other anti-parasitic drugs that can be used include azithromycin and paromomycin. The protozoan parasite Entamoeba histolytica causes amoebiasis , which is known as amoebic dysentery in severe cases. The disease is most widespread in the developing world and is one of the leading causes of mortality from parasitic disease worldwide.
Disease can be caused by as few as 10 cysts being transmitted. Signs and symptoms range from nonexistent to mild diarrhea to severe amoebic dysentery. Severe infection causes the abdomen to become distended and may be associated with fever. The parasite may live in the colon without causing signs or symptoms or may invade the mucosa to cause colitis.
In some cases, the disease spreads to the spleen, brain, genitourinary tract, or lungs. In particular, it may spread to the liver and cause an abscess.
When a liver abscess develops, fever, nausea, liver tenderness, weight loss, and pain in the right abdominal quadrant may occur. Chronic infection may occur and is associated with intermittent diarrhea, mucus, pain, flatulence, and weight loss. Direct examination of fecal specimens may be used for diagnosis.
They sure can. Not all of them, but some of them. And without proper medical treatment, the person may never recover. Most protist diseases in humans are caused by animal-like protists , or protozoa. Protozoa make us sick when they become human parasites. Three examples of parasitic protozoa are described below. Members of the genus Trypanosoma are flagellate protozoa that cause sleeping sickness , which is common in Africa.
They also cause Chagas disease , which is common in South America. The parasites are spread by insect vectors. The vector for Chagas disease is shown in Figure below. Then they spread to other tissues and organs. Some protozoa are parasites, which means that they need to live on or in another organism like an animal or plant to survive. For example, the protozoa that causes malaria grows inside red blood cells, eventually destroying them.
Some protozoa are encapsulated in cysts, which help them live outside the human body and in harsh environments for long periods of time. Germs: Bacteria, Viruses, Fungi, and Protozoa. Larger text size Large text size Regular text size. What Are Germs? Bacteria Bacteria are tiny, single-celled organisms that get nutrients from their environments.
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