Protozoan disease

Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected female Anophelesmosquitoes. It is preventable and curable. There are 5 parasite species that cause malaria in humans, and 2 of these species – Plasmodium falciparumand Plasmodium vivax– pose the greatest threat. In 2020, nearly half of the world's population was at risk of malaria. Most cases and deaths occur in sub-Saharan Africa. However, the WHO regions of South-East Asia, Eastern Mediterranean, Western Pacific, and the Americas also report significant numbers of cases and deaths. There were an estimated 247 million cases of malaria in 2021, and the estimated number of malaria deaths stood at 619 000. The WHO African Region carries a disproportionately high share of the global malaria burden. In 2020, the region was home to 95% and 96% of malaria cases and deaths, respectively. Children under 5 years of age are the most vulnerable group affected by malaria; in 2021, they accounted for nearly 80% of all malaria deaths in the WHO African Region. Malaria is an acute febrile illness. In a non-immune individual, symptoms usually appear 10–15 days after the infective mosquito bite. The first symptoms – fever, headache, and chills – may be mild and difficult to recognize as malaria. If not treated within 24 hours, Plasmodium falciparummalaria can progress to severe illness, and lead to death. Children with severe malaria frequently develop one or more of the f...

\( \newcommand\) • • • • • • • • • • skills to develop • Identify the most common protozoans that can cause infections of the GI tract • Compare the major characteristics of specific protozoan diseases affecting the GI tract Like other microbes, protozoa are abundant in natural microbiota but can also be associated with significant illness. Gastrointestinal diseases caused by protozoa are generally associated with exposure to contaminated food and water, meaning that those without access to good sanitation are at greatest risk. Even in developed countries, infections can occur and these microbes have sometimes caused significant outbreaks from contamination of public water supplies. Giardiasis Also called backpacker’s diarrhea or beaver fever, giardiasis is a common disease in the United States caused by the flagellated protist Giardia lamblia, also known as Giardia intestinalis or Giardia duodenalis ( G. lamblia uses a large adhesive disk to attach to the intestinal mucosa. The disk is comprised of microtubules. During adhesion, the flagella of G. lamblia move in a manner that draws fluid out from under the disk, resulting in an area of lower pressure that promotes its adhesion to the intestinal epithelial cells. Due to its attachment, Giardia also blocks absorption of nutrients, including fats. Transmission occurs through contaminated food or water or directly from person to person. Children in day-care centers are at risk due to their tendency to put items into their mo...

Learning Objectives • Identify the most common protozoans that can cause infections of the GI tract • Compare the major characteristics of specific protozoan diseases affecting the GI tract Like other microbes, protozoa are abundant in natural microbiota but can also be associated with significant illness. Gastrointestinal diseases caused by protozoa are generally associated with exposure to contaminated food and water, meaning that those without access to good sanitation are at greatest risk. Even in developed countries, infections can occur and these microbes have sometimes caused significant outbreaks from contamination of public water supplies. Protozoan Gastrointestinal Infections Protozoan GI infections are generally transmitted through contaminated food or water, triggering diarrhea and vomiting that can lead to dehydration. Rehydration therapy is an important aspect of treatment, but most protozoan GI infections can also be treated with drugs that target protozoans. Figure \(\PageIndex\): Protozoan infections of the GI tract.

Trypanosoma Protozoa 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 Figure Trypanosoma parasites enter a person’s blood when the vector bites. Then they spread to other tissues and organs. The diseases may be fatal without medical treatment. Vector for Chagas Disease. In Chagas disease, the Trypanosoma parasite is spread by an insect commonly called the “kissing bug.” A bite from this bug could be the kiss of death. The discovery of Chagas disease is unique in the history of medicine. That’s because a single researcher—a Brazilian physician named Carlos Chagas—single-handedly identified and explained the new infectious disease. In the early 1900s, Chagas did careful lab and field studies. He determined the pathogen, vector, host, symptoms, and mode of transmission of the disease that is now named for him. Plasmodium Protozoa Plasmodium protozoa cause malaria. The parasites are spread by a mosquito vector. Parasites enter a host’s blood through the bite of an infected mosquito. The parasites infect the host’s red blood cells, causing symptoms such as fever, joint pain, anemia, and fatigue. Malaria is common in tropical and subtropical climates throughout the world (see Figure Worldwide Distribution of Malaria. This map shows where malaria is found. The area is determined by the mosquito vector. The mosquito c...

• Equine protozoal myeloencephalitis (EPM) is caused by the protozoal parasites Sarcocystis neurona and Neospora hughesi, although most cases are due to S. neurona. • The definitive host for S. neurona is the opossum, and horses become infected when they ingest feed or water contaminated with opossum feces. • An estimated 50-90% of horses in the U.S. have been exposed to the organism, but only a small percentage (typically <1%) develop EPM. • A thorough neurologic examination and diagnostic testing are required to distinguish between EPM and other neurologic diseases that can have similar clinical signs. *Download a printable pdf of this article Equine protozoal myeloencephalitis is caused by infection of the central nervous system with the protozoan parasites Sarcocystis neurona and, less commonly, Neospora hughesi. It is often a progressively debilitating disease and can affect any part of the nervous system, from the front of the cerebrum to the end of the spinal cord. Equine protozoal myeloencephalitis is considered the most prevalent cause of neurologic disease of horses in the Americas. The range of the opossum, the definitive host of S. neurona, defines the geographic range of clinical EPM in horses. In areas where the opossum is common, approximately 50% of horses are seropositive (have antibodies to the parasite in the blood), indicating exposure to the organism. Opossums shed the infective sporocysts (egg-like stages of development) in their feces. Horses become ...

Overview Trichomoniasis is a common sexually transmitted infection caused by a parasite. In women, trichomoniasis can cause a foul-smelling vaginal discharge, genital itching and painful urination. Men who have trichomoniasis typically have no symptoms. Pregnant women who have trichomoniasis might be at higher risk of delivering their babies prematurely. Treatment for trichomoniasis is taking an antibiotic — either metronidazole (Flagyl), tinidazole (Tindamax) or secnidazole (Solosec). To prevent being infected again, all sexual partners should be treated at the same time. You can reduce your risk of infection by using condoms correctly every time you have sex. Symptoms Most people with trichomoniasis have no signs or symptoms. However, symptoms may develop over time. When signs and symptoms develop, they are different for men and women. In women, trichomoniasis signs and symptoms include: • A large amount of a thin, often foul-smelling discharge from the vagina — which might be clear, white, gray, yellow or green • Genital redness, burning and itching • Pain with urination or sex • Discomfort over the lower stomach area In men, trichomoniasis rarely causes symptoms. When men do have signs and symptoms, however, they might include: • Itching or irritation inside the penis • Burning with urination or after ejaculation • Discharge from the penis When to see a doctor See your health care provider if you have any symptoms of trichomoniasis or if you become aware that a sexual ...

The most important intestinal protozoan infections are amoebiasis ( Entamoeba histolytica), giardiasis ( Giardia lamblia), cryptosporidiosis ( Cryptosporidium sp), cyclosporiasis ( Cyclospora cayetanensis) and isosporiasis ( Isospora belli). Intestinal protozoa are transmitted by the faecal-oral route (soiled hands, ingestion of food or water contaminated with faeces) and may cause both individual cases of diarrhoea and epidemic diarrhoea outbreaks. Clinical features • Amoebiasis gives rise to bloody diarrhoea (see • Clinical presentation of giardiasis, cryptosporidiosis, cyclosporiasis and isosporiasis is very similar: • Diarrhoea is usually mild and self-limiting, except in children and patients with advanced HIV disease (CD4 < 200). These patients are likely to develop severe, intermittent or chronic diarrhoea that may be complicated by malabsorption with significant wasting (or failure to gain weight in children) or severe dehydration. • Stools are usually watery, but steatorrhoea (pale, bulky, fatty stools) may be found in the event of secondary fat malabsorption; stools may contain mucus. • Diarrhoea is usually associated with non-specific gastrointestinal symptoms (abdominal distension and cramps, flatulence, nausea, anorexia), but patients have low-grade fever or no fever. Laboratory Definitive diagnosis relies on parasite identification in stool specimens (trophozoites and cysts for giardia; oocysts for cryptosporidium, cyclospora, isospora). Two to three samples,...