Protozoan Infections and Entamoeba histolytica

Protozoan Infections

• Diagnosis is by detection of cysts in the faeces, requiring several samples taken at different times due to irregular shedding.

Treatment

• Infection is usually self-limiting, but may be treated with metronidazole if necessary.

Entamoeba Histolytica

• Found worldwide, but most prevalent in subtropical and tropical countries, where it can exceed 50% prevalence.
• Trophozoite stages live in the large intestine and reproduce by binary fission.
• Resistant encysted forms are produced and passed out of the body, contaminating food and drink.

Protozoan Infections Table

• GI Tract: Cryptosporidium, Giardia, Entamoeba (ingestion)
• Blood: Plasmodium, Trypanosoma (insect bite)
• Lung: Pneumocystis (inhalation)
• Vagina: Trichomonas (contact)
• All Tissues: Toxoplasma (ingestion)

Leishmania

• Causes cutaneous disease characterized by a large ulcer developing from a small papule on the skin.
• Heals with scarring, leaving the patient relatively immune to further infection.
• Also known as Baghdad boil and Delhi sore.
• In immunodeficient patients, cutaneous leishmaniasis resembles leprosy, with visceral leishmaniasis being a major complication of HIV in the tropics.

Trichomonas Vaginalis

• Normally a non-pathogenic flora of the vagina, but can cause trichomonas vaginitis.
• Symptoms include itching, burning, and foul-smelling discharge.
• Men may be asymptomatic carriers, with possible inflammation of the urethra.

Giardia Lamblia (Duodenalis)

• Formerly known as G.intestinalis.
• Trophozoites have 2 nuclei, giving a characteristic owl's face.
• Causes giardiasis (beaver fever).
• Inhabits the lumen of the duodenum or upper ileum.
• Carriage can range from asymptomatic to malabsorption syndrome.
• Onset is associated with watery, but not bloody, diarrhoea.

Morphology of T. Vaginalis

• Ovoid shape
• 4 free anterior flagella
• 5th flagellum is recurved and attached to the body, forming an undulating membrane
• Single nucleus
• No mitochondria, with energy generated by hydrogenosomes

Diagnosis, Prevention, and Treatment of T. Vaginalis

• Diagnosed by microscopy of vaginal swab
• Prevented by good toilet hygiene, safe sex, and not sharing clothes or toilet articles
• Treated with metronidazole for both partners

Route of Infection of T. Vaginalis

• Cysts are shed in human and animal faeces
• Infection arises from ingesting cysts, which excyst in the host's gut
• Spread can be person-to-person in unsanitary conditions
• Most common route is by drinking improperly treated water
• 6,000 cases per annum in England and Wales

Chagas Disease

• Caused by T.cruzi spread by reduviid bug (kissing bug) in poor areas
• All species of mammal act as reservoirs of infection
• Parasite can live in host macrophages and cardiac muscle cells
• Causes chronic disease involving the heart and intestinal tract
• Death often results from myocarditis

Leishmania

• Causes disease in South and central America, India, Middle East, Africa, and the Mediterranean coast
• Old world leishmaniasis: dogs act as reservoirs of infection
• Two types of disease: visceral (liver and spleen) and cutaneous
• Caused by different species
• Visceral causes chronic disease, kala-azar with eventual liver failure

Sleeping Sickness

• Caused by T.brucei, spread by the tsetse fly, and restricted to equatorial Africa
• Parasite remains extracellular in the tissues near the insect bite and then in the blood
• Swollen chancre appears near the bite, with swollen lymph nodes in the neck
• Parasite spreads rapidly in the blood, causing fever, splenomegaly, and heart involvement
• Headache, psychological changes, and then coma

Trypanosomes

• Three species of flagellated protozoan Trypanosomes cause disease:
  • T.brucei gambiense
  • T.brucei rhodiense cause African trypanosomiasis or sleeping sickness
  • T.cruzi causes South American trypanosomiasis, Chagas disease

This quiz covers the detection, treatment, and characteristics of protozoan infections, specifically Entamoeba histolytica. Learn about the diagnosis and management of this intestinal protozoan infection.