Parasitology 2 Flashcards
What is the classification of Trypanosoma?
Kingdom: Protista
Subkingdom: Protozoa
Phylum: Sarcomastigophora
Subphylum: Mastigophora
Class: Zoomastigophora
Order: Kinetoplastida
Family: Trypanosomatidae
Section: Salivaria
Genus: Trypanosoma
Species: brucei
Subspecies: gambiense, rhodesiense
What are the general characteristics and structure of a Trypanosoma trypomastigote?
A trypomastigote is 14 to 33 µm long, has a tiny kinetoplast at the posterior end, a centrally located nucleus, an undulating membrane, and a flagellum. It is the only stage found in patients. Humans are the main host except for T. b. brucei.
What causes African Sleeping Sickness, and how is it transmitted?
African Sleeping Sickness is caused by protozoan parasites of the genus Trypanosoma and is transmitted to humans by the tsetse fly (Glossina genus). Specifically, T. brucei rhodesiense causes East African trypanosomiasis, and T. brucei gambiense causes West African trypanosomiasis.
Describe the symptoms and illness progression of T. brucei gambiense trypanosomiasis.
- Early symptoms: Fever, rash, swollen lymph nodes, fatigue, headaches.
- Late symptoms: Weight loss, confusion, personality changes, daytime sleepiness with nighttime sleep disturbances, neurologic problems.
- Untreated progression: Coma and death after several years.
Where is African trypanosomiasis found, and what is its current epidemiological status?
It is found in 36 sub-Saharan African countries, especially in rural areas dependent on agriculture, fishing, animal husbandry, or hunting. Currently, less than 10,000 new cases are reported yearly, although many go undiagnosed and unreported.
How is African trypanosomiasis diagnosed?
Diagnosis relies on microscopy to find parasites in body fluids or tissues. T. b. rhodesiense is detected in blood, while T. b. gambiense is found in lymph node aspirates. Serologic testing is used for screening; definitive diagnosis requires microscopic observation of parasites.
What are the economic impacts of Trypanosomiasis?
Trypanosomiasis significantly impacts agriculture in Africa, particularly affecting cattle, leading to reduced meat and milk production and decreased agricultural productivity due to less draught power.
What is Trypanosoma cruzi, and what disease does it cause?
Trypanosoma cruzi is a parasite that causes Chagas disease, a devastating human disease found in the Americas.
What are the registered drugs for treating Human African Trypanosomiasis (HAT)?
- Pentamidine: T. b. gambiense
- Suramin: T. b. rhodesiense
- Melarsoprol: Both gambiense and rhodesiense infections
- Eflornithine: Only T. b. gambiense
- Fexinidazole: All oral drug for T. gambiense, introduced in 2020
Why is the immune response to Trypanosoma brucei ineffective?
T. brucei is not killed by the immune system due to its thick glycoprotein (VSG) coating, which makes it hard to recognize. Frequent antigenic variation also allows the parasite to evade the immune response.
What are the modes of transmission and geographical distribution of Ascariasis?
Transmission occurs mainly via ingestion of water or food contaminated with Ascaris lumbricoides eggs. It has a worldwide distribution but is especially prevalent in underdeveloped countries with poor sanitation.
Describe the life cycle of Ascaris lumbricoides.
The life cycle includes the following stages:
- Eggs are laid in the small intestine and passed out through feces.
- Eggs develop into L1 and L2 larvae outside the host.
- Ingested eggs hatch in the small intestine, and larvae migrate to the liver, heart, and lungs.
- Larvae are coughed up, swallowed, and return to the small intestine to mature and mate.
What are the symptoms associated with Ascariasis?
- Migration of larvae: Eosinophilic pneumonia, cough, breathing difficulties.
- Adult parasites in the intestine: Usually asymptomatic, but can cause abdominal discomfort, nausea, and malnutrition in severe cases.
How is Ascariasis diagnosed and treated?
Diagnosis is done through stool microscopy, eosinophilia detection, and imaging techniques. Treatment includes antiparasitic medications such as mebendazole, albendazole, pyrantel pamoate, ivermectin, piperazine citrate, and levamisole.
