Protozoa post-midterm Flashcards
How are Glossina vectors attacked in west africa?
Larvae are laid in moist soil along rivers, so people often spray insecticides along the vegetation where the flies rest. This can result in aquatic contamination
How have some people constructed Tsetse fly traps that take advantage of their blood seeking abilities?
They are most stimulated by contrast and movement, so people construct large traps out of blue tarp (Sprayed with insecticide) with a black tarp over the front
Out of 20 species of tsetse flies, about ____ can transmit. That means the others are ______.
5.
Refractory
What is the taxonomic breakdown of the vectors of Chagas disease?
They are members of the subfamily Triatominae, of the family Reduviidae, of the Hemiptera
What are the most important/famous species that acts as a vector for Chagas disease?
Rhodnius prolixus
Triatoma infestans
How is Chagas disease actually transmitted, in detail?
When the organism is feeding blood from a host, they must reduce the amount of blood they take in so they may fly after. During feeding, they filter plasma and other junk from blood and then shit it onto you. This is how the parasite is transmitted. After a bite, your skin will be itchy, so as you scratch the parasites can enter your body
What is the causative agent of Chagas disease?
Trypanosoma cruzi
Chagas disease is a _____notic disease
Zoonotic
Describe the life cycle of T. cruzi
Bug is infected by feeding on infected blood. Parasites multiply and differentiate in the insect gut to become infective metacylic trypomastigotes. They are release via insect feces to the site of the bite wound. Once in the body, they infect cells, particularly white blood cells. Here they become intracellular amastigotes. After this, they form a “pseudocyst” and are stimulated to become trypomastigotes once more. They cannot replicate in the blood at all, but they will move to other cells such as the liver, but they main problem is that they sometimes attack muscle cells and nerve cells.
They never divide in trypomastigote form
Why are the vectors for Chagas disease called “kissing bugs”?
Because they often bite near the mouth due to an affinity for CO2
How does T. cruzi enter the body
they may enter the body through a scratch. They can also enter through mucous membranes, which happens often because the insects like to bite near the nose, mouth and eyes. Sometimes they may be transmitted through blood transfusion, via the placenta, or in lab accidents
Where is Chagas disease distributed?
Americas, from southern USA to Southern Argentina. Usually in poor, rural areas of Central/South America.
What are the two forms of Chagas disease?
Transient, acute disease which can be followed by a chronic, asymptomatic period before suddenly showing symptoms
Acute disease - only lasts a little while, never returns
What kinds of alternate hosts are there for T. cruzi?
Opposums, sloths, armadillos
Describe what “pseudocysts” are in reference to Chagas disease
Pockets of amastigote T. cruzi that form in the muscle tissues
Why is chagas disease so difficult to diagnose?
It’s hard to do any diagnosing when there are frequent power cuts (no PCR), long term biopsy waits, no microscopes, no small animals to innoculate
How is chagas diagnosed?
Microscopic examination of blood for motile parasites or of blood smears stained with Giemsa. Or inoculation into mice, culture in special media, or xenodiagnosis
What does the term “xenodiagnosis” mean in relation to chagas disease?
Uninfected reduviid bugs are fed on patient’s blood, gut contents examined 4 weeks later
What is unique about chagas disease treatment?
Treatment starts before confirmatory diagnosis based on epidemiological evidence and symptoms. People die too quickly to wait for diagnosis
Describe the symptomatic chronic stage of chagas disease?
May take years-decades to occur. Includes cardiomyopathy, megaesophagus/megacolon (smooth muscle infected, can’t retain shape), weight loss
Describe the symptoms associated with the acute stage of Chagas disease
Localised lesion at the site of inoculation (chagoma). It is usually asymptomatic but may have anorexia, fever, myocarditis, lymphadenopathy, hepatosplenomegany
How is chagas disease treated?
With “Nitrofurans” such as benznidazole/nifurtimox, which produce “free radicals”. T. cruzi are sensitive to free radicals because they lack enzymes necessary to break them down. Ketoconazole is in antifungal that is also being used (under the table, not approved).
Treatment is usually effective in the acute stage but no medication has been proven to be effective in the chronic stage.
__________ are places where organisms naturally live
“ecotopes”
How does house construction in endemic areas contribute to Chagas disease rates?
Houses are often made of clay bricks with palm thatch roofs. This allows the bugs to become “nest animals”, resting in the palm thatch or cracks between bricks in the house, waiting for humans to come back
What are the primary epidemiological risk factors for Chagas disease?
Houses with cracks or thatch roofs (ex. adobe mud brick, wood), Bahareque houses (wood frame shoved with mud), close proximity to animals
Why do insects carrying Chagas disease like to live in tiny cracks?
Thigmotropism - like to be surrounded on each side by stuff
How can one make a Bahareque house that is less hospitable to bugs
Fill in cracks with clay then smooth down the clay. USe tin roof.
Can also paint house with insecticide
How is chagas disease a big drain on the economy of countries in which it is common?
Costs a lot to prevent and treat it, chronic disease results in people who cannot work
Why is it that just addressing human chagas disease isn’t an effective control method?
Other vertebrate reservoirs exist, such as possums, pigs, goats, dogs, cats, armadillos, sloths.
How can chagas rates be curbed without culling animals?
Shelters can be modified to be less hospitable to insects. Livestock animals can be kept separate from human dwellings.
T. cruzi is considered highly adaptable. Why is this?
lives in 52 species of bugs, 14 of which live in domestic/peridomestic environments. 130 mammals have been found naturally infected. Infection rates of bugs can be up to 68%. Over 20 species of palm tree also house Triatomines.
What are risk factors for chagas disease?
Roughness of walls, number of dogs, chickens, pigs in domestic/peridomestic environment, number of Triatomine habitats (ex. trash, chicken houses)
As number of chagas insect hosts goes up, feedings success goes _____
down
