Protozoa post-midterm

Question 1

How are Glossina vectors attacked in west africa?

Answer 1

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

Question 2

How have some people constructed Tsetse fly traps that take advantage of their blood seeking abilities?

Answer 2

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

Question 3

Out of 20 species of tsetse flies, about ____ can transmit. That means the others are ______.

Answer 3

5.

Refractory

Question 4

What is the taxonomic breakdown of the vectors of Chagas disease?

Answer 4

They are members of the subfamily Triatominae, of the family Reduviidae, of the Hemiptera

Question 5

What are the most important/famous species that acts as a vector for Chagas disease?

Answer 5

Rhodnius prolixus

Triatoma infestans

Question 6

How is Chagas disease actually transmitted, in detail?

Answer 6

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

Question 7

What is the causative agent of Chagas disease?

Answer 7

Trypanosoma cruzi

Question 8

Chagas disease is a _____notic disease

Answer 8

Zoonotic

Question 9

Describe the life cycle of T. cruzi

Answer 9

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

Question 10

Why are the vectors for Chagas disease called “kissing bugs”?

Answer 10

Because they often bite near the mouth due to an affinity for CO2

Question 11

How does T. cruzi enter the body

Answer 11

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

Question 12

Where is Chagas disease distributed?

Answer 12

Americas, from southern USA to Southern Argentina. Usually in poor, rural areas of Central/South America.

Question 13

What are the two forms of Chagas disease?

Answer 13

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

Question 14

What kinds of alternate hosts are there for T. cruzi?

Answer 14

Opposums, sloths, armadillos

Question 15

Describe what “pseudocysts” are in reference to Chagas disease

Answer 15

Pockets of amastigote T. cruzi that form in the muscle tissues

Question 16

Why is chagas disease so difficult to diagnose?

Answer 16

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

Question 17

How is chagas diagnosed?

Answer 17

Microscopic examination of blood for motile parasites or of blood smears stained with Giemsa. Or inoculation into mice, culture in special media, or xenodiagnosis

Question 18

What does the term “xenodiagnosis” mean in relation to chagas disease?

Answer 18

Uninfected reduviid bugs are fed on patient’s blood, gut contents examined 4 weeks later

Question 19

What is unique about chagas disease treatment?

Answer 19

Treatment starts before confirmatory diagnosis based on epidemiological evidence and symptoms. People die too quickly to wait for diagnosis

Question 20

Describe the symptomatic chronic stage of chagas disease?

Answer 20

May take years-decades to occur. Includes cardiomyopathy, megaesophagus/megacolon (smooth muscle infected, can’t retain shape), weight loss

Question 21

Describe the symptoms associated with the acute stage of Chagas disease

Answer 21

Localised lesion at the site of inoculation (chagoma). It is usually asymptomatic but may have anorexia, fever, myocarditis, lymphadenopathy, hepatosplenomegany

Question 22

How is chagas disease treated?

Answer 22

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.

Question 23

__________ are places where organisms naturally live

Answer 23

“ecotopes”

Question 24

How does house construction in endemic areas contribute to Chagas disease rates?

Answer 24

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

Question 25

What are the primary epidemiological risk factors for Chagas disease?

Answer 25

Houses with cracks or thatch roofs (ex. adobe mud brick, wood), Bahareque houses (wood frame shoved with mud), close proximity to animals

Question 26

Why do insects carrying Chagas disease like to live in tiny cracks?

Answer 26

Thigmotropism - like to be surrounded on each side by stuff

Question 27

How can one make a Bahareque house that is less hospitable to bugs

Answer 27

Fill in cracks with clay then smooth down the clay. USe tin roof.
Can also paint house with insecticide

Question 28

How is chagas disease a big drain on the economy of countries in which it is common?

Answer 28

Costs a lot to prevent and treat it, chronic disease results in people who cannot work

Question 29

Why is it that just addressing human chagas disease isn’t an effective control method?

Answer 29

Other vertebrate reservoirs exist, such as possums, pigs, goats, dogs, cats, armadillos, sloths.

Question 30

How can chagas rates be curbed without culling animals?

Answer 30

Shelters can be modified to be less hospitable to insects. Livestock animals can be kept separate from human dwellings.

Question 31

T. cruzi is considered highly adaptable. Why is this?

Answer 31

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.

Question 32

What are risk factors for chagas disease?

Answer 32

Roughness of walls, number of dogs, chickens, pigs in domestic/peridomestic environment, number of Triatomine habitats (ex. trash, chicken houses)

Question 33

As number of chagas insect hosts goes up, feedings success goes _____

Answer 33

down