American Trypanosomiasis

Question 1

What is another name for American trypanosomiasis?

Answer 1

Chaga’s disease

Question 2

What is the responsible organism in Chaga’s disease?

Answer 2

T.cruzi

Question 3

How does T.cruzi appear different to T.b.gambiense/rhodesiense seen in Africa?

Answer 3

Large kinetoplast

More curved

Question 4

What is the vector of Chaga’s disease?

Answer 4

Triatomine bugs

Question 5

What are the alternative names for triatomine bugs?

Answer 5

Reduviid bugs
Assassin bugs
Kissing bugs

Question 6

When do triatomine bugs bite?

Answer 6

ONLY at night (unlike Tetse flies causing African trypanosomiasis)
The bites are generally painless, feeding can last 1-25 mins, in areas with large bug populations, blood loss can exceed 2ml per night and thus contribute to anaemia

Question 7

What is the annual incidence of Chaga’s disease?

Answer 7

40,000

Question 8

How many deaths are there related to Chaga’s disease per year?

Answer 8

10,000

Question 9

What is the prevalence of Chaga’s disease?

Answer 9

8-10 million

Question 10

What are the reservoirs of infection the semi-domestic cycle?

Answer 10

Rats
Dogs
(which infect the fly, the fly’s faeces then infecting humans)

Question 11

What are the reservoirs of infection in the wild cycle?

Answer 11

Small marsupials e.g. racoons, opossums, armadillo

Question 12

How does infection with Chaga’s disease occur?

Answer 12

• Reduviid faeces in a wound
• Reduviid faeces in the conjunctiva
• By blood transfusion - blood donors in high risk areas should be screened and gentian violet can be added to the blood
• Congenital infection - as is the case in 10% of seropositive mothers
• Breast milk
• Contaminated fruit juice, in particular acai

Question 13

Which cells do the trypanomastigotes tend to infect?

Answer 13

Neuroglia

Muscle cells

Question 14

What happens in the pseudocyst cycle once the trypanomastigotes have infected a cell?

Answer 14

Amastigotes –> promastigotes –> epimastigotes –> pseudocyst ruptures releasing trypomastigotes (infective form)

Question 15

What is the incubation period of Chaga’s disease?

Answer 15

5-14 days

Question 16

How long does it take for a reduviid bug to become infective?

Answer 16

8-10 days, remaining infective for life, 2 years-ish

Question 17

Where does T.cruzi multiply in the reduviid?

Answer 17

The HINDGUT, they then being excreted via the faeces

Question 18

What are the signs and Sx of acute Chaga’s disease?

Answer 18

• Cutaneous oedema - a Chagoma
• Orbital oedema - Romana sign
• Febrile reaction
• 1-2/52 later, may develop lymphadenopathy, hepatomegaly, splenomegaly

Question 19

Who is acute Chaga’s more common in?

Answer 19

Children

Question 20

What proportion of people with acute Chaga’s are symptomatic?

Answer 20

Only 1/3rd

Question 21

What is the clinical course of acute Chaga’s?

Answer 21

If has Sx - lasts 1-3/12 before spontaneously resolving. If assympto, pt’s may continue to have for many years - 15-40% then going on to develop chronic Chaga’s

Question 22

When does chronic Chaga’s occur?

Answer 22

10-20 years after initial infection

Question 23

What are the 3 clinical manifestations of chronic Chaga’s disease?

Answer 23

1. Cardiac disease
2. Mega-oesophagus/Mega-colon
3. Similar mega disorders of other hollow organs - e.g. ureters

Question 24

What type of cardiac disease does chronic Chaga’s disease?

Answer 24

Biventricular cardiomyopathy, rhythm disturbance - often heart block

Question 25

How does mega-oesophagus and mega-colon present?

Answer 25

Mega-oesophagus - aspiration pneumonia | Mega-colon - intractable constipation

Question 26

How is Chaga's disease diagnosed?

Answer 26

- Microscopy - thick or thin,centrifugation increases sensitivity - Culture - Xenodiagnosis - allowing an un-infected fly to feed on a suspected patient, then disected 3-4/52 later to look for gut infection - Biopsy

Question 27

What are the alternative methods of Dx?

Answer 27

PCR - can be sued in acute but not chronic Serological testing - but remains +ve even after cure Complement fixation/ELISA - but X-reactivity with other parasites results in poor specificity --These methods may also help differentiate type of T.cruzi

Question 28

How is Chaga's disease treated?

Answer 28

Nifutimoox and benznidazole - can shorten the course of acute infection, but only 50-80% will result in complete infection clearance (rather than progression to chronic disease) Chronic disease requires symptomatic treatments, e.g. pacemakers

Question 29

How are the vectors of Chaga's disease controlled?

Answer 29

- Pyrethroid insecticide - some resistance - Elimination fo cracks in mud walls of houses, roofing with iron sheets in order to limit the number of places the vectors can live in a domestic setting

Question 30

By what degree has Chaga's disease decreased in the last 20 years?

Answer 30

60-99%