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DTM&H > American Trypanosomiasis > Flashcards

American Trypanosomiasis Flashcards

1
Q

What is another name for American trypanosomiasis?

A

Chaga’s disease

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2
Q

What is the responsible organism in Chaga’s disease?

A

T.cruzi

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3
Q

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

A

Large kinetoplast

More curved

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4
Q

What is the vector of Chaga’s disease?

A

Triatomine bugs

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5
Q

What are the alternative names for triatomine bugs?

A

Reduviid bugs
Assassin bugs
Kissing bugs

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6
Q

When do triatomine bugs bite?

A

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

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7
Q

What is the annual incidence of Chaga’s disease?

A

40,000

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8
Q

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

A

10,000

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9
Q

What is the prevalence of Chaga’s disease?

A

8-10 million

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10
Q

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

A

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

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11
Q

What are the reservoirs of infection in the wild cycle?

A

Small marsupials e.g. racoons, opossums, armadillo

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12
Q

How does infection with Chaga’s disease occur?

A
  • 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
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13
Q

Which cells do the trypanomastigotes tend to infect?

A

Neuroglia

Muscle cells

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14
Q

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

A

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

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15
Q

What is the incubation period of Chaga’s disease?

A

5-14 days

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16
Q

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

A

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

17
Q

Where does T.cruzi multiply in the reduviid?

A

The HINDGUT, they then being excreted via the faeces

18
Q

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

A
  • Cutaneous oedema - a Chagoma
  • Orbital oedema - Romana sign
  • Febrile reaction
  • 1-2/52 later, may develop lymphadenopathy, hepatomegaly, splenomegaly
19
Q

Who is acute Chaga’s more common in?

A

Children

20
Q

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

A

Only 1/3rd

21
Q

What is the clinical course of acute Chaga’s?

A

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

22
Q

When does chronic Chaga’s occur?

A

10-20 years after initial infection

23
Q

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

A
  1. Cardiac disease
  2. Mega-oesophagus/Mega-colon
  3. Similar mega disorders of other hollow organs - e.g. ureters
24
Q

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

A

Biventricular cardiomyopathy, rhythm disturbance - often heart block

25
Q

How does mega-oesophagus and mega-colon present?

A

Mega-oesophagus - aspiration pneumonia

Mega-colon - intractable constipation

26
Q

How is Chaga’s disease diagnosed?

A
  • 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
27
Q

What are the alternative methods of Dx?

A

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

28
Q

How is Chaga’s disease treated?

A

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

29
Q

How are the vectors of Chaga’s disease controlled?

A
  • 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
30
Q

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

A

60-99%

DTM&H (8 decks)

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