Trypanosoma Parasites

Question 1

Life Cycle of African Trypanosoma

Answer 1

1. Tsetse fly takes a blood meal injecting metacyclic trypomastigotes (MT).
2. Injected MT’s transform into bloodstream trypomastigotes, which are carried to other sites.
3. Trypomastigotes multiply by binary fission in various body fluids.
4. Circulating trypomastigotes in blood during acute phase; usually undetectable in latent phase.
5. Tsetse fly takes a blood meal where the bloodstream trypomastigotes are ingested.
6. Bloodstream trypomastigotes transform into procyclic trypomastigotes in the vector midgut. Procyclic trypomastigotes multiple by binary fission.
7. Procyclic trypomastigotes leave the midgut and transform into epimastigotes.
8. Epimastigotes multiply in salivary gland. They transform into metacyclic trypomastigotes.

Question 2

Vectors

Answer 2

African trypanosomes are transmitted by several species within the genus Glossina, commonly known as the tsetse.

American trypanosomes are transmitted by Triatomine bug (reduviid bug, kissing bug)

Question 3

Control

Answer 3

Disease transmission is suppressed through vector control

Question 4

T. brucei

Answer 4

infects game animals/livestock (causes nagana)

Question 5

T. rhodesience

Answer 5

causes E. African trypanosomiasis
ungulate-fly-human transmission
harbors in native game animals

Question 6

T. gambiense

Answer 6

causes W. and Central African sleeping sickness
human-fly-human transmission
no reservoir host

Question 7

T. cruzi

Answer 7

Trypanosoma cruzi is the causative agent of Chagas’ disease. Chagas’ disease exhibits a patchy distribution throughout south and central America.

Animal reservoir hosts.

Question 8

Type of parasite

Answer 8

heteroxenous

salivarian or sterccorarian

Question 9

Salivarian typanosomes

Answer 9

Salivarian trypanosomes develop in an anterior station of the digestive tract (e.g., salivary glands) of their insect host. This group includes a mechanically transmitted parasite.

Question 10

Stercoranian trypanosomes

Answer 10

Stercoranian trypanosomes develop in posterior station of the digestive tract (hind gut) of their insect host.

Question 11

Signs and Symptoms

Answer 11

A small sore (chancre) develops at the site of infection and then disappear in 1-2 weeks.

T. rodhesiense cause acute infection killing the host before invasion of the nervous system.

In contrast, T. gambiense, tends to have a chronic disease that eventually results in invasion of the nervous system. This causes the well known sleeping sickness and ends in death.

The lymph nodes become swollen, resulting in the famous Winterbottom’s sign, which were used by slave traders to select sick slaves and throw them from ships.

Question 12

Diagnosis

Answer 12

Diagnosis is achieved by finding parasites in blood, lymph or cerebrospinal fluid or antigen-antibody agglutination test.

Treatment was previously done with toxic arsenical drugs. Recently suramin, pentamidine and Berenil have been the drug of choice

Question 13

Life Cycle of Trypanosoma Cruzi

Answer 13

1. Triatomine bug (reduviid bug, kissing bug) takes a blood meal in which trypomastigotes enter the bite.
2. Metacyclic trypomastigotes penetrate various cells at bite would site. Inside cells they transform into amastigotes.
3. Amastigotes multiply by binary fission in cells of infected tissues.
4. Intracellular amastigotes transform into trypomastigotes then burst out of the cell and enter the bloodstream.
5. Triatomine bug takes a blood meals in which the tyrpomastigotes are injested.
6. Epimastigotes in midgut
7. Multiply in midgut
8. Metacyclic trypomastigotes in hindgut

Question 14

Pathogenesis and Immunology (T. cruzi)

Answer 14

Pathogenesis starts with an acute phase due to entrance of metacyclic trypanosomes into cells of subcutaneous tissue and spread of parasite to lymph nodes and formation of Pseudocysts

The local inflammation at the site of parasite inoculation results in a red nodule called Chagoma

In 50% of cases inoculation occur in eye lid and conjunctiva, causing Romana sign

Pseudocysts rupture cause acute inflammation with degeneration and necrosis of nerve cells in the vicinity, especially ganglion cells. This is an important pathological change in the infection that occur in most organs including the heart.

Acute phase is common in children while chronic phase is common in adults.

The symptoms of the chronic phase are due to central and peripheral nervous system dysfunction. Most serious is the loss of heart muscles tone, which result in cardiac death.

Chagas disease accounts of 70% of cardiac death in young adults of latin America