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8.0 Trypanosoma (T. brucei) (Blood Flagellates/ Hemoflagellates) - Coggle…
8.0 Trypanosoma (T. brucei) (Blood Flagellates/ Hemoflagellates)
Kinetoplasta’s class
Trypanosoma
T. brucei (African Trypanosomiasis)
-T. b. brucei (Nagana disease)
-T. b. gambiense
-T. b. rhodesiense
-T. cruzi (American Trypanosomiasis)
Leishmania
-Leishmania major
-Leishmania tropica
-Leishmania braziliensis – Mucocutaneous Leishmaniasis
-L. donovani -
Amastigote
- a common morphology during an intracellular lifecycle stage in a mammalian host. All Leishmania have an amastigote stage of the lifecycle. Leishmania amastigoes are particularly small and are among the smallest eukaryotic cells. The flagellum is very short, projecting only slightly beyond the flagellar pocket.
Promastigote (leptomonad)
- a common morphology in the insect host. The flagellum is found anterior of nucleus and flagellum not attached to the cell body. The kinetoplast is located in front of the nucleus, near the anterior end of the body.
Epimastigote -
a common form in the insect host and Crithidia and Blastocrithidia, both parasites of insects. The flagellum exits the cell anterior of nucleus and is connected to the cell body for part of its length by an undulating membrane. The kinetoplast is located between the nucleus and the anterior end.
Trypomastigote -
characteristic of the genus Trypanosoma in the mammalian host bloodstream as well as infective metacyclic stages in the fly vector. The kinetoplast is near the posterior end of the body, and the flagellum lies attached to the cell body for most of its length by an undulating membrane.
Trypanosomatid life cycles vary with respect to:
Host species
Vectors
Behaviour of parasites in vectors and in hosts
Lifecycle stages in which reproduction occurs
Genus Trypanosoma
1 .All Trypanosoma (except T. equiperdum) are heteroxenous or at least transmitted by animal vectors..
2.Importance to the health of humans and domestic animals.
3.Most live in blood and tissue fluids, but some will occupy intracellular habitats as well (e.g T. cruzi).
Section Salivaria (Trypanosoma brucei
)
Three sub species:
-T. b. brucei
-T. b. gambiense
-T. b. rhodesiense
Morphologically indistinguishable.
Vary in infectivity for different species of hosts and produce somewhat different pathological syndromes.
Tsetse fly (Glossina) as an intermediate host for all three species.
Tsetse flies are viviparous
The freshly-laid free-living larva, does not need to feed and burrows into the soil where its skin hardens and blackens into a puparium and within the puparium, pupation and metamorphosis take place.
Nagana
1.Nagana means in Zulu “to be in low or depressed spirits”.
2.“Nagana” is caused by T. brucei brucei (tissue parasite), T. congolense and T. vivax (hematic parasites).
Most important in cattle but can also produce serious losses in pigs, camels, goats, and sheep.
Most important in cattle but can also produce serious losses in pigs, camels, goats, and sheep.
Several drugs are available for treatment (Berenil) and prophylaxis (Samorin, Trypamidium Chloride), but resistance is a problem.
African Sleeping Sickness:Disease course and symptoms
First stage
Trypanosomes multiply in the tissue around the initial bite site.
This often results in a characteristic local inflammation the trypanosomal “chancre”. Usually not painful.
From there they enter the blood and lymphatic system
Enlargement of the lymphatic glands (especially in the posterior triangle of the neck) can be an early sign of the disease (Winterbottom sign – swollen lymph nodes, not as common in rhodesiense infection).
Aspiration of swollen gland often reveals parasites.
After 1-2 week period of asymptomatic incubation, parasites invade blood leading to fever and headache.
Once parasites enter blood stream fever sets in (low and irregular in gambiense and high and periodic in rhodesiense).
General toxic symptoms include headache, facial edema, nausea and vomiting, back and bone pain.
Symptoms at this stage are rather mild in gambiense but can be severe in rhodesiense with often fatal outcome
Second Stage
The second stage of trypanosomiasis is characterized by progressive anemia and cachexia (“wasting syndrome” is loss of weight, muscle atrophy, fatigue, weakness, and significant loss of appetite)
Diagnosis
Trypansosomiasis is best diagnosed by demonstration of parasites in (i) blood smears, (ii) lymph node exudates or (iii) spinal fluid.
Parasitemia can be very low at times resulting in false negative results. It is more likely to find parasites during symptomatic periods.
Several techniques can be used to enrich rare parasites in blood sample (centrifugation, chromatography).
The Card Agglutination Test for Trypanosomiasis (CATT) and serodiagnostic test to identify anti-T. brucei antibodies (gambiense).
Prevention and control
Avoid bites of the Tsetse fly
Screens on windows and around beds
Elimination of Tsetse flies is impractical
Many different species
Wide geographic range
Eliminate the native reservoirs
Eliminates the tourist trade
Pesticides including DDT and benzene hexachloride
Creation of nagana resistant cattle breeds