Prevention
Symptoms
Causes
Complications
What is African trypanosomiasis?
Human African trypanosomiasis, also known as sleeping sickness, is a vector-borne parasitic disease. It is caused by infection with protozoan parasites belonging to the genus Trypanosoma. They are transmitted to humans by tsetse fly ( Glossina genus) bites which have acquired their infection from human beings or from animals harbouring human ...
What is the name of the parasite that causes trypanosomiasis in cattle?
In cattle, the disease is called Nagana. Trypanosomiasis in domestic animals, particularly in cattle, is a major obstacle to the economic development of affected rural areas.
Where do people get tsetse fly?
The people most exposed to the tsetse fly and to the disease live in rural areas and depend on agriculture, fishing, animal husbandry or hunting. Human African trypanosomiasis takes 2 forms, depending on the subspecies of the parasite involved: Trypanosoma brucei gambiense accounts for more than 95% of reported cases.
What is the WHO's coordination network?
In 2014 a coordination network for human African trypanosomiasis was established under WHO leadership to ensure strengthened and sustained efforts to eliminate the disease. The stakeholders include national sleeping sickness control programmes, groups developing new tools to fight the disease, international and non-governmental organizations, and donors.
How many forms does trypanosomiasis have?
Human African trypanosomiasis takes 2 forms, depending on the subspecies of the parasite involved:
What causes sleep sickness?
Sleeping sickness is caused by parasites transmitted by infected tsetse flies and is endemic in 36 sub-Saharan African countries where there are tsetse flies that transmit the disease. Without treatment, the disease is considered fatal.
How many cases of African trypanosomiasis in 2019?
In 2009 the number reported dropped below 10 000 for the first time in 50 years, and in 2019 there were 992 cases recorded. Diagnosis and treatment of the disease is complex and requires specifically skilled staff. Human African trypanosomiasis, also known as sleeping sickness, is a vector-borne parasitic disease.
What is the life cycle of a triatomine bug?
Life Cycle. An infected triatomine insect vector (or “kissing” bug) takes a blood meal and releases trypomastigotes in its feces near the site of the bite wound. Trypomastigotes enter the host through the bite wound or intact mucosal membranes, such as the conjunctiva . Inside the host, the trypomastigotes invade cells near the site of inoculation, ...
How is Trypanosoma cruzi transmitted?
Trypanosoma cruzi is transmitted by kissing bugs (Hemiptera: Reduviidae). The most common genera responsible for transmission of the disease are Triatoma, Rhodnius, and Panstrongylus. Infection usually occurs after bugs defecate on the bite site and are rubbed into the wound by the host scratching.
What is the causative agent of Chagas disease?
Causal Agent. Trypanosoma cruzi, is a parasitic protozoan that is the causative agent of Chagas disease (American trypanosomiasis). Currently, six distinct lineages of T. cruzi are classified into discrete typing units (TcI-VI), which vary in their geographic occurrence, host specificity, and pathogenicity.
How do amastigotes multiply?
The amastigotes multiply by binary fission and differentiate into trypomastigotes, and then are released into the circulation as bloodstream trypomastigotes . Trypomastigotes infect cells from a variety of tissues and transform into intracellular amastigotes in new infection sites.
How long are trypanosomes?
Trypanosomes measure from 12 to 30 µm in length. Trypomastigotes may be seen in cerebrospinal fluid (CSF) in central nervous system infections; also the amastigote stage parasite may be seen in histopathology specimens from affected organs.
What is the diagnosis of Chagas disease?
Molecular diagnosis of Chagas disease is performed for cases of suspected acute infection (including transfusion or transplant transmission), congenital Chagas disease, and for monitoring of suspected laboratory exposures. For chronic Chagas disease, serology is generally most appropriate, although molecular detection may be performed for re-activated cases associated with immunosuppression.
What is T cruzi stained with?
T. cruzi in thin blood smears stained with Giemsa.
How many cases of trypanosomiasis in Africa?
There are >10,000 cases/year of Human African Trypanosomiasis (HAT) [1] with an estimated burden of ∼1.3 million Disability Adjusted Life Years (DALYs) [2] and economic losses in excess of $1 billion due to human and animal trypanosomiasis [3]. While interventions can be directed against the vector or the parasite, emphasis has usually been on the use of drugs to treat the disease both in humans and in livestock.
How to control Rhodesian sleeping sickness?
In settled areas of Uganda with few wild hosts, control of Rhodesian sleeping sickness is likely to be much more effectively controlled by treating cattle with insecticide than with trypanocides.
What is the R-O model for trypanosomiasis?
An R o model for trypanosomiasis was generalized to allow tsetse to feed off multiple host species. Assuming populations of cattle and humans only, pre-intervention R o values for T. vivax, T. congolense, and T. brucei were 388, 64 and 3, respectively. Treating cattle with trypanocides reduced R0 for T. brucei to <1 if >65% of cattle were treated, vs 100% coverage necessary for T. vivax and T. congolense. The presence of wild mammalian hosts increased the coverage required and made control of T. vivax and T. congolense impossible. When tsetse fed only on cattle or humans, R0 for T. brucei was <1 if 20% of cattle were treated with insecticide, compared to 55% for T. congolense. If wild mammalian hosts were also present, control of the two species was impossible if proportions of non-human bloodmeals from cattle were <40% or <70%, respectively. R0 was <1 for T. vivax only when insecticide treatment led to reductions in the tsetse population. Under such circumstances R0 <1 for T. brucei and T. congolense if cattle make up 30% and 55%, respectively of the non-human tsetse bloodmeals, as long as all cattle are treated with insecticide.
Can Tsetse be treated with insecticide?
Where tsetse can feed off wild mammals or reptiles which cannot be treated with insecticide it will, of course, be more difficult to control trypanosomiasis using ITC. Calculations similar to those above can be used to estimate the probability of a fly surviving a feeding cycle. As is obvious from Figure 3, even when all cattle are always treated with an insecticide of 100% efficacy, the R0 for T. vivax for cattle and wildlife combined cannot be reduced to <1 – under the assumption that the tsetse population is constant ( Figure 4A ). For T. congolense in cattle the proportion of cattle among non-human hosts would have to be >40% for ITC to be able to force R0 <1 ( Figure 4A ). Even at that level, however, R0 in wildlife would still be >10 and would provide a constant source of re-infection. To make R0 <1 for T. congolense in cattle and wildlife combined >70% of the non-human bloodmeals would need to be taken from cattle. Cattle would need to comprise ∼40% of non-human tsetse bloodmeals for R0 <1 in T. brucei – even if all cattle are treated ( Figure 4B ).
Can a monitor lizard get trypanosomiasis?
If the wild vertebrate host is a monitor lizard, which does not get infected with trypanosomiasis when bitten by an infected tsetse, the dynamics of the disease are identical to the situation where a proportion of cattle are kept permanently on perfectly effective trypanocides. In both cases a proportion of tsetse blood meals are taken from hosts that neither suffer from nor transmit trypanosomiasis. The situation is thus represented by the results in Figure 1 and we need only change the label on the abscissa, to read: ‘Proportion of non-human tsetse meals taken from lizards’.
How many forms of trypanosomiasis are there in Africa?
Human African trypanosomiasis takes 2 forms, depending on the parasite involved: Trypanosoma brucei gambiense accounts for more than 98% of reported cases. Sustained control efforts have reduced the number of new cases.
How is tsetse disease transmitted?
Infection and symptoms. The disease is mostly transmitted through the bite of an infected tsetse fly but there are other ways in which people are infected: Mother-to-child infection: the trypanosome can cross the placenta and infect the fetus.
Where is Trypanosoma brucei rhodesiense found?
Trypanosoma brucei rhodesiense is found in 13 countries in eastern and southern Africa. Nowadays, this form represents under 3% of reported cases and causes an acute infection.
Where is Trypanosoma found?
Human African trypanosomiasis takes 2 forms, depending on the parasite involved: Trypanosoma brucei gambiense is found in 24 countries in west and central Africa. This form currently accounts for 97% of reported cases of sleeping sickness and causes a chronic infection.
Where does trypanosomiasis occur?
Only Uganda presents both forms of the disease, but in separate zones. Another form of trypanosomiasis occurs mainly in Latin America. It is known as American trypanosomiasis or Chagas disease. The causal organism belongs to a different Trypanosoma subgenus and is transmitted by a different vector.
What is the first stage of trypanosomes?
In the first stage, the trypanosomes multiply in subcutaneous tissues, blood and lymph. This is also called haemo-lymphatic stage, which entails bouts of fever, headaches, joint pains and itching
How was the 1920s epidemic controlled?
The 1920 epidemic was controlled thanks to mobile teams which carried out the screening of millions of people at risk. By the mid-1960s, the disease was under control with less than 5000 cases reported in the whole continent. After this success, surveillance was relaxed, and the disease reappeared, reaching epidemic proportions in several regions by 1970. The efforts of WHO, national control programmes, bilateral cooperation and nongovernmental organizations (NGOs) during the 1990s and early 21st century reversed the curve.
