A tsetse fly, a vector of sleeping sickness (Burkina Faso) -
© Jacarandatree / Wikimedia / IAEA - CC BY-SA 4.0
Sleeping sickness killed several million people in the 1920s and 1930s, according to a study published by our partner The Conversation.
Today "controlled", this threat continues to be monitored because a possible re-emergence is still possible.
The analysis of this health fight was carried out by Vincent Jamonneau, researcher and doctor at the Institute for Research for Development (France), Dramane Kaba, researcher and doctor at the Pierre Richet Institute in Bouaké (Côte d'Ivoire) and Mathurin Koffi, geneticist and lecturer at the University Jean Lorougnon Guédé (Côte d'Ivoire).
Finally some good news in terms of Health!
The Africa regional office of the World Health Organization (WHO) announced on August 27, 2020 the elimination of sleeping sickness as a public health problem (EPSP) in Togo.
Enthusiastic, the journalists did not hesitate to speak of "eradication".
But beware !
You should not sell the skin of the trypanosome (the parasite that causes the disease) before having "treated" it: it has already shown what it is capable of if given the opportunity.
Indeed, if the considerable efforts of control carried out in the first half of the XXth century made it possible to contain an epidemic which made several millions of deaths in the years 1920 and 1930, and to declare the disease "residual" in the years 1960 , the slackening that followed, in a context of new interactions between man and his environment, was responsible for a re-emergence and then a very deadly epidemic situation again in the 1990s.
Screening session for sleeping sickness by a mobile team "under the mango tree", Bonon focus (locality in the center-west of Côte d'Ivoire), October 2019 © V. Jammoneau / IRD
Thanks to an effective response organized around national structures dedicated to the fight against the disease, with the support of WHO and the support of research, the number of cases reported annually fell in 2018 below the bar. 1,000 for the first time in history.
Like this development, no case has been declared in Togo since 1996 despite a surveillance system deemed effective by a committee of experts which therefore validated the EPSP on the basis of a file submitted by the ministry. of Health.
A well-defined elimination process
Sleeping sickness (or human African trypanosomiasis / HAT) is caused by a parasite, the trypanosome.
It is rife in tropical Africa in the range of the tsetse fly (tsetse fly), which transmits the parasite to humans by biting them after becoming infected from humans or from humans. 'carrier animals.
If the first symptoms are often mild (recurrent fevers and headaches, skin signs), the disease progresses slowly (sometimes over several years) to generalized neurological damage (including sleep disorders) which is fatal in the absence of treatment.
It affects the most vulnerable rural populations in areas called the “end of the track”, because they are difficult to access and far from health centers.
It is classified in the group of neglected tropical diseases to attract the attention of policy makers and donors.
Illness at the end of the trail.
To avoid a new re-emergence, WHO and its public and private partners have defined indicators to monitor the process of HAT elimination and ensure that the objectives set are met.
This process takes place in three stages:
(1)
EPSP with measurable targets which, when achieved, require measures to be put in place to achieve
(2)
interruption of transmission defined by zero incidence (no new cases) and then to
(3)
eradication which results in the permanent absence of the parasite without risk of reintroduction.
These steps are evaluated by a committee of independent experts who make recommendations to achieve the following objective.
The targets set in 2012 by the WHO were the validation of EPSP in 2020 and the verification of interruption of transmission in 2030.
The road to eradication is therefore still long for a disease like HAT which involves trypanosomes, vectors and potential animal reservoirs.
It should also be remembered that in the history of infectious diseases, only smallpox has achieved this status.
We will then understand that the choice of words used at each stage of the process is really important.
A "successful" epidemiological transition, supported by research
In the absence of vaccine and chemoprophylaxis - the administration of a chemical substance to prevent disease - sleeping sickness control strategies aim to detect, treat cases and control the vector tsetse to limit the risk. transmission.
Passing in twenty years from an epidemic context to an elimination context, sleeping sickness has undergone an unprecedented epidemiological transition to which control strategies and tools have had to adapt.
This was notably the case in Côte d'Ivoire thanks to significant support from multidisciplinary research in the service of the National Elimination Program, which made it possible to fight the disease on all fronts.
Several strategies and tools currently used in Africa to fight sleeping sickness have been developed and / or evaluated there, for example rapid diagnostic tests which have considerably facilitated access to screening in health centers in rural areas, and Vavoua traps (named after a town in central western Côte d'Ivoire where they were first assessed) or insecticide-impregnated screens to control tsetse flies.
Installation of an insecticide-impregnated screen to combat tsetse flies, Sinfra outbreak (departmental capital in Côte d'Ivoire), October 2019 © V. Jammoneau / IRD
The spectacular results obtained - only nine cases reported between 2015 and 2019 - also enabled Côte d'Ivoire to submit to WHO in August 2020 its EPSP validation application file.
Meeting the challenge of elimination by strengthening passive surveillance
The complex itinerary of one of the last cases detected in Côte d'Ivoire and recently described in a scientific article published in the journal
Plos Neglected Tropical Diseases
, illustrates the fact that the road to the eradication of HAT is still long.
This is an 11-year-old girl who was likely infected as a child in the endemic focus of Sinfra.
Following the onset of symptoms in October 2014, out of school, stigmatized, accused of being possessed by a "demon" because of neurological disorders due to the disease, it is in a comatose state that she will finally be detected and treated. in September 2017. Accompanied by her mother who had had to cease her activity to take care of her daughter, she had nevertheless consulted dozens of public or private health centers and asked more than a hundred health workers, who prescribed inappropriate treatments without making the correct diagnosis.
Our "Epidemics" file
This delay in diagnosis is largely due to the current situation of the disease, which has been gradually forgotten by the medical profession and which is no longer seen as a threat by the populations.
The research and control teams have therefore adapted their strategies by strengthening passive surveillance in “sentinel” sites at the national level and by emphasizing the training of health workers.
A socio-anthropological study is underway to enable us to improve the awareness of these key players as well as the populations who are just as important.
The girl, now in great physical shape, has neurological consequences that prevent her from living her adolescent life to the full.
It will therefore have to be followed for several years in order to be definitively cured.
This individual story highlights the difficulty of achieving the elimination of sleeping sickness in Côte d'Ivoire and in countries which have succeeded in sharply reducing transmission in recent years.
Above all, it reminds that research, control and surveillance efforts must be maintained in order to one day succeed in eradicating the disease from the African continent.
Overcoming a disease sustainably would allow developing countries to be able to prioritize their efforts to face the multiple health risks that may suddenly focus the attention of health authorities as is currently the case.
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This analysis was written by Vincent Jamonneau, researcher and doctor at the Institute for Research for Development (France), Dramane Kaba, researcher and doctor at the Pierre Richet Institute in Bouaké (Côte d'Ivoire) and Mathurin Koffi, geneticist and lecturer at the University Jean Lorougnon Guédé (Ivory Coast).
The original article was published on The Conversation website.
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