Sleeping sickness is a threat to millions of people in sub-Saharan Africa. It is carried by a parasite, the trypanosome, which is transmitted to humans by the bite of the Tsetse fly. In a little over a century, this disease surged several times, reaching epidemic status. Since the beginning of the 2000s, new efforts have been made to limit the number of new cases per year. Now is the time to step up actions to try and eliminate this disease. This includes controlling the Tsetse fly, improving detection and developing a treatment.
"This article is a translation of "Regain d'intérêt pour la maladie du sommeil" by Timothée Froelich.
New detection test for sleeping sickness. PLoS Negl Trop Dis7(2):e2087.doi:10.1371/journal.pntd.0002087
Sleeping sickness, or Human African trypanosomiasis (HAT) is caused by a parasite, called a trypanosome, and transmitted by the bite of the Tsetse fly. This endemic disease affects mostly poor and rural people in sub-Saharan Africa and constitutes a threat to more than 70 million people. If not treated, this disease can be lethal. The parasite develops in the blood and within the lymphatic system for a variable period of time. There are no particular symptoms until the trypanosome invades the central nervous system.
Over a bit more than a century, Africa has suffered from several large and particularly devastating HAT epidemics. In 1920, when several countries were affected, the outbreak was eliminated thanks to a screening campaign organized by mobile teams from the World Health Organization (WHO). After it almost disappeared in the 60s, a decrease in surveillance led to a strong resurgence of the disease in 1970. For more than 20 years, the coordinated efforts of the WHO, national programs for protection against epidemics, bilateral cooperation projects, and NGOs all contributed to decreasing the number of new cases per year: down from 30,000 to 50,000, the number has stood at less than 10,000 since 2009. Today, there are around 30,000 active cases.
To finally overcome this disease, it is necessary to detect new cases quickly, in order to treat them. The spread of the parasite is consequently slowed down, or even stopped, and the chances for healing increase. But there are still many obstacles ahead: it can be difficult to access affected populations—in rural and remote areas or civil war zones—and deploying adequate screening techniques requires highly qualified teams and considerable equipment. Over the last five years, the evolution of techniques has contributed to developing new types of tests that can detect anti-trypanosome antibodies in the blood.
The team of Prof. Ferguson (Dundee University) recently published in PLOS, Neglected Tropical Diseases a study describing a simple-to-use and inexpensive test. This test works on the same principle as a pregnancy test, except blood or serum replace urine. When two lines appear, it indicates contact with the parasite. Dr. Lauren Sullivan, who participated in the study, explained that many antigens were examined and some of them, published or not, were very promising for detecting any current or past presence of the trypanosome. After this test, the infection remains to be confirmed by microscope or by detecting the parasite’s DNA. Dr. Sullivan is confident that in the long term, these additional tests will not be necessary any more.
Another similar test was developed by a partnership between FIND (Foundation for Innovative New Diagnostics) and Standard Diagnostics, a Korean company. It is currently being field-tested in the Democratic Republic of the Congo, an area still particularly affected by sleeping sickness. Dr. Joseph Ndung’u, head of the HAT and Other Neglected Diseases Department at FIND, in Geneva, adds that the different outcomes will be compared and the best method—that is, the most reliable and inexpensive—will be kept. At the same time, FIND is working to set up detection centers in the field. After the first step of quick and economical detection, the disease will quickly be confirmed, thanks to the proximity of other necessary structures—microscopy and DNA detection if needed—. Then, treatment could begin without delay and with greater efficacy.
There are very few medications available to treat HAT. For years, the only option for treating a person in an advanced stage was an arsenic derivative, which had many side-effects and killed one in a twenty patients. Recently, the Drugs for Neglected Diseases Initiative (DNDi) managed to replace it by administrating NECT, a combination of two old medicines: eflornithine and nifurtimox. The pharmaceutical companies Sanofi and Bayer donate these molecules, allowing the treatment of patients for free. Further work is in progress to develop an oral route for the treatment, which would be easier to administrate and could help to set up a less cumbersome system, consequently healing more people. Thanks to the progress made in detecting and treating sleeping sickness, it is now possible to imagine its eradication in a not-so-distant future.
Find out more:
Médecins sans frontières/Doctors without frontiers: https://msf.org.uk/issues/sleeping-sickness.
FIND’s section about HAT and Other Neglected Diseases: https://www.finddx.org/.
Caption photo Front Page: https://en.wikipedia.org/wiki/NASA.
