Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Record morbidity in Africa from a little-understood emerging disease

04.09.2006
Borreliosis, or relapsing fever, is a disease provoked by bacteria of the genus Borrelia. Two of these are encountered in tropical Africa: Borrelia crocidurae in the Sahara and Sahel, Borrelia duttoni in East Africa. This infection causes recurrent fevers over a long period that can lead to severe meningoencephalitis and sometimes death.

The human vector of Borrelia crocidurae in West Africa is the tick Ornithodoros sonrai, which lives in burrows of small wild rodents and is therefore in close contact with them. This disease was considered rare up to the end of the 1980s when a team of IRD researchers showed that in a rural area of the Dakar region tick-borne relapsing fever was the second most frequent reason for patients’ consultation at the local dispensary.

Since 1990, the IRD launched a comprehensive research programme on this disease, first in Senegal, then in the whole of West Africa. In Senegal, the investigation showed that the tick had colonized savannah and that the disease’s expansion was closely linked with the decrease in average rainfall since the long drought began in 1970. The advance of borreliosis prompted the research team to extend their epidemiological research and study the long-term trends, by 14 years of measurement of the infection’s incidence in a rural Senegalese community which was the subject of continuous demographic and health monitoring programme run jointly by the IRD, the Pasteur Institute and the University of Dakar.

The study was conducted from 1990 to 2003 on people in Dielmo, a village in the savannah in the Sine-Saloum region of Senegal, in order to determine the frequency and describe the clinical manifestations of malaria, tick-borne relapsing fever and other fevers not linked to these two diseases. The research team lived permanently in the village so that they could visit each inhabitant daily. Medical examinations and biological tests were systematically carried where someone had a fever or other symptoms that might signal the disease. The presence of Borrelia crocidurae was also tested in people without symptoms at least once a year. All rodent burrows near houses and inner yards of concession were counted and recorded. They were searched for ticks and the latter’s infection rate by the bacterium determined. Rodents and insectivores were captured in order to study the bacterial reservoir.

... more about:
»Borrelia »Malaria »Senegal »crocidurae »relapsing

Over the period of study as a whole, an average 11 % of the population suffered from borreliosis each year, an exceptional incidence rate for a disease, whatever its cause. Only malaria, among the parasitic diseases and in any case to a lesser degree, and influenza, among viral diseases, are known to produce a comparable incidence level over such a long period. Tick-borne relapsing fever is the second cause of illness after malaria. All age groups were affected by it in the population studied.

The IRD team then conducted systematic surveys in Senegal, Mali and Mauritania in order to define the geographical distribution of the tick, determine the infection rate over the whole of its area of distribution and establish the proportion of villages affected by the disease. The results showed that the vector is present in massive numbers in these three countries in any area where average rainfall is below 750 mm. Out of 30 villages studied, 26 (87 %) were colonized by the tick which was present on average in 31 % of the burrows in the villages with a Borrelia crocidurae infection rate of 21 %. Two-thirds of the villages studied showed an exposure rate to tick-borne relapsing fever among inhabitants even higher than that of the people in Dielmo. It is in most of the rural areas of Senegal and Mali and in all parts of Mauritania that the disease is a major public health problem.

Paradoxically, this emerging disease is still completely misunderstood by health care personnel, although it has become one of the most frequent bacterial infections. Laboratory testing for determining the cause of a disease is rarely possible in tropical Africa, particularly in the rural areas. Borrelia crocidurae can be detected in blood samples only during peaks of fever. Its density is usually very low and diagnosis requires the skills of an experienced microscopist. The symptoms of the disease are exactly similar to those of malaria which is very frequent in the same populations. The disease is therefore systematically confused with malaria, and failure of treatment is attributed to antimalarial drugs. Furthermore, the existence of an animal reservoir and the omnipresence of rodents in rural areas makes prevention of the disease hardly feasible. However, a cheap effective treatment is possible which involves the use of antibiotics of the tetracycline family which are available in most clinics in the bush.

Marie Guillaume | alfa
Further information:
http://www.ird.fr/fr/actualites/fiches/2006/fas245.pdf

Further reports about: Borrelia Malaria Senegal crocidurae relapsing

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Epoxy compound gets a graphene bump

14.11.2018 | Materials Sciences

Microgel powder fights infection and helps wounds heal

14.11.2018 | Health and Medicine

How algae and carbon fibers could sustainably reduce the athmospheric carbon dioxide concentration

14.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>