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S de La Rocque

Publications and source records attributed to S de La Rocque.

10 recordsLinked to original sources
PubMed2005

Geographical Information Systems in parasitology: a review of potential applications using the example of animal trypanosomosis in West Africa.

The epidemiology of vector-borne diseases is complex due to the variability in the ecology of the different actors involved, i.e. hosts, parasites and vectors. The transmission of African animal trypanosomosis in the West-African savannah region is an excellent example of this complexity: riverine tsetse flies have an heterogeneous distribution along the rivers, depending of suitable habitats, and transmit pathogenic trypanosomes were they use domestic animal as feeding hosts. Contrasting epidemiological situations may thus occur at the local scale, and a broad view of the overall environment is necessary to quantify the interfaces in time and space between hosts and vectors. Geographical Information Systems (GIS) can provide new insight into the study of such complex epidemiological processes. GIS is a powerful technology that has been used mainly in map-making, and an enormous amount of knowledge can be gained simply by geographical data projection. GIS also allows juxtaposition of different types of information, creation of new variables, testing of theories and correlation, and generating of predictive models. The purpose of the present paper is to exemplify the potential application of GIS using a recent study carried out on animal trypanosomosis in a cattle-raising area of Burkina Faso.

Africa, Western↗
PubMed2002

[Tsetse fly wings, an identity card of the insect?].

The size of tsetse flies is often associated with population dynamics and vectorial capacity parameters. Adult fly size is generally estimated from measurements of wing segments. To take measure of the wing, a semi-automatic software was developed by CIRAD-EMVT and IRD. It was used in wild populations of Glossina tachinoides Westwood and G. palpalis gambiensis Vanderplank (Diptera: Glossinidae) trapped near Bobo-Dioulasso, Burkina Faso. From an numeric picture of the wing, the software calculates the length of vein segments, the ratios between these lengths, the surface of the tsetse characteristic "hatchet cell", and the greyness on the wings. The data were interesting at the level of taxonomy. In addition, they help specify physiological characteristics of the studied populations.

Algorithms↗
PubMed2001

Spatial trypanosomosis management: from data-layers to decision making.

The use of geographical information systems (GIS) in the management of African animal trypanosomosis in sub-Saharan Africa offers potential in assisting decisions on allocation of resources, prioritization of control areas, and planning and management of field operations. Here, Guy Hendrickx and colleagues review approaches being used to develop reliable data-layers and to incorporate these data into GIS models. They argue that techniques should be further refined to produce more-detailed data layers and to include a dynamic element, a problem rarely addressed until now.

Africa South of the Sahara↗
PubMed2001

The changing distribution of two riverine tsetse flies over 15 years in an increasingly cultivated area of Burkina Faso.

Changes in the distribution of two riverine tsetse flies, Glossina tachinoides Westwood and Glossina palpalis gambiensis Vanderplank are described in an agro-pastoral area of Burkina Faso subject to increasing human population pressure and land use change. Two similar entomological surveys (one trap every 100 m, 120 km of river) were conducted in 1981 and 1996. Changes in tsetse distribution were compared to land use changes through high resolution remote sensing imagery (LANDSAT, SPOT). There was a close relationship between proximity of crops relative to riverine forest and the density of Glossina. Where fields encroached on riverine vegetation, tsetse populations declined. Where the geomorphological structure was not well suited to agricultural activity, riverine vegetation and tsetse fly populations were relatively unaffected, even with intense agricultural activity nearby. In contrast, increased human activity and higher cattle densities in the surrounding savannah areas were associated with increased tsetse numbers. The results demonstrated a wide diversity of tsetse distribution and habitat within a few kilometres in an agro-pastoral landscape in West Africa.

Agriculture↗
PubMed1999

Polymerase chain reaction as a diagnosis tool for detecting trypanosomes in naturally infected cattle in Burkina Faso.

African animal trypanosomoses constitute the most important vector-borne cattle diseases in sub-Saharan Africa. Generally it is considered that there is a great lack of accurate tools for the diagnosis of the disease. During a trypanosomosis survey in the agro-pastoral zone of Sideradougou, Burkina Faso, 1036 cattle were examined for trypanosomes using microscopy. The PCR was applied on a subset of 260 buffy-coat samples using primers specific for Trypanosoma congolense savannah and riverine-forest groups, T. vivax, and T. brucei. Parasitological examination and the molecular technique were compared, showing a better efficiency of the latter. In the near future, the PCR is likely to become an efficient tool to estimate the prevalence of African trypanosomoses in affected areas.

Animals↗
PubMed1999

Intraspecific variability in natural populations of Glossina palpalis gambiensis from West Africa, revealed by genetic and morphometric analyses.

Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) from West Africa (Senegal and Burkina Faso) were analysed for microsatellite DNA polymorphisms and size of the wings. In the overall sample a strong heterozygote deficiency was found at two polymorphic microsatellite loci. It led to a highly significant value of Fis (within-sample heterozygote deficit) in the western zone of Sideradougou area in Burkina Faso. Genetic differentiation was significant on a macrogeographic scale, i.e. between tsetse coming from Senegal and Burkina Faso. Wing measures also differed between these two countries; flies from Senegal appeared to be smaller. Microsatellite loci further allowed differentiation of populations of G. palpalis gambiensis trapped on the same hydrographic network a few kilometres apart. The results are interpreted as indicating that further investigations will allow the study of genetic variability of tsetse flies in relation to the dynamics of transmission of human and animal trypanosomoses.

Africa, Western↗
PubMed1995

[Comparison of the sensitivity of the Woo test and a test for detecting antigens to Trypanosoma vivax in 2 sheep experimentally infected with a Guyanese strain of the parasite].

A trapping ELISA for the detection of circulating antigens of Trypanosoma vivax with a specific monoclonal antibody was developed by Nantulya and Lindqvist in 1989. With the African strains tested, its sensitivity proved very high. Using reagents supplied by ILRI, the sensitivity of this test was compared with that of the Woo test in two sheep experimentally infected with a Guyanese strain of T. vivax. Blind tests carried out at CIRDES and ILRI confirmed the results obtained in French Guiana. The animals were bled regularly during the first 130 and 285 days of infection. Whatever the period of infection ans whether there was patent parasitaemia or not, the mean sensitivity of the ELISA test was very low: 2.1% of positive results, far below the Woo test's 54% of positive results. Associating the two techniques did not improve the sensitivity. The mean optical densities recorded during these long periods of infection (0.010 +/- 0.004 and 0.012 +/- 0.002) are so close to the sensitivity threshold of the ELISA readers that they cannot be proposed as a cut-off threshold to improve the sensitivity of the test. A complementary study of the sensitivity of this test is in progress at ILRI. As already observed in Burkina Faso and The Gambia, this poor sensitivity may greatly affect the results of the epidemiological surveys being carried out with these reagents in Africa. New monoclonal antibodies must be developed to produce a test for T. vivax antigens with more satisfactory sensitivity.

Animals↗
PubMedDate not supplied

Review on the molecular tools for the understanding of the epidemiology of animal trypanosomosis in West Africa.

The epidemiology of animal trypanosomosis around Bobo-Dioulasso (Burkina Faso, West Africa) benefited a lot in the last years from the progress of molecular tools. The two most used molecular techniques were the polymerase chain reaction for the diagnosis of the disease in cattle and the characterization of the trypanosomes in the host and the vector on one hand, and the microsatellite DNA polymorphism in tsetse flies to study the intraspecific genetic variability of the vector on the other hand. The results obtained in the Sideradougou area during a recent two year survey with these techniques, associated with many other georeferenced informations concerning vector and cattle distribution, natural environment, landuse, ground occupation, livestock management, were combined in a Geographical Information System. This new approach of a complex pathogenic system led to a better evaluation of the risk of trypanosome transmission.

Africa, Western↗