[Production of sporozoites of human Plasmodium in Bobo-Dioulasso (Burkina Faso)].
Mass production of P. falciparum sporozoites requires an intensive production of mosquitoes and an experimental infection of this vector. A gambiae is the main vector of P. falciparum, and P. ovale in Burkina. In the first part we study 3 factors interfering with breeding and experimental infection of this anopheline species. They are: insectarium temperature, pattern and rhythm of blood feeding. In the second part, we study "parasite", "host" and "mosquito" parameters which interfere with the yield of experimental infections. The increase of temperature promotes growth of parasite, but it also enhances bacterial and mycosal pollution; and so, it reduces survival of mosquitoes. Natural feeding on rabbit gives a better laying and a larger blood meal than experimental feeding through an artificial membrane. Meanwhile, it requires a rabbit rearing. We finally adopted the following compromise: the two first blood meals are taken on rabbit, the next are taken on membrane covered devices. It is necessary to give non-parous females two consecutive blood meals that allow the first gonotrophic cycle. The optimal time is on the 3-4 day after emergence. For the mosquitoes reserved for experimental infections, it is necessary to infect them very soon to have more surviving females at the end of the sporogonic cycle. These mosquitoes receive their first and single blood meal an day 2 and can be infected on day 5. There is a positive correlation between the intensity of egg production and the mosquito mortality. Although blood meals are important for parasite development, we prefer to give only one blood meal on day 6 after infection to promote the vector survival rather than maturity of the parasite. This study has allowed to standardize breeding conditions and to obtain regularly 10,000 mosquitoes per day. The infection rate depends on parasite factors. P. falciparum gametocytes may be infectious to mosquitoes at densities as low as 5/mm3 of blood. Maximum infectiousness is reached between 50 to 450/mm3. At higher densities, infectiousness of gametocytes seems to decrease. In natural conditions, sex-ratio and maturity of gametocytes do not appear to interfer with infectiousness. The infection rate also depends on host parameters. They are yet unknown. We saw a specific phagocytosis of sexual stages in mosquito midgut, after infection with a high density gametocyte carrier, without any infected mosquito. On the other hanb, infectiousness of gametocytes seems to decrease with age of the gametocyte carrier. The role of immunity inmodulating the infectivity of gametocytes cannot be excluded. Finally, the infection rate depends on mosquito factors.(ABSTRACT TRUNCATED AT 400 WORDS)
Boudin
C
C
Lyannaz
J
J
Bosseno
M F
MF
Chaize
J
J
Carnevale
P
P
D000821:Animal Feed; D000818:Animals; D000852:Anopheles / Q000254:growth & development* / Q000469:parasitology; D001769:Blood; D001947:Breeding; D002050:Burkina Faso; D005260:Female; D010963:Plasmodium falciparum / Q000254:growth & development*; D011156:Population Density; D013696:Temperature
Production de sporozoïtes de Plasmodium humains à Bobo-Dioulasso (Burkina Faso).