[Role of Culex quinquefasciatus in the transmission of bancroftian filariasis in the Federal Islamic Republic of Comoros (Indian Ocean)]. / Role de Culex quinquefasciatus dans la transmission de la filariose de Bancroft dans la République Fédérale islamique des Comores (Océan Indien).

In October 1988-January 1989, as a part of a malaria and filariasis control programme in Federal Islamic Republic of Comoros an entomological survey was carried out in 19 rural and urban localities of Grande Comore. Anjouan and Moheli Islands. The potential breeding places were examined and pyrethrum spray catches were made to evaluate the indoor resting densities of mosquitos. A total of 14.578 adult mosquitos potential vectors of filariasis was collected: 94.5% Culex quinquefasciatus, 3.5% Anopheles gambiae s. str. 1.9% A. funestus and 0.1% other anopheline species. A. funestus, uniformly spread in Moheli, was present only in the south-west coast of Anjouan and absent in Grande Comore. A. gambiae and Cx quinquefasciatus were present in Grande Comore. A. gambiae and Cx quinquefasciatus were present in the three islands with different densities in the villages. Only Cx quinquefasciatus specimens la maximum of 150 for each locality) were dissected to search filaria larvae being the Anopheles specimens used to evaluate the malaria transmission. The global infection rate (9.4%) and the infectivity rate (0.9%) observed in Cx quinquefasciatus are higher than indices reported in previous surveys. All the larvae in the third development instar (L3) were identified as Wuchereria bancrofti. The results suggest that in FIR of Comoros W. bancrofti is well adopted to local Cx quinquefasciatus population. Because of the presence of high mosquito density this species plays a prominent role in the transmission of lymphatic filariasis in that area. The high transmission levels calls for the implementation of a specific control program.

[Impact of the use of larvivorous fish Poecilia reticulata on the transmission of malaria in FIR of Comoros]. / Impact de l'utilisation du poisson larvivore Poecilia reticulata sur la transmission du paludisme en RFI des Comores.

Field tests were conducted in the Grande Comore Island, Federal Islamic Republic of Comoros, in order to evaluate the potential of the larvivorous fish Poecilia reticulata for the control of the malaria vector Anopheles gambiae s.s. Due to the high permeability of soil, Anopheles breeding sites in all island occurs only in the man-made water reservoirs. The study was carried out from November 1987 to November 1988 within a framework of a malaria and filariasis control programme, supported by WHO and UNDP in collaboration with the Government of the FIR of Comoros. All larval breeding places of An. gambiae existing in the village of Hantsambou were recorded (59 ablutions basins and 61 cisterns) and provided initially with 3-5 specimens of P. reticulata/m3 in November 1987, after the importation of the larvivorous species from Mayotte Island. The percentage of breeding places positive for An. gambiae decreased from 41% to 6% after one year. Pyrethrum spray catch showed a reduction of indoor resting density from 5.5 to 0.3, while the ma value, number of Anopheles bites/man/night, obtained by night-biting catches, decreased from 6.3 to 1.2. At the same time of the reduction of entomological indices parasite index for P. falciparum and spleen rate drop steadily in 5-9 years school children. The tested vector control method, well accepted by the community, could be implemented in malaria control through primary health care, being the ecological conditions in the entire island very peculiar.

The Anopheles gambiae complex in the Federal Islamic Republic of Comoros (Indian Ocean): some cytogenetic and biometric data.

Samples of adult females of the Anopheles gambiae complex from thirteen localities of three islands of the Comoro Archipelago (Anjouan, Grande Comore and Moheli) were identified by analysis of ovarian polytene chromosomes as An. gambiae s.s. The samples showed only the inversion polymorphism 2La, the mean frequency of the inverted arrangement being 38%. A significantly higher frequency of the inverted arrangement 2La was observed in the localities with a lower annual rainfall. Similarities between the chromosomal polymorphism of the samples from Comoros and that of coastal eastern African countries suggest a probable continental origin of the An. gambiae s.s. populations in the Comoro Archipelago. A biometric analysis was carried out on the palpal index and the number of coeloconic sensilla, two characters partially diagnostic between fresh- and salt-water members of the gambiae complex. The palpal index of the 2La homozygous inverted females of An. gambiae s.s. was found to be significantly higher than the index of standard homozygotes and heterozygotes, suggesting a relation between the inversion and this biometric character. No An. merus was identified, although larvae of An. gambiae s.l. were observed breeding in brackish water.