Seasonal density, sporozoite rates and entomological inoculation rates of <i>Anopheles gambiae</i> and <i>Anopheles funestus</i> in a high‐altitude sugarcane growing zone in western kenya

Shililu, Josephat; Maier, Walter; Seitz, H. M.; Orago, Alloys S. S.

doi:10.1046/j.1365-3156.1998.00282.x

Cited by 82 publications

(77 citation statements)

References 8 publications

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“…1) during 2002 and 2003, of which 181 (3.9%) mosquitoes were infected by P. falciparum oocysts, with 6.0 Ϯ 0.7 oocysts per infected mosquito (Table 1), values similar to those obtained in previous studies of the same region (24,25). The allele frequencies (Table 2) are based on 613 oocysts from 145 mosquitoes; some oocysts were lost during extraction from the mosquito guts.…”

Section: Resultssupporting

confidence: 81%

“Clonal” population structure of the malaria agent Plasmodium falciparum in high-infection regions

Razakandrainibe

Durand

Koella

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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The population genetic structure of Plasmodium falciparum, the agent of malignant malaria, has been shown to be predominantly ''clonal'' (i.e., highly inbred) in regions of low infectivity; in highinfectivity regions, it is often thought to be panmictic, or nearly so, although there is little supporting evidence for this. The matter can be settled by investigating the parasite's genetic makeup in the midgut oocysts of the mosquito vector, where the products of meiosis can directly be observed. The developmental stages of P. falciparum are haploid, except in the oocysts of infected mosquito vectors, where two gametes fuse, diploidy occurs, and meiosis ensues. We have investigated genetic polymorphisms at seven microsatellite loci located on five chromosomes by assaying 613 oocysts in 145 mosquitoes sampled from 11 localities of Kenya, where malignant malaria is perennial and intense. There is considerable allelic variation, 16.3 ؎ 2.1 alleles per locus, and considerable inbreeding, Ϸ50% on the average. The inbreeding is caused by selfing (Ϸ25%) and nonrandom genotype distribution of oocysts among mosquito guts (35%). The observed frequency of heterozygotes is 0.43 ؎ 0.03; the expected frequency, assuming random mating, is 0.80 ؎ 0.05. Linkage disequilibrium is statistically significant for all 21 pairwise comparisons between loci, even though 19 comparisons are between loci in different chromosomes, which is consistent with strong deviation from panmixia and the consequent reproduction of genomes as clones, without recombination between gene loci. This is of considerable evolutionary significance and of epidemiological consequence, concerning the spread of multilocus drug and vaccine resistance.epidemiology ͉ evolutionary genetics ͉ parasitism ͉ population genetics

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Section: Resultssupporting

confidence: 81%

“Clonal” population structure of the malaria agent Plasmodium falciparum in high-infection regions

Razakandrainibe

Durand

Koella

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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“…Samples were considered positive if the optical densities (OD) were at least twice the mean of four negative wells on the same plate. 21 Positive controls were female mosquitoes with known blood meals. Negative control contained male mosquito triturates.…”

Section: Identification Of Blood Meal Originmentioning

confidence: 99%

“…Any sample giving an OD that was at least twice that of the mean OD for the negative controls on the same plate was considered CSP positive. 21 Positive samples were retested for confirmation.…”

Section: Plasmodium Falciparum Sporozoite Ratementioning

confidence: 99%

Transmission dynamics of malaria in four selected ecological zones of Nigeria in the rainy season

et al. 2009

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Background:Two of the problems of malaria parasite vector control in Nigeria are the diversity of Anopheline vectors and large size of the country. Anopheline distribution and transmission dynamics of malaria were therefore compared between four ecotypes in Nigeria during the rainy season. Methods: Polymerase chain reaction (PCR) was used in molecular identification after morphological identification microscopically. Enzyme linked immunorsorbent assay (ELISA) was used for the blood meal analysis and sporozoite detection. Results: Five species were identified out of 16,410 anophelines collected. An. gambiae s.s made up approximately 29.2%-36.6% of the population in each zone. All five species acted as vectors for P. falciparum. An. gambiae s.s had the highest sporozoite rate. The most infected mosquitoes were found in the rain forest. More blood meals were taken from bovids, except the savannah forest, where 73.3% were on humans and Human Blood index (HBI) was 57.3%. The Entomological inoculation rate (EIR) was a mean of 13.6 ib/p but was highest in the rainforest zone. Conclusions and limitations:This study demonstrates the complex distribution of anophelines and the considerable variations in the intensity of malaria transmission in Nigeria. We highlight the need to consider diverse epidemiological situations when planning countrywide control programmes. Key words: Malaria; vectors; Plasmodium falciparum; transmission dynamics; ecotypes RésuméFond: Deux des problèmes de la commande de vecteur de parasite de malaria au Nigéria sont la diversité des vecteurs d'Anopheline et grande taille du pays. La distribution d'Anopheline et la dynamique de transmission de la malaria ont été donc comparées entre quatre ecotypes au Nigéria pendant la saison des pluies. Méthodes: La réaction en chaîne de polymérase (PCR) a été employée dans l'identification moléculaire après identification morphologique au microscope. L'analyse immunorsorbent liée par enzyme (ELISA) a été employée pour la détection d'analyse et de sporozoite de repas de sang. Résultats: Cinq espèces ont été identifiées sur 16.410 anophelines rassemblés. gambiae s.s composés approximativement 29.2-36.6% de la population dans chaque zone. Chacune des cinq espèces a agi en tant que vecteurs pour P. falciparum. gambiae s.s a eu le taux de sporozoite le plus élevé. Les moustiques les plus infectés ont été trouvés dans la forêt tropicale . Plus de repas de sang ont été pris des bovids, excepté la forêt de la savane, où 73.3% étaient sur des humains et l'index humain de sang (HBI) était 57.3%. Le taux entomologique d'inoculation (EIR) était un moyen de 13.6 ib/p mais était le plus haut dans la zone de forêt tropicale.

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“…[1][2][3][4][5][6][7] This species is the primary malaria vector in large regions of southern Zambia. 8 Unlike its sibling species An.…”

Section: Introductionmentioning

confidence: 99%

Frequency of Multiple Blood Meals Taken in a Single Gonotrophic Cycle by Anopheles arabiensis Mosquitoes in Macha, Zambia

Norris¹,

Fornadel

Hung

et al. 2010

The American Society of Tropical Medicine and Hygiene

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Anopheles arabiensis is a major vector of Plasmodium falciparum in southern Zambia. This study aimed to determine the rate of multiple human blood meals taken by An. arabiensis to more accurately estimate entomologic inoculation rates (EIRs). Mosquitoes were collected in four village areas over two seasons. DNA from human blood meals was extracted and amplified at four microsatellite loci. Using the three-allele method, which counts ≥ 3 alleles at any microsatellite locus as a multiple blood meal, we determined that the overall frequency of multiple blood meals was 18.9%, which was higher than rates reported for An. gambiae in Kenya and An. funestus in Tanzania. Computer simulations showed that the three-allele method underestimates the true multiple blood meal proportion by 3–5%. Although P. falciparum infection status was not shown to influence the frequency of multiple blood feeding, the high multiple feeding rate found in this study increased predicted malaria risk by increasing EIR.

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Seasonal density, sporozoite rates and entomological inoculation rates of Anopheles gambiae and Anopheles funestus in a high‐altitude sugarcane growing zone in western kenya

Cited by 82 publications

References 8 publications

“Clonal” population structure of the malaria agent Plasmodium falciparum in high-infection regions

“Clonal” population structure of the malaria agent Plasmodium falciparum in high-infection regions

Transmission dynamics of malaria in four selected ecological zones of Nigeria in the rainy season

Frequency of Multiple Blood Meals Taken in a Single Gonotrophic Cycle by Anopheles arabiensis Mosquitoes in Macha, Zambia

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