The online version of this article (doi:10.1186/1475-2875-11-380) contains supplementary material, which is available to authorized users.
The authors declare that they have no competing interests.
Conceived, designed and managed the study protocol: PJM, TM, IH, MM. Undertook the field collections and laboratory analyses: TM. Interpreted, analysed data and wrote the paper: TM, PJM, IH. All authors read, edited and approved the final version of the manuscript.
Although malaria is highly prevalent throughout Malawi, little is known of its transmission dynamics. This paper describes the seasonal activity of the different vectors, human biting indices, sporozoite rates and the entomological inoculation rate in a low-lying rural area in southern Malawi.
Vectors were sampled over 52 weeks from January 2002 to January 2003, by pyrethrum knockdown catch in two villages in Chikhwawa district, in the Lower Shire Valley.
In total, 7,717 anophelines were collected of which 55.1% were Anopheles gambiae sensu lato and 44.9% were Anopheles funestus. Three members of the An. gambiae complex were identified by PCR: Anopheles arabiensis (75%) was abundant throughout the year, An. gambiae s.s. (25%) was most common during the wet season and Anopheles quadriannulatus occurred at a very low frequency (n=16). An. funestus was found in all samples but was most common during the dry season.
Anopheles gambiae s.s. and An. funestus were highly anthropophilic with human blood indices of 99.2% and 96.3%, respectively. Anopheles arabiensis had fed predominantly on humans (85.0%) and less commonly on cattle (10.9%; 1.2% of blood meals were of mixed origin). Plasmodium falciparum (192/3,984) and Plasmodium malariae (1/3,984) sporozoites were detected by PCR in An. arabiensis (3.2%) and An. funestus (4.5%), and in a significantly higher proportion of An. gambiae s.s. (10.6%)(p<0.01). All three vectors were present throughout the year and malaria transmission occurred in every month, although with greatest intensity during the rainy season (January to April). The combined human blood index exceeded 92% and the P. falciparum sporozoite rate was 4.8%, resulting in estimated inoculation rates of 183 infective bites/ person per annum, or an average rate of ~15 infective bites/person/month.
The results demonstrate the importance of An. gambiae s.s., An. arabiensis and An. funestus in driving the high levels of malaria transmission in the south of Malawi. Sustained and high coverage or roll out of current approaches to malaria control (primarily insecticide-treated bed nets and indoor residual house spraying) in the area are likely to reduce the observed high malaria transmission rate and consequently the incidence of human infections, unless impeded by increasing resistance of vectors to insecticides.
Malawi Demographic and Health Survey 2010. 2011, Zomba: National Statistical Office, http://www.measuredhs.com/pubs/pdf/PR4/PR4.pdf,
Davey JB, Newstead R: Mosquitoes and other blood-sucking arthropods of the Upper Shire River. Nyasaland Ann Trop Med Parasitol. 1921, 15: 457-462.
Lamborn WA: The seasonal habit of the common anophelines of Nyasaland, with a note on its relation to the seasonal incidence of malaria. Bull Entomol Res. 1924, 15: 361-376. CrossRef
Berner WA: Mosquitoes of the Shire River system, Nyasaland. Ann Entomol Soc America. 1955, 48: 214-218. CrossRef
Hawley WA, Sexton JD, Tambala P, Macheso A, Zimba C, Chitsulo L, Nyanwayu D, Nyasulu Y, Franco C, Kazembe P: Malaria vector assessment, Malawi: Oct 1991 - Sept 1992. 1992, USAID, Lilongwe, Malawi: Unpublished report
Spiers AA, Mzilahowa T, Atkinson D, McCall PJ: The malaria vectors of the Lower Shire Valley, Malawi. Malawi Med J. 2002, 14: 4-7.
Chiphwanya JA: Evaluation of insecticide susceptibility in malaria vector mosquitoes and their role in malaria transmission in central Malawi. 2003, Johannesburg: University of Witwatersrand
President's Malaria Initiative: Malaria Operational Plan (MOP) Malawi Year Five - FY2011. 2011, http://www.pmi.gov/countries/mops/fy11/malawi_mop-fy11.pdf,
Skarbinski J, Mwandama D, Wolkon A, Luka M, Jafali J, Smith A, Mzilahowa T, Gimnig J, Campbell C, Chiphwanya J: Impact of indoor residual spraying with lambda-cyhalothrin on malaria parasitemia and anemia prevalence among children less than five years of age in an area of intense, year-round transmission in Malawi. AmJTrop Med Hyg. 2012, 86: 997-1004. CrossRef
WHO: Manual on Practical Entomology. Part II. Methods and Techniques. 1975, Geneva: World Health Organization
Gillies MT, Coetzee M: A supplement to the Anophelinae of Africa south of the Sahara (Afrotropical Region). 1987, Johannesburg: The South African Institute for Medical Research
Gillies MT, de Meillon B: The Anophelinae of Africa south of the Sahara (Ethiopian Region). 1968, Johannesburg: The South African Institute for Medical Research
Collins FH, Mendez MA, Rasmussen MO, Mehaffey PC, Besansky NJ, Finnerty V: A ribosomal RNA gene probe differentiates member species of the Anopheles gambiae complex. AmJTrop Med Hyg. 1987, 37: 37-41.
Scott JA, Brogdon WG, Collins FH: Identification of single specimens of the Anopheles gambiae complex by the polymerase chain reaction. AmJTrop Med Hyg. 1993, 49: 520-529.
Mendis C, Jacobsen JL, Gamage-Mendis A, Bule E, Dgedge M, Thompson R, Cuamba N, Barreto J, Begtrup K, Sinden RE, Høgh B: Anopheles arabiensis and An. funestus are equally important vectors of malaria in Matola coastal suburb of Maputo, southern Mozambique. Med Vet Entomol. 2000, 14: 171-180. CrossRefPubMed
Thompson R, Begtrup K, Cuamba N, Dgedge M, Mendis C, Gamage-Mendis A, Enosse SM, Barreto J, Sinden RE, Hogh B: The Matola malaria project: a temporal and spatial study of malaria transmission and disease in a suburban area of Maputo, Mozambique. AmJTrop Med Hyg. 1997, 57: 550-559.
Githeko AK, Service MW, Mbogo CM, Atieli FK, Juma FO: Plasmodium falciparum sporozoite and entomological inoculation rates at the Ahero rice irrigation scheme and the Miwani sugar-belt in western Kenya. Ann Trop Med Parasitol. 1993, 87: 379-391. PubMed
Fornadel CM, Norris DE: Increased endophily by the malaria vector Anopheles arabiensis in southern Zambia and identification of digested blood meals. AmJTrop Med Hyg. 2008, 79: 876-880.
Kent RJ, Thuma PE, Mharakurwa S, Norris DE: Seasonality, blood feeding behavior, and transmission of Plasmodium falciparum by Anopheles arabiensis after an extended drought in southern Zambia. AmJTrop Med Hyg. 2007, 76: 267-274.
Fornadel CM, Norris LC, Glass GE, Norris DE: Analysis of Anopheles arabiensis blood feeding behavior in southern Zambia during the two years after introduction of insecticide-treated bed nets. AmJTrop Med Hyg. 2010, 83: 848-853. CrossRef
Beier JC, Killeen GF, Githure JI: Entomologic inoculation rates and Plasmodium falciparum malaria prevalence in Africa. AmJTrop Med Hyg. 1999, 61: 109-113.
Slutsker L, Khoromana CO, Hightower AW, Macheso A, Wirima JJ, Breman JG, Heymann DL, Steketee RW: Malaria infection in infancy in rural Malawi. AmJTrop Med Hyg. 1996, 55 (1 Suppl): 71-76.
- Entomological indices of malaria transmission in Chikhwawa district, Southern Malawi
Ian M Hastings
Malcolm E Molyneux
Philip J McCall
- BioMed Central
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