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Malaria vectors in Angola: distribution of species and molecular forms of the Anopheles gambiae complex, their pyrethroid insecticide knockdown resistance (kdr) status and Plasmodium falciparum sporozoite rates

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Cuamba, N., Choi, K.S. and Townson, Harold (2006) 'Malaria vectors in Angola: distribution of species and molecular forms of the Anopheles gambiae complex, their pyrethroid insecticide knockdown resistance (kdr) status and Plasmodium falciparum sporozoite rates'. Malaria Journal, Vol 5, Issue 2.

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Abstract

Background: Malaria is by far the greatest cause of morbidity and mortality in Angola, being responsible for 50% of all outpatient attendance and around 22% of all hospital deaths, yet by 2003 only 2% of under-5s used insecticide-treated nets. Entomological studies are an essential foundation for rational malaria control using insecticide-treated nets and indoor residual spraying, but there have been no published studies of malaria vectors in Angola over the 27 years of the civil war, to its end in 2002. This paper describes studies arising from a WHO-sponsored visit in support of the National Malaria Control Programme.
Methods: During April 2001, mosquitoes were sampled by indoor pyrethrum spray collection from four sites in the semi-arid coastal provinces of Luanda and Benguela and two sites in Huambo province, in the humid tropical highlands. Collections took place towards the end of the rainy season and were used to determine the Anopheles species present, their sporozoite rates and the frequency of a kdr allele conferring resistance to pyrethroid insecticides.
Results: A PCR test for the Anopheles gambiae complex showed a preponderance of An. gambiae, with indoor resting densities ranging from 0.9 to 23.5 per house. Of 403 An. gambiae identified to molecular form, 93.5% were M-form and 6.5% S-form. M and S were sympatric at 4 sites but no M/ S hybrids were detected. The highest proportion of S-form (20%) was in samples from Huambo, in the humid highlands. Anopheles funestus was found at one site near Luanda. The sporozoite rate of mosquitoes, determined by an ELISA test, was 1.9% for An. gambiae (n = 580) and 0.7% for An. funestus ( n = 140). Of 218 An. gambiae (195 M-form and 23 S-form) genotyped for the West African kdr-resistance allele, all were homozygous susceptible.
Conclusion: An. gambiae M-form is the most important and widespread malaria vector in the areas studied but more extensive studies of malaria vectors are required to support the malaria control programme in Angola. These should include standard insecticide resistance biossays and molecular assays that can detect both metabolic resistance and target site insensitivity.

Item Type: Article
Uncontrolled Keywords: incipient speciation west-africa identification s.s. differentiation populations coastal melas assay pcr
Subjects: QW Microbiology and Immunology > QW 45 Microbial drug resistance. General or not elsewhere classified.
QX Parasitology > Protozoa > QX 135 Plasmodia
QX Parasitology > Insects. Other Parasites > QX 515 Anopheles
QX Parasitology > Insects. Other Parasites > QX 600 Insect control. Tick control
QX Parasitology > Insects. Other Parasites > QX 650 Insect vectors
WA Public Health > Preventive Medicine > WA 110 Prevention and control of communicable diseases. Transmission of infectious diseases
WA Public Health > Preventive Medicine > WA 240 Disinfection. Disinfestation. Pesticides (including diseases caused by)
WB Practice of Medicine > Therapeutics > WB 340 Drug Administration
WB Practice of Medicine > Medical Climatology > WB 710 Diseases of geographic areas
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 750 Malaria
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 765 Prevention and control
Faculty: Department: Groups (2002 - 2012) > Vector Group
Digital Object Identifer (DOI): https://doi.org/10.1186/1475-2875-5-2
Depositing User: Sarah Lewis-Newton
Date Deposited: 11 Feb 2011 10:58
Last Modified: 06 Feb 2018 13:01
URI: http://archive.lstmed.ac.uk/id/eprint/1466

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