Abstract
BackgroundThe Republic of Yemen has the highest incidence of malaria in the Arabian Peninsula, yet little is known of its vectors or transmission dynamics.MethodsA 24-month study of the vectors and related epidemiological aspects of malaria transmission was conducted in two villages in the Taiz region in 2004–2005.ResultsCross-sectional blood film surveys recorded an overall malaria infection rate of 15.3 % (250/1638), with highest rates exceeding 30 % in one village in May and December 2005. With one exception, Plasmodium malariae, all infections were P.falciparum. Seven Anopheles species were identified among 3407 anophelines collected indoors using light traps (LT) and pyrethrum knockdown catches (PKD): Anopheles arabiensis (86.9 %), An. sergentii (9 %), An. azaniae, An. dthali, An. pretoriensis, An. coustani and An. algeriensis. Sequences for the standard barcode region of the mitochondrial COI gene confirmed the presence of two morphological forms of An. azaniae, the typical form and a previously unrecognized form not immediately identifiable as An. azaniae. ELISA detected Plasmodium sporozoites in 0.9 % of 2921 An. arabiensis (23 P. falciparum, two P. vivax) confirming this species as the primary malaria vector in Yemen. Plasmodium falciparum sporozoites were detected in An. sergentii (2/295) and a single female of An. algeriensis, incriminating both species as malaria vectors for the first time in Yemen. A vector in both wet and dry seasons, An. arabiensis was predominantly anthropophilic (human blood index = 0.86) with an entomological inoculation rate of 1.58 infective bites/person/year. Anopheles sergentii fed on cattle (67.3 %) and humans (48.3; 20.7 % mixed both species), but only 14.7 % were found in PKDs, indicating predominantly exophilic behaviour. A GIS analysis of geographic and socio-economic parameters revealed that An. arabiensis were significantly higher (P < 0.001) in houses with televisions, most likely due to the popular evening habit of viewing television collectively in houses with open doors and windows.ConclusionsThe predominantly indoor human biting vectors recorded in this study could be targeted effectively with LLINs, indoor residual spraying and/or insecticide-treated window/door curtains reinforced by education to instil a perception that effective and affordable malaria prevention is achievable.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1179-8) contains supplementary material, which is available to authorized users.
Highlights
The Republic of Yemen has the highest incidence of malaria in the Arabian Peninsula, yet little is known of its vectors or transmission dynamics
Malaria is the most important vector-borne disease in the Republic of Yemen, where approximately 65 % of the population are estimated to be at risk of infection and where the majority of malaria cases in the Arabian Peninsula occur [1, 2]
Plasmodium falciparum is widespread and responsible for more than 95 % of all cases, with the remainder caused by P. vivax and P. malariae [1, 3, 4]
Summary
The Republic of Yemen has the highest incidence of malaria in the Arabian Peninsula, yet little is known of its vectors or transmission dynamics. Malaria is the most important vector-borne disease in the Republic of Yemen, where approximately 65 % of the population are estimated to be at risk of infection and where the majority of malaria cases in the Arabian Peninsula occur [1, 2]. The World Health Organization (WHO) reported that the number of confirmed cases fluctuates from year to year and precise estimates of incidence of malaria have been difficult to produce [1]. Malaria can be the primary cause of paediatric hospital admissions (up to 40 % in the peak malaria season), with a 0.9 % mortality rate among infected individuals [6]
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