Elsevier

Acta Tropica

Volume 121, Issue 2, February 2012, Pages 85-92
Acta Tropica

Entomological and epidemiological attributes for malaria transmission and implementation of vector control in southern Iran

https://doi.org/10.1016/j.actatropica.2011.04.017Get rights and content

Abstract

Bashagard is an important malaria endemic area in south of Iran. An epidemiological and entomological survey was performed during 2002–2010. The aim of study was to determine malaria situation, species composition of anopheline mosquitoes and susceptibility status of main vectors to insecticides/larvicides. A total of 13,490 malaria cases were recorded, Plasmodium vivax (99.64%), P. falciparum (0.35%) and mix cases (0.01%). The highest and lowest Annual Parasite Incidence (API) were observed in 2007 (145.72/1000) and 2009 (6.29/1000), respectively. Anopheles culicifacies, An. dthali, An. stephensi, An. superpictus, An. fluviatilis, An. moghulensis, An. turkhudi and An. apoci were collected from the area. Two peak activities occur in April and October. The first five species were confirmed as malaria vectors in Iran. No indication of sporozoite in mosquitoes using molecular method was performed. Susceptibility tests using diagnostic dose of insecticides and larvicides showed only resistance of An. stephensi to DDT. Tolerance in An. stephensi to deltamethrin and bendiocarb is reported. The same phenomenon was observed in An. culicifacies to DDT, propoxur and deltamethrin, and in An. dthali to malathion and deltamethrin. Larvae of vectors were susceptible to all larvicides, except for An. stephensi that exhibited tolerance to fenthion. In conclusion it should be emphasized that malaria transmission is a complex process in Bashagard. This event is attributed to five proven vectors with different behaviors which are active in the area. Regarding tolerance of vectors to deltamethrin, resistance management is suggested by using new insecticide with novel mode of action.

Graphical abstract

Plasmodium vivax and Anopheles culicifacies s.l. are the main parasite and vector of malaria in Bashagard County, respectively. Resistance to DDT was found in An. stephensi.

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Highlights

Malaria is the most important vector borne disease in Hormozgan province, southern Iran. Bashagard district is one of the important malaria endemic areas in this part of the country. During 2002–2009 a total of 13,490 malaria cases were recorded, caused mainly by Plasmodium vivax. Anopheles culicifacies, An. stephensi, An. dthali, An. superpictus and An. fluviatilis, the five proven malaria vectors in Iran, were collected from the study area. An. stephensi was resistant to DDT 4%.

Introduction

Malaria is one of the most important vector-borne diseases in Iran. The total population at risk is 2,714,648 persons, who mainly live in endemic foci of the disease including provinces of Kerman, Hormozgan, and Sistan and Baluchistan. First report of malaria situation in Iran is back to Gilmour (1925) who had estimated that 60% of the total population was living in highly endemic areas for malaria, with 4–5 million cases annually. The national malaria eradication program was started in 1958 and renewed to malaria control in 1987 and the changing policy is due to the existence of serious technical problems and administrative difficulties (Manouchehri et al., 1992). Since 1988, malaria control activities have been integrated in primary health centers. According to the Ministry of Health of the country (unpublished data) the total number of malaria cases in Iran had been declined to 2900 cases in 2010.

Over the past 85 years, many investigators have worked on malaria and their findings were used to manage the control programs. Altogether a total of 33 Anopheles, including siblings, biological forms and genotypes were recorded, among which a total of 7 (including 17 siblings, biological forms and genotypes) have been implicated as main vectors. An. stephensi, An. dthali, An. culicifacies, An. fluviatilis, An. superpictus, An. sacharovi and An. maculipennis, while An. pulcherrimus is also reported as a suspected vector (Jalali-Moslem, 1956, Manouchehri et al., 1975, Manouchehri et al., 1992, Eshghi et al., 1976, Zaim et al., 1993, Yaghoobi-Ershadi et al., 2001, Zahirnia et al., 2001, Naddaf et al., 2003, Oshaghi et al., 2003a, Oshaghi et al., 2006, Sedaghat et al., 2003a, Sedaghat et al., 2003b, Edrissian, 2006, Vatandoost et al., 2006a, Vatandoost et al., 2007, Azari-Hamidian, 2007).

Insecticide/larvicide resistance status of vectors has been monitored under laboratory and field conditions. Resistance to DDT, dieldrin and malathion is reported in a number of species, however almost all vectors are susceptible to larvicides (Manouchehri et al., 1992, Zahirnia et al., 1998, Vatandoost, 2001, Salari Lak et al., 2002, Enayati et al., 2003, Vatandoost et al., 2004, Vatandoost et al., 2005, Vatandoost et al., 2009a, Vatandoost and Borhani, 2004, Vatandoost and Vaziri, 2004, Vatandoost and Hanafi-Bojd, 2005, Hanafi-Bojd et al., 2006, Edrissian, 2006, Davari et al., 2007, Abai et al., 2008, Vatandoost and Zahirnia, 2010). Different repellents have been evaluated to find the suitable compound for travelers to the endemic area of the disease (Oshaghi et al., 2003b, Vatandoost and Hanafi-Bojd, 2008, Vatandoost et al., 2008). Bed-nets are also tested under field and laboratory conditions (Vatandoost et al., 2006b, Vatandoost et al., 2009b, Kayedi et al., 2008, Rafinejad et al., 2008). There are some reports on the olfaction of An. stephensi to different chemicals for potential use in magnet traps (Omrani et al., 2010a, Omrani et al., 2010b).

Around 68% of malaria positive cases belonged to provinces of Sistan and Baluchistan, Hormozgan, and Kerman in 2002, whereas it increased to 95% in 2007 (Raeisi et al., 2009). Hormozgan province is highly endemic area for malaria. It constitutes 38% of all country malaria cases (Raeisi et al., 2009). In this province approximately 625 cases of malaria were reported during 2009. Bashagard district constitutes only 2.18% of the total population of Hormozgan province. Its malaria cases contributed 33% of total malaria cases solely (Hormozgan Health Center, unpublished data). Tropical climate and socio-economic conditions make appropriate situation for occurrence and persistent transmission of malaria in this district. Active and passive case detection, indoor residual spraying, larviciding, and long lasting impregnated bed-nets, Olyset® are the main malaria control activities in this area.

The purpose of this study was to review the current malaria situation. The results could be used to vector control interventions cost-effectively.

Section snippets

Study area

Bashagard district is located in the north-east of Hormozgan province, southern Iran. Latitude and longitude of the center of this district, called Sardasht, is 26°21′N and 57°54′E (Fig. 1). Bashagard had a total population of 31,292 in 2009. The area is mountainous with low precipitation. It has hot and dry climate. Rainfall usually occurs during the year in shower type. During the study period relative humidity was ranged between 30 and 65%. Average annual rainfall was 265 mm with two peaks in

Malaria situation

A total of 13,490 malaria cases were recorded and treated in Bashagard district during the study period. P. vivax (99.64%) was the main causative agent, although P. falciparum (0.35%) and mix infection (0.01%) were reported. Epidemiological evidence showed the majority of cases of indigenous, while the imported cases were rare (0.13%). Males were infected more than females. Population under 14 years old had the highest infection rate (Table 1). Z test showed significant difference between male

Discussion

The API showed an increasing rate from 2002 to 2007, except for 2004. This increasing trend has interrupted after 2005 in Bandar Abbas County, another malaria focus in Hormozgan province, by management of control activities (Hanafi-Bojd et al., 2010). The malaria incidence had the same trend with rainfall prior to 2007, when the implication of impregnated bed-nets was not the control activities. Only in 2004 total amount of precipitation is not followed the pattern. In this year a heavy

Acknowledgements

This article is a part of the results of the first author's dissertation for fulfillment of a Ph.D. degree in Medical Entomology and Vector Control from Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. The authors are very grateful to the National Institute of Health Research, Bandar Abbas Research Station, Health Center of Hormozgan province and Hormozgan Meteorological Center for their kind collaboration during

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