Microsoft Word - 3-vatandoost-Rtl.doc Iranian J Arthropod-Borne Dis, (2007), 1(1): 21-27 H Vatandoost et al.: Ecology of Anopheles… 21 Original Article Ecology of Anopheles dthali Patton in Bandar Abbas District, Hormozgan Province, Southern Iran *H Vatandoost, M Shahi, AA Hanafi-Bojd, MR Abai, MA Oshaghi, F Rafii Dept. of Medical Entomology and Vector Control, School of Public Health and Institute of Public Health Research, Medical Sciences/Tehran University, Iran (Received 9 Oct 2006; accepted 19 Feb 2007) ABSTRACT Ecology of Anopheles dthali was studied in Bandar Abbas County, where there is indigenous malaria. Anopheles dthali plays as a secondary malaria vector in the region. It is active throughout the year in mountainous area with two peaks of activity, whereas in coastal area it has one peak. There is no report of hibernation or aestivation for this species in the re- gion. Precipitin tests on specimens from different parts showed that 15.6-20.8% were positive for human blood. This species usually rests outdoors. It has different larval habitats. Insecticides susceptibility tests on adult females exhibited susceptibil- ity to all insecticides recommended by WHO. LT50 for the currently used insecticide, lambda-cyhalothrin, is measured less than one minute. The irritability tests to pyrethroid insecticides, showed that permethrin and lambda-cyhalothrin had more irritancy compared to deltamethrin and cyfluthrin. Larval bioassay using malathion, chlorpyrifos, temephos and fenithrothion did not show any sing of resistance to these larvicides at the diagnostic dose. It is recommended that all the decision makers should consider the results of our study for any vector control measures in the region. Keywords: Ecology, Anopheles dthali, Malaria vector, Iran, Resistance INTRODUCTION Anopheles dthali is a malaria vector in some parts of the world. This species has been sus- pected as a vector of malaria in Saudi Arabia (Patton 1905). In 1961 Rishikesh reported that An. dthali was a secondary vector in the north- ern region of Somalia. Anopheles dthali Patton is widespread in north Ethiopia and Somalia, Socotra, north Africa to north west of Pakistan, Southwest of Saudi Arabia, around the Red sea and Adan Gulf (Christophers 1933, De Meillon 1947, Stone et al. 1959, Gillies and De Meillon 1968) and Eritrea (Shililu et al. 2003). This species in also one of the malaria vec- tors in Iran and has been found in southern parts of Zagros chain (Manouchehri and Rohani 1975). Bandar Abbas County is contained within the Hormozgan area of the Iran where malaria was prevalent in hyperendemic in the region up to 1958 before the national malaria eradication program was started in Iran. Anopheles dthali is one of the malaria vectors in Hormozgan. This species is responsible for maintaining malaria transmission in the area when An. stephensi is absent (Manouchehri et al. 1972). In October 1965, during entomological studies in highland area of Bandar Abbas out of 143 An. dthali dis- sected, two were found with infected salivary glands to sporozoites (IHR 1965). Therefore the study on the ecology of An. dthali might be valuable for planning and man- agement of malaria control in the areas concerned. In Iran, An. dthali has been found in southern parts of the Zagros chain, in the provinces of Hormozgan, Baluchestan, Kerman, Fars, Yazd, Khuzestan, Kermanshah, Khorassan and coastal area of the Persian Gulf up to 1410 m altitude *Corresponding author: Dr H Vatandoost, Tel: +98 21 88951393, E-mail: hvatandoost@yahoo.com Iranian J Arthropod-Borne Dis, (2007), 1(1): 21-27 H Vatandoost et al.: Ecology of Anopheles… 22 in Hamadan (Manouchehri et al. 1972). In Hor- mozgan province An. dthali is widespread throughout the coastal and mountainous areas from southwest to the southeast. It has been re- ported from coastal areas of Hormozgan from Bandar Lengeh to Jask county and Qeshm island. This species can be found mainly outdoors in animal houses, as well as human dwelling. Manouchehri and Rohani (1975) found that this species is more prevalent in animal shelters, tent and human dwellings. This species rests in water reservoir, warehouse, septum of well, cave and natural shelters such as holes in river- banks. The adults are very sensitive to light and often disturbed by torchlight. It has been re- ported (Gillies and De Meillon 1968) that in southern Arabia, Mauritania and Somalia the adults are not uncommon indoors. This species is a secondary vector in some parts of southern Iran especially in mountainous areas of Hormozgan province (Manouchehri 1972). In hilly areas and valley of Hormozgan it is associated with An. fluviatilis and An. ste- phensi (Manouchehri et al. 1972). In the coastal areas of the province the density of An. dthali is negligible. In Qeshm island this species is ac- tive in early May reaches a high peak in Au- gust, and then gradually decreases (Fig.1). In mountainous area of province An. dthali is ac- tive during the autumn season and absent dur- ing the cold winter (December-February) and hot weather (Jun-August). In southern Iran two Magoon traps with hu- man and cow bait were used for the collection of anopheline from May to December, the re- sults showed that 87.5% of An. dthali were collected from the trap with cow bait and only 12.5% from the trap with human bait (Manouche- hri and Rohani 1974). Precipitin tests on 517 specimens of this spe- cies, showed that 12.5% were positive for hu- man blood (Edrissian et al. 1985). Another pre- cipitin tests on females caught in houses from the north Bandar Abbas, showed 20.8% posi- tive for human blood. From 4165 blood smears taken from An. dthali have been examined only 15.6% were positive for human blood, it should be emphasized that anthropophilic index de- pends on the area, varying from 1% in Izah, a sheep rearing area, to 25% in Bandar Abbas. The results of precipitin tests from this species caught in houses from mountainous area of Bandar Abbas showed that 20% were positive for human blood (Manouchehri et al. 1972). In Arabia areas, Patton (1905) found the lar- vae of An. dthali in springs and wells. At Mus- cat, Gill (1916) found them in pools, and espe- cially in holes of volcanic rock fed by under- ground water. In Hormozgan this species breeds in pebbly margins of rivers, springs, pits around the springs with or without vegetation, pools in dried-up river beds and palm irrigation canal. In Bandar Abbas county larvae were also found in mineral water. It is also found in water with high salinity (2.7 parts per 1000). The tempera- ture ranging was between 13 ºC and 28 ºC with a pH of 6.9-8.0. Larvae were more abundant during September and October, which is the end of the hot season in southern Iran (Manouche- hri and Rohani 1975). MATERIALS AND METHODS Study area Hormozgan province has two different areas, coastal bond in south and mountain area in north. The study area is located in mountainous part of Bandar Abbas county with surface area of 65379 km2 located in south of Iran (between 25° 24’- 28° 57’ N latitudes and 52° 41’-59° 15’ E longi- tudes). Hormozgan Province located in south and eastern south part of Iran; its eastern neighbors are Kohkiloye and Boyerahmad Province. In the east boarder it is adjacent to Sistan and Balu- chestan and in the southern boarder it is adja- cent to Persian Gulf and Oman Sea and it has Kerman Province in northern boarder and Fars Province in western north boarder. This prov- ince has subtropical climate and a suitable place for preserving and transmission of malaria dis- ease. The total annual rainfall was 100-150 mm and the mean annual relative humidity is 59.5%. Iranian J Arthropod-Borne Dis, (2007), 1(1): 21-27 H Vatandoost et al.: Ecology of Anopheles… 23 The maximum and minimum mean annual tem- peratures are 52 and 6 °C, respectively. Seasonal activity In order to find the seasonal activity of vec- tors, the standard method of WHO (1992) based on total catch were performed in the study area Susceptibility to insecticides Adult and larval susceptibility tests were carried out according to WHO method (World Health Organization 1981). Female mosquitoes were exposed to a diagnostic dose of DDT 4%, dieldrin 0.4%, malathion 5%, fenitrothion 1%, propoxur 0.1%, bendiocarb 0.1%, permethrin 0.75%, deltamethrin 0.05%, lambdacyhalothrin 0.05% and cyfluthrin 0.15%. The room tem- perature and Relative Humidity was 25-29 ºC and 65-80%, respectively. The following lar- vicides were used in this investigation; malathion (3.125 mg/lit), temephos (0.25 mg/lit), feni- trothion (0.125 mg/lit) and chlorpyrifos (0.025 mg/lit) at the diagnostic dose. Butanone 2% in absolute ethanol was used as control. All the concentrations were provided by WHO. Larvae were collected from mountainous area of Ban- dar Abbas County (Siahoo rural district) during 2002, and larviciding tests were carried out on them. In each test there was two control and 4 replicates beakers for testing a single diagnostic dose of larvicides. Mosquito larvae were tested at the late third and early 4th instar according to the method described by WHO 1981. The lar- vae were exposed to a diagnostic dose of lar- vicides. At each concentration, at least 100 lar- vae representing four replicates of 25 were tested. The larvae were fed with Bemax and mortality counts were made after 24 h exposure period. The irritability to lambda-cyhalothrin, permethrin, cyfluthrin and deltamethrin by WHO insecticides impregnated paper were deter- mined. The number of takes off was recorded for 15 min in one min intervals. RESULTS This species is widespread throughout the coastal and mountainous areas with high den- sity in mountain areas. In these areas An. dthali is active throughout the year with two peak, first in September-October and the other in April (Fig.1). This species is associated with An. stephensi and An. fluviatilis in Hormozgan Province. This species has different larval habi- tats. Anthropophility index is varied between 1- 25% depend on locality. A total of 1602 Anophe- les dthali were collected in study areas and tested by WHO method with 10 insecticides and 4 larvicides. The results are shown in tables 1 and 2. Although the Hormozgan Province had been sprayed with DDT since 1952 and subsequently with malathion from 1968, but An. dthali remained susceptible to DDT 4% and dieldrin 0.4%. Furthermore, this species is highly susceptible to organophosphates, carbamat and pyrethroides insecticides. The LT50 and LT90 of lambda-cyhalothrin in sprayed area of Bandar Abbas District were estimated to be 0.74 min and 2.86 min, respectively. The results showed that An. dthali is susceptible to diagnostic dose of these insecticides. DISCUSSION Anopheles dthali is widespread in semi-arid regions from the Atlantic coast of north Africa to Baluchestan, northwest Pakistan and south- ern Iran. It is common in many areas boarding the Red sea and the Gulf of Aden and extends from the Sudan coast through Ethiopia, south- western Arabia and Somalia almost to Moga- dishu (De Meillon 1947, Stone et al. 1959, Gillies and De Meillon 1968). In Iran, An. dthali has been suspected as a vector of malaria. In Octo- ber 1963 during entomological studies in Ban- dar Abbas County of Hormozgan Province a number of An. dthali dissected which three were found with infected salivary gland (Manouchehri et al. 1972). Anopheles dthali has a wide distribution in Hormozgan areas and was collected in all in- spected rural districts. The species showed two peaks of density in Fig.1 and one peak in coastal area of Bandar Abbas area. In Bandar Abbas Iranian J Arthropod-Borne Dis, (2007), 1(1): 21-27 H Vatandoost et al.: Ecology of Anopheles… 24 County which is a mountainous area, An. dthali is associated with An. stephensi. Larvae of this Anopheles were found in water with high salin- ity (2.7 part per 1000) in rural areas. The an- thropophilic index of this species has been re- ported between 12.5 and 20% from south of Iran (Manouchehri et al. 1972, Edrissian et al. 1985, IHR 1966). Precipitin tests on specimens from Morocco and Saudi Arabia carried out by the Lister Institute of Preventive Medicine in England showed that 4-18.7% were positive for human blood (Bruce-Chwatt et al. 1966). The results showed that the biting time of An. dthali on human bait started at 18.00 h and continued until 04.00 h, with a peak between 20.00 h, and 21.00 h. About 90% of the bites took place in the first half of the night (18.00- 24.00 hours) and only 2.5% in the three hours before sunrise (IPHR 1970). In total, 1602 An. dthali larvae collected from the study area and tested with ten insecticides and four larvicides. Results are shown in tables 1 and 2. According to the latest WHO recommenda- tion on the diagnostic dose of insecticides for adult malaria vector in 1998, the susceptibility level of adult and larvae of An. dthali to DDT 4%, dieldrin 0.4%, malathion 5%, fenitrothion 1%, propoxur 0.1%, bendiocarb 0.1%, permethrin 0.75%, deltamethrin 0.05%, lambda-cyhalothrin 0.05%, cyfluthrin 0.15% were measured and exhibited susceptibility to all insecticides. Different larvicides including malathion, te- mephos, fenitrothion and chlorpyrifos were used for their larvicidal activities. The results of the susceptibility tests of An. dthali to these insecticides showed that this spe- cies is susceptible to diagnostic dose of all lar- vicides mentioned. Irritability level of An. dthali to lambda-cy- halothrin, permethrin, cyfluthrin and deltame- thrin revealed that this species is more irritant to permethrin than other pyrethroids. 0 1 2 3 4 Ap ri ma y Ju n Ju l Au g Se p Oc t No v De c Ja n Fe b M ar M onth Sh el te r Fig. 1. Monthly average density of An. dthali in mountainous area of Bandar Abbas County, Hormozgan Province, southern Iran, 2002 Iranian J Arthropod-Borne Dis, (2007), 1(1): 21-27 H Vatandoost et al.: Ecology of Anopheles… 25 Table 1. The mortality rate of adult An. dthali to diagnostic doses of different insecticides, Bandar Abbas, Hormozgan Province, Iran, 2002 Insecticides Replicates No. mosquito tested No. dead Mortality (%) SE DDT 4% 4 99 99 100 0.00 Dieldrin 0.4% 3 73 73 100 0.00 Malathion 5% 4 86 86 100 0.00 Fenitrothion 1% 3 94 94 100 0.00 Propoxur 0.1% 4 96 96 100 0.00 Bendiocarb 0.1% 4 88 88 100 0.00 Permethrin 0.75% 3 71 71 100 0.00 Deltamethrin 0.05% 4 96 96 100 0.00 Lambdacyhalothrin 0.05% 4 100 100 100 0.00 Cyfluthrin 0.15% 4 94 94 100 0.00 Control 8 204 13 6.3 1.7 Table 2. The mortality rate of larvae An. dthali to diagnostic doses of different larvicides with 24 hours exposure time, Bandar Abbas County, Hormozgan Province, Iran, 2002 Larvicides Replicates No. Larvae No. dead Mortality (%) SE Malathion 4 99 99 100 0.00 Temephos 4 102 102 102 0.00 Fenitrothion 4 99 98 99 1.00 Chlorpyrifos 4 101 101 100 0.00 Control 4 100 11 11 3.12 Iranian J Arthropod-Borne Dis, (2007), 1(1): 21-27 H Vatandoost et al.: Ecology of Anopheles… 26 Table 3. The mean number of take-off /adult/ min by An. dthali to different pyrethroid insecticides, Bandar Abbas County, Hormozgan Province, Iran, 2002 Deltamethrin 0.05% (n=30) Cyfluthrin 0.15% (n=30) Premethrin 0.75% (n=30) Lambdacyhalothrin 0.05% (n=30) Insecticide SE Mean No. Take off SE Mean No. Take off SE Mean No. Take off SE Mean No. Take off Time (Min.) 0.06 0.03 1 0.08 0.06 2 0.06 0.03 1 0.08 0.05 2 1 0.10 0.10 3 0.10 0.1 3 0.10 0.1 3 0.10 0.1 3 2 0.15 0.16 5 0.16 0.23 7 0.12 0.16 5 0.16 0.2 6 3 0.16 0.23 7 0.17 0.3 9 0.18 0.33 10 0.17 0.26 8 4 0.19 0.30 9 0.20 0.36 11 0.20 0.53 16 0.20 0.36 11 5 0.25 0.33 10 0.25 0.46 14 0.27 0.93 28 0.24 0.53 16 6 0.27 0.50 15 0.33 0.56 17 0.39 1.26 38 0.35 0.76 23 7 0.28 0.43 13 0.30 0.73 22 0.35 1.36 41 0.36 1.26 38 8 0.24 0.46 14 0.22 0.56 17 0.26 0.83 25 0.30 0.9 27 9 0.22 0.36 11 0.18 0.40 12 0.27 0.7 21 0.26 0.63 19 10 0.17 0.26 8 0.19 0.33 10 0.20 0.6 18 0.24 0.43 13 11 0.16 0.20 6 0.20 0.43 13 0.18 0.36 11 0.16 0.23 7 12 0.11 0.13 4 0.14 0.23 7 0.21 0.26 8 0.10 0.13 4 13 0.10 0.10 3 0.12 0.16 5 0.13 0.2 6 0.11 0.1 3 14 0.10 0.10 3 0.10 0.10 3 0.11 0.13 4 0.08 0.06 2 15 0.17 0.24 7.4 0.18 0.33 10.13 0.20 0.51 16.66 0.19 0.40 13.13 Average Table 4. The mean number of take-off/ adult/min of An. dthali in control test, Bandar Abbas County, Hormozgan Province, southern Iran, 2002 ACKNOWLEDGMENTS The authors would like to appreciate the col- laboration received from Dr M Baghaii, the staff of health center province in Bandar Abbas University of Medical Science, Dr G Zamani, and other personnel of Bandar Abbas Health Re- search Center for their kind assistance and help. REFERENCES Bruce-Chwatt LJ, Garett-Jones C, Weitz B (1966) Ten years study (1955-64) of host selection by anopheline mosquitoes. Bull WHO. 35: 405-439. Christophers SR (1933) The Fauna of British India, Diptera, Vol. IV. London. De Millone B (1947) Publications of the South African Institute for Medical Research, No. 49. SE Mean No.of take-offs Time (Min) 0.04 0.04 2 1 0.04 0.04 2 2 0.05 0.07 3 3 0.01 0.02 1 4 0.05 0.07 3 5 0.04 0.04 2 6 0.01 0.02 1 7 0.09 0.10 5 8 0.01 0.02 1 9 0.04 0.04 2 10 0.04 0.04 2 11 0.05 0.07 3 12 0.10 0.07 3 13 0.10 0.02 1 14 0.04 0.04 2 15 0.03 0.04 2.2 Average Iranian J Arthropod-Borne Dis, (2007), 1(1): 21-27 H Vatandoost et al.: Ecology of Anopheles… 27 Edrissian GH, Manouchehri AV, Hafizi A (1985) Application of an enzyme linked im- monosorbent assay (ELISA) for determination to the human blood index in anopheline mosquitoes collected in Iran. J Am Mosq Control Assoc. 1(3): 349-352. Gillies MT, DeMeillon B (1968) The Anopheli- nae of Africa South of the Sahara. Publica- tion of the south African Institute for Medi- cal Research, No. 54, Johannesburg. Institute of Public Health Research (1965, 1966, 1970) Annual entomological studies in Hor- mozgan province. Annual reports of IPHR, Bandar Abbas, south of Iran. Manouchehri AV, Ghiasseddin M, Shahgudian ER (1972) Anopheles d’thali Patton, 1905, a new secondary vector in southern Iran. Ann Trop Med Parasitol. 66: 537-538. Manouchehri AV, Rohani F (1975) Notes on the ecology of Anopheles d’thali Patton in southern Iran. Ann Trop Med Parasitol. 69: 393-397. Manouchehri AV, Zaim M, Emadi AM (1992) A review of malaria in Iran (1975-90). J Am Mosq Control Assoc. 8(4): 381-385. Patton WS (1905) The Culicidae fauna of the Adenhinterland. J Bombay Natural Hist Soc. 16: 623-627. Shililu J, Ghebremeskel T, Mengistu S, Fekadu H, Zerom M, Mbogo C, Githure J, Gu W, Novak R, Beier JC (2003) Distribution of anopheline mosquitoes in Eritrea. Am J Trop Med Hyg. 69(3): 295-302. Stone A, Knight KL, Starcke H (1959) A syn- optic catalogue of the mosquitoes of the world (Diptera: Culicidae). Thomas Say Foun- dation, Entomological Society of America, Washington. WHO (1992) Entomological Field Techniques for Malaria Control. Part I. Learner’s Guide. World Health Organization, Geneva.