Abstract
Background
Mosquito-borne diseases are a major public health threat in Iran. The objective of this study was to determine the fauna of culicinae mosquitoes for future mosquito control programs.
Methods:
Three genera and eleven species of the subfamily Culicinae (Diptera: Culicidae) were collected by dipping technique and identified in Chabahar County, Sistan and Baluchistan Province, southeastern Iran, during January, February, and March 2007.
Results:
The collected species included: Aedes vexans (new occurrence record for the province), Culex arbieeni, Cx. bitaeniorhynchus, Cx. deserticola, Cx. hortensis, Cx. perexiguus, Cx. pipiens, Cx. pseudovishnui, Cx. pusillus, Cx. quinquefasciatus, Cx. sinaiticus, Cx. theileri, Cx. tritaeniorhynchus, Culiseta longiareolata, Ochlerotatus caballus, Oc. caspius, and Uranotaenia unguiculata.
Conclusion:
Our observations indicate that, in South of Iran hot and wet climatic conditions support the persistence of culicinae mosquitoes. As our study, regular monitoring of culicinae mosquitoes in this area could be the most useful for mosquito control and mosquito-borne disease prevention.
Keywords: Culicinae, mosquito, fauna, Chabahar, Iran
Introduction
Mosquito-borne diseases such as malaria, West Nile, Sindbis viruses, Japanese encephalitis, and RiftValley fever are a major public health in some Asian countries (Yasoka and Levis 2007). Some of diseases such as malaria, West Nile, Sindbis as well as Dirofilaria immitis (dog heart worm) and D. repens (dirofilariasis) had been previously reported in Iran (Naficy and Saidi 1970, Saidi et al. 1976, Azari-Hamidian et al. 2007). Malaria transmission in Chabahar County occurs through the year, most of the malaria cases were observed from May to Nov almost in the age groups of 5–25 yr old (Moosa-Kazemi et al. 2006).
Malaria is transmitted by five species: Anopheles culicifacies Giles s.l., An. dthali Patton, An. fluviatilis James s.l., An. stephensi Liston and An. superpictus Grassi (Moosa-Kazemi et al. 2006). By now, 64 species, 3 subspecies, and 7 genera of mosquitoes have been reported in Iran (Azari-Hamidian 2007). Four genera of Culex, Culiseta, Ochlerotatus, Uranotaenia and 18 species of the subfamily Culicinae have been reported from Sistan and Baluchistan Province (Lotfi 1973, Zaim 1987). Zaim (1987) mentioned four genera and sixteen species of the subfamily Culicinae (Diptera: Culicidae) in Sistan and Baluchistan Province as follow: Culex arbieeni Salem, Cx. bitaeniorhynchus Giles, Cx. deserticola Kirkpatrick, Cx. hortensis Ficalbi, Cx. perexiguus Theobald, Cx. pipiens Linnaeus, Cx. pusillus Macquart, Cx. pseudovishnui Colless Cx. quinquefasciatus Say, Cx. sinaiticus Kirkpatrick, Cx. theileri Theobald, Cx. tritaeniorhynchus Giles, Culiseta longiareolata Macquart, Ochlerotatus caballus Theobald, Oc. caspius Pallas, and Uranotaenia unguiculata Edwards. It is noteworthy that Culex mimeticus and Cx. territans is found by Lotfi (1973) in this area.
There is only one recent study on the mosquitoes in the county in relation to malaria and anophelines (Moosa-Kazemi et al. 2006). While it is necessary to study mosquitoes in Chabahar, there are no more references on the culicine mosquitoes of the county. This paper presents the first report of the results of the recent surveys of the culicinae mosquitoes from samples taken from a range of larval breeding sites in which they occur in nature, and adult culicinae mosquitoes captured from various places.
The aim was to obtain new data, which would be valuable to develop programmes for future planning of mosquito control in this area of southeastern Iran.
Materials and Methods
To better understand the Culicinae fauna of Chabahar County and gather information on their distribution and the kinds of larval breeding sites in which they occur in nature, a field trial study was performed from Jan to Mar 2007 in Sistan and Baluchistan Province. This study took place in five randomly selected rural villages in Chabahar County (57°14′N, 26°19′E). The County is bounded by Pakistan in the east, Hormozgan Province in the west, Kerman Province in the north, and Oman Sea in the south (Fig. 1). In 2007, the max and min mean monthly temperature was 33 °C and 5.5 °C in July and Jan, respectively. The total annual rainfall was 221 mm, the minof 3.5 mm in July and max of 64 mm in Apr. The mean annual relative humidity was 75%. The main economic activity of the people is husbandry of cow, goats and fishing. Based on available epidemiological data from the Chabahar Health Center, some villages were short-listed and entomological surveys were carried out.
Fig. 1.
Map of Iran indicating the location of the study area in Chabahar County (Ch) situated in the south of Sistan and Baluchistan Province (S and B)
On this basis, five villages with 1118 houses and 5513 population were selected. To study the mosquito fauna, sampling was carried out by dipping technique for collecting larvae and pyrethrum space spray collection (PSSC) for adult mosquitoes. The specimens were collected from five villages in the different topographical areas of the district including Baho-kalat, Beris, Dak-baho, Pollan, and Soldan. Pyrethroum space spray mosquitoes collection were conducted between 05.00 and 08.00 h monthly in eight fixed animal and human shelter randomly on each villages before spraying, all the eaves, windows, doors and other exit points were closed and cloth sheets were spread on the floor. Pyrethrum (0.2% in kerosene) was sprayed using a pressurized hand sprayer. After spraying, the room was kept closed for 15 min and the knocked-down mosquitoes were then collected from the floor sheet with forceps and placed in Petri-dishes lined with moist cotton. All collected mosquitoes were pinned and then were identified using the keys of Zaim and Cranston (1986), Harbach (1988), and Darsie and Samanidou-Voyadjoglou (1997). Mosquito name abbreviations were cited based on Reinert (2001).
Larval habitats present within 500 m around each village were studied for mosquito larvae two times per month. Five randomly selected larval breeding places located within a 500-m radius of the study site were also included and formed the sampling unit for mosquito larvae. All larvae were collected from natural habitats, generally feeding with seepage water, such as swamps, seepages, streams, river banks, drying river beds, pools, and grasslands. Samples were taken at intervals along the edge of each larval breeding place using a standard mosquito dipper (350 ml) depending on the size of the habitat.
The larvae for each habitat were placed separately in whirl paks and transported to the laboratory where they were sorted by genus and instar counted and recorded. The pupae were reared to adults in emergent cages and identified to species by morphological characters. Because we did not have enough emergent cages to separate the pupae from each habitat by date of collection, samples for each habitat type were pooled together in each site irrespective of date of collection. The larvae were preserved in lactophenol and the microscopic slides of the preserved larvae were prepared using Berlese medium. The culicinae larvae along with the description of their breeding sites were sent to the School of Public Health, Tehran University of Medical Sciences, where the author identified using the aforementioned keys.
Results
The number of the culicine mosquito species at the various sites of Chabahar is shown in Table 1. A total of 3824 adults and 5031 larvae of the culicine mosquitoes were collected, and were recognized including; Aedes vexans Meigen (indicate new occurrence records for the province), Culex arbieeni, Cx. bitaeniorhynchus, Cx. deserticola, Cx. hortensis, Cx. perexiguus, Cx. pipiens, Cx. pseudovishnui, Cx. pusillus, Cx. quinquefasciatus, Cx. sinaiticus, Cx. theileri, Cx. tritaeniorhynchus, Culiseta longiareolata, Ochlerotatus caballus, Oc. caspius s.l., and Uranotaenia unguiculata. In PSSC collection Overall, Culiseta longiareolata predominated (22.8%), followed by Cx. perexiguus (16.8%), Cx. pipiens (14.2 %), and Cx. tritaeniorhynchus (8.8%). In the larval collection, of 5031 culicinae larvae collected, Culiseta longiareolata predominated (19.5%), followed by Cx. perexiguus (16.9%), Cx. pipiens (13.6 %), and Cx. tritaeniorhynchus (9.1%) respectively (Table 1). Seven species including Culiseta longiareolata, Ochlerotatus caspius s.l., Cx. perexiguus, Cx. pipiens, Cx. sinaiticus, Cx. theileri, and Cx. tritaeniorhynchus accounted for 85.1%, and 79.2% of the adult and larval collection respectively. The other species were less than 6% of the total.
Table 1.
Number and prevalence of adult and larvae culicinae mosquitoes collected by pyrethrum space spray and larval collections in Chabahar County, Sistan and Baluchistan Province during January, February, and March 2007
| Species | Larvae | Adult | ||
|---|---|---|---|---|
|
| ||||
| No | Percentage | No | Percentage | |
| Aedes vexans | 120 | 2.4 | 61 | 1.6 |
| Culex arbieeni | 15 | 0.36 | - | - |
| Cx. bitaeniorhynchus | 30 | 0.59 | 49 | 1.3 |
| Cx. deserticola | 120 | 2.4 | 137 | 3.6 |
| Cx. hortensis | 65 | 1.3 | 111 | 2.9 |
| Cx. perexiguus | 851 | 16.9 | 643 | 16.8 |
| Cx. pipiens | 685 | 13.6 | 543 | 14.2 |
| Cx. pseudovishnui | 120 | 2.4 | 5 | 0.13 |
| Cx. pusillus | 206 | 4.1 | 202 | 5.3 |
| Cx. quinquefasciatus | 146 | 2.9 | - | - |
| Cx. sinaiticus | 267 | 5.3 | 291 | 7.6 |
| Cx. theileri | 418 | 8.3 | 291 | 7.6 |
| Cx. tritaeniorhynchus | 458 | 9.1 | 337 | 8.8 |
| Culiseta longiareolata | 982 | 19.5 | 875 | 22.8 |
| Ochlerotatus caspius s.l. | 327 | 6.5 | 279 | 7.3 |
| Oc. caballus | 156 | 3.1 | 0 | - |
| Uranotaenia unguiculata | 65 | 1.3 | - | - |
| Total | 5031 | 100 | 3824 | 100 |
Culiseta longiareolata was the most frequent culicine mosquito collected at Chabahar, with total of 982, and 875 specimens, by larval collection and PSSC, respectively. Aedes vexans is recorded for the first time in Chabahar County and Sistan and Baluchistan Province. Number and localities of the larvae of culicinae mosquitoes collected in this survey are shown in Table 2. Uranotaenia unguiculata, Oc. caballus, Cx. quinquefasciatus, and Cx. arbieeni were collected only in the larval stage. Number and localities of the adult of the culicine mosquitoes collected in this survey are shown in Table 3. Culiseta longiareolata, Cx. perexiguus, and Cx. pipiens were the most prevalent species respectively, and collected in almost all of the villages (Table 2 and 3). The highest numbers of culicines were collected in the Dak-Baho (1206 larvae and 717 adult specimens), and the lowest in the Beris (965 larvae and 627 adult specimens) (Table 2 and 3). Ochlerotatus caballus, Cx. quinquefasciatus, and Cx. arbieeni were collected from larval collection and other species from both SPSS and Larval (Table 2 and 3).
Table 2.
Number and locality of the culicine mosquito larvae, Chabahar County, Sistan and Baluchistan Province, January–March 2007
| Species |
Villages
|
||||||
|---|---|---|---|---|---|---|---|
| Baho-Kalat | Beris | Dak-Baho | Pollan | Soldan | No | % | |
| Aedes vexans | 40 | - | 51 | 29 | - | 120 | 2.4 |
| Culex arbieeni | - | 1 | 9 | - | 5 | 15 | 0.36 |
| Cx. bitaeniorhynchus | 6 | 8 | 7 | 4 | 5 | 30 | 0.59 |
| Cx. deserticola | 29 | 24 | 36 | 31 | - | 120 | 2.4 |
| Cx hortensis | 14 | 13 | 15 | 11 | 12 | 65 | 1.3 |
| Cx. perexiguus | 243 | 84 | 192 | 204 | 128 | 851 | 16.9 |
| Cx. pipiens | 178 | - | 201 | 217 | 89 | 685 | 13.6 |
| Cx. pseudovishnui | 29 | 14 | 28 | 32 | 17 | 120 | 2.4 |
| Cx. pusillus | 40 | 37 | 39 | 51 | 39 | 206 | 4.1 |
| Cx. quinquefasciatus | 29 | 68 | - | 49 | - | 146 | 2.9 |
| Cx. sinaiticus | - | 94 | - | - | 173 | 267 | 5.3 |
| Cx. theileri | 124 | 101 | 98 | - | 95 | 418 | 8.3 |
| Cx. tritaeniorhynchus | 94 | 83 | 101 | 54 | 126 | 458 | 9.1 |
| Culiseta longiareolata | 209 | 304 | 272 | 101 | 96 | 982 | 19.5 |
| Ochlerotatus caspius s.l. | 69 | 71 | 78 | 63 | 46 | 327 | 6.5 |
| Oc. caballus | - | 63 | 48 | - | 45 | 156 | 3.1 |
| Uranotaenia unguiculata | - | - | 31 | 16 | 18 | 65 | 1.3 |
| Total | 1104 | 965 | 1206 | 862 | 894 | 5031 | 100 |
Table 3.
Number and locality of the adult culicine mosquitoes collected by Pyrethrum space spray, Chabahar County, Sistan and Baluchistan Province, January–March 2007
| Species |
Villages
|
||||||
|---|---|---|---|---|---|---|---|
| Baho-Kalat | Beris | Dak-Baho | Pollan | Soldan | No | % | |
| Aedes vexans | - | 16 | 21 | 11 | 13 | 61 | 1.6 |
| Cx.bitaeniorhynchus | 13 | 8 | - | 19 | 9 | 49 | 1.3 |
| Cx. deserticola | 45 | 48 | 44 | - | - | 137 | 3.6 |
| Cx. hortensis | - | - | 63 | 34 | 14 | 111 | 2.9 |
| Cx. perexiguus | 151 | 116 | 164 | 183 | 29 | 643 | 16.8 |
| Cx. pipiens | 89 | 96 | 101 | 76 | 181 | 543 | 14.2 |
| Cx. pseudovishnui | - | - | 5 | - | - | 5 | 0.13 |
| Cx. pusillus | 69 | - | - | 121 | 12 | 202 | 5.3 |
| Cx. sinaiticus | 81 | 94 | - | 46 | 70 | 291 | 7.6 |
| Cx. theileri | 103 | - | 48 | 82 | 58 | 291 | 7.6 |
| Cx. tritaeniorhynchus | 59 | - | 15 | 142 | 121 | 337 | 8.8 |
| Culiseta longiareolata | 167 | 172 | 219 | 153 | 164 | 875 | 22.8 |
| Ochlerotatus caspius s.l. | 38 | 77 | 37 | 70 | 57 | 279 | 7.3 |
| Total | 815 | 627 | 717 | 937 | 728 | 3824 | 100 |
Discussion
Five genera and 17 species of culicine mosquitoes were collected and identified from Chabahar County in Sistan and Baluchistan Province, including the first record of Ae. vexans in the province.
From 18 species of culicinae mosquitoes in Sistan and Baluchistan Province (Lotfi 1973, Zaim 1987), 16 species, which had already been recorded, were also collected in this investigation. Two species Culex mimeticus and Cx territans are not recorded in this study. However, the occurrence of Aedes vexans in the province was not mentioned before (Zaim 1987), although some references counted Aedes vexans as the more common species of Guilan and Isfahan Provinces (Azari-Hamidian et al. 2002, Mousakazemi et al. 2000).
In this study, two species of the tribe Aedini including; Ochlerotatus caspius s.l. and Oc. caballus were recorded in Chabahar County. These species were differentiated from each other in larval stage (Zaim and Cranston 1986). There is no information about the Oc. caspius sibling species (A or B) in the country (Azari-Hamidian 2007).
Culex mimeticus and Cx. territans had been previously repoted by Lotfi (1973) in Sistan and Baluchistan, whereas in this study have not been found.
Culex pipiens was one of the most frequent culicine mosquitoes collected at Chabahar, with total of 573 and 685 specimens, by PSSC and larval collection respectively. Culex pipiens can be separated from Cx. torrentium, and Cx. vegans by Harbach’s (1988) key using seta 1-III-V, seta 1-M, seta 1-X, seta 1-C, and some other characters. Based on this key, only Cx. pipiens was identified.
One species of Culiseta, Cs. longiareolata was found in this investigation. Results of this survey are the same of finding by previous study in Sistan and Baluchistan Province (Zaim 1987).
In this study were collected other culicine mosquitoes such as, Culex. theileri, and Cx. Tritaeniorhynchus. This species are potential vectors of human and domesticated animal pathogens (Horsfall 1955, Harbach 1988).
The species Cx theileri was one of the culicine mosquitoe collected at Chabahar, with total of 291, and 418 specimens by means of PSSC and larval collection, respectively. This species is the more prevalent species at higher altitudes and in rural areas of Isfahan (Mousakazemi et al. 2000), Zanjan (Ghavami and Ladonni 2005) and East Azerbaijan Provinces (Abai et al. 2007). Observations made during the present study agree with those of Simsek (2004) who noted that Cx. theileri in Turkey prefers large natural larval habitats that are generally present in rural areas.
In conclusion, regular monitoring of mosquitoes in this area could be the most timely and sustainable way to follow up mosquito ecology and raise awareness about mosquito control and mosquito-borne disease prevention.
Acknowledgments
The authors are grateful to Dr S Azari-Hamidian, School of Health, Guilan University of Medical Sciences, Rasht, for reviewing the article. We also would like to express our appreciation to the people of villages in Chabahar for their kind cooperation during the study, many thanks also dedicated for the efforts of the field staff of Iranshahr Health Research and Training Chabahar Health Centers. This study was financially supported by Diseases Management Center, Iranian Ministry of Health and Medical Education, and the Institute of Public Health Research, Academic Pivot for Education and Research, Tehran University of Medical Sciences. The authors declare that they have no conflicts of interest.
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