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ORIGINAL ARTICLE  
Year : 2017  |  Volume : 10  |  Issue : 1  |  Page : 182-186
Some ecological aspects of Phlebotomine sand flies (Diptera: Psychodidae) in an endemic area of leishmaniasis in Darab district, Fars province, southern Iran


1 Department of Medical Entomology and Vector Control, School of Health, Shiraz University of Medical Sciences, Shiraz, Iran
2 Research Center of Health Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
3 Department of Public Health, School of Health, Mamassani Higher Education Complex for Health, Shiraz University of Medical Sciences, Shiraz, Iran
4 Darab Health Center, Shiraz University of Medical Sciences, Shiraz, Iran

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Date of Web Publication5-May-2017
 

   Abstract 

Background: Phlebotomus species are solely responsible for transmitting leishmaniasis in the old world. The disease is endemic in several parts of Iran. Darab district located in Fars province of southern Iran is one of the most important endemic foci of cutaneous leishmaniasis. Sand flies and Methods: To identify the distribution of sand flies, a total of 5019 sand flies were collected in Darab district from May to September 2012. To determine the monthly activity, 2039 sand flies were biweekly collected from indoors and outdoors of two villages at lowland and highland regions. The relationship between the frequency of sand flies and wind speed (greater than 3 m/s as the influential factor) was studied. To determine the number of sand flies' bites per night, a native volunteer exposed his body every 1 h from sunset to sunrise. Results: In total, 13 species of Phlebotomine (five Phlebotomus spp. and eight Sergentomyia spp.) were identified. Besides, a relatively significant relationship was found between the frequency of sand flies and wind speed more than 3 m/s, especially in June and July 2012. Moreover, evaluation of the night blood-feeding peak during 8:00 P.M.–6:00 A.M. indicated that most bites occurred at 11:00-12:00 P.M. and 9:00-10:00 P.M. with 125 and 110 bites, respectively. Conclusion: Phlebotomus papatasi was the dominant species (49.2%). Additionally, wind speed more than 3 m/s showed a preventive effect on sand flies' activity. Thus, insecticide-treated nets are recommended to be used for all inhabitants, especially children and pregnant women, to prevent sand flies' bites through the night.

Keywords: Iran, leishmaniasis, Phlebotomus papatasi, sand flies

How to cite this article:
Askari MB, Fakoorziba MR, Kalantari M, Alavi A, Azizi K. Some ecological aspects of Phlebotomine sand flies (Diptera: Psychodidae) in an endemic area of leishmaniasis in Darab district, Fars province, southern Iran. Ann Trop Med Public Health 2017;10:182-6

How to cite this URL:
Askari MB, Fakoorziba MR, Kalantari M, Alavi A, Azizi K. Some ecological aspects of Phlebotomine sand flies (Diptera: Psychodidae) in an endemic area of leishmaniasis in Darab district, Fars province, southern Iran. Ann Trop Med Public Health [serial online] 2017 [cited 2019 Dec 10];10:182-6. Available from: http://www.atmph.org/text.asp?2017/10/1/182/205584

   Introduction Top


Leishmaniases are endemic in different parts of Iran.[1] Cutaneous leishmaniasis (CL) is an increasing public health problem in 14 provinces of the country.[2] For the first time, CL was described in southern Iran in1977.[3] In this area, the yearly incidence of CL has increased over the last decade.[4] Sand flies are vectors of at least three kinds of diseases to human, with leishmaniasis being the most important one. Leishmania major is the main causative agent of wet lesions of CL and is mainly seen in rural areas. Moreover, infection transmits to humans by the bite of infected sand flies.[5]

In Iran, CL has also been found in urban areas where the results of Leishmania tropica infection have been observed.[6] Additionally, both anthroponotic cutaneous leishmaniasis (ACL) and zoonotic cutaneous leishmaniasis (ZCL) are caused by L. tropica and L. major. It seems that ACL is restricted to some large- and medium-sized cities, whereas ZCL is endemic in rural areas of different parts of the country.[7] Perfect detection of the parasite(s) causing each case of CL is needed if the local measures for the disease control are to be effective.[8]

The characterizing techniques, such as microscopical examination of direct smears and/or the culture of biopsies, are not sensitive enough, but diagnostic methods based on DNA have now made the sensitive and quick detection of the microorganism probable.[9],[10]

Phlebotomus species are solely responsible for transmitting leishmaniasis in the old world.[11] Characterization of the disease vector in endemic areas is vital for both chemotherapy and prognosis.[12] Moreover, assessment of leishmania vectors and understanding their transmission dynamic are required for planning leishmanial-controlling policies.[13]

Generally, sand flies' frequencies and activities are influenced by temperature, relative humidity, soil moisture, and wind speed.[14] Temperature and moisture also affect the height structure of sand flies' occurrence.[15] Sand flies are very sensitive to wind velocity and their preferred breeding places are those protected from the wind. In fact, high wind velocity reduces or even stops flight movement.[16] Beyond that, temperature (at least 11°C), humidity (about 10%), wind (less than 3 m/s), and light intensity have been mentioned as the main factors increasing the nocturnal activity of sand flies.[17]

The present study aims to determine the geographic distribution, fauna, and monthly activity of sand flies in Darab district, Fars province, southern Iran.


   Materials and methods Top


Study area

Fars province is located in southern Iran and has an area of 122,400 km2. This study was carried out in Darab district, Fars province. This region is situated at 28° 45' 7" North, 54° 32' 40" East, and 1200 m above the sea level. Because of the suitable biological conditions for Leishmania reservoir hosts, vectors, and reservoirs diversity, Darab has always been considered to be one of the foci of visceral leishmaniasis (VL) and CL.[18]

Collection and examination of sand flies

Between May and September 2012, sand flies were collected monthly by sticky paper traps (castor oil-coated white papers, 20632 cm) from outdoors (rodent burrows, agricultural plantations surrounding the houses, etc.) in ten regions, including Aarab-Ghanbari, Banouj, Behrouz-Abad, Doulat-Abad, Fadami, Ghale-Biaban, Kheir-Abad, Nasir-Abad, Sange-Charak, and Talle-Bargah villages. In each sampling, at least 30 sticky paper traps were set in the evening and collected early in the next morning. Sand flies were mounted in Puris medium.[19] The samples were identified based on specific taxonomic criteria.[20],[21]

In order to determine the monthly activity of sand flies, they were caught from indoors and outdoors of two villages, namely Behrouz-Abad (as the lowland) and Sange-Charak (as the highland), during April to November 2012. Moreover, considering the impact of wind speed (more than 3 m/s) on the frequency of sand flies, the charts of daily wind velocity were prepared from April to November and then, the relationship between the number of caught sand flies and daily wind speed was studied.[14]

To evaluate the feeding peak of sand flies, the number of bites were recorded every 1 h and inserted into a table. In addition, some sand flies were caught for morphological identification.[17]


   Results Top


Among the 5019 sand flies collected in this study, five species of Phlebotomus and eight species of Sergentomyia were identified, consisted of P. papatasi, P. alexandri, P. sergenti, P. bergroti, P. eleanorae, Sergentomyia dentata, S. tiberiadis, S. clydei, S. theodori, S. sintoni, S. squamipleuris, S. baghdadis, and S. antennata [Table 1].
Table 1: Distribution of sand flies collected in Darab district, southern Iran

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In monthly activity studies, 2039 specimens were collected from Behrouz-Abad (810 samples) and Sange-Charak (1229 samples). The results indicated a significant relationship between the reduction of the number of caught sand flies and increase of wind speed (more than 3 m/s), particularly in June and July 2012 [Figure 1] and [Figure 2].
Figure 1: The relationship between wind speed (m/s) and frequency of sand flies caught in Behrouz-Abad village in Darab district, Fars province, southern Iran

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Figure 2: The relationship between wind speed (m/s) and frequency of sand flies caught in Sange-Charak village in Darab district, Fars province, southern Iran

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Considering the determination of sand flies' feeding peak, a total of 658 bites were recorded. Besides, 165 of them were caught and identified as P. papatasi (109 samples), P. bergroti (25 samples), P. alexandri (22 samples), S. theodori (5 samples), and S. dentata (4 samples). Furthermore, the peak of biting was recorded at 11:00–12:00 P.M. with 125 bites [Figure 3].
Figure 3: The frequency of sand flies in Darab district, Fars province, southern Iran in different periods of time (every 1 h)

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   Discussion Top


CL seems to be the main common vector-borne hygienic problem in Iran where most ZCL cases are caused by L. major.[22] Fars province involves a wide spectrum of sand flies fauna because of its high bio-natural variety. P. papatasi, P. major, P. keshishiani, and P. alexandri have been described as the vector(s) of ZCL and VL in this province.[23] In addition, P. papatasi has been described as the main proven vector of L. major in all endemic foci of this province.[24] P. papatasi was also the main species in the present study (49.2%).

The findings of the current study confirmed that wind speed more than 3 m/s had a protective influence on sand flies' activity. Additionally, their nocturnal activity increased slowly after sunset (7:00–8:00 P.M.). The number of sand flies augmented at 9:00 P.M., and the highest level of sand flies' activity was observed during 11:00–12:00 P.M. Furthermore, a significant difference was detected in sand flies' activity at midnight. A significant difference was also observed in the prevalence of species during the night. Based on the results, P. papatasi was active and predominant until sunrise.

It seems that relative humidity was the most important factor affecting sand flies' nocturnal activity. According to the results, sand flies' activity began immediately at sunset, increased rapidly when the average humidity increased to more than 10%, continued virtually constant until midnight, and decreased quickly when the average humidity values were over 50%. These results are in agreement with those of the studies, which demonstrated that the most important factor affecting sand flies' activity was low humidity followed by high temperature and low wind speed. In our study, the sand flies had continuous activity through the night, which was significantly affected by relative humidity. However, many surveys have shown cyclic variations in the nocturnal activity of sand flies. The results of some other studies indicated that the main factors affecting sand flies' activity were light intensity, low relative humidity, low wind velocity, and temperature.[14] Sand flies have been reported to be very active in the optimum humidity of 10%, maximum wind speed of 3 m/s, and minimum temperature of 11°C.[17] It should also be noted that sand flies' circadian activity increases promptly at sunset. In our study, the high level of activity was fairly constant from around 9:00 P.M. until dawn when it reduced quickly. Nevertheless, some studies have reported that a few flies will be still active about 1.5 h after sunrise.[17] Other studies have also examined the nocturnal activity patterns of sand flies in the old world.[25],[26] A study in southern Iraq revealed that the peak activity period shifted from early in the evening in April and October to late at night in May and June.[27] Comparably in Morocco, north of Africa, sand flies' activity was found to be continuous all night in August, but turned down fast after midnight in October.[28] Consequently, more detailed researches are required to be conducted on the effects of seasonal variations and abiotic situations other than temperature and relative humidity, such as cloud cover, wind speed, and lunar cycle, on the nocturnal activity of sand flies in order to improve our knowledge of this epidemiologically important area.

In conclusion, since the feeding peak occurred at midnight, insecticide-treated nets (ITNs) are recommended to be used for all inhabitants, particularly children and pregnant women, to prevent sand flies' bites through the night.

Financial support and sponsorship

Nil

Conflicts of interest

There are no conflicts of interest

 
   References Top

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14.
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22.
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24.
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27.
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28.
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[PUBMED]    

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Correspondence Address:
Dr. Kourosh Azizi
Department of Medical Entomology and Vector Control, School of Health, Shiraz University of Medical Sciences, Shiraz
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1755-6783.205584

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