Phlebotomine sandflies (Diptera: Psychodidae) are widespread in the tropics and subtropics (Lane, 1993). They include many potential vectors for both cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). CL is an endemic disease in many areas of Saudi Arabia including the Western Provinces (Al-Qurashi et al., 2000; El-Badry et al., 2008). The disease is more common on the foothills and high plateau of Asir Region in the southwest of the Kingdom (Al-Zahrani et al., 1989; Abdelwahab & Abdoon, 2005). VL infections also recovered from the south-west of the Kingdom (Al-Zahrani et al., 1988a; Ibrahim et al., 1995; Al-Jaser, 2006).
Several reports are available on the distribution of the sandfly fauna in several regions of Saudi Arabia (Lewis & Büttiker, 1980, 1982; Killick-Kendrick et al., 1985; Morsy & Al Seghayer, 1992; Abu-Zinada, 1999; Aldawood et al., 2004; Al Barrak, 2005; El-Badry et al., 2009; Doha & Samy, 2010) revealing the presence of 25 species with the dominance of P. papatasi (Mustafa et al., 1994). In only three occasions (Lewis & Büttiker, 1982; Abdelwahab & Abdoon, 2005; Alahmed et al., 2010), the sandflies were surveyed in Asir with 22 species identified.
During the past few decades, Saudi Arabia has viewed tremendous efforts in social development and urbanization in all provinces, and insect fauna, particularly sandflies was affected. The expansion of agricultural projects, urbanization and development of water resources, lead to creation of new breeding sites for sandflies (Alahmed et al., 2010).
The Asir area has also been a subject for various development and tourist projects as well as resettlement programs which presumably have impact on distribution of sandflies. However, few reports (Lewis & Büttiker, 1982; Abdelwahab & Abdoon, 2005; Alahmed et al., 2010) described sandflies in Asir region although CL has long been recognized as an important public health problem in this area (Al-Zahrani et al., 1988b). Therefore, this study aimed at identifying and updating the sandfly species composition, their geographical distribution, periodical abundance and species diversity in some localities representing different altitudes in Asir Region as one of CL-endemic areas in Saudi Arabia. The study could be important for implementing any large-scale control project.
Materials and methods
Asir Region (19°00´N, 42°00´E to 19°00´N, 43°00´´E) in the south-west of Saudi Arabia has an area of 81,000 km2 and a population of 1,913,392 (2010 Census). It is a mountainous area divided into 3 distinct topographical zones: i) Sarawat Asir which is a mountain range extending north-south along the coastal plains of the Red Sea and that rise to almost 3000 m at Jebel Sawdah near Abha the capital; ii) Asir Plateau and iii) Tehamah Plain (Tehama) which is a narrow sandy coastal strip of lowlands at sea level. The Region receives more rainfall than the rest of the country and falling in two seasons: spring (March and April) and summer (June to August). Temperature in Asir highlands is generally lower than in the other part of the Region and the rest of the kingdom as well. The coastal plain zone is generally characterized by lower rainfall, high temperature and relative humidity (RH). The study included nine localities representing different altitudes.
Collection of sandflies
Sandfly collections were carried out monthly (June 2009 to May 2010) in Abha, Bishah, Muhayil and Tanomah (Al Namas), and twice during the year period in the Sarat Abidah, Rejal Almaa, Balqarn, Al Bark and Tathleth. In each locality, 2-3 collection sites were selected to represent different habitats: wadies (valleys), farms, dumpsites and sheep raising farms. Sandflies were collected by the Center for Disease Control (CDC) miniature light traps (John W Hock Co, Gainesville, FL, USA). The traps (3 traps/site/night) were set before sunset and collected after sunrise next morning. Collected phlebotomines were preserved in 70% alcohol, cleaned in chloral hydrate: phenol (1:1 vol/vol) and then mounted in Puri’s medium for identification using different keys (Lewis, 1982; Lane, 1986; Kakarsulemankhel, 2009, 2010). Along with fly collections, the elevation of the collection site above sea level, the weather temperature, RH and wind velocity (km/h) were recorded.
The periodic abundance of the common Phlebotomus spp. was examined in localities representing lowlands, moderately altitude areas and highlands.
The relations of sandfly density (No/trap) to the locality altitude and weather conditions (temperature, RH and wind velocity) were examined respectively by simple and multiple regression analysis. The slopes of the regression equations were tested for deviation from 0 by t-test. For the four localities that were monthly surveyed during the year period, the diversity of the sandfly based on the Simpson (1-D) and Shannon (H) indices was examined. The Paleontological statistics (Past) software ver. 2.08 was used for data analysis (Hammer et al., 2001).
Species composition and relative abundance
A total of 972 sandflies (454 males and 518 females) of two genera were collected: Phlebotomus which was more common (621 fly: 63.89%) and Sergentomyia (351 fly: 36.11%). Six hundred forty flies (246 males and 394 female) were identified into 10 species (Table 1): 6 Phlebotomus and 4 Sergentomyia. Phlebotomus arabicus was the most common species (32.19%) followed by P. bergeroti (29.38%), P. sergenti (15.00%), P. orientalis (11.09%), P. papatasi (5.94%), S. clydei (3.44%), and P. alexandri (2.03%). S. africana, S. palestinensis and S. christophersi were rare (0.31% each).
Based on the present and previous surveys a complete list of sandfly species (8 Phlebotomus spp. and 15 Sergentomyia spp.) reported in Asir is presented in Table 2.
The species composition varied among the surveyed localities (Figure 1). The reported species were encountered in all altitudes, except S. christophersi and S. africana which were reported only in low lands (<500 m) and P. alexandri and S. palestinensis which were collected only from highlands (>2000 m). Sandflies were more common (8 species) and more abundant in lowlands (48.10% of collected flies) than in moderately altitude areas (27.99%) or in high lands (23.9%) (Table 3). Regression analysis indicated that fly density (fly/trap) was inversely related to the altitude (b=–0.003, P<0.05).
The diversity for the sandfly sampled monthly in the four localities was examined. The results revealed maximum diversity in Muhayil (low altitude) with the highest Simpson index (1-D=0.69) and Shannon index (H=1.48). On the other hand, Abha (high altitude) represented the site with the minimum diversity indices (1-D=0.59 and H=1.10). The rest of the localities exhibited medium biodiversity indices (Figure 2).
Effect of weather conditions
Regression analysis indicated that the fly density (fly/trap) was directly related to temperature (b=0.413, P<0.01) and inversely related to RH (b=–0.002, P<0.05) and wind velocity (b=–0.170, P<0.05).
The seasonal activity patterns of the two common species (P. arabicus and P. bergeroti) across the different altitudes were examined (Figures 3 and 4). Generally, sandflies were more active during spring months (March to May; mean temperature=30°C, RH=24%, wind=6 km/h) with moderate activity during summer (June to August; mean temperature=36°C, RH=35%, wind=7 km/h) and autumn months (September to November; mean temperature=29°C, RH=33%, wind=9 km/h) and very low density or absent during winter months (December to February; mean temperature=20°C, RH=47%, wind=14 km/h).
Discussion and conclusions
The present study is a report of the results of an entomological survey of sandflies in Asir region.
During the study, 10 sandfly species were identified: 6 belong to genus Phlebotomus and 4 to genus Sergentomyia. Phlebotomus spp. were dominating (ca 96%), which is a Palaearctic feature (Lewis & Büttiker, 1980), its distribution is in agreement with the previous observation (Alahmed et al., 2010). All the encountered species in this study were reported earlier from Asir region (Lewis & Büttiker, 1982; Abdelwahab & Abdoon 2005; Alahmed et al., 2010) except S. palestinensis, which is considered a new record from this region, and it occurs only at high altitude (Tanomah). The species was previously reported from Al Baha, Makkah, Al Madinah and Jizan (Lewis & Büttiker, 1982).
Of the identified Phlebotomus species (612 fly), P. arabicus (ca 34%) and P. bergeroti (ca 31%) were the commonest species followed by P. sergenti, P. orientalis, P. papatasi and P. alexandri. P. bergeroti was reported as a rare species in Saudi Arabia (Nadim et al., 1979; Büttiker et al., 1982), however, Abdelwahab & Abdoon (2005) and Alahmed et al. (2010) indicated that in Asir, P bergeroti is the most abundant species while P. sergenti is second in abundance. In Al Baha, P. bergeroti is also the most abundant constituting 41.7% of the collected flies (Doha & Samy, 2010). Phlebotomus alexandri revealed also very low density (Abdelwahab & Abdoon, 2005; Alahmed et al., 2010). Phlebotomus arabicus is rare (Abdelwahab & Abdoon, 2005), in contrast to our findings and that of Alahmed et al. (2010). Phlebotomus orientalis was considered rare (Abdelwahab & Abdoon, 2005), but represented 5.85% of the collected flies in Abha (Alahmed et al., 2010) and 12% in the present study. Among the Sergentomyia species (28 sandflies), S. clydei was dominating (ca 79%), while S. christophersi, S. africana and S. palestinensis each represented about 7%, numbers similar to previous findings. S. christophersi, S. clydei, S. africana numbered 37, 31 and 24, respectively out of 558 collected sandflies (Alahmed et al., 2010).
Several investigators (Büttiker et al., 1982; Lewis & Büttiker, 1982; Aldawood et al., 2004; Al Barrak, 2005; El-Badry et al., 2008) reported P. papatasi as a dominant species in Saudi Arabia. However in this study, P. papatasi was not common and represented only about 6% of the collected sandflies. Only 13 specimens (2.38%) (Alahmed et al., 2010) and 19 specimens (0.95%) (Lewis & Büttiker, 1980) of P. papatasi were previously collected in Asir. This confirms the marked affinity of sandfly fauna of Asir (Abdelwahab & Abdoon, 2005) as in southern Sinai, Egypt (El Sawaf et al., 1987) where P. bergeroti and P. sergenti constituted the highest percentage of collected sandflies whereas P. papatasi was a poorly represented species.
Sandflies were more common and abundant in lowlands respect to higher altitudes. The lowest abundance was observed in highlands in agreement with the previous observation (Büttiker et al., 1982). In Asir region (Abdelwahab & Abdoon, 2005), the highest abundance of Phlebotomus sandflies was found in Tehamah foothills in lowland and in the coastal plain while the lowest fly densities were reported at higher altitudes in Sarawat Mountains and Asir plateau. This was confirmed in the present study by regression analysis, which indicated that the density of flies inversely related to the altitude (P<0.05). Meanwhile, the results revealed maximum diversity indices in Muhayil (lowland) and minimum ones in Abha (highland) due to the low richness of the species in this locality (n=4 spp). This may indicate that the lowlands are the most favourable sites for the breeding and activity of sandflies. Lower fly abundance at higher altitudes may be due to low temperature (annual mean=21.6°C), fog and strong winds (annual mean=11.92 km/h) in comparison with lowlands (annual mean of temp=32.03°C and of wind velocity=6.43 km/h)
It was reported (Abdelwahab & Abdoon, 2005) that the species composition of the sandflies is not affected by altitude, although it was found (Büttiker et al., 1982) that the species spectrum shows a tendency for more species to occur at higher altitudes than in the Tehamah districts (lowlands). Moreover, in Sinai, Egypt (El Sawaf et al., 1987), a remarkable difference in sandfly species composition at different altitudes was observed. The present study indicated that although most sandfly species were encountered in all altitudes, some species were found restricted to certain altitudes: S. christophersi and S. africana in lowlands and P. alexandri and S. palestinensis in highlands. This agrees with previous research (Büttiker et al., 1982) that is P. papatasi and P. bergeroti prefer lower altitudes whereas P. orientalis and P. arabicus are species of higher altitudes.
The knowledge of the seasonal activity of sandflies is of importance in predicting the period of maximum risk of Leishmania transmission and for carrying out an effective control program. Results indicated that in different altitudes, Phlebotomus flies were more active during spring, with moderate activity during summer and autumn and very low density or absent during winter seasons. Almost similar observations were previously reported (Abdelwahab & Abdoon, 2005) where the highest abundance of sandflies was recorded during the spring and summer (March to September) and the lowest fly abundance was throughout the period from November to February. Morsy et al. (1995) found that the greatest number of P. papatasi in Riyadh occurred most commonly during the summer season with two peaks in June and September. During the winter season no insects were found and then the population density started to appear again from March. Regression analysis indicated that fly density was directly related to the weather temperature (P<0.01) and inversely related to RH and wind velocity (P<0.05). Previous analysis (Abdelwahab & Abdoon, 2005) showed a significantly positive correlation between fly density and temperature and negative correlation with RH at Asir foothills.
Cutaneous leishmaniasis is an endemic disease in many areas of Saudi Arabia (Al-Qurashi, 2000; El Hassan, 2013) and is widespread in villagers of the Asir plateau (Al-Zahrani et al., 1988b). The disease is more common on the foothills and high plateau of Asir region (Al-Zahrani et al., 1989). Visceral Leishamniasis infections occur in Jizan (Al-Zahrani et al., 1988a; Ibrahim et al., 1995; Al-Jaser, 2006).
Of the reported sandfly species, several are implicated as vectors of leishmaniasis in Asir and other regions of the kingdom.
P. bergeroti is assumed as a secondary vector of leishmaniasis in Asir mountain plateau (Büttiker et al., 1982) and as a suspected vector of L. tropica (anthroponotic cutaneous leishmaniasis) in Makka (Lewis, 1982) and in some African countries as well as in Egypt, Iran, Oman and Yemen (Maroli et al, 2013). Based on dominance of this species and the recorded increase in the number of leishmaniasis cases after few months of its peak of abundance (Abdelwahab & Abdoon, 2005) may highlight its role as a probable vector of Leishmania in Asir area. Recently, P. bergeroti was found positive for Leishmania-like flagellate infection in Al Baha (Doha & Samy, 2010). However, studies are needed to clarify the possible role of this highly abundant species in Leishmania transmission in Asir where this disease is widely spread;
P. papatasi is the main vector of CL in many parts of Saudi Arabia (Lewis & Büttiker, 1982; Mondragon-Shem et al., 2015), may be the major vector in Al Qassim Region (Lewis & Büttiker, 1980; Al Barrak, 2005) and is a proven vector of L. tropica in many countries including Yemen, Iraq, Egypt, Algeria, Iran, Jordan, Morocco and Tunisia (Maroli et al., 2013). Moreover, P. papatasi, was found to be a proven vector of L. major (zoonotic cutaneous leishmaniasis) in the Sinai Peninsula, Egypt (Samy et al., 2014). Although, P. papatasi is the most widespread and dominant species in all investigated areas of Saudi Arabia (Mustafa et al., 1994; Alahmed et al., 2010), however, in the present study this species was not common (6% of collected sandflies). This may indicate that this species has little or no role in Leishmania transmission in Asir Region. This assumption agrees with what has been found in Kuwait where P. papatasi did not appear as an urban species and was not regarded as a possible vector of leishmania in that country (Abdelwahab & Abdoon, 2005);
P. alexandri and P. orientalis are suspected to be the main vectors of L. donovani (VL) in the southwestern part of Saudi Arabia (Al-Zahrani et al., 1997). The role of the two species in transmitting L. donovani is fully documented in other countries. P. alexandri is the main vector from North Africa to western China (Lane, 1993) while P. orientalis is a proven vector in Sudan (Maroli et al., 2013);
P. arabicus was found naturally infected with Leishmania-like flagellates in Al Baha (Doha & Samy, 2010).
In conclusion, the present findings indicate that the distribution and abundance of sandflies in Asir Region are influenced by a combination of ecological and topographical factors (temperature, RH, wind velocity and altitude). The obtained results could be important for the successful implementation of leishmaniasis control programs. Among the reported species, S. palestinensis is considered a new record from Asir.