An entomological survey was undertaken in and out of domestic premises in three different districts of Punjab, i.e. Lahore (217 m), Sheikhupura (214 m), and Faisalabad (184 m) (Figure 1) during May-June (pre-monsoon) and October- November 2013 (post-monsoon). During last five years large number of dengue cases were recorded in the selected three districts. Different places /houses were surveyed for Aedes breeding sites in water storage containers following the method of Sanchez et al. (2006). A total of 100 places /houses were surveyed from each study district and the larval density was expressed as house index (HI), container index (CI), breteau index (BI) and premises index (PI).

Figure 1 Location where Aedes albopictus and Aedes aegypti were collected from Punjab, Pakistan

1.4 Breteau Index (BI)

1.5 Collection of mosquito larvae and pupae

2.1 Dengue Vector Abundance before the Monsoon
A total of 206 immature specimens (larvae and pupae) were collected from the three districts of Punjab before monsoon (Table 1). The results revealed that in Lahore highest collection of Ae. aegypti (n=66) and Ae. albopictus (n=41) was recorded. In Sheikhupura, Ae. aegypti (n=45)was higher than Ae. albopictus (n=32). In Faisalabad, Ae. aegypti (n=14) was higher than Ae. albopictus (n=8) as well. Overall, Ae. aegypti (60.68%) was found to be higher than Ae. albopictus (39.32%).
 

2.2 Dengue Vector Abundance after the Monsoon
A total of 327 immature specimens (larvae and pupae) were collected from the three districts during post-monsoon seasons (Table 1), which was higher than the pre-monsoon collection. The highest number of Ae. aegypti (𝑛=96) was recorded in Lahore followed by Sheikhupura (𝑛=62), and Faisalabad (𝑛=39). Likewise, Ae. albopictus was found to be abundant in Lahore (𝑛=54), followed by Sheikhupura (𝑛=48) and Faisalabad (𝑛=28). A total number of Ae. aegypti larvae (60.24%) in containers was higher than Ae. albopictus larvae (39.76%) after the monsoon. The main breeding sources were the plastic containers, grinding stones, discarded tins, earthen pots, tyres, coconut shells, drainage canals and cement tanks, for both Ae. aegypti and Ae. albopictus after the monsoon (Table 2, Figure 2).

Table 2 Details of different habitat collection of dengue vectors from three districts of Punjab

2.3 Pre- and Post-Monsoon Indices of Aedes
The house index (HI) of Lahore was 18.00%; CI, BI and PI were 13.17, 27.00 and 40.27 % respectively, during the pre-monsoon season. The post-monsoon HI, CI, BI and PI indices of Lahore were 29, 30.39, 69 and 44.32%, respectively. The house index of Sheikhupura was 16%; while CI, BI and PI were 12.25,19 and 31.25%, respectively, during the pre-monsoon season. The post-monsoon HI, CI, BI and PI indices of Sheikhupura were 17, 14.09, 21 and 34.21%, respectively. The pre-monsoon house index of Faisalabad was 12%; while CI,BI and PI were 11.40,13, and 24.40% respectively while the post-monsoon HI,CI,BI and PI indices of Faisalabad were 14,11.22,11 and 27.92% respectively (Tables 3 and 4).

Table 3 Index profile for dengue vectors during pre-monsoon collection

Table 4 Index profile for dengue vectors during post-monsoon collection

3 Discussion
A total of 533 immature specimens was collected from different habitats of three districts of Punjab and reared the adult stages in the laboratory. The diversity of dengue vector fauna differed among these metropolitan areas, indicating the existence of variation in the spatial distribution pattern. The variation in the diversity and distribution are mainly associated with specific ecological condition of the selected sites. Altogether two species were recorded from total emerged adults (𝑛 = 533) that belong to the genera Aedes. Among the recorded species, i.e. Ae. aegypti and Aedes albopictus, we detect the positive sample with DENV, but this was perhaps due to the high viral load in the post-monsoon season (peak season). There was no mortality recorded during the transport of larvae /pupae to the laboratory. Plastic containers and discarded tins have contributed a maximum number of dengue vector specimens. The number of recorded Ae. aegypti immature was higher (𝑛=197) during the post-monsoon season than pre-monsoon season (𝑛=125). Likewise, Ae. albopictus collection was also higher during post-monsoon (𝑛=130) than pre-monsoon collection (𝑛=81). In total, Aedes aegypti (𝑛=322) was dominant, followed by Aedes albopictus (𝑛 = 211). The highest Aedes indices were found in Lahore in post-monsoon season, where HI was 29.00, CI was 30.39, BI was 69.00 and PI was 44.32. These results support the previous studies, in which dengue vectors are being reported as major in other parts of the world (Tewari et al., 2004; Amala et al., 2011). The earlier studies conducted regarding the metropolitan area in the Asia also showed high entomological indices and even during the dry months (Gill et al., 2000; Sharma et al., 2005). Therefore, it is quite clear that higher authorities need to give more attention to implement control measures to overcome the mosquito-breeding problem. Mosquito breeding surrounding the metropolitan area is not just a simple local health problem or biting nuisance, it is a serious threat to global health security. Thus, a careful invigilation by the trained scientists /vector control personnel is recommended to prevent the mosquito breeding. Moreover, future research priorities should include regular surveillance of arthropod vectors, in the metropolitan areas. A rapid action team of trained scientist and health workers, equipped with conventional and modern scientific instrumentations and suitable vector control tools, would be able to counter vector breeding during any epidemics and outbreaks situation.

WHO 2008, International Health Regulations 2005, 2^nd Ed. ©World Health Organization; http://www.who.int/csr/ihr/IHR_2005_en.pdf [accessed 9 April 2012