Among the hematophagous genera, Culicoides have assumed significance and notoriety worldwide due to its ability to transmit a wide range of pathogens of public and veterinary importance [1]. Presently India records 535.78 million as major farm animals i.e cattle, buffalo, poultry, sheep and goat including indigenous and exotic breeds, with a total bovine population of 302.79 million (buffalo, cattle, mithun, yak) [2]. Such presence of large numbers and variety of livestock and density of livestock is at risk in transmission of an orbivirus bluetongue (BT) by Culicoides midges and which may lead to outbreak of BTD. Besides, This virus causes bluetongue disease (BTD) in goats, sheep, cattle and other small and wild ruminants [3]. Although the disease was dominant in temperate zones, introduction of non-native breeds in virus endemic tropical and subtropical zones also caused BT outbreak [4]. The spread of range of BT in the temperate was also attributed to global warming [5]. Presently seroprevalence of bluetongue virus (BTV) has been reported across all the Indian states [6]. The BTD outbreak has been witnessed frequently owing to the significant density of livestock, high prevalence of the Culicoides along with conducive climatic conditions helping in propagation of vectors and the virus [7, 8]. BTV was first recorded from the state of Maharashtra [9] and also occurrences of BTV from Indian states covering western, northern and southern regions followed [10, 11]. Although eastern and north eastern India is yet to witness an outbreak, high seroprevalence in livestock has appeared in several scientific articles [11, 12]. Presently 22 of the 28 serotypes (worldwide) have been recorded from India [13]. Moreover BT seropositivity in different animals depicts 34% in buffalo, 16% in camel, 38% in cattle, 43% in goat, 39% in sheep and 66% in mithun [13]. According to [2] state of West Bengal shares 6.9% of total livestock population comprising 8.25% cattle, 0.8% of sheep and 10.93% goats’ population. The economy of West Bengal, especially in Burdwan district is agriculture based (mixed farming) in which livestock and animal husbandry plays a pivotal role. The villagers form a cluster of self help groups (SHG) which market livestock products to generate revenue [14]. The seroprevalence in goat (66.95%), sheep (57.66%) and cattle (52%) has been reported across 7 districts of West Bengal [15, 16]. Despite such high seroprevalence, BTD outbreak remains unreported from West Bengal [17]. BTD outbreak and its economic implications has been well documented from the southern Indian states, however, there remains critical knowledge gaps and understanding of biology of the potent vector species prevalent in this tropical region. Few studies on biology, ecology and taxonomy of the Culicoides spp were carried out [8, 17]. Besides, [18] has reported prevalence of 7 putative vectors C.oxystoma, C. fulvus, C. orientalis, C. dumdumi, C. imicola, C. peregrinus and C. brevitarsis from southern India. In the eastern state of West Bengal, C. fulvus, C. peregrinus and C. oxystoma were the prevalent species in mixed farms and cattle sheds [8, 17] thereby posing considerable risk in the spread of disease. Further a coloured LED light trap based extensive surveillance program was also conducted in the same site to ascertain the prevalence of the aforesaid species in the cattle sheds [8].
Information available on host seeking activity, ecology and biology of Culicoides are limited across the globe [19, 20]. The aforesaid information was imperative for implementation of control measures in disease epidemiology [20]. Although the disease causing pathogens vectored by Culicoides were a matter of concern, relatively scant information on its bionomics exists in India [18] and Europe [20, 21, and 22]. In the light of forecasting disease transmission, limited information on the host-vector association has led to assumptions that all the Culicoides species prevalent in the cattle sheds fed on host with equal facility on which various predictions were based [21]. Besides difficulty in aspirating Culicoides from the host body also limits studies on host seeking activity of the Culicoides [19].
In this study the catch data obtained by two different methods (light trap and aspirator) were evaluated and compared in order to separate two adult activity of Culicoides spp. in real time: flight activity and biting activity. The two study sites were selected at Burdwan district of West Bengal due to report of seroprevalence of BTV from this region [12] as well as high seasonal abundance of potent vector species of Culicoides associated with livestock from this district [17]. Moreover, the evaluation enables validation of the time and preferential landing of Culicoides on cattle body parts which is critical at farmer’s level to reduce the host-vector contact.
