Abundance and Diversity of Culicoides Species (Diptera: Ceratopogonidae) in Different Forest Landscapes of Karnataka, India: Implications for Culicoides Borne Diseases

Investigating the influence of blood meal sources on the composition of culturable haemolytic gut bacteria of a wild-caught BTV vector Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae)

Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) transmits many pathogens, including seven viruses, four protozoa and one nematode. This species has a wide distribution range across northern Afro-tropical, Palearctic, Australian, Indo-Malayan realms with a broad host spectrum, including cattle, buffaloes, sheep, pigs, dogs, horses and even humans. The heterogeneous nature of Culicoides' blood-feeding patterns is well documented, but the influence of various host blood meal sources on gut bacterial composition remains scant. Adult midges were collected during April (2023) by operating UV light traps in cattle, buffalo sheds and poultry farm in Purulia (India). Besides C. oxystoma, eleven Culicoides species were collected across the sheds and farm, seven of which are vectors. Culicoides liui Wirth and Hubert and C. thurmanae Wirth and Hubert are reported from India for the first time. In all the sheds, engorged females of C. oxystoma were ubiquitous. Identification of culturable gut bacteria and the host blood meal of C. oxystoma were done through the polymerase chain reaction (PCR)-based method. Blood meal analysis confirmed the following hosts: cattle, buffaloes and humans. Identification of blood meal of engorged C. oxystoma caught from poultry farm showed positive results for humans but not for birds. Among bacteria, Bacillus cereus was abundant in all of the engorged females. Bacillus paramycoides and Enterococcus faecium were identified from females feeding on cattle and buffaloes' blood, while Alcaligenes faecalis was found in the gut contents of females that fed on cattle and human blood. The gut bacteria Alcaligenes faecalis exhibited alpha haemolytic activity. In contrast, Bacillus sp., B. cereus, B. flexus, B. licheniformis, B. thuringiensis, B. paramycoides, E. faecium, Paenibacillus sp. and Pseudomonas sp. exhibited beta haemolysis. This is the first report on the composition of gut bacteria, with particular emphasis on the haemolytic bacteria of C. oxystoma with different host blood meals. The pathogenic bacteria B. cereus, B. licheniformis and A. faecalis within the females could potentially impact pathogen acquisition and increase the probability of their zoonotic transmissibility.

A preliminary account of Culicoides (Diptera: Ceratopogonidae) from the Andaman and Nicobar Islands with 13 new records and updated species inventory from India

BACKGROUND

The detection of multiple bluetongue virus serotypes, increasing trend in livestock density, rich biological diversity with high endemism, and the status of the Andaman and Nicobar Islands as a popular tourist destination underscore the need for a faunistic survey of medically and veterinary significant vector species, specifically Culicoides, in this region. Moreover, scattered information on Indian Culicoides species complicates the planning and implementation of preventive measures for pathogens transmitted by these vectors. This study aims to provide the first comprehensive account of the Culicoides fauna in the Andaman and Nicobar Islands, India, along with an updated checklist of Indian Culicoides species and their state-wise distribution.

METHODS

Surveys were conducted across various habitats in the Andaman and Nicobar Islands in September 2022 and 2023. Midges were collected using CDC light traps, light sheets, Malaise traps, and manual collection from exposed body parts of the author and volunteers (biting collection). Identification was carried out using relevant taxonomic keys and original descriptions. Additionally, an updated checklist of Indian Culicoides, based on published and grey literature from 1910 to the present, is provided, with an emphasis on their potential role in pathogen transmission.

RESULTS

A total of 3529 adult Culicoides were trapped during the survey, representing 5 subgenera and 3 unplaced species groups. The study recorded 23 Culicoides species, including 13 new species records for India: C. barnetti, C. gouldi, C. flaviscutellaris, C. flavipunctatus, C. hui, C. histrio, C. guttifer, C. perornatus, C. okinawensis, C. quatei, C. obscurus, C. coronalis, and C. kusaiensis.

CONCLUSIONS

The Indian Culicoides fauna now includes 93 valid species, with many of them recognized as confirmed or potential vectors of important pathogens of animal health. The enriched species composition highlights the importance of systematic surveys in this island ecosystem and the need to determine the role of midges, if any, in pathogen transmission.

Bluetongue Risk Map for Vaccination and Surveillance Strategies in India

Bluetongue virus (BTV, Sedoreoviridae: Orbivirus) causes an economically important disease, namely, bluetongue (BT), in domestic and wild ruminants worldwide. BTV is endemic to South India and has occurred with varying severity every year since the virus was first reported in 1963. BT can cause high morbidity and mortality to sheep flocks in this region, resulting in serious economic losses to subsistence farmers, with impacts on food security. The epidemiology of BTV in South India is complex, characterized by an unusually wide diversity of susceptible ruminant hosts, multiple vector species biting midges (Culicoides spp., Diptera: Ceratopogonidae), which have been implicated in the transmission of BTV and numerous co-circulating virus serotypes and strains. BT presence data (1997-2011) for South India were obtained from multiple sources to develop a presence/absence model for the disease. A non-linear discriminant analysis (NLDA) was carried out using temporal Fourier transformed variables that were remotely sensed as potential predictors of BT distribution. Predictive performance was then characterized using a range of different accuracy statistics (sensitivity, specificity, and Kappa). The top ten variables selected to explain BT distribution were primarily thermal metrics (land surface temperature, i.e., LST, and middle infrared, i.e., MIR) and a measure of plant photosynthetic activity (the Normalized Difference Vegetation Index, i.e., NDVI). A model that used pseudo-absence points, with three presence and absence clusters each, outperformed the model that used only the recorded absence points and showed high correspondence with past BTV outbreaks. The resulting risk maps may be suitable for informing disease managers concerned with vaccination, prevention, and control of BT in high-risk areas and for planning future state-wide vector and virus surveillance activities.