Light traps with incandescent globes are used in a national monitoring program to detect the presence of Culicoides spp. responsible for the transmission of viruses to livestock and native animals. Recent events have suggested that the efficiency of these traps should be reconsidered and possibly improved. Subsequently, the response of eight species of Culicoides to light‐emitting diodes (LEDs) was determined at two locations in New South Wales. Culicoides austropalpalis Lee & Reye, C. bunrooiensis Lee & Reye and C. marksi Lee & Reye were attracted to blue light. Responses to blue and green light could not be separated for C. bundyensis Lee & Reye, C. dycei Lee & Reye, C. nattiensis Lee & Reye and C. victoriae Macfie. Culicoides brevitarsis Kieffer was significantly attracted to green light. This species is the major vector of Akabane and bluetongue viruses in Australia. These responses were all significantly greater than the responses to the incandescent lights currently used in the light traps. The response to red light was less than the response to incandescent light for all species. Catches of C. brevitarsis were also related to the intensity of the green LEDs. These were more effective than the currently used incandescent globes at intensities between 46% and 142% of the incandescent intensity.
A study of responses by Culicoides spp. to light traps with light-emitting diodes (LEDs) confirmed that the livestock virus vector, Culicoides brevitarsis Kieffer, was preferentially attracted to green light. Four species shown previously to respond to blue light exhibited significantly higher responses to ultraviolet (UV) light. Field trials comparing green LEDs with incandescent lights in New South Wales, Northern Territory and East Timor confirmed the superiority of green LEDs for catching C. brevitarsis. The green LED traps also had a significant advantage over incandescent traps for a wide range of Culicoides species. These included: species whose ultimate preference was for UV, most species that are proven or potential vectors of viruses affecting Australian livestock and native animals and the main species affecting humans in northern Australia. Use of green LEDs has been adopted for trapping C. brevitarsis, especially in its marginal and low-density areas, and for detecting incursions of new Culicoides spp. into Australia. Use could be possible for species in other insect Orders.
The distribution and seasonal movements of C. brevitarsis and the viruses it transmits were studied at the southern limits of the distribution of the vector in the seasons 1990 to 1993. Distinct patterns of spread of the vector from the Manning region to the Hunter Valley and down the southern coastal plain were observed each season. All adult stages of C. brevitarsis apparently were involved in rhese movements. Distributions were compared by averaging data from sites within six zones (starting a t I with the Manning Region) separated by the monrh that C. brevitarsis was recorded at a site for the first time. The species was most abundant in autumn and numbers were progressively lower away from the Manning. The number of generations in each zone ranged from seven (zone I ) to zero (zone 6 ) and was dependent on the month that the species was first recorded in a zone. Average generation time was 4.13 0.71 weeks ranging from 5 weeks (NovemberDecember) to 3 weeks (March-April). Fewer males than females were recorded, although, within zones, sex ratios were constant. Differences in sex ratios were recorded between the zones. Parous ratios were related to temperature and an increase in parous ratio in summer preceded maximum numbers in autumn. Temperature affected population growth and was suitable for C. brevirarsis activity for varying periods. Wind patterns that were consistent with the observed direction of spread occurred during most of the season. There were no clearly defined effects of rainfall on spread although, once established, numbers increased in autumn following the summer rains. A high incidence of infection of cattle with Akabane and Palyam viruses was recorded in 1990191 and 1992193. Initial levels of seroconversions were related to the population size of vectors which ranged from 2 to >2,000 (as recorded by light traps) in the month prior to infection. The first occurrence of the virus was positively related to the time of first occurrence of the vector with delays in the appearance of the virus of 4 and 3 months in 1990191 and 1992193, respectively.
Culicoides brevitursis is a biting midge and a vector of several viruses affecting livestock in Australia. An emergence chamber for collecting Culicoides spp. from dung was evaluated to determine its suitability for the study of C. brevitursis developing in dung at different temperatures in the laboratory. It enabled experiments to be carried out in the natural breeding medium, relative humidity to be maintained at high levels and temperature through the dung to be stabilised at treatment temperatures relatively quickly. C. brevitursis emerged within a temperature range of 17°C to 36°C with the greatest numbers between 25°C and 36°C. Males were dominant at low temperatures and females were dominant at high temperatures. Development times (to 50% emergence from deposition of the dung) and response times (to 50% emergence after starting to emerge) were least at the highest temperatures. Development times at the same temperature differed between experiments and this was associated with the temperature in the field before the dung was placed at a temperature treatment. Some survival occurred outside the 17°C to 36°C range, but emergence was dependent on the temperature eventually being changed to a more suitable level. The approximate lower threshold for emergence was about 17°C. At this temperature, numbers emerging were low, development was delayed significantly and none survived for more than 50 d. High numbers of adults started to emerge within 24 h from dung held at 17 "C for up to 42 d from the deposition of the dung when the temperature was raised to 25 "C or 28 "C. The results support field temperature data and were used in predicting the areas that may be free of the vector.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.