Topic:Culicoides
Culicoides are small biting midges that are often associated with horses due to their role as vectors for various equine diseases. These insects can cause irritation and allergic reactions in horses, commonly referred to as "sweet itch" or "summer eczema," which is an allergic response to the saliva of the Culicoides. Additionally, they are known to transmit pathogens that can lead to conditions such as African horse sickness and equine encephalitis. This page aggregates peer-reviewed research studies and scholarly articles that explore the biology, behavior, and impact of Culicoides on equine health, as well as strategies for their management and control in equine environments.
Equine Culicoides hypersensitivity in Florida: biting midges aspirated from horses. Nine species of Culicoides were aspirated from horses in Florida during the second phase of a study of equine Culicoides hypersensitivity (CHS). Approximately 90% of the 2933 midges were Culicoides insignis Lutz, 4% were C.stellifer (Coquillett), 3% were C.niger Root and Hoffman, 2% were C.alachua Jamnback and Wirth and the remaining 1% included C.venustus Hoffman, C.scanloni Wirth and Hubert, C.lahillei Iches (= C.debilipalpis Lutz), C.pusillus Lutz, and C.edeni Wirth and Blanton. Culicoides were sampled on seven farms located throughout Florida. The location and seasonality of lesion develop...
Equine insect hypersensitivity: skin test and biopsy results correlated with clinical data. Forty-four seasonally pruritic horses and 21 asymptomatic horses in Florida, USA, were tested for insect, grass and mould hypersensitivity by intradermal injection of allergenic extracts. The affected horses ranged in age from 10 months to over 30 years and included a variety of breeds. Affected horses reacted to varying dilutions of extracts made from Culicoides, mosquitoes, horse flies and black flies. Reactions to Culicoides were more intense than those caused by injection of antigens from other arthropods. Mild pruritus existed from the end of February until the end of June when the condit...
Specific immunotherapy in the treatment of Culicoides hypersensitive horses: a double-blind study. Fourteen privately owned horses completed a six month, controlled, double-blind trial to assess the efficacy of immunotherapy using an aqueous extract of whole, unfed Culicoides variipennis in the treatment of Culicoides hypersensitivity. Selected horses had a history of a seasonal, pruritic dermatitis, clinical signs and distribution compatible with Culicoides hypersensitivity, failed to improve in response to ivermectin therapy, and reacted to several dilutions of Culicoides extracts without significant reactivity to other possible allergens including insects, moulds and feeds. One horse fro...
Trajectory analysis of winds and vesicular stomatitis in North America, 1982-5. Outbreaks of vesicular stomatitis, serotype New Jersey, during epidemics in the United States and northern Mexico, 1982-5, were examined by backward trajectories of winds to investigate spread and possible sources. The outbreaks selected for analysis did not involve introduction of disease by infected animals. The findings indicate that wind could have been responsible for carrying infection from northern Mexico to Arizona and New Mexico and thence to Colorado and Utah and on to Wyoming, Idaho and Montana. The results of these analyses are consistent with the findings from T1 RNAse fingerprint...
Immunogenicity and allergenicity of Culicoides imicola (Diptera: Ceratopogonidae) extracts. Summer seasonal recurrent dermatitis (SSRD) or "sweet itch" is a seasonally occurring allergic dermatitis of horses provoked by biting midges. The allergic skin reactions have been attributed to allergens present in various Culicoides species. C. imicola is the suspected etiological agent of SSRD in Israel. Whole body extracts of this midge induced hypersensitivity reactions upon injection into susceptible horses and in this study attempts were made to define components of C. imicola which have immunogenic and allergenic properties. Immunogenic potency was evaluated by raising antisera to whol...
[Current information on the subject of African horse sickness (AHS)]. The objective of the present review was to summarize current knowledge of African horse sickness (AHS), based on available literature (which is nonetheless relatively scant) and recent information obtained from the O.I.E. Brief description is made of the biology of AHS virus (an arbovirus, transmitted by Culicoides imicola), isolation of the agent, diagnosis by serotyping procedures, and preventive measures (such as protection of horses from insect infestation, or vaccination programs) which may be taken. The recent outbreaks in Spain, Portugal, and Morocco, have demonstrated that much more re...
Intradermal challenge of Icelandic horses with extracts of four species of the genus Culicoides. Twenty-three Icelandic horses were challenged with extracts of four species of biting midges: Culicoides pulicaris, C chiopterus, C obsoletus and C impunctatus. Fourteen of the tested horses were affected with summer eczema. The horses were challenged intradermally with 0.1 ml of whole-body extracts of midges at a concentration of 0.01 or 0.005 per cent weight/volume. The skin reactions were measured after 30 minutes, 60 or 180 minutes and four, 24 and 48 hours after injection. Antigen titration showed that the reaction was dependent on the antigen concentration. Eight of nine unaffected horse...
Potential of infra-red thermography for the detection of summer seasonal recurrent dermatitis (sweet itch) in horses. The feasibility of using infra-red thermography for early and out of season detection of summer seasonal recurrent dermatitis (sweet itch) was tested on 13 sensitive and six insensitive horses in Israel. In summer (June, July and September) six affected mares and two unaffected sensitive mares (one of them a pony) were clearly 'warmer' in the affected zones than three insensitive mares. In winter (February and March) unaffected sensitive horses could be differentiated from insensitive mares by the warm areas detected in the affected zones. Small numbers of Culicoides imicola bites may have bee...
Preferred landing sites of Culicoides species (Diptera: Ceratopogonidae) on a horse in Israel and its relevance to summer seasonal recurrent dermatitis (sweet itch). Six hundred and twenty culicoides of five species were collected from a bait horse at Kannot, Israel, between April and September 1986. Seventy-two per cent of the midges were collected from the belly and 27 per cent from the dorsal aspect of the body, ie, the sweet itch summer seasonal recurrent dermatitis (SSRD) zone. Midges were active mainly from half an hour prior to half an hour after sunset. Only Culicoides puncticollis, C imicola and C schultzei group were collected in considerable numbers. While C imicola was present continuously throughout the season, the appearance of the two other ...
The hypersensitivity of horses to culicoides bites in british columbia. Culicoides hypersensitivity is a chronic, recurrent, seasonal dermatitis of horses that has a worldwide distribution, but has only recently been reported in Canada. It is characterized by intense pruritus resulting in lesions associated with self-induced trauma.A survey of veterinarians and horse-owners in British Columbia showed no differences in susceptibility due to the sex, color, breed, or height of the horses. The prevalence of the disease in the 209 horses surveyed was 26%. Horses sharing the same pasture could be unaffected. The disease was reported primarily from southwestern British ...
Factors influencing the ingestion of Onchocerca cervicalis microfilariae by Culicoides variipennis (Diptera: Ceratopogonidae). Culicoides variipennis were fed under controlled conditions on two ponies that exhibited seasonal changes in Onchocerca cervicalis microfilarial (mf) skin density and skin distribution. The seasonal changes did not radically affect mf ingestion. Flies were fed on the umbilicus of infected ponies by two methods: individual feeding in consecutive order at the same site, or by mass feeding. Linear regression analysis indicated that ingestion of microfilaria was independent of feeding time and engorged weight. In the individual feeding data, there was a trend toward an increased ingestion of mf as...
Equine Culicoides hypersensitivity in Florida: biting midges collected in light traps near horses. Twenty-three species of Culicoides were trapped near pruritic horses during a 2-year survey in Florida. Nearly 99% of the biting midges collected were represented by Culicoides insignis Lutz, C. edeni Wirth and Blandon, C. stellifer (Coquillett), C. niger Root and Hoffman, C. haematopotus Malloch and C. venustus Hoffman. The relative contribution to the total catch by each of these species varied among collection sites. Seasonally, different species attain their largest population sizes at different times. Association of species collected in light traps with the seasonality of lesion developme...
Intradermal challenge of Icelandic horses in Norway and Iceland with extracts of Culicoides spp. A skin test survey was carried out in Icelandic horses in Norway and Iceland using extracts of Culicoides spp. as antigen. Eleven horses with recurrent seasonal dermatitis reacted with an immediate hypersensitivity response to intradermal challenge with antigen. All except one of thirty-three clinically normal horses in Norway showed a negative response in skin tests. These findings indicate that Culicoides spp. may be the major cause of the disease in Norway. Only one of the 110 horses tested in Iceland showed any skin test reaction (weak), demonstrating that the horses were not sensitized to...
Seasonal changes in density and tissue distribution of Onchocerca cervicalis microfilariae in ponies and related changes in Culicoides variipennis populations in Louisiana. Seasonal changes in density and spatial distribution of Onchocerca cervicalis microfilariae were studied in ventral-midline skin of 15 infected pony mares in southern Louisiana. Triple running mean analysis of data over a 13-mo period indicated that a distinct pattern exists in total microfilariae population density and in microfilariae occurrence in different levels of the dermis. Microfilariae density reaches peak levels in the spring followed by a 58% decrease in the summer, a 19% increase in the fall, and a decrease to the lowest numbers in the winter. Microfilariae were found in all level...
Dermal reactivity to histamine, serotonin and bradykinin in relation to allergic skin reactions of the horse. The reactivity of horse skin to intradermal inoculation of histamine, serotonin and bradykinin was investigated, and the resulting reactions compared with those produced in the same horses by a 1% whole-body extract of Culicoides. Both histamine and bradykinin produced large reactions, but there was no significant correlation between the dermal responsiveness to insect allergen and either histamine or bradykinin. Two anti-histamine drugs (promethazine hydrochloride and tripelennamine hydrochloride) were effective in reducing the reaction produced by the insect extract.
Preferential landing and engorging sites of Culicoides species landing on a horse in Ireland. An investigation of the landing and engorging sites of midges on a bait horse was made in Ireland as part of a project examining the aetiology of sweet itch. Ten species were recovered, seven of which engorged. Culicoides obsoletus and C dewulfi were the most commonly represented, accounting for 89.9 per cent of midges landing and 90.5 per cent of midges engorging. Only 4.69 per cent of midges attracted to the bait were C pulicaris. Overall, the preferential landing sites for midges were along the mane and lower leg regions. Few culicoides were attracted to the head, front and underside of the...
Culicoides hypersensitivity in the horse: 15 cases in southwestern british columbia. The investigation of a chronic, seasonal dermatitis of horses in southwestern British Columbia is described. Typically the history indicated an insidious onset, followed by a gradual progression in the severity of the signs each year. Lesions appeared during the warmer months of the year and tended to regress during the winter. The clinical signs consisted of areas of pruritus and excoriation, affecting predominantly the ventral midline, mane and tailhead. In all cases corticosteroid therapy relieved the pruritus and allowed the lesions to heal.The salient pathological findings were hyperkerat...
Main Drain virus as a cause of equine encephalomyelitis. Main Drain virus, which is thought to be transmitted normally among rabbits and various rodents by its natural vector, Culicoides variipennis, was isolated repeatedly from brain tissue of a sick horse from Sacramento County, California, and was implicated as the causative agent. Signs of illness were incoordination and ataxia, stiff neck, head pressing, inability to swallow, fever, and tachycardia.
Sweet itch: responses of clinically normal and affected horses to intradermal challenge with extracts of biting insects. In a study of the skin reactivity of horses with lesions of sweet itch, six clinically normal horses and seven affected horses were challenged intradermally with extracts of Culicoides, Stomoxys, Tabanidae and Culex species. All the affected horses and three of the normal horses responded strongly to the culicoides extract. The skin reactions in the affected horses reached their maxima within 4 h in the majority of animals. Skin reactivity to culicoides was transferred to normal horses with serum from affected animals confirming that the reaction was an immediate hypersensitivity reaction. Thr...
Epidemiological and immunological studies of sweet itch in horses in Israel. A survey of sweet itch in horses in Israel based on a questionnaire to owners reported that 158 of 723 horses (21.8 per cent) had sweet itch lesions. The results indicated that the likelihood of a horse acquiring sweet itch decreased with increasing altitude but no definite association with rainfall zones was evident. Variation in the density of the horse population, however, obscured these observations. In the population surveyed, stallions were more sensitive than mares and pale horses appeared to be less sensitive than dark ones, but the sample size of this latter group was much smaller. In...
Viruses isolated from Culicoides midges in South Africa during unsuccessful attempts to isolate bovine ephemeral fever virus. Five viruses, unrelated to bovine ephemeral fever virus (BEFV), were isolated from Culicoides biting-midges collected during the summer months of the years 1968-69 and 1969-70 near a cattle herd in which cases of BEF occurred and at an open horse stable at Onderstepoort. These viruses were investigated by means of serological, electron-microscopical and physicochemical tests. It was established that 2 isolates, Cul. 1/69 and Cul. 2/69, were related to each other and belonged to the Palyam subgroup of the genus Orbivirus, that isolate Cul. 3/69 belonged to the equine encephalosis subgroup of th...
A report on clinical aspects and histopathology of sweet itch. Sweet itch is an intensely pruritic dermatitis of horses recurring annually in Ireland from April to November. The tissue changes of sweet itch have similarities to immediate-type hypersensitivity reactions which occur in skin sensitised to the saliva of bloodsucking insects. There was subepidermal oedema, and marked eosinophilia; the blood vessels were tortuous and enlarged. Microfilaria were not found in serial sections of lesions of 5 affected horses. The histopathology of the immediate dermal remal reaction to the intradermal injection of Culicoides extract shows dermal vasodilation and eo...
Failure to propagate equine infectious anemia virus in mosquitoes and Culicoides variipennis. Laboratory-colonized mosquitoes, Culex tarsalis, aedes aegypti, Culiseta inornata, and Anopheles free-borni, and the biting gnat, Culicoides variipennis, were exposed to equine infectious anemia virus. Exposure to the virus was by intrathoracic inoculation for mosquitoes and by oral ingestion of an infective blood meal through a membrane for C variipennis. After various intervals, groups of 15 to 20 insects were homogenized and inoculated into susceptible ponies. Positive immunodiffusion test results were used as criterion for equine infectious anemia infection in ponies. Virus was not detecte...
Antibodies to Akabane virus in Australia. Neutralising antibody to Akabane virus was shown to develop in cattle in northern Australia throughout the year and also on the east coast of New South Wales in the summer during 1975/1976. Other species found to have antibody to Akabane virus were buffaloes, horses, camels and sheep, but no antibody was found in domestic chickens, ducks, wallabies or man. The biting midge Culicoides brevitarsis has been detected in all the major areas where antibody was demonstrated in this study.
A survey of biting flies attacking equines in three states of the southwestern United States, 1972. A survey of biting flies in the southwestern United States resulted in the recovery of 34 species as they attacked equines. The geographic distribution of each species at 15 sites and the abundance of attacking flies were used to determine that 22 species commonly attack equines. Culicoides variipennis (Coquillett) was the most common species collected; it was recovered at 12 sites and comprised the highest percentage (29.8%) of the total survey catch for all species collected. The next 2 most common species were Psorophora columbiae (Dyar & Knab) and Aedes vexans (Meigen). C. variipennis was ...
The growth of African horse-sickness virus in embryonated hen eggs and the transmission of virus by Culicoides variipennis Coquillett (Diptera, Ceratopogonidae). Seven-day-old embryonated hen eggs were infected with African Horse Sickness virus by the yolk sac and intravenous routes. Virus reached a high titre in the blood of infected embryos. Culicoides variipennis midges which took a blood meal from infected eggs became infected with virus, and after 7 days at 26 degrees - 27 degrees C transmitted African Horse Sickness virus to uninfected eggs. C. variipennis may therefore be considered a biological vector of African Horse Sickness virus in the laboratory.