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Topic:Vector-borne disease
Vector-borne diseases in horses are illnesses transmitted by vectors such as mosquitoes, ticks, and flies. These diseases can affect equine health by introducing pathogens like viruses, bacteria, or parasites into the horse's system. Common vector-borne diseases in horses include West Nile Virus, Equine Infectious Anemia, and Lyme disease. The transmission dynamics, clinical manifestations, and management strategies for these diseases vary depending on the pathogen and vector involved. Understanding these aspects is important for developing preventive measures and treatment protocols. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, pathogenesis, and management of vector-borne diseases in equines.
Prospective study of progeny of inapparent equine carriers of equine infectious anemia virus. Progeny of a band of horses, positive by the agar-gel immunodiffusion (AGID) test for equine infectious anemia (EIA) antibody, were observed through their weaning over a 4-year period. Sentinels (AGID test-negative) were allowed to mingle with EIA-infected mares and their foals in pasture situations in an area with high populations of potential vectors. Of 27 adult sentinels, 8 (30%) seroconverted in annual rates ranging from 0% to 75%. In contrast, only 2 of 31 (6%) foals weaned became infected. Difference in infection rates between adult sentinels and foals was significant (chi 2, P less tha...
The use of an animal-baited net trap for collecting mosquitoes during western equine encephalitis investigations in Argentina. A large net trap was used to sample mosquito populations attracted to horses at three sites each in Santa Fe and Rio Negro Provinces, Argentina, during the austral summer of 1984. These provinces, as well as others in Argentina, were affected by a severe epizootic of western equine encephalitis (WEE) during 1982-83. Totals of 2,752 and 6,929 mosquitoes were collected in Santa Fe and Rio Negro Provinces during five and three trap nights, respectively. Culex mosquitoes of the subgenus Culex were predominant (45.8% of total) in the Santa Fe collections, although Aedes albifasciatus also was preva...
Detection of eastern equine encephalomyelitis virus and Highlands J virus antigens within mosquito pools by enzyme immunoassay (EIA). II. Retrospective field test of the EIA. Enzyme immunoassays (EIAs) for eastern equine encephalomyelitis (EEE) and Highlands J (HJ) virus antigens were compared in a retrospective study with standard virus isolation procedures (VIP) for detection of alpha virus-infected mosquito pools. The original VIP was a plaque assay in chick embryo cell culture, and was performed in the years from 1979 to 1981. Using the original VIP as the reference standard, the sensitivity rate of the EIA was 0.7674 and the false negative rate was 0.2326. However, when the storage age and the initial virus titer of the sample were considered, the sensitivity ...
Study of an outbreak of cutaneous leishmaniasis in Venezuela. The role of domestic animals. During an outbreak of cutaneous leishmaniasis in a locality (Las Rosas, Cojedes State, Venezuela) previously non-endemic, 12.9% of humans, 7% of dogs and 21.4% of donkeys (Equus asinus) had lesions with parasites. The agent in the three hosts was identified as Leishmania braziliensis, subspecies braziliensis at least in man and donkey. The probable vector was Lutzomyia panamensis. No infection was found in a small sample of wild mammals examined. The outbreak was apparently linked with the importation of donkeys with ulcers, from endemic areas. The authors call attention to the fact that not o...
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...
Studies on equine infectious anemia virus transmission by insects. There are several factors involved in the mechanical transmission of equine infectious anemia (EIA) virus by insects. Large hematophagous insects, especially tabanids, which feed from extravascular sites (ie, pool feeding) appear to be the most efficient vectors. The biology of the host-seeking and blood-feeding behavior of the vectors are important variables that have been overlooked in the mechanical transmission of pathogens like EIA virus. The biology, population levels, and diversity of the vectors, in addition to the clinical status and proximity of EIA virus-infected horses maintained w...
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.
Equine onchocerciasis in Queensland and the Northern Territory of Australia. Investigations were conducted on the taxonomy, distribution in the carcase, pathology and transmission of Onchocerca spp. in equids from Queensland and the Northern Territory. Examination of small groups of horses and ponies revealed high infection rates with O. cervicalis, while lesser numbers were infected with O. gutturosa. O. reticulata was not found. Neither of the Australian species is likely to be of economic importance to the horsemeat industry. The findings support the belief that O. cervicalis is a pre-disposing factor in the aetiology of equine nuchal disease, most commonly seen cli...
Ross River virus activity along the south coast of New South Wales. The sera of 468 blood donors and 63 domestic animals, collected from the south coast of New South Wales, were tested for the presence of antibodies to Ross River virus. Antibodies were detected in 7% of human sera, 25% of cow sera and 65% of horse sera. Using the blood donors as 'human sentinels', seroconversions were demonstrated in two donors from the Nowra-Kiama region and from a patient in the same area; none of the three had been outside of the study area during the period of seroconversion or at the time of infection. Of the 15 seropositive horses, 6 (40%) had lived continuously since bi...
Serologic evidence of Jamestown Canyon and Keystone virus infection in vertebrates of the DelMarVa Peninsula. Serological data accumulated during the past decade indicated that a variety of feral and domestic animals of the Delaware-Maryland-Virginia (DelMarVa) Peninsula were infected with Jamestown Canyon (JC) and/or Keystone (KEY) viruses (Bunyaviridae, California serogroup). Neutralizing (N) antibody to JC virus was most prevalent in white-tailed deer, sika deer, cottontail rabbits and horses. KEY virus N antibody was detected most frequently in gray squirrels and domestic goats. N antibody indicative of past infection by one or both viruses also was found in raccoons, horses and humans. JC and/or ...
Variation in arbovirus infection rates in species of birds sampled in a serological survey during an encephalitis epidemic in the Murray Valley of South-eastern Australia, February 1974. There was extensive and exuberant breeding of waterbirds before and during an epidemic of arboviral encephalitis in the Murray Valley of south eastern Australia in 1974. As estimated by haemagglutination inhibition tests on 432 bird sera collected between 4th and 13th February, 1974, infection with Murray Valley encephalitis virus, Kunjin virus and possibly other flaviviruses was concentrated in species of the Order Ciconiiformes (55% positive) and Pelecaniformes (41%), compared with only 5% in Anseriformes. Although Sindbis virus infections were also highest in these 2 Orders (56% and 46%, re...
[Study of combined foci of mosquito-transmitted arbovirus infections]. A total of 5227 serum specimens from humans, horses and swine collected in the seasons of 1968--1976 in 15 administrative areas of the Primorskiy Kray were examined with antigens of a number of mosquito-borne arboviruses: Japanese encephalitis (JE), West Nile (WN), Getah, and Sindbis. Both independent and combined circulation of these viruses in the region was established. Sindbis virus was found to be circulating separately most frequently, West Nile virus the least frequently. According to the results of the serological analysis, the conditions for combined circulation are most closely relat...
Studies with equine infectious anemia virus: transmission attempts by mosquitoes and survival of virus on vector mouthparts and hypodermic needles, and in mosquito tissue culture. Biological and mechanical transmission trials with Psorophora columbiae (Dyar and Knab) and Aedes sollicitans (Walker) and ponies acutely infected with equine infectious anemia virus (EIAV) were negative. The EIAV antigen was detected by radioimmunoassay in Ae sollicitans immediately after the mosquitoes had fed on an acutely ill pony, but not 14 days after feeding. Psorophora columbiae mosquitoes had detectable EIAV antigen as determined by radioimmunoassay 24 hours after they fed on an acutely ill pony; this antigen was not detected again until 6 days after feeding and was still detected 14 ...
Intestinal threshold of an enzootic strain of Venezuelan encephalitis virus in Culex (Melanoconion) taeniopus mosquitoes and its implications to vector competency and vertebrate amplifying hosts. The minimal intestinal dose of an enzootic strain of Venezuelan encephalitis (VE) virus for Culex (Melanoconion) taeniopus mosquitoes caught at a marsh habitat of VE virus in Guatemala was less than five plaque forming units (pfu) of virus. Ingestion of this dose of virus in blood of viremic hamsters resulted in transmission of virus to other hamsters. This low intestinal threshold of an enzootic strain of VE virus indicates that the natural Guatemalan population of Cu. (Mel.) taeniopus can acquire VE virus from vertebrates that have viremia levels as low as 1,000-5,000 pfu/ml of blood, provid...
Complement fixation tests for equine piroplasmosis (Babesia equi and B caballi) performed in the UK during 1976 to 1979. The results of complement fixation (CF) test for equine piroplasmosis on sera from horses destined for international movement from Great Britain and Ireland are presented and analysed. No horses born and continuously resident in the British Isles were found carrying CF antibodies to either Babesia equi or B caballi. Positive animals were found to have association with the following countries where known tick vectors occur: Spain, Portugal, Belgium, France, Poland, USSR and Arabian Gulf countries. Data on the persistence of CF antibodies in animals subjected to repeated testing showed that some...
Arthropod-borne encephalitides in the Americas. The arthropod-borne encephalitides are an important cause of equine and human morbidity in the Americas. Between 1975 and 1978, 6970 human cases of arboviral encephalitis were reported in the United States of America; however, this represents only a fraction of the true incidence. St Louis encephalitis (4824 cases), California encephalitis (1035 cases), and western equine encephalitis (WEE, 947 cases) accounted for 98.5% of all reported infections. Approximately 1000-4000 cases of equine encephalitis occur annually in the United States, the majority due to WEE. In tropical America, important o...
California encephalitis virus activity in mosquitoes and horses in southern Ontario, 1975. A study was undertaken in 1975 to determine California encephalitis virus activity in southern Ontario. Three thousand and sixty-one mosquitoes, primarily Aedes species, were divided into 104 pools and inoculated into suckling mice. Isolates of snowshoe hare virus were obtained from one pool each of Aedes fitchii and A. triseriatus mosquitoes collected in the Guelph area. Serological testing of horse sera revealed extensive virus activity in southern Ontario and indicated that horses may serve as excellent monitors for California encephalitis virus.
Eastern equine encephalomyelitis in upstate New York: studies of a 1976 epizootic by a modified serologic technique, hemagglutination reduction, for rapid detection of virus infections. An extensive outbreak of eastern equine encephalomyelitis (EEE) occurred in upstate New York during the summer of 1976, with 37 cases confirmed in horses by isolation of virus and/or by serologic examination. Other specimens collected in the affected area yielded 16 further isolates: 9 from 818 pools of 33,365 mosquitoes, 5 from tissues of 64 birds and 2 from 4 sentinel pheasants with serologic conversions. EEE antibodies were also detected in 81 of 499 wild birds tested. Our data implicate sparrows, cowbirds, and catbirds in the amplification of EEE virus and Culiseta melanura mosquitoes as v...
Rates of infection in, and transmission of, African horse-sickness virus by Aedes aegypti mosquitoes. Very low infection rates (less than 3%) were obtained when Aedes aegypti mosquitoes ingested blood contained 5.8--6.5 log10 MLD50/0.02 ml African horse sickness virus (AHSV). When A. aegypti mosquitoes were inoculated intrathoracically with virus, however, high infection rates were achieved. Mosquitoes infected by inoculum failed to transmit virus to embryonated hens eggs by bite, and virus could not be detected in membrane or blood when inoculated mosquitoes were allowed to engorge on uninfected blood through a chick skin membrane. It was concluded that the mosquito A. aegypti is unlikely to ...
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...
