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Topic:Tick-Borne Diseases
Tick-borne diseases in horses refer to illnesses transmitted by tick vectors, affecting equine health through various pathogens. These diseases can lead to a range of clinical symptoms, including fever, lethargy, and lameness, depending on the specific pathogen involved. Common tick-borne diseases affecting horses include Lyme disease, equine piroplasmosis, and anaplasmosis. Diagnosis often involves serological tests, PCR assays, and clinical evaluation. Understanding the ecology of ticks and their interaction with horses is essential for managing and preventing these diseases. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, pathogenesis, diagnosis, and management of tick-borne diseases in horses.
Nematocera (Ceratopogonidae, Psychodidae, Simuliidae and Culicidae) and control methods. The biology, veterinary importance and control of certain Nematocera are described and discussed. Culicoides spp. (family Ceratopogonidae) transmit the arboviruses of bluetongue (BT), African horse sickness (AHS), bovine ephemeral fever (BEF) and Akabane. Some other arboviruses have been isolated from these species, while fowl pox has been transmitted experimentally by Culicoides. These insects are vectors of the parasitic protozoans Leucocytozoon caulleryi and Haemoproteus nettionis, and the parasitic nematodes Onchocerca gutturosa, O. gibsoni and O. cervicalis. They also cause recurrent summ...
Epizootiology and vectors of African horse sickness virus. African horse sickness (AHS) virus causes a non-contagious, infectious, arthropod-borne disease of equines and is enzootic in sub-Saharan Africa. The major vectors are species of Culicoides but mosquitoes and ticks may be involved. Periodically the virus makes excursions beyond its enzootic zones but until recently has not been able to maintain itself outside these areas for more than 2-3 consecutive years. This is probably due to a number of factors including the absence of a long term vertebrate reservoir, the prevalence and seasonal incidence of the vectors and the efficiency of control mea...
Studies on oral transmission of Potomac horse fever. Eight normal ponies placed in direct contact with ponies experimentally infected with Ehrlichia risticii for 30 to 90 days did not develop signs of Potomac horse fever. They also did not seroconvert, and they remained susceptible to IV infection. One of 8 ponies that were force fed fresh feces from infected ponies while in direct contact with ponies experimentally infected with E. risticii developed Potomac horse fever and seroconverted. The other 7 remained asymptomatic, did not seroconvert, and were susceptible to IV infection. Six of 9 ponies inoculated with E. risticii via nasogastric intu...
The development of Babesia (Theileria) equi (Laveran, 1901) in the gut and the haemolymph of the vector ticks, Hyalomma species. The development of the piroplasm Babesia equi was studied by light microscopy in the gut and the haemolymph of three different Hyalomma species during and after the nymphs had engorged on parasitaemic horses. The stock of B. equi used was isolated from a horse imported from Turkmenistan (CIS) in 1991. The existence of gamogony was identified by the occurrence of gamonts and gametes in the gut contents of the nymphs at between 3 and 4 days after infestation of the nymphs, before the ticks dropped off the experimentally infected horses. Zygotes and kinetes were observed in the intestinal cells f...
Medically important arboviruses of the United States and Canada. Of more than 500 arboviruses recognized worldwide, 5 were first isolated in Canada and 58 were first isolated in the United States. Six of these viruses are human pathogens: western equine encephalitis (WEE) and eastern equine encephalitis (EEE) viruses (family Togaviridae, genus Alphavirus), St. Louis encephalitis (SLE) and Powassan (POW) viruses (Flaviviridae, Flavivirus), LaCrosse (LAC) virus (Bunyaviridae, Bunyavirus), and Colorado tick fever (CTF) virus (Reoviridae, Coltivirus). Their scientific histories, geographic distributions, virology, epidemiology, vectors, vertebrate hosts, transm...
Serologic evidence of canine and equine ehrlichiosis in northeastern United States. In a retrospective study, indirect fluorescent-antibody staining methods were used to detect immunoglobulins to Ehrlichia canis and Ehrlichia risticii in canine and equine sera that had originally been analyzed for antibodies to Borrelia burgdorferi. Analyses of 60 dog serum specimens collected in Connecticut and New York State during 1986 revealed antibodies to E. canis in 7 (11.7%) specimens; titration endpoints ranged from 1:40 to 1:320. Three of these dogs had anemia. Of the 187 equine serum specimens obtained in Connecticut during 1985 and analyzed by indirect fluorescent-antibody stainin...
Potomac horse fever. E. risticii, the cause of classic Potomac horse fever, is now known to produce two disease syndromes: EEC and EEA. The pathogen appears to commonly infect horses based on seroepidemiologic studies; however, the method of transmission remains unknown. The most common clinical disease is EEC, commonly called Potomac horse fever, which presents a wide spectrum of clinical signs. Diagnosis is currently dependent on serology, which frequently does not lead to a definitive diagnosis and at best results in a retrospective diagnosis. A new diagnostic approach, polymerase chain reaction, may offer a ra...
[Selected ectoparasitoses in animals]. Selected ectoparasitoses of animals are reviewed with special reference to the situation in Switzerland. The review contains information on the parasitoses leishmaniasis of dogs, parafilariasis of equines and cattle, onchocercosis of cattle and horses, ixodiosis, demodicosis of dogs and scabies of domestic animals, fly infestation, myiasis, and infestation with fleas and black flies (simuliidiosis). In addition to information on prevalence, biology and pathogenic effects of ectoparasites, the review provides indications on diagnosis and control.
African horse sickness: transmission and epidemiology. African horse sickness (AHS) virus causes a non-contagious, infectious, arthropod-borne disease of equines and occasionally of dogs. The virus is widely distributed across sub-Saharan African where it is transmitted between susceptible vertebrate hosts by the vectors. These are usually considered to be species of Culicoides biting midges but mosquitoes and/or ticks may also be involved to a greater or lesser extent. Periodically the virus makes excursions beyond its sub-Saharan enzootic zones but until recently does not appear to have been able to maintain itself outside these areas for more t...
Antibody to a recombinant merozoite protein epitope identifies horses infected with Babesia equi. Horses infected with Babesia equi were previously identified by the presence of antibodies reactive with a merozoite surface protein epitope (D. P. Knowles, Jr., L. E. Perryman, L. S. Kappmeyer, and S. G. Hennager. J. Clin. Microbiol. 29:2056-2058, 1991). The antibodies were detected in a competitive inhibition enzyme-linked immunosorbent assay (CI ELISA) by using monoclonal antibody 36/133.97, which defines a protein epitope on the merozoite surface. The gene encoding this B. equi merozoite epitope was cloned and expressed in Escherichia coli. The recombinant merozoite protein, designated equ...
A monoclonal antibody defines a geographically conserved surface protein epitope of Babesia equi merozoites. Babesiosis is a tick-borne hemoparasitic disease affecting horses worldwide. To investigate mechanisms of immunity to this parasite, the antibody response of infected horses to Babesia equi merozoite proteins was evaluated. Immunoprecipitation of B. equi merozoite antigens with sera from infected horses revealed 11 major proteins of 210, 144, 108, 88, 70, 56, 44, 36, 34, 28, and 25 kDa. Monoclonal antibody (MAb) 36/133.97, which binds to live merozoites, immunoprecipitated proteins of 44, 36, 34, and 28 kDa. When immunoprecipitations were performed with in vitro translation products of merozoi...
Seroepidemiologic survey of antibodies to Ehrlichia equi in horses of northern California. The prevalence of antibodies to Ehrlichia equi in horses from the foothill regions of northern California and from the Sacramento valley (non-foothill area) was determined, using an indirect fluorescent antibody test. Horses from foothill regions had a higher prevalence of seropositivity (10.4%) and higher titer (1:10 to 1:80) than did those from non-foothill regions (3.1%; titer less than or equal to 1:10). Fifty percent of healthy horses on a foothill farm enzootic for E equi had titer to E equi, suggesting that infection with E equi can be subclinical. Six veterinarians surveyed from northe...
Ehrlichiosis–a disease of animals and humans. Ehrlichiae are one of several kinds of obligate intracellular bacteria. Taxonomically, they are grouped with rickettsiae, but they can be distinguished by their unique tropism for circulating leukocytes. Ehrlichia canis causes a pancytopenia in dogs that becomes chronic if untreated. Certain breeds develop severe infections, characterized by fever, anorexia, dramatic weight loss, marked pancytopenia, anemia, peripheral edema, and hemorrhage. Ehrlichia risticii, a recently discovered species, is the cause of a serious diarrheal disease of horses. Other species of ehrlichiae have been documented...
The transovarial transmission of Babesia caballi by Hyalomma truncatum. Babesia caballi, isolated from a horse that originated from South West Africa/Namibia, was transmitted transovarially by adult Hyalomma truncatum. B. caballi proved to be highly infective for adult H. truncatum. Forty-five per cent of ticks feeding on a reacting animal with an extremely low parasitaemia became infected. In spite of a low parasitaemia, the ticks were severely affected by the parasite. Seventy per cent of the infected ticks either died during oviposition or after laying only a few eggs. The features of the infection in horses were: a prepatent period of 10 days, very low parasit...
Class-specific and polyvalent enzyme-linked immunosorbent assays for detection of antibodies to Borrelia burgdorferi in equids. Class-specific and polyvalent ELISA were developed to detect IgM antibody or total immunoglobulins to Borrelia burgdorferi in equine sera. Analyses of 122 serum specimens, collected during 1985 from horses and ponies in tick-infested areas of Connecticut, revealed IgM antibody in 41 (34%) samples; titration end points ranged from 1:160 to 1:2,560. In polyvalent ELISA, 73 (16%) of 454 serum specimens contained IgM and/or IgG antibody. Seropositivity was highest (32%) for blood samples collected during May. Both ELISA procedures had comparable sensitivities.
Epidemiology of Potomac horse fever: an investigation into the possible role of non-equine mammals. A serological study of antibodies to Ehrlichia risticii was carried out on 10 species of wild and domestic mammals found on or near 21 horse farms in an area of the USA in which Potomac horse fever is endemic. No antibodies were found in 133 peridomestic rodents (Norway rats and house mice), nor in 108 wild rodents (white-footed mice and meadow voles) captured on farms. Three of the six domestic animal species examined, cats, pigs and a goat, showed serological evidence of exposure to E risticii. Seropositive animals were detected on three of the 21 premises. The eight seropositive cats (of 48...
White-footed mice: tick burdens and role in the epizootiology of Potomac horse fever in Maryland. One hundred ten white-footed mice (Peromyscus leucopus) were captured on horse farms in south-central Maryland, examined for ticks, and tested for specific antibodies to Ehrlichia risticii, the causative agent of Potomac horse fever. Peromyscus leucopus were consistently infested with immature American dog ticks (Dermacentor variabilis), with monthly prevalences as high as 80%. Sera from all 97 P. leucopus tested for antibodies to E. risticii were negative. This indicates that P. leucopus is not a reservoir of E. risticii, and suggests that immature D. variabilis do not acquire E. risticii in ...
Repetitive DNA probes for the detection of Babesia equi. This report describes DNA probes for the identification of Babesia equi. A genomic library of B. equi was constructed in pUC13. Several clones were identified that hybridized strongly to B. equi DNA. Clone pBE33 hybridized specifically to B. equi DNA and did not hybridize to horse DNA nor to DNA from Babesia caballi, Babesia bovis or Babesia bigemina. Two subclones of pBE33 (pSB20 and pEH21) containing B. equi repetitive sequences, could detect 0.49 ng and 0.97 ng B. equi DNA, respectively.
Prevalence of piroplasmosis in equines in the Colombian province of Cordoba. Eighty-two equine sera from 13 farms in northern Colombia were examined for antibodies to Babesia caballi and B. equi using the complement fixation (CF) and the indirect fluorescent antibody (IFA) test. Seroreactors to both piroplasms were present on all farms. The IFA test indicated a prevalence of 90% for B. caballi and 94% for B. equi. The CF test detected antibodies to B. caballi in 41% and to B. equi in 65% of the animals. The prevalence of seroreactors in different age groups revealed a significant decline in CF antibodies to B. caballi in animals older than three years. IFA titres for b...
Isolation of pure Babesia equi and Babesia caballi organisms in splenectomized horses from endemic areas in South Africa. Both Babesia equi and Babesia caballi are endemic in large parts of South Africa. Attempts were made to obtain pure local isolates of both B. equi and B. caballi for the purpose of developing serological tests to study the epidemiology of equine babesiosis in this country. The indirect fluorescent antibody test was used to screen horses for B. equi and B. caballi in an endemic area. Seven horses and 3 donkeys between 3 and 36 months of age that tested negative were subsequently splenectomized. The splenectomy operation was performed through the abdominal approach. A 100% survival rate was achi...
Borreliosis in equids in northeastern United States. During 1982 and 1985, blood samples from 705 equids were examined for antibodies to Borrelia burgdorferi. By indirect immunofluorescence staining, IgM and total immunoglobulin (IgM and IgG) antibodies were detected in 37 (5.3%) and 90 (12.8%) serum specimens, respectively. The geometric mean titer for IgM antibody (140.4) was highest during July, whereas total immunoglobulin ranged from 94.1 in October to 338 in May. Eighty-six equids with total immunoglobulin to B burgdorferi lived in areas of Connecticut where the primary tick vector, Ixodes dammini, was present. Of the 86 equids, 9 from Lym...
Epidemiologic studies of Lyme disease in horses and their public health significance. A serologic survey of horses in the New Jersey-Pennsylvania area demonstrated that about 10% (6.2-14.2%) have significant levels of serum antibody to Borrelia burgdorferi. However, in a highly endemic area of central New Jersey, up to 60% of the mares and yearlings samples on one farm were seropositive. In 1983, sera from this same farm exhibited only 12% positives in mares and 35% positives in yearlings. Longitudinal studies of paired sera obtained from individual yearlings over a 6-month period in 1985 showed that 34% of them declined during the period. A new clinical syndrome associated wit...
