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Topic:Parasites
Parasites are organisms that live on or within a host, deriving nutrients at the host's expense. In horses, parasitic infections can affect various systems, including the gastrointestinal tract, skin, and respiratory system. Common equine parasites include strongyles, ascarids, tapeworms, and bots. These parasites can lead to a range of health issues, from mild discomfort to severe disease, depending on the type and burden of the infestation. This page compiles peer-reviewed research studies and scholarly articles that explore the biology, life cycle, and impact of parasites on equine health, as well as strategies for diagnosis, treatment, and prevention of parasitic infections in horses.
Natural infections of Strongyloides westeri: prevalence in horse foals on several farms in central Kentucky in 1992. During the period 28 February-1 July 1992, fecal samples were collected and examined for eggs of Strongyloides westeri once from each of 382 horse foals (364 Thoroughbreds, 16 Standardbreds, one Lippizaner, and one draft-type horse) in central Kentucky. Ages of the foals at the time of sampling ranged from 7 to 63 days (mean 22 days). The nine farms in the study were considered to have overall excellent deworming programs. None of the foals had been treated with an antiparasitic compound before the study. Eggs of S. westeri were found in 6% (22 of 382) of the foals on 78% (7 of 9) of the farms...
Equine abortion and stillbirth in central Kentucky during 1988 and 1989 foaling seasons. Pathologic and microbiologic examinations were performed on 1,211 aborted equine fetuses, stillborn foals, and placentas from premature foals in central Kentucky during the 1988 and 1989 foaling seasons to determine the causes of reproductive loss in the mare. Placentitis (19.4%) and dystocia-perinatal asphyxia (19.5%) were the 2 most important causes of equine reproductive loss. The other causes (in decreasing order) were contracted foal syndrome and other congenital anomalies (8.5%), twinning (6.1%), improper separation of placenta (4.7%), torsion of umbilical cord (4.5%), placental edema (4...
Disseminated Halicephalobus deletrix infection in a horse. A 13-year-old Quarter Horse gelding was referred for evaluation of a draining tract and fracture of the right hemimandible of 4 weeks' duration. Two days prior to admission, the horse had developed pigmenturia. Radiography of the mandible revealed a fracture of the vertical ramus of the right hemimandible, loss of the right lower second premolar, and osteomyelitis involving an extensive portion of the hemimandible. Ultrasonography of the left kidney revealed loss of normal renal architecture. Histologic examination of tissue obtained from the right hemimandible revealed granulomatous osteomyel...
Evaluation of agar gel immunodiffusion and indirect fluorescent antibody assays as supplemental tests for dourine in equids. The agar gel immunodiffusion (AGID) and indirect fluorescent antibody (IFA) assays were evaluated as supplemental tests to the complement-fixation (CF) test, the official US importation certification test for dourine in equids. The American stabilate (n = 10 animals) or the Canadian stabilate (n = 6 animals) of Trypanosoma equiperdum cultured in rat blood was administered by catheterization and infusion in the urogenital tract of 16 equids. To assess parasitemia and serologic responses by use of the CF, AGID, and IFA tests, a total of 787 serum and blood samples were obtained from equids befor...
Generation and partial characterization of an eosinophil chemotactic cytokine produced by sensitized equine mononuclear cells stimulated with Strongylus vulgaris antigen. Supernatants generated by stimulation of peripheral blood mononuclear cells (PBMC) from Strongylus vulgaris sensitized or immunized ponies were assayed in vitro for eosinophil chemotactic activity (ECA) using the filter system in blind well chambers. The supernatants from these cultures were chemotactic for eosinophils, but not for neutrophils. Supernates from cultures of unsensitized PBMC stimulated with S. vulgaris antigen were not chemotactic for eosinophils. ECA was first detected in culture supernatants after 1.5 h of incubation and was dependent on both antigen and PBMC concentrations, b...
Comparison of five tests for the serologic diagnosis of myiasis by Gasterophilus spp. larvae (Diptera: Gasterophilidae) in horses and donkeys: a preliminary study. Sera from 41 horses and 159 donkeys, from twelve States of México, were tested to ascertain anti-Gasterophilus circulating antibodies by double immunodiffusion (DD), counterimmunoelectrophoresis (CIE), indirect haemagglutination (IH), thin layer immunoassay (TIA) and diffusion-in-gel ELISA (DIG-ELISA) methods using crude somatic antigen from third instar larvae of G. intestinalis (DeGeer). At necropsy, 33/41 horses and 24/159 donkeys were found to be parasitized by G. intestinalis and/or G. nasalis (L.). Gasterophilus intestinalis was the species most commonly found in the equines. Analysis o...
Development of neutralizing antibody in horses infected with Ehrlichia risticii. The role of the humoral immune response in ehrlichial infection is unknown. Development of neutralizing antibodies during a course of Ehrlichia risticii infection in a pony was examined in vitro by determining the inhibition of E. risticii infection of P388D1 cells in the presence of the sera. The pony experimentally infected with E. risticii developed significant neutralizing activity in the sera by 15 days postinfection when parasitemia started to decline. Neutralizing activity continued to rise after recovery from the disease up to 34 days postinfection at which time the experiment was term...
Host preferences of the sand fly Lutzomyia longipalpis at an endemic focus of American visceral leishmaniasis in Colombia. Blood meals from 579 Lutzomyia longipalpis (Diptera:Psychodidae), collected in an endemic focus of American visceral leishmaniasis in Colombia, were identified by precipitin test. Sand fly collections were made during a 16-month period from the inside walls of two houses, a pigpen, and rock crevices in a small community (El Callejon) within the endemic area. Feeding patterns of the sand flies varied with locality and date of collection. Overall, bovine feedings predominated, but feedings were also recorded on pigs, equines, humans, dogs, opossums, birds, and reptiles. Calculation of the forage...
[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.
Ivermectin treatment of horses: effect on the distribution of lawns and roughs in horse pastures. A study was carried out to assess the feasibility of determining the grazing patterns of horses bimonthly via aerial survey and standard cartographic techniques. The grazing patterns in pastures with equivalent stocking rates of horses treated bimonthly with 200 micrograms of ivermectin kg-1 or 10 mg of oxibendazole kg-1 was assessed using aerial survey mapping performed three times during a grazing season. The distribution patterns of lawns and roughs in pastures were similar at all times during the study. Aerial survey was determined to be a very efficient and objective method of determining...
Besnoitiosis in a horse. Besnoitiosis was confirmed in a pony which presented with inspiratory dyspnoea, scleroderma and ventral oedema. Numerous cysts were visible in the sclerae. Histological examination of the skin confirmed the presence of numerous cysts. The parasite could not be transmitted by subcutaneous injection of homogenised skin from the infected horse to rabbits and a horse. Ultrastructural morphology of the crescent-shaped bradyzoites was not compatable with Besnoitia besnoiti or B. jellisoni and it is proposed that the infection was caused by B. bennetti.
Critical tests of thiabendazole, oxibendazole, and oxfendazole for drug resistance of population-B equine small strongyles (1989 and 1990). Critical tests were conducted in horses (n = 11) with naturally acquired infections of benzimidazole (BZ)-resistant population-B small strongyles in 1989 and 1990. Anthelmintics administered were thiabendazole (44 mg/kg of body weight, n = 4), oxibendazole (10 mg/kg, n = 3), and oxfendazole (OFZ, 10 mg/kg; n = 4). All compounds were paste formulations administered orally except for 1 of the OFZ treatments, which was a suspension formulation given by stomach tube. Aggregate mean efficacy was calculated for all species of small strongyles, drug-resistant and non-resistant. The highest efficacy w...
Dung dispersal and grazing area following treatment of horses with a single dose of ivermectin. Environmental consequences of treating horses with recommended dosages of ivermectin paste were studied in two controlled experiments with 29 horses in Ohio. In 1988, dung dispersal rates were measured by changes in dry weight over time of 48 copromes (300 g) formed from feces taken from four treatment and four control horses 3 days post ivermectin treatment. There was delayed dispersal of copromes from horses treated with ivermectin in June, resulting in significantly heavier ivermectin copromes compared with those of control horses by September. There was no difference in ivermectin or contr...
A review of regional and temporal use of avermectins in cattle and horses worldwide. Ivermectin and abamectin are two members of the group of parasiticides known as the avermectins; ivermectin was first registered as an injectable treatment for cattle in 1981. Since then, abamectin has been registered for cattle and ivermectin for horses. The relative popularity of the avermectins amongst farmers and veterinarians can be attributed to their spectrum of activity, convenience, wide margin of safety and the improved health and performance of stock following their use. Patterns of use in grazing animals apply equally to the avermectins as to other antiparasitics, particularly anth...
Control strategies for ruminant and equine parasites to counter resistance, encystment, and ecotoxicity in the USA. The need for improved parasite control strategies to conserve anthelmintic efficacy and to avoid drug-related problems are addressed. Recent surveys have revealed a trend for sole dependence on ivermectin by livestock owners in the USA, with little regard for epidemiologic-based strategies, or the annual rotation of unrelated anthelmintic groups. Innovative parasite control strategies for cattle, sheep, and horses in northern USA are presented. The importance of closer monitoring and more rational use of anthelmintics is stressed.
Are tapeworms associated with equine colic? A case control study. Faeces samples from 116 horses with colic and 115 non-colic cases were assayed by a centrifugation/floatation method for the presence of tapeworm eggs. Analysis of these data failed to demonstrate an association between tapeworm infection and colic of all types. The data were further analysed according to anatomical site of the lesion causing colic. The risk of ileocaecal colic was increased in the presence of tapeworms. Age, breed and sex were evaluated as possible confounding factors but had no association with the incidence of colic. This study suggests an association between tapeworms and ...
Two fatal cases of diarrhoea in horses associated with larvae of the small strongyles. Detailed pathological examinations of two horses with subacute fatal diarrhoea suggested an association between the diarrhoea and damage to the colonic and caecal mucosae caused by large numbers of cyathostome larvae (larval cyathostomiasis). The affected animals deteriorated rapidly, and died after a short illness.
Culture confirmation of the carrier status of Babesia caballi-infected horses. Culture of horse blood for Babesia caballi identified four carrier horses among nine previously infected horses. Three of the carriers had no detectable parasitemias on stained blood smears, and sera from two carrier horses were complement fixation test negative. Three cultures were continuously cultivated. Cryopreserved fourth-passage B. caballi was successfully reestablished in vitro. Blood from a 10th horse previously subinoculated with blood from a suspected carrier was cultured, with negative results.
Serological diagnosis of Trypanosoma evansi (Steel, 1885) in horses using a direct agglutination test. A direct agglutination test is described to diagnose 'Mal de Caderas' caused by Trypanosoma evansi. The antigen used was a suspension of trypsin-treated parasites stabilized with formalin. The test was evaluated in horses with both natural and experimental infections. Test sensitivity and specificity were 94 and 97%, respectively. Treatment of serum with 2-mercaptoethanol before testing permitted the differentiation of IgM and IgG antibodies, and possible differentiation of current infection from past exposure to the parasite. The antigen was stable over a 6-month evaluation period and also sh...
Evaluation of ivermectin at an elevated dose against encysted equine cyathostome larvae. The efficacy of a high dose of ivermectin (1.0 mg per kg Eqvalan liquid drench) on encysted cyathostomes was tested in a controlled study using 12 adult ponies with naturally acquired cyathostome infections. Six treated ponies and six non-treated controls were held in separate stalls for a period of 5 weeks. Cyathostome burdens, which included lumenal larvae, adults and encysted larvae, were determined at necropsy. The viability of encysted larvae, based on morphologic integrity, was assessed by observation of mural transillumination and by the histologic appearance of 12 larvae per pony. Effi...
The reappearance of eggs in faeces of horses after treatment with ivermectin. The reappearance of nematode eggs in faeces after ivermectin treatment was studied in 104 horses on 10 farms during the stabling period. Faecal samples were taken at weekly intervals. Sampling was discontinued when the mean egg output per farm was > 10% of the pre-treatment egg output. This point was reached after 63 days, when the mean output of eggs had decreased to 70.3%. Before treatment, 95.9% of the cultured larvae were of the cyathostome type, the others belonged to Gyalocephalus capitatus, Strongylus vulgaris, S. edentatus, Oesophagodontus/Poteriostomum spp., Triodontophorus spp. an...
Pathological lesions associated with Anoplocephala perfoliata at the ileo-caecal junction of horses. The intestinal tracts of 20 horses, killed at a local abattoir and of unknown age, sex and previous clinical history were examined for the presence of Anoplocephala perfoliata attached to the ileo-caecal junction. Four horses had no tape-worms, nine had one to 20 tapeworms attached to the mucosa and seven had more than 100 attached to the mucosa. The histological changes of thickening, ulceration and eosinophil infiltration of the mucosa at the ileo-caecal junction were more severe when more than 100 parasites were present.
Trypanosomiasis of domestic animals in China. Trypanosomiasis caused by Trypanosoma evansi (surra) is a problem of great economic importance in livestock in China because it affects important working animals: buffaloes in the south and east, and horses and cattle in the north and west. In addition, buffaloes are an important source of meat and leather for the Chinese population. In the north and west, T. evansi is found mainly in camels, whereas in the east, the south and the southwest, it is primarily buffaloes, cattle and horses that are affected by this parasitic flagellate. Although trypanosomiasis is one of the most important parasit...
Anthelmintic resistance. In populations of livestock in which anthelmintics have become the only means of control, individual worms in some species of helminths evade the effects of specific anthelmintics. If these resistant individuals are selected (by removing the susceptible individuals in the population) then the resistant worm population on individual farms becomes dominant in both numbers and effect. This selection of anthelmintic resistant populations is most often reported in equids and small ruminants (the hosts in which anthelmintics are used most frequently). There is little evidence of anthelmintic resista...
Echinococcus granulosus hydatid cysts in the livers of two horses. No abstract available
[Biological and parasitic variations in horses infested and reinfested by Trichinella spiralis]. Seven mares were infected with 20,000 Trichinella spiralis larvae; 2 of them were reinfected 22 wk later with the same amount of larvae. The course of infection in horses was assessed by serology (ELISA), biochemistry (aldolase activity), parasitology and histopathology. In each animal, infection was followed by a significant rise in specific antibody titers culminating at 5-10 wk post-infection (pi) and decreasing thereafter. Reinfection was followed by a slight rise in antibody levels. Aldolase activity increased during the first infection, but was not modified by reinfection. The parasite b...
[Efficacy of the oral antiparasitic mebendazole plus trichlorfon (telmin plus trichlorfon) against Gasterophilus in the horse]. The combined drug Mebendazole plus Trichlorfon (Telmin plus Trichlorfon, Janssen Pharmaceutica, Beerse/Belgium) has been tested in a field trial against naturally acquired Gasterophilus spp. infestations in horses. 44 foals (1 to 1.5 years old, 350-450 kg body-weight) originating from different endemic areas of Switzerland, have been randomly allocated to two groups as follows: 28 foals were treated with Mebendazole plus Trichlorfon, 16 animals served as untreated controls. The drug (paste) was administered and dosed according to the user's instruction. Macroscopic examinations of the digestiv...
[Resistance of small strongyles in an equine stud in South Africa to the benzimidazole anthelmintics]. This paper is apparently the first report of resistance of helminths of equids to anthelmintics in South Africa. While a strain of Cyathostominae from an Arab horse stud near Pretoria showed greatly reduced susceptibility to benzimidazoles in faecal egg reduction tests, ivermectin was apparently still unaffected. It is suggested that integrated methods of control such as alternation of horses and ruminants on pasture and mechanical removal of faeces should be used in addition to anthelmintics.
