Topic:Cyathostomins
Cyathostomins, commonly referred to as small strongyles, are parasitic nematodes that inhabit the gastrointestinal tract of horses. They are among the most prevalent internal parasites affecting equine populations globally. These parasites undergo a direct life cycle, with larvae developing in the environment and being ingested by horses, where they mature into adult worms within the large intestine. Cyathostomins are known for their ability to encyst in the intestinal wall, which can complicate treatment and management strategies. This page compiles peer-reviewed research studies and scholarly articles that explore the biology, epidemiology, and control measures of cyathostomins in horses, as well as their impact on equine health and well-being.
Comparative efficacy of moxidectin and ivermectin against hypobiotic and encysted cyathostomes and other equine parasites. Efficacies of moxidectin and ivermectin were compared in four groups of eight ponies with natural parasite infections: placebo (Control), oral moxidectin gel at 0.3 mg kg-1 of body weight (Mox 0.3), oral moxidectin gel at 0.4 mg kg-1 of body weight (Mox 0.4), and oral ivermectin paste at 0.2 mg kg-1 of body weight (Ivermectin). Fecal samples were taken 0 and 2 weeks after treatment. Animals were necropsied and worms were collected 2 weeks after treatment. Moxidectin and ivermectin showed similar efficacy (99%) against adult cyathostomes, Strongylus spp., Triodontophorus spp. and Habronema musc...
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...
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.
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...
[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.
[Parasitic helminths of the cecum and colon of equidae in Italy]. Intestinal helminths from coecum and colon were studied in 93 equidae including 40 horses, 36 donkeys and 17 mules. A total of 38 species, 36 nematodes and 2 cestodes, were identified as follows: 1) Triodontophorus serratus, 2) Triodontophorus brevicauda, 3) Strongylus equinus, 4) Strongylus edentatus, 5) Strongylus vulgaris, 6) Cyathostomum tetracanthum, 7) Cyathostomum coronatum, 8) Cyathostomum labiatum, 9) Cyathostomum labratum, 10) Cyathostomum alveatum, 11) Cyathostomum pateratum, 12) Cyathostomum catinatum, 13) Cyathostomum sagittatum, 14) Cylicodontophorus bicoronatus, 15) Cylicocyclus...
The development of naturally acquired cyathostome infection in ponies. Groups of animals of different ages and experience of previous parasite exposure were allowed to graze a single pasture for 5 weeks in autumn (7 October to 11 November). There was evidence that previous exposure modified cyathostome development, as acquired burdens in foals which had previously grazed were smaller and developed more slowly than those of helminth-naive animals of the same age. The burdens acquired by yearling and adult ponies were of a similar size to those of the previously grazed foals, but the incidence of arrested development was higher in the younger groups of foals and ye...
The effect of ivermectin treatment against inhibited early third stage, late third stage and fourth stage larvae and adult stages of the cyathostomes in Shetland ponies and spontaneous expulsion of these helminths. A controlled and critical test on the efficacy of ivermectin against larval and adult stages of the cyathostomes was carried out in six yearling castrated male Shetland ponies. The ponies grazed together as one group from 3 May to 4 October 1990, after which they were housed. Three ponies were treated with ivermectin on 29 October while the others served as controls. The shedding of helminths in the faeces was followed in all ponies until necropsy on 14 November. Comparison of worm counts of both groups before and after necropsy showed no evidence for an effect of ivermectin against inhibited ...
Prevalence of benzimidazole-resistance in equine cyathostome populations in south east England. In order to study the prevalence of benzimidazole-resistance in equine cyathostomes, 30 stables in south east England were selected according to strict criteria but with minimum bias to provide three matched groups of 100 horses. One group was treated with fenbendazole, one with pyrantel embonate and the third was left untreated. The overall efficacies of fenbendazole and pyrantel embonate, as judged by the faecal egg-count reduction test, were 56.3 and 95.8 per cent, respectively. The numbers of horses at individual stables were too small to draw conclusions at each stable, but whereas effica...
Chronic diarrhoea in adult horses: a review of 51 referred cases. A retrospective analysis of the clinical and laboratory findings from 51 adult horses with chronic diarrhoea revealed that the most common conditions were larval cyathostomiasis (14 cases), idiopathic chronic colitis (nine cases) and alimentary lymphoma (five cases). Five animals had diarrhoea as a result of non-alimentary disease. A diagnosis was reached in 37 cases, but only 15 were made ante mortem. Among the 18 animals (35 per cent) which survived, there were five cases of larval cyathostomiasis, one case of colonic impaction and 12 cases were undiagnosed. The most frequent abnormalities d...
The prevalence of anthelmintic resistance of horse strongyles in The Netherlands. A survey to determine the prevalence of anthelmintic resistance of horse strongyles was carried out with 616 horses on 22 farms. The tested drugs were cambendazole, pyrantel pamaote and ivermectin. Based on egg count reduction tests the efficacy of cambendazole varied from 0% to 93% and of pyrantel from 93% to 100%. Ivermectin treatments were 100% effective on all farms. Larval cultures after cambendazole treatments revealed exclusively cyathostome larvae. After pyrantel treatments besides cyathostome larvae other types of larvae were also found. After ivermectin treatments only a few cyathost...
Identification of thiabendazole-resistant cyathostome species in Louisiana. A critical trial was performed with five ponies 6-9 months of age and raised on a horse farm with demonstrated benzimidazole-resistant cyathostomes. Eleven species of cyathostomes were recovered, seven of which had resistance to thiabendazole. Degrees of resistance varied among ponies and from species to species. Resistant species were Cyathostomum coronatum, Cyathostomum catinatum, Cylicostephanus minutus, Cylicostephanus calicatus, Cylicostephanus longibursatus, Cylicostephanus goldi and Cylicocylus nassatus. This is the first study identifying resistant cyathostome species in the Gulf Coast...
A field evaluation of anthelmintics for control of cyathostomes of horses in Brazil. The anthelmintic efficacy of ivermectin (IVM), piperazine citrate (PPZ) and fenbendazole (FBZ) alone, and combinations of FBZ with varying dosages of PPZ, was evaluated for the control of strongyles of Mangalarga equids. In all cases of positive strongly egg counts per gram of faeces (EPG) before and after treatment, pure populations of cyathostome larvae with eight gut cells were consistently observed in faecal cultures. The faecal egg count reductions (FECR) were evaluated between Day 7 and Day 56 post-treatment. Significant differences (P less than or equal to 0.05) were found between Day 7...
Effect of early season ivermectin and pyrantel treatments on strongylid infections in young Shetland ponies in The Netherlands. Two groups of three ponies were used to study the effect of three ivermectin or pyrantel treatments given at intervals of 5 weeks at the beginning of the grazing season. Although each pyrantel treatment resulted in a greater than 95% reduction in faecal egg counts during the first 3 weeks, high pasture larval counts were seen from the beginning of August onwards and substantial cyathostomine burdens were found at necropsy in December. The ivermectin treatments resulted in an even more pronounced reduction in faecal egg output, and the pasture larval counts and cyathostomine burdens at necropsy...
Effects of three anthelmintic schedules on the incidence of colic in horses. Four privately owned herds (25 to 49 animals per herd) were used in a five-year trial designed to evaluate the effect of anthelmintic schedules on the incidence of colic. These herds had been treated bi-monthly with non-ivermectin, non-benzimidazole drugs for two years before the trial. Prior parasitological studies showed that they had substantial pre-treatment faecal egg counts (900 to 2200 eggs per gramme), and that they were infected with benzimidazole-resistant cyathostomes. In Years 1 and 2 of the trial, all herds (A, B, C, D) were treated bi-monthly with non-ivermectin anthelmintics (Sc...
Seasonally inhibited development of cyathostomine nematodes in Shetland ponies in The Netherlands. Two groups of three yearling Shetland ponies were used in 1988 to study the epidemiological significance of inhibited development of the Cyathostomine nematodes. In Group 1, acquisition of infections was prevented throughout the grazing season whereas in Group 2 strongylid infections were acquired from the beginning of July until the end of September. Worm counts showed that the Cyathostomine nematode populations of Group 1 ponies mainly consisted of adult worms and those of Group 2 ponies of inhibited early third stage larvae (L3). These results indicate that a large proportion of Cyathostomi...
Reduced efficacy of anthelmintics in young compared with adult horses. Studies on a Thoroughbred breeding farm in Ohio from 1982 to 1988 demonstrated the value of three anthelmintic pastes (ivermectin, oxibendazole, pyrantel pamoate) in controlling benzimidazole resistant cyathostomes (small strongyles) in adult horses. However, a comparison of drug efficacy in suppressing faecal egg counts for the full period between treatments showed a significant reduction in efficacy of all drugs in yearling horses compared with adults. Mean faecal egg counts of adult horses were generally kept below 100 eggs per gram (epg) of faeces when using oxibendazole or pyrantel pamoat...
Emergence from inhibited development of cyathostome larvae in ponies following failure to remove them by repeated treatments with benzimidazole compounds. The effect of three albendazole treatments at 5-week intervals, beginning at turnout in April, on cyathostome infections in Shetland ponies was compared with the effect of sequential treatments with albendazole, oxfendazole and oxibendazole. The results showed a substantial reduction in faecal egg output after the first albendazole treatment. Since faecal egg counts remained very low, no estimation of the effect of the second treatment was possible. The third treatment with albendazole and oxibendazole was followed by an increase in faecal egg counts to values of greater than 100 eggs g-1 with...
Internal parasites of horses on mixed grassveld and bushveld in Transvaal, Republic of South Africa. Between 1980 and 1982, the gastrointestinal tracts of 17 horses which had been grazing on mixed grassveld at Potchefstroom and bushveld at Onderstepoort in the province of Transvaal, Republic of South Africa, were examined at necropsy and processed for parasite recovery. The large strongyles and their prevalences were as follows: Strongylus vulgaris and associated lesions (88-94%), Strongylus edentatus (24%), Strongylus equinus (30%), Triodontophorus nipponicus (35%) and Craterostomum acuticaudatum (18%). The seven most prevalent and abundant cyathostomes collected were Cylicostephanus longibu...
Efficacy of four anthelmintics against benzimidazole-resistant cyathostomes of horses. In order to confirm benzimidazole resistance as recommended at a workshop of the Commission of the European Communities the isolate 'E' of cyathostome strongyles originating from a stud where benzimidazole resistance had been demonstrated by egg hatch tests and by egg count reduction tests was investigated in two series of critical tests. Each of 11 foals reared strongyle-free was infected with 130,000 third stage cyathostome larvae. One animal remained untreated, two pairs of foals were treated with paste formulations of the (pro)benzimidazoles cambendazole (20 mg/kg bodyweight) or febantel (...
A survey in Louisiana of intestinal helminths of ponies with little exposure to anthelmintics. Ponies reared with minimal or no exposure to anthelmintics were surveyed for intestinal helminths in order to estimate prevalence and intensity of parasite populations unaltered by frequent exposure to anthelmintics. Thirty-seven mixed breed ponies of varying ages were examined. Thirty-four species of nematodes and 2 species of cestodes were found. Twenty-four of the nematode species (including 1 new species) were in the subfamily Cyathostominae (small strongyles). Eighty-seven percent of the total burden of adult small strongyles in the large intestine was composed of 10 species. By comparing...
Comparison of two control systems for cyathostome infections in the horse and further aspects of the epidemiology of these infections. The small strongylid infections of two groups of three yearling female Shetland ponies and one yearling Shetland tracer pony were studied. One group was set stocked from April to November and was treated monthly with 5 mg kg-1 albendazole from two days before turnout until July. The other group grazed similar pasture until July, was treated with 5 mg kg-1 albendazole and subsequently removed to pasture grazed by sheep from April to July. The tracer ponies were added to both groups in September. The efficacy of both methods was not completely satisfactory probably because of low efficacy of ant...
Serum protein changes in ponies on different parasite control programmes. Serum protein responses were examined in 52 ponies divided into five groups and subjected to various control strategies that resulted in pasture infectivity ranging from 706 to 18,486 infective third stage, cyathostome and Trichostrongylus axei larvae per kilogram of herbage (L3/kg) by 17 September 1984. Major protein changes occurred only in young ponies (Groups 4 and 5) and were observed before exposure to maximum numbers of pasture larvae (Group 4; 10,210 L3/kg, Group 5: 10,042 L3/kg) on 17 September. It appeared that a primary infection of T axei was a greater stimulus to serum beta-globul...
Anatomic distribution of encysted cyathostome larvae in the horse. The large intestines of 6 horses were divided by length into 12 segments, and each segment was washed and weighed. At least 5% by weight of each segment was examined by mural transillumination, and encysted cyathostome larvae were counted. Total numbers of larvae in each segment were calculated. Encysted larvae (98%) were present in the proximal 7 segments of the large intestine (cecum and proximal 75% of the ventral colon), and 2% were present in the distal 25% of the ventral colon and entire dorsal colon. Encysted larvae (6%) were located in the dorsal colon of 1 heavily infected horse. Larv...
Comparison of two techniques for quantitation of encysted cyathostome larvae in the horse. Haustral portions of intestine of 6 horses were isolated by excising the taeniae coli from the cecum and the ventral colon. Uniform 5-cm X 5-cm sections were cut from the haustra and were illuminated from the serosal side with a strong light source (mural transillumination). Cyathostome larvae encysted in the mucosa and submucosa were observed at 15 X magnification and counted. Two separate counts of the larvae in 80 replicates of tissue by the mural transillumination technique (MTT) revealed no significant (P less than 0.05) difference between sample means. Larvae in tissue sections were coun...
Tissue-invading ciliates associated with chronic colitis in a horse. Ciliates resembling Polymorphella ampulla (Dogiel, 1929) were found in large numbers in the crypts and lamina propria of the caecum and colon of a one-year-old Thoroughbred gelding that had shown recurring bouts of chronic diarrhoea and weight loss over a 5-month period. A heavy burden of helminths, mainly cyathostomes (trichonemes) was present at post-mortem examination and no significant bacterial pathogens were recovered. It was considered that the Polymorphella (which is normally a commensal organism) had in this case assumed a secondary pathogenic role.