Larvae in relation to horses refers to the immature stages of various parasitic organisms that can infect equine hosts. These larvae can originate from different species of internal and external parasites, such as gastrointestinal nematodes and bots. The presence and development of larvae in horses can lead to various health issues, including digestive disturbances, weight loss, and colic. Common parasitic larvae affecting horses include those of Strongylus vulgaris, Parascaris equorum, and Gasterophilus spp. Understanding the life cycle, transmission, and impact of these larvae is essential for effective parasite management and control in equine populations. This page compiles peer-reviewed research studies and scholarly articles that explore the biology, pathology, and management strategies related to larval parasitism in horses.
Principato M.Comparative data collected over 4 years show the most frequent species of Gasterophilus infesting free-ranging horses in Umbria (Central Italy) to be G. intestinalis (93.8%), G. nasalis (76.5%) and G. inermis (71%). G. pecorum and G. haemorrhoidalis were less frequent and appeared in 39.3 and 10.8% of the animals, respectively. For each of the 5 species, the duration of gastric and enteric lesions, the average numbers of larvae isolated throughout the year and the probable duration of oral lesions were discussed.
Soule C, Dupouy-Camet J, Georges P, Ancelle T, Gillet JP, Vaissaire J, Delvigne A, Plateau E.Three groups of three horses each were, respectively, infected with 5000, 20,000 and 50,000 larvae of Trichinella spiralis. The strain used was isolated from a human biopsy during horsemeat-related outbreaks of trichinellosis in France. Transient muscular disorders were only observed in two of the horses infected with 50,000 larvae but none of the horses had fever. A significant increase in blood eosinophils was noticed in 5 horses. Serum LDH, aldolase and CPK peaked at the fifth week post-infection. Specific IgG assayed by indirect immunofluorescence and ELISA, appeared 2-5 weeks post-infecti...
Hendrikx WM, Jansen J, de Vries TJ.An infection with second-stage larvae of the warble-fly H. diana in a horse is described. The second-stage larvae were incapable of developing into the third stage, because horses are unsuitable hosts and because the infected horse was treated with an insecticide. Since the horse was used for dragging trees in the forests, the infection was likely contracted via contact with H. diana, a normal parasite of roe deer in the Netherlands.
Morgan SJ, Storts RW, Stromberg PC, Sowa BA, Lay JC.Factors involved in the proliferation of equine vascular smooth muscle cells were studied in vitro. The most prominent proliferative responses in cultured vascular smooth muscle cells were induced by Strongylus vulgaris larval antigen extract (LAE) and platelet-derived factors. Less significant proliferative responses were obtained with conditioned media from S. vulgaris LAE stimulated and from unstimulated equine mononuclear leukocytes. Additionally, vascular smooth muscle cells exposed to S. vulgaris LAE developed numerous perinuclear vacuoles and were more spindle-shaped than control or smo...
DiPietro JA, Lock TF, Todd KS, Sanecki RK.A controlled test was carried out on 15 pony foals inoculated with 1,500 +/- 108.8 infective Parascaris equorum eggs. The foals were assigned to 3 treatment groups. Treatments given on postinoculation day 11 included 0.2 mg of ivermectin/kg of body weight, formulated as paste (n = 5), or liquid (n = 5), or no treatment (controls; n = 5). The foals were euthanatized on postinoculation day 25, and examined for larvae in the small intestine, lungs, and liver. Larvae were not found in foals treated with ivermectin liquid or paste, whereas significantly (P less than 0.05) higher mean numbers (960.9...
Duncan JL, Arundel JH, Drudge JH, Malczewski A, Slocombe JO.These guidelines have been designed to assist in the planning, operation and interpretation of studies which would serve to assess the efficacy of drugs against internal parasites of horses. Although the term anthelmintic is used in the title and text, these guidelines include studies on drug efficacy against larvae of horse bot flies, Gasterophilus spp, which are non-helminth parasites commonly occurring in the stomach of horses. The advantages, disadvantages and application of critical and controlled tests are presented. Information is also provided on selection of animals, housing, feed, do...
Drudge JH, Lyons ET, Tolliver SC, Lowry SR, Fallon EH.Observations were completed over an 18-year period (1966 through 1983) in Thoroughbred mares (15/year) and yearlings (11 to 24/year) on a farm where benzimidazole-resistant small strongyles had emerged previously (1962 to 1965). This farm was operated as a closed, nonboarding type, which included a racing stable for its home-bred foals. At 2-week intervals, counts of worm eggs per gram of feces (EPG) and larvae per gram of feces were done to monitor strongyle infections and efficacies of bimonthly (every 8 weeks) antiparasitic treatments that were administered by stomach tube or were fed (dich...
French DD, Klei TR, Taylor HW, Chapman MR, Wright FR.The efficacy of ivermectin in oral paste formulation at a dosage of 200 micrograms/kg of body weight was tested against naturally acquired larval and adult stages of Parascaris equorum, in a controlled study. Twenty infected pony foals 18 to 27 weeks of age were randomly allocated to 2 groups of 10 each and were placed in dry lots. Foals in 1 group were given ivermectin on day 0. Necropsies and parasite recoveries from small intestines and lung tissues were performed on 5 foals in each group at 2 weeks after treatment (WAT) and on the remaining foals at 5 WAT. Ivermectin was 100% effective aga...
Folz SD, Pax RA, Klei TR, Thomas EM, Ash KA, Conder GA, Bennett JL.An in vitro assay involving the use of a horse strongyle (Strongylus edentatus) and the micromotility meter has been developed to test for equine anthelmintic activity. Three commercially available equine anthelmintics (dichlorvos, ivermectin, and pyrantel pamoate) and an investigational drug (p-toluoyl chloride phenylhydrazone) were evaluated in this assay at four concentrations. After a 24-h incubation, greater than or equal to 10 micrograms/ml of all four drug treatments significantly (P less than or equal to 0.05) reduced the motility of ensheathed L-3 S. edentatus larvae, thereby indicati...
Kobluk CN, Smith DF.An intramural hematoma involving a 40-cm segment of the distal portion of the jejunum caused intestinal obstruction and colic in a mature mare. The involved intestine was resected, and an end-to-end anastomosis was performed. The mare recovered completely, but 4 years later had colic caused by incarceration and volvulus of the distal portion of the jejunum, involving fibrous abdominal adhesions. The cause of hematoma was not identified; however, rupture of an intramural vessel after migration of Strongylus vulgaris larvae was considered a possibility because of the histologic observation of an...
Principato M.Listed and described herein are the main macroscopic lesions produced along the whole digestive tract of free-ranging horses by larvae of the five Gasterophilus spp., occurring in Umbria, a region of central Italy: Gasterophilus intestinalis, Gasterophilus nasalis, Gasterophilus pecorum, Gasterophilus inermis, Gasterophilus haemorrhoidalis. Lesions are classified on the basis of their sizes and shapes and the host's anatomic sites infested, and they are examined in relation to the developmental stages of larvae causing them. The examination of the lesions shows that it is very difficult to dif...
Nansen P, Grønvold J, Henriksen SA, Wolstrup J.Interactions between the predacious hyphomycete Arthrobotrys oligospora and third-stage larvae of nine animal-parasitic nematodes were tested in vitro. The trap-inducing capabilities of the ruminant trichostrongylus Cooperia oncophora, C. curticei, Haemonchus contortus and Ostertagia ostertagi and of equine cyathostomes were almost comparable to those of free-living soil nematodes, and significantly higher than those of the porcine Oesophagostomum dentatum and Oe. quadrispinulatum and of the murine Nematospiroides dubius. The trap-forming potential of Dictyocaulus viviparus was poor. All anima...
Mfitilodze MW, Hutchinson GW.The development of the free-living stages and yields of infective third stage strongyle larvae in faeces from a horse with a mixed natural infection deposited on pasture plots were studied over a 2-year period in a coastal area in tropical north Queensland. Two sets of faecal masses (one exposed to, and the other protected from the action of a natural population of dung beetles) were deposited monthly and after 7 days faecal samples were taken for larval recovery and counts. Hatching and development of the free-living stages occurred in faeces on pasture throughout the year. Development was ra...
Slocombe JO, Valenzuela J, Lake MC.The transmission of strongyles among 54 Shetland-cross mature ponies was examined from May 30 to November 22, 1983 when the ponies were on pasture and over the ensuing winter when they were in loose housing. Fecal and pasture herbage samples were taken fortnightly through the pasture season and periodically thereafter. Three foals born and reared on pasture were weaned and removed from pasture, two in early August and one in mid-September, and housed for a period before necropsy. Daily maximum and minimum air temperature and total precipitation were recorded. The mean fecal strongyle egg count...
Price RE, Stromberg PC.Stomachs of 271 horses and ponies from 2 sources were evaluated for the presence of Gasterophilus intestinalis and G nasalis larvae, through 2 overlapping 12-month periods of bot fly activity in southern Texas. Equids (n = 140) from one source had nearly 96% of their stomachs infected, whereas equids (n = 131) from another source had 44% of their stomachs infected by Gasterophilus spp. Seasonal dynamics of the bot infection indicated the highest average number of bot larvae per infected stomach occurred in the winter and spring. The smallest average number of bots per infected stomach occurred...
Enileeva NKh.The paper describes the flight periods and dynamics of abundance of horse botflies, life span of females and males, effect of environmental factors on the activity of flies and their behaviour, potential fecundity of different species of botflies, duration of embryonal development, preservation of viability of larvae in egg membranes, localization of different stages of botflies in the host, and methods of their control.
Smith HJ, Snowdon KE.Light Trichinella infections were established in three ponies given 1000, 5000 and 25000 T. spiralis spiralis infective larvae respectively by stomach tube. A predilection site of infection in all ponies was the tongue. Anti-Trichinella antibodies were detected in all ponies by the enzyme-linked immunosorbent assay using a T. spiralis spiralis excretory-secretory antigen. The ponies given 5000 and 25000 infective larvae reacted positively on days 26 and 24 postinfection, respectively, using a criterion of greater than or equal to 5 X mean optical density readings of preinfection sera as positi...
Vandermyde CR, DiPietro JA, Todd KS, Lock TF.Fifteen pony foals were inoculated with 1,500 +/- 298.7 infective Parascaris equorum eggs. The foals were assigned to 3 treatment groups. Treatments included 10 mg of fenbendazole/kg given once on postinoculation day (PID) 11, 10 mg of fenbendazole/kg given daily on PID 11 to 15, and no treatment (controls). The foals were euthanatized on PID 25 and examined for P equorum larvae in the small intestine, lungs, and liver. Significantly (P less than 0.05) lower mean numbers of P equorum larvae were found in the small intestine of foals treated on PID 11 to 15 (1.4 [range, 0 to 6]) than in the sma...
Borgsteede FH, Bruin G, Smolders EA.In 1983 and 1984 the effect of a deworming scheme, in which horses were treated at turn out and 4 and 8 weeks later, on the egg output, larval differentiation, weight gain, herbage infestation and in 1984, the percentages of some serum proteins were tested. In 1983 the experiment was done with 42 mares, 54 two year old male horses and 42 male yearlings, kept in groups with permanent or rotational grazing. In 1984 only 90 male yearlings were investigated. In 1983 albendazole and ivermectin were used, 1984 ivermectin. The results of the faecal examinations showed that after ivermectin treatment ...
Dart AJ, Hutchins DR, Begg AP.A 12-year-old Thoroughbred mare, with a history of anorexia, dramatic weight loss, fluctuating pyrexia and intermittent diarrhoea after an episode of colic, was presented for examination with depression, emaciation and ataxia. Thoracic and abdominal paracenteses yielded copious quantities of inflammatory exudate. Palpation per rectum revealed an enlarged spleen. The primary alterations in haematology included a severe leucocytosis with a left shift, and a hyperproteinaemia characterised by hypoalbuminaemia and hypergammaglobulinaemia. Post-mortem examination revealed a low grade pleurisy and p...
DiPietro JA, Lock TF, Todd KS, Reuter VE.Twenty ponies less than 18 months of age and infected with Parascaris equorum were treated with either 0.2 mg of ivermectin/kg of body weight (n = 10) or a placebo (n = 10; controls). Five control and 5 ivermectin-treated ponies were euthanatized 14 and 35 days after treatment, respectively. At necropsy, the small intestinal contents, lungs, and liver were examined for larvae and/or adult P equorum. Significantly (P less than 0.02) higher mean total numbers of P equorum were found in the small intestinal contents of the controls on day 14 (51) and on day 35 (21) than in the ivermectin-treated ...
Slocombe JO, McCraw BM, Pennock PW, Ducharme N, Baird JD.A preliminary investigation was made into the effect of fourth-stage Strongylus vulgaris larvae sequestered in the tunica media of ileocolic arteries of pony foals treated with ivermectin. The foals had been reared parasite-free, inoculated with infective larvae and given orally a placebo or ivermectin paste. Two foals received subsequently one or two further inoculations with larvae and treatment with ivermectin. Arteriography was used to identify the lesions in the ileocolic artery following inoculation and their regression following treatment. At necropsy, foals were examined for lesions an...
Kent JE.The concentrations of haptoglobin, immunoglobin (Ig)G(T) and IgG were measured in the serum of four previously parasite-free pony yearlings following a single dose of 700 (Group H) or 200 (Group L) stage three Strongylus vulgaris larvae (L3) and following a reinfection with the same doses 34 weeks later. The results are compared with an uninfected control pony. The haptoglobin concentration increased during Weeks 1 to 6 and 14 to 17 after infection in the serum of the ponies receiving 200 L3, but in only one pony dosed with 700 L3 (during Weeks 1 to 16). The serum haptoglobin also increased du...
Eysker M, Wemmenhove R.The epidemiology and control of helminth infections in the horse were studied in four small grazing experiments between 1981 and 1984 at the University of Utrecht. At autopsy in November or December negligible Strongylus vulgaris burdens were found in the cranial mesenteric artery of four groups of ponies, which had been treated with an anthelmintic in July and subsequently transferred to a clean pasture. Considerable arterial S. vulgaris burdens were seen in three groups of ponies which were treated with an anthelmintic in July without a move to clean pasture, and in another group of ponies i...
Mfitilodze MW, Hutchinson GW.In a series of laboratory studies the optimum conditions for the development and survival of the free-living stages of strongyle parasites occurring in horses in tropical north Queensland were determined. No differences in behaviour were noted between the strongyle species. Development to the infective stage occurred only between 10 and 35 degrees C. The rate was affected by temperature, taking 15-24 days and 3 days, respectively, at the lowest and highest temperatures for the developing stages to reach the infective third stage. Yields of infective larvae were very low outside the range 20-33...
Herd RP.Seasonal rises in mean faecal egg output were observed in grazing ponies in spring (578 eggs per gram) and in summer (930 epg) on 30 April and 2 September, respectively, in untreated ponies. Pasture infectivity reached a peak of 18,486 third stage larvae (L3)/kg on 17 September, two weeks after peak egg counts, coincidental with abundant September rainfall (103.0 mm). Differentiation of infective larvae from pasture showed the cyathostomes (small strongyles) to be predominant, but Trichostrongylus axei assumed major importance from late August to October. The large strongyles were rarely detec...
Eysker M, Jansen J, Kooyman FN, Mirck MH, Wensing T.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...
Herd RP, Kent JE.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...
Bauer C, Bürger HJ.A paste formulation containing 14.3 per cent of oxibendazole and 44 per cent of trichlorfon was administered to 33 ponies and horses. The dose rate used was equivalent to 10 mg and 30 mg/kg bodyweight, of oxibendazole and trichlorfon respectively. After treatment 25 animals passed between one and 82 third stage larvae of Gasterophilus intestinalis in their faeces. Dosing with 0.2 mg ivermectin/kg bodyweight three weeks later resulted in six animals expelling between one and four bots. The efficacy of the oxibendazole-trichlorfon paste was on average 96.2 per cent. This drug combination given t...
Pauli B, Althaus S, Von Tscharner C.Migrating fourth-stage larvae of Strongylus vulgaris, a parasite of equines, damage the intima of the anterior mesenteric artery and its larger branches and induce thrombus formation on the injured sites. As the time of larval passage through each of these branches has been exactly determined in earlier experiments, the aim of the present studies is to contribute to a more complete understanding of repair mechanisms in the process of time after thrombotic vascular injuries. Methods: five foals were separated individually to specially cleaned stables and given anthelmintic treatment till the ag...
Kent JE, Blackmore DJ.The turbidimetric analysis of IgG(T) in the serum of horses is described. Reference values are provided for 'worm-free' ponies (2.6 +/- 0.7 g/litre), stabled Thoroughbreds two years old and over (4.1 +/- 1.3 g/litre), grazing Thoroughbred broodmares (7.1 +/- 2.4 g/litre) and regularly wormed adult and young ponies grazing pasture contaminated with intestinal parasite eggs and larvae.
Reinemeyer CR, Scholl PJ, Andrews FM, Rock DW.A 3 m, video gastroscope was used to screen 47 horses suspected of being naturally infected with equine bot larvae. 17 of 47 (36.2%) candidate horses harbored Gasterophilus nasalis larvae in the proximal duodenum and 46 of 47 (97.9%) had G. intestinalis larvae in the stomach. All horses infected with G. nasalis had concurrent infections with G. intestinalis. 14 horses with dual infections were allocated randomly to two treatment groups. Seven horses in Group 1 received 2% moxidectin oral gel once at a dosage of 0.4 mg/kg bodyweight (BW), and seven horses in Group 2 were untreated controls. 14 ...
Levine JF, Levy MG, Nicholson WL, Gager RB.Larval Dermacentor variabilis (Say) (n = 327) were fed on Balb/C mice inoculated with Ehrlichia risticii, the etiologic agent of equine monocytic ehrlichiosis (Potomac horse fever). All mice displayed clinical signs of E. risticii infection at the time of feeding. After molting, resulting nymphs (n = 74) were fed on susceptible mice. No clinical signs were observed, and the mice remained seronegative for 6 wk after feeding.
Wijesundera WS, Chandrasekharan NV, Karunanayake EH, Dharmasena SP.Two repetitive sequences (IpSdM and IpSdS) have been cloned and sequenced from the genome of Setaria digitata. When IpSdM (214 bp) and IpSdS (201 bp) were aligned, a high degree of homology (85%) was observed, indicating that they belong to the same family of repeats. IpSdM represents a complete repeating element while IpSdS consists of two partial repeating elements arranged in tandem. The elements are present in about 10 000 copies comprising 2.8% of the S. digitata genome. As a diagnostic probe IpSdM detects as little as 100 pg DNA of both S. digitata and S. labiato-papillosa. It can also d...
Shefstad DK.The lesions caused by larvae of Gasterophilus intestinalis in the cardiac region of the equine stomach were funnel-shaped ulcers surrounded by a rim of hyperplastic epithelial cells. Bacteria were commonly seen on the rim of epithelial cells, at the base of some ulcers, and within the cavities produced by the hooks of the larvae. Cellular debris and mucus were within the ulcer.
Ribbeck R, Heide H, Schicht W, Hiepe T.Observations were carried out from May 1977 to May 1980 on occurrence, fauna, and seasonal dynamics of Gasterophilus spp. in 2,539 horses for butchering from all districts of the German Democratic Republic and also in 79 horses after control against gasterophilosis. 99.98% of the 13,742 second and third instar larvae of horses for butchering were Gasterophilus intestinalis, only 0.02% Gasterophilus nasalis. Out of 7,765 larvae passed after control measures Gasterophilus intestinalis dominated with more than 96%. Only in four districts of the German Democratic Republic Gasterophilus nasalis was...
Lyons ET, Tolliver SC, Drudge JH, Swerczek TW, Crowe MW.Prevalence of natural infections of the lungworm, Dictyocaulus arnfieldi, was investigated in Kentucky in 5,437 live equids (horses, ponies, and asses) on 91 farms by examination of fecal samples over a 15-month-period from January 28, 1983 to April 19, 1984. For the 91 farms investigated, asses only were examined on 1 farm; for the other 90 farms, examinations were made of horses on all of them, of ponies on 4 farms, and of asses on 9 farms. Larvae of D arnfieldi were found in fecal samples of 112 (2%) of 5,379 horses on the 90 farms of which 38% had greater than or equal to 1 infected animal...
Dongus H, Beelitz P, Schöl H.The female reproductive system of Thelazia lacrymalis (Nematoda: Thelaziidae) was investigated by light and scanning electron microscopy (SEM) with regard to the developmental stages and the stage deposited by the gravid nematode. Female T. lacrymalis have a didelphic and opisthodelphic type of reproductive system with paired ovaries, oviducts and uteri and a single vagina and vulva. Round and spindle-shaped primary oocytes are documented within the ovaries and oviducts, respectively. The distal part of each uterus provides a fertilization chamber filled with spermatozoa, followed by a sphinct...
Merlin A, Ravinet N, Sévin C, Bernez-Romand M, Petry S, Delerue M, Briot L, Chauvin A, Tapprest J, Hébert L.Cyathostomins are considered as the most prevalent and pathogenic parasites of grazing horses. The development on pastures of the free-living stages of these gastrointestinal worms is particularly influenced by outdoor temperature. Understanding the bionomics of free-living stages is an important prerequisite to implement mathematical models designed to assess the parasitic risk for grazing equids. The aim of this study was to assess the effect of 3 constant temperatures under laboratory conditions (10 ± 1 °C, 23 ± 2 °C, 30 ± 2 °C) and one fluctuating temperature under outdoor c...
Kobluk CN, Smith DF.An intramural hematoma involving a 40-cm segment of the distal portion of the jejunum caused intestinal obstruction and colic in a mature mare. The involved intestine was resected, and an end-to-end anastomosis was performed. The mare recovered completely, but 4 years later had colic caused by incarceration and volvulus of the distal portion of the jejunum, involving fibrous abdominal adhesions. The cause of hematoma was not identified; however, rupture of an intramural vessel after migration of Strongylus vulgaris larvae was considered a possibility because of the histologic observation of an...
Slocombe JO, McCraw BM, Pennock P, Ducharme NG, Baird JD.Twenty pony foals (reared worm free), 6.5 to 10 weeks of age, were inoculated with Strongylus vulgaris and allocated to 5 groups, each with 4 foals. One week after inoculation, 1 group of 4 foals was given oxfendazole (OFZ) at a dosage rate of 10 mg/kg of body weight, another group was given 2 such treatments 48 hours apart, and a 3rd group was given a placebo. All treatments were administered by stomach tube. Three weeks later, foals were euthanatized and necropsied in a test for efficacy against early 4th-stage larvae. Oxfendazole was 80% and 94.9% effective against early 4th-stage S vulgari...
Kent JE.The concentrations of haptoglobin, immunoglobin (Ig)G(T) and IgG were measured in the serum of four previously parasite-free pony yearlings following a single dose of 700 (Group H) or 200 (Group L) stage three Strongylus vulgaris larvae (L3) and following a reinfection with the same doses 34 weeks later. The results are compared with an uninfected control pony. The haptoglobin concentration increased during Weeks 1 to 6 and 14 to 17 after infection in the serum of the ponies receiving 200 L3, but in only one pony dosed with 700 L3 (during Weeks 1 to 16). The serum haptoglobin also increased du...
van der Kolk JH, Sloet van Oldruitenborgh-Oosterbaan MM, Gruys E.A six-year-old pregnant Haflinger mare of 510 kilograms died from bilateral pleurisy following a hospitalisation period of ten days, during which she was treated with various antibiotics. At necropsy a bilateral fibrinopurulent pleurisy accompanied by an ulceration of the cardia of the stomach measuring once cm2 was found. In the wall of the oesophagus, close to the cardia, there was a fistula harbouring a 3rd stage Gasterophilus larva. The epithelial layer at this site was unimpaired and no gross connection between the fistula and the ulceration of the cardia was observed. The fistula was in ...
Guerrero J, Newcomb K, Seibert BP, Michael BF.Two controlled tests were conducted in equine foals and yearlings to determine the optimal oral dosage and the duration of activity of closantel for the prevention of Gasterophilus spp larval infections. Additional data were collected on the activity of closantel against Strongylus vulgaris larval infections. In experiment 1, 12 foals and 12 yearlings were equally allocated to 4 experimental groups, and were given oral treatments with closantel at dosages of 0 (nontreated controls), 2, 5, or 8 mg/kg of body weight every 2 months during bot season. The foals and yearlings were allowed to graze ...
Molento MB, Canever RJ.Cyathostomins are the most prevalent nematodes of horses, and multidrug resistance has been reported worldwide. There is a need to implement alternative drug monitoring analytical tests. The objective of this study was to determine the consistency (5 repetitions) of the larval migration on agar test (LMAT) using ivermectin, moxidectin, pyrantel or albendazole against cyathostomin infective-stage larvae in eight different concentrations. LMAT showed a strong coefficient of determination (R2 > 0.91), between the test repetitions (n=5). The average 50% effective concentration (EC50) for iverme...
Berry CR, Merritt AM, Burrows CF, Campbell M, Drudge JH.Five weanling ponies were subjected to an intensive 6-week deworming program after which 4 Ag-AgCl bipolar electrodes were implanted surgically on the distal ileum. For 3 hours each day for 5 consecutive days, ileal myoelectrical activity was recorded from fed ponies under 3 sequential conditions: preinoculation, after oral administration of 1,000 killed Strongylus vulgaris infective larvae (3 ponies), and after oral administration of 1,000 live S vulgaris infective larvae. Recordings were analyzed for slow wave frequency, percentage duration of phases I, II, and III of the migrating myoelectr...
English AW.The seasonal changes in longevity on herbage of the infective larvae of strongylid nematodes of the horse were studied. During the summer months, 1% of the larvae survived on herbage for 2-3 weeks, with 0.2% still viable for a further 2-3 weeks. Equivalent survival periods in winter were 7-11 weeks and over 11 weeks respectively. During spring and autumn, larvae survived for periods varying from 3-8 weeks. On Rhodes grass (Chloris gayana) growing vigorously in the summer of 1976, the majority of larvae remained in the lowest layers of the pasture, within 10 cm of the soil surface. Very few rea...
Pawlas-Opiela M, Jawor P, Galli J, Zak-Bochenek A, Gorczykowski M, Galli J, Sołtysiak Z, Stefaniak T.Infection with Gasterophilus intestinalis (botfly) larvae often occurs in horses. The aim of the study was to isolate the larvae of G. intestinalis and evaluate the serum and salivary humoral immune response using self-developed ELISA in G. intestinalis infected horses. Blood serum or saliva samples were taken from 125 infected horses and 54 uninfected slaughtered horses. The antigens from G. intestinalis larvae were used for development of ELISA in order to evaluate the intensity of G. intestinalis IgG, IgM, and IgA antibody reactivity in the serum or saliva of naturally infected horses and h...
DiPietro JA, Lock TF, Todd KS, Sanecki RK.A controlled test was carried out on 15 pony foals inoculated with 1,500 +/- 108.8 infective Parascaris equorum eggs. The foals were assigned to 3 treatment groups. Treatments given on postinoculation day 11 included 0.2 mg of ivermectin/kg of body weight, formulated as paste (n = 5), or liquid (n = 5), or no treatment (controls; n = 5). The foals were euthanatized on postinoculation day 25, and examined for larvae in the small intestine, lungs, and liver. Larvae were not found in foals treated with ivermectin liquid or paste, whereas significantly (P less than 0.05) higher mean numbers (960.9...
Hubert JD, Seahorn TL, Klei TR, Hosgood G, Horohov DW, Moore RM.The objective of this study was to determine the effect of infection with Strongylus vulgaris on serum cytokines and plasma nitric oxide (NO) concentrations in helminth-naive ponies. Group 1 (n = 21) was given 500 S. vulgaris L3 larvae and group 2 (n = 7) received a saline control. Ponies were monitored daily for clinical signs, and blood was collected for complete blood cell counts and serum cytokines (TNF, IL-1, IL-6) quantification. Group 1 ponies were depressed, anorexic, and febrile for variable periods of time. Plasma NO was increased on day 21 in group 1 and on days 9 and 21 in group 2....
Eysker M, Jansen J, Wemmenhove R, Mirck MH.Gastro-intestinal helminth infections of a group of three yearling mare Shetland ponies, which were set-stocked on a small pasture from February until September, were compared with those of a similar group of ponies, which grazed a similar pasture from February to July and subsequently was removed to a pasture which had been grazed by sheep from April to July. In addition both groups were treated with cambendazole when the latter group was removed to the sheep pasture. Pasture larval counts and worm counts demonstrated that the group grazed after the sheep acquired considerably smaller burdens...
Todhunter KH, Cawdell-Smith AJ, Bryden WL, Perkins NR, Begg AP.Pregnant mares were experimentally exposed to whole caterpillar or exoskeleton of the Processionary caterpillar (Ochrogaster lunifer) via gavage. Tissues were collected from resulting abortions and near or full-term pregnancies consisting of 13 aborted fetuses, 3 fetuses from treated euthanized mares, membranes of 5 foals, and organs from 3 foals. Three control membranes and 1 control fetus and membranes were examined. Caterpillar setal fragments were present in the allantochorion of the 3 fetuses from the euthanized mares and 11 of 12 aborted fetuses (92%) embedded in the chorion (villi or st...
Scare Kenealy JA, Steuer AE.All horses are susceptible to the equine gastrointestinal parasite, Strongylus vulgaris, which is known to cause significant disease and death. The parasite undergoes development from the egg through the first (L1), second (L2) and third (L3) larval stages outside the horse. The L3 is the infective stage. The universally available technique for detection of S. vulgaris larvae is the larval culture method. This requires a 10-14 day culture period to induce development from egg to L3, followed by Baermannization and identification of the L3s to genus and/or species. It is unknown if the culture ...
Buzzell GR, Tariq S, Traversa D, Schuster R.The infective larva of the spirurid nematode Habronema muscae, a parasite of houseflies, was measured and specimens fixed in Karnovsky's fluid were examined by scanning electron microscopy. The oral opening contains six teeth and is surrounded by large bilobed dorsal and ventral lips and smaller lateral lips. A pair of amphids lie behind the lateral lips. There are two rows of four cephalic papillae. The body is deeply ridged, both transversely and longitudinally. The caudal end of the worm is studded by small papillae. The position of the anal opening is somewhat ambiguous. These larval morph...
Milillo P, Traversa D, Elia G, Otranto D.Larvae of Rhinoestrus spp. (Diptera, Oestridae) infect nasal and sinus cavities of horses, causing a nasal myiasis characterized by severe respiratory distress. Presently, the diagnosis of horse nasal botfly relies on the observation of clinical signs, on the post mortem retrieval of larvae or on molecular assays performed using pharyngeal swabs. The present study was carried out to characterize larval somatic proteins and salivary glands of Rhinoestrus spp. in a preliminary assessment towards the immunodiagnosis of equine rhinoestrosis. Out of the 212 necropsied horses 13 were positive for th...
Scháňková Š, Maršálek M, Wagnerová P, Langrová I, Starostová L, Stupka R, Navrátil J, Brožová A, Truněčková J, Kudrnáčová M....Nine ponies, aged 12 months at the time of infection, were randomly allocated to one of three groups. Each pony was infected with 30,000 infective cyathostome larvae stored 4 weeks under the natural environmental conditions of the Czech Republic. Horses of Group A were infected with larvae conditioned from August 16 to September 12 (the first phase of the experiment). Horses of Group B were inoculated with larvae conditioned from October 10 to November 4 (the second phase of the experiment). In the third phase, horses from Group C received larvae stored under natural conditions (from 8.11 to 1...
Dauparaitė E, Kupčinskas T, Varady M, Petkevičius S.Control of strongyle infections presents a global challenge for horse practitioners due to the development of anthelmintic resistance (AR), however comprehensive information on AR in Lithuania is still lacking. The aim of this study was to assess the current situation of fenbendazole (FBZ) AR in horses at stable level in Lithuania. Results: Faecal samples from 121 horses from six stables were examined using the Mini-FLOTAC method. Of these, 89 horses met the inclusion criteria that included strongyle faecal egg counts (FEC) exceeding 200 eggs per gram (EPG). Faecal egg count reduction tests (F...
Andersen S, Fogh J.During a 5 months' period from January to May 1981 faecal samples of 176 donkeys from 59 herds all over the country were examined at the Institute of internal medicine, The Royal Veterinary and Agricultural University, Copenhagen. In addition, the investigation also included 106 horses from 30 of the donkey herds and 34 horses hospitalized with symptoms of dyspnoea and chronic coughing. In all, 87.5% of the donkeys were shown to excrete D. arnfieldi larvae, often in very high numbers, and the larval excretion was the only symptom of lungworm infection. There was no significant correlation betw...
Zhang K, Ju Z, Zhang Y, Wang C, Mubalake S, Hu D, Zhang D, Li K, Chu H.The genus Gasterophilus (Diptera, Gastrophilidae) is an obligate parasite of the equine family that causes widespread myiasis in desert steppe. Based on four common naturally excreted Gasterophilus larvae collected systematically in the Karamaili Ungulate Nature Reserve from March to September 2021, this paper studies the population dynamics and ontogenetic laws of horse flies, and discuss the coexistence pattern and population dynamics prediction of horse flies. The results showed that the Gasterophilus larvae had obvious concentrated development period, and the time of population peaks was d...
