Parasites of the stomach in donkeys of the highveld of Zimbabwe

Summary

Fourteen donkeys from a communal area of the Zimbabwean highveld were examined for stomach parasites during July and November of 1986 and January and April of 1987. All 14 animals were infected. Habronema muscae occurred in 12, Draschia megastoma in 11, H. majus in 9, Trichostrongylus axei in 9, Gasterophilus intestinalis in 14 and G. nasalis in 1 donkey. The lowest level of infection was in January for the helminthes and in April for Gasterophilus larvae. The peak burdens of parasites were in July for Habronema spp. and in November for D. megastoma and Gasterophilus larvae. Infections with spirurid worms and Gasterophilus develop mainly from the middle of the rainy season to the beginning of the dry season (Januari to May/June). G. intestinalis seems to have an annual cycle.     

Observations on the epizootiology of gasterophilus intestinalis and G. nasalis in horses in morocco

Ninety four horses from the Settat region of Morocco were examined for Gasterophilus intestinalis and G. nasalis larvae. All the horses were infected with G. intestinalis and 89 with G. nasalis; the mean larval burdens were 219 and 153, respectively. Third instar larvae of both species were present throughout the year. Second instar larvae of G. intestinalis were absent in April and May and those of G. nasalis in April only. More than 50% of horses had total burdens of more than 300 larvae and 4% harboured more than 1000 larvae. Young horses had higher infections than older animals. The period of adult activity of G. intestinalis is from April to October, with a maximum in summer. Second instar larvae of G. intestinalis are present in peak numbers from July to January and the third instars are voided in the faeces mainly in spring and summer.Infection with G. nasalis starts sooner than that with G. intestinalis. Second instar larvae are present from May to December in peak numbers. During January to March, many second instars of G. nasalis were found trapped in nodules.     

Analysis on the relationship between winter precipitation and the annual variation of horse stomach fly community in arid desert steppe,Northwest China (2007–2019)

Gasterophilus spp. have been found to be widespread in reintroduced Przewalski's horses in the Kalamaili Nature Reserve (Northwest China). However, data on the annual variation in Gasterophilus infections are lacking. To analyze the epidemiological features and determine the cause of the annual variation in Gasterophilus infections, we treated 110 Przewalski's horses with ivermectin and collected Gasterophilus larvae from fecal samples each winter from 2007 to 2019. All 110 Przewalski's horses studied were found to be infected by Gasterophilus spp., and a total of 141 379 larvae were collected. Six species of Gasterophilus were identified with the following prevalence: G. pecorum (100%), G. nasalis (96.36%), G. nigricornis (94.55%), G. haemorrhoidalis (56.36%), G. intestinalis (59.09%), and G. inermis (3.64%). The mean infection intensity of Gasterophilus spp. larvae in Przewalski's horses was 1285 ± 653. G. pecorum (92.96% ± 6.71%) was the most abundant species. The intensity of Gasterophilus spp. (r = –0.561, P < 0.046) was significantly correlated with winter precipitation. Our findings confirmed that, in the Kalamaili Nature Reserve, gasterophilosis is a severe parasitic disease in Przewalski's horses. Winter precipitation at the beginning of the year can indirectly affect the intensity and composition of Gasterophilus spp. in Przewalski's horses at the end of the year. Therefore, the water-related ecological regulation should be carried out to help reduce the parasite infection of Przewalski's horses.     

Control of helminth parasites in juvenile horses

Parasite control in juvenile horses remains a substantial challenge for veterinary practitioners and their clients. This age group is at risk for various types of parasitic disease because their worm burdens tend to be larger and more diverse than in mature horses. This contrast is largely attributable to marked differences in relative levels of acquired immunity. Frequent, perennial anthelmintic treatment is not a sustainable approach for parasite control in this age group, but the simple, surveillance‐based parasite control strategies recommended for mature horses are not appropriate for juveniles either. Maneuvering through the early years of a horse's life requires up‐to‐date knowledge about biology and epidemiology of the parasite species in play as well as local evidence regarding the anthelmintic resistance status of each herd. This article provides an overview of the most important helminth parasites to target in a control programme for juvenile horses, and highlights how the target species change as horses age. Young foals (<2 months) are exposed to Strongyloides westeri and Parascaris spp., whereas the primary target parasite in foals between age 2 months and weaning is Parascaris spp. Beyond weaning, the focus shifts away from ascarids, and the targets instead are strongyles and tapeworms. Gasterophilus spp. and Oxyuris equi are also discussed.     

Gasterophilosis: a major cause of rectal prolapse in working donkeys in Ethiopia

A retrospective study was conducted to investigate the cause of rectal prolapse in working donkeys in Ethiopia. Analysis of data on rectal prolapse cases obtained from the Donkey Health and Welfare Project clinic at the School of Veterinary Medicine, Addis Ababa University, from 1995 to 2004 revealed that 83.6% (n = 177) of the cases were associated with Gasterophilus nasalis. The rest 10.7% and 5.7% were associated with work-related (overloading) cause and diarrhoea, respectively. The mean and median numbers of G. nasalis recovered from the rectum of infected donkeys were 66 and 64, respectively, with a range of 2–195. Over 100 G. nasalis larvae were recovered from the rectum of 22% of the donkeys. Circular demarcated ulcer-like and deep circumferential pits or ring-like mucosal lesions were found at the larval attachment sites. G. nasalis infection and the associated rectal prolapse were observed year round. However, the intensity of rectal larval infection and incidence of rectal prolapse were significantly higher during the rainy season (P < 0.01). Age and sex of the donkeys had no significant effect on the intensity of rectal larval infection and incidence of rectal prolapse (P > 0.05).     

The anthelmintic efficacy of cambendazole in horses

The anthelmintic activity of cambendazole 31% paste was evaluated in a controlled trial against naturally acquired gastro-intestinal parasites of the horse. Four groups of five adult horses were treated at dose rates of 0, 15, 20 and 25 mg/kg. The three dose levels of cambendazole tested were efficacious against the large strongyles Strongylus edentatus and S. vulgaris, the stomach worm Trichostrongylus axei, the pinworms Oxyuris equi and Probstmayria vivipara and all the species of small strongyles present. No efficacy was demonstrated against the tapeworm Anoplocephala perfoliata or the horse bots Gasterophilus intestinalis or G. nasalis     

Prevalence of some internal parasites found (1971–1989) in horses born on a farm in central kentucky

Prevalence of several species of naturally acquired internal parasites are reported from a total of 97 horses (mostly mixed lighthorse type) from a farm in central Kentucky. The horses were born and raised in 2 adjacent fields (No. 4 - n=44 and No. 10 − n=53) over a 19-year-period (1971–1989). They were 100 to 537 days old (av. 281) when examined; an exception was a 819-day-old not calculated in the average age. Some of the horses were not examined for all of the parasites. These horses (never previously treated) were all used in critical or controlled tests for evaluation of antiparasitic activity of drugs. Dams and other horses in the fields rarely were given an antiparasitic compound.Prevalence and aggregate mean numbers of parasites in infected animals (in parentheses) for the 97 horses are: bots — Gasterophilus intestinalis 2nd instar, 65%(45), 3rd instar, 96%(210), Gasterophilus nasalis 2nd instar, 18%(10), 3rd instar, 63%(10); stomach worms — Habronema muscae, 73%(78), Draschia megastoma, 42%(53); ascarids — Parascaris equorum mature, 75%(45), immature 36%(29), tapeworms — Anoplocephala perfoliata, 33%(7); large strongyles — Strongylus vulgaris, 95%(80) (data on horses ≥180 days old), Strongylus edentatus, 94%(34) (data on horses ≥330 days old); pinworms — Oxyuris equi, 43%(87); eyeworms — Thelazia lacrymalis, 61%(6); S. vulgaris in cranial mesenteric artery, 92%(53); and S. edentatus in ventral abdominal wall, 98% (56). Differentiation was made for the data by season and by age of the horses when they were examined. Information from this research reflects the transmission patterns and prevalence of these parasites under natural conditions.     

Evidence‐based considerations for control of Parascaris spp. infections in horses

Parascaris spp. infection is virtually ubiquitous in young foals and worm burdens can achieve high numbers. The most important disease manifestation is impaction of the small intestine, which occurs in a small proportion of infected foals but is associated with a guarded prognosis for survival. Control of Parascaris spp. is complicated by emerging resistance to currently available anthelmintic drug classes. Resistance to macrocyclic lactones has been reported worldwide and a few studies have also documented signs of resistance to pyrantel salts and benzimidazoles. Foals generally develop immunity to Parascaris spp. parasites around age 6 months, but a proportion of weanlings and yearlings can harbour smaller burdens at age 8–10 months. Older horses have occasionally been reported with substantial ascarid burdens as well. Qualitative detection of ascarid eggs has good diagnostic value whereas an actual egg count does not correlate well with the size of the worm burden. A recent investigation documented the applicability of a transabdominal ultrasound technique for semiquantitatively monitoring ascarid burdens in foals. Control of ascarids is complicated by the limited drug classes available for treating this parasite, and by the fact that foals are often concurrently infected with strongyles. In many cases, none of the 3 available anthelmintic classes are simultaneously effective against both parasite groups, so close monitoring is required to select the most appropriate anthelmintic in each case.     

Gasterophilus spp. infections in horses from northern and central Kazakhstan

A cross-sectional survey was performed to obtain current data on the gastrointestinal myiasis of horses in the provinces of Kostanay, Akmola and Karagandy, northern and central Kazakhstan. The stomach, small intestine and rectum of 148 slaughter horses were examined for Gasterophilus spp. larvae during a 26-month study period. All horses were infected with 2nd and 3rd stage larvae (mean intensity: 803 ± 350), and 22% of them harboured >1000 Gasterophilus spp. larvae each. Four species were identified: G. intestinalis (prevalence: 100%; mean intensity: 361 ± 240 larvae), G. haemorrhoidalis (100%; 353 ± 191), G. nasalis (100%; 73 ± 36) and G. pecorum (91.2%; 18 ± 10). Horses aged < 2 years were higher infected with Gasterophilus larvae than 2–4 years old animals. Both the prevalence and extremely high intensity of Gasterophilus infections of horses in these Kazakh regions suggest respective control measurements to improve the health and performance of the animals and to increase the economic income of horse owners.     

Seasonal Variations in the Abundance of Gasterophilus spp. Larvae in Donkeys in Northern Jordan

One hundred and five donkeys were examined over a 12-month period for the presence of Gasterophilus spp. larvae in their stomachs. G. intestinalis and G. nasalis were found, but there was a distinct seasonal variation in their abundance. The numbers of second-stage larvae (L₂) peaked during the early winter and early summer, but they were absent or at low levels during the early spring and early autumn. This suggests that there are two periods of adult fly activity (late autumn and late spring) for both G. nasalis and G. intestinalis. Third-stage larvae (L₃) were found throughout the year, but the lowest levels were seen in the late summer and autumn. The parasites also had an aggregated distribution, which may be due to host selection by the fly. The numbers of larvae did not vary significantly with age, which may be due to a lack of acquired protective immunity or to tolerance after repeated exposure.     

Parasites of the stomach in donkeys of the highveld of Zimbabwe

Fourteen donkeys from a communal area of the Zimbabwean highveld were examined for stomach parasites during July and November of 1986 and January and April of 1987. All 14 animals were infected. Habronema muscae occurred in 12, Draschia megastoma in 11, H. majus in 9, Trichostrongylus axei in 9, Gasterophilus intestinalis in 14 and G. nasalis in 1 donkey. The lowest level of infection was in January for the helminths and in April for Gasterophilus larvae. The peak burdens of parasites were in July for Habronema spp. and in November for D. megastoma and Gasterophilus larvae. Infections with spirurid worms and Gasterophilus develop mainly from the middle of the rainy season to the beginning of the dry season (January to May/June). G. intestinalis seems to have an annual cycle.     

Seasonal occurrence and distribution of Gasterophilus intestinalis and Gasterophilus nasalis in the stomachs of equids in Texas

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 in the fall. Higher percentages of early (2nd instar plus young 3rd instar) larvae of G intestinalis were observed in the fall in equids from both sources. The late (more fully developed older 3rd instar) G intestinalis larvae outnumbered the early larvae in the winter, spring, and summer. Seasonal variation in numbers and development status of the larvae was consistent with the largest period of adult bot fly activity occurring during the fall. The 2 species of bots had different predilection sites of attachment. Gasterophilus intestinalis larvae concentrated in the nonglandular portions of the stomach near the margo plicatus on the cranial (parietal) surface of the stomach and in the most dorsal extent of the saccus cecus. Gasterophilus nasalis larvae attached almost exclusively in the first ampulla of the duodenum. Predilection sites for both Gasterophilus spp occurred in dorsally positioned areas in the alimentary tract favoring increased availability of oxygen.     

Occurrence of second and third instars of Gastrophilus intestinalis and Gastrophilus nasalis in horses in the mid-atlantic united states

Seventy-four ponies and horses were necropsied over a 4-year period (April 1973–April 1977). Prevalence data on second and third instar larvae of Gastrophilus intestinalis and G. nasalis were collected. Second instar G. intestinalis were found from late July through March of the following year. Third instar G. intestinalis were found throughout the year with minimum numbers in August, September and October. Second instar G. nasalis were recovered from two animals in February and November respectively. Third instar G. nasalis occurred too infrequently to provide sufficient data for analysis except to note they appeared to be present all year. Four animals were not infected with either species.     

Incidence and monthly prevalence of Gasterophilus spp. larvae (Diptera: Gasterophilidae) in the stomach of donkeys (Equus asinus) in Egypt

The stomachs of 118 donkeys were examined at postmortem during the period from March 1982 to February 1983 for Gasterophilus spp. larvae. G. intestinalis larvae clustered in groups near the boundary of the glandular and non-glandular epithelium of the stomach and infested 98.3% of the donkeys with highest numbers in July and lowest numbers in October. G. nasalis larvae were mainly attached near the pylorus and first part of the duodenum and infested 87.3% of donkeys with highest incidence in December and lowest in October. The ratio of the second and third instars of G. intestinalis to G. nasalis ranged from 71% to 29%. The percentage of donkeys infested with 1-100, 101-200 and 201-300 larvae was 72.0, 18.6 and 4.3% for G. intestinalis and 76.3, 8.5 and 0.8% for G. nasalis.     

Epidemiological observations on Gasterophilus intestinalis and G. nasalis in donkeys from Morocco.

During a 24 month period, 198 donkeys were examined for Gasterophilus intestinalis and Gasterophilus nasalis larvae. Gasterophilus intestinalis was found in 97.5% and G. nasalis in 95.5% of donkeys. The third instars (L3) of both species occurred during all months of the year and so did the second instars (L2), except in April (G. nasalis) and May (G. intestinalis). Over 75% of the animals had up to 200 larvae and 1.5% had over 600 larvae. The maximum number of both L2 and L3 larvae found in any animal was 418 G. intestinalis, 433 G. nasalis and 715 of both species combined. The seasonal variation in the numbers and development status of larvae indicated that the period of greatest activity of adult flies of G. intestinalis was from August/September to November, and that of G. nasalis from May to September. Consequently, the L2 larvae in the stomachs were in peak numbers between November and January for G. intestinalis and between July and September for G. nasalis. The L3 larvae of G. intestinalis had peak numbers between December and July, and those of G. nasalis between October and March. During January-March, most of the L2 larvae of G. nasalis were trapped in polypous nodules near the pyloric end of the stomach. It is concluded that the high-risk period for infection is during late spring and autumn, leading to the heavy larval burden of Gasterophilus in the stomach of donkeys during winter.     

Prevalence study in horses infected by Gasterophilus sp. in an eastern region of Poland

A survey to determine current prevalence of Gasterophilus spp. (bot flies) in equids (n = 400) at necropsy in slaughtered horses was conducted at the abattoir in Rawicz. The evaluation was performed according to sex, age, larval stages, severity of infestation and localization, respectively. Only Gasterophilus intestinalis and Gasterophilus nasalis were detected. The prevalence determined in the eastern part of Poland was of 47%. The high prevalence of this parasite infection in the Polish horse population confirms that Gasterophilosis spp. has to be taken into serious consideration and prophylactic measures might be indicated.     

Efficacy of moxidectin equine oral gel against endoscopically-confirmed Gasterophilus nasalis and Gasterophilus intestinalis (Diptera: Oestridae) infections in horses

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 days after treatment, all horses were necropsied and the stomach and proximal duodenum harvested from each. Bot larvae were recovered, identified to species and instar, and counted. At the label dosage, moxidectin oral gel was 100 and 97.6% effective (P < 0.05) against third-instar G. nasalis and G. intestinalis, respectively. In addition to demonstrating the boticidal efficacy of moxidectin, this trial illustrated that gastroscopy/duodenoscopy is a feasible method for confirming infections with different species of bot larvae in the horse.     

Equine gastric ulcer syndrome in adult donkeys: Investigation on prevalence,anatomical distribution,and severity

The study was performed on 39 live donkeys that underwent gastroscopic examination. The lesions were recorded in accordance with the European College of Equine Internal Medicine Consensus Statement guidelines. The presence of Gasterophilus sp. larvae was also recorded. Larvae were collected and identified to species level. Fisher's exact test was used to compare different prevalence values for sex, age, and anatomical distribution of lesions. Gastric lesions were present in 20/39 (51.3% [35.6–67%]) donkeys; 19/39 (48.7% [95% confidence interval = 33–64.4%]) were affected only by equine squamous gastric disease (ESGD), while 1/39 (2.6% [0–7.5%]) showed both ESGD and equine glandular gastric disease (EGGD), thus 95% of positive donkeys showed lesions located in the nonglandular mucosa. The ESGD grade was 0/4 (48.7% [33–64.4%]) in 19/39, 1/4 (12.8% [2.3–23.3%]) in 5/39, 2/4 (25.6% [11.9–39.5%]) in 10/39, 3/4 in 4/39 (10.3% [0.7–19.8%]) and 4/4 in 1/39 (2.6% [0–7.5%]) donkeys, respectively. The EGGD lesion was a mild depression in the ventral glandular fundus. ESGD was primary in all the donkeys included and lesions were located around the cardia and along the lesser curvature. Gasterophilus sp. larvae were present in all animals and were identified as third‐stage larvae of Gasterophilus intestinalis. No animals showed clinical signs of equine gastric ulcer syndrome (EGUS). No significant differences relating to sex, age or breed were found in the prevalence of EGUS in this study, while the proportion of donkeys affected by ESGD was statistically higher than those affected by EGGD. To the best of our knowledge, this is the first report on the gastroscopic evaluation of EGUS in live donkeys. Our results show a higher prevalence of EGUS in live donkeys than values previously reported by other authors in donkeys that were dead or had been subjected to euthanasia. The detection of third‐stage G. intestinalis larvae was not unexpected since these can be found in the stomach of equids throughout the year, and G. intestinalis has been reported as the most common Gasterophilus sp. in Italy.     

Species composition of Gasterophilus spp. (Diptera, Oestridae) causing equine gastric myiasis in southern Italy: parasite biodiversity and risks for extinction

Horse gastrointestinal myiasis caused by larvae of Gasterophilus spp. (Diptera, Oestridae) flies has a worldwide distribution and, where present, it is primarily caused by larvae of Gasterophilus intestinalis and Gasterophilus nasalis. Other species, i.e., Gasterophilus inermis, Gasterophilus pecorum and Gasterophilus haemorrhoidalis, present in different or in the same regions of the gastrointestinal tract, were only occasionally reported in very limited areas of eastern European Countries and in central Italy. With the aim to contribute data on the species composition of Gasterophilus and on the seasonal variation of the infection pattern in southern Italy, 152 native horses were necropsied from January to December 2003 and Gasterophilus larvae were collected from the stomach, the small intestine and the rectum of each of them. On the whole, 125 (82.2%) horses were infected by larvae of Gasterophilus spp. and 214 second stage larvae (L2) and 13,342 third stage larvae (L3) collected. Five species of Gasterophilus were identified with the following prevalence: G. intestinalis=95.2%, G. nasalis=44.8%, G. inermis=15.2%, G. pecorum=2.6% and G. haemorrhoidalis=0.8%. L3 were retrieved throughout the observation period with the highest mean burdens from January to August 2003 while the lowest mean was registered from September to November 2003. L2 were collected in February-March 2003 and from September to December 2003. The majority of the animals (n=66, 43.4%) were infected with a single Gasterophilus species, however, 45 animals (29.6%) harboured 2 species, 12 animals (7.9%) 3 species and 2 animals (1.3%) 4 species. The trend of abundance in the L3 of G. intestinalis and G. nasalis, the most represented species, was highly concordant (r=0.5, p<0.001). A retrospective comparison of our results and of other data from four seasons of observation (1983-1986) in central Italy showed that the number of G. inermis, G. pecorum and G. haemorrhoidalis have been decreasing relative to G. intestinalis and G. nasalis which may suggest tendency toward the extinction of the three former species of Gasterophilus.     

Une étude expérimentale sur la variation du taux d'anticorps sériques suivant le cycle évolutif des oestres du cheval

The changes of antibody titers in the sera of colts infested naturally or artificially with Gasterophilus have been determined in relation to the life cycle of this arthropod using passive hemagglutination, complement fixation, double diffusion techniques and saline extracts of antigens from the third larval stages of Gasterophilus intestinalis and G. nasalis.

In the sera of the infected animals the hemagglutinating antibodies were present at low titers at the third week post-infestation by using somatic extract of G. intestinalis and at the seventh week in case of G. nasalis. At eight weeks post-infestation the antibody titers reached their maximum 1:8192 (G. intestinalis) and 1:4096 (G. nasalis), then dropped at 12 weeks post-infestation.

The complement fixing antibodies were present occasionally between the seventh and 11th weeks after infestation. Precipitating antibodies were absent in all sera.