Occurrence of second and third instars of Gasterophilus intestinalis and Gasterophilus nasalis in stomachs of horses in Kentucky.

The occurrence of 2nd and 3rd instars of Gasterophilus intestinalis and Gasterophilus nasalis was determined in 476 horses during the 22-year period from 1951 to 1973. Overall, G intestinalis infected 98.7% of the horses and averaged 168/horse; whereas G nasalis infected 80.7% of the horses and averaged 52/horse. Aggregate average total numbers for G intestinalis ranged from a low of 50 in September to a high of 229 in March, and for G nasalis, from a low of 14 in September to a high of 82 in February. Horses were infected by 2nd or 3rd instars of both species on a year-round basis. Differentiation between the instars provided insight into the dynamics of the infections. For G intestinalis, the data indicated (1) 2nd instars from the previous year's generation of flies continue to arrive in the stomach until April; (2) arrival of the current year's crop of 2nd instars starts in July; and (3) 3rd instars from the previous year's generation of flies are not voided in appreciable numbers until August, when numbers of the current year's crop of 3rd instars appear in the stomach. For G nasalis, the data indicated (1) arrival in the stomach of the current year's generation of 2nd instars starts in July and terminates in January and (2) 3rd instars from the previous year's generation of flies are voided over a period beginning in March and extending into August, when the current year's crop of 3rd instars begin to appear. Acquisition of infections of horses with G intestinalis is nearly a year-round process, except for April, because of the persistence of viable larvae in eggs for a prolonged period after development and fly activity has ceased in the fall. In contrast, infection with G nasalis is interrupted between December and May, because eggs hatch naturally after a short period of development, and fly activity ceases in the fall.     

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.     

The prevalence of Gasterophilus intestinalis and G nasalis in horses in Ireland.

During the months October-May inclusive 90-8% of horses slaughtered at an abattoir near Dublin and 66-9% of those at an abattoir near Belfast were infected with Gasterophilus intestinalis; 28-6% of horses at the former abattoir harboured G nasalis while none of the horses examined at the latter abattoir was found to be infected with this species.     

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.     

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.     

First-time endoscopic detection of larvae of Gasterophilus spp. in the oral cavity in 14 warmblood horses

Intraoral endoscopy is used as a standard diagnostic technique at the reporting clinics in horses presented with stomatological problems. Endoscopy of the oral cavity was performed using a chip camera, camera control unit, xenon cold light source and a rigid endoscope. In a three year period (2002 to 2004), second instars of Gasterophilus spp. were diagnosed in 14 warmblood horses 2 to 17 years of age. All horses were presented with masticatory problems or problems accepting the bit. In one horse oesophageal obstruction occurred in the course of larval migration. Oral endoscopy can not only be used for the diagnosis of dental disease but also for detection of instars of Gasterophilus spp. in the interdental spaces of maxillary cheek teeth.     

Efficacy of an oxibendazole-trichlorfon paste formulation against third stage larvae of Gasterophilus intestinalis and its safety in horses

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 to 52 ponies and horses at the indicated dose rate and to six ponies at twice that dose was tolerated without side effects except transient softening of the faeces in several animals and mild symptoms of colic in two horses.     

A non-lethal method for assessment of efficacy of antiparasitics against parasites in horses such as Anoplocephala perfoliata and Gasterophilus intestinalis

Sourcing of horses naturally infected with parasites such as Anoplocephala perfoliata and Gasterophilus intestinalis for antiparasitic efficacy slaughter studies is often difficult, expensive, and usually excessive numbers of animals must be slaughtered before significant data can be obtained. To overcome this problem a "Modified Critical Treatment Method" was developed. This method does not require the horses to be sacrificed, but relies on the collection and processing of all faecal material containing expelled parasites from test animals. Efficacy is assessed by comparing, in the same horses, the numbers of parasites expelled with the test compound with the total numbers removed with test and reference endectocides. This, for the most part, means that farms that were previously unavailable, e.g. studs, can now be used for the collection of efficacy data.     

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.     

The treatment of laminitis in horses

The structural and vascular anatomy of the healthy equine foot is compared with the pathologic changes in the foot of horses with acute and chronic laminitis. The structural and vascular abnormalities present in the foot of horses with laminitis are demonstrated in order to explain the abnormal manner in which their feet grow. The medical, surgical, dietary, and endocrine management of acute and chronic laminitis is discussed. Various forms of hoof trimming beneficial to the reestablishment of normal digital perfusion, normal hoof growth, and normal spatial orientation among the distal phalanx, hoof wall, and sole are described. Guidelines for the provision of frog support provided by adjustable heart-bar shoes are presented.     

Classification of the main macroscopic lesions produced by larvae of Gasterophilus spp. (Diptera:Gasterophilidae) in free-ranging horses in Umbria

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 differentiate the hemorrhagic impressions caused by migrating 1st and 2nd instar larvae of all the species in the absence of the specific parasite. It is also difficult to differentiate between the gastric lesions caused by Gasterophilus intestinalis and Gasterophilus pecorum. It has been found that an easy identification is possible even in the absence of parasites for gum lesions and for lesions on the soft palate produced respectively by Gasterophilus intestinalis and Gasterophilus pecorum, for duodenal lesions caused by Gasterophilus nasalis, for rectal lesions caused by Gasterophilus inermis and for duodenal and rectal lesions produced by Gasterophilus haemorrhoidalis.     

Evaluation of success rate of laparoscopic castration without orchidectomy in 32 mature horses

The surgical success of laparoscopic castration without orchidectomy results from avascular necrosis of the testes. However, failures and subsequent production of testosterone and stallion‐like behaviour have been previously identified. Laparoscopic castration without removal of the testes was performed in 32 horses with 2 normal descended scrotal testes between July 2006 and October 2012. The objectives of our study were to evaluate the success rate of laparoscopic castration without orchidectomy on descended testes in our population and assess complications and recovery time. Endocrine tests were performed after surgery and owners also asked to report on their horse's behaviour and ability to resume exercise. Castration was deemed successful if endocrine test results were in accordance with gelding values. Failed horses were castrated using a conventional technique and histology performed when possible. Basal testosterone levels decreased below 3 nmol/l after surgery in 30/32 cases. However, in 2 horses, stallion behaviour persisted and histological evaluation after inguinal castration showed residual viable tissue. Two horses maintained high testosterone levels after surgery associated with stallion‐like behaviour. Based on these results, 12.5% of horses (4/32 horses) failed to be considered a gelding based on either endocrine tests and/or histology. All horses, with one exception, were able to resume exercise less than a week after the procedure. Laparoscopic castration without orchidectomy appears to be a safe procedure. When assessing the success of laparoscopic castration, our total failure rate was 12.5% (4/32 horses) which is significantly higher than previously reported.