Population genetic analysis of the heritability of gutteral pouch tympany in Arabian purebred foals

The objective of the present study was to analyse the importance of the influences of the sex, inbreeding coefficient and the additive genetic contribution to the occurrence of guttural pouch tympany in Arabian foals. Horses affected by guttural pouch tympany were ascertained in the Clinic for Horses, School of Veterinary Medicine Hannover. The data comprised 27 Arabian purebred foals with guttural pouch tympany. Of these 27 animals 22 were patients of the Clinic for Horses between 1994 and 2001 and 5 Arabian foals were sampled on the studs. Information on the pedigrees of these patients allowed us to sort in the affected foals into four families with a total of 276 animals. Female foals were more often affected by guttural pouch tympany. The difference was 11.9% in favour of female foals. The size of the inbreeding coefficient was not important for the occurrence of guttural pouch tympany. The heritability estimate for the frequency of guttural pouch tympany using a threshold model was 0.49 +/- 0.28. This is the first report that could show a genetic component responsible for guttural pouch tympany in foals.     

Gutteral pouch tympany in German warmblood foals: influence of sex,inbreeding and blood proportions of founding breeds as well as estimation of heritability

The objective of the present study was to analyse the importance of the influences of sex, inbreeding coefficient, proportion of genes of the original breeds and the additive genetic contribution to the occurrence of guttural pouch tympany in foals belonging to German Warmblood breeds. Foals affected by guttural pouch tympany were ascertained in the Clinic of Horses, School of Veterinary Medicine Hannover. This data set comprised 22 German Warmblood foals with guttural pouch tympany, which were patients of the Clinic for Horses between 1994 and 2001. Information on the pedigrees and all available relatives of these patients allowed us to group the affected foals into five families with a total of 289 animals. Female foals were significantly more often affected by guttural pouch tympany. The difference was 16.6% in favour of female foals. The size of the inbreeding coefficient was not important for the occurrence of guttural pouch tympany. The proportion of the genes of the breeds Arabian, Thoroughbred and Trakehner were not significantly different from a randomly selected sample of 10% of foals born in the same birth years and the same region. The heritability estimates for the frequency of guttural pouch tympany using a threshold model was 0.81 +/- 0.16. This is the first report that could show a genetic component responsible for guttural pouch tympany in horses.     

Pharyngeal neuromuscular dysfunction associated with bilateral guttural pouch tympany in a foal

A 2-month-old warmblood filly was presented for a 1-week history of a large, nonpainful, fluctuant swelling of the parotid and laryngeal area. Bilateral guttural pouch tympany was diagnosed. Surgical correction resolved the guttural pouch tympany; however, postoperative pharyngeal neuromuscular dysfunction developed.     

Genetics of upper and lower airway diseases in the horse

Genetic predispositions for guttural pouch tympany, recurrent laryngeal neuropathy and recurrent airway obstruction (RAO) are well documented. There is also evidence that exercise‐induced pulmonary haemorrhage and infectious diseases of the respiratory tract in horses have a genetic component. The clinical expression of equine respiratory diseases with a genetic basis results from complex interactions between the environment and the genetic make‐up of each individual horse. The genetic effects are likely to be due to variations in several genes, i.e. they are polygenic. It is therefore unlikely that single gene tests will be diagnostically useful in these disorders. Genetic profiling panels, combining several genetic factors with an assessment of environmental risk factors, may have greater value, but much work is still needed to uncover diagnostically useful genetic markers or even causative variants for equine respiratory diseases. Nonetheless, chromosomal regions associated with guttural pouch tympany, recurrent laryngeal neuropathy and RAO have been identified. The association of RAO with other hypersensitivities and with resistance to intestinal parasites requires further study. This review aims to provide an overview of the available data and current thoughts on the genetics of equine airway diseases.     

Standing endoscopic electrosurgery.

Common equine upper respiratory conditions are diagnosed via endoscopy. Endoscopic surgery facilitates correction of many conditions without general anesthesia or laryngotomy, reducing the morbidity and cost of the procedures. Modalities of endoscopic surgery include the Nd-YAG laser or electrosurgery, which may be complementary. The least expensive method is electrosurgery, and instruments are available that can be passed through the biopsy channel of the endoscope. Conditions amenable to such procedures include entrapped epiglottis, rostral displacement of the palatopharyngeal arch, pharyngeal cysts or polyps, retropharyngeal abscesses within the guttural pouch, guttural pouch tympany, and ethmoid hematoma.     

Nonsurgical removal of chondroid masses from the guttural pouches of two horses

Chondroid masses were successfully removed from the guttural pouches of 2 horses, using an endoscope, a snare, and a vacuum pump. This technique is an alternative to surgical removal of chondroid masses in patients when basic lavage of the affected guttural pouch is ineffective. Complications were not encountered. Advantages of this snare technique include avoidance of surgery and its potential complications, minimal recovery time, and minimal expense.     

Outcome of treatment in 35 cases of guttural pouch mycosis

This paper describes the outcome of treatment of 30 cases of guttural pouch mycosis by ligation of the internal carotid artery on the cardiac side of the lesion and lavage of the affected pouch with natamycin. Twenty-three horses recovered fully following this treatment while laryngeal hemiplegia persisted in one case and slight dysphagia caused by pharyngeal hemiplegia in another. The remaining five horses died or were destroyed. Five horses with guttural pouch mycosis, which had shown no epistaxis but had pharyngeal hemiplegia, were treated by topical natamycin alone. Only two of these survived, of which one remained slightly dysphagic. Ligation of the internal carotid artery of the cardiac side of the lesion is an effective means of reducing the chance of fatal epistaxis in cases of guttural pouch mycosis. Some cases of pharyngeal hemiplegia can make a complete recovery although it may take 12 to 18 months.     

Traumatic bilateral stylohyoid bone fracture in an Appaloosa

An Appaloosa gelding presented for a traumatic puncture wound of the head ventral to the base of his left ear, bilateral epistaxis and upper respiratory compromise. The horse did not exhibit dysphagia or cranial nerve deficits. The horse suffered bilateral oblique fractures of both stylohyoid bones due to the traumatic incident, diagnosed upon endoscopy of the guttural pouches. Treatment consisted of anti‐inflammatory medication, broad‐spectrum antibiotics, guttural pouch lavage and dietary management with soft feeds. At a one‐month follow‐up examination, endoscopic evaluation revealed a union at both stylohyoid bone fracture sites. Guttural pouch mycosis was diagnosed in the left guttural pouch on the lateral wall at the entrance of the lateral compartment. The guttural pouch mycosis was treated with a nystatin and gentamicin flush, followed by a course of oral fluconazole. At the 3‐month re‐evaluation, the guttural pouch mycosis had completely responded to treatment.     

Surgical site infection after occlusion of the internal carotid artery with a thrombectomy catheter: Five cases

Although rare, guttural pouch mycosis is a potentially life-threatening disease in the horse. The disease is most commonly treated surgically. One surgical option is occlusion of the internal carotid artery with a combination of ligation and use of a balloon tipped venous thrombectomy catheter. Complications of such treatment are rarely reported. This case series of five individuals describes the appearance, diagnosis and management of medium (>2 weeks) and long-term (>10 years) complications (including abscess formation, draining sinuses and wound dehiscence) of internal carotid artery occlusion with a venous thrombectomy catheter and management of these surgical site infections. The clinical presentations included swelling and/or discharging tracts in the parotid region. In one horse, an osseous reaction of the basisphenoid bone and penetration of the contralateral guttural pouch by the implant were identified by computed tomography. In all five horses, the surgical site infections were successfully resolved following removal of the venous thrombectomy catheter.     

Carotid and cerebral angiography in the horse

Carotid and cerebral angiography has been found to be a relatively simple technique to carry out in the horse. At most it involves a cutdown approach to the carotid artery, followed by catheterisation of the artery and selective catheterisation, if necessary, of one of its three branches. The technique can be carried out with standard equipment normally available within equine hospital facilities. The authors have employed angiography as a routine aid to diagnosis over the past nine years, without encountering any serious complications or adverse reactions. Carotid angiography has been especially valuable in the investigation of horses with guttural pouch mycosis. The technique has permitted the presence of aneurysms to be detected in many cases and significant vascular abnormalities in four cases. This information is valuable for the surgical treatment of horses with guttural pouch mycosis by ligation of the appropriate artery. Other indications for the use of carotid angiography include the investigation of ethmoidal haematoma, idiopathic Horner's syndrome, neoplasia of the head, venous aneurysms and arterial aneurysms in sites not associated with the guttural pouch. There are fewer occasions for the use of cerebral angiography in the horse, but it is indicated as an aid to the differential diagnosis of some abnormalities of the central nervous system.     

Guttural pouch empyema caused by Corynebacterium pseudotuberculosis in a pregnant mare

During medical management of mild colic in a 12‐year‐old Quarter Horse, mid‐gestation mare, unilateral purulent nasal discharge from the right nostril was noted. Endoscopic examination revealed guttural pouch empyema. Culture was positive for Corynebacterium pseudotuberculosis and negative for Streptococcus equi ssp. equi. A synergistic haemolysis inhibition titre of 1024 was consistent with C. pseudotuberculosis infection. Treatment included serial lavages and local infusion of antibiotics into the guttural pouches along with a 6‐week course of oral trimethoprim–sulfamethoxazole and rifampicin. Overall, no additional sites of infection were identified and the mare responded well to treatment, delivering a healthy, full‐term foal. This case emphasises that C. pseudotuberculosis, although uncommon, should be considered as a differential for guttural pouch empyema.     

Fistula between the guttural pouches and the dorsal pharyngeal recess as a sequela to guttural pouch mycosis in the horse

An unusual case of a two year old gelding with severe unilateral epistaxis due to guttural pouch mycosis is reported. The lesion had spread to involve the dorso-medial aspects of the right guttural pouch and had formed a fistula between the dorsal pharyngeal recess and both the left and right guttural pouches. The diagnosis, surgical treatment and postoperative management are described.     

A Case of Equine Aspergillosis: A Novel Sampling Procedure for Diagnosis

Aspergillus spp. may induce equine respiratory infections such as fungal pneumonia, guttural pouch mycosis, and systemic infection in immunocompromised individuals. This study describes a case of probable respiratory aspergillosis in a horse presenting clinical signs of the upper airway disease different from those previously reported. Nasopharyngeal swabs and guttural pouch centesis were performed, and Aspergillus flavus was isolated and identified. Following 30 days of pharmaceutical treatment with itraconazole, clinical signs resolved. Results suggested that aspergillosis should be included in the differential diagnosis of upper airway infections, guttural pouch centesis may be useful to make a correct diagnosis, and itraconazole is efficacious in the treatment of A flavus infection.     

Guttural pouch leiomyosarcoma causing nasopharyngeal compression in a pony

A 14‐year‐old Connemara cross gelding presented with abnormal respiratory noise and exercise intolerance. Upper airway endoscopy, ultrasonography, radiography and computed tomography revealed a large mass within the left guttural pouch causing marked left dorsal nasopharyngeal collapse and displacement and compression of the right guttural pouch. The horse was subjected to euthanasia and a post‐mortem examination confirmed the above findings. Histological and immunohistochemical examinations of the mass confirmed a diagnosis of guttural pouch leiomyosarcoma, a lesion previously unreported at this site.     

Fistulation of the auditory tube diverticulum (guttural pouch) with a neodymium:yttrium-aluminum-garnet laser for treatment of chronic empyema in two horses

Two horses with chronic empyema of the auditory tube diverticulum (guttural pouch) were refractory to medical treatment; empyema was bilateral in 1 horse and unilateral in the other. Both horses were treated by fistulation of the cartilage of the pharyngeal orifice by use of a neodymium:yttrium-aluminum-garnet laser in a noncontact manner. To maintain patency of the fistulae, indwelling catheters were placed into the openings created by the laser. For both horses, long-term follow-up did not reveal complications, and both owners were satisfied with results of the procedure. The authors recommend this procedure for horses that are unresponsive to medical treatment for chronic guttural pouch empyema.     

Guttural pouch empyema secondary to a periocular foreign body

This report describes a 3‐year‐old gelding presenting with signs of injury to its left eye following an accident in which the horse crashed into a hedge. The first treatment attempted to treat infections in the eye and respiratory tract due to secretions identified in the trachea. The horse did not improve and further clinical and radiographic evaluations detected a guttural pouch empyema. Surgical drainage was performed and antimicrobial treatment continued. However, the horse presented with severe epistaxis and euthanasia was elected due to suspected arterial rupture. At necropsy, a round and stiff branch plant was found creating a fistula from the left orbit to the left guttural pouch. Another branch was found inside the pouch, confirming the origin of the persistent infection and severity of the tissue lesion.     

Standing surgical removal of inspissated guttural pouch exudate (chondroids) in ten horses

OBJECTIVE: To report use of a modified Whitehouse approach in standing horses for management of inspissated guttural pouch empyema. STUDY DESIGN: Retrospective study. ANIMALS: Adult horses (n=10) with guttural pouch empyema. METHODS: Inspissated exudate in 1 or both guttural pouches was removed surgically through a modified Whitehouse approach, with the horses standing and sedated. Medical records of affected horses were reviewed to determine history; physical, endoscopic, and radiological examination findings; surgical technique; complications, and outcome. RESULTS: All horses had purulent nasal discharge; 3 horses had dysphagia, 2 had recurrent laryngeal neuropathy on the side affected by guttural pouch empyema, and 1 had persistent soft palate displacement. Inspissated exudate was removed safely without causing apparent discomfort. Eight horses returned to their previous level of athletic activity after surgery; 1 horse dysphagic before surgery, was euthanatized because of persistent dysphagia after surgery, and 1 horse died 1 week after surgery for unknown reasons. Streptococcus equi subsp equi was isolated from the affected guttural pouch of 3 horses. CONCLUSIONS: Inspissated exudate can be removed surgically from the guttural pouch in standing horses through a modified Whitehouse approach. CLINICAL RELEVANCE: To eliminate risks associated with general anesthesia and avoid surgical suite contamination, removal of chondroids can be performed in standing sedated horses through a modified Whitehouse approach.     

Elimination of guttural pouch infection and inflammation in asymptomatic carriers of Streptococcus equi

Three protracted outbreaks of strangles were investigated using endoscopic examination and a total of 14 asymptomatic carriers of Streptococcus equi were identified of which 13 showed evidence of carriage in the guttural pouch. Treatment was initiated to eliminate S. equi colonisation since these animals posed an infectious risk to susceptible horses. Two further horses were referred to us with severe guttural pouch pathology and from which S. equi was cultured, and treatment of these cases is also described. Treatment in the first instance was directed towards removal of gross guttural pouch pathology as seen on endoscopic examination. This was done with a combination of irrigation of the pouch with moderate to large amounts of saline, suction of fluid material and endoscopic manipulation of chondroids. Subsequently, antibiotic treatment was used to eliminate S. equi infection. All animals received systemic antibiotics, in some cases combined with topical antimicrobial treatment. Treatment was generally regarded as successful when the guttural pouches appeared normal and S. equi was not detected in nasopharangeal swabs and pouch lavages on 3 consecutive occasions. Successful treatment of one carrier required surgical intervention due to occlusion of both guttural pouch pharyngeal openings. Fourteen of 15 carriers were successfully treated by endoscopic removal of inflammatory material and antibiotic treatment, without surgical intervention. Five carriers originally given potentiated sulphonamide (33%) required further therapy with penicillin or ceftiofur, administered both systemically and topically, before S. equi infection and associated inflammation of the guttural pouches were eliminated.     

Diseases of the guttural pouches.

Guttural pouches are unique anatomic structures in Equidae. Conditions affecting the guttural pouches present with clinical signs that are not observed in other domestic species, and treatment of some of these conditions can be challenging. This article describes the anatomy and examination of the guttural pouches and reviews the presenting signs and treatment of the more common conditions affecting them, including empyema, tympany, mycosis, and stylohyoid arthropathy.     

The mystery of fungal infection in the guttural pouches

Advances in the understanding of guttural pouch physiology and novel therapeutic approaches to mycotic infections in the horse are reviewed. It is suggested that the guttural pouches may contribute to the regulation of arterial blood temperature, cooling the circulation to the brain to below body temperature. Aspergillus spp. is the major organism found in a guttural pouch affected with mycosis but it is unclear why this agent becomes aggressive. Conventional therapy aims to prevent fatal haemorrhage and to treat any neurological lesions but it is desirable to try to prevent the disease. A technique consisting of inserting a transarterial coil into the internal carotid, external carotid and maxillary arteries in normal and affected horses has been reported to be rapid, safe and effective in occluding the arteries and in inducing regression of the mycotic lesions without adjunctive medical treatment. When faced with acute and uncontrollable epistaxis in the field, the most effective means to reduce haemorrhage is probably the occlusion of both common carotid arteries. However, how such arterial occlusions can result in the successful management of guttural pouch mycosis without antifungal medication remains a mystery.