Dysphagia (Including Feed From Nares and Excessive Salivation)

Bradford P. Smith

Dysphagia is used here to refer to abnormalities of prehension, mastication, or swallowing. It is associated with diseases of the mouth, lips, teeth, pharynx, esophagus, mandible, or masseter muscles or, in the case of neurologic problems, with central or peripheral lesions resulting in malfunction in these areas.

The causes of dysphagia can be divided into three clinical categories: 1) pain induced, 2) neurologic, and 3) obstructive (Boxes 7.18 and 7.19). A fourth category is mechanical interfer­ence with prehension and swallowing, but this usually manifests in a manner resembling the manifestation of painful lesions. Particularly in horses, worn, missing, capped, abscessed, overgrown, or broken teeth often result in mechanical interfer­ence with chewing, resulting in half-chewed feed being dropped from the mouth (quidding). Observation of the animal as it attempts to eat and a good physical examination including oral inspection and passage of a stomach tube to rule out choke are essential in determining the cause of dysphagia. Use of a fiberoptic endoscope to visualize the pharynx, guttural pouches, and esophagus may be helpful. Plain film radiographs and barium swallows may also be indicated to see functional abnormalities in the guttural pouches, pharynx, and esophagus during swallowing and to rule out fractures of the hyoid or mandible. Ultrasound should also be employed.

Pain is probably the most frequent cause of dysphagia in ruminants and horses. Oral lesions, oral foreign bodies, and poor teeth result in decreased feed intake, in increased salivation, and often in dropping feed from the mouth while attempting to chew.

When dysphagia is associated with loss of large amounts of saliva, metabolic acid-base and electrolyte disorders may develop. Cattle and sheep have saliva high in sodium (136 to 201 mEq/L) and bicarbonate (108 mEq/L), with potassium and chloride values in the 14 to 15 mEq/L range.^36,37 As a result, losses of large amounts of saliva can result in hypovolemia and severe metabolic acidosis. In contrast, horses have relatively high levels of salivary chloride (48 to 82 mEq/L) with relatively low salivary bicarbonate (44 to 52 mEq/L). Equine salivary

■ BOX 7.18

Causes of Dysphagia in Horses

Pain

Tooth root abscess or periodontal disease Worn, missing, capped, overgrown, or broken teeth Foreign body in mouth, pharynx, nose

Oral vesicles, erosions, ulcers, or growths Pharyngeal abscess, cellulitis, trauma, fistula, or neoplasia Esophageal choke, trauma

Strangles

Rupture of rectus capitus ventralis muscle Snake bite

Oral, mandibular, or maxillary fracture, neoplasia, or granulomas White muscle disease

Epiglottiditis, epiglottic cysts

Trauma or excessive traction to tongue Hyoid bone injury

Nasal mass (granuloma) Neurogenic dysphagia

Obstruction

Pharyngeal abscess, cellulitis, trauma, fistula, or neoplasia Esophageal choke, trauma, megaesophagus

Strangles

Rostral displacement of palatopharyngeal arch Damaged or abnormal esophagus

Cleft palate

Dorsal displacement of soft palate Epiglottiditis, epiglottic cysts

Nasal mass (granuloma) Lymphosarcoma

Purpura hemorrhagica

Neurologic, Neuromuscular

Yellow star thistle (nigropallidal encephalomalacia) Guttural pouch mycosis, infection, or tympany Megaesophagus

Botulism

Lead toxicity Rabies

Snake bite

Tetanus

Tick paralysis

Encephalitis, meningitis Encephalopathy, hepatic

White muscle disease Cerebrospinal nematodiasis

Electrocution

Transit or lactation tetany Lymphosarcoma

Myeloproliferative disease

Myotonia

Otitis interna and media

Pontomedullary, brainstem neoplasia, pituitary abscess, trauma, neoplasm

Postanesthetic myasthenia Herbicide toxicity

White snakeroot (tremetol) toxicity Moldy corn poisoning

Locoweed (Astragalus, Oxytropis) toxicity West Nile fever

Borna disease, Near East encephalitis (exotic) Grass sickness (exotic)

potassium is 14 to 18 mEq/L, and sodium is 54 to 90 mEq/L.^38,39 As a result, horses with esophageal fistulas that have lost saliva have a transient metabolic alkalosis.³⁸

In the horse a common cause of acute dysphagia is choke (esophageal obstruction), followed in frequency by pharyngeal

■ BOX 7.19

■ BOX 7.20

Causes of Dysphagia in Ruminants

Pain

Oral vesicles, erosions, ulcers, growths (see following section) Foreign body

Pharyngeal abscesses, cellulitis, or tumor

Traumatic or irritant stomatitis

Snake bite

White muscle disease

Actinobacillosis

Actinomycosis

Worn, missing, overgrown, or broken teeth Periodontal disease or tooth root abscesses

Oral, maxillary, or mandibular neoplasia

Fractured mandible or maxilla

Stomatitis

Necrotic laryngitis (calf diphtheria) Ruptured or damaged esophagus

Obstruction

Foreign body

Pharyngeal abscess, cellulitis, or tumor Choke

Snake bite

Actinobacillosis

Oral, maxillary, or mandibular neoplasia

Megaesophagus

Hiatal or diaphragmatic hernia

Cleft palate Bovine leukosis

Neuromuscular

Listeriosis

Rabies

Tetanus

Botulism

Tick paralysis

Encephalitis, encephalopathy

Brain abscess

White muscle disease

Megaesophagus

Paresis of masseter muscles (mandibular branch of trigeminal) Bovine leukosis

GM1 gangliosidosis in Friesian cattle

Meningitis

Encephalitis or encephalopathy

Atlantoaxial subluxation or occipitoatlantoaxial malformation Hypocalcemia

Otitis media and interna

Pontomedullary brainstem neoplasia, trauma, infection, inflammation

Pituitary abscess

Pseudorabies

White snakeroot (tremetol) poisoning Fireweed (Kochia scoparia) poisoning

Locoweed (Astragalus, Oxytropis) poisoning Mercury poisoning

Kikuyu grass (Pennisetum clandestinum) poisoning (exotic) Ibaraki disease (exotic) (B)

Geigeria poisoning (exotic)

Ephemeral fever (exotic) (B)

B, Bovine.

paresis (neurologic) resulting from lesions in the guttural pouch that affect the pharyngeal nerves.

Common Causes

Vesicular stomatitis

Phenylbutazone toxicity

Yellow bristle grass (Setaria lutescens or Setaria glauca) ulcers Other plant awn stomatitis

Oral foreign body

Less Common Causes

Irritant or caustic chemical stomatitis

Periodontal gingivitis

Blister beetle (cantharidin) toxicity

Uremia

Drug eruption

Oral neoplasia

identified by using a nasogastric tube, whereas pharyngeal paresis may be associated with a number of neurologic or neuromuscular conditions, such as botulism or guttural pouch mycosis, which require careful differentiation. The most frequent serious problem associated with choke or pharyngeal paresis is inhalation (aspiration, foreign body) pneumonia. Mineral oil or other material that is particularly damaging if it gains entry into the lung should never be used in choke for this reason. In any animal with dysphagia, care must be taken to prevent aspiration pneumonia and to evaluate the thorax periodically.

Animals with facial paralysis often drool from the affected side and may pack feed into the cheek on the affected side. Listeriosis in ruminants is frequently associated with facial paralysis. In horses facial paralysis is usually caused by halter trauma or a blow to the head.