There are four primary digestive system functions—digestion, absorption, motility, and evacuation—and, correspondingly, four primary modes of dysfunction.
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Digestive System
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Digestive System Introduction
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Congenital and Inherited Anomalies of the Digestive System
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Congenital and Inherited Anomalies of the Mouth
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Congenital and Inherited Anomalies of the Teeth
- Cysts and Sinuses of the Head and Neck
- Congenital and Inherited Anomalies of the Esophagus
- Hernias
- Congenital and Inherited Anomalies of the Stomach
- Congenital and Inherited Anomalies of the Small and Large Intestine
- Congenital and Inherited Anomalies of the Liver
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Dental Development
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Dentistry
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Overview of Dentistry in Large Animals
- Congenital and Developmental Anomalies of the Mouth and Dentition in Large Animals
- Abnormal Tooth Eruption in Large Animals
- Irregular Wear of the Dentition in Large Animals
- Periodontal Disease in Large Animals
- Dental Caries in Large Animals
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Periodontal Disease in Small Animals
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Endodontic Disease in Small Animals
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Tooth Resorption in Small Animals
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Developmental Abnormalities of the Mouth and Dentition in Small Animals
- Dentofacial Trauma in Small Animals
- Dental Caries in Small Animals
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Pharyngeal Paralysis
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Diseases of the Rectum and Anus
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Enteric Campylobacteriosis
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Salmonellosis
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Tyzzer Disease
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Amebiasis
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Coccidiosis
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Cryptosporidiosis
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Giardiasis (Giardia)
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Diseases of the Mouth in Large Animals
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Diseases of the Esophagus in Large Animals
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Gastrointestinal Ulcers in Large Animals
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Diseases of the Ruminant Forestomach
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Diseases of the Abomasum
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Acute Intestinal Obstructions in Large Animals
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Colic in Horses
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Intestinal Diseases in Ruminants
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Intestinal Diseases in Horses and Foals
- Overview of Intestinal Diseases in Horses and Foals
- Diarrheal Disease in Horses
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Clostridia-associated Enterocolitis in Horses
- Colitis-X in Horses
- Coronavirus in Horses
- Parasitism (Gastrointestinal) in Horses
- Sand Enterocolopathy in Horses
- Recurrent Diarrhea in Horses
- Infiltrative Colonic Disease in Horses
- Miscellaneous Causes of Diarrhea in Horses
- Foal Heat Diarrhea
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- Viral Diarrhea in Foals
- Miscellaneous Causes of Diarrhea in Foals
- Weight Loss and Hypoproteinemia
- Gastrointestinal Neoplasia in Horses
- Inflammatory Bowel Disease in Horses
- NSAID Toxicosis in Horses
- Small-intestinal Fibrosis in Horses
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Intestinal Diseases in Pigs
- Overview of Intestinal Diseases in Pigs
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Clostridium difficile Enteritis in Pigs
- Clostridium perfringens Type A Enteritis in Pigs
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Clostridium perfringens Type C Enteritis in Pigs
- Edema Disease in Pigs
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Enteric Colibacillosis in Pigs
- Hemorrhagic Bowel Syndrome in Pigs
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Intestinal Salmonellosis in Pigs
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Intestinal Spirochetosis in Pigs
- Parasitism (Gastrointestinal) in Pigs
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Porcine Proliferative Enteritis
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Transmissible Gastroenteritis in Pigs
- Other Intestinal Viruses of Pigs
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Gastrointestinal Parasites of Ruminants
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Gastrointestinal Parasites of Horses
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Gastrointestinal Parasites of Pigs
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Fluke Infections in Ruminants
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Hepatic Disease in Large Animals
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Overview of Hepatic Disease in Large Animals
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Acute Hepatitis in Large Animals
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Infectious Hepatitis and Hepatic Abscesses in Large Animals
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Cholelithiasis, Choledocholithiasis, and Hepatolithiasis in Large Animals
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Chronic Active Hepatitis in Large Animals
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Hyperlipemia and Hepatic Lipidosis in Large Animals
- Hepatic Neoplasia in Large Animals
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Miscellaneous Hepatic Disorders in Large Animals
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Hyperbilirubinemia Syndromes in Large Animals
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Malassimilation Syndromes in Large Animals
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Abdominal Fat Necrosis
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Diseases of the Mouth in Small Animals
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Diseases of the Esophagus in Small Animals
- Cricopharyngeal Achalasia in Small Animals
- Dilatation of the Esophagus in Small Animals
- Esophageal Dysmotility in Small Animals
- Esophageal Strictures in Small Animals
- Esophagitis in Small Animals
- Esophageal Foreign Bodies in Small Animals
- Esophageal Diverticula in Small Animals
- Bronchoesophageal Fistula in Small Animals
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Diseases of the Stomach and Intestines in Small Animals
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Constipation and Obstipation in Small Animals
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Gastric Dilation and Volvulus in Small Animals
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Gastrointestinal Neoplasia in Small Animals
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Gastrointestinal Obstruction in Small Animals
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Gastrointestinal Ulcers in Small Animals
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Helicobacter Infection in Small Animals
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Hemorrhagic Gastroenteritis in Small Animals
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Inflammatory Bowel Disease in Small Animals
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Malabsorption Syndromes in Small Animals
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The Exocrine Pancreas
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Gastrointestinal Parasites of Small Animals
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Hepatic Disease in Small Animals
- Overview of Hepatic Disease in Small Animals
- Hematology in Hepatic Disease in Small Animals
- Coagulation Tests in Hepatic Disease in Small Animals
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Enzyme Activity in Hepatic Disease in Small Animals
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Other Serum Biochemical Measures in Hepatic Disease in Small Animals
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Hepatic Function Tests in Small Animals
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Imaging in Hepatic Disease in Small Animals
- Cholecystocentesis in Hepatic Disease in Small Animals
- Liver Cytology in Small Animals
- Liver Biopsy in Small Animals
- Pathologic Changes in Bile in Small Animals
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Nutrition in Hepatic Disease in Small Animals
- Fulminant Hepatic Failure in Small Animals
- Hepatic Encephalopathy in Small Animals
- Portal Hypertension and Ascites in Small Animals
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Portosystemic Vascular Malformations in Small Animals
- Acquired Portosystemic Shunts in Small Animals
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Other Hepatic Vascular Disorders in Small Animals
- Hepatotoxins in Small Animals
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Infectious Diseases of the Liver in Small Animals
- Feline Hepatic Lipidosis
- Biliary Cirrhosis in Small Animals
- Canine Cholangiohepatitis
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- Lobular Dissecting Hepatitis in Small Animals
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- Metabolic Diseases Affecting the Liver in Small Animals
- Hepatocutaneous Syndrome in Small Animals
- Nodular Hyperplasia in Small Animals
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Hepatic Neoplasia in Small Animals
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Miscellaneous Liver Diseases in Small Animals
- Diseases of the Gallbladder and Extrahepatic Biliary System in Small Animals
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Cholecystitis in Small Animals
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- Other Disorders of the Gallbladder in Small Animals
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Other Disorders of the Bile Ducts in Small Animals
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Extrahepatic Bile Duct Obstruction in Small Animals
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Cholelithiasis in Small Animals
- Biliary Tree Rupture and Bile Peritonitis in Small Animals
- Feline Cholangitis/Cholangiohepatitis Syndrome
- Hepatobiliary Fluke Infection in Small Animals
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Vomiting
Digestive System Sections (A-Z)
Abdominal Fat Necrosis
Hard masses of necrotic fat are occasionally identified in the peritoneal cavity of mature cattle, especially the Channel Island breeds, Japanese Black cattle, and beef cattle grazing fescue for long periods. The disease has also been seen in goats and some species of deer maintained on pastures consisting primarily of tall fescue. The masses are commonly mistaken for a developing fetus on palpation per rectum because they feel like “floating corks” similar to cotyledons. The masses of necrotic fat usually do not cause clinical signs but in advanced cases can create an extraluminal obstruction that results in episodes of moderate abdominal pain, distention of intestine proximal to the fat, and the passage of small amounts of feces.
Acute Intestinal Obstructions in Large Animals
Intestinal obstructions are seen in all large animal species but are most common in horses. Cattle are the most commonly affected ruminants; diagnosis in sheep and goats is rare, except for intestinal volvulus in lambs. Other than inguinal hernias, intestinal obstructions are infrequently recognized in pigs.
Amebiasis
Amebiasis is an acute or chronic colitis, characterized by persistent diarrhea or dysentery, that is prevalent in tropical and subtropical areas worldwide. Its prevalence has declined in the USA over the past several decades, but the disease is still important in many tropical areas, particularly in times of disasters. It is common in people and nonhuman primates, sometimes seen in dogs and cats, and rare in other mammals. Several species of amebae are found in mammals, but the only known pathogen is Entamoeba histolytica. People are the natural host for this species and the usual source of infection for domestic animals. Mammals become infected by ingesting food or water contaminated with feces containing infective cysts. E dispar is a noninvasive, nonpathogenic ameba that is molecularly distinct but morphologically indistinguishable from the pathogenic species E histolytica. E invadens of reptiles is also morphologically identical to E histolytica, but it is not transmissible to mammals.
Coccidiosis
Coccidiosis is usually an acute invasion and destruction of intestinal mucosa by protozoa of the genera Eimeria or Isospora. Clinical signs include diarrhea, fever, inappetence, weight loss, emaciation, and in extreme cases, death. However, many infections are subclinical. Coccidiosis is an economically important disease of cattle, sheep, goats, pigs, poultry (see Coccidiosis), and also rabbits, in which the liver as well as the intestine can be affected (see Coccidiosis). In dogs, cats, and horses, coccidiosis is less often diagnosed but can result in clinical illness. Other genera, of both hosts and protozoa, can be involved (see Cryptosporidiosis, Sarcocystosis, and Toxoplasmosis).
Colic in Horses
In its strictest definition, the term “colic” means abdominal pain. Throughout the years, it has become a broad term for a variety of conditions that cause a horse to exhibit clinical signs of abdominal pain. Consequently, it is used to refer to conditions of widely varying etiologies and severity. To understand these etiologies, make a diagnosis, and initiate appropriate treatments, veterinarians must first appreciate the clinically relevant aspects of equine GI anatomy, the physiologic processes involved in movement of ingesta and fluid along the GI tract, and the extreme sensitivity of the horse to the deleterious effects of the structural components of the bacteria that reside within the lumen of the intestine.
Congenital and Inherited Anomalies of the Digestive System
Congenital cysts, sinuses, or fistulae of the branchial arch apparatus or thyroglossal duct have been reported in horses, dogs, cats, and ruminants, yet are very rare. These structures arise from persistent embryologic pharyngeal pouches, arches, or clefts, or the thyroglossal duct. Animals typically present with nonpainful, fluid-filled masses in the cervical region. Clinical signs are typically due to the space-occupying mass and include dyspnea, respiratory stridor, intermittent esophageal obstruction, and coughing. Animals may present later in life; it is not known why a cyst may suddenly enlarge but may be associated with respiratory infection. Diagnostic imaging includes radiography, ultrasonography, video endoscopy, and contrast CT to determine whether there is communication with the pharynx. Branchial cysts (also called lateral cervical cysts) in horses are typically seen on the right side, although a bilateral case has been reported. Surgical excision is curative, although complications include right laryngeal hemiplegia, seroma formation, and pneumonia. Alternatively, some horses have been treated with marsupialization and iodine sclerotherapy with good results. In dogs and cats, few complications have been noted. Embryologic origin of branchial cysts has been mostly of the third pharyngeal pouch, although anatomic location has also suggested origin of the fourth and sixth pouches in some cases.
Cryptosporidiosis
Cryptosporidiosis is recognized worldwide, primarily in neonatal calves but also in lambs, kids, foals, and piglets. Cryptosporidia cause varying degrees of naturally occurring diarrhea in neonatal farm animals. The parasites commonly act in concert with other enteropathogens to produce intestinal injury and diarrhea.
Dental Development
All domestic animals have a diphyodont dentition, ie, a deciduous and a permanent set of teeth. The morphology as well as the dental formula (see Table: Dental Formulas) of mammalian teeth, however, are variable and closely related to the animal’s alimentation.
Dentistry
Most large animals are herbivores, and efficient dental function is the key to food intake and to the maintenance of normal body condition. The variations in anatomic structure, dental formula, and eruption schedule for deciduous and permanent teeth is fundamental veterinary knowledge and should be reviewed before performing dentistry on any species (see Table: Dental Formulas).
Digestive System Introduction
The digestive tract includes the oral cavity and associated organs (lips, teeth, tongue, and salivary glands), the esophagus, the forestomachs (reticulum, rumen, omasum) of ruminants and the true stomach in all species, the small intestine, the liver, the exocrine pancreas, the large intestine, and the rectum and anus. Gut-associated lymphoid tissue (tonsils, Peyer’s patches, diffuse lymphoid tissue) is distributed along the GI tract. The peritoneum covers the abdominal viscera and is involved in many GI diseases. Fundamental efforts to manage GI disorders should always be directed toward localizing disease to a particular segment and determining a cause. A rational therapeutic plan can then be formulated.
Diseases of the Abomasum
Abomasal disorders include left displaced abomasum (LDA), right displaced abomasum (RDA), abomasal volvulus (AV), abomasal ulceration, and impaction. Displacement or volvulus is seen most commonly in dairy cows but can also be seen in dairy bulls and calves. Except for AV, abomasal displacement is rare in beef cattle and essentially undiagnosed in small ruminants. Abomasal ulcers are seen in dairy and beef cattle and in calves and lambs; they are rarely diagnosed in small ruminants. Impactions can be primary, which is most frequent in beef cattle, or secondary, which develop most often in dairy cows as a form of vagal indigestion. Impactions may have a hereditary basis in some black-faced sheep.
Diseases of the Esophagus in Large Animals
Esophageal obstruction (choke) occurs when the esophagus is obstructed by food or foreign objects. It is the most common esophageal disease in large animals. Horses most commonly obstruct on grain, beet pulp, or hay. Esophageal obstruction can also occur after recovery from standing chemical restraint or general anesthesia. Cattle tend to obstruct on a single solid object, eg, apples, beets, potatoes, turnips, corn stalks, or ears of corn.
Diseases of the Esophagus in Small Animals
Cricopharyngeal achalasia is characterized by inadequate relaxation of the cricopharyngeal muscle, which leads to a relative inability to swallow food or liquids. It is seen primarily as a congenital defect but is occasionally seen in adult dogs. The cause is generally unknown, but in adult animals it may be associated with acquired neuromuscular disorders. Repeated attempts to swallow are followed by gagging and regurgitation. Aspiration pneumonia is a common complication. An accurate diagnosis requires fluoroscopic evaluation of swallowing after oral administration of contrast material alone and mixed with food. Abnormal function (lack of relaxation) of the cricopharyngeal muscle results in retention of barium in the posterior pharynx.
Diseases of the Mouth in Large Animals
Wounds of the lips and cheeks occur frequently in horses. The most common cause is external trauma or secondary to the use of inappropriate bits or restraint devices. Lip lacerations may be accompanied by mandibular or incisive bone fractures with or without dental fractures and tooth avulsions. These occur when a horse grasps objects with its mouth and then pulls back when startled. Lip lacerations without bone or teeth involvement can be sutured, usually with a good result. Healing is rapid because of the good blood supply to the head. Lacerations left to heal by second intention can result in orocutaneous fistula, which may require resection and primary wound closure. Rarely, skin grafts or mucosal flaps are required to manage orocutaneous fistula.
Diseases of the Mouth in Small Animals
For a discussion of developmental diseases of the mouth, see Congenital and Inherited Anomalies of the Mouth. For eosinophilic granuloma complex, see Eosinophilic Granuloma Complex.
Diseases of the Rectum and Anus
Diseases of the Ruminant Forestomach
Diseases of the Stomach and Intestines in Small Animals
The colon helps maintain fluid and electrolyte balance and absorb nutrients; it is also the major site of fecal storage until expulsion and provides an environment for microorganisms. Disruptions to normal colonic function lead to changes in both absorption and motility; clinically, this often manifests as large-bowel diarrhea. Approximately one-third of dogs with a history of chronic diarrhea have colitis. Chronic colitis is defined as inflammation of the colon that is present for ≥2 wk. Inflammation of the colon reduces the amount of water and electrolytes absorbed and changes colonic motility by suppressing the normal colonic contractions that mix and knead and by stimulating giant migrating contractions (ie, more powerful contractions that rapidly propel intestinal contents). Colitis has been classified into four forms: lymphocytic-plasmacytic, eosinophilic, neutrophilic, and granulomatous. Lymphocytic-plasmacytic is the most common form in both dogs and cats. Most dogs are middle-aged, and there is no sex predilection. There may be an association between colitis and perianal fistula, especially in German Shepherds. Cats with chronic colitis tend to be middle-aged and more commonly purebred. Typically, there is an increased number of lymphocytes and plasmocytes in the lamina propria (less frequently in the submucosa and muscularis).
Enteric Campylobacteriosis
Campylobacter spp are spiral, microaerobic, gram-negative bacteria that cause gastroenteritis in people and animals. Several Campylobacter spp are zoonotic. Many domestic animals develop acute gastroenteritis after ingestion of Campylobacter spp, including dogs, cats, calves, sheep, pigs, ferrets, mink, monkeys, and several species of laboratory animals. (See also Bovine Genital Campylobacteriosis, see Zoonotic Diseases, and see Avian Campylobacter Infection.) Infection with C jejuni is one of the most common causes of gastroenteritis in people worldwide and is the most extensively studied Campylobacter species.
Fluke Infections in Ruminants
Fasciola hepatica, the most important trematode of domestic ruminants, is the most common cause of liver fluke disease in temperate areas of the world. In the USA, it is endemic along the Gulf Coast, the West Coast, the Rocky Mountain region, and other areas. It is present in eastern Canada, British Columbia, and South America and is of particular economic importance in the British Isles, western and eastern Europe, Australia, and New Zealand. Fasciola gigantica is economically important in Africa and Asia and is also found in Hawaii. Fascioloides magna has been reported in at least 21 states (USA) and in Europe. In North America, Dicrocoelium dendriticum is confined mainly to New York, New Jersey, Massachusetts, and the Atlantic provinces of Canada. It is also widespread in some areas in Europe and Asia. Eurytrema spp, the pancreatic flukes, parasitize sheep, pigs, and cattle in Brazil and parts of Asia. Several species of paramphistomes or rumen flukes are found throughout much of the world.
Gastrointestinal Parasites of Horses
Horse bots, which are found in the stomach, are the larvae of bot flies, Gasterophilus spp. Three major species are distributed worldwide, and a number of minor species are found in parts of Europe, Africa, and Asia. The adult flies are not parasitic and cannot feed; they survive long enough to mate and lay eggs and die as soon as the nutrients remaining from the larval stage are used, usually in ~2 wk. The three important species can be differentiated in any stage of their development. The eggs of G intestinalis (the common bot) are glued to the hairs of almost any part of the body but especially the forelimbs and shoulders. The larvae hatch in ~1 wk when stimulated, usually by the animals’ licking. The eggs of G haemorrhoidalis (the nose or lip bot) are attached to the hairs of the lips. The larvae emerge in 2–3 days without stimulation and crawl into the mouth. G nasalis (the throat bot) deposits eggs on the hairs of the submaxillary region. They hatch in ~1 wk without stimulation.
Gastrointestinal Parasites of Pigs
Also see Coccidiosis of Pigs.
Gastrointestinal Parasites of Ruminants
Many species of nematodes and cestodes cause parasitic gastritis and enteritis in sheep and goats. The most important of these are Haemonchus contortus, Teladorsagia (Ostertagia) circumcincta, Trichostrongylus axei, intestinal species of Trichostrongylus, Nematodirus spp, Bunostomum trigonocephalum, and Oesophagostomum columbianum. Cooperia curticei, Strongyloides papillosus, Trichuris ovis, and Chabertia ovina also may be pathogenic in sheep; these and related species are discussed under GI parasites of cattle (see Gastrointestinal Parasites of Cattle).
Gastrointestinal Parasites of Small Animals
Adult Spirocerca lupi are bright red worms, 40 mm (male) to 70 mm (female) long, generally located within nodules in the esophageal, gastric, or aortic walls. Infections are seen in southern areas of the USA as well as in many tropical and subtropical regions worldwide (eg, Greece, India, Israel, Japan, South Africa). Dogs are infected by eating an intermediate host (usually dung beetle) or a transport host (eg, chickens, reptiles, or rodents). The larvae migrate via the wall of the celiac artery to the thoracic aorta, where they usually remain for ~3 mo. Eggs are passed in feces ~5–6 mo after infection.
Gastrointestinal Ulcers in Large Animals
Gastric ulcers are important in adult horses, foals, and pigs. Abomasal ulcers (see Abomasal Ulcers) in mature cattle and calves appear to be increasing in importance.
Giardiasis (Giardia)
Giardiasis is a chronic, intestinal protozoal infection seen worldwide in most domestic and wild mammals, many birds, and people. Infection is common in dogs, cats, ruminants, and pigs. Giardia spp have been reported in 0.44%–39% of fecal samples from pet and shelter dogs and cats, 1%–53% in small ruminants, 9%–73% in cattle, 1%–38% in pigs, and 0.5%–20% in horses, with higher rates of infection in younger animals. Farm prevalences in production animals vary between 0% and 100%, with the highest prevalence in younger animals. The cumulative incidence on a farm where Giardia has been diagnosed is 100% in cattle and goats and nearly 100% in sheep.
Hepatic Disease in Large Animals
Hepatic Disease in Small Animals
The liver performs numerous functions, including but not limited to lipid, carbohydrate, and protein metabolism; storage, metabolism, and activation of vitamins; storage of minerals, glycogen, and triglycerides; extramedullary hematopoiesis; and synthesis of coagulant, anticoagulant, and several acute phase proteins. It also influences immunologic responses and contributes to digestion through synthesis and enterohepatic circulation of bile acids and detoxification of many endogenous and exogenous compounds, toxins, and xenobiotics. Because the liver has a large functional reserve and the ability to regenerate, hepatic injury must be considerable or chronic and recurrent to cause overt hepatic dysfunction or failure.
Intestinal Diseases in Horses and Foals
Intestinal disease in horses and foals is suggested by diarrhea, weight loss, hypoproteinemia, and abdominal pain. (Also see Colic in Horses.)
Intestinal Diseases in Pigs
Pigs of all ages are susceptible to intestinal diseases, and diarrhea is the sign common to nearly all such disorders. Transmission of infectious agents that cause enteropathies is by the fecal-oral route. At least 16 different etiologic agents, including bacteria, viruses, and parasites, can cause primary intestinal disease. Porcine circovirus type 2 (PCV 2) virus may be isolated from the intestines of pigs with diarrhea. PCV 2 is the cause of several multisystemic diseases in pigs, including postweaning multisystemic wasting syndrome (see Porcine Circovirus Diseases). Diarrhea in a herd may be due to a single agent, but concurrent infections are common. Because some diseases are age-dependent, differential diagnosis is best considered by age group (see Table: Distribution of Diarrheal Diseases in Pigs by Age Group).
Intestinal Diseases in Ruminants
Determination of the cause of intestinal disease in cattle is based on clinical, epidemiologic, and laboratory findings. Nonspecific therapy includes oral and parenteral fluid therapy to restore the fluid, electrolyte, and acid-base homeostasis. Specific therapy and prevention are detailed under the individual disease headings. Intestinal diseases of neonates are discussed separately, although some of the causes also affect older animals.
Malassimilation Syndromes in Large Animals
Malassimilation is a decreased ability of the GI tract to incorporate nutrients into the body, either due to maldigestion or malabsorption. Maldigestion is the failure of adequate degradation of dietary constituents within the GI tract, which is required to facilitate absorption due to defects in pancreatic exocrine function, bile acid content, or brush border enzymes. Malabsorption is the failure of passage of nutrients from the intestinal lumen into the bloodstream. Some disease processes involve both maldigestion and malabsorption, such as is seen in young animals with lactase deficiency. Maldigestion alone is an infrequent cause of malassimilation in large animals. In horses, diseases causing malabsorption are much more common than diseases causing maldigestion. In cattle, small ruminants, and camelids, the forestomach bacteria and protozoa contribute to nutrient degradation, which makes maldigestion a very rare condition.
Pharyngeal Paralysis
Pharyngeal paralysis may be the result of a central or peripheral nervous system disorder or may develop secondary to severe local disease that may cause collapse, obstruction, or malfunction of the pharynx. Of the CNS disorders, rabies (see Rabies) is the most important of the viral causes of encephalomyelitis, although perhaps not the most frequent. CNS intoxication, lead poisoning, cranial trauma, intracranial abscessation, and neoplasia may also result in pharyngeal paralysis in many species.
Salmonellosis
Salmonella, a rod-shaped gram-negative bacterium belonging to the family Enterobacteriaceae, is the causative agent of salmonellosis. Salmonellosis in warm-blooded vertebrates is in most cases associated with serovars of Salmonella enterica. The most common type of infection is the carrier state, in which infected animals carry the pathogen for a variable period of time without showing any clinical signs. Clinical disease is characterized by two major syndromes: a systemic septicemia (also termed as typhoid) and an enteritis. Other less common clinical presentations include abortion, arthritis, respiratory disease, necrosis of extremities, and meningitis.
The Exocrine Pancreas
The pancreas has both endocrine and exocrine functions. The exocrine pancreas is made up of pancreatic acinar cells and a duct system that opens into the proximal duodenum. Pancreatic acinar cells synthesize and secrete digestive enzymes (eg, amylase, lipase, and others) or inactive proenzymes, and zymogens (eg, trypsinogen, chymotrypsinogen, proelastase, prophospholipase, and others) of digestive enzymes, which are essential for the digestion of dietary components such as proteins, triglycerides, and complex carbohydrates. The exocrine pancreas also secretes other essential substances, such as large amounts of bicarbonate, which buffers gastric acid, intrinsic factor, which is needed for cobalamin absorption, and colipase, which is an essential cofactor for pancreatic lipase.
Tyzzer Disease
Tyzzer disease is an enterohepatic syndrome of a wide range of animals (also see Tyzzer Disease in rabbits) and is seen worldwide. Tyzzer disease was first described in mice in 1917. Several years later, it was reported in laboratory rabbits and then in other small laboratory mammals, including guinea pigs, hamsters, gerbils, and rats. It is a highly fatal disease of young foals. The disease is rare in other domestic animals, including dogs, cats, and calves. It has been reported in a variety of wildlife, including muskrats, cottontail rabbit, coyote, gray fox, lesser panda, snow leopard, raccoon, marsupials, and white-tailed deer.
Vomiting
Vomiting is the reflexive, forceful expulsion of part or all of the contents of the stomach and proximal small intestines through the mouth. It involves a series of involuntary spasmic movements requiring visceral, diaphragmatic, and abdominal muscular contractions. The act of vomiting is usually preceded by a number of stereotypical prodromal clinical signs, including excessive salivation, repeated swallowing, retching, and marked contractions of the abdominal musculature. Vomiting must be differentiated from regurgitation, dysphagia (difficulty swallowing), and various forms of esophageal dysfunction. Regurgitation is a passive process whereby partially or completely undigested food or liquid is released from the esophagus and/or stomach through the mouth without effort or muscular contractions (ie, through gravity and body position). Although dysphagia involves active but ineffective muscular contractions and may produce movements that closely resemble the retching associated with vomiting, the process represents a dysfunctional movement of liquid and/or food into, not out of, the GI tract.
Also of Interest
Test your knowledge
Ruminants (cattle, sheep, and goats) lack which of the following teeth?