Veterinary Pathology Quiz on Obstructive Disorders

Adult Ruminant Non-Stomach Conditions

• Learning Objectives: Students should be able to construct differential diagnoses for non-stomach GI diseases in ruminants, choose appropriate diagnostics, determine appropriate medical and surgical interventions, estimate prognosis for individual animals and herds, and identify control measures for disease prevention.

Differential Diagnoses

• Infectious: Johne's Disease, Bovine Viral Diarrhea, Salmonella, Winter Dysentery, Parasitic Gastroenteritis
• Poisoning: Acorn, Yew
• Obstruction: Choke, Caecocolic dilation and volvulus, Mesenteric torsion
• Other: Peritonitis

Johne's Disease

• Description: Chronic wasting disease, chronic granulomatous enteritis and lymphadenitis. Signs appear 2-5 years after a stressful event.
• Clinical Signs: Reduced production and fertility, 10% decrease in milk yield before clinical signs, 20% decrease after, severe progressive weight loss, intermittent diarrhea, absence of blood or mucus, submandibular edema, emaciation, and death.
• Diagnosis: Ziehl-Neelsen staining of faecal smear or histologic section, bacteriological culture of faeces, faecal PCR, blood or milk ELISA (detect antibodies, but often late).
• Control/Prevention: Minimum yearly testing of red cows, culling cows when prevalence is low. Protect calves from manure and milk from amber cows, use responsible replacements from accredited herds, separate positive animals. Don't test for Johne's within 6 weeks of TB testing.

Bovine Viral Diarrhea Virus (BVD)

• Types: Type I (UK), Type II (Europe)
• Disease Forms: Acute, immunosuppression (particularly calves), reproductive.
• Clinical Signs (Mucosal Disease): Fatal disease of PI animals, BVDV mutation into cytopathic form, animals 6-24 months old typically will show depression, anorexia, drooling, and mucosal lesions (lips, gums, tongue, esophagus, and intestines). Diarrhea (foul-smelling, bloody, or mucous), death in 5-7 days
• Clinical Signs (Acute): Any animal, small production losses, lasts less than 14 days. Immunosuppression, particularly calves, can lead to scours and pneumonia.
• Diagnosis: MDA can interfere with Ab testing until 4-5 months, PCR for antigen, re-test for 4 weeks, ear notch testing for antigen ELISA or PCR, bulk tank PCR for herd screen. Can do 10-animal young-stock screen at 9-15 months via Ab ELISA. Test all animals after positive results of PI, test for 12 months after removal.
• Control: Vaccination (prevents foetal infection, will not remove PIs), biosecurity (avoid buying from antibody-positive pregnant animals).

Salmonella

• Description: High infective dose or altered GIT motility allows bacteria to invade the small intestine. Most common in calves 2-6 weeks old. Zoonotic.
• Herd Level Risk Factors: Buying-in animals; direct contact with other animals, neighboring herds being seropositive, visitors not wearing appropriate PPE, increased herd size and stocking density, surface water on farm, liver fluke infestation on farm.
• Clinical Signs: Clinical signs - higher doses produce more severe clinical signs, acute enteritis ( +/- systemic involvement), pyrexia, severe watery feces, putrid odor, mucous, and fibrin casts, pneumonia, septicemia, arthritis, and sloughing of extremities, abortions 5-8 months
• Diagnosis: Enriched Salmonella faecal culture in clinically ill animals, Se 60 – 100%, isolation from chronic or treated animals is difficult, and culture of aborted foetal stomach.
• Treatment: Antimicrobials if septicaemic (TMPS, be cautious of resistance), fluids, NSAIDs, vaccination reduces abortions and shedding.
• Control Points: Calving pen management to reduce exposure, removal of calves, low stocking density, regular bedding and cleaning, pre-weaning management, and good colostrum. Avoid feeding waste milk, keep separate from cows, and hygiene.

Winter Dysentery

• Description: Acute, highly contagious disease causing watery diarrhea, mostly in housed adult dairy cows in the winter. Bovine Coronavirus is a probable cause. Faeco-oral route.
• Clinical Signs: Acute onset explosive diarrhea (sometimes dysentery), dark greenish-black color, may have blood and mucus. Variable anorexia/depression/dehydration, drop in milk production, mild respiratory signs, high morbidity but spontaneous recovery in 2 -3 days.
• Risk Factors: Diet changes, cold temperatures, high stocking density, poor ventilation, concurrent microorganisms.
• Diagnosis: Exclusion of other pathogens (BVD, Salmonella), negative cultures, and Coronavirus ELISA.
• Treatment: Mostly spontaneous recovery (3-5 days), supportive therapy (fresh water, palatable feed, free-choice salt, fluids - IV in severely affected).

Parasitic Gastroenteritis (Cattle)

• Type I: Late summer/early autumn, larvae ingestion causes immediate maturation of large numbers, dry summers transition to wet summers. Sudden, profuse green diarrhea, high morbidity, low mortality, potential for 10% weight loss.
• Type II: Infective larvae ingested from autumn onwards, arrested development (stage L4 within abomasal glands). Mass emergence late winter, profuse, unresponsive diarrhea, poor treatment response.
• Diagnosis: History, grazing pattern, weather, previous anthelmintic treatments, faecal egg counts (Type I probably high, Type II probably absent), pepsinogen levels.
• Treatment (Cattle): Type I: All anthelmintics (avoid resistance!), Type II: Group 3 anthelmintics (avermectin). Supportive therapy.
• Prevention (Cattle): Grazing management, strategic anthelmintic treatments (Type I: 3, 8 and 13 weeks post turnout, Type II: Ivermectin at housing); faecal egg counts.

Parasitic Gastroenteritis (Lambs)

• Cause: Nematodirus battus immature larvae (L3). Ingestion of infectious L3 from pasture during overwintered mass-hatches onto pasture following warm seasons ( >10°C, forecasts). Development in the small intestine.
• Clinical Signs: Weight loss, diarrhea, focal staining around perineum, dehydration, death (usually in spring in young lambs & later in season w/older ones).
• Diagnosis: Feco-specific tests helpful/unhelpful for monitoring efficacy; Clinical signs, and post-mortem.
• Treatment: Strategic benzimidazole anthelmintics (white drench).
• Control: Do not graze next-year's lambs on previous pastures (contamination). Use of risk forecast to predict mass hatchings of L3.

Acorn Poisoning

• Cause: Phenols and tannins
• Clinical Signs: Severe kidney damage, anorexia, depression, weight loss, rumen stasis, foetid tarry diarrhea, sudden death (4-7 days).
• Treatment: Supportive.
• Prevention: Avoid grazing around oak trees in autumn.

Yew Poisoning

• Cause: toxic alkaloids affecting heart muscle
• Clinical Signs: Sudden death. Muscle tremors, incoordination , nervousness, difficulty breathing, vomiting, diarrhea, and convulsions. Lethal dose of fresh material is 1-10g/kg BW. Usually even more toxic after cutting.
• Prevention: Prevent access.

Choke

• Cause: Oesophagus obstructed by food (e.g., root vegetables), foreign objects.
• Clinical Signs: Free-gas bloat, ptyalism, nasal discharge of food and water, may be bloated and in distress or recumbent. Sever free-gas bloat can cause asphyxia.
• Diagnosis: Inability to pass a stomach tube (if no other causes).
• Treatment: Trocar in left paralumbar fossa, massage free solid objects, caution with oesophageal rupture.

Jejunal Haemorrhage Syndrome

• Cause: Uncertain aetiology, often C. perfringens type A bacterial infection of the small intestines causing localized necrotizing hemorrhagic enteritis, leads to the formation of blood clots.
• Clinical Signs: Sudden onset of abdominal pain, progressing to sternal recumbency, shock, and death. Proximal accumulation of intestinal fluid and gas, varying degrees of anemia.
• Diagnosis: Often requires exploratory laparotomy or necropsy. Ultrasounds may help.
• Treatment: Supportive (hospital cases may try laparotomy to remove blood clots).

Obstructive Disorders

• Cause: Often unknown aetiology, often altered intestinal motility, mesenteric or caecocolic volvulus, ingestion of rapidly fermentable substrates, peritonitis adhesions, intussusception.
• Clinical Signs: Anorexia, reduced faecal output (mucous, blood tinged), sudden milk drop, cardiovascular effects, injected mucous membranes,.
• Diagnosis: Abdominal contour (lower right quadrant for small intestine distension), auscultation (pings & splashes), rectal examination (dilated caecum), ultrasound exam (right paralumbar fossa or rectum, small intestinal distension, increased peritoneal fluid), abdominocentesis (haemorrhagic - strangulating obstructions),

Peritonitis

• Primary: Subsequent to septicemia, injury, calving injuries, abomasal ulcers, TRP, intestinal torsion, liver abscess, surgery
• Secondary: Chronic or non-specific clinical signs, Localized vs Diffuse, Abdominal tenderness and rigidity, Pyrexia, anorexia, and milk drop, Rumen stasis and ileus, low faeces output. Chronic condition = fluid output. Acute condition = dry output.
• Diagnosis: Abdominal contour, auscultation for rumen stasis, abdominocentesis (protein >3g/dl, neutrophils), ultrasound for free fluid in abdomen, rectal examination for lack of movement of rectal wall, exploratory laparotomy.
• Treatment: Supportive fluids, NSAIDS, antibiotics (broad spectrum), surgery in necessary cases, debridement, irrigation and drainage (ultrasonography guided).
• Prognosis: Guarded.