Bovine Hemorrhagic Bowel Syndrome Study Guide

Overview and Clinical Importance

Hemorrhagic Bowel Syndrome (HBS), also known as Jejunal Hemorrhage Syndrome (JHS), is a sporadic, acute, and often fatal intestinal disease primarily affecting adult dairy cattle. First described in 1991, HBS is characterized by segmental necrohemorrhagic enteritis of the small intestine, predominantly the jejunum, leading to intramural hematoma formation and luminal obstruction.

The syndrome has emerged as an economically significant disease in North American and European dairy herds, with case fatality rates reported between 85-100%. Affected animals typically die within 12 to 48 hours after onset of clinical signs. While the exact etiology remains unclear, Clostridium perfringens type A and Aspergillus fumigatus have been implicated as potential causative agents.

Etiology and Pathophysiology

Proposed Etiologic Agents

The exact cause of HBS remains uncertain and is believed to be multifactorial. Two primary organisms have been implicated:

Clostridium perfringens Type A

C. perfringens type A is a normal inhabitant of the bovine gastrointestinal tract. It has been isolated from affected cattle at higher frequencies than from cattle with other intestinal diseases. The organism produces alpha toxin and in some isolates, beta-2 toxin, which may contribute to mucosal damage and hemorrhage. However, its ubiquitous presence in healthy cattle and rapid postmortem proliferation complicate interpretation of culture results.

Aspergillus fumigatus

A. fumigatus is a common mold in feed and forages. Research has detected fungal DNA in the blood and tissues of affected cattle. This organism can invade the gastrointestinal tract in immunosuppressed animals and secretes toxins that suppress blood clotting, potentially contributing to uncontrolled hemorrhage.

Pathogenesis

Recent pathological studies have elucidated the mechanism of lesion development in HBS. The primary lesion is characterized by:

• Mucosal erosions or lacerations: Small, dispersed erosions (4-45 mm) develop in the jejunal mucosa
• Lamina muscularis mucosae (LMM) splitting: Unique histological feature where the smooth muscle layer dissects
• Dissecting hemorrhage: Blood accumulates within the split LMM, creating an intramucosal hematoma
• Hematoma expansion: The hematoma propagates along the intestinal wall, causing luminal obstruction
• Mucosal detachment: The mucosa separates from the submucosa due to hemorrhage accumulation

Epidemiology and Risk Factors

Signalment and Demographics

Risk Factors

Clinical Signs and Physical Examination

Clinical Presentation

HBS presents as a peracute to acute syndrome. Affected cattle may be found dead without premonitory signs, or present with rapid deterioration over 12-48 hours.

Exam Focus: The "ping" on right-sided auscultation can mimic right displaced abomasum (RDA). However, HBS presents with more severe systemic signs (shock, pallor) and melena. Many cows initially diagnosed with RDA are ultimately found to have HBS at surgery.

Diagnosis

Diagnostic Approach

Definitive diagnosis of HBS is challenging antemortem and is often confirmed at exploratory laparotomy or necropsy. A presumptive diagnosis can be made based on clinical presentation combined with supportive diagnostic findings.

Ultrasonography

Transabdominal ultrasonography is the most useful antemortem diagnostic tool:

• Dilated small intestinal loops: Diameter greater than 4-12 cm (normal less than 3 cm)
• Amotile intestines: Absence of normal peristalsis
• Homogeneous echogenic material: Consistent with intraluminal blood clots (seen in approximately 19% of cases)
• Fluid between intestinal loops: With or without fibrin strands

Laboratory Findings

Differential Diagnosis

Pathology

Gross Pathology

At laparotomy or necropsy, HBS is characterized by a distinctive lesion in the small intestine:

• Location: Predominantly the jejunum (distal jejunum most commonly affected)
• Appearance: Segmental, dark red to purple, distended intestinal loop
• Serosal surface: Severe subserosal hemorrhage; fibrin tags may be present
• Affected segment: Firm, coiled, and distended
• Cross-section: Reveals INTRAMURAL hematoma with detached mucosa
• Intestinal contents: Dark clotted blood in cecum and colon

Histopathology

• Lamina muscularis mucosae splitting: Pathognomonic finding - dissection of the smooth muscle layer
• Massive submucosal hemorrhage: Blood accumulation in submucosa and lamina propria
• Mucosal detachment: Mucosa separated from intestinal wall by hematoma
• Fibrinoid vascular necrosis: In submucosa adjacent to hemorrhagic areas
• Inflammatory infiltrate: Neutrophils, eosinophils, and lymphocytes
• Gram-positive bacilli: May be present in necrotic areas

Treatment and Management

Treatment of HBS is challenging with poor outcomes regardless of approach. The overall mortality rate is 77-100%. Economic considerations often favor euthanasia.

Surgical Treatment

Surgery offers the best chance for survival when performed early, though prognosis remains guarded. Three surgical approaches have been described:

Medical Treatment

Prevention and Control

No definitive preventive strategies have been identified. Management recommendations are based on reducing known risk factors:

Nutritional Management

• Avoid sudden diet changes, especially increases in fermentable carbohydrates
• Ensure adequate effective fiber in TMR diets
• Monitor feed quality; avoid moldy or spoiled feeds
• Proper silage management to reduce fungal contamination

Vaccination

Vaccination against C. perfringens types C and D has shown anecdotal short-term benefit in some herds, though no controlled studies confirm efficacy. Vaccines containing high levels of alpha toxoid may be beneficial. Vaccination 2-3 times yearly has been recommended by some practitioners.

Feed Additives

Anecdotal reports suggest that certain feed additives (such as OmniGen-AF) may reduce HBS incidence by supporting immune function, though controlled studies are pending.

Prognosis