Describe the etiology, clinical signs, postmortem lesions and control of hemorrhagic septicemia in buffaloes.

Etiology of Hemorrhagic Septicemia

The primary causative agent of HS is *Mannheimia haemolytica*, although other bacteria like *Pasteurella multocida* and *Actinobacillus pleuropneumoniae* can also be involved. The bacterium is ubiquitous in the environment and commonly found in the respiratory tract of healthy animals. HS typically occurs in young, rapidly growing animals or those experiencing stress due to nutritional deficiencies (particularly phosphorus), poor management, or sudden environmental changes. The bacteria produce potent toxins (alpha-toxin, gamma-toxin) that cause widespread necrosis and hemorrhage.

Clinical Signs

HS is notoriously acute, with animals often appearing healthy and then succumbing rapidly. Early signs are often subtle and easily missed:

• Fever: A sudden increase in body temperature (often >104°F or 40°C) is a common, though not always present, initial sign.
• Lethargy: Animals become depressed and unresponsive.
• Loss of Appetite: Refusal to eat or drink.
• Respiratory Distress: Labored breathing, dyspnea.
• Lameness: Sudden onset of lameness, often affecting multiple limbs. This is a key diagnostic clue.
• Hemorrhages: Bleeding from the nose, mouth, or rectum may be observed in advanced stages.

The rapid progression of the disease often leads to sudden death, making diagnosis challenging until postmortem examination.

Postmortem Lesions

Postmortem examination reveals characteristic lesions:

• Extensive Hemorrhages: Large areas of subcutaneous, intramuscular, and serosal hemorrhages, particularly in the neck, chest, and abdominal regions. These appear as dark, bluish-black discoloration.
• Necrotic Tissue: Areas of necrosis and tissue damage, often with gas bubbles.
• Edema: Swelling of the tissues.
• No Lesions in Internal Organs: Importantly, internal organs often appear relatively normal, which can complicate diagnosis.
• Characteristic Odor: A foul, putrid odor may be present.

The absence of lesions in internal organs is a key differentiating factor from other diseases with similar clinical signs.

Control of Hemorrhagic Septicemia

Control of HS requires a multi-faceted approach:

Prevention

• Vaccination: This is the most crucial control measure. Formalin-killed vaccines are widely used. Booster doses are necessary to maintain immunity. Vaccination is typically done annually, starting at 3-6 months of age.
• Improved Nutrition: Ensuring adequate phosphorus intake through mineral supplementation is vital. Phosphorus deficiency weakens the immune system and increases susceptibility.
• Stress Reduction: Minimizing stress through good management practices, proper housing, and avoiding overcrowding.
• Biosecurity: Strict biosecurity measures to prevent the introduction and spread of the disease.

Diagnosis

• Clinical Suspicion: High index of suspicion based on clinical signs, especially lameness.
• Postmortem Examination: Characteristic lesions are diagnostic.
• Bacterial Isolation & Identification: Isolation of *Mannheimia haemolytica* from tissue samples.
• PCR: Polymerase Chain Reaction (PCR) can be used to detect the bacterial DNA.

Treatment

Treatment is often unsuccessful due to the rapid progression of the disease. However, supportive therapy may be attempted:

• Antibiotics: Broad-spectrum antibiotics may be administered, but their effectiveness is limited.
• Fluid Therapy: To combat shock and dehydration.
• Anti-inflammatory Drugs: To reduce fever and inflammation.

Rapid diagnosis and preventative measures are far more effective than treatment.

Aspect	Details
Causative Agent	Mannheimia haemolytica (primarily), Pasteurella multocida, Actinobacillus pleuropneumoniae
Primary Risk Factors	Phosphorus deficiency, poor management, stress, sudden environmental changes
Key Clinical Sign	Sudden lameness
Major Control Measure	Vaccination