Special Veterinary Pathology

STRANGLES

Synonym : Adenitis equorum, distemper

Definition

Acute contagious disease of young horse characterized by sudden onset of fever, muco purulent inflammation of upper respiratory tract, followed by swelling and abscess formation on the submaxillary and pharyngeal lymph nodes and occasionally other parts caused by Streptococcus equi

Etiology

• Streptococcus equi - Streptococcus – Gram positive spherical chain occuring in man and animals

Transmission

• Inhalation is the most important route of infection. Ingestion is also possible

Pathogenesis

• Incubation period: 4 to 8 days.
• Infection of the pharyngeal and nasal mucosa an acute pharyngitis and rhinitis. Drainage to lymph node results in abscessation
• Infection spread to other organs causing suppurative process in the l ung, kidney, liver, spleen, brain, tendon sheath and joints
• After an attack of strangles has subsided, purpura haemorrhagica (many petechial or ecchymotic haemorrhages) may occur due to the development of sensitivity to streptococcal protein.

Clinical signs and lesions

• Oedematous swelling on the pharyngeal region producing dyspnoea giving an impression that the animal is strangling
• Abscess containing -Cream yellow pus
• Spread of infection through lymph and blood –produces abscess in lung, kidney, liver, spleen and brain.
• Abscesses in the retropharyngeal lymph nodes may drain into the guttural pouches, leading to empyema (accumulation of pus)
• Death may be due to septicemia and pyaemia

Diagnosis

• Bilateral nasal discharge
• Unilateral nasal discharge in the case of glanders.
• Purpura haemorrhagica is a complication of strangles sh owing subcutaneous oedema and haemorrhages.
• Demonstration of organisms in pus smears