An outbreak of strangles in young ponies.

This research paper describes an occurrence of a strangles disease outbreak among 19 young experimental ponies in Glasgow University veterinary school, discussing the clinical signs, morbidity, treatment, and post mortem studies, along with detailed microbiological analysis.

Outbreak and Clinical Symptoms

• In the paper, the researchers explore an outbreak of strangles, a contagious respiratory disease caused by the bacterium Streptococcus equi, in a group of 19 young ponies.
• 11 ponies were diagnosed with the disease within the first two days upon their arrival at Glasgow University veterinary school, while five more showed clinical signs within the next four days. This resulted in an overall morbidity rate of 84%.
• The symptomatic ponies exhibited typical signs of strangles such as general dullness, anorexia, fever, swollen lymph nodes, occasionally leading to the rupture of the lymph node, an inflammatory condition of the eye (conjunctivitis), and a nasal discharge containing both mucus and pus.

Treatment Outcomes and Mortality Rates

• Nine out of the affected ponies were euthanised during the clinical phase of the disease for post mortem studies, to understand the impact and spread of the disease.
• The duration of the disease in the remaining seven affected ponies lasted approximately 21 days, although one pony had to be put down 10 days post clinical signs due to the development of septic arthritis.

Investigation and Laboratory Results

• All of the affected ponies demonstrated an increase in the number of white blood cells (neutrophils) and high plasma fibrinogen levels, a significant response to inflammation or tissue damage.
• From 18 out of the 19 ponies, beta-haemolytic streptococci, a type of bacteria that damages red blood cells and is associated with various infections, were isolated via nasopharyngeal swabbing.
• However, Streptococcus equi, the bacterium notoriously associated with the strangles disease, was confirmed only in three animals within the first four days of the outbreak. Most of the other bacterial isolates identified to species level were S. zooepidemicus, another species of Streptococcus.
• It’s further noted that the beta-haemolytic streptococci bacteria were still present in six ponies even 40 days after they clinically recovered. Additionally, the bacteria were regularly isolated from three ponies who did not develop any clinical strangles symptoms but remained in proximity with affected animals all through the study.