Strangles is a highly contagious respiratory disease characterised by fever, depression, anorexia, pussy nasal discharge, cough and abcessation of the lymph nodes of the head and neck; and has been rated as amongst the most important endemic horse diseases by the equine industry.
An Australian study Strangles in Horses investigated the very early interactions between the horse and Streptococcus equi subsp. equi (the bacteria which causes Strangles), to identify the early developmental signs to enable improved control strategies and the ability to develop improved vaccines for prevention. (P.J. Canfield, D.N. Love, J.Rainger, G.D. Bailey, Strangles in Horses, RIRDC Project US – 24A, February 2000)
The early changes identified by the study occur before the traditionally recognised Strangles signs of swelling of the lymph nodes of the head and neck; and before the excretion of organisms from the horse’s nose.
Signs for the early development of Strangles:
- Increase in the horse’s temperature
- Elevation of total white blood cell count
- Changes in size and texture of the submandibular nodes
The study also found that nasal discharge and the excretion of Streptococcus equi subsp. equi are not necessarily associated. With some horses able to carry Strangles organisms, excreting them into the environment without showing any signs of nasal discharge or other signs of the disease, especially some time after infection.
Additionally many horses which develop Strangles and show clinical signs do not go on to develop the classic abscessed lymph nodes or pussy nasal discharge. These horses however may excrete Streptococcus equi subsp. equi from their nasal passages and be a source of infection to other susceptible horses.
Both of these types of horses create a significant risk to the control of Strangles on the stud farm.
Recommendations for Strangles Control:
- Education of stud workers of the early warning signs for the detection of subtle changes in the horse
- Vaccinate all horses
- Quarantine suspect horses
- Seek veterinary attention for suspect cases to identify and treat the disease
- Include the taking nasal swabs of suspect horses for bacteriological examination in routine procedures
- Take tissue samples from the guttural pouches for the diagnosis of infected carrier horses or horses suspected of early infection.