Page 658 - The Veterinary Care of the Horse

Recovered animals should not be turned out into the same field as healthy horses for 6–8
•
weeks after the symptoms have resolved as they could still be a source of infection.
VetBooks.ir CONTROL MEASURES

• When an outbreak occurs, any horse developing a temperature or a nasal discharge

should be segregated from unaffected horses.
• Horses recovering from the infection may shed bacteria for at least 6 weeks following

apparent recovery. To test for this the horse should have three nasopharyngeal swabs or
guttural pouch washes taken within a 2-week period. If none grow Streptococcus equi

then the horse is unlikely to be a source of infection to others.
• The whole yard should be treated as an isolation area until 4 weeks after the last abscess

has healed. No new horses should be allowed into the yard and no horses should go to
public events such as shows or lessons, or visit other yards until they have had three

negative nasopharyngeal swabs.

A comprehensive document entitled ‘Strategy to eradicate and prevent strangles (STEPS)’
can be found in the HBLB Code of Practice 2019 (codes.hblb.org.uk)

CARRIERS

The strangles story is further complicated by carriers: the apparently healthy horses
harbouring the disease. Some horses can remain as carriers or shedders for a year or even

longer. This makes disease control and elimination of the infection difficult and is the usual
explanation for a spontaneous outbreak. Although the vet can test if a horse is a carrier by
taking swabs from the nasopharynx or by collecting samples via an endoscope, some horses

only shed the bacteria intermittently. Thus in most, but not all, cases if three swabs are
negative, the horse is clear. As it cannot completely guarantee a horse is free from infection,

vigilance is still required.

THE GUTTURAL POUCH

Around 10% of animals can become chronic carriers and intermittent shedders of the bacteria

due to a low-grade persistent infection of the guttural pouch. This may occur if the
retropharyngeal lymph nodes burst and drain into the guttural pouch. Such infections require
drainage and flushing of the guttural pouches as they do not respond to systemic antibiotic

therapy alone. In some cases solid lumps of dried pus known as chondroids form in the
guttural pouches and must be removed. These horses are identified with a guttural pouch

wash, six weeks after apparent recovery.