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Recent research underscores the difficulty in identifying “silent carriers” of strangles---horses who can continue to infect herdmates months after an outbreak seems to have subsided.
Caused by Streptococcus equi bacteria, strangles is characterized by a high fever, depression, appetite loss and enlargement of the lymph nodes between the jawbones. Thick, yellow pus may drain from the infected horse’s nostrils, and abscessed nodes in the throat may burst and drain. In severe cases, large abscesses may obstruct the airways, causing the horse to struggle to breathe, hence the disease’s descriptive name.
Strangles can spread rapidly through a herd as
S. equi bacteria are shed in mucus and airborne droplets. Isolating sick horses is a key part of controlling an outbreak, but some infected horses do not show signs of illness, making them difficult to identify. These horses, known as “silent carriers,” can continue to introduce infection to susceptible members of the herd for months or even years.
Looking for a way to detect silent carriers, researchers at the Swedish University of Agricultural Sciences in Uppsala, the Equine Veterinary Clinic in Destedt, Germany, and the Animal Health Trust in Suffolk, England, joined forces to study more than 100 horses involved in three different strangles outbreaks.
Six to 10 months after each outbreak began, the researchers examined all the horses on the affected farms, looking for fever, swollen lymph nodes, nasal discharge or other residual effects of strangles.
They also performed nasopharyngeal lavage, as well as guttural pouch endoscopy and lavage, on the horses, and used polymerase
Some horses infected with Streptococcus equi bacteria show no signs of illness but can introduce infection to susceptible herdmates for months or even years.