Parker County Today October 2017 - Page 78

our expertise: VET COLUMN Get A Grip On “Strangles” BY TOM HUTCHINS, DVM, DABVP Dr. Tom Hutchins S 76 trangles is caused by the organism Streptococcus equi subspecies equi (S. equi). The infection is an acute respiratory infection characterized by fever, lethargy, nasal discharge, respiratory noise and regional lymph node abscessation. Some horses may exhibit signs of difficulty eating or swallowing and coughing. S. equi is inhaled or ingested after direct contact with purulent discharge from infected horses or contaminated equipment. Eventually it spreads to the regional lymph nodes, such as the submandibular or the retropharyngeal lymph nodes. The submandibular lymph nodes are between the jaw bones and just in front of the throat latch. This is the common site that many people notice enlargement. The retropharyngeal lymph nodes lie just above and behind the larynx and often times swelling is not noted until they become large enough to see swelling behind the jaw bones and above the throat latch. Fever occurs 3-14 days after exposure. Nasal shedding of the organism occurs 2-3 days after the onset of fever, persisting for 2-3 weeks. Seventy- five percent of horses develop immunity after natural infection that can last up to five years. Older horses can develop a mild form of strangles. Disease occurs sporadically on farms, but once present, infection rates will depend on the age of the animals (ranging from 32% to 100%). Death rates are generally very low in uncomplicated cases (<2%) but higher for cases of bastard strangles where the infection has spread to other locations throughout the body. Definitive diagnosis via cultures from nasal swabs, nasal washes, guttural pouch washes, or pus aspirated from abscesses is the gold standard. Diagnostic imaging is typically not performed in uncomplicated cases. Swellings of the upper respiratory tract can obstruct the airway which can be seen on radiographs. Abscesses in the abdomen may be detected with ultrasound depending on the location of the mass. Endoscopy and radiographs of the guttural pouches aid in the diagnosis. A dry and isolated stall, rest, and soft, moist palatable food may be all that are necessary while letting the disease run its course. Early phase of the fever and depression can be treated with antibiotics but this will prevent protective immunity in the future. It can prevent the formation of abscessation. Antibiotic treatment is controversial because it has been argued that this will make the animal more susceptible to infection and further abscess formation in other lymph nodes. Horses with lymph node abscesses can benefit from hot-packing or topical treatment with ichthammol to encourage maturation of the abscess and drainage, followed by flushing with an antiseptic solution once opened. Judicious use of anti-inflammatories can decrease swelling and promote eating. Horses with complications