Strangles is primarily diagnosed based on the characteristic clinical signs. Strangles is a very common disease in certain specific locations. For example, some horse barns are known to "harbor" a risk for this disease, and whenever the condition has already occurred in one horse, strangles should be highly suspected if another horse develops similar signs.
New cases of strangles are common following introduction of a new horse (possibly a carrier of strangles) onto a farm on which strangles has not been previously or recently identified. On the other hand, cases of strangles sometimes arise in new horses that are brought onto a farm where the disease is known to occur. Strangles is commonly diagnosed in horses that have been acquired at a horse sale barn.
The diagnosis of strangles is specifically corroborated by demonstrating Streptococcus equi through bacteriological culturing from fluids draining from abscesses or from the throat. In most horses, the pathogen disappears quickly following drainage of an abscess, so failure to identify the pathogen several days following abscess drainage should not rule out that strangles was present.
The most likely location from which a positive culture can be obtained in most horses is the guttural pouch. Culture of the guttural pouch is used to identify asymptomatic carriers. However, these carrier horses represent an important source for future infections of new horses and for contamination of the environment.
Affected horses should be isolated as soon as this disease is recognized, and specific protocols should be instituted in order to minimize the risk of transmitting the disease to other horses. Other horses at risk should be carefully monitored for signs of strangles (by measuring the rectal temperature on a regular basis).
Currently, it is strongly recommended that antibiotics (such as penicillin) should NOT be used in most typical cases of strangles. Rather, the affected horse should be monitored carefully and treated symptomatically. The use of antibiotics commonly leads to increased risk for complications of strangles and interferes with the development of immunity, thus prolonging the course of the infection.
Symptomatic treatments include strict rest, the provision of a soft ration (increased comfort during swallowing), vitamin supplementation and the use of non-steroidal anti-inflammatory agents, as needed, to increase comfort and to enhance water consumption and appetite.
It is important to encourage development and maturation of abscesses that are identified in the throat and under the jaw. A common misconception suggests that abscess development should be inhibited by the use of antibiotics. The fastest recovery can be anticipated for those horses in which an abscess develops and is ruptured to drain through the skin (or internally into the throat).
Although some horses develop more than one abscess before they resolve the infection (by the development of immunity), in most instances, rupture of a single abscess is needed before the recovery phase ensues. Certainly, the use of antibiotics interferes with both the maturation of abscesses and the development of immunity. Abscess maturation can best be accomplished using hot compresses held against the affected area. Your veterinarian knows when to facilitate drainage of an abscess (lancing) and may also base his/her decision on the ultrasonographic appearance of the maturing abscess.
In complicated or atypical strangles, the use of penicillin is usually indicated. Internal abscesses (metastatic strangles) at remote sites carry an unfavorable prognosis and must be treated with long-term antibiotic injections. Treatment of immune-mediated complications (purpura hemorrhagica, myositis, heart irregularity, and kidney disease) usually warrants the use of steroids alongside antibiotics.
Penicillin is usually administered to young foals affected with strangles.
It is usually necessary to insert a special tube (tracheotomy) into the wind pipe to assist breathing in those horses that develop very large abscesses near the larynx and which are presented in respiratory distress.
Severe infection of the guttural pouches may necessitate surgical drainage.