Strangles

Strangles represents one of the most contagious diseases you'll encounter in horses, causing throat infections characterized by fever, nasal discharge, and swelling and abscessing of the lymph nodes under the jaw. The disease gets its unfortunate name from the risk that severe abscessing can compress the throat and literally strangle the horse if it becomes extensive, though this is rare with modern treatment. You'll recognize strangles by its distinctive presentation - a sick horse with swollen cheeks and jaw area, often accompanied by yellow or purulent nasal discharge.

The causative organism is Streptococcus equi, a bacteria highly adapted to horses and relatively easy to transmit between infected and exposed animals. A single horse with strangles can infect an entire barn within days if precautions aren't taken. The disease spreads through respiratory secretions, contaminated equipment, and contact with infected discharge. Even recovered horses can shed bacteria for weeks or months, making quarantine and isolation critical for control.

You've probably heard strangles discussed with a mix of respect and wariness in horse communities, and rightly so. While strangles is almost always survivable with proper treatment and care, it causes significant illness, creates tremendous economic hardship when it breaks out in a barn or facility, and requires serious quarantine measures to prevent spread. Horses with strangles are highly contagious, and owners of exposed horses face the reality that their animals will likely get sick despite best efforts at prevention.

The disease typically affects horses of all ages but is particularly common in young horses, newly purchased animals, or horses under stress. Once a horse recovers from strangles, he usually develops immunity, though reinfection can occur. Understanding strangles, recognizing early signs, and knowing how to manage the disease appropriately helps minimize its impact on your horse and prevents transmission to others.

This guide explains what strangles is, how it spreads, what symptoms to watch for, how veterinarians diagnose and treat it, and what management practices prevent transmission. You'll understand how to care for an affected horse, when to isolate animals, and what recovery looks like. Armed with this knowledge, you can respond quickly to suspected strangles and work effectively with your veterinarian to minimize the disease's impact.

Strangles is caused by Streptococcus equi, a bacterium that evolved specifically to infect horses. This pathogen is highly contagious and spreads efficiently between horses through respiratory secretions. When an infected horse coughs, sneezes, or has nasal discharge, bacteria-laden droplets contaminate the environment and anything the discharge contacts. Other horses that inhale these droplets or contact contaminated equipment become infected and typically develop clinical disease within days.

Direct contact with infected discharge is the most common transmission route. A horse that shares a water bucket with an infected horse, eats from contaminated hay, or has contact with discharge from an infected horse easily contracts the disease. Even casual contact in a shared paddock or across stall partitions can result in transmission, particularly if respiratory secretions are present. The bacteria can survive briefly on fomites (objects like halters, buckets, or equipment), making indirect transmission possible if contaminated items contact the nose or mouth of exposed horses.

CloseLivestock gatherings and new horse introductions represent high-risk situations for strangles transmission. A newly purchased horse incubating strangles can infect the entire herd. Horse shows, sales, or training facilities where horses from multiple sources gather create perfect conditions for spread. A single sick horse in a multi-horse facility can expose everyone within days.

Young horses face higher risk of developing clinical strangles than older horses, though age isn't absolute protection. Foals and weanlings show higher disease rates, likely due to incomplete immunity and potentially weaker immune response. Newly weaned foals separated from maternal antibodies become particularly vulnerable. This age susceptibility explains why strangles outbreaks in young horse populations are common and sometimes severe.

Stress predisposes horses to developing clinical disease after exposure. Transportation, training, competition, diet changes, or co-infections with other viruses lower immune responsiveness and increase likelihood of clinical illness. A horse exposed to strangles while under stress is more likely to develop disease than one exposed while healthy and unstressed. This explains why newly arrived horses under the stress of adjustment sometimes develop strangles shortly after arrival.

Underlying health problems increase disease risk and severity. Horses with previous respiratory disease, parasitic infections, or other systemic illnesses show higher strangles disease rates. Nutritional deficiency or poor body condition might increase susceptibility. The organism takes advantage of any immune system compromise to establish infection and cause disease.

Previously uninfected horse populations face highest risk of severe strangles outbreaks when the organism is introduced. Herds where many horses have prior immunity experience less severe disease and slower spread. In contrast, a strangles-naive herd suddenly exposed can experience devastating outbreaks affecting many or all horses simultaneously. Geographic areas where strangles is rare might see sudden outbreaks when the organism appears, affecting naive populations.

Early signs of strangles include fever, lethargy, and decreased appetite. Your horse might seem sick and unwilling to eat, with obvious fever (temperature typically 102-104 degrees Fahrenheit). Some horses show mild respiratory signs initially - slight cough or minimal nasal discharge. These early signs might be subtle, easily missed, or attributed to other causes. Within days, more obvious signs develop.

Swelling under the jaw becomes the characteristic sign of strangles. The lymph nodes in this area enlarge dramatically, creating visible swelling on one or both sides of the jaw. This swelling progresses from simple enlargement to obvious lumps that might make the jaw appear asymmetrical. The swelling is typically firm and possibly tender. Some horses show dramatic swelling that makes their entire head look distorted.

Nasal discharge typically appears as the disease progresses. Initially, discharge might be serous (clear and watery), but it quickly becomes mucopurulent (thick, yellow, and creamy) as bacteria proliferate. The discharge can be profuse, coating the nostrils and dripping from the nose. A horse with strangles might look very sick with a filthy discharge-covered face.

Cough develops as the disease affects the respiratory tract. Some horses develop significant cough, though cough severity varies. The cough is often productive of discharge. Coughing continues for several days and gradually resolves as the acute disease phases into abscess development.

Difficulty swallowing or pain on swallowing occurs as throat inflammation develops. Some horses show reluctance to eat or drink due to throat pain. Affected horses might eat or drink differently, appearing uncomfortable during eating. Severe throat involvement can cause dysphagia (difficulty swallowing) that affects nutrition.

Abscess formation typically begins within one to two weeks of symptom onset. The swollen lymph nodes under the jaw develop into obvious abscesses that might rupture and drain purulent material. One or multiple abscesses might form. Rupture typically provides relief as pressure and pain decrease. Drainage can be impressive - a single abscess might drain large volumes of thick, smelly pus. After rupture and drainage, recovery typically begins.

Unusual presentations occur in some horses. Some horses develop submandibular or retropharyngeal abscesses rather than those in the standard jaw location, creating different swelling patterns. Bastard strangles describes disseminated infection affecting internal lymph nodes, creating systemic illness without obvious external swelling - a more serious form requiring different management.

Completely asymptomatic shedding occurs in some horses that carry and spread the organism without showing clinical disease, making them silent disease sources that complicate control and prevention efforts.

Clinical diagnosis based on typical signs is often obvious - a fever-sick horse with swollen jaw and purulent nasal discharge almost certainly has strangles. However, confirmation through culture or PCR testing is important for diagnosis certainty and for determining when quarantine can safely end. Nasal swab or discharge samples sent for bacterial culture confirm Streptococcus equi and sometimes provide antibiotic sensitivity information.

PCR testing provides rapid confirmation, sometimes within twenty-four hours, compared to bacterial culture which requires several days. PCR can detect bacterial DNA even from horses that aren't actively shedding bacteria, potentially identifying carriers. The choice between culture and PCR sometimes depends on facility capabilities and test availability.

Hemogram (blood test) sometimes shows elevated white blood cell count and other signs of bacterial infection. However, blood work isn't required for diagnosis when clinical signs and culture/PCR results are available.

Treatment focuses on supportive care and managing the disease process. Most horses recover with rest, good nutrition, and supportive care. Complete rest is essential - no work or even lunging during acute illness. A quiet environment with good hay and water encourages recovery. Many horses lose appetite initially but gradually return to eating as illness phases into abscess development and recovery.

Antibiotics are somewhat controversial in strangles management. Early high-dose systemic antibiotics (before abscess formation) might prevent abscess development and reduce disease severity, though they might also drive the disease underground, creating chronic infections. Many practitioners use antibiotics early in disease if horses are very ill or if prevention of abscess formation is desired. Once obvious abscess formation has occurred, systemic antibiotics are less beneficial. Local abscess treatment becomes more important than systemic antibiotics at that point.

Abscess management after rupture involves gentle flushing of the cavity with dilute antiseptic solutions. Frequent flushing removes pus and debris, promotes continued drainage, and accelerates healing. Hand-walking or light exercise encourages continued drainage and healing. Some practitioners prescribe topical treatments or medications applied to the abscess cavity.

Pain management with non-steroidal anti-inflammatory drugs helps affected horses feel better and encourages eating. Fever management and pain control improve quality of life during acute illness.

Complications can occur but are rare with appropriate treatment. Severe airway obstruction from throat swelling is uncommon but potentially life-threatening. Bastard strangles (internal abscess formation) requires aggressive treatment and carries worse prognosis. Acute kidney injury or other systemic complications occur rarely but might indicate need for intensive care.

Recovery typically takes two to four weeks from onset of clinical signs. Most horses return to normal health, appetite, and function within this timeframe. Some horses take longer to fully recover, particularly those with severe disease or complications.

Isolation and quarantine are absolutely critical to prevent transmission. A horse with suspected or confirmed strangles must be completely isolated from other horses. Stabling in a separate facility or a separate barn is ideal. Minimum acceptable is a separate paddock with no shared facilities with other horses. Complete separation of equipment, grooming supplies, tack, and anything else the horse contacts is essential. Caregivers should not move between the sick horse and healthy horses without changing clothes and thoroughly washing hands.

Hygiene measures prevent spread of bacteria in the environment. Discharge-contaminated areas should be cleaned and disinfected. Stall surfaces, buckets, and any contaminated equipment should be disinfected with appropriate cleaners effective against Streptococcus equi. Hand washing between handling the infected horse and any other contact is non-negotiable.

Nutrition during illness should encourage eating despite appetite loss. High-quality hay, preferred feeds, and treats encourage consumption. Soaked hay or feed might be easier to swallow for horses with throat pain. Fresh water continuously available is essential. Most horses gradually return to normal eating as illness resolves.

Exercise must be strictly limited during acute illness. Complete stall rest during the fever and acute phase is appropriate. Once fever breaks and the horse begins recovering, hand-walking provides gentle activity that encourages recovery. Gradually, light exercise can be resumed as the horse recovers completely. Return to work should be conservative, gradually increasing activity only after complete recovery.

Discharge management helps maintain sanitation. Regular cleaning of the muzzle and face removes dried discharge. Changing contaminated bedding frequently limits environmental bacteria accumulation. Some horses are kept in stalls with excellent drainage during acute illness to manage the impressive discharge volumes.

Direct abscess care after spontaneous rupture or after therapeutic lancing involves flushing the cavity with warm, dilute antiseptic solution. Daily or twice-daily flushing for several days promotes continued drainage and healing. Gentle manipulation encourages continued pus drainage. Hand-walking in the sun encourages healing and drainage.

Plannedlancing of abscesses is sometimes performed when abscesses are very large, causing severe swelling or potential airway compromise. Your veterinarian can assess whether lancing would benefit your horse's specific situation.

Monitoring for complications throughout the recovery period alerts you to problems needing veterinary attention. Increased fever, severe respiratory distress, inability to eat, or other concerning signs warrant immediate veterinary evaluation. Most horses recover uneventfully, but complications can occur requiring intensive management.

Vaccination against strangles is available and provides some protection, though vaccination doesn't prevent strangles entirely. Vaccinated horses might still contract strangles but often experience milder disease. Multiple vaccination products are available, with varying efficacy. Consult your veterinarian about whether vaccination makes sense for your situation and which vaccine to use. Vaccination is particularly recommended for horses at high risk - young horses, those attending shows or sales, or those at facilities with frequent disease exposure.

Quarantine of newly purchased horses prevents introducing strangles to your existing herd. A two-week quarantine period allows time for strangles to develop if the new horse is incubating the disease. Isolating new arrivals completely until you're confident they're healthy protects your existing herd. Some facilities extend quarantine to four weeks for maximum safety.

Managing exposed horses depends on exposure risk assessment. Horses that had potential exposure might benefit from prophylactic treatment, isolation, or increased monitoring. Your veterinarian can advise on appropriate management for horses with potential exposure based on specific exposure circumstances.

Nutrition and general health management support immune function and disease resistance. Well-nourished, healthy horses in good body condition show better disease resistance than stressed or poorly maintained animals. Maintaining good body condition, providing excellent nutrition, and minimizing stress support overall health.

Prognosis for strangles recovery is generally excellent with appropriate treatment and management. Most horses recover completely without lasting problems. Mortality from strangles alone is rare with modern treatment. Some horses develop chronic drainage or carrier status where they continue shedding bacteria, requiring ongoing isolation and management.

Complications can worsen prognosis. Bastard strangles with internal abscessing carries worse prognosis. Extreme airway compromise threatening suffocation would require emergency intervention. These complications are fortunately rare, and most horses have straightforward disease courses and excellent recovery.

Long-term immunity after natural strangles infection is generally solid, though reinfection can occur. Once a horse has had strangles, likelihood of reinfection from future exposure is lower than for naive horses. However, reinfection is possible, particularly if exposed to particularly virulent strains or if time has eroded immunity.

The herd management implications of strangles are significant. One infected horse can compromise an entire population if exposed. Prevention through quarantine of new horses, vaccination when appropriate, and good biosecurity practices protects herd health. Should strangles enter your facility, aggressive isolation and management of affected horses limits spread and allows the disease to run its course in affected individuals while protecting unexposed horses.