Strangles is a bacterial infection that is highly contagious and affects horses. It is caused by Streptococcus equi and can be transmitted through horse-to-horse contact and environmental factors.
Fever, loss of appetite, swollen lymph nodes, nasal discharge, and the formation of abscesses characterize Strangles. Timely diagnosis, appropriate treatment, and implementation of preventive measures are crucial in managing this disease effectively.
This article will explore the causes, symptoms, diagnosis, treatment, and prevention of strangles in horses.
What are Strangles in Horses?
Strangles is a highly contagious bacterial infection that affects horses. It is caused by the bacterium Streptococcus equi. The infection spreads through direct contact between horses or indirect means, such as humans, tack, drinking troughs, and other environmental factors.
The disease gets its name from one of its prominent symptoms: swelling and inflammation of the lymph nodes in the throat and under the jaw. This swelling can cause difficulty in swallowing, and horses may hold their heads low with their noses extended forward to alleviate discomfort and aid breathing.
Other common signs include a sudden onset of fever (high temperature), loss of appetite, and a nasal discharge that starts as a thin watery fluid and progresses to thick yellow pus.
As the infection progresses, abscesses form within the affected lymph nodes. These abscesses can rupture externally or internally into the back of the throat, releasing thick yellow pus. Most horses recover fully after the abscesses rupture and the infection resolves, but veterinary assistance should be sought promptly.
Younger horses are more susceptible to strangles, but horses of any age can be affected. However, older or debilitated horses are at higher risk of infection or reinfection. Once a horse recovers from strangling, it develops immunity to the infection for several years.
Causes of Strangles in Horses
Strangles in horses is caused by the bacterium Streptococcus equi. The bacterium is highly contagious and can be transmitted through direct or indirect horse-to-horse contact. Here are the primary causes and modes of transmission for strangles:
Bacterial Infection: The primary cause of strangles is the infection with Streptococcus equi bacteria. The bacterium enters the horse’s body through the respiratory tract, typically inhaling respiratory droplets that infected horses expel. The bacteria then colonize and multiply in the lymph nodes of the upper respiratory system, leading to the characteristic symptoms and abscess formation.
Direct Horse-to-Horse Contact: Strangles is highly contagious among horses. The infection can spread when healthy horses come into close contact with infected horses, particularly through respiratory secretions. This can occur during nose-to-nose contact, sharing of water troughs, feeding from the same manger, or contact with objects contaminated by infected horses, such as tack, grooming equipment, or shared stabling.
Humans: Humans can act as carriers of the Streptococcus equi bacteria, although they do not typically become sick themselves. However, humans can transmit the bacteria to horses through direct contact. This can occur when handling infected horses, contaminated objects, or through inadequate hygiene practices.
Fomites: Inanimate objects or fomites can also play a role in transmitting the bacteria. Contaminated objects, such as water buckets, feed containers, grooming equipment, or shared tack, can harbor the bacteria and spread it to other horses. Depending on environmental conditions, the bacteria can survive on surfaces for varying periods.
Once a horse recovers from strangling, it can still act as a carrier of the bacteria. Carrier horses often harbor the bacteria in their guttural pouches, a small sac-like structure in the upper respiratory tract. These carrier horses may not show signs of illness but can intermittently shed the bacteria and infect other horses, particularly during stress or immunosuppression.
Strangling prevention relies on good biosecurity measures, such as isolating new horses, practicing proper hygiene, disinfecting equipment, and minimizing contact between horses to reduce the risk of transmission.
Symptoms of Strangles in Horses
The symptoms of strangles in horses can vary in severity but typically include the following:
Fever: One of the early signs of strangles is a sudden onset of fever. The horse’s body temperature may rise significantly above the normal range (usually above 101.5°F or 38.6°C).
Loss of Appetite: Infected horses often exhibit a decreased appetite or may refuse to eat altogether. They may show disinterest in their usual feed or hay.
Difficulty Swallowing: Strangles can cause discomfort and swelling in the lymph nodes of the throat, which can lead to difficulty swallowing. Horses may exhibit pain or resistance when attempting to eat or drink.
Swollen Lymph Nodes: The most characteristic symptom of strangles is the swelling of the lymph nodes. The swelling can be visually noticeable, forming firm, hot, and painful masses. The lymph nodes located under the jaw and in the throat area become enlarged and sensitive.
Nasal Discharge: Initially, the nasal discharge in strangles is usually thin and watery. As the infection progresses, it becomes thicker and yellow. The discharge may be accompanied by coughing or sneezing.
Abscess Formation: Within a few days of the initial symptoms, abscesses typically develop in the swollen lymph nodes. These abscesses can vary in size and number. The abscesses may sometimes rupture and release thick, yellow pus externally or internally into the throat.
Respiratory Distress: The swelling of the lymph nodes in the throat can cause respiratory distress in severe cases. Horses may hold their heads low and extend their necks to ease breathing. They may exhibit labored breathing, rapid breathing, or audible breathing sounds.
It is important to note that the severity of symptoms can vary among individual horses. Some horses may experience mild symptoms and recover relatively quickly, while others may develop more severe complications or a chronic disease known as “bastard strangles.” Prompt veterinary attention is recommended for properly diagnosing, treating, and managing strangles in horses.
Diagnosis of Strangles in Horses
The diagnosis of strangles in horses is typically based on a combination of clinical signs, history, and laboratory tests. A veterinarian will perform a thorough examination and may employ the following diagnostic methods:
Physical Examination: The veterinarian will assess the horse’s overall health and look for characteristic signs of strangles, including fever, swollen lymph nodes, nasal discharge, and respiratory distress. They will also inquire about the horse’s medical history and recent exposure to other horses.
Nasal Swab: A swab sample may be taken from the nasal discharge to test for the presence of Streptococcus equi bacteria. The swab is then sent to a laboratory for culture and bacterial identification.
Lymph Node Aspiration: If abscesses are present in the lymph nodes, the veterinarian may perform an aspiration or fine-needle aspiration to collect a sample of the pus or fluid from the abscess. This sample can be sent to a laboratory for analysis, including bacterial culture, to confirm the presence of Streptococcus equi.
Blood Tests: Blood samples may be taken to evaluate the horse’s white blood cell count and inflammatory markers. An elevated white blood cell count and increased inflammatory markers indicate an active infection.
Serology: Blood samples may also be tested for antibodies against Streptococcus equi. Serology can help determine if the horse has been exposed to the bacteria in the past or has developed an immune response.
Different diagnostic methods may have varying sensitivity and specificity. A combination of multiple diagnostic approaches is often used to increase the accuracy of the diagnosis.
Additionally, in cases of suspected carrier horses, specialized diagnostic techniques, such as deep nasopharyngeal swabs or guttural pouch washes, may be performed to detect the presence of the bacteria in the carrier state.
Accurate diagnosis of strangles is essential to determine the appropriate treatment and management techniques and to stop the infection from spreading further. Therefore, consulting a veterinarian is essential for an accurate diagnosis and tailored care plan for affected horses.
Treatment of Strangles in Horses
Treating strangles in horses focuses on supportive care, managing complications, and preventing the spread of infection. The specific treatment approach may vary depending on the severity of the disease and the individual horse’s condition.
Consulting with a veterinarian for proper diagnosis and treatment recommendations is important. Here are some common treatment options for strangles in horses:
Isolation: Infected horses should be isolated from healthy horses to prevent further spread of the disease. They should have separate water and feed managers, grooming equipment, and tack. One person should handle the infected horse(s) exclusively and avoid contact with other horses.
Antibiotics: The use of antibiotics in treating strangles is a topic of debate among veterinarians. While antibiotics can kill the bacteria, they may also prolong the infection and delay abscess formation. However, antibiotics may be necessary in certain cases, such as when abscesses are large or pose a risk to the horse’s health. A veterinarian should choose antibiotics and may include penicillin or other suitable options.
Abscess Management: Warm compresses or hot towels may encourage abscesses that have matured and are ready to burst. This can help relieve pressure and promote drainage. Once the abscesses have ruptured, the cavities should be flushed with dilute povidone-iodine solutions to aid in cleaning and healing.
Supportive Care: Providing supportive care is essential for horses with strangles. This includes ensuring they have access to clean water, good-quality forage, and a comfortable environment. Proper hydration and nutrition are important for their overall well-being and immune response.
Veterinary Monitoring: Regular veterinary monitoring is necessary to assess the horse’s progress, manage complications, and make necessary treatment adjustments. The veterinarian may perform follow-up examinations, collect samples for testing, and provide guidance on the horse’s recovery and potential return to normal activities.
Some horses may develop complications or a chronic form of the disease called “bastard strangles.” These cases may require more intensive treatment, including additional medications, supportive therapy, and close monitoring.
Prevention is also a crucial aspect of managing strangles. Implementing appropriate biosecurity measures, such as the isolation of new horses, regular temperature checks, disinfection of equipment, and practicing good hygiene, can help prevent the spread of infection and reduce the risk of strangles outbreaks.
Prevention of Strangles in Horses
Prevention and control of strangles in horses involve implementing strict biosecurity measures and management practices to minimize the risk of infection and limit the spread of the disease. Here are some key steps for preventing and controlling strangles:
Isolation: When introducing new horses to premises, isolating them for 2-3 weeks is crucial. This allows time to monitor their health and identify any signs of illness before they come into contact with other horses. Isolation helps prevent the introduction of strangles to a herd.
Regular Monitoring: Regularly monitor the body temperature of all horses on the premises, especially if there has been recent contact with other horses or potential sources of infection. Elevated body temperature can be an early sign of strangles.
Prompt Identification and Isolation of Infected Horses: If a horse shows any signs of strangles, such as fever, nasal discharge, swollen lymph nodes, or difficulty swallowing, it is important to isolate that horse immediately from others. Separate them into a designated isolation area with different equipment and personnel to minimize the risk of transmission.
Hygiene and Disinfection: Practice good hygiene by regularly cleaning and disinfecting shared equipment, stables, trailers, and other areas where horses come into contact; Disinfect grooming tools, feeders, water buckets, and other equipment that may be shared among horses. Use a phenolic disinfectant known to be effective against Streptococcus equi.
Avoid Horse-to-Horse Contact: Minimize direct contact between horses, especially those from different groups or unknown health statuses. This can reduce the risk of transmission through respiratory droplets or direct contact with nasal discharge.
Quarantine and Testing of New Horses: Quarantine and test new horses before introducing them to the general population. This includes monitoring their body temperature, conducting laboratory tests (e.g., nasal swabs, serology), and observing them for signs of illness.
Vaccination: Vaccination against strangles is controversial, and the efficacy of intramuscular vaccines is relatively low. However, intranasal vaccines containing an attenuated live strain of Streptococcus equi have shown better results. Vaccination may be considered in consultation with a veterinarian, considering the risk factors and individual horses’ health status.
Management of Carrier Horses: Identify and manage horses that are asymptomatic carriers of Streptococcus equi. These horses may intermittently shed the bacteria and pose a risk of infecting others. Consult with a veterinarian for specific strategies, such as guttural pouch medication, to reduce the risk of transmission.
Education and Communication: Educate horse owners, staff, and visitors about the signs and risks of strangles. Encourage them to practice good biosecurity measures and promptly report any suspected cases to the appropriate authorities or veterinarians.
Prevention and control of strangles require a comprehensive approach involving good management practices, biosecurity measures, and veterinary guidance. Work closely with a veterinarian to develop a tailored prevention and control plan suitable for your circumstances.
Conclusion
Strangles is a highly contagious bacterial infection in horses. It causes fever, swollen lymph nodes, nasal discharge, and abscess formation. Prevention involves strict biosecurity measures and vaccination. Diagnosis involves a physical examination and sample collection.
Treatment includes isolation, supportive care, and sometimes antibiotics. Working with a veterinarian is essential for effective management and control of strangles.
