Q: What is the difference between S. equi and S. zooepidemicus?

Both are subspecies of Streptococcus equi. S. equi is the specific cause of strangles, a highly contagious and severe disease. S. zooepidemicus is an opportunistic pathogen that can cause a variety of infections, including respiratory disease, uterine infections, and wound infections. It can also cause strangles-like symptoms, making laboratory differentiation important.

# Strangles in Horses: Streptococcus equi Isolation and Treatment Protocol ## Key Takeaways - Strangles is caused by *Streptococcus equi* subspecies *equi* (S. equi), a highly contagious bacterium primarily affecting the upper respiratory tract and lymph nodes of horses, leading to fever, nasal discharge, and characteristic abscesses under the jaw or throat. - Accurate diagnosis is critical and relies on molecular methods like PCR (including FRET-qPCR for differentiation from *S. zooepidemicus*) and LAMP assays, alongside bacterial culture, serology (e.g., P92 ELISA), and guttural pouch endoscopy for carrier detection. - Transmission occurs via direct contact with infected horses or indirectly through contaminated equipment, feed, and water troughs; approximately 10% of infected horses become persistent carriers, often with guttural pouch chondroids. - Management focuses on immediate isolation, strict biosecurity protocols, and supportive care including hot packing of abscesses and NSAIDs; antibiotic use is controversial and reserved for specific early-stage or complicated cases due to potential resistance and interference with immunity. - Prevention strategies include rigorous quarantine of new arrivals, meticulous hygiene, and vaccination with DIVA-compatible vaccines like Strangvac, which reduces clinical signs and incidence without interfering with diagnostic serology for natural infection. - Complications such as bastard strangles (metastatic abscessation) and purpura hemorrhagica can significantly worsen the prognosis, with mortality rates up to 10% in severe or untreated cases. --- **Owner Triage Summary:** Strangles is a highly contagious bacterial infection of horses caused by *Streptococcus equi* subspecies *equi*. If your horse has a sudden fever, nasal discharge, or swollen lymph nodes under the jaw or in the throat area, isolate them from all other horses immediately and call your veterinarian. Do not share water, feed, or equipment. Early diagnosis through PCR or culture is critical for controlling the outbreak and preventing the spread to neighbouring animals. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Understanding Strangles and *Streptococcus equi* Strangles is a prevalent and globally significant infectious disease of equids, caused by the bacterium *Streptococcus equi* subspecies *equi* (S. equi) [1][2]. It is one of the most common infectious agents diagnosed in horses worldwide [2]. The disease is characterized primarily by fever and the formation of abscesses in the lymph nodes of the head and neck, which can become so large they restrict the airway, giving the disease its name [3]. While the upper respiratory tract is the primary site of infection, the disease can have severe complications and can be fatal in up to 10% of cases, depending on the horse's immune status, the development of complications, and the effectiveness of biosecurity measures [4]. The bacterium is a Gram-positive, chain-forming, Lancefield group C beta-hemolytic *Streptococcus* [5]. It is closely related to *Streptococcus equi* subspecies *zooepidemicus* (S. zooepidemicus), which is an opportunistic pathogen that can also cause respiratory disease and strangles-like presentations in horses [6][7][8]. This close relationship makes accurate laboratory diagnosis essential, as the clinical signs can be similar, but the epidemiological implications and management strategies differ significantly [6][8]. ## At a Glance: Key Facts for Horse Owners | Feature | Details | | :--- | :--- | | **Causative Agent** | *Streptococcus equi* subspecies *equi* (S. equi) [1] | | **Primary System Affected** | Upper Respiratory Tract [6] | | **Key Clinical Signs** | Fever, nasal discharge, swollen and abscessed lymph nodes (under jaw, throat), coughing [4][3] | | **Transmission** | Direct contact, contaminated equipment, water, feed; often via commingling at events or new arrivals [9][4] | | **Diagnosis** | PCR, bacterial culture, serology (blood tests), and endoscopy of guttural pouches [6][10][7] | | **Treatment** | Supportive care, hot packing of abscesses, pain relief; antibiotics are controversial and used in specific cases [11][12] | | **Prevention** | Strict biosecurity, quarantine, and vaccination (e.g., Strangvac) [1][7][4] | | **Long-term Carrier State** | Approximately 10% of infected animals become persistent carriers, often with guttural pouch infection [7][13] | ## Anatomy and Pathogenesis: How S. equi Causes Disease To understand the clinical signs and diagnostic approach, it is helpful to understand the disease process. S. equi is inhaled or ingested and initially attaches to the mucosal surfaces of the upper respiratory tract, specifically the tonsils and the lining of the throat and nasal passages. The bacteria then invade the local lymph nodes, which are part of the immune system's first line of defense [3]. The bacteria have several virulence factors that allow them to evade the immune system and cause disease. One of the most important is the M protein (SeM), which is a surface protein that helps the bacteria resist phagocytosis (being engulfed and killed by white blood cells) [14][15][16]. Another key factor is IdeE, an immunoglobulin-cleaving enzyme that breaks down antibodies, disabling a key part of the horse's immune defence [3]. Research into these proteins has been central to developing new vaccines and diagnostic tests [10][15][3]. The infection leads to a massive inflammatory response, resulting in the formation of abscesses within the lymph nodes. These abscesses can enlarge, causing pain and swelling. When they are in the lymph nodes of the head and neck, they can compress the trachea (windpipe) and larynx, causing the characteristic respiratory distress and the "strangles" presentation [3]. ## Causes and Transmission: How Strangles Spreads The sole cause of strangles is infection with S. equi. The disease is highly transmissible and is a significant biosecurity challenge on equine farms worldwide [14]. The primary route of transmission is through direct contact with an infected horse, particularly through nasal discharge and pus from ruptured abscesses. Indirect transmission is also very common and occurs through contaminated objects, including: - **Shared feed containers and water troughs:** Studies have shown that horses that share feed containers and drink from the same water troughs are significantly more likely to contract strangles [9]. - **Grooming equipment, halters, and lead ropes:** These can carry the bacteria from one horse to another. - **Human hands and clothing:** People can easily carry the bacteria on their hands, boots, or clothing from an infected horse to a susceptible one. - **Contaminated environment:** The bacteria can survive in the environment, especially in damp, dark areas, although it is primarily spread through direct or indirect contact [14]. The commingling of horses at events, sales, or when introducing new horses to a farm is a major risk factor for outbreaks [4]. The movement of horses between different stabling environments is a well-documented route of disease introduction [4]. ### The Carrier State: A Hidden Reservoir A critical aspect of strangles epidemiology is the carrier state. Approximately 10% of horses that recover from the acute infection remain persistently infected [7]. These carriers may show no clinical signs of disease but continue to shed S. equi intermittently, serving as a hidden reservoir for new outbreaks [7][13]. The most common site for persistent infection is the guttural pouch, a unique air-filled sac located in the horse's throat area. The bacteria can form an infection in this pouch, leading to the formation of solid concretions called "chondroids" [7]. These chondroids can harbour live bacteria for months or even years, allowing the carrier horse to infect others without appearing sick. This is why screening protocols involving guttural pouch endoscopy and lavage are so important for preventing the introduction of strangles into a new herd [7]. ## Clinical Signs and Differential Diagnoses The clinical signs of strangles can vary from mild to severe. The classic presentation includes: - **Sudden onset of high fever** (often exceeding 103°F or 39.4°C). - **Nasal discharge**, which can be clear at first and then become thick and purulent (containing pus). - **Swollen, painful lymph nodes** in the submandibular (under the jaw) and retropharyngeal (throat) regions. - **Coughing and difficulty swallowing**. - **Lethargy and decreased appetite**. - **Abscess formation and rupture** of the affected lymph nodes, which can drain thick, creamy pus. The clinical signs of strangles are not unique to S. equi infection. Other respiratory pathogens can cause a very similar presentation, including *Streptococcus equi* subspecies *zooepidemicus*, equine influenza virus, and equine herpes virus [7]. In fact, virulent strains of S. zooepidemicus can cause strangles-like presentations that are clinically indistinguishable from true strangles [7]. This is why laboratory confirmation is essential for a definitive diagnosis and appropriate management [7][8]. ## Veterinary Examination and Diagnostic Isolation of S. equi A prompt and accurate diagnosis is the cornerstone of strangles control. The diagnostic approach involves a combination of clinical examination and laboratory testing. The goal is not only to confirm the disease but also to identify carriers and prevent further spread. ### 1. Clinical Examination The veterinarian will perform a thorough physical examination, paying close attention to the horse's temperature, respiratory rate and effort, and palpation of the lymph nodes. They will also assess the horse's overall demeanor and look for any signs of nasal discharge or coughing. ### 2. Molecular Diagnostics (PCR and LAMP) Polymerase chain reaction (PCR) is a highly sensitive molecular technique used to detect the genetic material (DNA) of S. equi directly from clinical samples. It is considered a rapid and reliable method for diagnosing strangles [9]. - **Real-time PCR (qPCR):** This is a common laboratory-based method that can detect and quantify the bacteria in a sample [6][14]. - **FRET-qPCR:** A newer, advanced form of qPCR, known as fluorescence resonance energy transfer (FRET)-based PCR coupled with high-resolution melting (HRM) analysis, can rapidly distinguish S. equi from the closely related S. zooepidemicus. This is a significant advantage, as it can identify mixed infections and prevent misdiagnosis, with results available in under 2 hours [8]. - **[Loop-mediated Isothermal Amplification](/knowledge/diagnostics/molecular/lamp-assay-rapid-detection-african-swine-fever-virus-oral-fluids) (LAMP):** LAMP is a newer, field-deployable diagnostic technology that can detect S. equi DNA quickly and accurately. It can be performed with a portable real-time fluorometer, making it a valuable tool for on-farm testing [6]. One study demonstrated a LAMP assay targeting the SeM gene that could detect S. equi within about 13 minutes, with a clinical sensitivity of 91.3% and specificity of 93.3% [14]. The addition of guanidine hydrochloride (GuHCl) has been shown to enhance the assay's performance [14]. ### 3. Bacterial Culture and Isolation Bacterial culture involves attempting to grow S. equi from a clinical sample on a nutrient medium like sheep blood agar. While it is a traditional "gold-standard" method, it is less sensitive than PCR and can take several days to yield results [6][14]. The bacteria appear as beta-hemolytic colonies, and their identity can be confirmed through biochemical tests, such as sugar fermentation profiles (e.g., lactose, maltose, sorbitol, trehalose) [17][5]. However, culture can be unreliable, especially if the horse has already started antibiotic treatment or if the sample is of poor quality [14]. ### 4. Serology (Blood Testing) Serological tests detect antibodies against S. equi in the horse's blood. These tests are useful for: - **Confirming exposure** to the bacteria. - **Identifying carriers** and horses that have been recently infected. - **Monitoring the immune response** after vaccination. A common serological test is the indirect ELISA (iELISA). Traditional tests often use the SeM protein, but newer tests are being developed that are more accurate. For example, a new single-antigen test using a protein called P92 has shown a significantly higher accuracy (95% area under the curve) than the SeM ELISA (88%) for detecting infected horses [10]. This is a major advancement in serological testing [10]. ### 5. Guttural Pouch Endoscopy and Lavage For horses suspected of being carriers, especially those with a history of strangles or those being screened before entering a new facility, guttural pouch endoscopy is essential. This involves passing a flexible camera into the guttural pouch to visually inspect it for abnormalities, such as chondroids or pus. A lavage (washing) of the pouch is then performed, and the fluid is submitted for PCR and culture to detect S. equi [7]. ### 6. Molecular Typing and Epidemiology In addition to confirming the presence of S. equi, molecular techniques like whole-genome sequencing (WGS) and SeM gene sequencing are used in epidemiological investigations. This helps track the spread of specific strains and understand transmission patterns within and between populations [2][18][19]. For example, studies have identified numerous SeM alleles, some of which may be associated with different levels of virulence [16]. This information is valuable for outbreak control and understanding the global epidemiology of strangles [2][19]. ## Evidence-Based Management and Treatment Protocol The management of a strangles outbreak requires a multi-faceted approach focusing on biosecurity, supportive care, and the judicious use of antibiotics. ### 1. Immediate Isolation and Biosecurity Upon suspicion or confirmation of strangles, the most critical step is to isolate affected horses immediately from all other horses on the premises. The goal is to create a "strangles-free" zone and prevent the spread of the bacteria. - **Isolate confirmed cases:** Move affected horses to a separate, well-ventilated area, ideally far away from other horses. - **Dedicated personnel:** Assign specific people to care for the sick horses, and ensure they do not come into contact with healthy horses without changing clothes and boots and washing their hands. - **Dedicated equipment:** Use separate halters, lead ropes, grooming kits, and feed and water buckets for the isolated horses. Do not share these items with other horses. - **Prevent commingling:** Do not allow horses to share feed containers or water troughs, as this is a major risk factor for transmission [9]. - **Screening new arrivals:** Implement a strict screening protocol for any new horse entering the property, including clinical examination, paired serology samples taken 6 weeks apart, and guttural pouch endoscopy with lavage for PCR and culture [7]. This is critical to prevent the introduction of carriers. ### 2. Supportive Care For most horses with uncomplicated strangles, the primary treatment is supportive care. The goal is to keep the horse comfortable and help its immune system fight the infection. - **Hot packing:** Applying warm compresses to swollen lymph nodes can help accelerate the maturation and rupture of abscesses, providing pain relief and promoting drainage. - **Anti-inflammatory medication:** Non-steroidal anti-inflammatory drugs (NSAIDs), such as phenylbutazone or flunixin meglumine, may be prescribed by your veterinarian to reduce fever and inflammation and improve the horse's comfort. - **Nutrition and hydration:** Ensure the horse has access to fresh water and soft, palatable feed, such as soaked hay or mashes, to encourage eating despite a sore throat. - **Drainage of abscesses:** Once an abscess has matured, your veterinarian may lance it surgically to allow the pus to drain. The area should then be flushed gently with a dilute antiseptic solution to keep it clean and promote healing. ### 3. The Controversial Role of Antibiotics The use of antibiotics in the treatment of strangles is a subject of considerable debate in veterinary medicine. The decision to use them depends on the stage of the disease and the individual horse's condition. - **Early infection (before abscess formation):** Antibiotics (e.g., penicillin) may be used in the very early stages of the disease, before abscesses have formed, in an attempt to eliminate the bacteria. However, this is not always recommended, as it may interfere with the development of a strong immune response, leaving the horse susceptible to re-infection. - **Established abscesses:** Antibiotics are generally contraindicated once abscesses have formed. The antibiotics cannot penetrate the thick abscess wall effectively, and their use can delay the natural maturation and drainage of the abscesses. It is generally believed that allowing the abscesses to mature and drain is the best way to clear the infection and promote immunity. - **Severe cases:** Antibiotics are necessary for treating severe complications, such as metastatic abscessation (bastard strangles) or infection in other parts of the body. The choice of antibiotic should be based on culture and antimicrobial susceptibility testing, as resistance is a growing concern. Studies have shown significant resistance to common antibiotics like tetracycline, erythromycin, and clindamycin in various regions [17][9]. For example, one study in Ethiopia found high levels of resistance to tetracycline (81.5%) and erythromycin (81.5%) [9]. Another study in Brazil reported multidrug resistance in 60% of isolates [17]. This highlights the importance of susceptibility testing to guide treatment decisions. ### 4. Alternative and Emerging Therapies Research is ongoing into alternative treatments, particularly given the rise in antimicrobial resistance. - **Plant extracts:** A study investigated the *in vitro* antibacterial activity of ethanol extracts from the *Combretum molle* plant against S. equi. The root extract showed the best antibacterial effect, with a minimum inhibitory concentration (MIC) of 250 µg/ml [11]. While this is promising, these are *in vitro* results, and further research is needed to determine their safety and efficacy in live horses. ## Prevention and Vaccination Prevention is far better than cure when it comes to strangles. A comprehensive prevention plan includes strict biosecurity and, in some cases, vaccination. ### 1. Biosecurity Protocols - **Quarantine:** All new horses should be quarantined for a minimum of 3 to 4 weeks before being introduced to the resident herd. The screening protocol should include clinical exams and, ideally, guttural pouch endoscopy and serology [7]. - **Hygiene:** Maintain high standards of hygiene, including regular cleaning and disinfection of stables, water troughs, and feed bins. - **Traffic control:** Limit visitors and vehicles to the farm. If visitors must come into contact with horses, they should wear protective clothing and footwear. - **Show safety:** Be cautious when taking horses to shows or events. Avoid sharing water buckets and equipment, and try to prevent nose-to-nose contact with other horses. ### 2. Vaccination Vaccination can be a valuable tool in reducing the incidence and severity of strangles, but it is not a substitute for good biosecurity. - **Strangvac:** This is a newer, multicomponent subunit vaccine that has been shown to effectively reduce clinical signs of strangles and reduce its incidence [1][3]. It contains a combination of proteins, including CCE, Eq85, and IdeE, which are key protective components [1][3]. A study in a natural outbreak setting found that none of the vaccinated horses developed strangles, even when exposed to the disease [1]. - **Immune Response:** Vaccination with Strangvac induces a significant antibody response against its components, including the ability to neutralize the IdeE enzyme [3]. This immune response can last for at least 12 months after the second vaccination [3]. - **DIVA Compatibility:** Strangvac is a DIVA (Differentiating Infected from Vaccinated Animals) compatible vaccine. This means that the vaccine does not contain the SeM protein, so vaccinated horses will not test positive on the antigen A/C iELISA, which is used to detect natural infection [1]. This is a major advantage, as it allows for the serological monitoring of a herd to detect natural exposure to S. equi without confusion from vaccine-induced antibodies [1][4]. ## Prognosis and Complications The prognosis for a horse with uncomplicated strangles is generally good, with most horses recovering fully within 3 to 4 weeks. However, the disease can be fatal in up to 10% of cases [4]. The prognosis is worse for very young, very old, or immunocompromised animals. Several complications can arise from a strangles infection: - **Bastard Strangles (Metastatic Abscessation):** This is a severe complication where the bacteria spread through the bloodstream to form abscesses in other organs, such as the lungs, liver, spleen, or brain. This is often difficult to treat and carries a poor prognosis. - **Purpura Hemorrhagica:** This is an immune-mediated disease that can occur 2 to 4 weeks after a strangles infection. It is characterized by inflammation of the blood vessels, leading to swelling of the legs, head, and trunk, and the appearance of pinpoint hemorrhages on the mucous membranes. It is a serious condition that requires aggressive veterinary treatment. - **Guttural Pouch Empyema and Chondroids:** As mentioned earlier, this is the most common cause of the carrier state. The infection persists in the guttural pouch, and the horse can continue to shed bacteria. - **Laryngeal Hemiplegia (Roaring):** Damage to the nerves controlling the larynx can occur due to the inflammation and abscessation of the nearby lymph nodes, leading to a breathing noise during exercise. ## Limitations and When to Contact a Veterinarian This article provides a comprehensive overview of strangles but cannot predict the specific outcome for an individual horse. Breed-level information cannot predict an individual's susceptibility to infection or the severity of the disease. The clinical presentation and response to treatment can vary significantly between horses based on their age, immune status, underlying health conditions, and the specific strain of S. equi involved [16]. **You should contact your veterinarian immediately if you observe any of the following:** - A sudden fever (temperature above 102.5°F or 39.2°C). - Swelling under the jaw or in the throat area. - Nasal discharge, especially if it is thick and yellow or green. - Difficulty breathing or swallowing. - Coughing or loss of appetite. - Lethargy or depression. Early intervention is critical for managing the disease and preventing its spread to other horses. Do not attempt to treat strangles at home without veterinary guidance, as inappropriate treatment can worsen the disease or contribute to antimicrobial resistance. ## Frequently Asked Questions ### 1. How long is a horse contagious with strangles? A horse is contagious from the onset of fever and nasal discharge until all abscesses have completely healed and there is no more pus draining. However, about 10% of horses become long-term carriers and can shed the bacteria intermittently for months or even years, often from their guttural pouches, even without showing clinical signs [7][13]. ### 2. Can a horse get strangles more than once? Yes, it is possible for a horse to get strangles more than once. The immunity that develops after a natural infection is not always long-lasting or fully protective. Horses that are treated with antibiotics early in the course of the disease may not develop a strong immune response and can be re-infected more easily. ### 3. Is there a vaccine for strangles? Yes, there is a vaccine available called Strangvac. It is a multicomponent subunit vaccine that has been shown to reduce the clinical signs and incidence of strangles. It is also a DIVA-compatible vaccine, meaning it allows for serological testing to differentiate between vaccinated and naturally infected horses [1][3]. ### 4. What is the difference between S. equi and S. zooepidemicus? Both are subspecies of *Streptococcus equi*. S. equi is the specific cause of strangles, a highly contagious and severe disease. S. zooepidemicus is an opportunistic pathogen that can cause a variety of infections, including respiratory disease, uterine infections, and wound infections. It can also cause strangles-like symptoms, making laboratory differentiation important [6][8]. ### 5. Should I use antibiotics for my horse with strangles? Antibiotics are not always recommended for strangles. They are most useful in the very early stages of the disease before abscesses form, or for treating severe complications. Once abscesses have developed, antibiotics are often avoided as they can delay the natural maturation and drainage of the abscesses. The decision should be made by your veterinarian based on your horse's specific condition [17][9]. ### 6. How is a strangles carrier horse detected? Carrier horses are typically detected through a combination of guttural pouch endoscopy to look for chondroids or pus, and a guttural pouch lavage which is then tested for S. equi using PCR and culture [7]. Serological tests can also help identify horses that have been exposed to the bacteria [10]. ### 7. What is "bastard strangles"? Bastard strangles, also known as metastatic abscessation, is a severe complication where the S. equi bacteria spread through the bloodstream from the lymph nodes of the head and neck to form abscesses in other organs of the body, such as the lungs, liver, spleen, or brain. It is a serious and often difficult-to-treat condition. ### 8. How long does S. equi survive in the environment? S. equi can survive in the environment for a period of time, especially in dark, damp conditions, but it is not a highly resilient environmental organism. The primary mode of transmission is through direct contact with infected horses or indirect contact with contaminated equipment and human handlers. Good hygiene and disinfection are effective at killing the bacteria in the environment. ## Sources [1] [Reining in strangles: Absence of disease in horses vaccinated with a DIVA-compatible recombinant fusion protein vaccine, Strangvac, following natural exposure to Streptococcus equi subspecies equi.](https://pubmed.ncbi.nlm.nih.gov/41276995/) [2] [Molecular study of Streptococcus equi isolated from horses with strangles in Iraq.](https://pubmed.ncbi.nlm.nih.gov/40201849/) [3] [Neutralisation of the Immunoglobulin-Cleaving Activity of Streptococcus equi Subspecies equi IdeE by Blood Sera from Ponies Vaccinated with a Multicomponent Protein Vaccine.](https://pubmed.ncbi.nlm.nih.gov/41150447/) [4] [Closing the Stable Door on Strangles: Serological Responses of Vaccinated Horses on a Farm Following the Arrival of a New Horse.](https://pubmed.ncbi.nlm.nih.gov/41463869/) [5] [Phenotypic, Biochemical and Molecular Characterization of Streptococcus equi Isolates in Northern India.](https://pubmed.ncbi.nlm.nih.gov/40655359/) [6] [Real-time fluorometric isothermal assays for detection of Streptococcus equi subspecies equi and Streptococcus equi subspecies zooepidemicus in horses: Validation, comparison and evaluation of their clinical application.](https://pubmed.ncbi.nlm.nih.gov/41024428/) [7] [Effectiveness of a screening protocol employed at a UK rescue centre to prevent introduction of strangles.](https://pubmed.ncbi.nlm.nih.gov/41031843/) [8] [High-resolution melting curve FRET-qPCR rapidly distinguishes Streptococcus equi subsp. equi and zooepidemicus.](https://pubmed.ncbi.nlm.nih.gov/40736350/) [9] [Streptococcus equi subspecies equi from strangles suspected equines: molecular detection, antibiogram profiles and risk factors.](https://pubmed.ncbi.nlm.nih.gov/39180060/) [10] [A new single-antigen serological test accurately detects horses infected with Streptococcus equi subsp equi.](https://pubmed.ncbi.nlm.nih.gov/42419360/) [11] [Invitro antibacterial activity of bark, leaf and root extracts of combretum molle plant against streptococcus equi isolated from clinical cases of strangles in donkeys and horses.](https://pubmed.ncbi.nlm.nih.gov/38481214/) [12] [Streptococcus equi subsp. equi isolated from horses in Southern Brazil: molecular and phenotypic analyses.](https://pubmed.ncbi.nlm.nih.gov/41032072/) [13] [The prevalence of Streptococcus equi subsp. equi carriers in the Netherlands.](https://pubmed.ncbi.nlm.nih.gov/42036105/) [14] [Enhancement of loop-mediated isothermal amplification (LAMP) with guanidine hydrochloride for the detection of Streptococcus equi subspecies equi (Strangles).](https://pubmed.ncbi.nlm.nih.gov/39421427/) [15] [Immunogenic Streptococcus equi cell surface proteins identified by ORFeome phage display.](https://pubmed.ncbi.nlm.nih.gov/41288106/) [16] [Variation in SeM genotype is associated with virulence of Streptococcus equi subspecies equi in mice.](https://pubmed.ncbi.nlm.nih.gov/40203958/) [17] [Prevalence and antimicrobial susceptibility of Streptococcus equi isolated from horses in Santa Catarina state, Southern Brazil.](https://pubmed.ncbi.nlm.nih.gov/39155341/) [18] [Genetic analysis based on next generation sequencing of Streptococcus equi subsp. equi isolated from horses imported into Japan.](https://pubmed.ncbi.nlm.nih.gov/38897953/) [19] [Unwelcome neighbours: Tracking the transmission of Streptococcus equi in the United Kingdom horse population.](https://pubmed.ncbi.nlm.nih.gov/40684376/) [20] [Immunization but not natural infection of horses results in antibody activity against the S protein of Streptococcus equi subsp equi.](https://pubmed.ncbi.nlm.nih.gov/39681079/) ## Related Clinical & Scientific Guides * [Equine Hematologic Disorders: Anemia and Coagulopathies](/knowledge/veterinary-medicine/equine-care/equine-hematologic-disorders-anemia-coagulopathies) * [Equine Lifespan: Factors Influencing Longevity in Horses](/knowledge/veterinary-medicine/equine-care/equine-lifespan-factors-influencing-longevity-in-horses) * [Miniature Horse Care Guide](/knowledge/veterinary-medicine/equine-care/miniature-horse-care)