Bacti Final Exam

• Strangles is one of the most important disease of horses in developed countries, accounting up to 30% of reported infectious disease episodes.
• Why is strangles so important?

  1. disruption of management of commercial horse establishments

  2. time necessary to treat affected horses

  3. esthetic unpleasantness of the horses with runny noses and draining abscesses
• What is strangles in horses caused by?

  Streptococcus equi subsp. equi
• Strangles is a highly contagious disease that affects what age group of horses?

  all; it's more common in young animals
• What are the clinical findings of strangles in horses?

  -Acute onset of fever, anorexia, depression

  -Submandibular and pharyngeal

  -lymphadenopathy w abscessation and rupture

  -Copious purulent nasal discharge

  -Metastatic infection in other organ systems

  -lesions
• What are the characteristics of the lesions caused by S. equi? lymphadenopathy with rhinitis and pharyngitis, pneumonia, and metastatic infections in severe cases
• How is S. equi diagnosis confirmed? Culture of S. equi or PCR
• How is S. equi treated? Systemic administration of Penicillin and local treatment of abscesses
• How is S. equi controlled? Isolation and testing; Vaccination
• Etiology of S. equi Gram-positive, cocci o Facultative anaerobic o Catalase and coagulase negative o Beta-hemolytic o Highly adapted to Equidae
• Beta-Hemolysis of S. equi
• What species does strangles occur in? horses, ponies, donkeys, and mules worldwide
• Why is strangles so important?

  1. disruption of management of commercial horse establishments

  2. time necessary to treat affected horses

  3. esthetic unpleasantness of the horses with runny noses and draining abscesses
• What is strangles in horses caused by? Streptococcus equi subsp. equi
• Strangles is a highly contagious disease that affects what age group of horses? all; is more common in young animals
• What are the characteristics of the lesions caused by S. equi? lymphadenopathy with rhinitis and pharyngitis, pneumonia, and metastatic infections in severe cases
• How is S. equi diagnosis confirmed? Culture of S. equi or PCR
• How is S. equi treated? Systemic administration of Penicillin and local treatment of abscesses
• How is S. equi controlled? Isolation and testing; Vaccination
• Etiology of S. equi Gram-positive, cocci o Facultative anaerobic o Catalase and coagulase negative o Beta-hemolytic o Highly adapted to Equidae
• Beta-Hemolysis of S. equi
• What species does strangles occur in? horses, ponies, donkeys, and mules worldwide
• Strangles can affect horses of any age, although morbidity rate is higher in younger horses.
• How fatal is strangles?

  -Case fatality rate without treatment is about 9%

  -with adequate early treatment it may be 1-2%
• Where do strangles outbreaks often occur?

  -breeding farms, and in polo and racing stables, where infection is introduced by asymptomatic new arrivals or horses that are taken to fairs and riding schools
• S. equi is an obligate parasite of horses and all infections are attributable to transmission from infected horses either directly or by fomites.
• What is the source of infection in S. equi?

  -Nasal and abscess discharges from infected animals contaminating pasture, track, stalls, feed and water troughs, grooming equipment, and hands and clothing of grooms and veterinarians
• How long can S. equi survive in the environment?

  less than 3 days in the environment so prolonged quarantine of facilities not required
• Approximately 10-40% of recovered horses have persistent infection and are important sources of infection.
• How are carriers of S. equi detected? PCR on nasal swabs or guttural pouch lavage fluid
• What is the resistance to S. equi associated with?

  production of serum and mucosal antibodies to the streptococcal M protein (SeM)
• Animals that have previously had the disease are less likely than naïve animals to develop the disease on subsequent exposure. Around 25% horses that recover from the disease do not developprotective immunity. The immunity developed after a natural exposure to the disease wanes over time!
• What are the virulence factors of S. equi?

  1. M proteins on the surface of bacteria

  2. Hyaluronic acid capsule

  3. Production of a Leukocidal toxin
• M proteins are associated with what three things?

  Adhesion to oral nasal and pharyngeal tissue

  Invasion of pharyngeal tonsils

  Evasion of the innate immunity
• What does the capsule of S. equi help with?

  resistance to phagocytosis
• Following adhesion, S. equi lodge and multiply in pharyngeal and tonsillar lymphoid tissue
• Toxins produced by S. equi cause direct cell damage. Migration of neutrophils into the lymph nodes causes swelling and abscessation. Swelling of retropharyngeal lymph nodes may interfere with respiration. Most abscess eventually rupture and drain, and infection resolves with development of an effective immune response.
• Gutteral Pouch Mycosis Aspergillus fumigatis
• How long does shedding of S. equi persist? 2-3 weeks; can be longer in exceptional cases
• How is strangles treated? Penicillin to in-contact and infected horses before development of lymphadenopathy. Of limited benefit if abscesses have formed