Unit 1 - Streptococcus equi Flashcards
Why are Strep. equi ss equi infections known as strangles?
Initially called strangles because of upper airway obstruction by retropharyngeal LN enlargement in severe cases that lead to “strangulation” of airflow.
What animals is strangles most often observed in?
Most commonly observed in young horses 1-5 years of age, but can occur at any age. Foals up to 3 months born from immune mares are usually resistant.
What are the clinical signs of strangles?
Fever until the LN abscesses and drains Lymphadenitis > abscessation - mandibular and retropharyngeal lymph nodes are often involved Mucopurulent nasal discharge Painful pharyngitis GP empyema Chondroid formation
Describe the pathogenesis of Strep. equi ss equi infections.
- SEE enters via oral or nasal cavities
- attaches to/penetrates crypt cells of tonsillar tissue
- translocates to LNs within hours
- complement derived chemotactic factors recruit PMNs into the LN, but HA capsule, SeM protein, Mac protein, and other factors prevent PMN killing
- abscessation after 3-5 days
- nasal shedding for 2-3 weeks
____% of recovered animals from strangles are expected to have waning immunity for ~5 years if they did not get treated with ________.
75, antimicrobials
What is the primary route of introduction of strangles to naive horse populations?
Outwardly healthy animals that continue to shed organism ( intermittently) are the primary route of introduction of the organism to a naive population of horses.
What is required to determine the asymptomatic carriers of strangles?
Culture or molecular diagnostics would be required to determine these horses.
How do you diagnose Strangles?
Samples of a mature LN abscess, nasopharyngeal swab & wash, guttural pouch lavage. Culture (false negatives possible), PCR, serology (useful for vaccination not diagnosis), cytologic examination, serial monitoring of rectal temperatures may assist in finding febrile horses for isolation.
Immunity to strangles is mediated at the ____ level by blocking SEE entry.
mucosal
True or false: vaccination is recommended in horses exposed to SEE in an outbreak.
false
How many doses of IM extract vaccines are required to be effective?
2-3 doses at 2 week intervals
How old must a horse be to get the live intranasal vaccine?
1 year of age.
Requires 2 doses in naive horses at 2-3 weeks.
It’s recommended to not administer the live intranasal on the same day as injectable vaccines because of the risk of accidentally injecting it, which would cause massive abscess.
How many weeks should new horses to a herd be isolated?
3 weeks
When should you test horses for SEE if they have been treated with antibiotics?
Not until 3 weeks after the cessation of treatment.
How do you control transmission of strangles?
Prevent the spread of SEE to horses on other premises and to new arrivals on the affected premises.
Establish whether convalescing horses are infectious at least 3 weeks after clinical recovery.
Eliminate SEE infection from the GPs.
Prevent indirect cross-infection by SEE from horses in the “dirty” area to those in the “clean” area of the premises.
How do you treat SEE cases with early clinical signs??
Early clinical signs: it’s highly controversial to use antibiotics at this stage, but if exposed horses are immediately started prior to clinical signs, there may be a chance to eliminate infection if given prior to sequestration of SEE in the LN.
How do you treat SEE cases with uncomplicated LN abscessation?
Uncomplicated cases are treated with benign neglect and supportive care.
How do you treat SEE infections with complicated cases of LN abscessation?
Complicated cases: systemic antimicrobials, IV fluids, NSAIDs, and enteral nutrition. Potentially temporary tracheostomy in cases of dyspnea.
What is the most effective therapy for LN abscessation?
The most effective therapy for LN abscessation is surgical drainage after a mature abscess develops. Can be accelerated using a hot compress and topical 20% ichthammol ointment.
What are the recommended drugs for treating SEE when necessary?
Beta lactams - Pen G procain, potassium penicillin, ceftiofur, crystalline-free Ceftiofur
Note: never give macrolides to horses over 6 months of age
What can GP empyema from SEE infection eventually become?
Chondroids
Any horse that has persistent SEE infection of the GPs is a ______.
carrier
What do liver, kidney, mesentery, and spleen metastatic SEE infections often present as?
Colic
True or false: mortality rates for metastatic SEE disease are around 2%.
False - it is around 62%
_____ ______ is an aseptic, immune-mediated, necrotizing vasculitis that occurs as a type III hypersensitivity in mature horses after repeat exposure to natural disease or after vaccination.
purpura hemorrhagica
What clinical signs are associated with purpura hemorrhagica?
pitting edema of the head, trunk, and ost commonly distal limbs, petechiae, and ecchymoses
What is it called when vasculitis progressis to thrombosis, resulting in infarction of large muscle groups?
infarctive purpura which leads to massive rhabdomyolysis/necrotic muscle and ultimately open wounds
How do you treat infarctive purpura?
Treat with corticosteroids and supportive care (leg wrapping, analgesics, fluid therapy, nutrition support)/
What breed of horses are known to get Strep Myositis?
Quarter horses
