Unit 1 - Streptococcus equi

Question 1

Why are Strep. equi ss equi infections known as strangles?

Answer 1

Initially called strangles because of upper airway obstruction by retropharyngeal LN enlargement in severe cases that lead to “strangulation” of airflow.

Question 2

What animals is strangles most often observed in?

Answer 2

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.

Question 3

What are the clinical signs of strangles?

Answer 3

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

Question 4

Describe the pathogenesis of Strep. equi ss equi infections.

Answer 4

1. SEE enters via oral or nasal cavities
2. attaches to/penetrates crypt cells of tonsillar tissue
3. translocates to LNs within hours
4. complement derived chemotactic factors recruit PMNs into the LN, but HA capsule, SeM protein, Mac protein, and other factors prevent PMN killing
5. abscessation after 3-5 days
6. nasal shedding for 2-3 weeks

Question 5

____% of recovered animals from strangles are expected to have waning immunity for ~5 years if they did not get treated with ________.

Answer 5

75, antimicrobials

Question 6

What is the primary route of introduction of strangles to naive horse populations?

Answer 6

Outwardly healthy animals that continue to shed organism ( intermittently) are the primary route of introduction of the organism to a naive population of horses.

Question 7

What is required to determine the asymptomatic carriers of strangles?

Answer 7

Culture or molecular diagnostics would be required to determine these horses.

Question 8

How do you diagnose Strangles?

Answer 8

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.

Question 9

Immunity to strangles is mediated at the ____ level by blocking SEE entry.

Answer 9

mucosal

Question 10

True or false: vaccination is recommended in horses exposed to SEE in an outbreak.

Answer 10

false

Question 11

How many doses of IM extract vaccines are required to be effective?

Answer 11

2-3 doses at 2 week intervals

Question 12

How old must a horse be to get the live intranasal vaccine?

Answer 12

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.

Question 13

How many weeks should new horses to a herd be isolated?

Answer 13

3 weeks

Question 14

When should you test horses for SEE if they have been treated with antibiotics?

Answer 14

Not until 3 weeks after the cessation of treatment.

Question 15

How do you control transmission of strangles?

Answer 15

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.

Question 16

How do you treat SEE cases with early clinical signs??

Answer 16

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.

Question 17

How do you treat SEE cases with uncomplicated LN abscessation?

Answer 17

Uncomplicated cases are treated with benign neglect and supportive care.

Question 18

How do you treat SEE infections with complicated cases of LN abscessation?

Answer 18

Complicated cases: systemic antimicrobials, IV fluids, NSAIDs, and enteral nutrition. Potentially temporary tracheostomy in cases of dyspnea.

Question 19

What is the most effective therapy for LN abscessation?

Answer 19

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.

Question 20

What are the recommended drugs for treating SEE when necessary?

Answer 20

Beta lactams - Pen G procain, potassium penicillin, ceftiofur, crystalline-free Ceftiofur
Note: never give macrolides to horses over 6 months of age

Question 21

What can GP empyema from SEE infection eventually become?

Answer 21

Chondroids

Question 22

Any horse that has persistent SEE infection of the GPs is a ______.

Answer 22

carrier

Question 23

What do liver, kidney, mesentery, and spleen metastatic SEE infections often present as?

Answer 23

Colic

Question 24

True or false: mortality rates for metastatic SEE disease are around 2%.

Answer 24

False - it is around 62%

Question 25

_____ ______ 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.

Answer 25

purpura hemorrhagica

Question 26

What clinical signs are associated with purpura hemorrhagica?

Answer 26

pitting edema of the head, trunk, and ost commonly distal limbs, petechiae, and ecchymoses

Question 27

What is it called when vasculitis progressis to thrombosis, resulting in infarction of large muscle groups?

Answer 27

infarctive purpura which leads to massive rhabdomyolysis/necrotic muscle and ultimately open wounds

Question 28

How do you treat infarctive purpura?

Answer 28

Treat with corticosteroids and supportive care (leg wrapping, analgesics, fluid therapy, nutrition support)/

Question 29

What breed of horses are known to get Strep Myositis?

Answer 29

Quarter horses