Download Streptococcus equi

Strangles
“a sore throat with a
vengeance”
Colin Mitchell BVM&S MRCVS
Hexham
Strangles
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Cause
Epidemiology
Clinical signs
Diagnosis
Notification
Complications
Strangles
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Disease transmission
Prevention
Control of infection
Treatment
Confirmation of freedom from disease
Cause
• Bacteria
• Streptococcus equi
• Severity of infection related to health &
inherent resistance of the individual horse,
rather than variations in the organism itself
Epidemiology
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Highly contagious – spread by direct and
indirect contact
1. Carrier animals main source of infection –
carried in guttural pouch for up to 5 years
2. Survives well in moist discharges – will
survive for 7 – 9 weeks on wood,
depending on temperature
Clinical Signs
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Incubation period 3 – 10 days
High temperatures ( > 103 F )
Depression / inappetance
Nasal discharge
Enlarged lymph nodes on head
Difficulty swallowing
Noisy breathing
Nasal Discharge
Enlarged Lymph Nodes
Diagnosis
• Clinical signs
• Culture bacteria from the pus of abscessated
lymph nodes, nasal discharge or throat
swabs
• Swabs – extra long shaft and absorbent
heads
Naso-pharyngeal swabs
Culture swab tips
Diagnosis of carrier state
• Sequential throat swabs
• Endoscopic examination & guttural pouch
washes
Notification
• No legal notification procedures
• Advisable to inform the relevant breeders
association if infection occurs
Complications
• Less common – up to 8% of cases
• Infection usually restricted to head and neck
• Can spread to lungs, muscles, heart, kidneys
and intestines
• These complications can be fatal
Disease Transmission
“can it spread from horse to horse?”
Definitions
• Infectious
Capable of being communicated by an
infection – eg, tetanus
• Contagious
Capable of being transmitted from animal to
animal – eg, influenza
Strangles
• NOT a zoonosis
• Our throats and lymph nodes are quite safe!
Disease Transmission
Direct Contact
Indirect Contact
• horse – horse
• fairly close contact
between infected and
susceptible animals
• Personnel
• Equipment
• Water troughs
Disease Transmission
• Bacteria shed from draining abscesses and
the nose
• Survives in the environment
• for example : bacteria survive on wood for
up to 9 weeks, depending on temperature
• Good hygiene is essential in controlling the
disease
Do all horses have draining
abscesses?
Disease Dynamics
infection
healthy
incubation
signs
healthy
Disease Dynamics
infection
healthy
susceptible
incubation
latent
signs
healthy
infectious
immune, then susc
Disease Dynamics
infection
healthy
incubation
susceptible
latent
susceptible
latent
signs
healthy
infectious
immune, then susc
infectious “carriers”
Prevention
• ALL horses entering any premises should
be monitored closely during the period
immediately after arrival.
• Any horse that develops a nasal discharge
should be separated and swabbed by a vet
for presence of Strep equi.
Control of infection
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Why even attempt to control ?
Control of infection
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Why even attempt to control ?
1. Animal welfare
2. Financial complications
Control of infection
• Can limit spread by early detection of
shedders among newly affected horses and
their in-contacts
• Segregate suspected cases immediately
• All infected horses and their in-contacts
should remain in strict isolation.
• Horses should not enter an affected
premises unless can be isolated
Control of infection
• Due to chronic nature and common
occurrence of carrier animals, it is
impossible to tell when it is safe to mix
convalescing horses with others
Disease Dynamics
infection
healthy
incubation
susceptible
latent
susceptible
latent
signs
healthy
infectious
immune, then susc
infectious “carriers”
Control of infection
• No infected or in-contact animal should be
released from isolation until three
consecutive negative swabs have been taken
over a 2 week period
• Carrier animals can retain potential to
spread disease, even after 3 negative swabs
• Need endoscopic examination
Treatment
• Depends on stage of disease
• Controversial area
• Some ( ? a minority of ? ) vets consider
antibiotics to be detrimental
My approach
1. Horses with early clinical signs :
( nasal discharge / difficulty swallowing )
• Intra-muscular penicillin
• May inhibit formation of natural immunity
My approach
2. Horses with lymph node abscesses :
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Drainage and flushing of abscesses
Antibiotics may prolong time to taken for
abscesses to resolve
My approach
3. Horses exposed to Strep equi :
• Treat with penicillin until isolated from
infected horses
My approach
4. Horses with complications :
• Therapy aimed at specific problems
Treatment
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General nursing
Clean nose / abscesses
Change water frequently
Feed soft, palatable feeds
Recovery usually takes 4 weeks
Free from disease ???
• Shedding of the bacteria usually ends
rapidly after recovery, although it may be
intermittent.
• No convalescent horse, or in-contact, can be
considered free from infection until had
three negative swabs over a 2 week interval.
• But, carriers can still exist
Immunity
• 75% of horses that have the disease, won’t
develop the disease again for at least 4 years
Vaccination
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Not available in UK
Short duration of immunity
Still see disease where vaccine used
Serious side – effects
Unknown effect on carrier animals
Conclusions
• Outwardly healthy carriers pose real
problems
• Vaccine not straightforward
• Control measures are effective but
expensive
When I grow up……..