Strangles“a sore throat with a

vengeance”

Colin Mitchell BVM&S MRCVS

Hexham

Strangles

• Cause

• Epidemiology

• Clinical signs

• Diagnosis

• Notification

• Complications

Strangles

• 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

• 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

• 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

• horse – horse• fairly close contact

between infected and susceptible animals

Indirect Contact

• 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 incubation signs healthy

susceptible latent infectious immune, then susc

Disease Dynamics

infection

healthy incubation signs healthy

susceptible latent infectious immune, then susc

susceptible latent 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

• Why even attempt to control ?

Control of infection

• 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 signs healthy

susceptible latent infectious immune, then susc

susceptible latent 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 :

• 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

• 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

• 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……..