Strangles in Horses Flashcards Preview

Respiratory > Strangles in Horses > Flashcards

Flashcards in Strangles in Horses Deck (19):
1

strangles - which bacteria causes it

Streptococcus equi subspecies equi

2

Strep. equi equi

gram positive
Not a normal inhabitant of URT
Does not require prior viral infection for colonisation
Highly infectious, particularly weanlings and yearlings
Equine specific

3

epidemiology

Infection primarily 1-5 yo
Foals born from immune mares resistant for 3 months
Morbidity 100%
Mortality up to 10% with appropriate therapy
20% complication rate
Immunity not lifelong
75% still immune after 3-4 years
transmission by direct contact

4

pathogenesis

Incubation period 2 – 6 days, Recover over 2-3 weeks
Nasal shedding for 3-6 weeks after disease
31% ofhorses become carriers
Incomplete clearance of pus from GP

5

3 main clinical presentations

Classic acute disease
Atypical strangles
Complications

6

Classic Acute Disease - Clinical Signs

Fever, depression, inappetence
Abscessation of mandibular, parotid or retropharyngeal lymph nodes, rupture after 7-10 days
Dyspnoea and dysphagia if abscesses compress larynx or
interferes with cranial nerve to pharynx
Mucoid to purulent nasal discharge
Cough

7

Atypical Strangles - Clinical signs

Mild inflammation of URT
Slight nasal discharge
Cough
Fever
Self limiting lymphadenopathy - dependent on bacterial strain plus immunity + genotype of the horses

8

Complications - Clinical Signs

Internal abscessation
Purpura hemorrhagica
Anemia
Guttural pouch empyema and chondroids
Retropharyngeal abscessation
Laryngeal hemiplegia
Horner's syndrome
CNS abscess
Endocarditis or myocarditis
Agalactia
Tracheal compression due to cranial mediastinal LN
abscess
Suppurative bronchopneumonia ie LRT signs
Myopathies

9

Internal abscessation

Intermittent colic
PUO
Anorexia
Depression
Weight loss
Depends on site of abscess

10

Purpura hemorrhagica

generalized vasculitis caused by Type III hypersensitivity reaction
1-2% of infected horses
Thrombosis of small arteries can occur
Skin and muscle necrosis may result
Ventral edema, body swelling and petechial haemorrhages on mucus membranes
Death due to pneumonia, cardiac arrhythmia, renal failure, GI disorders

11

Diagnosis

Clinical signs
Leucocytosis, hyperfibringenaemia
Isolation (culture) or detection (PCR) of S. equi from LN, nasopharyngeal swab, GP lavage fluid
Culture of 3x n/ph swabs

12

Treatment - horses exposed to strangles

Treat with penicillin until isolated from infected horses
Will not become immune

13

Treatment - horses with early clinical signs

Penicillin
May inhibit natural immunity so may contract the disease again with continued exposure
General nursing, anti-pyretics, soft food

14

Treatment - horses with LN abscesses

Poulticing and drainage of abscesses
Antibiotics may prolong resolution of the abscess
General nursing, anti-pyretics, soft food

15

Treatment - with abdominal abscesses

long term antibiotics (usually penicillin or trimethoprim sulfa/rifampin) for up to 6 weeks)

16

Treatment - with Guttural pouch empyema +/- chondroids

drainage via the pharyngeal openings or surgical drainage
antibiotics

17

Purpura hemorrhagica - treatment + prognosis

Penicillin
Dexamethasone
Prednisolone
Analgesics – NSAIDS
Fluids
Palliative measures e.g. hydrotherapy, massage
prognosis - guarded

18

management of outbreaks

Isolate premises + affected horses
good hygiene between horses for staff
confirm resolution of disease + test for carriers

19

prevention

vaccine
Isolate new horses for 3-4 weeks