Equine Strangles Flashcards
how quickly do the mandibular/suprapharyngeal lymph nodes drain the tonsils?
within hours
what are the clinical signs of Streptococcus equi subsp equi?
fever
anorexia
depression
lymphadenopathy
rhinitis
nasal discharge
abscesses
which lymph nodes are impacted by strangles?
submandibular
retropharyngeal
parotid
cranial cervical lymph nodes
where can you sample for strangles?
nasal swab
nasopharyngeal wash
guttural pouch wash
abscess aspirate
what is the best sample to take for strangles?
aspirate of mature abscessed lymph node
is PCR or culture more sensitive?
PCR
what does the PCR look for?
DNA sequence for SeM (anti-phagocytic M protein)
how many false negatives are there with culture?
40%
what is serology looking for?
systemic antibody to SeM
what should you not do with a high or very high serology for systemic antibody to SeM?
do not vaccinate
suspect purpura hemorrhagica or metastatic
should you use antibiotics for lymph node abscessation?
no- now contraindicated
what are the negatives of using penicillin for early clinical signs of strangles?
often just returns
no protective immunity
how long does nasal shedding usually last?
2-3 weeks
can last years
what does disease severity correlate with?
dose and frequency of bacterial challenge
why should isolate cases!
what are the steps of outbreak management?
report
test
quarantine
hygiene
is strangles reportable?
yes- in most states
what are the most common causes of outbreaks?
apparently healthy shedders
should you vaccinate affected animals with strangles?
no
what percentage of horses with strangles develop good immunity?
75%
limited time: 2 years
what is prevention like?
very difficult
isolate new horses for 3 weeks
vaccination
what are the main problems with the intranasal vaccine?
occasional residual virulence
accidental IM abscesses
what are the complications of strangles?
carrier status
metastatic/bastard strangles
purpura hemorrhagica
myopathy
what can you use to diagnose prolonged carriers?
endoscopy
pharyngeal wash
not serology
what is the mortality rate of metastatic strangles?
62%
what is purpura hemorrhagica?
type III immune: aseptic necrotizing vasculitis
what do the virulence factors cause with the immune system?
ineffective neutrophil response
when does strangles shed?
1-2 days after first fever
what is the fever like with strangles?
high and persistent
tends to resolve when abscesses rupture
how long do the abscesses take to rupture?
1-4 weeks
what do abscesses always do?
neutrophilic leukocytosis
hyperfibrinogenemia
serum amyloid A elevated in more acute
hyperglobulinemia
similar response in R. equi
how are samples ranked for diagnosis of strangles?
aspirate of mature abscessed lymph node > guttural pouch wash > pharyngeal wash > nasal swab
is culture considered gold standard for diagnosing strangles?
no- 40% false negatives
what does a weak positive on serology indicate?
very recent or residual or vaccinal exposure
does antibiotic treatment increase risk of metastatic strangles?
no
which horses with strangles should get antibiotics?
depressed, anorexic, dyspneic
pregnant mares, foals not nursing: maybe
cranial nerve signs
how can you establish horses clear of strangles?
nasal swabs: three negatives at 5-7 day intervals
guttural pouch/nasal wash: one negative may be enough
both with PCR
what should you do once an animal has strangles on a farm?
stop all movement on/off
segregate groups, rectal temps on all twice daily
all horses potentially contagious for at least 6 weeks after secretions dry
do not vaccinate affected animals
why might older horses develop mild disease?
persistent immunity
can still transmit
what do you need to reach with the intranasal vaccine?
pharyngeal and lingual tonsils
how long can an animal be positive on nasal wash for strangles after vaccination?
6 weeks
what percentage of animals become prolonged carriers of strangles?
10%
what is in the guttural pouch of carriers?
empyema
chondroids
what can you give to aid in treatment of empyema in prolonged carriage?
20% acetylcysteine
how likely is metastatic strangles to occur?
2-20% of cases
how can you treat metastatic strangles?
prolonged antibiotics- 2.5 months
some surgical
how can you prevent purpura hemorrhagica?
do not vaccinate for 1-2 years after natural infection or if high titers
happens 2-4 weeks after other respiratory infections too
