Bacterial Diseases Flashcards
most important bacterial diseases for horses
▪ Streptococcus equi subsp. equi
▪ Sequelae of Strep equi subsp. equi
▪ Bacterial pneumonia
Streptococcus
equi subsp equi
- what type of bacteria is this? what common disease does it cause?
▪ Gram + B-hemolytic coccoid
▪ Primary pathogen
▪ Causative agent of Strangles
> Very common infectious disease
> Highly contagious
Strep equi subsp equi
▪ Epidemiology, morbidity, mortality, transmission?
▪ Most common in 1-5 year olds
▪ Naïve populations
> Morbidity= 100%
> Mortality= 10%
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Transmission
▪ Nasal and abscess discharge
▪ Shedding for 4-6 weeks post-infection (intermittent)
▪ Asymptomatic carriers
Strep equi subsp equi
▪ Pathogenesis
▪ Adheres to epithelial cells
▪ Translocates across basement membrane
▪ Enters local lymphatics and lymph nodes
> Replicates extracellularly
> Attracts large numbers of neutrophils
▪ Lymph node abscessation
> 10-14 days post-infection
Strep equi subsp equi
▪ Clinical signs
▪ Fever
▪ Lethargy
▪ Inappetance
▪ Hyperemic mucous membranes
▪ Serous- mucopurulent nasal discharge
▪ Serous- mucopurulent ocular discharge
▪ Lymphadenopathy > Rupture in 7-14 days
what is strangles? signs? length?
Strep equi subsp equi > lymphadenopathy sequelae
▪ Stridor
▪ Dysphagia
▪ Respiratory distress
▪ Rupture into guttural pouch
▪ Neuropathy
▪ Empyema
▪ Chondroid formation
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Disease course
▪ 23 day average
Strangles diagnosis
▪ Clinical signs
▪ Culture or PCR
> Nasopharyngeal lavage
> Guttural pouch lavage
▪ Upper airway endoscopy
structures in the medial compartment of the guttural pouch
▪ Internal carotid artery
▪ Cranial cervical ganglion
▪ Cranial sympathetic trunk
▪ Glossopharyngeal nerve
▪ Vagus nerve
▪ Accessory nerve
▪ Hypoglossal nerve
important structures in the lateral guttural pouch compartment
▪ Maxillary artery
▪ External carotid artery
▪ Facial nerve (VII)
▪ Mandibular branch of the trigeminal nerve
Strep equi subsp equi
▪ Treatment
▪ Supportive care
> Anti-inflammatories
▪ Abscess care
> Hot packing
> Lancing
> Lavage
▪ Guttural pouch
> Lavage
> Instillation of penicillin gel
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- mostly do not need antimicrobials
Strep equi subsp equi
▪ When to use antimicrobials?
- sequelae?
▪ Acutely and severely affected
> Prior to abscess formation
▪ Respiratory distress
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Carriers (usually do not need systemic antimicrobials)
▪ In conjunction with local therapy
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Sequelae of antimicrobial use
▪ Metastatic abscesses
▪ Purpura hemorrhagica
▪ Delayed disease progression
strangles outbreak management
- goals and actions
▪ Primary goal
> Immediately quarantine the property
▪ Establish isolation area on property
▪ Establish cleaning and handling protocols
▪ Perform endoscopy on all horses
> Apparently healthy
> Affected
▪ Collect nasopharyngeal lavages from all recovering horses
> 3 negative samples in a row
strangles prevention
▪ Quarantine new arrivals > 3 weeks
▪ Screening
> Guttural pouch endoscopy, Culture +/- PCR
> Nasopharyngeal lavage
> Serology: Does not indicate active infection, Use with caution
▪ Excellent biosecurity
vaccination for strangles
- who not to give?
- types
▪ DO NOT vaccinate recently infected horses
▪ DO NOT vaccinate when SeM ≥ 1:3200
▪ Extract vaccine > Decreases risk by 50%
▪ Attenuated live vaccine > Intranasal
Strep equi carriers
- how many? who are the carriers?
- how long? what forms?
- diagnosis?
▪ ~ 10% of horses in an outbreak
> Fail to clear infection
▪ ~40% of horses positive @ 40 days
> Median duration= 60 days
▪ Persists for months to years
> Empyema
> Chondroids
▪ Diagnosis
> Culture or PCR
Strep equi carriers
▪ Treatment
Empyema
▪ Repeated lavage
▪ Penicillin gel
▪ Acetylcysteine
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Chondroids
▪ High-volume lavage
▪ Acetylcysteine
▪ Endoscopic-guided
▪ Surgical intervention
Metastatic abscesses from strep equi equi
- what are these? how common?
- clinical signs?
- bastard strangles - spread throughout body
▪ ~ 2-20% of cases
▪ Exact pathogenesis unknown
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Clinical signs:
▪ Fever
▪ Lethargy
▪ Inappetance
▪ Weight loss
▪ Organ system specific
Metastatic abscesses (bastard strangles) diagnosis, treatment, prognosis
Diagnosis:
▪ SeM titer >1:12,800
▪ Abscess on advanced imaging
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Treatment:
▪ Supportive care
▪ Surgical intervention
▪ Long-term antimicrobials
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Prognosis:
▪ Mortality rate = 62%
Purpura Hemorrhagica
- cause? how common?
- risk factors
- what is this?
- strep equi equi: 6-7% of cases
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Risk factors
▪ Re-exposure to bacteria
▪ Vaccination
▪ 2-4 weeks post infection
▪ SeM serum titer >1:3200
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▪ Type III immune-mediated hypersensitivity reaction > because they have a lot of antibody already
Purpura Hemorrhagica clinical signs
“cellulitis on all four limbs” is what we often hear from clients
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▪ Fever
▪ Tachycardia & tachypnea
▪ Reluctance to move
▪ Edema
> Limbs, head, ventrum
> Serum exudation→ ulceration
> Skin sloughing
▪ Petechia and ecchymosis
▪ Colic or diarrhea
▪ Cardiac arrhythmias
▪ Renal failure
▪ Muscle infarction
Purpura Hemorrhagica
▪ Diagnosis
▪ History and clinical signs
▪ Skin biopsy (not really a great idea as it can take a long time to heal)
> Leukocytoclastic vasculitis
▪ SeM titer > 1:12800
Purpura Hemorrhagica
▪ Treatment, mortality rates
Limbs
▪ Hydrotherapy
▪ Bandaging
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Systemic
▪ Corticosteroids > immunosuppressive
▪ Non-steroidal anti-inflammatories
▪ Antimicrobials > if you think they still have an active infection, which they may not!
▪ Intravenous fluid therapy
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▪ Mortality rate= 5-7 %
Immune-mediated myositis
- who gets it?
- associations / triggers?
- clinical signs?
▪ Quarter horses
▪ < 8 or >17 years
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40% associated with trigger
▪ Strep equi
▪ Vaccination
▪ Respiratory virus
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Clinical signs
▪ Muscle atrophy
▪ Stiffness & malaise
▪ Weakness & recumbency
Immune-mediated myositis
▪ Diagnosis, treatment, prognosis
Diagnosis
▪ Genetic testing
▪ Muscle biopsy > Epaxial or gluteal
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Treatment
▪ Corticosteroids
> 1 month
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Prognosis
▪ Full recovery possible
▪ 50% recurrent episodes
bacterial pneumonia in horses - pathogenesis in general
Disruption of host defenses
▪ Mucociliary elevator dysruption
▪ Immunosuppresion
▪ Bypass of upper airway
▪ Pre-existing inflammation
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▪ Colonization of airways
▪ Extension into parenchyma
most common agent causing bacterial pneumonia in the horse?
strep zooepidemicus
Bacterial pneumonia
▪ Clinical signs
Clinical signs
▪ Fever
▪ Inappetence
▪ Lethargy
▪ Coughing
▪ Nasal discharge
▪ Tachypnea
▪ Increased respiratory effort
▪ Respiratory distress
▪ Weight loss
Bacterial pneumonia
▪ Diagnosis
▪ Physical examination
▪ Thoracic ultrasound
▪ Thoracic radiographs
▪ Endoscopy
▪ Culture and sensitivity
Bacterial pneumonia
▪ Treatment
▪ Antimicrobials > Based on sensitivity
▪ Anti-inflammatories
▪ Intravenous fluids
▪ Supportive care
▪ Correct underlying condition
possible sequelae of bacterial pneumonia
▪ Pleuropneumonia
▪ ARDS
▪ Laminitis
▪ Septicemia
