Exam 2 - Rhodococcus Equi, Foal Pneumonia Flashcards
what is the leading cause of disease & death in foals in texas > 1 month old?
pneumonia
what agent is the most common cause of severe pneumonia in post-neonatal, older than 1 week old, foals?
rhodococcus equi
in the united states, what is the 3rd leading cause of disease & 2nd leading cause of death in foals?
pneumonia
why does r. equi have a significant economic impact at endemic farms?
high incidence, high case fatality rates, labor/expense of diagnostic screening, prolonged, & expensive treatment
what is the etiology of rhodococcus equi?
pleomorphic, gram positive coccobacillus
what are the routes of infection for r. equi?
inhalation & ingestion
what is the pathogenesis of r. equi?
bacteria survive & replicate within alveolar macrophages - inhibits phagosome-lysosome fusion
T/F: r. equi infections in humans is becoming increasingly recognized in human patients
true
what are the clinical syndromes of r. equi? what is the most common?
- subclinical infection
- chronic, progressive, infection
- acute on chronic
- peracute onset of respiratory distress
- sudden death
subclinical infection
when are foals most commonly affected by r. equi?
most are exposed early in life & become infected shortly after
clinical signs between 3-16 weeks of age
T/F: r. equi is rare in adult horses & foals older than 6 months
true
what kind of pneumonia does r. equi cause?
pyogranulomatous pneumonia - focal, multifocal, or regional
why are clinical signs of r. equi pneumonia variable?
dependent on the stage & severity of pulmonary pathology
what are the main clinical signs of r. equi pneumonia?
productive or non-productive cough, tracheal rattle - mucopurulent exudate in airways, nasal discharge
increased respiratory effort
cyanosis
what clinical signs are associated with peracute r. equi pneumonia?
sudden onset of fever & respiratory distress & sudden death
what clinical signs are associated with chronic r. equi pneumonia?
unthrifty & failure to grow at a normal pace
what is included in extrapulmonary disorders?
metastatic sites of infection, immune-mediated disorders, & adverse effects pf treatment such as diarrhea & hyperthermia
T/F: EPD are prevalent & can occur concurrent or independent of r. equi pneumonia
true
why are EPDs bad?
challenging to detect ante-mortem
can negatively affect case outcome despite successful treatment of pneumonia
how is the prognosis of r. equi different with EPD?
foals with EPD have a lower survival rate
what are some EPDs that carry a poor prognosis?
uveitis, abdominal abscesses, septic synovitis/osteomyelitis
why is identifying EPDs important?
awareness & recognition of them help vets better advise their clients regarding treatment & outcome
what causes diarrhea in foals?
r. equi infection of gi tract or adverse effect of macrolide therapy
what is seen on necropsy of a foal with ulcerative enterotyphlocolitis?
ulcerative, pyogranulomatous lesions of small intestines, cecum, colon with intralesional bacteria & positive r. equi culture
what lesion is seen here?
ulcerative enterotyphlocolitis
in foals with r. equi gi infections, what were the clinical signs?
only 40% had diarrhea, 30% had failure to grow, & 90% have concurrent abdominal abscess or lymphadenopathy
how is abdominal lymphadenitis diagnosed in foals?
enlarged abdominal lymph nodes & lymphangiectasia
ultrasound
necropsy
what lesion is seen?
abdominal lymphadenitis
what lesion is seen?
abdominal lymphangiectasia
what clinical signs are associated with abdominal abscessation?
diarrhea, failure to grow, recurrent colic
large abscesses with caseous center
how is abdominal abscessation diagnosed?
abdominal ultrasound, u/s guided aspirates for culture & cytology, & necropsy
what lesion is seen?
abdominal abscessation
what is the prognosis of foals with abdominal abscessation?
very poor
how is abdominal abscessation treated?
long term antimicrobials & surgical excision/drainage (unsuccessful because of adhesions)
how is peritonitis diagnosed?
ultrasound & peritoneal fluid analysis
what are the common concurrent EPD seen in foals with peritonitis from r. equi?
abdominal abscesses, abdominal lymphadenopathy, & ulcerative enterotyphlocolitis
what is pyogranulomatous hepatitis?
pyogranulomatous microabscesses in the liver
how is pyogranulomatous hepatitis diagnosed?
no elevations in liver enzymes, ultrasound, & necropsy
what lesion is seen on ultrasound?
pyogranulomatous hepatitis
what are the suggested causes of uveitis in foals with r. equi?
immune-mediated & septic animals
septic complication associated with the severity of lung disease
how is uveitis diagnosed?
ophthalmologic exam - aqueous flare, hypopyon, iris discoloration, miosis, & blindness
how is uveitis treated?
topical steroids & atropine
TPA
what is the prognosis uveitis?
associated with non-survival
what percentage of foals are affected by polysynovitis when they have r. equi?
25%
what is polysynovitis?
effusion of 1 or more synovial structures without lameness - often bilaterally symmetrical
deposition of immune complexes in synovial membranes
what joints are commonly affect in polysynovitis?
tarsocrural, carpal, front & rear fetlocks, stifle
median number of joints affected = 5
how is polysynovitis diagnosed?
usually recognized based upon clinical signs
how is polysynovitis treated in foals?
generally none - resolves with the resolution of pneumonia
how is septic synovitis diagnosed?
synovial effusion with lameness & synovial fluid analysis - 10% of foals affected
what is the prognosis of foals with r. equi associated septic synovitis?
poor prognosis
what is the treatment for foals with r. equi associated septic synovitis?
joint lavage
systemic antimicrobials
intra-articular antimicrobials
regional limb perfusion
what are the clinical signs of mediastinal lymphadenopathy?
enlargement of the mediastinal lymph nodes, respiratory distress, respiratory noise
how is mediastinal lymphadenopathy diagnosed?
rads, ultrasound, & necropsy
what disease process is shown on this rad?
mediastinal lymphadenopathy
what is the prognosis of foals with r. equi bacteremia?
poor prognosis
what lymph nodes are typically affected with peripheral lymphadenopathy in foals with r. equi?
submandibular, retropharyngeal, & inguinal lymph nodes
what clinical signs are associated with vertebral body osteomyelitis in foals with r. equi?
fever, stiffness, pain, neuro signs, cauda equina syndrome
what is seen on this rad?
cauda equina syndrome
what lesion is pictured?
paravertebral abscess
what is the treatment of hyperthermia in foals with r. equi?
water or alcohol baths
environmental control
what are the clinical features of hyperthermia in foals with r. equi?
body temperature > 104, tachypnea, tachycardia, respiratory distress
adverse effect of macrolide treatment - environmentally dependent
what is the gold standard for diagnosing r. equi pneumonia in foals?
isolation of r. equi from a tracheobronchial aspirate from a foal with clinical signs of pneumonia
how is a diagnosis of r. equi pneumonia supported?
cytologic evidence of septic inflammation & gram positive pleomorphic coccobacilli in TBA specimens
radiographs or ultrasound of pulmonary abscessation or consolidation
when should r. equi be considered as a differential?
any infectious disease during age period 3-24 weeks
history of endemic farm should raise clinical index of suspicion
what may be heard on thoracic auscultation of a foal with r. equi pneumonia?
crackles, wheezes, referred large airway sounds, & attenuated bronchovesicular sounds
what may be some clin path findings in a foal in r. equi?
leukocytosis with mature neutrophilia, WBC useful as a screening method
hyperfibrinogenemia
thrombocytosis
serum amyloid a
serum chemistries - effects of hypoxemia & metastatic infection
arterial blood gas
what does r. equi look like on cell culture?
irregularly round, smooth, semitransparent, mucoid, salmon-pink colonies
what bacteria is this?
r. equi
why can false negatives occur on culture for r. equi?
prior antimicrobial therapy
overgrowth of other bacteria
why can false positives occur on culture for r. equi?
environmental contamination & growth of avirulent isolates
what is PCR used for in r. equi infections?
high sensitivity & specificity for detecting virulent r. equi in tba fluid of affected foals - should not replace culture but used in conjunction
what is culture needed for r. equi?
antimicrobial susceptibility testing
T/F: PCR & cultures run on nasal/nasopharyngeal swabs has a high sensitivity for detecting r. equi
false - poor sensitivity
why are thoracic rads helpful in diagnosing r. equi infections?
valuable for detecting pulmonary lesions, images can be taken in the field, diagnostic/screening values
assessment of treatment
what patterns are commonly seen on thoracic rads of foals with r. equi?
interstitial & alveolar patterns
why is ultrasound useful for foals with r. equi?
detects, localizes, & characterizes peripheral lung consolidations & abscesses, more sensitive than rads, & useful for detection of clinical & subclinical pulmonary disease
what are the disadvantages of using ultrasound for foals with r. equi?
can’t penetrate air-filled lung - can miss deep lung or mediastinal abscesses
what abnormalities are seen on ultrasound of foals with r. equi pneumonia?
comet tails
consolidation - architecture of lung is intact
abscessation - architecture is lost
pleural effusion
