Fever & Immune Flashcards
Describe the difference between a fever and hyperthermia
Fever = raised thermoregulatory set point; hyperthermia = no alteration in the thermoregulatory set point but there is abnormalities with heat production or dissipation
What controls the thermoregulatory set point?
Anterior hypothalamus
Give examples of endogenous and exogenous pyrogens
Endogenous: inflammatory cytokines (IL1 and TNFalpha), exogenous: LPS, toxins
What can cause hyperthermia?
Exercise, medications, seizures, environmental changes, stress, etc.
____ is when the body is trying to cool; ______ is when the body is trying to create more heat
Hyperthermia; fever
What can cause a fever?
neoplasia, infection, immune-mediated disease, inflammation (NIII)
When do we consider a fever of unknown origin (FUO) in vet med?
Fever persists long enough that many common or self-limiting causes are ruled out (viruses, simple abscess, etc.). Initial diagnostics don’t reveal a cause of fever (history, PE, CBC/chem/urinalysis, imaging, failure to respond to antibiotic therapy)
Clinical signs of fevers are specific or non-specific?
non-specific
_____ and _____ can give important diagnostic clues to fevers!
History and physical exam
Where do you even start to look when diagnosing a fever case
Look for a focus of disease, try to localize where the problem is to a system
What are some first tier diagnostics (safe, inexpensive, simple, easy to interpret)
CBC with blood smear, biochem, UA, urine culture, FeLv/FIV in cats, imaging
What are some second tier diagnostics?
Serial/repeated PE, blood culture, additional imaging (CT, U/S), joint taps (cytology + culture), specific infectious disease panels, FNA (mass + LN), CSF collection, biopsies
What are some differentials for non-inflammatory joint disease causing pain?
Developmental joint disease, Degenerative joint disease, Trauma, Tumor
What are some differentials for inflammatory joint disease causing pain?
Neutrophillic inflammation in joints, septic or sterile (within joint), joint emboli (septic, immune complexes < type 3 hypersensitivities can cause this)
What’s the pathogenesis of how immune complexes could cause inflammation in a joint?
Immune complexes deposited in joint –> complement activation –> inflammation < usually sterile within joint
When is sepsis and sterile inflammatory joint disease MORE LIKELY to occur?
Septic more likely to occur when: single swollen/painful joint, history of sx or trauma near/of joint, previous or current infection (hematogenous spread)
sterile more likely when multiple joints affected (smaller, distal joints), history of recent antibiotic use or vaccination.
What’s the gold standard diagnostic test for septic OR sterile inflammatory joint disease?
JOINT TAPS AND CULTURE/CYTOLOGY THE FLUID
When should we do a joint tap? X3
Solitary joint disease (inflammation, systemic illness), polyarthritis, fever of unknown origin (might not demonstrate joint pain or effusion but they like to hide here!)
What should you always do with joint fluid once you obtain it?
culture
Which of the two (polyarthritis or solitary joint disease) are you more likely to see in smaller vs bigger joints?
Polyarthritis think smaller joints, single joint disease think bigger joints
What does normal joint fluid look like grossly and on cytology?
Grossly: clear, colourless, viscous (long stringy); cytologically: low cellularity (<2/hpf on 50x), mixture of mononuclear cells (large and small), <10% neutrophils
What might synovial fluid look like grossly and on cytology if it’s abnormal?
Grossly: turbid/cloudy, discoloured (red: streaks = iatrogenic?, yellow = prior hemorrhage, high bilirubin?), thin and not sticky; cytology: high cellularity, >20% neutrophils (degenerate or non-degenerate), maybe bacteria
On cytology what are the main differences between sterile vs septic inflammatory synovial fluid?
Sterile inflammatory: mostly non-degenerate neutrophils; septic inflammation: degenerate neutrophils with/without bacteria
What kind of cells are mostly present in a degenerative or traumatic etiology synovial joint tap fluid?
Mostly mononuclear cells
What kind of bone mainly is destroyed by erosive polyarthritis?
Subchondral bone mainly (very uncommon disease), but mostly affects carpal bones of small, middle aged dogs
What’s more common, primary or secondary non-erosive joint disease?
Primary > secondary
what’s the most common form of inflammatory joint disease?
Idiopathic (primary)
What kind of joint disease (inflammatory, non-inflammatory, etc) is systemic lupus erythematosus? And what is it’s most common clinical sign
Inflammatory joint disease, non-erosive immune mediated polyarthritis. The most common clinical sign is polyarthropathy
What’s the signalement/who is most often affected by idiopathic/primary IMPA
No inciting causes, middle-aged dogs > cats, no sex or reed predilections
What are some causes of Reactive (secondary) IMPA
Underlying causes are distant from the joint: infectious (if it were in the joint we would call it septic), septic arthritis can arise from bacteremia, medications (antibiotics, vx), neoplasia, dietary elements (uncommon)
What’s the pathogenesis of Type 3 hypersensitivities causing IMPA?
Chronic inflammation –> circulating immune complexes deposited in joint –> complement activation –> inflammation
What kind of clinical signs specific to joints might you see with IMPA?
Lameness manifesting as a stiff gait, walking on egg shells look, joint pain or swelling (1 or >1), reluctance to move
We know IMPA C/S are non specific, but if it gets polysystemic, what c/s will we see?
Dermatologic signs like pallor or bleeding, mucocutaneous ulcers
What percentage will be lame or have palpable joint effusions with vague systemic signs?
50%
Will you see a fever with IMPA?
Yes it’s a common sign and cause of FUO (but not always present)
What might syou see on cytology from an IMPA arthrocentesis?
Non-degenerative neutrophilic inflammation in multiple joints, negative culture
Before you can say “idiopathic” you have to rule out other diseases by doing….
thorough serial PE, CBC, chem, UA, infectious disease testing (tick borne diseases like Erlichia), urine or blood cultures, imaging
Why do we do radiographs for IMPA? What are we looking for?
Osteomyelitis
How many blood cultures do we run in a stable vs unstable patient?
Stable: 3 samples over 24 hour period; Unstable: 2-3 separate samples 30-60 minutes apart
If we have an intermittent fever from IMPA, how should we collect blood cultures?
Separate sites, serially, increases sensitivity and specificity
The SNAP 4Dx plus and Accuplex (Antech) measure what?
Antibodies to: anasplama, Borrelia burgodoferi (Lyme), Ehrlichia canis, ewingii. Antigens for heartworm
Why might we get a false negative on the above tests?
It could be too early to test since it takes body up to a month to make antibodies
If we have a case of joint pain and systemic fever, additional tests are unremarkable… what treatment do we do?
Treat with immunosuppressive dose of prednisone (1-2 mg/kg/day). If they’re previously on an NSAID, we need a washout period between getting NSAID and prednisone.
What’s a good monitoring plan for an animal with IMPA?
Recommend a repeated joint tap in 1 month, prior to tapering prednisone (owner declines this often though due to costs).
If multisystemic immune, monitor other parameters that can be assessed.
If a dog’s on prednisone, should you taper? If so what else do we do?
Taper dosage over time if the disease is controlled, can add in a second line like cyclosporine
Bacterial endocarditis more often affects mitral or aortic?
Mitral > aortic ( if it’s on aortic = worst prognosis due to it putting pressure on closed valves)
What are some common bacterial agents that cause endocarditis?
Staph, Strep, E. coli, Pasteuerella, Bartonella
What’s the pathogenesis of bacterial endocarditis?
Bacteremia –> colonization of valves –> damage to valve + development of vegetative lesions
What’s the typical signalement of dogs that are affected by bacterial endocarditis?
Large breed, males > females, have a predisposing factor (immunosuppressed, recent surgery, infection, wound, pyoderma, indwelling catheter, dental disease (sorta))
T/F: bacterial endocarditis is associated with MMVD
FALSE
How do we treat bacterial endocarditis?
Bactericidal broad-spectrums (ampicillin + aminoglycoside; ampicillin + clavulanate + enrofloxacin; doxycycline + enro or rifampin for bartonella), treat cardiac disease, thromboprophylaxis
