Bovine Respiratory Disease Flashcards
Why are cows prone to respiratory disease?
cow lungs are very small relative to the animal’s oxygen requirements, abundant interstitial tissue, diffusion across air blood border is less efficient
most common CS of BRD in early disease? worsening disease?
nasal/ocular discharge, depression, anorexia, fever as high as 42, tachypnea, moist cough
worsening condition: resp distress, crusty muzzle, dyspnea, pleural friction and muffled lung sounds, exudate in trachea, abducted elbows and extended neck
why are neutrophils nasty little bastards when it comes to BRD?
there’s nowhere for them to drain into and they do a lot of damage/collateral damage, they cause a huge cytokine storm
list viruses involved in BRD
how do these viruses do damage?
BVDV, parainfluenza type 3, BHV-1, coronavirus
not commensal, but can be latent for long periods
viruses damage the mucocliliary mechanism, damage tracheal epithelial cells which allows bacteria to attach, they deplete host defences, and suppress the immune system
ultimately compromise the host immune system which allows bacteria to attack
IBR is caused by what? how does it cause damage? CS?
BHV-1
epitheliotropism, massive URT and tracheal epithelium damage
CS: seros nasal discharge, conjunctivitis, abortions, white plaques on nasal mucosa
can be latent for a while and then re appear in times of immunosuppression/stress
how do you tell the difference between tracheitis and expectorated material from the lungs?
expectorated material: easily wiped away to reveal smooth healthy mucosa
tracheitis: exudate adhered to mucosa, and mucosa underneath is eroded and ulcerated
BVDV is highly ____. CS?
immunosuppressive
wide variety of lesions, leukopenia, bacterial bronchopneumonia progresses quikcly due to immuneosuppression
which BRD pathogen causes mild disease unless complicated by secondary bacterial agents and infects alveolar macrophages?
parainfluenza virus 3
what BRD pathogen causes interstitial pneumonia which can be severe and diffuse? what other CS are present?
bovine respiratory syncytial virus (BRSV)
acute onset, high fever, open mouth breathing with audible grunt
you see a cow in a feedlot that was fine yesterday and is now presenting with dyspnea, open mouth breathing with an audible grunt, and has a high fever. what pathogen do you expect?
BRSV
what do you see and what pathogen caused this likely?
BRSV
emphysema and interstitial edema
which virus is a pneumoenteric virus associated with calf diarrhea and calf resp disease, winter dysentery, and combined penumonia and diarrhea in calves and adults
coronavirus
do BRD viral pathogens often work alone?
they can but not usually, they like to team up and are usually a precursor for bacterial proliferation
list the bacterial pathogens involved in BRD
manheimia haemolytica
pasturella multocida
histophilus somni
mycoplasma bovis
biberstinia trehalosi
MANY are commensals in the resp tract
what is the role of stress in BRD?
within 4 hours, healthy/non stressed animals are able to clear 90% of an inhaled administered dose of bacteria
which BRD bacteria is a gram neg rod, commensal, produces an endotoxin/leukotoxin lethal to macrophages, and converts to a more dangerous serotype?
mannhaemia haemolytica
it converts/overgrows to a pathogenic serotype, A1, that is more virulent, under stressful stimuli
it’s bad on it’s own, it has lots of virulent factors
mortality rate is high when a virulent strain is combined with preexisting viral infection for which BRD bacteria?
M. haemolytica
M. haemolytica causes what pathological lesions?
bilateral fibrinous bronchopneumonia with 25-75% of lungs involved, anterior ventral distribution
what pathogen do you suspect
fibrinous bronchopneumonia
M. haemolytica
which BRD pathogen is:
- gram neg commensal
- common in younger calves esp dairy
- can cause neonatal septicemia
- relies on predisposing factors
pasturella multocida
what pathogen do you suspect?
suppurative bronchopneumonia
pasturella multocida
usually a firm red lung with no fibrin
which BRD pathogen is:
- gram neg commensal
- prefers the LRT
- causes fubrinopurulent bronchopneumonia but also abscessing laryngitis, thromboembolic meningoencephalitis, polyarthritis-polyserositis, fibrinous pericarditis, sudden death via left ventricular papillary muscle necrosis
histophilus somni
be sus of what pathogen is a herd has cattle showing pneumonia, CNS disease, sudden death from heart failure, and lameness?
histophilus somni
which pathogen is most similar to histophilus? in what ways are they similar
mannhaemia haemolytica
vasculitis, endothelial cell damage, thrombosis
what pathogen?
fibrinous pleuritis!
H somni
sometimes only severe pleuritis is seen
what BRD pathogen:
- lacks a cell wall
- a “newer” pathogen
- can act as a primary pathogen
- causes otitis and arthritis as well as pneumonia
- good at evading the immune system
- reoccurs in periods of stress
mycoplasma bovis
what pathogen?
head tilt–>otitis media
microabscesses in lungs
mycoplasma bovis
which pathogen is a virulent fast acting relative of mannhaemia haemolytica that tends to effect the healthiest cows?
biberstinia trehalosi
what are some ways to diagnose BRD based on clinical signs?
DART (depression, appetite, respiratory signs, temp) system for feedlot checking
Wisconsin Scoring Resp Chart for dairy scoring
T or F: auscultation of lung field and trachea is not very useful in diagnosing respiratory diseases
true! it has poor sensitivity unless severe pneumonia present, and cattle typically do not have crackles and wheezes
“sucking soup” noise in the thorax often referred from distal trachea and is indicative of
lung consolidation
diagnostic testing options of BRD in live cattle and pros and cons of each
deep nasopharyngeal swab: easy to do and non invasive, but interpretation can be tricky, best used when you have multiple animals to sample
trans-tracheal wash: usually less contamination from upper airways, but more invasive and more time and skill
BAL: best diagnostic interpretation of pathogen and can do cytology, but more invasive and blind placement and you need special equipment
paired sera: good for when you’re chasing a virus
what samples should I send from a necropsy?
lungs: at least 4 sections, be sure to get the border of normal and abnormal, handle with care
be sure to send other tissues too like kidneys, brain, etc
say I had a bronchopneumonia in a dead cow and I want to send it for bacterial testing. how should I sample the tissues?
dont freeze it, collect a >4cm slab, get an area with normal and abnormal tissue, avoid abscesses
pros and cons of modified live vaccines and killed vaccines
modified live: fewer doses are needed, less expensive, induce complete humoral and cell long lasting immunity
killed: get humoral response but less cell immunity, requires 2 doses 21 days apart, expensive but more “safe”
this is just a reminder that your BRD vaccine needs to include both BVD types!!!!!
!!!!!!
what role do intranasal vaccines play in regards to BRD?
usually used in young animals when the maternal antibodies have an inhibitory effect on parenteral vaccine induced immune response–>goal is that the antigenic mass from the vaccine will generate an immune response even with maternal antibiodies and the antibodies produced protects the mucosal surfaces
what are Dr Bradleys hot tips for vaccine choices and protocols regarding BRD?
- choose your vaccine protocol based on field BRD trials with strong evidence
- collaborate with experienced vets
- listen to your clients and make protocols user friendly
should you give NSAIDs to BRD cows?
ideally, but the evidence says they dont do much, the only way they would do something is if you gave them early on to prevent the cytokine storm and prevent permanent lung damage
what antibiotics can you use in dairy cows?
aminopenicllins or TMS
tetracylines for BRD?
injection lasts 3 days so likely have to repeat, broad spectrum, some resistance concerns
TMS for BRD?
daily injection (short acting only), broad spectrum, resistance concerns
aminopenicillins for BRD?
gets some gram neg bacteria, need daily injections
cephalosporins for BRD?
they are category 1, gets some gram neg, need daily injection, SQ formulation lasts 5-7 days but controversial
phenicols for BRD?
has good post antibiotic effect, broad spec, good if you give just 1 SQ injection
macrolides for BRD?
category 1, not good for gram neg, concentrates well in the lungs, good post antibiotic effects, lasts 10 days with one injection
fluoroquinolones for BRD?
category 1, good gram neg coverage, can be bad for growing animal cartilage, SHOULD ONLY BE USED FOR TREATING INDIVIDUAL CASES AFTER 1ST LINE TREATMENT HAS FAILED
