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
what pathogen do you suspect?
suppurative bronchopneumonia
pasturella multocida
usually a firm red lung with no fibrin
what pathogen?
fibrinous pleuritis!
H somni
sometimes only severe pleuritis is seen
what pathogen?
head tilt–>otitis media
microabscesses in lungs
mycoplasma bovis
