Lecture 6 10/15/24 Flashcards
What are the characteristics of bovine respiratory syncytial virus?
-causes formation of syncytial cells in the lungs
-very common
-most cattle are likely seropositive
What are the two manifestations of BRSV?
-upper respiratory, which is more common
-lower respiratory
What are the clinical signs of an upper BRSV infection?
-high fever
-ptyalism
-cough
-increased lung sounds
-anorexia
-oculonasal discharge
What are the characteristics of lower BRSV infection?
-causes interstitial pneumonia that alters the architecture of the lungs
-inflammation occurs between alveoli
-ruptured alveoli result in emphysematous bullae and subcutaneous emphysema
What are the clinical signs seen in calves with interstitial pneumonia due to BRSV?
-expiratory dyspnea
-open-mouthed breathing
-respiratory collapse
What is the signalment of cattle with BRSV?
cattle can be in any age group
Why is BRSV difficult to culture?
the virus is very fragile and not likely to grow/survive
Which diagnostic methods are used for BRSV?
-immunohistochemistry
-FA
-PCR
-necropsy (easiest diagnostic method)
How is BRSV treated?
-corticosteroids
-NSAIDs
-antihistamines
How is BRSV prevented?
vaccination (MLV available)
What are the clinical signs of para-influenza 3 virus?
-often subclinical
-fever
-cough
-nasal and ocular discharge
What is the pathophysiology of para-influenza 3 virus?
weakens immune system to allow for synergistic infections
How is para-influenza 3 virus diagnosed?
-PCR
-virus isolation
-serology
How is para-influenza 3 virus prevented?
vaccination
What are the clinical signs of bovine coronavirus?
-fever
-nasal and ocular discharge
-coughing
-diarrhea
What are important characteristics of bovine coronavirus?
-same virus that causes neonatal diarrhea and winter dysentery also causes resp. disease
-clinical signs of viral infection can worsen following secondary bacterial pneumonia
How is bovine coronavirus prevented from causing resp disease?
by using the bovine rota-coronavirus vx off label as an intranasal vx
What is the importance of Mannheima haemolytica serotypes?
-all serotypes can be commensals of the nasal cavity
-serotypes A1 and A6 are commonly pathogenic under correct conditions
What are the characteristics of M. haemolytica leukotoxin?
-main virulence factor
-binds to beta-2 integrins on ruminant leukocyte and punches hole in cell
-increases number of beta-2 receptors and induces apoptosis
-induces cell lysis
Why is the lysis of neutrophils in M. haemolytica infection important?
toxic compounds in the neutrophils spill out and damage the tissue
What are the characteristics of M. haemolytica endotoxin?
-induces cytokine storm
-production of IL-8 increases neutrophil migration into lungs
Which pathogen is the most economically significant in cattle?
M. haemolytica
What must be contained in a good vaccine against M. haemolytica?
purified leukotoxoid
What is important to note about the M. haemolytica toxoid vx?
immunity is short lived
What are the characteristics of Pasteurella multocida?
-not as severe as M. haemolytica
-cattle inhale small amounts of bacteria from the nasopharynx
-small area is colonized by the bacteria; slowly expands to form larger lesion
What is the pathophysiology of P. multocida?
-chronic resp damage is necessary for bacteria to colonize lung
-seen in dairy calves housed in poorly ventilated barns
-takes over after an infection with M. haemolytica in feedlot cattle
What type of pneumonia is caused by M. haemolytica?
fibrinous pleuropneumonia
What type of pneumonia is caused by P. multocida?
bronchopneumonia that is less severe than that associated with M. haemolytica
What are the downsides to vaccinating against bacterial pathogens?
-not efficacious
-not long lasting
-disrupting effects of stress and viral infections is more beneficial
What is the pathophysiology of Histophilus somni?
-forms lesions on endothelial membranes
-causes vasculitis and thrombosis
-affects multiple organ systems
-induces endothelial cell death and exposes the basement membrane, activating the coag. cascade
What are the four “flavors” of Mycoplasma bovis?
-pneumonia
-mastitis
-otitis
-septic arthritis
What is important about M. bovis infection?
-causes multisystemic manifestations
-most infections likely start as a pneumonia and the bacteria spread elsewhere in the body
Why are M. bovis infections difficult to treat?
-chronic and non-responsive to antibiotics
-no cell wall; beta-lactams are useless
Why is M. bovis difficult to vaccinate against?
the surface proteins are variable
Which diagnostic methods are primarily used to diagnose bacterial pathogens?
-culture
-PCR
Which samples can be used to diagnose bact. infections?
-nasal swab
-deep nasopharyngeal swab
-TTW
-BAL
-pleurocentesis
-lung tissue biopsy
Why is diagnosing bacterial pathogens difficult?
many of the bacterial pathogens that cause disease are also commensals of the nasal cavity
What is the importance of ultrasound?
-best tool for evaluating pulmonary surface
-can be used for early detection of pulmonary disease
What are the two triggers for treating calves with pneumonia?
-clinical signs such as poor appetite, lack of rumen fill, depression, and increased resp. rate
-increased temperature; greater than 104
What are the problems with the current method for identifying calves requiring pneumonia treatment?
-sensitivity is 62% and specificity is 63%
-greater than 50% of calves with evidence of pneumonia at slaughter were never treated
How is treatment duration determined?
-attitude
-appetite
-weight gain
-rectal temp
How long are cattle given to respond before changing antibiotic/treatment?
3 days
Which methods can be useful in the identification of pneumonia and treatment duration determinations?
-biomarkers such as haptoglobin and haptoglobin-MMP
-activity monitors
What is BRD metaphylaxis?
treating animals that are at high risk for BRD/are incubating BRD but do not yet have clinical signs
Why is it important to culture an animal prior to treatment whenever possible?
-culturing before treatment allows for identification of the pathogen and its actual sensitivity profile
-culturing after treatment can cause pathogen to be missed or sensitivity profile to show resistance
What are the two perspectives on NSAID use in treating BRD?
one cow at a time:
-want to control inflammation causing pneumonia
-NSAIDs cause clinical improvement
many cows at a time:
-treatment costs outweigh benefits of NSAID use
-no effect on weight gain or economic improvement
