Bronchopneumonia in Food Animals Flashcards
what are the 2 mechanisms of colonization resistance?
- direct microbe-microbe inhibition: bacteria themselves interact with other pathogens and resist colonization
- indirect microbe-stimulated host immunity: innate system maintains host defense: leukocytes, epithelial cells active, etc
mucociliary apparatus
glands produce mucin and peptides as part of immune defense. host epithelium maintains the mucociliary defense
what maintains the mucociliary apparatus?
host epithelium
central hypothesis with BRD pathogenesis
immunocompromised host with risk factors, virus infects and causes damage to the resp epithelium and immune suppression. this allows commensals to overgrow
expanded hypothesis with BRD pathogenesis
immunocompromised host but also environmental factors: air quality, smoke, etc, that impacts airways, viral infx
- pathobionts: commensal bacteria that live in the resp microbiome that have a good beneficial relationship with host to not allow other pathogens to colonize RT, but in situations where they overgrow, can express pathogenic virulent factors. have a dual virulent factor
- get a dysbiosis in the URT and LRT, and the pathobionts start to dominate and express virulence factors
pathobionts
pathobionts: commensal bacteria that live in teh resp microbiome that have a good beneficial relationship with host to not allow other pathogens to colonize RT, but in situations where they overgrow, can express pathogenic virulent factors. have a dual virulent factor
how does BRD present?
complex and many clinical presentations
- clinical vs subclinical
- localization: URT, lng
- duration: acute vs chronic
- also depends on what part of the production cycle these animals are in
beef animals may just have decreased appetite/rumen fill and no nasal discharge
calves can show nothing at all and have no outward signs of disease
what are major risk factors for BRD?
- FPI: failure of passive immunity
- stress!! impacts the immune system substantially
risk factors for BRD
FPI and stress!!
genetics, viral infx,, group housing, air quality, dehydration, weaning, weather, transport, co mingling, nutritional deficiencies, surgical procedures
T/F: we have made significant advancements in BRD thanks to prevention and therapeutics over the last 50 years
false. we have not made significant changes despite advancements in prevention and therapeutics
- colostrum quality super important
- stress and nutriton
- vaccination
all of these affect disease susceptibility
when are calves typically weaned?
<56 days
what do you have to differentiate BRD from with preweaned calves?
aspiration!! contamination, improper feeding, etc
enzootic calf pneumonia
- weaned calves (2-5 months)
- viral exposure, stress (mixing groups)
weaned calf BRD
- weaned calves (most common 2-5 months)
- viral exposure, stress (mixing groups)
replacement heifers and cows BRD
more commonly sporadic, metastatic
cow-calf beef BRD
- up to 10% pre-weaned calves (3-5 months)
- nadir if IgG: cows relying on own adaptive immunity
- a shorter calving interval will make the herd immunity low
weaned calves beef BRD
- shipping fever: transported to facility or stock area before feedlot
- highest morbidity during 1st 21 days post arrival!!** EXAM
when do we see the highest morbidity in the beef industry with BRD?
in weaned calves: shipping fever
- highest morbidity during the 1st 21 days (3 weeks) post arrival!!! ***
finishers (feedlot) beef BRD
- sporadic outbreaks, interstitial pneumonia
- rule out altitude induced pulmonary hypertension
pathophysiology of BRD in lungs
- depends on dominant pathobiont and/or infectious agent and passive transfer status
- innate immune system stimulated thru pattern recognition receptors to increases chemotaxis of neutrophils and macrophages to cause inflammation = oxidative host damage
- pro inflammatory cascade
- secondary invaders, opportunists cause consolidation of airways or pulmonary abscesses, pleuropneumonia
mannheimia hemolytic
- Pasteurellae, Gram neg, aerobic rod
- normally in animals in their nasopharynx
- opportunistic in lungs: dysbiosis allows it to take over
- viral infx increase severity!
virulence factors with mannheimia hemolytic
- leukotoxin: cytolysis of ruminant leukocytes
- endotoxin/LPS: proinflammatory (neutrophil chemotaxis)
pathology of mannheimia hemolytic
lobar pneumonia –> necrotizing fibrinous pleuropneumonia
peracute rapidly consolidating syndrome
T/F: mannheimia hemolytic is commonly associated with shipping fever
true
