Calf Pneumonia Flashcards
what is pneumonia
acute or chronic disease marked by inflammation of the lungs and caused by viruses, bacteria, other microorganisms and sometimes physical and chemical irritants
in cattle is usually a result of interactions between a complex mixture of pathogens and environmental stressors
what is bovine resp disease complex
non-infectious predisposing factors
infectious predisposing factors –> viruses, mycoplasma, bacteria, lungworm
what are the general principles of resp infections
how is BRD multifactorial
- may start with a viral infection
- viruses damage cells lining the resp tract
- damaged cells normally involved in bacterial removal
- bacteria invade –> tracheitis, bronchitis, pneumonia
what are common causes of young calf pneumonia
RSV: bovine respiratory syncytial virus
PI3: parainfluenza virus 3
BVD: bovine viral diarrhea
IBR: infectious bovine rhinotracheitis
what are common causes of BRD in calves housed in autumn
RSV
PI3
BVD
IBR
what are common causes of BRD in calves bought at market
IBR
RSV
PI3
BVD
what is RSV
respiratory syncytial virus
primary cause of serious calf pneumonia
epidemiology not understood, peak times of disease in winter months
no evidence of how virus is maintained in populations (persistently infected animals, overwinering in buildings)
vaccination has variable success but is essential for autumn house cattle
what does RSV cause
creates substances which damage lung remote from the areas of viral multiplication
what are the symptoms of RSV
clear watery discharge (nasal)
coughing
fast laboured breathing, frothy saliva
bouts of coughing
may die if severe
what is PI3
primary cause of calf pneumonia but usually less severe than RSV –> may predispose to bacteria
is there a vaccine for PI3
vaccination has variable success
what is the epidemiology of PI3
transit fever –> moving animals and big groups in feedlot
where does PI3 replicate
in epithelial cells
where does damage occur in PI3
primarily in the lower resp tract
what does PI3 cause
causes bronchitis, bronchiolitis, alveolitis
in acute stage proliferation and necrosis of bronchiolar epithelial cells
widespread descruction of cilia and of ciliated cells in small bronchi and bronchioli
infects alveolar macrophages
what is bovine herpesvirus type 1 - IBR virus
primary pathogen
usually tracheitis but can progress to pneumonia
what does IBR cause
occasionally causes fatal neonatal disease
reduced appetite, watery eye, nose, coughing, fever, purulent discharge, coughing (may be thick blood stained material coughed up)
may be secondary bacteria and death
what is the epidemiology of IBR
crucial in the persistence of disease is the latently infected carrier
sheds virus at times of stress (moving, housing, calving)
all unvaccinated, seropositive animals should be considered latently infected
what is the IBR vaccine
deletion mutant vaccines exist to differentiated vaccinated animals from wild type infected animals
vaccination good at controlling
what are other viruses that cause BRD
- adenovirus type 3
- orthomyxovirus
- coronavirus
- BVDV
how can viral infections be diagnosed
taking ocular and nasal swabs, lung fluid
for control –> collection of blood samples 2 weeks apart
post mortem
what are bacterial species involved in BRD
- manheimia haemolytica
- pasteurella multocida
- histophilus somni
what are the features of the bacteria that cause BRD (6)
- gram negative
- non-motile
- pleomorphic cocco-bacilli
- aerobic/facultatively anaerobic
- most species are pathogenic
- optimal growth at 37 degrees
what are the virulence factors in pasteurellaceae
the LPS and lipooligosaccharide (LOS)
what are the toxic effects of LPS
initiation of complement and coagulation cascades –> increased vascular permeability and coagulation –> accumulation of inflammatory cells, edema and fibrin deposition in the lung
what are the characterisitcs of H. somni
- small to med sized, gram negative, coccobacilli
- non-motile and capable of fermenting sugars
- fastidious nature, will not grow on some laboratory media, CO2 sometimes required
- found on mucosal surfaces of cattle and are extremely host specific
what are the virulence factors of H.somni
capsule –> form protective coat around the bacterium and allows it to evade host defenses
antibodies to somatic antigens (membrane proteins and LPS) may also distinguish distinct serotypes
what are the exotoxins that H.somni produce
weak hemolysin
what other virulence factors does haemophilus
- proteases: destroy mucosal IgA
- outer membrane proteins that bind to the Fc receptor of normal IgG and block binding of specific IgG
- binding nucleotides on the cell surface to enhance survival in or killing of phagocytic cells
- antigenic phase variation of its lipooligosaccharide
what is the host specificity of haemophilus
due to the ability of a species to obtain iron only from a single host
under iron-limiting conditions the bacteria produce outer membrane proteins that are able to obtain from the host transferrin molecules
iron regulated outer membrane proteins (IROMPS)
how is haemophilus diagnosed
isolation of the bacteria from normally sterile sites or in pure culture from infected area is necessary to confirm the isolate is present as a pathogen and not as normal flora
most isolate from animals require only NAD, and therefore will grow either on commercial chocolate agar or on blood agar with a streak of staphylococcus to provide NAD
what are the specific diseases of H.somni
spectrum of diseases in cattle
- thromboembolic meningoencephalitis (TEME): weakness, fever, staggering, somnolence, dyspnea, paralysis, sudden death–> lesions of fibrinous meningitis with thrombosis and necrosis
- pneumonia with pleuritis and arthritis
- repro failure –> endometritis, metritis or late abortion, mastitis, vaginitis
what are the general characteristics of pasteurella and manheimia
- gram negative, short to medium sized coccobacilli, bipolar staining
- facultatively anaerobic
- ferment glucose, gas is not produced
- M. haemolytica is B-hemolytic on blood agar will grow to some extent on MacConkey agar
- pasteurella species are normal commensals of mucosal membranes of resp tract
what are the types of pasteurella multocida
A, B, D, E
what is the most common serotype of pasteurella multocida isolated from BRD
A3
what does type D pasteurella multocida produce
dermonecrotoxin
how many serotypes of manheimia are there and what are the main ones
13
a1 and 16 are the main ones in resp disease in cattle
when does disease from manheimia occur
results following stress, such as transport, inclement weather or predisposing infections
which bacteria are encapsulated
p. multocida and p. haemolytica
what role does LPS play in virulence factors
- protect the organism from host defenses through the carbohydrate moeity
- induce inflammation through the lipid A component
what are the exotoxins in pasteurella
a dermonecrotoxin produced by type D and some type A strains of P. multocida and is considered an important virulence factor in the pathogenesis of atrophic rhinitis
m. haemolytica produces a labile leukotoxin (RTX toxin) important in the pathogenesis of shipping fever and resp disease
how is pasteurella diagnosed
isolation
gram or giemsa stain: bipolar organisms
grow on blood agar
isolation from nasal tract is of little significance because they are part of the normal flora
what are the risk factors for bronchopneumonia
- poor ventilation
- low space per calf
- management procedures
- animals of different in ages in the same airspace
- pooling calves from many sources
- poor colostrium management
- dam minerals/vitamin deficiency
- insufficient energy/protein
what is the pathogenesis of bovine pneumonia
- commensal colonization
- predisposing factors: stress transport, virus, mycoplasmas
- decreased mucociliary clearance impaired alveolar macrophages function
- proliferation and inhalation of nasopharyngeal M. haemolytica A1 colonization of lung
- release of leukotoxin, endotoxin, and other virulence factors
- mast cell degranulation, complement activation, cytokine release, infilatration and lysis of neutrophils, macrophages
- fibrinous pneumonia
how is resp disease controlled
- management –> grazing systems, reduced sotcking density, segregation of ages, minimize stress, environment
- vaccination –> managed health problems
- antimicrobial metaphylaxis
how can the environment be improved to reduce BRD
- reduce moisture
- improve ventilation –> intro of clean air, removal of used air, dry comfortable, well distributed inlets, no draughts
how can cattle pneumonia be treated
wide range of antibiotics are effective againts bacterial pneumonias (penicillins, tetracylcines, fluroquinolones, sulphonamides, macrolides)
what are the vaccine types
- live
- killed
- marker (live/killed)
- nasal (live)
- injected
what are the advantages of live vaccines (3)
- more rapid onset of immunity
- single dose
- used in young calves in presence of maternally derived antibodies
what are the advantages of killed vaccines
safety: will not cause disease
can often be used in pregnancy
what are the advantages of marker vaccines
can differentiate vaccinated and infected
what are the advantages of nasal vaccines
can get rapid immunity
good for outbreaks
can be used in young calves in presence of MDA
what are the advantages of injected vaccines
security of dosing
what are the disadvantages of injected vaccines
local reaction
what are the disadvantages of live vaccines
can cause mild version of disease
some cannot be used in preg
what are the disadvantages of killed vaccines
may not get as good immunity
adjuvant many –> local reaction
what are the disadvantages of nasal vaccines
can cause mild version of disease
can shed vaccine strain
what is the ideal vaccine
IBR, PI3, BRSV, BVD
some combo of these viruses
probably modified live attenuated MLA to enhance mucosal immunity
