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BVDV in feedlots: Concurrent infections. Dr. John Campbell University of Saskatchewan. Acute BVD Infections. Immunocompetent calf infected with BVD virus Majority of acute infections are subclinical Outbreaks attributed to acute BVD in feedlot calves Definitive diagnosis is difficult

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bvdv in feedlots concurrent infections

BVDV in feedlots: Concurrent infections

Dr. John Campbell

University of Saskatchewan

acute bvd infections
Acute BVD Infections
  • Immunocompetent calf infected with BVD virus
  • Majority of acute infections are subclinical
  • Outbreaks attributed to acute BVD in feedlot calves
  • Definitive diagnosis is difficult
  • Recovery of virus is unlikely in acute cases
  • Must rely on IHC or titer changes
acute bvd and other infections
Acute BVD and other infections
  • Immunosuppressive effects of BVD have been well documented
  • Potentiation of multiple diseases has been described
  • Salmonellosis
  • Rotavirus and Coronavirus
  • Bovine papular stomatitis
  • E. coli
bvdv as a primary pathogen
BVDV as a primary pathogen
  • Potgeiter et al. induced mild respiratory disease and interstitial pneumonia in 4-6 month old calves (Am J Vet Res 1984)
  • Potgeiter et al. also demonstrated variation in pneumopathogenicity of various strains of BVDV (Am J Vet Res 1985)
  • However, most evidence focuses on BVDV as a synergistic pathogen
bvd s role in bovine respiratory disease
BVD’s role in Bovine Respiratory Disease
  • Synergistic effects between BVDV and other respiratory pathogens have been documented
  • Potentiation of IBR, Mannheimia hemolytica, and BRSV has been demonstrated in experimental studies
  • BVDV was identified frequently in BRD outbreaks in Quebec where multiple viral infections were identified (Richer et al, CVJ; 1988)
martin et al 1986
Martin et al 1986
  • Population: 322 calves, small pen research
  • % Seropositive on arrival: 55.8%
  • Arrival titer associated with decreased risk? NO
  • % of Cattle seroconverting: 24%
  • Seroconversion associated with increased BRD risk? YES

Can J Vet Res 1986; 50:351-358

martin et al 1989
Martin et al, 1989
  • Population: 279 cases of BRD and 290 controls, small pen research
  • % Seropositive on arrival: 32% cases, 42% controls
  • Arrival titer associated with decreased risk? YES
  • % of Cattle seroconverting: 42% cases, 33% controls
  • Seroconversion associated with increased BRD risk? YES

Can J Vet Res 1989; 53: 355-362

durham et al 1991
Durham et al, 1991
  • Population: 283 bull calves, Sk bull test.
  • % Seropositive on arrival: 21%
  • Arrival titer associated with decreased risk? YES
  • % of Cattle seroconverting 13%
  • Seroconversion associated with increased BRD risk? NO

Can Vet J 1991; 32:427-429

allen et al 1992
Allen et al, 1992
  • Population: 59 cases of BRD, 60 controls from small pen research feedlot
  • % Seropositive on arrival ?
  • Arrival titer associated with decreased risk? ?
  • % of Cattle seroconverting 51%
  • Seroconversion associated with increased BRD risk? NO

Can J Vet Res 1992;52: 26-33

martin et al 1999
Martin et al, 1999
  • Population: 700 Ont and Alta calves
  • % Seropositive on arrival 24%
  • Arrival titer associated with decreased risk? YES
  • % of Cattle seroconverting 50%
  • Seroconversion associated with increased BRD risk? YES

Can Vet J 1999; 40: 560-570

booker et al 1999
Booker et al, 1999
  • Population: 200 head case control study from 22,000 head Alta feedlot
  • % Seropositive on arrival ?
  • Arrival titer associated with decreased risk? YES
  • % of Cattle seroconverting ?
  • Seroconversion associated with increased BRD risk? YES

Can Vet J 1999; 40: 40-48

fulton et al 2000
Fulton et al, 2000
  • Population: 120 Tennessee calves shipped to Texas
  • % Seropositive on arrival: 18.3% Type I, 13.3% Type II
  • Arrival titer associated with decreased risk? All calves treated!!
  • % of Cattle seroconverting 38.5% Type I, 27.9% Type II
  • Seroconversion associated with increased BRD risk? YES

Can J Vet Res 2000; 64: 151-159

o connor et al 2001
O’Connor et al, 2001
  • Population: 852 calves from 3 Ont feedlots
  • % Seropositive on arrival 39%
  • Arrival titer associated with decreased risk? YES
  • % of Cattle seroconverting 45%
  • Seroconversion associated with increased BRD risk? YES

Can J Vet Res 2001; 65: 137-142

fulton et al 2002
Fulton et al, 2002
  • Population: 325 Tennessee calves
  • % Seropositive on arrival 23-34% Type 1a, 17-20% Type 2
  • Arrival titer associated with decreased risk? ?
  • % of Cattle seroconverting: Sick calves 32-48%, Healthy 16-28%
  • Seroconversion associated with increased BRD risk? YES

Can J Vet Res 2002; 66: 181-190

schunicht et al
Schunicht et al.
  • Late outbreak of BRD in feedlot cattle
  • Cases greater than 70 days on feed
  • Blood sampled sick and healthy cattle
  • Sick cattle were 4.5 times more likely to have a high titre to BVD virus

Can Vet J 2003; 44: 43-50

the mycoplasmas
The Mycoplasmas
  • Mycoplasmas are unusual self-replicating bacteria (Class Mollicutes)
    • “Evolutionarily advanced procaryotes”
  • Very small genome
  • Lacking cell wall components
  • Require cholesterol for membrane function and growth
  • Intimate association with host target cells
    • Host adapted survival!
the mycoplasmas26
The Mycoplasmas
  • Relatively host specific
  • Require special culture media, growth substances and conditions
  • Require longer incubation periods than other bacterial pathogens
  • Further tests are necessary to perform species differentiation on colony
mycoplasma a controversial organism
Mycoplasma: A controversial organism
  • Many recently proposed controversial associations of mycoplasmas to various human diseases
    • Accelerating the progression of AIDS
    • Malignant transformation of cells
    • Crohns disease
    • Gulf War Syndrome
    • Rheumatoid Arthritis and other Human Arthritides
mycoplasma bovis
Mycoplasma bovis
  • Recognized as the most invasive and destructive of bovine mycoplasmas in North America
  • Associated with a number of syndromes
    • Pneumonia
    • Polyarthritis, tenosynovitis
    • Mastitis in adult dairy cattle
    • Otitis media in dairy calves
    • Conjunctivitis
    • Decubital abscesses
prevalence of m bovis
Prevalence of M. bovis
  • Organism is isolated frequently from calves
    • Found in normal and pneumonic lungs
  • Allen et al, Can J Vet Res 1992:
    • Nasopharyngeal swabs and BA lavage from 59 BRD cases and 60 control calves entering an Ontario research feedlot
    • When a BRD case was selected, the case and a control calf would be sampled and then subsequently followed up with other samples
prevalence of m bovis in feedlot calves
Prevalence of M. bovis in feedlot calves

Allen et al, Can J Vet Res 1992

is it a pathogen or normal flora
Is it a pathogen or normal flora?
  • It would appear that a very high proportion of feedlot calves are exposed to M. bovis
  • Evades normal lung clearance mechanisms
    • Attachment to ciliated epithelium
    • Antigenic mimicry of host antigens
    • Immunosuppression of host humoral and cell mediated responses
  • Ubiquitous and persistent
    • How long?: Several weeks or months?
is it a pathogen or normal flora32
Is it a pathogen or normal flora?
  • Associated with an increased proportion of inflammatory cells in BAL fluid
  • Mycoplasma bovis was cultured from all nonresponders and relapsers
  • No other organisms were cultured from non-responders

Allen et al, Can J Vet Res, 1992

seroepidemiological evidence
Seroepidemiological evidence
  • Rosendal and Martin, Can J Vet Res, 1986
  • 322 heifers and steers from 5 Ontario feedlots
  • Serum taken at arrival and 28 days later
  • Titers to M. bovis increased at all 5 locations
  • Mycoplasma dispar titers were significantly associated with a higher risk of treatment for BRD
seroepidemiological evidence34
Seroepidemiological evidence
  • Martin et al, Can J Vet Res 1989
  • Prevalence of titers to M. bovis at arrival to feedlot was approximately 70%
  • Approximately 45% of calves seroconverted to M. bovis by day 28
  • Cases had significantly higher titers at arrival
  • Concluded that there was a lack of evidence to support an etiological role for M. bovis
seroepidemiological evidence35
Seroepidemiological evidence
  • Martin et al, Can Vet J; 1999
  • Case control study sampling feedlot calves in Alberta and Ontario
  • 5% of calves were seropositive for M. bovis at arrival
  • Only 14% of calves seroconverted to M. bovis
  • Suggested M. bovis was not widespread and not associated with BRD
seroepidemiological evidence36
Seroepidemiological evidence
  • Booker et al, Can Vet J 1999
  • 100 UF cases and 100 controls
  • Bled at arrival, selection and day 33
  • Quartiles and median titers reported only
  • M. bovis and M. alkalescens titers were common at arrival and there was significant seroconversion by day 33
  • Mycoplasma alkalescens was associated with an increased risk of morbidity
the chronic pneumonia polyarthritis syndrome
The Chronic Pneumonia-Polyarthritis Syndrome
  • Outbreaks of pneumonia and/or polyarthritis associated with M. bovis have been described for many years in the veterinary literature
  • Allen et al, 1978; Boothby et al, 1983; Adegboye et al, 1995; Adegboye et al, 1996; Haines et al, 2001.
  • Experimental infections with M. bovis demonstrate varying degrees of lung involvement
  • If M. bovis given first, Mannheimia experimental infections were much more severe in terms of lung consolidation
cpps sequence of events
CPPS: Sequence of Events
  • Initially treated for high temperature

eg. > 40.5oC

  • Temperature decreases but remain sick and sore
  • Over next 10 days joints enlarge
  • Calf retreated several times
  • Does not respond to therapy
cpps sequence of events39
CPPS: Sequence of Events
  • Difficulty with getting up and lying becomes apparent
  • Severe, painful lameness
  • Emaciation, hypothermia, frostbite become complications
cpps working hypothesis
CPPS: Working Hypothesis
  • Infection occurs via respiratory tract, therefore, Broncho Pneumonia
  • M. bovis invades blood stream and is distributed to other parts of body
  • Organism invades Bronchi, joints, tendon sheaths, and pleural space
  • Antibiotics cannot penetrate these lesions or are not effective against M. bovis
  • Characteristic lesions lead to extreme “ill thrift”
cpps outcomes
CPPS: Outcomes
  • Some completely recover with patience
  • Some partially recover and can be salvaged
  • Some become complicated
    • unable to get up
    • become very thin
    • develop secondary syndromes
    • must be destroyed or inevitably die
bvd and mycoplasma bovis
BVD and Mycoplasma bovis
  • Haines et al demonstrated BVDV by IHC in 40% of cases of chronic respiratory disease +/- arthritis (CPPS) (Can Vet J, 2001)
    • M. bovis demonstrated in 80% of 49 cases
    • 45% of joints, 71% of lungs
    • Only bacterial pathogen identified in joints
bvd and mycoplasma bovis52
BVD and Mycoplasma bovis
  • Shahriar et al found BVDV in 64% of 48 cases of retrospective cases of CPPS using IHC(Can Vet J, 2002)
  • Also demonstrated BVDV in 9/16 prospective cases
  • M bovis was present in 44/48 and 15/16 cases respectively
association between bvdv titer and morbidity on convalescent pen entry
Association between BVDV titer and morbidity on convalescent pen entry
  • RR = 3.0 (CI, 1.7 to 5.2) ( p < 0.001)
  • A calf with a high titer to BVD virus upon entry to the convalescent pen is 3.0 times more likely to be a treatment failure for arthritis than a calf with a low titer to BVD virus

Morbidity category

UF or

lame (not PA)

Arthritis

54

32

43

7

29

<54

association between bvdv titer and mortality on convalescent pen entry
Association between BVDV titer and mortality on convalescent pen entry
  • RR = 2.1 (CI, 1.2 to 3.5) (p < 0.001)
  • A calf with a high titer to BVD virus upon entry to the convalescent pen is 2.1 times more likely to have lesions of the CPPS than a calf with a low titer to BVD virus

Mortality category

CPPS

Histophilus somni

54

3

24

3

4

<54

immunohistochemical diagnosis of bvdv in causes of feedlot mortality

Immunohistochemical Diagnosis of BVDV in Causes of Feedlot Mortality

J. Campbell, E. Janzen, E. Clark, F. Schumann

objectives
Objectives
  • How commonly can we see evidence of BVD infection in feedlot mortalities?
  • Does the prevalence of BVD infection differ among various disease categories?
  • What proportion of mortalities are due to persistent infections with BVD virus?
study design
Study Design
  • Feedlot mortalities during fall and winter of 2002 at 3 central Saskatchewan feedyards
  • Gross necropsy performed by attending feedlot veterinarians
  • Tissue samples collected from heart, lung, ileum, and skin
  • Formalin fixed and submitted for IHC for BVD virus
slide60

Another example of vasculitis due to BVDV, this time in a myocardial muscular vein. The same focus of inflammation and necrosis in the vessel wall stains positive for the virus. This is very different than positive staining seen in vessel walls in PI calves.

Primary BVDV infection

comparisons of bvd prevalence in tissues of various mortality categories
Comparisons of BVD prevalence in tissues of various mortality categories
  • BRD (33.3%) vs Non-infectious (15.3%) (p=0.03)
  • BVD (44.4%) vs. Non-infectious (15.3%) (p=0.04)
  • CPPS (37.0%) vs. Non-infectious (15.3%) (p<0.01)
  • Histophilus (17.0%) vs. Non-infectious (15.3%) (p=0.8)
does bvdv play a role in mycoplasma bovis and other infections
Does BVDV play a role in Mycoplasma bovis and other infections?
  • It would seem likely that BVDV has a synergistic effect with a number of other pathogens in the feedlot and may contribute significantly to feedlot mortalities
  • There are similar associations with Mycoplasma infections and evidence of acute BVDV infections
  • Histophilus somni does not seem to be synergistic with BVDV
international conference on bovine mycoplasmosis
International Conference on Bovine Mycoplasmosis
  • July 7-9, 2009
  • Saskatoon, Saskatchewan
  • www.bovinemycoplasma.ca