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BVDV in feedlots: Concurrent infections

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

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  1. BVDV in feedlots: Concurrent infections Dr. John Campbell University of Saskatchewan

  2. 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

  3. We see evidence of acute BVD infections in feedlot cattle

  4. 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

  5. BVDV and BRD

  6. 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

  7. 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)

  8. Sero-epidemiological Evidence

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. Chronic pneumonia-Polyarthritis Syndrome in Feedlot Cattle: Mycoplasma Infections

  20. 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!

  21. 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

  22. 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

  23. 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

  24. 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

  25. Prevalence of M. bovis in feedlot calves Allen et al, Can J Vet Res 1992

  26. 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?

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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

  32. 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

  33. 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

  34. CPPS: Sequence of Events • Difficulty with getting up and lying becomes apparent • Severe, painful lameness • Emaciation, hypothermia, frostbite become complications

  35. 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”

  36. 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

  37. FDO for CPPS, Histophilus somni infections & BRD

  38. Mortality Curves forCPPS, Histophilus somni infections & BRD

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