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BVDV in feedlots: Concurrent infections

BVDV in feedlots: Concurrent infections

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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