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Mycoplasma Infections in Chickens

Mycoplasma Infections in Chickens. David G S Burch Octagon Services Ltd (www.octagon-services.co.uk). Major mycoplasmal infections in chickens. Mycoplasma gallisepticum (MG) Chronic Respiratory Disease (CRD) Mycoplasma synoviae (MS) Infectious synovitis (IS). Introduction:.

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Mycoplasma Infections in Chickens

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  1. Mycoplasma Infections in Chickens David G S Burch Octagon Services Ltd (www.octagon-services.co.uk)

  2. Major mycoplasmal infections in chickens • Mycoplasma gallisepticum (MG) • Chronic Respiratory Disease (CRD) • Mycoplasma synoviae (MS) • Infectious synovitis(IS)

  3. Introduction: • Review of some of the disease aspects • Incidence • Clinical effect • Pathogenesis • Epidemiology • Diagnostics • Controlling mycoplasmas in the field • Avoidance – biosecurity • Vaccination – killed / live • Therapy – antimicrobials • Conclusions

  4. Incidence of MG & MS in chickens • MG is officially controlled (OIE – list B) • UK limited data available, eradication • Occasional outbreaks in layers and breeders • Free-range layers 30% (10 million) - high risk • Widespread in pheasants (30 million/year) • NL some data • 3-9% layer farms • 0.5-4% breeders • MS not OIE listed – does occur more • UK 78.6 % layers (Hagan et al, 2004) • NL 95% layers (Feberwee et al, 2003)

  5. Clinical signs Respiratory signs: coughing, sneezing (snicking), respiratory râles, nasal discharge, sinusitis (MG) – less severe MS usually Contributory factors - virus infections IB, ND – live vaccination trigger - poor ventilation, ammonia, dust, stress Locomotory signs: lameness, swollen joints, tendon sheaths and bursae (MS) Other: mortality increase, reduced egg production, reduced hatchability, reduced growth & FCE – more severe MG than MS

  6. Production losses caused by M. gallisepticum Breeder Egg drop 10-20% Egg production (chronic infection) 5-10% Embryo mortality 5-10% Broiler Poor chick mortality 5-10% Depressed weight gain 10-20% Depressed feed conversion 10-20% Overall mortality (CCRD) 20% (Kleven, 1990)

  7. Broiler breeders - MG effect (Stipkovits et al 1993)

  8. Layers – MG effect (Mohammed et al, 1987) • Review of 366 commercial layer farms in S. California • Chronic MG infection reduced egg production by 5.3% (16 eggs/hen – 52 weeks cycle) against uninfected flocks (cost 0.72 Euros/hen) • F strain MG vaccination improved production in infected flocks by 2.5% (8 eggs/hen) (cost still 0.36 Euros/hen) • (Assumptions 310 eggs/hen 0.57Euros/12 eggs)

  9. Layers MS effect • 0-3.3% reduction in egg production – chronic infection • Acute form often coinciding with IB seroconversion and challenge in UK • Lameness outbreaks can be severe and affects egg production • Medication with chlortetracycline every 6-8 weeks – controls economic impact in UK? • Pathogenicity of strains – 1980s MS as bad as MG in UK broilers – 20% mortality

  10. Pathogenesis – respiratory spread

  11. Pathogenesis – attachment to epithelial cells and cilia

  12. Pathogenesis –spread of infection • Respiratory tract – trachea, lungs and air sacs • Other sites • Synovial membranes – sheaths and joints (MS) • Cloaca (isolation) • Reproductive tract of layers (eggs) and cocks (semen) • Brain - occasionally

  13. Mild airsacculitis

  14. Colisepticaemia

  15. Development of CRD and CCRD in broilers CCRD CRD Weeks

  16. Egg peritonitis – increased mortality

  17. Embryo mortality

  18. Swollen joints

  19. Synovitis -increased joint fluid

  20. Tenosynovitis- foot pad

  21. Transmission • Horizontal • Direct contact (other birds) • Airborne (other flocks/houses) • Contaminated materials, transport • Vertical • Sexual transmission • Egg • Chick

  22. Spread in chickens Vertical transmission Horizontal transmission

  23. Survival of MG & MS • Outside the host • hair: 3 days • nose: 1 day • feathers/dust: 2-4 days • straw/cotton/rubber: 1-2 days • egg material: 6-18 weeks!!! (watch the hatchery) • water: 41 days • feed: 21 days • Within the host • long time - escape from the immune system by epitope (surface antigens) switching • chronically infected flocks are a source of new infections

  24. Avian mycoplasma diagnostics Two basic approaches • Organism - culture / antigen protein / DNA based • Antibody tests

  25. M. gallisepticum diagnostics • Culture – Frey’s (serum-enriched) medium, plus thallous acetate and penicillin • Colony clear fried egg appearance • Ferments glucose and maltose but not lactose, dulcitol or salicin and rarely sucrose • Reduces 2,3,5-triphenyl terazolium – becomes red • Reacts MG antiserum • Direct immunofluorescence test

  26. MG culture

  27. Mycoplasma diagnostics Strain differentiation • SDS PAGE (sodium dodecyl sulphate-polyacrylamide gel electrophoresis) - protein banding • PCR (polymerase chain reaction) – DNA amplification – increased sensitivity – nucleotide sequencing – commercial test kits – taking over from culture • RAPD (random amplified polymorphic DNA) – primers – sensitive – strain differentiation • AFLP (Amplified fragment length polymorphism) – DNA – further development

  28. Strain identification by RAPD-PCR MPM 19 20 R 6/85 ts-11

  29. Mycoplasma diagnostics Serology • RSA (rapid slide agglutination) test – quick, cheap, sensitive – false positives (<15%) from MS & vaccines – commercial test kits – main screen (Ig M) – not in eggs • SPA (serum plate agglutination) – same (US) • HI (haemagglutination inhibition) test – confirmatory test – time consuming, not very sensitive (Ig G) • ELISA (enzyme-linked immunosorbent assay) – increased sensitivity and specificity – egg yolk, bronchial secretions also (Ig G) – commercial kits available

  30. Rapid slide agglutination test - MS

  31. Ig CURVES AFTER MG AND MS INFECTION (Cerda, 2002) Ig M (RSA/SPA) Immunoglobulin titre Ig G (ELISA – HI) 5-7 d 5-7 d 10-15 d 3 months 8-10 months

  32. RSA/SPA(Cerda 2002) Progeny of infected non-treated breeders Progeny of infected treated breeders Ig M titre 4-6 weeks 4-6 weeks 4-6 months

  33. Comparison of diagnostic methods • Culture versus PCR • both show high sensitivity and specificity • sensitivity of both is high during the first weeks after infection • PCR has replaced culture and IFA in eradication programmes • Classical MG and MS serology versus ELISAs • similar to undiluted RPA, undiluted ELISAs also show false positive reactions (<15%) • RPA and HI show high sensitivity and specificity • replacing RPA and HI by ELISAs or adding ELISAs does not necessarily improve sero-diagnostics • ELISA good for egg testing

  34. Control Breeders  absence/eradication/monitoring  vaccination (killed/live)  treatment  egg dipping/injection Broilers  treatment Replacement pullets  vaccination (killed/live)  treatment Layers  vaccination  treatment

  35. Absence of MG – general biosecurity rules (Morrow, 2004) • Source from mycoplasma-free farms • Single age farms • At least 2km from other poultry farm • ‘All in – all out’ housing • Secure barrier perimeter & controlled access • Wild bird proofing of facilities • No staff should own poultry at home or have contact with other birds

  36. Absence of MG – general biosecurity rules (Morrow, 2004) • Shower on and off facilities on farms • Visit clean flocks before infected flocks • Visit youngest flocks first • Hatch chicks form infected flocks separately • Plan feed and egg transport to minimise risk • Implement monitoring program and regular testing to define status of birds

  37. MG vaccines • Bacterins (killed MG & MS) – administration by injection • Live vaccines – easy to administer • ts-11 by eye drop • 6/85 by spray - >6 weeks old • F strain spray or water • Seroconversion / survival of vaccine strain • ts-11 – yes / may spread • 6/85 – rarely / dies out after about 15 weeks • F strain – yes / may spread – path in turkeys • Anamnestic response to challenge

  38. MG vaccines • No cross protection MG / MS • Live ones susceptible to antimicrobials • Failure in preventing field strain colonisation • F strain can displace field strains • Risk of reversion with live vaccines? • Confuse diagnostics – use only when outbreaks common locally • Protection & production efficiency?

  39. Comparative protection at 30, 60 & 90 days after vaccination(Abd-El-Motelib & Kleven, 1993)

  40. Vaccinal effect • Killed bacterin – major effect for 3 months • F strain gives strongest protection • Ts-11 and 6/85 give moderate protection but can breakdown in face of severe challenge – field reports

  41. Treatment – antimicrobial activity – M. gallisepticum MICs (20)(Hannan et al, 1997)

  42. Treatment – antimicrobial activity – M. synoviae MICs (20)(Hannan et al, 1997)

  43. Antimicrobial therapy • Available option – risk of resistance development prolonged usage • Some antibiotics have developed resistance – tylosin and oxytetracycline • Treatment offers more flexible approach • Mixture of organisms • mycoplasma + E. coli etc • Can be used in egg treatment – tylosin for dipping and injection

  44. Conclusions: • MG is still an important pathogen in chicken production and also MS, to a lesser extent • Its epidemiology is complex – many carriers – difficult to control • Biosecurity essential • Diagnostics still developing – PCR techniques for strain differentiation • Vaccines useful where infection common – reduces disease impact • Therapy also offers opportunities for control and elimination

  45. Thank you for your kind attention www.octagon-services.co.uk

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