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Mycoplasma Infections in Chickens

Learn about major mycoplasmal infections in chickens, including Mycoplasma gallisepticum and Mycoplasma synoviae, their clinical effects, pathogenesis, diagnostics, and control measures. Explore the impact on egg production, mortality, and growth in broiler breeders and layers. Discover transmission routes, survival outside the host, and diagnostic approaches for avian mycoplasma.

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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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