Application of diagnostic tools for better monitoring and control of respiratory disease

Transcription

1 Application of diagnostic tools for better monitoring and control of respiratory disease AW (Dan) Tucker MA VetMB PhD DECPHM University of Cambridge, UK June, 8th Dublin

2 Summary Background: Justification for investing in diagnostics and monitoring tools Respiratory disease is complex Comprehensive approach to investigation Key points for key pathogens Monitoring strategies Opportunities and outcomes Conclusion: disease control must be based on robust clinical and laboratory evidence.

3 Respiratory disease is expensive PROFIT = Net output (variable costs + fixed costs) Number pigs sold/sow Ave. daily gain FCE Mortality Carcase grading Feed Water Energy Veterinary services Vaccines Medicines Buildings supply Finance Labour Respiratory disease impacts on most of these parameters Annual cost of PRRS estimated at $668m p.a. in US (Holtkamp JSHAP 2013) Pleurisy associated economic losses in UK; each 1% prevalence at slaughter 0.26d delay to slaughter and 70g reduction in ave. carcass weight (Jager, IPVS 2010) 3

4 Principal types of respiratory disease Pneumonia Rhinitis AHVLA AHVLA Pleurisy 4

5 Key pathogens in respiratory disease Pneumonia Primary pathogens Actinobacillus pleuropneumoniae Actinobacillus suis Bordetella bronchiseptica Mycoplasma hyopneumoniae Mixed pathogens Haemophilus parasuis Mycoplasma hyorhinis Pasteurella multocida Streptococcus suis Trueperella pyogenes Bacteria Viruses Primary pathogens Aujeszky s Influenza PRRSV Mixed pathogens PCMV PCV2 PRCV TTV 5

6 Susanna Williamson APHA Respiratory disease is usually multi-agent Porcine respiratory disease complex (PRDC): a polymicrobial disease Agents identified in this case: PCV2 PRRSV M. hyopneumoniae P. multocida A. pleuropneumoniae 6

7 PRDC is poly-microbial at farm level 2008 UK study found 4-9 pathogens by studying 6 acutely dyspneic pigs per herd Farm PRIMARY PATHOGEN SECONDARY PATHOGEN APP Mhyo PRRS SIV HPS Mhr PCV2 Pmult SS Tpyo 1 X X X X X X 2 X X X X 3 X X X X X 4 X X X X 5 X X X 6 X X X X 7 X X X X X X 8 X X X X X X X X X 9 X X X X X X 10 X X X X X 11 X X X X X 12 X X X X 7 Tucker et al,

8 Respiratory disease: an imbalance between 3 factors Pig susceptibility Pathogens Environment 8

9 Diagnostics are one element of a comprehensive investigation Preparation: Review production records: Mortality, ADG. Review herd structure & production flow. Review all health monitoring data: Slaughter pathology, lab investigations. Medicines and vaccines usage The herd visit Clinical & environmental evaluation Initiate preliminary sampling & investigations Plan statistical sample sizes Consider sensitivity and specificity of tests Reporting and agree actions May include on going monitoring Follow-up visit and verify actions Trends in slaughter pathology (EP-like lesions) at farm level England N. Ireland Scotland Eze, J. I., Correia-Gomes, C., Borobia-Belsué, J., Tucker, A. W., Sparrow, D., Strachan, D. W., & Gunn, G. J. (2015) PloS one, 10(5), e

10 Diagnostic and monitoring tools Progressive and non-progressive atrophic rhinitis (PAR & NPAR) Clinical signs: Progressive lesions Snout scoring Nasal swabs: Culture for B. bronchiseptica ELISA for dermonecrotoxin antigen (de Jong 2006) of P. multocida PCR for dermonecrotoxin gene (Register and de Jong 2006) Strategies: Diagnosis or confirmation of absence. Monitoring typically based on clinical signs David Taylor APHA 10

11 Stan Done Stan Done Diagnostic and monitoring tools PRRSV EU (Type I) and US (Type II) genotypes Clinical signs: Reproductive & respiratory Antibody testing: Serum, oral fluid Indirect ELISA, with IPMA for confirmation of false positives (and Type). Must take account of vaccination and maternal antibody PCR detection: Fetal material, lung tissue and blood; oral fluid; semen. Escape from primers reported (false neg). Sequencing of ORF5 region for phylogeny. Strategies: Longitudinal and cross-sectional surveys by OF PCR: age at peak circulation; strain ID. Combined PCR and ELISA to monitor for exclusion; and track eliminations. 11

12 APHA Clinical signs: Diagnostic and monitoring tools Influenza A viruses Acute coughing in pandemic form: depression, rapid spread to all pigs. Recovery over 7-14 days. Increase in secondary diseases. Antibody testing: Serum or oral fluid (n.b. vaccination and maternal antibody may complicate). ELISA: no typing HAIT (haemagglutination inhibition test): some strain differentiation. Nasal swab or oral fluid: Virus culture, isolation and typing Real time PCR Matrix gene, N gene, H gene Sequencing recombinants. Strategies: M-gene PCR for surveillance/diagnosis followed by typing PCRs for best vaccination strategy. 12

13 Diagnostic and monitoring tools Porcine circovirus 2 (PCV2) Clinical signs PCV2-SD (PMWS), also repro / gut / respiratory. Subclinical infection Immunohistochemistry Classic lymph-node pathology (lymphocyte depletion); interstitial pneumonia; viral staining PCR (real time and quantitative PCR): Serum, oral fluid. Virus load in serum and pooled OF are not equivalent. Strategies: Cross-sectional surveys by qpcr in serum or OF High viral load may indicate need for vaccination review. Antibody tests (ELISA) of limited value other than for investigation of high MDA in suspected vaccine interference.

14 Diagnostic and monitoring tools Mycoplasma hyopneumoniae (M. hyo) Clinical signs Hard, dry cough, bright pigs Antibody detection PCR: indirect and competitive ELISAs Note: slow seroconversion, maternal antibody and vaccine antibodies. Low sensitivity of tests; some specificity issues Samples: lung tissue, nasal / tonsil swab, oral fluid. Immunohistochemistry Staining & classic cuffing mononuclear infiltrate in lung Strategies: Use of serology to demonstrate absence of infection. PCR to confirm suspected break v. false positive ELISA; to track eliminations PCR to determine peak age of shedding for investigating efficiency of control David Taylor 14

15 Diagnostic and monitoring tools Actinobacillus pleuropneumoniae (APP) Clinical signs: Severe dyspnoea and coughing; age >6 wks Pyrexia, depression, inappetance. High mortality. Antibody detection: ApxIV (toxin) ELISA: not indicative of pathogenicity; other apx ELISAs lack specificity. Serotype specific LPS-ELISAs (e.g. 1,2,5,9,11) Culture and typing: Molecular serotyping PCR (Bosse, J Clin Micro 2014) Molecular toxin typing PCR (Rayamahji 2005) Strategies: Diagnostic confirmation of lung isolates by culture and typing; higher diversity in tonsil? Confirmation of absence by ApxIV serology - but will detect less-significant serotypes. 15

16 Monitoring strategies Opportunities based on pig flow and simple, affordable platforms Juan Hernandez Different opportunities and purposes based on different types of pig flow Non-invasive platforms (e.g. oral fluid) widen uptake: Advantages: non-invasive, less expensive Disadvantages: sample quality, a pool of individuals, sensitivity 16

17 DL Harris: Multi-site Production, 2000 Traditional single site farrow-to-finish continuous flow unit Breed / suckle Weaners / growers Finishers Infections maintained in grow/finish stages Traditionally later weaning >4-5 weeks permits pathogen colonisation from dam.

18 DL Harris: Multi-site Production, 2000 Traditional single site farrow-to-finish continuous flow unit Multi-site production Site 1: Breed / suckle Breed / suckle Weaners / growers Site 2: Weaners Finishers Site 3: Growers/ finishers Infections maintained in grow/finish stages Traditionally later weaning >4-5 weeks permits pathogen colonisation from dam. Interrupts infection dynamics between each stage. Variable AIAO at each site.

19 DL Harris: Multi-site Production, 2000 Traditional single site farrow-to-finish continuous flow unit Breed / suckle Multi-site production Site 1: Breed / suckle Multi-site, multisource, AI-AO batch production Breeder 1 Breeder 2 Breeder 3 Weaners / growers Site 2: Weaners Finishers Site 3: Growers/ finishers Wean-finish 1 Wean-finish 2 Wean-finish 3 Wean-finish 4 Infections maintained in grow/finish stages Traditionally later weaning >4-5 weeks permits pathogen colonisation from dam. Interrupts infection dynamics between each stage. Variable AIAO at each site. Complete segregation of 3- week batches. Multi-sourcing complicates infections post-weaning. Logistics only justified for larger herd sizes.

20 DL Harris: Multi-site Production, 2000 Traditional single site farrow-to-finish continuous flow unit Multi-site production Breed / suckle Weaners / growers Finishers Site 1: Breed / suckle Site 2: Weaners Site 3: Growers/ finishers Monitoring outcomes: For confirmation of health of breeding stock supplier. Steps to increase pig resistance: Vaccination Adapt acclimatization Colostrum management Decisions on elimination Infections maintained in grow/finish stages Traditionally later weaning >4-5 weeks permits pathogen colonisation from dam. Interrupts infection dynamics between each stage. Variable AIAO at each site.

21 DL Harris: Multi-site Production, 2000 Traditional single site farrow-to-finish continuous flow unit Breed / suckle Weaners / growers Finishers Infections maintained in grow/finish stages Traditionally later weaning >4-5 weeks permits pathogen colonisation from dam. Multi-site production Monitoring Site outcomes: 1: Breed / suckle Steps to increase pig resistance: Vaccination Site 2: Weaners Acclimatization Colostrum management Decisions Site on elimination 3: Growers/ Opportunities finishers to design mixed source flows based on breeding herd health Opportunities to match lower health sources to grow-outs between with each better stage. environment/management. Interrupts infection dynamics Variable AIAO at each site. Multi-site, multisource, AI-AO batch production Breeder 1 Breeder 2 Breeder 3 Wean-finish 1 Wean-finish 2 Wean-finish 3 Wean-finish 4 Complete segregation of 3- week batches. Multi-sourcing complicates infections post-weaning. Logistics only justified for larger herd sizes.

22 Disease control must be based on evidence worth investing in robust diagnostics and monitoring Thorough diagnostic investigation: Track prevalence in slaughter pathology Sample enough appropriate (acute) pigs Request the right tests: Expect multi-pathogen profile; antibiotic senstivity Interpret the results properly (Se and Sp). Review of pig susceptibility: Passive immunity / colostral quality & quantity Review factors affecting active immunity: Immune-suppressive infections (PRRSV, PCV2, Mhyo) Stress and other factors. Review vaccination strategy and methods. Review of environment and management factors Active monitoring Designed according to pig source and flow. Future opportunities: New tools for detection of disease causing strains of endemic bacteria (H. parasuis, S. suis). Benefits Improved production efficiency; reduced antibiotic usage

23 Thank you 23