Gumboro Disease: where are we with IBDV epidemiology. J.J. (Sjaak) de Wit, DVM, PhD, dipl ECPVS GD Deventer, The Netherlands

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1 Gumboro Disease: where are we with IBDV epidemiology J.J. (Sjaak) de Wit, DVM, PhD, dipl ECPVS GD Deventer, The Netherlands

2 Gumboro-virus (IBDV) Avibirna-virus: 2 segments of dsrna Non enveloped virus Very resistant - 52 days survival in water, feed and manure days after removal infected flock still present in the chicken house - Sensitive to formaldehyde, chloramine, quats

3 Risk factors IBD (Gruyters et al, Sanchez et al. (Prev. Vet. Med 2005), M.Folden-Flensburg et al 1999 and 2002 (Avian Pathology) Gruyters: flocks, Danish studies: >3000 flocks No vertical transmission Infected faeces/birds/house Trucks (hatchery, feed, manure, slaughtery (thinning)), people, machines Short distance: air IBD in previous flock: 6 x higher IBD risk Farms within 7 km and 10 days since IBD-case: 15 x higher IBD risk Highest risk of spreading till 20 km in the first 20 days. Increased risk for 8 months Flock specific vaccination based on vaccination date prediction lowers IBD risk

4 Control of IBDV Biosecurity, cleaning, disinfection, management Vaccination Monitoring, movie, no picture Prevalent field strains: yes/no, which one Take of vaccinations

5 Challenge? was there a challenge, when, which strain? Clinical: despite vaccination, vvibdv, other classical strain, variant strain? Subclinical: vaccinated flock, vvibdv, variant strain?

6 IBDV Serotype 1: Classical-like stains (Faragher, vvibdv, vaccines) Clinical signs, swelling, atrophy of bursa Illness and immunosuppression Variant-like strains (Del E, GLS, etc) No clinical signs, atrophy of bursa Immunosuppression Serotype 2: turkeys, no clinical symptoms in the chicken, only histopathological lesions

7 Detection of infections Detecting the IBDV virus: Infectious particles (virus isolation) Antigen (staining) Genome (RT-PCR) Detection of the antibody response

8 Clinical outbreak (classical, vvibdv) Acute phase of infection (inflammation of bursa) Maximal amount of virus at time of clinical signs Max. virus titre: first 3-6 days in bursa Detectable virus: 1-2 weeks in non-protected birds Less and shorter in (partially) protected birds Seroconversion

9 Subclinical case E.g. biological variant (e.g. Del E) variant strain : a biological relevant variant (decided by the (vaccinated) chicken) No visible signs, so when to sample? Frequent sampling (e.g. weekly) of 5 bursa s at week 1, 2, 3, and 4. If suspicion (retrospectively) of infection: testing pools of (small) bursa of every week for the presence of virus (+ typing) Seroconversion

10 19 groups?

11 Vaccination 3 main kinds of Gumboro vaccines for active immunity Conventional vaccines (water application, eye drop, spray) Antibody/antigen complex vaccines Vector-based vaccines

12 Gumboro vaccination

13 Deventer formula, Block et al, Avian Pathology 2007 Field experiment 1 16 broiler flocks (Ross, Cobb) Blood 3-12 days (Deventer formula, IDEXX) 2-5 days prior to vaccination: second blood to check and confirm Vaccination at day of estimation (intermediate vaccine) 0, 7, 14, 21 days post vaccination: PME, 30 blood, 5 bursa (RT- PCR, sequencing, histology)

14 Experiment 1. Serology at 7, 14 and 21 d.p.v. Experiment 1, RT-PCR and histology post vaccination percent positive to days post vaccination % RT-PCR positive histology

15 Deventer formula, Block et al, Avian Pathology 2007 Field experiment 2 20 broiler flocks (Ross, Cobb) Vaccination at general recommendation, intermediate vaccine Blood 3-7 days (retrospective, Deventer formula, IDEXX) retrospective 3 groups: Group 1: vaccinated before the estimated day (-8 to 1 day) Group 2: vaccinated at the estimated day Group 3: vaccinated after the estimated day (1 to 6 days) 0, 7, 14, 21 days post vaccination: PME, 30 blood samples, technical performance)

16 Experiment 2. Serology at 7, 14 and 21 d.p.v.

17 Recent data: 2013 European IBV + IBDV study by Ceva and GD Study population and sampling 234 flocks (farms) originating from 10 European countries Sampling flocks with respiratory distress (suspicion of IBV) 5 trachea and 5 kidney samples were pooled per house IBV RT- PCR (S1 and D1466), sequencing for genotyping 5 bursas per flock (house) for Gumboro RT-PCR + sequencing 10 blood samples for ELISA Gumboro

18 IBDV RT-PCR positive for vaccine

19 Gumboro antibodies post vaccination

20 Mean percentage of ELISA IBDV antibody positive sera in 93 broiler flocks vaccinated aganst IBDV by the drinking water sampled in week 1 (n=3), 2 (n=23), 3 (n=33), 4 (n=24), 5 (n=8), 6 (n=1), or 7 (n=1) post vaccination 100 percentage of flocks or birds all sera positive 75-99% positive per flock 50-74% positive per flock % positive per flock 0-24% positive per flock average percentage of positive sera sampled in days post vaccination

21 Conclusion epidemiological study 2013 few vvibdv and potential variant (Note: sampling based on IBlike symptoms) Vaccination by drinking water or hatchery (Transmune) : average detectable vaccine replication (RT-PCR) post drinking water vaccination was delayed compared to that of the average hatchery vaccinated flocks average vaccine antibody response post drinking water vaccination was delayed compared to that of the average hatchery vaccinated flocks Most likely due to the timing or quality of the application

22 Checking the take of vaccinations and the presence of (subclinical) infections Costs time and money Make a movie, no picture Does not make your life more easy in the short term. But in the long term, it helps you to make more rational decisions based on knowledge, instead of belief or trust Serology: do not only use it when there are already outbreaks. Monitoring at slaughter: information about vaccination and indication of field pressure: prevent problems Preventing problems saves money

23 Thank you very much for your attention

Laboratory tools for monitoring and understanding IBDV infection and vaccination

Laboratory tools for monitoring and understanding IBDV infection and vaccination J.J. (Sjaak) de Wit, DVM, PhD, dipl ECPVS GD Deventer, The Netherlands Gumboro-virus (IBDV) Avibirna-virus: segments of