Worldwide perspective on Infectious Bronchitis Ruth Bouwstra, DVM, PhD Turkey February 2017
Infectious bronchitis virus Corona Virus, a ssrna virus - Relatively high rate of mutations (0,0012 subst per nt per year) - Also recombinations Many serotypes/genotypes: Massachusetts (M41, H120), D274, D1466, Ark, De072, GA98, 793B (4/91, CR88), D388 (QX), B1648/D8880, Q1, variant 2, etc, etc leader Replicase 1a Replicase 1ab 5 UTR Viral genome organization of infectious bronchitis virus. Spike Membrane Nucleocapsid Gene 5 3a 3b a b 3 UTR b Envelope sensitive to detergents (fat) and disinfection (proteins) Take care of faeces!
IBV globally Increase of nephropathogenic strains??? QX: Europe, Asia, parts of Africa Q1: Latin America, Middle East, Asia, Europe Variant 2 (Israel 1494/06): Middle East BR-I Australia: 3 subgroups How many genotypes???? Three new ones in last 3 months (at GD alone) Role of wild birds???
IBV-like strains in non-chickens Pheasant: IBV-like virus, genetically not very different Respiratory signs, nephritis In chicken: no disease, some ciliostasis, seroconversion IBV in pheasant: no infection Many IBV-like viruses in other species, however, unknown whether they are a danger for chickens Might be the source when a completely new genotype appears (D1466, DE072,.) Wild birds, Muradrasoli et al, 2010
Infectious bronchitis virus Increasing number of countries have to deal with an increasing number of variants Some variants stay for a longer time, others come and go (and may reappear) In many countries, broad protection is needed
Disease IBV depends on: pathotype strain (variation within serotypes) type of chicken age climate: ammonia, dust, E. coli, ORT co-infections (viruses, Mycoplasma) protection: vaccination, serotype, protectotype Diagnostic challenge
IB and co-infections 1 + 1 = 3 examples IB + E. coli (Cook et al, 1996) ILT (40% mortality) + IB (0% mortality) resulted in 80% mortality
IB and co-infections IB (0% eggshell apex abnormalities (EAA)) + Ms EAA strain (12%) resulted in 24% eggs with egg shell abnormalities (Feberwee et al, 2009) IB (0% arthritis) + a Ms amyloidosis strain (21%) resulted in 33% and 55% amyloidosis (Landman et al, 2004) Mg, Coryza, H9N2, ORT, 1 + 3= 3
IB and co-infections, H9N2 and IB 20 day old broilers Negative Control, H9N2 alone, H9N2+H120 Combination: much more respiratory signs, 10% mortality, longer excretion of H9N2 3 1 = 1
Damage IBV in broilers decreased feed intake and growth sneezing, gasping, rales, nasal discharge flip-overs: sudden deaths by choking swollen head syndrome airsacculitis by secondary bacterial infections, Mg, Ms, Coryza (E. coli, O. rhinotracheale, etc) condemnations nephritis: gout, mortality, very wet litter
Colibacillosis
Damage IBV in layers/breeders decreased feed intake cage : sometimes sneezing, wet eyes ground : sometimes SHS drop egg production, egg quality decreased (shell, protein, dirty), hatchability peritonitis (coli) nephritis, gout damage of the testis false layers
False layers (IBV D388/QX) Look and act like laying birds, pelvic bones are wide open, no egg Irreversible damage of the oviduct, active ovary Very early infection with a (very) pathogenic IBV strain in chickens without relevant maternally derived antibodies against that strain
Clinical signs by IBV infection of kidney Strain dependent Age dependent: more problems in very young birds (Cold) stress dependent Feed Diagnostic challenge
IBV strain typing protectotype (primary, secondary) serotype (VNT) epitope type (Mab, IFA, ELISA) genotype (RT-PCR, RFLP, sequencing)
Protectotyping Most relevant for the chicken: is the vaccinated chicken well protected against challenge? Yes: vaccine and challenge strain are of the same protectotype Requires animal experiments: expensive
Genotyping Characterization of strains based on (part of) the genome High variability between IBV strains: high demands for suitable primers to be able to detect all strains Several approaches possible RT-PCR for the S1 gene, product of RT-PCR is used for genotyping: RFLP (restriction enzymes) Sequencing Possible complications with mixtures of strains Panel of genotype-specific RT-PCR s, preferably combined with general PCR for IBV (e.g. nucleoprotein) looking for expected/known strains no differences detectable within a genotype Hardly any complicatons with mixtures of strains
Relation genotype and protectotype Correlation S1 genetic homology and level of cross-protection (De Wit et al, Avian Pathology 2011) percentage of cross-protection 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 percentage of homology in (part) of S1 Cavanagh et al, 1997 Gelb et al, 2005 Meir et al, 2004 Abdel-Moneim et al, 2006 Cook et al., 2001 Ladman et al., 2006 Liu et al., 2009
Protection A meta-analyses 18 IBV vaccination-challenge experiments 137 groups, 10 clusters Vaccines of 6 serotypes, live and inactivated 8 challenge viruses (serotypes)
Overview of mean TOC score per category of 137 groups of chickens in 18 vaccination/challenge experiments (De Wit et al, Avian Pathology, 2013) cluster vaccines Mean ciliostasis protection score (%) young No (neg. control) 99 No (pos. control) 4 Homologous (excl D1466) 97 D1466 54 Homologous, field applied 33 Heterologous single 53 (15-92) Heterologous 2 strains 75 (40-100) In lay Homologous, with an inact. 81 Heterologous, including inact. 64 Heterologous, only live 44
IBV vaccinations, (very) general rules Young birds: In general, homologous strains provide best protection against homologous challenge Broadening of cross-protection by repeated vaccination (day 0, day 14) of suitable combinations of IBV vaccines by a vaccination at day of hatch with a suitable combination of IB vaccines not every variant requires a special vaccine
Broad protection by combinations of live IBV vaccines Day 0 and 14 Hatchery reliability for the first vaccine Reliability application in het field? No/far less influence of maternally derived antibodies anymore No interference between IBV vaccines (when of different protectotype) Combined at day 0 Hatchery reliability for both vaccines More influence of maternally derived antibodies Potential interference between IBV vaccines (lower efficacy?)
Layers and breeders Need a long lasting protection against the relevant field strains of that area Main goal: protection against damage of the egg production and egg quality
Live and / or inactivated vaccines Live: local protection (most important for broilers), low antibody titres, protection lasts not very long (field), Inactivated vaccines: low local protection, higher level of antibodies (after live priming) longer period of protection
Induction of a high antibody response (HI, VNT) useful? Low number of papers about protection against IBV in the production period E.g. Box et al, several papers Higher serotype specific antibodies (against challenge virus) is correlated with a higher protection against egg-drop
Egg production after IBV M41 challenge (wk 38) in layers (Box and Ellis, Avian Pathology, 1985) % egg producton 100 90 80 70 60 50 40 30 20 10 0-4 to -1 1 2 3 4 5 no vacc. (comm pullets) 2x inacm41 wk 3 and 16 H120 wk 3 + inac Mass wk 16 H120 wk 3 + H52 wk 15 weeks post challenge
Box et al, 1988 Vaccinations Challenge (HI antigen) HI- IBV titre (log 2 ) at challenge Drop in egg production after challenge H120, H52 or H120 and Inact M41 or H120, H52 and Inact M41 M41 (M41) 4 16% 5-7 6% 8-9 2% H120, K100, Inacts (non, M41 or trivalent) D3896-like (M41) 4 6.7% 5-7 5.0% 8-9 1.8% H120, Inact M41+D274 D274 (2x) (D274) 4 18% 5-7 7% 8-9 5%
Relevance of difference in level virus neutralizing antibodies in laying birds Experiments GD with 6 serotypes 1 log 2 higher titre resulted in a 9% lower drop in egg production after challenge
Use of inactivated vaccines highly recommended for areas with challenge depending on situation (chicken decides): homologous vaccine (of high quality) heterologous vaccine (of high quality) more strains in inactivated vaccine can be helpful to induce more antibodies against other strains (in general) also dependent on strains, amount and quality of antigen per dose, adjuvant and application for specific strain: you have to test
Titres against EDS component in a vaccin % titres oke, none, low Vaccination crew 1 Vaccination crew 2 Vaccination crew 3
Application of live IBV vaccines Hatchery or in the field Results of experiments indicate that the application of live IBV vaccines (especially under field conditions?) can easily be underestimated, what might result in decreased efficacy At the moment: many different opinions, very little controlled field data
Protection in relation to IBV vaccine application, field trail (Doorn) Vaccine application Percentage of M41 protection after 2 weeks 3 weeks 4 weeks Eye drop 100 100 100 In rings on farm < 25 50 100 In chicken box on farm Nd 50 100 Automatic spray at hatchery 93 97 Nd Hand spray at hatchery 32 86 Nd
Type No of flocks Average percentage of IgM positive sera per flock post IBV spray vaccination Broiler 88 38 (P<0,001 GP) Layer pullet 178 46 (P=0,004 GP) Broiler breeder 58 52 Broiler grandparents 36 61
IBV field trial (360 spray vaccinated flocks), practical translation (De Wit et al, Avian Pathology, 2010, pp 123-132) Better results when: Ventilation off during spray (15.5%, P=0,037) (sufficient) Light on during spray (41%, P=0,009) Second IBV vaccination not within 2 weeks (2,5% per extra day, P=0,005) cold water was used (3,2% per C, P=0,021) Flock size/housing type: unclear Cages significantly lower responses than floor housing (31% vs 53%, P=0,01) Bigger flocks significantly lower results (1% per 1000 extra birds, P=0,04)
IBV vaccinations, (very) general rules Broilers: In general, homologous strains provide best protection against homologous challenge Broadening of cross-protection Laying birds by repeated vaccination (day 0, day 14) of suitable combinations of IBV vaccines by a vaccination at day of hatch with a suitable combination of IB vaccines Broad live priming of high quality Use of inactivated vaccines for boosting not every variant requires a special vaccine
But please don t forget Never ever underestimate the difficulties of applying vaccines by mass-application methods (especially in the field)
Known advantages of a better application Higher average level of protection Earlier protection Less rolling reactions including secondary bacterial complications (E. coli, Or, Mg, Ms) Lower risk for reversion to virulence Less interference with other vaccinations Better disease prevention, higher performance, better return on investment
Thank you for your attention