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

sensitive to detergents (fat) and disinfection (proteins)

Take care of faeces!

     Viral  genome  organization  of  infectious  bronchitis  virus.  

                 

Replicase  1a Spike

Envelope  

Gene  5 Membrane Nucleocapsid

3a 3b b

a b  

Replicase  1ab

3’UTR 5’UTR

leader

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

•  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

Infectious bronchitis virus

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

•  3 - 1 = 1

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

•  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

0 20 40 60 80

100

0 10 20 30 40 50 60 70 80 90 100

perc

enta

ge o

f cro

ss-p

rote

ctio

n

percentage of homology in (part) of S1

Correlation S1 genetic homology and level of cross-protection (De Wit et al, Avian Pathology 2011)

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

0 10 20 30 40 50 60 70 80 90

100

-4 to -1 1 2 3 4 5

% e

gg p

rodu

cton

weeks post challenge

Egg production after IBV M41 challenge (wk 38) in layers (Box and Ellis, Avian Pathology, 1985)

no vacc. (comm pullets)

2x inacM41 wk 3 and 16

H120 wk 3 + inac Mass wk 16

H120 wk 3 + H52 wk 15

Box et al, 1988 Vaccinations Challenge

(HI antigen) HI- IBV titre (log2)

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 log2 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

Vaccination crew 1 Vaccination crew 2 Vaccination crew 3

% titres oke, none, low

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

•  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

•  Laying birds –  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