infectious bronchitis holistic appraoch

Nuevos desafíos para combatir la bronquitis aviar

Jane K A Cook Consultant Microbiologist

Huntingdon, UK

Plan of talk

•  The virus and disease it causes

•  Variants – what they are; how they arise

•  Variants - worldwide situation

•  Variants – how to improve control

What is infectious bronchitis (IB)?

•  A highly infectious disease of chickens of all ages and type

•  Primary infection site – upper respiratory tract

•  Spreads systemically in the chicken, causing: – nephritis - poor egg production and egg quality •  Worldwide importance – in areas free of ND & AI

IB in broilers Respiratory infection

Section of a normal tracheal section

5 days post infection

Renal damage

Birds appear depressed

Scouring, wet litter

Kidneys pale & swollen

Urate deposits in ureters

Increased condemnation

Mortality may reach 30% in severe cases

IB in laying hens

0

20

40

60

80

30 32 34 36 38 40 42 44 46 48

Inoculated ControlAge (weeks)

% egg production

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20

40

60

80

22 24 26 28 30 32 34 36 38 40 42

% egg production

Age (weeks)

Pale shelled eggs

Left: normal egg Right: “watery white”

Egg production Egg quality

Transmission of IBV

•  Highly infectious

•  Spread by aerosol and faeces

•  May persists in the chicken for many weeks

•  May survive in litter for many days

•  All very important for IB epidemiology

Control of IBV infections

•  Good hygiene

•  Strict biosecurity

•  Both essential, but not enough:

•  Vaccination is necessary - live attenuated and inactivated vaccines used

Infectious bronchitis virus

•  A coronavirus; single-stranded RNA virus

•  Therefore able to change continually by:

- random mutation - genetic recombination •  This results in changes in

the genome structure

•  Significant when changes occur in the surface spike (S) protein

The spike (S) protein

A few amino acid changes in S resulting from mutation or recombination may result in a new IB variant

IB variants •  Result from mutation or genetic mutation •  A new variant is recognised in the laboratory by:

•  serotyping (traditional method; now used less)

•  genotyping (increasingly used)

•  The number of new variants is increasing all the time

•  This has serious implications for the implementation of effective control measures

Typing IB variants

Virus/ serum

USA Br. Hond Isr. Japan Taiwan S A UK

USA 560 _ _ _ _ _ _ _

Brazil _ 110 _ _ ND _ ND _

Hond _ _ 240 _ _ ND _ _

Israel _ _ _ 870 _ _ _ _

Japan _ _ _ _ 560 _ ND _

Taiwan _ _ _ _ _ 1000 _ _

S Africa _ _ _ _ _ _ 490 _

UK _ _ _ _ _ _ _ 800

Genetically by PCR – phylogenetic tree

Serologically- by neutralisation test

May not get identical results with the two methods

Value of molecular techniques to study IB variants Using reverse-transcription polymerase chain reaction (RT-PCR) and sequence analysis of S glycoprotein gene

•  Use of RT-PCR enables variants to be detected much more quickly than before

•  Realisation that IBV treated with phenol can be analysed was very important

•  Availability of FTA cards makes it easy to send samples worldwide

PCR – a word of caution!! How do we interpret the results?

Virus

PCR Virus isolation

Disease?

A

Yes Yes Yes

B

Yes++ No Rarely

C

Yes Yes Yes

Detection of an IB variant by PCR does not always mean it is an important cause of disease

History of IB variants

•  1st report – Connecticut, USA 1950s; did not protect against the original isolate from Massachusetts

•  Variants may have existed since before then

•  Much work in Europe & UK in 1970s (improved techniques to study them)

•  1990- availability of molecular techniques revolutionised study of IB variants

•  Now detected in increasing numbers

Variants can behave very differently!

•  Majority fail to replicate

•  Some persist for only a short time

•  Some are found only in very small areas (maybe only one country)

•  Some are found (almost) worldwide e.g. Massachusetts

•  A few continue to be found for many years and are of major welfare & economic importance

IB variants in the field

More than one type may be present in a flock at the same time

Type 1

2

Year 3

4

5

6

A + + - - - -

B - + - - - -

C - - + + + +

D - - - + - -

E - - - - + +

Prevalent type may change with time

Type M

N

Flock P

S

T

A + + + - -

B - + - + +

F - + + - -

G - - - + +

Survey in USA: (Jackwood et al., Avian Diseases (2005) 49; 614)

•  1511 IB isolates obtained over an 11 year period

•  82 different variants identified

•  Only 2 persisted & caused widespread disease

Evolution of IB variants

IB variants in USA - historically

Many different ones reported: •  Massachusetts (first IBV to be described) •  Connecticut •  Holte (first to be associated with nephritis) •  Grey •  Iowa 97 •  Iowa 609 •  Florida •  JMK ………………………………….. many more

IB variants in USA – current situation

1.  Arkansas •  First reported in 1997; still causing problems •  Subtypes are now recognised •  Existing vaccines still effective if used carefully

2.  Delaware 072 (DE072) •  Major disease in vaccinated flocks •  Genetic shift & recombination is occurring •  New variant has evolved (Georgia 98) •  New vaccines needed!

•  Other variants emerging in different states

IB variants – the European situation well studied

•  Variants known since the 1980s -D274; D1466 etc

•  Many different ones identified in Europe (some widespread; some in only small areas)

•  1990s – 793B (4/91; CR88) first reported and became a major problem; interesting pathology

•  More recently, RT-PCR surveys have led to the detection of many more ……….

IB variants in Western Europe 2002-2006 (RT-PCR)

IB genotype % distribution Mass 24.1 793B 33.8 It02 12.6 QX 10.0 D274 8.5 D1466 2.3 Arkansas 6.0 B1648 0.3 Others 2.5

From: Worthington et al, (2008).Avian Pathology, 37, 247

* D1466, only from 2005

IB variants from the Middle East

Israel

•  Variant I. >90% similar to 4/91/793B (Jackwood et al.)

•  Variant II. 80% similar to D274 (Jackwood et al.)

Jordan & Iran •  4/91–like viruses detected by RT-PCR

Egypt •  Egypt/Beni-Seuf/01. Also found elsewhere in the region. (In Israel called IS/885)

IB variants in Asia Work being done in many countries, including: •  Malaysia, Singapore and Taiwan Local variants detected as well as ones found elsewhere •  Japan •  Thailand Variants “unique” to Japan/Taiwan as well as ones similar to those found in USA & China, (Mase et al., Shieh et al., 2004; Hwang et al., 2004)

•  Korea

•  China

IB in Asia - Korea

•  IB problems since at least 1980s

•  Mass vaccination initially successful

•  Now – increased incidence of kidney problems in vaccinated flocks

•  At least 4 local IB variants recognised

IB in Asia - China

•  IB probably under control before 1980s

•  Many groups now working on IB

•  Large amounts of data are being produced

•  Local variants as well as ones found elsewhere

•  Globally important variants have come from this area, including QX and Q1

QX – an IB variant of global concern

•  First described in China; then spread to Russia

•  Now present in many European countries

•  A cause of nephritis in broilers

•  “False layers” after infection at a very young age

•  Birds appear healthy during rear but infection causes permanent damage to the oviduct •  Egg laying performance is severely affected

•  Birds showed peculiar stance (penguin-like) and

pendulous abdomen

•  Poor production (30%- 55%) in “healthy” flocks •  Post mortem: frequently cystic oviducts with watery

content (one litre), or (partially) atrophic oviducts with large cystic dilatations

•  Thin, transparent oviduct wall in cystic areas

•  Functional, normal ovaries

Infectious Bronchitis QX in layers

Infection with IB QX

QX – an IB variant of global concern

•  Nephritis may now be more important than the effect on egg laying performance

•  This is now reported in many countries worldwide (not USA)

•  Question: Is better vaccination preventing very early infection?

•  Point to remember: QX is different from Q1 (both 1st described in China!)

IB variants in Australia

•  Because Australia has maintained ‘closed’ boarders, IB has evolved uniquely

•  Many different variants, found only there (and possibly New Zealand)

•  Different from those in all other countries

IB variants from different areas showing wide diversity

De Wit et al., Avian Pathology, 2011

Taiwan

Thailand

4/91/793B

Australia

China (Q1)

China (QX)

History of IB variants in Latin America

•  1950s: IB reported in Brazil (Hipolito)

•  1960s: 1st variant (Arkansas) reported in Brazil (Branden & Da Silva) •  1976: IB first reported in Chile (Hidalgo et al)

•  1980s: 1st report of variants in Chile (Hidalgo et al)

•  1990: More variants; Mass vaccines gave poor protection (Cubillos et al.)

•  Mexico - Several unique variants (Escorcia et al., 2000)

•  Honduras – Variant identified; Mass vaccines do not protect (Cook et al.,,1999)

•  Colombia – Several variants identified (Alvarado et al. 2005)

•  Chile - Variants a cause of major concern

•  Brazil – many different variants; Mass vaccines give poor protection (di Fabio, et al., 2000; Abreu et al, 2006; Villarreal et al., 2007a; b; Montassier et al, 2008; Villarreal et al., 2010)

Variants from Latin America

Example of genotyping Brazilian IB isolates

Villarreal et al., Avian Diseases. (2010)

Some group with 4/91

Some group with Mass

Some are unique to Brazil

IB in Chile since late 2000s

The problem: •  Broilers: respiratory disease, high condemnation

rates, nephritis

•  Breeders: respiratory problems, poor egg production, enteric problems

•  Current vaccination programmes not effective

•  IB variant Q1 commonly identified by RT-PCR

What about the current situation in South America?

•  Argentina – 3 variant groups identified in 2000s (Rimondi et al., 2009)

•  IB now causing major problems in Argentina, as in

Chile

•  Situation may be similar elsewhere, but research has not been undertaken in all countries

•  Many variants identified, but frequently Q1

What can be done to improve control of IB variants?

First things: •  Attention to improving management and biosecurity •  Careful use of available vaccines

This may not be enough: •  Apply the “protectotype” concept •  Consider using an IB vaccine to a variant strain in the

programme •  Used successfully in many areas (Arkansas in USA;

4/91-type elsewhere)

The protectotype concept

•  IB variants arise because of very small changes in the genetic makeup of the virus

•  Most of the virus has not changed

•  Good protection using vaccines already available

•  Use two very different live-attenuated IB vaccines (Must be strong immunogens and genetically different)

•  Mass & 4/91-type meet these criteria (probably others too, such as Arkansas in USA)

How does it work?

Day old 2 weeks Mass None None 4/91-type Mass + 4/91-type None None None

Vaccination

Challenge at 5 weeks

Assess protection 5-7 days later based on damage to ciliated epithelium of the trachea (ciliostasis test)

Normal IB infected

Ciliostasis test

Give a score to the damage and quantify protection

Benefit of using two different IB vaccines in protecting against variants from Asia

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60

80

100

No vaccine Ma5 IB 4/91 Both vaccines

% Protection

IB vaccines used

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40

60

80

100


Protection against challenge with an IB variant from Honduras

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100


% Protection

IB vaccines used

Protection against challenge with a Mexican IB variant

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80

100


% Protection

IB vaccines used

Protection against challenge with a Brazilian IB isolate

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100


% Protection

IB vaccines used

Timing of IB vaccinations

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40

No vaccine Both(do) M(do);B(2w)0

10

20

30

40

No vaccine Both(do) M(do);B(2w)

Homologous challenge Heterologous challenge

Heterologous challenge; benefit from delaying 2nd vaccination

How we can improve control of IB variants

•  Optimise the use of the IB vaccines already licensed

•  Consider using a second IB vaccine in the programme

•  Ideally, do not introduce vaccines to strains not already present

•  Sometimes this may be necessary

•  Ideally, leave 2 weeks between the 2 vaccines, but in some situations, it is necessary to give both together at day-old and this is beneficial

None

Ma5(day-old)

Ma5+4/91

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40

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80

100

Isolate 1 Isolate 2 Isolate 3 Isolate 4

% Protection

Protection against challenge with recent IB variants isolated in Chile

Conclusions •  IB variants are a global problem

•  Because of the type of virus that IBV is, new variants will continue to occur

•  Some will have limited geographical distribution/ limited importance

•  Others will be found in many countries

•  Some will disappear quickly

•  Some will persist for many years, causing economic and welfare problems

•  How can we deal with the problem……….?

What can we do about IB variants?

•  Improve management practices

•  Good biosecurity

•  Careful use of the vaccines available

•  Learn from experiences in other countries because a new vaccine may be needed

•  Continue to watch the situation carefully

•  We have to learn to live with the problem!

Thank you for your attention

infectious bronchitis holistic appraoch

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