New Diseases or Re-emerging Threats
Current Knowledge state- Avian Reoviruses and
Clubbed Down Syndrome
SWCA 8th April 2014
Philip P Hammond BVetMed PGCert Avian Health (hons) MAHM MRCVS
Crowshall Veterinary Services
Topics Covered:
1) Reovirus tenosynovitis
2) Clubbed Down Syndrome
•
•
•
•
•
Presentation
Investigations
Epidemiology
Treatment and Prevention
Future Research
Clinical History
•
•
•
•
Integrated company
Initially one house on one farm affected May
2013
Ross 308 broilers
Age 14 days of age at onset of symptoms
Presentation:
•
•
•
•
Birds reported lame “walking on
their hocks using wings to
balance”- acute onset at 13-14
days of age.
Approximately 5% affected (1200
birds)
Poor uniformity
Poor growth rates
Courtesy of AAAP
First Step:
Post mortem examination:
•
•
•
Birds demonstrated mild bilateral
tenosynovitis
of
gastrocnemius
tendon- increased fluid in hocks
Concurrent
mild
pericarditis/epicarditis
No other gross pathology
Courtesy of AAAP
Differential Diagnoses:
Primarily considered likely infectious agent given
inflammation and effusion of tendon
•
•
•
•
Mycoplasma synoviae
Staphylococcus tenosynovitis arthritis
Enterococcus tenosynovitis/arthritis
Reovirus tenosynovitis/arthritis
Course of investigation:
Step 1- Staphylococcus tenosynovitis/ arthritis
• Swabs taken from hocks, tendons and
pericardial tissues
• Results – no growth after 48 hours
• Birds swabbed not being treated with
antibiotics and investigation undertaken at
early stage of infection
•
NOT STAPHYLOCOCCUS OR ENTEROCOCCUS
TENOSYNOVITIS/ARTHRITIS
Step 2
Mycoplasma synoviae
Serology:
Rapid serum agglutination on sera of 20
birds showing symptoms in affected
flock- taken at time of site visit
Results- negative
However- serology relies on antibody
production- acute vs convalescent
phase of infection- could not rule out
on the basis of this test alone
Mycoplasma synoviae PCR
•
•
PCR
(Birds NOT on antibiotics)
•
CULTURE- Chanocks- NEGATIVE
•
NOT MS INFECTION
ALSO…….
Mycoplasma synoviae infection is both vertically and horizontally transmitted
All PS in integrated company MS negative as monitored serologically throughout
lay- some flocks also Poultry Health Scheme status
Histology:
Tendons, joint capsule and tendon sheath- mixed inflammatory infiltrateboth heterophilic and lymphoplasmacytic
NOT POSSIBLE TO DETERMINE WHETHER BACTERIAL OR VIRAL FROM
HISTOLOGY ALONE
Then……..
Over course of following 2 months- multiple cases on multiple farms all within
same integration
Issues also being reported all over UK and throughout Europe
8-12% mortality due to culling
No response to antibiotic treatment either antimycoplasmal or amoxycillin
Welfare concerns due to lameness
Poor conversion 1.80+ vs 1.62
Poor uniformity
Some response to aspirin treatment•
better mobility, lower culling rates
Data analysis:
•
•
•
•
•
Common link for the above case- 80% of cases affected progeny from a
specific flock- breeder flock between 28-40 weeks- 35000 birds in 6 houses
Not all progeny from specific flock were affected
Other flocks placed at the same time from the same hatch day were
occasionally affected
Chicks were hatched in two different hatcheries- problem occurred in chicks
from both
Broiler farm location did not appear to be related to incidence
Step 3- Virus isolation
•
•
•
Aseptically extracted tendon tissue
from first case
Virus isolation conducted by AHVLA
Weybridge
3 Passages
• Reovirus
isolated
FROM
TENODON TISSUE
Gene Sequencing Undertaken
“ACTGAGCATACTGCAAATAATAGCACAATGATGGATGGATTTTTGCGTGCTTGGATTCCTTCCTCT
GGCGCGTCTGATGTGCTGAAGAAGTTTTGCAAATCCATTTCGATACAACGGAATTATGTTTGTCA
GGGTGACGATGGTTTGATGGTTGTTGACGGGCTGTCGACGGGTAAGTTATCAGGTGAGATAATT
”
86% similarity with the virus T17811.
“Arch Virol. 2013 Jun 16. Detection and characterization of a divergent avian reovirus strain
from a broiler chicken with central nervous system disease. ”
Dandár E, Bálint A, Kecskeméti S, Szentpáli-Gavallér K, Kisfali P, Melegh B,Farkas SL,
Bányai K.
NOT A NEW VIRUS ???
Development of SNT to virus by AHVLA Weybridge:
•Some evidence of seroconversion in
broilers- not consistent
•Evidence of seroconversion in one
parent flock from where majority of
affected progeny derived
•Low rate of seroconversion
•
Cases of Reovirus tenosynovitis have been reported
through the UK in a number of integrations this year
• Cases of Reovirus tenosynovitis have been reported
throughout Europe throughout the last year
Unanswered Questions!
•
•
•
•
•
•
Why have so many companies and countries suddenly reported this
syndrome?
Why have some flocks which have not been derived from the known positive
PS also developed symptoms?- cross infection in hatchery?
Why did some flocks from the same parent flock not show symptoms?- age
related resistance?
Is this a new strain of Reovirus or is it a previously recognised strain?Reoviruses appear to be continuously involving
What methods are being used to type Reovirus and are these consistent
throughout laboratories?- there is no consistency at this time
Will double Nobilis Reo inac vaccination confer protection?
What can we do to prevent?
• Biosecurity- hatching egg
hygiene
• Hatchery hygiene
• Vaccination- double
vaccination strategy advised
in UK
• Sigma B antibodies
• Autogenous vaccination
Affect of 2 x Nobilis Reo inac adminsitered at 14 and 18
weeks of age on ELISA antibody titres at 22 weeks of age in
Broiler PS (Biochek)
Mean Reovirus Titres 22 weeks of age
30000
24212
25000
Mean Titre
20399
20000
14059
15000
10000
5471
13991
8530
6584
10101
5000
0
Series1
Farm1
5471
Farm2
6584
Farm 3
14059
Farm 4
8530
Farm 5
10101
Farm Name
Farm 6
13991
Farm 7
20399
Farm 8
24212
Clubbed Down Syndrome
The symptoms and definition:
Definition:
• Chicks with clubbed down will have matted down, in which the
down feathers remain held together and look like clubs. (banana
down)- may also be hairy
• The defective down is most commonly seen on the ventral aspect
of the chick especially around the vent.
• Reduced hatchability, due to weak chicks and increased late dead,
with most demonstrating clubbed down.
• Chicks in a normal hatch (<0.5%) may show some down
abnormalities, including clubbed down.
• With clubbed down syndrome the incidence of chicks with clubbed
down is greater than 2%, usually with a similar loss of hatch. It is
only clubbed down if the condition is seen in all hatches over a
period of time (weeks to months) from a specific source flock.
Observations:
• Breeders no clinical signs, production levels are normal and egg quality
both internal and external looks the same
• Chicks have to be culled in hatcher baskets, usually 3-30%, but often
many weak chicks resulting in further losses at around 4-6 days of age on
broiler farm
• Sometimes parent flocks improve rapidly whilst others take many weeks
to show any improvement, others may never fully recover
• Spread between breeder houses on a farm can be very slow leading to a
protracted disease progression
Possible Causes of Clubbed Down:
Riboflavin deficiency – histology has ruled out in recent cases
Zinc deficiency – blood analysis on chicks indicates low levels in
affected chicks
• Feed analysis of breeder rations shows no deficiency so a more complex
situation
Viruses
•
•
•
•
Entero like viruses
Circovirus,
Adenovirus
Astroviruses
AFBI Stormont Work and recent corroboration
Previously Virus Isolation
•
•
•
•
An “entero-like virus” (11672) has previously been isolated from chicks with
clubbed down
In SPF eggs, killed embryos and cause stunting. But no CD seen with embryo
inoculation.
Not all Clubbed Down flocks positive for this virus
This virus has now been identified as an Avian Astrovirus
• Recent cases where we have been able to
demonstrate seroconversion to Chicken
Astrovirus using acute and convalescent sera
from the parent stock
Update on Clubbed Down Research:
1) Causal agent has not been identified
•
Previously Fowl adenovirus 8 was thought to be involved but now
ruled out
2) Can Chicken Astrovirus be ruled out as the cause?
•
•
Research has shown that if Chicken Astovirus is the causal agent, it
does not cause clubbed down by replicating in the embryo
Therefore, may be infecting the breeder hen and affecting the
formation of normal eggs- it may be acting physiologically to reduce
transfer of nutrients in to the egg hence why progeny show
symptoms of typical nutrient deficiency
Further investigation are
required to understand more
about this syndrome:
By infecting a known negative flock with Chicken
Astrovirus it may be possible to ascertain if:
• Clubbed down can be reproduced
• Where the virus replicates in the bird
• How the virus affects hatchability (direct or
indirect)
• If vertical transmission is occurring at all?
Diagnosis
Molecular diagnostics to quantify the levels of Astovirus present
• Kidney, gut, ovaries, oviduct
Serology- monitoring of breeder flocks- will commercial assays be available one day?
• indirect immunofluorescence assay
• ELISA
One major diagnostic challenge is that by the time the issue is observed in the progeny the virus
may have already gone 4 weeks later. How to overcome- routine storage of tissues and sera from
PS??? Practicalities?
Control
Ultimate aim to vaccinate breeders to prevent infection.
Astroviruses may be common place on broiler farms with limited clinical effects but the effects on
breeders in lay may be the major issue as seen with Chick Anamia virus and Avian
Encephalomyelitis. We may need to have a test to see if flocks have seroconverted in rear and then
vaccinate if they have failed to do so
With thanks to the following in respect of
Investigations:
Kathy Blake -Crowshall Veterinary Services LLP
Stephen Lister -Crowshall Veterinary Services LLP
Claire Knott -Crowshall Veterinary Services LLP
Ian Lowery -Crowshall Veterinary Services LLP
Vanessa Ceeraz, AHVLA Weybridge
Scott Reid, AHLVA Weybridge
Richard Irvine, AHLVA Luddington
Bill Cox, AHVLA Weybridge
Tibor Cserep, MSD Animal Health UK
Victoria Smyth AFBI Northern Ireland
We do not have all the answers but by working together we can help to
understand and focus the limited research resources we have to gain the
most knowledge. Microbiological agents are always evolving and at a
much faster rate than either us or the chicken!
Thank you for listening
phammond@crowshall.co.uk
www.crowshall.co.uk