avian insight vol3 2013
TRANSCRIPT
7/27/2019 Avian Insight Vol3 2013
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avianinsightA L O H M A N N A N I M A L H E A L T H N E W S B R
Further Viral Arthritis/Tenosynovitis UpdatesIntroduction
Within the past few years,
there has been no shortage
of discussion concerning
viral arthritis and
tenosynovitis across the
industry. This has been
fueled by an increase in
the “classic” forms of the
disease both well-defined
and well-diagnosed in
chickens, but also by the emergence of similar signs
and lesions in meat-type turkeys proven to be
associated with avian reovirus. Several issues can be
associated with avian reoviruses in chickens such asstunting syndrome, immunosuppression, enteric
disease, and respiratory disease. Of these, viral
arthritis/tenosynovitis is the most readily diagnosed
and arguably of the most economic importance.1
Although reoviruses have been associated with other
diseases in commercial turkeys, tenosynovitis has
historically been a very uncommon finding.
Economic Losses
Since the reoviruses that cause tenosynovitis are
present worldwide in most commercial poultry
operations, the potential for large economic losses is
a constant threat in unprotected flocks.2
Both acute and chronic cases produce a varying
degree of lameness which leads to increased cull
rates and mortality in broiler and hen flocks alike. In
affected flocks, clinical signs and lesions are muc
less pronounced at younger ages but increase
severity as the age increases. Uniformity and fee
conversion also suffer partially due to the physic
lameness, but also due to the intens
immunosuppressive nature of the virus which ca
cause the birds to be more susceptible to diseas
Hens exhibit decreased weights and uniformity whic
directly affects egg production. Breeding male
undergo the same weight challenge which direct
affects fertility.
As broiler flocks approach processing age, oth
losses become more obvious resulting in higher feeconversions, lower average daily gains, and sometime
higher medication costs.3 Automated evisceratio
equipment relies on a certain level of flock uniformit
Poor flock uniformity results in higher contaminatio
and condemnation rates due to physical damage t
the carcasses. Gastrocnemius tendon ruptures a
Volume 3, 2013
inside
Since approximately
2008, the incidence
ate of “classic”
enosynovitis in
hens and broiler
flocks has been
on the increase,
even in the face
of comprehensivevaccination
programs.
Further Viral Arthritis/Tenosynovitis
Updates, p.1
Notes from the Director of Sales,
US & Canada, p.4
Jim Stockam, Technical Services Veterinarian
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often very pronounced in these flocks and
produce increased condemnation rates of
leg quarters due to the green color observed
after picking.
4
Disease Control History
The role of immunization in attempts to
control viral arthritis/tenosynovitis is welldocumented and has been generally
successful. Vaccination programs are
designed to protect breeders and broilers
through the use of multiple vaccinations.5
Protection from ongoing challenges is
typically acquired through the application of
three live vaccines given to pullets and
males within the first 6 weeks of age
followed by one or two inactivated vaccines
between 10 and 18 weeks of age. Programs
such as these have historically induced
adequate protection for production hens
and provided early parental immunity
protection to broiler chicks. The fact that
severe forms of the disease have rarely been
encountered for several years in well-
protected flocks is clear evidence that the
vaccine strains have delivered sufficient
cross protection to the general population of
field strains commonly found in the industry.
Current Issues
Since approximately 2008, the incidence rate
of “classic” tenosynovitis in hens and broiler
flocks has been on the increase, even in theface of comprehensive vaccination programs.
The flocks present with pronounced clinical
lameness, swollen hocks, joint immobility,
ruptured gastrocnemius/ digital flexor tendons - and mortality in the same manner
as has been seen in unprotected flocks.
Flocks in question usually exhibit reovirus
titers much higher than clinically normal
flocks that have received the same
vaccination protocols. Also, reovirus can
readily be isolated from both acute and
chronic lesions. During the same time frame,
the Midwest turkey industry has witnessed
the emergence of a similar syndrome
affecting tom turkeys. This condition is
characterized by many of the same clinical
signs and lesions seen in chickens with viral
arthritis/tenosynovitis.6 Exclusive to turkeys,
however, is the dramatic increase in aortic
ruptures and the distinctive correlation
between ruptured digital flexor tendons
and aortic rupture mortality in the same
animal. Avian reovirus strains have been
isolated from turkey lesions but are reported
to be antigenically different from S1133
Also, the turkey isolates have been shown
to be pathogenic to both turkeys and
chickens when introduced into the foot pad.
There appears to be considerable variation
in disease severity in both the chicken and
turkey outbreaks. Some flocks exhibi
varying degrees of lameness but very little
mortality. Other flocks suffer an increase in
mortality of 2-5%. The same inconsistencie
have also been noted in weight gain, feed
conversion, and susceptibility to secondary
infection. Resistance to reovirus infections
does increase with age and hens wil
eventually seroconvert to field challenges
which may provide an insight as to the
variability of outbreaks.
Possible Explanations
The question remains as to why previou
immunization methods appear to have
recently lost some of their efficacy. One
possible explanation is that variant strains
of reoviruses have always been present buare just now beginning to play a prominent
role as etiologies of the disease. Anothe
consideration could be that previously
known pathogenic strains may have
undergone genetic reassortment much in
the same way as influenza viruses do.
Orthoreoviruses are double stranded
RNA viruses that are non-enveloped and
possess a genome consisting of 10 segments
Due to these properties, they could maintain
the ability to undergo reassortment and
produce viruses that may be different in
antigenicity or pathogenicity. In other words
they have the ability to “reshuffle” genetic
material in order to produce a different virus
while maintaining similar characteristics o
the old one. The new virus may cause the
same “disease” with the same clinica
signs and lesions, but is antigenically
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different enough that conventional reovirus
vaccines are not as effective in immunizing
the animal against the new virus.
Although there is no hard evidence to
substantiate the role of reassortment as it
relates to the current situation, virus
neutralization assays used to compare the
strains have shown that while some of these
viruses are of the same serotype, they differ
antigenically from the chicken viral arthritis
strain S1133.6 Further attempts are
underway to characterize these novel strains
in hopes of gaining knowledge that will lead
to effective live and inactivated vaccines.
Summary
Poultry operations should strive to attain an
accurate diagnosis of lameness thought to
be caused by reoviruses. The goal should be
to avoid clouding the issue with those
factors unassociated with viral arthritis/
tenosynovitis, so that a true disease
assessment can be made. A combination of
serology, histopathology, virus isolation, andantigen specific testing can be employed to
rule in or rule out the presence of a variant
field strain. Once determined, integrators
may opt to use an inactivated autogenous
product in hopes of creating some level of
immunity to the new virus strains. However,
due to the variability of disease severity and
lack of field information, evaluation of these
products is difficult and more specific
challenge studies need to be completed.
Also, without an effective live primer, the
level of immunity derived from autogenous
products may not be as effective as
immunization programs geared toward
traditional strains. Hopefully, with a greater
understanding as to the characteristics of
these novel strains, more effective vaccines
can be developed to assist in control of the
changing viral arthritis/tenosynovitis issue.
References
1. Rosenberger, J.K. and N.O. Olson. 1997. In
B.W. Calnek, H.J. Barnes, C.W. Beard, L.R.
McDougald, and Y. M. Saif (eds.). Diseases
of Poultry, 10th ed. Iowa State University
Press, Ames, IA, 711-718.
2. Dobson, K.N., and J.R. Glisson. 1992.
Economic impact of a documented case
of reovirus infection in broiler breeders.
Avian Diseases 36:788-791.
3. Jones, R.C. Reovirus Infections. 2010.
In: Diseases of Poultry. Y. M. Saif, J. R.
Glisson, A. M. Fadly, L. R. McDougald, L. K.
Nolan, and D. E. Swayne (eds). Blackwell
Publishing, Ames, IA, 311-___
4. Johnson, D.C. and L. Van der Heide. 1971.
Incidence of tenosynovitis in Mainebroilers. Avian Diseases 15:829-834.
5. Schat, K.A., and M.A. Skinner. 2008. Avian
Immunosuppressive Diseases and
Immunoevasion. In: Avian Immunology. G.
Davison, B. Kaspers and K. A. Schat (eds).
Elsevier, Ltd., London, U.K. pp 314-337.
6. J. Rosenberger, J. Trites, D. Mills, J. Stockam,
S. Rosenberger, and M. Markis. 2012.
Characterization of reoviruses isolated
from tendons of turkeys presenting with
tenosynovitis and digital flexor tendon
rupture. Proceedings of the 61st Western
Poultry Disease Conference. p 13.
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Being able to respond to new and
emerging challenges in the poultry
industry is a priority for Lohmann
Animal Health. Accomplishing thisrequires commitment, dedication
and collaboration.
The Technical Service Team at
Lohmann Animal Health plays a
key role in our ability to respond
to challenges. Members of that
team include Jim Stockam, D.V.M.
(author of this Avian Insight), Keith
Honegger, D.V.M., Mariano Salem,
D.V.M., Sandy Aehle, M.S.; and Andy McRee D.V.M. (Headof Technical Services). This group of avian professionals is
committed to assisting customers as well as acting as liaisons
between industry, the Research and Development Team at
Lohmann Animal Health and many research and diagnostic labs.
Our R&D team in Winslow, Maine is dedicated solely to poultr
research. This allows Lohmann to respond to emerging issue
in addition to the improvement and development of current an
new poultry biologicals. We are grateful for collaboration witour customers, as well as research and diagnostic labs, as we a
share the common goal of improving the poultry industry.
LAHI offers a number of commercial vaccines with REO isolate
for the domestic and international markets. Most commo
products used domestically are AviPro® 226 BTO2-Reo and AviPro
442 ND-IB2-BTO2-Reo. Lohmann is always looking at ways to
improve products to best match current challenges. Producin
a USDA licensed product does take time; Lohmann Anima
Health recognizes the poultry industry doesn’t always have tha
“time.” For that situation, Lohmann can offer the poultry industr Autogenous Vaccines to help manage through those challenges
Talk to one of our avian professionals today to learn more abou
Lohmann Animal Health and how we can help you or visit ou
website at www.lahinternational.com.
Notes from the Director of Sales
f or more information:
avianinsight(+1) 207-873 3989 (+1) 800-655 1342 www.lahinternational.com
Tim Hopson
Director of Sales, US & Canada
Lohmann Animal Health
International, Inc.
Lohmann Animal Health Internationa
375 China RoadWinslow, Maine 04901, USA
Phone: (+1) 207-873 3989