Avian Insight Vol3 2013

7/27/2019 Avian Insight Vol3 2013

http://slidepdf.com/reader/full/avian-insight-vol3-2013 1/4

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



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



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.



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

Documents

Avian Insight Vol3 2013