REO Virus Infections in Broiler Breeders and Progeny - Prevention Strategies

By Dr. Richard Phillips
Schering-Plough Animal Health
New Jersey

Avian Reoviruses

...are ubiquitous viruses in nature, and are commonly isloated from a variety of tissues in poultry affected my multiple disease conditions such as viral arthritis/tenosynovitis, sttunting syndrome, respiratory disease, enteric disease, and malabsorption syndrome.

Economic Losses

Cause by Avian Reovirus:

1. Poor feed conversion
2. Poor flock uniformity
3. Reduced weight gains
4. Unthriftiness
5. Mortality
6. Severe Lameness

Historical Perspective

  • The initial avian reovirus was isolated in 1954 by Fahey and Crawley from the respiratory tract of chickens.
  • Olsen et al. Isolated a reovirus from chickens with naturally occurring synovitis in 1957 that were unrelated to MG or MS.
  • During the late 70's and early 80's a nonspecific malabsorption syndrome due to avian reovirus was described.

Incidence and Distribution

  • Reovirus infections are prevalent worldwide in chickens and turkeys.
  • Viral arthritis/tenosynovitis is found primarity in meat-type chickens and turkeys.
  • Reoviruses are commonly found in the digestive and respiratory tracts of clinically normal chickens and turkeys.

Transmission

Horizontal transmission

    1. Intestinal tract (fecal contamination)
    2. Respiratory tract
    3. Age related resistance

Vertical Transmission

  1. Egg transmission low (<2.0%)
  2. Hens infected via oral, tacheal, and nasal inoculation were able to transmit reovirus to their proge

 

Avian Reovirus (Vaccine Strains)

Strain Association Live/Killed
S1133  Tenosynovitis Live and Killed
UMI 203  Tenosynovitis Live
2408  Malabsorption/Tenosynovitis Killed
1733 Malabsorption/Tenosynovitis Killed
CO8 Malabsorption Syndrome Killed
305 Malabsorption/FHN/BBD Killed
ss412 Malabsorption/proventriculitis  Killed

Avian Reovirus (Live Vaccine)

Route of Administration Efficacy
1. Subcutaneous (SQ) Good
2. Wingweb Good
3. Water Good
4. In Ovo  Poor

Diagnosis

  • Presumptive diagnosis may be made on the basis of signs and lesions.
  • Virus isolation in chicken embryo liver cells or FA test on infected tendon sheaths.
  • Histopathology of infected tendons.
  • Serology - AGP, IFA, VN and ELISA test.  

Avian Reovirus Serology (Broiler Breeder IDEXX ELISA System@ 1:500 dilution)

Age Poor Fair Good
12 Wks <1000 1200 >1600
16 Wks <3500 4000 >5000
24 Wks <4500  5000  >6500
38 Wks <3000 3500 >4500
44 Wks <2750 3000 >3500
58 Wks <1000 2000 >2500

Clinical Signs/Gross Lesions

Viral arthritis/tenosynovitis

  1. Lameness
  2. Joint swelling
  3. Thickened/ruptured tendons

Malabsorption syndrome

  1. Runting/Stunting
  2. Poor pigmentation
  3. Abnormal feathering
  4. Skeletal abnormalities
  5. Increased mortality
  6. Enlarged proventriculus
 

Pathogenicity

Reoviruses have been identified as the etiology of other disease conditions such as:

  1. Arthritis/tenosynovitis
  2. Runting/stunting
  3. Pericarditis/myocarditis/hydropericardium
  4. Hepatitis
  5. Bursal and thymus atrophy

Prevention Strategies

  1. Good Husbandry Programs
  2. Biosecurity Programs
  3. Vaccination Programs

Vaccination (Broiler Breeders)

Purpose:

  1. Prevent VA in the breeders
  2. Prevent egg transmission to progeny
  3. Produce maternal antibodies for the progeny

Vaccination Strategies (Broiler Breeders)

Program 1: 1st Live
1st/2nd Live
2nd/3rd Live
 1-2 Wks
3-8 W 
8-16 Wks
 SQ/Water
SQ/Water/Wingweb
SQ/Water/Wingweb
       
Program 2: 1st Live             
2nd Live            
2nd/3rd Live    
1st Killed          
2nd Killed         
1 week               
3-4 Wks            
6-8 Wks            
10-14 Wks        
14-20 Wks
 SQ/Water
SQ/Water
SQ/Wingweb/Water
SQ/IM
SQ/IM
  

Current Challenges

1. Sporadic outbreaks on broiler farms throughout the Southeast US.

2. Clinical signs include runting/stunting as early as 7-14 days of age, poor weight gains, poor feed conversions with significant feed passage.

3. Broiler Breeder ELISA titers for reovirus > 15-20,000.

4. Reovirus has been isolated by Dr. J.K. Rosenberger that may be different

than the current vaccine types.

Summary

1. Reoviruses are ubiquitous in nature.

2. Healthy birds can harbor the reovirus without exhibiting clinical signs.

3. Good husbandry and biosecurity practices will help reduce the spread of reovirus from flock to flock.

4. A solid broiler breeder vaccination program is necessary to reduce losses

due to reovirus in both broiler breeders as well as their progeny.