Egg Industry - November 2008

www.WATTpoultry.com November 2008 volume 113 volume 113 number 11

Preventing immunosuppressive infections
Our industry will become stronger
Controlling rodents in the poultry house
Experience, science guide UEP president
Product news
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Preventing immunosuppressive infections

Part 1 of a two-part series: Controlling diseases that impact egg production and egg safety through effective immunization.

By Kalen Cookson, DVM, MAM, ACPV,

Fort Dodge Animal Health, Overland Park, Kansas

The old adage, “An ounce of prevention is worth a pound of cure,” captures the value of flock immunization which is directed at efficient production of eggs of optimal quality. A properly designed vaccination program averts economic losses due to infections that may cause immune suppression, mortality, drops in egg production or compromised egg quality and safety. In addition, control of prevalent diseases by vaccination reduces the need to

Kalen Cookson
use antibiotics as

therapy for secondary infections including E.coli.

The process of administering vaccines does not necessarily assure the desired level of protective immunity. A successful vaccination program requires following accepted standard techniques that result in uniform vaccine coverage. Instituting a monitoring system provides necessary feedback and accountability for the entire process of maintaining health.

Protecting the immune system

For any vaccination program to be successful, one must first ensure that each flock is capable of responding ap-

propriately to the vaccines given, which requires an intact and functional immune system.

Vaccines stimulate humoral immunity (circulating antibodies) and local cellular immunity (activation of macrophages and T–lymphocytes). While resistance to some infections such as Newcastle disease and avian influenza rely mostly on antibody production, others including infectious bronchitis and laryngotrache-itis rely on cellular immune function. The two most important diseases negatively affecting the immune system are Marek’s disease (compromising cellular immunity) and infectious bursal disease (depressing antibody production).

Marek’s Disease

The Disease—Marek’s disease, caused by a herpesvirus, is known for its ability to cause variable to high mortality in pullets over eight weeks of age due to tumors affecting nerves and internal organs. Marek’s disease virus also causes significant immune suppression. The “silent” effect on the immune sys-

A sound vaccination program is essential
for a productive layer flock and a safe
egg supply.

tem is frequently more significant than the impact of mortality.

Vaccination—Chicks should receive a full dose of a combination serotype 2 and 3 Marek’s vaccine, usually comprising SB-1 and HVT strains. In areas of high challenge, a serotype 1 Rispens vaccine, with or without HVT, is highly recommended. The choice of Rispens vaccine is critical in high challenge areas as low-passaged (less attenuated)