12 years experience in poultry field, 8 of them in layer field working in EL Banna Co. for poultry production
This article reflects field experience for Newcastle virus infection in commercial layer flock and after we ensured the cause is only Newcastle virus and not accompanied with influenza
H9N2 we used the two weapons we have in hand (vaccinate emergency in one time and don’t vaccinate until infection is over).
In case of Newcastle virus infection poultry veterinarian differs between two opinions:
First: Once egg production decreases don’t vaccinate until decrease stops and begin to increase.
Second opinion: if the cause of infection only ND so do emergency vaccination within 5 days of decrease of production.
So, in our case: white Babcock layer flock (100,000 birds) aged
32 weeks reach 95% production then production begin decrease 3% within 4 days reaching 92% so we took blood samples and the results for ND were.
The influenza H9 result similar to our baseline in farms in Egypt (we see infection and production decrease by H9N2 when titer reaches 12).
So we took decision with emergency vaccination and we did it after 7 days of beginning of production decrease (unfortunately we delay for regulatory affairs and may this delay cause strong decline of production).
So what happened after lasota spray vaccination?
Production decrease drastically to 83.6% within 12 days (8.5% decrease) then after 12 days it begin to increase to reach 91% in also 12 days then it reach to maximum to 94.2% after 2 weeks later.
Then another ND infection happened for the same flock at age 41 weeks and we took blood samples for ND and AI H9N2 and results were:
So again we have ND here, after discussion we thought the first infection have already antibodies in the flock and we don’t want that sever decrease of the production that happened before so we didn’t vaccinate.
So what happened?
Slowly decrease in egg production within 6 weeks it reach to 83.3% and begin to increase in the 7th week gradually and it reach its beak production at 88.4% after 5 weeks from beginning of the increase.
1. Emergency vaccination in case where there is only ND is the best choice.
2. ND infection can reoccur in the same flock within 9 weeks.
3. Not to vaccinate decision aid spreading of the infection to other flocks while emergency vaccination accelerate the end of infection.
4. Not to vaccinate decision was based on idea of presence of antibodies from previous infection, so if there is not infection it would be worse unless the challenge is small.
5. Earlier emergency vaccination is better.
6. In old flocks around 80 weeks or with Mycoplasa or other stress conditions we didn’t recommend emergency vaccination