Article by Vet. Mostafa abd Ellatif
12 years of experience in the poultry field, 8 of them in the 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 by influenza H9N2 we used the two weapons we have in hand (vaccinate emergency in one time and don’t vaccinate until the infection is over)
In case of Newcastle virus infection poultry veterinarian differs between two opinions:
- first: Once egg production decreases don’t vaccinate until the decrease stops and begins to increase.
- Second opinion: if the cause of infection is only ND so do emergency vaccination within 5 days of a decrease in production
So, in our case: a white Babcock layer flock (100,000 birds) aged 32 weeks reach 95% production then production begin to decrease by 3% within 4 days reaching 92% so we took blood samples and the results for ND were
|houses||sera||NDV( HI titer log -2 )|
While influenza H9 was as usual titers in the farm:
|houses||sera||AI H9N2 ( HI titer log -2 )|
The influenza H9 result is similar to our baseline in farms in Egypt (we see infection and production decrease by H9N2 when titer reaches 12)
So we took the decision with emergency vaccination and we did it after 7 days of the beginning of production decrease (unfortunately we delay for regulatory affairs and may this delay cause a strong decline of production)
So what happened after lasota spray vaccination? the production decrease drastically to 83.6% within 12 days ( 8.5% decrease) then after 12 days it begins to increase to reach 91% in also 12 days then it reach to the 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 the results were:
|houses||sera||NDV ( HI titer log – 2)|
|houses||sera||AI H9N2 ( HI titer log – 2)|
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 severe decrease of the production that happened before so we didn’t vaccinate.
So what happened?
Slowly decrease in egg production within 6 weeks it reaches to 83.3% and begin to increase in the 7th week gradually and it reaches its beak production at 88.4% after 5 weeks from the beginning of the increase.
- Emergency vaccination in case where there is only ND is the best choice
- ND infection can reoccur in the same flock within 9 weeks
- Not to vaccinate decision aid in spreading of the infection to other flocks while emergency vaccination accelerate the end of the infection
- Not to vaccinate decision was based on the idea of the presence of antibodies from previous infection, so if there is not infection it would be worse unless the challenge is small
- Earlier emergency vaccination is better
- In old flocks around 80 weeks or with Mycoplasa or other stress conditions we didn’t recommend emergency vaccination ( field experience)