Serosurvey of infectious laryngotracheitis in laying hens, and economic impact of vaccination in Algeria

Published on: 11/16/2016
Author/s : Hammami-Boukais N. 1, Bouzouaia M. 2, Yousfi S. 1, Lounes A. 1, Bouderbal A. 2, Rahal K. 1. / 1 Veterinary Science Department of University Saad Dahlab Blida; 2 CEVA Animal Health - Algeria.

Introduction: The purpose of this study was to demonstrate the presence of virus disease of infectious Laryngotracheitis (ILT) in Algeria in laying hen farms; through the demonstration of seroconversion signing a recent viral passage and also a comparative study cost / benefit of vaccination against this disease. Up ‘til 2011, no study was conducted to highlight the presence of the virus s...

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Sataluri Satagopa Raja Ayyangar Sataluri Satagopa Raja Ayyangar
B .Sc ( Mathematics , Physics and Chemistry ) ; P G Diploma in Environmental Studies ; P G Diploma in Industrial Pollution Management ; Industrial Chemistry ( B I E T )
November 16, 2016
It is better to go for herbal and natural aromatic oils to prevent any disease in the long run for the better health of end user and the bird .Only the thing is to get acquainted with areomatic oils and herbals with the latest
equipments and laboratory. Think echofree for the future generations.
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November 17, 2016
Congratulations for this study. Now, you have the proof of the existence of the ILT virus in the laying flocks in Algeria. The clinical symptoms can be very mild and we can be mislead in the diagnosis especially if the disease had not been reported earlier in the country. So, it is important if there is a suspicion of the disease to carry out the necessary laboratory tests.
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Mohamed.Amine BOUDERBAL Mohamed.Amine BOUDERBAL
Business Development Manager
November 17, 2016

Dear,
Thank you for your comment,
Indeed it is the first serological confirmation of the disease, we thought that we were indemn. There was just some suspicion a few years ago because of some clinical signs.
We need to run another study in order to support this one.

Reply
Mohamed.Amine BOUDERBAL Mohamed.Amine BOUDERBAL
Business Development Manager
November 17, 2016
By indemn i mean FREE FROM ILT
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Dr. Phan Quang Vinh Dr. Phan Quang Vinh
DVM, Ph.D. Physiology and Biochemistry
November 23, 2016
Please check. All figures shown in Table 1 are not decimal log values. Your interpretation of the serum titers got from farms E1,E2,E3 and E7 are biased . Look at the average titers and their ranges from E3 which were considered as negative versus the averages and the ranges of serum titers of E1,E2 and E7 which were interpreted as positive. What is the implication of highly variable and high CV values you got here?( in terms of viral infections in these farms?
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Mohamed.Amine BOUDERBAL Mohamed.Amine BOUDERBAL
Business Development Manager
November 30, 2016
Here is the calculation formula for the antibody titers positive threshold according to the recommendations of the biochek kit
S/P = (DO Ech – DOm CN)/(DOm CP – DOm CN).
Log10 Titre = 1,10 x Log10 S/P + 3,361
Titre = Antilog (Log10 Titre)
The mean title is a representative values according to the indications of the Elisa Kit compared to the threshold of positivity,
It is true that cv% exceed 30% , why ?: Our sampling is not homogeneous because the values should be between 30-40% of the cv% to say that it is a representative mean title, but as we were sampling from unvaccinated subjects and we intervened at a time t 0 considered the Beginning of the laying drop and 3 weeks after that, the titers are based on the time of sampling compared to the presentation of the kinetic curve of the antibodies (beginning of production, middle or end)
About houses 1,2,3 and 7 we cannot speak of bias because the chickens were taken at random the only criterion is the appearance of a fall of lay
And the values are LOG OF 10 according to the indicated formula.
Don’t we forget again that is field results and the purpos of the study was to find antibodies

Reply
Dr. Phan Quang Vinh Dr. Phan Quang Vinh
DVM, Ph.D. Physiology and Biochemistry
February 15, 2017
Dear Dr. Bouderbal, I guessed you should make the corrections in Table 1. The figures shown are the actual titers when you used the formula to compute, not the value of log10 of titers any more. But you indicated in the Table as Log10 of titers. I said you should check for your biased conclusion because in E7 the average titer was 1253 and your conclusion is positive whereas in E3 the average titer was 2916 and your conclusion was positive. Thanks
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Lalit Belwal Lalit Belwal
Chief Technology Officer
February 18, 2017

I agree with Dr.Phan,

The titers in Table#1 appear to be direct conversion of S/P ratios and tabulated as such . These should be converted to respective Log10 values to justify the Table heading. Also that , Dr Phan may have meant 'Negative' when he mentions the discrepancy in E3 Farm data ( 2nd comment, quote, "E3 the average titer was 2916 and your conclusion was positive" unquote. )

However, it may be helpful to rule out other possible causes of egg production drop such as , EDS, ND and IB because , as a general rule seropositivity should be higher across the farms showing drop in production ( Ref Table 2), with progression of time since ILT is very contagious and more birds should seroconvert over the weeks. In this data the seropositivity seems to decline in later weeks.

Nevertheless, it was a good attempt at resolving possibility of ILT prevalence in Algeria and a better structured research is called for to confirm the prevalence as well as for decision regarding vaccinations.
Regards
Reply
Dr. Phan Quang Vinh Dr. Phan Quang Vinh
DVM, Ph.D. Physiology and Biochemistry
February 20, 2017
Thank you Lalit Belwal for your correction regarding the average titer of E3. I meant it was considered negative by the authors of the article. Actually if the data in Table 1 is subjected to statistical analysis you will not be surprised to see that all are not significantly different from each other considering the fact that all CV 's are very high ( therefore treatment variances are also high.
Reply
February 28, 2017

In addition to the positivity of the sera, it would be necessary to confirm with histopathology by looking for intranuclear inclusions.

Reply
February 28, 2017
It is true that ILT is very contagious and the seroconversion is obtained in a shorter deadline but operating on unvaccinated flocks the presence of the positive in addition to a histopathology seems sufficient for confirmation.
Reply
Mohamed.Amine BOUDERBAL Mohamed.Amine BOUDERBAL
Business Development Manager
January 8, 2018
Nouh Baraa thank you for your comment Dr
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