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

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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.

By indemn i mean FREE FROM ILT

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?

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

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

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

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.