Maternal immunity plays significant role in protecting commercial layer chicks against Newcastle Disease at early stage of life. The level of protection depends on the protective antibody titre across the flock which declines fast by the end of first week. However maternal antibody still persists below protective level for another few weeks. Presence of maternal immunity above protective level can neutralise the live vaccine virus during early first week and subsequently making the birds susceptible to NDV infection when the titre moves down to below protective level by the end of second week. Protective efficiency of attenuated vaccines are always questioned in any such interference. This advocates the necessity of vaccinating the birds at right time to protect them against NDV and at the same time minimize the maternal antibody interference. In view of these a study was conducted to quantify the maternal antibody titre against NDV at early stage of commercial layer to determine the right time of vaccination with minimal interference. A suitable cost effective intervention programme against NDV is possible only when the issue of maternal antibody interference is addressed properly.
Maternal immunity for Newcastle Disease (ND) can be quantified with Haemagglutination Inhibition(HI) test. Titres are expressed as log 2 values. Titres in a group are analysed statistically and mean titre in a group depicts status of flock immunity. Quantification of HI titre at day old age and subsequent quantification at weekly interval can determine the maternal antibody interference in normal vaccination. Vaccination schedule can, therefore, be modified accordingly to address the issue of maternal antibody.
Materials and Methods
Six hundred numbers of day old commercial chicks were procured and housed in aseptic environments separately in groups of 200 numbers each. The chicks were identified as group A,B and C. Serum antibody titre for ND was determined on 1st day of life for all the chicks to check whether it was protective (25)or not. Group A chicks received commercially available lentogenic strain vaccine on 1st day of life. Group B chicks were vaccinated with the same vaccine on 7th day of life. Group C chicks received no vaccine and kept as negative control. All the chicks were reared up to 20th day of life on same diet with similar aseptic environment. Serum antibody titres were determined on 7th, 10th, 15th day of life for all the groups. The parameters were analysed statistically. HI titres were expressed in log 2 values for determination of mean and standard error.
Results and Discussions
The serum antibody titre recorded at the first day of life showed protective immunity level of above 1.50515±.001 (more than 25) for all the groups. This finding signifies the presence of maternal immune response at a protective level after hatching.
The antibody titre on 7th day old chicks showed below protective titre for group A and marginally protective titre for group B, however unvaccinated group C still leading the table with higher titre.
The antibody titre detected on 10th day showed significant reduction of titre in group A and in unvaccinated group C, The titre for the group B found to be well above the protection level.
The titre of 15th day showed marked intervention of maternal antibody in vaccinated group A. The reduction in unvaccinated control group C was obvious. The static level of titre in group B from the previous titre on 10th day marked the need for booster vaccination.
Summery andConclusion:
From the results obtained, it was observed that very early vaccination against NDV results in the neutralization of the live vaccine virus in the system which was clearly reflected in their antibody titres. The already existing circulatory maternal antibodies bind with the live antigens forming antigen antibody interactions resulting the titre to drop below protective level.
Recommendation: In highly endemic areas where vaccination can’t be delayed owing to maternal antibody interference, a very early dose of live attenuated virus or inactivated antigen can be administered to negate the existing maternal antibodies. It should be kept in mind that this will neither protect nor increase the titre level but will only pave the way for a highly successful live vaccination at early second week once maternal antibodies are neutralised.
References
Alexander, D.J., 1978. Newcastle disease diagnosis. In: D.J. Alexander (ed.), Newcastle Disease Diagnosis and Vaccination, (Boston: Kluwer Academic Publishers), 147-160
Alexander, D. J., 1997. Newcastle disease and other avian paramyxovirus infections. In: Diseases of Poultry, Tenth Edition, Calnek , B. W., Barnes, H. J., Beard, C. W., Iowa State University Press. Iowa. USA. 541570.
Alexander, D. J., Banks, J., Collins, M. S., & Aldous, E. W., 1999. Antigenic and genetic characterization of Newcastle disease viruses isolated from outbreaks in domestic fowl and turkeys in Great Britain during 1997. Vet Rec. 145. 417-421.
Aldous, E. W., & Alexander, D. J., 2001. Technical Review: Detection and differentiation of Newcastle disease virus. Avian Pathol. 30, 117-128
Office International des Epizootics. (2000 & 2004). Report of the meeting of the OIE Standard Commission, November 2004, Paris, Franch.
Serological evaluation is a way of estimating the protection levels in the flock. This is the guideline to judge the effectiveness of vaccines practiced everywhere. Challenge is another tool. It requires a controlled facility to expose birds to live virus and count the mortality. Somebody with facility can take it up. it is a proven fact that birds with higher levels of antibodies live better when challenged with live virus. Yes, birds with low levels of antibodies also live till they are exposed to disease. Once they are exposed, the group having low titers face more mortality. HI titer evaluation as a response to vaccination at different points is a good lead for further research like exposure evaluation. As a poultry grower, I will postpone my ist vaccine to 5th day from day one to avoid maternal antibody interference.
Good work. day old live vaccine can be a reason for the failure of vaccine as it is neutralized by mab. Many people are now a days attributing the failure to emergence of new strains of nd which may require revision in the thinking. n.d is known to be a single strain for a long time.
Did you check whether this affects the sub conjunctival or intra ocular means of vaccination with B1 hitchner or B1 lasota? I guess strongly that subconjuctival immune glands called haderian gland will prevent the antigen to get to the bloodstream for antisera attack. Could you please discuss this?
In high epidemic area, such as the middle east -especially gulf region-, we should vaccinate at day old in spite of high maternal abs level in chicks due to vaccination at day old will provide local immunity which important for protection against Nd challenge and prevent filed strain to attach with receptors So you can review about using ND vector vaccine which did not interfere with maternal abs and may provide cell mediated and humoral immunity. Thanks & regards.
The vaccintaion method at DO (group A) and at 7 days (group B) wasn't mentioned in the Materials and Method - by eye drop? or spray?. if it spray - same droplet size at DO and 7 days?
l think it was better to collect blood samples at 1st , 10th , 15th & 20th days..l suggest to include ELISA Test at same time on the same samples to compare the results..l think the results will be much clear & nearly accurate.
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