key: cord-0008634-i0o25spx authors: MUNEER, M.A.; NEWMAN, J.A.; HALVORSON, D.A.; SIVANANDAN, V.; NAGARAJA, K.V.; COON, C.N. title: Efficacy of infectious bronchitis virus vaccines against heterologous challenge date: 2018-08-23 journal: Res Vet Sci DOI: 10.1016/s0034-5288(18)30889-0 sha: 197ed55c90d44740ff7453e48e2b32affddffec4 doc_id: 8634 cord_uid: i0o25spx Twenty-four-week-old white Leghorn layers were inoculated subcutaneously with a killed Newcastle disease-infectious bronchitis (Massachusetts type) virus (mibv) vaccine. Twenty-eight weeks after vaccination, the birds were challenged intraocularly with the Arkansas strain of infectious bronchitis virus (aibv) to determine the effects of heterologous virus exposure on egg production, egg quality and serum antibody response of the birds. The challenged hens laid significantly (P<0·005) fewer eggs than the unchallenged layers. Eggs laid by the unchallenged groups weighed significantly more (P<0·005) than those laid by the challenged groups. Further, the internal quality (Haugh units) and shell quality of eggs laid by the aibv-challenged hens was significantly (P<0·005) inferior to those from the unchallenged hens. In addition, the aibv-challenged hens laid more soft-shell, misshapen and small eggs than the unchallenged hens. The Arkansas serum haemagglutination inhibition (aibv-hi) titres of aibv challenged birds increased up to four weeks after challenge. The corresponding mibv haemagglutination-inhibition (mibv-hi) titres decreased during the same period. The study indicates that killed mibv vaccine offered no protection to birds exposed to heterologous aibv. Twenty-four-week-old white Leghorn layers were inoculated subcutaneously with a killed Newcastle disease-infectious bronchitis (Massachusetts type) virus (MIBV) vaccine. Twenty-eight weeks after vaccination, the birds were challenged intraocularly with the Arkansas strain of infectious bronchitis virus (AIBV) to determine the effects of heterologous virus exposure on egg production, egg quality and serum antibody response of the birds. The challenged hens laid significantly (P: the same time. The data for production, egg and eggshell weights and Haugh unit scores were pooled in five-day increments until day 40 after AIBV challenge. The data were analysed by analysis of variance. The serum samples from 10 birds in each group were collected on days 0, 7, IS, 22, 29 and 37 after AIBV challenge and analysed using the HI test. No appreciable signs of illness could be detected in Arsv-challenged or unchallenged birds, except the presence of slight nasal and ocular discharges on day 8 after challenge in four unvaccinated Arnv-challenged birds. These signs were not seen after day 10 after AIBV challenge. The data on effects of AIBV challenge on egg production, egg weight, eggshell weight and internal egg quality are presented in Figs I to 4. An overall comparison of percentage egg production, average egg weights, eggshell weights, SWUSA and Haugh unit scores of eggs from birds of various treatment groups is summarised in Table I Overall total 40 days study period t Shell weight (mgl per egg surface area Icm 2 ) * Mean and standard deviation data § 1 Massachusetts killed virus vaccinated unchallenged 2 Unvaccinated (Massachusetts killed virus) unchallenged 3 Massachusetts killed virus vaccinated AIBV challenged 4 Unvaccinated I Massachusetts killed virus I AIBV challenged a.b Any two means carrying the same superscript in the same column are not significantly different from each other 25 production occurred between AIBV challenged and unchallenged birds from day 15 after challenge onwards. The birds in both the vaccinated and unvaccinated groups had significant drops in production throughout the post-challenge period (Fig I) . In addition the AIBV challenge in both vaccinated and unvaccinated groups caused laying of soft-shelled, misshapen and small eggs. Quite a large number of eggs (3' 9 per cent) laid by the AlBv-challenged birds were either soft-shelled, small or had calcareous papule-like deposits on the egg shells. These types of effects were negligible (0' 75 per cent) in the unchallenged birds. The differences in mean egg weights are presented in Fig 2. Mean egg weights from unchallenged and AlBV challenged groups were also significantly different. Although all the birds receiving AIBV challenge showed a decrease in egg shell weight (Fig 3) , the birds that were vaccinated as adults and challenged had relatively lower effects on shell weights up to day 15 after challenge than those challenged birds not receiving MlBV vaccine as adults. The SWUSA of unchallenged birds remained more or less at similar levels throughout the study period, whereas a trend towards a decrease in SWUSA score was noted in challenged birds. The average SWUSA scores of eggs from unchallenged birds were significantly higher (P<0'005) than those of challenged birds. The mean egg surface area (cm-) and SWUSA scores of eggs from birds in various treatment groups are presented in Table 2 . The Haugh unit scores are presented in Fig 4 and the overall percentages of egg production by grades are summarised in Table 3 . The Haugh unit scores of eggs from AIBV challenged groups dropped significantly (P723) were observed in killed MIBv-vaccinated birds on day 22 after vaccination. A consistent drop in MIRV GMT-HI titres was noted from day 22 after vaccination to the end of the study. Very low MIBV GMT-HI titre (GMT<20)were detectable on day 231 after killed MIRV vaccination in unchallenged birds. The unvaccinated and unchallenged birds had quite negligible HI titres (MIBV or AIBV) throughout the study period (GMT<28). The MIBV GMT-HI titres for post-challenge period are presented in Many factors such as age, natural feed ingredients and drug intake can affect the egg quality of laying chickens (Sherwood 1958) . In the present work the experimental birds were at the prime of their laying period, they were not on any kind of medication and birds in all the four groups received the same ration. Therefore it is unlikely that the above factors would have contributed to the drop in egg production or other qualitative changes. The authors' studies with the AIBV indicate that this virus strain contributes towards a decrease in egg production and quality. The thickness of an egg shell depends on the amount of shell present relative to the egg surface area. The egg surface area is dependent on the size of the egg and can be calculated from the egg weight (Carter 1975) . For an increase in shell thickness, either the shell weight must increase, egg surface area must decrease or a combination of both. The relative SWUSA can be calculated from the surface area by dividing the shell weight by its surface area. The authors' work has demonstrated that the AIBV challenge definitely influences egg surface area (cm-) and SWUSA. This study has highlighted the effects of AIBV exposure in layers with regard to egg production, quality and the serological response to AIBV challenge. The frequency of such heterologous exposures is probably great under field conditions. The data on egg production shows that AIBV challenge significantly lowers egg production and increases the laying ofsoft-shelled, small sized and misshapen eggs. In addition the AIBV challenge resulted in considerable loss of internal egg quality, which is evidenced by the laying of more Band C grade eggs by the Arsv-challenged hens. The data obtained through the present work suggest that challenge with AIBV may have the adverse effects indicated above on birds which showed a good antibody production response against a killed Massachusetts type vaccine and had significant levels of antibodies at the time of AlBV exposure. Furthermore titres in response to the Massachusetts vaccine which were lower than reported in this study did confer immunity against a homologous virus challenge (data not presented). There is a need to vaccinate the birds against AIBV to provide protection against this virus. The study also stresses the need for development of a polyvalent IBV vaccine which could confer immunity against multiples of lBV types. US Poultry Magazine 43