- Email: [email protected]
Decay of maternal antibodies in broiler chickens
Decay of maternal antibodies in broiler chickens Saad Gharaibeh*1 and Kamel Mahmoud† *Faculty of Veterinary Medicine, and †Faculty of Agriculture, Jordan University of Science and Technology, Irbid 22110, Jordan ABSTRACT The objective of this study was to determine the decay rate of maternal antibodies against major broiler chicken pathogens. A total of 30 oneday-old broiler-chicks were obtained from a commercial hatchery and reared in isolation. These chicks were retrieved from a parent flock that received a routine vaccination program. Chicks were bled at hatch and sequentially thereafter every 5 d through 30 d of age. Maternal antibody titers were measured by ELISA for avian encephalomyelitis (AEV), avian influenza virus (AIV), chicken anemia virus (CAV), infectious bursal disease virus (IBDV), infectious bronchitis virus (IBV),
infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), and reovirus (Reo). Maternal antibody titers for Newcastle disease virus (NDV) were measured using a hemagglutination inhibition test. Half-life estimates of maternal antibody titers were 5.3, 4.2, 7, 5.1, 3.9, 3.8, 4.9, 4.1, 6.3, and 4.7 d for AEV, AIV, CAV, IBDV, IBV, ILTV, MG, MS, NDV, and Reo, respectively. The statistical analysis revealed significant differences among halflives of maternal antibody titers against certain pathogens. Furthermore, all maternal antibody titers were depleted by 10 d of age except for IBDV.
Key words: maternal antibody, decay, half-life, broiler 2013 Poultry Science 92:2333–2336 http://dx.doi.org/10.3382/ps.2013-03249
INTRODUCTION Maternal antibody (mAb) levels play crucial role in the health status of the modern-day broiler-chicken industry because of the short lifespan of broiler chickens. Commercial broiler chickens are being protected against certain pathogens such as chicken anemia virus (CAV; Otaki et al., 1992), avian encephalomyelitis virus (AEV; Westbury and Sinkovic, 1978), and reovirus (Reo; van der Heide et al., 1976) solely by providing sufficient levels of maternal antibodies from their parent flock. Maternal antibodies also play a major role in modulating early life live vaccine strategy for commercial broiler flocks. Maternal antibodies against Newcastle disease virus (NDV), as an example, have a favorable effect of decreasing the severity of live vaccine reaction; however, they also decrease the immunity after vaccination (Chu and Rizk, 1975). On the other hand, a high level of mAb against infectious bursal disease virus (IBDV) neutralizes the vaccine virus and results in complete failure of immunization (Naqi et al., 1983). There is also recent evidence indicating that mAb decreases the efficacy of killed vaccine against avian influenza virus (AIV; De Vriese et al., 2010; Maas et al., 2011; Abdelwhab et al., 2012). Therefore, ©2013 Poultry Science Association Inc. Received April 18, 2013. Accepted May 27, 2013. 1 Corresponding author: [email protected]
estimating the half-life of mAb has become necessary and valuable information that can be used in designing vaccination programs for broiler chickens to minimize the cross reaction between mAb and the vaccination programs. Duration of mAb in broiler chickens has been studied extensively for IBDV. Half-life of mAb against IBDV ranged from 3 to 8 d in several previous studies (Wyeth and Cullen, 1976; Skeels et al., 1979; Wood et al., 1981; Fahey et al., 1987; Al-Natour et al., 2004). Allan et al. (1978) and Darbyshire and Peters (1985) reported that the half-life of mAb against NDV and infectious bronchitis virus (IBV) was 4.5 and 5 to 6 d, respectively. Previous results from our laboratory estimated the rate of mAb transfer from the parent flock to their chicks (Gharaibeh et al., 2008). This study was designed to estimate the half-life of these mAb against different pathogens in broiler chicks.
MATERIALS AND METHODS Chicks and Housing Thirty 1-d-old broiler chicks (Lohmann) were obtained from a commercial hatchery. The parent flock was 40 wk of age when the eggs that hatched the broiler chicks were laid. The parent flock vaccination program is detailed in Table 1. Chicks were housed in an isolated and environmentally controlled room in the Ani-
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Table 1. Vaccination program of the parent flock related to the pathogens discussed in this study1 Age
Vaccine
Type, method
Manufacturer, country
1d 7d 7d 9d 15 d 19 d 14 d 27 d 40 d 8 wk 8 wk 9 wk 10 wk 11 wk 12 wk 18 wk 18 wk 30 wk 40 wk
IBV+NDV IBV+NDV AIV (H9N2) IBDV Reo IBDV IBV+NDV IBDV NDV (Lasota) ILTV IBV (4/91) NDV (Lasota) MG (F-strain) Reo AEV IBDV+IBV+NDV AIV (H9N2) IBV+NDV IBV+NDV
L, Spray K, Subcutaneous K, Subcutaneous injection L, Drinking water L, Intramuscular injection L, Drinking water L, Spray L, Drinking water L, Spray L, Eye drop L, Eye drop L, Spray L, Spray K, Intramuscular injection L, Drinking water K, Intramuscular injection K, Subcutaneous injection L, Spray L, Spray
Fatro, Italy Fatro, Italy Merial, France Fatro, Italy Fatro, Italy Fatro, Italy Intervet, the Netherlands Fatro, Italy Fatro, Italy Fatro, Italy Intervet, the Netherlands Fatro, Italy Schering-Plough, United States Fatro, Italy Fatro, Italy Fatro, Italy Merial, France Fatro, Italy Fatro, Italy
1AEV = avian encephalomyelitis virus; AIV = avian influenza virus; IBDV = infectious bursal disease virus; IBV = infectious bronchitis virus; ILTV = infectious laryngotracheitis virus; K = killed; L = live; MG = Mycoplasma gallisepticum; NDV = Newcastle disease virus; Reo = reovirus.
mal House Facility at Jordan University of Science and Technology. Commercial broiler feed and water were available ad libitum. Light was provided continuously throughout the study period.
Serological Analysis Blood was collected from each of the 30 chicks at 1, 5, 10, 15, 20, 25, and 30 d of age. Commercial ELISA kits (Synbiotics Co., San Diego, CA) were used to determine the titer of mAb (IgG/IgY) against AEV, AIV, CAV, IBDV, IBV, infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), and Reo. The ELISA kits were used according to the manufacturer’s protocol using an automated microplate reader (ELx800, BIO-TEK Instruments Inc., Winooski, VT). The antibody titer in each individual sample was quantified using the software provided by the manufacturer. The geometric mean titer (GMT) for each group of serum samples was also calculated using the same software. All serum samples were read against positive and negative control antisera provided by the kit and used in each run. Hemagglutination inhibition (HI) test using β procedure (constant antigen and varying serum dilutions) was used to quantify antibodies (IgG/IgY, IgM, and IgA) against NDV (Thayer and Beard, 1998). A 2-fold serial dilution was used to run the serum samples in the HI test and the GMT was calculated (Villegas, 1998). Appropriate controls for the HI test (positive antiserum control, negative antiserum control, antigen control, and erythrocyte control) were included in each run.
Statistical Analysis Half-life of mAb against the pathogens studied in this experiment was calculated similar to a previous study (Fulton et al., 2004) by simple linear regression using
PROC REG of SAS (SAS Institute, 1996). For each mAb against different pathogens, the regression equation was used to estimate the time required by mAb levels to drop by half (half-life) in each individual. An ANOVA using the GLM procedure of SAS (SAS Institute, 1996) was used to examine the equality of halflives of maternal antibodies among all pathogens. Least squares means were separated using Fisher’s protected least significant difference with a P-value of 0.05. Coefficient of variation and quartile range were estimated using the MEANS procedure of SAS (SAS Institute, 1996) for the half-lives of mAb against each pathogen.
RESULTS Table 2 summarizes the GMT for mAb against different pathogens in broiler chicks. All mAb against different pathogens showed a significant decrease in titer and were almost depleted by 10 d of age except for IBDV, where mAb persisted through 20 d of age and was almost depleted at 30 d of age. For mAb against NDV, titer was analyzed by HI rather than ELISA and hence GMT titer numbers for mAb against NDV appear persistent at low levels even at 30 d of age. This is because it is common to get nonspecific HI results at the first dilutions of the HI test plate (Thayer and Beard, 1998). Table 3 lists half-life, CV%, and quartile range for mAb against different pathogens. Half-life of mAb against different pathogens varied slightly and ranged from 3.8 d for ILTV to 7.0 d for CAV. Although CAV mAb had the highest half-life, it showed the highest variation among all other mAb as indicated by its CV% and quartile range. There are some significant differences among half-life means of mAb. Maternal antibodies against CAV had the longest half-life of 7.0 d and were statistically different than mAb against all the other pathogens except for mAb against NDV (6.3 d) and AEV (5.3 d). The shortest half-life was for mAb
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DECAY OF MATERNAL ANTIBODIES Table 2. Geometric mean titers
(GMT)1
for maternal antibodies against different pathogens at different ages Days of age
Pathogen2
Parent-flock3
0
5
10
15
20
25
30
3,839 1,910 9,283 35,012 19,472 3,146 3,165 4,881 8.5 2,761
405 668 1,985 21,104 6,706 209 1,134 828 5.9 790
29 37 108 16,295 860 10 365 21 4.9 41
2 2 18 10,643 15 2 5 3 3.5 4
0 1 1 3,983 0 2 1 1 3.5 0
0 0 1 546 0 1 0 0 3.1 0
0 0 0 84 0 0 0 0 2.4 0
0 0 0 2 0 0 0 0 1.1 0
AEV AIV CAV IBDV IBV ILTV MG MS NDV Reo 1All
GMT were calculated by ELISA software except for NDV, where hemagglutination inhibition log2 GMT titer was used. = avian encephalomyelitis virus; AIV = avian influenza virus; CAV = chicken anemia virus; IBDV = infectious bursal disease virus; IBV = infectious bronchitis virus; ILTV = infectious laryngotracheitis virus; MG = Mycoplasma gallisepticum; MS = Mycoplasma synoviae; NDV = Newcastle disease virus; Reo = reovirus. 3Parent-flock geometric mean titer at the day they laid the eggs that hatched the broiler chicks used in this study (40 wk of age). 2AEV
against ILTV (3.8 d) and IBV (3.9 d), but they were not statistically different than mAb against MS (4.1 d), AIV (4.2 d), Reo (4.4 d), or MG (4.9 d). Quartile range and CV% were highest for mAb against CAV, AEV, and Reo, which are the 3 pathogens we protect against in broiler chickens by mAb only.
DISCUSSION Previously, our laboratory outlined a set of unique data that describes the vertical transfer of mAb against 10 different pathogens from a parent flock to their 1-dold hatchlings under field conditions (Gharaibeh et al., 2008). The results of this study came to address the persistency and half-life of mAb against major chicken pathogens in newly hatched unvaccinated broiler chicks. Passively transferred mAb to the hatchlings was high at hatch and declined, subsequently registering a Table 3. Half-life (mean ± SE) of maternal antibodies against different pathogens with their CV1 % and quartile range Pathogen2 AEV AIV CAV IBDV IBV ILTV MG MS NDV Reo
Half-life (d) 5.3 4.2 7.0 5.1 3.9 3.8 4.9 4.1 6.3 4.7
± ± ± ± ± ± ± ± ± ±
0.5bc 0.4cde 0.4ab 0.4cd 0.4e 0.5e 0.4cde 0.4de 0.4b 0.4cde
CV%
Quartile range
53.7 18.4 74 11.1 7.6 13.6 13.4 34 27.7 44.7
2.3 1.2 6.2 0.9 0.4 0.8 0.8 0.9 0.6 1.8
a–eMeans not sharing a common superscript differ significantly (P < 0.05). 1CV = coefficient of variation ([SD/average] × 100%); measured using the MEANS procedure of SAS (SAS Institute, 1996) for half-lives of maternal antibodies against each pathogen. 2AEV = avian encephalomyelitis virus; AIV = avian influenza virus; CAV = chicken anemia virus; IBDV = infectious bursal disease virus; IBV = infectious bronchitis virus; ILTV = infectious laryngotracheitis virus; MG = Mycoplasma gallisepticum; MS = Mycoplasma synoviae; NDV = Newcastle disease virus; Reo = reovirus.
half-life between 3.8 and 7 d. Most of mAb titers exhibited a zero GMT by d 20 posthatch except IBDV and ND, where they persisted through d 30 posthatch with a very low GMT. For NDV, it is not unusual to get nonspecific HI results at the first dilutions of the HI test plate (Thayer and Beard, 1998), and this may explain the low persistent mAb titer of NDV. Thus, it would be safe to say that mAb against all pathogens except IBDV were depleted by 10 d of age. When the results of our study are compared with previous reports in the literature, we noted divergence in the rate of decay for certain mAb titers and comparable rates in other mAb. For example, we reported a half-life of 5.1 d for mAb against IBDV in accordance with Al-Natour et al. (2004) where they reported a half-life of 5.5 d. However, they used virus neutralization (VN) rather than ELISA. Other previous studies using layer chicks indicated an IBDV mAb half-life of 6 to 8 d (Wood et al., 1981) and 4 d (Wyeth and Cullen, 1976) using a quantitative agar gel precipitation test (QAGPT). Fahey et al. (1987) used ELISA but showed a half-life of 6.7 d, whereas Skeels et al. (1979) used VN and reported a half-life of 3 d. These IBD mAb half-life variations may stem from factors related to differences in chicken lines and types, and the types of serological tests used in each study because QAGPT and VN will detect all types of immunoglobulins (IgG/ IgY, IgM, and IgA), whereas the ELISA used in this study only detects IgG/IgY. The reported half-life for IBV mAb in this study was 3.9 d compared with previously reported half-life of 5 to 6 d by Darbyshire and Peters (1985). This divergence might be explained by the serological tests that were used. Darbyshire and Peters (1985) used the serum neutralization and HI test, where ELISA was the test used in this study. Furthermore, the 2 and one-half decades of genetic selection pressure might partially provide an explanation for the offset IBV mAb half-life. To the contrary, NDV mAb half-life was longer than what was cited in the literature 3 decades ago. We showed
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that NDV mAb half-life was 6.3 d compared with 4.5 d as previously reported using the HI test (Allan et al., 1978). Reovirus mAb half-life did not show a discrepancy from what has been reported in the literature. Our results showed a half-life of 4.7 d compared with a previous study by Uchimura et al. (1990) where they reported a half-life of 5 d. There is no universal vaccination program for broilers. Different geographical areas have different vaccination programs depending on biosecurity level, field challenge, and the specific regulations for vaccines in each country. Regardless of the level of mAb, broilers are usually primed with live vaccines against IBV and NDV at 1 d of age even if the immunological response will have reduced efficacy because of mAb (Chu and Rizk, 1975; Klieve and Cumming, 1988). The mAb, at this age, play the favorable role of reducing the vaccine reaction. Booster doses with live vaccines for both IBV and NDV are usually given at 10 d of age. Based on the information provided in Table 2, a killed vaccine for AIV (H9N2) and a live vaccine for IBDV may be best given around 10 and 20 d of age, respectively. In conclusion, the results of this study represent a guide for determining the half-life of mAb against many chicken pathogens. Half-life of mAb against different pathogens ranged from 3.8 to 7.0 d. Protection conferred by mAb should not be relied upon after 10 d of age except for IBDV.
REFERENCES Abdelwhab, E. M., C. Grund, M. M. Aly, M. Beer, T. C. Harder, and H. M. Hafez. 2012. Influence of maternal immunity on vaccine efficacy and susceptibility of one day old chicks against Egyptian highly pathogenic avian influenza H5N1. Vet. Microbiol. 155:13–20. Al-Natour, M. Q., L. A. Ward, Y. M. Saif, B. Stewart-Brown, and L. D. Keck. 2004. Effect of different levels of maternally derived antibodies on protection against infectious bursal disease virus. Avian Dis. 48:177–182. Allan, W. H., J. E. Lancaster, and B. Toth. 1978. Newcastle disease vaccines—Their production and use. FAO Animal Production and Health Series No. 10. FAO, Rome, Italy. Chu, H. P., and J. Rizk. 1975. The effect of maternal immunity, age at vaccination and doses or live vaccines on immune response to Newcastle disease. Dev. Biol. Stand. 28:451–463. Darbyshire, J. H., and R. W. Peters. 1985. Humoral antibody response and assessment of protection following primary vaccination of chicks with maternally derived antibody against avian infectious bronchitis virus. Res. Vet. Sci. 38:14–21. De Vriese, J., M. Steensels, V. Palya, Y. Gardin, K. M. Dorsey, B. Lambrecht, S. Van Borm, and T. van den Berg. 2010. Passive protection afforded by maternally-derived antibodies in chickens and the antibodies’ interference with the protection elicited
by avian influenza-inactivated vaccines in progeny. Avian Dis. 54:246–252. Fahey, K. J., J. K. Crooks, and R. A. Fraser. 1987. Assessment by ELISA of passively acquired protection against infectious bursal disease virus in chickens. Aust. Vet. J. 64:203–207. Fulton, R. W., R. E. Briggs, M. E. Payton, A. W. Confer, J. T. Saliki, J. F. Ridpath, L. J. Burge, and G. C. Duff. 2004. Maternally derived humoral immunity to bovine viral diarrhea virus (BVDV) 1a, BVDV1b, BVDV2, bovine herpesvirus-1, parainfluenza-3 virus bovine respiratory syncytial virus, Mannheimia haemolytica and Pasteurella multocida in beef calves, antibody decline by half-life studies and effect on response to vaccination. Vaccine 22:643–649. Gharaibeh, S., K. Mahmoud, and M. Al-Natour. 2008. Field evaluation of maternal antibody transfer to a group of pathogens in meat-type chickens. Poult. Sci. 87:1550–1555. Klieve, A. V., and R. B. Cumming. 1988. Infectious bronchitis: Safety and protection in chickens with maternal antibody. Aust. Vet. J. 65:396–397. Maas, R., S. Rosema, D. van Zoelen, and S. Venema. 2011. Maternal immunity against avian influenza H5N1 in chickens: Limited protection and interference with vaccine efficacy. Avian Pathol. 40:87–92. Naqi, S. A., B. Marquez, and N. Sahin. 1983. Maternal antibody and its effect on infectious bursal disease immunization. Avian Dis. 27:623–631. Otaki, Y., K. Saito, M. Tajima, and Y. Nomura. 1992. Persistence of maternal antibody to chicken anaemia agent and its effect on the susceptibility of young chickens. Avian Pathol. 21:147–151. SAS Institute. 1996. SAS/STAT User’s Guide: Statistics. Version 6, 4th ed. SAS Institute Inc., Cary, NC. Skeels, J. K., P. D. Lukert, O. J. Fletcher, and J. D. Leonard. 1979. Immunization studies with a cell-culture-adapted infectious bursal virus. Avian Dis. 23:456–465. Thayer, S. G., and C. W. Beard. 1998. Serological procedures. Pages 255–266 in A Laboratory Manual for the Isolation and Identification of Avian Pathogens. 4th ed. D. E. Swayne, J. R. Glisson, M. W. Jackwood, J. E. Pearson, and W. M. Reed, ed. Am. Assoc. Avian Pathologists, Kennett Square, PA. Uchimura, T., K. Takase, K. Matsuo, and M. Yamamoto. 1990. Passive immunization with inactivated antigen of avian reovirus (strain 58–132). J. Jpn. Soc. Poult. Dis. 26:26–30. (In Japanese). van der Heide, L., M. Kalbac, and W. C. Hall. 1976. Infectious tenosynovitis (viral arthritis): Influence of maternal antibodies on the development of tenosynovitis lesions after experimental infection by day-old chickens with tenosynovitis virus. Avian Dis. 20:641–648. Villegas, P. 1998. Titration of biological suspensions. Pages 248–254 in A Laboratory Manual for the Isolation and Identification of Avian Pathogens. 4th ed. D. E. Swayne, J. R. Glisson, M. W. Jackwood, J. E. Pearson, and W. M. Reed, ed. Am. Assoc. Avian Pathologists, Kennett Square, PA. Westbury, H. A., and Y. Sinkovic. 1978. The pathogenesis of infectious avian encephalomyelitis. 4. The effect of maternal antibody on the development of the disease. Aust. Vet. J. 54:81–85. Wood, G. W., J. C. Muskett, and D. H. Thornton. 1981. The interaction of live vaccine and maternal antibody in protection against infectious bursal disease. Avian Pathol. 10:365–373. Wyeth, P. J., and G. A. Cullen. 1976. Maternally derived antibodyeffect on susceptibility of chick to infectious bursal disease. Avian Pathol. 5:253–260.
infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), and reovirus (Reo). Maternal antibody titers for Newcastle disease virus (NDV) were measured using a hemagglutination inhibition test. Half-life estimates of maternal antibody titers were 5.3, 4.2, 7, 5.1, 3.9, 3.8, 4.9, 4.1, 6.3, and 4.7 d for AEV, AIV, CAV, IBDV, IBV, ILTV, MG, MS, NDV, and Reo, respectively. The statistical analysis revealed significant differences among halflives of maternal antibody titers against certain pathogens. Furthermore, all maternal antibody titers were depleted by 10 d of age except for IBDV.
Key words: maternal antibody, decay, half-life, broiler 2013 Poultry Science 92:2333–2336 http://dx.doi.org/10.3382/ps.2013-03249
INTRODUCTION Maternal antibody (mAb) levels play crucial role in the health status of the modern-day broiler-chicken industry because of the short lifespan of broiler chickens. Commercial broiler chickens are being protected against certain pathogens such as chicken anemia virus (CAV; Otaki et al., 1992), avian encephalomyelitis virus (AEV; Westbury and Sinkovic, 1978), and reovirus (Reo; van der Heide et al., 1976) solely by providing sufficient levels of maternal antibodies from their parent flock. Maternal antibodies also play a major role in modulating early life live vaccine strategy for commercial broiler flocks. Maternal antibodies against Newcastle disease virus (NDV), as an example, have a favorable effect of decreasing the severity of live vaccine reaction; however, they also decrease the immunity after vaccination (Chu and Rizk, 1975). On the other hand, a high level of mAb against infectious bursal disease virus (IBDV) neutralizes the vaccine virus and results in complete failure of immunization (Naqi et al., 1983). There is also recent evidence indicating that mAb decreases the efficacy of killed vaccine against avian influenza virus (AIV; De Vriese et al., 2010; Maas et al., 2011; Abdelwhab et al., 2012). Therefore, ©2013 Poultry Science Association Inc. Received April 18, 2013. Accepted May 27, 2013. 1 Corresponding author: [email protected]
estimating the half-life of mAb has become necessary and valuable information that can be used in designing vaccination programs for broiler chickens to minimize the cross reaction between mAb and the vaccination programs. Duration of mAb in broiler chickens has been studied extensively for IBDV. Half-life of mAb against IBDV ranged from 3 to 8 d in several previous studies (Wyeth and Cullen, 1976; Skeels et al., 1979; Wood et al., 1981; Fahey et al., 1987; Al-Natour et al., 2004). Allan et al. (1978) and Darbyshire and Peters (1985) reported that the half-life of mAb against NDV and infectious bronchitis virus (IBV) was 4.5 and 5 to 6 d, respectively. Previous results from our laboratory estimated the rate of mAb transfer from the parent flock to their chicks (Gharaibeh et al., 2008). This study was designed to estimate the half-life of these mAb against different pathogens in broiler chicks.
MATERIALS AND METHODS Chicks and Housing Thirty 1-d-old broiler chicks (Lohmann) were obtained from a commercial hatchery. The parent flock was 40 wk of age when the eggs that hatched the broiler chicks were laid. The parent flock vaccination program is detailed in Table 1. Chicks were housed in an isolated and environmentally controlled room in the Ani-
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Table 1. Vaccination program of the parent flock related to the pathogens discussed in this study1 Age
Vaccine
Type, method
Manufacturer, country
1d 7d 7d 9d 15 d 19 d 14 d 27 d 40 d 8 wk 8 wk 9 wk 10 wk 11 wk 12 wk 18 wk 18 wk 30 wk 40 wk
IBV+NDV IBV+NDV AIV (H9N2) IBDV Reo IBDV IBV+NDV IBDV NDV (Lasota) ILTV IBV (4/91) NDV (Lasota) MG (F-strain) Reo AEV IBDV+IBV+NDV AIV (H9N2) IBV+NDV IBV+NDV
L, Spray K, Subcutaneous K, Subcutaneous injection L, Drinking water L, Intramuscular injection L, Drinking water L, Spray L, Drinking water L, Spray L, Eye drop L, Eye drop L, Spray L, Spray K, Intramuscular injection L, Drinking water K, Intramuscular injection K, Subcutaneous injection L, Spray L, Spray
Fatro, Italy Fatro, Italy Merial, France Fatro, Italy Fatro, Italy Fatro, Italy Intervet, the Netherlands Fatro, Italy Fatro, Italy Fatro, Italy Intervet, the Netherlands Fatro, Italy Schering-Plough, United States Fatro, Italy Fatro, Italy Fatro, Italy Merial, France Fatro, Italy Fatro, Italy
1AEV = avian encephalomyelitis virus; AIV = avian influenza virus; IBDV = infectious bursal disease virus; IBV = infectious bronchitis virus; ILTV = infectious laryngotracheitis virus; K = killed; L = live; MG = Mycoplasma gallisepticum; NDV = Newcastle disease virus; Reo = reovirus.
mal House Facility at Jordan University of Science and Technology. Commercial broiler feed and water were available ad libitum. Light was provided continuously throughout the study period.
Serological Analysis Blood was collected from each of the 30 chicks at 1, 5, 10, 15, 20, 25, and 30 d of age. Commercial ELISA kits (Synbiotics Co., San Diego, CA) were used to determine the titer of mAb (IgG/IgY) against AEV, AIV, CAV, IBDV, IBV, infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), and Reo. The ELISA kits were used according to the manufacturer’s protocol using an automated microplate reader (ELx800, BIO-TEK Instruments Inc., Winooski, VT). The antibody titer in each individual sample was quantified using the software provided by the manufacturer. The geometric mean titer (GMT) for each group of serum samples was also calculated using the same software. All serum samples were read against positive and negative control antisera provided by the kit and used in each run. Hemagglutination inhibition (HI) test using β procedure (constant antigen and varying serum dilutions) was used to quantify antibodies (IgG/IgY, IgM, and IgA) against NDV (Thayer and Beard, 1998). A 2-fold serial dilution was used to run the serum samples in the HI test and the GMT was calculated (Villegas, 1998). Appropriate controls for the HI test (positive antiserum control, negative antiserum control, antigen control, and erythrocyte control) were included in each run.
Statistical Analysis Half-life of mAb against the pathogens studied in this experiment was calculated similar to a previous study (Fulton et al., 2004) by simple linear regression using
PROC REG of SAS (SAS Institute, 1996). For each mAb against different pathogens, the regression equation was used to estimate the time required by mAb levels to drop by half (half-life) in each individual. An ANOVA using the GLM procedure of SAS (SAS Institute, 1996) was used to examine the equality of halflives of maternal antibodies among all pathogens. Least squares means were separated using Fisher’s protected least significant difference with a P-value of 0.05. Coefficient of variation and quartile range were estimated using the MEANS procedure of SAS (SAS Institute, 1996) for the half-lives of mAb against each pathogen.
RESULTS Table 2 summarizes the GMT for mAb against different pathogens in broiler chicks. All mAb against different pathogens showed a significant decrease in titer and were almost depleted by 10 d of age except for IBDV, where mAb persisted through 20 d of age and was almost depleted at 30 d of age. For mAb against NDV, titer was analyzed by HI rather than ELISA and hence GMT titer numbers for mAb against NDV appear persistent at low levels even at 30 d of age. This is because it is common to get nonspecific HI results at the first dilutions of the HI test plate (Thayer and Beard, 1998). Table 3 lists half-life, CV%, and quartile range for mAb against different pathogens. Half-life of mAb against different pathogens varied slightly and ranged from 3.8 d for ILTV to 7.0 d for CAV. Although CAV mAb had the highest half-life, it showed the highest variation among all other mAb as indicated by its CV% and quartile range. There are some significant differences among half-life means of mAb. Maternal antibodies against CAV had the longest half-life of 7.0 d and were statistically different than mAb against all the other pathogens except for mAb against NDV (6.3 d) and AEV (5.3 d). The shortest half-life was for mAb
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DECAY OF MATERNAL ANTIBODIES Table 2. Geometric mean titers
(GMT)1
for maternal antibodies against different pathogens at different ages Days of age
Pathogen2
Parent-flock3
0
5
10
15
20
25
30
3,839 1,910 9,283 35,012 19,472 3,146 3,165 4,881 8.5 2,761
405 668 1,985 21,104 6,706 209 1,134 828 5.9 790
29 37 108 16,295 860 10 365 21 4.9 41
2 2 18 10,643 15 2 5 3 3.5 4
0 1 1 3,983 0 2 1 1 3.5 0
0 0 1 546 0 1 0 0 3.1 0
0 0 0 84 0 0 0 0 2.4 0
0 0 0 2 0 0 0 0 1.1 0
AEV AIV CAV IBDV IBV ILTV MG MS NDV Reo 1All
GMT were calculated by ELISA software except for NDV, where hemagglutination inhibition log2 GMT titer was used. = avian encephalomyelitis virus; AIV = avian influenza virus; CAV = chicken anemia virus; IBDV = infectious bursal disease virus; IBV = infectious bronchitis virus; ILTV = infectious laryngotracheitis virus; MG = Mycoplasma gallisepticum; MS = Mycoplasma synoviae; NDV = Newcastle disease virus; Reo = reovirus. 3Parent-flock geometric mean titer at the day they laid the eggs that hatched the broiler chicks used in this study (40 wk of age). 2AEV
against ILTV (3.8 d) and IBV (3.9 d), but they were not statistically different than mAb against MS (4.1 d), AIV (4.2 d), Reo (4.4 d), or MG (4.9 d). Quartile range and CV% were highest for mAb against CAV, AEV, and Reo, which are the 3 pathogens we protect against in broiler chickens by mAb only.
DISCUSSION Previously, our laboratory outlined a set of unique data that describes the vertical transfer of mAb against 10 different pathogens from a parent flock to their 1-dold hatchlings under field conditions (Gharaibeh et al., 2008). The results of this study came to address the persistency and half-life of mAb against major chicken pathogens in newly hatched unvaccinated broiler chicks. Passively transferred mAb to the hatchlings was high at hatch and declined, subsequently registering a Table 3. Half-life (mean ± SE) of maternal antibodies against different pathogens with their CV1 % and quartile range Pathogen2 AEV AIV CAV IBDV IBV ILTV MG MS NDV Reo
Half-life (d) 5.3 4.2 7.0 5.1 3.9 3.8 4.9 4.1 6.3 4.7
± ± ± ± ± ± ± ± ± ±
0.5bc 0.4cde 0.4ab 0.4cd 0.4e 0.5e 0.4cde 0.4de 0.4b 0.4cde
CV%
Quartile range
53.7 18.4 74 11.1 7.6 13.6 13.4 34 27.7 44.7
2.3 1.2 6.2 0.9 0.4 0.8 0.8 0.9 0.6 1.8
a–eMeans not sharing a common superscript differ significantly (P < 0.05). 1CV = coefficient of variation ([SD/average] × 100%); measured using the MEANS procedure of SAS (SAS Institute, 1996) for half-lives of maternal antibodies against each pathogen. 2AEV = avian encephalomyelitis virus; AIV = avian influenza virus; CAV = chicken anemia virus; IBDV = infectious bursal disease virus; IBV = infectious bronchitis virus; ILTV = infectious laryngotracheitis virus; MG = Mycoplasma gallisepticum; MS = Mycoplasma synoviae; NDV = Newcastle disease virus; Reo = reovirus.
half-life between 3.8 and 7 d. Most of mAb titers exhibited a zero GMT by d 20 posthatch except IBDV and ND, where they persisted through d 30 posthatch with a very low GMT. For NDV, it is not unusual to get nonspecific HI results at the first dilutions of the HI test plate (Thayer and Beard, 1998), and this may explain the low persistent mAb titer of NDV. Thus, it would be safe to say that mAb against all pathogens except IBDV were depleted by 10 d of age. When the results of our study are compared with previous reports in the literature, we noted divergence in the rate of decay for certain mAb titers and comparable rates in other mAb. For example, we reported a half-life of 5.1 d for mAb against IBDV in accordance with Al-Natour et al. (2004) where they reported a half-life of 5.5 d. However, they used virus neutralization (VN) rather than ELISA. Other previous studies using layer chicks indicated an IBDV mAb half-life of 6 to 8 d (Wood et al., 1981) and 4 d (Wyeth and Cullen, 1976) using a quantitative agar gel precipitation test (QAGPT). Fahey et al. (1987) used ELISA but showed a half-life of 6.7 d, whereas Skeels et al. (1979) used VN and reported a half-life of 3 d. These IBD mAb half-life variations may stem from factors related to differences in chicken lines and types, and the types of serological tests used in each study because QAGPT and VN will detect all types of immunoglobulins (IgG/ IgY, IgM, and IgA), whereas the ELISA used in this study only detects IgG/IgY. The reported half-life for IBV mAb in this study was 3.9 d compared with previously reported half-life of 5 to 6 d by Darbyshire and Peters (1985). This divergence might be explained by the serological tests that were used. Darbyshire and Peters (1985) used the serum neutralization and HI test, where ELISA was the test used in this study. Furthermore, the 2 and one-half decades of genetic selection pressure might partially provide an explanation for the offset IBV mAb half-life. To the contrary, NDV mAb half-life was longer than what was cited in the literature 3 decades ago. We showed
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that NDV mAb half-life was 6.3 d compared with 4.5 d as previously reported using the HI test (Allan et al., 1978). Reovirus mAb half-life did not show a discrepancy from what has been reported in the literature. Our results showed a half-life of 4.7 d compared with a previous study by Uchimura et al. (1990) where they reported a half-life of 5 d. There is no universal vaccination program for broilers. Different geographical areas have different vaccination programs depending on biosecurity level, field challenge, and the specific regulations for vaccines in each country. Regardless of the level of mAb, broilers are usually primed with live vaccines against IBV and NDV at 1 d of age even if the immunological response will have reduced efficacy because of mAb (Chu and Rizk, 1975; Klieve and Cumming, 1988). The mAb, at this age, play the favorable role of reducing the vaccine reaction. Booster doses with live vaccines for both IBV and NDV are usually given at 10 d of age. Based on the information provided in Table 2, a killed vaccine for AIV (H9N2) and a live vaccine for IBDV may be best given around 10 and 20 d of age, respectively. In conclusion, the results of this study represent a guide for determining the half-life of mAb against many chicken pathogens. Half-life of mAb against different pathogens ranged from 3.8 to 7.0 d. Protection conferred by mAb should not be relied upon after 10 d of age except for IBDV.
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