Comparative 50% protective dose assays (PD50) of Marke's disease virus strain CVI988

Boer, G. F. de; Orthel, F.W.; Krasselt, Marco; Oei, H.L.; Pereboom, WJ; Barendregt, L.G.

doi:10.1016/s0092-1157(81)80061-3

Cited by 10 publications

(4 citation statements)

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“…vaccinated female chickens in trial 3 was similar to the mean of six PD 50 's observed for various CVI-988 pre-parations in a previous study (De Boer et al, 1981). The four PD 50 estimates calculated for experimental MDV CVI-988 CEF 65 clone C vaccine were all considerably below the PD SO values of commercial CVI-988 vaccine.…”

Section: Discussionsupporting

confidence: 82%

“…It should be realised, however, that the safety margin of the protective efficacy of MD vaccines is reduced up to 4-fold if s.c. vaccination becomes the normal practice. In previous studies it was demonstrated that maternal antibodies slightly increase the PD SO estimate (Witter and Burmester, 1979;De Boer et al, 1981). Since maternal antibodies are to be expected in the majority of chickens in the field, the safety margin of the protective efficacy of commercial MD vaccines becomes smaller than that observed in SPF chickens.…”

Section: Discussionmentioning

confidence: 95%

“…Trial 4 was performed in modified Horsfall-Bauer isolators as used in previous PD 50 studies of MD vaccines (Witter and Burmester, 1979;De Boer et al, 1981). One isolator was employed per vaccine dose group.…”

Section: Experimental Chickens and Housingmentioning

confidence: 99%

“…With this programme the 50% protective dose (PD SO ) and the slope of the probit regression line were calculated from the results in the MD susceptible part of the experimental flock. The PD 50 is defined as the number of plaque forming units (PFU) of vaccine virus, determined in an in vitro assay, required to protect 50% of the MD-susceptible part of a group of chickens from clinical symptoms and macroscopical lesions of MD (De Boer et al, 1981).…”

Section: Experimental Designmentioning

confidence: 99%

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Comparison of intramuscular and subcutaneous administration of marek's disease vaccine

Oei¹,

Boer²

1986

Avian Pathology

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SUMMARYFour trials employing 50% protective dose (PD 50 ) assays were performed to compare the efficacy of Marek's disease vaccine after intramuscular (i.m.) and subcutaneous (s.c.) inoculation of specific-pathogenfree (SPF) chickens. Female chickens were employed in trials 1 and 2. In trials 3 and 4 the results were separately recorded for both sexes. Cell-associated Marek's disease virus serotype 1 vaccines derived from strain CVI-988 were used. Intramuscular administration yielded PD 50 estimates which were below the PD 50 obtained by the s.c. route in all five pairs of comparable assays. A 4-fold difference of PD 50 estimate, in favour of i.m. inoculation, was observed between the two series of female chickens of the trial which most properly fulfilled the requirements for a PD 50 assay. By comparing 25 individual pairs of vaccine dose groups, the best protection was observed in 24 groups of chickens which received the vaccine by i.m. route. These data were statistically analysed by comparing the average degrees of protection provided by i.m. or s.c. inoculation. In trials 1 and 2 the i.m. vaccination provided significantly better protection than the s.c. route. Although not significantly different, the differences in trials 3 and 4 were in the same direction. It is recommended that the potency of the minimally acceptable field dose should be increased if s.c. administration becomes the normal practice.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 95%

Section: Experimental Chickens and Housingmentioning

confidence: 99%

Section: Experimental Designmentioning

confidence: 99%

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