Resistance of Marek's Disease at Hatching in Chickens Vaccinated as Embryos with the Turkey Herpesvirus

Abstract

Chickens vaccinated with herpesvirus of turkey (HVT) as 18-day embryos or at hatching were challenged as neonates with pathogenic Marek's disease (MD) virus (MDV). Embryonally vaccinated chickens had much greater resistant to challenge than chickens vaccinated post-hatch. Embryos became readily infected with HVT regardless of whether the vaccine was deposited into the body of the embryo or extraembryonally, such as in the amniotic sac. Embryonally vaccinated chickens were viremic with HVT at hatching and remained persistently viremic through the duration of the experiment. The titer of recoverable virus was higher in the embryonally vaccinated chickens than in the chickens vaccinated post-hatch. Embryonal vaccination did not affect hatchability. Vaccination at any stage of embryonation tested protected better against neonatal challenge than did vaccination at hatching. Protection against an early challenge was greatest when the embryos were 17 or 18 days old at the time of vaccination. Lower protection in chickens vaccinated as 11-day embryos was not due to humoral immunologic tolerance. Chickens vaccinated at the 11th day of embryonation were poorly protected against MDV challenge at three or eight days of age but were well protected if the challenge was delayed until the 14th day of age.

Comparison ofin ovoand post‐hatch vaccination with particular reference to infectious bursal disease. A review

“…In ovo-vaccinated embryos with Herpes-Virus of Turkeys (HVT) had higher NK cell reactivity than at hatch-vaccinated chicks (86). Embryos in ovo vaccinated with HVT at embryonation day 18, were better protected against post-hatch challenge on day 3 than those subcutaneously vaccinated after hatch (83,85).…”

“…Inductions of optimal and protective levels of humoral and/or cellular immune responses require several days following vaccination. In ovo vaccination is therefore proposed to stimulate an early immune response in young chicks (83).…”

“…Vaccines are deposited into the extra-embryonic compartment mainly into the amniotic sac (83,86) and are also injected directly into the embryonic tissues in the area of the neck, shoulder and breast. The deposition of the vaccine into the cloacal sucking in the uptake of in ovo-injected substances has been also described (42).…”

Influence of vaccine deposition site on post-vaccinal viraemia and vaccine efficacy in broiler chickens following in ovo vaccination against Marek's disease

“…Experimental in ovo vaccination has been used for a number of diseases including Marek's disease (MD) (Sharma & Burmester, 1982;Sharma & Graham, 1982;Sharma et al, 1984), infectious bronchitis (Wakenell & Sharma, 1986;Walkenell et al, 1995), infectious bursal disease (Sharma, 1985), Newcastle disease (Ahmed & Sharma, 1992), coccidiosis (Ruff et al, 1988;Watkins et al, 1995) and a combination of diseases (Gagic et al, 1999;. However, to date, this technology is most widely used to vaccinate broiler chickens against MD (Ricks et al, 1999).…”

“…However, to date, this technology is most widely used to vaccinate broiler chickens against MD (Ricks et al, 1999). The two main objectives of in ovo vaccination are: (1) to maximize the interval between vaccination and possible early natural challenge by virulent virus, allowing sufficient time for adequate vaccinal immunity to develop (Sharma & Burmester, 1982); and (2) to reduce handling of chicks and labour costs in the hatchery associated with post-hatch subcutaneous vaccination (Gildersleeve et al, 1993). Automated in ovo vaccination against MD was introduced to the Australian broiler industry in 1996 during an outbreak of MD, which caused severe losses in both the layer and broiler industries.…”