Document Type : Original Article
Authors
1
MVSc student
2
Department of Parasitology and Animal Diseases, National Research Centre, 33 Bohouth Street, Dokki, Giza, 12622, Egypt.
3
Dept of Poultry. Diseases, Vet. Res. Division, National Research centre
4
Department of Poultry Diseases. Faculty of Veterinary Medicine. Cairo University. Postal Code: 12211 Giza, Egypt.
Abstract
This study evaluated the effectiveness of chicken IgY for the prevention and control of Newcastle disease virus (NDV) genotype VII in vaccinated chickens. The 1/5 and 1/10 diluted IgY had ND titers of 6.87±0.99 and 5.8±0.83, respectively, through subcutaneous (s.c) or intramuscular injections (i.m) of 0.5 ml/bird for 3 successive days. At 21 days of age, after the 3rd injection, NDV-HI titers in prophylactic groups were increased to 6.8±0.89, 5.9±1.14, 5.6±0.83 and 5.5±0.83 in groups given dilution 1/5 and 1/10, by i.m and s.c injections, respectively. The infected (106 EID50), non-treated birds exhibited symptoms such as respiratory distress, congested comb, greenish diarrhea within 24 hours, and swollen face within 48 hours. The mortality rate was 7.5% by the third-day post-infection. Dead birds were positive for NDV using reverse transcription-polymerase chain reaction (RT-PCR) with a cycle threshold (CT) value 17. Chicken received IgY by i.m or s.c, injections, either showed increased HI titers against NDV at 37 days of age after being challenged with the virus.
The feed conversion ratio (FCR) at 37 days in the prophylactic groups were 1.81, 1.70, 1.71, and 1.76, respectively. There was no significant difference in FCR between the different IgY dilutions or routes of administration. The prophylactic groups had higher FCR values. The control negative group showed 85.71% mortality within 3-7 days post-infection.
The prophylactic and control groups injected with 1/5 showed a 100% protection rate. While groups received 1/10 showed 85.71% and 92.85% for i.m and s.c routes, respectively. RT-PCR analysis of cloacal swabs from treated groups was negative, while nontreated showed positive RT-PCD with CT-17. Groups that received 1/5 diluted IgY showed better results than those that received 1/10 with milder histopathological lesions.
In conclusion: The study demonstrated that the use of chicken IgY against NDV genotype VII in broiler chickens resulted in increased HI titers, mild signs, high protection rates, and FCR. The prophylactic administration of IgY showed better results than control.
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