Comparision of pathogenic properties of Vors-07 isolate and Marek disease referent virulent MD5 strain

UDC 619:578.825.1:578.72

Chicherina E.A., Irza V.N., Chernykh O.Yu.

Summary. Marek disease is a highly contagious viral disease of chickens and turkeys in 2 forms: classic (lesions of the peripheral and central nervous system) and acute (development of malignant lymphomas in visceral organs). Main reason for the change of Marek disease pathogenicity is specific viral mutations of genes that modify the induction of tumors, reduces the rate of replication in vitro. Studies to compare pathogenicity of field Marek disease virus isolate "Vors-07" and referent virulent strain "Md5" for immunized chickens have been conducted. Both viruses belonged to serotype 1. Day-old chicks were vaccinated with mono– HVT (Vladimir strain), bi- (HVT + SB1) and trivalent (HVT + SB1 + 3004 strain (serotype 1)) vaccine, each group with one of these vaccines and challenged on day 8 with "Vors-07" and "Md5" strains at dose of 1000 PFU/0,2 ml. It was shown that in 120 days observation period typical Marek disease virus induced limphomas were found in vaccinated and challenged then with "Vors-07" groups in 20% of birds immunized with MDV3, 10% – MDV 2+3 and 10% – MDV1+2+3. For groups immunized the same way and challenged with "Md5" the percentage of birds with neoplastic lesions was 40%, 20% and 20%, respectively. In control non-vaccinated groups "Md5" virus caused typical lesions in 80% of birds, "Vors-07" – in 70%. Patological lesions in viscera were found at autopsy, typical to Marek disease that is described above. In groups of birds vaccinated with the monovalent vaccine and infected "Vors-07" and "Md5" at autopsy showed signs of Marek’s disease in 20% and 40% of chickens, respectively. In the groups vaccinated with bi- and trivalent vaccines and infected "Vors - 07" and "Md5" – 10% and 20% of poultry, respectively. Authors established exhaustion, retarded growth, disorders of the musculoskeletal system. Deviations from the physiological norm were not revealed by the control group. Thus it was ascertained in experiments that Marek disease virus isolate "Vors-07" is a virulent strain having pathogenicity for chickens similar to "Md5" virulent referent strain.

Key words: virus, virulent strain, serotype, Marek disease, outbreak, isolate, pathogenicity, lymphoid tissue, lymphoma, infiltration, vaccine.

References:

1. Glantz S. Mediko-biologicheskaya statistika [Biostatistics]. – Praktika". – Moscow, 1999. – 460 p.

2. Kulyashbekova Sh.K., Borisov A.V., Drygin V.V. Bolezn Mareka [Marek disease]. – Transit-IKS. – Vladimir, 2008. – 214 p.

3. A recombinant field strain of Marek’s disease (MD) virus with reticuloendotheliosis virus long terminal repeat insert lacking the meq gene as a vaccine against MD / S.Su, N. Cui,Y.Zhou [et al.] // Vaccine. – 2015. - Vol. 33. – P. 596-603.

4. Hildebrandt E, Dunn J, Cheng HH. Characterizing in vivo stability and potential interactions of a UL5 helicase-primase mutation previously shown to reduce virulence and in vivo replication of Marek’s disease virus // Virus Res. – 2015.

5. Pathogenic characteristics of Marek’s disease virus field strains prevalent in China and the effectiveness of existing vaccines against them / Y.P. Zhang, Z.J. Li, K.Y. Bao [et al.] // Vet Microbiol. - 2015 Jan.

6. Woźniakowski G., Samorek-Salamonowicz A.E. Molecular evolution of Marek’s disease virus (MDV) field strains in a 40-year time period // Avian Dis. -2014. Vol. 58. - P. 550-557.

Author affiliation:

Chicherina Ekaterina A., head of the Department for biosecurity and sanitary regimen of the All-Russian Scientific-Research Institute of Animal Health; Yurjvets mcd., Vladimir, 600901; phone: (4922) 26 06 14; e-mail: chicherina@arriah.ru.

Irza Victor N., D.Sc. in Veterinary Medecine, Head of the Department for Poultry Diseases of the All-Russian Scientific-Research Institute of Animal Health; Yurjvets mcd., Vladimir, 600901; phone: (4922) 26 18 67; e-mail: irza@arriah.ru.

Responsible for correspondence with the editorial board: Chernykh Oleg Yu., D.Sc. in Veterinary Medicine, director of the Kropotkin territorial veterinary laboratory; 303, Krasnoarmeyskaya st., Kropotkin, 352380; phone: 8(86138) 6-23-14; e-mail: gukkvl50@kubanvet.ru.