Isolation and Characterization of an Isolate (HN) of Marek's Disease Virus with Low Pathogenicity

Abstract

A cytopathic agent was isolated and characterized as an isolate of Marek's disease herpesvirus (MDHV) with low pathogenicity, and referred to as the HN isolate. This isolate of MDHV did not cause clinical Marek's disease (MD) or death in a highly susceptible line of chickens within 5 weeks after exposure. Gross lesions of limited extent were noted in a few of the inoculated birds. Microscopic nerve lesions in the inoculated and contact-infected birds were invariably minimal, closely resembling C-type MD lesions.

An Overview on Marek’s Disease Virus Evolution and Evidence for Increased Virulence in Brazil

“…However, the increasing virulence of MDV strains may however compromise the success of control through vaccination (Witter, 1997) and reports of vvMDV are spread worldwide (López-Osório et al, 2017). The pioneering experiments with vaccines were developed almost immediately after the description of MD etiology (Churchill & Biggs, 1967), with its attenuation by the end of the 1960's (Churchill et al, 1969) and the discovery of a virulent strains in turkeys (Witter et al, 1970) and chickens (Biggs & Milne, 1972;Cho & Kenzy, 1972).…”

“…The understanding of the transmission mechanism and risk of infection was achieved when experimental infection with cell-free MDV of feather follicle desquamation epithelium was demonstrated (Beasley et al, 1970;Calnek et al, 1969;Calnek et al, 1970a). The virus was serially passaged in primary kidney cell monolayers and successfully attenuated (Churchill et al, 1969), and given to one-day-old chicks induced protection against the challenge (Calnek et al, 1970b), subsequently also acquired by naturally a virulent strains isolated from turkeys (Witter et al, 1970b) and chickens (Biggs & Milne, 1972;Cho & Kenzy, 1972). Among the isolated a virulent low virulence MDV strains, the CVI 988 vaccines became popular or of (Rispens et al, 1972) and SB-1 (Schat & Calnek, 1978 Marek's disease virus MDV is classified as Gallid Herpesvirus 2, genus Mardivirus, famíly Herpesviridae, subfamíly Alphaherpesvirinae, and divided into three serotypes MDV-1 (RB-1B, Md5 and CVI988), MDV-2 (SB-1 e HPRS24), and the antigenically related Meleagrid Herpesvirus-1 (known as serotype three; herpes vírus of turkeys-strain FC126) (ICTV, 2018;Dunn et al, 2014).…”

Toxicological evaluation of different solvent fractions of Waltheria indica linn. root in male wistar rats

“…Many strains of MDV have been 120 identified. Oncogenic strains are classified as serotype 1 (MDV1) while the naturally non on-cogenic chicken strains (Cho & Kenzy, 1972) and herpesvirus of turkeys (HVT) (Witter et al,1970) belong to serotypes 2 (MDV-2) and 3, respectively. Marek's disease was first described as polyneuritis (Marek, 1907).…”