Marek's disease virus / gallid herpesvirus 2 (MDV or GaHV2)

Test code: S0264 - Ultrasensitive qualitative detection of Marek's disease virus (gallid herpesvirus 2) by real time polymerase chain reaction

Gallid herpesvirus 2 (GaHV-2), also known as Marek’s disease virus (MDV), is a highly contagious alphaherpesvirus in the family herpesviridae. The virus is an enveloped, double-stranded DNA virus with a large genome (~160–180 kb) encoding over 100 genes. The virus primarily affects chickens, though it can occasionally infect turkeys, quail, and pheasants. The virus causes Marek’s disease (MD), a lymphoproliferative and neuropathic condition.

Transmission of this virus is via inhalation of feather dust or dander containing infectious viral particles. Horizontal spread is the major route. Vertical transmission is not common. This virus can survive for months in poultry house dust or litter, making environmental persistence a key factor in outbreaks.

The incubation of infection can be long and variable (2–7 weeks), with clinical signs appearing 3–20 weeks post-infection, depending on strain virulence and host factors. Symptoms of infection include weight loss, pale combs, and ataxia. Visceral organs, such as the liver, spleen, and kidney, can be enlarged. The mortality rate can reach 10–50% in unvaccinated flocks.

Culture detection of this virus is slow and not practical. Serological detection of the viral antibody is only useful to screen for prior exposure to the virus or vaccination against the virus. PCR is useful to confirm infection before any clinical signs show up, which usually takes 3-20 weeks post-exposure (Zelnik, 2021). Thus, it is useful to screen new chickens by PCR before introducing them to the flock. Furthermore, routine monitoring of broiler house dust is often done using PCR (Walkden-Brown et al., 2013).

Utilities:

• Help confirm the disease causing agent
• Environmental monitoring
• Help ensure that bird populations are free of MDV / GaHV2
• Early prevention of spread of the virus among bird populations
• Minimize human exposure to the virus
• Safety monitoring of biological products and vaccines that derive from birds

References:
Walkden-Brown, S.W., Islam, A.F., Groves, P.J., Rubite, A., Sharpe, S.M. and Burgess, S.K. (2013) Development, application, and results of routine monitoring of Marek's disease virus in broiler house dust using real-time quantitative PCR. Avian Dis. 57(2 Suppl):544-554.

Zelník, V. (2021) Use of nucleic acids amplification methods in Marek's disease diagnosis and pathogenesis studies. Acta Virol. 65:27-32.

Specimen requirements: 0.2 ml feces, or cloacal swab, or feather tips, or 0.2 ml whole blood in EDTA (purple top) tube, or 0.2 ml fresh, frozen or fixed tissue, or 0.2 ml cell culture, or environmental swab or swipe.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected