First report of Serotype-1 Marek’s disease virus (MDV-1) with oncogenic form in backyard turkeys in Turkey: a molecular analysis study

Abstract

Background Marek’s disease (MD) is a lymphoproliferative disease caused by Gallid alphaherpesvirus 2 (GaHV-2, MDV-1), which primarily affects chickens. However, the virus is also able to induce tumors and polyneuritis in turkeys, albeit less frequently than in chickens. Results This is the first study in Turkey reporting the molecular characterization of a MDV-1 strain detected in a flock of backyard turkeys exhibiting visceral lymphoma. Here, MEQ, vIL-8, pp38 and 132-bp tandem repeat regions, which are frequently preferred in the pathotyping of MDV-1, were examined. It was determined that the MEQ gene of MDV-1/TR-21/turkey strain obtained in the present study encoded 339 amino acids (1020 nt) and had four proline-rich repeat regions (PPPP). Based on the nucleotide sequence of the MEQ gene of the MDV-1/TR-21/turkey strain, a phylogenetic tree was created using the MEGA-X software with the Maximum Likelihood Method (in 1000 replicates). Our strain was highly identical (> 99.8) to the Italian/Ck/625/16, Polish (Polen5) and some Turkish (Layer-GaHV-2-02-TR-2017, Tr/MDV-1/19) MDV-1 strains. Also, nt and aa sequences of the MEQ gene of our strain were 99.1 and 99.41% identical to another Turkish strain (MDV/Tur/2019) originated from chickens. Sequence analysis of pp38 and vIL-8 genes also supported the above finding. The identity ratios of nucleotide and amino acid sequences of vIL-8 and pp38 genes of MDV-1/TR-21/turkey strain were 99.64–100% and 99.79–100%, respectively, when compared with those of the Polish strain. According to 132-bp tandem repeat PCR results, the MDV-1/TR-21/turkey strain had five copies. Conclusions These results suggested that the MDV-1/TR-21/turkey strain obtained from backyard turkeys can be either very virulent or very virulent plus pathotype, though experimental inoculation is required for precise pathotyping.

First Report of Marek’s Disease Virus in Commercial Turkeys in Slovenia

“…Moreover, recent detection of the GaAHV-2 partial DNA polymerase gene nt sequence in Ural owls in Slovenia raises the possibility that free-living birds should also be considered as a risk for GaAHV-2 infection [36]. However, even though most documented MD cases were reported in turkeys that were reared with or close to chickens [12,14], in the cases presented here, no other poultry species were present at the farms during the fattening cycle nor in the past. All three flocks have the same veterinarian.…”

“…MD has been described in commercial turkeys from the Netherlands [7], France [8], Germany [9], Israel [10], and the UK [3,11]. Most recently, tumors associated with GaAHV-2 infection were confirmed in commercial free-range turkeys in Italy [12] and backyard turkeys from the US [13] and Turkey [14]. The clinical signs associated with MD in turkeys are non-specific, and they mostly appear between 12 and 30 weeks of age.…”

Circulating hypervirulent Marek’s disease viruses in vaccinated chicken flocks in Taiwan by genetic analysis of meq oncogene

“…The MDV-1 genome encodes more than 200 genes, some of which are unique oncogenes primarily involved in viral pathogenesis [8]. The Meq oncoprotein encoded by the meq oncogene was the first discovered oncoprotein whose N-terminal basic-leucine-zipper (bZIP) domain and C-terminal proline-rich transactivation domain were identified as major functional factors associated with MDV-1 virulence and oncogenicity [9].…”

Virulence of Circulating Marek’s Disease Virus Strains in Vaccinated Chicken Flocks in Taiwan: Data on Genetic Analysis of the meq Oncogene

“…The MDV-1 genome encodes more than 200 genes, some of which are unique oncogenes that are mostly involved in viral pathogenesis [9]. The Meq oncoprotein encoded by the meq oncogene was the first discovered oncoprotein whose N-terminal basic-leucine-zipper (bZIP) domain and Cterminal proline-rich transactivation domain were identified as major functional factors associated with MDV-1 virulence and oncogenicity [10,11].…”