Detection and Molecular Characterization of a Natural Coinfection of Marek’s Disease Virus and Reticuloendotheliosis Virus in Brazilian Backyard Chicken Flock

Abstract

Marek’s disease virus (MDV) and the reticuloendotheliosis virus (REV) are two of the primary oncogenic viruses that significantly affect chickens. In Brazil, there have been no previous published reports on the presence of field REV alone or in coinfection. This retrospective study analyzes samples from a case of lymphoproliferative lesions from a backyard chicken flock. MDV and REV were detected by PCR and classified as MDV1 and REV3, respectively, through sequencing and phylogenetic analysis based on the glycoprotein B (gB) genes for MDV and the polymerase (pol) and envelope (env) genes for REV. Real-time PCR reactions were performed for MDV to rule out the presence of the Rispens vaccine strain. This is the first report of the presence of REV in coinfection with a MDV clinical case in Brazil and the first molecular characterization of REV in South America. This study highlights the importance of molecular diagnosis for REV and MDV in poultry. In addition, this study highlights the distribution of these two viruses worldwide and the latent risk of them solely or in coinfection to this part of the world.

An atypical clinicopathological manifestation of fowlpox virus associated with reticuloendotheliosis virus in commercial laying hen flocks in Brazil

“…Similarly, the atypical clinical manifestations of FP (Back et al, 1995;Hess et al, 2011;Sentíes-Cué et al, 2010) could be explained by the contribution of REV in the pathology of these birds. All these results indicate that REV arrived in Brazil and South America several years ago, as was previously reported (Canal & Corrêa, 2009;Chacón et al, 2019), as well as other parts of the world (Kim & Tripathy, 2001). These findings highlight the importance of monitoring for REV in the poultry industry because its immunosuppressive effects may be masked by other opportunistic or coinfecting infectious agents.…”

“…Positive controls included a commercial vaccine (Poximune ® AE, Ceva Animal Health) for FPV and a liver sample from a previously confirmed bird with REV (Chacón et al., 2019). Skin from specific pathogen‐free (SPF) chickens resuspended in 1.5 ml of phosphate‐buffered saline (PBS) was used as a negative control.…”

“…During the last decades, some outbreaks of avian poxvirus have been reported in poultry worldwide (Arathy et al., 2010; Beytut & Haligur, 2007; Biswas et al., 2011; Odoya et al., 2006; Okwor, Eze, & Chah, 2014; Prukner‐Radovčić et al., 2006; Singh et al., 2000), as well as in Brazil (Back, Soncini, Ruthes, Madureira, & Flores, 1995; Da Silva et al., 2009; Ferreira et al., 2018). Moreover, the first case of coinfection with REV and MDV in backyard chicken flocks in Brazil was described recently (Chacón et al., 2019).…”

Occurrence of Marek’s disease in Poland on the basis of diagnostic examination in 2015–2018

“…For many years, an increase in the pathogenicity of MDV strains has been observed despite immunoprophylaxis being used in day-old chicks. Such an increase was observed as early as 1997 in the vaccinated flocks of birds ( 3 , 4 ).…”

“…Investigations in Brazil also confirmed that MDV infection is a significant problem. In addition, double infection with MDV and reticuloendotheliosis virus was diagnosed in samples from a flock from the vicinity of San Paulo ( 4 ). Birds from this flock had not been vaccinated against Marek’s disease.…”