Outbreak of cutaneous form of avian poxvirus disease in previously pox-vaccinated commercial turkeys

Abstract

This study describes an outbreak of avian poxvirus disease in previously pox-vaccinated turkeys in Brazil. The turkeys had suggestive gross lesions of cutaneous avian poxvirus in the skin of the head and cervical area without changes in the flock mortality rates. In the slaughterhouse, 30 carcasses were removed from the slaughter line to collect tissue from cutaneous lesions for histological analyses and characterization of the virus. The virus was identified by conventional polymerase chain reaction (PCR) and subsequent gene sequencing. Acanthosis, hyperkeratosis, and hydropic degeneration were seen on skin histopathology. Eosinophilic intracytoplasmic inclusion bodies (Bollinger) on keratinocytes were observed in 46.6% of the samples. Avian poxvirus DNA was detected on PCR in 83.3% of the total samples. PCR associated with histopathology had 93.3% of positivity for avian poxvirus. In the phylogenetic study, samples show 100% matching suggesting that the outbreak occurred by a single viral strain and was different from those strains affecting other wild birds such as canaries and sparrows. A single mutation (Adenine for Guanine) was detected in our study’s strain and in the strains of turkey, chickens, and vaccine strains published in GenBank. Also, when the sequence strain of the present study and sequences from GenBank of canarypox and sparrowpox strains were aligned, a Thymine was found replacing the Adenine or Guanine. The in ovo vaccination method as single-use in turkeys of this study apparently did not provide adequate protection against avianpox disease, but additional vaccination administered by wing-web when turkeys were 45-60 days old in the new flocks controlled the disease. In the subsequent year, new cases of this disease were not found. It was not possible to confirm the source of the virus strain, but infection with a field strain derived from chickens is one possibility, considering the poultry farm population in the area and biosecurity aspects. For wide characterization of avipoxvirus and differentiation among strains, the complete sequence of the viral genome is required.

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

“…These findings may suggest non-specific response to REV caused by a different primary tropism. All macroscopic and microscopic findings of the skin are in accordance with previous reports (Arathy et al, 2010;Back et al, 1995;Ferreira et al, 2018;Joshi et al, 2019;Motha & Egerton, 1987;Mzula et al, 2014;Sentíes-Cué et al, 2010).…”

“…Particularly in this study, it is likely that the entire REV provirus gave rise to autonomous fragments, which in turn cause immunosuppression and increased pathogenicity, as previously suggested (Bi et al., 2018; Wang, Meers, et al, 2006) and causing an accumulative effect, thus permitting FPV to be expressed in an atypical region (feathered skin of bids). From this perspective, it is very interesting to consider that some outbreaks of FPV in previously vaccinated flocks (Fallavena et al., 2002; Ferreira et al., 2018; Odoya et al., 2006; Puro et al., 2017) may be influenced by the presence of a complete REV provirus; however, these studies did not consider testing REV presence. 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.…”

“…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).…”

Pathological, molecular and phylogenic study of fowlpox virus in domesticated chickens of Tikrit City, Iraq

“…These results agree with a group of researchers who classified FPV clades into clade A (Fowlpox virus), including mainly Galliformes and Columbiformes order, clade B (Canarypox virus), and clade C (Psittacinepox virus) (Jarmin et al, 2006;Manarolla et al, 2010). Columba livia in the current study arranged in clade B and wild birds from Morocco and UAE set in separated clade C, which is mentioned by most researchers as a subclade of clade B (Ferreira et al, 2018;Le Loc'H et al, 2014). Clade C appeared as a separated clade in the current study because of the extensive genetic distance of the wild birds' viruses in comparison with other poxviruses aligned sequences.…”

“…Over 200 wild and domesticated avian species were reported infected by FPV (Giotis & Skinner, 2019;Lecis et al, 2019). The cutaneous form of the disease still causes economic losses to the avian industry, even in vaccinated and low mortality flocks (Ferreira et al, 2018). Lesions of poxvirus (Pock) in chicken observe on the wattles, comb, legs, and eyelids (Gilhare et al, 2015).…”