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Cutaneous fowlpox is a disease of chickens and turkeys caused by the fowlpox virus (FWPV), characterized by the development of proliferative lesions and scabs on unfeathered areas. FWPVs regularly carry an integrated, active copy of the reticuloendotheliosis virus (REV), and it has been hypothesized that such FWPVs are more problematic in the field. Extensive outbreaks are usually observed in tropical and sub-tropical climates, where biting insects are more difficult to control. Here, we report an epidemic of 65 cutaneous fowlpox cases in Austria in layer chickens (91% of the cases) and broiler breeders and turkeys, all of them unvaccinated against the disease, from October 2018 to February 2020. The field data revealed appearance in flocks of different sizes ranging from less than 5000 birds up to more than 20,000 animals, with the majority raised indoors in a barn system. The clinical presentation was characterized by typical epithelial lesions on the head of the affected birds, with an average decrease of 6% in egg production and an average weekly mortality of 1.2% being observed in the flocks. A real-time multiplex polymerase chain reaction (PCR) confirmed the presence of FWPV-REV DNA, not only in the lesions but also in the environmental dust from the poultry houses. The integration of the REV provirus into the FWPV genome was confirmed by PCR, and revealed different FWPV genome populations carrying either the REV long terminal repeats (LTRs) or the full-length REV genome, reiterating the instability of the inserted REV. Two selected samples were fully sequenced by next generation sequencing (NGS), and the whole genome phylogenetic analysis revealed a regional clustering of the FWPV genomes. The extensive nature of these outbreaks in host populations naïve for the virus is a remarkable feature of the present report, highlighting new challenges associated with FWPV infections that need to be considered., (© 2022 The Authors. Transboundary and Emerging Diseases published by Wiley-VCH GmbH.)

Fowlpox is an economically significant viral disease in poultry, characterized by two forms of clinical signs, including cutaneous and diphtheritic lesions. This infection can have several adverse effects on flock performance, such as a reduction in egg production and growth and an increase in mortality. In winter 2018, an infection suspected to fowlpox was reported from a Hy-line W-36 laying farm in Isfahan province, Iran. The birds were 38 weeks of age and showed obvious diphtheritic signs in mucous membranes with increased mortality and reduced egg production. In total, 20 samples were collected from diphtheritic lesions (Trachea and Esophagus) of infected birds. The Polymerase Chain Reaction method was used to amplify a 578 bp fragment of the poxvirus 4b core protein gene. Phylogenetic relationships of avian poxviruses are usually analyzed using the 4b core protein-coding gene sequences with molecular weights of 75.2 kDa. The major elements had the fowlpox genome, and sequencing was performed for one isolate as representative. The nucleotide sequence result showed that this isolate (FP\UT-POX-2018) had a similarity rate of 99.53% with the previous Iranian fowlpox isolate (FP\GHPCRLAB.3) sequenced in the GenBank.Moreover, there was a 100% similarity among the current isolate nucleotide sequence, FP/NobilisVarioleW, and FP/FPV-VR250. The derived phylogenetic tree showed that these isolates were clustered in A1 subclades. Therefore, Iranian isolates of fowlpox virus have remained in the same subclade of phylogenetic classification (subclade A1), and they show high genomic similarity with previous isolates of Iran. Veterinarians and farmers must not underestimate fowlpox. However, they should consider the importance of vaccination against this disease like any other disease care., (Copyright © 2021, Author(s). Published by Kowsar.)

Analysis of scab samples collected from poultry during outbreaks of fowlpox in Mozambique in 2016 revealed the presence of clade E avipoxviruses. Infected poultry were from flocks that had been vaccinated against fowlpox virus. These findings require urgent reevaluation of the vaccine formula and control strategies in this country.

Infectious diseases can be serious threats for the success of reinforcement programmes of endangered species. Houbara Bustard species (Chlamydotis undulata and Chlamydotis macqueenii), whose populations declined in the last decades, have been captive-bred for conservation purposes for more than 15 years in North Africa and the Middle East. Field observations show that pox disease, caused by avipoxviruses (APV), regularly emerges in conservation projects of Houbara Bustard, despite a very strict implementation of both vaccination and biosecurity. Data collected from captive flocks of Houbara Bustard in Morocco from 2006 through 2013 and in the United Arab Emirates from 2011 through 2013 were analysed, and molecular investigations were carried out to define the virus strains involved. Pox cases (n = 2311) were observed during more than half of the year (88% of the months in Morocco, 54% in the United Arab Emirates). Monthly morbidity rates showed strong variations across the time periods considered, species and study sites: Four outbreaks were described during the study period on both sites. Molecular typing revealed that infections were mostly due to canarypox-like viruses in Morocco while fowlpox-like viruses were predominant in the United Arab Emirates. This study highlights that APV remain a major threat to consider in bird conservation initiatives., (© 2015 Blackwell Verlag GmbH.)

Concurrent fowlpox and candidiasis diseases occurred in a backyard chicken flock. Four deceased chickens (one Nagoya breed and three white silkie chickens) were examined for diagnosis. At necropsy, white curd-like plaques were observed in the crop. Fungal elements that stained positive for Candida albicans with immunohistochemistry were distributed throughout the tongue, choanal mucosa, esophagus, and crop. Typical fowlpox lesions, composed of proliferating epithelial cells with ballooning degeneration and viral intracytoplasmic inclusions, were observed in the conjunctiva, nasal mucosa, and skin around the cloaca. Interestingly, hyperplastic interfollicular epithelium with rare virus inclusions was observed in the bursa of Fabricius (BF). Some bursal follicles were replaced by proliferating epithelial cells. These proliferating cells immunohistochemically stained positive for cytokeratin. PCR and subsequent genetic sequencing detected the C. albicans gene in the crop, and fowlpox virus genes in the BF. These results indicate that this outbreak was a rare presentation of fowlpox in spontaneously infected chickens, with unusual pox lesions in the BF.

With the aim of assessing the antigenic characteristics of a circulating pool of fowlpox virus (FPV) that exists in the backyard poultry system in India, one of the field isolates generated was characterized by in vitro immunologic techniques. FPV was isolated from clinically positive fowlpox cases (n  =  10) from the Jhargram (West Midnapur district) and Kakdwip (South 24 Pargana district) areas of West Bengal State, India. Initially, FPV-specific PCR was performed for confirmation of the samples. Isolation of FPV was done using embryonated chicken eggs and the choreoallantoic membrane route. Subsequently, FPV antigen was prepared from chicken embryo fibroblast cell culture-adapted field isolate. Biologic transmission of FPV was performed in Rhode Island red chickens experimentally to assess humoral and cell-mediated immune (CMI) responses. High level of anti-FPV antibodies were observed in test birds as assessed by indirect ELISA. Seroreactive polypeptides (B-cell antigens) of FPV antigen with molecular weights of 44.5, 66.5, 75, 90.5, and 99 kDa were detected by western blot analysis. Significant increases in CMI responses were observed in inoculated chickens as assessed by lymphocyte proliferation assay, cytotoxicity assay, and T-cell immunoblotting. The predominant T-cell antigen of FPV detected had a molecular weight of 66.5 kDa. The present study revealed the antigenic characteristics of FPV that exists in backyard poultry system in West Bengal for the first time, thus exploring the rationality of designing future T- and B-cell vaccines against fowlpox.

We investigated an acute outbreak of the cutaneous form of fowlpox among chickens in China in November 2009. Using pathologic and virologic methods, we identified a novel type of fowlpox virus that carried an integrated genomic sequence of reticuloendotheliosis virus. This highly pathogenic virus could lead to severe ecologic effects and economic losses.

Fowlpox virus (FPV) is one example of poultry viruses which undergoes recombination with Reticuloendotheliosis virus (REV). Trepidation had been raised, and it was well established on augmented pathogenicity of the FPV upon integration of the full intact REV. In this study, we therefore intended at assessing the integration of REV into FPV genome of the field isolates obtained in samples collected from different regions of Tanzania. DNA extraction of 85 samples (scabs) was performed, and FPV-specific PCR was done by the amplification of the highly conserved P4b gene. Evaluation of FPV-REV recombination was done to FPV-specific PCR positively identified samples by amplifying the env gene and REV long terminal repeats (5' LTR). A 578-bp PCR product was amplified from 43 samples. We are reporting for the first time in Tanzania the existence of variant stains of FPV integrated with REV in its genome as 65 % of FPV identified isolates were having full intact REV integration, 21 % had partial FPV-REV env gene integration and 5 % had partial 5' LTR integration. Despite of the fact that FPV-REV integrated stains prevailed, FPV-REV-free isolates (9 %) also existed. In view of the fact that full intact REV integration is connected with increased pathogenicity of FPV, its existence in the FPV genome of most field isolates could have played a role in increased endemic, sporadic and recurring outbreaks in selected areas in Tanzania.

Visceral lymphomas occurred in a 236-day-old layer flock previously diagnosed with reticuloendotheliosis virus (REV)-integrated fowlpox virus (FPV) infection at the age of 77 days. Common pathologic lesions were multiple neoplastic nodules of homogeneous lymphocytes in the livers and spleens of all submitted chickens. All neoplastic tissues were positive for the REV envelope (env) gene by PCR. In a retrospective molecular study of FPV-infected 77-day-old chickens from the same flock, we identified nearly full-length REV provirus integrated into the genome of FPV as well as the REV env gene in trachea samples, whereas only the REV LTR region was present in the FPV strain used to vaccinate this flock. The 622-bp REV env gene nucleotide sequence derived from the trachea and neoplastic tissues was identical. Commercial ELISA of serum samples revealed that all chickens aged between 17 and 263 days in this flock were positive for REV but not for avian leukosis virus. Taken together, the evidence suggests that the visceral lymphomas were caused by a REV-integrated FPV field strain. FPV infections of commercial chickens should be followed up by careful monitoring for manifestations of REV infection, including lymphomas and immune depression, considering the ease with which the REV provirus appears to be able to integrate into the FPV genome.

The present report documents the occurrence of a poxvirus infection in commercial meat turkeys. The affected farm had six flocks, with a total of 11,680 birds at different ages; birds from two of these flocks were affected. The clinical picture was characterized by severe epithelial lesions and proliferations on the head and neck regions as reported for the cutaneous form of poxvirus infection. Except for these lesions, no adverse clinical signs or gross pathologic lesions were observed. Only a low number of birds was affected (n = 20) and no increase of mortality could be seen. Bacteriologic investigations from the lesions revealed multiresistant Staphylococcus aureus. Eosinophilic inclusions (Bollinger bodies) in histologic examinations in the cytoplasm of keratinocytes were noticeable. Typical pox virions were demonstrated by electron microscopy, and poxvirus was isolated on the chorioallantoic membrane of specific-pathogen-free chicken eggs. Further identification of the poxvirus species was carried out by PCR and sequencing, revealing an infection with the species fowlpox. Layers in vicinity of the turkey farm that also were affected by fowlpox were considered as potential source of infection. Although it is assumed that avian poxviruses are strongly species specific, the present case report reinforces the changing picture of poxvirus infections in turkeys. Furthermore, it supports the assumption of previous data that fowlpox virus has to be seen as recently emerging pathogen in turkeys.

Fowl poxvirus (FPV) infection was observed in unvaccinated backyard chickens. A total of 15 birds were affected in a flock of 37. Pock lesions were observed on the comb, eyelids, beak and wattles. The birds appeared sick with roughened feathers and stunted growth. No mortality was recorded. DNA was isolated from scabs and polymerase chain reaction (PCR) was performed to amplify the 4b core protein gene of FPV, the envelope (env) gene of reticuloendotheliosis virus (REV) and the region of FPV flanking REV 5´ long terminal repeat (LTR). Correct-size PCR products of 578 bp, 807 bp and 370 bp, respectively, were observed in agarose gel electrophoresis. Sequence analysis of these products suggests that the virus was an FPV with a genome containing an integrated near full-length REV provirus. Given the fact that REV has been associated with immunosuppression, its presence in the genome of FPV appears to play an important role in the pathogenesis of fowl pox and presumably prolongs persistence of FPV in bird populations. In the present case, fowl pox has been observed to have persisted for about three years in fowl that were reared in backyard systems in villages.

An unusual cutaneous fowl pox outbreak occurred in 8-wk-old broilers in California. Rounded and longitudinal, proliferative scratch-associated lesions were found only in feathered areas of the body. Both sides of the hip, the lower abdomen, pericloacal area, and lateral lower neck area were involved. The head, legs, feet, and toes did not have lesions. Birds in only one section of one of five houses were affected. Fifteen percent condemnations occurred in birds from the affected house due to the skin lesions. A diagnosis of fowl pox was achieved by histopathology, viral isolation, and direct electron microscopy. The unusual distribution of pox lesions was assumed to be associated with skin scratches. There was no evidence that mosquitoes or other types of insects were involved in this outbreak. To the knowledge of the authors, this is the first report of this kind of unusual fowl pox in the United States.

Two 1-mo-old local breed chickens, with gross lesions in the skin of the head region suspected to be fowl poxvirus infection, were submitted to the Diagnostic Laboratory of the School of Veterinary Medicine, Grenada, West Indies. Cutaneous lesions were collected from these birds for virus isolation, histopathologic diagnosis, and molecular analysis. Fowl poxvirus infection was confirmed by virus isolation in chicken embryo and by histopathology. Molecular characterization of the fowl poxvirus was conducted by PCR amplification of selected genomic fragments and by nucleotide sequencing. Integration of reticuloendotheliosis virus fragments into the fowl poxvirus genome was confirmed by PCR and DNA sequencing. This is the first report from the Caribbean region on the preliminary molecular characterization of a fowl poxvirus isolate.

The presence of avian pox in endemic birds in the Galápagos Islands has led to concern that the health of these birds may be threatened by avipoxvirus introduction by domestic birds. We describe here a simple polymerase chain reaction-based method for identification and discrimination of avipoxvirus strains similar to the fowlpox or canarypox viruses. This method, in conjunction with DNA sequencing of two polymerase chain reaction-amplified loci totaling about 800 bp, was used to identify two avipoxvirus strains, Gal1 and Gal2, in pox lesions from yellow warblers (Dendroica petechia), finches (Geospiza spp.), and Galápagos mockingbirds (Nesomimus parvulus) from the inhabited islands of Santa Cruz and Isabela. Both strains were found in all three passerine taxa, and sequences from both strains were less than 5% different from each other and from canarypox virus. In contrast, chickens in Galápagos were infected with a virus that appears to be identical in sequence to the characterized fowlpox virus and about 30% different from the canarypox/Galápagos group viruses in the regions sequenced. These results indicate the presence of canarypox-like viruses in endemic passerine birds that are distinct from the fowlpox virus infecting chickens on Galápagos. Alignment of the sequence of a 5.9-kb region of the genome revealed that sequence identities among Gal1, Gal2, and canarypox viruses were clustered in discrete regions. This indicates that recombination between poxvirus strains in combination with mutation led to the canarypox-like viruses that are now prevalent in the Galápagos.

A mixed breed rooster, from a backyard flock of 13 chickens, was received at California Veterinary Diagnostic Laboratory System-Turlock Branch for postmortem examination. The bird presented with thickened, featherless, scab-encrusted skin around the head region. Numerous sticktight fleas were found attached to the encrusted skin. Microscopic evaluation of the skin revealed a lymphoplasmacytic reaction in the dermis with visible embedded flea mouthparts. Also noted histologically in this region were epidermal hyperplasia and ballooned epidermal cells containing intracytoplasmic inclusions indicative of fowl poxvirus.

An unusual fowl pox outbreak occurred in two integrated broiler operations. The uncommon characteristic of this outbreak was that the pox lesions were manifested in the feathered parts of the body, mainly in the posterior dorsal area and external part of the thigh. Diagnosis was made by means of histopathology and virus isolation. Severe losses were incurred at the processing plant as a consequence of condemnation due to dermatitis. Vaccination of day-old chicks with mild fowl pox vaccine combined with Marek's disease (HVT) vaccine in the area of the outbreak appeared to be important in controlling the disease.

Avian pox is an important disease in birds of prey in Bahrain. A live pigeon pox vaccine was administered to hunting falcons (Falco species) together with other therapeutic methods to arrest the development of primary stage pox lesions and for the treatment of well established secondary stage pox lesions. Quarantine and general hygiene procedures were also used as an integral part of the management and control of the disease.

Poxvirus infection was diagnosed on the basis of gross and microscopic appearance plus the presence of typical inclusion bodies in a juvenile American green-winged teal (Anas crecca carolinensis) in Alaska. This constitutes the first known report of avian pox in migratory ducks and the first report of poxvirus infection in wild birds in Alaska.

An outbreak of avian pox, with an estimated 12-fold increase in the incidence of infection, occurred among wild bobwhites (Colinus virginianus) in the southwestern Georgia/northcentral Florida region. The outbreak was first detected in July, 1978, and continued at least until March, 1979. During this period, 26 separate clinical case accessions involving 43 bobwhites from 8 counties in Florida and Georgia were diagnosed as avian pox. A survey of 2,586 bobwhites from 6 southeastern states revealed avian pox infections in 312 bobwhites from Florida, Georgia, North Carolina, and Tennessee. Seventy-seven percent of the infected birds in the survey had only mild lesions on the legs and feet; however, 23% had more extensive lesions on the head. Severely affected birds had lesions around the eyes, nares, and in the mouth which impaired vision, respiration, and/or feeding. Infection rates were not related to age or sex of the birds but varied greatly among locales, even on adjoining properties. A morbidity rate of approximately 2% and a mortality rate between 0.6 and 1.2% were estimated for a 13,000 km2 region in Georgia and Florida.

California quail (Lophortyx californicus) from several locations in Oregon were examined seasonally between fall 1975 and summer 1978 for avian pox. Pox lesions were present on 66 of 256 (26%) birds from the E.E. Wilson Wildlife Area. None of the remaining 41 birds from other areas was infected. Rates of infection of males and females were equal; juveniles had a slightly, but not significantly, higher prevalence of pox than did adults.

Over a 7-year period in Trinidad, 9,514 birds were examined for avian pox and four species were found infected: the golden-headed manakin, Pipra erythrocephala (7% infected), the white-bearded manakin, Manacus manacus (5%), the violaceous euphonia Euphonia violacea (1%), and the bare-eyed thrush, Turdus nudigenis (less than 1%). The elaborate courtship displays of manakins may have a bearing on a "common source" type of infection. The apparently abrupt appearance of the disease at three localities in Trinidad in 1964 perhaps indicates introduction of the virus by migratory birds.

An introduced population of Merriam's wild turkeys (Meleagris gallopavo) was examined for poxvirus when birds were trapped from January through April in 1981 and 1982. Poxvirus lesions were found in three of 113 (2.6%) turkeys. All infected birds were immature males.

During a 6-week period at the San Diego Zoo, avian pox occurred in 9 pheasants representing 5 species. Lesions were limited to facial skin and consisted of epithelial cell hyperplasia, secondary inflammatory changes, and intracytoplasmic eosinophilic inclusion bodies which, by electron microscopy, were shown to contain pox virus. The disease was self-limiting in 7 pheasants, but 2 pheasants died. Free-ranging Indian red junglefowl were implicated as the source of the infection.

Lesions caused by an avian poxvirus were identified on the face and nares of fledgling white-tailed tropicbirds (Phaethon lepturus catesbyi) in the natural environment on Bermuda. Between 1958 and 1978, 6 of 81 fledglings found off the nest and unable to fly at departure time had lesions suggestive of poxvirus infection. More detailed nest-site surveys from 1974 to 1978 indicated an overall prevalence of less than 0.5%, involving the fledgling population only.

Atypical fowlpox occurred in several poultry farms in Kenya. On two occasions layers had their eyes closed and egg production dropped. Fowlpox virus was isolated from lesions on the inner surfaces of the closed eyelids. Other chickens had lesions covered by yellow caseous necrotic material in the mouth, around the epiglottis, and in the trachea and choanae. Typical proliferative cutaneous lesions were observed in birds of all ages in other flocks examined. Fowlpox virus was recovered from both cutaneous and diphtheritic lesions. The infected chorioallantoic membranes had focal hyperplastic lesions containing pink-staining intracytoplasmic inclusion bodies in most cells. Transmission studies showed that the virus was highly virulent to susceptible chickens.

An outbreak of avian pox in a bird research colony was reported. Although 10 species of passerine birds were housed within the facility, clinical signs and mortality were restricted to canaries and house sparrows. Post-mortem lesions initially occurred in the upper and lower respiratory tracts and were characterized by proliferative rhinitis, proliferative bronchopneumonia, and proliferative airsacculitis, and diphtheritic lesions occurring in the esophagus were characterized by proliferative granulomatous esophagitis. Cutaneous lesions occurred subsequently in some birds, and a diagnosis was made by histopathology, electron microscopy, and virus isolation. The occurrence of diphtheritic lesions in pox infections of wild birds has been rare, and a sparrow showed an unusual combination of both diphtheritic and acute systemic lesions previously undescribed.