Development of a Multiplex PCR Assay for Rapid Differentiation of Fowlpox and Pigeonpox Viruses

The aim of this study was to develop a multiplex PCR assay capable of rapidly differentiating two major Avipoxvirus (APV) species, Fowlpox virus (FWPV) and Pigeonpox virus (PGPV), which cause disease in bird species. Despite the importance of a rapid differentiation assay, no such assay exists that can differentiate the APV species without sequencing. To achieve this, species-specific target DNA fragments were selected from the fpv122 gene of FWPV and the HM89_gp120 gene of PGPV, which are unique to each genome. Nine samples collected from unvaccinated chickens, pigeons, and a turkey with typical pox lesions were genetically identified as FWPV and PGPV. The designed primers and target DNA fragments were validated using in silico analyses with the nucleotide Basic Local Alignment Search Tool. The multiplex PCR assay consisted of species-specific primers and previously described PanAPV primers (genus-specific) and was able to differentiate FWPV and PGPV, consistent with the phylogenetic outputs. This study represents the first successful differentiation of FWPV and PGPV genomes using a conventional multiplex PCR test. This assay has the potential to facilitate the rapid diagnosis and control of APV infections.

Isolation of Reticuloendotheliosis Virus from Chorio-allantoic Membrane of SPF Chicken Eggs inoculated with Fowl Pox Virus

Fowl Pox Viruses (FPV) infect chickens and turkeys giving rise to pock lesions on various body parts like combs, wattles, legs, shanks, eyes, mouth etc. The birds, affected with FPV, also show anemia and ruffled appearance which are clinical symptoms of Reticuloendotheliosis. Interestingly, the field strains of FPV are integrated with the provirus of Reticuloendotheliosis Virus (REV). Due to this integration, the infected birds, upon replication of FPV, give rise to free REV virions, causing severe immunosuppression and anemia. Pox scabs, collected from the infected birds, not only show positive PCR results upon performing FPV-specific 4b core protein gene PCR but also show positive results for the PCR of REV-specific env gene and FPV-REV 5'LTR junction. Homogenized suspension of the pock lesions, upon inoculating to the Chorio-allantoic Membrane (CAM) of 10 days old specific pathogen-free embryonated chicken eggs, produces characteristic pock lesions in serial passages. But the lesions also harbor REV mRNA or free virion, which can be identified by performing REV-specific env gene PCR using REV RNA from FPV-infected CAMs. The study suggests successful replication and availability of REV mRNA and free virion alongside the FPV virus, although the CAM is an ill-suited medium for any retroviral (like REV) growth and replication.

Whole-genome based strain identification of fowlpox virus directly from cutaneous tissue and propagated virus

Fowlpox (FP) is an economically important viral disease of commercial poultry. The fowlpox virus (FPV) is primarily characterised by immunoblotting, restriction enzyme analysis in combination with PCR, and/or nucleotide sequencing of amplicons. Whole-genome sequencing (WGS) of FPV directly from clinical specimens prevents the risk of potential genome modifications associated with in vitro culturing of the virus. Only one study has sequenced FPV genomes directly from clinical samples using Nanopore sequencing, however, the study didn't compare the sequences against Illumina sequencing or laboratory propagated sequences. Here, the suitability of WGS for strain identification of FPV directly from cutaneous tissue was evaluated, using a combination of Illumina and Nanopore sequencing technologies. Sequencing results were compared with the sequence obtained from FPV grown in chorioallantoic membranes (CAMs) of chicken embryos. Complete genome sequence of FPV was obtained directly from affected comb tissue using a map to reference approach. FPV sequence from cutaneous tissue was highly similar to that of the virus grown in CAMs with a nucleotide identity of 99.8%. Detailed polymorphism analysis revealed the presence of a highly comparable number of single nucleotide polymorphisms (SNPs) in the two sequences when compared to the reference genome, providing essentially the same strain identification information. Comparative genome analysis of the map to reference consensus sequences from the two genomes revealed that this field isolate had the highest nucleotide identity of 99.5% with an FPV strain from the USA (Fowlpox virus isolate, FWPV-MN00.2, MH709124) and 98.8% identity with the Australian FPV vaccine strain (FWPV-S, MW142017). Sequencing results showed that WGS directly from cutaneous tissues is not only rapid and cost-effective but also provides essentially the same strain identification information as in-vitro grown virus, thus circumventing in vitro culturing.

Identification of Clade E Avipoxvirus, Mozambique, 2016

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.

Detection and differentiation of re-emerging fowlpox virus (FWPV) strains carrying integrated reticuloendotheliosis virus (FWPV-REV) by real-time PCR

Current strains of fowlpox virus (FWPV) carrying circulating reticuloendotheliosis virus (FWPV-REV) sequence are becoming more pathogenic to poultry. This is evidenced by the fact that vaccination with current available FWPV vaccines provides limited protection against them. To characterize REV insertions in a collection of both older and more recent field isolates, we developed three different types of adjacent oligoprobes and primer sets from specific genomic locations of FWPV and REV: REV-ENV (accession no. K02537, 1382-2260), FWPV-REV integration site (accession no. AF006064, 86-1328), FWPV (accession no. AF198100, 232461-232670), and REV-LTR (accession no. V01204, 305-496). The data indicated that the primers from the REV-ENV region and the TaqMan probes specifically targeted REV-ENV sequences of FWPV-REV strains. Furthermore, the strains were differentiated based on quantitative melting temperature (T(m)) of their amplified products using FRET-based probes. The amplified products were further characterized by sequencing and multiple sequence alignment analysis. The results suggest that integrated REV-ENV sequences are both common and mostly conserved in field isolates. However, the minor variations found within the short-targeted ENV sequence from FWPV-REV strains suggest that these strains could have either undergone periodic point mutational changes or integration with different REV-ENV subtypes.

Development of a method for bacteria and virus recovery from heating, ventilation, and air conditioning (HVAC) filters

The aim of the work presented here is to study the effectiveness of building air handling units (AHUs) in serving as high volume sampling devices for airborne bacteria and viruses. An HVAC test facility constructed according to ASHRAE Standard 52.2-1999 was used for the controlled loading of HVAC filter media with aerosolized bacteria and virus. Nonpathogenic Bacillus subtilis var. niger was chosen as a surrogate for Bacillus anthracis. Three animal viruses; transmissible gastroenteritis virus (TGEV), avian pneumovirus (APV), and fowlpox virus were chosen as surrogates for three human viruses; SARS coronavirus, respiratory syncytial virus, and smallpox virus; respectively. These bacteria and viruses were nebulized in separate tests and injected into the test duct of the test facility upstream of a MERV 14 filter. SKC Biosamplers upstream and downstream of the test filter served as reference samplers. The collection efficiency of the filter media was calculated to be 96.5 +/- 1.5% for B. subtilis, however no collection efficiency was measured for the viruses as no live virus was ever recovered from the downstream samplers. Filter samples were cut from the test filter and eluted by hand-shaking. An extraction efficiency of 105 +/- 19% was calculated for B. subtilis. The viruses were extracted at much lower efficiencies (0.7-20%). Our results indicate that the airborne concentration of spore-forming bacteria in building AHUs may be determined by analyzing the material collected on HVAC filter media, however culture-based analytical techniques are impractical for virus recovery. Molecular-based identification techniques such as PCR could be used.

Retention of 1.2 kbp of 'novel' genomic sequence in two European field isolates and some vaccine strains of Fowlpox virus extends open reading frame fpv241

The emergence of variant fowlpox viruses (FWPVs) and increasing field use of recombinants against avian influenza H5N1 emphasize the need to monitor vaccines and to distinguish them from field strains. Five commercial vaccines, two laboratory viruses and two European field isolates were characterized by PCR and sequencing at 18 loci differing between attenuated FP9 and its pathogenic progenitor. PCR failed to discriminate between the viruses and sequence determination revealed no significant differences at any locus, except for a polymorphic locus encompassed by deletion 24 (9.3 kbp) in FP9. Surprisingly, 'novel' previously unreported sequence (spanning 1.2 kbp) was found in both European field isolates and three of the vaccines. It was absent from the other two vaccines, removed by a 1.2 kbp deletion identical to that surprisingly also observed in the completely sequenced genome of FPV USDA. This locus (H9) adds a potentially useful tool for discriminating between FWPV field isolates and vaccines.

Evaluation of immune effects of fowlpox vaccine strains and field isolates

The immune effects of fowlpox virus (FPV) field isolates and vaccine strains were evaluated in chickens infected at the age of 1 day and 6 weeks. The field isolates and the obsolete vaccine strain (FPV S) contained integrated reticuloendotheliosis virus (REV) provirus, while the current vaccine strain (FPVST) carries only REV LTR sequences. An indirect antibody ELISA was used to measure the FPV-specific antibody response. The non-specific humoral response was evaluated by injection of two T-cell-dependent antigens, sheep red blood cells (SRBC) and bovine serum albumin (BSA). There was no significant difference in the antibody response to FPV between chickens infected with FPV various isolates and strains at either age. In contrast, antibody responses to both SRBC and BSA were significantly lower in 1-day-old chickens inoculated with field isolates and FPV S at 2-3 weeks post-inoculation. Furthermore, cell-mediated immune (CMI) responses measured by in vitro lymphocyte proliferation assay and in vivo using a PHA-P skin test were significantly depressed in chickens inoculated with field isolates and FPV S at the same periods. In addition, thymus and bursal weights were lower in infected chickens. These immunosuppressive effects were not observed in chickens inoculated with the current vaccine strain, FPVST, at any time. The results of this study suggest that virulent field isolates and FPV S have immunosuppressive effects when inoculated into young chickens, which appeared in the first 3 weeks post infection. REV integrated in the FPV field isolates and FPV S may have played a central role in the development of immunosuppression.

Pathology of Cutaneous Fowlpox with Amyloidosis in Layer Hens Inoculated with Fowlpox Vaccine

Cutaneous fowlpox occurring in vaccinated layer hens was investigated pathologically and microbiologically. Anorexia, decrease of egg production, increased mortality, yellow scabs on faces, and alopecia of feathered skins with yellow scabs were observed in affected hens. Histologically, proliferative and necrotic dermatitis with eosinophilic ring-shaped cytoplasmic inclusions (Bollinger bodies) and clumps of gram-positive cocci (Staphylococcus hyicus) were noted in the affected birds. Fowlpox lesions were primarily observed in the feathered skins. Proliferation of feather follicle epidermal cells, with cytoplasmic inclusions and degeneration of the feather, and bacterial clumps in the feather follicles were noted in the affected skins. Ultrastructurally, characteristic fowlpox viral particles were observed in the cytoplasmic inclusions of hyperplastic epidermal cells. Amyloid deposition was observed in the Disse space of the liver, splenic sinus, and lamina propria of the bronchiolar, bronchial, and tracheal areas. Amyloidosis could be one factor inducing the fowlpox infection in vaccinated chickens.

Construction and characterization of a fowlpox virus field isolate whose genome lacks reticuloendotheliosis provirus nucleotide sequences

Fowlpox virus (FWPV) has been isolated from vaccinated chicken flocks during subsequent fowlpox outbreaks that were characterized by a high degree of mortality and significant economic losses. This inability of current vaccines to induce adequate immunity in poultry could be reflective of an antigenic and/or biologic distinctiveness of FWPV field isolates. In this regard, whereas an infectious reticuloendotheliosis virus (REV) provirus is present in the majority of the field viruses' genomes, only remnants of REV long terminal repeats (LTR) have been retained in the DNAs of each vaccine strain. Although it has not been demonstrated whether the partial LTRs can provide an avenue for FWPV to reacquire the REV provirus by homologous recombination, utilizing viruses of which genomes lack any known integrated retroviral sequences could resolve concern over this issue. Therefore, such an entity was created by genetically modifying a recently isolated field strain of FWPV. This selection, in lieu of a commercial vaccine virus, as the progenitor was based on the probability that a virus circulating in the environment would be more antigenically similar to others in this locale and thus might be a better candidate for vaccine development. A comparison in vivo of the pathogenic traits of the parental wild-type field isolate, its genetically modified progeny, and a rescue mutant in whose genome the REV provirus was inserted at its previous location, indicated that elimination of the provirus sequence correlated with reduced virulence. However, even with elimination of the parasitic REV, the modified FWPV was still slightly more invasive than a commercial vaccine virus. Interestingly, both types of attenuated FWPV elicited a similar degree of antibody production in inoculated chickens and afforded them protection against a subsequent challenge by a field virus, the origin of which was temporally and geographically distinct from that of the progenitor strain. Due to its antigenicity being retained despite a decrease in virulence, this REV-less FWPV could potentially be developed as a vaccine against fowlpox.

CHARACTERIZATION OF CANARYPOX-LIKE VIRUSES INFECTING ENDEMIC BIRDS IN THE GALÁPAGOS ISLANDS

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.

Detection of specific reticuloendotheliosis virus sequence and protein from REV-integrated fowlpox virus strains

The detection is described of reticuloendotheliosis virus (REV) protein in tissue culture of chicken embryonated cells (CEFs) infected with field isolates of fowl poxvirus (FPV). By the polymerase chain reaction (PCR), five out of the six field isolates, but two out of the seven vaccine strains of FPV, were found to have had a 291 bp repeat sequence of REV-LTR integrated in their genomic DNA. An immunofluorescence (IF) method was employed using a monoclonal antibody (MAb) known to specify strain common envelope proteins for REV and allowed to detect the presence of a specific REV protein. The IF results indicate the localization of REV proteins in boundaries defined precisely within cells infected with these field strains of FPV carrying REV (FPV-REV). Furthermore, by immunoblotting (IB) using a chemiluminescent detection kit, the REV protein reacted specifically with the MAb and had a relative molecular mass (RMM) of 62 kDa. The data have the potential to advance substantially the current understanding of the integrated REV in FPV strains; and the identification of a unique protein associated with variant forms of FPV will also offer great potential for identification of novel vaccine candidates for use in poultry against variant forms of FPV.

Development of a monoclonal blocking ELISA for the detection of antibodies against fowlpox virus

To provide a fast and easy method to detect antibodies against fowlpox virus (FWPV) particularly in high numbers of chicken sera we established a monoclonal blocking enzyme-linked immunosorbent assay (ELISA). We chose two different monoclonal antibodies (mAb), anti-FWPV 3D9/2B3 and anti-FWPV 8F3/2E11, which are both directed against the 39-kDa protein of FWPV strain HP-1. The blocking ELISA depends on the blocking of mAb binding to solid-phase antigen in the presence of positive serum. For an epidemiological study a total of 184 serum samples from Gambian chicken flocks were analysed against each of the mAbs. Four of the sera were shown to contain FWPV antibodies. These four sera showed a positive cut-off value of more than 50% inhibition exclusively in the test against the mAb anti-FWPV 8F3/2E11. This phenomenon can be explained by the binding of the mAbs to distinct epitopes on the same protein.

Serological monitoring on layer farms with specific pathogen-free chickens

To monitor the existence of avian pathogens in laying chicken flocks, specific pathogen-free (SPF) chickens were introduced into two layer farms and reared with laying hens for 12 months. SPF chickens were bled several times after their introduction and examined for their sero-conversion to avian pathogens. As a result, antibodies to eight or ten kinds of pathogens were detected in SPF chickens on each farm. Antibodies to infectious bronchitis virus (IBV), avian nephritis virus, Mycoplasma gallisepticum and M. synoviae were detected early within the first month. Antibody titer to IBV suggested that the laying chickens were infected with IBV repeatedly during the experiment on both farms. However, antibodies to infectious bursal disease virus and 6 pathogens were not detected.

Application of the polymerase chain reaction for the diagnosis of fowl poxvirus infection

The polymerase chain reaction (PCR) was used to amplify a 578-bp fragment of the fowl poxvirus (FPV) genome and with a set of primers framed a region within the gene coding for 4b core protein. An amplified product was detected with six strains of FPV, whereas none was obtained from uninfected cell cultures, skin tissue or four unrelated avian pathogens. The sensitivity of PCR was tested with nucleic acids from the FPV-infected cell cultures. The detection limit was 10(-1) TCID50 in an ethidium bromide-stained gel. In addition, this assay system was used to detect FPV in tissue specimens of skin and respiratory swabs collected from commercially reared chickens. The identity of the amplification products from the tissue specimen preparations was determined further by using a simple, rapid procedure in which an internally nested, end-labeled probe was used.

Comparative immunological and genomic characterization of fowlpox virus isolates

Chickens infected with fowlpox virus (FPV) IVRI vaccine strain and two field isolates collected from clinical cases of disease (Bareilly isolate and Panchmahal isolate) produced humoral antibody response after 2nd week post-infection, with a noticeable variation in degree of immune response. Serum antibody titre peaked at 4th week post-infection with a titre of 25,600, 25,600 and 51,200 being detected in ELISA and neutralization index of 2.75, 2.43 and 3.12 in serum neutralization test (SNT) with IVRI vaccine strain, Panchmahal isolate and Bareilly isolate, respectively. Cellular immune response was detected as early as 1st week post-infection by leukocyte migration inhibition test (LMIT). Per cent migration inhibition too peaked at 4th week with a value of 40.30 +/- 3.45, 36.93 +/- 4.11 and 45.45 +/- 3.66 being detected with the three viruses respectively. The Hind III and Hae III restriction fragment profile of viral DNA showed almost similar pattern both in vaccine strain and two field isolates. Hind III digestion produced 47 well resolved fragments of sizes between 24.30 and 1.20 kb and the total genomic size was estimated to be between 305.81 and 306.06 kb. Hae III digestion revealed 34 well resolved fragments of sizes between 27.55 and 1.32 kb. The three viruses could not be differentiated on the basis of their genomic restriction pattern. However immunogenic and antigenic differences were noticed by ELISA and SNT tests.

Isolation of poxvirus from debilitating cutaneous lesions on four immature grackles (Quiscalus sp.)

Poxvirus was isolated from nodules on four immature grackles (Quiscalus sp.) collected in two residential areas of Victoria, Texas. All of the birds were emaciated and had nodules on the eyelids, bill, legs, toes, and areas of the skin on the wings, neck, and ventral abdomen. These pox nodules were extensive and probably interfered with both sight and flight. The preliminary diagnosis was confirmed by virus isolation, histopathology, and electron microscopy. Poxvirus was isolated on the chorioallantoic membrane of embryonated hen's eggs and in Muscovy duck embryo fibroblast cell culture. Phaenicia calliphoridae (blowfly) larvae were found in one of the pox nodules, raising the possibility of mechanical transmission of the virus by contaminated adult blowflies.

An improved dot-blot method for virus detection in chicken embryo fibroblast cultures

A simplified dot-blot procedure is described for the detection of fowlpox virus (FPV) in infected monolayers of chicken embryo fibroblasts (CEF) cultured in 96-well microtiter plates. The relative resistance of DNA to hot NaOH, which hydrolyzes other macromolecules including RNA and protein, was exploited to solubilize virus infected cells and denature intracellular DNA in a simple, quick manner. Moreover, there was no need to purify virus or isolate viral DNA from cellular DNA prior to dot blotting. After incubation of CEF with FPV, the extracellular fluid from infected cells was collected for storage in 96-well microtiter plates. The remaining cell monolayers in each well were then solubilized with hot NaOH. The solubilized and denatured DNA was transferred to a nylon membrane using a dot-blot vacuum filtration manifold. Hybridization was carried out with a 32P-labeled FPV DNA probe. With this methodology it was possible to detect specific viral DNA sequences following the infection of cell monolayers with as little as 1 infectious unit per well. The ability to detect specific viral DNA sequences in infected cells, without the need to isolate pure viral DNA, made it possible to analyze large numbers of samples in a single experiment. Moreover, sufficient fowlpox virus was present in the extracellular media from each well for further amplification and analysis of selected samples.

Detection of fowlpox virus DNA by in situ hybridization using a biotinylated probe

In situ hybridization was applied to detect fowlpox virus (FPV) DNA in formalin-fixed paraffin-embedded sections of the skin from infected chickens by using a biotinylated probe and a streptavidin-alkalinephosphatase conjugate. The immunohistochemical examination was applied to compare the distribution of the FPV DNA to that of related antigenic protein in serial sections. In the infected epithelial cells, FPV DNA was detected in cytoplasmic inclusion bodies and in the rest of cytoplasm. Likewise, immunohistochemical examination revealed the virus antigen in cytoplasm. Ultrastructurally, virions were observed in the cytoplasmic inclusion bodies, and immature virus particles were in the rest of the cytoplasm. The study proved restricted distribution of FPV DNA in the cytoplasm.

Structural proteins of two different plaque-size phenotypes of fowlpox virus

Structural polypeptides of two plaque-purified variant isolates of fowlpox virus differing in plaque morphology and size were examined by Coomassie blue-staining and immunoblot analysis of purified virions. A total of 30 structural polypeptides were observed, ranging in molecular weight from 14,100 to 122,600. A late polypeptide of 36,400 molecular weight was quite prominent in the small-plaque clone but absent in the large-plaque clone. Two other polypeptides, of 33,700 and 34,800 molecular weight, were present in virions from large-plaque virus and cell lysates of both clones but were absent in the small-plaque virions. These differences were observed whether the viruses were grown in chorioallantoic membrane or in chicken embryo fibroblast cultures. No difference was observed between the growth curves of the two virus clones. Differences observed in the polypeptides of the two viruses may be due to changes in the less conserved regions of viral DNA and may be used for differentiation of virus isolates.

Pathogenicity and immunogenicity of mynah pox virus in chickens and bobwhite quail

An avian pox virus was isolated from cutaneous proliferative lesions removed from greater hill mynahs (Gracula religiosa) imported from Malaysia. Cutaneous inoculation of specific pathogen-free chickens and bobwhite quail with the mynah pox virus resulted in severe proliferative cutaneous lesions similar to those seen in the naturally infected mynah birds. Microscopically, the reaction in the chickens and quail at sites of virus inoculation was characterized by marked epithelial hyperplasia with ballooning degeneration and formation of cytoplasmic inclusion bodies. Inoculation of conjunctival and oral mucosae of chickens by applying pox virus with a cotton swab did not result in gross or microscopic lesions. In cross-protection studies, chickens and bobwhite quail immunized with either quail, fowl, pigeon, turkey, or psittacine pox vaccines were not protected from challenge with mynah pox virus. Following vaccination of quail and chickens with mynah pox virus vaccine, there was no resistance to challenge by quail, fowl, pigeon, turkey, or psittacine pox viruses. Significant protection against development of lesions following inoculation with mynah pox virus was attained only when the homologous virus was used as a vaccine.

Studies on pathogenesis of fowl pox: virological study

One-month-old WLH chickens were inoculated with a field isolate of fowl pox virus (FPV) by intradermal (i.d.) and intratracheal (i.t.) routes. In intradermally infected chickens, the virus in titrable amounts was first detected in the skin at the inoculation site on day 2 and in lungs on day 4 followed by viraemia on the day 5 post-infection (p.i.). Subsequently the virus was recovered from liver, spleen, kidney and brain, but not from the heart. The chickens infected by i.t. route showed an almost similar outcome with minor differences as the virus was first demonstrated in the lungs on day 2 p.i., viraemia occurred on day 4 p.i. Initiation of pocks at the inoculation site in i.d. infected birds was observed on days 3 to 4 p.i., generalized cutaneous pock lesions appeared from 7 to 8 days p.i.

Infection and immunity with a virus isolate from turkeys

Avian pox virus was isolated from cutaneous pox lesions removed from turkey breeders that had been vaccinated three times with a commercial fowl pox vaccine. In three cross-immunization experiments with turkeys and two with chickens, the turkey pox isolate, designated NC5271, proved immunologically different from fowl, pigeon, and quail pox viruses. Significant protection against NC5271 virus infection and inducement of pox lesions was only attained when the homologous isolate was used as a vaccine. The potential need in the field for such a vaccine was discussed.

Avian pox: infection and immunity with quail, psittacine, fowl, and pigeon pox viruses

Quail, chickens, and turkeys vaccinated with pigeon and fowl pox viruses were not protected against challenge of their immunity with quail pox virus and they developed severe cutaneous lesions of pox. When quail and chickens were vaccinated with quail pox virus and given pigeon and fowl pox challenge viruses, no protection was present. Thus, quail pox virus had no immunologic relationship to pigeon and fowl pox viruses. Psittacine pox virus applied as a vaccine in quail and chickens also failed to protect against quail pox virus challenge. However, quail, chickens, and turkeys vaccinated with quail pox virus were protected against quail pox virus challenge. An isolate of psittacine pox virus, applied as a vaccine, protected chickens against challenge with the same virus isolate and also against challenge with two other psittacine pox virus isolates, confirming a close or identical antigenic relationship with each other. When combined in a multivalent vaccine, quail, psittacine, and fowl pox viruses induced excellent protection in chickens against challenge with the three respective viruses. The presence or absence of "takes" or reactions following vaccination by the wing web route did not necessarily correlate with the presence or absence of immunity noted from challenge by feather follicle virus application. The role of quail and psittacine pox viruses as potential pathogens for poultry was discussed briefly.

Psittacine pox virus: virus isolation and identification, transmission, and cross-challenge studies in parrots and chickens

An avian pox virus was isolated from Amazon parrots dying with severe diphtheritic oral, esophageal, and crop lesions. The virus was propagated on chorioallantoic membranes (CAM) of 10-day-old chicken embryos, and a homogenate of the infected CAM was rubbed vigorously onto the conjunctiva, oral mucosa, and defeathered follicles of two healthy Amazon parrots and three conures. All experimental birds developed cutaneous and ocular pox lesions, and one parrot developed oral pox lesions. Specific-pathogen-free chicks inoculated with the virus isolate developed skin lesions identical to those of the parrots. Chickens vaccinated with fowl and pigeon pox vaccines and inoculated with the psittacine isolate developed lesions typical of avian pox. Chickens vaccinated with the psittacine virus were susceptible to fowl and pigeon pox virus infection. This pox virus isolate may thus be regarded as a potential pathogen for chickens.

Fowlpox virus in the Sudan

A virulent fowlpox virus was isolated from a natural outbreak of the disease in the Sudan. The virus was used for experimental transmission of the disease to susceptible chickens. Scarification and intravenous methods were used to infect one-month-old chickens. Scarification induced typical pox lesions at 5-7 days postinoculation, whereas intravenous injection induced only swelling of combs or wattles, at 10-11 days postinoculation, although neutralizing antibodies against fowlpox virus were detected 2, 3, and 4 weeks postinoculation. The histopathological features of the pox lesions obtained in both natural and experimental infection were described.

Pox infection among captive peacocks

An outbreak of avian pox was detected among captive peacocks (Pavo cristatus) at Baghdad Zoological Park during spring, 1978. A total of 45 of the 60 birds in the aviary developed pox lesions around the beaks and eyes. Morbidity was 75% and mortality was 13%. A virus isolated from the skin lesions produced large plaques on the chorioallantoic membrane of developing chicken embryos and induced cytopathic effect characteristic for pox viruses in chicken embryo cell cultures. The virus neither haemagglutinated nor haemadsorbed to chicken erythrocytes. It was ether resistant and chloroform sensitive. Chickens inoculated with the virus by scarification developed localized pox-like lesions, while turkeys had only transient swelling of feather follicles at the site of inoculation. Virus partially purified with Genetron 113 was precipitated by antisera to fowlpox and pigeon pox viruses.

TRANSMISSION OF AVIAN POX FROM STARLINGS TO ROTHCHILD'S MYNAHS

Several wild species of birds, including starlings (Sturnus vulgaris), house sparrows (Passer domesticus) and pigeons (Columba livia) gained access to an aviary housing Rothchild's mynahs (Leucospar rothchildii) and over 100 additional birds representing a variety of species. Six of approximately 15 mynahs became infected with avian pox and all of them died. None of the other birds in the aviary developed lesions. Pox virus was isolated from mynah facial lesions on chicken chorioallantoic membrane and in duck embryo fibroblast cell culture. It did not produce lesions in white Leghorn chickens, but did produce lesions in 4 of 11 wild starlings captured outside the aviary. Results indicated the agent was an indigenous starling pox capable of infecting and producing disease in mynah birds. Destruction of the captive starlings and isolation of the remaining mynahs immediately stopped the mortality.