Antibody response to and maternal immunity from an experimental psittacine beak and feather disease vaccine.

Adult umbrella cockatoos, Moluccan cockatoos, African grey parrots, and a yellow-headed Amazon parrot were inoculated IM or SC with beta-propiolactone-treated psittacine beak and feather disease (PBFD) virus. Thirty- to 45-day-old African grey parrot, umbrella cockatoo, and sulphur-crested cockatoo chicks also were vaccinated with the same inoculum. The hemagglutination inhibition (HI) and agar-gel diffusion tests were used to assay for post-vaccination development of anti-PBFD virus antibodies. All adult vaccinates seroconverted and had increases in HI and precipitating antibodies. The vaccinated chicks had increased concentrations of HI antibodies, but precipitating antibodies could not be detected. To demonstrate that chicks from vaccinated hens are protected from PBFD virus challenge, 3 African grey parrot chicks and 2 umbrella cockatoo chicks from vaccinated hens and 1 African grey parrot chick and 1 umbrella cockatoo chick from nonvaccinated hens were exposed to purified PBFD virus. Chicks from the vaccinated hens remained clinically normal during the 50-day test period. Chicks from the nonvaccinated hens developed clinical and histologic lesions of PBFD. Infected tissues from these birds were confirmed to contain viral antigen, using immunohistochemical staining techniques. The PBFD virus was recovered from the affected birds. These findings indicate that adult and 30- to 45-day-old psittacine birds will seroconvert following vaccination with beta-propiolactone-treated PBFD virus. Also, hens inoculated with beta-propiolactone-treated PBFD virus produce chicks that are, at least temporarily, resistant to virus challenge.     

Laboratory diagnosis of psittacine beak and feather disease by haemagglutination and haemagglutination inhibition

SUMMARY Simple and sensitive haemagglutination and haemagglutination Inhibition assays were developed for psittacine beak and feather disease (PBFD) virus and serum antibody, respectively. The assays were used in the examination of samples from 73 birds clinically affected with PBFD. High antigen titres (log₂ 9 to log₂ 12) were detected In feathers, faeces and cloacal contents of PBFD-affected birds. Antigen was not detected In either faecal or feather samples from 20 normal galahs (Eolophus roselcapillus) and 9 normal sulphur crested cockatoos (Cacatua galerita). After kaolin treatment and haemadsorption of serum, haemagglutination inhibition (HI) antibody titres could not be detected in serum from 42 PBFD-affected birds, whereas serum HI titres from 64 normal psittacine birds ranged from less than log₂ 1 to log₂ 8. Serum and yolk HI antibody responses of 6 PBFD virus-inoculated layer hens were measured. Pre-inoculation chicken sera contained high concentrations of non-specific haemagglutination inhibitors (not detected in chloroform-extracted yolk), which were removed by kaolin treatment and haemadsorption.     

Routes and prevalence of shedding of psittacine beak and feather disease virus.

Psittacine beak and feather disease (PBFD) virus was recovered from the feces and crop washings from various species of psittacine birds diagnosed with PBFD. High concentrations of the virus also could be demonstrated in feather dust collection from a room where 22 birds with active cases of PBFD were being housed. The virions recovered from the feces, crop, and feather dust were confirmed to be PBFD virus by ultrastructural, physical, or antigenic characteristics. Virus recovered from the feather dust and feces hemagglutinated cockatoo erythrocytes. The specificity of the agglutination was confirmed by hemagglutination inhibition, using rabbit antibodies against PBFD virus. During the test period, 26% (8 of 31) of the birds screened were found to be excreting PBFD virus in their feces, and 21% (3 of 14) of crop washings were positive for PBFD virus. Some birds in the sample group had active cases of diarrhea, whereas others had normal-appearing feces. Diarrhea was found to be the only significant indicator of whether a bird was likely to be excreting virus from the digestive tract. These findings suggest that exposure of susceptible birds to PBFD virus may occur from contact with contaminated feather dust, feces, or crop secretions. Viral particles that were morphologically similar to parvovirus (20- to 24 nm-icosahedral nonenveloped virions) also were recovered from feces of some of the birds.     

Vaccination and challenge studies with psittacine beak and feather disease virus

SUMMARY: Psittacine beak and feather disease virus (PBFDV) was administered to adult galahs ( Eolophusroselcapillus ) by mouth or by intramuscular injection. Concentration of PBFDV antibodies in serum and excretion of PBFDV were monitored by haemagglutlnation inhibition (HI) and haemagglutination (HA) respectively. After oral administration, 17 of 18 galahs remained clinically normal and a small rise in antibody titre was detected in 3 of 18 birds. After intramuscular administration, antibody was detected in all birds. PBFDV was not detected in the feather dander of birds in either group. One bird developed diarrhoea and high faecal HA titres within 4 days of oral administration and then died. Adult and nestling cockatoos were vaccinated with an experimental inactivated double-oil emulsion vaccine. PBFDV antibody responses are comparable to those induced by a primary-oil emulsion vaccination regimen using Freund's adjuvants. Both vaccines protected nestlings. Three sibling wild-caught sulphur-crested cockatoos were vaccinated but died of PBFD before experimental challenge despite antibody responses in all birds. Unvaccinated control chicks developed acute PBFD within 4 weeks of challenge, probably from PBFDV-induced hepatitis since high concentrations of PBFDV were detected in their livers.     

A universal polymerase chain reaction for the detection of psittacine beak and feather disease virus.

A universal PCR assay was designed that consistently detected psittacine beak and feather disease virus (BFDV) in psittacine birds affected with psittacine beak and feather disease (PBFD) from different geographic regions across Australia. Primers within open reading frame 1 (ORF1) of the BFDV genome consistently amplified a 717 bp product from blood and/or feathers of 32 birds with PBFD lesions. The PCR did not amplify a product from the feathers or blood from 7 clinically normal psittacine birds. Primers based on regions outside of ORF1 did not consistently produce a PCR product, suggesting there was some genomic variation outside ORF1. The amplified ORF1 PCR products of 10 BFDV isolates, from different psittacine species and from various regions around Australia, were cloned and comparative DNA sequence analysis demonstrated 88-99% of the ORF1 fragments. The derived amino acid sequences of the amplified ORF1 fragments demonstrated similar identity between all 10 isolates. Within ORF1, there was complete conservation of the putative nucleotide binding site and marked conservation of 2 other motifs previously identified as essential components of the replication-associated proteins of other circoviruses and geminiviruses.     

Severe leukopenia and liver necrosis in young African grey parrots (Psittacus erithacus erithacus) infected with psittacine circovirus

This paper describes the signs, clinical pathology, and postmortem findings in 14 young African grey parrots (Psittacus erithacus erithacus) that were naturally infected with psittacine beak and feather disease (PBFD) virus (psittacine circovirus). All but two of the parrots had severe leukopenia at clinical presentation. Two other parrots also had severe anemia. All birds died within 3 wk after presentation. Postmortem examination documented liver necrosis in 11 of 14 birds and secondary bacterial or fungal infections in 9 of 14 birds. Tests for Chlamydia psittaci, polyomavirus, and Salmonella sp. were negative. PBFD viral infection could be demonstrated in all birds by polymerase chain reaction. Supporting evidence of PBFD viral infection was gathered by histologic examination of the bursa of Fabricius, electron microscopy, and DNA in situ hybridization. Electron microscopic examination of both the bursa of Fabricius and liver revealed virus particles resembling circovirus. DNA in situ hybridization of six liver tissue samples confirmed the presence of PBFD virus and excluded the presence of avian polyomavirus. Our findings suggest that a specific presentation of peracute PBFD viral infection, characterized by severe leukopenia, anemia, or pancytopenia and liver necrosis in the absence of feather and beak abnormalities, may occur in young African grey parrots.     

Beak and feather disease virus haemagglutinating activity using erythrocytes from African Grey parrots and Brown-headed parrots

Psittacine beak and feather disease (PBFD) is a common viral disease of wild and captive psittacine birds characterized by symmetric feather loss and beak deformities. The causative agent, beak and feather disease virus (BFDV), is a small, circular single-stranded DNA virus that belongs to the genus Circovirus. BFDV can be detected by PCR or the use of haemagglutination (HA) and haemagglutination inhibition (HI) assays that detect antigen and antibodies respectively. Erythrocytes from a limited number of psittacine species of Australian origin can be used in these tests. In South Africa, the high cost of these birds makes them difficult to obtain for experimental purposes. Investigation into the use of erythrocytes from African Grey parrots and Brown-headed parrots yielded positive results showing the haemagglutinating activity of their erythrocytes with purified BFDV obtained from confirmed clinical cases of the disease. The HA activity was further confirmed by the demonstration of HI using BFDV antiserum from three different African Grey parrots previously exposed to the virus and not showing clinical signs of the disease.     

Psittacine beak and feather disease: a first survey of the distribution of beak and feather disease virus inside the population of captive psittacine birds in Germany

Psittacine beak and feather disease (PBFD) is the most common viral disease of wild and captive psittacine birds. Here, we designed the first survey to investigate the existence of subclinical infections and the distribution of the causative agent named beak and feather disease virus (BFDV) inside the population of captive psittacine birds in Germany. DNA was isolated from feathers of 146 symptom-free birds from 19 different genera (all psittaformes) taken from 32 independent breeders from all over Germany. The presence of BFDV was analysed by performing polymerase chain reaction assays. Fifty-eight (39.2%) samples were found to be positive for BFDV. As expected, there was no significant predominance of one sex to be infected with BFDV.     

Psittacine beak and feather disease virus in budgerigars and ring-neck parakeets in South Africa

Psittacine beak and feather disease (PBFD) is a common disease of the psittacine species and is caused by the psittacine beak and feather disease virus (PBFDV). In this study the occurrence of the disease in ring-neck parakeets and budgerigars in South Africa suffering from feathering problems, using polymerase chain reaction as a diagnostic test was investigated. The genetic variation between viral isolates was also studied. Results indicate that PBFDV can be attributed to being the cause of feathering problems in some of the ring-neck parakeets and budgerigars in South Africa. Genetic variation of isolates occurs between species and individuals. A cheap and easy to use method of blood sample collection on filter paper for diagnostic purposes was also evaluated. It proved to be less stressful to the birds and did not inhibit further processes.     

Production and characterization of monoclonal antibodies to psittacine beak and feather disease virus.

Monoclonal antibodies specific for the virus that causes psittacine beak and feather disease (PBFD) were produced by fusing spleen cells from mice immunized with purified concentrated PBFD virus with mouse myeloma cell line Sp2/0. The resulting hybridomas were tested for reactivity against whole purified virus by an enzyme-linked immunosorbent assay (ELISA) system. Four clones, designated 15H8, 8E3, 11G12, and 2C3, were subcloned by limiting dilution. Isotyping indicated that clone 15H8 was secreting IgG, whereas the remaining clones secreted IgM. The secreted immunoglobulins were characterized by reactivity against purified PBFD virus using immunoblotting procedures, by immunohistochemical staining of virus-induced lesions in infected tissues, and by inhibition of PBFD virus agglutination of cockatoo erythrocytes. Antibodies secreted by clones 15H8 and 8E3 had the strongest activity against purified whole virus. Only immunoglobulin secreted by the clone 15H8 could be used to detect viral antigen in infected tissues. None of the monoclonal antibodies had hemagglutination-inhibition activity.     

The sensitivities of various erythrocytes in a haemagglutination assay for the detection of psittacine beak and feather disease virus

The erythrocytes of various species were tested in psittacine beak and feather disease (PBFD) virus haemagglutination (HA) and haemagglutination inhibition assays to determine which are suitable for use in these assays. HA activity was observed for erythrocytes of the salmon-crested cockatoo, the sulphur-crested cockatoo, the umbrella cockatoo, the goffin's cockatoo and the cockatiel, with differences amongst individuals within species, but not for erythrocytes of humans, the pig, the guinea pig, the chicken, the goose, the rose-ringed parakeet or the budgerigar. Anti-PBFD virus rabbit sera inhibited the virus-induced agglutination of erythrocytes, confirming the specificity of HA activity. This suggests that selection of suitable psittacine species as well as suitable individuals within a species is necessary when obtaining erythrocytes for the PBFD virus HA assay.     

Serum antibody responses of chickens following sequential inoculations with different infectious bronchitis virus serotypes

Sequential inoculations of chickens with different live infectious bronchitis virus (IBV) antigenic types had major effects on virus-neutralization (VN) and hemagglutination-inhibition (HI) serum antibody responses. Antibody production in IBV-inoculated chickens that were reinoculated 8 weeks later with heterologous virus was largely directed against the virus used for initial inoculation rather than the virus used for reinoculation. In addition, chickens inoculated sequentially with IBV produced a broadened spectrum of serum antibodies that reacted with IBV types to which the birds had never been exposed (JMK and Florida). Chickens inoculated sequentially with heterologous IBV tended to produce higher levels of cross-reacting antibody than birds given homologous virus inoculations. Levels of cross-reacting antibodies were lower than levels of specific antibodies directed against viruses that the birds had received. Limited studies indicated that birds with cross-reacting antibodies were not protected against challenge with the virus that the cross-reacting antibody was directed against. Implications of the research for interpreting serological data from commercial chicken flocks are discussed.     

Immunological response of chickens to eastern equine encephalomyelitis virus

The dominant immunoglobulin against eastern equine encephalomyelitis (EEE) virus and its duration and the longevity of the EEE virus haemagglutination inhibition (HI) antibodies were determined in sentinel and 125 immunised and hyperimmunised domestic chickens by enzyme-linked immunosorbent assay and the HI test respectively. The chickens ranged in age from 10 weeks to 18 months, were of varied pedigrees and from different countries. Results show that the HI antibody (IgG) is short-lived. It peaks and disappears within 30 days. The secondary response is dominated by the IgM immunoglobulin which is relatively long-lasting. These results are contrary to classical expectations and were observed in all the chickens studied. If these observations are found to be characteristic of birds generally, the present standard method of EEE virus seroepidemiological surveillance must be modified to be effective.     

福建省部分地区鹦鹉喙羽病的分子流行病学调查及其病原Cap蛋白抗原表位预测

为了解2017—2018年鹦鹉喙羽病在福建省某些地区鹦鹉中的流行情况,收集了福建省部分地区298份鹦鹉粪便样品,采用PCR方法进行粪便样品检测,对其中鹦鹉喙羽病病毒检测呈阳性的5个地区的样品进行衣壳蛋白(Cap)基因测序后比较其同源性,绘制系统进化树,分析氨基酸序列,并通过生物信息学及序列分析软件预测Cap蛋白二级结构及B细胞抗原表位。结果显示:鹦鹉喙羽病病毒的平均阳性率为41.28%,福州市某动物救助站和福州动物园的阳性率较高,分别为65.17%和64.29%,其次为三明动物园、福州市花鸟市场和福州市某鹦鹉繁殖基地,南平动物园的阳性率最低;所测5个毒株Cap基因与GenBank中新西兰株(AY518913)亲缘关系较近;Cap蛋白有丰富的二级结构和多处抗原指数较高的区域,具有潜在的B细胞抗原表位,位于5~27、110~127和141~153位氨基酸残基或其附近。研究结果对防控鹦鹉喙羽病,保障鹦鹉健康养殖有重要参考意义。     

Serological evaluation of some psittaciformes for budgerigar fledgling disease virus

Breeding psittaciform birds (psittacines) from three geographically separated aviaries experiencing fledgling mortality were monitored during 1983 and 1984 for specific serum antibody to budgerigar fledgling disease virus (BFDV) using a fluorescent-antibody virus-neutralization test. Neither the time nor the extent of exposure to the virus was known. Serological titers were positive in 45% of birds sampled from Aviary 1, 25% from Aviary 2, and 11% from Aviary 3. Several species of psittacine birds within each aviary were serologically positive for BFDV. The results indicated that a papovavirus similar to BFDV appears to infect a wide range of captive adult psittacine birds. Macaws (Ara sp. and Anodorhynchus sp.) were evaluated for distribution of infection. Each species within these two genera showed positive serological titers to BFDV. Three groups of birds showed a decrease in serum antibody titer to BFDV at 1 and 2.5 months after the first sampling. Positive titers decreased from 66 to 20% for one group and from 60 to 50% for a second group in 1 month, and they decreased from 42 to 17% for a third group in 2.5 months.     

Serodiagnosis of western equine encephalitis virus infections: relationships of antibody titer and test to observed onset of clinical illness

Sera from horses and human beings with clinically diagnosed western equine encephalitis (WEE) virus infections were tested for hemagglutination-inhibition (HI), complement-fixation (CF), and neutralizing (N) antibody to WEE virus. These tests confirmed infection in 43.8% (HI), 56.3% (CF), and 80.4% (N) of horses and 54.5% (HI), 59.1% (CF), and 77.3% (N) of human beings. Use of the N test as an adjunct to the HI and CF tests increased the likelihood of serologic confirmation to 91.7%. In both horses and human beings, N antibody increased steeply at the end of the 1st week after onset. The results suggested that the presence of a high HI, CF, and/or N antibody titer in a single serum obtained from horses during the acute phase of illness caused by WEE virus can be used as presumptive evidence for infection with this virus.     

Extracutaneous viral inclusions in psittacine beak and feather disease

Thirty-five birds that died with naturally acquired psittacine beak and feather disease (PBFD) were necropsied to identify extracutaneous viral inclusions. Inclusions were found in various tissue sections from 34 of 35 birds. By immunoperoxidase staining, intranuclear and intracytoplasmic inclusion bodies were shown to contain PBFD viral antigen. Inclusion-bearing lesions were widely disseminated but often closely associated with the alimentary tract. Lesions within the palate, esophagus, crop, intestine, bursa of Fabricius, and liver probably serve as sources for viral shedding into the feces.     

Evaluation of the infectivity, length of infection, and immune response of a low-pathogenicity H7N2 avian influenza virus in specific-pathogen-free chickens

The H7N2 subtype of avian influenza virus (AIV) field isolate (H7N2/chicken/PA/3779-2/97), which caused the 1997-98 AIV outbreak in Pennsylvania, was evaluated for its infectivity, length of infection, and immune response in specific-pathogen-free (SPF) chickens. The composite findings of three clinical trials with various concentrations of virus indicated that this H7N2 subtype contained minimal pathogenicity for chickens. The concentration of the virus in the inoculum proved critical in the establishment of a productive infection in a chicken. Seven-day-old SPF chickens were not infected when inoculated with 10(0.7-2.0) mean embryo lethal dose (ELD50) of the H7N2 virus per bird. At this dose level, the immune response to this virus was not detected by the hemagglutination-inhibition (HI) test. Nonetheless, chickens at ages of 5 and 23 wk old tested were successfully infected when exposed to 10(4.7-5.7) ELD50 of H7N2 infectious doses per bird by various routes of administration and also by direct contact. Infected birds started shedding virus as early as 2 days postinoculation, and the period of virus shedding occurred mostly within 1 or 2 wk postinoculation (WPI). This H7N2 subtype of AIV induced a measurable immune response in all birds within 2 wk after virus exposure. Antibody titers were associated with AIV infectious doses and age of exposure of birds. Challenge of these infected birds with the same H7N2 virus at 5 and 10 WPI indicated the infective virus was recoverable from cloacal swabs at 3 days postchallenge and disappeared thereafter. In these challenged birds, the antibody levels as measured by the HI test spiked within 1-2 wk.     

Latent infection and subsequent reactivation of pseudorabies virus in swine exposed to pseudorabies virus while nursing immune dams

The ability of pseudorabies virus (PRV) to infect and establish latency in pigs with passively acquired (maternal) antibody for PRV was tested by exposing such pigs to the virus and subsequently attempting to reactivate latent virus by administering large doses of dexamethasone. Pigs of each of 4 litters that had nursed gilts with relatively high (512, gilts 1 and 2), moderate (32, gilt 3), and no (less than 2, gilt 4) serum titers of virus-neutralizing (VN) antibodies for PRV were allotted to 3 treatment groups (A, B, C) when they were 2 weeks old. Group-A pigs were separated from littermates and dam and thereafter kept in isolation; group-B pigs were experimentally exposed oronasally to PRV and 1 hour later returned to their dam; group-C pigs were kept with their dam and potentially exposed to PRV by contact with littermates of group B. Sera obtained from pigs at selected intervals until they were 17 weeks old were tested for VN activity and for precipitating activity for radiolabeled viral proteins. All group-A pigs remained clinically normal throughout the experiment. Depending on the initial amount of passively acquired antibody, little or no serum VN or precipitating activity remained by the time these pigs were 17 weeks old. Group-B and -C pigs, with relatively high amounts of passively acquired antibody when exposed to PRV, also remained clinically normal. However, most became latently infected as subsequently evidenced by either dexamethasone-induced or noninduced virus reactivation. Noninduced reactivation may have been initiated by weaning the pigs when they were about 8 weeks old.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection of pigeon circovirus by polymerase chain reaction

Pigeon circovirus was identified by polymerase chain reaction (PCR) in young pigeons belonging to 12 different lofts. Viral DNA was extracted from formalin-fed, paraffin-imbedded tissues containing primarily bursa and occasionally liver and spleen with a commercial kit. PCR primers were selected from a published sequence for columbid circovirus and evaluated in a PCR assay. The histopathologic examination of various tissues revealed basophilic globular intracytoplasmic inclusions in the mononuclear cells of the bursa of Fabricius and occasionally in the spleen characteristic for a circovirus. Transmission electron microscopy of a few bursas of Fabricius revealed virus particles measuring 18-21 nm. All the samples were negative by PCR for psittacine beak and feather disease (PBFD) virus and chicken infectious anemia virus. The primers for both pigeon circovirus and PBFD virus did not react in PCR with the chicken anemia virus DNA. Most of the circovirus-infected pigeons had concurrent infections of Escherichia coli, Salmonella, Pasteurella, Aspergillus, candidiasis, nematodiasis, or capillariasis.