Comparative response of turkeys and chickens to avian lymphoid leukosis virus

Response of turkeys and 151(5)x7(1) chickens to prenatal or neonatal inoculation with the avian leukosis virus RAV-1 was compared. Virus-inoculated turkeys and chickens developed viraemia and antibody to. RAV-1. Many of the chickens remained persistently viraemic through the duration of the experiment, whereas in turkeys viraemia was transient. Circulating antibodies were detected earlier in turkeys than in chickens. Inoculation of turkeys with RAV-1 resulted in a high incidence of inflammatory and lymphoproliferative, but non-neoplastic, lesions in various visceral organs, including spleen, pancreas, heart, bursa and thymus, 3 to 5 weeks after virus inoculation. The lesions in chickens were those typical after RAV-1 infection, i.e. neoplastic, and appeared after a latent period of 9 weeks.     

A new influenza A virus infection in turkeys

Summary In transmission experiments, the influenza A virus isolate turkey/ Ontario 7732/66 caused an acute disease in chickens and turkeys, but was apathogenic to ducks, geese and pigeons. After an incubation period from two to eight days, turkeys and chickens became rapidly depressed and died usually within the following four days. Other clinical signs were variable for the two gallinaceous species, such as exudative head swellings and gangrenous comb lesions in chickens, and diarrhea in turkeys. Infection by even minimal virus doses was fatal in turkeys, whereas chickens sometimes recovered from the disease or remained unaffected by the infection. Serial passage of the virus in chicken embryos accentuated this difference in species susceptibility still more. The infection spread easily by close contact among turkeys, but less among chickens.The signs and course of the disease by virus 7732 are compared to those described for classical fowl plague, and it is concluded that these two avian influenza virus infections cannot be differentiated by clinical criteria.     

An in-vivo infectivity assay for cloned retroviruses lacking a susceptible cell culture.

The lymphoproliferative disease virus (LPDV) of turkeys is the retroviral agent of etiology of a rapidly developing, naturally occurring, lymphoproliferative process. Recently we have molecularly cloned the viral genome. The lack of a susceptible cell culture which can sustain LPDV replication hampered the analysis of the infectious capability of the cloned genome. Based on the efficient in-vivo replication of LPDV we have developed a sensitive in-vivo approach aimed at establishing the infectious capability of the cloned provirus. According to this approach, peripheral leukocytes withdrawn from 3-week-old turkeys were transfected with the cloned DNA and the transfected leukocytes were re-injected into the turkey from which they had been obtained. The injected leukocytes enabled the efficient expression of the viral genome and the release into the blood stream of LPDV virions, which thereafter could travel to their appropriate in-vivo target lymphoid cells and start multiple replication cycles, resulting in the development of a detectable viremia. The applicability of this in-vivo assay for other cloned viral genomes is discussed.     

Host specificity of avian metapneumoviruses

To date, four subgroups of avian metapneumoviruses have been defined (AMPV-A, B, C and D) based on genetic and antigenic differences. The extent of infection in the three principal species (turkeys, chickens and ducks) by these subgroups is, however, not well defined. Here, a series of controlled and ethically approved experimental infections were performed in specific pathogen-free turkeys, chickens and ducks with each of the four AMPV subgroups. For subgroup C, one strain isolated from turkeys in the USA (turkey AMPV-C) and one isolated from ducks in France (duck AMPV-C) were compared. Globally, these extensive experimental trials demonstrated that AMPV-A, B, turkey C and D were well adapted to Galliformes, especially turkeys; however, chickens showed limited clinical signs and differences in seroconversion and transmission. Notably, chickens did not transmit AMPV-A to contacts and were shown for the first time to be susceptible to AMPV-D. The duck AMPV-C was well adapted to ducks; however, chickens and turkeys seroconverted and were positive by virus isolation. In addition, seroconversion of contact turkeys to duck AMPV-C demonstrated horizontal transmission of this virus in a non-palmiped species under our experimental conditions. Interestingly, in chickens and turkeys, duck AMPV-C isolation was possible despite a lack of detection of viral RNA. Likewise, the turkey AMPV-C virus was well adapted to turkeys yet was also isolated from chickens despite a lack of detection of viral RNA. These results would suggest a selection for viral genetic sequences that differ from the original strain upon adaptation to a ‘non-conventional host’.     

Diagnosis of lymphoproliferative disease virus infection of turkeys by an indirect immunofluorescence test

An indirect immunofluorescence (IIF) test for the detection of lympho-proliferative disease virus (LPDV) is described. Results presented show that smears of buffy coat cells and frozen sections of spleen, but not thymus, form suitable test materials for a rapid and specific diagnosis of LPDV infection of turkeys. Between 0.1 and 0.6% of buffy coat cells from infected birds were antigen positive, and spleens from 18/18 and thymuses from 11/18 birds respectively, tested 16 months after viral inoculation, were positive. Antisera containing group-specific antibodies to avian reticuloendotheliosis virus (REV) and avian sarcoma-leukosis virus (ASLV) did not cross-react with LPDV-infected buffy coat cells or spleens.     

Characterisation of lymphoproliferative disease virus of turkeys. Structural polypeptides of the C-type particles

Summary Lymphoproliferative disease virus of turkeys (LPDV), a C-type retrovirus, was shown to contain 3 major [32 kilodaltons (kd, p 32), 26 kd, 22/21 kd] and 2 minor (41 kd and 12 kd) polypeptides. Preliminary evidence suggests a glycoprotein of 76 kd (GP 76) and a major doublet polypeptide of 13.5/13 kd to be also of viral origin. Of these GP 76 was susceptible to bromelain action implying its surface location in the virion, while p 32, p 26 and p 13.5/13 were the main constituents of viral cores. p 13.5/13 bound an RNA probe, suggesting it to be the main constituent of viral ribonucleoprotein. p 22/21 was not cleaved by bromelain, and was absent in viral cores suggesting its intramembrane location between virion envelope and core. The polypeptide profile of LPDV is distinct from those of avian sarcomaleukosis viruses and avian reticuloendotheleosis viruses.     

Avian metapneumovirus infection of chicken and turkey tracheal organ cultures: comparison of virus–host interactions

Avian metapneumovirus (aMPV) is a pathogen with worldwide distribution, which can cause high economic losses in infected poultry. aMPV mainly causes infection of the upper respiratory tract in both chickens and turkeys, although turkeys seem to be more susceptible. Little is known about virus–host interactions at epithelial surfaces after aMPV infection. Tracheal organ cultures (TOC) are a suitable model to investigate virus–host interaction in the respiratory epithelium. Therefore, we investigated virus replication rates and lesion development in chicken and turkey TOC after infection with a virulent aMPV subtype A strain. Aspects of the innate immune response, such as interferon-α and inducible nitric oxide synthase mRNA expression, as well as virus-induced apoptosis were determined. The aMPV-replication rate was higher in turkey (TTOC) compared to chicken TOC (CTOC) (P?<?0.05), providing circumstantial evidence that indeed turkeys may be more susceptible. The interferon-α response was down-regulated from 2 to 144 hours post infection in both species compared to virus-free controls (P?<?0.05); this was more significant for CTOC than TTOC. Inducible nitric oxide synthase expression was significantly up-regulated in aMPV-A-infected TTOC and CTOC compared to virus-free controls (P?<?0.05). However, the results suggest that NO may play a different role in aMPV pathogenesis between turkeys and chickens as indicated by differences in apoptosis rate and lesion development between species. Overall, our study reveals differences in innate immune response regulation and therefore may explain differences in aMPV – A replication rates between infected TTOC and CTOC, which subsequently lead to more severe clinical signs and a higher rate of secondary infections in turkeys.     

Experimental assessment of the pathogenicity of the Newcastle disease viruses from outbreaks in Great Britain in 1997 for chickens and turkeys,and the protection afforded by vaccination

The Newcastle disease virus isolated from healthy turkeys in outbreak GB 97/6 was used to challenge 4-week-old turkeys and chickens, which were either not vaccinated or had received a single dose of Hitchner B1 live vaccine 14 days earlier, by one of the intramuscular, intranasal or contact routes. Similar experiments were done in 38-day-old turkeys and chickens using virus isolated from severely sick chickens in outbreak GB 97/1. All vaccinated chickens showed low but measurable immune responses 14 days after vaccination, but only three of the turkeys had detectable antibodies. No vaccinated turkey or chicken showed any clinical sign after challenge with either virus. The virus from healthy turkeys in outbreak GB 97/6 induced clinical signs in 12/30 unvaccinated turkeys after challenge and 7/30 died. In unvaccinated chickens, challenge with this virus produced clinical signs in 25/30 birds and 21/30 died. In challenge experiments with the virus from outbreak GB 97/1 in chickens, 3/30 unvaccinated turkeys showed clinical signs and all three subsequently died. In contrast, 30/30 unvaccinated chickens challenged with this virus showed clinical signs and died. Vaccination did not prevent infection and excretion of either challenge virus. However, when compared with unvaccinated birds, vaccination reduced significantly the length of time virus was excreted and the overall proportion of swabs that were positive.     

Distribution of viral antigen gp85 and provirus in various tissues from commercial meat-type and experimental White Leghorn Line 0 chickens with different subgroup J avian leukosis virus infection profiles.

Immunohistochemistry and polymerase chain reaction (PCR) were used to test for the presence of avian leukosis virus (ALV) J viral antigen gp85 and proviral DNA, respectively, in various tissues (adrenal gland, bone marrow, gonad, heart, kidney, liver, lung, pancreas, proventriculus, sciatic nerve, spleen, and thymus). Tissues were collected from 32-week-old commercial meat-type and Avian Disease and Oncology Laboratory experimental White Leghorn Line 0 chickens with the following different infection profiles: tV + A-, included in ovo-tolerized viraemic chickens with no neutralizing antibodies (NAbs) on any sampling; ntV + A-, included chickens that were viraemic and NAb-negative at the time of termination at 32 weeks post hatch, but had NAbs on up to two occasions; V+ A+, included chickens that were viraemic and NAb-positive at the time of termination at 32 weeks post hatch, and had NAbs on more than two occasions; V - A+, included chickens that were negative for viraemia and NAb-positive at the time of termination at 32 weeks post hatch, and had antibody on more than two occasions; V - A-, included chickens that were never exposed to ALV J virus. There was a direct correlation between viraemia and tissue distribution of gp85, regardless of the NAb status and strain of chickens, as expression of ALV J gp85 was noted in only viraemic chickens (tV + A-, ntV + A-, V+ A+), but not in non-viraemic seroconverted chickens (V - A+). Of the four oligonucleotide primers pairs used in PCR to identify ALV J provirus, only one primer set termed H5/H7 was useful in demonstrating ALV J proviral DNA in the majority of the tissues tested from non-viraemic, antibody-positive chickens (V - A+). The results suggest that PCR using primer pair H5/H7 is more sensitive than immunohistochemistry in identifying ALV J in chickens that have been exposed to virus, but are not actively viraemic.     

Direct (non-vector) transmission of West Nile virus in geese

During a recent epizootic, losses due to West Nile virus (WNV) infection in young goose flocks were estimated to be far greater than expected if mosquito-borne transmission was the principal route of infection. Contact transmission was investigated experimentally as an alternative explanation. A group of 10, 3-week-old geesewere inoculated subcutaneously and placed in one insect-proof room with 20 geese of the same age. A group of10 geese were housed in an adjacent insect-proof room to serve as an environmental control. All geese in theinoculated group produced antibodies, eight became viraemic and five died between 7 and 10 days afterinfection. Virus was shed from the cloaca and oral cavity by three geese. Two of the in-contact birds died ondays 10 and 17 after infection, and WNV was recovered from another three birds. None of the environmentalcontrol group became infected. This result strongly suggests that horizontal transmission of WNV can occur incommercial flocks and may be aggravated if cannibalism and feather-picking of sick geese occur.     

Suppression and enhancement of mitogen response in chickens infected with Marek''s disease virus and the herpesvirus of turkeys.

The kinetics of phytohemagglutinin (PHA) response of peripheral blood lymphocytes from chickens infected with oncogenic Marek's disease (MD) virus (MDV) or nononcogenic herpesvirus of turkeys (HVT) was studied with a whole blood microassay. At about 7 days after inoculation, a depression in PHA response was observed in MDV-inoculated resistant line N or susceptible line 7(2) chickens and in HVT-inoculated line 7(2) chickens. All chickens initially regained their PHA responsiveness. Susceptible chickens that died of MD or developed MD lymphoma in later stages of virus infection showed a second severe depression in PHA response. No depression was observed in HVT-vaccinated chickens when challenged with MDV. The PHA response of MDV-inoculated chickens that survived MD, HVT-inoculated chickens, and HVT-vaccinated MDV-challenged chickens showed evidence of enhancement. The depression of PHA response was studied and was attributed to the suppressive effect of macrophages on T-cell response, a finding consistent with our previous studies on MDV suppression of PHA response.     

Geese not susceptible to virulent subgroup J avian leukosis virus isolated from chickens

ABSTRACT

To determine whether geese are susceptible to infection by avian leukosis virus (ALV), 702 serum samples from domestic and foreign goose breeds were screened for p27 antigen as well as being inoculated into DF-1 cell cultures to isolate ALV. Although 5.7% of samples were positive for p27 antigen, reactivity appeared to be non-specific because no ALV was detected in the corresponding DF-1 cultures. To further determine whether geese are susceptible to ALV-J isolated from chickens, ALV-J strain JS09GY7 was artificially inoculated into 10-day-old goose embryos, with one-day-old hatched goslings then screened for p27 antigen and the presence of ALV. In all cases, the results of both tests were negative. Liver tissues from the 1-day-old goslings were screened using a polymerase chain reaction-based assay, which failed to amplify ALV-J gene fragments from any of the samples. Further, no histopathological damage was observed in the liver tissues. ALV-J was further inoculated intraperitoneally into one-day-old goslings, with cloacal swabs samples and plasma samples then collected every 5 days for 30 days. All samples were again negative for the presence of p27 antigen and ALV, and liver tissues from the challenged geese showed no histopathological damage and were negative for the presence of ALV-J gene fragments. Furthermore, p27 antigen detection, PCR-based screening, and indirect immunofluorescence assays were all negative following the infection of goose embryo fibroblasts with ALV-J. Together, these results confirm that virulent chicken-derived ALV-J strains cannot infect geese, and that p27 antigen detection in goose serum is susceptible to non-specific interference.     

Variations of four Aedes aegypti mosquito strains in their susceptibility to and transmissibility of Tahyna virus

Aedes aegypti mosquitoes originating from different colonies were infected with Tahyna virus by sucking on viraemic newborn mice (peak titre 10(2) X 5 mouse i.c. LD50/0.01 ml). The mosquitoes of laboratory strain "London" proved most susceptible (infection rate 74.2%, transmission rate 60%), while mosquitoes of the laboratory strain "Basel" and strain "Bangkok" (Southeast Asia) were less susceptible (infection rate 23.7 and 17.6%, respectively, transmission rate 6.0 and 10.0%, respectively). Mosquitoes of "Ifakara" strain (East Africa) were found resistant to Tahyna virus infection.     

Characterisation of two highly oncogenic strains of Marek's disease virus

The RB-1B and ALA-8 strains of Marek's disease (MD) virus, which were isolated from chickens with MD and which had been vaccinated with the herpesvirus of turkeys (HVT), were evaluated for their oncogenic potential in genetically susceptible (P-line) and resistant (N-line, PDRC) chickens. RB-1B and ALA-8 were both highly oncogenic, causing a high incidence of MD in both susceptible and resistant birds. Vaccination of P-line birds with SB-1 or HVT did not protect satisfactorily against RB-1B. However, a bivalent vaccine consisting of SB-1 and HVT enhanced protection significantly. HVT alone, and the bivalent vaccine, protected PDRC and N-line chickens well against RB-1B, but SB-1 was less protective in PDRC birds. HVT protected equally well against challenge with ALA-8 and the standard JM-10 strain. Differences in the pathogenesis of viral infection could not be detected among ALA-8, RB-1B and JM-10 between 4-7 days post-infection (d.p.i.). However, after d.p.i. 12 RB-1B caused significantly higher levels of viral internal antigen and virus isolation rates than did JM-10 in the same genetic strain. Prior vaccination prevented the expression of ALA-8 at 5 and 20 d.p.i., but not that of RB-1B. Pathogenetic events such as expression of VIA or level of virus infection appeared to be directly related to the level of protection observed in challenged birds.     

Role of cell-mediated immunity (CMI) in chickens inoculated with avian leukosis/sarcoma virus

Immunosuppression of chickens infected in ovo with avian leukosis virus (RAV-1) by the injection of antilymphocyte serum (ALS) did not significantly (P > 0.05) alter the incidence or distribution of lesions in chickens between 3 and 6 months of age as compared to control groups. Antilymphocyte serum treatment of Rous sarcoma virus [RSV (RAV-2)]-infected chickens significantly (P < 0.05) inhibited tumour regression and enhanced tumour metastasis. It was concluded that cell-mediated immunity was not a significant factor in effecting the survival of viraemic chickens Viraemic leukosis virus infected-chickens responded as well as normal chickens to sensitization to Mycobacterium tuberculosis H37Ra. The results were based on in vivo wattle tests and in vitro cell-mediated cytotoxicity assays. It was concluded that subclinical avian leukosis virus infection had no effect on the thymus-dependent lymphocyte (T-cell) population associated with cutaneous delayed hypersensitivity and cell-mediated cytotoxicity.     

In vitro and in vivo studies in chickens and turkeys on strains of turkey rhinotracheitis virus isolated from the two species

Some biological properties of two strains of turkey rhinotracheitis virus, isolated 10 years apart in South Africa, one from turkeys and one from chickens, have been compared. Whilst in vitro cross-neutralization tests showed them to be closely related antigenically they showed different in vivo properties. Both strains elicited an antibody response and caused clinical signs of infection in both chickens and turkeys although the signs tended to be more marked in the species from which the TRTV had been isolated initially. Replication of each virus strain occurred principally in the upper respiratory tract with little virus being recovered from other tissues. The chicken isolate replicated to very high titre (approximately log(10) 6.0 median ciliostatic doses of virus per g) in nasal tissue of both chickens and turkeys, whilst the turkey isolate was only recovered in such large amounts from nasal tissue of the turkeys. There appeared to be little difference in the clinical signs which the chicken isolate caused when seven different inbred chicken lines were inoculated intranasally with it.     

Generation and infectivity titration of an infectious stock of avian hepatitis E virus (HEV) in chickens and cross-species infection of turkeys with avian HEV

Avian hepatitis E virus (HEV), a novel virus identified from chickens with hepatitis-splenomegaly syndrome in the United States, is genetically and antigenically related to human HEV. In order to further characterize avian HEV, an infectious viral stock with a known infectious titer must be generated, as HEV cannot be propagated in vitro. Bile and feces collected from specific-pathogen-free (SPF) chickens experimentally infected with avian HEV were used to prepare an avian HEV infectious stock as a 10% suspension of positive fecal and bile samples in phosphate-buffered saline. The infectivity titer of this infectious stock was determined by inoculating 1-week-old SPF chickens intravenously with 200 microl of each of serial 10-fold dilutions (10(-2) to 10(-6)) of the avian HEV stock (two chickens were inoculated with each dilution). All chickens inoculated with the 10(-2) to 10(-4) dilutions of the infectious stock and one of the two chickens inoculated with the 10(-5) dilution, but neither of the chickens inoculated with the 10(-6) dilution, became seropositive for anti-avian HEV antibody at 4 weeks postinoculation (wpi). Two serologically negative contact control chickens housed together with chickens inoculated with the 10(-2) dilution also seroconverted at 8 wpi. Viremia and shedding of virus in feces were variable in chickens inoculated with the 10(-2) to 10(-5) dilutions but were not detectable in those inoculated with the 10(-6) dilution. The infectivity titer of the infectious avian HEV stock was determined to be 5 x 10(5) 50% chicken infectious doses (CID(50)) per ml. Eight 1-week-old turkeys were intravenously inoculated with 10(5) CID(50) of avian HEV, and another group of nine turkeys were not inoculated and were used as controls. The inoculated turkeys seroconverted at 4 to 8 wpi. In the inoculated turkeys, viremia was detected at 2 to 6 wpi and shedding of virus in feces was detected at 4 to 7 wpi. A serologically negative contact control turkey housed together with the inoculated ones also became infected through direct contact. This is the first demonstration of cross-species infection by avian HEV.     

Effects of avian viruses on cultured chicken bone-marrow-derived macrophages

Cultured chicken bone-marrow-derived macrophages have been assayed for their susceptibility to infection with various avian viruses. Three criteria of infection were employed: (1) Virus-induced alterations in cell morphology ; (2) presence of intracellular viral antigens detectable by immunofluorescence; (3) kinetics of virus release by infected macrophages. Macrophages proved to be resistant to Marek's disease virus (MDV), herpesvirus of turkeys (HVT-FC126), infectious bronchitis virus (IBV) and reticuloendotheliosis virus (REV). MDV included the pathogenic HPRS-16 strain prepared from feather follicles, and the apathogenic HPRS-24 strain adapted to growth in chick embryo fibroblast cultures. IBV included both embryo-propagated and tissue culture-adapted variants of the apathogenic Beaudette strain and a pathogenic Massachusetts-type strain. REV comprised the strains REV-C, CSV and oncogenic virus of the REV-F strain. Adenovirus, infectious laryngotracheitis (ILT) virus, reovirus, infectious bursal disease virus (IBDV) and Newcastle disease virus (NDV) replicated in macrophages causing different but characteristic cytopathic effects, or alterations in cell morphology associated with macrophage activation. The most prominent effect of IBDV and lentogenic NDV infection were morphological signs of macrophage activation, i.e. enlargement or 'transformation' of cells which tended to survive in infected cultures and were usually free of detectable amounts of immunofluorescent viral antigens. Macrophage cultures were less susceptible to infection with adenovirus (OTE strain), pathogenic ILT virus and lentogenic NDV (B1 strain) than permissive chicken kidney cell (CKC) cultures. In contrast, macrophage cultures were significantly more susceptible to infection with reovirus than CKC cultures, indicating that bone-marrow-derived macrophages might be the major target cells of this virus species. Virus restriction by cultured bone-marrow-derived macrophages was expressed to various degrees among the different avian virus species and among different strains of the same virus species, however, it was not generally correlated with the pathogenicity of these viruses in chickens.     

Lack of a threshold of genetic resistance to Marek's disease and the incidence of humoral antibody

On challenge exposure of genetically susceptible (Line 7) and genetically resistant (Line 6) chickens to graded doses of Marek's disease virus, Line 5 chickens were at least 10(6)-fold more resistant to clinical Marek's disease than Line 7 chickens. Hence, if there was a "threshold" of resistance of Line 6 chickens to the disease, it was not overcome by 10(6) times the dose of Marek's disease virus required to induce neoplastic response in Line 7. Approximately similar doses of virus were required to induce a precipitating and virus neutralizing antibody response in Lines 6 and 7, indicating that both types of chickens were equally susceptible to infection with Marek's disease virus. As opposed to the marked resistance of maternal antibody positive Line 6 chickens used above, maternal-antibody-negative chickens of this line were highly susceptible to clinical Marek's disease. Since the genetic homogeneity of maternal antibody positive and maternal antibody negative populations of Line 6 chickens was equivocal, the difference of Marek's disease susceptibility between the two populations could not with certainty be attributed to maternal antibody alone. Line 7 chickens that survived an infection with Marek's disease virus produced virus neutralizing antibody as did genetically resistant Line 6 chickens. In many susceptible chickens, the virus neutralizing antibody and nerve lesions coexisted. Agar gel precipitin, immunofluorescent, and virus neutralizing antibody tests on 50 sera from birds inoculated with Marek's disease virus indicated that virus neutralizing and immunofluorescent tests were more sensitive for detecting Marek's disease antibody than the agar gel precipitin test. Among the sera positive by all 3 antibody tests, titers of virus neutralizing and immunofluorescent antibody were higher than those of agar gel precipitin antibody.