Feather-pulp lesions in chickens with naturally occurring Marek's disease lymphomas

Feather pulps of 15-to-35-week-old chickens with Marek's disease (MD) lymphomas were examined histopathologically. Of the 64 chickens, 59 (92.2%) had lymphoproliferative (T-type) lesions in the feather pulp. The T-type feather-pulp lesion (FPL) occurred in all regions, but more frequently in the upper column of the pulp. Severe lesions were distributed throughout the feather pulp. Some of the T-type FPLs regressed to inflammatory lesions consisting of necrosis or loss of constituent cells, edema, and infiltration by small lymphocytes, heterophils, and plasma cells. The regressive T-type FPL was usually diffuse throughout the tumorous lesions, but proliferative foci were often seen concomitantly with regressive lesions. The grade and histologic picture of T-type FPLs in chickens correlated well with those of the visceral lymphomas. These findings suggest that the severity of MD lymphoma is predictable without autopsy by examining feather-pulp samples.     

Ocular lesions in chickens inoculated with Escherichia coli.

Specific-pathogen-free chickens (two, four and ten weeks of age) which were inoculated via the air sac with Escherichia coli developed ocular lesions. Histologically, the main ocular lesions consisted of hyphema, hemorrhages of the iris, hypopyon, keratitis and uveitis. Hyphema was associated with hemorrhages of the iris, and hypopyon with keratitis and uveitis. Cyclophosphamide treatment enhanced the incidence and severity of hyphema and hemorrhages of the iris in the chickens.     

Marek's disease vaccination of chickens

Interpretive summaries of interesting articles on veterinary pharmacology are provided by the Pharmacology Chapter of the Australian College of Veterinary Scientsts     

Cyclophosphamide-induced amelioration of Marek's disease in Marek's disease-susceptible chickens.

Bursa- and thymus-dependent functions were examined in Marek's disease (MD)-susceptible normal chickens and in chickens treated with 5 and 16 mg of cyclophosphamide (CY) at the time of hatching. Chickens not exposed to Marek's disease virus (MDV) and treated with CY temporarily lost mitogenic response to concanavalin A but regained full response after 5 weeks. Bursa-dependent functions, such as presence of germinal centers in spleen and cecal tonsils, morphologic features of bursa, and sheep red blood cell antibody response were completely lost in chickens treated with 16 mg of CY and only partly retained in chickens treated with 5 mg of CY. In chickens exposed to MDV, the degree of thymus-dependent spleen cell mitogenic response was directly related to frequency and severity of MD. Chickens treated with 16 mg of CY had a mild mitogenic depression and low frequency and severity of MD lesions, whereas those treated with 5 mg of CY and those not treated had marked mitogenic depression and high frequency and severity of MD. Suppressions of bursa- and thymus-dependent functions by MDV alone were also evident when comparing MDV-exposed and nonexposed chickens. The results also indicate that presence of small, residual amounts of humoral factor(s) may enhance MDV oncogenesis.     

Serum protein changes in chickens with experimental Marek's disease

Serum protein alterations in chickens contact-exposed to Marek's Disease Virus (MDV) were studied by crossed immunoelectrophoresis. Total protein values of infected chickens were initially, i.e. in the 4th week, low and later not significantly changed from those of the controls. In all infected chickens a significant increase was seen in the IgG components. Three of 6 infected chickens showing a prolonged period of clinical illness presented the most pronounced changes in other serum proteins, moderate or drastic decrease of albumin and alpha-1 lipoproptein and marked increase of arc 24 glycoprotein. Ceruloplasmin and C3 complement beta-1-C and beta-1-A were also increased in infected chickens. No such changes were seen in sera from control chickens. The significance of these changes with reference to previous work and induced pathology is discussed.     

Kidney lesions associated with mortality in chickens inoculated with waterfowl influenza viruses

Seventy-six type A influenza viruses recovered from waterfowl in Wisconsin, California, South Dakota, Florida, Texas, Alabama, and Nebraska were tested for virulence in chickens. The challenge to chickens was intravenous inoculation of first-, second-, or third-egg-passage virus. Each of the virus strains was tested separately in three or four chickens. Eighteen of the 76 viruses caused the death of one or more chickens following inoculation. Postmortem lesions were similar in all dead birds. In decreasing order of frequency, gross lesions included: swollen kidneys evident as accentuated lobular patterns, urates in the pericardial sac, and urates on the surface of the liver. Microscopic lesions present in kidneys were consistent with visceral gout. Mortality was associated with inoculations having higher concentrations of infectious virus. These results indicate that the influenza A viruses circulating in duck populations may include strains potentially pathogenic for chickens.     

Pathogenesis of Marek's disease in chickens with maternal antibody.

Histopathological lesions were studied in chickens with maternal antibody against MD virus at 14-day intervals after their exposure by contact to HPRS-16 of MD virus in the first-day of life. The first lesions occured 14 days after infection in the liver, kidney, heart, brain and the sciatic nerves. Relatively, the most expressive changes were observed between 56th and 70th day after infection. Lesions were characterized as light to heavy infiltrations formed by immature and mature pleomorphic mononuclear cells. Among these cells myeloid type cells occured too. In some cases expressive tumorous lesions with intensive mitosis were observed mainly in the liver. Intranuclear inclusion bodies were also observed mainly among the proliferating epithelial cells of the proventriculus. 14-days after infection changes in the brain were classified as nonpurulenta encephalitis. Gross lesions characteristic of MD occured the most frequently in the gonads, liver and the kidney. In one case 56 days after infection herpesvirus-like particles were observed by electron microscopy in the tumorous gonads and liver. They measured about 200 to 260 nm in diameter. Degraded and/or aberrant incompleted virus-like particles occured the most often and completed (enveloped) ones with electrondense nucleoids were observed occasionally. It was concluded that MD in chickens with materanal antibody against MD virus shows monophasis progress.     

Chronological observations of Marek's disease-associated feather-pulp lesions in field chickens

Fourteen test groups consisting of a total of 541 field chickens in six rearing farms, all of which were vaccinated with turkey herpesvirus at one day old, were investigated for chronological changes in Marek's disease (MD)-associated feather-pulp lesions (FPL) and their association with nuclear-inclusion (NI) formation in the feather-follicle epithelium (FFE) and with incidence of MD. The FPL observed were categorized into R1-type (non-tumorous lymphoid lesion), R2-type (inflammatory lesion consisting of plasma cellular infiltration, edema or collagenosis of the pulp, and germinal-center formation) and T-type (tumorous lymphoproliferative lesion). In every test group, the incidence of R1-type lesions was highest at 2-4 weeks of age, in spite of the low incidence of NI formation in the FFE. The initial R1-type lesions were generally transitory and were followed occasionally by R2-type lesions. In each test group, incidence of NI formation in the FFE peaked between 9 and 16 weeks of age. The second peak of incidence of R1-type lesions coincided with the period of peak NI formation. Subsequent skin samples revealed that the incidences of R1-, R2-, and T-type lesions in individual chickens or test groups were closely related to the incidence of NI in the FFE and to the incidence of MD.     

Effect of diluting Marek's disease vaccines on the outcomes of Marek's disease virus infection when challenged with highly virulent Marek's disease viruses

Dilution of Marek's disease (MD) vaccines is a common practice in the field to reduce the cost associated with vaccination. In this study we have evaluated the effect of diluting MD vaccines on the protection against MD, vaccine and challenge MD virus (MDV) kinetics, and body weight when challenged with strains Md5 (very virulent MDV) and 648A (very virulent plus MDV) by contact at day of age. The following four vaccination protocols were evaluated in meat-type chickens: turkey herpesvirus (HVT) at manufacturer-recommended full dose; HVT diluted 1:10; HVT + SB-1 at the manufacturer-recommended full dose; and HVT + SB-1 diluted 1:10 for HVT and 1:5 for SB-1. Vaccine was administered at hatch subcutaneously. One-day-old chickens were placed in floor pens and housed together with ten 15-day-old chickens that had been previously inoculated with 500 PFU of either Md5 or 648A MDV strains. Chickens were individually identified with wing bands, and for each chicken samples of feather pulp and blood were collected at 1, 3, and 8 wk posthatch. Body weights were recorded at 8 wk for every chicken. Viral DNA load of wild-type MDV, SB-1, and HVT were evaluated by real time-PCR. Our results showed that dilution of MD vaccines can lead to reduced MD protection, reduced relative body weights, reduced vaccine DNA during the first 3 wk, and increased MDV DNA load. The detrimental effect of vaccine dilution was more evident in females than in males and was more evident when the challenge virus was 648A. However, lower relative body weights and higher MDV DNA load could be detected in chickens challenged with strain Md5, even in the absence of obvious differences in protection.     

Immunological aspects of Marek's disease in chickens with maternal antibodies]

The dynamics of the production of immunoprecipitation antibodies to Marek's disease virus was studied in the serum of chickens with maternal antibodies in relation to the occurrence of the immunoprecipitation antigens of Marek's disease virus in feather follicles. One-day-old chickens were infected by the contact method with Marek's disease virus. The first occurrence of immunoprecipitation antigen was detected on the 14th day after infection and this occurrence persisted throughout the experiment, i. e. until the 112th day after infection. The antibodies were first detected the 28th day after infection and their titre kept rising until the 98th day after infection. Immunoprecipitation antibodies and antigens of Marek's disease virus were detected in some tumorously changed kidneys. Immunoelectrophoretic examination revealed in the same kidneys immunoglobulins of the class IgY, IgA and beta-globulin. The slowest-migrating fraction of IgY, together with IgA, beta-globulin and C-reactive protein were detected in the skin extracts from infected poultry. Indirect haemagglutination enabled the detection of the presence of haemagglutination antibodies in rabbit immunoglobulin to the skin antigen of Marek's disease virus, and in avian immunoglobulin to the same virus. Haemagglutination antigen was revealed in the extract from tumorously changed kidneys.