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Biomedical subjects

R W Winterfield

Publications and source records attributed to R W Winterfield.

At least 37 records · Page 2Linked to original sources
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Immunity to infectious bronchitis virus from spray vaccination with derivatives of a Holland strain.

Study was made of the protection of chickens from spray vaccination with different modifications of a Holland (H) strain of infectious bronchitis virus (IBV). Noted in each trial were the virus-serum-neutralizing antibody titers induced and the virulence of the vaccine virus at different passage levels. Protection against respiratory signs was good from challenge with a homologous virus serotype as well as with 5 heterologous IBV isolates. This occurred from vaccinating day-old chicks possessing homologous IBV antibodies as well as vaccinating susceptible 4-week-old chickens. The tracheal virus shed-rate following challenge was considered low (20% or less) with 4 of the challenge viruses. The challenge virus shed-rate was somewhat higher from vaccination at one day old than from vaccination at 4 weeks; the virus-serum-neutralization titers were lower, or even insignificant, with early-age vaccination. The immunogenicity and virulence of the vaccine virus was apparently reduced in the higher embryo passages employed. None of the vaccine derivatives was considered virulent under these conditions.

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Vaccination and revaccination with a Holland (H) strain of infectious bronchitis virus.

One-day-old chickens possessing maternally derived immunity to Massachusetts-type infectious bronchitis virus (IBV) were vaccinated by the eyedrop route with a Holland (H) IBV strain of the Massachusetts type. Vaccination was done with the 72nd and 92nd passages in chicken embryos. Attenuation of the virus was done in the authors' laboratory. Four weeks postvaccination the immunity was challenged with 8 different IBV serotypes. A broad spectrum of protection from respiratory signs was obtained in each of the challenged groups (compared with unvaccinated controls). With 5 of the challenge viruses, protection against tracheal virus shed was good (70% or greater). Revaccination at 4 weeks old by the aerosol route with the 53rd and 72nd passages did not greatly enhance protection. However, the virus-serum-neutralizing (VN) titers with Massachusetts-type IBV as an indicator were high, and an anamnestic response was demonstrated at 8 weeks of age. The VN titers observed at 4 weeks old were generally low and did not correlate necessarily with the protection engendered.

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Role of the bursa of Fabricius in the pathogenicity of inclusion body hepatitis and infectious bursal disease viruses.

Chickens were chemically bursectomized with cyclophosphamide at 3 days old, and studies made of the effects of infection by inclusion body hepatitis virus (IBHV) and infectious bursal disease virus. In another experiment, 3-week-old chickens were infected with infectious bursal disease virus before inoculation with IBHV. Interference with the bursa of Fabricius by cyclophosphamide or by infectious bursal disease virus enhanced the pathogenicity of IBHV. In contrast, cyclophosphamide effects on the bursa protected chickens against infectious bursal disease.

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Pathogenesis of H13 nephropathogenic infectious bronchitis virus.

A nephropathogenic Massachusetts strain of infectious bronchitis virus (IBV) designated H13-IBV was isolated from the kidneys of commercial broilers. H13-IBV caused respiratory distress, depression, and diarrhea in specific-pathogen-free chickens. Gross renal lesions included pale coloration, swelling, and urate deposition. Histologic renal changes were interstitial mononuclear cell infiltration and degeneration and necrosis of tubular epithelial cells. Lesions in respiratory tissues included thickening and edema of the air sacs, congestion of the tracheal mucosa, and frothy serous exudate. Histologic tracheal lesions were deciliation, mucous gland distortion, inflammatory cell infiltration, and squamous metaplasia. Clinically, H13-IBV was highly pathogenic in birds infected at 1 day of age and mildly pathogenic in birds infected at 4 weeks of age. Kidney lesions were of marked severity only in birds infected at 1 day of age. Tracheal lesions were similar in severity in both age groups.

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Immune response and pathogenicity of different strains of infectious bursal disease virus applied as vaccines.

Eight strains of infectious bursal disease virus (IBDV) were characterized by the criteria of immunity and pathogenicity engendered in young chickens. Some strains have been used commercially, and the others are potential candidates for vaccines. They were administered by drinking water, eyedrop, vent drop, and subcutaneous and aerosol routes. The viruses varied widely in pathogenicity in terms of bursal damage, morbidity, and mortality. Immunity induced with different routes of administration also differed markedly when measured by challenge, virus serum-neutralizing antibody titers, and the agargel precipitin test. Maternally derived immunity interfered with stimulation of active immunity by some of the less pathogenic strains. The more virulent strains, however, were able to provide protection under similar circumstances, although bursal damage was frequently severe. Two strains proved relatively virulent by the criteria employed. Characteristics desirable for IBDV strains to be given as vaccines under field conditions to young chickens are discussed briefly.

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Mycobacterium infection in a gray-cheeked parakeet.

A gray-cheeked parakeet, approximately 3 years of age, was submitted for necropsy. Clinical signs included diarrhea, decreased feed consumption, fluffing of feathers, shivering, weight loss, and limping. Necropsy revealed enlargement and pale discoloration of the spleen and intestines. The liver contained multifocal pale foci. Granulomas, some of which had necrotic centers, were present along the subserosa of the intestinal tract. Microscopic examination revealed diffuse granulomatous splenitis, enteritis, and multifocal granulomatous hepatitis. Numerous acid-fast bacteria were demonstrated in the spleen, liver, and intestine.

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An outbreak of nephropathogenic H13 infectious bronchitis in commercial broilers.

A nephropathogenic Massachusetts strain of infectious bronchitis virus, designated H13-IB virus, was isolated from the kidneys of broilers in a commercial flock. Respiratory distress, diarrhea, depression, and high mortality were present. Gross renal lesions consisted of pale coloration, mottling, urate deposition, and swelling. The trachea contained a serous to catarrhal exudate. Microscopically, renal changes were primarily associated with the medullary region. Lesions included an interstitial mononuclear cell infiltration, urate deposition, edema, and degenerative and necrotic tubular changes. Tracheal changes included marked thickening of the mucosa, desquamation of ciliated and glandular epithelia and replacement with a stratified undifferentiated epithelium, and inflammatory cell infiltration.

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Relationship between delayed onset of egg production and involution of the bursa of Fabricius in White Leghorn chickens.

The relationship between delayed onset of oviposition and involution of the bursa of Fabricius is described. Chickens studied were 26 weeks of age and had not come into production. The bursae of nonlaying chickens were compared with those of age-matched chickens that had laid the first egg 1, 9 to 11, or 24 days before. The bursae from the nonlaying chickens were similar in weight and morphology to the functional bursae of immature pullets. Bursae of laying chickens, even on the day of the first egg, were markedly involuted. Age of the chicken was not a factor in determining bursal involution. The onset of egg production was directly related to bursal involution.

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Immunization against psittacine pox.

Pox virus isolated from psittacine birds was used as a vaccine in trials with love birds (Agapornis roseicollis). The vaccine was applied by wing-web puncture using single- and double-needle applicators. Immunity was effective against challenge with virulent psittacine pox virus administered via the feather follicle/thigh. When unvaccinated contact control birds were placed with the vaccinated individuals immediately post-vaccination, virus spread was evident. However, susceptible birds placed with vaccinated ones at 27 days postvaccination remained uninfected for 11 weeks. The importance of a high vaccine virus titer was observed.

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Comparison of the nephropathogenicity of four strains of infectious bronchitis virus.

Experiments were conducted to characterize renal lesions in chickens induced by four strains of infectious bronchitis virus (IBV); each has been described as nephropathogenic. Those strains were also compared in vaccinated and unvaccinated older chickens for nephropathogenicity. The younger birds were much more susceptible to the nephritogenic effects of the strains. All four strains produced acute renal changes consisting of tubular damage and interstitial inflammatory cell infiltration and edema. Although both cortex and medulla were involved, the latter was generally affected more severely. The Holte strain proved to be the least pathogenic, followed by the more pathogenic Gray and Italian strains and finally by the Australian strain. All four strains produced similar chronic renal changes in unvaccinated birds, with no correlation to the severity of lesions seen at the acute phase. Chronic active and inactive types of interstitial nephritis were seen at the chronic phase. Vaccinated birds challenged with the Australian strain had the highest prevalence of the chronic active type of interstitial nephritis. The implication of renal viral persistence in the development of chronic active interstitial nephritis is discussed.

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