PubMed Health⌕ Search

Biomedical subjects

D H Thornton

Publications and source records attributed to D H Thornton.

53 records · Page 3Linked to original sources
PubMed1979

Comparison of two infectious bursal disease vaccine strains: efficacy and potential hazards in susceptible and maternally immune birds.

Two infectious bursal disease vaccines were administered to separate groups of maternally immune and susceptible chickens at various ages. Vaccine B caused no damage to the bursae of chickens examined histologically at nine and 20 days after vaccination. The bursae of chickens given vaccine A were shown to be severely damaged when similarly examined. Both vaccines protected all the susceptible groups against challenge, but only vaccine A protected the groups of maternally immune chickens. Susceptible chickens vaccinated at one day of age with vaccine A showed a lowered response to Hitchner B1 Newcastle disease vaccine given at 14 days of age, judged by the haemagglutination-inhibition response and Newcastle disease challenge. The performance of the Newcastle disease vaccine was not affected in chickens given vaccine B. Bedding used by birds given vaccine A was shown to be capable of transmitting vaccinal virus to susceptible chickens, causing severe bursal damage.

Animals↗
PubMed1979

Measurement of immunosuppression in chickens caused by infectious bursal disease vaccines using Brucella abortus strain 19.

The serological response of chicks to Brucella abortus strain 19 was monitored over a period of seven weeks to assess the degree of immunosuppression caused by vaccination at one day of age with two infectious bursal disease vaccines. One of the vacy. This vaccine caused severe immunosuppression judged by the minimal serological response following B abortus inoculation. The test also detected a significant delay caused by the other vaccine in the development of the serological response but the maximum titre was not significantly different from that in chicks which had received no infectious bursal disease vaccine.

Animals↗
PubMed1976

Standard requirements for vaccines against infectious bursal disease.

A variety of criteria must be considered when examining the suitability of preparations of live infectious bursal disease (IBD) virus for use as vaccines: identity and purity of the vaccine strain, lack of spread, or of tendency to revert to virulence, lack of immunosuppressive effect, safety and potency. Arguments as to th identity of IBD virus are well documented, and after ensuring that the virus strain is in fact IBD virus, it must be ascertained that it is free from contaminating agents. If the vaccine strain spreads, lack of reversion to virulence must be determined by several direct chick to chick passages: histological observations of bursae from first and final passages must be made to ensure that no change has occurred. In order to formulate proposals for standard tests of safety, lack of immunosuppressive effect and potency for IBD vaccines, comparative studies were made of products of different origins. Safety of the vaccines was assessed by observing young chicks after administration and measuring loss in weight gain. The effect on the bursa was judged by weighing and making microscopic observations at intervals. The immunosuppressive effect of the vaccines was assessed by comparing the serological and protective responses to subsequent Newcastle disease (ND) vaccination with the response in chicks given no IBD vaccine. Potency of the vaccines was determined by challenge of vaccinated chicks with virulent IBD virus. Various properties were found in the products examined. Some were concluded to be insufficiently attenuated because of the effect on the bird or upon its bursa and the consequent effect on the bird's immune competence. The ability to confer protection was not correlated with the degree of damage caused in the bursa. Vaccines which had no adverse effect on the health of the bird, caused little or no damage to the bursa and conferred adequate protection against challenge were considered to be of a satisfactory standard.

Animals↗