Transmission of infectious bronchitis virus within vaccinated and unvaccinated groups of chickens.
The aim of this study was to determine whether vaccination against infectious bronchitis virus (IBV) reduces virus transmission, i.e. to test whether IBV transmission among vaccinated chickens is significantly reduced compared to that among unvaccinated chickens. In two vaccinated and two unvaccinated groups of SPF chickens, a standard measure for virus transmission, the reproduction ratio (R) was determined. R is defined as the average number of new infections caused by one typical infectious individual during its entire infectious period. A single vaccination by eye-drop with IBV H120 reduced the transmission of the IBV challenge virus among the vaccinated chickens (estimated R = 0.69, s.e. = 0.33) significantly (P < 0.05) compared to the transmission among the unvaccinated chickens (estimated R = 19.95, s.e. = 12.41). The possible implications for further study, including selection or development of vaccines are discussed.
The effect of parameter selection in evaluation of infectious bronchitis virus vaccine. I. Evaluation of the Connecticut strain by virus recovery tests.
SUMMARY The Connecticut strain of infectious bronchitis virus (IBV) vaccine was evaluated for effectiveness in immunizing against the Massachusetts strain of virus. Efficiency of immunization was determined by the frequency of reisolation in eggs of the challenge virus from tracheal swabs from immunized and unimmunized birds. On days 7 and 14, the immunized and unimmunized groups differed markedly in the number of tracheal swabs yielding viable challenge virus. The number of virus isolations was about 1/3 as great for the immunized group as for the unimmunized control group. When a vaccine was evaluated by tallying dead embryos, as compared with dead and/or dwarfed embryo responses, samples that were negative under the former system might be considered positive by the latter system. Suggestions are included on standardization of tests for vaccine evaluation.
Gut immunity in Lepidopteran insects.
Lepidopteran insects constitute one of the largest fractions of animals on earth, but are considered pests in their relationship with man. Key to the success of this order of insects is its ability to digest food and absorb nutrition, which takes place in the midgut. Because environmental microorganisms can easily enter Lepidopteran guts during feeding, the innate immune response guards against pathogenic bacteria, virus and microsporidia that can be devoured with food. Gut immune responses are complicated by both resident gut microbiota and the surrounding peritrophic membrane and are distinct from immune responses in the body cavity, which depend on the function of the fat body and hemocytes. Due to their relevance to agricultural production, studies of Lepidopteran insect midgut and immunity are receiving more attention, and here we summarize gut structures and functions, and discuss how these confer immunity against different microorganisms. It is expected that increased knowledge of Lepidopteran gut immunity may be utilized for pest biological control in the future.