In ovo application of a live infectious bursal disease vaccine to commercial broilers confers proper immunity.

Infectious bursal disease (IBD) is an economically important disease of young chickens caused by the Avibirnavirus infectious bursal disease virus (IBDV). Besides biosecurity, vaccination is the most important measure for IBDV control. Sufficient levels of maternally derived antibodies (MDA) protect against early challenge and also interfere with the take of live conventional vaccines. Recently, the field surveys conducted in four countries, published by Ashash, U., Noach, C., Perelman, B., Costello, C., Sansalone, P., Brazil, T. & Raviv, Z. [(2019). In ovo and day of hatch application of a live infectious bursal disease virus vaccine to commercial broilers. Avian Diseases, 63, 713-720] using the MB-1 vaccine strain by in ovo application or sub-cutaneous route at the day of hatch seem to conflict with the rule that very early application of a conventional live vaccine in birds with significant levels of MDA has very little chance of a successful immune response. An in ovo vaccination-challenge controlled experiment with MB-1 vaccine was performed using commercial broilers with high levels of MDA against IBDV and a vvIBDV challenge at 22 or 36 days of age. Clinical signs, bursa-bodyweight ratios, histology, serology, RT-PCR, Sanger- and deep sequencing were used to study the efficacy and safety of the in ovo-applied MB1 vaccine in comparison to an established immuno-complex vaccine. The study findings confirmed that the in ovo application of the live MB-1 vaccine in commercial broilers was successful and induced full protection against a vvIBDV challenge at 22 and 36 days of age, demonstrated by the bursa lesion score and qPCR and IBDV genotyping. Comparable to the field studies, a delayed viral replication of 2-3 weeks, following the in ovo administration of the MB1 vaccine, was observed.

The role of the bursa of Fabricius in the immune response to vaccinal antigens and the development of immune tolerance in chicks (Gallus domesticus) vaccinated at a very young age.

Vaccination is recognized to be the most cost-effective means of preventing, controlling, and even eradicating infectious diseases. Conventional poultry are vaccinated through various routes including eye/nose drops, drinking water, vent brush, or injection. Efficient vaccination is an essential part of any good poultry management.The bursa of Fabricius is intimately connected to the cloaca and the intestinal system. It is well-known as a primary lymphoid organ in the chicken and a major channel through which environmental antigens stimulate the immune system. In this study we tested whether direct instillation of various viral vaccines and antigens into the cloaca (per bursam), could stimulate higher antibody titers and generate improved protection. Despite the very rapid absorption of the vaccines or antigens from the cloaca to the lumen of the Bursa of Fabricius, per bursam inoculation failed to generate a satisfactory immune response. In contrast conventional administration of live or inactivated commercial vaccines led to an acceptable level of seroconversion and protection against challenge.An interesting finding in this study was the fact that administration of a single priming dose of antigenic material at age 1 or 5 days, did not improve the response to a second administration at 14 days of age as expected. Instead, in most cases there was a reduced serum antibody response suggesting the induction of tolerance. This was true for all routes of administration (intramuscular, per ocular and per bursam) and for all formulations of vaccine.The current study reveals: 1) no advantage for direct application of live or inactivated vaccines or antigens into the bursa of Fabricius compared to common routes of vaccination, 2) that apparent desensitization or tolerance effects have important implications for poultry management, since in many countries, vaccination of day old chicks is compulsory or a well-accepted part of flock vaccination.According to our results, early vaccination can in fact reduce or inhibit a secondary immune response to subsequent vaccination and increase susceptibility to disease agents.

Twenty Years of Neighborhood Effect Research: An Assessment.

This paper reviews the magnitude and empirical findings of social epidemiological neighborhood effects research. An electronic keyword literature search identified 1369 empirical and methodological neighborhood effects papers published in 112 relevant journals between 1990 and 2014. Analyses of temporal trends were conducted by focus, journal type (e.g., epidemiology, public health, or social science), and specific epidemiologic journal. Select papers were then critically reviewed. Results show an ever-increasing number of papers published, notably since the year 2000, with the majority published in public health journals. The variety of health outcomes analyzed is extensive, ranging from infectious disease to obesity to criminal behavior. Papers relying on data from experimental designs are thought to yield the most credible results, but such studies are few and findings are inconsistent. Papers relying on data from observational designs and multilevel models typically show small statistically significant effects, but most fail to appreciate fundamental identification problems. Ultimately, of the 1170 empirically focused neighborhood effects papers published in the last 24 years, only a handful have clearly advanced our understanding of the phenomena. The independent impact of neighborhood contexts on health remains unclear. It is time to expand the social epidemiological imagination.

A tetrazolium-based colorimetric assay for titration of neutralizing antibodies against vaccinia virus.

A colorimetric assay for titration of neutralizing antibodies against vaccinia virus was developed. The test is based on the ability of live cells in culture to reduce the yellow tetrazolium salt MTT (thiazolyl-blue), to its blue formazan derivative. Antisera from individuals vaccinated with vaccinia virus against smallpox were serially diluted, incubated with 100 plaque-forming units (PFU) of vaccinia virus for 1 hour at 37 degrees C, and then transferred to a 96-well plate containing monolayers of B-SC-1 cells. After incubation for 3 to 4 days at 37 degrees C, when more than 80% of the control infected cultures exhibited high degree of cytopathogenic effect, MTT was added. The absorbance of the formazan formed and extracted by dimethylsulfoxide was read at 492 nm by an automatic microplate spectrophotometer. A good correlation was found between the results obtained using this newly developed method and those of the plaque-reduction assay.