Expert Elicitation Provides a Rapid Alternative to Formal Case-Control Study of an H7N9 Avian Influenza Outbreak in the United States.

An expert elicitation was staged to rapidly decipher plausible routes and risks of pathogen transmission in the 2017 H7N9 avian influenza (AI) outbreak in the four-state region of Tennessee, Alabama, Georgia, and Kentucky. The process included the identification of risk factors found in a preponderance of commercial broiler breeder case farms over matched controls and an opinion-based weighting of risks and mitigations perceived influential to this outbreak. Although the two highly pathogenic AI case farms had general location and company ownership in common, obvious connections were lacking for the remainder of H7N9-infected (all low pathogenicity) commercial farms. Expert elicitation of differences between known cases and controls suggested a key role for environmental rather than lateral (business network) pathways in the distribution of low pathogenicity AI across commercial broiler breeder operations. Factors with greatest strength as predictors of disease, whether or not they were causal, included mesopredator or rodent incursions, enclosure defects, and habitat disturbance that might attract wildlife to the farm (e.g., feed spills and vacating of neighboring properties). Business affiliations that may have facilitated farm-to-farm transfer, in contrast, were limited. Biosecurity standards varied across this study group but were no more or less stringent among cases over controls. However, results from a parallel hypothetical scenario staged to address field data gaps suggest that uniformity and consistency in the implementation of biosecurity practices may impact risk of disease introduction. Importantly, this study was conducted within a few weeks and with little disruption to emergency response activities. As such, the approach offers an alternative model for interim field investigation of new or emerging high-consequence diseases with immediate decision support needs.

Lack of interaction between avian leukosis virus subgroup J and fowl adenovirus (FAV) in FAV-antibody-positive chickens.

Unfounded field speculation has suggested that avian leukosis virus subgroup J (ALV-J) predisposes young meat-type chickens to inclusion body hepatitis caused by fowl adenovirus (FAV). To address this hypothesis, we infected 1-day-old grandparent meat-type chickens carrying maternal antibodies against FAV with a field isolate of FAV associated with inclusion body hepatitis in broilers, ALV-J, or both FAV and ALV-J. We examined the effects of FAV alone or in combination with ALV-J on the basis of clinical signs, overall mortality, growth rate, and gross and microscopic lesions. With such criteria for evaluating possible interactions, we found no significant differences in the dually infected birds in comparison with chickens that received a monovalent challenge with either FAV or ALV-J.

Dynamics of Salmonella contamination in a commercial quail operation.

Control of carcass contamination requires knowledge of the source and dynamics of spread of Salmonella in commercial poultry production. We examined Salmonella contamination at a U.S. commercial quail operation. Pulsed-field gel electrophoresis (PFGE) was used to type isolates in order to trace Salmonella throughout this production environment. During a 6-mo survey, Salmonella serotypes hadar, typhimurium, typhimurium variant Copenhagen, and paratyphi were encountered within this poultry operation. Ninety-four percent of the Salmonella isolated from breeder and production houses and from carcass rinses belonged to Salmonella serotypes typhimurium variant Copenhagen and hadar. There were six distinct S. typhimurium variant Copenhagen genetic types, as identified by PFGE, present within this particular poultry operation. Seventy-nine percent of S. typhimurium variant Copenhagen identified from the environment of the breeder and production houses produced the same PFGE pattern. Thirty-eight percent of S. typhimurium Copenhagen isolated from carcass rinses and the breeder house shared the same PFGE DNA pattern. This study demonstrates the transmission of salmonellae throughout this production environment, from the breeders to their progeny and to the birds ultimately processed for human consumption.