Statement of Research Problem:
This project develops a FDA science base for insect vectors of Salmonella, Listeria and E. coli that is comparable to similar science bases under development for livestock. Flies are a recognized contributing epidemiological factor in the spread of food borne pathogens, especially E. coli, Listeria, Salmonella and Shigella. Houseflies are a recognized risk factor as vectors of E. coli O157:H7 in dairy farms and cattle farms and as vectors of Salmonella in broiler houses and dog kennels. The housefly is the most competent fly vector of Salmonella. Recent studies have show that wild populations of houseflies and blowflies harbor pathogens over entire breeding seasons. Studies conducted on litter beetles in broiler houses found that litter beetles infected with Salmonella transmit the infection to previously uninfected flocks under laboratory and field conditions. No research has been conducted to determine if flies have a similar vector competence for infecting layer house flocks. No studies have been conducted to assess the reservoir competence or other risk factors associated with insects in or near layer houses and fresh produce facilities. Recent findings that fruit flies can transmit E. coli O157:H7 to apples and that litter beetles can also transmit E. coli indicate that this project should include fresh produce and vectors other than the housefly.

Statement of Project Objective(s):

1. Determine which vectors should be included in risk assessment models for shell eggs and produce.
   
2. Validate a method for estimating and monitoring vector population densities, expressed in the standard WHO/CDC epidemiological formula, for use in risk assessment modeling.
   
3. Develop a science base for determining what are unacceptable numbers of flies in layer houses or other food production facilities.
   
4. Determine the capacity of an adult housefly to deliver food borne pathogens (Listeria and Salmonella).

Anticipated Impact on FDA Regulatory Program:

1. Develop HACCP guidance for insect vectors associated with fruit juice and seafood.
   
2. Develop egg safety guidance for insect vectors associated with layer houses.
   
3. Develop a Compliance Policy Guide to define the density of fly activity and other factors that represent a reasonably likely hazard to health as a contributing factor to the transmission of food borne pathogens.
   
4. Provide data suitable for inclusion in risk assessment models for shell eggs and produce.

Project Priority Changes During FY2000:
With the publication of Olsen and Hammack (August, 2000), objective 1 is accomplished, identifying the housefly, Musca domestica L., and the dump fly, Hydrotaea aenescens (Wiedemann), as the vectors that should be included in risk assessment models. For FY2001, the project priority will shift to objective 2 (monitoring population densities) and objective 3 (establishing acceptable levels of flies).

Research Personnel:

Name	Office/Division	FTE [00, 01, 02]	Component
Alan R. Olsen	OPDFB/DNP	0.5, 0.5, 0.5	1,2
John R. Bryce	OPDFB/DNP	0.5, 0.5, 0.5	1,2
	Total FTE:	1.0, 1.0, 1.0	1,2

Collaborators: Thomas S. Hammack (microbiologist), OSRS/DMS, HFS-516.

Component 1 Objectives:

1. Aseptically sample flies during layer-house trace back inspections for analysis for pathogens.
   
2. Measure relative fly population densities at trace back layer houses using WHO epidemiological protocol.
   
3. Identify fly species that are natural vectors of pathogens.
   
4. Test pools of vector flies for pathogens.
   
5. Provide risk assessment data on which fly species are likely vectors of pathogens.
   
6. Provide risk assessment data to determine if there is a statistical relationship between vector population density and incidence of pathogens.

1. Conduct three to five layer house trace back inspections
   
2. Conduct laboratory testing of flies from trace back inspections for pathogens
   
3. Conduct fly identifications and prepare voucher /reference specimens.
   
4. Publish preliminary data if available.

1. One trace back inspection conducted (Pennsylvania). This was an audit of the state egg QA program. No environmental samples were collected for Salmonella testing.
   
2. Deliverable 3 completed. Approximately 300 reference specimens prepared and identified. Vouchers deposited at the Smithsonian Institution on 8/14/00.
   
3. Deliverable 4 completed. Publication of results identifying the species that are natural vectors of pathogens (Olsen and Hammack, 2000).
   
4. Component objectives 1, 3, 4 and 5 completed. Data provided to egg safety coordinator (Balmer) for inclusion in risk assessment database.

1. Scheduling of trace back inspections are dependent on the incidence of outbreaks, which may vary from year to year and could result in fewer than three trace backs in a fiscal year.

1. Conduct three to five layer house trace back inspections.
   
2. Conduct monitoring of vector population densities during trace back inspections.
   
3. Conduct fly identifications and prepare voucher /reference specimens.

1. Establish guidance for acceptable levels of flies in caged-layer houses.
   
2. Develop field identification system for use by investigators in enforcing the guidance.
   
3. Deposit voucher specimens at Smithsonian.
   
4. Prepare data for publication.

1. Field testing of field identification system during trace back inspections
   
2. Publication of field identification system for distribution to FDA investigators.

Component 2 Objectives:

1. Determine vector competence of the housefly as a vector of pathogenic Salmonella spp. by exposing newly-emerged individual housefly adults to pathogens and then to sterile culture media under laboratory conditions to quantitatively evaluate the capacity of the fly to transmit pathogens
   
2. Determine vector competence of the housefly as a vector of pathogenic Escherichia coli.
   
3. Determine vector competence of the housefly as a vector of Listeria monocytogenes.
   
4. Determine vector competencies for other fly species.

1. Establish fly colony.
   
2. Laboratory testing.
   
3. Analyze data for publication and CPG development.

1. Establish fly colony.
   
2. Begin preliminary laboratory testing.

1. Laboratory testing.

1. Laboratory testing.