Direct and indirect contact rates among beef, dairy, goat, sheep, and swine herds in three California counties, with reference to control of potential foot-and-mouth disease transmission

Objective-To estimate direct and indirect contact rates on livestock facili ties and distance traveled between herd contacts. Sample Population-320 beef, dairy, goat, sheep, and swine herds, 7 artifici al insemination technicians, 6 hoof trimmers, 15 veterinarians, 4 sales yar d owners, and 7 managers of livestock-related companies within a 3-county r egion of California. Procedure-A questionnaire was mailed to livestock producers, and personal a nd telephone interviews were conducted with individuals. Results-Mean monthly direct contact rates were 2.6, 1.6, and 2.0 for dairie s with <1,000, 1,000 to 1,999, and <greater than or equal to>2,000 cattle, respectively. Mean indirect contact rates on dairies ranged from 234 to 743 contacts/mo and increased by 1 contact/mo as herd size increased by 4.3. M ean direct monthly contact rate for beef herds was 0.4. Distance traveled b y personnel and vehicles during a 3-day period ranged from 58.4 to 210.4 km . Of livestock arriving at sales yards, 7% (500/7,072) came from greater th an or equal to 60 km away, and of those sold, 32% (1,180/3,721) were destin ed for a location greater than or equal to 60 km away. Fifty-five percent ( 16/29) of owners of large beef herds observed deer or elk within 150 m of l ivestock at least once per month. Conclusions and Clinical Relevance-Direct and indirect contacts occur on li vestock facilities located over a wide geographic area and at a higher freq uency on larger facilities. Knowledge of contact rates may be useful for pl anning biosecurity programs at the herd, state, and national levels and for modeling transmission potential for foot-and-mouth disease virus.