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 facilities and distance traveled between herd contacts.


METHODS
320 beef, dairy, goat, sheep, and swine herds, 7 artificial insemination technicians, 6 hoof trimmers, 15 veterinarians, 4 sales yard owners, and 7 managers of livestock-related companies within a 3-county region of California.


METHODS
A questionnaire was mailed to livestock producers, and personal and telephone interviews were conducted with individuals.


RESULTS
Mean monthly direct contact rates were 2.6, 1.6, and 2.0 for dairies with < 1,000, 1,000 to 1,999, and > or = 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. Mean direct monthly contact rate for beef herds was 0.4. Distance traveled by 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 > or = 60 km away, and of those sold, 32% (1,180/3,721) were destined for a location > or = 60 km away. Fifty-five percent (16/29) of owners of large beef herds observed deer or elk within 150 m of livestock at least once per month.


CONCLUSIONS
Direct and indirect contacts occur on livestock facilities located over a wide geographic area and at a higher frequency on larger facilities. Knowledge of contact rates may be useful for planning biosecurity programs at the herd, state, and national levels and for modeling transmission potential for foot-and-mouth disease virus.
Bates
T W
TW
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
Thurmond
M C
MC
Carpenter
T E
TE
D000383:Agriculture; D017750:Animal Technicians; D000818:Animals; D002140:California / Q000453:epidemiology; D002417:Cattle; D005260:Female; D005536:Foot-and-Mouth Disease / Q000453:epidemiology / Q000517:prevention & control* / Q000635:transmission*; D029544:Foot-and-Mouth Disease Virus / Q000254:growth & development*; D006041:Goats; D006801:Humans; D007407:Interviews as Topic; D008954:Models, Biological; D018986:Motor Vehicles; D012756:Sheep; D011795:Surveys and Questionnaires; D013552:Swine; D018634:Veterinarians