Dr. Clell V. Bagley, D.V.M.
USU Extension Veterinarian

    There are some human health risks which come with living on, or even visiting, a dairy farm. Data are accumulating which better define and identify some of these risks. This information can enable you as a dairy owner / manager to make knowledge-based decisions in relation to procedures and policies on your dairy. It can also enable individuals with special health problems or conditions to better protect themselves.

    The chart below summarizes some of the microbiological (infectious) disease risks that are present on most dairies.

AgentTypical Age of Cattle Shedding AgentPrevalence
Cryptosporidia 7 - 21 days of ageOn 90 % of dairies; 50 - 92% of calves in age group shed.
GiardiaOver 21 days of ageCommon (most dairies). 100% of calves on some dairies.
SalmonellaUnder 30 days of ageCommon (most dairies). Level depends on sanitation and multiple other factors.
E. Coli O1573 - 4 months age range (1 month post weaning)Common; found on >75% of dairies; 5% of these calves shed in feces, dropping to 1% among older calves.
E. Coli O157, Salmonella, Listeria, Campylobacter, Yersinia, Staph aureusBulk tank (raw) milkOver 33 % contain one or more pathogens. 60% of dairy families use milk that is un-pasteurized.

    The human groups that are at higher than normal risk include children (including those of farm families), the elderly, and those with reduced immune system function from a variety of causes. These individuals should be aware, or be made aware, of some of the special risks that may occur to them on a dairy farm.

    Some suggested precautions are listed below that can be taken to reduce human health risks on dairies.

Farm Family:
Farm Children: (At increased risk from handling calves, especially those that are ill.)
Farm Visitors: (School groups, etc.)
    These risks are not overwhelming nor unique to dairies but they are real and should be recognized. Similar risks occur in other areas of life such as at Day Care Centers and community swimming pools, eating uncooked hamburger, or drinking unpasteurized apple cider. Recognition of the risks and planning allow us to minimize any real problems.