By Anthony Kalife
California is the number one milk producing state in the US, producing 19% of the nation’s milk. The California Department of Food and Agriculture reports that California has more than 1,300 dairy farming families, with over 1.75 million milk cows.
Taking care of all of these cows is an around the clock task that requires a large, robust labor force. Dairy tasks include working in the milking parlor, feeding calves, managing manure, and handling nutrition, while dealing with large animals and machinery. The success of the California dairy industry can be greatly attributed to the hands-on work of a large, often immigrant, workforce.
Zoonotic disease - infections that are transmitted from animals to humans or vice versa - is a health risk for all those involved in animal husbandry, including dairy workers. California dairy farms often have one or more cattle infected with zoonotic pathogens, such as Shiga-toxin producing E. coli, Salmonella, Cryptosporidium parvum, Listeria monocytogenes, or Campylobacter. These bacteria and parasites can cause mild to severe sickness in humans, including diarrhea, stomach cramps, and fever.
Workers can be exposed to these pathogens on their clothing, hands and faces when handling manure or administering drugs to sick cattle. This is especially true if workers improperly use their protective equipment or if they work on dairy farms with poor safety culture or deficient engineering or administrative controls.
Dr. Robert Atwill, DVM, MPVM, PhD, and epidemiology graduate student Jennifer Chase of UC Davis are seeking to better understand the occupational risk of zoonotic infection for California dairy workers in order to better protect them. Through a project funded by the WCAHS Small Grant Program, they have been developing laboratory methods to quantify bacterial pathogens that are endemic in dairy cattle populations in large commercial California dairies.
They are collaborating with two working dairies in the California Central Valley. Fecal samples were collected from individual adult animals during routine health screen visits. The samples were screened for the presence of Escherichia coli O157, Salmonella spp., and Listeria monocytogenes using a real-time molecular method (qPCR). Additionally, Atwill and Chase are establishing a novel protocol to quantify Campylobacter jejuni in dairy cattle feces.
The goal is to simultaneously quantify these specific pathogens while investigating exposure risks in the dairy worker population. Once this can be decisively done, the next step is to focus on the “human context” - discovering what personal protective strategies are actually incorporated by dairy workers and what risky behaviors can be reduced. For this aspect, Atwill and Chase envision having dairy workers observed as they complete their daily tasks and using wearable technology, like GoPros, to validate what is seen by the human observers.
The project will also identify which type of occupational task poses the highest risk for workers to acquire zoonotic disease in order to enhance farm safety protocols and engineering controls as needed. These modifications include reinforcing current protective methods that, as Dr. Atwill states, “make the safety practices more effective and dairy-specific.” Doing so will serve to minimize any linguistic or cultural impediments to the training, further improving the safety of dairy workers.
Dr. Atwill and Jennifer Chase are committed to helping improve California’s dairy industry. The project allows Chase to pursue her research interests, one of which includes identifying specific human risk factors that facilitate the spread of infectious diseases. For Dr. Atwill, the project furthers his knowledge of how microbial hazards from livestock can directly impact human health. Both researchers hope that their findings with allow workers to carry out their practices with increased safety and success.