What if we could see the invisible on farms? What if we could see pathogens that are shed by animals, get tracked by people, are transferred with other materials, take up residence in pens, and ultimately infect another animal? What would we do differently?
What gets transmitted simply because the pathogen is shed? Kay Riddell reported at the recent 2013 meetings of the American Association of Bovine Practitioners on an effort that her team at Auburn University has been working on to develop a new surveillance test for Bovine Viral Diarrhea Virus (BVDV) on farms. To identify farms with the virus, they have been taking swab samples from feed troughs and water fountains because the virus is shed in saliva and respiratory secretions. They were able to isolate BVD from the feed troughs 20 minutes to six hours after infected calves fed there. The virus was easily spread to uninfected calves feeding at the same trough.
What about pathogens that are not shed in saliva? Are they lurking on farms too? The September 2013 issue of the Journal of Dairy Science contained a research from a team at the University of Pennsylvania School of Veterinary Medicine led by J. D. Toth. They selected 13 farms in southeast and south central PA to look for five animal-borne pathogens in samples of fresh and stored manure, bedding, field soil, stream water and milk filters.
The presence of Salmonella enterica, E. coli O157:H7, Campylobacter jejuni, Mycobacterium avium, ssp. paratuberculosis (MAP) and Cryptosporidium parvum was investigated in samples taken from dairies ranging in size from 41 to 275 cows. They found that on all but one dairy they were able to isolate at least one of these pathogens and that on seven of 13 dairies they isolated multiple pathogens.
E. coli O157:H7 was detected in half of the positive samples and on six of the 13 farms. MAP, the bacterium that causes Johne’s Disease, was identified on 10 farms and from 20 of the 46 positive samples. Salmonella, Campylobacter and Cryptosporidium were found on fewer farms but at least one of these pathogens was isolated from six of the 13 farms. Their results show that pathogens are present on farms and have the opportunity to be spread not only to other animals, but potentially to people. That may have serious consequences as E. coli O157:H7 has caused fatalities among infected people.
To the extent that these farms are typical, it likely means that bacteria and viruses that cause disease are probably present on your farm if you could see them. Not seeing them can lead people to act as though the pathogens don’t exist, but it makes more sense for us to assume that the pathogens are there. Michigan State University Extension recommends taking specific steps to reduce the exposure of vulnerable animals to what we cannot see.