It is not a surprise MRSA took the opportunity to infect these animals. Use of antibiotics is very common in animal farms. Antibiotics are often mixed into feed to prevent diseases in livestock crowded into barns. Pigs, calves and other farm animals are often fed antibiotics at low doses for disease prevention and growth promotion, creating perfect conditions for antibiotic resistance to flourish.
This "farmed MRSA" has also been transmitted from farm animals to farmers. In the Netherlands, farmers are being admitted to the hospital with MRSA (pig strain ST398). Emerging Infectious Diseases reports that MRSA from animals is now responsible for more than 20% of all human MRSA infections in the Netherlands.
Up until now, MRSA infection rates in the Netherlands were far lower than those of many other countries throughout the world. Some attribute this to Dutch efforts to restrict the human spread of MRSA bacteria. The Netherlands began a rigorous program in 2002, called "Search and Destroy", after having seen a slow increase in MRSA. As part of this program, health care workers and patients being admitted to Dutch hospitals are regularly tested for MRSA.
"Search and Destroy" seemed to be very effective, until MRSA found its own weapon--farm animals--to pass MRSA to farmers who then must be hospitalized. A recent issue of Clinical Infectious Diseases Journal, outlines the Dutch investigation: "In their investigation, they found a 'strong and significant relationship' between non-typable MRSA and exposure to pigs or calves".
"In the second half of 2006, the investigators screened a total of 57 patients who reported exposure to pigs or calves and found that 18 (32%) were MRSA positive. The carriers consisted of 11 pig farmers, 1 pig farmer's wife, 1 artificial inseminator, 1 student from an agricultural university, 3 calf farmers and 1 calf farmer's daughter", they report.
"Based on their data, Dr. van Rijen and colleagues calculate that people exposed to pigs and calves have a risk of nontypable MRSA that is roughly 1000 times higher than that of the general population in the Netherlands".
"Our findings show that resistance to antibiotics is not limited to society and hospitals but is now spreading into the wild. Escalating resistance to antibiotics over the last few years has crystallized into one of the greatest threats to well-functioning health care in the future", said researcher Jonas Bonnedahl, an infectious disease physician at Kalmar University in Sweden.
This new finding shows MRSA is being transmitted back and forth throughout the whole world. From a high school football player to his pet, his pet to a vet, a vet to farm animals, farm animals to farm workers, farm workers to hospital workers and almost any other back and forth combination you can think of!