Facts about livestock-associated (LA) MRSA CC398 from pigs
Almost 10 years ago, the special Methicillin-Resistant Staphylococcus Aureus (MRSA) type from pigs, MRSA CC398, also known as livestock-associated MRSA, was detected in Denmark and many other countries around the world with intensive livestock production.
Pigs typically carry livestock-associated MRSA on their skin or in their snout. In the pig shed, livestock-associated MRSA will be found in the dust, on all surfaces and in the air. It is therefore impossible for those who spend time in pig herds to avoid coming into contact with livestock-associated MRSA. Individuals will not be aware that they are carrying livestock-associated MRSA.
This has demonstrated that it is primarily people living in rural districts, and with a connection to pigs, who may be infected with livestock-associated MRSA.
Livestock-associated MRSA is widely distributed in Danish pig production where it is found in approximately 70 % of the pig herds. The pigs are asymptomatic carriers and do not show any signs of disease. The bacteria are probably located mainly in the nasal cavity.
Livestock-associated MRSA in pigs is not a specific Danish issue, but as with all other aspects of animal and human health, Denmark has a full transparency policy, and therefore, a high public awareness has been reflected in the coverage in the media.
The background for the appearance of the MRSA discussion in Denmark is that, in general, the Danish hospital sector is extremely aware of the risk of introduction of MRSA bacteria. In order to maintain one of the lowest prevalences of MRSA in hospitals on a global basis, monitoring of the prevalence in livestock as one of the sources of the bacteria has been ongoing for the last decade. The prevalence of hospital-acquired MRSA in Denmark is less than 1 %, which is lower than in most other countries.
The human mortalities due to livestock-associated MRSA infections described in Danish media have been in persons with terminal chronic diseases who have acquired the infections during hospitalization.
Minimal risk of being infected through meat
The “MRSA risk assessment” from December 2014 concludes that in relation to the human consumption of meat the risk of infection is negligible as MRSA bacteria are not able to survive the passage of the stomach and intestine. It also states, that there are no need for additional action regarding meat other than the existing recommendations for common good kitchen hygiene.
Therefore DVFA have not changed its policy on MRSA CC398 risk in food. The DVFA recommend that consumers follow general hygiene recommendation when handling food in the kitchen. This will reduce any risk of MRSA CC398 infection just like the potential risk of becoming ill as a result of Salmonella or other bacteria, if present in meat.
Based on scientific and epidemiological studies and the risk assessment from the expert group the DVFA concludes that the transmission of MRSA infection by food, in particular fresh meat, is recognized to be very rare. The DVFA therefore do not take specific measures when MRSA is detected in food.
Based on scientific and epidemiological studies and the risk assessment from the expert group the Danish Veterinary and Food Administration concludes that the transmission of livestock-associated MRSA infection by food, in particular fresh meat, is assessed to be limited. The Danish Veterinary and Food Administration, therefore, does not take specific measures when livestock-associated MRSA is detected in food.
Danish measurements to reduce livestock-associated MRSA infection from pig herds
In 2014, the Danish Minister of Environment and Food implemented a five point action plan in order to mitigate the risk of spread of livestock-associated MRSA to humans.
Five-point plan June 2014
Infection takes place between animals, but it is not known with certainty how widespread this is. With a view to limiting infection from pig herds to humans outside the herd setting, the Danish Minister of Environment and Food launched a five-point plan in June 2014 as follows:
Individuals who work with pigs must change their clothes and wash their hands when leaving the pig shed.
The farmer and his/her veterinarian must draw up an infection protection plan that includes initiatives to reduce infection within the herd and the risk of bacteria being carried out of the herd.
Routine mass treatment of pig herds should be discontinued. Such a treatment should only be prescribed after a veterinarian has examined the animals and diagnostic samples have been sent for analysis.
An advisory service for pig workers and health workers should be established.
It should be investigated whether the use of antibiotics can be regulated and whether the incentive for using vaccination as an alternative can be increased.
Risk assessment December 2014
In August the Minister of Environment and Food in conjunction with the Ministry of Health decided that an interdisciplinary expert group with experts from the human and veterinary side should draw up a new risk assessment of the livestock-associated MRSA situation.
In December 2014, the report “MRSA risk assessment” was published by the Danish Minister of Environment and Food.
The expert group came up with a number of recommendations for reduction of the spread of livestock-associated MRSA to the environment and humans.
Action plan for controlling livestock-associated MRSA (LA MRSA CC398) April 2015
Based on the recommendations from the report "MRSA risk assessment from December 2014" from the expert group the Minister of Food and Environment launched a national action plan for the control of livestock-associated MRSA. The plan is for 4 years and contains a long term control strategy which is to be supported by continuously control strategies for a 4 year period. The action plan initiates initiatives in line with the recommendations of the expert group with the following topics:
- 15 pct. reduction of the use of antibiotics in pigs from 2015 to 2018.
- Hygiene measurement with focus on prevention on spreading livestock-associated MRSA to the society and the interests of the working environment.
- Reduction of contamination in the herds.
- Surveillance of the development of the prevalence of livestock-associated MRSA over time.
- Research in the routes of transmission for livestock-associated MRSA.
- International effort, among which a continued pressure to promote joint EU strategy to reduce antibiotic resistance.
Danish surveys of livestock-associated MRSA
In 2010 and 2011, the Danish Veterinary and Food Administration performed a national survey, which consisted of a random sample of around 200 pig herds. The results revealed that 16% of the herds in the random survey tested positive for livestock-associated MRSA.
In 2014, the Danish Veterinary and Food Administration conducted a new national survey for livestock-associated MRSA in pigs. The survey was performed in around 200 randomly selected finisher herds and 70 herds in Danish pig production at breeding level. The results of studies in finisher herds showed a prevalence of 68% and in breeding herds the prevalence was 63 %.
In 2015, Denmark as part of the action plan for livestock-associated MRSA conducted a screening of other production animals for livestock-associated MRSA. The screening was conducted in ecological pigs, mink, poultry, calves for slaughter, horses and dogs. The percentages of positive animals were as follows: horses 0 %, dogs 1 %, poultry 2%, ecological pigs 6 %, calves for slaughter 10 % and mink 16 %.
As a part of the Danish food hygiene control the Danish Veterinary and Food Administration has examined Danish and foreign meat for livestock-associated MRSA. In studies of pork in 2009-2011, livestock-associated MRSA was found in 5-10% of pork samples. The level of livestock-associated MRSA was roughly the same for Danish and foreign pork.
In 2008, the European Food Safety Authority (EFSA) studied the occurrence of livestock-associated MRSA in pig herds in the EU Member States. The study showed that Denmark was among those EU countries with a low incidence of livestock-associated MRSA in pig herds. Since 2008, no comparable investigations have been carried out in the EU.
It should be noted that the prevalence of livestock-associated MRSA in pigs is not unique to Danish pig production. It is found in varying degrees in most countries around the world having intensive pig production.
In 2012, the European Food Safety Authority (EFSA) concluded in a scientific report “Technical specifications on the harmonized monitoring and reporting of antimicrobial resistance in methicillin-resistant Staphylococcus aureus in food-producing animals and food“ (EFSA Journal 2012;10(10):2897) http://www.efsa.europa.eu/de/efsajournal/pub/2897.htm
, the following on the risk of MRSA in meat:
“MRSA has been identified in numerous types of meat (de Boer et al., 2009; Tenhagen et al., 2011), in raw milk and raw-milk products, and it is considered that the presence of MRSA in food may be associated with a risk of introduction of the bacteria into households. However, the role of food as a source of human colonisation or infection with MRSA is presently considered to be minor, since epidemiological studies have shown that livestock-associated MRSA is fairly infrequent among people without direct or indirect contact with livestock, who cannot be exposed other than through food or the environment (Bisdorff et al., 2012). The transmission of livestock-associated MRSA infection by food, in particular fresh meat, has been recognised to be very rare (EFSA, 2009a), and food has not been considered an important source of livestock-associated MRSA in human colonisation.“
Low use of antimicrobials in Danish pigs
The use of antimicrobials in the Danish pig sector is very low. Among those European countries with a high number of food-producing animals (France, Spain, Belgium, Germany, Netherlands and Denmark) the latest ESVAC report shows, that Denmark is the country with the lowest consumption of antimicrobials per food producing animal.
All sales of Veterinary Medicine Products (VMP’s) are registered in the Danish database VetStat with relevant information, e.g. product name, active substance, quantity, animal species, animal group and farm number. The registrations are done primarily by the pharmacy. The database was established in 2000. VetStat belongs to the Danish Veterinary and Food Administration. The Danish Veterinary and Food Administration uses the information in VetStat to monitor the use of VMP's – especially antimicrobials – at farm level.
VetStat offers a very high transparency on the use of VMP's and enables the Danish Veterinary and Food Administration to make targeted policies. During the period 2009 – 2015, the use of antimicrobials in the Danish pig sector has been reduced by 22 percent. This is primarily due to the Yellow Card initiative implemented in 2010. The initiative aims to lower the use of antimicrobials further in the pig sector. The system has been very effective in restricting and reducing the use of antimicrobials for pigs.
Despite the low use of antimicrobials in Denmark, the Danish government has implemented further measures in order to reduce the livestock-associated MRSA problem. The main target is to ensure that the livestock-associated MRSA bacteria are kept at the farm and to reduce the level of LA MRSA in the animals. Mandatory increase of hygiene measures such as change of clothes and hand wash before leaving the pig stable has been implemented. In addition to that, introduction of further requirements in order to reduce the use of antimicrobials will be initiated.
Denmark has a comprehensive control and surveillance activity on the use of Veterinary Medicine Products (VMP) in food producing animals, especially on the use of antimicrobials. Activities are carried out at farm (inspections) and at central level (administrative control of registrations in the database VetStat). Furthermore, Denmark has a very strict sanction policy in cases of fraudulence with illegally acquired VMPs.
A range of EU and national rules secures, that antimicrobials are available and that they are used in a responsible manner:
All VMPs are prescription only and can only be distributed from pharmacies and companies specially approved by the Danish Medicines Agency.
The veterinarian is the “gate keeper” as only veterinarians can prescribe VMP’s for treatment of food producing animals.
Private veterinary practitioners are not allowed to profit from the sale of VMP’s and may only add a small fixed service charge to the cost price.
To ensure a high quality in the handling of health problems at farm level, farmers and the veterinary practitioners enter a one-to-one relationship in a so called “Veterinary Advisory Service Contract”. This ensures frequent visits and high quality advisory service on animal health and welfare.
Very few cases of fraudulent use of illegally acquired antimicrobials are seen in Denmark. During the last ten years the Danish Veterinary and Food Administration has only seen one case of fraudulent use of illegally acquired antimicrobials in pig production. The case is pending in the legal system.
To sum up, the very low level of antimicrobial use in the Danish pig sector is due to:
a very high general animal health level,
Veterinary Advisory Service Contracts,
the veterinarian acts as the “gate keeper” when VMPs are prescribed,
very high hygiene demands in the pig production,
the Yellow Card System – restricting the use of antimicrobials,
credible and substantial records on use of antimicrobials in the database VetStat, and
a reliable and efficient control system and very few cases of fraudulence.