The annual report on antibiotic resistance
and the use of antibiotics in livestock shows encouraging results: resistance is decreasing. But we need to stay alert, says Dik Mevius.
By Jan Braakman
Dik Mevius is pleasantly surprised. The researcher of the Centraal Veterinair Instituut and professor of antimicrobial resistance at the Faculty of Veterinary in Utrecht, the Netherlands knew of course that the decrease in the use of antibiotics would have to lead to a decrease in resistance. However, he did not dare to hope for the effects to be visible so soon, and so clearly, as they are in the latest Maran-report.
Recently, the Maran-figures (Monitoring of Antimicrobial Resistance and Antibiotic Usage in Animals in the Netherlands) on the use of antibiotics in livestock and in human health care were presented. On both fronts developments are hopeful. In human health care, the increase in resistance is declining and use is decreased. The decrease in use in livestock is spectacular and the gratifying effect is that resistance in livestock decreases as well.
Mevius is enthusiastic about the results. “I had thought that resistance was so deeply embedded in livestock that it would take much more time before we would see a decrease.” At the same time he warns: “We are not there yet. If we revert to our old habits, resistance will return. However, the results we see today are hopeful.”
He contributed to the Maran-report which shows a marked decrease in the resistance for almost all antibiotics. “These are the pictures that everyone wants to see,” says Mevius. “Until 2010 we saw a rise in resistance. The reduction of antibiotic use makes the environment in the intestines of the animals less favourably to the drug-resistant strains. That is the positive signal.”
In the spotlight
Until this spring, Mevius was closely involved in the veterinary medicines authority SDa, the independent supervisor who keeps track of how all veterinarians and farmers deal with the use of antibiotics. The authority has succeeded to map out the data of 40,000 companies in a short time. This provides a wealth of information which not only helps to get an overview of the actual usage, but which can also lead to knowledge on the opportunities to further reduce the use. Foreign colleagues watch with wonder and some jealousy how livestock production sectors in the Netherlands achieve these results.
Mevius seizes every opportunity to tell the story about how the sectors – without any government legislation – succeed to reduce antibiotic use. “This story very favourably draws the spotlight on us.”
The objective is to reduce the use of antibiotics as far as possible, by moving the livestock industry towards a different footing. “The livestock sector should ensure the health of animals without cheap antibiotics. We already see some inspiring examples, such as the Keten Duurzaam Varkensvlees (Chain Sustainable Pork). Others should follow suit.”
Still, there are some drawbacks. There is a significant decrease in the resistance, but the level should still be lowered further. “We will at some point reach a stable level, I expect. However: we will never completely get rid of antibiotic resistance. If we stop this policy now, we will fall back again just as easily. Due to 70 years of antibiotic use, the resistance is so embedded in the normal flora and fauna, that it will always be present, below or above the surface. We must continue to regulate.”
Concern about resistance to carbapenem antibiotics – which has not yet been found in livestock farming in the Netherlands – persists. “We have to continue to be alert.” Carbapenems are among the antibiotics to be used as a last alternative in human health care.
Extended-spectrum beta-lactamases (ESBL)-producing bacteria remain another concern. These are able to neutralise the effects of antibiotics. ESBL’s were found in large quantities in poultry. The notable downward trend can also be seen in the occurrence of those at Dutch poultry farms, which is probably the result of the discontinued use of cephalosporins in poultry farming. Cephalosporins are among the third generation of antibiotics, the use of which is reserved for human health care as much as possible. Mevius says that cephalosporins were not used only in poultry farming, but pigs and cattle were also administered with these antibiotics. There were no market incentives not to use it, says Mevius. “It was not about unwillingness, it was just that it was
beneficial to everyone.”
Imported risks from South America
The Dutch results draw attention. Not only neighbouring countries use the Dutch example to achieve reduced usage of antibiotics, there is a show of interest from South and North America as well. “In Brazil ESBL’s are not an issue. The attention there is still focused on reducing salmonella infections. They do, however, come over to hear about what we do. And they understand why we think ESBL’s are important.”
The Maran-report shows that specific ESBL infections are found in meat of foreign origin. These are so specific that Mevius can predict with a certain degree of probability that a batch of meat comes from Brazil based on the detected resistance. “We see that we import certain risks from South America. We will have to think about that, though the solution is complicated. Apart from that: it is important to start with yourself.”
There are other possible sources of resistance: Mevius mentions herbs and vegetables which have been in contact with manure containing resistant bacteria, fish and seafood from local businesses in Southeast Asia and the use of antibiotics in some vegetable crops.
“And of course man himself: resistant bacteria from humans enter the environment through sewage overflows and even simply via the Rhine river. When it comes to the ESBL infections in humans, we know that contact between humans is the main route of infection.”
Source: World Poultry, Vol 31, Issue 1, 2015
Results per sector
• Broiler sector – In 2013 the use of antibiotics in broiler farms was 17.6 defined daily doses per animal year (DDDA). Antibiotic use on broiler farms has dropped by 49% since 2009. The use of third choice antibiotics was 0.6 DDDA in 2013. Since 2011 the use of third choice antibiotics has dropped by 75%. The broiler sector has taken additional actions to further reduce the use of third choice antibiotics. In 2013 the use of antibiotics in breeding farms for (grand) parent stock in the broiler industry was 13 DDDA. 2.9 DDDA thereof concerns third choice antibiotics and 3.3 DDDA second choice antibiotics. The use of third choice antibiotics at breeding farms is a concern. During 2013 we do see a sharp drop in this use of third choice antibiotics. The industry is working on a plan to further reduce this use of third choice antibiotics. In 2013 the use of antibiotics in production farms with (grand) parents in the broiler sector was 3.0 DDDA of which 0.4 was third choice antibiotics and 0.6 DDDA was second choice antibiotics.
• Egg sector – The use of antibiotics in all poultry farms was 1.1 DDDA in 2013. This includes breeding farms (for grandparent animals, for older animals and for laying hens) and production farms (for grandparent animals, for older animals and for laying hens). In 2013 the use of third choice antibiotics in the egg sector was 1% (of 1.1 DDDA).
• Turkey farms – In 2013 the use of antibiotics in turkey farms was 52.6 DDDA. This is 23.9% less than in 2012 when the average antibiotic use was 67.8 DDDA and 32% lower than in the benchmark year 2011 (77.2 DDDA). After a rise of over 40% in 2012, the use of third choice antibiotics decreased considerably in 2013, but is still high. Third choice antibiotics are used for first week problems, complicated
respiration problems and immunosuppression. There are, in practice, little or no viable alternatives for these third choice antibiotics. The turkey sector is working on an approach to prevent certain conditions enabling to further reduce the use of third choice antibiotics.