About antibiotics and anthelmintics in animals

Reducing the need for antibiotics

We live in an era where medicinal use in humans has never been higher, but where use of medicines in food-producing animals seems to be less and less tolerated. Nonetheless, for one particular kind of drugs, our society aims to greatly reduce the use both in humans and animals: antibiotics. Bacteria that have become resistant against antibiotics take human lives. Bacteria can pass from animals to humans or vice-versa. The more antibiotics are used, the more bacteria develop resistance.  As a consequence, we need to reduce their use in both humans and animals. Makes sense. However, we have to be careful not to throw out the baby with the bathwater. The human and animal lives saved by antibiotics outweigh immeasurably the lives lost because of antibiotic resistance. They remain invaluable medicines, for which we need to refine what is considered responsible use, not just indiscriminately ban the use. Countries set up plans to reduce antibiotic use by implementing arbitrarily chosen reduction targets.  In our ambitions to achieve such targets, we must not forget that they are arbitrarily chosen, and when poorly monitored it can lead to undesired consequences such as a resurrection of animal disease, animal welfare issues, and reduced productivity of farms. We must remain both vigilant and flexible in adapting our strategy along the way. How antibiotic usage in animals affects antibiotic resistance in humans remains poorly quantified. Research into such aspects as well as into alternatives to antibiotics will be more important than ever.  By reducing (the market of) antibiotic use, one also reduces industry-driven innovation in the field, making innovation and incentives to develop alternatives for antibiotics a major public responsibility.


Anthelmintics next?

Once the wind on antibiotics abates, another problem to tackle is anthelmintics. The Nobel prize 2015 for Physiology and Medicine was awarded to the developers of avermectin, which has become  the single most important drug class against parasitic worm diseases in livestock. Since its first commercialisation in 1981, this drug and its derivatives have revolutionised parasite control in animals: for the first time, a single substance class that was safe, efficacious and easy to use against the majority of important endo- and ectoparasites of all livestock and companion animals was available. In ruminant livestock, strategic anthelmintic use has been very successful in reducing clinical parasitic disease and enhancing resource-efficient livestock production. This contributed to cheaper food prices (milk, meat) and reductions in water use and greenhouse gas emission per output produced. Today, and as a consequence of frequent worm exposure to the drug, the ruminant livestock industry is increasingly confronted with parasitic worms that have become drug resistant. Anthelmintic resistance (AR) is widespread in sheep and emerging in cattle. For maintaining its current levels of productivity, the industry needs to shift from strategic to more selective treatment approaches, where anthelmintics are given based on increased veterinary supervision and a diagnosis before treat approach. This is expected to extend the life of current as well as future anthelmintics, but will also require more and good diagnostics. Besides changing the way in which anthelmintics are used, the industry will also require a broader panel of control options, in order to shift between options according to the situation and establish integrated parasite control. Such options ideally include vaccines, nutraceuticals and (pasture) management procedures. Promising Proof-Of-Concept studies are available for each, but extensive further (basic) research remains required before applicable solutions are in place.

A major bottleneck for the management of AR are the lack of tools to quantify the problem. How can we talk on managing AR if we lack (i) good and/or easy-to-use tests to detect AR and (ii) anthelmintic usage data at user level? Further basic research is needed to discover the various molecular mechanisms of resistance development to promote the development of diagnostic tests. Anthelmintic efficacy tests, based on faecal egg counts need to be made more cost-effective and user-friendly. We need an objective methodology to quantify anthelmintic use at user level. Such methodology could be used along the mechanisms that are currently rolled out by countries to monitor antibiotic usage in animals and can be used to compare usage levels with AR profiles, between farm types and regions. The costs of AR, but also the costs of potential solutions including increased diagnosis and monitoring need to be assessed and compared. These are all elementary, but essential data if we want to get a grip of the problem and promote strategies for better usage.

Johannes Charlier

12 January 2018

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