Claire E Whitehead BVM&S MS MRCVS
There has been quite a lot of chatter in the European press recently about the use of antibiotics in human and veterinary medicine, more specifically on how to limit the emergence of antibiotic resistant bacteria: this concern is a global one and of massive importance for both animal and public health. One cannot have failed to notice sensationalist headlines in recent years about multi-drug resistant strains of bacteria such as MRSA (methicillin-resistant Staph aureus). On the 17th November 2011, the European Commission unveiled its ?action plan against antimicrobial resistance: 12 concrete actions for the next five years? with the aims of limiting the spread of resistance and developing new antimicrobials. Although the use of antibiotics in humans is thought to be responsible for the majority of drug resistance seen, it?s animal use that is often blamed most loudly: perhaps consequently, more of the ?actions? proposed govern control over use of antibiotics in animals than in humans.
Decisions made by the politicians can have a drastic effect on what antibiotics we as vets and animal owners may use in the future. It is increasingly likely that antibiotics will only be available for use in animals when prescribed by a vet. We have a vital role to play in ensuring that the antibiotics we have at our disposal remain useful to us and the animals that we treat. Our ability to prescribe antibiotics to camelids could be particularly at risk since all the drugs we use are used ?off-label? (there are no licensed drugs for use in camelid species in the UK) and we could be in trouble if legislation is created that restricts the use of antibiotics to licensed uses only? It is highly unlikely that pharmaceutical companies will spend the money required to license drugs in minority species like ours. This mandatory drug-licensing scenario is unlikely given the number of exotic species for which drugs are commonly prescribed by vets using the ?cascade system of prescribing? since this would compromise animal welfare which has a high priority here in the UK. [Under the cascade system, drugs may be used for a condition for which the drug is licensed in another species for example.] However, we have a responsibility to use drugs appropriately in order to safeguard their use in the future.
How does antibiotic resistance happen?
Some bacteria are inherently resistant to certain antibiotics because of their actual structure or makeup. For example, an antibiotic may target something that is not present or accessible in a particular bacterial species. Others acquire resistance by developing mechanisms to resist the action of antibiotics through genetic mutation or the acquisition of genes encoding for resistance via insertion of ?plasmids?. This is a completely random process and contact with an antibiotic actually doesn?t just cause the bacteria to go out and start mutating. Basically, bacteria replicate extremely rapidly, allowing many opportunities for random mutations to occur: some of these mutations, completely by chance, may confer resistance to an antibiotic and this provides a selective advantage to these bacteria such that they are more likely to survive and replicate, thus spreading the gene more widely. Obviously this selection will only occur if the bacteria are exposed to the antibiotic in question.
Who?s to blame??
This is a complex question and it?s extremely difficult to point to any one source. Bacteria are everywhere in the environment as well as all over and inside our (and animals?) bodies, so it?s quite complicated. Consumption of meat containing antibiotic residues is often blamed. Antibiotics as ?growth promotors? have been banned in Europe due to a decision made in 1998, but they are still in use in the USA. There are strict regulations in food-producing animals for withdrawal periods ? the time after a drug has been used before which meat or milk from those animals can enter the food chain ? and provided licensed dosing is practiced and withdrawal periods are adhered to, the risk for antibiotic resistance transferring to humans is minimal. Transmission of resistance may occur when animals carrying resistant bugs move between herds, via exposure through the environment, via contact with infected humans (transmission to animals and vice versa) and movement via contaminated vehicles, insects and birds. Fertilisation of land with infected slurry may result in contamination of soil, water and crops and this may transfer to humans. On the human side, irresponsible use of antibiotics includes the inappropriate prescription of antibiotics to people with uncomplicated viral infections, people using antibiotics incorrectly, and the massive problem of over-the-counter drugs in the developing world. Additionally, using antibiotics at less than recommended dosages or for less than the recommended course (eg stopping the course early before all bacteria have been killed, even though clinical signs may have resolved) will potentially result in resistance developing.
What can you do to minimise Antibiotic Resistance?
? MINIMISE INFECTION RISK
o Develop an infection control plan for your farm. This is particularly important for large farms but equally as important if you only have a few animals. Essentially we?re talking about biosecurity here. The chances of infection increase when buying in new animals, taking animals to shows (and returning them home again) or any time your animals come into contact with other animals, including other species. You can get your vet to help you with this and there are various other avenues for help.
o We?re talking about general cleanliness, disinfection of sick pens, routine housing management, quarantine practices, waste disposal and personal hygiene. Don?t forget the latter: you want to try to prevent transfer of bacteria and antimicrobial resistance to humans.
o Remember to include protocols for any emergency situations in your plan. For example, extra biosecurity measures in the face of a foot and mouth outbreak; a plan for if you have several animals ill at one time ? where will you put them and how will you manage them? Having rested clean pasture available? Foot dips etc?
? ONLY USE ANTIBIOTICS WHEN DIRECTED TO DO SO BY YOUR VET
o Now I know that there are many alpaca owners and breeders out there who don?t trust their vets or would rather just have the drugs and give them when you want to?. You know I?m right. I hear it all the time on the phone. However, whether your vet is particularly knowledgeable about alpacas or not, they spent a long time at university learning how to do what they do in a load of different species. And there are some great vets out there but you need to trust them. Vets are trained to have an integrated understanding of medicine, surgery, microbiology and pharmacology as well as animal management. And if your vet isn?t familiar with alpacas, that?s not his or her fault. Try to introduce them to your animals when they?re healthy: allow them to examine healthy animals before suddenly pulling a dying one on them. If they don?t know a healthy alpaca, it?s going to be challenging for them to suddenly know what to do when one is sick. Unfortunately camelids do not comprise a significant part of their education and they only have a very small budget to spend on continuing education each year. So, if you want your vet to know more, and inspire more confidence in you, you may want to consider funding their attendance at a course? Or at least making sure that they know who to call when they have problems that they?re unfamiliar with.
o It may be very tempting to just pull out whatever antibiotic you have saved up in the drug cupboard, but antibiotics are not always necessary, and the antibiotic you choose may be inappropriate to the problem.
o This may be the rule of the future?
? FOLLOW DOSING INSTRUCTIONS COMPLETELY
o This includes the dose, the frequency of administration and the duration of treatment. Don?t independently decide to give more or less, or to give a drug less frequently because it?s difficult. If you?re having trouble, speak to your vet about it and he or she may be able to suggest a solution.
o Never finish an antibiotic course before instructed to do so by your vet. A minimum course is required to help minimise the possibility of resistance and to ensure proper treatment. The obvious clinical signs of disease may have resolved but the underlying problem may still require treating. At the very least, this should be three days but I am often more comfortable with five, depending on the drug.
o Some antibiotics may be given pre-operatively in which case only a single dose is necessary. This is usually where a surgical procedure is being carried out in the field and there is the chance of bacterial contamination (eg castration). Antibiotics given under these circumstances should always be given before any procedures are done: after it?s finished and you?ve rather missed the boat.
? USE WEIGH SCALES
o Buy a set of weigh scales that will allow you to weigh adult animals and set them up so that you can use them easily. Also have scales available that are suitable for crias. These are not expensive: you can buy a set of weigh bars for less than £250 and they are worth their weight in gold. They can be integrated into any handling facility. They will allow you to dose animals properly, on the basis of weight and not guesstimates. This prevents you overdosing a drug that may be toxic, or underdosing a drug so that it is less or in-effective. Underdosing also increases the chances of causing antibiotic resistance.
? USE ANTIBIOTICS KNOWN TO BE EFFECTIVE IN CAMELIDS
o There are a number of antibiotics that have been subjected to pharmacokinetic research in camelids. For example ceftiofur (Excenel, Pfizer), gentamicin, florphenicol (Nuflor, MSD Animal Health) and enrofloxacin (Baytril, Bayer). Also antibiotics that we know are safe to be used at doses used in other species (eg penicillin and tetracycline). There are also antibiotics that we know are not safe to be used in camelids such as tilmicosin (Micotil, Elanco), and antibiotics that we know have no efficacy when given by a certain route ? for example, trimethoprim sulpha drugs often given orally to horses are ineffective given via this route in alpacas (eg Duphatrim, Tribrissen granules or paste). Make sure that your vet knows which drugs are safe in camelids and at what doses they should be used.
o One drug I would just like to draw attention to here is commonly given because it?s cheap but I believe is of no use to us. Penicillin/streptomycin combinations are commonly given: however, this combination means that you are only giving approximately 60% of the penicillin dose needed in order to avoid streptomycin toxicity. In addition you can only give it once daily for the same reason when penicillin should be given twice daily.
? ENCOURAGE USE OF CULTURE
o Wherever possible, it is a good idea to culture and base antibiotic choice on the results of sensitivity testing. Your vet may suggest culturing something in order to make sure that they use the correct antibiotic for the job. I would urge you to pay for this testing: even if you think it?s expensive, it may actually be cheaper in the long run because you won?t be spending money on antibiotics that aren?t effective. You can waste a lot of time and money using guesswork?. While waiting for culture, it?s reasonable to start using a broad-spectrum antibiotic and then refine the choice if necessary once the results are in. Culture and sensitivity testing usually takes 48-72 hours once samples reach the lab.
? STORAGE AND USE OF ANTIBIOTICS
o Make sure you follow storage instructions properly. For example, if you have bottles of antibiotics, they need to be kept at the correct temperature ? some antibiotics need to be kept in the fridge while others can be kept in the cupboard.
o Most antibiotics need to be thrown away after 28 days once the bottle is opened. After that time, the effectiveness of the antibiotic cannot be guaranteed and may in fact be harmful. Remember to write the date on the bottle when you open it so that you know when it should be thrown away. Some antibiotics have a shorter shelf-life than this so make sure you always check on the label.
o Always use a clean needle and syringe when drawing up antibiotics out of the bottle. Re-use is false economy and can introduce bacteria into the bottle.