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Keeping one step ahead of resistance

by
01 July 2011, at 1:00am

DEBORAH McGEOWN of Norbrook explains how a deeper understanding and awareness of ‘foreign’ parasites is necessary to treat patients and advise clients

ANTHELMINTICS are one of the most widely-used groups of drugs across all our domestic species. Whether they are used to improve animal production, to protect human health or to treat clinical disease, they are undoubtedly a very important tool in veterinary medicine. 

We are being faced with a continually changing parasitic landscape. Some diseases such as fascioliasais, angiostrongylosis and echinococcosis are on the rise. Some previously disregarded parasites are taking on a new importance such as paramphistomiasis, as well as all the old favourites still posing an everyday challenge to our patients.  

In our small animal companions, with increasing international travel and climate change we are seeing more “exotic” diseases landing on our consulting table. The choice of anthelmintic is no longer just to treat domestic nematodes and tapeworms but we have to have a deeper understanding and awareness of “foreign” parasites now in order to treat our patients and advise our clients on travel with their pets.

 There has been a move towards using topical broad-spectrum “spoton” treatments to cover both endoand ectoparasites in dogs and cats. These can be single agent, e.g. selamectin, or combination products, e.g. imidacloprid/moxidectin. 

As our pets are becoming more and more part of our families, owners want complete peace of mind that they are not harbouring parasites that may be harmful to them or us. These combination “spot-on” treatments certainly seem to be the future with owner confidence and compliance improving. 

There is no completely comprehensive one application/one dose treatment that covers all ectoand endoparasites and so we must not forget the oral tapeworm treatment, particularly with diseases such as echinococcosis becoming more prevalent in the UK. Older, more established products, however, such as fenbendazole (Wormazole Granules, Norbrook) still have a role to play and are certainly more cost effective and selective when nematodes are the main target, e.g. in puppies. 

In our food producing species, there is no doubt that gastrointestinal worms and lungworms have a major effect on health and production but other parasites, including ectoparasites and liver fluke can also have a major effect on health and production.  

Weight gain, milk production and fertility can all be reduced due to sub-clinical as well as heavier parasite burdens. With the human population set to double by 2050, it is crucial that we get to grips with parasite control so that we can maximise the potential of our food-producing animals to produce safe, plentiful food.  

Anthelmintic resistance has become a global phenomenon in gastro-intestinal nematodes of farm animals, including multi-drug resistance against the major classes of anthelmintics. Such resistance poses a threat to the economic viability of farming and food production. 

Integrated parasite management approaches have recently been considered important in parasite control but so far have not shown sufficient effect without using suitable supportive anthelmintic therapy. 

Norbrook offers a comprehensive range of anthelmintics for livestock and horses, namely our Noromectin range, Parafend range and Levacide/Levafas range as well as the pioneering Closamectin range. 

As diseases such a liver fluke are on the rise in the UK, and are requiring new approaches as resistance develops, the Closamectin range of products helps in the control of liver fluke as well as other endo- and ectoparasites in sheep and cattle. As yet there is no reported resistance in liver fluke to closantel.  Closamectin, a combination of ivermectin and closantel, can be applied as a pour-on to cattle and as an injection to cattle and sheep. It has greater than 95% efficacy against adult and late immature larval stages of fluke, as well as more than 95% efficacy against gutworms, lungworm and ectoparasites.  

As with all anthelmintics, a veterinary surgeon should establish appropriate drug dosing programmes and advise on appropriate stock management to reduce the likelihood of anthelmintic resistance developing. However, there certainly is an urgent need for novel anthelmintic drugs and with developments like the amino-acetonitrile derivatives showing promise it may be that we are facing a future with a totally new generation of anthelmintics on board.  

Companies such as Norbrook have a vital role to play by investing in and expanding their research and development programmes in order to develop novel strategies for controlling parasites in both large and small animals and keep one step ahead of the resistance problem.