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Anthelmintic Resistance (view source)
Revision as of 10:02, 4 November 2008
, 10:02, 4 November 2008no edit summary
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Anthelminitic resistance is starting to emerge in the UK as a significant problem and has already had huge effects in the southern hemisphere. It has mainly been seen in the nematode population and is now starting to appear in the trematodes. In the UK [[benzimidazoles]] seem to have the most resistance against them, especially in sheep and horses. Now ivermectin and levamisole resistance is starting to develop. It is a concern and prudent use of the current products needs to occur to halt the progression of resistance, with a shift of thinking towards parasite control that reduce the reliance upon chemicals.
==Mechanisms of Resistance==
This is still an area of research, but most methods of resistance seem to revolve around a reduced binding site affinity. For [[benzimidazoles]] it seems that there is less affinity to the tubulin binding site. [[Macrocyclic Lactones]] seem to have increased expression of a non-specific transmembrane efflux pump that can eject toxins out of thenematode.
==Investigating Resistance==
Any poor response to anthelminitic therapy is often viewed as resistance, this is not the case. Often there are other underlying reasons for the failure of the drug, here are some more come causes:
* Misdiagnosis
* Underdosing - usually resulting from underestimating the body weight of the animal
* Failure to follow drug instructions
* Poor maintenance of the dosing equipment
* Dogs and cats rejecting tablets and so the dose
* Not removing stock from, or reintroducing stock to heavily contaminated pastures
* Inappropriate choice of drug or dosing regime
If none of these reasons are discovered to hold true then an appropriate test must be performed to confirm resistance.