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These are chemicals used to treat and control parasites that reside on, or in, the skin and coat of animals. They are a diverse set of products that can be applied in various ways. Some important terms must be discussed first before mentioning how each drug works.
These are chemicals used to treat and control parasites that reside on, or in, the skin and coat of animals. They are a diverse set of products that can be applied in various ways. Some important terms must be discussed first before mentioning how each drug works.
'''Insect Growth Regulators''' don't kill adult stages but are able to prevent hatching, larval development or metamorphosis.
'''Insect Growth Regulators''' don't kill adult stages but are able to prevent hatching, larval development or metamorphosis.
==Modes of Action==
==Modes of Action==
These drugs mainly act on the parasites nervous system and neuromuscular junction. They are selectively toxic by having a greater affinity for the parasite receptor than the animal receptor. They can either by '''contact posions''' - arbsorbed through the parasites exoskeleton, or are '''stomach poisons''' - they are absorbed through the parasites stomach and so the parasite must bite to be affected. Thus the stomach poisons are usually given systemically to the host animal.
These drugs mainly act on the parasites nervous system and neuromuscular junction. They are selectively toxic by having a greater affinity for the parasite receptor than the animal receptor. They can either by '''contact posions''' - arbsorbed through the parasites exoskeleton, or are '''stomach poisons''' - they are absorbed through the parasites stomach and so the parasite must bite to be affected. Thus the stomach poisons are usually given systemically to the host animal.
===Insecticides===
===Insecticides===
'''Synthetic Pyrethroids - Cypermethrin, Deltamethrin'''
'''Synthetic Pyrethroids - Cypermethrin, Deltamethrin'''
* Many products and are in widespread use.
* Many products and are in widespread use.
* In high concentrations these products can cause adverse reactions in cats and dogs.
* In high concentrations these products can cause adverse reactions in cats and dogs.
* '''Piperonyl butoxide''' is a syngeristic product that is often put in formulations to potentiate the action of the pyrethroids.
* '''Piperonyl butoxide''' is a syngeristic product that is often put in formulations to potentiate the action of the pyrethroids.
'''Semicarbazones - Metaflumizone'''
'''Semicarbazones - Metaflumizone'''
* A new group of insecticides
* A new group of insecticides
* They work by blocking sodium ion channels in the axonal membrane of nerves, this prevents the propagation of nerve impulses leading to paralysis of the insect and hence death.
* They work by blocking sodium ion channels in the axonal membrane of nerves, this prevents the propagation of nerve impulses leading to paralysis of the insect and hence death.
'''Organophosphates and Carbamates - Diazinon, Dichlorvos'''
'''Organophosphates and Carbamates - Diazinon, Dichlorvos'''
* Their use has been limited of late as they are potentially neurotoxic to animals and man, and can cause environmental damage.
* Their use has been limited of late as they are potentially neurotoxic to animals and man, and can cause environmental damage.
* They are anticholinesterases and so resukt in the build up of acetylcholine in the parasites's synapses, leading to paralysis and death.
* They are anticholinesterases and so resukt in the build up of acetylcholine in the parasites's synapses, leading to paralysis and death.
'''Neonicotinoids - Imidacloprid, Nitenpyram'''
'''Neonicotinoids - Imidacloprid, Nitenpyram'''
* These are mainly used for pest control in crop protection schemes. The above two drugs though are both currently used for flea control.
* These are mainly used for pest control in crop protection schemes. The above two drugs though are both currently used for flea control.
* They work by stimulating and then blocking post-synaptic nicotinic acetylcholine receptors which leads to paralysis and death.
* They work by stimulating and then blocking post-synaptic nicotinic acetylcholine receptors which leads to paralysis and death.
'''Phenylpyrazoles - Fipronil, Pyripole'''
'''Phenylpyrazoles - Fipronil, Pyripole'''
* These are used for flea control and work by blocking GABA transmitted impulses, thus blocking the influx of chlorine ione into nerve cells.
* These are used for flea control and work by blocking GABA transmitted impulses, thus blocking the influx of chlorine ione into nerve cells.
'''Macrocyclic Lactones - avermectins and milbemycins'''
'''Macrocyclic Lactones - avermectins and milbemycins'''
* These are endectocides are will be discussed in full on the anti-helminth pages.
* These are endectocides are will be discussed in full on the anti-helminth pages.
'''Amidines - Amitraz'''
'''Amidines - Amitraz'''
===Inert Inorganics===
===Inert Inorganics===
These are inert substances, often powder, that are used to treat the environment in a properly managed flea control scheme. They work by dessication of the flea eggs or by clogging their spiracles. An example is '''Sodium polyborate'''.
These are inert substances, often powder, that are used to treat the environment in a properly managed flea control scheme. They work by dessication of the flea eggs or by clogging their spiracles. An example is '''Sodium polyborate'''.
===Insect Growth Regulators===
===Insect Growth Regulators===
'''Insect juvenile hormone analogues - methoprene, pyriproxyfen'''
'''Insect juvenile hormone analogues - methoprene, pyriproxyfen'''
These work by blocking receptor sites for insect juvenile hormone. This stops the juvenile insect from continuing along it's natural course of development so it never reaches adult status.
These work by blocking receptor sites for insect juvenile hormone. This stops the juvenile insect from continuing along it's natural course of development so it never reaches adult status.
'''Chitin Inhibitors - Cyromazine, dicyclanil, lufenuron'''
'''Chitin Inhibitors - Cyromazine, dicyclanil, lufenuron'''
==Points to Consider When Choosing an Ectoparasiticide==
==Points to Consider When Choosing an Ectoparasiticide==
When choosing an ectoparasiticide treatment for a particular animal it is always key to have in mind what animal you are dealing with, what is the main parasite problem, what sort of environment does the animal reside in and how much owner compliance do you think there will be. It is also important to understand the following properties of your drug options:
When choosing an ectoparasiticide treatment for a particular animal it is always key to have in mind what animal you are dealing with, what is the main parasite problem, what sort of environment does the animal reside in and how much owner compliance do you think there will be. It is also important to understand the following properties of your drug options:
==Application==
==Application==
There are numerous ways in which ectoparasiticides are formulated. They can be in solutions, suspensions, emulsions, powders and shampoos. A common formulation seen in practice is when they become incorporated into a plastic matrix, which the product can be released slowly. This use is often seen in flea collars or in cattle ear tags. They can also be given orally or systemically.
There are numerous ways in which ectoparasiticides are formulated. They can be in solutions, suspensions, emulsions, powders and shampoos. A common formulation seen in practice is when they become incorporated into a plastic matrix, which the product can be released slowly. This use is often seen in flea collars or in cattle ear tags. They can also be given orally or systemically.
===Dipping===
===Dipping===
The dipping of sheep is a requisite to control ectoparasites in the sheep population. It is though quite a tricky process to get right and a failure at any one of the points could mean that the sheep aren't covered against parasites or that resistance may build up within the parasite population. On the other hand if the concentration of the dip is too high there is significant danger of toxicity to both the sheep and the handler.
The dipping of sheep is a requisite to control ectoparasites in the sheep population. It is though quite a tricky process to get right and a failure at any one of the points could mean that the sheep aren't covered against parasites or that resistance may build up within the parasite population. On the other hand if the concentration of the dip is too high there is significant danger of toxicity to both the sheep and the handler.
As the process of dipping is both dangerous to the sheep and handler a set of legal requirements have been put in place, these are:
As the process of dipping is both dangerous to the sheep and handler a set of legal requirements have been put in place, these are:
* A certificate of competence in the UK is needed to purchase and handle sheep-dip and a COSSH risk assessment must be performed before dipping.
* A certificate of competence in the UK is needed to purchase and handle sheep-dip and a COSSH risk assessment must be performed before dipping.
* Protective clothing must be worn.
* Protective clothing must be worn.
* There are specific ways od disposing of sheep dip, please see the Defra website for more information; http://www.defra.gov.uk/environment/water/ground/sheepdip/index.htm
* There are specific ways od disposing of sheep dip, please see the Defra website for more information; http://www.defra.gov.uk/environment/water/ground/sheepdip/index.htm
==Problems with Ectoparasiticides==
==Problems with Ectoparasiticides==
The main problem with ectoparasiticides are their potential toxic nature. This is an increased risk compared to other pharmaceutical products because of the large volumes and high concentrations that are used. This is not only a risk to animals, but to man and to the environment. Man and animals can experience acute toxicty if concentrations are calculated incorrectly. It has been suggested that chronic neuropathic toxicity can occur with repeated exposure to organophosphate dips, this is highly controversial at the moment and currently there has been no absolute proof of this. Due to their potential ability to reach waterways specific regulations have been put in place concerning their disposal. Please look at the above defra link if you want more information.
The main problem with ectoparasiticides are their potential toxic nature. This is an increased risk compared to other pharmaceutical products because of the large volumes and high concentrations that are used. This is not only a risk to animals, but to man and to the environment. Man and animals can experience acute toxicty if concentrations are calculated incorrectly. It has been suggested that chronic neuropathic toxicity can occur with repeated exposure to organophosphate dips, this is highly controversial at the moment and currently there has been no absolute proof of this. Due to their potential ability to reach waterways specific regulations have been put in place concerning their disposal. Please look at the above defra link if you want more information.
==Resistance==
==Resistance==
Like all anti-infective agents resistance is starting to develop as a very serious problem within this set of drugs. This has been because the parasites experience high selection pressure, with the vast majority of the parasite population coming in contact with the toxicant. This leads to a higher prevelance of the resistant gene amongst the subsequent surviving generations.
Like all anti-infective agents resistance is starting to develop as a very serious problem within this set of drugs. This has been because the parasites experience high selection pressure, with the vast majority of the parasite population coming in contact with the toxicant. This leads to a higher prevelance of the resistant gene amongst the subsequent surviving generations.
It must be remembered that most reports of resistance aren't in fact this but are a failure of treatment. This can be because of a poor choice of product, poor application or because of an overwhelming environmental challenge.
It must be remembered that most reports of resistance aren't in fact this but are a failure of treatment. This can be because of a poor choice of product, poor application or because of an overwhelming environmental challenge.
[[Category:Biting_Flies]]
[[Category:Biting_Flies]]