Parasite treatments for dogs. Are there safer alternatives?
If you watched BBC's Springwatch Episode 10 on 10 June 2024 you will have learned that certain parasite treatments that are used to kill fleas and ticks on dogs have been found to be polluting rivers throughout the UK where they may affect wildlife.
Which parasite treatments have been found in rivers
There is a very wide range of parasite treatments available for use in dogs. The two parasite treatment ingredients that have been found to be polluting rivers are fipronil and imidacloprid. Before focusing on these, first we will explain the differences between the different types of parasite treatments.
Prescription and non-prescription parasite treatments
Parasite treatments for dogs contain substances that kill the common parasites that affect dogs (fleas and ticks), and there is a wide range of parasite treatments for dogs on the market. Products that are marketed as treatments for pets are classed as veterinary medicines and must have a licence (marketing authorisation) from the Veterinary Medicines Directorate. Some of these parasite treatments can be bought without a veterinary prescription, however others are available only with a veterinary prescription.
Different formulations
There are several different types of parasite treatment products for dogs. They are:
spot-on solutions
collars
tablets
sprays
shampoos.
Different ingredients
All products that treat or prevent flea and tick infestations contain an ingredient that has an insecticide effect (to kill fleas). Some also have an acaricide effect (to kill ticks - ticks are acarids not insects).
Fipronil has both insecticide and acaricide effects; imidacloprid has insecticide effects only. But these are only two out of around 20 insecticide/acaricide ingredients contained in parasite treatments for dogs in the UK.
Different ways parasite treatments work
There are two main types of parasite treatments, and these are primarily differentiated based on how they work.
Treatments which stay on the dog's skin. These kill fleas and ticks through direct contact when fleas or ticks arrive on the dog's body. Most spot-ons and all collars work in this way. The solution spreads out from the point of application or the collar (which acts as a reservoir) to cover the whole body. The solution remains on the skin for at least a month, so that they can have a continuous effect. Because the solution stays on the skin, it can wash off into water when the dog swims or is bathed. It can also rub off onto hands, bedding and textiles and be washed down the drain to water treatment plants (where the insecticide/acaricide are not removed by treatment plants) and then into rivers as a result. Fipronil and imidacloprid are in this type of parasite treatment product. Fipronil is in many spot-on products (Frontline was the original brand, now there are many more). Imidacloprid is found in many spot-ons and collars. Fipronil and imidacloprid are the most common ingredients in most parasite treatment products that you can buy without a veterinary prescription.
Treatments which are absorbed into the dog's blood stream. They kill fleas and ticks when these parasites bite the dog to take a blood meal and ingest the insecticide/acaricide. Some prescription-only spot-ons work in this way (the ingredient is absorbed across the skin into the dog's blood system). But most parasite treatments that work in this way are given as tablets. Most of these parasite treatments are only available with a veterinary prescription.
So which parasite treatments have been found in rivers?
So, you see, there is a complicated range of parasite treatments for dogs on the market. That is why we feel it is helpful to explain about them.
In short, fipronil and imidacloprid have been found in UK rivers in concentrations that are known to adversely affect invertebrates in the wild, and this can have knock-on effects further up the food chain (e.g. on birds and other animals which eat invertebrates). Fipronil and imidacloprid are found in spot-ons and collars available both with and without a prescription. They are the most common ingredients in non-prescription flea and tick treatments, and they work by remaining on the dog's skin. This means they can wash off into water, both directly and via hands and textiles.
Are there safer alternatives to fipronil and imidacloprid?
The reason there is a spotlight on these two ingredients is that researchers have been actively looking for them in rivers. As we've already said, there are many more insecticide/acaricide ingredients in parasite treatments for dogs. They are all effective at killing fleas and ticks but none can distinguish fleas and ticks from other insects and acarids, so where they end up in the environment they will continue to have an effect there. So far, the fate and effects of other insecticide/acaricides in the environment have not been studied much.
What about parasite treatments that are absorbed?
Parasite treatments that are absorbed into the dog's body leave the dog's body in a dog's poo. So while they do not wash off the dog's body they will still enter the environment.
What about natural remedies?
In general there is a lack of evidence to show that 'natural' remedies (such as garlic) can prevent or treat a parasite infestation. Prevention and treatment are different. It might seem reasonable to some people to try a 'natural' remedy with the aim of preventing a flea or tick infestation (if the dog does is not exposed to fleas you will know if the remedy was having an effect), but you should not rely on them - especially if the aim is to prevent the transmission of diseases carried by parasites. If you are dealing with a flea infestation you will need an effective product to break the flea lifecycle.
What can you do to mitigate harm to the environment?
The problem of parasite treatments and water pollution is not just about the products themselves. It is also about how we use them, or how pet owners are told to use them. There has been a trend in recent years for pet owners to be encouraged to use parasite treatments all year round. Online subscription schemes and veterinary pet health plans encourage this. This might be appropriate for some dogs (such as those with flea allergy dermatitis), but year-round treatment is not required for all. The British Veterinary Association now advises against this type of routine use of parasite treatments. Flea infestations and tick activity tend to be seasonal, so consider the following points, or discuss them with your vet:
Does my dog have a history of fleas or ticks?
How likely is it that my dog will become infested with fleas or ticks?
Is flea/tick prevention really needed? An infestation can be treated effectively with correct product use. It is crucial to b reak the flea life-cycle.
If a parasite treatment is needed, which type of product is most suitable for my dog? If your dog swims or is bathed often don't use collars or spot-ons that stay on the skin.
Read the advice that comes in the package with parasite treatments
Always bag and bin dog poo.
How Veterinary Prescriber helps vets on parasite treatments
Veterinary Prescriber was founded to provide vets with a source of information on veterinary medicines that is not influenced by promotion, and to help with treatment choice: the issue of parasite treatments was one of the first areas for us to work on. It might surprise you to know that vets did not have access to a source of information that showed them all the many available parasite treatments and helped them compare products. That is why we created the Parasiticide Guide. Our main aim is to help vets by providing unbiased information. To do this, it is crucial that we are independent, so we do not carry advertising or sponsorship. If you would like to find out more, please take a look at our About page.