Like many vets around the country, I’ve had a sudden wave of panicked calls and emails from clients about a dramatic article that appeared in USA Today yesterday. The article essentially claims that the Seresto flea and tick collar is injuring and killing huge numbers of dogs and some humans. Despite all the weaselly linguistic tricks to imply neutrality and plausible deniability if called out on making this accusation, no reasonable person could read this article and not get the message that this product is deadly and that the EPA is callously ignoring the danger, likely because they are in the pocket of Big Pesticide.
This article is an example of the horrifyingly bad journalism that we see all too often concerning the safety of pet healthcare products. It is full of anecdote and innuendo and guilt-by-association, but devoid of the kind of actual data that might tell us whether the fear the author wants to incite is justified. As veterinarians, we have all been through this before. The web sites, Facebook pages, sloppy journalism, and even lawsuits claiming the pets are being harmed by Rimadyl and other NSAIDs, and Trifexis, Febreeze, Swiffer, and of course vaccines are a fact of life for anyone in pet health professions.
It is easy to blame a particular product or treatment for something bad that happens to our pets. We naturally search for explanations when our companions are sick, and we tend to fixate on concrete things we can see and touch and potential causes we are primed to be suspicious of. Both reports of the real dangers of some pesticides, industrial chemicals, and medicines as well as the irrational demonization of all of these by opponents of mainstream medicine have implanted an automatic anxiety about the safety of such products in all of our minds.
When a pet falls ill suddenly, we look around for a reason. The food or medicine or vaccines or pest control products we may be using come readily to mind. Invisible viruses and bacteria, internal causes inside the body that we can’t see, and other common but intangible causes are less noticeable, and so less likely to be blamed. This availability bias is a classic psychological quirk that impedes our ability to accurately assess risk and identify the causes of undesirable events. It’s why we are more afraid of airplanes and sharks than cars and mosquitoes, even though the former are a lot less likely to hurt us than the latter.
Finally, there is an unfortunate tendency in the media to shock and disturb rather than inform, which this article illustrates. Such media coverage can easily lead to excessive and inappropriate panic about risks that are smaller than made to appear in the media or even entirely unreal. The Satanic Abuse panic of the 1980s is a classic illustration of this. Hysterical and dramatic reporting of individual claims that people had been ritually abused by Satan worshippers went from fringe publications to mainstream media. Despite years of widespread coverage and the ruining of people’s lives by unfounded allegations, hard evidence never emerged to substantiate these claims. While some individuals undoubtedly did experience abuse of some kind, the media generated both a fictional cause to blame and a surge of unreliable anecdotes by presenting the initial reports in a melodramatic and irresponsible way. Sadly, finding and fixing the really dangers behind such claims was only hampered by this media coverage, and the same is often true of health scares such as those I mentioned earlier.
Before we try to answer the question whether or not the Seresto collar is safe for our dogs, let’s look at the claims of this article and what they are based on. The writer begins, as usual in these kinds of scare pieces, with a heartbreaking anecdote of a pet dying. The owner believes this death was caused by the flea and tick collar she used, and the writer of the article jumps right from that to the claim that this product has been “linked to hundreds of pet deaths, tens of thousands of injured animals and hundreds of harmed humans.” The emotional setup here is clear, and the message that the product is dangerous probably doesn’t require any actual evidence for most people at this point. But the author does provide a link to support this claim. So what is that about?
The link is to a collection of reports on the EPA web site of illnesses and deaths in dogs using the Seresto collar. Seems pretty damning, doesn’t it? Here’s the trouble: Those numbers are simply collections of spontaneous reports made to the agency. Zero investigation has been done to show the reports are accurate or that there really is a connection between the product and the events described. The purpose of such reporting sites is to create a place for people to raise concerns. Agencies in charge of various public health areas collect and monitoring these spontaneous reports for signals suspicious for a problem that merits investigation. If a pattern is seen that suggests there might be a safety issue, the agency can investigate to determine if there is a real concern or not.
This is what happened with the issue of grain-free diets and heart disease that I have written about several times. The FDA saw a change in the number of reports received and began an investigation. Two years later, the nature of any association between these diets and the disease is still being studied, and their role, if any, in causing heart disease is still unclear. The fact that people reported their observations about heart disease and what they were feeding their dogs isn’t proof of a causal role, just a collection of anecdotes that may or may not signal a real problem. Rigorous scientific investigation is how we find out if health products are causing harm, not simply accepting every scary anecdote as true.
The same issue has come up innumerable times over many years with regard to vaccines and the Vaccine Adverse Event Reporting System (VAERS), managed y the CDC and the FDA. VAERS collects unsubstantiated anecdotal reports about possible harm from vaccines. Despite the overwhelming evidence for the safety of vaccination in general and most vaccines in common use, these reports are frequently cited by antivaccine activists to “prove” that vaccines are causing tremendous harm. One doctor actually submitted a report that a vaccine caused him to turn into the Incredible Hulk, and this report would still be in the VAERS database if he had not allowed the government to delete it.
Such databases are useful surveillance tools that can provide early signals of real problems, but they are also full of uncorroborated and inaccurate reports and speculation. They are not reliable evidence for a causal role of any product or medicine in harm done to people or animals. This, again, requires appropriate scientific investigation.
What else does this article rely on to support the clear claim that Seresto collars are killing dogs and injuring people? There are several strategies at play here. One is the use of unrelated cases of harm from pesticides to poison the well and imply that claims about the dangers of Seresto must be true since other pesticides have caused harm. The fact that claims have been made about harm from other pesticides (some true and some also unproven) aren’t relevant at all to the question of whether Seresto is safe or not, but they exacerbate the general anxiety or fear about pesticides to strengthen the reader’s willingness to accept negative claims about it. Clever rhetorical technique, I suppose, but not a legitimate form of argument that leads to the truth.
The citation of experts is also used to suggest Seresto is unsafe and the EPA is failing to protect the public. Quotes are provided from a “senior scientist… who has a doctorate in cell and developmental biology” at an environmental watchdog group and a “retired EPA employee… who worked as both a scientist and communications officer.” Noticeably absent from the expertise consulted is anyone with a specialty in veterinary toxicology or parasitology. Since assessing the safety and effectiveness of parasite control methods and the impact of toxins on veterinary patients is the central area of expertise for people in these fields, such individuals would have been far more likely to have relevant and informed opinions on the scientific question of whether or not Seresto is safe. Not including them is a pretty transparent technique for building a one-sided argument. I have heard from two veterinary toxicologists, a parasitologist, and a veterinarian with a national poison control center, and none of them found the allegations of widespread serious harm from the Seresto collar credible. Hopefully, people with appropriate expertise will weigh in on this issue publicly soon.
So is there scientific evidence and, if so, what does it tell us? There are published studies and reviews of the safety of both active ingredients in Seresto, imidacloprid and flurmethrin, as well as studies of the combination in the product itself. As usual, these provide a much more nuanced picture of the risks and benefits. It would be implausible and unreasonable to claim that no dog had ever experienced adverse effects from this or any other parasite preventative. As I point out forcefully and often, no medical intervention that does anything at all is without risks, so the important issue is understanding what the risks and benefits actually are and how they compare.
Imidacloprid is a common pesticide that has been used and studied extensively for decades. This EPA document provides a relative recent overview of the available evidence. Research in dogs and cats has shown extremely low risk, and this product has been used extensively for many years without any consistent or reliable evidence of the kinds of extreme harm depicted in this article. As always, some adverse effects from excessive or inappropriate use or in unusually susceptible individuals can occur, but overall there is nothing in the evidence concerning imidacloprid to justify the level of anxiety directed at Seresto in this piece.
The other ingredient, flumethrin, is a synthetic pyrethroid pesticide, a class that has also been studied and used extensively for a long time in dogs. Cats are especially sensitive to this class of agents, and they are not typically recommended for this species, but dogs are much less likely to experience adverse effects when pyrethroids are used properly. Those cases of harm that do occur are typically associated with improper dosing. Studies of flumethrin in dogshave found limited evidence of toxicity at doses well above recommended use for parasite prevention.
More importantly, there is published research evidence investigating the use of the combination of these ingredients in the Seresto collar. These have shown some adverse effects, but nothing even approaching the kind of common and devastating effects suggested by this article:
In cats, a total of 28 events were suspected to be related to study medication… 23 in the [Seresto] (9.0%) and 5 in the control group (5.6%) [using a different parasite collar]. This difference was not statistically significant (p > 0.4; Fisher’s exact test). [These events were] were generally mild dermal reactions (alopecia, pruritus, mild contact dermatitis).
In dogs, in the [Seresto] group 3 events (alopecia, hair coloration, dermatitis) and in the [control] group 4 events (alopecia, flea infestation, pruritus, aggressive behaviour towards a collar wearing animal) were scored as being related to the study medication. The difference between the two groups was not statistically significant (P > 0.16; Fisher’s exact test)
Small Non-Controlled Clinical Safety Study
No clinically relevant adverse event related to der- mal or systemic safety occurred and no abnormalities concerning general health were noticed during the course of the study.
Controlled safety studies – Seresto®/ Advocate®
All dogs tolerated the treatment well. Two out of 51 treated dogs showed transient skin alterations in the region of collar application, namely a crusty spot (approx. 1 cm diameter) on one day, respectively a moderate erythema of small (< 1 cm) to medium size (1 – 4cm) for about two days. Further findings in the treated group that were considered unlikely to be treatment related were conjunctivitis and a congested nasolacrimal duct in one dog, and a hot spot in the tail region of the same dog that showed erythema in the collar region. In the control group one dog also showed wounds and crusts in the neck region. No further clinical signs were present.
Blood hematology and clinical chemistry
No clinically relevant changes were detected for any parameter in the dog or cat study.
There are neither dermal nor systemic safety issues with the particular combination of the three actives imidacloprid, flumethrin and moxidectin in adult cats and dogs…
There is also research evidence showing that this product is effective in reducing flea and tick infestations, which can have the benefits of reducing allergy symptoms and protecting dogs against infectious diseases (and 2, 3) spread by these parasites. These benefits have to be weighed against any potential harm.
Finally, in terms of safety the available data has been evaluated by public agencies in many countries and found not to support claims of significant health risks. While the article accuses the EPA of a gross failure and dereliction of duty in not acting aggressively on the anecdotal reports it has received, as I pointed out earlier, such reports appear with many healthcare products, and these often turn out not to be accurate. It is possible that the risk here has been underestimated, but the burden of showing that with hard evidence remains on those making the claim.
One more issue that this article ignores is the subject of knockoff or lookalike products. Unfortunately, if a veterinary product is successful, it is common for other companies to make products that appear similar but have different ingredients in order to capture some of this market. It is also not unusual for fake replicas of a brand-name product to be produced in some countries and sold online as if they were the original product. These knockoffs have not passed the regulatory safety testing required of properly approved products. They may very well be less safe, and this can confound efforts to assess the accuracy of adverse event reports for these products. Such fake Seresto collars have made their way into the market, and it is possible some reports of harm may involve these rather than the original product.
So what’s the bottom line? Is Seresto a perfectly safe and effective parasite preventative or a poison decimating the dog populations? The truth, of course, is between these extremes. There are undoubtedly some risks to this product, and it is possible that they are greater than has so far appeared in the scientific literature. The research done on this product has mostly come from companies and investigators with a financial interest in it, and that always raises some concern about the potential for bias in the data. On the other hand, such concern doesn’t somehow make collections of unsubstantiated anecdotes a reliable source of data. The fact that some people think Seresto has harmed them or their dogs is not, alone, evidence that it has.
I don’t personally recommend Seresto for my patients because I find other parasite preventatives more convenient to use. I do have clients using it, and some doctors at my practice do prescribe it, and none of us have seen the kind of terrible effects depicted in this article. That is, of course, only more anecdote, but before we panic because of scary stories, it is worth remembering that there are many veterinarians and pet owners who have not had any negative experience with this product.
I hope that additional research shows that the concerns raised in this article are unfounded, but if it turns out the risks are greater than we currently realize, that will be important information. Unfortunately, rigorous scientific investigation takes time; a lot more time and work that sensationalist medial reporting. My hope is that reasonable people will respond to this latest example of poor-quality reporting in a reasonable way. We likely should take a careful, objective look at the safety data for this product, and perhaps conduct further research if warranted. We should not panic and blame every bad thing that happens to us or our dogs on the latest media bogeyman.