Why does warfarin kill rats

It is moderate to high in toxicity to other aquatic life. However, registered bromadiolone products may not legally be applied to water. Therefore, it is unlikely to come in contact with other aquatic life. Research with bromadiolone on snakes and earthworms has demonstrated no toxic effects. NPIC provides objective, science-based answers to questions about pesticides.

Please cite as: Wick, K. NPIC fact sheets are designed to answer questions that are commonly asked by the general public about pesticides that are regulated by the U.

Environmental Protection Agency U. This document is intended to be educational in nature and helpful to consumers for making decisions about pesticide use. NPIC provides objective, science-based information about pesticides and pesticide-related topics to enable people to make informed decisions.

Environmental Protection Agency cooperative agreement X The information in this publication does not in any way replace or supersede the restrictions, precautions, directions, or other information on the pesticide label or any other regulatory requirements, nor does it necessarily reflect the position of the U. Bromadiolone General Fact Sheet. What is bromadiolone? What are some products that contain bromadiolone? How does bromadiolone work?

How might I be exposed to bromadiolone? What are some signs and symptoms from a brief exposure to bromadiolone? What happens to bromadiolone when it enters the body? Is bromadiolone likely to contribute to the development of cancer? Has anyone studied non-cancer effects from long-term exposure to bromadiolone? Are children more sensitive to bromadiolone than adults? What happens to bromadiolone in the environment? ARs work by interfering with the blood's ability to clot. But there is a huge variation in how susceptible individual birds and animals are to the poisons, says Maureen Murray, a wildlife veterinarian from Tufts Cummings School of Veterinary Medicine in North Grafton, Massachusetts, who has worked with hundreds of injured birds of prey, many suffering from AR poisoning.

Similar variation is seen among humans who take blood-thinning drugs such as warfarin. Governments are moving to address the problem. On 1 January, Canada will start restricting most outdoor household use of ARs to the less-toxic first-generation compounds, says Elliott.

And in most situations, bait will have to be contained in tamper-resistant bait stations or in other locations not accessible to non-target wildlife. There is also a move towards increased use of a potent neurotoxin called bromethalin, said Anne Fairbrother, director of ecosciences at Exponent, a science and engineering consultancy in Bellevue, Washington.

A survey conducted last summer found that "a lot" of operators put their products outside and leave them there for a long time. Nor is she enamoured with the idea of switching to bromethalin. AR poisoning, by contrast, can be treated using vitamin K. Better policy, says Fairbrother, might be to ban permanent bait stations and to require pest-control operators to use ARs only as needed.

Consumers should also be told about the potential ecological effects of such compounds. Beginning about , similar reports of apparent resistance emerged from North Carolina, New York and California. To make matters worse, warfarin-resistant rodents appeared to be resistant to some of the other anticoagulants that had been developed, such as chloro-phacinone and diphacinone. This phenomenon was labeled "cross-resistance.

In response to the discovery of warfarin-resistant rodents, the pest control industry fell back upon the acute, single-feeding rodenticides.

At the same time, rodenticide manufacturers pushed to developed new, more potent anticoagulants. The effort was successful, with compounds like brodifacoum, bromadiolone and most recently difethialone appearing on the U.

These "second-generation" anticoagulants are strong enough to be considered acute toxicants, since a single feeding can kill a rat or mouse. The mode of action is the same as warfarin, and vitamin K is antidotal.

While some cases of "cross-resistance" have been reported, the second generation of anticoagulants have been effective replacements for warfarin for several decades now. However, a regulatory backlash has been building as reports of non-target incidents attributed to the second-generation products have accumulated over the years.

In , the EPA issued the first of a series of documents that may lead to new limits on the use of second-generation anticoagulants.

The REDs describe data gaps in the toxicology profile of each rodenticide. Individual companies must generate the missing research data in order to keep their product registrations active and on the market.

The draft version of an EPA "comparative assessment of rodenticide risks" was issued in The final version is to be issued this summer.

In this case, rodenticide manufacturers have joined together and formed a task force to respond to the agency. A carefully crafted industry response was very critical of the draft document. This response has been made available for public viewing as an EPA Docket Document and can downloaded at www.

In spite of this, indications are that the final document will not be very different from the draft version. In Dec. This graph can be downloaded at www. Warfarin is ranked among the safest rodenticides by the EPA.

This can be attributed to two characteristics of the compound. First, the slow action provides a large window for medical intervention in cases of accidental child or pet poisoning. Second, warfarin is rapidly metabolized and excreted from the body.

The half-life, or the time required for the warfarin load in the body to decrease by one half, is about 42 hours. Warfarin is also used in humans, under the trade name Coumadin, for blood clot and stroke prevention. Most people who undergo surgeries such as coronary by-pass or joint replacements, take Coumadin for clot prevention. By contrast, the second-generation anticoagulants are not readily metabolized. Warfarin is not as potent as many other rodenticides.

It is typically formulated at parts per million, about five times higher than other anticoagulants. The low potency and slow action required that baits be supplied in relatively large quantities with closely spaced placements, and that fresh bait be offered for a longer time than is sometimes needed with other rodenticides. The length of exposure may not be as important as originally thought with warfarin.

Historical data from our studies of both first- and second-generation anticoagulants reveal that mortality curves, or time until death after ingestion of bait, is surprisingly similar among all the anticoagulant compounds. Maintaining a constant supply is the most critical factor to success with warfarin baits. Mice are generally harder to control with warfarin than rats. They are erratic feeders, and the availability of even small quantities of alternative foods will dilute the dietary concentration of the rodenticide.

However, recent studies in our laboratory have demonstrated that percent mortality in mice can be achieved after five days of exposure. Poor acceptance was a problem often associated with warfarin baits in the past. But now it has been well established that the problem lies with impurities found in poor quality warfarin. Highly purified warfarin mixed with fresh, high-quality ingredients is well accepted by rodents.

Buyers prepared their own baits. Often an inappropriate grain was selected, or poor quality grain was used, and the predictable result was poor acceptance. Probably the greatest concern surrounding warfarin is resistance. How important is this in most situations? The answer is that it will rarely be an issue. However, in the case that a pest management professional encounters this problem, he or she must be aware of the situation and monitor it carefully.

Genetic resistance to warfarin among rats is not widespread. Wild house mice we have trapped from various locales where resistance had been reported in the s, failed to survive the World Health Organization WHO screening test with warfarin.

In addition, the very definition of warfarin resistance has been called into question in recent years. According to WHO standards, rats that can survive six days of feeding on a 50 part-per-million ppm warfarin bait are "resistant. In this test the rats were offered a choice between the warfarin bait and conventional rodent chow. Tests by the N. State Health Department showed that repeated exposures to 50 ppm warfarin baits alternated with 30 day "clean-out" periods will kill almost all "resistant" Norway rats.

Researchers Stephen Frantz and Constance Madigan concluded that, "… resistant Norway rats are likely to die upon re-exposure to warfarin, the very product which is used to identify or define their resistance. Warfarin baits are still very effective for routine rat control.

Adrian Meehan, in the classic reference Rats and Mice: Their biology and control , states that "It is generally recognized that long-term feeding of warfarin to susceptible brown rats will invariably produce complete mortality. According to Robert M. Corrigan, Ph. So, does warfarin belong in the rodent control arsenal of the pest professional? Any rodenticide should be just one part of a well-considered IPM program. A good IPM program will include educating the client, reducing and removing conditions that attract pests, and minimizing the use of pesticides.

When pesticides are necessary, select the least toxic, safest pesticide that will get the job done. In many cases warfarin can fill the bill. In other cases, alternative products will do the job. Just as with controlling insects, pest management professionals must use all of the available tools in their toolbox. Professor Marsh notes that "Warfarin has the greatest non-target safety margin of all currently used anticoagulant baits, [and] efficacy is only marginally sacrificed for safety.

Warfarin may be preferred where safety to non-targets is a greater concern than resistance. The author is a senior scientist with Genesis Laboratories Inc.

He can be reached at jbaroch giemedia. Springtails are minute insects that cause concern with homeowners due to their jumping habits and the large numbers in which they can be found. These insects can build up enormous populations in the landscaping areas around our structures and also in damp areas inside of homes basements, cellars, bathrooms, kitchens, etc. They usually become problematic in spring and summer, but certainly in some areas of the country they can be found all year-round.

These insects are generally not considered medically important since they do not bite humans, spread disease nor damage structures or furnishings. Springtails, while small, do appear in different shapes and sizes. The first detection of rodent resistance occurred in rats in Scotland in Basically mice have a genetic mutation to be immune to warfarin. The mutation to vkorc1, a gene found in all mammals that manages vitamin K, makes mice resistant to the anticoagulant.

Warfarin works to reduce vitamin K creating blood clots. So, the production of more vitamin K is the obvious way to overcome poisoning. Mice have evolved to become poison resistant. Genes adapt through spontaneous mutations during DNA replication.