Anticoagulant Rodenticides Research Articles

The Public Health Response to a Large Poisoning Outbreak Involving an Illicit Substance: Synthetic Cannabinoids Contaminated With a Long-Acting Anticoagulant Rodenticide, Illinois, March-July, 2018.

During March-July 2018, the Illinois Department of Public Health responded to an acute outbreak of severe coagulopathy among patients with recent synthetic cannabinoid use. Toxicological testing indicated that cases were exposed to brodifacoum, a long-acting anticoagulant rodenticide. A total of 174 confirmed and probable cases, including 5 deaths, were linked to this outbreak. On the basis of the experience of responding to this complex outbreak, we recommend several steps for consideration to improve health department preparation for acute outbreaks involving illicit substances including strengthening communication between public health and law enforcement agencies, reviewing legal authority to investigate noninfectious acute disease outbreaks, continuing strong partnerships with state poison control centers, partnering with substance abuse and mental health agencies to provide services to patients, and determining health department ability to rapidly enter into public-private partnership agreements.

Pesticides threaten an endemic raptor in an overseas French territory

The Réunion harrier is an endangered raptor that is endemic to Réunion Island. Anticoagulant rodenticides (ARs) are widely applied on the island to prevent leptospirosis transmission to humans and limit the damage to sugarcane crops caused by rats and house mice. As these pesticides exhibit a high risk of secondary poisoning for rodent predators, we examined whether the Réunion harriers were exposed to and potentially poisoned by ARs. The AR concentrations in the livers of 58 harrier carcasses collected from 1999 to 2016 were measured. Both the temporal and spatial trends were analysed, and the influences of individual and landscape characteristics on the liver concentrations and potential poisoning were determined. AR residues were detected in 93% of the harriers. Difenacoum was the most frequently found (73% of positive cases), while brodifacoum and bromadiolone showed the highest concentrations. Both the numbers of harriers exposed to ARs and of individuals that were potentially poisoned increased over time. This is particularly alarming as the number of harriers potentially poisoned by brodifacoum increased dramatically beginning in 2014. We also showed that the landscape composition of the townships influenced the AR exposure, as the concentrations increased with the proportion of urban areas and showed a peak at 25% of the township under sugarcane cultivation. We conclude that AR poisoning is likely a main threat for Réunion harrier conservation and propose several actions to limit poisoning.

Medical outcomes of bromethalin rodenticide exposures reported to US poison centers after federal restriction of anticoagulants

Background: Exposures to bromethalin rodenticides have increased since restrictions were placed on long acting anticoagulant rodenticide (LAAR) registrations in 2008. Bromethalin works, in part, by uncoupling mitochondrial oxidative phosphorylation. Toxicity in humans is not well characterized and no antidote is available.Methods: This retrospective observational study analyzed data from the National Poison Data System (NPDS). The data set was derived from single substance bromethalin ingestions followed to a known medical outcome that were reported to US poison centers from 01/01/2008 to 12/31/2017.Results: There were 2674 bromethalin exposures in the NPDS database that met inclusion criteria. Of these exposures 2227 (83.28%) were pediatric, aged 16 days–12 years. Within this population, no effects were seen in 2143 (96.38%) of the exposures, 74 (3.32%) had minor effects, and 10 (0.45%) had moderate effects. No major clinical effects or deaths occurred in pediatric patients, although one patient with a major effect was of unknown age. Exposures in patients >12 years encompassed 391 patients aged 13–94 years. No effect was seen amongst 257 (65.73%) of the patients, 100 (25.58%) had minor effects, 23 (5.88%) had moderate effects, nine (2.30%) had major effects, and two (0.51%) patients died. Intentional ingestions among these patients accounted for one (0.25%) death and four (1.02%) major effects. Case details of the intentional ingestion death suggest the possibility of a miscoded long acting coagulant rodenticide.Conclusions: No major effects or deaths were seen in pediatric exposures. A majority of the possible bromethalin exposures involving adults reported to poison centers resulted in minor or no effects, though seizures, death and one questionable case of coagulopathy were documented. This dataset suffers from its retrospective nature, reliance on caller information, selection bias, information bias, and miscoding. It is possible that one or both deaths attributed to bromethalin exposure were not actually due to bromethalin.

Effects of different odours on the reproductive success of Mus musculus as an alternative method of control

The house mouse (Mus musculus) is a cosmopolitan rodent that has become adapted to living in close association with humans and is considered a serious pest because it poses a risk to human health, and causes economic losses due to food and crop consumption and damage to buildings. Its control in livestock farms is achieved mainly through the application of anticoagulant rodenticides, but the effect of these compounds is limited due to the presence of resistant individuals and aversive behaviours. A potential alternative method is the use of chemical signals to reduce rodent reproductive success. In this study, we assessed the effects of odours from an unfamiliar male, 17β-oestradiol, overcrowding, cat urine and 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) on the reproductive success of laboratory Mus musculus females. According to the generalized linear mixed models, cat urine odour increased the proportion of abortions per female, unfamiliar male odour decreased the mean number of offspring born per female, and TMT had an overall negative effect on mean offspring production at birth and at weaning. The other odours had no significant effects on reproductive success. TMT seems to be the best candidate for population control because it caused a decrease in the mean number of offspring born and the mean number of live offspring at weaning. TMT also has the advantage of being available in commercial forms. To be useful for rodent management in field conditions, these results should be confirmed using wild house mice females. © 2019 Society of Chemical Industry.

Anticoagulant Resistance in Synanthropic Rodents in the Stara Zagora Region, Bulgaria

Abstract The anticoagulant rodenticides are the most commonly used toxicants to control rodents nowadays. Therefore, developing resistance to them is an issue of great importance for pest control. The aim of this study was to investigate the sensitivity of synanthropic rodents in the Stara Zagora region, Bulgaria to some of the most significant first (warfarin and coumatetralyl) and second (bromadiolone and brodifacoum) generation anticoagulants. Resistance tests were carried out by a standard protocol using lethal feeding period tests and blood clotting response tests according to the European and Mediterranean Plant Protection Organization (Paris, France) standard. Studies were performed on 278 wild synanthropic rodents – 67 house mice (Mus musculus), 153 roof rats (Rattus rattus) and 58 brown rats (Rattus norvegicus). The rodents belonged to 11 populations inhabiting 9 animal farms in the region of Stara Zagora, Southern Bulgaria. High-level resistance to warfarinwas established in 100% of surveyed house mice and 92.1% of roof rats. Resistance to coumatetralyl was registered in 62.5% of the tested roof rats. Low-level resistance to bromadiolone was found in 38.5% of the surveyed roof rats and 23.1% of house mice. There was no resistance registered in brown rats. The sensitivity of all three rodent species to the strategic anticoagulant brodifacoum was high, and there were no signs of resistance. The results proved the resistance among synanthropic rodents and led to the conclusion that the resistance in house mice and roof rats to warfarin and coumatetralyl tends to be the main issue in pest control.

Recent history, current status, conservation and management of native mammalian carnivore species in Great Britain

AbstractAfter historical declines in population sizes and ranges, we compare and contrast the recent history and contemporary variation in the status of Great Britain's eight native mammalian carnivore species from the 1960s to 2017.WildcatFelis silvestrisconservation status is unfavourable and is masked by hybridisation with domestic catsFelis catus. Red foxesVulpes vulpesremain widespread but are currently declining. European otterLutra lutra, European pine martenMartes martesand European polecatMustela putoriuspopulations are characterised by rapid recovery. Otters have almost completely recolonised Great Britain, polecats have expanded their range throughout southern Britain from refugia in Wales and pine martens have expanded their range from the Scottish Highlands. European badgersMeles meleshave generally increased in population density. Status assessments of stoatsMustela ermineaand weaselsMustela nivalisare data‐deficient but available evidence suggests that stoats may have increased while weasels may have declined.Anthropogenic processes influencing carnivore status include legal protections, habitat quality, reintroductions, predator control, pollutants, hybridisation and diseases and their associated control practices. Population effects of contaminants, such as anticoagulant rodenticides, remain poorly characterised. The widespread interface with domestic and feral cats makes the wildcat's situation precarious. Recent declines in rabbitOryctolagus cuniculuspopulations are a concern, given that several carnivore species depend on them as food.We conclude that, with the exception of the wildcat, the status of Great Britain's mammalian carnivores has markedly improved since the 1960s. Better understanding of the social aspects of interactions between humans and expanding predator populations is needed if conflict is to be avoided and long‐term co‐existence with people is to be possible.

The relative toxicity of brodifacoum enantiomers

Brodifacoum (BDF) is a potent, long-acting anticoagulant rodenticide that can cause fatal poisoning in humans. The chemical structure of BDF includes 2 chiral carbons, resulting in 2 pairs of diastereomers, BDF-cis (R/S and S/R) and BDF-trans (R/R and S/S). However, the relative potency of these molecules is not known. The purpose of this study was to compare the in vitro and in vivo toxic effects of the 2 BDF diastereomer pairs. In adult Sprague-Dawley rats BDF-cis was significantly more toxic than BDF-trans (LD50 values of 219 versus 316 μg/kg, respectively) while racemic BDF had intermediate potency (266 μg/kg). In adult New Zealand white rabbits, BDF-cis had a longer half-life than BDF-trans which could contribute to its observed increased toxicity. Lastly, BDF-cis (10 μM), but not BDF-trans, damaged cultured SH-SY5Y human neuroblastoma cells by attenuating mitochondrial reductive capacity. Taken together, these data suggest that different toxic manifestations of BDF poisoning in mammals could be attributed, in part, to differences in relative enantiomer concentrations present in racemic formulations of this commercially-available toxicant.

Widespread anticoagulant poison exposure in predators in a rapidly growing South African city

Anticoagulant rodenticides (ARs) are used worldwide to control rodent populations. ARs bioaccumulate across trophic levels and threaten non-target wildlife. We investigated the prevalence of AR exposure in seven predator species in the rapidly developing Greater Cape Town region of South Africa – a mosaic of natural, urban, and agricultural areas within a global biodiversity hotspot. We focused sampling on caracals (Caracal caracal, n = 28) as part of a larger caracal ecology study, but also opportunistically sampled Cape Clawless otters (Aonyx capensis, n = 9), large-spotted genets (Genetta tigrina, n = 4), honey badger (Mellivora capensis, n = 1), water mongoose (Atilax paludinosus, n = 1), small gray mongoose (Galerella pulverulenta, n = 1), and Cape Eagle owl (Bubo capensis, n = 1). We tested livers from all species, and blood from ten caracals, for eight AR compounds to assess prevalence and amount of exposure for each compound. We used generalized linear models to test spatial, demographic, and seasonal risk factors for ten measures of AR exposure in caracals. We detected at least one of the four most toxic AR compounds in six species. Exposure was high for caracals (92%) and all species combined (81%). For caracals, proximity to vineyards was the most important AR exposure risk factor. Vineyards in Cape Town do not use ARs to protect their vines but do host commercial hospitality structures where ARs are used. Vineyards may thus link caracals that forage within vineyards to the rat poisons used in and around their commercial structures. Residue levels were unexpected in large-spotted genets and Cape Clawless otters, suggesting invertebrate vectors. ARs may present a cryptic threat to populations already vulnerable to increasing habitat loss, vehicle collisions, poachers and fire. Targeted mitigation should include a mix of environmentally responsible policies that reduce AR use, particularly in areas near wildlife habitat.

Exposure of non-target small mammals to anticoagulant rodenticide during chemical rodent control operations.

The extensive use of anticoagulant rodenticides (ARs) results in widespread unintentional exposure of non-target rodents and secondary poisoning of predators despite regulatory measures to manage and reduce exposure risk. To elucidate on the potential vectoring of ARs into surrounding habitats by non-target small mammals, we determined bromadiolone prevalence and concentrations in rodents and shrews near bait boxes during an experimental application of the poison for 2weeks. Overall, bromadiolone was detected in 12.6% of all small rodents and insectivores. Less than 20m from bait boxes, 48.6% of small mammals had detectable levels of bromadiolone. The prevalence of poisoned small mammals decreased with distance to bait boxes, but bromadiolone concentration in the rodenticide positive individuals did not. Poisoned small mammals were trapped up to 89m from bait boxes. Bromadiolone concentrations in yellow-necked mice (Apodemus flavicollis) were higher than concentrations in bank vole (Myodes glareolus), field vole (Microtus agrestis), harvest mouse (Micromys minutus), and common shrew (Sorex araneus). Our field trials documents that chemical rodent control results in widespread exposure of non-target small mammals and that AR poisoned small mammals disperse away from bating sites to become available to predators and scavengers in large areas of the landscape. The results suggest that the unintentional secondary exposure of predators and scavengers is an unavoidable consequence of chemical rodent control outside buildings and infrastructures.

Effect of GINGER AGAINST THE TOXICITY OF BRODIFACOUM ON ALBINO MALE MICE

Brodifacoum is a 4-hydroxycoumarin anticoagulant rodenticide of Rodents. This denotes a high possibility that contaminated the diet of man and his farm animals this fact alarmed some scientists to study their biological influence. Ginger (Zingiber officinale) has been used as an antioxidant and preventing agent against numbers of diseases. The study deals with effects of brodifacoum on the chromosome and on the liver and testis of male mice as well as and the protective effects of ginger extract. 130 Adult albino male mice were used in this study. Group (G1) served as control. Groups (G2&3) was received ginger extract doses 1.5% and 3%. Groups (G4&5) received single dose (1/10 LD50) of brodifacoum for group (G4) and (1/20 LD50) for group (G5). Groups (G6, 7, 8 & 9) received brodifacoum then ginger extract. Groups (G10, 11, 12&13) received ginger extract then brodifacoum. Animals from all the groups were sacrificed and their bone marrow cells were analyzed for chromosomal damage. Liver and testis samples are collected for histopathological examination. The animals of the groups that treated with brodifacoum showed significant increase of chromosomal aberrations and the value of mitotic index were reduced. Treated male mice with brodifacoum induced various histological changes in liver and testis. Treated animals with brodifacoum and ginger lead to reduction in chromosomal aberrations, significant increase in mitotic index and slight improvement in the histological change in liver and testis. Results obtained from this study demonstrated that brodifacoum has a mutagenic effect on chromosome and histopathological change in different organ (liver and testis) and the use of ginger may be a potent protective against the toxicity of brodifacoum anticoagulant rodenticide.

A rapid multi-class, multi-residue UHPLC-MS/MS method for the simultaneous determination of anticoagulant rodenticides, pesticides and veterinary medicines in wild animals, pets and livestock

UHPLC-MS/MS method simultaneously detects, identifies and quantifies over 150 multi-class chemicals that could contaminate or poison wildlife, pets or livestock.

Rodent pest control

Background. Rodent pests are natural reservoirs and vectors of a vast array of human and animal diseases caused by bacteria, rickettsia, viruses, protozoans, fungi and some parasites. The most important risk factor for human infection with Trichinella is the rearing of pigs on small farms and by rural households, if rodent pest control is not conducted regularly. Rodent pests cause economic losses by consuming, contaminating and/or damaging foods intended for human or animal consumption. Scope and Approach. The aim of this work is to point out the epidemiological and epizootiological importance of regular rodent control, and the importance of integrated use of all measures in deratization, as well as mistakes which can be made in implementing this procedure. Key Findings and Conclusions. The control of populations of pest synanthropic and hemisynanthropic rodents is a very complex and delicate task to carry out. Given all characteristics of the majority of rodent pest species, e.g. high reproductive potential, extraordinary adaptation to life in a variety of habitats and ability to develop resistance to anticoagulant rodenticides, the issue of controlling the number of rodent pests is considerably more problematic than it might seem at first glance. Therefore, appropriate scientific and professional knowledge is necessary to accomplish effective rodent control, which if done improperly, can have far-reaching negative consequences for human populations, non-target species and workers performing the task.

Superwarfarin (Long-Acting Anticoagulant Rodenticides) Poisoning: from Pathophysiology to Laboratory-Guided Clinical Management.

Superwarfarins are long-acting anticoagulant rodenticides developed from warfarin. The mechanism of action is by inhibition of vitamin K epoxide reductase, resulting in the inability of the body to recycle vitamin K. Deficiency of vitamin K thereafter leads to inability for the body to synthesise vitamin K-dependent coagulation factors, factor II, VII, IX, and X, leading to prolonged prothrombin time. Due to the bulky aromatic sidechains, superwarfarins have a much longer half-life when compared to warfarin, and exposure to superwarfarins results in a prolonged period of anticoagulation which can result in clinical bleeding. Diagnosis is straightforward in patients with known history of superwarfarin exposure but has proved difficult for patients who did not report superwarfarin intake. Superwarfarin poisoning should therefore be suspected in all patients with unexplained prolongation of prothrombin time, and can be confirmed by their detection in serum. Treatment for superwarfarin poisoning includes rapid correction of factor deficiencies with either 4-factor prothrombin complex concentrate or fresh frozen plasma in patients with active bleeding, and high dose vitamin K therapy given multiple times per day for a prolonged period of weeks to months.

A review: poisoning by anticoagulant rodenticides in non-target animals globally.

Worldwide use of anticoagulant rodenticides (ARs) for rodents control has frequently led to secondary poisoning of non-target animals, especially raptors. In spite of the occurrence of many incidents of primary or secondary AR-exposure and poisoning of non-target animals, these incidents have been reported only for individual countries, and there has been no comprehensive worldwide study or review. Furthermore, the AR exposure pathway in raptors has not yet been clearly identified. The aim of this review is therefore to comprehensively analyze the global incidence of primary and secondary AR-exposure in non-target animals, and to explore the exposure pathways. We reviewed the published literature, which reported AR residues in the non-target animals between 1998 and 2015, indicated that various raptor species had over 60% AR- detection rate and have a risk of AR poisoning. According to several papers studied on diets of raptor species, although rodents are the most common diets of raptors, some raptor species prey mainly on non-rodents. Therefore, preying on targeted rodents does not necessarily explain all causes of secondary AR-exposure of raptors. Since AR residue-detection was also reported in non-target mammals, birds, reptiles and invertebrates, which are the dominant prey of some raptors, AR residues in these animals, as well as in target rodents, could be the exposure source of ARs to raptors.

Use of blood clotting assays to assess potential anticoagulant rodenticide exposure and effects in free-ranging birds of prey

Non-target wildlife, particularly birds of prey, are widely exposed to and acutely poisoned by anticoagulant rodenticides (ARs). An unresolved issue surrounding such exposure, however, is the potential for sublethal effects. In particular, the consequences of AR exposure and resulting coagulopathy on health and survival of unintentionally exposed animals, which often encounter a multitude of anthropogenic stressors, are understudied. In a wildlife rehabilitation setting, AR intoxication may be masked by more obvious injuries related to collision with vehicles or electrocution, thereby obfuscating proximate from ultimate cause of mortality. An assessment of coagulation function of admitted wildlife may provide a means of identifying animals exhibiting sublethal coagulopathy, and ultimately ensuring provision of appropriate and swift treatment. In conjunction with routine diagnostics for injury and disease, we performed two blood clotting assays (prothrombin time, Russell's viper venom time) affected by vitamin K-dependent coagulopathy of samples from six species of live raptors admitted to a rehabilitation facility. We also measured clotting time in pre-fledgling barn owl chicks (Tyto furcata) from 10 nest sites in Lower Mainland Canada. Prolonged clotting time or failure to form a clot altogether was observed in 23.0% of 61 sampled raptors admitted to the rehabilitation facility. This is a biologically significant proportion of individuals given the fortuitous and likely biased nature by which raptors are found and admitted to rehabilitation facilities. In contrast, there was little evidence of coagulopathy in 19 pre-fledgling barn owl chicks. The utility of avian coagulation tests for diagnosing AR exposure is promising, yet there remains a need to establish species specific reference values and standardize assay methodologies among testing facilities.

Effects of physical barriers and eradication on recolonization of rodents in poultry farms

Mus musculus, Rattus rattus and Rattus norvegicus are pests in poultry farms, causing economic losses and transmitting diseases. Control is commonly conducted through anticoagulant rodenticides, but this control is not effective through time. We aimed to assess the effect of rodent exclosure on long-term success of rodent control in poultry farms of the pampean region, Argentina, and to evaluate indirect estimators of rodent abundance. In both exclosure and non-exclosure sheds rodent abundance decreased significantly after eradication but mice populations showed a recovery, suggesting that the eradication was not complete. Rats did not recover, but the low abundance found at the beginning of the experiment does not allow an accurate conclusion.

The research of synthesis and bioactivity of the novel indanedione anticoagulant rodenticides

Three new anticoagulant rodenticides R1, R2, and R3 were designed. The containing fluorine acute toxicity groups was added to 1,3-indandione derivative. Analysis method of synthesized anticoagulant rodenticides were IR, 1H NMR. Acute bioactivity of the new rodenticides was evaluated, including the coefficient of absorb food and median lethal dose (LD50). Average coefficient of absorbed food for R1 was 0.54 and LD50 of R1 was 2.15mg/kg. Average coefficient of absorbed food for R2 was 0.59 and the acute oral LD50 of R2 was 2.65mg/kg. Average feeding coefficient of R3 was 0.68 and the acute oral LD50 of R3 was 3.12mg/kg. Experiments showed that rat's death peak was at about 72h and rodenticides had good characteristics of acute medicine. The LD50 of three new fluoride anticoagulant rodenticides showed that they had good palatability for big white rats, and they had a strong poison effect on rodent. The result of all experiments proved that the synthesis of 1,3-indan diketone used as parent compound of new anticoagulant rodenticides could replace the current 4-hydroxyl coumarin as parent compound of the second-generation anticoagulant rodenticides. 1,3-Indan diketone would be widely used as parent compound of anticoagulant rodenticides.

Urbanization and cattle density are determinants in the exposure to anticoagulant rodenticides of non-target wildlife

The persistence and toxicity of second generation anticoagulant rodenticides (SGARs) in animal tissues make these compounds dangerous by biomagnification in predatory species. Here we studied the levels of SGARs in non-target species of wildlife and the environmental factors that influence such exposure. Liver samples of terrestrial vertebrates (n = 244) found dead between 2007 and 2016 in the region of Aragón (NE Spain) were analysed. The presence of SGARs was statistically analysed with binary or ordinal logistic models to study the effect of habitat characteristics including human population density, percentage of urban surface, livestock densities and surface of different types of crops. SGARs residues were detected in 83 (34%) of the animals and levels >200 ng/g were found in common raven (67%), red fox (50%), red kite (38%), Eurasian eagle-owl (25%), stone marten (23%), Eurasian buzzard (17%), northern marsh harrier (17%), and Eurasian badger (14%). The spatial analysis revealed that the presence of SGARs residues in wildlife was more associated with the use of these products as biocides in urban areas and cattle farms rather than as plant protection products in agricultural fields. This information permits to identify potential habitats where SGARs may pose a risk for predatory birds and mammals.

Evaluating the susceptibility of invasive black rats (Rattus rattus) and house mice (Mus musculus) to brodifacoum as a prelude to rodent eradication on Lord Howe Island

The use of anticoagulant rodenticides to eradicate invasive rodents from islands has become a powerful tool to prevent species extinctions and to restore degraded ecosystems. Success is dependent on all targeted individuals consuming rodenticide and dying as a result. Because susceptibility to anticoagulants can vary among rodent populations, it is important when planning an eradication to understand the efficacy of the proposed rodenticide on the target animals, particularly where there has been historic exposure to anticoagulants. The aims of this study were to investigate brodifacoum-susceptibility of black rats Rattus rattus and house mice Mus musculus on Lord Howe Island (LHI), Australia, where an eradication program is being planned. Black rats and house mice were subjected to various dosages of brodifacoum in a series of laboratory feeding trials. The results showed that rats on LHI died after consuming doses of rodenticide within expected ranges (60% died at 0.5 mg kg−1 and 100% died at 0.8 mg kg−1) when exposed to bait for 24 h. Mice, on the other hand, were more tolerant of the rodenticide, with 82% of individuals surviving doses of up to 2.0 mg kg−1 consumed over 24 h and some individuals needing 6.0 mg kg−1 consumed over 4 days to ingest a lethal dose. A laboratory experiment designed to simulate field application showed that all mice tested succumbed to brodifacoum poisoning when given the opportunity to consume sufficient bait (at least 6 days of exposure to toxic bait), although some individuals took 22 days to die. The results of these studies will help inform the Lord Howe Island rodent eradication.

Do bromadiolone treatments to control grassland water voles (Arvicola scherman) affect small mustelid abundance?

The use of pesticides can affect non-target species by causing population declines through indirect intoxication. Small mustelids (SMs; weasels, Mustela nivalis L.; stoats, Mustela erminea L.) consume water voles (WVs, Arvicola scherman S.) and can be exposed to bromadiolone, an anticoagulant rodenticide used in some countries to reduce WV damage to grasslands. Here, we investigated whether bromadiolone affected SM abundance. We monitored SM abundance using footprint tracking tunnels in spring and autumn at ten sites. Among these sites, four were treated with bromadiolone, while six were not treated. We found reduced SM abundance at these four sites from spring to autumn (treated sites, mean±SE SM abundance change=-1.68±0.42; untreated sites, 0.29±0.25). Using a linear model, we observed that SM abundance decreased as a function of the quantity of bromadiolone applied during the 3months before the autumn estimate. We found that WV abundance increased at treated sites (linear model, treated sites, mean±SE WV abundance change=1.4±0.4; untreated sites, 0.33±0.25). Thus, at treated sites, SM abundance declined despite increased food availability. By analyzing residues in vole livers and SM scats we showed that SMs may be exposed to bromadiolone at the sites where this compound was used. This study is the first to document the relationship between SM abundance and bromadiolone usage for small mammal control. Declines in SM abundance were observed at treated sites, where bromadiolone residue was found in SM scats. This correlative approach suggests that bromadiolone treatment may lead to seasonal SM declines and associated WV increases. © 2018 Society of Chemical Industry.