Recipient Organization
TUFTS UNIVERSITY
200 WESTBORO ROAD
N. GRAFTON,MA 01536
Performing Department
Environmental & Population Health
Non Technical Summary
As human development continues to encroach upon wildlife habitat, wildlife and humans are increasingly faced with the need to co-exist in close proximity. Human alteration of the environment impacts wildlife in countless ways. This proposed project directly addresses one such human impact on wildlife - human environments attract commensal rodents, which need to be controlled to protect human health, which in turn threatens wildlife health when poisons are used for this purpose. It is clearly a necessity to control commensal rodent populations in human-dominated environments for reasons of sanitation and public health. The methods employed to achieve rodent control present an area of conflict between the needs of people and the health of wildlife. The use of rodent poisons is widespread in urban, suburban, and agricultural areas. If rodent poisons must be used to safeguard human health, this conflict can be addressed by ensuring that the poisons with the least potential to harm wildlife health are employed. The goal of this project is to document the effectiveness and consequences of recent EPA action, which took effect in June 2011 and is intended to decrease the risk to wildlife from second generation anticoagulant rodenticides (SGARs). From 2006 to 2010, this investigator conducted research on exposure to and mortality from SGARs in four species of birds of prey in Massachusetts. The results showed that 87% of 161 birds tested had residues of SGARs in liver tissue. This study will investigate exposure and risk of toxicosis in four species of birds of prey from several rodenticides (rodent poisons) which have been impacted by regulations enacted by the US EPA in June 2011. These new regulations prohibit the sale to general consumers of one category of rodenticide, the second generation anticoagulants (SGARs), which have been shown to cause illness and death in birds of prey. However, SGAR use will still be allowed by licensed pest professionals and agricultural users, allowing them to potentially remain in the food chain. The restriction of SGARs from the general market has led to their replacement with two other categories of rodenticides, the first generation anticoagulants (FGARs) and the neurotoxic agent bromethalin. The risks of FGARs to birds of prey are not well studied, and there is little information on the potential effects of bromethalin. This project will be the first to investigate the risk of bromethalin to birds of prey. The study population will be four species of free-living birds of prey from an area where widespread exposure to SGARs prior to new EPA regulations has been documented. This project presents a rare opportunity to evaluate whether recent EPA action will have the intended result of decreasing the threat of poisoning from SGARs in wildlife. Additionally, this study will begin evaluating SGAR alternatives, the risks of which to wildlife are not well understood, as their availability to general consumers increases following EPA action.
Animal Health Component
30%
Research Effort Categories
Basic
50%
Applied
30%
Developmental
20%
Goals / Objectives
Different types of rodenticides are employed to control nuisance rodent populations. In recent decades, the anticoagulant rodenticides (ARs) have been widely used. In target and non-target animals alike, ARs interfere with blood clotting, resulting in fatal hemorrhage. ARs are subdivided into first generation (FGAR) and second generation (SGAR) compounds. All ARs present a threat to wildlife either from direct ingestion of bait (primary poisoning) or consumption of poisoned prey (secondary poisoning). SGARs are thought to present a greater threat to wildlife than FGARs as they are more potent, more toxic, and persist in body tissues longer, resulting in bioaccumulation in the food chain. Poisoning and mortality of birds of prey from ARs has been documented in the United States. A 2011 study by this investigator showed widespread exposure among 4 species of birds of prey in Massachusetts, particularly to the SGAR brodifacoum. In 2008 the U.S. EPA issued the Final Risk Mitigation Decision for Ten Rodenticides disallowing the sale of brodifacoum and three other SGARs through general consumer outlets, effective June 2011. The decision allows the sale of SGARs to agricultural users and pest management professionals, however, allowing SGARs to potentially remain in the food chain. Rodenticide manufacturers have registered replacement products with the EPA. Therefore the use of products containing the FGARs chlorophacinone and diphacinone and the neurotoxic agent bromethalin is likely to increase. Studies have shown that raptorial species of birds are very sensitive to the toxicity of FGARs. Bromethalin acts to disrupt intracellular metabolism, resulting in fatal swelling in the brain. There is little information on the potential risks of bromethalin to birds of prey or other wildlife species. Bromethalin has been determined experimentally by the EPA to be highly toxic to birds if directly ingested. Sublethal amounts of bromethalin in birds have been documented to result in lethargy, ataxia, reduced food consumption, reduced body weight, and convulsions. The lack of data on bromethalin's potential to cause secondary poisoning or long- term effects in birds and other wildlife is a critical gap in knowledge about this agent. The specific objectives of this study are threefold. 1. Document the percentage of birds (4 species of birds of prey) exposed to SGARs. This percentage will be compared to a previous study by this investigator among a population in the same geographic area prior to new EPA regulations. 2. Evaluate levels FGARs in these 4 species. These FGARs are present in newly registered products for the general consumer market to replace SGARs. 3. Investigate the potential toxicity of bromethalin, a neurotoxic rodenticide also present in products newly registered for the general consumer market. The hypotheses are 1) the percentage of birds exposed to SGARs (compared to previous data) will decrease but will remain high; 2) the percentage of birds exposed to FGARs will increase; 3) exposure to and mortality from bromethalin will be detected.
Project Methods
Birds included in this study will be free-living red-tailed hawks (Buteo jamaicensis), barred owls (Strix varia), eastern screech-owls (Megascops asio), and great horned owls (Bubo virginianus). Birds will be recovered from urban, suburban, and semi-rural communities surrounding the clinic. No birds will be euthanized for the purpose of this study. Birds will be sampled regardless of clinical suspicion of rodenticide toxicosis to investigate subclinical and toxic levels of exposure. Post-mortem examinations will be performed within 24 hours of death. Liver samples will be collected. Screening and quantification of ARs and bromethalin will be performed at a laboratory in CA. If AR toxicosis is suspected, histopathology will be performed to confirm the diagnosis. Tissues will be collected and histopathology will be performed by a laboratory in NH. In addition, histopathology will be performed on birds that die showing central nervous system abnormalities in order to confirm or rule out bromethalin toxicosis, as bromethalin toxicosis mimics signs of traumatic brain injury and is difficult to diagnose without histopathology. Statistical analysis will be performed using nonparametric tests, as the data is expected not to be normally distributed. P values smaller than 0.05 will be considered significant. Different tests / statistical analyses will be used for comparison purposes. As species differences in sensitivity to rodenticides exist, further statistical analyses will be conducted on each species independently. Special tests will be used to evaluate cause of death and body condition in relation to rodenticide level to determine if sublethal effects, such as malnutrition, are evident.