Chlordane-Induced Neurotoxicosis in Urban and Suburban Detroit, Michigan Striped Skunks (Mephitis mephitis)

Abstract

Despite the ban of technical chlordane, contamination from this persistent organic pollutant has threatened wildlife and human health nearly forty years since its last application. The purpose of this study is to highlight the need for more systemic, broad-scale research efforts to monitor technical chlordane in wildlife sentinel species in urban settings to understand the nature and extent of pesticide pollution and mitigate risk associated with exposure to these compounds. This study presents an unusual finding of neurotoxicosis and elevated chlordane metabolite concentrations in Michigan striped skunks in the absence of other viral or toxic etiologies. In this study, eight of seventeen skunks displaying illness and neurologic signs had brain tissue concentrations of combined oxychlordane, heptachlor epoxide, and trans-nonachlor exceeding the 1000 ng/g wet weight diagnostic threshold for toxicosis. Liver tissue concentrations were ten-fold greater than those of the brain when measured on a lipid weight basis, which can help predict lethal brain residues in skunks. The ongoing presence of chlordane in the environment is expected to cause further unintended consequences for wildlife across the Detroit Metropolitan Area for decades to come. Together, veterinary toxicologists, wildlife biologists, environmental toxicologists, ecologists, and policy makers must utilize a One Health transdisciplinary approach and continue to evaluate the long-term effects of chlordane exposure. As with other pollutants in the River Rouge and River Raisin Areas of Concern, the presence of chlordane in the urban environment presents a significant risk for animal, human, and ecological health.

Keywords: Great Lakes watershed; chlordane; neurotoxicosis; organochlorine; persistent organic pollutants; skunk; wildlife.

Figure 1

The sum chlordane-related compounds in the brain and liver on a wet weight and lipid weight basis. Concentrations of chlordane-related metabolites in the brain on a wet weight (A) and lipid weight (B) basis and liver on a wet weight (C) and lipid weight (D) basis in skunk tissues (n = 17) with a 95% confidence interval of the mean in red.

Figure 2

Chlordane-related compounds in the brain and liver on a wet weight and lipid weight basis. Concentrations of oxychlordane, heptachlor epoxide, trans-nonachlor, and total chlordane components in the brain on a wet weight (A) and lipid weight (B) basis and liver on a wet weight (C) and lipid weight (D) basis in skunk tissues (n = 17).

Figure 3

Liver versus brain total chlordane plus metabolite concentrations (ng/g) on a wet weight (w.w) (left) and lipid weight (l.w.) (right) basis.

Figure 4

Total PCB versus chlordane and chlordane metabolite concentrations in liver (left) and brain (right) l.w.

Figure 5

Skunk geographic distribution by summed brain chlordane compound exposure level (wet weight). Summed oxychlordane, heptachlor epoxide, and trans-nonachlor concentrations are divided into three levels of exposure: low (<1000 ng/g), intermediate (1000–9999 ng/g) and high (>10,000 ng/g). Individual animals are represented by pins on the map of Michigan based on their exposure level and county of origin. The River Raisin and River Rouge Areas of Concern are highlighted with shaded ovals overlapping the counties that contain these watersheds.