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Fluoride has been identified as a ubiquitous contaminant of soils where petrochemical wastes have been disposed. The purpose of this study was to assess how widespread toxicity risks are to resident vertebrates from chronic exposure to fluoride in the soil of petrochemical-contaminated waste sites. In total, 573 wild cotton rats (Sigmodon hispidus) were examined. The rats that were seasonally collected from 12 contaminated and 12 ecologically matched reference sites across Oklahoma over a 3-yr period. The risks of cotton rats exposed to fluoride were analyzed by means of gross examination, histopathology, and scanning electron microscopy of rat incisors. Cotton rats from reference sites showed no pathologic changes in incisors (98%). In comparison, 46% of cotton rats from contaminated sites had various degrees of dental lesions. The prevalence and severity of dental lesions in cotton rats from contaminated sites were significantly influenced by season. There was a 45% increase in prevalence and a 65% increase in severity of dental lesions from summer to winter. This study demonstrated that cotton rats are very sensitive biomonitors for assessing toxicity risks from soils contaminated with fluoride and that such assessments should consider seasonal influences.

Various chemical mixtures exist in soil contaminated with petrochemical wastes, yet no comprehensive assessment of their impact on terrestrial ecosystems has been conducted. The purpose of this study was to evaluate hematotoxicity risks to wild populations of cotton rats (Sigmodon hispidus) residing in habitats previously contaminated by petroleum industrial wastes. Resident cotton rats were monitored on nine contaminated sites and nine ecologically matched reference sites in Oklahoma. The possible toxicological interactions of petrochemical wastes on bone marrow was investigated by using the assay of colony formation of granulocyte-macrophage progenitor cells. There was a consistent significant 21 to 39% decrease in the number of colony-forming units of granulocyte-macrophage (CFU-GM) in cotton rats from petrochemical-contaminated sites compared to matched reference sites, with no marked changes in hematological or histopathological parameters. These results suggest that bone-marrow progenitor cell culture is a sensitive indicator for the assessment of ecotoxicity risks associated with petrochemical wastes that are generated by the oil refining industry. Long-term exposure to hazardous wastes associated with the petroleum industry may represent a subtle risk to the hematopoietic system in humans.

Land-treatment of petrochemical wastes is a widely used method to dispose of hazardous and non-hazardous waste by biodegradation. However, no comprehensive assessment of the impact of such disposal techniques on terrestrial ecosystems has been conducted. Despite the presence of suspected immunotoxicants in the soil, wild rodents frequently reside on these waste sites after closure or abandonment. We explored the seasonal sensitivity of the immune system of the hispid cotton rat (Sigmodon hispidus) to in situ exposures on sites land-treated with petrochemical wastes. Animals were monitored on five contaminated land-treatment sites and five ecologically matched-reference sites in Oklahoma, USA, over two seasons (summer and winter). Most hematological parameters were not adversely affected by land-treatment; however, platelet counts were 26% greater in cotton rats from land-treatment sites compared to reference sites in winter. Significant treatment-related differences were observed in total serum protein concentrations, organ mass and organ cellularity, but these differences were not consistent across the five land-treatment units. Lymphoproliferative responses of cotton rat splenocytes stimulated in vitro were elevated for a T-cell mitogen and depressed for a B-cell mitogen in animals from land-treatment compared to reference sites. The ability of splenocytes to proliferate in response to interleukin-2 receptor-binding was not influenced by treatment. Total yields of peritoneal cells, yield of peritoneal macrophages, and yield of peritoneal lymphocytes were influenced to varying degrees by land-treatment. Functionally, in vitro metabolic activity of peritoneal macrophages was 114% greater in cotton rats from land-treatment sites compared to reference sites during summer. These results indicate that petrochemical wastes applied to soils on these five land-treatment sites had variable immunomodulatory effects in resident cotton rats. Immune alterations for some assays were indicative of enhancement on some land-treatment sites while suppressive on other land-treatment sites, which could have been a function of type and concentration of immunotoxicants present on each site and highlights the uniqueness of each land-treatment site.

Land-treatment of petroleum wastes is a widely used industrial practice, yet there has been no comprehensive evaluation of the long-term risks to human or terrestrial ecosystems from such practices. We evaluated cotton rat (Sigmodon hispidus) populations on three sites in Oklahoma (USA) that historically used land-treatment for disposal of various petroleum wastes (July 1995-March 1997). Average concentrations of fluoride in soil from these sites ranged from 878 to 4317 mg/kg. A census of resident cotton rats on land-treatment sites revealed a high incidence (40% overall) of dental lesions compared to reference populations (<1% dental lesions). During winter there was a 34% to 65% increase compared to summer in frequency of dental lesions in cotton rats on two of the three land-treatment sites. Incidence of dental lesions on two land-treatment sites was greater (9-16%) in female cotton rats compared to males. Cotton rats from land-treatment sites had higher concentrations of fluoride in bone and greater severity of dental lesions compared to reference animals. Dental lesions were considered to be most consistent with dental fluorosis because of elevated fluoride in bone. Neither concentration of fluoride in soil nor level of fluoride in bone was a good predictor of severity of dental lesions in cotton rats on land-treatment sites.

The ways in which comprehensive condition profiles, incorporating morphometric, histologic, physiologic, and diet quality indices, responded to changes in density of a white-tailed deer (Odocoileus virginianus) population were examined. Changes in these condition indices were monitored in a northeastern Oklahoma deer herd as density declined from peaks of 80 and 72 deer/km2 in 1989 and 1990 (high-density) to lows of 39 and 41 deer/km2 in 1991 and 1992 (reduced-density), respectively. Compared to a reference population (6 deer/km2), deer sampled during high-density exhibited classic signs of nutritional stress such as low body and visceral organ masses (except elevated adrenal gland mass), low fecal nitrogen levels, reduced concentrations of serum albumin, elevated serum creatinine concentrations, and a high prevalence of parasitic infections. Although density declined by one half over the 4-yr study, gross indices of condition (in particular body mass and size) remained largely unchanged. However, selected organ masses, serum albumin and non-protein nitrogen constituents, and fecal nitrogen indices reflected improvements in nutritional status with reductions in density. Many commonly used indices of deer condition (fat reserves, hematocrit, total serum protein, and blood urea nitrogen) were not responsive to fluctuations in density.

We determined the effects of sex, age, and environment (inbred, captive-wild, and wild animals) on selected blood parameters of the cotton rat (Sigmodon hispidus) in central Oklahoma (USA) from 1990 to 1994. Male and female cotton rats had similar blood profiles. Age-related differences were confined to differential white blood cell counts where adults possessed greater numbers of neutrophils and lower numbers of lymphocytes compared to juveniles. Environment had a strong influence on many hematological parameters. Hematocrit, hemoglobin concentration, RBC count, and eosinophil number were generally greater for wild stocks compared to inbred animals, and differences were more pronounced for adults than juveniles.

We have developed an in situ mammalian model for evaluating environmental contamination using wild cotton rats. In a series of experiments, 200 male cotton rats were captured during 4 collection periods (spring 1991 = 35; fall 1991 = 60; spring 1992 = 53; fall 1992 = 52). A total of 103 of these cotton rats were captured from control sites, and the remaining 97 were captured from an abandoned oil refinery. All sites were located in the vicinity of Cyril, Oklahoma. There were alterations in the incisors of cotton rats captured from the refinery site. Normal color of cotton rat incisors is deep yellow-orange, which is imparted by a pigment normally produced by ameloblasts. Grossly, the upper incisors of 37 of 97 rats and lower incisors of 54 of 97 rats were affected. The affected incisors were white, chalky, and thin with striations and erosions of the enamel. Microscopic examination revealed that there were dysplastic and necrotic changes in the ameloblasts. The bone fluoride levels were significantly higher in rats captured from the refinery as compared to the rats captured from the control sites.

Calcification of the urinary bladder epithelium was observed in 19 of 30 and 18 of 30 wild cotton rats from control and petrochemical-contaminated sites, respectively. The rats in the two sites did not differ significantly in respect of serum calcium and phosphorus concentrations. The calcification was considered to be dystrophic in nature. An unidentified factor common to both control and petrochemical-contaminated sites was considered to be responsible for this syndrome.

Radio-telemetry was used to monitor movements and mortality of 56 white-tailed deer (Odocoileus virginianus) in response to intensive military training activities on West Range (18,000 ha), Fort Sill Military Reservation, Oklahoma. Cause-specific mortality was determined for 22 radio-collared deer, including adults (greater than or equal to 2.0-yr-old), yearlings (0.6-1.9-yr-old), and fawns (less than or equal to 75-day-old age group) from 1987 to 1989. Winter home ranges were largely confined to a 14,411 ha impact area centrally located on West Range. The mean annual mortality rate was 0.50 for adults and yearlings combined. Fifty percent of all adult and yearling mortality was attributed to military training activities, 28% to hunting, 16% to collisions with automobiles, and 6% to unknown causes. The mean monthly mortality rate was 0.61 for neonatal fawns and predation accounted for three of four mortalities. All captured deer in the greater than or equal to 2.6-yr-old, 82% in the 1.6-yr-old, 10% in the 0.6-yr-old, and all deer in the less than 7-day-old age groups were seropositive for bluetongue virus (BTV). Our study strongly suggests that the consequences of military training activities should be considered in the management of white-tailed deer herds on military installations.

Thirty-one of 40 cotton rats (Sigmodon hispidus) collected from central Oklahoma were infected with Strongyloides sp. (78% prevalence). Larvae of Strongyloides sp. (rhabditiform or filariform) were not demonstrable in intestinal contents and scrapings. Female nematodes recovered from intestinal contents and scrapings had morphological similarities with Strongyloides sigmodontis. Cotton rats infected with Strongyloides sp. were indistinguishable clinically from non-infected hosts. Infected animals had no significant gross lesions, but the presence of Strongyloides sp. in the intestinal mucosa was associated with villus atrophy and mild to moderate infiltration of the lamina propria by lymphocytes, plasma cells and occasional eosinophils. Other organs or tissues examined were free from lesions induced by Strongyloides sp.