Submitted to: Journal of Comparative Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/21/1998
Publication Date: N/A
Citation: Interpretive Summary: Raccoons in the USA have been found to have high lead levels in their tissues and clinical cases of lead poisoning have also been reported in this country. Lead is an environmental toxin. Experimentally it has been shown that administration of lead may produce impairment of immune functions, resulting in increased susceptibility to infectious diseases. It has, therefore, been speculated that raccoons with lead in their bodies may have an increased susceptibility to certain infections and also, may not produce an adequate immune response when vaccinated against diseases such as rabies. The purpose of this investigation was to study effects of lead in raccoons. It was anticipated that the study would reveal the optimal dose for inducing lead poisoning without killing raccoons. This information would then be available for a subsequent experiment to study the effects of lead on oral rabies vaccination in raccoons. Eight raccoons were used for this study. Two were controls. The remainder were given daily oral doses of lead acetate for 8 weeks and were sacrificed at the end of this period. The animal were examined on daily basis and samples (blood and tissue samples) were obtained for laboratory tests. At the end of the 8-week experimental period most raccoons had either maintained or gained body weight and none showed clinical signs of lead poisoning. The results of this study suggest that raccoons are fairly resistant to lead. Therefore, they may be of value in studying the interactions between lead exposure and oral vaccination of wildlife against rabies.
Technical Abstract: Four pairs of raccoons were treated orally with the following doses of lead acetate (mg/kg; 5 days/week, for 8 weeks): 0 (control), 1, 2 and 4. In the six experimental animals, this treatment produced dose-dependent increases in blood lead, without clinical signs or changes in hematological parameters. After 8 weeks, the liver and kidney of all lead-treated animals and the calvarium and radius of those receiving doses of 2 and 4 mg/kg contained elevated concentrations of lead. Acid-fast inclusions were observed by light and electron microscopy in the kidneys of all raccoons receiving the two highest doses and in one animal receiving the lowest dose. Hepatic acid-fast inclusions were seen in only one animal (dose 4 mg/kg). No inclusions were seen in osteoclasts of the radius. It is suggested that the findings, which support earlier observations that raccoons are fairly resistant to lead, may be of value in studying interactions between lead exposure and oral vaccination of wildlife against rabies.