| Popis: |
This project included (a) experiments to define the gross, microscopic and hematologic changes associated with lead poisoning in 5 and 18-week-old mallard ducks, (b) experiments to define the gross and histologic changes associated with Pasteurella multocida (P-19781-2) infection (avian cholera) in mallard ducks, (c) experiments to study possible interaction between ingested lead, lead-iron and iron shot and P. multocida infection in mallard ducks and (d) an experiment to determine the effect of various concentrations of lead, as lead acetate, on the in vitro growth of P. multocida on blood agar culture plates. Young mallards were less vulnerable to the effects of lead than were older mallards. Birds fed whole mixed grain had increased mortality and a higher prevalence of lesions than did ducks fed a commercial ration. The retention of pellets in the gizzard of 18- week-old mallards was greater than was shot retention in 5-week-old birds, but no difference was observed in the dissolution rate of shot between the two age groups. The dissolution rate of lead pellets approximated 6.7 mg/pellet/day. Blood lead concentrations in lead and lead-iron dosed ducks peaked at approximately day 9 post-dosing and then declined. Blood lead concentrations in the ducks were several times higher than those reported in lead-poisoned mammals, but the soft tissue lead retention in the birds was comparable to soft tissue lead retention in mammals. Demyelinating peripheral neuropathy and focal encephalopathy were observed in lead-dosed mallards that were in good body condition, not anemic and feeding normally. Inoculation with Pasteurella multocida (P-19781-2) produced septicemia in mallards that died acutely and chronic localized lesions in surviving birds. P. multocida could be cultured from localized lesions which supported the concept of a "carrier" state. A dosetime- mortality response was observed in P. multocida infection trials. None of the shot types tested increased the susceptibility of mallard ducks to P. multocida. Shot types containing lead had a protective effect against infection that appeared related to blood lead concentration. In vitro experiments showed that lead, at concentrations equivalent to the blood lead concentrations in leadpoisoned birds, inhibited growth of P. multocida on blood agar plates. A similar bacteriostatic action of lead was postulated to explain the in vivo results. Birds pre~dosed with lead shot had histologic evidence of degenerative changes in lymphoid tissue, spleen and bursa of Fabricius. The possible significance of these morphological changes was discussed. **NOTE: There was no page 161 in the original thesis |
