Field evaluation of the immunocontraceptive GonaCon(TM) in reducing eastern gray squirrel fecundity in urban areas.

摘要

The purpose of this study was to evaluate the immunocontraceptive GonaCon(TM) in reducing fecundity in Eastern gray squirrel (EGS) (Sciurus carolinensis ) in urban areas. Using a modified box trap design, 317 EGS were captured during four trapping sessions on a 5.66 ha site on Clemson University's main campus. EGS were handled using a restraint cone and sexed, weighed, ear-tagged and implanted with a microchip at the nape of the neck on all "original" captures and later identified in subsequent captures as "recaptures." Blood samples and morphometric data were obtained on EGS before the immunocontraceptive GonaCon(TM) was administered by injection during three trapping sessions to 33 EGS (17m, 16f) in trapping session 1 (TS1), 23 (14m, 9f) in trapping session 2 (TS2), and 11 (8m, 3f) in trapping session 3 (TS3) at a dosage rate of 0.4 ml containing 400 ig of GnRH-blue protein conjugate intramuscularly in the thigh. Control EGS were given a sham injection containing 0.4 ml saline- AdjuVac(TM) during the three trapping sessions: 22 EGS (16m, 6f) in TS1, 20 (12m, 8f) in TS2, and 8 (4m, 4f) in TS3. In the last trapping session (TS4) 35 EGS were necropsied to evaluate histological changes in testes and ovaries as potential metrics of GonaCon(TM) efficacy and to determine its potential side effects.;EGS density on the study area was estimated to be 9 +/- (2.89) EGS/ha, based on the Lincoln-Peterson model. There were no significant differences in body weights of treated and control EGS by TS3 (p = 0.40), or testosterone (p = 0.32) and progesterone (p = 0.68) levels. However, there were significant differences in antibody titers between treated and control EGS by TS3 in both males and females active antibodies seen in the treatment group (chi2 = 5.656, df = 1, p = 0.017). There were highly significant differences in scrotal size of treated and control males with a reduction in scrotal size being observed in treated males (t = 10.14, df = 8, p = 0.001). There were marked histological changes in treated EGS males and no observable histological changes in treated EGS females. Although there were no serious side effects to the vaccine; 6 EGS developed injection site abscesses. GonaCon(TM) may be a potential tool to manage EGS overabundance in urban areas, but additional research is needed.