Abstract

The green vervet monkey (Chlorocebus aethiops) population on St. Kitts has resulted in a human-monkey conflict with monkeys causing significant damage to agricultural crops. A gonadotropin-releasing hormone (GnRH) immunocontraceptive vaccine (GonaCon™)^a was selected for a pilot trial to determine the efficacy and duration of a single vaccine administration in suppressing reproductive function. Four control and six experimental animals were chosen from a group of 22 sexually mature, captive, adult female vervet monkeys based on regular estrous activity. The control monkeys were given a 0.5-ml saline emulsion injection intramuscularly. The experimental monkeys were given a 0.5-ml, 500-microgram dose of the GnRH vaccine in the same manner. Two separate adjuvants (adjuvant 1 and 2 with associated controls) of the vaccine were used, as the first adjuvant caused significant localized reactions. Blood samples were collected on a weekly basis initially and then once a week for three weeks, with one week off in a repeating schedule. Serum from the females was analyzed for estradiol and progesterone using validated human ELISA kits. Currently 1/3 monkeys in the adjuvant 1 experimental group has started cycling at 33 weeks post-vaccination. 3/3 experimental monkeys in the adjuvant 2 group started cycling on average 25 weeks post-vaccination. It appears that adjuvant 1 provides a longer duration of activity than adjuvant 2 with a single vaccine administration. Unfortunately, both adjuvants led to an increased incidence of localized swelling at the injection site, many leading to abscess formation. An alternative adjuvant will be investigated.

Endnotes

a. GonaCon, USDA, APHIS, Wildlife Services, National Wildlife Research Center, Fort Collins, CO, USA