PZP puts elephant population control within reach

Delegates at the International Wildlife Management Congress in Durban recently heard of the successful use of the PZP (porcine zona pellucida) immunocontraceptive vaccine.

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PZP is controlling populations of wildlife species such as elephant, deer and zebra. PZP is a non-hormonal vaccine derived from pig eggs (oocytes). It causes the production of antibodies which block the reproductive process and prevent pregnancy. PZP has been used in SA to manage reproduction in 230 elephant cows at 13 parks, including Thornybush, Makalali, Phinda and Temba. The first PZP trials were undertaken in the Kruger National Park in 1996.

Research and development funding has been primariily provided by the Humane Society International (HSI). Audrey Delsink, HSI field director, said PZP exhibited efficacy in controlling population growth as part of a long-term management strategy. “PZP reduces populations without reducing fertility and is fully reversible. It has no physical or behavioural side effects. It addresses the impact of elephant numbers on water resources and vegetation and offers an alternative to culling excess animals.”

Elephant cows on PZP have exceeded the three to six year average intercalving interval (ICI) of the African elephant. “At Makalali, after 12 years of using PZP, all the treated cows passed the 4,5 year ICI. Between 2000 and 2003 (the founding years of the project), population growth declined from 30% to 15%. It has now stabilised at 3% because we only treat females after they have had their first calf,” said Delsink.

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Prof Henk Bertschinger, who heads the HSI-funded laboratory at the University of Pretoria where the PZP vaccine is produced, said the primary vaccine costs R440 and the booster R220. Global Supplies’ (specialists in immunocontraception) director JJ van Altena said PZP made managment of large populations of free-ranging elephants possible. “A herd of 12 cows can be darted in five minutes from a helicopter,” he said. HSI’s CEO Andrew Rowan said research into a single-dose vaccine was now being funded.