A South African province home to thousands of elephants is planning a birth control campaign for the pachyderms to prevent a population explosion that could threaten plants and wildlife, Reuters reported.

KwaZulu-Natal province is looking to expand a project running for more than a decade where elephant populations have been controlled by injecting cows with a vaccine that triggers an immune system response to block sperm reception.

South Africa, which had just over 100 elephants nearly a century ago, now has more than 20,000.

Studies have shown the vaccine is reversible, nearly 100 percent effective and has no adverse impact on elephant health or behavior.

据路透社报道，南非一个拥有数千头大象的省份计划启动大象生育控制行动，防止大象数量的激增危害到植物和野生动物。

夸祖鲁纳塔尔省正在考虑扩展一个进行了十多年的象群生育控制项目，该项目通过向母象体内注入一种疫苗，使其免疫系统阻止精子接纳，从而达到控制象群数量的目的。

近100年前，南非只有100多头大象，现在大象数量超过了2万头。

研究结果显示，这种疫苗是可逆的，有效性近100%，对大象的健康和行为没有不良影响。