The multibillion-dollar trade of exotic animals is much bigger and harder to stop than you think

The recent killing of a Zimbabwe lion named Cecil by an American dentist and trophy hunter not only triggered outrage on social media, it has also renewed concerns about the illegal wildlife trade, worth an estimated $10 billion (£6.4 billion) worldwide.

The buying and selling of exotic animals and animal parts, which may include the poaching of rhinos for their ivory or the hunting of lions and tigers for their skins, is at the center of a thriving underground black market.

In 2012, CNBC's Brian Schatman reported on the smuggling of live animals and animal products into the United States. With so much cargo coming into the country through various routes and very few wildlife inspectors, the report explained why the criminal enterprise is very difficult to stop.