Traditionally, the sign for elided words is the ellipsis, which is three dots. Those used to be created with periods. In modern word processing, it is its own symbol.
Trafficking in children from Togo, Nigeria, Mali, to Cote d’Ivoire’s plantation and domestic servants in Gabon, and of women from Ghana, Nigeria, Mali, and Sierra Leone as exploited sex workers in countries of the European Union has also taken root.
Trafficking... domestic servants... [from] Sierra Leone as exploited sex workers in countries of the European Union has also taken root.
The brackets are necessary around the "from" because it does not appear in that position in the original text.
There are a couple of cautions. Some of the other answers here seem to suggest that brackets are necessary around an ellipsis that's not in the original text. That's not a rule I've ever encountered, but it might be the new academic standard. Your own discipline may have a style guide that covers this situation.
Also, it's considered bad form to chop up someone else's words too much, since you can dramatically change meanings that way. Therefore, it may indeed be better in this case to just paraphrase the original, and indicate that fact when you cite it, as in the accepted answer.