There are numerous psychological treatments for pathological jealousy. If the cause of pathological jealousy, narcissistic entitlement or low self-esteem then we would address those issues in individual therapy. If the causes of pathological jealousy are relational in nature then we would bring a couple in and assign various exercises to the couple.
For instance, one of the exercises is called the Dutch Cow technique because cows always wear bells around their neck to let their owners know where they are. In that approach we would ask the jealous spouse to ask the non-jealous spouse to call her or him throughout the day every hour and to let the jealous spouse know where he or she is. In that way, this constant ringing, this constant bell becomes annoying and over time often the jealous spouse decides it's better not to be in constant contact with the non-jealous spouse.
There are also ways in which we write down causes for jealousy and wishes of how the partner should behave in a different way. And also examine negative cognitions or negative thoughts that people tend to ruminate on that would cause these jealous thoughts. There are numerous treatments for jealousy and they all depend on whether the jealousy is an individual or relational problem.