Well, in regards to the cause it's more or less the 3rd party affects i.e nutrition & water quality. It may be possible that certain species are more prone to it however I disagree when it comes to some not being susceptible at all. Either way, based of a couple studies it looks like "Activated Carbon" is a major possible cause. Other sources state that it's linked to over crowding, nutrition, lack of oxygen, and nitrates. (all of which being generic examples vs. specie specific vulnerability)
Conclusively, it looks most Cichlids can develop the illness, and will depending on the conditions. As far as treatment goes, there is probably a plethora of that information on the web as well.
Sources:
http://en.wikipedia.org/wiki/Head_and_lateral_line_erosion
http://www.fishchannel.com/fish-health/freshwater-conditions/hexamita.aspx
http://www.peteducation.com/article.cfm?c=16+2160&aid=2586