Last night I had the privilege to listen to an exceptional presentation on the topic of sandfly saliva at the Baltimore Tropical Medicine Dinner Club. Most people know I am weird and have an unhealthy obsession with all things infectious disease, but sandfly saliva doesn't necessarily stand out to the general public as being related to infectious disease. That is unless, of course, you're talking about leishmaniasis.
Leishmaniasis is a neglected tropic disease caused by a parasite that is spread by the sandfly and causes about a million cases a year in the both the "Old World" and the "New World", including a handful in the US (Texas and Oklahoma). It was more recently in the headlines after returning US soldiers were diagnosed with it (The Baghdad Boil).
There is no vaccine for this affliction and if it involves the viscera, it can be a severe disease. The lecture I attended by the NIH's Jesus Valenzuela discussed the ability of the saliva of the sandfly to modulate infection with the parasite. Using a ting-yang analogy, it was shown that not only does the saliva facilitate infection by giving the sandfly ready access to un-clotted blood in which the leishmania parasites can be injected--not surprising knowing how microbes can hijack any processes for their own needs. What the molecules in the saliva do in addition to this is what is truly fascinating. Uninfected sandfly saliva can prime the victim's immune system so that when subsequently exposed to leishmania at a later time, some protective immunity is engendered. Such a finding can be applied to a vaccine which will have sandfly saliva molecules as one of its components, in addition to leishmania antigens.
The lesson: sandfly spit is cooler than you thought.