This is an idea on how to reduce disease spread by mosquitoes. The mosquito's saliva glands produce an enzyme (reactive protein) that prevents blood coagulation (thins the blood) when they bite. It could be really easy to genetically change that enzyme so that it is caustic to viruses and bacteria. If the disease (such as malaria) is dissolved/killed at the point of transference, the disease cycle is broken.
If changing the enzyme so that it is antiviral/ antibacterial is too hard for some reason, though I think it could be very simple, or is uncomfortable in some way such as causing a sting instead of an itch (although I think it could cure the itch), there is another way. If you genetically transplant the code for an antibacterial and antiviral enzyme that is produced by individual cells into the saliva glands of the mosquito, it could have the same effect of killing the virus/bacteria at the point of transference. The active ingredients of lemon balm (melissa officialis), or any other antiviral organically produced compound could do the job.
This idea can be extended possibly into using mosquitoes for immunisations. If you transplanted quinine production into mosquitoes, for instance, the more you are bitten by the designed mosquito, the more immunised you are against malaria, for instance. The idea can also be extended into any disease carrying pests, such as ticks, flies, cockroaches etc.
Dispersing the genetically improved mosquito looks like a technical nightmare for the financially minded (how do you make money from it?), but it isn't really. Firstly, it would take decades to cure the whole world even if we all worked really hard at it. Basically, the area would have to be gassed to kill the original mosquitoes, or the larva killed, or timed when the numbers are low, but are about to seasonally increase. There are channels already to sell the products relating to those tasks. Then you could have a "Good Mosquito Kit" (rest assured, financially minded people, it's a sure bet in the right locations) to start a population of benign mosquitoes in the treated area. It could be like an ant farm or a sea monkey kit. Children can do it. The new population would take up mosquito territory, thus preventing or diluting the return of the disease spreading mosquitoes. Anywhere where mosquitoes are deadly would be very interested, as well as anyone who finds them annoying to them or their livestock etc. Because the kit would be relatively low cost (essential), people all over the world could use it. High turn over is the way with this idea, as well as an essential niche market, that great business trophy. And it has a feel good buzz!