For more than half a century of medical research, the scientists at the Gorgas Memorial Institute of Tropical and Preventive Medicine have survived deadly tropical diseases.

They have endured bouts of malaria, leishmaniasis and potentially fatal infections such as Chagas' disease, which is spread by the kissing bug--a clever, thumb-sized, blood-sucking insect that likes to bite people on the lips and makes one wonder why anybody in their right mind ventures into the tropics.

This spring, the institute's researchers encountered adversaries that make the kissing bug look tame: the budgeteers and policymakers of the Reagan administration.

Seeking to shift money to other forms of biomedical research, the government has proposed that Gorgas, a private organization in Panama with headquarters in Washington and advocates in Maryland, be cut from the 1984 budget.

The funds cut from Gorgas and 53 other research centers in the United States would be applied to the National Institutes of Health research grants program.

"No one is saying these others aren't doing good work," said Norman Mansfield, a budget officer at NIH. "The basic policy choice is that NIH is likely to get a better payoff in the acquisition of knowledge. You pick things that give you the biggest payoff. Gorgas wasn't one of them."

That choice, say the officers of Gorgas, will mean an organization that has been supported by the United States since 1928 will be sacrificed like a lab rat.

"If we do not get our appropriation in October, we are on the trash heap," said the institute's volunteer president Leon Jacobs, who is leading the fight to get Congress to restore funds for the Gorgas Insitute. "We are absolutely dead."

Created as a living memorial to Gen. William C. Gorgas, the man who all but eradicated the yellow fever mosquitoes and thus enabled construction of the Panama Canal, the institute is hardly the last line of defense against the kissing bug and its disease-carrying cohorts.

Laboratories in many countries are conducting research into tropical maladies. Moreover, NIH officials emphasize that the "investigator-initiated" project grants are scrutinized more thoroughly by other scientists.

But Gorgas proponents argue that the institute is unique--a field laboratory that allows scientists the chance to probe tropical diseases in the swamps and jungles of origin.

In recent years, an annual appropriation of about $1.8 million, plus a contribution from the government of Panama, have funded the institute's Washington office and its laboratory in Panama City. The institute employs a staff of 100.

It was work at the institute that did much to document the way the kissing bug transmits the microsocopic trypanosome parasite that causes Chagas' disease. The kissing bugs bite rats or possums and pick up the parasite.

Next the blood-suckers slip onto humans, looking for a set of lips or some other suitably juicy area. As they bite, they excrete the parasite which enters the human body through the wound. In acute cases, the tiny trypanosome can weaken the heart muscle so severely that the cardiac membrane will burst like a water balloon.

Chagas' disease affects millions of people in Central and South America, and a cure continues to elude researchers.

Supporters of the institute, among them representative Rep. Beverly B. Byron (D-Md.) and Hagerstown plastic surgeon and Gorgas board member Dr. John W. Clark, also argue that the institute's financial lifelines should be restored because the laboratory has had a beneficial influence in a troubled region.

President Jacobs, a former NIH scientist and "tropical disease man" who devoted much of his career to studying toxoplasmosis (he contracted the disease and has instructed his colleagues to examine his brain tissue after his death for traces of the bug), put it more strongly:

"Considering the turmoil going on down there, this is one of the most stupid acts the American government has ever done. It's an absolutely ridiculous idea to cut out the one research organization that is apolitical and is trying to do a job that is not only related to Panama, but to the health of the United States as well. I'm a retired guy. This is eating away at my life."