Army medical researchers at Fort Detrick have successfully completed preliminary human testing a new vaccine for Rocky Mountain spotted fever, a disease which, based on the number of reported cases, is occurring at a record rate in Maryland this year.

No vaccine currently is available for the rickettsia virus, cause for Rocky Mountain spotted fever. The disease, usually carried by ticks, causes damage to the kidneys, the liver and the nervous system in 20 percent of the known cases.

In 5 to 10 percent of cases that have been treated, the disease has proved fatal, according to researchers at the Atlanta-based Center for Disease Control.

Maryland Health officials say 44 cases of Rocky Mountain fever had been reported by the end of last week, more than twice the 18 reported during the first six months of 1977.

Nationwide, the number of known cases of the disease has declined slightly from last year, when a record number of cases were reported. Health officials say that the "tick season" generally runs from May through September in most areas.

The new vaccine under study has been developed by Dr. Richard Kenyon, the assistant chief of rickettsiology at Fort Detrick. Kenyon thus far has tested the vaccine in diluted form on two small groups of human adults, with "very encouraging" results, he said.

More extensive testing on humans, using undiluted samples of the vaccine, is expected to begin soon, he said.

Testing on larger groups of adults, and on children - whom the disease most often strikes - must still be carried out before the drug is approved, the FDA's Elisberg said.

The vaccine has been found to be completely effective in preventing all strains of Rocky Mountain spotted fever when tested in animals, according to Kenyon.

Kenyon also predicted that the vaccine he has developed "could be on the market within a year, if there is enough demand for it."

Officials at the federal Food and Drug Administration, which must license the new vaccine, are less optimistic.

"If people really wanted it, if the money were available and it were put on a high priority, it could be done in a year," said Dr. Bennett Elisberg, director of the FDA's Pathology Division of Biologies.

"But I don't think there's much interest in the drug or the disease by the American public, so it could be a matter of two to three years.

Kenyon, who, with two assistants, has been working to develop the vaccine for more than eight years, said that the vaccine is produced from chick embryos.

According to Kenyon, cell cultures from the embryos are grown on a metal sheet. Individual cells in the tissue are then infected with the virus - causing protective antibody agents to form - and then purified with formaldehyde.

The resulting vaccine, when injected into humans, is expected to protect them from any infection of Rocky Mountain Spotted Fever, if the initial tests results are corroborated by more extensive human testing.

The new vaccine, Kenyon hopes, will replace one manufactured by the Lederle Pharmaceutical Co., which Lederle officials took off the market this year after an FDA study showed it to be ineffective.

Should the new vaccine prove effective, officials say, it could stop what has been a steadily increasing incidence of the disease over the past several years.

Last year, a record 1,115 cases of Rocky Mountain spotted fever were reported nationwide - most of these in the "tick belt" states of Maryland, Virginia, North Carolina, South Carolina and Georgia - according to the CDC. So far this year, 229 cases have been reported, CDC officials said - about 50 less than at the same time last year.

Because April was either unusually dry or unusually cold in many areas, officials believe the tick population has declined in many states, causing the decrease in case reports.

In contrast, Maryland health officials theorize that an unusually moist period during April may have contributed to the dramatic rise in Rocky Mountain fever cases in the state.

According to Dr. Lawrence D'Angelo of the CDC, Rocky Mountain spotted fever has become increasingly widespread in the tick belt states since the early 70s, partly because of a large rise in the number of ticks.

"There has been a general drop in pesticide use," D'Angelo said, "partly because DDT can no longer be used, and partly because of reasons of practicality - states are not willing to undertake large-scale spraying programs."

D'Angelo also cited improved reporting of the disease and the rise in popularity of outdoor activities such as camping and hiking as causes behind the case increase.

In Virginia and Maryland, spraying programs against ticks have been abandoned and health officials in recent years have concentrated on publicizing the disease's symptoms - unusually high fever followed by rashes on the hands or feet.

Recently, researchers of the New York State Department of Health have been testing a new local spraying technique that they say could soon be commercially available to home owners.

Dr. Dennis White, one of the directors of the program, said that over the past two years researchers have identified four chemicals particularly effective against ticks in small areas.

The chemicals, he said, are "non-residual" - meaning that no trace of the active agents remains within hours after spraying.

White said that he is working with the Chevron Co. to market a spraying device that would allow home owners to use one of the chemicals, in an anti-tick spray. He said that the device would become available as soon as state and U.S. labels are obtained for it.