There are few things more repulsive than ticks. It's the combination of the blood sucker and the spider, I suppose.(Did you know ticks are spider cousins?)

But ticks in general are not cause for panic. The ones you have to worry about account for fewer than 10 percent of the total tick population. Those are the disease carriers, mostly of the organism that causes Rocky Mountain spotted fever, an illness rarely seen in the Rockies any more -- although it was discovered there -- but seems now to concentrate in the Mid Atlantic states.

This is the tick season. It can vary from year to year depending on the weather, and it's actually rather late this year because of the wet June. But ticks and their ills can be seen from May to September.

Dr. Harvey Fischman, Johns Hopkins University associate professor of Veterinary Medicine and one of several Hopkins experts researching ticks and their toxins, and Dr. Chad Helmick, the Rocky Mountain fever maven of the Center for Disease Control, have some sensible suggestions for coping with "tick season" and tips for recognizing so-called "tick fever."

First some facts:

There were, reports CDC, 1,153 cases of RMSF in the U.S. last year. Of these, 61 percent were in the South Atlantic states: the Carolinas, Oklahoma, Maryland, Virginia, Tenessee and Georgia.

According to the latest figures, says Helmick, 1981 will be another record year. As of last week there had already been more than 500 cases reported, 36 of them in Maryland and 46 in Virginia, where there already has been one fatality.

The organism that causes Rocky Mountain spotted fever is a rickettsia, something between a virus and a bacterium. It has been generally accepted that the tick needs to feed on the host for 6 to 8 hours before infection can occur, but the researchers note that this is an assumption not yet given enough scientific scrutiny.

There is no approved vaccine, although work continues on a promising one.

Young people seem particularly prone to contracting RMSF, with the highest risk ages 5 to 9. While those over 39 have a lower incidence of the illness, they are more likely to die of it. This may be because their symptoms more often do not follow the traditional pattern and the illness goes unrecognized until too late.

More whites get it than blacks, but again, cases in blacks more often end in death. (Because the illness responds well to certain antibiotics, the overall fatality rate is low, between 3 and 8 percent, or 49 people last year.) The illness must be treated promptly. Laboratory confirmation can take more than two weeks, much too long to wait, so treatment must be started on the basis of what doctors call clinical diagnosis.

Here are some defensive suggestions:

If you know you will be in the moist, woodsy or grassy areas where ticks abound, dress protectively in long sleeves, long pants and pants legs tucked into sturdy boots.

Make periodic tick checks. Ticks, notes Fischman, are upwardly mobile -- "they usually climb up" -- so a check should begin around the head. Don't miss ears, inside and out. You don't feel a tick while it is becoming imbedded, so you must search assiduously. Children should be checked every few hours in the summer, with special care before they go to bed.

If you find a tick "just roaming," you can (if you're outdoors), says Fischman, just brush it off.

Don't try to crush a tick with your bare hands. Scientists now believe tick excretions may contain the infective organism which can enter a human through a cut or scrape.

If you find an imbedded tick, the best technique for removal, suggest both Fischman and Helmick, is to use tweezers, grasping the tick firmly and pulling gently and steadily. Sometimes petroleum jelly or alcohol or nail polish will encourage the parasite to let go. (A hot matchhead may do the same, but it is just as likely to burn a child or animal.)

If the tick is engorged, try not to crush it. (It is stronger than it looks or feels.)

Leaving the tick's head in -- as often happens -- does not make the victim any more susceptible to the disease. But it is a foreign body and may be a source of (usually mild) infection.

Paint the bite liberally with alcohol or other antiseptic.

Rocky Mountain spotted fever usually starts about three days after the bite, but it can be sooner or later -- up to 12 days. Generally, says Helmick, "They come down with a fairly acute illness -- fever and headache -- and then about the third day there is a characteristic rash which begins around the wrists and the ankles and then spreads to the rest of the body. There may also be muscle pain, gastrointestinal pains and problems, bleeding into the skin and, if there is no treatment, more serious complications which can lead to death."

Ticks can transmit several other organisms that can cause illnesses in people (and pets). These include tularemia, Q-fever, hemorraghic fever, Colorado tick fever and various kinds of encephalitis.In Connecticut in recent years, tiny ticks have been linked to an ailment called Lyme arthritis.

Some ticks contain a powerful toxin which can cause weakness, even paralysis, in people and dogs. This can be fatal, but it quickly disappears once the tick is removed. Because the symptoms resemble polio and other neurologic ailments, a tick -- remember it is rarely felt -- may be overlooked.

Anytime any illness follows a tick bite, a doctor should be consulted promptly and informed that a tick bite occurred.