Remember the term 'vector' from your high school biology classes? Of course you do - it's that bird or bug or animal that transmits a disease from a host to a recipient - or victim, if it happens to be you.
In our part of the world, almost the only vector-borne illness is Lyme disease, named in 1975 for Lyme, Connecticut, where it had become almost epidemic.
The host in our area is likely to be the wild black-footed mouse, an inoffensive little fellow who just happens to be a carrier of the bacteria Borrelia burgdorferi, the cause of Lyme. The vector is the black-legged tick, Ixodes (hard-bodied) pacificus, a bug about the size of the head of a paper match, often orange-red on the back and rump.
Early in their two-year life, while still microscopic, ticks larvae bite mice for a meal of blood, become infected with B. burgdorferi (which does them no harm), then a year or more later bite and infect persons or animals. Deer are favourites, hence its common name: deer tick.
Only about one in a hundred ticks carry the bacteria, but if you are unlucky enough to be bitten by that one, you may break out in a rash, often characterized by a red 'bull's-eye' around the bite. 'May' because just about everything to do with Lyme disease is fraught with uncertainty, inconsistency and controversy.
Most bites produce an immediate allergic reaction to toxins - swelling, redness and itching - but B. burgdorferi is an infection, not an allergy, and may not manifest itself for days or even months. If the bacteria get into the bloodstream, a red rash may appear anywhere on the body, often accompanied by such flu-like symptoms as fever, chills, headache and joint pain.
Happily, B. burgdorferi is not transmitted by the tick for 36 to 48 hours, plenty of time to detect the beast and pull it out with tweezers. Unhappily, only about 20 per cent of Lyme victims recall being bitten, meaning that they were beset by ticks at their nymph stage, when they are about the size of a poppy seed.
Early stage Lyme can be treated with antibiotics, though not with total success. The disease has a way of turning up months or years later with a bewildering array of symptoms that mimic other conditions affecting the brain, nerves, eyes, joints and heart. The diagnostic tests to nail down this elusive disease are all unreliable in one way or another.
So, best not to get yourself infected in the first place. Tuck your pants into your socks, wear a hat and button your collar if you are hiking in the bush, especially at low elevation close to the coast. And most important: peel off and have someone inspect you head-to-toe when you get home.
Lyme disease often just fades away on its own after early symptoms, thanks to a healthy immune system. So keep topped up on vitamins A, B, C and E; minerals zinc, magnesium and manganese, and omega oils 3 and 6. Finally, there appears to be a correlation between heavy metals and Lyme disease. If you've had symptoms, heavy metal testing and chelation therapy may be in order.