About two weeks ago, as I bent over to give my dog Jack a good ear rub, I saw something float by and land on the carpet near him. Even though it’s only March and we’re still getting irregular temperatures with cool nights, I had a mosquito in the house. And she was carrying a full load that she’d sucked out of one of us.

Parasites are already starting to come out. If mosquitoes are on the wing, you know the ticks will be dropping, too, given just a warm day or two, and that means fleas (sigh) won’t be far behind.

It’s time to think about protecting your companion animals from these nasty little buggers for the warm season.

First off, think about heartworms. Cats are a bit luckier in this department: Although they’re not immune, they’re much less susceptible. Dogs, however, get them much more readily, and preventatives are your first line of defense.

If you don’t keep your dogs on heartworm medication year-round, don’t start by simply purchasing some and dosing. On the off-chance that he or she contracted heartworms last season, the medication could prove fatal, and here’s why:

Heartworms are transferred into a dog’s body through mosquito bites. Heartworms live not only in dogs and cats but also foxes, coyotes and wolves. When a mosquito sticks her nose into an infected animal, she picks up microfilaria from the blood and then transfers them to the next animal she bites.

These larvae undergo several growth stages, and then, when they reach adult form, travel along the blood highway, exiting at the right side of the animal’s heart. Here, six to seven months after they first entered the host animal, the females begin to reproduce at a rate of thousands of microfilariae a day, all of which will circulate in the animal’s bloodstream for up to three years.

The majority of damage is caused when adults burrow in, around and through the heart muscle and the veins leading to it, the arteries of the lungs and the veins of the liver. Adults can grow to 12 inches in length, and an infected heart looks like it is wrapped up in thin spaghetti.

Symptoms in the animal, which may appear a year or so after infection, include a cough that grows progressively worse as the number of adults increases, along with listlessness and fatigue. The animal can lose weight, and his or her general body condition will decrease. The animal may eventually cough up blood.

Treatment is often successful as long as the number of parasites is not too great, but it is not easy on the pet. The medicine contains small amounts of arsenic, which destroys the worms. The body can then gradually removes the debris, but the animal must be kept from any exertion, or the worm parts will dislodge too quickly, resulting in death for the host animal.

If an infected animal is given a heartworm preventative, this too can dislodge existing worms, which will also result in death. For this reason, you should take your pet in for a simple blood test before beginning any preventative treatment. Vets commonly do this test in the early spring, so your pet can start on a preventative before the mosquitoes begin to multiply for the year.

As for dealing with the other little pests that can drive your pets — and you — crazy, check with your veterinarian. He or she carries a great supply of products and can tell you which are the most effective and the safest. I don’t recommend the over-the-counter types that you can purchase at discount stores. One brand in the past few years ended up causing sickness and death in a number of the younger dogs, and the company was not quick to pull the product or make any changes. Animal poison control centers dealt with a good number of calls on that product.

Also note that some companies selling the “brand name products for less” may indeed have brand names on the boxes, but if you compare the amounts of the various ingredients in these boxes with what is purchased at your vet’s office, you’ll find the discount is not only in price but in quality. Your pet deserves better.

Flea and tick preventatives today are commonly topicals, applied between the shoulder blades. These can be tricky to put on, however. I learned quickly with my animals that, while I was busy applying the oil, the oil was busy finding a pathway from the skin to the fur and out again further down their backs. I’ve learned to apply it slowly so it stays against the skin.

Your pets enjoy the outdoors as much as you do. Help them have a safe and healthy summer by keeping them well inside and out.

— Sue Novak is a board member of the Lawrence Humane Society.