It’s only recently that we’ve begun to recognize Lyme disease in dogs. Unfortunately, vulnerability to the diseases carried by ticks is something that all members of the household share: human, canine, and sometimes even feline.

Lyme disease can occur all year round, but most humans and dogs are exposed to it during the warmer months when we’re most likely to be outdoors — spring through fall.

Researchers tend to see most cases of Lyme disease in the rural northeast, areas in the upper Midwest such as Minnesota and Wisconsin, and throughout a long stretch of the West Coast ranging from Oregon to southern California. However, that’s not to say you’re scot-free if you live in other parts of the country. Lyme disease has been reported in every state except Montana, and since 1975, numerous cases of Lyme disease in dogs have been diagnosed in over 40 of those states.

The ticks that contribute to most of our Lyme disease are on the tiny side. While the hulking American dog tick likes dogs so much it was named for them, it’s the smaller ones that transmit Lyme disease — the deer tick and the blacklegged tick.

These ticks primarily feed upon white-footed mice and white-tailed deer, both of which frequently travel through the grass lanes that ticks like to inhabit. Ticks themselves are mostly stationary — they don’t fly or jump, and they hardly crawl. Instead, they climb up midsize grasses or wooded areas, and wait for a mouse or a deer to walk by and brush against them. Ticks are very patient — many adult ticks feed only once in their lifetimes.

Deer and blacklegged ticks can attach themselves to any part of a dog’s body, although they often prefer the tender spots around his head, neck, ears or feet. Unlike the painful bites or stings from bees, fleas, or mosquitoes, it’s hard for man or beast to detect a tick bite. In fact, dogs can be literally covered with ticks without showing any signs of distress.

Symptoms of Lyme disease in dogs mirror those in humans, and include fever, listlessness, and the sudden onset of lameness, as well as an inflammatory reaction involving pain, swelling and unusual warmth around the joints. Sometimes dogs will display the telltale “bull’s-eye” circle of inflammation we often see in human victims of Lyme disease, but it’s very hard to detect this underneath the dog’s fur.

Because the ticks that carry Lyme disease are so small, don’t assume your dog can’t have Lyme disease if you haven’t seen any ticks on him. After gorging themselves, ticks will drop off your dog by themselves.

If you have any suspicion of Lyme disease in your dog, contact your vet right away. When recognized early, Lyme disease is easier to treat successfully, and you can save your dog from suffering. But once the infection reaches more advanced stages, your dog could experience paralysis. Left untreated, Lyme disease can progress to paralyzed front and hind limbs, and finally disable the muscles in the chest that support respiration. This can cause your dog to suffocate.

If you think your dog is suffering from a more advanced stage of Lyme disease, contact your vet, who may suggest a period of hospitalization. Lyme disease that’s taken root is difficult to treat, but new ways of treating it intravenously are showing more success.