One clear difference between Toronto and NYC (only 480 miles south-east of the former) is the number of fleas per square inch of dog or cat. In Toronto, I simply did not see the huge numbers of pets with fleas that I see here in NYC. Holy smokes.
I'd say at least 50% of the patients I see have fleas - at least. What's more striking is the nonchalance in reaction of their pet owners - holy smokes. What I tell owners about fleas: 1) they will be on planet Earth when humans are long gone, possibly ruling it, 2) 5% of the flea population are the actual adult fleas - those critters we actually see with the naked eye; the other 95% percent are those stages like the eggs, larvae, and stubborn pupae, that just litter the pet's environment, waiting to emerge to just pop back onto the pet when it goes by, 3) a puppy or kitten can die from a severe flea infestation from the anemia the fleas cause (like vampires, they feed on blood), and 4) most importantly: fleas carry infectious diseases, like the larval stages of tapeworms (if your dog or cat has tapeworms, she swallowed a flea somewhere down the road); Bartonella henselae is a bacterial organism, responsible for cat-scratch disease in humans, that is carried by fleas (usually a self-limiting disease in healthy people, but can be life-threatening in immunocompromised patients); Hemobartonella (now called Mycoplasma haemofelis), a blood parasite, is transmitted by fleas - these blood parasites sit on the surface of the red blood cells and can cause the cat's immune system to start destroying these cells as the system no longer recognizes the cells as "self." Fleas are also responsible for carrying the bacterium Yersinia pestis - you've all heard of this one - responsible for causing bubonic plague in cats and people, the disease which virtually decimated the entire human population in the middle ages (the cute word "booboo" likely comes from "buboes," the lesions that were seen in people with plague - somebody corroborate this for me, please). Fleas aren't fun, folks.
Flea control involves treating the pet, and crucially, treating the environment. Flea collars do bubkiss on toast. Get your flea-control medications from your vet. NEVER purchase these products from a pet store as 1) they don't work and 2) most, if not all, are toxic to cats.
Whatever you do, DON'T use homeopathic or "natural" products (like diatomaceous earth) as the fleas will just be hysterical laughing behind your back.
Bubonic plague: if only they knew about flea control...