Fleas Part Two : Is Zero Tolerance Possible?

Dr Mc Blog

September 14, 2014
In my previous column on fleas we discussed the mode of action and the suffering and disease which fleas inflict upon dogs, cats, and occasionally people.  I stated that the tapeworm of dogs, Diplydium caninum, did not infect people. Dr. Jerry Menefee of Los Banos called to tell me how much he enjoyed my column and to gently correct me: there have been a few cases of human infestation with the dog tapeworm, called Diplydiasis, primarily when a young child or infant has actually eaten an infected flea (same as the dog or cat) and the worm develops in their intestine. There is rarely any sign of illness, just little tapeworm segments passing in the diaper! Treament for the child is the same as used for the dog, with excellent success. I could find 2 medical papers printed on separate cases, one published in 1993, another in 2003. Diplydiasis appears to be extremely rare (but oh dear, aren’t you running to check the calendar to see if you’re up to date on your flea control?); I shall expose the mysteries of “human tapeworm”, an entirely different group of worms, in a future column. Today we are exploring methods of flea prevention, critical in our area because, as noted in Part One, our local climate favors fleas – we are a flea hospitality haven!

If a pest has been around this long, there’s been plenty of time to try to get rid of it. Because some pets and people seem to attract more than their fair share of attention and get more bites, researchers tried changing the way skin smells. As it turns out, fleas are NOT put off by garlic or B vitamins, nor are they scared away by clove oil, tea tree oil, cinnamon, lemon, etc. Whether ingested or applied topically, these products only make you or your pet less socially acceptable to other like creatures. Not recommended. It has been theorized that some dogs and cats are better able to groom out fleas with their teeth, so appear to be flea free and escape the ugly monikker “fleabag”.

So we’re talking pesticides to control pests. Thirty years ago we used flea powders, sprays and flea collars, all powered by chemicals in the carbamate and organophosphate family of pesticides. This group of chemicals were not at all selective to fleas – used improperly, they could poison your pet and you. It’s what we had (our “zero”), and we were desperate. The collars worked sometimes on very small pets, since they only covered the neck. Powders would do the job, if you could stand the dust all over your pets’ coat. Sprays were very effective, but required near daily application because as soon as your dog rolled in the grass they were lost in the dew. Forget spraying a cat- one puff and that cat was in the next county. Dips were also effective, though again, none lasted two weeks as dogs roll in the grass…..removing the substance. Most flea dips were toxic to cats, so if applied incorrectly to a cat it would die unless emergency treatment was sought. I spent hours counselling on time consuming methods of flea control that no one thanked me for.

Pest control companies were kept busy spraying yards and houses in an effort to control the flea in the environment. One product, malathion, a mainstay in pest control years ago, to overcome flea resistance had to be sprayed over your entire yard every 10 days to have any efficacy at all according to UC Davis! DIY (do-it-yourself) friendly, it was not. Again, clients were grumpy to receive this news. Today there are a rotating group of pesticides used by pest control companies to fight the flea and prevent resistant strains from developing. Environmental control in the yard is very important; even if your own pet never leaves home, wildlife and roaming pets will almost certainly introduce fleas. Your pet does not live in a bubble!

And then a new generation of medications were discovered. Wonderstuff. Applied topically to the skin of the pets neck or given as a chewey pill, and only ONCE a month, this stuff is amazing! This stuff works! Several products exist for both dogs and cats, all kill fleas within 12 hours of contact with the pet. Reinfesting fleas, flea eggs and larvae in the environment are killed following contact with the treated dog or cat. If you do no environmental control, expect it to take about 90 days to clean up your flea problem. Some of the chemical names we’ll discuss are imidacloprid, spinosad, fipronil and afoxolaner. Ahhh, what’s in a name? Tongue twisters all – the brand names are easier. Curiously, most of these products weren’t developed specifically for your pet.

Spinosad is a pesticide developed to safeguard our food supply, used commercially on fruit and vegetable crops. Spinosad is considered an “organic” insecticide found in a bacteria from sugar cane. Spinosad is considered a natural product, given a Class B designation for pregnant women: No evidence of risk in humans.  It is used on people in medication for human head lice. On dogs and cats it has been found effective primarily against only the flea.

Imidacloprid, another flea fighter available for dogs and cats, is also used on crops and home back yards. Acting as a neurotoxin to insects, when used IN THE YARD, it is a systemic chemical that is taken up by plant roots to its leaves, where sucking/chewing insects will ingest it and die. There has been some question if imidacloprid may adversely affect honeybees (colony collapse disorder), though bees do NOT chew flower or plant parts.

Fipronil is an insecticide that affects the nervous system of insects via pathways that don’t exist in mammals. A broad spectrum insecticide, it is highly toxic to fish and bees. It is widely used for protection of rice crops, field corn, and golf course lawn care. Humans can prevent tick bites by applying it (as directed) to their ankles and wrists. Fipronil can kill rabbits – do NOT use on rabbits for flea control! That said, for years the State of Hawaii has required the veterinarian-only application of Fipronil, specifically, to all dogs and cats 10 days prior to travelling to the state. Fipronil has been widely questioned in honeybee colony collapse disorder.

Afoxolaner is in the newest class of chemical, this one without apparent crop/plant use. It’s sole use is flea AND tick control in dogs. It’s a new isoxazoline parasiticide (I had to read that, why not you?) – its’ claim to fame is that it controls both fleas and ticks via an oral medication for an entire month. Tick control has always been difficult in dogs, and there are many serious tick-borne diseases. The class of isoxazaline drugs may be a breakthrough for livestock that suffer from both ticks and tick borne diseases worldwide.

The flea is here to stay. With considered use of the available products you may be able to control you and your pets’ exposure to fleas and the consequences of flea bites. We aren’t talking eradication. You are not expected to reach Zero.  As for your children, your home and yard, the truth is that flea control on the pet is not deemed of sufficient quantity to add to or create environmental issues at this time. Most of the products we’ve discussed are carried home from Garden Centers and Big Box stores by the quart and gallon weekly as yard and grass treatment for indiscriminate use and disposal by the homeowner. These products all appear much safer for mammals – you, your children, your dogs and cats – than previous options, and every year newer products are developed as we all cope to care for each other and our earth.

Christine B. McFadden, DVM
Valley Animal Hospital, Merced

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