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Written by leading veterinarians to provide you with the information you need to care for your pets.

The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Clinical Signs, Infectious Diseases, and Natural Treatment Options for Fleas

Fleas are a subject of much disdain for people and pets alike. No pet owner wants to see their beloved Fido or Fluffy subjected to the blood sucking physiologic needs of the flea. Preventing flea infestation takes a consistent effort on behalf of the caretaker and requires attention to our pets, environment, and lifestyle choices.

Flea Appropriate Climate

Fleas require a climate sufficiently warm and humid to support their lifecycle. Yet, indoor climates can be sufficient year-round regardless of geographic location. Temperatures between 70-90 °F and humidity levels of 50-75 percent are needed for fleas to hatch and thrive on pets, wildlife, and in our shared environment.

Fleas lay eggs in clusters of approximately 20 at a time; one to two weeks are needed for eggs to hatch into larvae. Another one to two weeks are required for larvae to develop into pupae, and a final one to two weeks is needed for the adult flea emerge. So, only four to six weeks must pass for flea eggs to develop into adults.

Considering there are only 52 weeks in a year, this process is relatively quick. A single flea needs only to get onto your pet or into your home to start this process. You may not even know that this is happening unless your pet starts to clue you in on the annoying presence of fleas.

Clinical Signs of Flea Infestation

Fleas are opportunistic arthropods that seek out our pets as a food source. Yes, they need blood to survive. Once fleas get on your pet by jumping or crawling, they typically set up their habitat in hard to reach places, like the head, neck, tail, axilla (armpits), or inguinal area (groin). Licking, biting, or scratching at these places usually indicates the presence of nagging parasites.

Flea bite saliva is very allergenic (with some animals’ response being more pronounced than others), so flea allergy dermatitis (FAD, or skin inflammation due to flea bites and saliva) is not exclusive to the bitten body part. Additionally, the appearance of tapeworm proglottids (body parts) in a pet’s feces is another giveaway that a flea problem must be addressed.

A pet’s furry coat provides shelter for fleas, so our companion animals are often more affected by flea infestation than relatively hairless human bodies (plus, we bathe more frequently). The fur also helps to create the appropriate microclimate for flea eggs to develop into adults, and hides the flea excrement (AKA flea dirt).

Evidence of flea infestation can manifest as "ground black pepper-like" specks on your pet’s skin and coat. To differentiate flea dirt from day to day environmental debris, simply add water; moisten a white cloth and dab the area harboring the flea dirt. If the cloth becomes pink or red, then your suspicion of fleas has been confirmed.

Fleas Carry Disease

Fleas play host to a variety of infectious organisms, including bacteria, viruses, and parasites; Bartonella felis (the bacteria that causes cat scratch fever), Enterovirus (one of the causative agents of viral meningitis), Cestodes (tapeworm), and others.

These agents can be transmitted into dogs, cats, and other animals through multiple routes. When a flea feeds from its prey, the passage of blood allows for transfer of bacteria (and viruses). When irritated pets chew at themselves, they may consume the flea during their attempt to stop the nagging sensation.

Fleas act as an intermediate host for tapeworm, as adult fleas consume the tapeworm eggs. When the flea is consumed by the definitive host (your personal pet), the tapeworm then develops into an adult inside the host’s intestines. Tapeworm proglottids (body segments) appear like squirming grains of rice once the host’s feces exits the rectum. This is a big turn off for those of us who love rice with our sushi and creates the motivation to resolve and prevent infestations.

Naturally Rid Your Home of Fleas

Pet owners shouldn’t exclusively rely on topical and oral flea treatments to keep their dogs, cats, and households free of fleas (and ticks). Keeping the environment as flea-free as possible is my primary recommendation. Preventing your pet from going to heavy flea burden areas is my secondary recommendation.

Vacuuming your home has no direct toxic effects on your environment, home, or pet. Commit to performing a thorough vacuum job at least every seven days, including all rugs, upholstery, and even your car (if your pet accompanies you on vehicular excursions). Dispose of the canister or bag in a sealed container away from the house, as fleas and eggs may survive being sucked up into the vacuum and then emerge back into the environment.

Diatomaceous earth and boric acid can be sprinkled around your home and yard; both have a drying effect on flea eggs and adults. Use common sense when applying these agents, as both can create aerosolized debris that can be inhaled by pets and people. Keep your cats, dogs, and children out of the treated area until the dust has settled.

Adding garlic (fresh or powder) to your dog’s meals is another option (not for cats — garlic is toxic for cats!), yet there is not the same degree of established effectiveness as compared to vacuuming and drying agents. Garlic is a GRAS (Generally Recognized as Safe) ingredient according to AAFCO (American Association of Feed Control Officers). Garlic also has anti-inflammatory benefits, as well as anti-infectious organism and anti-cancer properties.

Additionally, reducing the ability for outdoor creatures (raccoons, skunk, rabbit,etc.) to enter your yard, closing windows and doors, repairing construction defects that could harbor fleas, and preventing your pets from going to areas potentially infested with fleas (boarding facilities, dog parks, etc.) are other ways humans can prevent a parasitic invasion.

Dr. Patrick Mahaney

Image: Steve Yager / via Shutterstock

Comments  8

Leave Comment
  • Environment
    07/03/2012 07:26am

    "Temperatures between 70-90 °F and humidity levels of 50-75 percent are needed for fleas to hatch and thrive on pets, wildlife, and in our shared environment."

    Would it be at all effective to keep the air conditioner below 70° (if you can afford it)?

  • 07/05/2012 01:35am

    That's a very good question? If you were to keep your home cold and dry enough to not create a flea appropriate environment, you would likely not foster any flea infestation.
    I don't know of any household containing pets that abides by this flea control plan.
    Hmmm....
    Thank you,
    Dr PM

  • blood sucking nuisance
    07/03/2012 09:29am


    Dr. Mahoney--it was great to meet you at Blog Paws!

    Great reminder that we can not wait until Coco and Chanel are scratching and biting. In addition to topical solutions, I do vacuum DAILY simply because I'm sure I bring home fleas from feeding the feral cats in neighborhood. I think I'm more sensitive to fleas than my cats. Also I stopped taking my dog with me to feed outdoor cats. But I worry about the feral cats and wonder what I can give them or put in their food. Will Ivermectin help? I know it does help with worms.

    Many thanks.

  • 07/05/2012 01:47am

    Great to meet you at BlogPaws 2012! It's always nice to put a face with a name. I appreciate your readership of my petMD The Daily Vet column. Your comments are always a plus!
    Amazing to hear that you are employing such good environmental control with DAILY vacuuming. You rock!
    So, you are looking to put something into the cat's food to help with fleas? You can try a product like Program (Lufenuron), which prevents flea eggs from developing into larvae (and then pupae-->adults). Oral Capstar (Nytenpyram) will kill all adult fleas on a pet for 24+ hrs, but does not help with developing generations of fleas.
    So, you have some options.
    Good luck,
    Dr PM

  • No garlic
    07/03/2012 11:00am

    I'm going to vote for NO garlic for any dog or cat, as it's not proven to work well for flea prevention. I see chronic toxicity from pet owners using it, and garlic is more concentrated and toxic than onions. Hence, I'd rather use other safer preventative measures.

    Dr. Justine Lee
    @drjustinelee
    www.drjustinelee

  • 07/05/2012 01:49am

    Thank you for your comments Dr Lee. As a veterinary toxicologist, I value your perspective.
    In my years of treating patients who eat commercial or home prepared diets having garlic, I have not seen any toxic effects from garlic. Yet, I recognize that garlic in food is not appropriate for all pets (I don't give it to cats or to anemic/thrombocytopenic patients or those having coagulopathy) and must be given in reasonable/small quantities).
    Do you have any research based information that tells the approximate range of quantity of garlic that is toxic to dogs and cats? That would be very helpful to reference in the future.
    Thank you,
    Dr PM

  • NO GARLIC
    07/05/2012 11:55am

    Yes, there's lot of research about the negative effects, and as a veterinarian, I wouldn't advocate the use of garlic at all. There's no proven benefit that it helps with parasite load, when there are much safer options out there:

    1. Yamoto O, Maede Y. Susceptibility to onion-induced hemolysis in dogs with hereditary high erythrocyte reduced glutathione and potassium concentrations. AJVR 1992; 53(1):134.
    2. Lee KW, Yamato O, Tajima M, et al. Hematological changes associated with the appearance of eccentrocytes after intragastric administration of garlic extract to dogs. AJVR 2000; 61(11):1446.
    3. Caruso, K. Applied Cytology Case Study of the month. NAVC Clinicians’ Brief 2003:2; 42-43.
    4. Cope, R.B. Allium species poisoning in dogs and cats. Veterinary Medicine 2005;100:562-566.
    5. Gfeller, Roger W., Messonnier, Shawn P. Handbook of Small Animal Toxicology and Poisonings. St. Louis, Mosby Inc., 1998.97.
    6. Hill AS, O’Neill R, Rogers QR, et al. Antioxidant prevention of Heinz body formation and oxidative injury in cats. Am J Vet Res 2001; 62:370-374.
    7. Jain RC, Vyas CR. Hypoglycemic action of onion and garlic. Lancet 1973; 2:1491.
    8. Plumlee, K. Clinical Veterinary Toxicology: Mosby, Inc. 2004:408-409.
    9. Peterson ME, Talcott PA. Small Animal Toxicology 2nd Ed. Saunders/Elsevier, 2006:323
    10. Robertson JE, Christopher MM, Rogers QR. Heinz body formation in cats fed baby food containing onion powder. J Am Vet Med Assoc 1998; 212[8]:1260-1266.
    11. Simmons, Denise M.: Onion Breath. Veterinary Technician 22 (8): 424-427, 2001.
    12. Yamato, O, et al. Heinz body hemolytic anemia with eccentrocytosis from ingestion of Chinese chive (Allium tuberosum) and garlic (Allium sativum) in a dog. Journal American Animal Hospital Association 2005; 41(1):68-73.

  • 07/08/2012 02:05am

    Thank you Dr Justine.


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