Fleas Love Fall

We’ve discussed fleas before, but it’s a topic that never gets old, and as fall tends to be when we see a spike in fleas, it’s a good time to revisit.

What exactly is a flea?

Fleas are small (~2-3mm), reddish-brown insects. They feed on the blood of mammals and birds. While they cannot fly, they have incredible jumping ability. According to the website fleascience.com(goes to new website)(opens in a new tab), the average flea can jump about 5 inches high and 9 inches horizontally, though they can reach 8 inches high and nearly 20 inches horizontally.

What diseases can they carry?

Fleas can cause symptoms of mild itchiness to severe itching/scratching and significant secondary bacterial infections, depending both on the flea burden and the individual animal’s sensitivity to flea bites. Additionally, in young puppies and kittens or severely infested animals, fleas can cause anemia due to blood loss.

Other parasites and diseases can also be carried or transmitted by fleas:

• The most common form of tapeworm, Diplydium caninum(goes to new website)(opens in a new tab), is carried by fleas. Tapeworms are rarely a significant health concern but can be uncomfortable to the pet and disturbing to the owner who discovers them.

• Bartonella, the causative agent of Cat Scratch Disease(goes to new website)(opens in a new tab), is also carried by fleas. Typical transmission is from the scratch of an infected cat (who got the disease from fleas), but there is some thought that infected fleas can transmit directly to humans via a bite.

• Plague(goes to new website)(opens in a new tab), caused by the bacteria Yersinia pestis, can also be transmitted by fleas.

What is the lifecycle of the flea?

Adult female fleas feeding on an animal can start laying eggs within hours, laying up to 50 eggs per day. Eggs develop in the environment, preferring cool dark places (like under fallen leaves — which is why we tend to see an increase in cases of flea infestations in the fall) and indoors along baseboards, carpets and crevices of furniture or floors.

Larvae then develop into pupae, typically preferring the same places as the larval stages. Finally, adults emerge from the pupal stage and start looking for a host to feed on. This whole process can take as little as a few weeks in optimal conditions. However, the larval and pupal stages can also lie dormant for months and hatch only once they sense the environmental factors are ideal (vibrations from movement, heat and CO2 can all trigger this).

Because of the prodigious egg-laying of the adult flea, it is possible for a single adult female to quickly lead to an infestation. The environment (outdoors or indoors) quickly becomes contaminated with eggs, larvae and pupae.

How do I know if my pet has fleas?

Sometimes you will actually see the flea moving along the skin under the hair coat or even jumping from the pet as you rub their belly. A more reliable way to detect them is to look for “flea dirt,” which is digested and excreted blood. The tail area and behind the ears are two common places to see this.

However, sometimes, it’s not a simple diagnosis, especially early on. Some pets are very sensitive to flea bites and will demonstrate intense itching with only a single bite — in these cases, it may be difficult to detect the fleas.

The classic signs of a pet with fleas are intense itching or chewing around the tail base (and in general). The itch associated with fleas is often more intense than we might see with other causes of itchiness (namely, allergies).

What is the best way to prevent fleas?

We are fortunate that there are now many effective topical and oral options for reliable flea prevention (long gone are the days of flea dips and sprays). Many of our canine patients are on an oral product of the isoxazoline class (for cats, this is typically administered as a topical product), which is exceptionally effective, though there are other older products that are still quite reliable. We recommend consulting your pet’s veterinarian about the options and what would be best for your pet.

A word of caution regarding cats — cats are especially sensitive to the pyrethrin class of flea preventatives. Be sure that the flea preventative you use on your cat, whether prescription or OTC, is approved for use in cats.

Are there any more natural alternatives for flea prevention?

Currently, there are no consistently reliable natural alternatives that work as well as conventional drugs. If you are looking for natural alternatives, it is recommended to do daily flea combing. This should be combined with environmental control, which includes very frequent vacuuming and cleaning of floors and baseboards in the home.

Additionally, boric acid or diatomaceous earth can be used on the carpet (following manufacturer recommendations) to kill larval stages — however, neither of these is completely free of potential side effects despite being more “natural.”

Do I really need to give flea prevention year-round?

In short, yes. Again, because all it takes is a single adult flea to set up an infestation in the home, we and the vast majority of veterinarians in our area recommend flea prevention year-round. It doesn’t matter if it’s below freezing outside, as the fleas will be happy little campers inside your toasty warm home.

What about my indoor cat that never goes outside?

It is true that an indoor cat with no dogs in the house has a lower risk of getting fleas than an outdoor cat; however, in our area, where many pets live in apartment buildings with their owners, it’s not uncommon for indoor cats to get fleas. Remember — fleas do not respect doorways.

It is especially important that cats living with dogs be on a regular flea preventative, as fleas can get inside on the dog, and then “set up shop” on the unprotected cat.

If my pet has fleas, do I need to have the house treated (“bombed”)?

It depends. In mild cases, often just treating the pet effectively, combined with diligent cleaning of the home, will be effective. However, if it’s been a long-standing problem, or there are multiple pets in the home, it is often best to get an exterminator involved to treat the environment.

A word of caution here — there are no available products that can kill the pupal life stage — so it is still imperative to have pets on regular preventative because those pupae will hatch into adults; without the pet being treated, those adult fleas will again be able to restart the cycle.

Additional Resources:

• Companion Animal Parasite Council – Fleas(goes to new website)(opens in a new tab)

• Companion Animal Parasite Council – the case for year-round flea and tick control(goes to new website)(opens in a new tab)

• Top 10 flea myths (from a veterinary dermatologist)(goes to new website)(opens in a new tab)

Written by Dr. Natasha Ungerer