As warmer weather approaches, an age-old battle reemerges — pet owners versus fleas. As our dogs and cats become more like family members, it is even less palatable to think about them bringing tiny hitchhikers into the house. And just as importantly, fleas are a significant cause of discomfort and distress to affected pets. As with any fight, the first order of business is to know the enemy.
So what are fleas? They are small, flightless insects which act as external parasites of many animals. There are multiple species, although the most common flea of both dogs and cats is the cat flea (Ctenocephalides felis). Adult fleas are obligate and permanent parasites — they live full time on their hosts, and cannot survive on their own. Their only source of nutrition is the blood that they obtain from that host. The fleas which affect cats and dogs cannot permanently colonize a human, but may bite humans and cause temporary itchiness. These fleas also thrive in warm, moist environments, but are present across the country.
Fleas have a well understood life cycle. As previously stated, adults live full time on their host. Within a day of obtaining their first blood meal, they will breed, and female fleas will begin to lay eggs. Each female flea can lay up to fifty eggs a day, and will continue to do so for her approximately hundred day lifespan. These eggs are laid on the host, but soon fall off into the environment. Within a few days, these eggs hatch into the immature flea life stage called a larva. Larvae feed on the incompletely digested blood found in adult fleas’ excrement. Essentially, feces from adult fleas falls off the host and serves as a source of nutrients for their young on the ground. Larvae molt several times, and then form a cocoon, or pupa. Depending on the environmental conditions and amount of available food, the time from hatching to pupating can range from about a week to several months. Each cocoon can lie dormant for up to a year if conditions are not favorable, and is resistant to heat, cold, drying out, and many chemical insecticides. If the environment is ideal, the adult flea can emerge from the cocoon in as little as a week. Stimuli to emerge include heat, vibration, and exhaled carbon dioxide. Because of this, animals or humans that enter an abandoned house or summer cottage with flea pupae present can trigger fleas to emerge within minutes. The new adult fleas begin seeking a host, and can only survive on their own for a few days. This means that fleas do not typically spread directly from one host to another, but from a contaminated environment. Pets can pick fleas up anywhere that other animals or wildlife have been present, especially in warm, grassy areas.
The main symptom of a pet with a flea infestation is pruritus, or itchiness. In severe infestations, especially in young animals, anemia (a low amount of red blood cells) can occur, and cause weakness, pale gums, and fatigue. But for most pets, the main effect of fleas is being unpleasantly itchy. The level of itchiness depends on how many fleas are present, but more importantly, how strongly the pet’s immune system reacts to the proteins found in flea saliva. Some pets suffer from a condition known as flea allergy dermatitis (FAD). This is a hypersensitivity response to the flea saliva, and causes more severe signs. Flea allergy is the most common type of allergy in both dogs and cats. It can cause crippling itchiness, as well as raised bumps, crusts, alopecia (hair loss), and secondary skin infections. Some pets may have increased wear on their teeth from excessive fur chewing. Most often, FAD affects the back half of a pet’s body, especially on and around the tail, but lesions can occur anywhere. Pets with FAD can have severe dermatologic disease due to as little as one flea bite a week. This means that even if no fleas are immediately visible, FAD is still a possibility.
Another possible effect of fleas is a tapeworm infestation. Cat fleas can carry larval tapeworms. When a flea is ingested by the host during grooming, the larval tapeworm may infest the host. Adult tapeworms live in the small intestine and feed on the material in the gastrointestinal tract. These adults pass segments of their bodies containing eggs in the host’s feces. These segments look similar to grains of white rice or sesame seeds, and may be found near the pet’s anus, under the tail, or in the feces itself. Most tapeworm infestations do not cause significant clinical signs, but can increase skin irritation in the perineal area.
Diagnosing a flea infestation can range from easy to difficult. In some cases, it is as simple as seeing fleas crawling on the pet. But some pets, especially cats, may groom so effectively that no fleas are visible. This is especially true if the pet has thick fur. A veterinarian may use a fine-toothed flea comb to pull fleas out of the fur. Another trick is to look for flea dirt, the blood-rich feces that fleas produce. This often looks like small, dark specks on the skin or fur. To differentiate it from regular dirt, the vet may place a small amount on a paper towel. When water is added, flea dirt will release a distinctive reddish brown color. Other times, finding tapeworm segments may be the only indicator that a flea infestation is present. If there is a high level of concern for FAD, treating for fleas may be indicated, even if no live fleas are found.
So how are flea infestations addressed? The best treatment is prevention, since infestations are much simpler to prevent than to treat. It is strongly recommended that all cats and dogs be on year round flea prevention. Pets in very clean environments can become infested just by passing through a patch of grass with fleas in it, and indoor only animals may be infested if other animals or contaminated materials bring fleas into the household.
There are an innumerable number of flea treatments available. Many effective options include two types of ingredients: an adulticide to kill adult fleas, and an insect growth regulator to prevent molting and/or reproduction of fleas. These products are available in a variety of formulations, including oral medications, topical spot ons, or collars. Most will last anywhere from a month to several months, depending on the product. Options such as sprays or flea shampoos are typically less effective. They may kill the fleas currently on the pet, but provide no lasting protection from reinfestation. If fleas are on a pet, they are almost certainly in the environment, and long term flea protection is a must.
It is ideal to obtain flea control products from a veterinarian. Many of the most effective products are only available with a prescription. Obtaining them directly from a veterinarian guarantees that the product has been handled appropriately, and that you can get a product known to be effective in your geographic area. Some generic flea control options may also contain the same active ingredients, but use a different carrier molecule and be less effective. Other over the counter products, like certain flea collars, kill only the fleas near the collar, and will not effectively control an infestation. Pets with severe flea allergy dermatitis may do best if given a combination of products, as they are more sensitive to even a single flea bite. They may also require anti-inflammatories or antibiotics for secondary skin infections.
There are several important facts to know about flea control. Firstly, it is best to give the medication year round. In warm areas, fleas can be found even in the winter. But even in colder climates, fleas may be found indoors at all times of the year. Another is that all pets in the household must be treated, even if live fleas were only found on one. If there is an untreated animal in the household, the flea life cycle will never be able to be permanently halted. Remember that animals should always be given species specific flea treatment. Giving cats a medication meant for dogs can be harmful or even fatal, as cats are more sensitive to certain compounds used in canine products. If a canine flea product is accidentally applied to a cat, immediately wash the animal with warm water and dish soap, and then take him or her directly to a veterinarian.
Finally, it is vital to realize that administering a single dose of a flea medication to an infested animal will not completely resolve the infestation. Because of the nature of the flea life cycle, viable eggs, larvae, and pupae will be present in the animal’s environment. As those eggs and pupae mature, additional fleas will jump onto the pet. This means that even if flea treatment is effective, you may continue to see the occasional live flea — even months after initiating treatment! This does not mean that the product has failed. The new flea has most likely hopped on from the contaminated environment. If the pet is still on an appropriate flea medication, the new flea will quickly be killed.
In order to hasten resolution of the infestation, the environment should be treated as well as the pet. Wash all bedding which has been in contact with the pet, and vacuum carpets several times a week to remove eggs and larvae. In severe infestations, it may be beneficial to hire a professional exterminator for the house. Other choices include products such as foggers, flea bombs, and environmental sprays. Make sure to read all product information to ensure that the product is used safely. Oftentimes, the outdoor environment cannot be completely cleared of fleas, as wildlife and feral animals can serve as a source of new parasites. However, decreasing the amount of leaves and brush in the yard, and keeping grass short, will help make the environment less ideal for fleas.
So if your pet has been affected by fleas, don’t despair! Although sometimes frustrating, flea infestations are a common and treatable problem. With a little help, your pet can soon be flea free.