Fleas and Ticks

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by Arnold Plotnick MS, DVM, ACVIM, ABVP

Introduction

Summer is a fun season for people, but it can be miserable for cats. Warm, humid weather is paradise for fleas and ticks. At best, these critters can make your kitty uncomfortable; at worst, they can transmit dangerous diseases.

The most common external parasite of cats is Ctenocephalides felis, the cat flea. Understanding the flea life cycle allows targeted use of flea control products.

The life cycle

Adult fleas spend their entire life on the cat. When fleas hop on, they immediately begin feeding on blood, which is rapidly digested. Excreted blood dries into reddish-black fecal pellets that we euphemistically term “flea dirt”. Fleas mate soon after feeding, and females begin producing eggs 24 to 48 hours later. Female fleas lay 40 to 50 eggs a day. Eggs fall from the coat, accumulating in areas where the cat sleeps or rests. Larvae hatch from flea eggs in 1 to 6 days and avoid light, burrowing into carpets, cracks in hardwood floors, and other humid areas such as concrete floors in damp basements. The larvae feed on organic debris, including flea dirt that has fallen from the cat’s fur. After 5 to 11 days, larvae spin a cocoon in which they transform into pupae, and then into adults. Adults typically emerge from the cocoon within 21 to 35 days, and then wait a cat to stroll by. They hitch a ride on your kitty, and the cycle begins anew. The entire flea life cycle takes 3 to 6 weeks.

Flea and tick-associated disorders

Fleas cause severe irritation in cats. While dogs usually bite or scratch at fleas, cat use their barbed tongues to remove them, often abrading the skin. Besides this mechanical irritation, fleas are associated with numerous diseases in cats (see sidebar).

Fleas pass Bartonella henselae, the organism responsible for cat-scratch disease in humans, from one cat to another” says Lisa Conti, DVM, MPH, Dipl ACVPM, CEHP, CPM, a veterinarian and Director of Division of Environmental Health, Florida Department of Health. “Most cases of cat-scratch disease are self-limiting. However Bartonella infections can cause very serious illnesses in people with immune deficiency disorders.” Most cats infected with Bartonella are clinically normal, however, infection in cats can lead to fever, lethargy, lymph node enlargement, eye inflammation and gingivitis in some cats.

Flea allergic dermatitis (FAD) is the most prevalent small animal skin disorder. When fleas repeatedly bite a cat, proteins in flea saliva can induce a hypersensitivity reaction. This allergic reaction causes severe itching, and cats often develop small crusty papules and hair loss on their neck and face, and most notably down their back, in the classic “racing stripe” pattern.

Fleas feed on blood, and can cause life-threatening anemia, especially in kittens. They’re also responsible for transmitting tapeworms to cats.

Ticks are less of a nuisance in cats as compared to dogs. Their meticulous grooming habits allows cats to remove most ticks from their coat before attachment. As blood-sucking parasites, ticks can transmit pathogenic organisms. “Fortunately, cats appear to be less susceptible and rarely fall victim to diseases like Lyme disease, Ehrlichiosis, and Rocky Mountain Spotted Fever, compared with dogs” notes Dr. Conti.

Treatment

Because some of the infectious agents transmitted by fleas may affect humans, the American Association of Feline Practitioners recommends year-round flea control. Historically, the most effective approach was the three-step method: treatment of the yard, home, and cat. The newer flea and tick control products, however, are so effective that treatment of the premises is rarely necessary. These new products are either applied directly to the cat or are given orally or by injection (see sidebar).

The goal of treatment is to eliminate fleas before they reproduce. Treatment with an “adulticide” eliminates adult fleas on the cat, and ideally kills newly acquired fleas as well. Insecticides are effective adulticides, but offer little residual activity, and reinfestation is common. When applied monthly as directed, products containing imidacloprid, fipronil, and selamectin kill most fleas before they reproduce, and provide residual activity between applications.

None of the monthly residual flea products are 100% effective against adults. A few fleas occasionally survive and reproduce between applications. Therefore, the best way to combat fleas is using a method called Integrated Flea Control. This is the combined use of an adulticide, an insect growth regulator (IGR) or insect development inhibitor (IDI), and mechanical means. IGRs and IDIs work by interrupting flea development or killing eggs and larvae, halting reproduction. The simultaneous use of compounds that work via different methods to target mature and immature flea stages gives the best control by bridging any potential loss of efficacy from solely using adulticides.
 
Mechanical control remains an important part of flea control. Blankets, throw rugs and cat carriers should be washed, and cat sleeping and resting areas vacuumed to remove eggs and larvae. Seat cushions and pillows on sofas and chairs should be vacuumed, as well as the areas beneath sofas and beds where flea eggs and feces can drop and accumulate.

Warning

In an effort to tap into the lucrative flea-control market, some manufacturers have produced flea control products with packaging similar to the veterinary products, i.e. in small, single dose tubes for topical application. These products contain permethrin, an insecticide commonly found in low concentrations in a variety of canine and feline flea sprays and shampoos. In low concentrations, cats tolerate these products with minimal adverse effects. These small single-dose tubes, however, contain concentrated permethrin (45% to 65%) as the active ingredient. Concentrated permethrin spot-on products are labeled for use in dogs only, and may cause severe and often fatal toxicosis if applied to cats.

Conclusion

Fleas and ticks have been a source of much misery for pet cats and dogs. They can transmit diseases to cats, as well as to humans. Fortunately, modern flea control products can provide a level of efficacy and convenience unheard of just a few years ago. Understanding the flea life cycle is critical in formulating a comprehensive flea-and-tick control strategy. Talk to your veterinarian about which products are right for you, as different products offer different benefits. Be aware, however, that improper use of these products can result in treatment failure, and use of unsuitable or mislabeled products can have dire health consequences.


Sidebar: Flea-associated illnesses in cats

Bartonella (the causative organism of cat-scratch disease in humans)
Flea allergic dermatitis (FAD)
Anemia
Tapeworms


Sidebar: some commonly prescribed flea control products

Bonus Sidebar: The top 20 cities for fleas and ticks, according to a 2002 study of 100 largest metropolitan areas (based on population) by the Hartz Mountain Corporation.

1.  West Palm Beach/Boca Raton, FL
2.  Fort Lauderdale, FL
3.  New Orleans, LA
4.  Mobile, AL
5.  Tampa/St. Petersburg/Clearwater, FL
6.  Baton Rouge, LA
7.  Sarasota/Bradenton, FL
8.  Houston, TX
9.  Orlando, FL
10. Charleston, NC
11. Miami, FL
12. Jacksonville, FL
13. Honolulu, HI
14. Birmigham, AL
15. Atlanta, GA
16. Memphis, TN
17. Nashville, TN
18. Greenville/Spartanburg/Anderson, SC
19. McAllen/Edinburg/Mission, TX
20. Little Rock, AK

        

Updated 3/28/06