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Fighting Fleas and Ticks

Back from vacationing at the beach, Fido and Kitty sniff out familiar haunts around the yard. Meanwhile, their owner, Mary, plops down on the family room carpet with a month's mail.

Mary scratches an ankle, then the other one, then a leg. Then she looks down and sees why she's scratching: Fleas!

Although Fido and Kitty are flea-free after dog and cat pesticide dips at the beach, the house is not.

During the weeks before vacation, fleas feeding and breeding on the pets deposited unborn offspring all over the homestead. And during the vacation, fleas at various life stages evolved, nourished by dried-blood flea excrement, "flea dirt," in the carpet and elsewhere. The result: A population explosion of fleas ravenous for fresh blood.

The scenario is fictional. But it depicts this fact: Left uncontrolled, bloodsucking pests can infest not just your cat or dog, but your entire house--and you!

Common household fleas don't usually transmit diseases to pets and people. (See "Human Problems.") The tiny insects are mainly "just a nuisance," says Marcia Larkins, D.V.M., chief of the companion and wildlife drugs branch in the Food and Drug Administration's Center for Veterinary Medicine. "They generally cause a lot of itching and scratching. They may also cause some discomfort due to possible allergic flea bite dermatitis."

Ticks, those other dreaded bloodsuckers, pose greater risk, annually giving pets and thousands of people illnesses such as Lyme disease.

Fortunately, a wide array of pest control products for pets are available: foggers, sprays, dips, powders, dusts, collars, oral liquids and tablets, and even a liquid one-spot topical treatment. There are new oral products that interrupt the flea's life cycle, a Lyme disease vaccine for dogs, and a pesticide product that mimics mouse nesting material to reduce ticks outdoors.

FDA shares regulation of these products with the Environmental Protection Agency and the U.S. Department of Agriculture. If a pest-control product for pets is given by mouth, injected, or absorbed through the skin, FDA regulates it. Otherwise, EPA does. USDA licenses products that treat or prevent animal illness caused by pests. States sometimes add licensing requirements.

American Fleas

While there are more than 200 species of fleas in this country, the main troublemaker for pets is the cat flea. Happy to feed on anyone in the household--cat, dog or human--these wingless insects will most likely choose a pet, whose fur provides warm camouflage for their breeding ground.

The flea life cycle, illustrated in a 794K PDF file, has four stages: eggs, larvae, pupae, and adults. Female fleas lay as many as 50 eggs a day, starting a life cycle that can be completed in as little as three weeks, depending on temperature and humidity. The eggs hatch into larvae, which feed on "flea dirt," excrement of partially digested blood. Larvae grow and molt twice, then spin cocoons, where they grow to pupae and then adults. The adult remains in the cocoon until vibrations indicate a host is nearby. This waiting can extend the life cycle. It also explains why large numbers of fleas often are seen when an empty building is reoccupied. Six-legged adults emerge and attach to a host to feed and breed, beginnning the cycle all over again.

Even when fleas elude detection on a pet, their black poppyseed-like excrement gives them away.

The main problem with fleas--itching--is due not only to their bites, but also to their crawling over the skin.

Other flea bite problems and their symptoms include:

• anemia in young, older or ill pets--pale gums, weakness, lethargy
• transmission of tapeworm to pets--irritability, erratic appetite, shaggy coat, mild diarrhea, weight loss, seizures
• transmission by rodent fleas of plague to cats--fever, swollen lymph nodes, mouth sores, swollen tongue, cough, pneumonia.

Preparations made from antigens extracted from fleas may help, says David Espeseth, D.V.M., deputy director of USDA's Division of Veterinary Biologics. USDA has licensed several.

"If a pet shows a reaction in a skin test," Espeseth says, "that antigen may be effective in treating the animal against that sensitivity. When allergic animals don't react in the skin, this may mean you don't have the right antigen."

FDA has approved new types of prescription flea-control products:

• Proban (cythioate), first oral insecticide for dogs--A liquid or tablet, Proban is given once every three days or twice a week. Several weeks' treatment may be needed if fleas reinfest the dog.
• Pro-Spot (fenthion), first topically absorbed insecticide for dogs--A liquid, Pro-Spot is applied to one spot between the dog's shoulder blades no more than once every two weeks. Treatment length depends on the rate of flea infestation.
• Program (lufenuron), first oral insect growth regulator (IGR) for dogs--A tablet, Program is given once a month with a full meal. The IGR interrupts the flea life cycle: Upon biting the pet, the female flea ingests the IGR, which deposits in her eggs to stop them from developing.
• Program (lufenuron suspension), first oral IGR for cats--A liquid, Program is given once a month, mixed with food. Cats must be at least 6 weeks old.

Tenacious Ticks

A tick has a one-piece body. The harpoon-like barbs of its mouth attach to a host for feeding. Crablike legs and a sticky secretion help hold the tick to the host. When attempting to remove a tick, to prevent the mouth part from coming off and remaining embedded in the skin, grasp the mouth close to the skin with tweezers and pull gently. (See "Preventing Tick-Borne Disease.")

Ticks are not insects like fleas, but arachnids like mites, spiders and scorpions. They have a four-stage life cycle, illustrated in a 794K PDF file: eggs, larvae, nymphs, and adults. Adult females of some species lay about 100 eggs at a time. Others lay 3,000 to 6,000 eggs per batch. Six-legged larvae hatch from the eggs. After at least one blood meal, the larvae molt into eight-legged nymphs--in some species, more than once. Final nymphs molt into adult males or females, also with eight legs. Depending on its species, a tick may take less than a year or up to several years to go through its four-stage life cycle. While ticks need a blood meal at each stage after hatching, some species can survive years without feeding.

The United States has about 200 tick species. Habitats include woods, beach grass, lawns, forests, and even urban areas.

Ticks may carry various infectious organisms that can transmit diseases to cats and dogs, including the following (listed with possible symptoms):

• babesiosis--lethargy, appetite loss, weakness, pale gums
• ehrlichiosis--high fever, muscle aches
• Lyme disease--lameness, swollen joints, fever, poor appetite, fatigue, and vomiting (some infected animals show no symptoms)
• tick paralysis in dogs--gradual paralysis, seen first as an unsteady gait from uncoordinated back legs (some infected dogs don't develop paralysis).

According to USDA's Espeseth, "There were early concerns about disease related to abnormal immune responses. But we've never seen this. Nor have we seen such responses with extensive safety testing prior to the final licensing."

In most cases, immunity lasts at least five or six months, Espeseth says. "The recommendations are for dogs actively in the field, subject to exposure. For dogs in apartments or those that very seldom get out or reside in regions where Lyme disease isn't prevalent, it's probably not worthwhile."

To reduce the population of deer ticks, which transmit Lyme and other diseases and often attach to the deer mouse, EPA has licensed a product named Damminix. It consists of tubes stuffed with cotton balls treated with the pesticide permethrin.

"The cotton balls mimic the nesting material for the deer mouse," says George La Rocca, a product manager in EPA's Office of Pesticide Programs. The label, he says, directs users to place the tubes containing the cotton balls in outdoor areas inhabited by mice, such as brush-covered and wooded areas. "It kills and repels ticks on the mice. It's not meant to eradicate Lyme disease, but to reduce its incidence."

(See "Preventing Tick-Borne Disease.")

Debugging

To protect pets from the discomfort and illness caused by fleas and ticks, it's important to rid the pets of the pests. It's also important to treat a pet's environment to prevent or reduce the incidence of reinfestation, says FDA's Larkins.

Products to control these pests are not risk-free, however. (See "Improving Safety.") Approved or registered products must warn users about the risks the product poses and give directions for safest use. Proban's label, for example, warns that the product is not for use in greyhounds, who are sensitive to the insecticide it contains, an organic phosphate. Also, some products should not be used together or when a pet is taking certain medicines.

Larkins advises, "Follow directions for use very carefully, even with over-the-counter products. If you don't understand the directions or have questions, talk to your veterinarian."

EPA product manager Rick Keigwin agrees. As pesticides are intended to kill pests, they generally are inherently toxic, he says. "Some products pose some risks, but they also offer significant benefits. We balance the risks with the benefits."

La Rocca adds that with cats, use only products labeled for cats. "Cats are more sensitive than dogs in general," he says. "It also has to do with their size--just like children are more sensitive than adults--and their grooming habits. Dogs groom, but cats groom more, so they would ingest more of a topical product."

Virtually hundreds of pesticides and repellents are approved or licensed to control fleas and ticks on cats and dogs or in their environment.

To select proper products for your pet's individual needs, talk to your veterinarian, says Larkins. "It's a personal choice between you and your veterinarian about the best product to use and how to treat the animal, as well as the environment."

Dixie Farley is a staff writer for FDA Consumer.

Improving Safety

The effort, coordinated by EPA policy analyst Janet Whitehurst, began early in 1994, when she learned that in just 18 months, EPA had received 853 reports of adverse effects, including 148 animal deaths and 58 reports of illness in humans. Most reports involved cats, which are more sensitive than dogs.

Improved labels would:

• Direct users to read the entire label before each use.
• Clearly state the animal for which the product is registered and the minimum age for safe use.
• Caution users to consult a veterinarian before treating certain animals, such as those that are ill or pregnant (unless safety is known).
• Warn about adverse reactions and interactions with medicines or other chemicals.
• Advise users to wash their hands after use.
• Clearly state limitations for reapplication.
• Give a phone number to call about proper use and emergencies.
• Include first-aid information.

Using Flea and Tick Products

• Read the entire label before use. If you don't understand something, ask your veterinarian.

• Follow directions exactly, using latex gloves if possible. Then wash your hands.

• On cats, use only products labeled for cats.

• Store products away from food and out of children's reach.

Preventing Tick-Borne Disease

The illustration at right shows proper tick removal procedures. Using fine-point tweezers, grasp the tick as close to the skin as possible and pull gently. Make sure you've cleaned your hands, the bite site, and the tweezers with disinfectant. You may want to wear latex gloves.

The Lyme Disease Foundation, Hartford, Conn., suggests:

• Apply tick-killing pesticides to your pets.
• Treat your pet's environment with tick-killing pesticides.
• Mow grass regularly.
• Avoid allowing your pet in grassy, wooded or beach areas, unless you take appropriate precautions. While in areas of tick exposure, examine pets closely for ticks on a daily basis, especially around the head and inside the ears.
• Remove ticks immediately. This is important because it can take hours for an infected tick to transmit disease. Using fine-point tweezers, grasp the tick where the mouth parts are embedded into the skin and pull gently. Make sure you've cleaned your hands, the bite site, and the tweezers with disinfectant. You may want to wear latex gloves.
• Place the tick in a small container, like a pill vial. Label the container with the date, pet's name, type of animal, and your name, address, and phone number. Call your veterinarian about having the tick analyzed for type and possible diseases it may transmit.
• Never remove a tick with your fingers, as the squeezing further injects infectious material.
• Never try to burn a tick off or to smother it with petroleum jelly or nail polish, as these methods don't work.

• Wear long-sleeved shirts tight at the wrists, long pants tight at the ankles and tucked in socks, and shoes covering the whole foot.
• Wear light-colored clothes that show ticks easily.
• On clothing, use a repellent containing permethrin. However, do not apply it to clothing while it is being worn, and allow the clothing to thoroughly dry before wearing.
• On skin, use a repellent containing DEET. But don't overdo it. Too much bug spray can cause breathing difficulty, especially in children.

Human Problems

Lyme disease is by far the most often reported tick-borne disease in humans in the United States: 13,083 cases in 1994, up from 8,257 in 1993. Most reports came from the Northeast and North Central regions of the country. Symptoms include fatigue, chills and fever, headache, muscle and joint pain, swollen lymph nodes, and a red, circular skin rash. (See "Getting Lyme Disease to Take a Hike," in the June 1994 FDA Consumer.)

The next most prevalent disease from ticks is Rocky Mountain spotted fever, characterized by fever, headache, rash, and nausea or vomiting. It affects more than 500 people each year, according to the national Centers for Disease Control and Prevention.

CDC received reports of 415 cases of human monocytotropic ehrlichiosis, a disease also transmitted by ticks, since it was identified in 1986. It is similar to Rocky Mountain spotted fever, but usually without the rash. In 1994, scientists identified another similar disease, human granulocytic ehrlichiosis, or HGE. About 170 cases have been reported.

The organism that causes the tick-borne disease babesiosis infects red blood cells, which burst and die, resulting in hemolytic anemia. Patients develop a malaria-like fever, chills, sweats, muscle aches, nausea, and vomiting; those with no spleen are at particular risk of developing severe disease. The reported incidence of babesiosis is about one-tenth that of Lyme disease, or even less, according to Sam Telford, Ph.D., a lecturer on tropical public health with the Harvard School of Public Health.

Lyme disease, HGE, and babesiosis are all transmitted by the deer tick. Ticks have been found to have any two of those disease-causing organisms. "I believe it's only a matter of time before we find a tick with all three," Telford says. The lone star tick transmits human monocytotropic ehrlichiosis.

Many exposed people never develop the diseases. Roughly 5 percent of the coastal Massachusetts' population has antibodies against babesiosis, Telford says. "We believe it's about the same for ehrlichiosis. For Lyme disease, it's maybe three times that."

Fleas or an infected animal can transmit bubonic plague. Seven cases, including one death, were reported to CDC in 1995, in Arizona, California, New Mexico, and Oregon. Another 13 cases, also including one death, were reported in 1994, in Arizona, California, Colorado, New Mexico, and Utah.

Symptoms of bubonic plague include fever, headache, vague discomfort, and very painful, swollen lymph nodes near the infection site. Septicemic plague is more serious because the bloodstream is infected, as is pneumonic plague, with its overwhelming pneumonia. Antibiotics are used for treatment. A plague vaccine is available for special groups at very high risk.

Early diagnosis and treatment give humans the best chance of recovery from these and other flea- or tick-transmitted diseases.

--D.F.