Fleas and Plague Fact Sheet No. 5.600 Insect Series|Home and Garden by W. Cranshaw and R. Wilson* Fleas are small (1/13 to 1/18 inch), dark, Quick Facts red di­ sh-brown in­sects that feed on blood. Adults are wingless, flattened laterally and • Flea problems on pets are are heavily armored. These characteristics uncommon in Colorado. help them survive on animal hosts. The hind Fleas reproduce poorly in the pair of legs is well-developed for jumping. low humidity of homes. Fleas are sometimes mistaken for other small insects that also hop, notably springtails and • Most flea problems originate flea beetles (see fact sheet 5.592,Flea Beetles). from fox or skunks that den in Adult fleas have specialized mouthparts to the vicinity of homes. suck blood. • Vacuuming the area around There are approximately 80 species of Figure 1: The human flea, Pulex irritans, a species where pets rest and using fleas in Colorado, among the greatest number commonly associated with denning fox. found in any state. However, flea problems insecticides and traps can around the home and on pets are not as are sites within the home where humidity is help manage flea problems. common as in other parts of the United sufficiently high. • Plague is a potentially life States. Colorado’s dry climate is unfavorable Other fleas that occasionally bite humans threatening disease that is for flea development, particularly the are associated with squirrels, ground moved among wild rodent immature stage. However, some types of fleas squirrels, prairie dogs and other wild rodents. populations by fleas – are common on wild animal hosts and in the Of these, the rock squirrel flea, Diamanus primarily the rock squirrel flea. burrows or nests of some mammals where montanus, is the primary species that the humidity may be high. Very few species transmits the bacteria that produces plague. of fleas are ever involved in bites of humans or domesticated pets. In Colorado, the most common flea Flea Bites that bites humans is the human flea, Pulex Flea bites to humans appear as itchy, red irritans. Despite the name, these fleas are spots usually sur­round­ed by a red halo. Bites normally associated with wild mammals often occur in clusters, partic­ularly at edges such as skunks, foxes and coyotes. Human of tight-fitting clothin­ g. Some indi­vidu­als bites occur when the dens of wild animals are are ext­remely sensi­tive to flea bites; however, abandoned and fleas scatter. These fleas may others are fairly immune and may react little. get picked up by pets or move directly into Hu m­ ans are not a favored host of fleas and a home. The cat flea, Ctenocephalides felis is most bites occur when the fleas are starved the most important flea in much of the U.S. from the absence of favored animal hosts. as it can reproduce on both dogs and cats. Clusters of small dark spots on bedding, the Fortunately, it is uncommon in Colorado. excrement pro­duced by fleas, is one clue that However, people moving into the state fleas are present. from areas where fleas are common (e.g., Texas, California, Florida) can bring heavily Life History and Habits infested pets with them. These cat fleas may become established in a home and perhaps Flea eggs are laid around areas frequently even overwinter indoors, provided there used by animal hosts. The larvae that hatch © Colorado State University from these eggs are rarely observed. They are Extension. 4/04. Revised 6/13. *W. Cranshaw Colorado State University Extension worm-like and do not feed on animal blood. www.ext.colostate.edu entomology specialist, and professor, bioagricultural Instead, they consume blood-rich waste from sciences and pest management; and R. Wilson, adult fleas or other organic material around DVM, research scientist, department of microbiology, the host animal’s den. Larvae require several immunology and pathology. 6/2013 by washing or thoroughly vacuuming pet if they are repeatedly wet or become bedding­ on a regular basis. Insecticides dirt encrusted. can also be applied to carpets, cracks and Spot-Ons. Another effective flea crev­ices around areas where the pet resides. treatment is to apply a topical medication Among the more effective treatments are between the shoulder blades of the animal. borax compounds and insecticides­ that These topical applications kill adult fleas, affect flea growth, such as metho­prene larval fleas and eggs. They are also effective (PrecorR) or fenoxy­carb. The drawback of at killing ticks. Two veterinarian-supplied these methods is that they require frequent products are currently available – Frontline® and thorough application to disrupt the life (fipronil) and Advantage® (imidacloprid). cycle. Also, particularly with some formerly These products kill fleas for at least one Figure 2: Cat flea (Ctenocephalides felis) adult used products, there are concerns with month. Frontline Top Spot® is effective for feeding. (Photo from the K. Gray collection.) potential side effects of treatment, such as up to 3 months on dogs. Another spot-on the toxicity of lindane to cats. product available through retail stores is Several new flea control products and Biospot®, which contains the insect growth applications have been developed in recent regulator pyriproxifen. years and are described below. These The best advice for the above- use preventive strategies that interrupt mentioned flea control products is to begin reproduction and break the flea life cycle. treatment early in the season. Treatments The Pill (Program®). This product that begin in spring greatly reduce the (lufenuron) prevents flea eggs from likelihood of serious flea problems hatching. It is administered orally to developing in the summer, when flea pets once a month at mealtime. Dogs are infestations tend to be greatest. Flea control given the tablet form and cats receive a applications should kill stray fleas that Figure 3: Cat flea (Ctenocephalides felis) eggs. liquid suspension. Both formulations can animals acquire outdoors or in kennels and (Photo from the K. Gray collection.) be mixed with the pet’s food. Dosage is can prevent the need for applying other flea adjusted for the size of the animal. When treatments in the home. months to reach the adult stage. Low a flea bites a treated animal enough of humidity, which is common in this region, the active ingredient gets ingested to ® Other Methods to greatly prolongs devel­ opment.­ Pupation prevent flea eggs from hatching. Program occurs when the full grown larvae move to is available only by prescription through Manage Fleas small cracks and produce a cocoon covered veterinarians. A companion product Adult fleas may also be trapped. with debris. (Sentinel) contains both lufenuron and a Several traps currently on the market use All fleas found in Colorado homes are heartworm medication. colored light and heat to attract fleas. The associated with wild animals nesting in Egg Stopper Collars. Unlike fleas become trapped on a sticky surface. or around the home. When the animal conventional flea collars that contain For limited infestations often found in leaves permanently or dies, the fleas scatter insecticides that kill adult fleas, these Colorado, traps can be quite effective. in search of new hosts. For example, the collars contain an insecticide (methoprene Flea infestations originating from wild human flea is commonly associated with or pyriproxyfen) that interferes with animals almost always die out on their own skunks or foxes and occurs in homes normal egg production and egg hatch. since fleas reproduce poorly in the dry air when these animals abandon their dens. Once a flea collar is placed on a pet the of the home. However, flea problems can The adult fleas scatter at this time and insect growth regulator releases from the be very annoying for several weeks. Since may readily get picked up by domestic collar and distributes over the fur of the adults are more resistant to dry conditions, animals or humans. Orchopeas howardi is a animal. These collars can be effective for six using contact insecticides can relieve some species of flea associat­ed with fox squirrels, months and can effectively break the flea of these problems. often entering homes when carried on life cycle. One such brand, Ovitrol/Ovitrol If the location of an abandoned animal dogs. Related fleas are found on certain Plus Flea Egg Collar® is available through den is known, the site can be treated mice (Peromyscus spp.) and wood rats veterinarians. Retail versions also include with insecticides to prevent fleas from (Neotoma spp.). Fleatrol Flea Egg Collar® and Relieve Collar®. migrating where pets may be more likely Make sure the flea collars contain as the to acquire them. Some formulations of active ingredient insect growth regulators permethrin-containing insecticides, such as Management of (methoprene or pyriproxyfen), as many flea deltamethrin (e.g., DeltaDust®), have been Fleas on Pets collars have other active ingredients that do used to treat animal dens for flea control. Flea control usually involves treating not disrupt insect growth. Treating lawn areas can also be useful if domestic animals with insecticide A drawback of the collars can be fleas have dispersed to these sites. shampoos, flea dips, flea collars, and using unequal distribution of the flea control flea combs that physically remove the product on the fur. This varies with the size insects. Flea control mea­sures should also of the animal and the thickness of the fur. include managing the egg and larval stages Collars sometimes also lose effectiveness Plague Symptoms Plague is a potentially life-threatening Symptoms of plague include rapid disease caused by an infection of the rise of temperature two to three days after bacterium Yersenia pestis. Even though exposure. This is usually accompanied by plague rarely affects humans in Colorado headache and general feelings of illness. As (typically around one case per year), it still the disease progresses there is swelling and holds great historical importance including inflammation of lymph glands, most often three major pandemics such as the at the base of limbs. This swelling of lymph devastating Black Death of the Middle Ages. glands, called buboes, gives rise to the term bubonic plague for the most common Since its establishment in the United States Figure 4: Cat flea (Ctenocephalides felis) larva. at the turn of the century, plague has been clinical form of the disease. (Photo from the K. Gray collection.) a persistent concern in California, Arizona, Plague also has a much rarer Colorado and New Mexico. In the 43 year pneumonic form. This occurs when period between 1957 and 1999, there were infectious respiratory droplets are coughed 45 confirmed plague cases originating in or sneezed from infected humans or Colorado, of which nine resulted in death. animals and inhaled by a susceptible Plague can infect all rodents. Cats are human. Pneumonic plague can also also very susceptible. Dogs can become occur secondarily as a complication of infected. However dogs are more resistant inadequately treated bubonic plague. This to infection than most mammals and is the means by which some historical seldom exhibit signs of illness. outbreaks of plague have primarily been spread. Transmission A recently recognized source of human Among rodents, where the disease infections involves contact with infected Figure 5: Rock squirrel flea, primary vector of plague in Colorado. is maintained, almost all spread occurs cats. Plague-infected cats are clearly ill. via fleas. Not all fleas effectively transmit Most characteristic of infection are swollen plague. Those that do become infective lymph glands, generally under the chin fed to pets are also available through days or weeks after ingesting blood from and these may drain pus. Persons that veterinarians. Monitor the pet closely for a plague-infected rodent. In Colorado, the are bitten or scratched by infected cats symptoms of plague development. If any primary flea vector is the rock squirrel flea typically develop bubonic plague but those suspicious symptoms are detected, take the and the primary hosts are rock squirrels, that inhale infectious material coughed animal promptly to a veterinarian. prairie dogs, wood rats and other rodents by a cat can develop the more dangerous Pets that have brought home infective that live in burrows or elaborate stick pneumonic form of the disease. fleas that have been exposed to plague- nests. The human flea, most commonly infected rodents, their burrows or nests Treatment encountered in homes, is not involved in may survive several weeks. Therefore it transmitting plague in Colorado. Plague can be successfully treated is often a good idea to quarantine the Once the plague bacteria are ingested given prompt diagnosis and appropriate pet to a restricted area for a few weeks by the flea, it reproduces within the gut medication (generally certain antibiotics). if possible exposure is expected. For and may form a plug of the flea’s digestive A physician’s immediate attention is further management, this restricted area system. Some time is required between essential if plague is suspected! should be treated for fleas as well, using when a flea is infected and when it is products effective against adult fleas, such capable of transmitting the organism; for Management as various pyrethroids (e.g., permethrin, deltamethrin) and carbaryl (Sevin), the rock squirrel flea this averages 53 days. Mass rodent die-off is a good indication as labeled. Since the plague organism also is lethal to of plague outbreak in an area. If such an the flea, due to the gut obstruction, fleas event is observed it should be promptly often die before they can transmit the reported to local health department disease. However, an effect of the bacteria authorities for confirmation and, if blocking the gut is that the infected flea necessary, prevention recommendations. becomes starved and thus more actively If there is plague in your area, treat bites and seeks a host. Fleas capable of pets that roam outdoors for fleas. Dips are transmitting the disease usually do so in the recommended for this purpose. Flea collars course of biting; less commonly, the plague are not recommended for this purpose as organisms are transmitted when scratching they may not be sufficiently reliable for the flea feces into bites or wounds. prevention of plague. Various medications

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