Ticks & Fleas

Fleas and ticks are the most important external parasites of pets, livestock and humans. Both fleas and ticks are very abundant, have irritating bites and can transmit disease. Fleas can transmit tapeworms. Ticks can transmit Lyme disease, Rocky Mountain spotted fever and relapsing fever. Lyme disease is transmitted in the Northern United States by the deer tick and in the Southern United States by the black legged, Gulf coast, American dog, lone star and relapsing fever tick. Lone star and American dog ticks can cause tick paralysis.

Cat flea, Ctenocephalides felis

The cat flea is the most important flea species in the United States and attacks both cats and dogs. Adults are 1/16” long and are usually found on the host. The flea inserts its mouthparts in the skin, injects saliva and sucks blood. The bite leaves a red spot on the skin. The saliva is irritating to the host, causing dermatitis and hair loss in allergic animals.

Flea eggs and feces

Adult female fleas lay white, shiny eggs on the host. The eggs are not glued to the host, so they fall off immediately into bedding and other areas. Adult flea feces are also found in areas the animals frequent. Female fleas can produce 24 eggs per day, and eggs hatch in 12 to 48 hours.

Flea larve

Larvae of fleas go through three stages in 10 to 14 days. They are about 1/4” long. Larvae prefer to feed on adult flea feces. They are mainly found in pet resting areas, both indoors and outdoors.

Flea cocoons

Flea larvae pupate within silken cocoons and change into the adult stage. Debris is incorporated into the cocoon, so they are difficult to find. Fleas can remain in the pupal stage for six to 12 months without a host. They are protected from insecticides and resist chemical treatments.

American dog tick, Dermacentor variabilis

This tick is one of the most prevalent tick pests in the Eastern United States. Adults are about 1/4” long, and the shield has variable white markings. The larvae and nymphs prefer to feed on mice. Adults prefers dogs and other large animals.

Brown dog tick, Rhipicephalus sanguineus

This tick is one of the most common pests of dogs. Adults are 3/16” long and are uniformly reddish-brown. All stages prefer to feed on dogs. This tick is prevalent in houses and kennels.

Gulf coast tick, Amblyomma maculatum

This tick is very prevalent in the Southeastern United States. The sexes are very different in appearance. The immature stages feed on ground-dwelling birds. Adults attach primarily to the ears of large animals such as deer and cattle.

Lone star tick, Amblyomma americanum

This tick is one of the most common ticks on humans and it has prevented the development of some areas. The female has a silvery spot on the dorsal shield. Its long mouthparts allow deep penetration of the skin, often causing pus sores.

Black legged tick, Ixodes scapularis

This tick is widespread in the Southeastern United States, and often is found along trails, paths and roadways. Adult ticks are dark reddish-brown with dark-brown to black legs.

Relapsing fever tick, Ornithodorus turicata

The relapsing fever tick is a soft tick, and its mouthparts are not visible from above. The relapsing fever tick mainly attacks rodents, and consequently is associated with rat and mouse habitats. It can transmit tick-borne relapsing fever.

1. This document is SP 95, one of a series of the Department of Entomology and Nematology, Florida Cooperative Extension Service, Institute of Foodand Agricultural Sciences, University of Florida. This document is available for sale as a high-quality, color publication. For ordering information or toorder using VISA or MasterCard, call 1-800-226-1764. Date first printed: May 1991 as ENY-509. Reviewed: June 2008 and January 2012. Please visit theEDIS website at http://edis.ifas.ufl.edu.

2. P.G. Koehler, professor; J.L. Castner, scientific photographer; Department of Entomology and Nematology, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A&M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean

Biology,Treatment, and Control of Flea and Tick Infestations

Flea and tick infestations of pets and the home environment are a common occurrence and their elimination can be an expensive and time-consuming problem. Many problems in control can be related to a lack of understanding of parasite biology and ecology. In fact many advances in control of fleas can be directly linked to advances in our knowledge of the intricacies of flea host associations, reproduction, and survival in the premises. Understanding tick biology and ecology is far more difficult than with fleas, because North America can have up to nine different tick species infesting cats and dogs compared to one primary flea species. The range and local density of certain tick species has increased in many areas because of changes in climate, vegetation, agricultural practices, wildlife host abundance, acaricide usage, and probably several other factors. Whatever the reason, tick infestation pressure may be much higher and associated tick-transmitted diseases may be more prevalent in some locations today than in the past.

FLEA OVERVIEW

Flea infestations are probably the most common ectoparasitic affliction of dogs and cats in North America. Although more than 2200 species and subspecies of fleas are known throughout the world, only Ctenocephalides felis felis (cat flea), Ctenocephalides canis (dog flea), Pulex simulans, and Echidnophaga gallinacea (poultry sticktight flea) occur in large numbers on dogs and cats with enough regularity to be of importance as nuisance pests.1,2 In North America, the most commonly encountered flea species on dogs and cats is C f felis (Fig. 1).1,2

The term ‘‘cat flea,’’ which is the approved common name for C f felis, can occasionally cause confusion. When it appears in print, it refers to the specific flea genus and species and not to fleas recovered from cats. There are four recognized subspecies of C felis throughout the world: Ctenocephalides felis damarensis and C felis strongylus occur primarily in East Africa, C felis orientis occurs in India and Australia, and the widespread C f felis occurs in all continents except Antarctica and is the only subspecies that occurs in North America.2 Therefore, most of the North American literature refers to the cat flea as C felis. Because the cat flea is the most common flea on domestic dogs and cats in North America and has been extensively investigated, the following discussions on flea biology will be confined to the cat flea.

The cat flea, C felis, is a clinically important parasite of domestic pets, being responsible for the production of allergic dermatitis, serving as the vector of various bacterial pathogens, and being the intermediate host for filarid and cestode parasites.

Flea allergy dermatitis (see later discussion for detail) is the most common dermatologic disease of dogs and a major cause of feline miliary dermatitis.1,2 It is an immunologic disease in which a hypersensitive state is produced in a host, resulting from the injection of antigenic material from the salivary glands of fleas. Blood consumption by fleas can produce iron deficiency anemia and even death in heavy infestations.1,2 Ctenocephalides felis has also been recently implicated in the transmission of Rickettsia typhi, Rickettsia felis, Bartonella henselae and other Bartonella spp, Mycoplasma haemofelis, and in rare cases, even Yersinia pestis.3–6 Ctenocephalides felis also serves as an intermediate host of the nonpathogenic subcutaneous filarid nematode of dogs, Acanthocheilonema (Dipetalonema) reconditum. Severalspecies of cestodes can also be carried by C felis, including Dipylidium caninum and Hymenolepis nana.1,2

FLEA BIOLOGY

Flea eggs are pearly white and oval, with rounded ends, and are 0.5 mm in length. Eggs will usually hatch in 1 to 10 days, depending on temperature and humidity.7,8 Newly hatched flea larvae are slender, white, segmented, sparsely covered with short hairs, and 2 to 5mmin length; they possess a pair of anal struts (Fig. 2). Larvae are free living, feeding on adult flea feces (which are essential for successful development), on organic debris that is found in their environment, and on flea eggs.1,2 Once the larvae have ingested adult flea feces or other material, they become darker. Flea larvae avoid direct sunlight in their microhabitat, actively moving deep into carpet fibers or under organic debris (grass, branches, leaves, or soil).2 Flea larvae undergo two molts, usually over 5 to 11 days, before developing into the pupal stage.7,8

Flea larvae are extremely susceptible to heat and desiccation.8,9 Moisture in the larval environment is essential for development, with relative humidity lower than 50% causing desiccation, and larvae that are maintained in soil with low moisture levels fail to develop.8 Because larvae are susceptible to heat and desiccation, development outdoors probably occurs only where the ground is shaded and moist. The flea-infested host also needs to spend a significant amount of time in these areas, so that adult flea feces will be deposited into the larval environment.

The mature third instar larva produces a 0.5-cm–long, whitish, loosely spun silklike cocoon in which it undergoes pupation. The cocoon is sticky and becomes coated with debris from the environment. Cocoons are found in soil, in carpets, under furniture, and on animal bedding. At 27 C (80.6 F) and 80% relative humidity, fleas begin to emerge approximately 5 days after pupation, and they reach peak emergence in 8 to 9 days.10,11 Once the pupa has fully developed, the pre-emerged adult flea within the cocoon can be stimulated to emerge from the cocoon by physical pressure, carbon dioxide, and heat.12 If the pre-emerged adult does not receive an emergence stimulus, it may remain quiescent in the cocoon for several weeks or months until a suitable host arrives.12

The entire life cycle of C felis can be completed in 12 to 14 days, or it can be prolonged up to 174 days, depending on temperature and humidity within the microenvironment. 12 However, under most household conditions, nearly all cat fleas will complete their life cycle within 3 to 8 weeks.

The adult C felis depends primarily on visual cues to locate hosts.13 Factors such as flea age, CO2, and temperature modify their responsiveness.13 It has been determined that C felis adults are most sensitive to green light with wavelengths between 510 and 550 nm.13,14 Ctenocephalides felis adults that have emerged in dark areas, such as under porches, in crawl spaces, or under beds or sofas, will orient and move toward a light source. They then jump when the light source is suddenly and temporarily interrupted (host-shadow).

If the newly emerged C felis adults do not immediately acquire a host, they can survive several days before requiring a blood meal. As with immature life stages, survival of adult fleas is highly dependent on temperature and humidity. In moisturesaturated air, 62% of adult C felis survived for 62 days, whereas only 5% survived for 12 days when maintained at 22.5C and 60% RH (relative humidity).10,15 It is unlikely that adult or immature fleas in the premises can survive during winter in northern temperate regions. It has been shown that no life cycle stage (egg, larva, pupa, or adult) can survive for 10 days at 3C (37.4F) or 5 days at 1C (33.8F).10

Numerous warm blooded animals play host to C felis. In North America, various nondomesticated hosts that harbor cat fleas have been reported, including coyotes, red and gray fox, bobcats, skunks, several rodent species, raccoons, opossums, Florida panthers, poultry, calves, and ferrets.1,2 With such a large number of alternative hosts, several of which often live in close proximity to humans and their pets, it is likely that flea-infested wild animals or feral dogs and cats are serving as continual sources of reinfestation. Newly emerged fleas, in carpets or outdoors, often bite humans before colonizing their preferred host. Because C felis is not highly cold-tolerant, it has been postulated that it is surviving in cold climates in the urban environment, as adults on untreated dogs and cats or on small wild mammals, such as opossums and raccoons.1,2 Because these animals pass through yards in the spring, or establish nesting sites in crawl spaces or attics, eggs drop off and develop into adults. Cat fleas may also survive the winter, as pre-emerged adults in microenvironments that are protected from the cold.1,2

Once on a host, C felis initiates feeding within seconds to minutes.16 In one study, approximately 25% of fleas were blood-fed within 5 minutes, and in another, the volume of blood consumed by fleas was quantifiable within 5 minutes.17,18 Mating occurs on the host after feeding and can occur within 8 to 24 hours.16 Female cat fleas begin egg production within 24 to 36 hours of their first blood meal.19 They lay eggs within the pelage of the host, but because the eggs are not sticky, they drop out of the hair into the surrounding premises. Ctenocephalides felis is a highly fecund organism, with the female reaching peak egg production at 40 to 50 eggs per day and producing approximately 1300 eggs during the first 50 days on a host. Ctenocephalides felis can continue to produce eggs at a gradually declining rate for more than 100 days.19 To produce such a large quantity of eggs, female cat fleas consume an average of 13.6 mL of blood per day, which is equivalent to 15.15 times their body weight.16 While feeding, female cat fleas excrete large quantities of incompletely digested blood, which dries within minutes into reddish-black fecal pellets or tubular coils that are often called ‘‘flea dirt’’ or ‘‘frass.’’ Flea feces can often be found matted into the pelage.

Actively feeding and reproducing C felis adults are fairly permanent ectoparasites. When normal grooming activity of cats was restricted, an average of 85% of female and 58% of male fleas were still present on cats after 50 days.19 When fleas that have been on a host for several days are removed, they die within 1 to 4 days.15 Although cat fleas rarely leave their host voluntarily, the host’s grooming activity plays a significant role in their survival and longevity on that host. When cats are allowed to groom freely, they will ingest or groom off a substantial number of fleas in a few days.10,20 When cat fleas were allowed to feed for only 12 hours and then removed from their host,5%were still alive at 14 days.15 This is of particular importance, because one study showed that when cats were housed adjacent to each other but physically separated, 3% to 8% of the fleas moved from one cat to another. However, when cats were housed in the same cage,2%to 15% of the fleas transferred. Therefore, it is possible for a few adult fleas to transfer from one host to another.21 However, it is far more likely that most flea infestations originate from previously unfed fleas emerging from environments that have supported development of immature life stages.

TICK OVERVIEW

There are two primary tick families, Argasidae (soft ticks) and Ixodidae (hard ticks). In North America, the ticks of most importance to dogs, cats, and their owners are the Ixodidae or hard ticks. Hard ticks are characterized by a hardened dorsal shield (scutum) and a head (capitulum) that extend in front of the body. Many species also have eye spots on the scutum and posterior indentations called festoons that can be used to aid in identification. Additionally, the Ixodidae commonly found on dogs and cats in North America are all three-host ticks, feeding once on a different host after molting in each motile stage (larva, nymph, and adult).22,23

Most ticks in motile life stages that infest dogs and cats use an ambush technique called questing, although Ixodes spp may use ambush and hunter tactics.23 Ticks do not jump onto hosts or drop out of trees. Ticks that use the ambush strategy climb onto weeds, grasses, bushes, or other leafy vegetation, extend their forelegs that contain a sensory apparatus called the Haller organ, and wait for passing hosts to brush against the vegetation. When the host brushes against the plant, the tick immediately releases the vegetation and crawls onto the host.

Mating by ticks in the genera Amblyomma, Dermacentor, and Rhipicephalus occurs on the host after feeding. Certain species of Ixodes often mate off the host before feeding, but may mate while on the host.24 During the first 24 to 36 hours following attachment to the host, little or no ingestion of blood takes place.25 During this period, ticks use their chelicerae to cut the epidermis and insert their hypostome, which contains backward directed spines. Following insertion of the hypostome, many ticks reinforce their attachment by secreting a cementlike substance from their salivary glands.23,26 Once the feeding site is established, the tick begins the second slow feeding phase, which lasts for several days. The slow feeding phase is followed by a rapid feeding phase. During the rapid feeding phase, which occurs 12 to 36 hours before detachment, the mated female tick may increase dramatically in size, often reaching 100 times her unfed body weight.25,26

TICKS SPECIES INFESTING DOGS AND CATS

The tick species that most commonly infest dogs and cats in North America are Amblyomma americanum (Lone Star tick), Amblyomma maculatum (Gulf Coast tick), Dermacentor occidentalis (Pacific Coast tick), Dermacentor variabilis (American dog tick), Dermacentor andersoni (Rocky Mountain wood tick) Ixodes pacificus (western black-legged tick), Ixodes scapularis (black-legged tick), Otobius megnini (spinose ear tick) and Rhipicephalus sanguineus (brown dog tick).22,23

Several factors have contributed to the increased range of A americanum, including increased habitat and wide host range that includes deer, small mammals, birds, and humans.27,29 This tick occurs most commonly in woodland habitats with dense underbrush. Substantial reforestation over the last century, in urban and rural habitats, has provided increased areas of habitat for white-tailed deer and for survival and expansion of A americanum.27,29 The white-tailed deer is considered a preferred host for A americanum, and all life stages will feed on white-tailed deer.27,29

It is well recognized that before and in the early-to-middle part of the nineteenth century, white-tailed deer were numerous and widespread throughout North America. Throughout the nineteenth century, unregulated hunting, loss of natural predators, and extensive loss of habitat decimated deer populations.27,29 By the beginning of the twentieth century, only an estimated 300,000 to 500,000 deer remained in North America.31 During the early and middle part of the twentieth century, restrictions were placed on deer hunting, numerous states began restocking efforts, and combined with an increase in natural habitat, there was a marked resurgence in deer populations to an estimated 18 million by 1992.29 As deer expanded their range and increased their numbers, there was a corresponding increase in the tick species that are closely associated with deer.

White-tailed deer populations are so important to the long-term survival of A americanum that exclusion of deer has a profound effect on its populations. In one study, exclusion of deer from a 71-ha forest over a 4-year period resulted in reductions of 88%, 53%, and 51% of the larvae, nymphs, and adults, respectively, as compared with control plots.30

Another excellent host for larvae and nymphs that uses similar habitats is the wild turkey.27,31 Areas with a deciduous forest canopy and high populations of white-tailed deer and wild turkey can have remarkably large populations of A americanum. Many other animals can be parasitized by this aggressive tick. Immature stages can be found on various ground-dwelling birds and numerous mammals such as red fox, rabbits, squirrels, raccoons, dogs, cats, coyotes, deer, and humans.22,27 A americanum also feeds on various hosts, including cats, cattle, coyotes, deer, dogs, horses, sheep, raccoons, and humans.22,27

As A americanum populations expand into new areas, seasonality of ticks found on dogs and cats can change. Nymphs are found from March to September, larvae are frequently encountered in the late summer into the fall, and adults are often encountered from late February to early June.27,31 Because all life stages can parasitize dogs and cats, A americanum could be encountered on pets, 8 to 9 months out of the year. Once hosts are acquired, larvae and nymphs engorge over a period of 3 to 9 days, and adults typically engorge within 9 days, but may take up to 2 weeks to do so.27,31 As with most ticks, peak seasonal activity can vary widely by geographic region. Similar to other ixodid ticks, unfed adults may survive for prolonged periods (>400 days) if hosts are not available. In temperate climates, the life cycle often takes 2 years to complete, whereas in warmer coastal climates, it can be completed within 1 year.32

A americanum is considered a major vector of animal and human pathogens, including Ehrlichia chaffeensis (causing human monocytic ehrlichiosis) and Ehrlichia ewingii.27 The Lone Star tick can also transmit Borrelia lonestari.33 It has also been implicated in the transmission of Francisella tularensis (causing tularemia).34 The Lone Star tick has also recently been demonstrated to be a competent vector of Cytauxzoon felis, the highly pathogenic and usually fatal protozoan parasite of cats.35

Another Amblyomma species that parasitizes dogs is the Gulf Coast tick, A maculatum (Fig. 4). Amblyomma maculatum is a three-host tick with larvae and nymphs feeding on small rodents and ground dwelling birds, such as quail, meadow larks, and cattle egrets. Adults primarily parasitize the ears of large mammals, such as cattle, but they will also feed on horses, pig, goats, dogs, bear, birds, bobcats, coyotes, rabbits, raccoons, deer, and humans.36 Once considered to be restricted within a 100-mile strip along the Gulf and Atlantic Coasts, A maculatum is now recognized to extend further inland, particularly in the Central United States, with expansion into Oklahoma and eastern Kansas.37–39 A maculatum transmits Hepatozoon americanum, the etiologic agent of American canine hepatozoonosis. The transmission of this disease is unique, in that dogs must ingest the tick to become infected.40 Amblyomma maculatum also has been documented to cause tick paralysis.22

a Department of Pathobiology, 166 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn AL 36849-5519, USA b Department of Diagnostic Medicine/Pathology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA * Corresponding author.

E-mail address: blagbbl@auburn.edu (B.L. Blagburn).

Amblyomma spp

Amblyomma americanum (Lone Star tick) is named for the characteristic and easilyrecognizable single white spot that occurs on the dorsal shield of the female (Fig. 3). The males are also ornate but have several white to yellow lines on the edge of their scutum instead of the single white spot (see Fig. 3). Amblyomma americanum have long palpi, a long hypostome, eye spots, and festoons.

The range of A americanum seems to be increasing across the southern plains and midwestern and eastern states. It was once considered to occur primarily in the south, with southern New Jersey being its northernmost range; its geographic range has since expanded.27 Focal populations now occur in many northern states, including Connecticut, Maine, Massachusetts, Michigan, New Jersey, and New York.27,28 The range of distribution extends south into Florida, west to Texas, and north through eastern Oklahoma and Kansas to Michigan.27