Types Of Fleas On Dogs. Treatment And Control

Fleas are small (1 – 5 mm), brown to black, wingless, laterally compressed insects. They reside in the hair coats of mammals including the dog. The life stages include eggs, larvae, pupae and adults. The adults are ectoparasites that feed on the blood of the host. Fleas have piercing mouthparts and inject saliva into the host as they feed.

Species infecting dogs

Although there are myriad of flea species only a few infest dogs. The most significant species include:

  • C. canis (the dog flea) – Commonly infects dogs in some countries (Australia, New Zealand, and Greece) but is rapidly being replaced by C. felis. The dog flea is rare in North America.
  • Ctenocephalides felis (the cat flea) – The most common flea affecting both dogs and cats worldwide. It also infests many different hosts including ferrets, raccoons, opossums, and wild canids.
  • Echidnophaga gallinacea (the poultry stick-tight flea) – This flea may be found deeply embedded on ear margins and along eyelids of dogs and cats.
  • Pulex irritans (the human flea) – This flea is commonly found on small to medium sized wild mammals and only occasionally infests dogs and cats.

Life Cycle

Eggs: Cat flea eggs are pearly white, oval with rounded ends and 0.5 mm in length. They are laid on the host and readily fall from the pelage into the environment. Hatching occurs in about 2 – 7 days.

Larvae: Flea larvae are small, white and have many setae. Larval development occurs in protected microhabitats that combine moderate temperatures, high relative humidity, and food. Larvae are voracious feeders. They will feed on a variety of organic debris including flea eggshells and other flea larvae. Blood (adult flea feces) is an essential component in the diet. Larvae exhibit positive geotaxis and negative phototaxis and will be found at the base of carpet fibers in homes. Flea larvae will not develop in areas exposed to the hot sun. Outdoor habitats that promote C. felis development provide RH > 50%, contain soil moisture 2 – 20%, and protect against temperatures above 35°C and below 4°C.

Pupae: Flea larvae spin a silk cocoon and develop into a pupa therein. The silk fibers are sticky and debris from the environment camouflage the cocoon. Cocoons can be found in soil, on vegetation, in carpets, under furniture, and on animal bedding. The pupal stage is resistant to desiccation with about 80% emerging as adults at 27°C and 2% RH.

Preemerged Adult in the Cocoon: delayed emergence occurs when there are no emergence stimuli. Mechanical pressure, CO2, and ⇑ temperatures stimulate emergence. Adult C. felis may remain quiescent in the cocoon for up to 30 weeks at 11°C and 75% RH.

Adults: C. felis can develop and emerge in as little as 13 days. In temperate climates 90 to 95% of fleas emerge within 21 to 35 days, with scattered emergence of a few fleas for 60 to 90 days depending upon temperature and humidity. In subtropical climates, 96 to 99% of fleas emerge within 14 to 28 days.


Host seeking by adults: Newly emerging fleas move to the top of the carpet pile or vegetation where they are more likely to encounter a passing host. Adult C. felis depend upon visual and thermal cues to locate hosts. They orient and move towards a light source, their activity is enhanced when the light source is temporarily interrupted (shadow cast by a passing host, thus eliciting a jump response). If newly emerged cat fleas do not immediately acquire a host and feed they can survive only a few days. In most homes newly emerged fleas die within 1 to 2 wks without a host.

Adult feeding and reproduction

Adult C. felis begin feeding almost immediately once they acquire a host. While the volume of blood ingested by males is unknown, female C. felis can consume 13.6 μl of blood daily. After rapid transit through the flea, the excreted blood dries into reddish-black fecal pellets or long tubular coils (“flea dirt”). Mating occurs after fleas have fed. Egg production begins within 20 to 24 hours after females take their first blood meal. Females are capable of producing 40 – 50 eggs per day during peak production and average 27 eggs/day for an average of 50 days. Fleas are able to sustain egg production for over 100 days.

Over Wintering and Recurrence in Temperate Climates: Survival of newly emerged adult fleas or immature stages during winter in northern temperate regions is important in the epidemiology of flea infestations. Fleas will survive in cold climates as adults on untreated dogs and cats or small wild mammals (such as opossums and raccoons) in the urban environment. Cat fleas may also survive the winter as preemerged adults in microenvironments protected from the cold.

Clinical features

Fleas consume relatively large amounts of blood. Heavy infestations may cause severe anemia and death, particularly in puppies. Pruritus and skin irritation are a common clinical sign of flea infestation. The salvia from feeding fleas is allergenic. Flea Allergy Dermatitis (FAD) develops in some flea infested animals. FAD is a frequent, severe skin disease of dogs and also an important disease of cats. It involves immediate and delayed -type immune responses. There may be areas of alopecia, scaling, hyperpigmentation, skin thickening and lichenification; pyoderma and seborrhea may ensue in uncontrolled FAD. In cats, there may be numerous small, papulocrusting lesions that are referred to as miliary dermatitis.

Tapeworm transmission by fleas

Ctenocephalides felis, C. canis and Pullex irritans are the intermediate hosts of the tapeworm Dipylidium caninum. Flea larvae ingest the eggs of the tapeworms and cysticercoids are found in the flea’s tissues. Dogs, cats and humans may become infected with tapeworms by swallowing infected fleas.

Diagnosis

Flea infestation can frequently be diagnosed by finding fleas moving throughout the hair coat especially over the tail head and belly. A fine-toothed comb can be used to recover fleas and flea dirt. If the combings are placed on white moist paper flea feces will stain the paper reddish brown indicative of blood.

Treatment and control

The primary goals of flea control are:

  1. Elimination of fleas on pet(s)
  2. Elimination of existing environmental infestation
  3. Preventing subsequent reinfestation

Flea control measures and client expectations have changed dramatically in recent years. Historically, flea control was achieved through repeated application of on-animal products and application of insecticides and insect growth regulators (IGRs) into the premises. The recent development of highly effective adulticides and IGRs with convenient dosage formulations and prolonged residual activity have improved flea control both on the pet and in the environment. New insecticides that are highly effective are Imidacloprid (Advantage; Bayer Animal Health), Fipronil (Frontline Topspot, Frontline Plus or Frontline Spray; Merial Animal Health), Selamectin (Revolution; Pfizer Animal Health) and Nitenpyram (Capstar; Novartis Animal Health).

If it is necessary to eliminate an existing infestation in the pet’s environment, concurrent administration of a topical or oral IGRs such as lufenuron, methoprene, or pyriproxyfen should be used as well as the repeated application of insecticides into the premises. Pump sprays, directed aerosols, total release aerosols (“bombs”) may be used or a Pest Management Specialist (Exterminator) contracted. If the yard is infested, cyfluthrin or permethrin spray may be used every 7 – 10 days. Mechanical control measures should always be initiated. The pet should be bathed, bedding and rugs should be washed and carpets vacuumed thoroughly.

Thiamine, Brewer’s yeast, sulfur, garlic, and ultrasonic flea collars have been proven to be ineffective. Other supportive care may be necessary if FAD is evident; corticosteroids, antihistamines, antibiotics (secondary pyoderma) etc.

The main groups of insecticides used in the control of fleas are as follows:

  • Pyrethrum is the initial plant extract of certain plant species of the genus Chrysanthemum, native to southwestern Asia, whose aromatic flower heads, when powdered, constitute the active ingredient in the insecticide called pyrethrum. Pyrethrum is a mixture of four compounds: pyrethrins I and II and cinerins I and II.
  • Pyrethrins are widely used insecticides in the home. They have a rapid “knockdown” for insects and have a low potential for producing toxicity in humans. For pyrethrins to be fully lethal to insects, it is generally combined with a ‘synergist’, such as piperonyl butoxide, a chemical that enhances the pyrethrins action on the nervous system. Numerous formulations exist for control of fleas and lice. Efficacy and duration are highly variable and typically very short actings.
  • Pyrethroids are synthetic pyrethrin compounds that are made in the laboratory. Common synthetic pyrethrins are allethrin, resmethrin, permethrin esvenvaluate, phenothrin, cyfluthrin, bifenthrin, and deltamethrin. Numerous formulations and combinations exist. Synthetic pyrethroids are designed for more potency and longer duration. Most pyrethroids are safe for use on dogs but extremely toxic for cats.
  • Imidacloprid (Advantage; Bayer Animal Health) is a neonicotinoid spot-on formulation that is approved for monthly flea control. Has efficacy against lice. A true insecticide, it also has efficacy against lice but very minimal efficacy against acarines (ticks and mites). Dogs and cats
  • Nitenpyram (CapStar; Novartis) A neonicotinoid in oral tablet form. It is rapidly absorbed with initial flea kill with 15 – 20 minutes and close to 100% mortality within 3 – 4 hrs. 94 – 97% of this chemical is eliminated unchanged in urine within 24 – 36 hrs. The duration of activity is 24 – 48 hours. Many clinical applications include: rapid and complete elimination of pet flea burdens, treatment prior to boarding or surgery, treatment prior to release from clinic, treatment of animals at animal shelters. Very safe for dogs and cats.
  • Fipronil (Frontline Topspot, Frontline Plus or Frontline Spray; Merial Animal Health); spot-on and spray formulations Frontline plus is a combination of fipronil and methoprene. It is approved for monthly flea and tick control and efficacy is also reported against lice including Sarcoptes sp. and Cheyletiella sp. Dogs and cats
  • Selamectin (Revolution; Pfizer Animal Health); spot-on formulation. Approved for monthly flea control and heartworm prevention in dogs and cats. Also control of Sarcoptes on dogs, Otodectes on cats & dogs, Toxocara sp. and Ancylostoma sp. in cats, and tick control in dogs. Reported efficacy against other lice including Notoedres sp. and Cheyletiella sp. Dogs and Cats
  • Older carbamate and organophosphate chemistries rarely used for flea control at this time

Public health significance

  • Murine typhus: Traditionally the primary vector of the Rickettsia typhi organism was the oriental rat flea, Xenopsylla cheopis. Murine typhus is a mild febrile disease characterized by development of headaches, chills, and skin rashes, with infrequent involvement of the kidneys and central nervous system. The disease occurs in humans and many small mammals, including rats and mice. Murine typhus occurs in the United States along the southeastern, southwestern and gulf coasts. In southern California, the principal transmission cycle involves opossums and C. felis.
  • Cat Scratch disease caused by Bartonella hensalae is an uncommon disease of humans. It is characterized by skin rashes, lymph node enlargement, low-grade fever and generalized muscle pain. The disease resolves over a period of 3 – 4 weeks (unless person is immunosuppressed) and most often occurs after a period of prolonged contact with a young cat. Most cats testing positive for B. hensalae are not ill. However in some affected cats, B. hensalae will cause fever, loss of appetite, hypersensitivity to noise or light, incoordination and/or enlarged lymph nodes. It has been shown that cat-to-cat transmission is through ingestion of flea feces.
  • Plague – Yersinia pestis. Plague occurs in the southwest U.S. It is vectored by a number of small mammal and rodent fleas cat fleas. The common cat flea, C. felis, is not capable of transmitting plague.

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