Etiology
Fleas are permanent, obligate parasites and are the most common external parasites of dogs and cats. They are wingless insects with laterally compressed bodies and are 1.5-4 mm in length. Adult fleas live on the host for their entire lives while the immature lifeforms are more commonly found in the pet’s immediate environment. Flea-free animals do not contract fleas by contact with infested animals. Rather, they contract fleas from an infested environment. Flea infestations are more common in warm weather.
Fleas have been present for about 60 million years, with the earliest fleas being found on prehistoric mammals. More than 2000 species and subspecies of fleas occur throughout the world. Of these, 95% parasitize mammals and the remaining 5% live on birds. The cat flea, Ctenocephalides felis, is the most common flea found on the dog and cat. However, dogs and cats can also be infested by the dog flea (Ctenocephalides canis), sticktight flea (Echidnophaga gallinacea), poultry flea (Ceratophyllus gallinae), and human flea (Pulex irritans).
Pathophysiology
Ctenocephalides fleas cause skin irritation by biting the skin. Flea saliva contains histamine-like substances, proteolytic enzymes, and antigens that can be irritating or allergenic. The severity of clinical signs associated with Ctenocephalides depends not only on the severity of the flea infestation but also on the patient’s hypersensitivity to flea saliva.
E. gallinacea lay their eggs under the host’s skin, which causes severe irritation. The eggs hatch on the host animal but the larva drop off during further maturation. These adult fleas prefer the facial region.
Fleas serve as the intermediate host of the tapeworm Dipylidium caninum. Fleas can be vectors for infectious organisms, such as Yersinia pestis, Rickettsia spp., Bartonella spp., hemoplasma (Mycoplasma) spp., and the promastigotes of Leishmania spp.
Life-cycle of Ctenocephalides fleas
Fleas spend their entire adult life on the host, rarely leave the host voluntarily, and can survive for >100 days. Adult fleas deposit 1-2 mm, ovoid, white eggs on the host animal. The female flea begins producing eggs within 24-36 hours after its first blood meal and continues to produce eggs for >100 days if she remains on the host.1-3 A female can lay 40-50 eggs per day and 50% of these eggs will be female.1,2 This rate of reproduction can result in rapid, exponential flea growth within an environment in as little as 2 months.
Eggs are laid on the host and drop off into the environment.3 After 2-12 days eggs hatch into larvae. The larvae ingest the blood-containing excrement of adult fleas and then undergo two molts over 9-200 days.1,2 At the third molt, white larvae spin a whitish-gray cocoon in which pupae develop within 7 days to one year.1,2 Pupae can delay emergence from the cocoon for up to 1 year until conditions are right. Vibration, heat, and CO2 stimulate emergence. The larval cocoon is resistant to insecticides, desiccation, freezing, and insect growth regulators (IGRs). Once adult fleas emerge from the cocoon they seek a new host. Newly emerged fleas can survive for 1-2 weeks before requiring a blood meal. However once a new host is acquired, adult fleas begin to feed within minutes.
Ambient temperature and relative humidity are critical for flea development. For larvae, optimum conditions are 65-80°F (18-27°C) and high humidity.
Transmission
Fleas live in the environment and jump onto nearby hosts. Fleas do not usually leave one host for another host. Transmission is more common in warm, humid environments optimal for flea reproduction. Transmission occurs most often in the warm months of the year (i.e. spring and fall).
Diagnosis
Identifying Morphologic Features: Fleas are diagnosed primarily on identification of the adult flea on the dog or cat. Rarely, eggs may be seen attached to the hairs of the animal, with magnification. An adult flea is dark brown in color, wingless, and has a laterally compressed body measuring 1.5-4mm in length. Male fleas are smaller than females. Their chitinous skeleton is glossy, which allows them to move easily through the dense hair coat of animals. Fleas have three pairs of long, strong legs adapted for jumping, with the last pair usually being the longest and strongest. Some flea species have unique combs or ctenidia on the head or thorax that can be used for identification. For example, fleas of the genus Ctenocephalides are easily identified by their prominent genal (cheek) and pronotal combs that contain 7-9 pointed spines. The eyes, antennae, suctorial mouthparts, legs, thoracic and reproductive structures in males and females are also used for identification.
Physical Examination Findings: If adult fleas cannot be found on a patient, the presence of “flea dirt” is diagnostic of flea exposure and environmental infestation. Flea dirt is synonymous with flea feces. It is dark brown, round to comma-shaped, 1-2 mm in length, and usually found close to the skin surface at the base of the hair shaft.8 The presence of significant amounts of flea feces on a host indicate the flea was present long enough to take a blood meal. Sometimes it can be difficult to discern the difference between flea feces and other particulate material (e.g. environmental dirt, crusts or scale from the animal).
The presence of flea feces can be confirmed by using the wet paper towel technique. Flea dirt is combed from the animal and placed on a wet, white paper towel. The fecal material is flattened and drug along the paper towel using a tongue depressor or hemostat. If a reddish streak forms, this confirms the presence of blood within the material and supports the presence of flea feces.
Animals that are hypersensitive to flea bites display pruritus (e.g. over-grooming, scratching, biting) that may lead to alopecia, excoriation, and secondary bacterial infections. Such infections are characterized by papules, pustules, crusts, and epidermal collarettes. Patients with high flea burdens may have blood loss anemia and associated signs, such as lethargy, pale mucous membranes, and pale skin.
Disease description in this species:
Etiology
Ctenocephalides felis are the most common ectoparasite of dogs.8 However, several other flea species can affect the dog, including Ctenocephalides canis (dog flea), Echidnophaga gallinacea(sticktight flea), Ceratophyllus gallinae (poultry flea), and Pulex irritans (human flea). Any sex, breed, and age of dog may be affected.
Clinical Signs
Clinical signs vary depending on flea burden and underlying diseases of the host. Most animals with fleas are not hypersensitive or allergic to them. In these animals no dermatologic abnormalities may occur aside from the presence of flea feces within the hair coat. The presence of tapeworm proglottids in the perianal area or fecal flotation exams positive for D. caninum eggs is also suggestive of previous flea exposure.
Patients with high flea burdens may have systemic signs, such as lethargy, pale mucous membranes, and pale skin. Young, small puppies are especially susceptible to blood loss anemia from severe flea infestations due to the amount of blood a flea can consume in one day.
In hypersensitive dogs, dermatologic signs may include pruritus, alopecia, erythema, papules, crusts and excoriations of variable severity (mild to severe). These lesions are usually located on the caudal half of the body, such as the caudal dorsum, tail, ventral abdomen, perianal area, and medial hind limbs. However, lesions can be generalized.8 Hypersensitive animals may also have positive wheal formation on intradermal testing using flea antigen or have an elevated level of flea-specific IgE in their serum.
Environmental Therapy
Not only is the patient treated with an adulticide and IGR, the environment must be treated as well. If necessary, clients can hire a professional exterminator to treat the home, garage, car, and yard environments for fleas. Clients can reduce the flea burden by discarding and replacing pet bedding; washing bedding and throw rugs regularly; vacuuming frequently (e.g. daily); reducing humidity within the home; eliminating excessive carpeting; removing leaves and brush from the yard; and keeping the grass cut short.
SUPPORTIVE THERAPY
Most animals require no supportive therapy unless they are experiencing side effects of a severe flea burden, such as blood loss anemia and/or infection with other parasites (e.g. tapeworm infection). Supportive care may include hospitalization for fluid therapy or blood replacement products, treatment with other antiparasitics, and treatment of secondary pyoderma.
MONITORING and PROGNOSIS
Dermatologic signs usually resolve over the course of 2-3 months as the flea population becomes controlled.5 Signs may never return if fleas are eradicated from the environment; however, dogs with flea bite hypersensitivity are at increased risk for clinical signs if flea exposure recurs. Due to the wide spread prevalence of fleas in most of british columbia, it is likely a dog will be exposed again in its lifetime.
Preventive Measures:
Monthly, year-round flea control for all pets in the household is recommended to help prevent emergence of a flea burden within the home environment. Some people advocate routine treatment of the environment (home and yard) in geographical areas with high flea burdens to help prevent re-establishment of fleas.
For the flea allergic patient continuous, excellent flea control is required to keep animals free of clinical signs. Even minimal exposure may be sufficient to perpetuate itching in a hypersensitive patient.
Special considerations:
Fleas and the infectious organisms they carry are potentially zoonotic. Flea bites cause erythematous, pruritic papules on the skin of people, especially the distal extremities. Human bites indicate environmental over-population of fleas. Bites are often due to newly emerged adults. Tapeworm (Dipylidium caninum) infections are possible because fleas serve as the intermediate host. Animals and people become infected when they ingest an infected flea.
Fleas are permanent, obligate parasites and are the most common external parasites of dogs and cats. They are wingless insects with laterally compressed bodies and are 1.5-4 mm in length. Adult fleas live on the host for their entire lives while the immature lifeforms are more commonly found in the pet’s immediate environment. Flea-free animals do not contract fleas by contact with infested animals. Rather, they contract fleas from an infested environment. Flea infestations are more common in warm weather.
Fleas have been present for about 60 million years, with the earliest fleas being found on prehistoric mammals. More than 2000 species and subspecies of fleas occur throughout the world. Of these, 95% parasitize mammals and the remaining 5% live on birds. The cat flea, Ctenocephalides felis, is the most common flea found on the dog and cat. However, dogs and cats can also be infested by the dog flea (Ctenocephalides canis), sticktight flea (Echidnophaga gallinacea), poultry flea (Ceratophyllus gallinae), and human flea (Pulex irritans).
Pathophysiology
Ctenocephalides fleas cause skin irritation by biting the skin. Flea saliva contains histamine-like substances, proteolytic enzymes, and antigens that can be irritating or allergenic. The severity of clinical signs associated with Ctenocephalides depends not only on the severity of the flea infestation but also on the patient’s hypersensitivity to flea saliva.
E. gallinacea lay their eggs under the host’s skin, which causes severe irritation. The eggs hatch on the host animal but the larva drop off during further maturation. These adult fleas prefer the facial region.
Fleas serve as the intermediate host of the tapeworm Dipylidium caninum. Fleas can be vectors for infectious organisms, such as Yersinia pestis, Rickettsia spp., Bartonella spp., hemoplasma (Mycoplasma) spp., and the promastigotes of Leishmania spp.
Life-cycle of Ctenocephalides fleas
Fleas spend their entire adult life on the host, rarely leave the host voluntarily, and can survive for >100 days. Adult fleas deposit 1-2 mm, ovoid, white eggs on the host animal. The female flea begins producing eggs within 24-36 hours after its first blood meal and continues to produce eggs for >100 days if she remains on the host.1-3 A female can lay 40-50 eggs per day and 50% of these eggs will be female.1,2 This rate of reproduction can result in rapid, exponential flea growth within an environment in as little as 2 months.
Eggs are laid on the host and drop off into the environment.3 After 2-12 days eggs hatch into larvae. The larvae ingest the blood-containing excrement of adult fleas and then undergo two molts over 9-200 days.1,2 At the third molt, white larvae spin a whitish-gray cocoon in which pupae develop within 7 days to one year.1,2 Pupae can delay emergence from the cocoon for up to 1 year until conditions are right. Vibration, heat, and CO2 stimulate emergence. The larval cocoon is resistant to insecticides, desiccation, freezing, and insect growth regulators (IGRs). Once adult fleas emerge from the cocoon they seek a new host. Newly emerged fleas can survive for 1-2 weeks before requiring a blood meal. However once a new host is acquired, adult fleas begin to feed within minutes.
Ambient temperature and relative humidity are critical for flea development. For larvae, optimum conditions are 65-80°F (18-27°C) and high humidity.
Transmission
Fleas live in the environment and jump onto nearby hosts. Fleas do not usually leave one host for another host. Transmission is more common in warm, humid environments optimal for flea reproduction. Transmission occurs most often in the warm months of the year (i.e. spring and fall).
Diagnosis
Identifying Morphologic Features: Fleas are diagnosed primarily on identification of the adult flea on the dog or cat. Rarely, eggs may be seen attached to the hairs of the animal, with magnification. An adult flea is dark brown in color, wingless, and has a laterally compressed body measuring 1.5-4mm in length. Male fleas are smaller than females. Their chitinous skeleton is glossy, which allows them to move easily through the dense hair coat of animals. Fleas have three pairs of long, strong legs adapted for jumping, with the last pair usually being the longest and strongest. Some flea species have unique combs or ctenidia on the head or thorax that can be used for identification. For example, fleas of the genus Ctenocephalides are easily identified by their prominent genal (cheek) and pronotal combs that contain 7-9 pointed spines. The eyes, antennae, suctorial mouthparts, legs, thoracic and reproductive structures in males and females are also used for identification.
Physical Examination Findings: If adult fleas cannot be found on a patient, the presence of “flea dirt” is diagnostic of flea exposure and environmental infestation. Flea dirt is synonymous with flea feces. It is dark brown, round to comma-shaped, 1-2 mm in length, and usually found close to the skin surface at the base of the hair shaft.8 The presence of significant amounts of flea feces on a host indicate the flea was present long enough to take a blood meal. Sometimes it can be difficult to discern the difference between flea feces and other particulate material (e.g. environmental dirt, crusts or scale from the animal).
The presence of flea feces can be confirmed by using the wet paper towel technique. Flea dirt is combed from the animal and placed on a wet, white paper towel. The fecal material is flattened and drug along the paper towel using a tongue depressor or hemostat. If a reddish streak forms, this confirms the presence of blood within the material and supports the presence of flea feces.
Animals that are hypersensitive to flea bites display pruritus (e.g. over-grooming, scratching, biting) that may lead to alopecia, excoriation, and secondary bacterial infections. Such infections are characterized by papules, pustules, crusts, and epidermal collarettes. Patients with high flea burdens may have blood loss anemia and associated signs, such as lethargy, pale mucous membranes, and pale skin.
Disease description in this species:
Etiology
Ctenocephalides felis are the most common ectoparasite of dogs.8 However, several other flea species can affect the dog, including Ctenocephalides canis (dog flea), Echidnophaga gallinacea(sticktight flea), Ceratophyllus gallinae (poultry flea), and Pulex irritans (human flea). Any sex, breed, and age of dog may be affected.
Clinical Signs
Clinical signs vary depending on flea burden and underlying diseases of the host. Most animals with fleas are not hypersensitive or allergic to them. In these animals no dermatologic abnormalities may occur aside from the presence of flea feces within the hair coat. The presence of tapeworm proglottids in the perianal area or fecal flotation exams positive for D. caninum eggs is also suggestive of previous flea exposure.
Patients with high flea burdens may have systemic signs, such as lethargy, pale mucous membranes, and pale skin. Young, small puppies are especially susceptible to blood loss anemia from severe flea infestations due to the amount of blood a flea can consume in one day.
In hypersensitive dogs, dermatologic signs may include pruritus, alopecia, erythema, papules, crusts and excoriations of variable severity (mild to severe). These lesions are usually located on the caudal half of the body, such as the caudal dorsum, tail, ventral abdomen, perianal area, and medial hind limbs. However, lesions can be generalized.8 Hypersensitive animals may also have positive wheal formation on intradermal testing using flea antigen or have an elevated level of flea-specific IgE in their serum.
Environmental Therapy
Not only is the patient treated with an adulticide and IGR, the environment must be treated as well. If necessary, clients can hire a professional exterminator to treat the home, garage, car, and yard environments for fleas. Clients can reduce the flea burden by discarding and replacing pet bedding; washing bedding and throw rugs regularly; vacuuming frequently (e.g. daily); reducing humidity within the home; eliminating excessive carpeting; removing leaves and brush from the yard; and keeping the grass cut short.
SUPPORTIVE THERAPY
Most animals require no supportive therapy unless they are experiencing side effects of a severe flea burden, such as blood loss anemia and/or infection with other parasites (e.g. tapeworm infection). Supportive care may include hospitalization for fluid therapy or blood replacement products, treatment with other antiparasitics, and treatment of secondary pyoderma.
MONITORING and PROGNOSIS
Dermatologic signs usually resolve over the course of 2-3 months as the flea population becomes controlled.5 Signs may never return if fleas are eradicated from the environment; however, dogs with flea bite hypersensitivity are at increased risk for clinical signs if flea exposure recurs. Due to the wide spread prevalence of fleas in most of british columbia, it is likely a dog will be exposed again in its lifetime.
Preventive Measures:
Monthly, year-round flea control for all pets in the household is recommended to help prevent emergence of a flea burden within the home environment. Some people advocate routine treatment of the environment (home and yard) in geographical areas with high flea burdens to help prevent re-establishment of fleas.
For the flea allergic patient continuous, excellent flea control is required to keep animals free of clinical signs. Even minimal exposure may be sufficient to perpetuate itching in a hypersensitive patient.
Special considerations:
Fleas and the infectious organisms they carry are potentially zoonotic. Flea bites cause erythematous, pruritic papules on the skin of people, especially the distal extremities. Human bites indicate environmental over-population of fleas. Bites are often due to newly emerged adults. Tapeworm (Dipylidium caninum) infections are possible because fleas serve as the intermediate host. Animals and people become infected when they ingest an infected flea.
Fleas on Dog | Fleas on Cat
what the big deal?
what the big deal?
