ANIMAL HEALTH
Fleas, Ticks, Lice,
Mites, and Flies
By Lynn P. Schmeitzel and
Peter J. Ihrke
Fleas are wingless, brown, fleas move rapidly on the skin
bloodsucking insects that and are most easily found on
may infest dogs and cats, and the rump and in the groin
other warmblooded animals. area.
Fleas transmit several dis- Sticktight fleas {Echidno-
eases (for example, plague) phaga gallinácea) are found
and parasites such as tape- on birds (especially chickens)
worms. Young animals heav- and may attack dogs and cats
ily infested with fleas may die exposed to infested birds. This
from severe blood loss. Fleas flea attaches to the face of the
prefer certain species of ani- animal and moves slowly.
mals but will attack any The human flea (Pulex
source of blood if the preferred irritans) may attack dogs and
animal is not available. cats.
The cat flea (Ctenocephal- Flea eggs laid on the host
ides felis) and the dog flea are smooth and quickly fall off
iCtenocephalides canis) both into the animal's environ-
infest dogs and cats. C. felis is ment. The eggs are oval,
the most common flea found white, and glistening.
on dogs and cats. Cat and dog Small larvae hatch from
the eggs and feed on the feces
from adult fleas. After several
molts, the last larval stage
Lynn P. Schmeitzel is Assistant forms a pupal case. While in
Professor of Dermatology, College
the case, the larva develops
of Veterinary Medicine, University
of Tennessee, Knoxville. Peter J.
into an adult flea. The adult
Ihrke is Assistant Professor of flea emerges from the pupal
Dermatology and Allergy, School case and searches for an
of Veterinary Medicine, University animal.
of California, Davis. Time required for the flea
464 Dogs and Cats
ANIMAL HEALTH
to develop from egg to adult have fleas. Therefore, all ani-
may be as short as 16 days mals in the household must be
during periods of warm tem- treated. All animals, the
peratures and high humidity. house, and premises should be
A small amount of flea sa- treated with appropriate in-
liva is deposited in the skin secticides at frequent inter-
each time the adult flea bites vals to prevent reinfestation.
an animal. This saliva is very Contrary to recent folk-
irritating and an allergic reac- lore, brewers yeast (a thia-
tion can cause severe itching, mine or B^ source), garlic, or
resulting in the skin disease sulfur are not effective in
termed flea allergy dermatitis. either repelling or killing
Biting and scratching fleas.
around the rump and groin
areas is the most common Ticks, Hard and Soft
sign of flea allergy. Hair loss, Ticks are bloodsucking arthro-
a red rash, and thickening of pod parasites of the skin.
the skin are commonly seen. They transmit many diseases
Fleas may be difficult to find such as Rocky Mountain Spot-
in allergic animals since very ted Fever to people and ani-
few flea bites are needed to mals. Severe blood loss may
cause an allergic reaction. In result from heavy infestation.
areas of the United States Tick paralysis is a rare dis-
where fleas are common, flea ease caused by a toxic sub-
allergy dermatitis is the most stance in the saliva of some
common itchy disease of the ticks. Recovery is rapid if the
skin. ticks are removed.
Flea feces (flea dirt) in Ticks have a four-staged
the haircoat confirms the pres- life cycle including an egg, a
ence of fleas. Flea dirt consists six-legged larva (seed tick), an
of dehydrated blood from the eight-legged nymph, and an
dog or cat and is reddish-black eight-legged adult. Ticks are
and comma-shaped. identified as one-host, two-
Successful treatment of host, and three-host ticks
flea allergy dermatitis re- depending on the number of
quires the absolute elimina- hosts required to complete
tion of fleas from contact with their life cycle.
the affected dog or cat. If one Hard ticks (Ixodidae) and
dog or cat in a household has soft ticks (Argasidae) are the
fleas, it may be assumed that two main families of parasitic
all animals in the household ticks.
Fleas, Ticks, Lice, Mites, Flies 465
ANIMAL HEALTH
Hard ticks have a hard dog but also can parasitize
shield on their backs distin- humans, wild animals, cattle,
guishing them from soft ticks and horses. Adult American
which do not. Most hard ticks Dog Ticks have white mark-
require three different hosts ings on the shield on their
to complete their life cycle backs. Outdoor areas such as
and each stage only feeds fields are the major sources of
once. American Dog Ticks.
Thirteen species of eco- Removal. Hard ticks usu-
nomically important ticks are ally are found securely at-
in the hard tick (Ixodidae) tached by their head to the
family. Most of these ticks are skin. Before removal, these
acquired outside except for the ticks should be sprayed with
Brown Dog Tick {Rhipice- an insecticide safe for use on
phalus sanguineus) which can animals, or soaked with alco-
infest buildings. hol. The head should be
The Brown Dog Tick is grasped with an instrument
widely distributed in North such as tweezers and pulled
America. Since this tick sur- on gently until removed. Ciga-
vives indoors, it can infest rettes, lighters, gasoline and
kennels and households. The kerosene can severely injure
Brown Dog Tick is a three- the skin and should never be
host tick but all three stages used to remove ticks. If the
can parasitize the dog. This ticks are Brown Dog Ticks,
tick also parasitizes cats, the kennels and household
horses, rabbits, and humans. premises may need repeated
The Brown Dog Tick has no treatment with pesticides.
white markings on the shield Soft ticks (Argasidae)
on its back. have a leathery outer cover-
The American Dog Tick ing. The Spinose Ear Tick
{Dermacentor variabilis) is (Otobius megnini) is the only
widely distributed in North medically important soft tick.
America but is most common This tick is most common in
on the Atlantic coast. These the southwestern parts of the
ticks, unlike the Brown Dog United States. The young
Tick, live only in grasses and stages (larvae and nymphs)
shrubs. live in the outer ear canal of
The larval and nymphal dogs, cats, cattle, and horses.
stages of the American Dog Adult soft ticks do not feed
Tick parasitize field mice. The and do not live on animals.
adult tick usually infests the The Spinose Ear Tick can
466 Dogs and Cats
I ANIMAL HEALTH
cause severe irritation to the mouthparts for obtaining a
ear canal and may occasion- blood meal, and have pincer-
ally cause paralysis and sei- like claws for clinging to the
zures in some animals. The hairs of their hosts. These lice
animal should be taken to a are grey to red depending on
veterinarian for removal of the amount of blood they have
these ticks since the eardrum ingested. Sucking lice may
may be damaged by improper cause severe anemia in heav-
removal of the ticks, espe- ily infested young or debili-
cially by sharp instruments. tated animals.
Sucking lice can infest
The Louse most domestic animals (except
Lice are wingless insects that birds and cats). Infested ani-
are uncommon parasites of mals are usually itchy and
dogs and cats and are common often have rough dry coats.
parasites of livestock and Sucking lice move slowly.
birds in the United States. Biting lice usually are
Lice spend their entire life yellow with a large rounded
cycle on the host and are not head and mouthparts adapted
readily transmitted from one for chewing and biting. Some
animal species to another species have legs for clasping,
(they are host specific). In others have legs for moving
other words cat lice will not rapidly. These lice may cause
usually infest dogs and vice severe hair loss from scratch-
versa. Lice are spread from an ing and rubbing. Biting lice
animal to another by direct can infest dogs, cats, cattle,
contact. sheep, goats, horses, and
Female lice attach their birds.
eggs (nits) to the hairs or Specific identification of
feathers on their hosts. The lice is difficult and is less im-
young lice undergo several portant than being able to de-
molts before becoming adults. termine if the louse is a biting
Development from egg to species or the more harmful
adult takes about 19 to 28 blood-sucking species.
days. The dog has one common
The two main types of lice biting louse (Trichodectes
include sucking lice (Ano- canis) and one common suck-
plura) and biting lice (Mallo- ing louse (Linognathus seto-
phaga). sus). The cat has only one
Sucking lice are larger common species, a biting louse
than biting lice, have piercing (Felicola subrostratus).
Fleas, Ticks, Lice, Mites, Flies 467
t ANIMAL HEALTH
Adult lice and eggs at- onstrated by a veterinarian
tached to hair and feathers performing a skin scraping,
may be seen with the unaided removing the superficial layer
eye. Lice and nits may be of a small area of skin with a
found more readily by using a scalpel blade. The debris is
magnifying hand lens with placed on a glass slide with
good lighting. mineral oil and examined
Many pesticides will kill with a microscope.
adult lice but the eggs are Affects Dogs. Demodi-
quite resistant. Consequently, cosis is a potentially serious
animals should be treated and disease in the dog. If large
then retreated two weeks numbers of Demodex canis
later to kill the lice that have mites are found in several
hatched from eggs not affected skin scrapings a diagnosis of
by the first treatment. demodicosis may be made.
There are two forms of
All About Mites demodicosis in the dog—local-
Demodectic mites {Demodex ized and generalized. Patchy
spp.) parasitize many domestic hair loss on the head, forelegs,
animals. These mites live in and trunk is called localized
hair follicles in the skin. They demodicosis. In generalized
crawl from the mother to the demodicosis hair loss, redden-
nursing puppy or kitten dur- ing, and crusts may involve
ing the first few days of life. the entire body. These ani-
They do not cause any harm mals also may develop severe
in small numbers and are con- bacterial infections in the skin.
sidered normal inhabitants of An inherited defect in the
the skin. These mites are not animal's immune system al-
contagious from animal to an- lowing the mites to multiply
imal, or animal to human. is believed to be an important
The skin disease caused by an factor in development of gen-
increased number of mites is eralized demodicosis. Since it
called demodicosis or demo- is believed that the defect of
dectic mange. the immune system is inher-
Demodex spp. are elon- ited, dogs with demodicosis
gated mites with short stubby should not be used for breed-
legs. The life cycle includes an ing. Demodicosis is not a
egg, a six-legged larva, an contagious disease. Affected
eight-legged nymph, and an puppies were born with a pre-
eight-legged adult. disposition to develop demodi-
These mites can be dem- cosis.
468 Dogs and Cats
ANIMAL HEALTH
Diagnosis and treatment temic diseases such as diabe-
of localized and generalized tes mellitus or feline leukemia
demodicosis should be super- virus infection. Diagnosis and
vised by a veterinarian. Local- treatment of feline demodi-
ized demodicosis often does cosis should be supervised by
not require any treatment and a veterinarian.
usually will spontaneously
cure in six to eight weeks. Oc- Sarcoptic Mites
casionally the localized form The family Sarcoptidae in-
will become generalized, so cludes the Sarcoptes spp. and
the affected areas and normal Notoedres spp. of mites. These
skin must be closely observed. mites may affect many species
No one can predict if a dog of animals but usually prefer
with localized demodicosis will one species. They are spread
spontaneously cure or develop by direct contact from one ani-
generalized demodicosis. mal to another.
A veterinarian usually This family of mites bur-
will treat generalized demodi- row within the superficial lay-
cosis with a series of parasiti- ers of the skin and the entire
cidal rinses after clipping the life cycle is spent on the host
hair. Antibiotics may be animal. The life cycle includes
needed for a secondary bacte- an egg, a six-legged larva, two
rial infection that is often eight-legged nymphal stages
present. and an eight-legged adult.
Rare in Cats. Demodicosis The development from egg to
is a rare disease in cats. There adult takes about 17 days.
are two types of demodectic The common skin disease
mites in the cat: Demodex cati caused by sarcoptic mites is
and an unnamed Demodex called scabies or sarcoptic
spp. In localized demodicosis mange. The variety Sarcoptes
there is patchy hair loss, red- scabei is named after a partic-
dening, and occasionally ular host (for example, Sar-
crusting on the neck, ears and coptes scabei var. canis—the
head. In generalized demodi- sarcoptic mite of dogs). In all
cosis hair loss, reddening, and animals, scabies is an in-
crusting may involve the en- tensely itchy disease causing
tire body. the animal to scratch, chew,
Generalized demodicosis and rub constantly.
may develop in cats secondary Canine scabies is a com-
to suppression of the immune mon, contagious skin disease.
system associated with sys- The most common signs are
Fleas, Ticks, Lice, Mites, Flies 469
ANIMAL HEALTH
scaling, crusting, and a red United States yet may be
rash on the head, ears, and common in certain local areas.
abdomen. The entire body These mites are highly conta-
may be affected. Many of the gious to other cats and occa-
skin lesions are self-induced sionally may be transmitted
since dogs with canine scabies to people and dogs. In the cat
are almost constantly scratch- there is hair loss, thickening
ing, chewing, and rubbing and crusting of the skin, usu-
their skin. Severe itching is ally affecting the head and
induced by very few mites and forelegs. These areas are se-
may be due to an allergic re- verely itchy.
action to the mites. Notoedres mites have
Scabies is highly conta- morphologic characteristics
gious from dog to dog. Dogs similar to Sarcoptes scabei
obtained from sources with mites. These mites may cause
large numbers of animals a red rash in humans. Usually
housed together such as this rash spontaneously re-
pounds, large puppy producing solves in people since No-
establishments, and some pet toedres cati mites cannot com-
shops are more likely to be af- plete their life cycle in human
fected by scabies. skin,
Scabies mites may be Parasiticidal rinses are
transmitted to a human, re- used to treat notoedric mange.
sulting in a red rash. Usually Since many parasiticides are
the disease in humans is self- highly toxic to cats, a veteri-
limiting since canine scabies narian always should super-
mites apparently cannot com- vise the use of any parasiti-
plete their life cycle in human cides in cats.
skin. Ear Mites. The Psoroptic
Since these mites often family of mites usually are
are difficult to find by multi- parasites of cattle and sheep.
ple skin scrapings, response to The life cycle includes an egg,
treatment with parasiticidal a six-legged larva, two eight-
rinses is often used by veteri- legged nymphal stages, and
narians to diagnose canine an eight-legged adult.
scabies. One member of this fam-
Cat Scabies, Mange. ily, Otodectes cyanotis, the ear
Feline scabies or notoedric mite, is a common cause of
mange caused by Notoedres ear problems in the dog and
catiis an uncommon skin cat. These mites generally are
disease in many parts of the found in the outer ear canal
470 Dogs and Cats
ANIMAL HEALTH
but may rarely be found on The North American
other parts of the body. The Chigger (Trombicula alfred-
mites are readily transmitted dugesi) is the most common
between dogs and cats. chigger that affects animals
Ear mites cause severe ir- and people. On animals they
ritation and thick, dry, black cause an itchy, red rash on
crusts in the ear canals. The the belly, face, feet, and legs.
mites may be seen with a Chiggers are orange-red in
magnifying instrument called color. They may be found in
an otoscope. They are large, the ears of cats.
white, and mobile. Eardrops The larval mites remain
usually are prescribed by attached to the skin for only a
veterinarians to treat this few hours, so the larvae often
disease. are difficult to find on the ani-
Walking Dandruff. Cheyle- mal. Since chiggers leave vol-
tiella spp. or Walking Dan- untarily, the only treatment
druff Mites are contagious that may be needed is some-
mites that live on the surface thing to stop the itching.
of the skin. These mites cause Chigger infested areas should
severe scaling, usually on the be avoided during summer
back. Some itching may be and fall months to prevent
seen but this disease usually recurrence.
is not as itchy as the other Flies. The larvae of Cuter-
skin diseases caused by mites ebra spp. flies infest cats,
in dogs and cats. The mites dogs, rabbits, squirrels, and
commonly affect dogs, cats, small rodents in the summer.
and rabbits. They may be seen Pets acquire the larvae by in-
with a magnifying hand lens vestigating rodent burrows.
or in skin scrapings. Consequently the neck is most
Chiggers are larval commonly affected.
stages of the Trombiculid The larva penetrates the
mites. Only the larval stages skin and forms a cavity under
are parasitic. The nymphs and the skin. A breathing pore
adults are free living. Chig- communicates with the out-
gers are seen most often in side. Cuterebra larvae should
the late summer and early fall be removed surgically by a
and are obtained by contact veterinarian.
with heavy underbrush.
Fleas, Ticks, Lice, Mites, Flies 471
