ECTOPARASITES of DOGS and CATS

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ECTOPARASITES of DOGS and CATS
ECTOPARASITES of DOGS and CATS
By Dr John B Malone September, 2000 www.vetmed.lsu
.edu/vmp/vetparasitology
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FLEAS Members of the Siphonaptera Adults have
laterally compressed, wingless, segmented bodies
with three pair of legs. The posterior thoracic
pair is adapted for powerful jumping). Fleas feed
exclusively on blood via slender piercing
mouthparts
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In the Southeastern USA, flea bite dermatitis is
the most common dermatological condition of dogs
and a major problem in cats. Human owners can
also become hypersensitive to flea saliva. Even
one or two fleas on flea allergic pets can cause
continuing signs. Flea saliva contains a complex
of histamine-like compounds, enzymes and
allergenic components, including a low-molecular
weight (MW) hapten and other gt 20KD MW allergens.
Flea allergy can develop experimentally in 12
weeks, but the most common age of onset is 3-6
years. Flea related diseases and control may
comprise 1/4 to 1/3 of many small animal
practices in the South. Over 2000 flea spp.
occur in mammals and birds. Except for
'straggler', temporary infestations, only a few
of these species occur in domestic animals
Alopecia and chronic inflammation associated with
flea bite dermatitis Fleas are in greatest
numbers near the tailhead, which is often most
affected
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Ctenocephalides felis - (Cat flea)

• Accounts for 99 of fleas on cats and 93 of
  fleas on dogs and is least host specific. It can
  feed on humans but cannot reproduce or persist
  more than 6-8 weeks without dog/cat blood meals.
• Pronotal and genal combs are present. The head is
  longer than the morphologically similar C. canis.
  
• -Ctenocephalides spp transmit Dipylidium caninum,
  Dipetalonema reconditum

Ctenocephalides canis is rarely found in the USA.
Similar genal and pronatal combs occur on a
shorter head than C. felis
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• Pulex irritans (Human flea)
• Frequent on dogs and in some local areas is the
  most prevalent species. It is rare on cats.
• No combs are present (vs Ctenocephalides) and no
  thickening present on mesopleuron (vs
  Xenopsylla). A characteristic seta (hair) is
  found below the eye

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• Echidnophaga ga1linacea (Sticktight flea)
• A flea of poultry, other birds of sporadic
  occurrence, especially in the southeastern US
• Can parasitize a wide variety of hosts,
  including dogs and cats
• Compressed head, no combs
• Mouthparts are embedded in the skin in clusters
  around the eyes and head of birds, dogs, cat and
  other species, causing ulcerations where they lay
  eggs. Larvae hatch and fall to the environment,
  becoming adults in
• 4 weeks. Can be fatal in young birds.

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• Xenopsylla cheopis (Rat flea)
• Rat-rat and rat-man cycle of bubonic plague
  (Yersinia pestis) the flea's proventriculus is
  blocked by organisms and regurgitated in next
  blood meals
• Sylvatic plague is maintained in the Southwest
  USA by other rodent fleas of ground and rock
  squirrels, prairie dogs
• A vertical, rod-shaped thickening present on
  mesopleron is diagnostic (see arrow).

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• The life cycle described is for C. felis and is
  similar for other flea species. The life cycle
  can be completed in 16-21 days
• Optimum conditions are 65-80F and 75-85
  relative humidity. Long periods of such
  conditions lead to rapid seasonal build-up of
  flea populations and 'bad flea years'

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-Fleas are 'nest' parasites Adults are mainly
found on the host, 95 of the population are
found as eggs, larvae and pupae, mainly in areas
frequented by hosts (10 eggs 7larvae 2 pupae 1
adult) -Adult fleas are short lived (2 weeks)
off of the host and thus prefer to stay on the
host. Crowding effect is seen ifgt200
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After feeding and mating in 12 hours, females
produce eggs in 2 days. They can produce up to
25-40 eggs per day with frequent blood meals, or
2000 eggs in a lifetime of up to lOO days (the
average flea lifespan is reported to be 4-6 wk).
Eggs dessicate if relative humidity drops to
lt50.
Blood meal results in flea dirt
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Eggs roll off of the host, develop in 2-5 days to
mandibulate larvae that feed on 'flea dirt,
feces produced from voluminous blood meals of
adult fleas, (arrow) and other organic matter.
Direct sunlight is lethal to larvae.
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Larvae molt twice to third instar larvae over
9-200 days depending on environmental conditions
when temperatures are gt65 F, then spin a whitish,
sticky cocoon and transform to debris-covered
pupae.
Larvae
Spinning cocoon
Cocoon
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Pupae in detritis
Larvae

• Pupae metamorphose from larvae to adult form in
  about one week.
• Some may hatch spontaneously in 1-4 weeks, but
  many remain quiescent up to 6 months awaiting
  emergence when stimulated by vibration, CO2 and
  warmth of approaching hosts, including humans who
  enter low- occupancy infested premises such as
  cabins
• This phenomenon is termed the pupal window' that
  most often frustrates flea control programs.

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Control Programs
Control of fleas must focus on both treatment of
the pet (and contact animals) and environmental
control for the 95 of the flea life cycle that
occurs off the host in the inside and/or outside
environment. In addition to older methods of
chemical on-animal and environmental treatments,
great strides have been made in recent years in
developing better, long-acting drugs and
preventive methods for flea control. Control
methods can be 1) chemical (chlorinated
hydrocarbons, carbamates, organophosphates,
pyrethrins, synthetic pyrethroids, imidocloprid,
fipronyl, desiccants, repellants, insect growth
regulators (IGR) and insect development
inhibitors (IDI), 2) mechanical (vacuum, flea
combs, remove debris/wash bedding in 'nest'
areas) or 3) biological (eg Steinernema
carpacapsae- nematodes that consume up to 90 of
larvae/pupae in soil). Integration of several
methods is often most successful.
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Control Programs
The egg stage is not susceptible to insecticides.
Both eggs and larvae are susceptible to control
by IGR's such as methyprene, fenoxycarb,
pyriproxifen or IDI such as lufenuron, a chitin
inhibitor. The pupae window is the most
difficult to control and larva are often the key
to control. Integrated use of drugs with more
than one mode of activity, plus management, is
most effective.
Pictures here
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Mites of Dogs and Cats Demodex canis
(demodectic mange, red mange, the follicle mite)
-cigar shaped, 4 pairs of stubby legs, cluster
in hair follicles -Normal fauna of 80-90 of
dogs (and other spp., human), in hair follicles
in low numbers
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Localized or squamous form 1-5 non-pruritic,
grey to red alopecic patches around eyes,
commissures of mouth, forelegs 80-90
spontaneously cure in 3-8 weeks
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In certain dogs
Generalized Form (often with pyoderma) Lesions
coalesce, extend to head, neck, leg, trunk the
abdomen is least involved gt5 lesions is
considered generalized.
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• Etiology and Transmission
• Not contagious Pups get from the bitch during
  nursing period
• 3 months to 1 year of age mainly (older dogs have
  poorer prognosis)
• Short-haired, purebreds are predisposed
• Hereditary susceptibility (breeding of purebreds
  not recommended if generalized Demodex is
  diagnosed)
• Possibly T-cell immunodeficiency of a transient
  nature in young, growing dogs
• Immunosuppressive effect by mites themselves is
  proposed
• Stress and poor diet contribute

Progression from normal follicle to
proliferative, alopecic and pyoderma stages. Note
organisms in follicles and dermatitis in
histosection below
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Demodex Lesion Distribution
Need pictures
Localized form
Generalized form
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Diagnosis

• Scalpel Mineral oil scraping
• Squeeze skin between thumb and forefingers and
  scrape until oozes blood, mount on slide and
  examine
• Adult mites, larvae (3 pairs of legs), nymphs
  and reddish, spindle-shaped eggs may be found
• Prognosis worse if ratio of adults to immature
  forms is 5050 or less
• Bacterial Culture
• Coagulase Staphylococcus or Pseudomonas ? poor
  prognosis

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Demodex scraping
Note the spindle shaped eggs and the adults with
4 pairs of legs
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Treatment

• Squamous form Local topical insecticides,
  rotenone etc are used but have questionable
  effectiveness, since most self-cure
• Generalized form
• Treatment often difficult
• Old methods involved clipping hair coat, use of
  soaking, antibacterial baths antibiotics for
  pyoderma
• Amitraz (Mitaban) with clip. If non-responsive
  use high daily doses of macrolide antibiotics
  (Milbemycin, Ivermectin) for months

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Feline Demodicosis

• Low prevalence, occur around eyes and ear pinnae
• Stubby tail Demodex forms are recovered in
  scrapings Separate species?
• Localized, self-limiting, often immunodeficient
  cats
• Local treatment preparations often effective
  (ointments, solutions, etc)

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Sarcoptes scabiei var canis (Sarcoptic mange,
Scabies)

• Oval, short-legged with long, unjointed leg
  stalks and terminal sucker discs
• A burrowing mite
• Chewing mouthparts
• Highly pruritic
• Highly contagious transmission via body contact
• High incidence Gulf Coast due to humidity, warmth
• No breed, sex, hair coat predisposition
• Mites survive only few days off of host

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• Life Cycle. Insecticidal treatment needed at
  7-10 day intervals to break the 2-3 week life
  cycle (eggs not affected)
• Adults mate on skin surface, burrow into stratum
  corneum of the epidermis
• Progress 2mm/day, leaving 3-4 eggs and fecal
  pellets behind in a tunnel
• Larvae hatch, form molting pockets beneath skin
  surface, become nymphs, adults
• Scratching exposes burrows, mites ? Acanthosis,
  hyperkeratosis, secondary trauma

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Lesion distribution
Need diagram
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Sarcoptes scabiei lesions on the tip of the ear
Sarcoptes scabiei lesions initially affect tips
of ears, elbows, less haired areas, then
generalizes over weeks to months ? thick, crusty,
pigmented skin with pyoderma
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Diagnosis of Sarcoptes

• Difficult to find by skin scraping in dogs mites
  are very low in number
• Scrape several active lesions ? ID mites, eggs or
  reddish fecal pellets, as with the elbow scraping
  below
• KOH-sugar flotation procedure (karyolytic action)
  is more accurate
• Response to treatment is often the diagnosis

• Treatment
• Responds well to many insecticides if repeat at
  7-10 days
• Ivermectin, 300ug/kg Amitraz Selemectin are
  effective

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Sarcoptes Scabiei
Note the diagnostic long, unjointed leg stalks
with terminal sucker discs on leg pairs 1 and 2
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Typical histopathologic findings of Sarcoptes
ancanthosis, hyperkeratosis, tunnels with mites
and evidence of self trauma due to scratching.
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Public Health
Sarcoptes scabiei var canis temporarily invades
human skin, especially at the beltline after
contact ? reddish papular nodules persist 2-3
weeks. Humans have their own sub-species, S.
scabiei var hominus that persists long term that
is sometimes referred to as the seven-year-itch
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Notedres cati (feline scabies, head mange)

• Resembles S scabiei in life cycle, morphology,
  clinical effect but cat only
• Uncommon, pruritic, contagious infection of
  kitten litters and old tomcats
• Initial lesions ear tips, then head, neck
• Occur in large numbers easily found in skin
  scrapings

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Cheyletiella spp (walking dandruff)

• Uncommon, mild pruritis, highly contagious,
  especially in kennels, catteries
• Entire litter may be affected, especially 2-8
  week-old pups lesions start at rump then extend
• Whitish walking dandruff mites are visible to
  the naked eye or by hand lens

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Diagnosis of Cheyletiella

• Light skin scraping, gross examination of the
  skin by a hand lens or KOH digestion-sugar
  flotation of skin debris and hair reveals
  characteristic mites with strong mandibulate
  moutparts.
• Mites live in pseudotunnels in
  hyperkeratinized skin where they periodically
  pierce the skin to suck lymph, sometimes leading
  to pustule formation
• Asymptomatic carriers can occur
• Zoonotic transmission to humans and other animals
  (eg rabbits) is possible.

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Treatment and control of Cheyletiella

• Cheyletiella may live 10 days off the host,
  therefore environmental control is needed 1-2
  times. Treat animals each 7-10 days with various
  insecticidal preparations to break the 3-week
  life cycle.
• Treat all animals on premises
• Ivemectin at 300ug/kg, repeated in 3-5 weeks is
  effective

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Otodectes cyanotes (ear mites)

• Ear canal of dogs and cats feeds on lymph and
  epdidermal debris
• Blackish crusts and cerumen build-up ?predisposes
  to secondary otitis
• Highly contagious, mainly by contact

Diagnosis

• Mineral oil preparation by ear swab or ear loop
• Find whitish motile mites by otoscope in ear
  canal
• Legs have short pedicles with terminal sucker
  discs and piercing mouthparts

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• A 3-week life cycle entirely in the ear canal
  eggs are cemented to substrate
• Treat with insecticidal preparations each 7-10
  days to break life cycle use with insecticidal
  baths to kill stray organisms on skin/hair coat
  outside of ear
• Ivermectin (300ug/kg), topical fipronil or
  selamectin are effective

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Chiggers (Eutrombiculid mites)

• Only larvae are parasitic
• Adults and nymphs are free-living scavengers
• One year life cycle seasonal incidence
• Low host specificity
• Clusters on skin of reddish, bleb-like organisms
  engorged with body fluid
• Treat soon or spontaneous cure occurs in 7 days
  as larvae drop to environment
• Intense pruritis as mites feed through
  stylostome

stylostome
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Dermanyssus gallinae ( Red Roost Mite)

• Periodic visits to poultry for blood meals,
  return to cracks, crevices of cage
• Piercing mouthparts, motile, long-legged caused
  hemorrhages under wing (below)
• Feeds on dog, cat, human incidentally not highly
  host specific
• Use insecticides to break 1-week life cycle
• Related species, Ornithonyssus bacoti of rodents
  and avian mites from attic nests, can cause
  similar problems

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Ticks and Tick-Borne Diseases

• There are 5 hard ticks that are important in
  small animals in the Southeastern US
• Cause of local lesions at attachment sites,
  especially when removed with the head parts
  remaining in the skin
• Possible anemia with heavy infestations
• As vectors of disease
• As a cause of tick paralysis
• Common US species can be identified to genus
  grossly by long vs short mouthparts and ornate vs
  inornate features

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Rhipicephalus sanguineus (Brown dog tick)

• A 3-host tick but high preference for dogs by
  larvae, nymphs and adults
• Worldwide commonest tick of dogs found around
  ears, between toes
• Inornate, brown short mouthparts with flared
  basis capitulum
• Adapted to domiciliary environments and can
  establish indoors in kennels, homes. Can climb
  walls 15 feet above floor. Difficult to eradicate
  once present
• Short 2-month life cycle allows several
  generations/year, fast population growth
• Transmits Babesia, Ehrlichia, Hepatozoon,
  Hemobartonella

Babesia canis pyriform organisms in RBC of an
infected dog
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Treatment and control
Rhiphicephalus tends to cluster around ears and
between toes. All three stages are found on the
same dog

• Control on infested premises can be done by
  environmental sprays (eg dursban) applied each
  1-2 weeks, including walls and ceilings, until
  controlled. Resistance is common - try higher
  dose, different class insecticide
• Treat or dip dogs weekly for 3-8 weeks, with
  daily removal of ticks
• Examine, quarantine and treat all incoming dogs
• Topical fipronil, selamectin are effective

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Amblyomma americanum (Lone Star Tick)

• Note the characteristic long mouthparts and
  ornate lone star marking on the female. Males
  are more diffusely ornate
• 1 year or more life cycle low host and stage
  specificity Larvae, nymphs and adults are often
  found on the same host
• Common on livestock, dogs in rural areas a wood
  tick

Amblyomma maculatum, the gulf coast tick, is more
diffusely ornate in both females and males.
Larvae, nymphs found on small birds, adults on
and around ears of cattle, dogs in the gulf coast
region
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Ixodes scapularis (black-legged shoulder tick)

• Ixodes spp are inornate with long mouthparts
• Larvae and nymphs feed on small mammals, adults
  on large mammals
• Ixodes spp transmit Lyme disease in the US, which
  is commonest in the northeast because I dammini,
  the most prevalent wood tick has a deer-deer
  mouse infection cycle that facilitates
  incidental disease transmission to humans and
  dogs.

I scapularis Southeast, Rocky Mountain Spotted
Fever, Tularemia, Lyme disease I dammini
Northeast, Lyme disease, Babesia microti I
pacificus Western USA, Lyme disease
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Dermacentor variabilis (American dog tick)

• Dermacentor spp are common wood ticks that have
  short mouthparts and ornate markings and are
  considered the major vector for rocky mountain
  spotted fever (RMSF). (D variabilis in the
  southeast, D andersoni in the rocky mountain
  area, D occidentalis in the pacific coast
  states).
• The RMSF transmission cycle is maintained by a
  feeding pattern of larvae and nymphs on small
  mammals and adult ticks on dogs, human, other
  large mammals. The total life cycle is as short
  as 3 months to as long as 3 years, depending on
  species and climate.

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• Flaccid, ascending motor paralysis fatal when
  progresses to respiratory and cardiac arrest
• Any tick, but especially Dermacentor, Amblyomma
  in large numbers
• Seasonal in late spring, summer
• A neurotoxin (acting on motor end plate?) is
  produced by engorging female ticks 5-9 days after
  attach concurrent with egg production or a late
  type of salivary gland
• Dramatic recovery in 1-4 hours after removal of
  engorging ticks labile toxin is rapidly
  metabolized
• Occurs in dog, cat, cattle, human, other hosts
  much variation in local tick strains one tick is
  sufficient (eg. hairline of child)

Tick Paralysis
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Tick feeding mechanism
The feeding mode of ticks explains much about
their efficiency as vectors and production of
toxins. The chilicerae and hypostome are used for
attachment, then anchored by cement substance
secreted around imbedded mouthparts. Saliva
containing lytic enzymes creates a pool of tissue
fluid-saliva that is exchanged in large volumes
during intermittent, pulsating feeding during
tick engorgement over several days, facilitating
transfer of disease agents and other substances.
Often ticks must be attached for a given number
of hours to transmit disease. In the case
of tick paralysis, neurotoxins are produced
late in the engorgement period by female ticks.
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Otobius megnini (spinous ear tick)

• Otobius is a soft tick (Argasidae) that occurs in
  the US mainly in the arid southwest. ID by the
  characteristic fiddle-shape and spines on the
  leathery tegument.
• Larvae and nymphs feed on lymph for 2-9 months in
  the external ear canal of cattle, horses and,
  occasionally, dogs and other mammals. Extreme
  irritation often results.
• Non-feeding adults become established in cracks,
  crevices in barnyards and pens. Adults may
  produce several generations per year
• Extended control measures are needed including
  environmental sprays for adults, repeated topical
  or systemic treatment of hosts. Manual removal
  with alligator forceps is usual for affected dogs.

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Pediculosis (lice)
Linognathus setosis, an anopleuran sucking louse

• Lice are uncommon to rare in dogs and cats,
  usually debilitated poorly cared for animals
• Lice are highly host-specific
• nits are attached to hair shafts
• Good response to commonly available insecticides
  Treat twice at 7-10 day intervals to break 3 week
  life cycle

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Trichodectes canis, a mallophagan chewing
louse. Heterodoxus spiniger, another chewing
louse, also occurs on dogs,
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Felicola subrostratus a chewing louse that is
rarely found on cats. Note the egg and the
grooved mouthparts that allow it to feed on hair
shafts
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Pthirus pubis the human crab louse
Pediculus capitus the human head louse
These human lice may temporarily infect dogs as
secondary hosts via contact with humans
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Cuterebra (grubs, wolves, bots)

• Cuterebra, an obligate myiasis agent, commonly
  occurs as many separate species in rodents,
  lagomorphs and other wildlife
• Dogs and cats are accidental hosts exposed by
  sticking their head into infected rodent burrows
• Adult flies are short lived, non-feeding, that
  emerge from overwintering pupae in the spring,
  breed and lay eggs around burrows of small
  mammals
• Body contact and warmth stimulates hatching of
  larvae, which actively penetrate the mucous
  membranes of the head region

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• Cuterebra first instar larvae from rodent burrows
  undergo a variable migration route (depending on
  the species), finally localizing and growing to
  very large, black, spinous third instar larvae
  that usually inhabit the subcutaneous tissues
  around the head and neck. They appear as nodular
  SQ swellings with a central opening for
  respiration via grubs trachea tubes. These are
  easily removed after widening the opening.
• The major problem with Cuterebra is with
  aberrant migrations, such as with this cat in
  which the grub localized in the medial canthus,
  destroying the orbit by pressure necrosis during
  growth. If there is CNS migration, it leads
  almost invariably to the death of the host,
  although ivermectin with very high doses of
  corticosteroids may be tried. One species, C.
  emasculina, localizes in dog testicles. Others
  cause respiratory signs in the migration phase.

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Facultative myiasis (fly strike)

• Fly strike is caused by larvae of metallic black,
  blue, copper or green bottle flies, blow
  flies (Phormia, Lucilia, Phaenicia), fleshflies
  (Sarcophaga) or secondary screwworms
  (Cochliomyia macellaria) that lay eggs and feed
  on carrion.
• They are drawn to suppurating wounds (dead
  tissue), skin and hair soiled with urine or feces
  (eg old incontinent dogs). Myiasis is a disease
  of neglect.
• Maggots hatch and rapidly grow to third instars
  in 3-6 days, producing toxemia, weakness and
  death as maggots penetrate tissues. Larvae
  produce tissue necrosis, then invade deeper (eg
  undermine subcutaneous tissues)

Treatment Manual debriding, removal of maggots
(eg Peroxide/antibiotic solution and forceps Do
not use insecticides in broken skin). Advanced
cases often die in 1-3 days.
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• Cochliomyia americanum, the primary screwworm,
  attacks live tissues of wounds, but has been
  eradicated. It can be differentiated from the
  others by darkly pigmented trachea tubes visible
  through the body wall or by spiricle plate
  morphology. It is reportable to USDA if found.
  The adult is metallic green, with black thoracic
  stripes of unequal length. Cochliomyia
  macellaria, the common secondary screwworm looks
  similar, but thoracic stripes are equal in
  length. It is an obligate parasite.

Cochliomyia americanum
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Phormia regina
Blow flies and bottle flies have metallic,
brilliant colors varying from black to blue,
green or copper.
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Sarcophaga spp (flesh flies)
Sarcophaga, a common facultative carrion fly or
secondary screwworm is gray with thoracic stripes
and a checkered abdomen
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Stomoxys calcitrans (stable fly)
Stomoxys, ordinarily a livestock parasite, may
build up large populations in the summer months
and attack dogs, feeding mainly on the tips of
the ears and the forelegs. Crusty bleeding
lesions and self-inflicted damage results,
including hotspots associated with feeding of
adult flies.
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Breeding site of Stomoxys
Usual breeding materials for Stomoxys are
livestock feces mixed with decaying organic
matter, such as hay. Similar breeding sites can
be found in suburban/urban settings far from
livestock, such as compost piles.

• Control
• Repellant sprays, salves
• Residual spray on resting places of flies, which
  visit the host only for occasional large blood
  meals during warm sunny days, then rest to digest
  on sunny walls and fences
• ID, turnover, /or spray insecticide on compost
  piles or other breeding sites

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Bees, wasps, venomous and other arthropods

• Culicoides, Simulium may cause dermatological
  problems similar to the stable fly in certain
  locations.
• Bee and wasp stings often cause local swelling,
  especially the face with blubber lips in dogs.
  Treat symptomatically with corticosteroids.
• Venomous arthropods cause specific reactions (eg.
  focal necrotizing lesions by the brown recluse
  spider)