Ectoparasites

Question 1

describe oxyuris equie (pinworms)

Answer 1

1. adult worms live in distal large intestine of host
   -horse is only domestic animal with a pinworm
   -females extrude out of anus and lay eggs in clumps around perineal skin
2. major problem: intense perianal pruritis
   -gelatinous material containing clumps of eggs is very pruritic
   -see tail rubbing in horses
3. diagnosis can be challenging, eggs may not be found in fecals

Question 2

describe arthropods

Answer 2

1. largest of the animal phyla
2. few are parasitic or serve as vectors of pathogens
3. characteristics:
   -segmented body
   -paired segmented appendages
   -bilateral symmetr
   -chitinous exoskeleton
4. importance in vet med:
   -annoyance: buzzing; no bite or sting, just annoy and distract from healthy activity (feeding)

-actual physical damage: parasitic; live in or on host (flies leaving open lesions after feeding, larval flies causing myiasis)

-vectors of disease-causing agents: transmits a disease-causing microorganism from infected to uninfected animals

Question 3

describe ectoparasiticides

Answer 3

1. activity against: ticks, mites, flies, fleas, lice
2. may be applied to animal or to environment
3. examples:
   -insecticides
   -acaricides
   -repellents
   -insect growth regulators: kill the babies
   -insect development inhibitors
   -synergists
   -many are used in both pet and agricultural (crop) settings
4. administration:
   -animal:
   –topical: spot-on, sprays, dip, shampoo, collar
   –systemic: oral, parenteral, topical

-environment: foggers, strips, premise sprays, dusts/powders

Question 4

describe the body morphology of the flea

Answer 4

1. holometabolous: metamorphosis stages distinguishable from each other
2. laterally compressed
3. wingless
4. well-developed eyes
5. internal antennae

Question 5

describe the flea life cycle

Answer 5

1. eggs: pearly white and oval, 0.5mm long
   -eggs lad on pet (25-40 eggs per day)
   -eggs fall off or are groomed off pet and hatch in environment
   -hatch in 1-5 days after deposition; dependent on humidity and temperature
   –optimum conditions: 65-80F, 75-85% humidity
2. larval:
   -elongate, legless, eyeless with setae (hairs), 4-10mm long
   -typically lasts 2-3 weeks but can be prolonged by unfavorable conditions
   -environment = nest or bedding of host or off host
   -nutrition: organic matter in nest or bedding of host, blood rich feces (flea dirt) from adults
   -very susceptible to desiccation
3. pupa: 2-4mm long
   -pupa in sticky silk cocoon (0.5cm) with debris collected on outside
   -exarate (visible external limbs)
   -pupation lasts 1-2 weeks: pre-emergent adults can remain in cocoon 4-5 months depending on conditions! less susceptible to desiccation
   -emergence from cocoon may be stimulated by: vibration, humidity, CO2 emissions by new hosts
   -HARDEST STAGE TO CONTROL
4. adult:
   -emerge from cocoon and begin to search for new host: body warmth, vibration, sudden changes in light
   -some fleas can live off host for over 1 year
   -on host, both male and female fleas imbibe blood: only stage that consumes blood as nutrient source
   -bloodmeal is required to produce eggs (anautogenous)

life cycle can be complete in as little as 12d or as many as 180
-average 21-28d

95% of fleas live as immature stages in the pets’ surroundings! so if see adult fleas = bad infestation

Question 6

describe environmental control of fleas (5)

Answer 6

1. not necessary to control/treat in every case but can speed up eradication
2. VACUUM:
   -decrease egg and larval numbers
   -pupae generally resistant though
3. chemical spraying:
   -adulticidal +/- larvicidal
4. restrict access to areas that can harbor immature fleas
5. treat all animals in contact!

Question 7

describe identification of fleas

Answer 7

1. length and angle of head
2. length/lack of genal and pronotal comb

will NOT be asked to ID different fleas

Question 8

describe ctenocephalides felis (cat fleas)

Answer 8

1. accounts for 99% of fleas on cats and 93% of fleas on dogs
2. will feed on humans but cannot reproduce or persist more than 6-8 weeks without dog/cat blood meals
   -can produce up to 25 eggs/day/month
3. can be a vector for:
   -dipylidium caninum (double pored tapeworm); intermediate host
   -acanthocheilonemia reconditum (intermediate host)
   -bartonella henselae (cat scratch disease)
   -rickettsia typhi (murine typhus)
   -rickettsia felis (flea-born typhus)

Question 9

describe flea allergy dermatitis

Answer 9

1. delayed skin irritation in reaction to the biting of adult fleas
   -most common dermatological condition in dogs in SE US, also a major problem in cats too
   -can be activate by as little as one flea bite (preventatives rarely help since they require a bloodmeal to kill)
2. presentation in dogs:
   -pruritis, often severe
   -primary lesion: papules
   -secondary lesions: excoriations, alopecia, lichenification, scaling, crusting +/0 secondary ifnections
   -typically caudal (lower back, perineum, TAIL HEAD), caudal thighs, umbilical region
3. presentation in cats:
   -alopecia/pruritis, licking, and other self traumas
   -miliary dermatitis
   -more around the head and neck (mohawk)

Question 10

describe flea anemia

Answer 10

1. presentation:
   -lethargy
   -pale MM
   -dehydration
   -shocky/decreased temp/low BP
   -PCV/HCT can be <10%
   -at risk: young, small animals, elderly cats, and outside animals
2. treatment:
   -if severe: fluids/blood transfusions/in-patient stays
   -fast acting treatments: flea baths if can tolerate, capstar

Question 11

describe lice

Answer 11

1. extremely host-specific
   -almost every mammal and bird is host to at least one species
2. obligate parasites: spend entire life on host
3. able to transmit pathogens
4. morphology:
   -wingless
   -dorso-ventrally flattened
   -stout legs and claws for holding on
5. 2 main groups:
   -anoplura: sucking lice; found exclusively on placental animals
   -mallophaga: biting/chewing lice; found on mammals and birds

Question 12

describe anoplura (sucking lice)

Answer 12

1. morphology:
   -head is slenderer and narrower than thorax
   -mouthparts function as sucking devices
   -pronounced claws
2. all are obligate blood feeders
   -may cause anemia

MAMMALS ONLY

Question 13

describe mallophaga (chewing/biting lice)

Answer 13

1. morphology:
   -head is broader than thorax
   -possess chewing mouthparts
2. feed by biting or scraping action of mandibles
   -some are blood feeders
   -most ingest skin debris/secretions, fur, feathers
   -cause skin irritations, pruritis, alopecia
   -can survive somewhat longer off host than anoplura but still only a short time

mammals AND BIRDS

Question 14

describe the lice life cycle

Answer 14

1. usually unable to survive more than 1-2 days off host
2. tend to remain with same host entire life (<30d)
   -transfer by direct contact
3. respond to warmth, humidity, chemical odors
4. in temperate habitats, populations are dynamic
   -cattle and sheep: increase late autumn/winter, decrease in warm weather
   -may be related to winter coats, winter housing, and poor condition

Question 15

describe control of lice

Answer 15

1. infestations generally a disease of neglect
   -associated with overcrowding and poor sanitation
2. keep animals isolated to prevent spread
   -spread by direct contact
3. good response to commonly available insecticides used as flea preventatives
   -fipronil
   -imidicloprid
   -selamectin
   -tropical permetrhin
4. treat twice at 7-10d intervals to break 3 week life cycle
   -nits are hard to control
5. little public health significance

Question 16

describe flies (oder diptera)

Answer 16

1. complete metamorphosis
2. one functional pair of wings
   -hindwings; haltares
3. antennae structure: important for classification
4. 3 major orders
   -nematocera
   -brachycera
   -cyclorrhapha

Question 17

describe myiasis common characteristics

Answer 17

1. myisasis= parasitic infection of body of a mammal by fly larvae (maggots)
   -invade living and sometimes nonliving vertebrates
   -ONLY larval stages
2. life cycle of flies includes;
   -egg, larval (3 instars), pupal, and adult
   -gravid female deposit large amounts of eggs on/near vertebrate host
   -larvae begin to feed and migrate to more specific sites
   -pupae drop from host and mature to the adult stages
3. longevity depends on species and environment: anywere from weeks to months

Question 18

describe common characteristics of myiasis

Answer 18

1. accidental: pseudomyiasis
   -animal accidentally ingests contaminated items
   -includes ingestion of fruit fly egg-contaminated food
2. facultative:
   -opportunistic flies that exploit living tissue
   -invasion of open sores by flies that usually feed on dead vertebrates/carrion
3. obligatory:
   -always parasitic
   -require living host for development
   -includes screwworm and bot flies

Question 19

describe cochliomyia hominovorax (myiasis flies)/new world screw worm/primary screw worm

Answer 19

1. members of calliphoridae (blow flies or bottle flies); known for pilished metallic colors (blue, green, bronze)
2. obligatory myiasis
3. gravid female attracted to open wounds
   -deposit over 200 eggs at once
   -life cycle complete after approx 21 days
4. alrvae feed on organs of host and eat them alive
5. eradicated in US and mexico
   -required BY LAW to report any case
6. ID:
   -larvae have wood screw shape and dark tracheal tubes
   -flies: shining and metallic or black
   -three thoracic stripes where the middle stripe is shorter than the outside 2
   -coloration similar to secondary screwworm but secondary screw worms’ stripes all equal

Question 20

describe cuterebra myiasia

Answer 20

1. obligate myiasis agent
   -commonly occurs in many separate species of rodent, lagomorphs, and other wildlife
   -also in cats and dogs
2. common in summer and fall
3. adult flies are short lived, nonfeeding, and breed and lay eggs around burrows of small animals
4. larvae enter skin via direct penetration, ingestion, or through body openings
   -larva migrates to a more specific site for maturation
5. larvae cut a hole in the skin and typically fall out after 30d
   -typical lesions around head, neck, and trunk
   -forms fistula/erythematous swelling (to treat can enlarge fistula and extract grub)
6. little health importance unless larva undergo aberrant migration like near the eyes

Question 21

describe fly strike

Answer 21

1. the action of flies ovipositing on host/carrion
2. caused by larvae of multiple myiasis flies invading wounded tissue
3. larvae are drawn to wound (dead tissue), and/or skin and hair soiled with urine or feces (old incontinent dogs)
4. maggots hatch and rapidly grow to third instars, producing toxemia, weakness, and death as maggots penetrate tissues
   -produce tissue necrosis and then invade deeper

Question 22

describe myiasis considerations and treatment

Answer 22

1. anima hair that is matted and broken skin is a prime location for larval stages to infect
   -will bring bacteria as a source of secondary infection
2. if infection is serious, more than one genera of fly may be found in the wound
3. adult stages often associated with human dwellings and readily fly from feces to food
4. inspect lesions multiples times, eggs may not all hatch at once
5. affected animals may aggressively groom the larval infestation

Question 23

describe mange

Answer 23

-hair loss, severe itching, and crusty skin
-can cause severe M&M; animals may die from emaciation and secondary infections

-a SYNDROME, not an etiologic diagnosis

-must rule out other causes of skin disease

Question 24

describe parasitic mites

Answer 24

1. mange mites
   -demodex, cheytiella, sarcoptes, notoedres
   -chorioptes, psoroptes, psorobia
2. ear mites: otodectes, psoroptes
3. nasal mites: pneumonyssoides
4. chiggers: trombicula

Question 25

contrast mites to ticks

Answer 25

1. similar life cycle 2. mites are microscopic (ticks are larger) 3. parasitic mite species stay on host 4. mites have smaller mouth parts relative to body size 5. mites feed on host tissue and cellular debris

Question 26

describe general rules of parasitic mites

Answer 26

1. relatively host specific 2. distribution of lesions aids in diagnosis 3. diagnose by skin scraping -some need to be deep (until see capillary bleeding) and others just superficial

Question 27

describe life history of mites (4)

Answer 27

1. egg: shed or retained in uterus 2. larva: preceded by nonfeeding stage 3. several nymph stages: may be nonfeeding 4. adult

Question 28

describe demodex canix

Answer 28

1. most common species found in canine demodecosis -also D. injae (deep mite) and D. cornei (superficial mite) -reside in hair follicles and rarely apocrine/sebaceous glands (deep) 2. morphology: -cigar shaped -4 pairs of stubby legs 3. normal skin fauna of dogs -typically in hair follicles in low numbers 4. two types of demodicosis -localized -generalized: juvenile or adult onset

Question 29

describe clinical signs of demodicosis

Answer 29

localized: 1. <5 lesions or one body region 2. alopecia around eyes, commissures of mouth, and/or forelegs 3. 90% spontaneously cure in 6-8 weeks: do not treat for mites (may mask generalized disease, steroids could worsen disease) generalized: 1. >5 lesions or more than one body region 2. secondary pyoderma is common 3. can commonly present with pododermatitis

Question 30

describe generalized demodicosis; juvenile and adult onset

Answer 30

juvenile: 1. usually starts as localized lesion then progresses 2. short-haired purebreds predisposed 3. hereditary susceptibility: breeding not recommended if generalized demodicosis is diagnosed 4 demodex-specific T cell defect is suspected adult-onset: 1. rare and poor prognosis 2. usually secondary to underlying immunosuppressive condition (hyperadrenocorticism, neoplasia, etc.)

Question 31

describe diagnosis of demodicosis

Answer 31

deep skin scraping 1. clip area to remove excess hair, squeeze skin firmly between thumb and forefinger 2. scrape with scalpel extensively: if don't see blood = not deep enough 3. mount on slide with mineral oil, coverslip and examine at 10x 4. demodicosis is diagnosed by finding many mites or mites at multiple locations -adult mites, nymphs, larvae (3 pairs of legs), and spindle shaped eggs may be found 5. scrape mulitple locations (3-5 minimum), multiple times 6. can be used to monitor treatment too

Question 32

describe feline demodicosis

Answer 32

1. D. cati -similar to D. canis; rare in cats, found in deep skin scrape -localized and generalized forms --localized generally self limiting --generalized can be associated with FeLV/FIV, DM, cushing's, neoplasia, toxoplasmosis 2. D. gatoi (short body): hard to find on scrapes (need broad superficial scrapes) -contagious!! -treat all cats in household -scrape asymptomatic cats: scraping between shoulder blades/fecal flotation -most common in gulf coast areas

Question 33

describe canine scabies (sarcoptic mange)

Answer 33

1. sarcoptic scabei var. canis (burrowing mite) 2. morphology: -oval, short legged with long unjointed leg stalks and terminal sucker discs on leg pairs 1 and 2 -chewing mouthparts 3. highly pruritic 4. transmission via body contact, highly contagious -can transiently infect humans (ZOONOTIC) -host specific but can have temporary colonization of man, cats, ferrets, and foxes 5. frequently found in gulf coast due to humidity and warmth 6. do not survive off host longer than 48 hours

Question 34

describe the life cycle of canine sarcoptes

Answer 34

1. takes about 21 days 2. adults mate on skin surface and then burrow into stratum corneum of the epidermis -deposit eggs and fecal pellets behind, resulting in tunnels 3. eggs hatch in 3-10 days 4. larvae hatch and form molting pockets beneath skin and develop into nymhs -both larvae and nymphs feed on skin

Question 35

describe lesion distribution of canine scabies

Answer 35

1. initially in places with less hair -pinnae -elbows -hocks -abdomen 2. lesions generalize over weeks to months -can get secondary pyoderma with thick crusty pigmented skin

Question 36

describe feline scabies

Answer 36

1. notoedres cati -resembles S. scabei in life cycle, morphology, and clinical effects -but only infects cats 2. uncommonly can cause pruritis, contagious infection of kitten litters and old tomcats 3. initial lesions on ear tips, then head and neck 4. occur in large numbers, easily found in skin scrapingg

Question 37

describe psoroptes spp life cycle

Answer 37

1. similar to s. scabei 2. do not burrow deep intro stratum corneum -primarily stay on surface of skin 3. occur in higher numbers than S. scabei 4. can live off of hosts for several weeks