Veterinary Entomology and Acarology: Parasitic Insects and Arachnids

Comprehensive vocabulary flashcards covering the taxonomy, morphological anatomy, clinical significance, pathology, and diagnostic features of veterinary ectoparasites across Class Insecta (flies, lice, fleas) and Class Arachnida (ticks, mites).

Simple Metamorphosis

A developmental life cycle characterized by three primary stages: egg, nymph, and adult, seen in ectoparasites such as lice, ticks, and mites.

Complex Metamorphosis

A developmental life cycle consisting of egg, larva, pupa, and adult stages, where complete restructuring of the organism occurs during pupation (e.g., flies and fleas).

Culicidae (Mosquitoes)

Delicate dipteran insects with long 14-to-15-segmented antennae and piercing-sucking proboscises that lay eggs in stagnant water; vectors of Dirofilaria immitis and West Nile virus.

Simulium sp. (Black Fly)

Small, stout-bodied flies with a characteristic humped back and serrated, scissor-like mouthparts that lay eggs in fast-running water and can kill livestock via salivary toxins.

Culicoides sp. (Biting Midges)

Tiny dipterans ($<2\,\text{mm}$), known as 'No-See-Ums', that breed in damp, marshy soil and inflict painful bites that can induce severe allergic hypersensitivity reactions in horses.

Tabanidae

A family of large, robust flies—including horse flies (Tabanus sp.) and deer flies (Chrysops sp.)—whose females possess piercing stylets and a spongy labellum to feed on host blood.

Chrysops sp. (Deer Fly)

A tabanid fly measuring $6\text{--}10\,\text{mm}$ with dark bands or patches across its wings that typically attacks moving animals around the head and shoulders.

Tabanus sp. (Horse Fly)

A large tabanid fly measuring $10\text{--}30\,\text{mm}$ with clear or uniformly cloudy wings that predominantly bites stationary livestock on the legs and ventral body.

Musca domestica (House Fly)

A non-biting muscid fly with a spongy labellum that feeds on secretions and wound exudates, breeding primarily in animal manure, garbage, and decaying organic waste.

Musca autumnalis (Face Fly)

A muscid fly that feeds on ocular and nasal discharges of pastured cattle and serves as the primary mechanical vector for Moraxella bovis, the causative agent of bovine infectious keratoconjunctivitis (pinkeye).

Stomoxys calcitrans (Stable Fly)

A blood-feeding muscid fly equipped with a forward-pointing bayonet-like proboscis; both sexes inflict painful bites on the ears, legs, and flanks, spending approximately $80\%$ of their life cycle off the host.

Haematobia irritans (Horn Fly)

A small, blood-feeding muscid fly with bayonet-like mouthparts that spends nearly its entire adult life clustered on cattle, frequently inducing seasonal midline dermatitis.

Melophagus ovinus (Sheep Ked)

A wingless, dorsoventrally flattened, leathery dipteran ectoparasite that spends its entire life cycle on sheep, feeding on blood and causing pruritus, wool damage, and anemia.

Myiasis

The parasitic infestation of the tissues or organs of a live vertebrate animal by dipteran fly larvae.

Primary Facultative Myiasis

A condition initiated by opportunistic blowfly species (such as Lucilia sp.) capable of establishing an active strike independently on intact, soiled, or damaged skin.

Secondary Facultative Myiasis

An infestation established by fly species (such as Musca domestica, Calliphora sp., or Phormia sp.) that cannot initiate strike independently and only invade preexisting wounds or established strikes.

Fly Strike

Cutaneous myiasis caused by blowfly larvae feeding on secretions, dead epidermal cells, and exudate within soiled or traumatized tissue, producing a characteristic pungent odor.

Surgical Maggots

Sterile larvae of select blowfly species utilized therapeutically in human and veterinary medicine to selectively debride necrotic tissue without damaging healthy flesh.

Cochliomyia hominivorax

The primary screwworm fly, an agent of obligatory myiasis endemic to Central and South America whose larvae obligately consume living host tissue; reportable in North America.

Wohlfahrtia vigil

The gray flesh fly, an obligatory myiasis producer whose larvae burrow into the skin of young mammals, creating discrete furuncular swellings with central respiratory pores.

Oestrus ovis

The sheep nasal bot fly, an obligatory parasite whose adult females deposit live larvae directly into the nares of sheep and goats, which then migrate into the frontal sinuses to mature.

Hypoderma spp.

Cattle warbles or grubs whose larvae migrate internally through the spinal canal (H. bovis) or esophagus (H. lineatum) before forming warbles with breathing holes along the dorsal subcutis.

Gasterophilus spp.

Equine stomach bot flies whose eggs are deposited on hairs, triggered to hatch by tongue friction and warm saliva, migrate through oral tissues, and attach to the gastric mucosa for $10\text{--}12\,\text{months}$.

Cuterebra spp.

The rabbit bot or rodent bot fly whose larvae enter through natural orifices or abrasions to develop in a subcutaneous nodule with an open breathing pore; crushing during extraction risks anaphylaxis.

Anoplura

The suborder of lice known as sucking lice, possessing a head narrower than the thorax and piercing mouthparts used exclusively for blood-feeding on mammalian hosts.

Mallophaga

The suborder of chewing or biting lice, characterized by a head wider than the thorax and ventral chewing mandibles used to feed on epidermal scales, sebum, and feathers in mammals and birds.

Nit

The pale, operculated egg of a louse firmly cemented to the hair shaft or feather of a host animal near the epidermal surface.

Siphonaptera (Fleas)

An order of laterally compressed, wingless insects with enlarged hind limbs adapted for leaping; adult stages feed obligately on host blood and lack strict host specificity.

Pronotal Combs

A row of heavy, backward-pointing cuticular spines located along the posterior margin of the first thoracic tergite of certain flea species, used for taxonomic identification.

Flea Dirt

Partially digested, dehydrated host blood excreted by adult fleas that falls from the coat into the environment, serving as the essential dietary staple for flea larvae.

Flea Allergy Dermatitis (FAD)

A pruritic hypersensitivity reaction in dogs and cats triggered by allergenic proteins injected through flea salivary secretions during blood feeding.

Insect Development Inhibitors (IDIs)

Compounds that disrupt insect chitin synthesis, inhibiting cuticular development so that flea eggs fail to hatch and larvae cannot successfully molt.

Insect Growth Regulators (IGRs)

Endocrine-disrupting chemicals that mimic or block natural insect juvenile hormones, halting development before adulthood or producing sterile adult fleas.

Acariasis

A comprehensive clinical term denoting an infestation of domestic animals or humans by parasitic mites or ticks belonging to the class Arachnida.

Capitulum

The anterior false head segment of ticks and mites containing the feeding mouthparts, which include the paired sensory palps, chelicerae, and the hypostome.

Hypostome

The central, ventral mouthpart of a tick that is armed with recurved backward-pointing barbs, anchoring the tick firmly into host skin and housing a median feeding groove.

Festoons

Small, uniform rectangular notches or divisions situated along the posterior margin of the body in select genera of hard ticks; absent in Ixodes spp.

Scutum

The rigid, chitinous dorsal shield of ixodid ticks that covers nearly the entire dorsal surface in males but remains restricted to the anterior dorsum in females and immatures.

Questing

A host-seeking ambush behavior where ticks ascend vegetation and extend their anterior legs, using sensory receptors to detect environmental $CO_2$, warmth, movement, and host scent.

Dermacentor variabilis (American Dog Tick)

The most common three-host hard tick in Manitoba, displaying an ornate, silver-gray patterned scutum; vector for Anaplasma marginale, Ehrlichia canis, and tick paralysis neurotoxin.

Ixodes scapularis (Blacklegged Tick)

A three-host hard tick characterized by an anterior anal groove and an absence of festoons; principal vector of Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti.

Borrelia burgdorferi

The spirochete bacterium responsible for Lyme disease, primarily transmitted to mammalian hosts when an infected nymphal or adult Ixodes scapularis feeds for $36\text{--}48\,\text{hours}$.

Tick Paralysis

A reversible, flaccid, ascending lower-motor-neuron paralysis induced by salivary neurotoxins secreted by feeding female ticks such as Dermacentor variabilis and Dermacentor andersoni.

Rhipicephalus sanguineus (Brown Dog Tick)

An inornate three-host tick adapted to feed on canines throughout all developmental stages; survives primarily indoors and in kennels because it cannot overwinter outdoors in cold climates.

Sarcoptidae

A family of sarcoptiform mites that burrow deep tunnels into the host epidermis, triggering profound pruritus, alopecia, hyperkeratosis, and crust formation.

Psoroptidae

A family of sarcoptiform mites that inhabit the skin surface or external ear canal without burrowing, subsisting on tissue fluids, exfoliated cells, and cutaneous secretions.

Caruncle

A membranous, sucker-like adhesive cup structure positioned at the distal terminus of pretarsi in various sarcoptiform mites.

Pedicel

The stalk connecting a caruncle to the distal tip of a mite's leg; its length and presence or absence of segmentation are critical diagnostic criteria in sarcoptiform identification.

Sarcoptes scabiei

A burrowing sarcoptiform mite with long, unsegmented pedicels and small caruncles that produces intensely pruritic sarcoptic mange and possesses significant zoonotic potential.

Trixacarus caviae

The burrowing sarcoptic mange mite of guinea pigs; severe infestations cause intense pruritus, alopecia, and hyperkeratosis, with scratching severe enough to precipitate convulsive seizures.

Notoedres cati

A feline burrowing mite that produces feline scabies, characterized by severe, highly contagious, crusting, and intensely pruritic lesions on the pinnae, face, and neck.

Knemidocoptes mutans

The scaly leg mite of poultry that burrows beneath the epidermal scales of the legs and feet, provoking marked hyperkeratosis, crusting, and distortion of the limbs.

Knemidocoptes gallinae

The depluming mite of birds that tunnels into feather follicles and adjacent skin, provoking intense irritation that causes poultry to pull out their feathers.

Psoroptes cuniculi

The non-burrowing ear canker mite of rabbits that infests the external auditory meatus, creating abundant, friable crusts that resemble dry cornflakes.

Chorioptes bovis

A surface-dwelling psoroptid mite featuring short, unsegmented pedicels and broad caruncles that causes chorioptic mange on the tail head, perineum, and coronary band of cattle.

Otodectes cynotis

A non-burrowing ear mite infesting dogs and cats that provokes severe otic pruritus and stimulates the production of thick, dark brown exudate resembling coffee grounds.

Demodex canis

A microscopic, cigar-shaped, host-specific follicular mite residing commensally in hair follicles and sebaceous glands of dogs, capable of producing localized or generalized demodicosis.

Cheyletiella spp.

Large, non-sarcoptiform surface mites known as 'walking dandruff' that create pseudo-tunnels in the keratin layer, feed on tissue fluids, and are diagnostic via cellophane tape preparations.