Arthropods (Exam 1)

Exam 1 of Parasitology is the Arthropods. Blue text is testable material, black text is general info or potential extra credit. General note: Dr. Wu uses the class name Secernentea, but Modern genetic studies use name Chromadorea (Secernentea is deeply nested within Chromadorea, making them closely related in taxonomy. Secernentea is not considered a separate, co-equal class; it is now typically reclassified as the order Rhabditida under the class Chromadorea)

Parasite

A smaller organism that lives on or in, and at the expense of a larger organism (a host)

Ectoparasite

A parasite that lives on the external surface of a host

Endoparasite

A parasite that lives within the body of a host

Ectoparasites cause an____

Infestation

Endoparasites cause an____

Infection

Obligate parasite

Parasites that always require a host

Facultative parasite

Parasites that only parasitize if given the opportunity

What is the prepatent period?

Time after infection before detection of the parasite

Definitive (final) Host

The host in which the adult parasite lives or sexual reproduction occurs

Paratenic host

Host in which No additional parasite development occurs

Intermediate host

A host required for larval development

Arthropods

Group of organisms encompassing insects, spiders, and crustaceans, that often have segmented bodies, jointed appendages

Insecta: include what, and physical description

Class of Arthropods that Include Flies, Fleas, Lice, Bugs

Segmented bodies with head, thorax and abdomen, 6 legs and up to 4 wings

Arachnida: Includes what and physical description

Class of Arthropods that includes Ticks and Mites

Fused Head, thorax and abdomen, have 8 legs as adults and 6 in larval stages

No wings

Name this insect (Scientific and Common names)

Arthropods > Insecta > Trichoptera (caddisflies)

Description: flies with 4 wings, short mouthparts, aquatic larvae in fresh water

Trichoptera (Caddisflies) are vectors of what disease?

Potomac Horse Fever

What is the causative agent of Potomac Horse Fever?

The bacterium Neorickettsia risticii in trematodes within Trichoptera (Caddisflies)

How do horses acquire Potomac Horse Fever?

Ingestion of Trichoptera (Caddisflies) in drinking water

Clinical Signs of Potomac Horse Fever

Acute enterocolitis, Abortion, laminitis

Treatment and Prevention of Potomac Horse Fever

Oxytetracycline, Turn off barn lights at night

Diptera

Arthropods > Insecta > Diptera (flies)

Flies with 2 functional Wings

Includes Nematocera, Brachycera, Cyclorrhapha

Name this Fly: identifying feature?

Arthropods > Insecta > Diptera (flies) > Nematocera

small delicate flies with long many segmented antennae (beads on a string appearance)

Females suck blood, males ingest nectar, aquatic larval forms

Name this Fly

Arthropods > Insecta > Diptera (flies) > Nematocera > Culicidae (mosquitoes)

Includes Culex and Anopheles genus

Long segmented antennae, elongated proboscis, eggs laid in water, aquatic air-breathing larvae, free swimming pupae

Females require blood proteins for ovary maturation

Autogeny

Process by which females can undergo ovarian maturation without a bloodmeal

Culicidae (Mosquitoes) are vectors for what diseases?

Dirofilaria immitis (heartworm), Plasmodium (malaria) via Anopheles mosquitoes, West Nile Virus, Dengue fever, Equine encephalitides, Rabbit myxomatosis

What disease is this and what is it vectored by?

This is Heartworm caused by the nematode/roundworm Dirofilaria immitis and vectored by Culicidae (Mosquitoes)

Name this Fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Nematocera > Simulidae (blackflies)

Small stout bodied black, gray or yellowish-brown flies with short antennae and short mouthparts

Breed in running water, larvae cling to surfaces with posterior hooks or anterior prolegs

How do Simulidae (Blackflies) feed?

Vicious biters: feed by lacerating tissues and making a blood pool

Diseases caused or vectored by Simulidae (Blackflies)

Hypersensitivity (dermatitis, pruritus, edema, blisters) due to bites

Vectors for Leucocytozoon in birds, Onchocerca in cattle, dogs and humans which is the causative agent of River Blindness in humans in Africa

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Nematocera > Ceratopogonidae (midges)

Tiny <2mm flies, long slender antennae, short mouth parts, mottled wings, adults are nocturnal, females are bloodsuckers

Culicoides spp. and clinical disease

Genus of biting midges in Ceratopogonidae family Arthropods > Insecta > Diptera (flies) > Nematocera > Ceratopogonidae (midges) > Culicoides

Have very painful bites (like cigarette ash burns)

Can cause allergic dermatitis “Queensland Itch” in horses due to hypersensitvity reaction

Name this disease and the causative agent vectored by?

African horse sickness, caused by an Orbivirus. Transmitted primarily by Culicoides biting midges

Ceratopogonidae (midges) vectors of what diseases?

Orbiviruses: Bluetongue, African Horse Sickness

Onchocerca in horses and cattle, Dipetalonema in humans, Hepatocystis in primates, Haemaproteus and Leukocytozoon in birds

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Nematocera > Psychodidae (phlebotomine sandflies)

small dull colored flies with long antennae

Wing veins radiate in straight lines

Phlebotomus in Old World

Lutzomyia in New World

Tropical distribution

What diseases does Psychodidae (Phleotomine sandflies) vector?

Pappataci fever virus, Bartonella bacilliformis in people

Leishmania spp.

What disease is this? What are the clinical signs?

Cutaneous and visceral forms of Leishmania spp. (a protozoan parasite that circulates in macrophages). Causes dermal lesions, lymphadenomegaly, splenomegaly, ocular disease, onychogryposis (nail abnormalities)

Vertical transmission possible

Methods of Fly Control for Caddisflies, Mosquitoes, Blackflies, Midges, Sandflies

Caddisflies: Cover water sources

Mosquitoes: Dinetofuran + pyrethroids (permethrin) (topical), isoxazolines (afoxolaner)

Blackflies: Smoke repels flies, chemical repellents (pyrethroids), petroleum jelly, fly masks

Midges: Insect repellents

Sandflies: Deltamethrin collars, spot-on pyrethroids (permethrin) + imidacloprid, isoxazolines (afoxolaner, fluralaner)

Pyrethroids

Drugs ending in -thrin (tetramethrin, permethrin, deltamethrin)

Synthetic substances based on molecular structure of natural insecticidal compounds from chrysanthemum flower

Available as shampoos, spot-ons, pour-ons, pastes, ear tags, collars, dusts, foggers, insect-repellent cloths, household sprays

Pyrethroids mechanism of action

Paralyze and kill arthropods by binding and disrupting voltage gated sodium and GABA channels, disrupting neurotransmission

More effective at lower temperatures so more effective in insects than warm-blooded mammals

Pyrethroid toxicity

Toxic to fish

Cats are highly sensitive to permethrin = causes hyperexcitability, depression, ataxia, vomiting, anorexia, tremors, convulsions

Practice question: What is the causative agent of Potomac Horse Fever, vectored by Trichopteran caddisflies?

A: Rickettsia ricketcii

B: Neorickettsia risticii

C: Borrelia burgdorferi

B = Neorickettsia risticii

Practice Question: Which of the following is the vector for onchocerciasis, the causative agent of river blindness in people?

A: Culicoides

B: Phlebotomus

C: Simulium

C = Simulidae

Practice Question: A bite from which of the following can result in a host hypersensitivity reaction known as Queensland Itch?

A: Culicoides

B: Culex

C: Phlebotomus

A = Culicoides (Ceratopogonidae) midges

Practice Question: A dog with the following lesions was likely bitten by which fly?

A: Phlebotomus

B: Caddisfly

C: Culicoides

A = Phlebotomine sandflies

Practice Question: Which of the following is true regarding pyrethroids such as permethrin?

A: They commonly result in depression and tremors in dogs

B: They are not approved for use in cattle

C: They are highly toxic to fish

C = They are highly toxic to fish

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Brachycera (tabanids)

Stout bodied, up to hummingbird sized with stout three-segmented antennae

Females require bloodmeal, males feed on nectar, sap, aphid feces, eggs laid in masses over water

Feed through laceration and blood pooling, attacks are painful

Brachycera (tabanids) vectors of?

Anthrax, tularemia, anaplasmosis, Equine infectipouos anemia virus, Trypanosoma evansi (surra disease), Trypanosoma theileri (nonpathogenic), Elaeophora schneideri

Class of Diptera (flies) this fly belongs to

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha

Family including Muscidae, Glossinidae, Hippoboscidae, Sarcophagidae, Calliphoridae, Oestridae

Three-segmented antennae with frond-like structure on end (arista), Mouthparts adapted to feeding habits

Larval forms of Cyclorrhapha: What is the name of the circled part, and the specific names for Muscids, Oestrids?

Circled part are Spiracles (breathing organs)

Muscids, Sarcophagids, Calliphorids = Maggots

Oestrids = Bots

Myiasis

Parasitism by fly larvae

Name this fly

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Muscidae > Musca (filth flies)

Musca domestica (house fly) and Musca autumnalis (face fly)

Retractable proboscis with terminal spongy organs (labella)

Eggs laid in manure or decaying matter, feed on secretions around eyes, nostrils, mouth, and blood around wounds

M. autumnalis overwinters in buildings, but stays out of buildings in the summer

Musca domestica can vector____

parasitic nematodes (Draschia, Habronema)

Musca autumnalis can vector____

Thelazia (eyeworm) and Moraxella bovis, which causes infectious bovine keratoconjunctivitis (pinkeye)

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Muscidae > Stomoxys (stable flies)

Stomoxys calcitrans stable fly

Long, pointed proboscis, palps shorter than proboscis

Stomoxys (stable flies) lay eggs in what?

Eggs laid in decaying organic material (hay, lawn clippings, manure)

Stomoxys (stable flies) feed on what?

Both sexes feed on blood

Painful bite interrupts animal feeding

Stomxys (stable Flies) vector of____

parasitic nematode Habronema microstoma

Name this Fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Muscidae > Haematobia (horn flies)

Haematobia irritans

Small fly with short proboscis, palps same length as proboscis

vector for nematode parasite Stephanofilaria stilesi

Haematobia (horn flies) lay eggs where? How long until eggs develop to adults?

Eggs laid in cow manure, hatch to adults within 6 days, eggs develop to new egg-laying adults within 2 weeks

Haematobia (horn flies) feed on what?

Bite cattle and suck blood

Active during warmer months

can irritate cattle, leading to decreased production

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Glossinidae (tse tses)

Localized to Africa

Long feather-like arista, Hatchet shape venation on wings, palps same length as proboscis

Larvae develop within mother feeding on uterine fluids

Bloodmeals required for larval development

Glossinidae (tse tses) vector for____

Protozoal parasite Trypanosoma brucei

Trypanosoma brucei causes what disease?

African sleeping sickness in humans, nagana in livestock

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Hippoboscidae (keds)

Dorsoventrally flattened, often wingless, piercing mouthparts, antennae embedded in head

Larvae develop within mother feeding on uterine fluids

Melophagus ovinus

Sheep Ked (Hippoboscidae)

Entire life cycle completed on sheep

Can vector Trypanosoma melophagium (nonpathogenic)

Hippobosca equinus

horse ked

Lipoptena cervi

deer ked

Hippobosca longipennis

Can vector nematode parasite Acanthocheilonema dracunculoides

Fly Control for Cyclorrhapha: musca, stomoxys, haematobia, brachycera, glossina, hippobosca

Removal of breeding sites:

Musca – garbage and feces, Spraying environment with insecticides like organophosphates (tetrachlorvinphos, dichlorvos, coumaphos), pyrethroids

Stomoxys – contaminated hay (with feces and urine), Pyrethroids, organophosphates (coumaphos, dichlorvos, chlorpyrifos, tetrachlorvinphos, phosmet)

Haematobia – animal feces, Ear tags impregnated with pyrethroids (fenvalerate), some resistance to many insecticides (including permethrin and fenvalerate), Feed-through organophosphates

Brachycera: Difficult to repel, chemical repellents

Glossina (tse tses): Eradication efforts involve release of sterile males

Hippobosca (keds): Organophosphate (coumaphos) dips or sprays, ivermectin

Organophosphates

Things ending in –phos or –vos (dichlorvos, tetrachlorvinphos, coumaphos)

Available in fumigants, resin strips, sprays, dips, powders, collars, ear tags

Organophosphates Mechanism of Action

Act via irreversible binding and inhibition of acetylcholinesterase (AChE)

Buildup of acetylcholine in synapse leads to constant stimulation

Organophosphate Toxicity and reversals

Toxicity in animals results in salivation, lacrimation, urination, and defecation (SLUD), convulsions, fasciculations

Atropine can be used to block overstimulation of Ach receptors

2-PAM (pralidoxime) can reverse effects by reactivating organophosphate-inhibited AChE

Practice Question: Which of the following is a distinguishing morphologic feature of tabanids?

Answer = stout, three segmented antenna

Practice Question: Which of the following is not considered a cyclorrhaphan fly?

Answer = Tabanids

Practice Question: Which of the following is a correct definition of myiasis?

Answer = Parasitism by fly larvae

Practice Question: Which of the following is transmitted by the tse tse fly (glossina)?

Answer = Trypanosoma brucei

Practice Question: Which of the following is an antidote to reverse the effects of organophosphate toxicosis?

Answer = Pralidoxime (2-Pam)

Name this Fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Sarcophagidae (flesh flies)

Large adults with longitudinal stripes on thorax and checkered abdomen

Large maggots with sunken spiracles

Two obligate parastite species Wohlfahrtia vigil and Cistudinomyia cistudinis

Sarcophagidae (flesh flies) can be _____, resulting in what clinical diagnosis?

Can be facultative parasites, with maggots resulting in myiasis in wounded or wet skin

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Calliphoridae (blow flies)

Metallic blue, green, copper, or black adults

“Blow” eggs or larvae on meat

Spiracles lie flush with face of larva

Calliphoridae (blow flies) are mostly what kind of parasite?

Most are scavengers or facultative parasites

Attracted to wet skin, wounds, necrotic tissue

Affect incapacitated animals, including sheep, dogs, cattle, and rabbits

What is this condition? Treatment and prevention?

Wool strike in sheep (myiasis)

Developing larvae feed on scales and exudate on skin surface, and penetrate tissues

Affects areas stained by urine or feces (perineum, prepuce), or areas wet from rain (flanks, withers, ventral neck)

Fleece rot (Pseudomonas aeruginosa) and lumpy wool (Dermatophilus congolensis) predispose to wool strike

Toxins absorbed from myiasis can lead to death

Treatment: Organophosphate (coumaphos) spray or dip, cyromazine (insect growth regulator)

Prevention: Clip wool around prepuce, tail docking

Mules’ operation: Removal of redundant skin folds

What Calliphoridae larvae is this? Identifying features?

Cochliomyia hominivorax: Obligate parasite

=American screwworm

Pigmented tracheal trunks in last 3-4 segments

Cause primary myiasis (feed on living tissue) vs. secondary myiasis (feed on dead flesh)

Eggs laid on fresh, uninfected wounds, maggots feed on living flesh and bone

Reportable

Method of fly control for Cochliomyia hominivorax?

Release of sterile males at the Panama Canal Border

This spiracle belongs to which fly larvae?

Musca

This spiracle belongs to which fly larvae?

Calliphoridae

This spiracle belongs to which fly larvae?

Sarcophagidae

This spiracle belongs to which fly larvae?

Stomoxys

Oestridae (Botflies)

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Oestridae (botflies)

Typically host-specific, site-specific parasites in larval stage (bots)

Name this Fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Oestridae (botflies) > Oestrus ovis

Sheep nasal botfly

Stout, grayish-brown adults, covered with short hairs

Active in bright sun

Where do Oestrus ovis lay eggs? This can cause what clinical signs?

Females deposit larvae in sheep nostrils

Larvae develop in mucosa of nasal cavity then frontal sinus, sneezed out and pupate = Heavy infection causes sneezing and nasal discharge

Treatment: macrocyclic lactones (ivermectin, eprinomectin)

Name this Fly

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Oestridae (botflies) > Hypoderma (Heelflies, Gadflies)

Hypoderma bovis and Hypoderma lineatum

Where do Hypoderma flies (heelflies, gadflies) lay eggs?

Adults oviposit on hairs of leg

Larvae burrow through skin and migrate through body

Cattle often react to flies presence by becoming excited and galloping off

Hypoderma lineatum accumulate in what?

The esophagus

Hypoderma bovis accumulate in what?

The Spinal Cord

What are Warbles?

Lumps on dorsum of cattle caused by third-stage Hypoderma spp. larvae

Warbles can be removed by injecting 3% hydrogen peroxide into breathing hole

Treatment for Hypoderma spp. (Heelflies, Gadflies)?

Macrocyclic Lactones

Organophosphate treatment can cause host-parasite reactions (bloat, salivation, ataxia, posterior paralysis), Due to toxins elaborated by dying larvae. Counteract with phenylbutazone pre-treatment or adrenaline

Name this fly: identifying features?

Arthropods > Insecta > Diptera (flies) > Cyclorrhapha > Oestridae (botflies) > Gasterophilus

Adult resembles bumblebee

Curved ovipositor beneath abdomen

Where do Gasterophilus flies lay eggs?

Eggs deposited on horse hairs, depending on species:

G. nasalis: Intermandibular space

G. hemorrhoidalis: Lip hairs

G. intestinalis: Forelegs and shoulder

First-stage larvae tunnel into tongue and between molars

Second stage larvae in interdental pockets, root of tongue, and stomach wall

Larvae pass out into feces and pupate in soil

Where are third stage larvae of Gasterophilus nasalis located?

Ampulla of duodenum of horses