ento 301 – medical & veterinary entomology (lectures 1-5) ento 301 – medical &...

ENTO 301 – MEDICAL & VETERINARY ENTOMOLOGY

(Lectures 1-5)

Dr Terry OlckersSchool of Biological & Conservation

Sciences

Introduction

• Insects have huge impact on health of humans & domestic animals– Irritation & diseases

• Relatively few species involved but serious social & economic consequences– Transmit diseases (vectors)– Inject venoms & transmit

allergens– Cause wounds– Create nuisance & phobias

• Other arthropod groups also very important

Leishmaniasis

Myiasis

Introduction

• Major insect orders– Diptera (flies)– Hemiptera (true bugs)– Phthiraptera (lice)– Siphonaptera (fleas)

• Diseases & causative pathogens

• Other arthropod groups– Acari (ticks & mites)– Araneae (spiders)– Scorpiones (scorpions)

Protozoan causing sleeping sickness

Nuisance & phobias

• Nuisance mostly related to high densities & not real hazards– Justified in case of biting, venomous

& filth-frequenting species

• Major causes of nuisance & irritation– Blood-feeding species– Lachrymal-feeders– Immunological reactions– Phobic responses (delusory

parasitosis)

• Large industries are focused on pest control

Mosquito feeding frenzy

Blood-feeding species

• Cause major annoyance & impacts– Humans: reduce tourism,

outdoor activities, land development & land values

– Domestic livestock: death via major blood loss; increases stress & grooming activities; lowers agricultural production

• Main culprits = flies, fleas, lice, bugs, ticks, mites

Mosquito

Bed bugs

Immunological reactions

• Caused by antigens in saliva of ectoparasites

• Long-term exposure to bites may lead to no skin reactions

• Host’s immune defences may be neutralized (immunosuppresion)– Saliva contains additives to aid feeding

& pathogen transmission [immunosuppressants + anticoagulants + vasodilators + pain inhibitors]

– Immunosuppressants inhibit production of macrophage molecules that kill pathogens

Allergic reaction to flea bite

Phobic responses

• Some organisms cause fear & panic in humans (snakes, spiders, insects)

• Delusory parasitosis (entomophobia)– Persistent bites & skin rashes has

psychological origin– Obsessive-compulsive disorder =

sensation of insects crawling, biting & burrowing into skin

– Sensation causes chronic itching & mental anguish & self-abuse

Delusory parasitosis

• Sufferers seem normal & condition is difficult to diagnose

• Symptoms mimicked by several conditions– Food & skin allergies, drug

abuse & medical conditions like diabetes, hepatitis etc

– Infestations of parasitic insects or microscopic mites

• Condition may have genetic basis & could be drug induced

• Treatment usually with drugs

Symptoms can be confused with skin allergies

Insect venoms

• Best known are social Hymenoptera– Bees, wasps & ants sting in defence of nests– Venom delivered via modified ovipositor

• Honey-bee stings are barbed & used once (sting + venom sac remain in wound)

• Wasp & ant stings are smooth & used repeatedly

• Some ants have reduced stings & spray venom into wound

– Reactions to venom• Dermatitis• Severe neurological & cytological symptoms• Localized or systemic allergic reactions• Secondary bacterial infections

Reactions to venom• Mostly local inflammatory

response• Systemic allergic reactions

after several exposures (hypersensitivity)– Release of histamine leads to

dilation of blood vessels– Effects include allergic responses,

tissue swelling & respiratory problems

– Immediate hypersensitivity (anaphylaxis) can be fatal

Systemic response from fire ants

Local response from wasp sting

Toxicity & fatalities

• Most fatalities caused by honey bees– Shock from multiple stings– Allergic response

(anaphylaxis) from single sting

– In non-sensitized people, LD50 varies

• 500 stings for children• 1100 for adult females• 1400 for adult males

– Allergic people must avoid allergens & carry medication

Other insect toxins

• Not all toxins inoculated via stings– Physical contact with body

parts, haemolymph, poisonous spines & defensive secretions

– Blister beetles (Meloidae) release toxins (cantharidins) when crushed or handled

• Cause blistering of skin• Cause inflammation of urinary &

genital tracts if taken orally (aphrodisiac ‘Spanish fly’)

Blister beetle

Skin blistering

Other insect toxins

• Body fluids of other beetles have potent toxins– Certain flea beetles

(Chrysomelidae) that feed on toxic plants are used for arrow poisons by San people

– Some rove beetles of genus Paederus (Staphylinidae) have contact poisons (paederin) that cause blistering & long-lasting ulceration

Paederus beetle

Ulcers from paederin

Urticating hairs• Larvae (also pupae) of some

beetles, butterflies & moths• Penetrate skin causing skin

irritations (urtication)• Structure & function of hairs

– Hollow spines with subcutaneous venom glands

– Setae (bristles & hairs) with irritating toxins

• Retain irritant properties long after being shed– Intense burning sensation on skin– Breathing difficulties if inhaled– Inflammation of mouth & throat if

ingested

Lonomia achelous

Venoms & discomfort levels

• Death in extreme cases– Mostly due to

hypersensitivity & anaphylaxis

• Discomfort (pain) lasts for variable periods– Few hours if

Hymenopteran stings– Few days if urtication– Few weeks if ulcerated

blistersAnaphylaxis = most

serious outcome

Arthropod allergens

• Repeated exposure to allergens (mostly proteins) causes excessive immunological reactions

• Many allergens are airborne & cause respiratory problems

• Allergens found in shed cuticle, faeces, saliva & dead bodies

• Entomologists may develop allergic reactions (rhinitis, asthma)

• Wide diversity of arthropods implicated– Insect cultures (e.g. mealworms,

bloodworms, cockroaches etc)– Mites in stored products cause ‘baker’s

itch’ or ‘grocer’s itch’– House-dust mites cause house-dust allergy

House-dust allergy is most widespread

Arthropods & disease

• In tropics & subtropics, many arthropod-transmitted pathogens cause disease– Protozoa, bacteria, viruses &

nematodes

• Arthropods may be causative agent– Human lice cause pediculosis– Skin-burrowing mites cause

scabies– Fly maggots invade living flesh

(as primary or secondary agents) & cause myiasis

Protozoa causing malaria

Scabies caused by mites

Transfer of pathogens

• Mechanical transfer– Occurs passively & externally

from host to host– Pathogen does not increase

inside vector– House flies & cockroaches

transfer bacteria from faeces to human food (on mouthparts, legs & body)

– Arthropods are one of several means; poor public & personal hygiene are main pathways

Musca domestica

Transfer of pathogens

• Biological transfer– Specific association between

vector, pathogen & host– All 3 components essential– Pathogen increases inside

vector (close specificity between them)

– Arthropod is vital link in disease transmission

Malaria cycle

Disease control

• Combination of 3 approaches– Reduce vector numbers in field

(spraying programmes)– Disrupt contact between vector

& host (pesticides & repellents)– Attack pathogen inside host

(prophylactic drugs)– Development of vaccines?

• Requires detailed knowledge of biology of vector, pathogen & host (research)

General disease cycles

• Biologically transferred diseases– Blood-feeding adult arthropods transmit

parasites• Animal to animal• Human to human• Animal to human• Human to animal (very rare)

• Human diseases have single or secondary cycles

Single cycles

• Pathogen completes life cycle only within vector & human host– Human malaria (parasite needs

Anopheles mosquitoes & humans)– Similar malaria parasites infect primates

& birds but don’t affect human malaria cycle

• Few human diseases with single cycles– Need coevolution of vector, pathogen &

man– Man is of recent evolutionary origin; short

time for evolution of unique insect-borne diseases that rely on man

Anopheles

Secondary cycles

• Pathogen completes life cycle within vector & animal or human host– Non-human vertebrates are primary hosts

• Monkeys (yellow fever); rats (plague); desert rodents (leishmaniasis) etc

– Animal diseases that affect man = zoonoses– Human inclusion in cycle is not essential to maintain

disease & animals act as disease reservoirs– Outbreaks occurs when humans spread into natural

ranges of vectors & disease reservoirs

Secondary cycles: yellow fever

• In Ugandan forests, disease has sylvan (woodland) cycle– Reservoir = canopy-dwelling

primates– Vector = primate-feeding

mosquito (Aedes africanus)– Humans & monkeys coincide at

banana plantations near forest– Second vector (Aedes

bromeliae) that feeds on both humans & monkeys transmits virus to humans

Secondary cycles: leishmaniasis

• In Arabia, sand flies feed on burrowing rodents & transmit protozoan parasites– Disease affects humans when

suburban expansion overlaps with rodent reservoir

– No change in vector when humans enter cycle

• Animal reservoirs maintain natural disease cycles & complicate control

Disease outbreaks

• Epidemics = outbreaks in human populations• Epizootics = outbreaks in animal populations• Pandemic = worldwide epidemic

Pathogens & transmission

• Pathogens transferred by arthropods– Viruses (arboviruses)– Bacteria (also rickettsias)– Protozoan parasites– Filarial nematode worms

• Need to replicate in vectors & hosts → complex life cycles

• Parasites generally don’t harm vectors

• Pathogen presence determined by– Dissection & microscopy– Biochemical means

Filarial nematodes

West Nile virus

Pathogens & transmission

• Pathogens transferred during infective stage & after replication in vectors

• Transfer from vector to host (or vice versa) occurs when blood-feeding arthropod feeds on vertebrate host– From host to uninfected vector via

parasite-infected blood– From infected vector to host via

injection with anticoagulants that keep wound open during feeding

• Transfer may also be via deposition of infected faeces close to wound (gets rubbed in)

Blood-feeding

Infected faeces

Major insect groups

• Most important taxa– Order Diptera (flies) – 11 families– Order Hemiptera (true bugs) – 2 families– Order Phthiraptera (lice) – 4 families– Order Siphonaptera (fleas) – 2 families

• Aspects considered– Key taxonomic features to aid identification– General biology & life history

Diptera (flies)• Large well-known group

– Thousands of important species

• Adult features– 1 pair of membranous fore-wings– Hind wings reduced to form

halteres– Mouth parts are proboscus-like for

sucking fluids or piercing & sucking for penetrating tissues

• Larval features– No conspicuous head– Legless– Slender bodies with pointed fronts

which broaden towards rear

Fluid sucking Piercing

Culicidae (mosquitoes)

• Transmit several parasites– Protozoa (malaria)– Filarial worms

(elephantiasis)– Arboviruses (yellow

fever, dengue fever, encephalitis)

• Identification– Long & narrow wings

with scales along veins & wing margin

Culicidae (mosquitoes)

• Biology– Almost all blood-sucking; only

females take blood; males take nectar & plant juices

– Eggs laid in flowing or still water; water collected in containers, tree cavities & leaf axils of plants

– Eggs laid singly or together in floating raft

– Larvae & pupae are aquatic; active swimmers & breathe via siphon tube

– Adults usually close to breeding sites Aquatic larva

Blood-feeding females

Culicidae (mosquitoes)• 2 subfamilies

– Anophelinae• Genus Anopheles (human

malaria)

• Adults rest with abdomen tilted at steep angle to substrate

• Larvae rest horizontally on water surface

– Culicinae• Genera Aedes & Culex

(arboviruses & filarial worms)

• Adults rest with abdomen parallel to substrate

• Larvae hang at angle from water surface

Eggs

Larvae

Pupae

Egg raft

Adults

Simuliidae (black flies)

• Females are blood-feeders– Vicious biters & cause major

distress to poultry, livestock & humans

– Cause extreme pain, itching & local tissue swelling

– Vast swarms cause livestock deaths via blood loss, suffocation & trauma

– In tropical Africa, Simulium damnosum transmit filarial worms that cause river blindness in humans

– Also transmit filarial worms, trypanosomes & Leucocytozon disease in poultry

Simuliidae (black flies)

• Identification– Small (2-5 mm) stocky

grey-black flies– Humped thorax

(buffalo gnats)– Clear wings without

hairs or scales– In SA most belong to

genus Simulium; S.damnosum occurs but not disease

Simuliidae (black flies)

• Biology– Aquatic larvae live in fastest

flowing parts of streams & rivers

– Larvae attach to rocks & vegetation (via silk & hooks)

– Larvae are filter-feeders using complex labral fans on head

– Pupate on rocks underwater– Adults may occur several km

from water

Head fans

Aquatic larva

Psychodidae (moth flies, sand flies)

• Mostly harmless, except blood-sucking sand flies (subfamily Phlebotominae)– Transmit several pathogens

• Protozoa (leishmaniasis)• Arboviruses (pappataci fever)• Bacteria (oroya fever)

• Identification– Small cryptic flies (2-4 mm)– Very broad & hairy wings

with long parallel veins– Wings held open over body

Psychodidae (sand flies)

• Biology– Adults hide in hyrax & rat

burrows during day; enter houses at night to feed

– Adults & larvae live near water

– Larvae live in moist soil or in cracks & crevices where they survive on condensed water

Ceratopogonidae (biting midges)

Females of some genera (Culicoides) are blood-suckers; males visit flowers– Painless bite is followed by

intense irritation & itchiness

• Identification– Very small flies (0.5-2mm)– Grey or yellowish bodies– Wings folded over body at rest– Wings have thick radial veins

crowded close to wing margin

Ceratopogonidae (biting midges)

• Biology– Larvae carnivores or

detritivores– Larvae mostly live in water

bodies with high organic content; some live in moist or terrestrial habitats

– Adult females transmit arboviruses in livestock

• Bluetongue virus in sheep

• African horse sickness

– Species that bite humans may transmit filarial worms & viruses

Infestation of Culicoides

Tabanidae (horse flies)

• Females are voracious blood-feeders– Serious pests of livestock

(suffer weight loss)– Also bite humans– Transmit several parasites

• Protozoa → surra (cattle, horses, camels)

• Bacteria → tularaemia & anthrax (humans)

• Filarial worms → loiasis (humans)

Tabanidae (horse flies)

• Identification– Large, stoutly built flies– Often have irridescent

eyes– Antennae have 3

segments; 3rd segment is elongated & annulated

– Wings have large calypters

– Wing veins diverge at wing tip to form an open ‘V’

Tabanidae (horse flies)

• Biology– Adults feed on nectar &

plant juices; females take vertebrate blood

– Larvae develop in moist habitats, often in mud at edges of water bodies

– Most larvae feed on decaying plant matter; some are predaceous

Glossinidae (tsetse flies)

• Single genus (Glossina)– 29 species & subspecies

groups = 3 ‘species groups’– Both sexes are host-specific

blood-suckers (bites are painful)

– Transmit protozoans (trypanosomes)

• Sleeping sickness (humans)• Nagana (livestock)

Tsetse bite

Glossinidae (tsetse flies)

• Identification– Medium sized flies with

very tough & leathery body (survive swatting)

– Flattened body & short forward-pointing proboscus

– Wings folded scissor-like at rest; conceal abdomen

– Wings have ‘hatchet cells’

Hatchet cell

Glossinidae (tsetse flies)

• Biology– Adults active during day– Occupy habitats with trees

(e.g. grasslands & woodlands)

– Both sexes feed on large mammals; humans only attacked in absence of game

– Females incubate single maggot in their bodies

• Nourished by ‘milk gland’

• Larvae pupate in soil; very soon after deposited

Typical tsetse habitat

Muscidae (house flies)

• Large group with many common flies & some important pests– Nuisance flies– Mechanical disease

transmitters

• Identification– Thorax lightly striped– Mostly based on prescence or

absence of bristles on thorax

• Biology– Larvae live in various types of

organic matter; manure, garbage, rotting vegetation

• 2 important subfamilies– Muscinae– Stomoxyinae

Muscidae (house flies)

• Muscinae– Non-biting species – short fleshy

proboscus for mopping up surface liquids

– Some species extract fluids from human food & faeces (e.g. house fly, Musca domestica)

– Such species mechanically transfer bacteria & viruses

• Cholera, poliomyelitis, leprosy, typhoid fever, dysentery etc

– Others feed on wounds or run off from wounds

– Some involved in myiasis

Muscidae (house flies)

• Stomoxyinae– Biting species – long piercing

mouth parts– Some species are

aggressive & persistent blood-suckers (e.g. stable fly, Stomoxys calcitrans)

– Torment wild & domestic animals (e.g. ears of dogs)

Stomoxys calcitrans

Calliphoridae (blow flies)

• Identification– Stoutly built flies– Shiny metallic (blue or

green) colour– Plumose arista (at least

2/3 of length)– 2-3 notopleural bristles

Calliphoridae (blow flies)

• Biology– Adults attracted to decaying flesh,

carrion & faeces; larvae develop inside

– Other species are involved in myiasis (genera Calliphora, Chrysomyia & Lucilia)

– Not normally involved with diseases, but may spread bacteria (e.g. anthrax)

• Postive attributes– Key components in forensic

entomology (murder cases)– Wound treatment (wartime)

Pig carcass

Sarcophagidae (flesh flies)

• Identification– Robust flies with grey

& black colour (never metallic)

– Striped thorax & checkerboard grey pattern on abdomen

– Arista plumose on basal half

– 4 notopleural bristles

Sarcophagidae (flesh flies)

• Biology– Adults feed on decaying

organic matter (mostly animal) & faeces

– Females deposit live larvae in above for further development

– Also involved in myiasis & develop in skin sores of vertebrates

Gasterophilidae (horse bot flies)

• Identification– Adults are dull yellow & bee-

like– Short-lived adults lack mouth

parts & don’t feed; rarely seen– Genus Gasterophilus

associated with myiasis– Larvae inhabit guts of large

mammals– Larvae are barrel-shaped &

armed with rows of spines

Gasterophilus sp.

Gasterophilidae (horse bot flies)

• Biology– Eggs laid on host’s fur;

near mouth or on forelegs– Larvae enter mouth of host

• Burrow through skin into mouth

• Eggs are licked & swallowed by host before hatching

– Larvae move to stomach & attach to wall

• Nourished by horse’s blood

• May damage guts & weaken animals

– Mature larvae pass out in faeces & pupate in soil

Oestridae (warble flies, bot flies)

• Identification– Large, stout, hairy flies

with large inflated head & mottled grey colour

– Adults don’t feed; short-lived & rarely seen

– Larvae are involved with myiasis

– Larvae are white, spiny, barrel-shaped & have black mouth parts

Oestridae (warble flies, bot flies)

• Biology– Larvae are internal parasites of

mammals• Nasal cavities of sheep, horses,

antelope etc• Under skin of cattle, antelope,

rodents etc– Skin parasites cause pus-filled boils

(warbles) that damage animal hides– Sheep nasal bot fly (Oestrus ovis)

• Living larvae deposited into nostrils; attack to sinus membrane & feed on mucous

• Sneezed out & pupate in soil– Other species of Oestrus &

Gedoelstia live in pulp cavity in horns of antelope & sheep

Warbles on cattle

Nasal bot larvae

Hemiptera (true bugs)

• Diverse in appearance– Piercing & sucking mouth parts– When present, 2 pairs of wings

(hind pair reduced)– Incomplete life cycle

• Immature stages = nymphs

• Nymphs are mostly small wingless replicas of adults

• No pupal stage

• Of lesser medical importance– Most are phytophagous or

predators of arthropods– Few blood suckers = 2 families

Cimicidae (bed bugs)

• Identification– Small, apricot-coloured &

wingless– Circular body & flattened

extensions of prothorax behind eyes

• Medical & veterinary importance– Most species are ectoparasitic

on rodents, poultry, birds & bats• 3 species parasitic on humans• Cimex lectularius occurs

worldwide

– Do not appear to vector any pathogens

Cimicidae (bed bugs)• Biology

– Adults & tiny nymphs hide in day• Any cracks & crevices

• Mattresses, clothing & under wallpaper

– Emerge at night to feed on blood• Survive without food for several

months, but need blood to moult & lay eggs

– Bites are painless; no response during sleep

• Many show allergic reactions (large red discs around bites; swelling & irritation for days)

• High densities can cause anaemia in children

Adult & nymphs feeding

Reduviidae (assassin bugs)

• Identification– Large robust bugs = ambush

predators of arthropods– Strong recurved beak for biting

• Inject paralytic toxin to subdue prey

• Bite very painful to humans• No species in SA usually bite

mammals

• Medical importance– South American subfamily

Triatominae (kissing bugs)• Feed on human & animal blood• Transmit Chagas’ disease

Reduviidae (assassin bugs)

• Triatominae (kissing bugs)– Live in woodland & forest habitats– Colonized human dwellings

• Live in ceilings, cracks & crevices etc.

– Behave like bed bugs & attack humans at night

– Spread protozoans which cause Chagas’s disease (American trypanosomiasis)

– Most notorious species are Triatoma infestans & Rhodnius prolixus

Triatoma infestans

Rhodnius prolixus

Phthiraptera (lice)• Small, flattened & wingless• Short stout legs; end in strong

claws• Permanent ectoparasites on

birds & mammals– Biting lice

• Biting & chewing mouth parts• Head is as wide as or wider

than thorax• Previously Suborder

Mallophaga; now 3 suborders• Mostly associated with birds

(also mammals)– Sucking lice

• Piercing & sucking mouth parts• Head generally narrower than

thorax• Suborder Anoplura• Associated with mammals (also

humans)

↙↙

Phthiraptera (lice)

• Biology– Entire life cycle occurs on host– Eggs (nits) are cemented onto

host’s hair or feathers– All stages (nymphs & adults are

blood sucking– Transmission via contact between

hosts– Unable to survive for long when

off hosts– Many species are host specific

• Attack one or few related species• Live in specific region of host’s

body• Identity often indicated by host• Only 3 species attack humams

Louse nit

Adults & nymphs

Biting lice

• Mostly associated with birds & don’t attack humans– Feed on feathers & mostly host

specific

• 2 important families– Menoponidae (biting bird lice)

• Antennae fold into grooves on side of head

– Philopteridae (bird lice)• Largest family of lice• Antennae not concealed in

grooves in head

– Pests of poultry• Heavily infested birds become

emaciated

– May bite humans when infested birds nest in houses

Head of Menoponidae

Sucking lice

• 2 important families (attack humans)

• Pthiridae (crab lice, public lice)– Broad, flat lice that appear crab-

like– Mid & hind legs are stout with very

large claws– Abdominal segments have distinct

lateral lobes– Single species (Pthirus pubus)

confined to human pubic region• Bites cause irritation & typical rash• Spread by close body contact

(usually sex)• No diseases

Crab louse

Rash caused by infestation

Sucking lice

• Pediculidae (human lice)– Elongated lice with abdomen

longer & wider than thorax (no lateral projections)

– All 6 legs are equally strong & developed

– 2 species (also called subspecies)

• Pediculus humanus (body louse)• Pediculus capitis (head louse)• Very similar but differ in habits• Annoying pests

Head louse

Body louse

Sucking lice

• Head lice– Suck blood from scalp & lay eggs on hair– Common & easily spread by close contact,

sharing of combs, brushes, hats etc

• Body lice– Suck blood from body & lay eggs on

clothing– Uncommon & spread by bodily contact,

sharing of clothing or bedding– Vector diseases (epidemic typhus, trench

fever, relapsing fever)

• Lousiness related to sanitation– Crowded conditions– Long periods without bathing or changing

clothes

Nits on human hair

Siphonaptera (fleas)

• Small, laterally flattened, wingless insects

• Large hind legs & spectacular jumps

• Parasitic on birds & mammals– All adults have piercing &

sucking mouth parts & feed on blood

– Females need blood to lay eggs

– Some species are host specific, but most feed on several hosts

– Annoying pests due to blood sucking, skin burrowing & transmission of diseases & parasites

Siphonaptera (fleas)• Biology

– Eggs are laid in host’s nest or habitat; eggs laid on host will drop off

– Larvae are slender, whitish & legless (maggot-like)

• Well developed head & 2 small hooks on back end

• Develop off host & feed on organic material in dirt or debris

• After 3 moults, pupate in silken coccons– Pupae are dormant for several months

• Hatch in response to vibrations from host’s movement

– Adults are very active• Move freely on host & between hosts• Can survive off host for long periods

– 2 important families (attack humans)

Tungidae (jigger or chigger fleas)

• 1 species (Tunga penetrans) in SA– Introduced from South America in 17th

century & widespread in tropical Africa– Very small (<1 mm)– Females burrow into skin of humans &

other mammals; usually on feet• Soft areas between toes

• Under toenails

• Condition called tungiasis

– Males & newly emerged females live like other fleas & feed on various hosts

– No diseases transmitted

Tungidae (jigger or chigger fleas)

• Tungiasis– After mating, females become

permanently imbedded in skin• Breathe, defecate & expel eggs through

small opening at back end• Abdomen becomes greatly distended as

eggs develop (swells to size of small pea)

– Host tissue becomes inflamed & swells to form boil-like sore

• Cause intense itching & bacterial infection

• Sores may develop into bad lesions• Can cause loss of digits, septicaemia &

lameness

– Less of problem today; many areas in South America still affected

Pulicidae (common fleas)

• Large diverse family & occurs worldwide– Most important pests (humans &

animals)– Disease vectors– Mostly generalists (attack humans &

animals), but often named after principle host

– Many pest species occur worldwide• Cat flea (Ctenocephalides felis)• Dog flea (Ctenocephalides canis)• Human flea (Pulex irritans)• Oriental rat flea (Xenopsylla cheopis)

Flea bites

Human flea

Pulicidae (common fleas)

• Economic importance– Cat flea

• Most common in houses in SA– Sticktight hen flea (Echidnophaga

gallacea)• Adults attach in tick-like manner & form

dense clusters on faces & combs of chickens

• Cause irritation & reduce growth & reproduction in bad cases

– Oriental rat flea• Transmits bubonic plague & murine typhus

to humans– Dog flea

• Intermediate host for dog tapeworm– Rabbit flea (Spilopsyllus cuniculi)

• Transmits myxoma virus which causes myxomatosis in rabbits

• Virus used for biological control of rabbits in Australia & UK

Oriental rat flea