Ectoparasites

Ectoparasites

* What are ectoparasites?
o Insects and arachnids which feed through or upon the skin
* How do they affect human health?
o Transmit disease
o Cutaneous irritation
o Allergic reaction

Biological Classification of Ectoparasites
* Superkingdom Eucaryotae
* Kingdom Animalia
* Phylum Arthropoda
o Class Insecta
o Class Arachnida

Bedbugs
* Class Insecta
* Family Cimicidae
* Order Hemiptera
* Genus Cimex
o Cimex lectularius
o Cimex hemipterus

Bedbugs - Data
* Size = 4-5 mm long/3 mm wide
* Color = varies with maturity and feeding state
o Adult = reddish brown
o Nymphs = yellowish white
* Other names = chinches, wall lice, red coats
* Feeding Apparatus – long sharp proboscis extends from anterior head into a groove under the thorax
* Feeding Pattern – nocturnal, gregarious, blood feeder
* Reproduction – fertile adult female lays yellowish-white eggs
o Eggs hatch into nymphs in 37 – 128 days depending on temperature
* Habitat – places where they can easily access humans at night
o Wood bedsteads, mattresses, loose wall paper, under rugs, etc

Bedbug - Epidemiology
* Distribution – bedbugs move from one human residence to another in various ways
o Water pipes
o Adjacent walls
o Clothing
o Travel bags/luggage
o Laundry
o Furniture

Bedbugs- Health Effects
* Bedbugs have never been associated with any disease transmission
o Their effect on humans is tied to the reaction to the bites
o Reaction varies with the individual
o Most severe reaction are due to cutaneous puncture and the effect of the salvia
+ Causing swelling (welts), irritation, allergic inflammation

Mosquitoes
* Class Insecta
* Order Diptera
* Family Culicidae
* Genus Aedes
* Genus Anopheles
* Genus Culex
* Genus Psorophora

Mosquitoes - Data
* Size = 3 – 5 mm long;
o A few species are much larger = 9 mm long
* Color – dark interspersed with while bands
* Females are blood feeders while males are plant feeders
o Females only mate once; then produce fertile ova for life
o Mosquito life expectancy ~ 5 weeks

Mosquitoes – Life Cycle
* Egg
o Female mosquitoes lay their eggs (oviposit) in aquatic settings
o Standing water, tree holes, buckets, tires, etc
o Generally do not oviposit in large bodies of water like lakes
* Larvae – aquatic life stage
o Hatches from eggs and actively feeds on aquatic debri
* Pupae – aquatic life stage
o Developmental stage – metamorphosis – not feeding
* Adults – male and female

Mosquitoes – Health Effects
* Biological Vectors of Disease Pathogens
o Yellow Fever
o Dengue Fever
o Malaria
o Encephalitis
o Microfilariae = nematode larvae
* Mechanical Vectors of Disease Pathogens

Ticks
* Class Arachnida
* Order Acarina
* Family Ixodidae – hard ticks
* Genus Dermacenter
* Genus Amblyomma
* Genus Ixodes
* Genus Rhipicephalus

Tick Data
* Blood feeders – sole source of nutrients
o All vertebrates esp. mammals are hosts for ticks
o Heavy infestations result in significant blood loss
+ Some ticks ingest up to 2 gms of blood per feeding
+ Both male and female feed
* Ticks have longevity- live many years
o Ixodid ticks may live from 7-21 years
o This increases their role as reservoirs for pathogens

Ticks – Health Effects
* Dermatosis – inflammation at bite site
* Envenomization – toxic effect of tick salvia
* Exsanguination – loss of much blood
* Tick Paralysis – damage to peripheral nerves by the bite
* Otoacariasis – damage in the auditory canal
* Disease transmission – vectors of microbial pathoges

Tick - Life Cycle
* Four life stages – tick life history
o Egg – fully engorged females may lay up to 18,000 eggs
o Larva – hexapod, having six legs
o Nymph – sexually immature octapod, eight legs
+ Only one nymphal stage in Ixodid ticks
o Adult – sexually mature
* Host animals
o Some ticks have many hosts, some only one
o Host animal may change with development stage
o Some ticks may molt as many as five times; requiring a different host for each molt
* Ticks sometimes transmit pathogens transovarially

Ticks- Vectors of Microbial Diseases
* Bacterial Disease Transmission
o Rocky Mountain Spotted Fever
+ Dermacentor variabilis – American Dog Tick
+ Amblyomma americanum – Lone Star Tick
o Tularemia
+ Amblyomma americanum
o Lyme Disease
+ Ixodes ricinus
* Viral Disease Transmission
o Tick-Borne Encephalitis
o Colorado tick fever

Sucking Lice
* Class Insecta
* Order Anoplura
* Family Pediculidae
* Genus Pediculus
* Genus Pthirus

Sucking Lice Data
* Blood sucking ectoparasites of mammals
* Flat-bodied with no wings
o Legs adapted for clinging to hair and feathers
o 1.5 – 3.0 mm in length
* Six families having medical or veterinary importance
o One of these contains the species that affect humans
* Significant Human Lice
o Pediculus humanus capitis – head louse
o Pediculus humans humunas – body louse
o Pthirus pubis – pubic (crab) louse

Louse – Life Cycle
* Egg
* Nymphs
* Adults – male and female
o Female may lay 250- 300 eggs per day for 30 days

Sucking Lice – Health Effects
* Bacterial Disease Transmission
o Epidemic Relapsing Fever
+ Borrelia recurrentis
o Epidemic Typhus Fever
+ Rickettsia prowazeki
o Murine Typhus Fever
+ Rickettsia typhi
o Trench Fever
+ Rickettsia quintana

Biting Lice
* Class Insecta
* Order Mallophaga
* Family – there are no families of biting lice

that affect humans health in the world
Most are ectoparasites of birds

Mites
* Class Arachnida
* Order Acarina
* Family Dermanyssidae
* Genus Liponyssoides
* Genus Dermanyssus
* Class Arachnida
* Order Acarina
o Suborder – Trombidiformes
* Family Trombiculidae
* Genus Trombicula

Trombiculid Mites = Chiggers
* Eggs – hatch one week
* Larva – six legged
o Only parasitic stage in this family
o Not host specific – feeds on many hosts
o Leaves host when fully fed or engorged
* Nymph – eight legged
o Live in the soil and feed on insect eggs and soil debri
* Adult – eight legged
o Live in the soil and feed on insect egges and soil debri
o Male and females
o In North American – 1 -2 generations per year

Chigger Dermatitis
* Larval mites – chiggers- do not burrow into the skin
* Larval mites – chiggers – do not suck blood
o They attach to the surface of the skin or at the base of hairs and inject a digestive fluid into the tissues which lyses cells
o They ingest the cell fragments and cellular contents
* The digestive fluid causes the bite to itch
* Common North American Chiggers
o Trombicula alfreddugesi
o Trombiula splendens
o Trombicula batatas

Mites- Vectors of Microbial Pathogens
* Scrub Typhus
* Rickettialpox
* Hemorrhagic Fevers

Fleas
* Class Insecta
* Order Siphonaptera
* Family Pulicidae
* Genus Pulex
o Pulex irritans – human flea
* Genus Tunga
* Genus Ctenocephalides

Flea Data
* Blood sucking ectoparasites of vertebrates
* No wings – do not fly
* Adapted for jumping – strong posterior legs
* Many hosts
* Larvae feed on debri within the nest of the host

Flea – Life Cycle
* Egg – large in comparison to the adult flea
o Hatch in 9 – 15 days under ideal conditions
* Larva – small worm-like organisms which feed on dried blood, cutaneous and fecal debri
* Pupa – inactive, quiet stage, contained within a coccoon
* Adult – laterally compressed, wingless, legs adapted for jumping
o Piecing-sucking mouthparts
o Life expectancy –starved- 100 -125 days
o Life expectancy – fed – 500 – 600 days

Fleas – Health Effects
* Disease transmission
o Plague
o Murine typhus
o Myxomatosis in rabbits
o Cestode intermediate host
* Cutaneous infestation
o Adult flea burrows into skin
+ Chogoe flea of humans – Tunga penetrans

Fly Larvae
* Myaisis
o Infestation with the larvae of diptera or flies
o Cutaneous
o Intestinal
o Urogenital
Leeches

Ectoparasites.ppt