Medically important Arthropods
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Transcript of Medically important Arthropods
Medically important Arthropods
Presenter – Dr. Sukumar T K
Arthropods
• Invertebrate animals with jointed legs.• Exoskeleton – chitin.• Segmented bodies.• Bilaterally symmetrical• Tubular alimentary canal with mouth and anus.• Coelom
Medical anthropodology
• Majority of arthropods are not harmful to humans.
• Arthropod related with human health.– Harmful – nuisance, discomfort, bites.– Ectoparasites – live and feed on exterior of host
without transmitting germs.– Mechanical transporters.– Vectors .
• Class Arachnida– Ticks and mites (order Acarina)
• Class Insecta– True flies (order Diptera)– True bugs (order Heteroptera / Hemiptera)– Lice (order Anoplura)– Fleas (order Siphonaptera)
Class
• Insecta– 3 disntict regions– 3 pairs of legs– Wings present– 1 pair of antennae– Segmented abdomen.
• Arachnids– 2 regions– 4 pair of legs– No wings– No antennae– Abdomen usually not
segmented.
Metamorphosis
• The change in form during an insect’s development is called metamorphosis.
• Complete metamorphosis.• Incomplete metamorphosis
Phylum Arthropoda
• Class Crustaceae – cyclops, crabs.
• Medical importance – Cyclops are intermediate hosts of the fish
tapeworm and Dranculus medinensis.
• Spiders, scorpions, ticks and mites.• 4 pair of legs• Pedipalps – aid in chewing• Incomplete metamorphosis
Order Acarina
• Only group in Arachnida that sucks blood and serves as vector.
• Commonly called• Ticks
– Hard tick (family Ixodidae)– Soft tick (Argasidae)
• Mite– Trombiculid mite, itch mite, dust mite
• Medical importance– Tick paralysis– Bite injury– Ixodidae – Borrelia burgdoferi, Babesia microti
and Ehrlichia spp.– Soft tick – vectors of endemic relapsing fever and
Q Fever.
• Soft tick– Body is often wrinkled.– Mouth parts are ventral and not visible.– Female and male – same appearance.
• Hard tick– Body is usually smooth.– An inflexible, dorsal scutum covers the idisoma of
the male and the anterior part of the idisoma of female.
– Mouth parts are terminal and visible from above.
• Soft ticks lay eggs more than once.– feed in night.
• Hard ticks lay eggs only once.– Feed on host for few hrs,
in day.
• Control– Environmental management– Acaricides– Personal protection
• Trombiculid mite– Larvae – reddish or orange, 3 pairs of legs.– Adult – bright red, hairy or granular, 4 pairs of
legs.
• Life cycle
• Chiggers – parasitic with low specificity.• Chigger dermatitis – reaction of host.• Scab – raised, reddened wheal with a
depressed center.• Scrub typhus• Epidemic haemorrhagic fever??
• Diagnosis– Recent h/o being to grassy area– Fever, itching papules, scab
• Prevention– Eradication of wild weed– Control of rats and mice– DDT– Personal protection
• Sarcoptes scabiei– Commonly called itch mite.– Causes scabies– Disc shaped with distinctive sculptured lines– Stubby legs– Male – 4th pair has amlulacra– Female – 4th pair terminate in long setae
• Female burrows in the skin and lays eggs in sinuous tunnel.
• Selects places where skin is thin and wrinkled, between fingers, elbows, feet, etc.
• Children – whole body.
Presentations
Treatment
• Prevention– Aggressive treatment of infested patients and all
close contacts,– Disposal or hot wash-dry sterilization of clothes.– Provision of improved access for personal hygiene
and health care– Aggressive control of outbreaks of zoonotic
scabies with the potential for human transmission
– House dust mite - Dermatophagoides pteronyssinus, Dermatophagoides farinae, Euroglyphus maynei.
– Morphology• White – tan• Tiny oval shaped• Covered with striations
Class Insecta
• Lice– Head louse - Pediculous humanus var capitis
• Pediculosis– Body louse - Pediculoushumanus var carporis
• Epidemic fever, Trench fever, Relapsing fever– Pubic / Crab louse – Pthrius pubis
• Morphology – Pediculous humans– Greyish, wingless, 3pairs of legs.– Abdomen
• Male – V• Female - W
Pediculous humanus capitis
Louse – life cycle
• Therapy – Management of pediculosis capitis includes two
topical or systemic treatments with pediculocides, 7 to 10 days apart.
– Removal of all viable nits by carefully combing wet hair.
• Pthirus pubis– Smaller– Broad body– Large claws on middle
and hind legs.
• Therapy– Management includes initial bathing with soap and
water, followed by two topical or systemic treatments with pediculicides, 7 to 10 days apart
Prevention
• Prevention strategies– Combinations of sanitizing the environment.– Eliminating all human reservoirs of head lice in
households, apartments, housing complexes, classrooms, and schools.
• Common preventive interventions– avoiding contact with potentially contaminated
items – soaking all combs and brushes in isopropyl alcohol
or 2% Lysol solution– sanitizing the household environment by high heat
cycle washing and drying of all bedding, clothing and headgear
• Fleas – Oriental / Tropical rat flea – Xynopsilla cheopis
• Plague, Endemic Typhus, Host of Hymenolipis tapeworm.
– Northern rat flea – Nasopsylla fasciatus• Endemic typhus
– Human flea – Pulex irritans• Skin irritation, Intermediate host of Hymenolepis and
Dipylidium tapeworm larvae.
• Morphology– Brown yellow colour– Body covered with
bristles
Tungiasis
• Bugs– Bed bugs – Cimex lectularius, Cimex hemipterus
• Allergy, secondary bacterial infection.– Reduvid bug – Rhodnius, Triatoma, Pastrongylus
• American trypanosomiasis ( Chaga’s disease)
• Diverse in appearance– Piercing & sucking mouth
parts– When present, 2 pairs of
wings (hind pair reduced)– Incomplete life cycle
• Identification– Small, apricot-coloured & wingless– Circular body & flattened extensions of prothorax behind eyes
• Reduvid bug• 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
• Flies– Sandfly – Phlebotomus, Lutzomyia
• Leishmaniasis, Bartonellosis, sandflyfever– Black fly/Buffalo gnats - Simulium
• Onchocercariasis / river blindness– Tsetse fly – Glossina
• African trypanosomiasis– Deer fly/ Yellow fly – Chrysops
• Loiasis, Tularemia– Domestic fly – Musca domestica
Sandfly Tsetse fly
Flies
• Morphology – 1pair of membranous fore wings– Hind wings reduced to form halters– Mouth parts – proboscus / piercing like.
• Larval– No conspicuous head.– Legless– Slender bodies.
• Mosquitoes– Anopheline
• Anopheles culcifacies – Malaria• Clear, stagnant/ sluggishly moving water.• Rest at an angle to the resting surface.
– Culicine• Filarial - Culex fasciatus
– Stagnant, polluted water– Lymphatic filariasis
• J.E - Culex gelidus, Culex tritaeniorhyncus, Culex fuscocephela
– Japanese encephalitis
• Aedes– Aedes aegypti
• Urban vectors.• Man made small collection of clear water.• Dusk and dawn biters
– Aedes albopictus• Rural vectors• Natural collections of clear water
• Dengue, Yellow fever, Chickungunya
• Mansonia– Rural vector– Breeds on the undersurface of water plants– Brugian filariasis, transmits Dirofilaria repens.
• Mosquitoes identification– Long and narrow wings– Anopheles – adults rest with abdomen steep angle
to substrate. Larvae rest horizontally to water surface.
– Culex and Aedes – rest with abdomen at an angle to substrate. Larvae hang at an angle from water surface.
Antennae
Male Female
• Egg– Anopheles boat shaped, single and float on water.– Culex cylindrical, laid together – rafts, no float.– Aedes olive shaped, single and bottom of water.
• Larvae
Anopheles
Culex
Aedes
References
• Meical Parasitology – Ruth Leventhal, Russel F. Cheadle.
• Principles and Practices of Infectious Diseases 7th Edition – Mandell, Douglous, Bennet.
THANK YOU