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34 Cards in this Set
- Front
- Back
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History
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8000BC - Oldest known direct head louse association; 10k y/o dig in Brazil
Combing is the oldest method of lice control (nit (egg) combs) 1536BC Ebers' Papyrus in Egypt Herodotus spoke of Egyptian priests shaving ALL body hair to prevent infestations Lice -- One of the 10 biblical plagues |
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Order Phthiraptera
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The only truly parasitic group among exopterygote insects
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Transmission
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Opportunistic; hosts must be in close contact
Exception: Phoresy involving louse fly (Fam: Hipoboscidae) and Ischnocera Phoretic movement spans long distances (allows lice to play role spreading pathogens) |
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Phoresy
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Hitching a ride on another organism in order to spread
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Cospeciation
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Process by which one population speciates in response to and in concert with another
E.g. Pocket gophers (hosts) and chewing lice (parasites) |
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Lice Characteristics
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Head lice do NOT transmit pathogens (yet)
Head louse: Pediculus humanus capitis Body lice DO transmit pathogens Body louse: Pediculus humanus humanus Wingless (apterous) 3 nymphal instars |
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Instar
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Period between molts that occur until sexual maturity is reached
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Hemimetabolous
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Incomplete metamorphosis, no pupa
Lice are hemimetabolous Order: Hemiptera (true bugs) -- Orthoptera (Grasshoppers) Blattodea (Roaches) -- Phthiraptera (Sucking lice) |
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Holometabolous
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Complete metamorphosis
Egg -- larvae -- pupa -- adult Order: Diptera (True flies) -- Hymenoptera (Wasps, ants, bees) -- Siphonaptera (Fleas) |
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Mouthparts for chewing lice vs. sucking lice
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Chewing lice -- Mallophaga -- Mandibles
Sucking lice -- Anoplura -- Stylets |
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Morphology
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2 segmented tarsal -- Mallophaga
1 segmented tarsal -- Anoplura Tarsal can close around hair follicle (coevolution at work) Dorsoventrally flattened head |
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Morphology pt. 2
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Reduced labial palps
No ocelli and no compound eyes (heat, odors, uv used, not sight) Antennae 3-5 segmented Capitate antenna key characteristic of Phtheraptera Recessed into head in subfamily Amblycera Filiform in subfamily Ischnocera Short in Anoplura |
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Chewing lice classifications
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Amblycera
Ischnocera Rhyncophthirina 2900 species Anoplura -- 500 species |
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Morphological Adaptation
Amblycera |
Mandibles and maxillary palps present
Hosts - birds, rodents, domestic animals Host specificity - moderate Good colonizers, more active and better dispersal |
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Ishcnocera
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Retain mandibles
Maxillary palps lost Enlarged labrum Feed on feathers, hairs, skin of animals |
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Rhyncophthirina
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Mandibles at end of long snout, cut into thick skin of host and feed on blood
One family and 1 genus: Haematomyzus Parasitize African and Asian elephants, warthogs, bush pigs |
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Anoplura
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Major PH importance
Haustellum - Highly modified mouth part supporting stylets Fascicle - bundle of stylets inside haustellum |
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Functional modifications of lice
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Modified legs for latching host/moving through hair
Modified body setae in pinniped lice (Anoplura; Echinophthiriidae) Sexually dimorphic antenna in Ishcnocera Hosts with curly hairs easier to grab hold of |
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Functional loss of structures (ON EXAM)
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Reduced thorax with fusion of segmental boundaries (Anoplura)
Reduced tarsus segmentation (a main mechanism for holding host) Compound eyes and antennae reduced (not needed) Reduced # spiracles (respiration) in some Anoplura; lower # combats dehydration |
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Life History
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Hemimetabolous development (incomplete)
3 numphal instars -- adult Development is time, temperature, and species dependent |
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Difference between human metabolism and louse metabolism
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Arthropods cold-blooded, physiology geared toward environmental temperatures. Too cold = too cold to be active
More heat = plateau of activity. After plateau, dehydration occurs |
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Mallophaga
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Chewing lice
2900+ species Some intermediate hosts (tapeworms) Feed on hair or feathers Do NOT pierce skin |
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Anoplura
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Blood sucking parasites of eutharian (mobile, warm blooded) mammals
6 medically important families Pediculidae, Pthiridae = infesting lice |
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Pediculosis
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Presence of lice on the body
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Effects on host
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Irritation -- Allergy
Disease transmission Feather damage Time + energy preening Reduced poultry egg production |
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Pthiridae (Crab louse)
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Pubic area, armpit, bear, eyelashes
Stationary Venereal - spread through shared blankets, objects Human infestation only (STI) Discoloration around bite Female lays 30 eggs, 30 day life cycle |
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Pediculidae (Head louse)
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Same size as crab louse, but only found on head
Females - 50-150 eggs on hair -- 3 nymphal instars -- 3 week development Capable of transmitting typhus (mechanical transmission caused by scratching the bite) |
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Pediculidae (body louse)
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Morphologically identical to head lice but slightly larger (not a good way to ID)
50-150 eggs in clothing seams -- 3 nymphal molts -- 3 weeks development Temperature sensitive Don't leave body until host dies (Queen Victoria) |
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Lice as Vectors
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Pediculus humanus humanus (body) is only vector
3 bacteria species: --Epidemic typhus fever (Rickettsia prowazekii) --Epidemic relapsing fever (Borrelia recurrentis) --Trench fever |
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Epidemic typhus fever
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Rickettsia prowazekii
High fever, headache, backache, confusion, skin hemorrhages (all symptoms from other conditions, so hard to diagnose) 10-100% mortality rates Brill-Zinsser disease - mild symptoms of louse borne typhus recurring years after primary attack |
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Epidemic typhus fever control methods
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Hygiene
Treat infected clothing with insecticides Permethrin .5% (EPA allowed) Temephos 2% Propoxur 1% Arbaryl 5% |
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Epidemic relapsing fever
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Borrelia recurrentis -- vectored by pediculus humanus humanus
Distribution related to war, poverty, crowding Africa, China, Peru 10m affected in WW2 Underrepresented disease Mechanical transmission when louse is crushed into bite wound |
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Epidemic relapsing fever
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Mortality mainly due to myocarditis
Antibiotics - high doses for adults; longer, low doses for children |
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Trench fever
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Western front trenches, 1914
Major cause of illness, death No unique symptoms, hard to diagnose |
