Lice As Parasites Flashcards
Lice
Arthropods Flattened dorso ventrally abd wingless Permanent obligate parasites Mallophaga Anopleura
Mallophaga
Biting/chewing lice
Mouthparts spec to bite a skin and pelage
Dont pierce the skin
Move quickly and difficult to diagnose if only small numbers present
Head is broader than thorax and is flattened
Smaller claws for looser attachment and grazing
Anopleura
Sucking lice
Mouthparts pierce the skin and suck blood from capillaries in epidermis or lymph
Head much narrower than thorax
Larger claws for more permanent attachment to aid with blood feeding
Finding a meal
Have well dev antennae to locate feeding sites through combo of smell and warmth
Some feed in clusters so use pheramones to attract each other
Patjogenesis
Heavy infestation of sucking lice can cause anaemia, worse affected when already debilitated
Chewing lice in large no can cause large irritation as they feed - skin reaction can cause hair to loosen and be displaced
And can cause hide dam/cockle
Pruritic cattle can cause significant enviro damage
Lifecycle
All spent on host, transmission by close contact (once removed die within a week)
Adult F lay eggs glued to hair shaft which hatch in 1-2wk into nymphs which mature through 3 stages to become adults that live for several weeks, mate on host and F lay eggs
Adults are easily displaced by rain and cycle takes 2-3wk dep on strain host tine of yr and is quickest in long coated or housed animals as lice prefer rough surf and warm dark enviro
Repro
Some species eg bovicola can swith between sexual and asexual repro tonincr rate of pop growth
Feeding
Take repeated small meals
Survival against host d
Strong Legs and curved claws and spines enable tight contact with pelage and reduced removal by grooming
Eggs glued to pelage and res to dessication and grooming
Highly host spec and adapted to digestion of hist tissue
Evolved saliva and feeding mechanisms to evade imm resp
Bovicola ovis
Chewing in sheep
Infection spread is slow as transfer req close contact
Dont drop off or survive long in enviro
Host spec so no interspecies spread
Irritation cause foot stamping displacement of wool tufts and rubbing and biting flanks etc
Chewing lice diagnosis
Rel large so see in hair or wool partings with naked eye or magnifying glass
Microscopy to ID species with clinical signs and history to help
Also ID lice antigens in wool samples
Chewing lice economic cost
Little evidence showing negative effect on prod
Heavy infestation can red wool quality
Cockle
Key differential for sheep scab
Lice management (large animals)
Pyrethroid pour ons
Disperse around body in wool grease and amount of grease determine effective conc of pour on
Most effective applied off shears
High dose req for long wool treatment
Req 6 wk to disperse around body and kill lice
Res problems
Wool residue probs
Single off shears application in sunmer can give all year round protection
Felicola subrostratus
Only species that infest cats
Broad yellowish chewing lice short slender legs with single claws and triangular heads woth a longitudinal groove tgat fits around host hair
Trichodectes canis
VECTOR!!!
Broad pale yellow chewing lice
Dogs
Broad head short stout legs with single claws to grasp base of hair mainly over head neck and tail
Similar lifecycle to linognathus vituli and bovicola bovis
Potentially harmful for puppies and old debilitated dogs
Very active and cause skin irritation causing matted coats skin dam and alopecia
Cluster around body orifices and moist wounds
Vector of diphlidium caninum (ingested during grooming)
Bovicola bovis
Small red brown colour
Broad head and ventral chewing mouthparts
Slender legs adapted for moving amongst hair and have small single claws and spurs
Entire cycle spent on cattle
Transmit by close contact
Bovicola bovis lifecycle
1 egg laid every 2 days on average that is glued to hair shaft, egg hatches in 7-10d into nymph which moults through 3 instars to become an adult
2-3wk
Adult can live up to 10wk
Can incr rate of pop growth by swapping between sexual and asexual repro
Bovicola bovis economic importance
Can cause irritation and skin reaction can loosen and displace hairs by rubbing causing unsightly patches
Hairballs can be found postmortem
High burden are normally ill throfty but not thought to be due to lice
Can cause localised skin reaction causing cockle
Supefficial wounds caused by rubbing and scratching can also red hide value
Linognathus vituli
VECTOR!!
Long nosed cattle live
Elongated head and body
Piercing mouthparts concealed within head and prutrude when feeding
Legs stout with large claws and tibial spurs
Nymphs similar bug smaller
Flattened elongated body so entire lifecycle can be spent in the coat
Entire life cycle on host
Transmit by close contact
1 egg laid per day glued ti hair
Linognathus vituli economic importance
Heavy infestation causes anaemia - animals debilitated for other reasons are worse affected
Can cause hide damage
Sucking lice can transmit anaplasmosis and theileriosis
Implicated in ringworm spread?
Haematopinus suis
Largest sucking louse Pigs Long narrow head and mouthparts Dont survive off host Close contact transfer Heavy infestation vause restlessness anaemia and red weight gain Inflam lesions arise at sites of bites due to neutro infiltration, epi necrosis, capillary prolif and fibroblast multiplication Vector of ASF and swine pox
Haematopinus suis lifecycle
Lay 1-6 eggs Lifespan of a mnth Eggs glued to hair on lower body ears and on neck skin folds Eggs hatchbin 2 wks Nymph dev to adults in 2wk
Haematopinus suis treatment
Organophosphates
Parenteral avermectins
Lice as vectors or intermediate hosts
Sicking can transmit theileriosis and anaplasmosis
Trichodectes canis int host for tapeworm (cystercercoid dev in louse and ingested by final host - flea infestation more important cause)
Louse management
All affected/in contact animals treated
Clip and burn long hair
Treat with live treatments
Bird lice
All are biting
Chewing at feather base can draw blood causing inflam
Other signs are pruritus loss of condition restlessness and depluming itch
Human lice
Crab louse
Head louse
Body louse
