Ectoparasites 1

Ectoparasites 1

1. Learning Objectives

   • Recall main features of arthropords in terms of structure, life cycles and classification
   • Give examples of mites of vet importance and how their interactions with the host lead to disease
   • Explain how variation in the life cycle of different mite species affects their epidemiology, and how good biological understanding can help achieve effective control
   • For the following genera, be able to state classification, life cycle, diseases caused in domestic animals, diagnosis of infection and principles of control: Chorioptes, Demodex, Dermanyssus, Psoroptes and Sarcoptes
   • ORDERS
     • ASTIGMATA order
       • SARCOPTIDAE FAM sarcoptes, trixicarus, notoedres
       • PSOROPTIDAE FAM psoroptes, chorioptes, otodectes
       • KNEMIDOKOPTIDAE FAM knemidokoptes spp
     • PROSTIGMATA order
       • DEMODICAE FAM demodex spp
       • CHEYLETELLIDAE FAM cheyeltiella spp
       • TROMBICULIDAE FAM neotrombicula autumnalis
     • MESOSTIGMATA order
       • MACRINYSSIDAE FAM ornithonyssus sylvarum
       • DERMANYSSIDAE FAM dermanyssus gallinae
     • Scabies and mange are different. Mange does not tell you what parasite is infecting
       • e.g. demodex not zoonotic, scabies is

2. Intro

   • Lives on/at expense of other organism
     • Relationships
       • Obligatory -> facultive
       • Continuous -> intermittent
       • CR - damage host/ immune response damages host
         • Blood loss - anaemia Tissue damage Inflammation and pruritis - itching/biting/scratching Allergic responses
         • May lead to - reduced time grazing (weight loss), skin wound (microbial infection)
           • skin wounds - secondary infection

3. Parasite structure

   • 1. Tagmatization - Head, thorax and abdomen
     • Tagma - functional units of arthropods Tagmatization - grouping of units into one functioning organism
   • 2. Legs - complex structure - end of leg - claws, tarsus and pretarsus -> identification of parasties
   • 3. Exoskeleton - Chitin protects organism from water loss
     • skin - designed to cope with hostile environment
     • SCLEROTIZED - on outside - more tough, more impermeable. Waxy layer for water run-off
     • CHITIN - epicuticle, exocuticle, endocuticle
     • Chitin - sits above epidermis and basement membrane
   • 4. Moulting
     • Hairs - seta/mitotrichia - attachment to trichogen cell - sensory - awareness of movement
   • 6-7. Essential structure is fluid filled sac
     • V simple heart - dorsal vessel runs length of body. Haemocoel equiv of blood - bathes tissue in nutrients
     • Simple gut/heart/nerve cord
     • Rigidity to trauma - shape
   • 8. Spiracles
     • Passive air absorption and SPIRACLES - opening in integument
       • TRACHEOLES - equivalent to lungs
     • Mites/Ticks have stigmata instead - chemicals kill by blocking entrances = drowning
       • ACARI - mites/ticks

4. Life cycles

   • Hemimetabolous (simple)
     • Lay eggs -> NYMPH -> 2ndary stage nymph -> ADULT
   • Holometabolous (complex)
     • Traditional insects - butterflies/maggots etc Flea life cycle Protected from chemicals, hoovering etc
     • Pupa -> v. long life cycles in environment and protect V WELL
       • Adult -> egg -> larva/maggot -> pupa -> adult

5. Taxonomy

   • PHYLUM = Arthropoda
     • 2 CLASSES = Insecta and Arachnida
       • Insecta -> lice, fleas, flies
       • Acari/Arachnida -> mites & ticks
         • Types of stigmata - differentiate mites - differentiate breathing

6. MITES

   • important - very prevalent on farms in UK e.g. sheep scab
   • Gnathosoma - mouth part
   • Idiosoma (rest of body)
     • Podosoma - leg attachment site
     • Opisthosoma - reproductive site
   • Mites have 4 pairs of hairy legs
   • Distal legs - On end - PRETARSUS (pedicel) and PULVILLUS (sucker) -> sucker is distinct to each, a defining feature
     • Suckers more distinct than other structures which are not critical to know Pretarsus also differentiates mites
   • Mouth parts - v distinctive
     • Difficult to remove -> HYPOSTOME drills into skin, CHELICERAE - teeth, aid attachment, PALPS - sense in contact with host
       • All attached to IDIOSOMA
       • Mouth parts critical - inject into body - saliva proteins, viruses eliciting immune response etc
   • Life cycle
     • egg - larva - nymph (protonymph -deutonymph - tritonymph), - adult
       • Larva has 3 s.o legs (do not confuse with insect w/3 legs), adult has 4 s.o legs
         • look at body shape to determine if larva mite or adult insect
         • Hairs and ornate shields help ID

7. MITES (1) *SARCOPTIDAE* (Sarcoptes, Trixicarus, Notoedres)

   • Scabies
     • Dogs with scabies - euthanasia
     • V ITCHY, v. difficult to find on host - look for 1 adult/egg for diagnosis. SHORT LEGS = CLOSE CONTACT (lieing together etc) causes infection
       • ADULT FEMALES - burrow in upper layers of skin
         • wavy pink = stratum corneum
           • Egg -> Adult = 17-21 days
             • Survival 2-3 weeks off host
               • Intense itching, inflammation, hair loss, crusts of dried exudate -> self-inflected wounding. Poss hypersensitivity. Death 2-4 months
   • Sarcoptic mange
     • SARCOPTIC SCABIAE
     • common in dogs & pigs - seen in humans and camelids, rare in cattle, goats, sheep, cats, horses..
       • Organic farms where chemicals to prevent mites not used
     • Infestation variation in host
       • Dog - pinnae, elbows, ventrum Pigs - external ear canals and dorsum
       • Infestation - asymptomatic for long periods - mites hard to find
   • Sarcoptiform mites
     • Guinea pigs - 12/10 itchiness - TRACARUS CAVIAE
       • Similar appearance to Sarcoptes Scabiei V distressing - will roll around on table
   • Ask owner if have lesions - red spots - papules -> cannot survive die but still cause intense itching
     • All species v similar appearance
       • 1. Sarcoptes scabiei 2. Notoedres cati 3. Trixicarus caviae - look at anus position for ID
         • 1. Anus terminal 2. Anus dorsal 3. Anus dorsal

8. MITES (2) *KNEMIDOKOPTIDAE* (Knemidokoptides spp)

   • Mite legs even shorter than Sarcoptes -> close contact in massive groups
     • Depluming itch/ Scaly leg - remove scales and mix with liquid paraffin to tease out mites
   • infects BIRDS
     • more backyad pets than poultry units

9. MITES (3) *PSOROPTIDAE* (Psoroptes, Chorioptes, Otodectes)

   • Psoroptes
     • Psoroptes ovis/cuniculi (sheep, rabbit)
     • Psoroptes ovis - v long legs, long pretarsus w/sucker = trumpet appearance, distinct structures for copulation - male tuburcle - shape used for ID
     • Male smaller than female
     • Pre-adult: 10-15 days, Adult: 20dys, Off-host mite: 16-18 dys
       • Adult -> 1-3 dys Larva -> 2-3 dys Protonymph -> 2-3 dys Tritonumph -> 2-3dys Adult
     • Psoroptes used to be notifiable disease - DIP w/ organophosphate - DIAZINON
       • Reportable in Scotland - notify APHA
       • Routine scab control - disease now difficult to manage in UK - resitance to macrocyclic lactone injection
         • V. contagious, treat whole flock if one infected - treat before enter common round - look for fleece left on gates/posts etc
     • Affect body of sheep but can also infect cattle -> more difficult to treat +MAJOR milk loss -> V V itchy & a welfare issue
       • Ears of rabbits, alpacas, goats - not TOO much of a problem
     • mistaken with Chorioptes bovis - big problem
   • Chorioptes - bovis & Ctexanus
     • Misdiagnosis as Psoroptes ovis - important to distinguish and identify parasite as CHORIOPTES minor skin disease and PSOROPTES is v detrimental to health!!
     • Differentiate by wine glass pretarsus and sucker appearance
     • use skin scrapings to ensure correct diagnosis - look for wine glass or funnel
     • Chorioptes bovis - 3 week lifecycle, 20 egg reporductive output
       • Ignored as smaller and usually not massive problem - common in horses. Lesions usually lower legs, base of tail perineum, udder, interdigital
       • Therapy is topical
   • Otodectes - Otodectes cynotis
     • hedgehogs, carnivores, cats, dogs - increased ear wax production, infection of ear
       • looks v v similar to Chorioptes, but C. only seen in livestock!!
     • white sructures seen in othoscope of dog - mobile, run from light
       • eggs distinctive in wax - swab sample
       • commonly seen in young and in rescue centres
     • Females - 2-3 week lifespan - 15-20 eggs, smaller than Psoroptes, pretarsi not jointed, deep ear canal, not as common as owners suspect

10. PROSTIGMATA (ORDER)

    • DEMODICAE FAM
      • Demodicosis
        • cigar shaped Demodex injai v long body Demodex cornei - new species or variation of canis?
        • Sebcaceous glands, hair follicles. Host specific. Life cycle 18-24 days. Deep in dermis and difficult to find - skin scraping & hair plucks/ skin biopsy
        • Demodex canis, D. injai, cannot live on host, usually absence of itching, dam to young via SUCKLING, common in dog - rare in other species
          • Do not have anus Occasionally seen in cats and hamsters Bats have them - up to 4 dif species
        • Demodex pathogenesis - inflammatory response heightened - affect on suppression of IS?
          • DIAGNOSIS - skin scraping on hailess skin, clip and squeeze to extrude parasites from hair follicle infundibulum, capillary ooze
            • look at base of follicles eggs are diamond shaped
    • CHEYLETIELLIDAE FAM
      • Cheyletiella
        • not seen often, allergic response = allergic to mite
        • survive on host up to 10days, large - move rapidly, mild but highly contagious, will infest human
          • large mouth parts bite
      • 'walking dandruff' - not common due to many flea products in UK
        • fur mites, barely penetrate skin - topical therapy - can bite owner
    • TROMBICULIDAE
      • Neotrumbicula - berry bug
        • mites w/3 pairs of legs (larval forms) - seen in autumnal period, head/feet of animals, ORANGE - feed on animals for short period and drop off to live rest of life in enviro

11. MESOSTIGMATID order

    • Mesostigmatid (gamesid) mites
      • northon fowl mite, red mite - RED MITE - affecting poultry industry - difficult to get rid of
        • Red mite sufferers get lice - not being treated with chemicals
          • most life cycle off host, feeds at night, short life cycle - 7days - nymphal and adult blood feed - off host survival 34 weeks
            • have to clean whole housing and repopulate with clean stock
        • Northon fowl mite
          • entire life on host, eggs at base of feather, life cycle 5-12 days, off host survival 1-3 weeks, only protonymph and adult blood feed
        • wild bird transmittance? Transmit salmonella etc. Cannot use chemicals as entering food chain
      • Clinical signs - irritant, anemia if sever, death, egg production decrease, transmit pathogens
        • Management - sprays - avermectins etc, licensed cleaning products, deep clean, avoid wild birds, biological control methods
          • diatomaceous earth - dessicmates mites - non chemical

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