Biology 625
Fall semester lecture note outline

Updated: 24 September 1999

The text below simply represents a crude lecture outline of one of the topics covered in class. It is not meant to substitute for attending lectures or ignoring the textbook. Additional material, including line drawings, kodachromes, and more extensive information on life-cycles and basic biology, will be supplied in the lectures.

TOPIC 47. Acari (ticks and mites)

  1. segmentation reduced so that body divided into 2 main portions
    1. prosoma (cephalothorax)
    2. opisthosoma (abdomin; essentially the area posterior to the legs)
  2. adults usually with 4 pair of legs
  3. other terminology as follows
    1. capitulum (gnathosoma) is an area anterior to the body and carries the feeding appendages
      1. hypostome (part of the mouthparts made up of the fused coxae of the pedipalps
      2. pedipalps (palps; segmented second pair of arthropod appendages)
    2. idiosoma (entire body excluding capitulum)
    3. Haller's organ (depression on the 1st tarsus, which functions as a humidity/olfactory receptor)
    4. classification of the subclass: Acari
      1. order: Ixodida (Metastigmata)
        1. ticks; relatively large in size
        2. hypostome with teeth and usually exposed anteriorly
        3. Haller's organ present, on first tarsi
        4. pair of spiracles near coxae of 4th pair of legs in adults
        5. all parasitic
        6. 2 families
          1. family: Ixodidae (hard ticks)
          2. family: Argasidae (soft ticks)
      2. order: Mesostigmata
        1. mites; small
        2. hypostome without teeth and and hidden ventrally
        3. Haller's organ absent
        4. pair of spiracles between second and fourth coxae
        5. both free-living and parasitic members
      3. order: Prostigmata
        1. mites; small
        2. hypostome without teeth and and hidden ventrally
        3. Haller's organ absent
        4. pair of spiracles sometimes present and, if present, paired and either between chelicerae or on dorsal surface near center of body
        5. both free-living and parasitic members
      4. order: Orbatida (Cryptostigmata)
        1. mites; small
        2. hypostome without teeth and and hidden ventrally
        3. Haller's organ absent
        4. spiracles absent
        5. all free-living
      5. order: Astigmata
        1. mites; small; poorly sclerotized
        2. hypostome without teeth and and hidden ventrally
        3. Haller's organ absent
        4. spiracles absent
        5. both free-living and parasitic members

FAMILY: Ixodidae (hard ticks)

  1. most species are dioecious, and females usually require a blood meal prior to egg production
  2. copulation usually on the host
  3. females usually drop off the host, and lay eggs in the soil
  4. 6-legged larval stages hatches, and requires a blood meal to molt
  5. 8-legged nymph is the next stage, and requires a blood meal to molt
  6. nymph molts into adult
  7. different host seeking strategies
    1. one-host ticks spend all life-cycle stages on the same host
    2. two-host ticks generally spend the larval and nymphal stages on one host, but the nymph drops off to molt and the adult seeks a second host
    3. three-host ticks represent the majority of species, and all stages of ticks drop off the host prior to molting, and the next stages needs to seek a new host
  8. although some species are host specific, many are generalists
  9. can survive for months and sometimes for many years without taking a blood meal
  10. dorsal surface is covered by a sclerite termed a scutum; in adult females the scutum does not cover the entire dorsal surface so that engorging may occur
  11. some species possess eyes on the scutum whereas other species have no eyes
  12. 5 genera occur in Kansas
    1. Ixodes spp.
      1. about 40 species in North America; 8 are known to occur in Kansas, most probably statewide, and several more are likely present
        1. Ixodes brunneus (migratory birds)
        2. Ixodes cookei (small-medium sized mammals)
        3. Ixodes dentatus (rabbits)
        4. Ixodes kingi (badger and other medium-sized carnivores)
        5. Ixodes scapularis (Black-legged tick; commonly on deer in eastern and southeast Kansas; sometimes canids, humans)
        6. Ixodes sculptus (burrowing mammals; skunk)
        7. Ixodes texanus (raccon, badger, museltids)
        8. Ixodes woodi (woodrats)
      2. no festoons
      3. anal groove extends anterior to the anus
      4. tend to be dark ticks, with females often larger than males
      5. mouthparts of females more elongate than those of the males
    2. Amblyomma spp.
      1. festoons present
      2. anal groove extends posterior to the anus
      3. secondary palp segment elongate
      4. 2 species in Kansas
        1. Amblyomma americanum (Lone star tick; occurs in the eastern and southern potion of the state; on many mammalian species and is the second most commonly encountered tick in eastern Kansas; female with white of pink spot at base of scutum; males smaller than females and with 2 inverted half circles at margin of scutum)
        2. Amblyomma maculatum (Gulf coast tick; occurs in southern and eastern portions of the state; relatively rare; on multiple mammalian species including ruminants and cervids)
    3. Dermacentor spp.
      1. festoons present
      2. anal groove extends posterior to the anus
      3. all three palp segments short
      4. 3 known species in Kansas
        1. Dermacentor albipictus (Winter tick; throughout Kansas; mainly on large mammals such as deer and ruminants in the Fall; dark brown to grey in color with little ornamentation)
        2. Dermacentor parumapertus (Rabbit dermacentor; rabbits)
        3. Dermacentor variabilis (American dog tick; throughout Kansas; on many mammalian species and the most common tick encountered in the state; varigated white ornamentation on scutum pronounced)
    4. Haemaphysalis spp.
      1. festoons present
      2. anal groove extends posterior to the anus
      3. secondary palp segment flared laterally
      4. 2 species in Kansas
        1. Haemaphysalis cordelius (Bird tick; probably widespread in Kansas)
        2. Haemaphysalis leporispalustris (Rabbit tick; unknown distribution in Kansas)
    5. Rhipicephalus sanguineus (Brown dog tick)
      1. festoons present
      2. anal groove extends posterior to the anus
      3. basis capitulum laterally pointed, so that capitulum appears hexagonal
      4. tend to be brown and ornamentation not colorful (indistinct)
      5. throughout Kansas; introduced along with canids throughout the world; mainly on canids
  13. some sample diseases transmitted by hard ticks
    1. Babesiosis (protozoan; Babesia spp.) transmitted by multiple species and genera of ticks, depending upon the protozoan species
    2. East coast fever (Theileria parva) in cattle by Rhipicephalus appendicularis in Africa
    3. Ehrlichiosis (bacterium; Ehrlichia spp.) transmitted by multiple species and genera of ticks, depending upon the bacterium species
    4. Lyme disease (bacterium; Borrelia burgdorferi) transmitted especially by Ixodes scapularis
    5. Q-fever (rickettsia); respiratory infection typically caused by Dermacentor spp.
    6. Rocky mountain spotted fever (rickettsia) transmitted especially by Dermacentor andersoni; also Haemaphysalis leporispalustris between rabbits, Rhipicephalus sanguineus between canids; Amblyomma americanum
    7. Texas cattle fever (Babesia bigemina) transmitted by Boophilus annulatus
    8. Tick paralysis (not a pathogen); ticks that bite near base of skull can sometimes induce a gradual, and reversible, paralysis due to the salivary secretions
    9. Tularemia (bacterium) transmitted especially by Dermacentor andersoni (and other Dermacentor spp.)
  14. I ran across a couple of ancient "remedies" that employed ticks.
    1. in Europe, to arrest menstruation, women were sometimes instructed to ingest 9-10 ticks from a goat in wine
    2. also in ancient Europe, and a male certainly had to have thought this one up, spread the crushed contents of an engorged tick onto the legs of a woman. This was supposed to help overcome the dislike of sexual intercourse
    3. in China, a reputed early smallpox vaccine. Cattle ticks were mixed (1 tick for each year of life of the afflicted) with rice powder and molded into a cake. The child would then eat the cake on an empty stomach. As soon as the child passed a "foul" stool, the child would be immune. Considering that cowpox works for variolation, and that some engorged cow ticks should contain the cowpox virus from the blood meal, this treatment might have a certain degree of efficacy in some instances

FAMILY: Argasidae (soft ticks)

  1. capitulum subterminal in nymphs and adults
  2. no scutum; leathery-like body
  3. no festoons
  4. 2-8 (typically 5) nymphal stages
  5. most species feed often; do not engorge like hard ticks and feed quite rapidly (matter of minutes); larvae may take longer.
  6. 11 genera (i.e. Antricola, Argas, Nothoaspis, Ornithodoros, Otobius) and about 180 described species (Antricola and Nothoaspis only infect cave dwelling bats in the Western hemisphere)
    1. Argas spp.
      1. most parasites of bats or birds; sometimes other animals
      2. body is obviously textured (wrinkled)
      3. noctural feeders,
      4. i.e. Argas persicus (fowl tick; many types of birds, including chickens and turkeys); Argas cooleyi (cliff swallows)
    2. Ornithodoros spp.
      1. about 100 species; many feed on bats
      2. most important genus with respect to disease transmission
      3. body minutely wrinkled (not overtly obvious)
      4. most noctural feeders
      5. i.e. Ornithodoros capensis (marine birds); Ornithodoros hermsi (rodents in the Western US; sometimes humans)
    3. Otobius megnini (spinose ear tick)
      1. nymphs spiny in appearence
      2. larvae and nymphs prefer to feed just inside ear; adults do not feed
      3. main host cattle
      4. in many countries in the world, including North America
      5. similar species Otobius lagophilus on faces of rabbits in North America
  7. a typical disease transmitted by soft ticks is relapsing fever (Borrelia recurrentis), especially by Ornithodoros hermsi

ORDER: Mesostigmata

  1. about 250 described species are parasitic on vertebrates
  2. spiracles located just posterior and lateral to the third coxae
  3. usually a tube (tracheal trunk) extends anteriorly from each spiracle and can be seen through the cuticle. This is termed the peritreme
  4. bristle-like organ, the tritosternum, usually present immediately ventral and behind the gnathostoma
  5. generally, heavily scleratized bodies
  6. typical genera and species
    1. Varroa jacobsoni (honey bee mite) commonly found on European honey bees (Apis mellifera); the mite is actually a species complex and not just one species
    2. Dermanyssus gallinae (chicken mite) commonly found on chickens and pigeons; cosmopolitan
    3. Ornithonyssus bacoti (tropical rat mite) often found infesting mice in laboratory rodent colonies; cosmopolitan
    4. Sternostoma tracheacolum (canary lung mite) in respiratory tract of canaries; cosmopolitan

ORDER: Prostigmata

  1. spiracles either between chelicerae or dorsal on the mid-portion of the body
  2. generally poorly armored
  3. some species parasitic as adults; others only as larvae
  4. typical genera and species
    1. Demodex canis (dog follicular mite) may cause red mange in canids when secondary Staphlococcus pyogenes invade lesions; many other species of the genus in various animals; all cosmopolitan. i.e. Demodex injai on dogs; Demodex folliculorum and Demodex brevis in humans; Demodex cati and Demodex gatoi on cats; Demodex equi on horses; Demodex phylloides on pigs
    2. Psorergates ovis (sheep itch mite) can cause dermal problems in sheep
    3. Pyemotes tritici (straw itch mite) on grain beetles may attack mammals
    4. Eutrombicula alfreddugusi (North American chigger) and some other genera have larval stages that feed on blood. Nymphs and adults free-living. Often brightly colored. Some species may transmit scrub typhus, a rickettsia.
    5. Hannemania penetrans (Anuran trombiculid mite) with larval stages encysting in reddish or orangish "mite pockets" in skin of frogs in North America

ORDER: Oribatida (oribatid mites)

  1. stigmata and tracheae usually present, opening into a porose area
  2. mouthparts drawn into a tube, the camerostome, which may have a hood-like sclerite covering it
  3. none parasitic

ORDER: Astigmata (itch mites)

  1. no tracheal systems; tegumental respiration
  2. claws absent; sucker-like structures on pretarsi
  3. many species and genera
    1. Chorioptes bovis (mange in a variety of mammals; pierce skin but are non-invasive)
    2. Dermatophagoides spp. (dust mites that can result in allergies)
    3. Knemidokoptes laevis (depluming mite of chickens, pheasants, and ducks)
    4. Knemidokoptes mutans (scaley-leg mite of chickens)
    5. Notoedres cati (ear and facial mange in rodents, cats, and dogs; invasive where females burrow into the dermis)
    6. Psoroptes communis; many subspecies (mange in a variety of mammals; pierce skin but are non-invasive)
    7. Otodectes cynotis (mange in felids, canids, mustelids; pierce skin but are non-invasive)
    8. Sarcoptes scabiei (many subspecies where females invade and tunnel through dermis causing intense dermatitis)
    9. Dermatophagoides pteronyssinus (European house-dust mite) and Dermatophagoides farinae (American house-dust mite) both have worldwide distributions. Live in bed clothes, mattresses, carpets, and house dust and may cause allergies

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