II.  Phylum Arthropoda--Class Arachnida

Reading Assignment:  
Foreyt pp. 104 - 105
(Morphology & ID Key)

Reading Recommendation:
Background Info on Biology of Ticks

1. Introduction
   
   
   1. Groups-
      1. Spiders  (venomous, not parasitic)
      2. Ticks
      3. Mites
         
         
   2. Infestation is called "acariasis" because ticks and mites belong to Order Acarina

    

2. Ticks
   1. General
      1. Type-  obligate periodic ectoparasites
      2. Host specificity-  low
      3. Food-  obligate blood feeders

2. Topology-
   
   1. Capitulum  (mouthparts)
   2. Basis capitulum  (connect mouthparts to idiosoma)
   3. Idiosoma  (fused head, thorax and abdomen)
   4. Scutum 
      • Ornate-  white markings
      • Inornate-  solid color
   5. 8 legs (4 pair)

3. Life cycle-

4. Pathology-
   
   

   1. Worry-  general loss of condition

      • Lack of weight gain or inability to maintain weight

      • Poor hair coat

      • Lack of stamina

      • "Ain't doin' right"
        
        

   2. Anemia-

      • Ticks ingest blood

      • Many ticks over a long period of time may cause anemia
        
        

   3. Dermatitis-

      • Bite is painless  (saliva has anesthetic)

      • Saliva also contains anticoagulant-  chemicals can cause immune response (pruritis)

      • Secondary bacterial infection may occur
        
        

   4. Vector-

      • Because ticks are blood-suckers, transmission of pathogens occurs, including...

      • Viruses  (such as the ones that cause encephalitis)

      • Bacteria  (such as the ones that cause plague & tularemia)

      • Rickettsias  (such as Ehrlichia and Borrelia)

      • Protozoa (such as Babesia)
        
        

   5. Paralysis -

      • Occurs only rarely in the United States (it can occur, but it is most common in Australia)

      • The most commonly affected animals are ruminants, with dogs and children also susceptible

      • The saliva of some females of some strains of some species of ticks causes an ascending flaccid paralysis
        
        

5. Tick Management and Control:
   
   

   1. The best way to deal with a tick infestation is to prevent it from happening in the first place!

      • Avoid likely tick-infested areas

      • Use repellents on animals-  tick collars, spottons (ex. Frontline(R), dips, sprays...)

      • Use repellents on people (DEET), wear long pants and long sleeves and tuck your pants into your socks!
        
        

   2. After entering a possible tick-laden site, search yourself and your friends (human and animal), using a routine pattern to examine the entire body
      
      

   3. When removing ticks, follow these precautions:

      • Wear gloves

      • Disinfect the bite site

      • Don't squeeze the idiosoma (it will inject whatever pathogens are present in the tick into the host!)

      • Dispose of the tick so that it cannot parasitize anyone or anything else
        
        

   4. Tick removal should be performed as follows:

      • Grasp the tick's capitulum as close to the skin as possible using forceps (tweezers)

      • Gently rock and pull the tick so that it releases it's hold

      • DON'T YANK...you'll leave part of the capitulum behind, possibly producing an infection!
        
        

   5. DO NOT USE:

      • Cigarettes, matches or other flames

      • Kerosene (especially just before using a cigarette!)

      • Vaseline...
        
        

6. Soft Ticks  (Family Argasidae)
   
   

   1. Appearance-

      • Ventral capitulum  (not visible)

      • Oval to pear-shaped

      • Inornate idiosoma

      • Thick leathery integument

      • No scutum
        
        

   2. Importance-

      • Most have minimal importance in the eastern US

      • Spend most of the time in nests or burrows

      • Feed nocturnally for several hours

      • May cause irritation, severe anemia and/or death
        
        

   3. Examples-

      • Argas persicus  (fowl tick of birds)

      • Otobius megnini  (spinose ear tick- cattle (dogs))
        
        

7. Hard Ticks  (Family Ixodidae)  (Pictorial key)
   
   

   1. Appearance-

      • Dorsal capitulum  (visible)

      • Scutum  (smaller on the female so she can ingest a larger blood meal)

      • May be necessary to send to a reference lab for accurate ID
        
        

   2. Life history-

      • Feeds once per life stage, then molts

      • Number of hosts needed varies with the species (one to three separate host for the life cycle)

      • Ticks looking for a host "quest"-  climb vertically on vegetation 
        
        

   3. Habitat of ticks varies, but is generally edges (brushy areas) between woods and fields, with populations extending into the woods and on to lawns
      
      

   4. Hosts-

      • Mature ticks are usually found on larger animals, such as dogs, deer and people

      • Immature ticks are usually found on smaller animals, such as mice, voles and rabbits
        
        

   5. Rhipicephalus sanguineus-

      • Brown dog tick

      • ID:  inornate scutum with posterior perianal groove, festoons, and hexagonal basis capitulum

      • Adult ticks are 5 - 15 mm longs

      • These ticks can move indoors in the winter (into barns, sheds, garages, etc.)
        
        

   6. Dermacentor variabilis-

      • American dog tick

      • ID:  ornate scutum, festoons and rectangular basis capitulum

      • Adult ticks are 5 - 15 mm long

      • The closely related Rocky Mountain wood tick (D. andersoni) transmits Rocky Mountain spotted fever and there are populations established in the eastern US  (D. variabilis is also capable of transmitting this pathogen)
        
        

   7. Ixodes scapularis-

      • When first identified, I. scapularis was named Ixodes dammini;  however, further study revealed that these two ticks were the same animal, and the original I. scapularis was adopted as the official name.

      • Common name-  deer tick

      • ID:  inornate scutum, anterior perianal groove, no festoons and a rectangular basis capitulum

      • Size-

        • Adult-  size of a sesame seed (2 - 4 mm)

        • Nymph-  size of a poppy seed (1 - 2 mm)

      • Habitat-  brushy areas and into lawns

      • Hosts-

        • Immature-  white-footed deer mouse (and others)

        • Mature-  white-tail deer (and any others)

      • Life history-

        • Each life stage feeds several days to repletion and then drops off and molts

        • Life cycle-
          Female lays eggs in spring in environment
          Larvae hatch in early summer
          Find host (mouse) & feed in July thru Sept
          Overwinter & molt into nymphs next spring
          Find new host (mouse) & feed in May thru August
          Drop off & molt into adult ticks in fall
          Adult ticks find & feed on host (deer)

      • Pathology-

        • General pathologic effects caused by any tick

        • Vector for Lyme disease & granulocytic ehrlichiosis

        • Lyme disease  (Borrelia bergdorferi)-
          Most common tick-borne diseae in the US
          Transmitted primarily by nymph
          Transmission 24-48 hr after beginning feeding
          

         

Review Questions:

1. What type of parasites are ticks?  What does this mean?

2. List the effects of ticks on the hosts.

3. Describe how to remove a tick from an animal.

4. What is the general habitat of a tick?

5. On what animals, in general, are immature ticks found? are mature ticks found?

6. What is the common name of Ixodes scapularis?  What is the previous scientific name?

7. On what animals are immature deer ticks found?  are mature deer ticks found?

8. What is the importance of Ixodes scapularis?