Ticks: Host Seeking Behavior, Feeding, and Control

Lecture 15

What is host seeking behavior?

includes specific behavioral reactions that contribute to finding a host (questing)

Define Nidicolous

ticks that live mainly in or near a host’s nest, burrow, or resting place rather than questing

Define Non-Nidicolous

ticks that do not live on or in the nests of their host animals during their feeding or resting phases

Questing Strategies in Nidicolous Ticks

• Nidicolous ticks rarely quest outside of the host dwelling

• Most of the argasid ticks are nidicolous

• Their behavior is coordinated with the activity of the host

  • EX: ticks will only drop off in the shelter occupied by the host

  • Ixodes lividus larvae hatch when sand martins arrive from their overwintering sites and molt into nymphs to feed on hatchling birds

• They are one-host ticks

Questing Strategies in Non-Nidicolous Ticks

• questing ticks seek a host in open opens: forests, meadows, pastures

• climb vegetation and spread their first pair of legs that contain their sensory organs (Haller’s organ) and wait for the host

• Moisture and temperature are the main factors determining the tick’s daily rhythm of climbing vegetation and descending to leaf litter

• height at which ticks climb depends on the size of the host

  • immature stages feed on smaller animals (rodents)

  • adults feed on large animals (deer)

• Ticks that live in harsh environments can mix strategies

  • EX: Hyalomma asiaticum immatures behave like nidicolous ticks but adults quest

    • Hyalomma adults can run

Evolution of Questing Strategies and Adaptations

• believed that nidicolous strategies are adaptations from questing strategies

• supported by the fact that the older subgenera of Ixodes (primitive genus) have questing strategies

Examples that Support Evolution of Questing Strategies & Adaptations

• I. trainguliceps

  • vertical migration is limited (size of the host)

• Hyalomma adapted their life cycle to harsh environments

Morphological Adaptations to Questing Strategies

1. Haller’s organ = olfactory organ

2. Strongest stimuli is direct contact: Surveillance

3. Simple eyes

   1. they do not have very good eyesight

4. Passive vs. hunting behavior

Define Haller’s organ

• located in the dorsal tarse I of the first pair of legs

  • CO2, pheromones, Kairomones

• Most characteristic adaptation to question

Define Eschar

scar lesion at site of tick bite

Duration of tick feeding

• Larvae —> 3-6 days

• Nymph —> 3-10 days

• Adult —> 6-12 days

Factors influencing feeding duration

1. Reproduction

2. Host species

Reproduction in Influencing Feeding duration

unmated females can extend their feeding up to several weeks

Host species in Influencing Feed duration

• body temperature influences feeding

• ticks take longer to complete feeding on reptiles

Day-night Rhythms of Drop-Off

NOTE: limited mobility so drop-off is key

• Day-night rhythms allow ticks to detach in favorable natural environments for development, oviposition and host location

• Host behavior regulates drop-off behavior

  • 2- or 1-host ticks that feed on the same host (cattle for example) drop off in stables at night in summer while in the fall and spring they can drop off either in pastures or stables.

Drop-offs for Nidicolous vs. Questing Ticks

• Generally, questing ticks drop off when their host is active

• Nidicolous ticks drop off when their host is not active

Tick Location on a Host’s Body

• Tick species that parasite one host have a preferred location depending on the stage

• In general, ticks feed on the ears and heads of small rodents and birds

• Factors that affect tick localization: microclimatic conditions and tick density

Examples of Preferred Tick Location on Host’s body

• H. anatolicum immatures parasite ears

• Adults parasite the groin, udder and axilla (cattle)

Tick Control

• Tick management relies on traditional approaches using pesticides and repellents

• Ticks are vectors for human diseases (animal) & cause an extensive economic loss

• There is not a “Magic bullet”

Tick Control for Commodity Protection

• Tick in control in agriculture is often based on the traditional integrated pest management (IPM) approach

  • the cost of the control program is compared to the value of the commodity protected in a cost-benefit analysis

  • Basically: See how much ticks are damaging the products or livestock (cows)

    • NOTE: If it’s worth treating, treat it. If not, don’t

• Integrated tick management requires the comparison of the effectiveness of various techniques, alone and in combination

  • EX: introducing tick vaccination of cattle with management methods such as the use of pesticides and sterile hybrid larvae release

Tick Control to Manage Human Disease Risk

• the benefit of preventing a case of human disease cannot be translated into dollars

• in this case, the question is how to apply available resources to minimize the disease risk

  • (1) Computer simulations

  • (2) Field trials

• Tick abundance and frequency of infection contribute to the human risk of acquiring diseases but not to how the disease circulates in animals

Issue with Computer Simulations and Field Trail in Tick Control

• (How to apply available resources to minimize disease risk)

• Computer simulations and field trials

  • Assume areas that have forests, but most people get bitten in their own backyard

• In order to field trials, you need studies that go on for 8-10 years

  • Tick populations are affected by the whole ecosystem

  • Difficult to figure out which factors are involved in tick abundance

Personal Protection

Includes Acaricides (permethrin) or Repellents (DEEY)

Advantages of personal protection against ticks

1. they can be applied by an individual

2. they can be combined with other tick management methods

3. few adverse environmental effects

Disadvantages of personal protection against ticks

1. problematic to implement at a larger scale

What are targeted pesticide applications?

• applied directly at ticks attached to animal host

Examples of Targeted Pesticide Applications

1. Tick tubes

2. Bait boxes

3. Four posts (rollers for deer)

Management targeted at tick reproduction

• mating disruption using sterile male techniques

  • a large number of individuals are released

  • sterilization does not interfere with mating

  • females only mate with one individual

• Mating disruption using tick pheromones

  • pesticides applied along with pheromones

What are the biological control of ticks?

1. Predators

2. Parasitoids

3. Pathogens

Define parasitoid

an organism that lives in close association with its host at the host’s expense, eventually resulting in the death of the host

Predators as a Biological Control of Ticks

• there are many generalist predators including invertebrates (spiders, beetles, ants), birds, and reptiles

• EX: Two African oxpecker species that specialize on ricks

  • Can control ticks on cattle

  • but population is decreasing due to insecticide toxicity

  • they like to eat them engorged

  • like to maintain wounds open and feed directly on the blood of cattle

Parasitoids as a Biological Control of Ticks

• EX: Ixodiphagus hookeri

  • poor results

Pathogens as a Biological Control of Ticks

• Virus

• Bacteria: Wolbachia

  • not well characterized in ticks

  • disrupt reproduction

  • cause mortality

• Fungi: Beauveria bassiana and Metarhizium anisopliae

Factors of Tick Control in Host and Habitat

1. Control of the reproductive host

2. Vaccination of host

3. Habitats and Landscape

Control of the Reproduction Host

• it has a limited impact

1. Hunting

2. Fencing

Vaccination of host

• to control tick population: already used in the cattle tick

• to control pathogen transmission

Habitats and Landscape

• tick abundance

• vertebrate host abundance and diversity

• landscape design affect human and tick encounters

Preventing Tick Bites

1. Know where to expect ticks

2. Treat clothing and gear

3. Use EPA-registered insect repellents

4. Avoid contact with ticks

5. Check clothing for ticks

6. Examine gear and pets

7. Shower soon after being outdoors

8. Check your body for ticks after being outdoors

Preventing ticks in the yard

1. Apply pesticides outdoors to control ticks

2. landscaping techniques that can help reduce black-legged tick populations

How to Remove a Tick

1. Pull upward with steady, even pressure. Don’t twist or jerk the tick; this can cause the mouth parts to break off and remain in the skin. If this happens, remove the mouth parts with tweezers. If you are unable to remove the mouth easily with clean tweezers, leave it alone and let the skin heal

2. After removing the tick, thoroughly clean the bite area and your hands with rubbing alcohol or soap and water

3. Use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible

4. Never crush a tick with your fingers. Dispose of a live tick by putting it in alcohol, placing it in a sealed bag/container, wrapping it tightly in tape, or flushing it down the toilet.