Prevent Disease, Disability and Premature Death

Tick Biology & Control Tick Biology & Control

Prevent Disease, Disability and Premature Death

Relate the biology of ticks to appropriate control measures.

Objectiveهدف

Prevent Disease, Disability and Premature Death

Characteristics

Life Cycle

Habits

Disease Agent Transmission

Surveillance and Control Measures

Overviewمرور

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Ticks are arachnids:cousins of spiders and scorpions

Represent a very important group of vectors of arthropod-borne diseases.

These diseases include:Rickettsiae: Boutonneuse Fever, Q-Fever, etc.Spirochetes: Relapsing fever, etc.Other bacteria: tularemia, mycobacterium, etc.Viruses: Crimean-Congo HFProtozoa: Babesia, Theileria, trypanosomes, etc.

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Disease Agents Transmitted By Ticks

Worldwide, they rank number two behind mosquitoes as vectors of disease.All life stages are obligate blood feeders Hosts can come from virtually any vertebrate group including mammals, reptiles, birds, and amphibians.Ticks are divided into two distinct families—hard ticks (Ixodidae) and soft ticks (Argasidae).

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GENERAL TICK MORPHOLOGY AND BIOLOGY

Hard ticks & soft ticks are very different in appearance,biology, and behavior.

Illustration available on-line at www.howstuffworks.com

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Which is which?Mouthparts NOT

visible from above

Mouthparts visible from

above

Soft Tick Hard Tick

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Hard Ticks (Family Ixodidae)Have a stiff, leathery cuticle on their back called a scutum

Covers entire back of the maleA small plate on back of female

Mouthparts project off the front of the tick and are visible from above

Males are smaller than females

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HARD TICKS (FAMILY IXODIDAE)

• Sexual Dimorphism: males are smaller than females

Left to Right: Attached male, attached gravid female, attached gravid & engorged female

Sexual dimorphism is the systematic difference in form between individuals of different sex within the same species.

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Life cycle of hard ticks

• Egg• Larva -- 6 legs• Nymph -- 8 legs, but

sexually immature• Adult -- 8 legs, sexually

mature• Molt (shed skin) only

once between each successive life stage

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Life cycle of hard ticks

• Female lays thousands of eggs at one time

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Life cycle of hard ticksLarval ticks emerge seemingly all at once and only have six legs during this stage

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Life cycle of hard ticks

After molting and developing their last pair of legs, nymphal ticks seek a blood meal from smaller animals.

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Life cycle of hard ticks• Nymphal ticks molt into

adults, and seek out larger animals for a blood meal.

• Adults attach tightly to host and feed over a period of hours, days, or weeks.

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Life cycle of hard ticks

• Adults mate on the host, usually reproduce only once.

• Adult female falls to the ground, lays eggs, and dies shortly thereafter.

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Soft Ticks (Family Argasidae)

Males and females are very similar in appearance

Lacks a scutum

Body ranges from fleshy to leathery in texture

Mouthparts are located underneath the body towards the front, and are not visible from above

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Soft Ticks (Family Argasidae)

Ventral side of a soft tick.

Note that the mouthparts are

tucked underneath

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Egg -- Very hardyLarva -- 6 legsNymph -- 8 legs, but sexually immature

Molt 5-7 times during nymphal life stage

Adult -- 8 legs, sexually mature

LIFE CYCLE OF SOFT TICKS

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Mate off the host, reproduce several times.Attach to host only to feed

Loosely attach & feed rapidly

Hide in cracks & crevices of host’s nest, bedding, or home

LIFE CYCLE OF SOFT TICKS

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High vector potentialGreat Reproductive Capability

Can lay a tremendous number of eggs

Production of several thousand eggs isn’t uncommon

Persistent Bloodfeeders

If they’re not feeding on a host, they’re looking for one

Ticks climb vegetation and “grabs” the host as it passes. This is known as “questing.”

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High vector potential

Relative Freedom from Natural Enemies

There’s not too many things that eat ticks

Fire ants seem to like them fine

Encyrtid Wasp only known parasitoid

Photo by: Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org

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High vector potentialSlow Feeding

Hard ticks take up to 2 hours to find an attachment point.

Usually requires 4 - 24 hours of feeding before the pathogens leave the tick and enter host

A hard tick may take 5 - 7 days to feed

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Wide Host Range1-, 2-, or 3- host ectoparasites. Risk of disease transmission greatly increases with multiple host ticksE.g., the black-legged tick feeds on mice as a larva, larger animals like raccoon as a nymph, and deer as an adult.

HIGH VECTOR POTENTIAL

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Longevity

Hard ticks may live 3 - 5 years

Soft ticks may live 15 - 20 years

Transovarial Transmission Of Pathogens

Pathogen is passed from the female tick to the embryonic egg

When the eggs hatch, the larvae emerge already infected with the pathogen

Ticks are thus reservoirs for diseases

HIGH VECTOR POTENTIAL (HARD TICKS)

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Hard Ticks“Transitional Zones”

Deep woods

Shrubby areas

Shorter grasses and weeds

Vegetation along animal trails

On the host

Soft Ticks

Cracks and crevices of host’s burrow

Abandoned dwellings and caves infested by animal hosts

TICK HABITAT

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Drag Cloth Method

TICK SURVEILLANCE

Flannel Sheet & Dry Ice

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Vegetation ReductionCut-back or totally remove habitats

Host ExclusionConstruct physical barriers to keep tick-infested hosts out of areas where personnel will inhabit.

TICK CONTROL

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Pesticides General area application for hard ticks is impractical since they spend most of time on host

Treatment is only temporaryMay serve well as a barrier treatment around tents or areas requiring protection against ticks

TICK CONTROL

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Personal Protection from Ticks

Avoidance

Refrain from entering areas that are known to be infested with ticks.

Reduce activities in those areas when complete avoidance is impractical.

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Proper Wear of Clothing

This includes wearing clothing that will prevent ticks from reaching your skin, such as long sleeves and long pants.

Tuck your shirt into your pants and your pant cuffs into your socks or boots.

Personal Protection From Ticks

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Personal Protection from Ticks

Tape Barriers Wrap double-sided tape or regular tape with the adhesive side out to form a sticky barrier which will form an external barrier on your uniform. Ticks are “unidirectional” (travel in one way—upward) and will get stuck as they climb up your pants.

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Repellents (covered in detail in PPE lecture)Permethrin (Aerosol or IDA kit) treatment of uniform.

DEET lotion for skin.

Personal Protection from Ticks

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Tick removal

Search for and remove ticks as soon as possible

The longer the tick remains attached, the more engorged and difficult it becomes to remove

The longer the tick remains attached, the more likely the chance of infection, disease transmission, or tick paralysis

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Tick removal

DON’T “bare hand” ticksTicks may shed pathogens in their feces at any time, and these may contaminate cuts or abraded skin

Fingers contaminated with infected feces may introduce pathogens (especially viruses & rickettsias) through the mucus membrane of the nose or eyes

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Tick removal

DON’T use VaselineWON’T WORK!!!Ticks cannot be suffocated (Acquires oxygen needs from your blood)Tick leaves only when it has finished feedingThe longer it remains attached, the greater chance for disease transmission

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Tick removal

DON’T use Fingernail Polish

WON’T WORK!!!Ticks cannot be suffocated (acquires oxygen needs from your blood)Tick leaves only when it has finished feedingSolvent in fingernail polish may irritate tickIrritated tick may regurgitate gut contents and pathogens into your blood…increasing chance of infection

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Tick removal

DON’T use Matches/Fire

WON’T WORK!!!Tick might be killed and will never leaveAt the very least, tick will be irritatedIrritated tick may regurgitate gut contents and pathogens into your blood…increasing chance of infectionPotential damage to skin may enhance pathogen transfer into body

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Tick removal

DON’T use Gadgets/PliersUsually Don’t Work!!!Tick will be crushed or at least squishedSquished tick will have gut contents and pathogens squished into your blood

May cut the tick from its mouthparts, leaving the mouthparts in the wound and causing possible infection

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Tick removal

USE Fine-Pointed ForcepsGrasp tick by mouthparts as close to skin as possible (Figure 1)Using slow & steady pressure, gradually pull tick from skin (Figure 2). Skin may stretch a bit, but that is okay.

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Tick removal

USE Fine-Pointed ForcepsAfter tick detaches, check the mouthparts (Figure 3)

If clump of your skin attached, you got the whole tickIf no clump of skin attached, mouthparts broke off in skinSecondary infection possible if mouthparts not removed

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Summary

Characteristics

Life Cycle

Habits

Disease Agent Transmission

Surveillance and Control Measures

Prevent Disease, Disability and Premature Death

Questions?

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