About Ticks

Representing the Orma J. Smith Museum of Natural History (where he curates insects), Dr. James Ryan gave a 45 minute lecture about ticks to an audience of 300 pest control operators.  The presentation was a component of the Environmental Care Association’s Pest Expo held at the Doubletree Hotel in Boise on Dec 8-9, 2011.  Bob Hayes, a long-time O.J. Smith Museum volunteer, was presented with a plaque of appreciation for his service on behalf of the ECA at this meeting.  Ticks obtain all of their nutrition as blood from their vertebrate victims.  Worldwide there are 905 recognized species of ticks.  Some species subsist by multiple rapid (1/2 hr) feedings on multiple hosts while others develop all life stages through long feedings on a single animal.  They can transmit diseases while feeding.  Saliva of some species can cause fatal paralysis.  Pest control professionals should be knowledgeable about tick biology and their potential to cause harm.

Ticks are small arachnids in the order Ixodida. Along with mites, they constitute the subclass Acarina. Ticks are ectoparasites (external parasites), living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians. Ticks are vectors of a number of diseases, including Lyme disease, Q fever (rare; more commonly transmitted by infected excreta), [1]Colorado tick fever, Rocky Mountain Spotted Fever, tularemia, tick-borne relapsing fever, babesiosis, ehrlichiosis, Tick paralysis and tick-borne meningoencephalitis, as well as bovine anaplasmosis.

Ticks in Idaho are known to transmit at least five different diseases to people, plus several significantly harmful diseases to livestock.  A dozen cases of Lyme disease are confirmed here annually but, despite occasional contrary reports, the Ixodes pacificus and I. scapularis tick vectors of Lyme disease are not Idaho residents.  These two species require humid conditions.  Dr. Leslie Tengelsen of Idaho Health and Welfare has sought to unravel details of this issue.  Other bacterial diseases spread by ticks include anaplasmosis and erlichiosis to cattle and other vertebrates including humans (Dr. Glen Scoles, Washington State University).  Anaplasmosis may be fatal to adult cattle which did not develop immunity through exposure while young.  Colorado Tick Fever is a human viral disease occasionally reported in Idaho.  Ticks divide into two groups: soft-bodied and hard-bodied ticks.  Soft-bodied ticks feed rapidly and walk efficiently.  They are commonly found at breeding bird colonies and in rodent burrows.  One Idaho species found in cabins and at deer bedding sites sometimes transmits a relapsing fever disease (Borrelia hermsii) to sleeping hunters and hikers.   Soft-bodied ticks may survive for years without feeding.  They behave like bedbugs (but do not resemble these insects).

Hard ticks are the group familiar to most out-of-doors enthusiasts.  Adults attach to feed for as many as 10 days.  They have three active feeding stages, from tiny six-legged “seed ticks” to 8 mm unfed adults.  Engorged adults are balloons of condensed blood, weighing up to 400X their unfed weight.  People active near rivers and lakes in springtime can acquire them when walking through vegetation.  Ticks usually move to a quiet part of the host, such as the waistband, neck, or back of a knee, where they attach to feed.  They change little in size until the final day of attachment, when females have a “feeding burst”.  Engorged ticks drop to the ground where they deposit an average of 6,000 eggs (maximum count 22,000).  Hard ticks “glue” their mouthparts into the host with saliva.  Some species, such as the rabbit tick Haemaphysalis leporispalustris, attach shallowly and are therefore comparatively easy to remove.  Some Ixodes ticks attach deeply and glue themselves so securely in place that skin may tear when they are removed.  When removing a tick, lift patiently at the site of attachment to allow it to withdraw its mouthparts.  Fine forceps, and tick lifters sold in sporting goods outlets, are effective tools for removing attached ticks.  Hot match heads, kerosene, and other such removal remedies endanger the host in many ways.  They should be avoided.

Idaho’s winter tick, Dermacentor albipictus, spends all three feeding stages—larva, nymph and adult—on one animal such as a moose.  In fall clusters of thousands of larvae climb grasses, clinging to each other in a cranberry-size clump.  They grab onto hairs of passing animals as strings of larvae.  Once aboard, these pirates feed, moult, feed again, moult again, feed AGAIN, mate and drop off.  Burdens on individual animals can reach half a million ticks, with the average burden being 30,000.  Moose distressed by tick salivary antigens may rub off so much hair that they are described as “ghost moose”.

Control of ticks and the diseases they transmit requires knowledge of tick biology. Rodents are critical links in the chain of several tick-borne diseases. The currently popular chemical Frontline paralyses ticks feeding on pets.  Feed lots limit the exposure of cattle to ticks.  Personal protection strategies include wearing light colored clothes to make ticks easy to see, tucking pant cuffs into boots, and using repellants.  Dogs and wildlife may carry engorged ticks into residential environments, where their offspring may create unusual loci of tick populations.  Thus, Bambi in the front yard may be understood to present a health risk (and a traffic hazard).