29
Aug
2012
TICKS: Part 2
ticksp2

Please remember that this blog cannot be a substitute for the expertise and services of a pest management professional, nor can all aspects of this important topic be covered in a blog.

In this second of two blogs on ticks, we’ll discuss the second group of two species, the American dog and brown dog ticks. American dog ticks are found where small and large animals frequent, readily bite humans, and vector/transmit diseases. Brown dog ticks are found only where dogs frequent and are commonly brought into homes on pet dogs, rarely bite humans, and usually do not vector/transmit the causal organisms of diseases affecting humans.

In the July blog on ticks, the first group of two species (black-legged/deer and long star ticks) was discussed. These species are typically encountered outside the home while walking in yards/parks or hiking and are important vectors of the causal organisms of diseases affecting humans. Also discussed in July was tick identification, avoiding tick bites, safe removal of ticks, and tick habits.

RECOGNITION. Ticks are arthropods but are not insects because they have only 2 body regions (insects have 3), lack antennae (insects have antennae), and they usually have 4 pairs of legs (insects have 3 pairs). Adults are usually oval in shape and flattened, but they swell up and become enlarged with a blood meal. Seed ticks are the first tick out of the egg and they have only 3 pairs of legs.

Identification to species is critical because different species vector different disease causing organisms. If bitten, be sure to carefully remove the specimen, put it in rubbing alcohol, and take it with you to the doctor. A pest management professional using a microscope is often necessary to confirm species identification.

American dog tick (scientific name is Dermacentor variabilis). Unengorged adults are about 3/16″, but when engorged with blood, they swell up to 5/8″ long and 3/8″ wide. Their color is brown with whitish to grayish markings on the area/shield just behind the mouthparts. This shield is restricted to the front half in the female, but covers most of the top in the male. Their abdominal has rectangular areas divided by grooves along its rear margin.

Brown dog tick (scientific name is Rhipicephalus sanguineus). Unengorged adults are about 1/8″, but when engorged with blood, they swell up to 1/2″ long. Their color is reddish brown, but when engorged with blood, the engorged parts of the body change to gray-blue or olive in color. Their dorsal shield (area just behind the mouthparts) is restricted to the front half in the female, but covers most of the top in the male. Their abdominal has rectangular areas divided by grooves along its rear margin.

DISEASES THEY VECTOR.

  • American dog tick. This tick is an important vector of Rocky Mountain spotted fever and tularemia, and also causes tick paralysis.
  • Brown dog tick. This tick will only occasionally feed on humans, and it may vector Rocky Mountain spotted fever.

DISEASES.

  • Rocky Mountain spotted fever (RMSF). There are about 2,000 cases reported each year in the United States. The typical indication of infection is fever, rash, and a history of a tick bite; other indications are malaise, severe headache, chills, and myalgias, and sometimes gastrointestinal symptoms of abdominal pain and diarrhea. The rash typically begins on the fifth day, starting on the extremities and then spreading to the rest of the body; there are a few cases of RMSF with no rash. It can be successfully treated about 96% of the time with one of the tetracyclines, but if left untreated, the mortality rate is about 20%.
    RMSF is transmitted by the bite of an infected tick. Of the ticks that vector the disease, generally only about 1-5% of such ticks in a given area are infected.
  • TICK PARALYSIS. No disease organism is involved. It is believed that a neurotoxin produced in the tick’s ovaries causes the problem. It travels to the salivary glands and is then secreted by the tick into the host as it feeds.

HABITS AND CONTROL.

  • American dog tick. Follow the habits and control information given in the July blog.
  • Brown dog tick.
    • Habits.
      • The problem is that the engorged adult female drops off the dog and climbs upwards to find a sheltered spot (wall hangings, pictures, ceiling, roof) to lay her mass of 1,000-3,000 eggs that hatch in 19-60 days.
      • Although dogs are the preferred host, they will feed on other mammals including domestic animals and humans.
    • Control.
      • The application of residual pesticides will be required more than non-chemical measures for this tick. Remember that this tick is a pest only in areas that dogs frequent, not in the fields and woods.
      • Removal of weeds and brush, along with properly mowed grass will reduce tick build up and the need for insecticide application.
      • Because these ticks can drop from any dog any time, leash laws are helpful as is a coordinated community control effort.
      • Inside the home or kennel, thoroughly clean and remove all debris to reduce tick hiding places and facilitate pesticide application. Wash pet bedding.
      • The dog/pet must be treated on the same day as the premises are treated.
      • The treatment of structures and grounds must be comprehensive, so the services of a pest management professional are advised.

-- Eric H. Smith, PhD, BCE
Dodson Bros.
8/2012