Dangers of Disease-Carrying Ticks
Posted By Nancy Houser on September 17, 2009
The ixodes, or deer tick.
With the fall quickly approaching, this is the time when the adult female blacklegged or deer tick (Ixodes scapularis) is capable of transmitting the Lyme disease infection, one of the most common tick-transmitted diseases in the world and caused by the spirochete Borrelia burgdorferi. Meanwhile, the nymphal stage of the tick transmits the infection in the spring.
The Dermacentor, or dog tick.
Other diseases transmitted by ticks are Rocky Mountain spotted fever and tularemia carried by the American dog tick (Dermacentor variabilis) and possibly ehrlichiosis (carried by both the dog and deer tick) which feeds on humans, medium to large mammals such as dogs and raccoons. The long star tick (Amblyomma americanum) transmits tularemia and other diseases including one similar to Lyme disease but milder.
Description of the tick
The tick belongs to the arachnids group — scorpions, spiders and mites — as they have four pairs of legs when adults and have no antennae. Meanwhile, insects have three pairs of legs and one pair of antennae. Ticks basically are the most efficient carriers of disease for several reasons:
- They attach firmly when sucking blood
- They feed slowly
- They are unnoticed for long lengths of time when they are feeding, which takes several days.
Stages of the tick involved four life stages: (1) an egg, (2) a six-legged larva or “seed tick”, (3) an eight-legged nymph, and (4) as an adult. Once the egg hatches, the seed tick begins to feed on an appropriate host with the larva molting or developing into the large nymph.The nymph then feeds on a host before changing into the larger adult. As male and female adults, they then find and feed on a host with the females laying her eggs after her feeding.
If a person finds a tick on their scalp, it probably has come from the lower parts of their body. The tick will patiently wait for host animals or people from the grass and shrub tips (not from trees). When a host brushes by, they will crawl onto them as they fly or jump. Some species of ticks are so determined to find a host they will crawl several feet toward it before attaching. Cooler weather is not a determinant as they can actively survive on winter days when the temperature of ground reaches 45 F. degrees.
Types of Ticks
The two types of ticks are the “hard tick” and the “soft tick”. The soft ticks are usually on birds or bats for feeding, seldom encountered by people unless the animals are roosting or nesting in an occupied building. With all the types of tick species in the world, the most common type to be encountered by people are the American dog tick, the lone star tick, the blacklegged (deer) tick, and the brown dog tick.
TYPES OF TICKS
American Dog Tick (Dermacentor variabilis): The most common tick encountered by people overall is the American Dog Tick which also is referred to as the wood tick. Its larvae and nymphs will feed on mice and birds, while as an adult it will feed on humans and medium to large mammals, for example the dog or raccoons.
As stated previously, the American dog tick is best known for transmitting Rocky Mountain spotted fever, tularemia and possibly ehrlichiosis to humans. Recently ehrlichiosis has been traced to both the dog and deer tick as carriers, with ticks transmitting the disease in their saliva. The clinical disease ehrlichiosis can occur after approximately a 1-to-3 week incubation period and can occur at any time of the year.
An engorged female deer tick before laying her eggs.
The Blacklegged or Deer Tick (Ixodes): In the eight-legged brown nymph stage, the deer tick will feed on mice, people and any warm-blooded host. In the fall, they are molting into adults and primarily feed on deer, with the females laying eggs the following spring. The adult deer tick is about half the size of the American dog tick.
Carrying one of the more serious diseases and most common tick-transmitted diseases in the world, the infection of the dreaded Lyme Disease takes place after the female tick has become engorged on the blood of the host.
Two periods when this disease becomes transferred is in the spring from the deer tick’s nymphal stage and in the fall as an adult female, with each Ixodes tick having a two-year cycle. The initial infection in the tick develops in the spring when the tick larvae is feeding on white-footed mice which are usually infected with the larvae molting in into nymphs, still feeding on mice.
Lyme vaccination has been found to be quite effective in dogs that have not been previously exposed to Lyme disease, so beginning the vaccinations in young dogs is advisable. Once the dog or human is infected from the bite of the tick, the incubation period prior to obtaining Lyme Disease is about 2-to-5 months.
Clinical signs of Lyme Disease:
- Recurrent acute arthritis
- Lameness with swollen and warm joints painful to the touch for 3-to-4 days
- Fever
- Anorexia
- Depression
- Stiff walk
Brown Dog Tick (Rhipicephalus sanguineus): The brown dog tick (also known as the kennel tick) is found in most of the United States, with dogs as its preferred host even though it can feed on a wide variety of mammals such as rodents or deer. Unique among ticks, the brown dog tick can complete its entire life cycle indoors which allows it to establish entire populations rather quickly in colder climates throughout the world. This is because it prefers warmer areas inside regardless of the weather temperature outside.
The brown dog tick is very small and reddish-brown in color. A fully blood-fed female brown dog tick can lay up to 5000 eggs; the number of eggs laid depends on the size of the tick and the amount of blood she ingested with heavier infestations occurring in warmer climates.
“High levels of infestation can cause skin irritation and damage in dogs, and the population can reach pest proportions in houses and kennels. In the U.S., R. sanguineus is a vector of disease in dogs; canine ehrlichiosis (Ehrlichia canis) and canine babesia (Babesia canis). These rarely cause disease in humans; only a few cases are known. In dogs, symptoms of canine ehrlichiosis include lameness and fever; those for babesiosis include fever, anorexia and anemia. Both have been found in Florida.’
“In parts of Europe, Asia and Africa R. sanguineus is a vector of Rickettsia conorii, known locally as Mediterranean spotted fever, boutenneuse fever, or tick typhus. Rhipicephalus sanguineus has not been shown to transmit the bacteria which causes Lyme disease.” (University of Florida, “Featured Creatures“)
The Lone Star Tick
The Lone Star Tick (Amblyomma americanum): The lone star tick’s distribution, abundance and range have seriously increased recently, known to readily and aggressively feed on humans, dogs and cats who bring them indoors on their body where they can exist very well. Their bite is very red and uncomfortable, known to be quite irritating.
The diseases this tick is known for is Human Monocytic Ehrlichiosis, Tularemia and possibly Rocky Mountain Spotted Fever. New information is available regarding a disease called STARI – Southern Tick Associated Rash Illness. Patients bitten by lone star ticks will occasionally develop a circular rash similar to the rash of early Lyme disease even though the tick does not transmit Lyme disease. This rash may be accompanied by fatigue, headache, fever, and muscle and joint pains. This condition has been named southern tick-associated rash illness (STARI).
Persons should monitor their health closely after any tick bite, and should consult their physician if they experience a rash, fever, headache, joint or muscle pains, or swollen lymph nodes within 30 days of a tick bite. Contact CDC at 970-221-6400 for more information (Tick Info)
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