Ticks are arthropods, like spiders. There are more than 800 species of ticks throughout the world. Ticks are the leading carriers (vectors) of diseases to humans in the United States, second only to mosquitos worldwide. It is not the tick bite but the toxins, secretions, or organisms in the tick’s saliva transmitted through the bite that causes disease.
Two families of ticks, Ixodidae (hard ticks) and Argasidae (soft ticks), are important to humans because of the diseases or illnesses they can transmit or cause. Hard ticks have a tough back plate or scutum that defines their appearance. The hard ticks tend to attach and feed for hours to days. Disease transmission usually occurs near the end of a meal, as the tick becomes full of blood. Soft ticks have more rounded bodies and do not have the hard scutum found in hard ticks. These ticks usually feed for less than one hour. Disease transmission from these ticks can occur in less than a minute. The bite of some of these ticks produces intensely painful reactions. Ticks can transmit disease to many hosts; some cause economic harm such as Texas fever (bovine babeiosis) in cattle that can kill up to 90% of yearling cows.
The following is a list of tick-borne diseases, the usual tick vector(s), and the pathogen(s) the tick transmits:
- Lyme disease — Ixodes species including deer ticks (hard ticks) — vectors for Borrelia species of bacteria
- Babesiosis — Ixodes species (hard ticks) — vectors for Babesia, a protozoan
- Ehrlichiosis — Amblyomma americanum or lone star ticks (hard ticks) — vectors for Ehrlichia chaffeensis and Ehrlichia ewingii bacterial species
- Rocky Mountain spotted fever — Dermacentor variabilis (American dog tick) and Rocky Mountain wood tick (Dermacentor andersoni) (hard tick) are the primary vectors and occasionally the brown dog tick (Rhipicephalus sanguineus); Amblyomma cajennense (hard tick) is the vector in countries south of the United States — vectors for Rickettsia bacteria
Outbreaks of tick-related illnesses follow seasonal patterns (about April to September in the U.S.) as ticks evolve from larvae to adults. Ticks go through life cycles that involve mating and larval formation and usually have several hosts. Ticks hide in low brush; this location allows them to physically contact a host. A recent study suggested that leaning against a tree or sitting on an old log was the quickest way to acquire ticks (about 30 seconds) in tick-infested areas. Ticks require a “blood meal” to grow and survive, and they are not very particular upon whom or what they feed. If ticks don’t find a host, they may die.
Once a tick finds a host (such as a human, a pet dog or cat, a deer, or a rabbit) and finds a suitable site for attachment, the tick begins to burrow with its mouthparts into exposed skin. Tick mouthparts are barbed, which helps to secure them to the host.
Often the tick secretes “cementum” to more firmly attach its mouthparts and head to the host. Ticks may secrete or regurgitate small amounts of saliva that contain neurotoxins. These nerve poisons cleverly prevent the host from feeling the pain and irritation of the bite. Consequently, individuals may never notice the tick bite or its feeding. The saliva may contain a blood thinner to make it easier for the tick to get its blood meal. Some people are allergic to these secretions and may have a quick and may have a quick and allergic reaction to a tick bite.
Cat and dog fleas are usually found together and are very similar in appearance. They are small, wingless insects about 1/8-inch long with piercing-sucking mouth parts. They are dark-colored and have very narrow bodies with well-developed legs which allow them to be great jumpers. Their bodies are covered with backward-projecting spines that help them move between the hairs on the host animal.
Cat and dog flea larvae are 1/4-inch long when fully developed and look much like fly maggots. They have 13 body segments, and are a dirty-white color with backward projecting hairs on each body segment. They also have a pair of hook-like appendages on the last abdominal segment.
Cat and dog fleas go through complete metamorphosis. The females lay four to eight eggs after each blood meal. The eggs fall into the nest of the host animal or wherever the animal happens to be at that time. The eggs hatch in about 10 days. The larvae feed on dried blood, bits of feces, and other types of food materials. When mature they spin silken cocoons within which they pupate. The pupal stage lasts from seven days up to a year. The adult cat flea will often stay within the cocoon until vibrations stimulate them to emerge. The adult fleas feed on blood with their pierce-sucking mouthparts. Cat and dog fleas prefer these two animals, but will readily feed on man.