TICKS - LET'S TALK ABOUT IT

Ticks

Ticks are obligate ectoparasites that infect every class of terrestrial vertebrates. Although there are some 800 species known world-wide, only a few cause major problems to humans, livestock and pets (dog, cat, rabbit, etc). These include the genera Ixodes, Dermacentor, Haemaphysalis, Amblyomma and Rhipicephalus, with Rhipicephalus sanguineus (brown dog tick) being the most frequently found in dogs.

The tick’s lifecycle

The tick’s lifecycle comprises 4 stages, and the vast majority of Ixodid ticks, including Rhipicephalus sanguineus, undergo a 3 host cycle (triphasic);

1. Egg
2. Larvae (6 legs) emerge from eggs immediately and look for a host meal. Once engorged they drop to the ground to moult and change into the nympheal stage.
3. Nymph (8 legs) then seeks a second host from which to engorge. Once again, it drops on the ground when ‘full’ and moult, thereafter becoming an adult tick.
4. Adults (male and female) seek a third host on which their copulate. After having ingested a large volume of blood (the volume of blood taken by nymphs and adult females may be up to 3X the apparent volume of the engorged tick), the female drops into the environment, lays eggs (2000 to 20000, dependent on species) an dies.

Furthermore, at each stage during the lifecycle the tick can survive unfed in the environment for several months; hence the total duration of the cycle is variable, being from few months to several years.

Many pathogens are transmitted from one developmental stage o the next (trans-dial) and in certain tick species, some pathogens are transmitted through the eggs (transovarian).

Hence, ticks are extremely efficient transmitter of diseases.

Rhipicephalus sanguineus is said to be monotropic since the three stages, larva, nymph and adult have a preference for the dog as a host. At times though, it does feed on other species such as cats, rodents, humans etc.