TICK: THE TICK-HOST INTERACTION

The tick attaches to the host (dog, cat, livestock, pet, etc) using its chelicerae to cut a hole through the epidermis and inserts its mouth part (hypostome) therein maintaining a blood flow from the host through the injection of an anticoagulant. In many species, cement produced by the salivary glands secures this attachment.

From here, two feeding phases follow:

1. The first phase is characterized by a slow, continuous blood uptake (slow engorgement with short alternation of suction and salivary secretion)
2. The second phase lasts for between one and three days and entails a massive engorgement and enlargement of the female tick. Salivary secretion and regurgitation are maximal at the end of this phase.

Tick: The blood meal and transmission of pathogens

Throughout the feeding period, ticks inject products that may contain pathogens into the host. The minimum attachment time for an efficient transmission of pathogens depends on the agent. Estimates range from a few hours for Ehrlichia to 48 hours for Babesia.

The blood meal last from 2 to 25 days (nymph and adult females). The regurgitation of saliva (hence the risk of transmission) is the greatest in the second part of the blood meal (rapid engorgement phase).

Practically, the longer the attachment time of the tick, the more likely a transmission by pathogens. Therefore, avoiding a lengthy attachment by ticks contributes to prevention of tick-borne diseases.

Tick: Clinical consequences of tick infestation

Local reactions: These include inflammation, local edema and hemorrhages. A local hypersensitivity may develop and irritation at site of the bite may persist for months after the tick has been removed.

Transmission of infectious diseases (viral, bacterial or protozoal): Ticks are second only to mosquitoes as transmitters of infectious diseases to dogs and humans. In dog many diseases are transmitted by Rhipicephalus sanguineus such as ehrlichiosis, babesiosis and hepatozoonosis.

Tick toxicosis: Certain ticks species may secrete toxins cause animal or human disease.

Tick: Why are ticks so difficult to control?

• Ticks are temporary parasites
• Ticks are widely dispersed in vegetation.
• Ticks have a remarkable longevity (months to years).
• Ticks have huge reproductive capacity (up to thousands of eggs/females).