What’s Eating You? Rhipicephalus Ticks Revisited
Rhipicephalus ticks are vectors of disease in humans and animals. Rhipicephalus sanguineus sensu lato (the brown dog tick) is one of the most geographically widespread tick species worldwide, likely due to its ability to colonize human and canine dwellings over a range of habitats. They transmit a variety of diseases to dogs and humans, including canine babesiosis, canine monocytic ehrlichiosis, hepatozoonosis, Mediterranean spotted fever, and Rocky Mountain spotted fever. Tick bites manifest as intensely pruritic, erythematous papules at the site of tick attachment; symptomatic relief usually can be achieved with topical antipruritics. Prevention of tick bites is best achieved through a combination of veterinary and environmental control; protective clothing; repellents, such as N,N-diethyl-meta-toluamide (DEET) and permethrin; and prompt identification and removal of ticks.
PRACTICE POINTS
- Rhipicephalus ticks are vectors of a variety of diseases, including the rickettsial diseases Rocky Mountain spotted fever and Mediterranean spotted fever.
- Presenting symptoms of a tick bite include intensely pruritic, erythematous papules and nodules at the site of tick attachment.
- If rickettsial disease is suspected, treatment with doxycycline should be initiated immediately; do not delay treatment to await results of confirmatory tests or because of the absence of a rash.
- Primary methods of prevention of tick-borne disease include repellents, protective clothing, vector control, and prompt removal of the tick.
Environmental and veterinary controls also are important methods of tick-bite prevention. A veterinarian can recommend a variety of agents for dogs and cats that prevent attachment of ticks. Environmental controls include synthetic or natural product-based chemical acaricides and nonchemical methods, such as landscape management (eg, sealing cracks and crevices in homes and controlling tall grasses, weeds, and leaf debris) to minimize potential tick habitat.20 Secondary prevention includes antibiotics for prophylaxis or for treatment of tick-borne disease, when indicated.
Numerous tick repellents are available commercially; others are being studied. DEET, the most widely used topical repellent, has a broad spectrum of activity against many tick species.21 In addition, DEET has a well-known safety and toxicity profile, with rare adverse effects, and is safe for use in pregnant women and children older than 2 years. Alternative repellents, such as those containing picaridin, ethyl butylacetylaminopropionate (IR3535 [Merck]), oil of lemon eucalyptus, and 2-undecanone can be effective; some show efficacy comparable to that of DEET.22 Permethrin, a synthetic pyrethroid, is a highly efficacious tick repellent and insecticide, especially when used in conjunction with a topical repellent such as DEET. Unlike topically applied repellents, permethrin spray is applied to fabric (eg, clothing, shoes, bed nets, camping gear), not to skin.
Indiscriminate use of acaricides worldwide has led to increasing selection of acaricide resistance in Rhipicephalus tick species, which is especially true with the use of acaricides in controlling R microplus livestock infestations; several tick populations now show resistance to all major classes of these compounds.23-25 For that reason, there has been an increasing effort to develop new chemical and nonchemical approaches to tick control that are more environmentally sustainable and strategies to minimize development and progression of resistance such as rotation of acaricides; reducing the frequency of their application; use of pesticide mixtures, synergists, or both; and increasing use of nonacaricidal methods of control.26
Prompt removal of ticks is important for preventing the transmission of tick-borne disease. Proper removal involves rubbing the tick in a circular motion with a moist gauze pad or using fine-tipped tweezers to grasp the tick as close to the skin surface as possible and pulling upward with a steady pressure.17,27 It is important not to jerk, twist, squeeze, smash, or burn the tick, as this can result in insufficient removal of mouthparts or spread contaminated tick fluids to mucous membranes, increasing the risk for infection. Application of petroleum jelly or nail polish to aid in tick removal have not been shown to be effective and are not recommended.16,28
