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3.17 Tick Infestation – Large Animals

Learning Objectives

  1. Know the economical importance of tick infestation in large animals.
  2. Learn the clinical signs and complications associated with tick infestation.
  3. Know how to manage tick infestation in large animals.

  1. General Considerations

    1. Ticks are hematophagous arthropods belonging to the class arachnids.
    2. They are important ectoparasites of goats, sheep, cattle and horses all around the world. They are not usually a problem in swine.
    3. Once they attach to a host for a blood meal, they can cause skin irritation and infection, anemia and transmit disease.
    4. Ticks can transmit bacterial, rickettsial, viral and protozoal diseases. Ticks can transmit bacterial, rickettsial, viral and protozoal diseases. Tick bites may also result in tick paralysis in heavy infestations.
    5. Heavy infestation with ticks causes significant debilitation, decrease production, and anemia.
    6. Ticks are economically the most important pests of cattle especially in tropical and subtropical areas of the world. Economic losses are related to decline of milk production, weight loss, hide damage, morbidity and mortality, cost of control and the effects of tick-transmitted hemoparasites.
    7. Sites of tick bites can attract flies resulting in myiasis.
    8. There are two major families of ticks: argasids (soft-shelled ticks) and ixodid (hard-shelled ticks).
    9. The only argasid tick of importance to large animals is the spinose ear tick Otobius megnini.

  2. Cause

    1. Argasid (soft) tick:
      1. Otobius megnini (the spinose ear tick).
Otobius megnini
Source: Wikimedia commons
    1. Ixodid (hard) tick:
      1. Several ixodid ticks infest large animals. Some examples are:
        1. Dermacentor albipictus.
Dermacentor albipictus
Wikimedia commons
        1. Amblyomma americanum.
Amblyomma americanum
Source: cdc.gov
        1. Boophilus microplus.
Boophilus microplus
Source: Wikipedia
        1. Ixodes spp.
Ixodes holocyclus
Ixodes holocyclus – Source: Wikimedia commons

  1. Clinical Signs

    1. Tick-related dermatoses are most commonly seen in spring and summer.
    2. Favorite areas are the ears, face, neck, axillae, groin, distal limbs, tail and mane (horses).
    3. Initial skin lesions consist of papules, pustules, wheals, and occasionally nodules.
    4. These initial lesions evolve to crusts, erosions, ulcers, and alopecia.
    5. Pain and pruritus are variable.
    6. Otobius megnini causes otitis externa, which can be manifested as head tilting, head shaking, and ear rubbing. Animals may appear lop-eared.

  2. Diagnosis

    1. Demonstration of ticks on physical examination.

  3. Treatment

    1. Therapy is usually directed at temporarily reducing the tick population.
    2. Suitable insecticides are applied to the entire body every 2 to 3 weeks throughout the tick season.
    3. Commonly used tickicides are: 0.025% amitraz, 0.05 to 0.1% chlorfenvinphos, 0.05% chlorpyrifos, 0.05% coumaphos, and 0.05% diazinon.
    4. Ivermectin at the dose of 200 µg/kg given subcutaneously every 2 to 4 weeks during the tick season has been effective.
    5. Otobius megnini can be treated by manually removing as many ticks as possible and the ears should be cleared of exudate.
    6. Lindane (one part), xylol (two parts), and pine oil (17 parts) can be applied every 3 to 4 weeks inside the ears and is an effective therapy.
    7. Rotenone (one part) in mineral oil (three parts) is also effective for the ear tick.
    8. Fipronil is used worldwide for the treatment and control of tick infestations in cattle. Fipronil applied as a pour-on to cattle infested with Boophilus microplus had a therapeutic efficacy greater than 99%.
    9. Spinosad applied topically to cattle using spray formulations has proved effective to control cattle tick infestations.
    10. Environmental control measures include limiting livestock access to wooded areas and clipping tall grass close to fences and along tree-lined edges.
    11. New animals entering the farm should be examined closed (especially ears, neck, chest/brisket) to look for any ectoparasites that could spread around the farm. Isolate them for 2 weeks and apply a parasiticidal to help kill external parasites you may have missed.

Important Facts

  • Ticks cause damage through blood sucking and through the transmission of infectious diseases.
  • Several species of ixodid ticks infest large animals and result in alopecia, papules, nodules, crusts and ulcerations with or without pruritus.
  • Otobius megnini is the only soft tick of importance in large animals and it causes otitis externa.
  • Treatment of tick infestations consists of mechanical removal of ticks and the application of appropriate insecticides throughout the tick season.
  • Environmental control measures such as clipping of tall grass and limiting livestock access to wooded areas can be helpful in reducing tick infestation.
  • Examine carefully and isolate for 2 weeks any new animal entering the farm to avoid the spreading of ectoparasites.

References

Rodriguez-Vivas RI, Jonsson NN, Bhushan C.  Strategies for the control of Rhipicephalus microplus ticks in a world of conventional acaricide and macrocyclic lactone resistance. Parasitol Res 2017. doi.org/10.1007/s00436-017-5677-6.

Scott DW. Large Animal Dermatology. 1st edn. Philadelphia: W.B. Saunders, 1988;  233-234.

Scott DW. Color atlas of farm animal dermatology. Ames, IA: Blackwell Publishing, 2007; 29.

Scott DW, Miller WH Jr. Equine dermatology. 2nd edn.  Philadelphia: W.B. Saunders, 2011; 225-227.

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Small and Large Animal Dermatology Handbook, Vol. 1 Copyright © 2025 by Sheila M.F. Torres, DVM, MS, PhD, DACVD is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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