"

3.22 Pelodera Dermatitis – Small Animals

Learning Objectives

  1. Know the cause of pelodera dermatitis.
  2. Learn the predisposing factors associated with peolodera dermatitis.
  3. Know to diagnose pelodera dermatitis.
  4. Learn how to manage pelodera dermatitis.

  1. General Considerations

    1. Pelodera or rhabditic dermatitis is an erythematous, nonseasonal pruritic dermatitis caused by the cutaneous infestation with the third-stage larva of Pelodera strongyloides.
    2. Pelodera strongyloides is a free-living nematode that completes its entire life cycle in organic matter.
    3. The adult parasite lives in damp soil or moist, decaying organic matter such as straw, leaves, hay, and rice hulls.
    4. Larvae may invade skin, which contacts the contaminated soil or organic material and initiates cutaneous inflammation.
    5. Various mammalian species can be affected including humans.

  2. Cause

    1. Third stage larva of the free-living nematode Pelodera strongyloides.

  3. Clinical Signs

    1. Lesions associated with this infestation are typically present in areas of the skin that contact the ground, such as feet, legs, perineum, ventral chest, abdomen and tail.
    2. Focal or diffuse alopecia, erythema and papules are initially present.
    3. Later, crusts, scales and secondary bacterial infection may occur.
    4. The skin may become lichenified and hyperpigmented in chronic cases.
    5. Pruritus can vary from mild to intense.
    6. Differential diagnoses include sarcoptic mange, atopic dermatitis, primary contact dermatitis, demodectic mange, hookworm dermatitis, and dirofilariasis.

  4. Diagnosis

    1. History and clinical signs.
    2. Deep skin scrapings will demonstrate the small motile nematode larvae (625 to 650 µm in length and 25-40 µm in diameter) in most cases.
    3. Trichoscopy may show the larva. Pluck various hairs from affected areas, place a few drops of mineral oil, cover with a coverslip, and look under the microscope.
    4. Skin biopsy can also reveal nematode segments within hair follicles and within pyogranulomatous reactions in the dermis when hair follicles rupture.
    5. If deep skin scrapings are negative, perform trichoscopy. If trichoscopy and skin scrapings are negative, perform a skin biopsy.

  5. Treatment

    1. Treatment is effective and simple.
    2. Change the animal’s environment, which is harboring the larvae.
    3. After cleaning the environment, spray all ground surfaces with malathion (one ounce of 57-59% malathion per gallon of water).
    4. New bedding consisting of wood chips, old blankets, or shredded paper can be utilized.
    5. Animals should be bathed with a medicated shampoo to remove the scales and crusts.
    6. The infestation is self-limiting and resolves spontaneously after the animals are removed from the source of contamination. However, two applications of moxidectin + imidacloprid (Advantage Multi®) has been shown to be effective. Other ectoparasiticides may also be efficacious but it is questionable if their use is needed.
    7. Appropriate antibiotic therapy should be used if secondary pyoderma is present (ideally topical treatment if feasible).
    8. Prednisone can be given for a few days if pruritus is intense.

Important Facts

  • Pelodera dermatitis is caused by the skin penetration of larvae of the free-living nematode Pelodera strongyloides.
  • The adult nematode lives in damp soil or moist decaying organic matter such as straw, hay and leaves.
  • Lesions consist of alopecia, erythema, papules and crusts and are located to the body sites that contact the ground.
  • Pruritus can be mild to severe.
  • Diagnosis can be confirmed based on deep skin scrapings, trichoscopy, or skin biopsy.
  • Treatment consists of cleaning the animal’s environment and using a parasiticide such as, malathion.
  • Once the environment is cleaned, the lesions should be self-limiting.
  • Ectoparasiticides may be needed in some cases and two applications of moxidectin+imidaclorid has been effective
  • Pelodera dermatitis has also been reported in cattle, horses, and sheep.
  • The clinical signs, diagnosis and treatment are the same as described for dogs.

References

Capitan RGM and Noli C. Trichoscopic diagnosis of cutaneous Pelodera strongyloides infestation in a dog. Vet Dermatol 2017; 28: 413-e100.

Di Bari MA, Di Pirro V, Ciucci P et al. Pelodera strongyloides in the critically endangered Apennine brown bear (Ursus arctos marsicanus). Res Vet Sci  2022; 145: 50–53.

Rasmir-Raven AM, Black SS, Richard LG et al. Papillomatous pastern dermatitis with spirochetes and Pelodera strongyloides in a Tennessee Walking horse. J Vet Diagn Invest 2000; 12: 287-91.

Saari SAM and Nikander SE. Pelodera (syn. Rhabditis) strongyloides as a cause of dermatitis – a report of 11 dogs in Filand. Acta Vet Scandin 2006; 48:18.

Scott DW, Miller WH, Griffin CE:  Parasitic Skin Diseases.  Small Animal Dermatology. 5th edn. Philadelphia: W.B. Saunders Co., 1995; 395-398.

Scott DW. Parasitic Diseases.  Large Animal Dermatology. 1st edn. Philadelphia, PA: W.B. Saunders, 1988;  265-266.

WB Willers. Pelodera strongyloides in association with canine dermatitis in Wisconsin. J Am Vet Med Assoc 1970; 156: 319-320.

License

Icon for the Creative Commons Attribution 4.0 International License

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.

Share This Book