Psoroptes spp in Horses (Equis) | Vetlexicon
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Psoroptes spp

ISSN 2398-2977


Introduction

Classification

Taxonomy

  • Phylum: Arthropoda.
  • Class: Arachnida.
  • Subclass: Acari.
  • Order: Astigmata.
  • Family: Psoroptidae.
  • Genus:Psoroptes.
  • Species:equi, cuniculi.

Distribution

  • Occurs worldwide.
  • P. cuniculiinfection observed occasionally - normally confined to ears.

Significance

  • Very rare.
  • P. equi- cause of body mange   Psoroptic mange  in horses.
  • P. cuniculi- infection limited to ears normally - may cause headshaking   Behavior: headshaking  .
  • Exact relationship between species ofPsoroptesremains unclear.
  • Also unclear the extent to which species on other hosts, egP. ovisfrom sheep can infect horses.

Active Forms

Active Form 1

Morphology

  • Non-burrowing mites.
  • Oval body shape, up to 0.8 mm in length, terminal anus.
  • Pointed mouthparts.
  • Long legs - pre-tarsi have 3 segmented pedicles.

Females

  • Leg pairs 1, 2 and 4 have suckers on end.
  • On the ventral surface of the mature female there is a U-shaped oviporus where eggs pass through.

Males

  • Leg pairs 1, 2 and 3 have suckers on end.
  • Rounded abdominal tubercles in males.

Tolerances

Temperature
  • Skin surface temperature.
Other
  • Mites may be able to survive for a number of days off the host (up to 84 days forP. cuniculi).
  • Non-zoonotic, as the adult mites do not affect humans.

Development

Reproduction
  • P. ovisfemales lay 30-40 eggs in her lifetime, at a rate of 1-5 per day.
Longevity
  • FemaleP. oviswill live for 11-42 days.

Resting Forms

Resting Form 1

Morphology

  • Oval, glistening, 250 µm in length.

Clinical Effects

Epidemiology

Lifecycle

  • Adult female lays eggs.
  • Larvae (approximately 330 µm) hatches - six legs.
  • Protonymph then tritonymph develop from larvae.
  • Female tritonymphs attach to males and remain attached until they moult to mature females.
  • Ratio of males to females is 1-2:4.
  • P. equilifecycle completed in about 3 weeks.

Transmission

  • Either direct contact with an infected animal or by transmission on fomites - mites can survive for some days in the environment.

Pathological effects

  • Non-burrowing mite - adults puncture the epidermis and feed on lymph and tissue fluid.
  • Cause scab formation, associated with hair loss   Tail: alopecia - psoroptic mange  and skin thickening.
  • Presence associated with pruritus.
  • May be foul smelling.
  • Pruritus, non-follicular papules, crusts, scales, excoriations, alopecia normally in angle of jaw, under mane and forelock, axilla and groin and outer ear.
  • P. cuniculilesions normally confined to ear.
  • Rarely lesions and mites may be found in other areas, eg face and limbs.
  • Can cause head shaking, irritation and exudate.

Control

Control via animal

  • Removal of crusts and exudate especially in ears.

Control via chemotherapies

  • Treatment with acaricide:
    • Otitis: rotenone twice per week for 3 weeks or thiabendazole.
    • Body mange: lime sulfur (2%) 6 oz/gallon of water once per week for 4 weeks or ivermectin   Ivermectin  200 µg/kg 1 time every other week 3 times.
  • Treat all animals in group (as others may be carriers).

Control via environment

  • Clean environment and grooming equipment.

Diagnosis

Useful samples

Specimen storage

  • In universal or similar container.
  • Examine as soon as practical - within 1-2 days preferably.

Transport of samples

  • In suitable sealed container.

Field diagnosis

  • Clinical signs.
  • Identification of mites using hand lens.
  • Differential diagnosis - atopy, rod allergy, other types of mange.

Laboratory diagnosis

  • Identification of mites on microscopic examination.
  • Add 10% KOH or liquid paraffin to material to facilitate examination.
  • Mites are easy to find on skin scraping.

Further Reading

Publications

Refereed papers