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InFocus

Feline scabies (notoedric mange)

David Grant continues his series looking at dermatological conditions.

FELINE SCABIES IS A
HIGHLY CONTAGIOUS
PARASITIC SKIN DISEASE
caused by the obligate parasite
Notoedres cati, a mite that can only
survive a few days off the host.

It has a worldwide distribution but
is generally considered to be rare,
with pockets of endemic infection in continental Europe for
example. In the
UK the mite was
very common
in the 1940s
and 1950s but
has virtually
disappeared since (Thomsett and
Baker, 1990).

With the advent of
pet travel there is a small risk of
acquiring the disease.

  • Notoedres cati is a member of the
    sarcoptiform family.
  • In appearance it is very similar to
    other members of the family such
    as Sarcoptes scabiei var canis of the dog
    with some differences.
  • Notoedres is smaller and the eggs
    are round (Paterson, 2008).
  • The two pairs of anterior legs
    have long-medium length unjointed
    stalks with suckers and the two
    posterior legs do not extend beyond
    the borders of the body, which is
    striated.
  • The most notable distinguishing
    feature of Notoedres cati is that unlike
    Sarcoptes scabiei, which has a terminal
    anus, it has a dorsal anus.
  • It is important to distinguish
    between the two species as Sarcoptes
    occasionally affects cats and may have a poorer prognosis as described
    under differential diagnosis.

Clinical signs

  • The disease is extremely pruritic
    and as it progresses will not respond to
    glucocorticoids.
  • Lesions begin on the medial side of
    the pinnal edge with a rapid spread to the face, eyelids,
    neck and become
    more generalised
    if not treated.
  • Affected
    animals
    sometimes resemble “battle scarred tom cats”
    (Thomsett and Baker, 1990).
  • Lesions are crusts – yellowish to
    grey in colour and the skin becomes
    thickened.
  • Excoriation due to severe pruritus.
  • Emaciation, anorexia and death is
    possible.
  • Transient pruritic lesions in humans
    are common. Spread to other animals
    such as dogs and rabbits is also
    possible.

Differential diagnosis

  • Otodectes cynotis – especially
    associated with hypersensitivity to the
    mite.
  • Pediculosis.
  • Dermatophytosis.
  • Demodicosis.
  • Hypersensitivity – flea bites, food
    or atopy.
  • Demodex gatoi.
  • Autoimmune diseases – pemphigus
    foliaceus.
  • Sarcoptes scabiei var canis.
    Cats appear to be resistant
    to infestation from contact
    with a canine scabies case.
    Occasional cases do present
    themselves in the UK (Hardy
    and others, 2012). These cats
    are extremely pruritic with
    generalised scaling.

There is often an abundance of
mites demonstrated by skin
scrapings or tape strips. Mites
in these patients will have
a terminal anus, important
in the differential diagnosis.
There is often an underlying
immunosuppression and
attempts should be made to
diagnose this and treat it if
possible, otherwise cure will
be difficult.

Diagnosis

  • The history and
    physical examination
    is very suggestive,
    with human lesions,
    failure to respond to
    glucocorticoids and
    rapid spread being
    important clues.
  • Tape strips. These
    should be employed first as they are
    easy to do and are
    minimally resented.
    A transparent tape
    strip is pressed
    against lesion areas
    and transferred to a
    slide.
  • Skin scrapings.
     With either
    technique, mites
    are usually easy to find – much more so
    than with the canine
    disease. Therefore a therapeutic trial
    is rarely necessary,
    although not to be
    discounted if doubt
    exists.

Treatment

  • Treatment is generally effective
    according to experience in those
    countries where the disease is present.
    Products that are used to treat canine
    scabies should be effective and three
    are mentioned here.
  • 2% lime sulphur dips (Dechra).
    Between six to eight weekly applications
    may be necessary.
  • Selamectin (Stronghold, Zoetis).
    This is applied as a spot-on at 30-day
    intervals for three applications. It is
    preferable that the professional staff
    of the clinic perform this to eliminate
    any possibility of poor compliance,
    particularly in the rare case where the
    treatment is a trial therapy.
  • Fipronil (Merial Animal Health.)
    Applied as a spot-on or spray.
  • Glucocorticoids will help alleviate
    the extreme pruritus but should only
    be used short-term and after there has
    been a definitive diagnosis.

References and further reading

  1. Hardy, J. and others. A case of feline sarcoptic
    mange in the UK. Vet Rec Case Rep 203 (1): 1-2.
    Hnilica, K. A. In: Small Animal Dermatology – A
    Color Atlas and Therapeutic Guide, 3rd edition,
    p138. Elsevier, 2011.
  2. Miller, W. H., Grif n, C. G. and Campbell, K. A.
    In: Muller and Kirk’s Small Animal Dermatology, 7th
    edition, pp319-320. Elsevier, 2013.
    Paterson, S. In: Manual of Skin Diseases of the
  3. Dog and Cat, 2nd edition, pp115-116. Blackwell
    Publishing, 2008.
    Thomsett, L. R. and Baker, K. P. In: Canine and
    Feline Dermatology, pp142-144. Blackwell Scienti c
    Publications, 1990.

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