Adult onset canine generalised demodicosis - Veterinary Practice
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Adult onset canine generalised demodicosis

David Grant continues his series looking at dermatological conditions.

in which there is an increased
number of Demodex mites, normal
inhabitants of canine skin. Three
mites have been identi ed, with
their usual site in brackets: Demodex
(hair follicle and sebaceous
gland), Demodex injai (hair follicle and sebaceous gland) and Demodex

of the disease is
associated with
immune deficiency
(Paterson, 2008). Demodex canis is
the most commonly seen mite and
is described in this article. Demodex
is less common although
clinically indistinguishable (Miller,
Grif n and Campbell, 2013).

Demodex injai has a different
clinical presentation, mainly a greasy
seborrhoea that tends to be dorsal,
with a breed predisposition for
terriers, especially the West Highland
white and Shih-Tzu. This form is
not described further in this article
and interested readers are referred
to other texts (Miller, Grif n and
Campbell, 2013; Paterson, 2008).

Clinical presentations

Demodicosis occurs in various
clinical manifestations. These are
localised, generalised (further divided into juvenile onset and adult onset)
and pododemodicosis, which may be
seen in both localised and generalised

Authors vary in their definitions
of what constitutes localised and
generalised, and also concerning the
age of onset. Paterson (2008) defines
localised demodicosis as having fewer than five patches
on the skin,
and one foot
only involved in localised

demodicosis is defined as more than five patches of affected skin and two or more feet in
the pododemodicosis form. Juvenile
onset disease is de ned as occurring
between three and 18 months of age
and adult onset after three years. There
is no uniformly accepted standard for
the above definitions but this author
prefers those described by Paterson.

Adult onset generalised
canine demodicosis


  • Age of onset is after three years and
    frequently older than this
  • Care needs to be taken with dogs
    presenting at around the three-year
    age group, as it is not unusual for
    the disease to remain undetected
    for several years if careful sampling has not been done. A
    detailed history will be
    essential in these cases.
  • Regardless of the age of onset
    the generalised
    forms are clinically
    indistinguishable. Early
    signs are erythema,
    alopecia, scaling,
    comedones, crusts and haemorrhagic
    lesions. Generalised
    erythema accounts for
    the old description of the disease “red
    mange”. This colour
    is highly suggestive of
    demodicosis but may be
    misdiagnosed as atopy.
  • With chronicity,
    secondary infection with Staphylococcus pseudintermedius
    is common. Occasionally Proteus
    and Pseudomonas can be involved.
    Bacterial infection in untreated cases
    is frequently severe with cellulitis,
    furunculosis and generalised
    lymphadenopathy. In chronic skin
    cases the skin is often a blue-grey
    colour and should suggest the disease
    and prompt skin scrapings.
  • Lesions tend to be most severe
    in the predilections sites – the facial
    area, neck and feet, but ultimately may
    involve the entire body.
  • Depression, lethargy and anorexia
    develop in advanced neglected cases
    and fatality is possible.

Underlying causes

  • In all cases of generalised
    demodicosis the immune system is
  • In adult onset cases, an immune
    suppressing disease occurring later
    in life is responsible for the sudden
    appearance of demodicosis.
  • These cases are much rarer than the
    juvenile onset cases.
  • Possible underlying causes
    include hyperadrenocorticism (both
    naturally occurring and iatrogenic),
    hypothyroidism, diabetes mellitus,
    neoplasia, leishmaniasis, and
    immunosuppressive treatments for
    neoplastic or immune-mediated
  • Underlying trigger diseases may
    become apparent some time after
    cutaneous lesions are apparent, thus
    these dogs should never be considered
    cured and frequent monitoring is


  • History and physical examination.
  • Identification of mites from hair
    plucks, acetate tape impression smears,
    deep skin scrapings, and in chronic cases,
    where the skin is
    lichenified particularly
    in interdigital areas, and
  • Complete blood
    count, biochemistry,
    endocrine function
    tests, radiography
    and ultrasonography
    depending on clues
    from the history and
    physical examination.


  • Successful treatment
    in adult onset cases is more difficult than in the juvenile
    onset cases.
  • Treatment of underlying causative
    diseases is essential and if successful
    will result in success rates comparable
    with juvenile onset cases.
  • In those cases where the
    underlying disease has not been
    diagnosed or has not yet manifested
    itself, some improvement and
    control may be possible but relapse
    will quickly occur on cessation of
    treatment. As many as 50% of cases
    may fall into the category.

Licensed treatments

  • Amitraz (Aludex, MSD). This is
    applied as a 0.05% solution (50ml in five litres) of water weekly. The dip
    is left on the coat and not rinsed off.
    Clipping long-haired dogs will aid
    penetration. Treatment is continued
    until two weeks after clinical cure and
    negative skin scrapings. Sedation is
    common particularly after the first
    application and tends to diminish as a problem subsequently. When
    secondary infection is confirmed cytologically, anti-bacterial treatment is
    essential. The product should not be
    used on Chihuahuas.
  • Moxidectin/Imidacloprid
    (Advocate, Bayer). This treatment is in
    the form of a spot-on applied weekly,
    and is continued for two weeks
    beyond clinical cure and negative skin

Success rates with both these
treatments vary according to the
literature. In the author’s experience
and with good compliance the success
rate in first opinion cases is in excess
of 90% in juvenile onset cases and a similar percentage in adult onset
cases where the underlying cause is
determined and successfully treated.
If this is not possible such cases need
maintenance therapy and frequent

Unlicensed treatments

Most of the unlicensed treatments
that have been used are avermectins.
Two are mentioned here:

  • Ivermectin. This drug is the most
    widely used at a dose of 0.2-0.6mg/
    kg by mouth daily. It is often started at
    0.1mg/kg and gradually built up over
    a few weeks to monitor for possible
    neurological side-effects. These are
    particularly common in Collie dogs
    and their crosses but can occur in
    other breeds.
  • Milbemycin. This is given at a
    dose of 0.5-2mg/kg by mouth daily.
    Neurological side-effects may occur
    but are less common compared to
    ivermectin. With both these drugs
    the success rate is equivalent to the
    licensed treatments.
  • Recent attention has focused on a
    product licensed for fleas and ticks in
    the UK.
  • Fluralaner (Bravecto, MSD). This
    product is a chewable tablet given
    once every three months. Fourie and
    others (2015) reported on a study
    involving 16 dogs that were treated
    for generalised demodicosis either
    with uralaner or imidacloprid/
    moxidectin spot on. Both treatments
    resulted in clinical cure but uralaner eliminated mites at 56 and 84 days,
    whereas mites were still present
    at these times with imidacloprid/
    moxidectin. However, the product
    was administered monthly in this study. Weekly administration
    according to the more recent license
    has been shown to give better results.
  • A larger open study in
    Poland (Karas-Teczay and
    Dawidowicz, 2015) treated 163
    dogs with uralaner for generalised
    demodicosis. The overall response
    to therapy was 100% with 87.1%
    skin scrape negative after one month
    and the remainder after two months; 37.4% of these dogs were over two
    years of age when the disease was
    diagnosed, which suggests that it
    may be effective in dogs with true
    adult onset disease. This definition of
    adult onset disease differs from that
    of Paterson described in this article.
    Further studies are under way to see
    if these promising results can be

References and
further reading

  • Fourie, J. and others. (2015) Ef cacy
    of oral administered uralaner
    (Bravecto) or topically applied imidacloprid/moxidectin (Advocate) against generalised demodicosis in
    dogs. Parasites and Vectors 8: 187.
  • Karas-Teczay, J. and Dawidowicz,
    J. (2015) Ef cacy of uralaner for the
    treatment of demodicosis. In: Proceedings
    of the Annual Congress of the
    European Society and College of
    Veterinary Dermatology, pp124-125.
    Miller, Grif n and Campbell (2013)
    In: Muller and Kirk’s Small Animal
    , 7th edition, p305.
  • Paterson, S. (2008) In: Manual of Skin
    Diseases of the Dog and Cat
    , 2nd edition,
    pp104-109. Blackwell.

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