to Chorioptes bovis (CB) differs between horse breeds. Those
that suffer most have abundant feather, such as the Ardennes,
Clydesdale, Friesian, North Swedish, Shire, and Tinker. According
to Dan Christensson, a parasitologist, CB is a very common
“To confirm the presence of CB one needs to get a sample
of the affected area of skin by scraping it deeply until it
starts to bleed. The sample is placed in glycerine or liquid
paraffin and then viewed under a microscope. Only one-third
of tests prove posetive, which means that the horse still
may be infected even though the biopsy has not confirmed the
presence of mites. This can occur because if your sample was
sent away to a laboratory any mites present can have died
during transport. If the horse then shows symptoms of complications
of CB, they may show up in the sample in the form of a fungal
infection. There are proven cases of CB in both Friesian and
Tinker horses. Hans Kinndahl, a veterinary surgeon, has personal
experience of CB in his own Tinker horse.
“CB is contagious and can easily by transferred by physical
contact, by holding in a common stable or by grooming horses
with the same brush. It is disputed how long CB mites can
survive in the absence of a host, but can be from 24 hours
up to 3 weeks, depending upon weather conditions, according
to information received. Mites thrive when it is cool and
damp. One should not confuse CB with Shoroptes bovis (SB)
which is far more contagious. There are at present no restrictions
in cases of CB and reporting is not compulsory though there
is no harm in reporting any occurrence to the County Veterinary
Surgeon, as many vets know little or nothing about CB.
“In mild cases, CB symptoms can be similar to those
of grease. The difference is that the affected area usually
is higher up than the pasterns, which is the part usually
affected by grease. Crustation breaks out especially around
the fetlock joints and canons, but can spread up the legs.
Even bald patches can occur on other parts – on its
belly in front of the sheath and even on the head. CB can
also affect the mane and tail, where it looks like eczema.
You can tell when a horse has been infected as it starts scratching
its tail and mane and stamps the ground. The horse is bothered
by itching which, in more severe cases, can be so tiresome
that it is psychologically irritated and gets bad habits such
as weaving or just switches off and becomes apathetic.
“What is typical of CB is that summer symptoms are milder
while those in February-March are more severe, when it’s
usually cold and snowy - which is not when grease is most
prevalent. As grease can be treated and cured, one should
be vigilant if the horse does not improve following treatment.
CB on the other hand is much more difficult to deal with and
can only be relieved (but not cured) by treating the infected
area as for fungus and grease.
“If you want to rid your horse of CB, we would recommend
treatment by Dan Christensson, Parasitologist at SVA (the
National Veterinary Institute) here in Uppsala (Sweden) (tel.no.
+46 (0)18 674000). He recommends Frontline, though this is
not registered for use on horses, only for cats and dogs.
It is forbidden for horses treated with Frontline to be slaughtered
for human consump-tion. Spring-Summer is the best time to
treat horses for CB as it is then that they are less troubled
by CB; in other words, they have fewer active mites to get
rid of. To be on the safe side, one should treat the horse
three times, at 1-2 week intervals. It takes about 16 days
for the eggs to hatch but this is not confirmed. Each treatment
should consist of Frontline spray, aimed at the infected area
on the legs. Spray first and then rub it well into the skin,
wearing rubber gloves. The remedy is then transported via
the subcutaneous fat upward in the horse, which is why it
is important to apply the spray low down on the legs even
if it is the mane and tail that are affected. If other horses
are stabled with the infected horse, then these too should
be treated, even if they are symptom-free.”
This is a free translation of an article published in
the Swedish Shire Horse Society’s members´ magazine
Giganten (The Giant), No. 2, 2002.
Present authors´ comment
on the above-quoted text
We have tried another product – Sebacil (Bayer) which
is also registered for use on dogs, pigs and sheep, with good
results. An intensive course of treatment using the de-worming
product Ivomectin can also give good results but we recommend
that you consult your veterinary surgeon first.