Horses confined to
paddocks or stables, are often in close proximity to other horses creating a
breeding ground for diseases and parasites that affect the skin.
Sarcoptes is perhaps the best known cause of itch
and hair loss in the mane and tail of horses.
The microscopic female mite when impregnated tunnels into the skin and
deposits eggs in the burrow. The larvae hatch in 3 to 10 days, move about on
the skin as they mature into adult mites.
Adult mites live three to four weeks in the host’s skin.
The action of the
mites moving within the skin and on the surface itself produces an intense itch
that may resemble symptoms of QLD Itch.
Their excreted faeces resemble dandruff or scurf and are often mistaken
as just that. Thinning of the hair
occurs as they damage the hair follicles causing reduced hair growth and hair
fallout.
Some skin disorders do
not cause itching, but secondary infections such as bacterial or yeast infections
cause the horse to itch and subsequently hair loss. It is possible the time the itch occurs the
initial skin disorder is long gone. Your
vet will perform a skin scraping to identify the cause of the itch, likely
parasites are considered as the first cause of an itch.
Treating
mites successfully requires application of a mite killing insecticide to be
applied externally every 4th day for at least three weeks to ensure
the breeding cycle is broken. As the
insecticides work only at the skin surface, each lot of hatchlings needs to be
treated, hence the ongoing treatment method to ensure a completely successful
eradication. Treating rugs and companion horses is also best practise. Seek
veterinary assistance to select a suitable insecticide.
Rain scald can be attributed to Dermatophilus
Congolensis. This organism likes to infect
traumatized skin, particularly in the presence of high moisture. Young horses with poorly developed immune
systems are at a higher risk of getting rain scald. Skin trauma can be initiated by abrasions,
insect bites or frequent rain exposure that softens the skin, particularly
along the horse’s topline.
Once dermatophilus
congolenis takes hold most likely secondary bacterial infections occur such as
staphylococcus (staph) and or streptococcus (strep). Hence it is of paramount importance to treat
the rain scald immediately before any secondary infections break out. A
The
best treatment is to wash the horse with antimicrobial and antibacterial
shampoos once a day for a week. Allow
the shampoo 10 minutes to sit before rinsing thoroughly. Condition and dry off. In severe cases prescription antibiotics will
need to be prescribed by a qualified vet.
QLD Itch is an allergic reaction to the saliva of
biting midge (biting insects that colonized near a water source and feast at
dusk and dawn on nearby stock). Getting
an accurate diagnosis from skin scraping or veterinary assessment is the first
step to managing this condition correctly.
Often
times sarcoptes mites are the culprit behind the itch, not the midge or biting
flies. Noticeable symptoms that extend
through the cooler months and exhibit dandruff symptoms are an indication the
itch is mite related. Sometimes the
horse is dealing with both mites and QLD Itch in warmer climates.
Prevention is the
likely successful approach. Warding off
the biting insects by rugging from dusk to dawn and applying a water resistant
insect repellent to the exposed areas will greatly reduce the rate of biting
flies.
Secondly try to
minimise the infections that occur to the broken skin from rubbing such as
bacterial and yeast infections. At this
stage people start to recognise their horse has QLD Itch.
Washing the horse with
a medicated shampoo each week, keeping rugs clean and the horse dry will
minimise the skin related infections.
Humidity also increases skin related infections, so do not allow the
horse to sweat underneath constant rugging in warm weather.
Science behind the itching reaction
A
mast cell is part of the immune system and contains many granules rich in
histamine and heparin. Although best
known for their role in allergy and anaphylaxis, mast cells play important
protective roles as well being intimately involved in wound healing including
angiogenesis and defence against pathogens.
Histamine as part of
the immune response to foreign pathogens, produced by both basophils and mast
cells. Histamine increases the
permeability of the capillaries to white blood cells and some proteins, to
allow them to engage pathogens in the infected tissue.
Heparin has been
proposed to defend at such sites against invading bacteria.
To signal the correct
response cytokines (small proteins) are released by cells to affect the
behaviours of other cells.
The
problem with allergic reaction occurs when incorrect signalling occurs at this
cytokine level. Loosely put they can signal
a Type 1 or Type 2 response to favour either a cellular immune response or an
antibody response.B Type2 (Th2
) over activation against auto antigen will cause Type1 IgE-mediated allergy
and hypersensitivity.
As a result of a faulty
allergic response the horse begins to rub from an ‘over reactive itch
response’, next pathogenesis occurs – the skin enters a diseased state and
becomes microbial infected, inflamed or has tissue breakdown.
The gastrointestinal
system plays a central role in the immune system.C New scientific approaches to managing an itchy
horse include feeding supplements that may work from the gut to down regulate
the over reactive immune response. Ask
at your local feed store for a supplement that works from the inside to benefit
holistically.
Veterinarian
approaches to managing the symptoms of classic QLD Itch include regular
bacterial skin washes, applying effective insect repellents and injections with
cortisone are administered in extreme cases.
External solutions
that can be applied to skin are popular methods to manage the new infections
occurring on the skin surface. Caution
should be exercised using any Iodine based preparations as these may lead to
hypothyroidism, result in hair loss and un-wellness with long term use.
Soothing oil
preparations with insect repelling properties are popular; however caution
should be exercised not to apply in the heat of the day. It is well know that healing skin must
breathe to heal successfully, so resting skin for a few days between applications
is best practise.
Pin Worms
The adult worm lives
in the rectum and lays its eggs on the surrounding skin externally. Pin worms cause severe irritation and
sometimes horses rub so badly so as to rub the tail head raw leading to
secondary infections and hair loss.
To treat successfully
some helpful tips include, using a pyrantel based wormer repeating every 6-8
weeks. Clean the horse’s rectum first
thing in the morning to remove eggs. Apply
Vaseline to surrounding skin to help reduce the number of eggs that stick to
the skin. Keep up treatment with wormer
for minimum of 12 months as the immature stages of the worm are less sensitive
to wormers so may survive post worming.
Neck Threadworms
Referred to as neck
worms the adult Onchocerca Cervicalis worms live in the large nuchal ligament
that runs from the poll to the withers.
The reproduction process lands the highly irritating microfilaria
(larval) around the face, shoulders, chest and abdomen on the horse where
biting flies come to feed. The
culicoides fly serves as the carrier, reinfecting and spreading the larvae. The
adult Onchocerca Cervicalis worms do not usually cause discomfort to the horse
and will reside within the neck for around 10 years meanwhile laying thousands
of eggs each year.
Often inflammation
occurs on the underbelly, ending in self trauma to the skin and chest as the
horse rubs intensely to relieve the itch.
Another tell tale sign includes a bullseye of hair loss and inflammation
on the horse’s forehead. Most horses
exhibit dermatitis, crustiness, hair loss, itching, swelling and self trauma,
often mistaken for QLD Itch.
Usually younger horses
even though infected may not have symptoms until the age of 5 or more, hence
the sudden onset of itch to a horse previously not itchy.
Treatment of the
microflilaria can be achieved with regular doses of ivermectin or moxidectin
(some recommend weekly or fortnightly) until symptoms subside. A horse that has neck worms will demonstrate increased
itching for 48-72 hours post worming.
The total onchererca life cycle lasts from 4 to 5 months, so consistent
treatment is a priority.
Excellent additional
reading can be found at http://thehorsesback.com/neck-threadworms/.
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