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Harvest Mite Infestation

Horner's Syndrome




Harvest Mite Infestation

The harvest mite (Trombicula autumnalis) is a mite the larval stage of which causes considerable discomfort to cat during the late summer and autumn.

The mite is particularly abundant in chalky areas and gardens where soft fruit is grown.

The six legged larval stage is the only stage which attacks warm blooded animals. They are active during the day and particularly in dry sunny weather.

When a warm blooded animal comes into contact with the larvae they swarm onto it and attach onto skin particularly in sparsely haired thin skinned areas. The larvae feed for 2 to 3 days and they drop off onto the ground to complete the life cycle. The larval mite is orange and only just visible to the naked eye.

What effect do harvest mites have on cats?

The six legged larval mite attaches to the skin of cats to feed. It fixes onto the skin by small hooked fangs and then injects fluid into the skin which liquifies cells.

The resulting liquified food is sucked back by the mite. The fluid injected by the mite is very irritable. Irritation causes the cat to scratch, bite and lick which may result in extensive self-inflicted injury.

The resulting skin lesions vary from crusted spots to areas of hair loss to raw moist bleeding areas.

In cats mites are most commonly found on the ear flaps, on the sparsely haired area in front of the ears and between the toes but they can be found almost anywhere on the body.

Individual cats vary greatly in their sensitivity to mites. Extreme sensitivity probably reflects the development of an allergy to the mite or its products and affected cats will cause severe self-inflicted damage.

How are harvest mite infestations diagnosed?

Sudden onset of intense irritation in July or August would make one suspicious that harvest mites might be involved although other ectoparasites and some forms of allergic skin disease can cause similar symptoms.

How can I get rid of harvest mites from my cat?

Your veterinarian will give you appropriate treatment which is usually a licensed spot-on treatment. The problem is that unless the product has excellent residual action as soon as the cat returns to the infested environment it will collect more mites.

To avoid this the cat can be restricted to indoors during the mite season. Fortunately there are now flea control products available with good residual action which may be able to prevent or considerably reduce reinfestation.

Such products should be applied to the cat during the harvest mite season (July to October) at the highest frequency suggested in the instructions.

What can be done to stop my cat itching?

In most cases treatment for the mites will rapidly make the cat feel more comfortable. In cats which are very sensitive to mites additional treatment with anti-inflammatory therapy and occasionally physical restraints such as Elizabethan collars may be necessary to prevent further self-trauma.

Do harvest mites affect people?

People can be affected by harvest mites. These are not caught from cats or dogs but from infested outdoor environments. Peoples' ankles become affected by walking through infested vegetation but more generalised lesions can follow sitting or lying in infested areas.

A typical human skin reaction consist of an intensely irritant rash. Specific treatment is usually unnecessary. Avoidance of infested environments is the best way of preventing the problem.


Horner's Syndrome

Horner's Syndrome is a group of signs that occurs when specific muscles of the face lose their stimulation by certain nerves. It is caused by some type of injury to, or lesion of the nerves.

The injury may occur at the level of the brain, upper spinal cord, or between the spinal cord and the face. In the cat, the most common causes are:

  • Idiopathic (cause unknown)
  • Car accidents with trauma to the head, neck, or chest
  • Bite wounds
  • Intervertebral disc disease in the neck area
  • Infections of the middle ear
  • Disease of the orbit (area behind the eye)
  • Cancer involving the brain or chest
  • As a result of a treatment (e.g.ear cleaning) or medication

Approximately 40-50% of the cases of Horner's Syndrome in dogs are idiopathic ie of no known cause.


The classic signs of Horner's Syndrome occur on the same side of the face as the injury, and include:

  1. Small pupil size (miosis)

  2. Protrusion of the third eyelid

  3. Drooping of the upper eyelid (ptosis)

  4. Sunken appearance to the eye

  5. Dilation of blood vessels on affected side of the face, which makes the area feel warmer to the touch

How is Horner's Syndrome treated?

Depending upon the location of the injury, phenylephrine eye drops are administered to relieve the clinical signs.

The underlying cause such as a bite wound or middle ear infection should be treated. In cases of idiopathic Horner's Syndrome, the condition often resolves after 6-8 weeks. Horner's Syndrome caused by injuries to nerves outside of the brain and spinal cord generally have a better prognosis.



Hypertension (high blood pressure) is common, particularly in older cats and can result in damage to blood vessels.

The blood vessels in the retina of the eye are particularly sensitive to hypertensive or high blood pressure damage, which may result in retinal detachment and sudden blindness. Affected cats appear confused and disorientated, with widely dilated pupils.

Retinal detachment is an emergency situation as blindness will become permanent unless the retina reattaches within a few days. Drugs that lower blood pressure are routinely used in the treatment of hypertension in cats.

Other diseases, for example, chronic renal failure can also lead to hypertension, meaning that a number of different tests may be required to establish the underlying cause of the increase in blood pressure.

Over recent years, the ability to measure blood pressure in cats has improved which has made the treatment of hypertension more successful.



Hyperparathyroidism is a condition in which the parathyroid glands (not the thyroid glands) produce too much parathyroid hormone. Parathyroid hormone is responsible for maintaining the correct balance of calcium and phosphorous in the blood.

If blood calcium is low, the parathyroid hormone level increases, which causes calcium to be taken out of the bone to maintain the correct calcium level in the blood and other tissues.

The parathyroid glands are located next to or actually inside the thyroid glands in the neck. There are two types of hyperparathyroidism.

Primary hyperparathyroidism

Primary hyperparathyroidism occurs when one or more of the parathyroid glands becomes cancerous or produces excess parathyroid hormone.

This causes the calcium levels in the blood to be higher than normal. Primary hyperparathyroidism is generally seen in older animals and is more common in dogs than cats.

Animals with primary hyperparathyroidism may lose their appetite, vomit, drink and urinate more, and may appear drowsy or listless.

The signs often come on gradually and considerable organ damage may occur before the animal shows significant symptoms.

The treatment of primary hyperparathyroidism is removal of the abnormal or cancerous gland. The removal of the gland causes a sudden decrease in the amount of parathyroid hormone, and there is a corresponding sudden drop in the blood calcium level.

For this reason, the animal must be monitored closely after surgery and given calcium if the level becomes too low.

Secondary (nutritional) hyperparathyroidism

Secondary hyperparathyroidism is more common and occurs most frequently in kittens fed an all-meat or organ diet (such as all liver) or a diet with an imbalance of calcium and phosphorous.

Meat contains an excess of phosphorous and inadequate amounts of calcium. Although cats are carnivores, they not only eat meat, but the bones as well, which supply the needed calcium and help to create a better calcium and phosphorous balance.

In secondary hyperparathyroidism, because the calcium intake is low, the parathyroid gland produces more parathyroid hormone, and calcium is removed from the bones. This imbalance may also occur with kidney failure.


The main symptoms are:

  1. Excessive drinking and urination
  2. Urinary incontinence
  3. Listlessness
  4. Exercise intolerance and weakness
  5. Stiffness
  6. Inappetance
  7. Muscle wasting
  8. Vomiting and constipation.


If the calcium levels are excessively high then this constitutes a medical emergency and the cat will need to be hospitalised, put on a drip and given drugs.

When the cat is stable then the underlying cause of the disease can be investigated. If the cause of the disease is a tumour, then this can be removed surgically.

If the disease is occurring secondary to a kidney problem, although any existing kidney damage cannot be repaired; steps can be taken by your vet to slow down any subsequent damage and address the calcium imbalance.


Hyperthyroidism results when the thyroid gland produces an excess of thyroid hormones. This happens most commonly when the thyroid gland has become cancerous.

Hyperthyroidism most commonly develops in cats over eight years old. Cats that are hyperthyroid are usually hearty eaters, sometimes even ravenous, yet they continue to lose weight in spite of how much they eat.

A more serious consequence of hyperthyroidism is the development of an increased heart wall muscle and resulting cardiomyopathy (disease of the heart). This is first detected by an increased heart rate which we will hear using the stethoscope.

A diagnosis of hyperthyroidism is made with a blood test sent to the laboratory which indicates an increase in the hormone thyroxine.

Treatment involves taking anti - T4 medication twice daily which reduce the size of the thyroid glands. Repeat blood tests are necessary to monitor the levels of thyroxine in the blood.

An overload of rich food can cause a diarrhoea and as your cat never feels satisfied, they have to constantly ‘ask’ you for food which is why they may suddenly become quite vocal.

Some cats respond very well to having the thyroid gland surgically removed.