Paralysis Ticks

Dogs and cats taken to the coast during the warm months run the risk of picking up the coastal paralysis tick. Ticks hatch out in great numbers in the spring, particularly after rain. Even during a prolonged dry period like that prevailing, ticks can be numerous around any source of moisture such as creeks or water holes.

Ixodes holocyclus

Ixodes holocyclus, commonly known as the Australian paralysis tick, is a three-host tick. This means that it must feed off three hosts to complete its life cycle. A fully engorged female tick falls from its host and lays between 2000 and 3000 eggs before dying.

Given suitable conditions of moisture and temperature the eggs hatch to produce a six-legged larva. After about a week this larval tick attaches to a suitable host, such as a bandicoot or possum, engorges, then drops off and eventually becomes an eight-legged nymph. The nymph, after about a week, attaches itself to a second intermediate host, engorges and drops off, and after some weeks becomes adult.

The adult tick climbs on to a low bush or fern and attaches itself to a dog or cat as it pushes its way through the bush. Most ticks are found on the head or neck region of the dog. Once attached to the final host, they embed their head into the deeper layers of the skin and suck blood.

The rate at which the tick engorges is dependent on the temperature. In warm weather the tick may become fully engorged in about six days, in cold weather the process may take two weeks or longer. Only the female tick attaches itself, the male is much smaller and wanders over the surface of the host, feeding occasionally and searching for unfertilized females.

Signs

The host animal may experience some slight discomfort from the bite of the tick but usually does not give any signs to indicate that a tick is embedded in its skin. The first ill effect noticed is weakness of the hind legs and an unsteady gait. The animal soon is unable to stand and has difficulty in breathing. Loud retching noises are often made and if the animal is not treated it will soon die of respiratory paralysis.

The toxin responsible for the paralyzing effect on the host animal is secreted in the saliva of the tick as an anticoagulant. The length of time between the attachment of the tick and the first signs of toxicity in the host is variable and depends mainly on the size of the host and the site of attachment. In a very small dog, nervous symptoms may be apparent in about four days. In a large dog ill effects may not be apparent for 7 to 10 days. If more than one tick is present the symptoms develop sooner and are more severe.

Treatment

Treatment of tick paralysis must be sought as soon as any of the nervous symptoms are observed. A careful search should be made for ticks and when found they should be removed by grasping them as close to the skin as possible with a pair of forceps or sharp nosed pliers. Do not try to burn the tick with a lighted cigarette or turpentine.

The veterinarian administers anti toxin intravenously and usually admits the animal to monitor its response. If vomiting has occurred, fluids may be given by injection. It must be remembered that there may be more than one tick present.

Preventive measures must be taken to protect dogs visiting coastal areas. It is risky to rely upon searching the animal each, night in the hope of finding ticks before they are large enough to harm the dog. It can be extremely difficult to find a tick in thick coated animals. There is now available a wash which, when applied once weekly, will prevent ticks attaching themselves to the skin.

Of course, if a dog swims regularly it will wash the insecticide off. In these dogs it is preferable to use tick tablets which when given daily and in the correct dosage, prevent infestation. Care should be taken to administer the tablet a day or so after returning from the coast in case a tick was picked up just before leaving.

Anti-tick serum is extremely expensive. Treatment is not always successful in acutely affected animals. The preventive measures are safe, relatively inexpensive and effective.

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