Disease of the Nervous System

By | June 24, 2010

Chorea

Involuntary regular muscle twitching is a serious sign, usually indicating a complication of distemper or related infectious disease. Tremors characteristi- cally occur around the head and shoulders, often appearing worse when the dog is asleep. Unfortunately Chorea often begins a couple of weeks after apparent recovery, then progresses to generalized muscular spasms and culminates in fits. The dog is in a poor state which usually requires euthanasia to stop further suffering.

Occasionally, twitching remains limited to a single group ofinuscies, on top of the head, and may even regress altogether. Whatever the course of the illness, professional attention is urgent as soon as such signs are noticed.

Distemper

Canine Distemper is a most miserable, often fatal affliction, caused by a virus still prevalent in Europe, although a highly effective vaccine is available. The disease, which is highly infectious, is usually seen in young dogs, but can affect individuals of any age. It is often fatal, but not immediately so, and an afflicted dog may endure a long illness, seem to recover only to succumb to com- plications several weeks later.

The classic signs of Distemper, not always immediately apparent, include thick discharge from eyes and nose with heavy encrustation, and persistent coughing. There is usually a fever with some vomiting and diarrhoea, and the disease may progress to pneumonia and death. With good nursing care and supportive therapy, the dog may recover completely; however, others appearing to make a good recovery become afflicted with nervous muscle twitches.

Vaccination will prevent almost all cases of Canine Distemper. The timing of injections and annual boosters is a matter for the Yeterinarian, based on the disease pattern in the locality.

Encephalitis

The brain may become inflamed, usually as a result of a viral infection, and lead to encephalitis. With this goes a variety of serious nervous symptoms, particularly seizures, incoordination. and aggression with infections such as rabies. The dog may lose consciousness and show obvious signs of eye defects and much pain around the head. A similar chronic condition, occurring in older dogs, is called Old Dog Encephalitis. All cases of encephalitis require urgent veterinary attention.

Facial Paralysis

The maintaining of muscle tone and power of contraction depend on the integrity of those nerves which innovate each muscle group. If nerves are damaged extensively, all power and tone is lost in the related muscle group. The motor nerve for the face is the VI Ith (facial) nerve; occasionally it is severed in a serious accident, but loss of power is often due to interference with nerve conduction by extension of severe inflammation of the middle ear. The result is a general sagging of the face on the affected side; the dog cannot take up food and drools a good deal of saliva.

Old Dog Encephalitis

It is often difficult to distinguish the process of ageing from pathological changes of certain diseases. Chronic inflammation of the brain (Encephalitis) can develop very slowly from middle to old age. Dogs become less mentally alert and may lose some of the habits they have acquired over the years. They may become depressed, appear completely unaware of their surroundings for certain periods and reasonably normal the rest of the time. Like very old people, they are unable to concentrate for very long. At advanced stages the dog may have difficulty balancing, it will hold its head on one side, and move around in circles. Many cases respond to treatment with cortico-steroid drugs, though improvement is usually short-lived.

Paralysis

Damage to the nerves which control limb movement results in some loss of function, or paralysis. Infections such as Distemper and Rabies may lead to some degree of limb paralysis. Lead poisoning usually shows as nervous signs which may include hindlimb paralysis. Other main causes of paralysis are disc protrusion and injury caused by violent accidents. Damage to the spinal cord is usually irreparable and complete loss of control of the hind, or all four 5 limbs, after a violent episode is a grave sign. If the nerves to the forelimb are severed, as sometimes happens after a blow near the first rib, the dog may drag its foreleg and cause extensive ulceration, often requiring limb amputation. Partial paralysis (paresis) may with diligent nursing respond to treatment.

Rabies

In countries such as Britain, where rabies is absent,, it is difficult to grasp the extent and effect of this disease. Rabies is an infectious virus disease affecting all warm-blooded animals, including man. Normally only animals which live by biting their prey spread the disease, but in almost all species, including humans, rabies comes to a dead end in every sense. Mercifully, human deaths are rare in Europe and North America, but other parts of the world, notably Africa and India, are much less fortunate.

The main vector of rabies differs around the world and includes bats, raccoon, skunk, mongoose and red fox, but dogs are the most likely to pass rabies to humans. It is possible to protect dogs against rabies where the disease is rife, and to give humans effective vaccination protection even after being exposed to rabies, provided this is done without delay.

In dogs, the disease runs its course in about ten days, although it may be several months before clinical signs develop – hence the six-month quarantine in most rabies-free countries. The first indication of the disease is usually a change of temperament: friendly dogs may become aggressive, and very active dogs subdued. Characteristically the bark rises in pitch. The main signs which follow involve the nervous system;. the widely held view that rabid dogs career around the countryside biting everything in their path is only true of a minority of cases. Many pass rapidly to a paralytic phase, so-called’dumb rabies’, where they become paralysed and unable to close their jaws. Eventually they die from respiratory failure.

Because of the health risks to thepublic, suspected rabies should be notified immediately, to the local veterinary surgeon and to the police.