Fits take a variety of forms in dogs, just as in other animals. The general behaviour described as a fit involves salivation with champing movements of the jaws, usually followed by the sudden onset of spasmodic muscular contractions involving the head and neck, limbs and, possibly, other parts of the body, accompanied in many instances by interference with consciousness, partial or complete.
The duration of the fit may be a matter of seconds or minutes only, or the attacks may be repeated at intervals. Sometimes the condition persists for hours or days without any marked periods of remission. The severity of such fits may be so marked that they continue even when the dog is under anaesthesia.
The attacks may disappear and never return or they may recur after long or short intervals during puppyhood, sometimes with occasional appearances throughout the animal's life. Much depends upon whether the cause can be discovered and is capable of removal, or if it involves irreversible changes that have taken place in the brain.
Fits vary enormously in their pattern, but in individual cases accompanied by frequent repetition the pattern usually remains fairly constant so long as the cause is unchanged.
Although dogs of most or all breeds may develop fits, there arc in some strains or families hereditary tendencies that may increase susceptibility. The type of temperament inherited may confer greater nervous sensitivity and a diminished capability to compete with the strains and stresses associated with domestication. This may account for some of the fits seen in quite young puppies, and it may be that they are born with a brain defect.
On the other hand, a simpler explanation may be that certain strains may be abnormally sensitive to the migration of worm (ascaris) larvae throughout their bodies and nervous mechanism. The primary infection may come through the dam.
The point of origin of a fit is situated actually within the brain or its coverings (meninges), or it may arise from increased pressure of fluid present in one of the normal brain cavities. When the brain itself remains normal the fit is produced by abnormal outgoing impulses from the brain being transmitted to the muscles of the body under the influence of ingoing messages transmitted to the brain from some part of the body subjected to abnormal irritation. The local irritation responsible for such messages to the brain may be situated in the ears, in some portion of the alimentary tract, from the skin or the eyes, or in fact, from any part of the body.
Other causes of brain irritation include the presence of chemical substances within the blood. These may come from poison taken in through the mouth or injected into the animal, or may be associated with the presence of a toxin, or to excess or deficiency of some necessary hormone. Not uncommonly, a hormone imbalance gives rise to a corresponding mineral imbalance with alteration in the blood content of calcium, magnesium or phosphorus, or all three. Sometimes in diabetic subjects the fits may arise from imbalance between blood sugar and insulin.
In dogs of any age, but more usually in young dogs, especially those that have not been vaccinated against distemper, virus hepatitis and leptospiral jaundice, fits may be the first manifestation of an attack of one of these diseases already involving the brain cells. Conversely, the brain symptoms may never make their appearance or they may crop up weeks after apparent recovery from the primary infection.
Fits may occur during the course of kidney infections owing to accumulation of toxic products in the blood. In heart conditions, particularly in older dogs, fainting attacks are sometimes accompanied by struggling, recurring at frequent intervals.
Lactation in bitches, resulting in a lowering of the calcium content of the blood may produce hypocalcaemic symptoms (milk fever), frequently including tetany (muscle stiffness) and convulsions.
Accidental injury to the brain during puppyhood, as from a fall upon the head, may cause fits immediately or at a later date, and in some instances these fits may occur at intervals throughout the animal's lifetime.
Teething, especially when changing the canine teeth, will sometimes produce fits in susceptible puppies. These usually disappear when the second teeth come down. Such fits may be confused with those produced by round worms, which frequently cause trouble at about this age. At teething time the administration of tablets containing calcium gluconate and vitamin D may be helpful.
In a recent survey, Dr. Phyllis G. Croft discussed 26o cases of fits in dogs, and recorded electroencephalograms from each. From the results it was assumed that 167 of the 260 affected dogs examined were effected with epilepsy. The ages ranged from one to ten years, more often between one and three years. The incidence diminished from the fourth to the ninth years with a slight rise again atten years. All the common breeds appear to have been represented.
Fits Associated with the Ears
The more characteristic symptom is the position of the head, drawn usually down on one side or lifted upwards and backwards. Apart from infection conveyed by ear mites, the possible presence of one or more rapidly burrowing barley grass awns must always be borne in mind.
Fits due to ear mites may be seen occasionally in puppies, only a few months old, that have obtained them from the ears of the mother.
Fits Associated with the Alimentary Tract
Overeating, especially at weaning age, may give rise to a fit or fits, usually of short duration, if the puppy is fasted for some hours.
The need to worm puppies is always apparent but great care must be taken in the choice of a vermicide. Veterinary surgeons nowadays stock efficient remedies that produce no side-effects.
Fits Associated with the Skin
Heavy infestation with lice or fleas, and certain allergic skin irritations, have been suspected as being the cause of fits. It is probable that such symptoms arise only when there is an inborn predisposition to epilepsy.
Eyes and Fits
It has been recorded that some strains of puppies showing a tendency to fits are less susceptible if kept in the dark, possibly because they see less that is likely to disturb them.
Certain strains of puppies will develop fits if exposed to strong sunlight or when electric lights are turned on after dark. The probability is that these strains have an epileptic background.
Fits Caused by Chemicals
Chemical substances capable of producing fits or convulsive symptoms resembling them, include lead, derived from drinking water and bad plumbing; agene, formerly used in bleaching flour—a very serious cause of so-called 'hysteria' in dogs during and before the war years—and strychnine, which produces muscular contractions, followed by death.
Slug bait in the form of methaldehyde is commonly laid in gardens and is readily eaten by dogs and cats. In small doses it causes intoxication. Larger doses produce incoordination of limb movements, rapid breathing, muscular twitching, rapid movements of the eyeballs (nystagmus),
followed by unconsciousness and heart failure. The hypodermic injection of apomorphine, followed by atropine, usually succeeds if the dose is not too large and the interval between ingestion and injection not too protracted.