Canine distemper is an acute highly contagious disease, which is caused by a filterable virus. The infection is spread from one dog to another by direct contact. Infection may also be spread by indirect means such as contact with an infected kennel or the consumption of food and water contaminated by the discharges of an infected animal.
Young dogs between the age of three months and one year are principally affected. Mature dogs as the result of previous exposure to infection are usually immune to the disease. Dogs of all ages which have not previously been exposed to the disease are highly susceptible. The mortality rate is high and it is estimated that from 30 to 50 percent of the dogs which become affected die of the disease.
The incubation period of the disease, i.e., the time which elapses from exposure to infection to the appearance of symptoms, under natural conditions is usually about seven days. Symptoms may appear as early as the third or fourth day or they may be delayed for as long as three weeks.
The earliest symptoms are rather indefinite and consist of listlessness and reduced appetite together with a slight watery discharge from the eyes and nose. During this period, there is a marked rise in body temperature, which may reach 105 degrees. After a few days, the symptoms become more definite.
There is a discharge of mucus and pus from the eyes and nose, shivering may be noticed, and a slight cough is usually present. The muzzle is hot-and-dry and may become blocked by the discharge causing the animal to breathe through its mouth.
The animal becomes increasingly dull and listless, is disinclined to eat, and lies down and sleeps almost continuously. Yellow pustules are sometimes observed on the hairless areas on the undersurface of the body.
After the end of the first week, various complications frequently make their appearance. These may include pneumonia which is denoted by constant and pronounced coughing and difficult respiration, gastroenteritis which pauses vomiting, diarrhea, and straining, and disturbances of the brain and spinal cord which may result in the development of convulsions, paralysis, and chorea (twitching of muscles).
In advanced cases of distemper, the animal becomes extremely weak and loses many conditions. In uncomplicated cases, the disease runs a course of three to four weeks. Where there are complications several months may elapse before recovery occurs.
Dogs that have recovered from an attack of distemper often suffer serious after-effects. Partial paralysis of the hindquarters associated with a swaying unsteady gait and chorea affecting the masticatory muscles which are accompanied by constant champing of the jaws are commonly observed. Recovery from the disease results in the development of strong and lasting immunity.
The treatment of severe and complicated disease such as distemper presents many problems requiring the services of a qualified veterinary surgeon. Whenever possible veterinary assistance should be obtained without delay. If treatment is commenced as soon as symptoms make their appearance the chances of recovery will be greatly increased.
In the early stages of the disease, the injection of canine anti-distemper serum is of considerable value. Given in a dose of 10cc or more (according to the weight of the animal) and repeated at intervals of 24 hours if necessary, anti-distemper serum will frequently bring about a reduction in the severity of the symptoms which is followed by the recovery of the animal.
When the disease has existed for a week or longer and particularly after complications have set in, the serum is generally of little value.
There are no drugs that have a specific action in the treatment of distemper, and beneficial effects cannot be expected from the various remedies reputed to possess curative properties. Recovery may be assisted by good nursing and careful attention to sick animals.
Dogs affected by distemper should be kept as quiet as possible and should under no circumstances be allowed exercise. They should be provided with clean, warm, dry, but well ventilated quarters, and should be kept clean by daily brushing and grooming.
The nose and eyes should be kept free of discharges. The eyes should be bathed with a warm solution of boric acid and the eyelids smeared with boric acid ointment to prevent gumming. The same ointment should be applied around the nostrils and will prevent cracking.
The appetite should be encouraged with nourishing, easily digestible food such as milk, broth, minced beef, and raw eggs. Food should be given in small quantities and at frequent intervals. Little and often is the rule which should be followed in the feeding of distemper cases. Food should not be forced upon an animal that struggles or resists; the exertion involved is more likely to aggravate the condition rather than improve it.
The treatment of the complications which occur in distemper is a matter for the expert attention of a veterinary surgeon and will vary considerably according to the symptoms exhibited by the affected animal. A discussion of such treatment would serve no useful purpose here.
In the control of distemper, it is important to prevent contact between infected and susceptible dogs. Since the disease is so widely distributed, this is difficult and is rarely possible in cities and towns where large numbers of dogs are kept.
In-country districts, the difficulties are usually not so great, and when the disease is known to be prevalent, contact between dogs on neighboring properties and especially with dogs in adjacent towns should as far as possible be prevented.
Newly-purchased animals should be isolated for three weeks before being allowed to come into contact with other dogs on the property.
After an outbreak of distemper has occurred and before a new dog is introduced, bedding and other material which may have been in contact with infected animals should be burnt and the kennels should be disinfected with 5 percent lysol solution. As an added precaution the kennels should be allowed to remain vacant for three or four weeks.
Distemper may be prevented by the immunisation of susceptible dogs. Dogs should be immunised during the first year of life. Three or four months is considered the most suitable age. They should be in good general health at the time of treatment and should be freed from parasites.
In the process of immunisation the animal is inoculated with a small dose of distemper virus followed an hour or two later by an injection of anti-distemper serum. In consequence of these injections the animal develops a mild controlled attack of distemper from which it rapidly recovers. This infection stimulates the formation of antibodies in the tissues and blood of the animal enabling it to resist the disease if subsequently exposed.
While undergoing immunisation the animal is capable of transmitting infection to other dogs, and must be isolated for fourteen days. During this period it should be kept under close observation and daily temperatures should be taken.
Apart from a moderate rise of temperature occurring usually on the fourth day the majority of dogs suffer no serious effects from the injections. In a small percentage of cases symptoms of distemper occur and this must be controlled by a further injection of serum.
Canine distemper virus is supplied by the manufacturers only to qualified veterinary surgeons. The virus is an extremely unstable product and unless handled in accordance with certain specified conditions it will lose its potency and prove quite useless as an immunising agent.
Moreover in the handling of a living virus special precautions need to be taken to prevent the spread of infection to other dogs. There are a number of equally important factors to be considered and it is consequently essential that treatment of this kind should be undertaken only by a veterinary surgeon. In view of the wide distribution of canine distemper the immunisation of young dogs and puppies may be recommended as a routine practice.
In districts where veterinary services are unavailable it should be possible by a cooperative effort to arrange for the treatment of a sufficient number of dogs to warrant a visit by a veterinary surgeon from some other area.