The incidence of distemper steadily declined to such an extent that many veterinary graduates in urban areas often were in practice for some time before a case of distemper came their way.
In human and veterinary medicine, when a disease has been efficiently controlled with a simple vaccination procedure, there is a tendency to become complacent and neglect the very procedures that brought about a diminution in the incidence of the disease. This has happened with canine distemper.
Veterinary practitioners in the U.S. have reported seeing a higher than the usual number of cases of distemper. In most cases, the dogs involved had not been vaccinated, but in the case of some greyhounds, they had received at least one vaccination.
Distemper in dogs is caused by a virus infection. The earliest signs of the disease are usually of yellowish discharge from the eyes and nose, accompanied by a mild fever. The owner often ignores these early signs as he thinks the dog merely has a cold.
As the virus proliferates in the dog’s body, it may attack the respiratory system causing tonsillitis and coughing and eventually pneumonia.
If it attacks the digestive system, vomiting and diarrhea occur, but the worst feature of the distemper virus is that it frequently attacks the nervous system producing a variety of serious symptoms.
The dog first develops localized nervous spasms affecting the muscles of the head or limbs. These gradually become more severe, producing violent fits and paralysis.
As the cause of distemper is a virus, antibiotics are useful in controlling only the effects of secondary bacterial infection. Once nervous symptoms become apparent the chances of recovery are very poor.
Some dogs seem to recover from the initial respiratory or enteric forms of the disease only to develop nervous symptoms 2 or 3 weeks later.
Vaccination is the only method of preventing canine distemper. The newer form of the vaccine is produced from live, non-virulent virus grown in tissue cultures.
Such pure standardized vaccine eliminates the problems that were experienced with older type vaccines, which occasionally included virulent infections or produced ill-effects due to the animal becoming hypersensitive to some of the impurities.
It is recommended that puppies be given the first distemper vaccination at 6 weeks of age. A second vaccination is then necessary at 12 to 14 weeks, then again a year later. Subsequent vaccination is then advised every 1 or 2 years, depending on the preferences of the individual veterinarian.
Breakdowns in immunity from vaccination are now fortunately rare. Where they have occurred they have usually been traced to the animal not receiving vaccinations after the initial puppy vaccination.
The immunity gained from a single vaccination before 12 weeks can be affected by the presence of immune factors derived from the mother. These can be present up to 12 weeks of age, hence the recommendation to vaccinate again after 12 weeks.
Dogs kept either in their own backyards or on rural properties do not have the opportunity to have their immunity challenged and subsequently reinforced by contact with other dogs carrying the natural disease. It is therefore most important to regularly re-vaccinate animals in isolated situations.
Distemper in cats is highly infectious, and widespread so that almost all cats during their lifetime will come in contact with the organism.
The virus of feline distemper survives for extremely long periods outside the host animal. It can remain infective in contaminated premises for at least a year. It is this characteristic that ensures that each crop of kittens in a particular area comes in contact with the virus.
While cases of feline distemper can occur at any time throughout the year, most epidemics occur in the autumn and early winter because it is at this time that the new year’s crop of kittens are 3 to 4 months old and have lost the temporary immunity gained from their mothers.
The incubation period of the disease is very short, usually about 5 or 6 days. Infected kittens become quiet, refuse food, and start to vomit. At first, the vomit consists of the previous meal, then white mucus, and as vomiting becomes more frequent and violent, it becomes colored by yellow bile.
In very acute cases of the disease the kitten may die within 24 hours, which frequently leads the owner to suspect that the kitten has been poisoned. More usually the disease is less acute, and the animal becomes very depressed, sits hunched over its water bowl, and cries if handled.
In the early stages of the disease, the animal’s temperature is elevated, but it soon falls to a subnormal reading, which is not a favorable sign when assessing, the prognosis of the case.
One of the characteristics of the virus is that it not only attacks the cells lining the intestinal tract but it quickly invades the blood, forming tissues in the bone marrow. This leads to a dramatic fall in the white blood cells in the bloodstream, which further decreases the animal’s resistance and chances of survival.
Treatment of the feline distemper must be begun at the first signs. If left for 2 or 3 days irreversible damage occurs in the cells of the intestinal tract and bone marrow.
Fluids are given intravenously to combat dehydration and loss of electrolytes through vomiting. Drugs are administered to limit vomiting and antibiotics used to prevent secondary bacterial infections of the bowel and further complications of the disease.
Fortunately, in recent years the incidence of distemper in cats has dropped dramatically. No longer do we see annual epidemics decimating the population of young kittens.
The sole reason for this is the widespread use of efficient vaccines. Most cat-owners are now aware of the need to protect their kittens and seek their veterinarian’s advice as soon as they acquire a new kitten.
It is most important, however, that we continue to be conscientious in these programs, as the large population of feral and stray cats surrounding our suburbs ensures, that the virus will always be present and that even the most carefully looked-after cat will at some stage of its life come in contact with the virus.
There is a large range of vaccines available to the veterinarian, and depending on which type he favors, the recommendations for the timing of vaccination programs may differ slightly.
Where a small kitten cannot be completely isolated it is advisable to vaccinate as early as 8 weeks. Vaccination at this time may not be effective for very long, because of the persistence of a passive immunity passed on from the mother.
Re-vaccination is necessary at 14 weeks, then a year later. If the kitten can be kept isolated from contact with other cats it is possible to wait until 12 weeks for the initial vaccination, which is then repeated a year later.
Recently a vaccine against feline influenza has been developed. The initial vaccination is given in two injections 3 to 4 weeks apart. Annual boosters of a single vaccination are necessary.
It is possible to obtain a combined vaccination containing feline distemper and feline influenza, and this is useful for kittens receiving their initial vaccinations arid for their annual boosters.