CANINE DISTEMPER. Distemper is an acute, contagious and infectious disease of dogs, septicaemic in nature and trans missible to certain other carnivorous animals. The condition occurs in all countries possessing a canine population. The early history of distemper has been lost in antiquity, but possibly it was introduced into Europe during the middle of the i8th cen tury. Carre, in 2905, and later, Lignieres, ascribed the cause of the disease to a filtrable virus. Ferry, McGowan and Torrey (1910 11) isolated a small, gram-negative bacillus, named by Ferry B. bronchisepticus. In 1923, the editors of the Veterinary Jour nal and the Field inaugurated the Field Distemper Research Fund, and since that date the disease has been the subject of extensive scientific research, carried out by veterinary and medical workers, under the Medical Research Council.
Although distemper is endemic in countries possessing a canine population, the disease becomes epidemic at varying in tervals, and outbreaks may assume an exceptionally severe form with a heavy mortality; in many of the animals which survive, a permanently impaired constitution remains. Large towns are seldom free from the disease. A few animals appear to possess a more marked power of resistance, but it is probable that many of these have developed the disease and acquired a degree of immunity, without being subjected to the secondary complica tions, which are more usually the causes of the various sequelae.
Young animals are more susceptible than old ; in suckling pup pies the condition is often rapidly fatal. Weakly animals and pedigree dogs, in which blood interrelationships exist, are gener ally less resistant than coarsely bred animals. Healthy animals may contract the disease by exposure to the crude or filtered nasal discharge of affected animals, and the same is true of the blood and body fluids, the secretions and excretions. This applies more especially in the early stages of the disease.
The disease is air borne, but mediate and immediate contagion are the more fruitful sources; drinking bowls, feeding utensils, brushes, the clothing and boots of attendants and contamination voided by infected dogs (more especially those in the early stages of the complaint) are all sources of infection. The early stages of the disease may pass unobserved; after exposure, an incuba tion period of 3-5 days elapses, malaise supervenes, and the thermometer reveals a temperature of 1o5°-1o6° F. This initial pyrexia is speedily followed by a fall of body heat to the region of normal, but the temperature may again rise after a few days. The patient is very infective during this period.
The most favourable course is towards resolution, and, save for some loss of condition and slight malaise, the disease may remain undetected; far more commonly, however, secondary in fections supervene. Organisms, normally present in, and non pathogenic to, the animal, may assume virulence ; also extraneous infections may be acquired, especially in animals existing in un hygienic and overcrowded surroundings. Predisposing causes, such as chills and getting wet also play a part.
A virulent form of the disease is sometimes met with, charac terized by persistent high temperature, asthenia, marked depres sion and death within a few days. The acute form is character ized by fever, often remittent, and the onset of symptoms showing a wide divergency. Although some of the symptoms may remain constant over a series of cases, they may be modified, or entirely absent, and the virus may appear to select some special group of organs, such as the respiratory, the alimentary tract, the central nervous system, the mucous membranes or the skin.
General malaise, rigors, capricious or complete loss of appetite, vomiting, diarrhoea or dysentery, may be some of the symptoms shown ; also serous, muco-purulent or sanguineous, discharges from the conjunctival and catarrhal mucous membranes; mat ting of the orbital hair and scalding of the eyelids, photophobia, ophthalmia, iritis, ulceration of the cornea, protrusion of Des cemet's membrane, synechia, and even extrusion of the lens; ulceration of the nostrils; herpetic rash round the lips, stomatitis, ulceration of the gums, lips, tongue and fauces. A characteristic short, moist cough is very common and indicates an inflammation or catarrh of the larynx which may be the onset of broncho pneumonia; later, mouth breathing and pouching of the lips in dicate that the lungs are the seat of consolidation. Vomiting may be troublesome; at first catarrhal in character it becomes watery and bile stained. The small intestine and lower portions of the alimentary tract becoming involved, there supervenes profuse diarrhoea, which becomes foetid and haemorrhagic.
Nervous symptoms may occur at any stage of the disease, or during convalescence, and are of grave significance. The animal may show hypersensitiveness to sounds; epileptiform fits and convulsive muscular spasms, with chattering teeth and foaming jaws, terminating in unconsciousness or a meningitis in which the patient is partially or completely blind, wandering about in circles or standing with its head pressed up against the side of the kennel; partial, or complete, paralysis, especially of the hind quarters and the sphincters of anus and bladder. One of the commonest sequelae to recovery from the nervous forms of dis temper is a persistent twitching of the muscles known as chorea; unfortunately this is usually permanent. In some cases a vesicular eruption develops which becomes pustular and may be confluent. If abraded, the vesicles are apt to form raw areas; otherwise they form dry, brownish scabs. These are to be looked for on hairless portions of the skin, such as under the armpits, thighs, and around the lips. Eruptions of this kind are, however, also seen in other conditions in puppies, such as teething.
The average duration of the disease is from a month to six weeks, the percentage of recoveries varying with the virulence of the disease. Catarrhal forms, associated with a free discharge from the nose and eyes, even when associated with some degree of bronchopneumonia or gastrointestinal catarrh, yield the highest percentage of recoveries. Skin lesions are troublesome, but comparatively unimportant, except as tending to exhaust the in dividual. Vomiting and diarrhoea, if severe, are of the utmost gravity as, naturally, they interfere with the nutrition of the patient, causing exhaustion and emaciation. The most hopeless type is that showing brain involvement associated with frenzy, convulsions or coma. Paralysis will often yield to proper treat ment and skilful nursing, but convalescence may take weeks, or even months, to establish.
There is no specific cure to suit every case, and treatment must be modified according to the symptoms shown. Expectorants, febrifuges, alimentary sedatives, astringents and antiseptics, nervine sedatives and, in the later stages tonics, all find uses. Various vaccines and anti-distemper sera have been advocated, but so far the results have not been satisfactory.
Laidlaw and Dunkin, working under the auspices of the Field Distemper Research Committee, have recently (1928) confirmed Carre's finding that the disease is due to a filter-passing virus (see FILTER-PASSING VIRUSES), and they have succeeded in con ferring an immunity on the ferret ; on the dog, however, their work is not yet complete and, although the reports published are very encouraging, it is too early yet to form any definite opinion. It is certain, however, that the possibility of immunization offers the best hopes, and, if success can eventually be achieved, an inestimable boon will have been conferred upon the canine world.
(F. T. G. H.)