Analysis of the Occurrence of Canine Distemper and Preventive Measures
Canine distemper is a highly contagious infectious disease caused by the canine distemper virus, a member of the genus Morbillivirus in the family Paramyxoviridae. We analyzed a total of 55 cases of canine distemper and suspected cases diagnosed and treated from February to April 2003. The occurrence patterns were diverse and rather complex. They are reported below for reference.
1. Occurrence of canine distemper
1.1 Causes of the disease. There are many and rather complex causes of this disease. According to the investigation, 22 cases (40%) developed the disease suddenly after being chilled from bathing; 28 cases (50.9%) developed canine distemper secondary to indigestion and food stagnation caused by overeating, excessive protein in the diet, or lack of coarse grains; and 5 cases (9.1%) developed the disease due to strong winds and temperature drops, continuous overcast and rainy weather, a sudden change of owner, a change of diet, long-distance transport, or traveling with the dog. From the perspective of vaccination, a total of 52 cases (94.5% of the total number of cases) developed the disease because they had not been vaccinated, or although vaccinated, the vaccine used was of poor quality or the vaccination was not carried out scientifically; a total of 3 cases (5.5%) still developed the disease despite strict vaccination as required.
1.2 Age of onset. From the 55 cases of canine distemper and suspected cases diagnosed and treated, the occurrence differed somewhat among dogs of different ages. There were 3 cases (5.5%) under 2 months of age; 37 cases (67.3%) from 2 months to 1 year of age; and 15 cases (27.3%) from 1 to 5 years of age. Clinically, no cases were seen over 5 years of age, but it has been reported that abroad the oldest dog to suffer from canine distemper was 8 years old.
1.3 Relationship between occurrence and breed. Among all cases, small and medium-sized dogs (such as Pekingese, Lhasa Apso, Pekingese-Lhasa Apso crossbreeds, Pug, Papillon, Chihuahua, Cocker Spaniel, Bulldog, Basset Hound, No. 3 Hound, No. 5 Hound, Pomeranian, etc.) accounted for 37 cases, or 67.3% of the total number of cases; large dogs (such as Dalmatian, Great Dane, Black Back, fighting dogs, Tibetan Mastiff, Greyhound, meat dogs, and ordinary hounds, etc.) accounted for 18 cases, or 32.7% of the total number of cases.
1.4 Occurrence in different months. In February, there were a total of 10 cases of canine distemper and suspected cases, accounting for 18.2% of the cases; in March, 17 cases occurred, accounting for 30.9% of the total number of cases; in April, 28 cases occurred, accounting for 50.9% of the total number of cases.
1.5 Types of onset. Canine distemper can be divided into four types, namely the nervous type, the macular type, the respiratory type, and the digestive type. Clinically, the nervous type and macular type are extremely rare; in the three months from February to April, only 2 cases of the nervous type and 1 case of the macular type were seen, accounting for 3.6% and 1.8% of the cases of canine distemper respectively. Simple respiratory-type canine distemper was also uncommon, with only 4 cases, accounting for 7.3%. The digestive type of canine distemper had the highest incidence; together with the combined digestive-respiratory type, there were 48 cases, accounting for 87.3%. However, during the progression of the digestive type and respiratory type of canine distemper, neurological symptoms appeared.
2. Typical manifestations of canine distemper
2.1 Nervous type. It manifests as sudden screaming, convulsions, and coma, with the dog falling to the ground and dying within a short time, but it should be distinguished from the symptoms of acute encephalitis in dogs. As neurological symptoms of the other types, it mainly manifests as twitching of the lips, foaming at the mouth, difficulty swallowing, drooling, spasmodic contraction of the limbs, unsteady standing, difficulty walking, or a recumbent posture with paddling-like movements of the limbs.
2.2 Digestive type. It manifests as typical symptoms of gastroenteritis, with reduced or absent appetite, reduced or stopped water intake, and persistent vomiting. Vomiting may occur even on an empty stomach, and at this time a viscous, foamy liquid is mostly vomited. Sometimes red blood streaks or dark red blood clots are vomited. Constipation occurs first, followed by diarrhea, with thin, foul-smelling feces mixed with various pathological products, such as blood, mucus, pus, gelatinous material, and sloughed intestinal mucosa. Systemic changes are obvious, such as elevated body temperature, accelerated breathing, and rapid heartbeat. In addition, a dry nose mirror, even keratinization and cracking, is seen. Sticky or mucopurulent eye discharge and excessive keratinization of the foot pads, even roughness with spiky projections, are also typical features of this disease.
2.3 Respiratory type. In addition to some symptoms similar to those of the digestive type of canine distemper, it is prominently manifested by coughing, sticky or mucopurulent nasal discharge, and difficulty breathing, but most still have an appetite.
2.4 Macular type. Canine distemper mainly manifests on the skin of the chest, under the abdomen, and other areas as scattered or diffuse red spots, erythema, vesicles, pustules, etc.
3. Preventive measures for canine distemper
3.1 Strict prevention. At present, the production, operation, and management of biological products on the market are relatively chaotic, and there are many counterfeit and inferior canine vaccines. Therefore, it is necessary to choose vaccines of well-known brands produced by legitimate manufacturers, distributed through legitimate channels, and recognized by the relevant functional departments, and to use them strictly according to the product instructions, such as vaccine storage, method of use, number of uses, interval between two uses, and booster immunization.
3.2 It is recommended that dogs that can be kept individually be kept in groups as little as possible, so that the kennels and environmental hygiene are good, which can reduce the occurrence of canine distemper.
3.3 Feed should be nutritionally complete, and feeding should be regular and quantitative, without overfeeding; do not feed spoiled and meat, raw meat, bones, animal offal, meat trimmings, or fish waste; bathe at appropriate times and to an appropriate degree. Otherwise, the above factors can all serve as triggers for canine distemper.
3.4 Reduce the influence of stress factors. Long-distance transport, traveling with the dog, leaving the dog in someone else's care, and sudden environmental changes can all lead to endocrine disorders, disturbances in material metabolism, and reduced body resistance. For this reason, an appropriate amount of hyperimmune serum can be injected beforehand.
3.5 When a household has previously had a case of death due to canine distemper, at least several months or more than half a year should pass before keeping a dog again, and the environment and utensils of the original dog should be thoroughly cleared, disinfected, or discarded to prevent continued transmission.
3.6 A bitch should be vaccinated once before mating, which can enhance its own immunity; a pregnant bitch should be vaccinated once in the late stage of pregnancy, which can enhance the immunity and disease resistance of the puppies.
3.7 For newly purchased puppies, before vaccination, an appropriate amount of hyperimmune serum should first be injected to regulate the antibody level in the body and stabilize it. After gradually adapting to life after weaning, vaccination should then be carried out. Immunization is generally carried out 2 to 3 weeks after injection of the hyperimmune serum, in order to reduce or avoid interference of antibodies with the effect of the vaccine.
It has also been reported that the canine distemper virus has a close antigenic relationship and common characteristics with the measles virus of the same genus. Before the first immunization, the use of attenuated measles vaccine can avoid interference from maternal antibodies and also produce relatively strong resistance and tolerance to the canine distemper virus. When immunizing puppies over 8 weeks of age, protective immunity is generally produced 8 hours after injection, and immune protection can last as long as 8 months. Therefore, in epidemic areas and during high-incidence seasons, for susceptible puppies that have just been weaned, first inject 2 to 3 human doses of freeze-dried attenuated human measles vaccine, and after an interval of two weeks, carry out routine immunization, which can achieve relatively ideal results.
4. Summary and discussion
4.1 From the occurrence of this disease, dogs during the suckling period rarely develop the disease. This is related to the care of the mother dog, the pampering of the owner, living mainly indoors, less outdoor activity, and rarely being affected by harsh environments and stress factors. But more importantly, breast milk contains large amounts of immune antibodies, and the milk temperature is suitable and it is almost uncontaminated, so it is very safe for puppies to consume and they also gain relatively strong immunity.
4.2 Lack of vaccination or unreasonable vaccination is the main primary factor of this disease. Dogs that have not been vaccinated have no or only a small amount of antibodies in the body and are susceptible to infection and disease. Unreasonable vaccination is mainly manifested as too-early vaccination, missed vaccination, and incorrect vaccination intervals. So-called too-early vaccination refers to vaccinating before the vaccination age is reached, causing the antibodies obtained by the puppy from the mother and breast milk to neutralize with the vaccine and thereby reduce or lose their due effect; missed vaccination means an insufficient number of consecutive vaccinations, so that the antibodies in the dog's body cannot reach the required level; incorrect vaccination intervals means that the interval between vaccinations is too long or too short, far from the requirement, resulting in immunization failure.
4.3 As a triggering cause of canine distemper, stress factors mainly work because stress can excite the sympathetic nerves, increase basal metabolism, and place the parasympathetic nerves in a relatively inhibited state, causing excessive consumption in the body, decreased physical strength, and disorders of digestion, absorption, and secretion, leaving the whole body in a low disease-resistance state and triggering canine distemper and other diseases. Therefore, in daily life, strengthening the feeding and management of dogs and reducing the influence of stress factors can reduce the occurrence of canine distemper.
4.4 Injection of hyperimmune serum is one of the important measures for preventing this disease. For a period after weaning, because the antibody level in the body gradually decreases, injection of hyperimmune serum can directly supplement antibodies. For dogs undergoing long-distance transport, traveling outside with their owners, or suddenly changing owners, stress reactions may occur. Injecting hyperimmune serum can improve immunity, enhance adaptability and disease resistance, and reduce the influence of stress factors.
4.5 From the occurrence of canine distemper, dogs that are strictly and properly immunized rarely develop the disease, and even if they do, the symptoms are quite mild. In the absence of other obvious influencing factors, the cure rate is very high. In contrast, dogs that are not properly immunized have very high morbidity and mortality rates. In addition, improper transport and storage of vaccines can also cause a decrease in titer, leading to immunization failure.