Etiology:
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There are a lot of viruses in various secretions, excretions (nasal discharge, saliva, tears, pericardial fluid, pleural effusion, ascites, urine), blood, cerebrospinal fluid, lymph nodes, liver, spleen, spinal cord and other organs of sick dogs, which can be detoxified by respiratory secretions and urine. Healthy dogs are in direct contact with sick dogs or infected by polluted air or food through respiratory tract or digestive tract. Besides puppies, foxes and minks in fur animals are also very susceptible to canine distemper.
Symptoms:
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The incubation period of canine distemper is 3-9 days. Symptoms are varied and related to virulence, environmental conditions, age and immune status. The initial symptom of canine distemper is an increase in body temperature, which lasts for 1-3 days. Then gradually disappear, much like the characteristics of a cold recovery. But after a few days, the body temperature rose again, and the duration was uncertain. Tears can be seen, conjunctiva is red and swollen, and eye secretions change from liquid to sticky pus. Dry nose, runny nose, serous runny nose first, then purulent runny nose. At the beginning of the disease, it was a dry cough, and later it turned into a wet cough, making it difficult to breathe. Vomiting, diarrhea, intussusception, and finally died of severe dehydration and weakness.
Neurosymptomatic canine distemper usually occurs about 10 days after the above symptoms appear. Clinically, cases of foot pad keratosis and rhinokeratosis cause frequent nervous system symptoms. The symptoms are different because the canine distemper virus invades the central nervous system in different places. The virus damages the brain, showing neurological symptoms such as epilepsy, turning in circles, abnormal standing posture, unstable gait, ataxia, paroxysmal convulsions of masticatory muscles and limbs. The prognosis of this nervous canine distemper is mostly poor.
Canine distemper virus can cause eye damage in some dogs, showing conjunctivitis and keratitis. Keratitis is most common about 15 days after onset, and the cornea turns white. In severe cases, corneal ulcer, perforation and blindness may occur.
The mortality rate of this disease in puppies is very high, and the mortality rate can reach 80 ~ 90%. It can also cause pneumonia, enteritis, intussusception and other symptoms.
Once the clinical symptoms of canine distemper appear, the prognosis is very poor. Especially dogs that have not been immunized. Although symptomatic treatment is carried out in clinic, it is difficult to control the development of the disease, and most of them die of nervous system symptoms and failure. Partially recovered dogs generally leave different degrees of sequelae.
epidemiology
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This disease can occur all year round, but it is more common in winter and spring. The disease has a certain periodicity and is prevalent once every three years. Dogs of different ages, sexes and breeds can be infected, but underage puppies are the most susceptible. Purebred dogs and police dogs are more susceptible to infection than native dogs, with serious reaction and high mortality. The most important sources of infection of this disease are nasal and eye secretions and urine. It has been reported that dogs infected with canine distemper virus still excrete urine after 60-90 days, so urine is a very dangerous source of infection. The main route of transmission is direct contact between sick dogs and healthy dogs, or infection through respiratory tract through air droplets. Once canine distemper is found in dogs in the same room, no matter how strict protective measures are taken, it is impossible to avoid the infection of dogs in the same room.
Diagnostic points:
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Epidemic characteristics of (1): this disease occurs mostly in cold season (10 to April of the following year), especially in units or areas where dogs are concentrated. Once a dog gets sick, it is difficult for other puppies to avoid infection unless they are in absolute isolation. Because suckling puppies can get antibodies from breast milk, they seldom get sick. Usually puppies from 3 months to 1 year are the most susceptible to infection.
(2) Clinical features: the body temperature is biphasic fever (that is, the initial body temperature is as high as about 4-C, which drops to normal after 1 ~ 2 days, and rises again after 2-3 days); When the body temperature rises for the second time (a few cases die at this time), respiratory symptoms appear, such as cough, sneezing, serous to purulent nasal discharge, nasal dryness, eyelid swelling, suppurative conjunctivitis, and corneal ulcer often occurs in the later stage; There are erythema, edema and purulent papules on the skin of lower abdomen and inner thigh; Frequent vomiting; Constipation at first, diarrhea soon, foul feces, sometimes mixed with bloodshot and bubbles. In a few cases, transitional keratosis can be seen in the skin of the foot palm and nose wing. About 10 ~ 30% of sick dogs have symptoms (spasm, epilepsy, convulsion, etc. The mortality rate of this disease can be as high as 30 ~ 80%. If mixed with canine infectious hepatitis, the mortality rate is high. Because the disease is often mixed with canine infectious hepatitis and other diseases, and secondary bacterial infection, the symptoms are complex. Therefore, only the above symptoms can make a preliminary diagnosis. Finally, the diseased materials (conjunctiva, bladder, stomach, lung, trachea, brain and serum) must be sent to the inspection unit for virus isolation, neutralization test and other specific inspections.
Preventive and control measures:
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(1) Regular vaccination: At present, the canine distemper vaccine produced in China is a cell culture attenuated vaccine. In order to improve the immunization effect, the following immunization procedures should be followed. The first immunization time was 6 weeks, the second immunization was 8 weeks, and the third immunization was 10 weeks. In the future, immunization 1 time every year, with an immunization dose of 2 ml each time, can achieve a certain immune effect. In view of the existence of maternal antibodies in puppies under 12 weeks of age, which can obviously affect the immune effect of canine distemper vaccine, it is best to vaccinate puppies under 12 weeks of age with measles vaccine (canine distemper virus and measles virus are both measles viruses with the same antigenicity). The specific immunization method is that puppies 1 month-old and two-month-old are immunized with canine distemper vaccine at the dosage of 1 ml (2.5 copies) per dog and 12 ~ 16 weeks old. According to some units, good immune effect can be obtained by using this immunization program.
(2) Strengthen veterinary health and epidemic prevention measures, and all farms should try their best to be self-supporting. In the epidemic season of this disease, it is forbidden to bring personal dogs to places where dogs gather.
(3) timely isolation treatment: timely detection of sick dogs, early isolation treatment and prevention of secondary infection are the keys to improve the cure rate. At the beginning of the disease, anti-canine distemper serum or dog serum (or whole blood) can be injected intramuscularly or subcutaneously. The dosage of serum depends on the condition and the size of the dog, generally 5 ~ 10 ml, which can achieve a certain curative effect. It has been reported that the use of high immune serum and Kangduling freeze-dried powder injection can improve the therapeutic effect. Usage and dosage are as follows: before treatment, dissolve kangduling with 20 ml of normal saline or water for injection, intravenous drip 2-4 bottles for medium-sized dogs, and reduce the dosage for puppies as appropriate. Antivenom can also be injected intramuscularly. In addition, early application of antibiotics (such as penicillin, streptomycin, etc. ) combined with symptomatic treatment is of great significance to prevent secondary bacterial infection and the rehabilitation of sick dogs.
(4) Thoroughly disinfect the kennel and sports ground: the kennel and sports ground should be disinfected with 3% caustic soda (also called sodium hydroxide) solution or 10% formalin.
Treatment:
After the clinical symptoms appear, a large dose of canine distemper serum can be injected to control the development of the disease. Giving a large dose of hyperimmune serum at the early stage of canine distemper fever can make the body enhance enough antibodies, prevent clinical symptoms and achieve the purpose of treatment. For the middle and late stage diseases with obvious clinical symptoms and neurological symptoms of canine distemper, it is difficult to cure most of them even by injecting canine distemper high immune serum.
Symptomatic treatment: Disinfect the kennel environment by supplementing sugar, fluid, reducing fever, preventing secondary infection and strengthening feeding management, which has a certain therapeutic effect on this disease.