Prevention and treatment of canine distemper in fox raccoon dog

The epidemic of canine distemper has occurred in some fox farms and @ # @ 251 farms. With regard to the prevention and control of canine distemper, we would like to talk about the following views:

With regard to the prevention and treatment of canine distemper, after decades of research, a variety of attenuated and eliminated vaccines have been developed in the aspects of disease origin, pathogenesis, epidemic characteristics, clinical symptoms, pathological diagnosis and immune prevention. and many vaccines have been supplied to the market as formal commodities, but in recent years, the prevalence of canine distemper and the losses to the world dog industry and fur animal industry have greatly exceeded people's expectations. The disease has been continuously prevalent in recent years, and the age of onset is not as statistics in the past, mainly occurring in puppies and foxes less than 3 months old or less than 1 year old. now even more than a dozen breastfeeding puppies, young foxes and adult dogs and adult foxes have also experienced the epidemic of canine distemper, with a mortality rate of 20% in the past, but it is now believed that the mortality rate can reach 40%.

Some domestic and foreign vaccines which were originally thought to be good for rabbit plague have experienced immune failure more than once after they have been used. Why did this happen and what measures should be taken to control it in the future? it has become a concern and attention of the vast number of dog breeders, fox breeders, mink breeders and epidemic prevention and control staff.

(1) discussion on the causes of immune failure

1. Whether there are mutated strains: canine distemper is a member of the genus measles virus of Paramyxoviridae, which has the basic characteristics of this genus of viruses. The fact that the immune effect of the same vaccine is different in different regions may be related to the inconsistency of canine distemper virus strains in different regions.

2. Maternal antibody interference: 77% of canine distemper serum antibodies equivalent to female foxes can be obtained from placenta and colostrum, of which 5% come from placenta and 95% from colostrum. The immunity level of female foxes is closely related to the antibody level in junior high school. Young foxes can not be infected by canine distemper virulent virus within a certain period of time, but also interfere with the immunity produced by canine distemper attenuated vaccine. This interference with attenuated vaccines far outweighs the resistance to virulent viruses. The results showed that more than 100 neutralizing antibodies against canine distemper could resist the infection of virulent canine distemper virus, but the titer of neutralizing antibody at 1:20 could seriously interfere with the immunity of canine distemper vaccine. this brings great difficulties in choosing the most suitable immunization time for canine distemper. Immunization is early, the high level of maternal antibody interferes with the production of active immunity, and can not resist the infection of virulent canine distemper virus. It is a good idea to wait for the maternal antibody to drop below 1:20 before immunization. However, due to the infection of canine distemper in foxes and minks around the country, the maternal antibody has not yet dropped to 1:20, and these foxes and minks have already developed the disease. Therefore, some people have proposed to determine the maternal antibodies of foxes before delivery. And determine the initial exemption time for foxes and minks. Although it is scientific to detect maternal antibodies and then immunize, it is actually not feasible because the vast number of fur farms do not have such research conditions.

It is also suggested that advance immunization should be used in canine distemper epidemic areas, that is, young foxes should be vaccinated before colostrum after birth, and after 3-4 hours until the attenuated vaccine has infected some cells, they should be allowed to eat the milk of the female fox. in order to avoid the neutralization of maternal antibodies to the attenuated vaccine.

In foreign countries, the maternal antibodies of canine animals such as foxes have disappeared by 80% at the eighth week, and all by the ninth week, according to this rule, the first exemption can be carried out at the age of 60 days.

According to the study of Shandong Agricultural University, the first immunization was given at the age of 45 days, and then the second or third immunization was given at an interval of 2 weeks. Because maternal antibodies decrease rapidly after 45 days of age, if immunization starts from 60 days old, 45-60 days old is the immune blank area, at this time the young fox is the most susceptible to infection. Zhou Xiangyang proposed to improve the level of maternal antibody. In order to improve the maternal antibody level of young foxes and minks, the method is that female foxes and minks are vaccinated with measles vaccine on the 30th day of pregnancy, and the protective antibodies against canine distemper can be produced within 5-7 days after injection, but they are not neutralized by canine distemper antibody. a week after injection, canine distemper vaccine was injected again, and a high level of canine distemper maternal antibody could be maintained in the colostrum of female foxes and minks during delivery. It can protect foxes and minks from canine distemper virus for a long time after birth. Using the above-mentioned methods, no abnormal conditions such as preterm delivery, abortion, malformation and stillbirth were found.

3. The influence of other exogenous and endogenous factors.

(1) genetic factors: female foxes or male foxes with incomplete immune function are prone to this disease, and foxes with inbreeding are common.

(2) mixed infection: the failure rate of canine distemper in epidemic fields such as parvovirus disease and coronavirus disease is higher, because in the epidemic process of these diseases, the immune function of fox is often suppressed. as to whether parvovirus vaccine and fox encephalitis vaccine will disturb canine distemper vaccine, the report is not consistent.

(3) parasitic infection: although the fox farms with toxoplasmosis, eperythrozoonosis, bursal disease, Ascaris lumbricoides and demodex are routinely immunized with canine distemper, canine distemper still occurs because this kind of parasite causes immunosuppression.

(4) Nutrition and environmental problems: high temperature and humidity, malnutrition during long-distance transportation, lack of sodium selenite and vitamin E in daily feed will sound the immune function of canine distemper. The above causes will not only cause the fox to be in a state of stress, the high temperature and humidity environment will also cause the fox body temperature to rise, thus affecting the proliferation of attenuated vaccine.

(5) severe virulent infection: although the neutralization antibody of some foxes can resist a certain number of canine fever virulent virus infection when produced above 1RV 100, this kind of fox can also cause immune failure if it is exposed to canine distemper virulent virus for a long time and is attacked by a large number of virulent viruses for a long time.

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