Episootic situation of canine distemper in the clinic of the city of Nur-Sultan

Annotation

epizootic canine distemper veterinary

this article describes an analysis of the epizootic situation for the disease of canine distemper in 2019-2020 in the clinic of veterinary medicine "Byzantium " in the city of Nur-Sultan. Studies of sick and suspicious animals for this disease were carried out with confirmation of the diagnosis by laboratory methods in the neutralization reaction and enzyme-linked immunosorbent assay.

Key words: canine distemper, antibodies, materials, epizootic situation, analysis, neutralization reaction, enzyme-linked immunosorbent assay.

Аннотация

Байкадамова Г.А., кандидат ветеринарных наук, доцент кафедры ветеринарной медицины Казахский агротехнический университет имени С.Сейфуллина Казахстан, г. Нур-Султан Камзатова А.Е., магистрант 2 курса специальности "Ветеринария" Казахский агротехнический университет имени С.Сейфуллина Казахстан, г. Нур-Султан

Currently, among the number of infectious diseases of dogs, a special place is still occupied by the canine distemper. This disease is a serious problem for veterinarians, dog handlers, breeders, amateur dog breeders. The pathogenicity of the viruses of these diseases varies widely. Even with successful treatment, the infectious processes associated with the canine distemper have time to cause irreversible changes in the animal's body from various organs or systems and may affect affect the growing body of the puppy. Subsequently, these changes affect the conformation of the dogs [1, p. 15-21].

The wide spread of the disease is explained by the fact that a large number of unvaccinated stray dogs are concentrated in large settlements, which, after recovering from the disease, are virus carriers. The presence of a large selection of specific prophylactic agents and their use do not lead to a decrease in morbidity, since immunization is carried out without taking into account the epizootic situation, age and conditions of keeping the dogs. During the first weeks of puppies' life, the immune system remains underdeveloped, as a result does not form a normal immune response of the animal's body to antigens that come from the environment (viruses, bacteria, etc.). During this period, the protection of the puppy's body is carried out by factors of passive immunity, primarily antibodies obtained from the mother. Maternal antibodies enter the puppy's body transplacentally and with colostrum. Their level is constantly decreasing and by a certain age of the animal there comes a period when the maternal antibodies can no longer protect the puppy's body from infection, and the introduced vaccine cannot yet cause a full-fledged immune response. This period is called the period of immunodeficiency or immune risk [2, p. 1254].

Canine distemper (Latin - Pestis carnivorum; English - Canine distemper; plague of dogs, Carrй's disease) is a highly contagious viral disease characterized by fever, purulent rhinitis, conjunctivitis, pneumonia, gastroenteritis, central nervous system damage, occurring in acute and subacute form other carnivores. Susceptibility and mortality rates vary greatly among different animal species. Mortality can be as high as 30-40% among adult animals and 80-100% among puppies [3, p. 20 - 24].

The canine distemper virus belongs to the Morbillivirus genus of the Paramyxoviridae family and is closely related to other viruses. The plague virus has a relatively large diameter (150-250 nm) with a single negatively intertwined RNA attached in a nucleocapsid helical symmetry [4, pp. 45-49]. The virus is surrounded by a lipoprotein envelope derived from viral glycoproteins incorporated into the cell membrane. Viruses encode proteins capable of integration into the cell membrane, rendering infected cells susceptible to damage by immune-mediated cytolysis. The virus can also induce cell fusion for direct cell-to-cell propagation. Genetic analysis of the P gene fragment with 388 BP and H - protein coding region was used to separate the genotypes of 75 types of vaccines. Under laboratory conditions, the virus is cultured in chicken embryos, tissue culture and in susceptible animals. When the virus multiplies in infected embryos, changes appear mainly on the chorion - allantoic membrane in the form of swelling and the formation of light gray nodules the size of a millet grain or light gray strands [5, pp. 60-63].

The virus is susceptible to ultraviolet light, although protein or antioxidants help protect it from deactivation. Extremely susceptible to heat and drying, the carnivorous plague virus is destroyed by high temperatures (50 ° C - 60 ° C within 30 minutes). In excised tissues or secretions, the virus remains virulent for at least an hour at 37 ° C and for 3 hours at 20 ° C. In warm climates, it does not persist in kennels after infected dogs have been removed from the premises. Storage and survival time are longer in colder temperatures. When frozen (0 ° C to 4 ° C), the virus stays alive for weeks. Below the freezing point, the virus is stable, surviving at -65 ° C for at least 7 years. Lyophilization reduces the volatility of the virus and is an excellent means of preserving it for commercial vaccine and laboratory use. The virus remains viable at pH 4.5-9.0. Susceptible to ether and chloroform, diluted formalin, phenol (0.75%) and ammonium chloride disinfectant (0.3%) [6, p. 22].

In the settlements of the threatened zone, veterinary specialists take measures to ensure the protection of farms from the introduction of the carnivorous plague virus into them. For these purposes, it is necessary:

• monitor the veterinary and sanitary state of animal farms, fur farms, dog kennels, settlements

• timely carry out the activities provided for by the instructions;

• all young carnivorous animals susceptible to plague should be registered and subject to mandatory vaccination against carnivorous plague;

EPISOOTOLOGICAL DATA.

All dogs are susceptible the canine distemper, regardless of their breed, but there are still differences in the specific resistance of breeds to the causative agent of the disease. However, this issue remains controversial and currently [7, p 568].

Among dogs of all breeds, the dependence of the incidence on age is clearly traced. Colostral antibodies protect about 80% of the livestock in the first months of life. The most critical age for puppies is 3-7 months.

The infection rate is usually well above the mortality rate. By most estimates, 25-75% of susceptible animals have subclinical illness but excrete the virus [8, p. 1308- 1313].

The epizootic process in the canine distemper manifests itself differently and depends on the virulence of the pathogen, the degree of susceptibility of animals, natural - geographical and economic factors. However, the index of contagiousness in the plague of 308 carnivores is quite high - from 70 to 100, and regular outbreaks of the disease are noted in carnivores living in freedom. The spread of canine distemper on many factors, and above all on the presence of an immune layer in a given animal population. The disease can occur at any time of the year and manifest itself as an epizootic or sporadically. Against the background of mass vaccine prophylaxis, the current level of morbidity in fur-bearing animals and dogs can be considered sporadic [9, p. 556-562].

ANALYSIS OF THE DYNAMICS OF THE EPISOOTIC SITUATION

The difficulty in analyzing the epizootic situation lies in the difficulty of making a diagnosis. Basically, practicing veterinary specialists, due to the lack of laboratory diagnostic tools on the ground, are based on the clinical picture of the disease in the animal, taking into account the age, availability of vaccinations, the seasonality of the disease and the general epizootic situation in the city.

Analysis of the dynamics of neutralizing antibodies (DNA) shows that the reported values of the diagnostic titer of serum neutralizing antibodies to the CP virus (1: 10-1: 16, etc.) are very relative. The titer of neutralizing antibodies in uninfected puppies during the suckling period and in vaccinated dogs can reach a significant value. If in animals that have never been vaccinated against CDV, such or a higher titer of DNA is revealed, and their age excludes the possibility of receiving antibodies from the mother, this indicates the presence of a disease or reillness of animals with CDV. However, zero or low DNA titer in the blood cannot be considered a criterion for the absence of CDV infection. On the contrary, this situation is typical for a significant number of cases of severe disease, resulting in death, and in recovered dogs, the DNA titer is usually very high. [10, p. 187-191].

MATERIALS AND METHODS

The collection and analysis of epizootic data on CDV was carried out on the basis of "Journals for registration of sick animals" and "Case histories" of veterinary institution in the city of Nur-Sultan ("Byzantium").

Biomaterial samples (washings from the conjunctiva and nasal cavity, saliva, blood samples, crusts from the skin and paw pads, pieces of organs) and blood serum were taken from the suspected animals. Selected bioassays were examined for the presence of the virus in enzyme-linked immunosorbent assay using the "Kit for detecting the antigen of the canine distemper of carnivores by enzyme-linked immunosorbent assay" in accordance with the instructions for use.

The study of blood sera from suspected CDV disease was carried out in a neutralization reaction (RN) on a Vero cell culture with a constant dose of the virus (100 TCID50 / cm3) of the Rock-Born strain.

The diagnosis of canine distemper was made on the basis of epizootic, clinical and laboratory data (ELISA and RN).

RESULTS OF STUDIES

Currently, there are about 5 thousand dogs in the city of Nur-Sultan, of which only 2 thousand are registered. The constant increase in the number of stray dogs worsen the epizootic situation for infectious diseases in the city.

In 2019, 22 cases of canine distemper were registered in the veterinary institutions of the city of Nur-Sultan. The highest incidence peak was observed in spring and autumn, only in March-May there were 10 officially registered cases, in October-November - 9.

Most cases of canine distemper have been reported in puppies between 2 months and 1 year of age and in adult dogs between 9 and 12 years of age. The most susceptible to the disease were mongrel and large breed dogs: Central Asian, German and East European Shepherd Dogs.

In 2020, 13 dogs with clinical signs were admitted to the clinics of the city of Nur-Sultan: lack of appetite, fever, discharge from the eyes and nasal cavity, vomiting, diarrhea, convulsions. Epizootic, clinical and laboratory data were taken into account for the diagnosis.

The results of laboratory studies of samples for the detection of antigens in ELISA and virus neutralizing antibodies in RN, taken from dogs of various ages, are presented in the table (Table 1).

Table 1.

The results of the study of samples from suspected canine distemper in neutralization reaction and ELISA

Note: " +" - positive reaction; "-" - negative reaction

The table shows that sick animals had different levels of virus-specific antibodies in the neutralization reaction (low <2.0 log2 or high >7.0 log2). In ELISA, all test samples from sick animals gave a positive reaction. And in dogs admitted with the same clinical signs and having different levels of virus-specific antibodies in RN, from low (<2.0 log2) to high (>7.0 log2), and in ELISA that did not give a positive reaction, the diagnosis of canine distemper not confirmed.

Based on the data in the table, it can be concluded that the most susceptible animals to canine distemper are between the ages of 2 months and 1 year and at the age of 8-12 years. In our opinion, this is due to the fact that young animals are being vaccinated without taking into account the level of colostral antibodies, which block the reproduction of viruses in vaccine strains, which affects the growth of virus- specific antibodies, thereby affecting the outcome of immunization. The cause of the disease in dogs at the age of 8-12 years was the termination of their vaccination at the age of 6 years.

CONCLUSION

In recent years, there has been a deterioration in the epizootic situation for canine distemper in the city of Nur-Sultan. In this regard, it is necessary to carry out a general set of preventive measures, the first place in which is given to the vaccination of animals. Vaccinations for puppies should be carried out taking into account the immunological maturity of the body and the level of colostral antibodies. Animals older than six years of age should be revaccinated annually.

The level of growth of virus-specific antibodies against canine distemper during vaccination of puppies depends on the presence of maternal antibodies. In this regard, it is necessary to immunize animals at the age of 10-14 weeks with a decrease in maternal antibodies to a certain level: for canine distemper - below 3.0 log2 in neutralization reaction.

Canine distemper is most dangerous for puppies between the ages of 2-12 months. Adult dogs can also contract this disease, but the course of the disease will be milder and the likelihood of death is less.

List of references

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