Methods of diagnosis of infectious animal diseases
Thanks to the correct and timely diagnosis can ensure the effectiveness of health measures, i.e. to quickly arrest occurred epizootic outbreak and prevent further spread of the disease.
Epizootological method. Is a system of studying the manifestations of epizootic process. To characterize the latter is necessary to collect accurate information on susceptible species, the source and reservoir of the pathogen, mechanism of transmission, the gate of infection, the intensity of epizootic process, seasonality, predisposing factors, morbidity, mortality, lethality. In addition, special attention on the factors determining ways of further spread of the disease — implementation of anti-epizootic measures and conditions in the external environment.
To characterize epidemic the state of the economy, compare and evaluate generalized epidemiological indicators obtained by statistical processing of data of primary accounting of diseases and preventive measures.
The clinical method. By clinical examination of animals suspected of infectious disease disease, you should always follow the rules of activities stipulated by sootvetstvuyuschaya.
A clinical study is recommended to start the measurement of body temperature of the animal. Next, inspect the animal in unfixed condition: pay attention to the position of the body reaction to various stimuli, receiving food and water, the nature of the faeces, especially of defecation and urination. Then proceed to the study of particular systems and organs according to the scheme universally accepted in clinical diagnosis of diseases.
Clinical signs of an infectious disease depend on many factors: the type and localization of the pathogen, trends, manifestations and stages of the disease, resistance of the organism and other causes. In all cases, clinical signs the same infectious disease in animals even of the same species vary greatly.
Pathomorphological method. Includes post-mortem and histological research methods. Pathological method is considered important, but not always definitive method of diagnosis. For example, when performing an autopsy of a corpse of an animal (bird) note the characteristic changes tubercles, immediately diagnosed tuberculosis, when detected in the spleen of the pig of regional hemorrhagic infarctions — the plague, hemorrhages at the border of the muscular and glandular stomach in chickens is Newcastle disease, etc.
Order post-mortem examination: assess the condition of the corpse, the skin and mucous membranes, then examined the lymphatic system, serous skin, the muscles and joints, respiratory organs, heart and blood vessels, liver, spleen, kidney, pharynx, esophagus, stomach, small intestine, large intestine, urinary bladder, organs of reproduction, the brain and spinal cord.
However, in many cases along with the pathology is used and the method of laboratory tests (histological, bacteriological, etc.). Using histological method establish an accurate diagnosis in diseases such as rabies (Taurus Babes—Negri), rhinopneumonitis (intranuclear inclusion-type Kodri), smallpox (Taurus enable).
Bacteriological method. This is a valuable method for diagnosis of infectious diseases. For bacteriological examination from sick or dead animals must be properly take pathological material and correctly fill in the accompanying document. The delivered biomaterial is treated depending on the intended disease, make brushstrokes-prints, paint them the appropriate methods, emit pure culture of sowing on nutrient (elective) environment to infect laboratory animals with sensitive material or pure culture (tab.1).
1. Bacteriological method of diagnosis of some infectious diseases
Based on the detection of pathogens in incoming material to establish an etiologic diagnosis.
Virological method. For virological studies directed to the laboratory of pathological material from sick animals taken during the period of existence of clinical signs (temperature reaction, depression, inflammation in the upper respiratory tract, accompanied by serous or mucous effusions of the nasal cavity, diarrhoea, the formation of vesicles, aphthae, and sometimes abortions), or slaughtered (martyrs) of animals taken no later than 2 hours after their death. Virologic method of diagnosis includes: detection of the pathogen in the pathological material by various methods (electron, fluorescent or light microscopy, the infection of cell cultures, laboratory animals etc.), isolation and identification of the virus in various serological tests, bioassay.
Hematological method. To the laboratory for hematological studies send blood, which is taken from the aseptically from a jugular vein into tubes with anticoagulant— 10 % solution of Trilon B, heparin, sodium citrate from the calculation of 0.02 ml of solution per 1 ml of blood.
Hematology is used as an auxiliary method, and in some infectious diseases (bovine leucosis, infectious anemia of horses) as the primary method of diagnosis. When bovine leucosis diagnosis is based on detection in the peripheral blood increase in the content of the main leukocytes of the lymphoid series in 1-10-3 ml of blood, as in infectious anemia of horses — on the basis of reducing the amount of erythrocytes in 1 • 103 ml of blood, hemoglobin, and delayed the erythrocyte sedimentation rate (ESR).
Immunological method. Includes serological diagnostics in laboratory tests serum to detect antibodies and Allergy test, which farms to identify animals with tuberculosis, paratuberculosis, brucellosis, low glanders, at least — anthrax, listeriosis, tularemia.
