Prevention and Treatment Methods for Tuberculosis in Farmed Nutria

Tuberculosis (Tubercu[.sis) is a chronic infectious disease shared by livestock, poultry, fur-bearing animals and humans, occurring as endemic outbreaks. Tuberculosis is characterized by the formation of caseated and calcified tuberculous nodules in the internal organs. (Pathogen) The pathogen of tuberculosis is Mycobacterium tuberculosis. This bacterium is a uniformly straight or slightly curved pleomorphic bacillus, 1.5—5 microns long and 0.2 to 0.5 microns wide, occurring singly or in clusters, forming neither a capsule nor spores, and is non-motile. It stains as acid-fast; ordinary aniline dyes do not readily color it, but after adding the mordant carbolic acid to carbol fuchsin and heating, it can be stained red, and once stained, it cannot be decolorized even with acid. Mycobacterium tuberculosis is an obligate aerobe, and its growth in culture media is relatively slow; adding an appropriate amount of glycerol, whole egg, egg yolk or egg white, and animal serum to the culture medium is suitable for the growth of this bacterium. Tuberculosis has strong resistance to dry environments and is relatively sensitive to sunlight and moist heat; under direct sunlight it is killed within a few minutes to a few hours. It is killed by 5% Lysol after 48 hours, and dies quickly in 10% bleaching powder. This bacterium is insensitive to sulfonamides and general antibiotics, but shows varying degrees of sensitivity to streptomycin, isoniazid and aminosalicylic acid. (Epidemiology) The occurrence of this disease has no seasonality and can occur in all four seasons, but is more common in summer and autumn. Narrow pens, dense rearing, accumulated manure, malnutrition, helminthiasis and colds can all promote the occurrence and spread of this disease. Young nutrias are susceptible to this disease, but adult nutrias and healthy nutrias are not easily affected, and the mortality rate is relatively low. (Clinical symptoms) Most cases show emaciation, with rough and lusterless fur. When lung lesions appear, the main symptoms are coughing, increased respiratory rate and difficulty breathing, and reluctance to move. Tuberculosis cases in parenchymal organs such as the liver and kidneys often show no visible clinical symptoms, while some diseased nutrias develop diarrhea or constipation and abdominal dropsy. When lymph nodes are invaded by Mycobacterium tuberculosis, long-lasting non-healing ulcers or nodules often appear.

Diagnosis: Tuberculosis in nutrias often lacks characteristic clinical symptoms, so clinical diagnosis is relatively difficult, and a definitive diagnosis must be made through pathological anatomy and bacteriological examination. Pathological anatomical changes: the affected organs develop specific caseated or calcified tuberculous nodules of varying sizes. Bacteriological examination method: first preserve the pathological material in 409 sterilized glycerol, make a smear from the pathological material, stain it by the Ziehl—Neelsen staining method, and only when red acid-fast tubercle bacilli are found on a green background can it be definitively diagnosed. (Prevention and control measures) Nutrias that test positive or suspicious for tuberculin should be raised in isolation until they are pelted. The pens where diseased nutrias have lived should be disinfected with a flame torch or 29,6 caustic soda solution, and the floor should be disinfected by spraying bleaching powder. Curing this disease is not easy and the course of treatment is long, so for those with no medical value, rather than treating them, it is better to cull them to avoid the spread of the epidemic.