What are the prevention and control measures for sheep salmonellosis?
Sheep salmonellosis is an infectious disease of sheep mainly caused by Salmonella typhimurium, Salmonella abortusovis, and Salmonella dublin. It is characterized by diarrhea in sheep and abortion in pregnant ewes.
Pathogen
The pathogen of sheep salmonellosis belongs to the family Enterobacteriaceae, genus Salmonella.
Epidemiology
Sheep salmonellosis can occur throughout the year, and livestock and poultry of all ages can be infected. Infection occurs mainly through the digestive tract, but mating and other routes can also cause infection; various adverse factors can promote the occurrence of this disease.
Symptoms
The incubation period varies in length, depending on the animal's age, stress factors, and route of invasion.
1. Diarrheal type lamb paratyphoid: Mostly seen in lambs aged 15—20 days. At the beginning of the disease, the lamb is depressed, body temperature rises to 40—40°C, head lowered and back arched, appetite reduced or refusal to eat. The body is weak and emaciated, lying on the ground unable to rise, and death occurs within 1—5 days. Most affected lambs show abdominal pain and diarrhea, pass large amounts of grayish-yellow pasty feces, and rapidly develop dehydration symptoms, with sunken eyeballs and weakened strength. Some affected lambs show symptoms such as rapid breathing, discharge of mucous nasal fluid, and coughing.
2. Abortive type paratyphoid: Abortion is mostly seen in the last two months of pregnancy. Before abortion, the affected sheep's body temperature rises to 40—41°C, with anorexia, depression, and some sheep have diarrhea symptoms and vaginal discharge. The live lambs delivered by affected sheep are relatively weak, do not suckle, and may have diarrhea, generally dying within 1—7 days. Affected sheep are complicated by enteritis, gastroenteritis, and septicemia.
Pathological changes
In sheep with the diarrheal type, the affected sheep appear emaciated. The abomasum and intestines are empty, the mucosa is congested, and the contents are thin. The mesenteric lymph nodes are enlarged and congested, the spleen is congested, and there are small hemorrhagic spots on the renal cortex and the endocardium and epicardium.
In sheep with the abortive type, stillbirth occurs or newborn lambs die within a few days, showing septicemic lesions. Tissue edema and congestion, enlarged liver and spleen, with gray necrotic foci. Placental edema and hemorrhage. Ewes have acute metritis, and the uterus of those that abort or deliver stillborn fetuses is swollen, with necrotic tissue, exudate, and retained placenta.
Diagnosis
A preliminary diagnosis can be made based on epidemiology, symptoms, and pathological changes, but confirmation requires laboratory diagnosis.
Prevention and control measures
Strengthen feeding management, do a good job in disinfection, and eliminate the source of infection.
Use oxytetracycline or neomycin; lambs are given 30—50 mg/Kg body weight per day orally in three divided doses; adult sheep are given 10—30 mg/Kg body weight twice daily by intramuscular or intravenous injection.