How to effectively prevent Bluetongue virus in sheep
Sheep Bluetongue virus is a viral Sexually transmitted infection of ruminant animals with insects as the transmission vector. It mainly occurs in sheep. Its clinical characteristics are fever, emaciation, ulcerative inflammatory changes in the mouth, nose and Gastric mucosa, pathological changes in the breast and hoof crown are also common, and lameness often occurs due to the invasion of the hoof dermis.
Bluetongue virus belong to Reoviridae Orbivirus. It is a double stranded RNA virus, and the virus genome consists of 10 double stranded RNA fragments of varying molecular weights and sizes. It is known that there are 24 Serotype of the virus, and there is no mutual immunity between them. Sheep kidney, fetal bovine kidney, calf kidney, and mouse kidney primary and secondary cells (BHK-21) can all be cultured and proliferated, leading to plaque or cytopathic changes. Nucleic acid probes can also be used for identification.
The incubation period is 3-8 days, and the initial body temperature rises up to 40.5-41.5 ℃. The symptoms of anorexia and fatigue persist for 5-6 days, lagging behind the sheep herd. Salivation, lip edema, spreading to the face and ears, and even the neck and abdomen. The oral mucosa is congested, followed by cyanosis, showing a bluish purple color. After a few days of fever, the oral cavity, along with the mucosa of the lips, gums, cheeks, and tongue, erodes, causing difficulty in swallowing; As the disease progresses, blood oozes from the ulcer site, saliva turns red, and the oral cavity stinks. Inflammatory and viscous secretions of nasal discharge, crusting around the nostrils, causing difficulty breathing and snoring. Sometimes inflammation occurs in the hoof crown and hoof leaves, causing sensitivity to touch and varying degrees of claudication, and even knee or lying motionless. Sick sheep are thin and weak, some have constipation or diarrhea, sometimes have dysentery with blood, and have Leukopenia in the early stage. The course of disease is generally 6~14 days, the incidence rate is 30%~40%, and the mortality is 2%~3%, sometimes up to 90%. Those who suffer from illness and do not die recover after 10-15 days, and their hooves also recover after 6-8 weeks. When the ewes who were pregnant for 4-8 weeks were infected, about 20% of the lambs delivered had developmental defects, such as Hydrocephalus, cerebellar hypoplasia, and excessive gyrus.
The symptoms of goats are similar to those of sheep, but generally mild.
Changes in dissection
Congestion, edema, and bleeding of various organs and lymph nodes; Subcutaneous adhesive infiltration in the neck and jaw region; In addition to erosion and bleeding of oral mucosa, there are bleeding spots in the mucous membrane of respiratory tract, digestive tract, membrane and Urinary system. The epithelium of breast and hoof crown falls off, but no blisters occur. The hoof leaf is inflamed and often festers.
The polymorphism of Bluetongue virus and the lack of cross immunity between different Serotype make immunization difficult. If vaccination is needed, the Serotype of the local epidemic virus should be determined first, and the vaccine of the corresponding Serotype should be selected to obtain satisfactory results. The attenuated vaccine can cause Viremia of different degrees after inoculation, and at the same time, it has an impact on the fetus, leading to abortion of ewes. Attention should be paid when using：
1. Every year, chicken embryo attenuated vaccine or tissue vaccine attenuated by bovine kidney cells should be injected. Sheep over half a year old should be injected subcutaneously according to the prescribed dosage, and immunity should develop after 10 days. The immune period is one year. Production ewes should be vaccinated before breeding or within 3 months of pregnancy.
2. If sick sheep are found, they should be slaughtered and treated harmless, and the site and equipment should be thoroughly disinfected.
3. Advocate for grazing in highlands and sheep returning to their pens for overnight stays.
4. It is strictly prohibited to introduce sheep from countries or regions with this disease;
5. Strengthen the management of frozen semen, and prohibit Artificial insemination with toxic semen;
6. Regularly take medicinal baths and insect repellents to control and eliminate the vector insects of this disease;
At present, there is no effective treatment, mainly to strengthen nutrition, careful nursing and Symptomatic treatment. Rinse the mouth with clean water, vinegar or 0.1% Potassium permanganate water, and then apply 1%~3% Copper(II) sulfate or iodine glycerin on the erosive surface, or use Bingbo powder for external treatment. When the hoof is ill, it can be washed with 3% Keliaolin or 3% Lysol and then smeared with Oxytetracycline ointment. Inject antibiotics to prevent secondary infections.
This disease is a common season in summer, and friends who raise sheep should do a good job in immunization, disinfect their pens, and observe the dynamics of the sheep to avoid unnecessary losses.