Diagnosis, prevention and treatment of infectious bovine rhinotracheitis

Many farmers who have raised cattle have encountered difficulties in breathing, pus in the nasal cavity, and congestion in the nasal mucosa. When these diseases appear, they should pay attention to them, because when combined with epidemiology, cattle are likely to get infectious rhinotracheitis. Infectious bovine rhinotracheitis, also known as "necrotizing rhinitis" and "red nose disease", is a contagious infectious disease of bovine respiratory tract caused by bovine herpesvirus type I (BHV-1). This disease is prevalent all over the world and has a great impact on the milk yield of dairy cattle, the fecundity of bulls and the serviceability of used cattle. The following pro-agricultural network will specifically introduce the main points of diagnosis and prevention and treatment of this disease:

First, clinical symptoms

The incubation period of artificial infection of bovine infectious rhinotracheitis virus is 1-3 days, while that of natural infection is 4-7 days, sometimes more than 20 days. There are five clinical types of the disease.

1. Respiratory type

Is the most important type. It can be a mild, unnoticed infection, or it can be a serious disease. It often occurs after transfer or transfer from pasture to shed feeding. The acute cases were mainly the whole respiratory tract, followed by the digestive tract. At the beginning of the disease, the body temperature suddenly increased (40-42 ℃), severe numbness, no food, and a large amount of mucus and purulent nose. The nasal mucosa is highly congested and fiery red (hence the name "red nose disease") with superficial ulcers, nasal alar and nasal endoscope necrosis. Because the nostrils of diseased cattle are clogged with inflammatory exudates, it is highly difficult to breathe and even open mouth to breathe, conjunctivitis and tears can be seen, and the exhaled gas stinks due to nasal mucosal necrosis. The frequency of breathing increased, and the cough of the white deep bronchus was frequently heard. Sometimes blood-stained dysentery can be seen.

two。 Genital type

At the beginning of the disease, it usually shows mild fever, severe infection shows tail upright and waving restlessness, frequent urination and pain, vaginal edematous swelling, pubic hair stained with blood-like ooze. The initial symptoms are redness of the vaginal mucosa and the formation of pustules, which give a granular appearance of the vulva vestibule and vaginal wall. Then accumulate mucus-like to mucopurulent exudate in the bottom wall of vagina. In some cases, pustules become more and more and fuse together, and then form a wide range of gray necrotic film in the vestibule and vaginal wall, leaving a reddish scratch when wiped off or removed, generally this type is not complicated with abortion. The course of the disease is usually 2 weeks, and if there are complications, it can reach 3-8 weeks. The male animal is characterized by infectious pustular glans prepuce, the lesion of the glans prepuce is similar to that of the vulva and vagina, and the affected tissue is accompanied by pustule formation and granulation appearance. Prepuce and penile edema caused phimosis dermatitis, there is scrotal swelling, but there is no confirmed orchitis.

3. Conjunctival type

Due to the affinity of the virus to the affected bovine mucosa, it can sometimes cause keratoconjunctivitis and usually does not cause corneal ulcers. This type of infection generally has no obvious systemic reaction, sometimes respiratory type can occur at the same time. Generally, there can be edema under the conjunctiva, which can form a gray necrotic membrane, resulting in a granular appearance, and the cornea can become slightly cloudy, suffering from bovine nasal serous purulent secretions.

4. Abortion. In some cases, wild virus or artificially attenuated virus (vaccine) can cause miscarriage in cattle, usually at any stage of pregnancy in first-born young cows. The incidence of miscarriages caused by the virus is unknown, but there has been a decrease in the number of miscarriages in recent years, possibly due to improved diagnostic methods and increased awareness of the disease. In many cases, an undiagnosed respiratory infectious disease may have been prevalent in cattle one to two months before abortion. The virus was isolated from aborted calves and inoculated into susceptible young cows can cause miscarriage.

5.。 Encephalitis type

The disease can be characterized by meningoencephalitis. It has been reported in the United States, Australia and other countries, but the incidence is very low. The diseased cattle are characterized by ataxia, depression, followed by excitement, spitting, convulsions, and finally lying down, corner arch stretching, leg swinging, and tooth grinding. The course of the disease is short and usually dies.

In general, the course of the disease varies widely depending on the severity of the disease, and it is difficult to detect mild cases. Some respiratory or encephalitis types can die within hours after symptoms are found, while in most cases the duration is a few days. There are also great differences in morbidity and mortality, depending on the virulence of the virus, age of diseased cattle, clinical type, feeding and management conditions of cattle, physical condition, etc.

Second, the main points of diagnosis

When the sick cattle died, it was found that there were fibrin exudates in the nasal cavity and trachea, which was an indicator of the disease.

The diagnosis of conjunctival type is less difficult. Granular appearance, fibrin necrotic membrane, subconjunctival edema and serous purulent secretions in the eyes and external nostrils are significant lesions of the disease. Catarrhal conjunctivitis caused by upper respiratory tract infection is helpful to support the diagnosis of the disease. Similarly, it is not difficult to make a clinical diagnosis for any bull and cow with genital type.

Abortion caused by the virus can be diagnosed by virus isolation (virus can be isolated from fetal pleural fluid or fetal membrane). The titer of antibody in cow serum increased during abortion. The encephalitis type of the disease can also be diagnosed by virus isolation and histopathological examination.

The virus can be isolated from the diseased parts, preferably during the period of fever, and can be isolated by tissue culture such as bovine kidney cells or pig kidney cells. The preliminary identification of the virus can be determined according to the rapid production of characteristic cytopathic changes (cell roundness, shrinkage, particle enlargement and condensation, and finally shedding) in tissue culture. serum neutralization test and fluorescent antibody test can also be used as diagnostic indicators.

III. Prevention and control measures

There is no specific treatment for the disease. The function of broad-spectrum antibiotics is to prevent the secondary infection of bacteria, and the use of comprehensive symptomatic treatment can reduce mortality. Convalescent cattle are immune for life. Vaccination is an important measure to prevent the disease. Generally, calves on the left side of half a year old are vaccinated. Immunity is produced 10 to 14 days after vaccination, and 9% of the immunized cattle can keep their antibodies for a long time. Calves can be passively immunized for 2 to 4 months when they eat cow colostrum. Pregnant cattle cannot be vaccinated because they may cause miscarriage.

Strengthening feeding management, improving sanitary conditions and epidemic prevention and isolation measures can prevent the spread of the disease. However, as susceptible cattle are very sensitive to the disease, these measures can only limit the widespread spread of active or hidden types. A large number of investigations show that 10% of the cattle with positive serum antibodies are the source of recessive infection, so the use of vaccine is still the main measure to control the disease. If you control the complications, you can take symptomatic treatment. In the case of respiratory type, sulfonamides and antibiotics can be used when bacterial complications are determined, but the residue of these drugs in milk and meat should be considered. For pustular vulvovaginitis and glans dermatitis, antibiotic ointment can be applied locally to reduce sequelae.

The above is about the diagnosis and prevention of infectious bovine rhinotracheitis, it has been mentioned above that there is no specific treatment for the disease, so daily protection, isolation of diseased cattle, timely use of vaccine control is the key. The pro-agricultural network will also continue to pay attention to the progress of the treatment of this disease, and the exact special treatment will inform the farmers' friends as soon as possible.