Eyelids may be swollen with conjunctiviti and there may be ulcerson the nose in severe cases. There are no oral lesions but there may be drooling of saliva due to ruminal stasis. There is halitosis from pus in the larynx and trachea, and varying degrees of dyspnoea.
Affected animals cough frequently and palpation of the larynx is resented. There is an increased respiratory rate but no abnormal lung sounds except sounds referred from the upper respiratory tract. Inappetence, weight loss and milk drop often occur and can be severe. Death is unusual but is caused by severe damage, necrosis and secondary bacterial infection of the trachea with accompanying inhalation pneumonia. IBR virus enhances the pathogenicity of Moraxella bovis pink eye and severe infectious keratoconjunctivitis lesions can develop in calves.
Recrudescence of chronic suppurative pneumonia in a dairy heifer two weeks after calving. IBR can be transferred by people, objects and farm utensils and can also be spread by semen from infected bulls. The latently infected animals really just act as a reservoir for virus. Once animals are latently infected or carriers they remain carriers for life. You can treat the animals individually as they show clinical signs but to control the disease and its impact on herd production you need to vaccinate.
There are two types of IBR vaccines, live vaccines and inactivated vaccines. Speak to your vet for more information on the advantages of live IBR marker vaccines and which vaccination regime is most suited to your herd circumstances. Keep an eye on our Twitter page for more information. More information here. Inactivated bovine herpesvirus 1 marker vaccines are more efficacious in reducing virus excretion after reactivation than a live marker vaccine. There is no direct treatment for viral diseases.
Infected animals should be isolated from the rest of the herd and treated with anti-inflammatory drugs and antibiotics for secondary infections if necessary. Carrier cattle should be identified and removed from the herd. Control of the disease is based on the use of vaccines. Since BHV-1 is a ubiquitous, highly contagious virus, vaccination is recommended as soon as passive immunity in calves has disappeared, usually around four to six months of age.
The timing of vaccination is at least as important as the choice of vaccine. Since maximum protection does not generally occur until approximately three weeks after vaccination, calves should be vaccinated two to three weeks before weaning at which time they start to be at risk of infection.
The use of marker vaccines is preferred since the antibody they stimulate can be distinguished from the BoHV-1 antibody that follows a natural infection and so secondary vaccination is required. BoHV-1 infection can also sporadically cause abortion in cattle. BoHV-1 infection affects animal health and productivity causing significant economic losses to cattle producers. Its main significance is as a barrier to the export of live cattle to other regions or countries within Europe which have already eradicated the disease.
It is also a significant disease for pedigree herds placing animals into AI stations. Structural proteins BoHV-1 is a DNA virus with several structural proteins among which at least 11 transmembrane glycoproteins.
Glycoproteins play important roles such as virus-cell interactions and interactions with the immune system. During primary infection, cattle shed virus in high titres in nasal and ocular fluids for approximately 14 days, which can infect in-contact animals.
After replication in the lining of the nose, BoHV-1 is transported along nerves and becomes latent in nerve tissue close to where the virus enters, where it remains during the lifetime of the animal. Stress or corticosteroid treatment can lead to the reactivation of BoHV-1, which is then transported back along the nerves to the primary infection site.
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