IBR

Pathogenic Agent

Serous nasal discharge...

Bovine Herpes Virus 1 (BHV 1)

Etiology

This infection is a serious economic problem for large livestock facilities nearly all over the word. Only a few countries are known to be free of IBR.

Often bought- in- animals are infected, but show no signs because of the virus capability to withdraw into the trigeminal ganglion. It is reactivated by stress caused e.g. through transport and new surroundings. The stressed animals start spreading virus by excretion in nasal, ocular and -in case of IPV- vaginal discharge. After only a couple of days, the entire herd may be infected.

Morbidity can go up to 100%, while mortality ranges from 2 to 12%.

Clinical Signs

...becomes purulent Diagnosis

Infection with BHV 1 may cause different clinical signs:

IBR is characterized by high fever, inflammation of the nose, which reddens and has earned IBR the name red nose disease.
There may also be serous nasal discharge, which later becomes purulent. The mucous membrane shows pin-sized white plaques and pustules.

Often animals also suffer from conjunctivitis and milk production drops. BHV 1 strains causing IBR may also cause abortion in any stage of pregnancy, usually about 3 to 8 weeks after respiratory diseases occur in herds.
IPV is another form of disease with some BHV 1 strains.Clinical signs are confined to the genital tract and recognized by inflammation of vulva and vagina. You can observe pustules on the mucous membranes and mucopurulent discharge. Frequently these symptoms are joined by temporary fertility disorders.
All signs may subside within a couple of weeks, but the infected animal remains a lifelong virus carrier. These cows start spreading the virus when reactivated by stress, infection by other agents (e.g. BVDV) or subsequent to immunosuppressive treatment.

IPV: pustules on the vaginal mucus membrane Control

Diagnosis can be confirmed by isolation of the virus from nasal or conjunctival swabs combined with serological tests.
At necropsy, you will discover focal necroses in liver and kidney by dissection of aborted fetuses.
Herd diagnosis is commonly based on serological tests, such as ELISA, VNT, etc. Bulk milk may also be tested. The presence of antibodies indicates a latent infection among the herd. Stressful events may trigger a reactivation of the virus. Some countries run national eradication programs by using gE-neg. marker vaccines.

Serological tests (gE ELISA) have been designed to distinguish the type of antibodies resulting from gE deleted marker vaccines from the ones that follow natural infection. Thus vaccinated herds maintain their IBR free status in spite of seroconversion.

Differential Diagnosis

Crowding Disease, enzootic bronchopneumonia, FMD, malignant catarrhal fever , BVD/MD, shipping fever pneumonia.

Prevention

• assure hygienic standards to prevent spreading of virus
• rodent control
• fly control
• disinfection
• optimize housing and management conditions
• do not purchase BHV 1 - positive - stocks
• isolate new animals for at least a week and screen them for diseases
• improve endogenous defense mechanisms in herds at risk by immunostimulation
• start a vaccination program
• vaccinate cattle with gE deleted marker vaccine to guarantee the distinction of vaccinated and infected animals
• vaccinate very young calves intranasally with live vaccine
• revaccinate after 5 weeks
• booster every 6 months
  ...or according to recommendations by your vaccine manufacturer

Treatment

The frequent occurrence of secondary bacterial infection requires antimicrobial therapy.

Symptomatic and supportive treatment includes immunostimulating drugs, bronchodilatators, secretolytics and non-steroidal anti-inflammatory drugs (NSAID) in severe cases.

Literature

• Blood, D.C., Radostis, O.M., Veterinary Medicine, 1989
• Fraser, C.M. et al., The Merck Veterinary Manual, 1991
• Larson, B.L., Immunization to Decrease Pregnancy Wastage in Beef Cattle. Part II. Available Vaccines, Compendium on Continuing Education, Vol. 18, No 5, May 1996
• Mantey, S., Heifer Enemy No.1, Dairy Herd Management, December 1993
• Roenfeldt, S., 5 Diseases you can't ignore, Dairy Herd Management, May 1997
• Smith, B. P., Large Animal Internal Medicine, 1990
• Thiry, E., Vaccination with Bovine Herpesvirus 1 Inactivated Vaccine Cannot be Considered as a Stimulus of Reactivation The Bovine Veterinarian, May 1997
• Wren, G., 5 common (but costly) viral diseases of cattle,The Bovine Veterinarian, September 1997