Nature of the disease
The Infectious Bovine Rhinotracheitis / Infectious Pustular Vulvovaginitis (IBR/IPV), sometimes called Red nose, is an infectious disease of cattle due to the bovine herpesvirus-1. The virus can infect the upper respiratory tract or the reproductive tract. Mortality is low but the economical loss can be important.

Etiology
Infectious Bovine Rhinotracheitis (IBR) is caused by Bovine Herpesvirus-1 that is capable of attacking many different tissues in the body leading to a variety of clinical diseases as listed above. Abortions caused by Infectious Bovine Rhinotracheitis (IBR) can be caused by exposure to a natural disease strain or exposure of non-protected pregnant cows or their calves with modified live IBR vaccine. In the first case, the virus replicates in the respiratory tract and circulates in the blood, crossing the placenta into the fetus. The virus begins to multiply in the fetus causing death 1-3 days after replication begins. Abortion occurs 2-7 days after death of the fetus. The time from infection of the cow to abortion can range from 18 days to 3 months (abortions occur during the 6th to 9th month). In the second case, modified viruses replicate in non-protected pregnant cows and pass through the placenta into the fetus causing infection and death.
The genital form of Infectious Bovine Rhinotracheitis (IBR) is seen in mature cows and bulls and is called Infectious Pustular Vulvovaginitis (IPV). The time course of the infection is 2-3 weeks and respiratory symptoms and abortions do not occur.

 

Classification
OIE List B disease

Susceptible species
Domestic and wild Bovines. Under experimental conditions goats, sheep and pigs have demonstrated infection.

Distribution
Infectious Bovine Rhinotracheitis (IBR) is present worldwide an very few country eradicated it (Austria, Denmark, Finland, Sweden, Switzerland). Many Pacific countries or territories reported serological evidence without clinical cases (Fiji, Guam, Niue, Samoa,  Solomon Islands, Tonga, Vanuatu), New Caledonia identified clinical cases, it could be absent from other countries.

Clinical signs
According to authors incubation period ranges from 2 to 20 days. The severity of symptoms highly depends on the strain of the virus and the susceptibility of cattle.

• Sudden onset of fever (up to 42°C) and anorexia,
• Severe hyperaemia of the nasal mucosa (Red nose) with numerous clusters foci of greyish foci of necrosis on the mucous membranes,
• Serous abundant Discharge from the nose and the eyes,
• Conjunctivitis,
• Hyper salivation,
• Dramatic drop in milk yield,
• Tachypnea and tachycardia, sometimes short explosive cough.
• Rarely there animals may die due to obstructive bronchiolitis, or secondary bronchopneumonia.

An abortion form can complicate the respiratory form with late abortion (between the 5th and 8ht month of pregnancy) and placenta retention. It can be the only manifestation.

In the genital form of the disease, the disease lasts for 2 to 3 weeks and symptoms include:

• Moderate fever
• Hyperaemia of genital mucosa with vesicles of 1-2 mm.
• White discharge of  the vulva,
• Pollakiuria
• Reduction of milk yield,
• Males exhibit a balanoposthitis.

In the young calf, less than 6 months old, the disease is more severe:

• Encephalitis (incoordination, hyperexitation and depression),
• Salivation
• Blindness
• High mortality rate

In new born calves the disease causes:

• Fever and lack of appetite,
• Salivation,
• Inflammation of the nasal mucosa
• Conjunctivitis,
• Erosions of the mouth mucous membranes covered with mucopurulent exudate,
• Respiratory distress is common due to swelling of the larynx and pneumonia,
• Some calves may develop diarrhoea.

• Swelling and congestion of mucosa, sometimes with necrotic foci,
• Petechiae,
• Profuse and fibrinopurulent exudate in severe case.

• Enzootic bronchopneumonia,
• Bovine Virus Diarrhoea/Mucosal Disease ,
• Gangrenous coryza,
• Rinderpest,
• Theileriosis

For the abortion form :

• Bovine Virus Diarrhoea/Mucosal Disease ,
• Brucellosis,
• Listeriosis,
• Leptospirosis,
• Coxiellosis

 

Specimens required for diagnosis
The virus can be isolated from blood on EDTA, nasal, pharyngeal, conjunctival, swabs, aborted foetus, placenta, vaginal swab, prepuce washing fluid and semen. Techniques include neutralisation or antigen detection methods using monospecific antisera or monoclonal antibodies,  PCR is also used for detection on semen. Samples should be stored in a transport medium (cell culture medium containing antibiotics and 2-10% foetal bovine serum to protect the virus from inactivation), cooled at 4°C, and rapidly submitted to the laboratory.
Serum can be submitted for virus neutralisation test and ELISA. ELISA test is also available to detect antibodies in milk.

Transmission
After infection, nasal and ocular viral shedding is detected for 10-14 days. It is also present in amniotic liquid, placenta, foetus and semen of infected bulls.
Transmission occurs through aerosols, contact direct and indirect (over short period of time) and artificial insemination.

Risk of introduction   
Infectious Bovine Rhinotracheitis / Infectious Pustular Vulvovaginitis (IBR/IPV) is more likely to be introduced by importation of infected animals and semen.

Control / vaccines  
Once introduced it is difficult and expensive to eradicate Infectious Bovine Rhinotracheitis / Infectious Pustular Vulvovaginitis (IBR/IPV) especially because as the disease establishes animals tend to become unapparent carriers. Systematic testing and elimination of positives has been successful in some countries.
Different type of inactivated vaccines are available. Officially free countries restrict the use of them.

 

Ref:  spc , ansci