Infectious Bovine Rhinotracheitis (IBR)

Infectious bovine rhinotracheitis (IBR), alternatively referred to as bovine infectious pustular vulvovaginitis, is a contagious respiratory disease in cattle caused by bovine herpesvirus 1 (BoHV-1). The clinical manifestations are diverse, primarily affecting the respiratory tract. Globally, the disease is prevalent, affecting the milk production of dairy cows, bull fertility, and draft cattle usability. As a leader in the animal disease industry, BioVenic has a comprehensive understanding of IBR and rich experience in diagnostics development.

Cause and Effect

BoHV-1 is a double-stranded DNA virus with a complex structure, that belongs to the family Herpesviridae and the genus Varicellovirus. It possesses various viral proteins and glycoproteins that play crucial roles in viral attachment, fusion, and replication within host cells. BoHV-1 can establish latent infections in the sensory ganglia, enabling the virus to persist and reactivate under certain conditions, leading to recurrent outbreaks. This persistence is the most typical feature of the disease.

BoHV-1 can induce respiratory diseases such as rhinitis, tracheitis, and bronchopneumonia. Moreover, IBR is associated with reproductive disorders. These reproductive complications can result in reduced fertility, abortions, and decreased productivity within affected herds. After BoHV-1 infection, it will be accompanied by conjunctivitis, mastitis, and sometimes calf encephalitis, which seriously restricts the healthy development of the cattle industry all over the world.

Fig. 1 Structural diagram of BoHV-1 under an electron microscope.¹

Transmission

• Respiratory secretions, including nasal discharge and saliva containing the virus, serve as the primary source of transmission.
• Aerosol transmission of BoHV-1 can also occur over short distances, particularly in enclosed environments.
• Furthermore, indirect transmission through contaminated equipment, feed, or water can contribute to the spread of IBR.

Epidemiology

In the early 1950s, the disease characterized by symptoms of infectious rhinotracheitis was first seen in the fattening cattle herd in Colorado, USA, and then appeared in places such as Los Angeles and California, and was named IBR. In addition to cattle, BoHV-1 can also infect various wild ruminants, such as deer and bison, but does not cause obvious clinical symptoms. BoHV-1 can be isolated from the conjunctiva, vulva, brain, and aborted fetuses of sick cattle.

Several factors influence the occurrence and spread of IBR in cattle populations. These include,

• Herd Density and Size: High-density and large-sized herds are more prone to rapid spread and transmission of the virus due to increased animal contact.
• Introduction of Infected Animals: The introduction of carrier animals or those with active IBR infection into susceptible herds significantly increases the risk of disease transmission.
• Lack of Biosecurity Measures: Inadequate biosecurity practices, such as poor quarantine protocols and contaminated equipment, contribute to the introduction and spread of BoHV-1 within and between herds.
• Stressful Conditions: Stress factors, such as transportation, crowding, or poor nutrition, can weaken the immune system of cattle, making them more susceptible to IBR infection and its clinical manifestations.

Pathogenesis

Upon infection, BoHV-1 primarily targets the respiratory epithelium of cattle. The virus enters the host cells through receptor-mediated endocytosis. Once inside, it undergoes replication and spread to adjacent respiratory tissues. BoHV-1-induced cell destruction leads to the release of inflammatory mediators, resulting in the characteristic clinical signs associated with IBR, such as nasal discharge, coughing, and fever.

Signs and Symptoms

Clinical signs of IBR can vary based on the stage and severity of the infection. Common symptoms include nasal discharge, coughing, fever, rapid and labored breathing, decreased feed intake, and depression. In severe cases, cattle may display conjunctivitis, corneal opacity, and even neurological signs. Additionally, reproductive disorders, such as infectious pustular vulvovaginitis (IPV) in cows and balanoposthitis in bulls, may also be observed.

Laboratory Diagnosis of BoHV-1

BioVenic develops or improves a variety of diagnostic kits for BoHV-1 to help customers achieve early detection of the disease, mainly including the following immunodiagnostic and molecular diagnostic methods.

• Virus isolation: Nasal swabs and genital swabs of sick cattle can be collected for virus isolation.
• PCR: PCR is mainly used to detect BoHV-1 DNA in semen after BoHV-1 artificial infection or natural infection.
• Antibody detection: ELISA and virus neutralization assay can be used to detect BoHV-1 antibodies in serum.
• Antigen detection: Collect swabs from the nose, eyes, and genital tract for fluorescence in situ hybridization (FISH), and ELISA.

Fig. 2 Schematic diagram of the main tissues in which BoHV-1 exists.²

Treatment

Regarding IBR, there is currently no specific drug available, and symptomatic treatment typically involves the use of antibiotics.

Prevention and Control

IBR prevention and control strategies include feeding management, immunization programs, and elimination of infected animals.

• Feeding Management
  
  • Strict quarantine is carried out on entry and exit animals, and the introduction of cattle from epidemic areas is strictly prohibited.
  • If the newly introduced cattle are not from the IBR clean field, the cattle must be isolated for 4 weeks, and the seronegative cattle can enter the field.
  • Avoid natural mating as much as possible, and use IBR-negative bull semen for artificial insemination.
  • Strengthen feeding management, improve sanitary conditions, and carry out regular quarantine.
  • Once a suspicious case is found, measures such as isolation, blockade, disinfection, and emergency vaccination should be taken immediately.
• Immunization Program
  
  • There are live attenuated vaccines and inactivated vaccines available at present, which can prevent clinical symptoms from appearing, reduce the number of pathogens in the field, and reduce the number of wild viruses infected.
  • Live attenuated vaccines can be administered intramuscularly or nasally, and pregnant cows can only be vaccinated with nasal drops. Inactivated vaccines reduce the risk of miscarriage.
  • Calves are immunized 2-3 weeks before weaning, and then given another dose when they enter the fattening farm, and then supplemented again after 60-70 days.
• Weed Out Infected Animals
  
  • Cattle that were PCR-positive for antibodies and had not been vaccinated were culled.

BioVenic is committed to providing effective diagnostics solutions for the prevention and control of IBR. Our research and development efforts focus on innovative vaccines that offer high efficacy and broad protection against BoHV-1. We aim to improve the health and productivity of cattle populations, contributing to the overall welfare and profitability of the livestock industry. If you need to know more details, please feel free to contact us.

References

1. Russell, Tiffany, et al. "Qualitative Differences in Capsidless L-Particles Released as a By-Product of Bovine Herpesvirus 1 and Herpes Simplex Virus 1 Infections." Journal of virology 92.22 (2018): 10-1128.
2. Queiroz-Castro, Vanessa Lopes Dias, et al. "Detection of bovine herpesvirus 1 in genital organs of naturally infected cows." Theriogenology 130 (2019): 125-129.