BOVINE VIRAL DIARRHEA: SYMPTOMS, PATHOGENESIS, TREATMENT - BIOLOGY - 2025

The BVD is a disease caused by infection with a virus that attacks cattle from the 60s of the twentieth century to the present. The causal agent of this disease is the virus belonging to the genus Pestivirus, which is located within the Flaviviridae family.

Currently, this disease is multifaceted and produces varied symptoms. Due to its degree of pathogenicity, it is considered the most dangerous viral disease in cattle.

A virus is the causative agent of bovine viral diarrhea. Source: pixabay.com

Four presentations or syndromes of this disease are recognized, known as: acute infection, persistent infection, intrauterine infection, and mucosal disease. Sick animals can reach a maximum of three years of life after diagnosis.

For the treatment of this disease, it is advisable to apply the vaccines and their corresponding reinforcements, as well as to have a health plan for the maintenance or elimination of the virus from the herd.

Symptoms

Bovine viral diarrhea can be recognized by numerous symptoms that also affect the immune, respiratory, digestive and reproductive systems in sick animals. The most common symptoms are the following:

- Fever, loss of appetite and lethargy.

- Development of ulcers in the mouth and digestive tract accompanied by hemorrhagic diarrhea. Sometimes the diarrhea can be traditional and not hemorrhagic.

- The reproductive capacity of the animal is negatively affected.

- Suppression of the immune system that gives rise to intestinal and respiratory diseases in young cattle.

- In the case of gestation of cows, this virus can cross the placenta and infect the fetus, thus causing a spontaneous abortion or the death of the embryo.

Diagnosis

Detection of the disease must be carried out based on the evidence of its symptoms. However, the presence of the virus must be confirmed by taking samples and subsequent laboratory analysis.

At this point, it is important that the animals that test positive are removed from the herd for about 3 or 4 weeks to avoid contagion from the rest of the animals.

Infected animals must be removed from the herd to avoid the spread of the virus. Source: State Hospital (Raleigh, NC)

In addition, great care must be taken with animals less than 6 months old, which may present antibodies obtained from colostrum and thus mask the virus antigen. For this, it is recommended to diagnose molecularly with the PCR or real-time PCR technique.

Pathogeny

The bovine diarrhea virus is caused by a pestivirus of the Flaviviridae family. It is related to the influenza virus or swine fever and the viral border disease that affects sheep.

This pestivirus has two serotypes: serotype 1 and serotype 2. Both serotypes can occur as cytopathic or non-cytopathic biotypes and can cause symptoms of varying severity on infected tissues.

Also, both cytopathogenic and non-cytopathogenic strains can recombine and produce genetic variability. The syndromes caused by bovine viral diarrhea are the following:

Acute infection

This type of infection occurs temporarily in animals that show susceptibility, immunocompetence and seronegativity to the bovine diarrhea virus. In this phase, the symptoms do not refer to the development of the disease but to its initial phase.

The infection cause to develop acute infection is persistent infection. Generally, this syndrome occurs simultaneously with pneumonia because it causes immunosuppression in animals that present it.

Intrauterine infection

It is caused when the acute infection affects a female in a gestational condition between months 1 and 3, hence the calf can be born persistently infected.

Persistent infection

This infection is the one that produces the greatest risk of contagion and dissemination of the disease and is the cause of mucosal disease. Many infected newborn animals go unnoticed and pose the greatest risk to the herd.

Animals younger than 6 months can mask the disease by ingesting colostrum. Source: pixabay.com

However, not only can cows transfer the virus to fetuses through the placenta, but the virus can also be transferred through semen.

Mucosal disease

The presentation of this infection as a mucosal disease is fatal. At this point, the primary infectious factors or agents that predispose this disease are Bovine Herpesvirus 1, Bovine Parainfluenza 3, Bovine Respiratory Syncytial Virus, among others.

These viruses generate lesions in the mucosa and compromise the respiratory tract against secondary pathogens such as bacteria.

Treatment

Treatment of this disease is not as effective. However, there are programs that preventively reduce or eliminate the presence of this virus in the herd.

In this sense, prevention is the application of reinforced or combined vaccines especially to cows in reproductive state, molecular analysis and biosecurity methods.

Vaccine

Against the infection of bovine viral diarrhea, vaccines have been developed with many available presentations. All vaccines that are marketed are attenuated or killed viruses. In other words, it is the chemically inactivated virus.

The treatment or prevention of the bovine viral diarrhea virus is through a vaccine. Source: pixabay.com

Regarding the formulation of vaccines, for example in Argentina, they are combined vaccines that are developed with the inclusion of other viruses or pathogenic bacteria that, like this pestivirus, are associated with the reproductive and respiratory systems of cattle.

The formulations are made up of reference strains of the virus such as those of subgenotype 1a, and some formulas include genotype 2.

The presentation of the vaccines can be aqueous or oily in which the adjuvant does not affect the efficacy of the vaccine. Additionally, the vaccines contain streptomycin and penicillin as preservatives.

Regarding the effectiveness of the vaccine, it is advisable to apply an annual booster of this simultaneously with the implementation of a sanitary plan to control or eliminate the virus in the herd.

Economic losses

According to the economic impact generated by the occurrence of viral diarrhea, heavy losses are recorded, especially in the case of animals with persistent infection, since in themselves, they are an economic loss.

On the other hand, infected animals fail to develop their full genetic potential, with the consequence that they fail to gain enough weight and, therefore, become more sensitive to other diseases. This causes an additional cost for its maintenance.

Bovine viral diarrhea virus can be transferred from the maternal placenta. Source: pixabay.com

In addition, sick animals must be euthanized, since those with persistent infection will continue to shed the virus throughout their lives. This results in a decrease in the reproduction of animals that are not immunized against this virus.

Finally, an infected female animal in the gestation period is exposed to a disastrous loss of the fetus or the death of the embryo, thus causing the economic loss related to a lower rate of conception and gestation of the herd.

References

1. Zoetis Argentina. (2013-2019). Bovine viral diarrhea (BVD). Taken from: ar.zoetis.com
2. Ramírez, R., Chavarría, B., López, A., Rodríguez, L., Nevárez, A. 2012. Presence of the bovine viral diarrhea virus and its association with other pathological conditions in cattle in feedlots. Veterinary Mexico 43 (3): 225-234.
3. Odeón, A. 2019. Bovine Viral Diarrhea. Taken from: agritotal.com
4. Pecora, A., Pérez, M. 2017. Update on bovine viral diarrhea, diagnostic tools and prevention strategies. INTA Editions. Argentina. 26 p.
5. Agrovit. 2019. BVD-Bovine Diarrhea Virus. Taken from: agrovit.com