Bovine Viral Diarrhea (BVD)

Bovine viral diarrhea (BVD) stands as a highly economically significant disease affecting cattle and other ruminant species on a global scale. Given its capacity to induce respiratory and reproductive issues, resulting in diminished productivity and substantial economic losses within the cattle industry, BVD poses a considerable threat. Leveraging a profound understanding of the disease, BioVenic offers customers comprehensive diagnostics solutions, as well as services for the development of vaccines and treatments tailored to address the challenges posed by BVD.

Etiology

BVDV serves as the primary causative agent of BVD, belonging to the Pestivirus genus within the Flaviviridae family. This single-stranded RNA virus displays substantial antigenic diversity. Through comparisons of nucleotide sequences, BVDV is categorized into at least two viral genotypes known as BVDV type 1 and BVDV type 2, each containing various subgenotypes.

The diverse nature of BVDV strains presents challenges for vaccination and control strategies, as different strains may possess varying antigenic properties that can influence the efficacy of vaccines.

Fig.1 Structural diagram of BVDV.^1,2

Distribution

Since the BVDV was first reported in the United States in 1946, it has spread worldwide, especially in Australia, Argentina, and regions where cattle farming is well developed, such as Africa and Europe.

Sustainable Animals

Cattle of all age groups are susceptible to BVDV infection. Clinical disease linked to BVDV is predominantly observed in young cattle, typically ranging from 6 to 24 months old. In addition to cattle, BVDV can infect other species including sheep, goats, alpacas, and pigs. It is also capable of affecting various ruminants such as camels, as well as some wild animals including deer and kangaroos.

Transmission

BVDV can be transmitted through various pathways, contributing to its widespread distribution. Intrauterine infections may occur when a susceptible dam gets infected during specific gestation periods, leading to persistently infected calves that continue to shed the virus throughout their lives. BVDV can also spread through direct contact between animals, contaminated objects (fomites), biting insects, semen, biological products, and potentially from other ruminant species.

Pathogenesis

BVDV can enter the body through various routes, proliferate in the mucosa of the digestive tract and respiratory tract, and then enter the blood to cause viremia. Viremia ends when the host develops neutralizing antibodies. Infection experiments with calves not ingesting maternal antibodies have proved that BVDV proliferation can cause lymphocyte necrosis in the circulating system, and then damage spleen and lymphatic tissues. In addition, the virus can also cause mummified fetuses and miscarriages through placental infection.

Signs and Symptoms

The clinical manifestations of the disease can be divided into subclinical infection, acute infection, persistent infection, and mucosal disease.

• Subclinical Infection
  
  • Clinical symptoms may not be readily apparent, but dairy cattle may exhibit specific signs, including a tendency for reduced milk production.
• Acute Infection
  
  • High fever
  • Diarrhea
  • Mucosal ulceration

  • Immune system suppressed
  • Thrombocytopenia and leukopenia
  • Reproductive disorders, etc.
• Persistent Infection
  
  • Persistent Infection (PI) is a distinct and notable type of BVDV infection. It occurs when pregnant cows are exposed to and infected with BVDV during the 45th to 130th day of pregnancy. The virus crosses the protective barrier of the mother's placenta, resulting in disease within the fetus, and miscarriage signs may be evident during this period. The fetus, in this case, becomes a lifelong infected and virus-shedding animal after birth, referred to as a PI (persistently infected) cattle.
• Mucosal Disease
  Mucosal disease is the most terrifying type clinically, with an incidence rate of about 5%, and once it occurs, its mortality rate approaches 100%. Symptoms of sick cows include,
  
  • High body temperature
  • Shortness of breath
  • Bloody feces

  • Extremely smelly exhaled breath
  • Large ulcers and erosions in the gastric and intestinal mucosa
  
  In addition, mucosal disease can also cause the number of white blood cells and platelets in the blood to decrease, causing immunosuppression, making it very easy to be infected by other pathogens.

Diagnosis

The diagnosis of BVD necessitates the consideration of clinical symptoms, gross and microscopic lesions, along with laboratory tests. BioVenic's diagnostics development services are designed to assist customers in swiftly and accurately identifying BVDV infections, facilitating timely intervention. Our BVDV kit development services primarily include the following types.

• Veterinary Immunodiagnostics Development
  
  • Antigen capture ELISA
  • Immunochemistry
• Veterinary Molecular Diagnostics Development
  
  • PCR
  • NGS

Treatment

Symptomatic treatment is usually adopted in the course of treatment to alleviate the clinical symptoms of sick cattle. Since BVD can lead to ulcers or necrosis in the digestive tract of cattle, which will affect the normal diet of cattle, fluid replacement, antidiarrheal, cardiotonic, and prevention of secondary infection can be taken.

Prevention and Control

There is a strong correlation between BVD and cattle sanitation and farmer feeding management. To prevent the spread of this disease, the prevention and treatment of this disease must adopt comprehensive measures, including disinfection and sanitation management, vaccination, strict Quarantine prevention, improvement of feeding and management level, elimination of persistently infected cattle, etc.

• Disinfection and Sanitation Management
  
  • In daily feeding, the cowshed should be cleaned and cleaned regularly, and disinfection.
  • Pay attention to the control of mosquitoes and other pests on the farm to prevent the infection of intermediate hosts.
• Vaccination
  
  • Vaccines for BVD are available, including modified live virus (MLV) and killed virus (KV) vaccines.
• Quarantine Precautions
  
  • Cattle farms must establish a sound health and quarantine system and regularly monitor the BVDV of cattle.
  • Standardize the introduction behavior of farmers and avoid raising animals from different sources in the same enclosure.
  • Once poisonous cattle are found, they should be isolated and treated immediately, and the sick cattle without any value should be culled.
  • It is strictly forbidden to import cattle from the epidemic area, and the transportation of cattle must be strictly isolated during the trading period.
  • To further prevent infection, imported meat, dairy products, and biological products should also be strictly quarantined.
• Improve the Level of Feeding Management
  
  • Provide balanced and nutritious feed to cows of all ages.
  • Pay attention to vitamin supplementation to improve the body's immunity to the herd.
• Culling of Persistently Infected Cattle
  
  • PI cattle are the largest source of BVDV infection, and PI cattle should be screened and eliminated early in the diagnosis and treatment process.

BioVenic is dedicated to the diagnosis, prevention, and treatment of animal diseases, specializing in the field of BVD. Our focus involves offering customers tailored diagnostics solutions, leveraging expertise in the epidemiology and pathogenesis of BVD. Additionally, we provide development services for effective vaccines and treatments, supporting customers in the prevention and control of BVD. If you want to get more information, please feel free to contact us.

References

1. Al-Kubati, Anwar AG, et al. "Recent advances on the bovine viral diarrhea virus molecular pathogenesis, immune response, and vaccines development." Frontiers in veterinary science 8 (2021): 665128.
2. Image retrieved from Figure 1 "The morphology and structure of BVDV virus." (Al-Kubati, Anwar AG, et al., 2021, used under [CC BY 4.0], the image title was changed to "Structural diagram of BVDV."