Viruses causing frequent and emergent gastrointestinal infections of cattle (review)

Pestiviruses are a common causative agent of gastrointestinal infections in calves. Viruses infect a wide range of domestic and wild animals, cause pathology of the gastrointestinal tract, respiratory, reproductive organs, and the immune system. According to the modern classification, the genotype of pestiviruses is designated by the letters of the Latin alphabet: A, B, C, etc. Common pestivirus infections include viral diarrhea-mucosal disease (VD-MD). The causative agent is pestivirus of genotypes A and B. The virus of genotype A is represented 20 subtypes (1a-1t) and three subtypes (2a-2c). The type A virus in newborn calves causes diarrhea with profuse watery discharge, dehydration. Infection of the type B virus is characterized by a malignant course of the disease in the form of fever, hemorrhagic inflammation of the gastrointestinal tract, and high mortality. In 2004, pestivirus infection of small ruminants was registered for the first time in several countries, caused by an atypical pestivirus, designated as Hobi virus, type D. respiratory organs in calves. Common pathogens include bovine coronavirus (cattle) from the Coronaviridae family, order Nidovirales, subgroup 2a. There are three forms of cattle coronavirus infection: diarrhea of newborn calves; winter diarrhea with the hemorrhagic syndrome in cows and transport fever. A disease similar in symptomatology is caused by rotaviruses. According to the antigenic properties of the main proteins, rotaviruses are divided into groups, subgroups, and serotypes. The main pathogens for calves are group A rotaviruses. Rotavirus diarrhea occurs in newborn calves in the first three weeks. Modern immunological, molecular genetic methods have made it possible to identify new enteropathogenic cattle viruses. Among them, norovirus, the causative agent of a highly contagious anthropozoonotic disease with a fecal-oral transmission mechanism, belongs to the Caliciviridae family, the Norovirus genus, genogroups III and V. Some viruses that cause gastrointestinal diseases are isolated both from sick calves and from animals without visible signs of the disease. Other pathogens are Nebovirus, a non-enveloped virus, a member of the Caliciviridae family, Cattle Torovirus, an enveloped virus of the Coronaviridae family, Astroviruses, a non-enveloped virus of the Astroviridae family. The family consists of the genera: Mamastrovirus mammals and Avastrovirus birds. Cattle picornaviruses, represented by kobuvirus (also called aichivirus B), belongs to the genus Enterovirus in the Picornaviridae family, found in the feces of calves with diarrhea. At the same time, other components of the microbiome of the gastrointestinal tract of calves: bacteria, fungi, rickettsiae - complicate viral infections or, on the contrary, have antiviral properties.