Mucosal disease, BVD
Pestivirus of the Flaviviridae family. RNA virus, with ability to recombine. Different serotypes. There are two byotipes of the virus, the cytopathic and the non-cytopathic form. They are only differentiable in cellular cultures by the lysis caused. Other diseases caused by pestivirus are Border disease of small ruminants and swine fever.
- Direct: (nasal-pharyngeal secretions, urine), aerosols and by venereal route. Faeces are a weak source of infection. The PII calf persistently (persistently infected immunotolerant) occurs when the fetus is infected before the 120th day of gestation; this is the time in which its immune system is mature and functional. The presence of PII animals in a group is key to the appearance of acute outbreaks of BVD, as it is highly infective throughout its lifetime.
It nearly always presents slight or unapparent clinical symptoms, except in two situations: when a gestating cow is infected or when there is a co-infection with another virus, for example, those of tropism of the respiratory tract (BRSV, IBR, PI-3, Adenovirus, etc.).
- Cow in heat: breeding and infertility (of 6 to 8 weeks). Early resorptions.
- Pregnant cow: infection in the first four months of gestation may lead to still births, mummification and early foetal death. - If the fetus becomes infected and is not aborted, it will be born a lifetime carrier of BVD (PII). Infection after 120 days may harm the fetus (cerebral Hypoplasia) but it does not become immunotolerant.
- Concomitant infections: BVD induces a marked immunosuppression that exacerbates concomitant infections and, more commonly, those that are respiratory in nature.
- Mucosal disease: secondary infections of a PII animal with the cytopathic type of BVD. Diarrhoea, anorexia; buccal and nasal ulcers and ulcers on the tongue. Limping, prostration and inevitable death in 5-10 days.
Oral ulcers, ulcers of the abomasum, small intestine and colon.
Isolation and identification - Serology: ELISA, IHA, SNT and PCR.
TREATMENT, PREVENTION AND CONTROL:
Elimination of PII animals from the group. Vaccinal prophylaxis of all animals. Live vaccines (contraindicated in gestating animals) and inactivated vaccine.