Viral Agents That May Contribute to Lameness Expression or Ataxia in Pigs

Vesicular viruses: Seneca Valley virus (Senecavirus A, or SVA), foot-and-mouth disease (FMD), swine vesicular disease (SVD, vesicular stomatitis (VS), vesicular exanthema (VE)

Regulatory or reportable agents. Vesicular lesions or ulcers around coronary bands or on snouts should always be thoroughly investigated. SVA is endemic in the US and causes transient clinical signs. FMD virus is not present in the US. SVD, VS, and VE viruses are reportable. Diagnosis is by direction of regulatory agency, based on PCR tests of vesicular material and histological examination.

Viruses as risk factors:^a              

CNS disturbances or immune dysfunctions:

EMCV

Rare; encephalitis and myocarditis

HEV

Common, subclinical, vomiting-wasting disease

IAV

Portal of entry for nasopharyngeal bacteria

MCFV

Rare; pigs in proximity with sheep

PCV-2

Immune compromise, possible encephalitis

PRRSV

Immune compromise, possible encephalitis

PRV

Encephalitis, portal of entry for bacteria

Viruses with direct effects: porcine teschovirus, porcine sapelovirus, porcine astrovirus 3, porcine “enteroviruses”, other sporadic viruses (eg, alphaviruses)

Usually myelitis. Concurrent encephalitis possible. All usually involve the spinal cord; less often the brain. Posterior paresis and paralysis most common, but may affect only forelimbs. All assumed to be common viruses but cause only sporadic disease, presumably when introduced to naive pigs. Usually nursery phase; occasionally, growers or adults.