Systematic Veterinary Virology

PATHOGENESIS

• It is described under different headings.
• Hosts affected
  • Pig is the main host. The virus also affects avians and humans.
• Transmission
  • This infection is transmitted by direct contact between pigs. The important source for spread is the nasal secretions. SIV can also be transmitted by aerosols over a short distance. The virus can be shed for 30 days after infection and has been recovered from clinically normal animals.
  • The disease is spread to new areas and farms by the movement of infected pigs or carrier people. The virus is easily carried and spread by avian species, particularly waterfowl and turkeys. In endemic areas virus is present throughout the year.
  • However in most other areas, outbreaks are seasonal occuring in late autumn and early winter. The epidemics are very severe, with outbreaks occurring on most pig farms in a locality over a short period.
  • The stress factors, which speed up the infection are transport, mixing of pigs, poor isolation facilities, marked diurnal (day and night) temperature fluctuations and overstocking.
• Incubation Period
  • The incubation period is very short 1 to 3 days. In very severe epidemics it can be as short as 4 hours.
• Morbidity and Mortality
  • Morbidity – upto 100%; mortality – very minimal 1%.