Changes

==Transmission and Epidemiology==

==Transmission and Epidemiology==

The virus is spread by contact with infected pigs, and infection also be transmitted by infected semen. Fomites, such as contaminated needles, boots, overalls and transport vehicles can also transmit PRRS, as can certain species of insects including house flies. It has been thought that aerosol transmission may occur, particularly under conditions of high humidity, low temperatures, and low wind speeds, but this has been difficult to reproduce in the field and experimentally. Once infected, adult animals shed PRRS virus for up to 86 days, and younger, weaned pigs for 157 days. Virus excretion in semen can persist for up to 93 days after infection. This lengthy persistence of infection is an important factor in the maintenance of infection within a herd.

The virus is spread by contact with infected pigs, and infection also be transmitted venereally via infected semen. Blood, saliva, urine, milk and semen from infected animals have all been shown to contain PRRS virus. Fomites, such as contaminated needles, boots, overalls and transport vehicles can also transmit PRRS, as can certain species of insects including house flies. Aerosol transmission is thought to occur, particularly under conditions of high humidity, low temperatures, and low wind speeds, but this has been difficult to reproduce in the field and experimentally. Once infected, adult animals shed PRRS virus for up to 86 days, and younger, weaned pigs for 157 days. Virus excretion in semen can persist for up to 93 days after infection. This lengthy persistence of infection is an important factor in the maintenance of infection within a herd.

 

established (Yaeger et al., 1993).

==Pathogenesis==

==Pathogenesis==