Systematic Veterinary Virology

CONGENITAL FORM

• Congenital CSF infection by virulent strains result in abortions or in the birth of diseased pigs, which will die shortly after birth.
• Transplacental transmission with low-virulent CSF strains result in mummification, stillbirth, or the birth of weak and "shaker" pigs.
• Malformation of the visceral organs and of the central nervous system occurs frequently. Some pigs may be born virtually healthy but persistently infected with CSF. Such infection usually follows exposure of fetuses to CSF of low virulence in the first trimester of fetal life.
• Pigs thus infected do not produce neutralizing antibodies to CSF and have a lifelong viremia. The pigs may be free of disease for several months before developing mild anorexia, depression, conjunctivitis, dermatitis, diarrhoea, runting, and locomotive disturbance leading to paresis and death.