Introduction

Abstract

African swine fever (ASF) is a complex and devastating disease of domestic swine. It has occurred in forms ranging from peracute to acute, subacute, chronic and inapparent and with mortality rates ranging from close to 100% to as little as 3%. Its causitive agent is a large icosahedral cytoplasmic DNA virus, and as such has been tentatively placed in the family Iridoviridae (1). It is the only member of the family that infects a mammal, and it is the only DNA virus presently known to satisfy the criteria for classification as an arbovirus (2). Although it has undoubtedly been present in soft ticks and the indigenous wild swine in Africa for a very long time, it did not emerge as a disease agent until breeds of domestic swine from Europe were brought into Africa. Then, that which existed unbeknown as an inapparent infection in warthogs now appeared as an acute, highly contagious and lethal febrile disease of domesticated swine that was readily mistaken for acute hog cholera (HC). Montgomery described the disease in a report published in 1921 that recounted his work on ASF in Kenya during 1909 through 1915 when fifteen outbreaks occurred involving 1366 pigs of which 1352 or 98.9% died (3). In addition to describing the disease, he established its viral nature, studied the transmission of the virus and its survival under a variety of environmental conditions, explored methods of immunization, studied the host range and indicated the possible role of wild swine in maintaining the virus in nature.