Preface

Several large dsDNA-containing viruses such as poxviruses (smallpox) and herpes viruses are well known among the scientific community, as well as the general populace, because they cause human diseases. The large dsDNA insect-infecting baculoviruses are also well known in the scientific community because they are used both as biological control agents and as protein expression systems. However, there are other large dsDNA-containing viruses, including the giant 1.2-Mb mimivirus, which are less well known even though all of them play important roles in everyday life. Seven of these virus families are reviewed in this book. Examples of their importance include the virus that causes white spot disease of shrimp (WSSV) (a single representative in the family Whispoviridae). WSSV is responsible for the loss of millions of dollars in the commercial shrimp farming industry every year. Likewise, some iridoviruses, such as members in the genus Megalocytivirus, cause serious diseases in commercial fish farms throughout Asia. Other Iridovirus members in the genus Ranavirus are the causative agent for approximately 50% of the documented cases of amphibian mortality reported in the United States between 1996 and 2001. African swine fever virus (ASFV) (a single representative in the family Asfarviridae), which is vectored by argasid ticks and may actually be a tick virus, is usually lethal to domestic swine and outbreaks of the virus have led to large swine kills in Southern Europe, primarily in Spain. Large dsDNA viruses that infect algae, family Phycodnaviridae, are also just beginning to be appreciated by the scientific community because of their influence on the global environment. That is, more than 50% of the CO2 fixed on the planet is by marine microorganisms, called phytoplankton. The majority of these microorganisms are photosynthetic cyanobacteria. However, a significant number of these microorganisms are eukaryotic algae. Studies in the past 10 years indicate that approximately 20% or more of these photosynthetic microorganisms are infected with a virus at any one time; thus viruses are playing a large role in the turnover of these microorganisms and their role in global CO2 fixation is only beginning to be appreciated by many marine scientists. Phycodnaviruses also contribute to the disappearance of some massive algal blooms, often referred to as red tides or brown tides.