Morphology

Abstract

Poxviruses have a distinct morphology of brick-shaped that can be identified using electron microscopy. Parapoxviruses have an ovoid structure, whereas the capripoxviruses and the orthopoxviruses have a brick shape. The average size of lumpy skin disease virus (LSDV) particle is 294 ± 20 nm in length and 262 ± 22 nm in width (Kitching and Smale 1986). Using transmission electron microscopy, capripoxviruses display a biconcave core consisting of the genome which is in a triple-folded coil or tube. The core and two lateral bodies are surrounded by the capsid (Fig. 7.1). The members of Capripoxvirus genus cannot be distinguished by their size (Kitching and Smale 1986) as well as other orthopoxviruses. Parapox and capripoxviruses can be differentiated using scanning electron microscopy since capripoxviruses have a round smooth appearance (Fig. 7.2), whereas parapoxviruses have a distinct geometric pattern (Fig. 7.3). There are two forms of poxvirus virions, the intracellular mature virion (IMV) and the extracellular enveloped virion (EEV). These two forms of the virus are infectious even though they have different envelopes. Like other poxviruses the IMV primarily infects surrounding cells, and the EEV can infect both the surrounding and distant cells (Fenner et al. 1987; Moss 2006). The prototype of lumpy skin disease virus is a Neethling strain which was first isolated in South Africa (Alexander et al. 1957).