PARAMYXOVIRIDAE AND PNEUMOVIRIDAE

A General Introduction has been added to each disease chapter in an attempt to give a brief updated overview of the taxonomic, biological and other characteristics of the virus family or group of bacteria/protozoa that cause disease in livestock and, where relevant, involve wildlife. As the text of the three-volume book Infectious Diseases of Livestock is currently under revision the Editors are aware that there are inconsistencies between the updated introductions to chapters and the content of the chapters themselves. Once the chapters have been updated – a process that is currently underway – these inconsistencies will be removed.

Paramyxoviridae and Pneumoviridae (formerly a subfamily within the Paramyxoviridae) are currently classified with 7 other families in the Order Mononegavirales.

The Paramyxoviridae consist currently of 54 viruses divided into 7 genera (Aquaparamyxovirus, Avulavirus, Ferlavirus, Henipavirus, Morbillivirus, Respirovirus & Rubulavirus).  Among these viruses are some of the most devastating infectious diseases of humans and livestock; measles in humans, canine distemper, rinderpest (cattle) and Newcastle disease (poultry) have arguably caused more death and destruction than any other group of animal viruses in recorded history. Pneumoviridae, a related family, on the other hand, consists of only two genera (Metapneumovirus & Orthopneumovirus) that have little impact on livestock. An exception is bovine respiratory syncytial virus, now classified as bovine orthopneumovirus within the genus Orthopneumovirus.

Paramyxoviruses occur only in vertebrates and all are transmitted directly between infected and susceptible hosts, i.e., none are dependent on vectors for transmission. This is one of the factors that enabled the global eradication of the rinderpest – the first animal disease officially to be recognised as such in 2011. The related high-impact disease of goats and sheep, peste des petits ruminants, has now similarly been targeted for global eradication using the same approach.

Viruses associated with a variety of wildlife species are classified as paramyxoviruses and it is likely that more will be uncovered in the near future. These include viruses associated with bats, i.e. members on the genera Henipavirus (e.g. Hendra- and Nipahviruses) and Rubulavirus (e.g. Menangle and Tioman viruses). These have crossed species barriers into horses, pigs and humans with high fatality rates among the latter, thereby resulting in considerable alarm.  

Paramyxoviruses and pneumoviruses have relatively large (150-300 nm in diameter) pleomorphic virions that are usually roughly spherical in shape but can also be filamentous. They are surrounded by an envelope derived from the host-cell membrane from which prominent glycoprotein “spikes” project that enable attachment to and fusion with host cells.  The genomes of these viruses consist of linear, single-stranded, negative sense RNA that encodes 6 to 10 open reading frames.¹

Table 1 Infections of mammalian livestock caused by viruses within the Paramyxoviridae and Pneumoviridae families