peste des petits ruminants virus

International Common Names

• English: pest of small ruminants virus

English acronym

• PSRV

French acronym

• PPRV

• Domain: Virus
•     Group: "Positive sense ssRNA viruses"
•         Group: "RNA viruses"
•             Order: Mononegavirales
•                 Family: Paramyxoviridae
•                     Genus: Morbillivirus
•                         Species: peste des petits ruminants virus

Peste des petits ruminants virus (PPRV) belongs to the family Paramyxoviridae within the order Mononegavirales. The virus species name was changed in 2016 to Small ruminant morbillivirus (SRM). However, it is still commonly known as PPRV by people working in the field (OIE, 2020). The virus exists as a single serotype but, by means of nucleic acid sequencing, it can be differentiated into four lineages (1-4). It is antigenically similar to Rinderpest virus, Measles virus and Canine distemper virus (OIE, 2020).

The virus is considered to have a typical paramyxovirus structure, with an envelope derived from the host-cell plasma membrane, containing two transmembrane glycoproteins surrounding a nucleocapsid. The presence of the envelope renders virions sensitive to heat, lipid solvents or detergents, non-ionic detergents, formaldehyde and oxidizing agents. The half-life of virus at 37°C was estimated at 2 h, and at 50°C infectivity was destroyed in 30 minutes (Lefevre, 1982). The virus is also sensitive to low pH, being destroyed after death by the low pH which accompanies rigor mortis, but can survive in lymph nodes for 8 days at 4°C. The typical structure of paramyxoviruses has been described (ICTV, 1995).

The transmembrane glycoproteins are important to the pathogenicity and antigenicity of the virus, with separate proteins having fusion (F) and attachment (haemagglutinin/neuraminidase - HN) functions. Haemagglutinin activity of the HN protein of PPRV has been detected, whereas in the closely related Rinderpest virus (RPV) only neuraminidase activity has been detected in this protein (Seth and Shaila, 2001). The haemagglutinin/neuraminidase protein of PPRV is biologically active when transiently expressed in mammalian cells. After attachment to cell receptors, virus entry is achieved by fusion of the virus envelope with the cell-surface membrane. Both the F and HN proteins are involved in this process, which leads to syncitia of cells after fusion, with an interaction of the two glycoproteins rather than independent, concerted action (Das et al., 2000). The transmembrane proteins form spike-like projections of 8 nm from the envelope, and one or two non-glycosylated membrane proteins are associated with the inner face of the envelope.

The viral nucleocapsid consists of a single strand of viral RNA and associated proteins, and has helical symmetry. The genome is of negative-sense, single-stranded RNA, and believed to be similar to genome size of other paramyxoviruses, of between 15 and 16 kb in length. Although PPRV and RPV share antigenic determinants, comparison of nucleotide sequences indicates that PPRV and RPV are no more related than to non-ruminant morbilliviruses (Das et al., 2000). The high degree of sequence conservation between the F proteins of different morbilliviruses probably accounts for the extensive cross-protection observed between different viruses of this genus; for example, the RPV vaccine was previously used to vaccinate against PPRV. The H proteins have more antigenic divergence, and also vary in haemagglutination properties, and may play a role in host-cell specificity.

Replication of virus occurs in the cytoplasm of the host cell, with the genome transcribed by virion-associated enzymes from the 3’ end into viral complementary mRNA molecules, which are then translated into viral proteins. The P, C and V mRNAs are thought to be synthesized by site-specific stuttering on the template, with a resultant frame-shift which enables more than ORF [open-reading frame] to be transcribed, and therefore more than one form of the protein to be translated from the coding sequence. Comparison of gene sequences has indicated significant genetic variation between PPRV isolates, with four distinct phylogenetic groups among 19 isolates from the Indian subcontinent, Middle East and Africa (Shaila et al., 1996).

PPRV causes pest des petits ruminants (PPR) in goats and sheep. The disease is on the list of diseases notifiable to the World Organisation for Animal Health (OIE). The distribution section contains data from OIE's Handistatus database on disease occurrence. For recent, detailed information on the occurrence of this disease worldwide, see the OIE World Animal Health Information Database (WAHIS) Interface.

PPR represents one of the most economically important animal diseases in areas that rely on small ruminants as a way of making a living. It has been targeted for eradication by 2030 by OIE and the Food and Agriculture Organization of the United Nations (FAO). For more information, see the OIE Peste des Petits Ruminants Portal.