Peste des petits ruminants pathogenesis on experimental infected goats by the Moroccan 2015 isolate

Background

Peste des petits ruminants (PPR) is a viral disease of major economic importance on small ruminants. Goats are usually known to be more susceptible to the disease. Infection chronology, virus circulation, and the disease early detection need to be better understood. This study evaluates the tissue tropism and pathogenesis of PPR following experimental infection of goats using a lineage IV virus, the most dominant in the world originated from Asia. PPRV infection was experimentally induced in 4 six-month-old goats by intra-nasal and intravenous route of cell virus suspension and from infectious mashed tissue. The clinical signs were observed and goats were euthanized at predetermined clinical score level for post-mortem examinations and PPRV detection by RT-PCR. Clinical signs of infection were present, pyrexia, serous-mucopurulent nasal discharges, coughing, diarrhea and asthenia, for both cell virus suspension and infectious mashed tissue. PPRV genome was highly detected in swabs and tissues with clinical signs dominated by pulmonary attack and digestive symptoms secondary.

Results

Results of this study indicates that PPRV is an invasive infection in animals that in a short period, less than 10 days, invade all vital organs. On live animals, early diagnostic may be easily done on lacrimal and rectal swabs.

Conclusion

The experimental PPRV-infection model using the cell virus suspension is suitable for vaccine evaluation as a standard model.

Re-emergence of Peste des Petits Ruminants virus in 2015 in Morocco: Molecular characterization and experimental infection in Alpine goats

Peste des Petits Ruminants (PPR) is a transboundary viral disease of small ruminants that causes huge economic losses in Africa, The Middle East and Asia. In Morocco, the first PPR outbreak was notified in 2008. Since then no cases were reported for seven years, probably due to three successive vaccination campaigns during 2008-2011 and close surveillance at the border areas. In June 2015, the disease re-emerged in Morocco, raising questions about the origin of the virus. The PPR virus was confirmed by qRT-PCR and virus was isolated from clinical samples on VeroNectin-4 cells. The disease was experimentally reproduced in Alpine goats using both sheep and goat derived outbreak isolates. Molecular characterization of the 2015 Moroccan PPR isolate confirmed the identity of the virus as lineage IV, closely related to the 2012 Algerian (KP793696) and 2012 Tunisian (KM068121) isolates and significantly distinct from the previous PPRV Morocco 2008 strain (HQ131927). Therefore this study confirms a new incursion of PPR virus in Morocco during 2015 and highlights the urgency of implementation of a common control strategy to combat PPR in Maghreb region in North Africa.

VeroNectin-4 is a highly sensitive cell line that can be used for the isolation and titration of Peste des Petits Ruminants virus

Peste des Petits Ruminants virus (PPRV) is a member of the Morbillivirus subgroup of the family Paramyxoviridae, and is one of the most contagious diseases of small ruminants throughout Africa and the rest of the world. Different cell lines have previously been used to isolate PPRV but with limited success. Thus, to improve the isolation of Morbilliviruses, human, canine, and goat homologues of the lymphocyte receptor signaling lymphocyte activation molecule (SLAM) have been introduced into cells that can support virus replication. However, the amino acid sequence of SLAM varies between species, and often requires adaptation of a particular virus to different versions of the receptor. The protein sequence of Nectin-4 is highly conserved between different mammals, which eliminate the need for receptor adaptation by the virus. Cell lines expressing Nectin-4 have previously been used to propagate measles and canine distemper viruses. In this study, we compared infections in Vero cells expressing canine SLAM (VeroDogSLAM) to those in Vero cells expressing Nectin-4 (VeroNectin-4), following inoculations with wild-type strains of PPRV. Virus isolation using VeroNectin-4 cells was successful with 23% of swabbed samples obtained from live infected animals, and was 89% effective using post-mortem tissues of infected sheep. By contrast, only 4.5% efficiency was observed from swab samples and 67% efficiency was obtained in virus isolation from post-mortem tissues using VeroDogSLAM cells. The average incubation period for virus recovery from post-mortem tissues was 3.4 days using VeroNectin-4 cells, compared with 5.5 days when using VeroDogSLAM cells. The virus titers of PPRV obtained from VeroNectin-4 cells were also higher than those derived from VeroDogSLAM cells. A comparison of the growth kinetics for PPRV in the two cell lines confirmed the superiority of VeroNectin-4 cells for PPR diagnostic purposes and vaccine virus titration.