Sample type is vital for diagnosing infection with peste des petits ruminants virus by reverse transcription PCR

Rapid Detection of Peste des Petits Ruminants Virus (PPRV) Nucleic Acid Using a Novel Low-Cost Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) Assay for Future Use in Nascent PPR Eradication Programme

Peste des petits ruminants (PPR) is a disease of small ruminants caused by peste des petits ruminants virus (PPRV), and is endemic in Asia, the Middle East and Africa. Effective control combines the application of early warning systems, accurate laboratory diagnosis and reporting, animal movement restrictions, suitable vaccination and surveillance programs, and the coordination of all these measures by efficient veterinary services. Molecular assays, including conventional reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR (RT-qPCR) have improved the sensitivity and rapidity of diagnosing PPR. However, currently these assays are only performed within laboratory settings; therefore, the development of field diagnostics for PPR would improve the fast implementation of control policies, particularly when PPR has been targeted to be eradicated by 2030. Loop-mediated isothermal amplification (LAMP) assays are simple to use, rapid, and have sensitivity and specificity within the range of RT-qPCR; and can be performed in the field using disposable consumables and portable equipment. This study describes the development of a novel RT-LAMP assay for the detection of PPRV nucleic acid by targeting the N-protein gene. The RT-LAMP assay was evaluated using cell culture propagated PPRVs, field samples from clinically infected animals and samples from experimentally infected animals encompassing all four lineages (I-IV) of PPRV. The test displayed 100% concordance with RT-qPCR when considering an RT-qPCR cut-off value of C_T >40. Further, the RT-LAMP assay was evaluated using experimental and outbreak samples without prior RNA extraction making it more time and cost-effective. This assay provides a solution for a pen-side, rapid and inexpensive PPR diagnostic for use in the field in nascent PPR eradication programme.

Molecular detection and phylogenetic analysis of Peste des petits ruminants virus circulating in small ruminants in eastern Amhara region, Ethiopia

Background

Peste des Petits Ruminants (PPR) is a severe, highly infectious and fatal viral disease of small ruminants. Four lineages of PPR virus have been identified globally based on sequence analysis of the nucleoprotein (N) and fusion (F) gene. The aim of this study was to isolate and genetically characterize recently circulating PPR virus in small ruminants in the eastern Amhara region in Ethiopia. A total of 28 anti-mortem samples (gum debris, nasal and ocular swab) were collected from clinically suspicious animals and examined for the presence of PPRV by a one-step RT-PCR assay. Samples positive with RT-PCR were subjected to isolation of the virus which were subsequently genetically characterized by sequencing of the nucleoprotein (N) gene and phylogenetic analysis of PPR virus (PPRV) strains.

Results

Of the 28 clinical samples examined, 46.4% were positive with RT-PCR for viral nucleic acid. The PPRV was successfully isolated on CHS-20 cell line with the ovine signaling lymphocyte activation molecule (SLAM) receptor expressed on the cell surface and confirmed with RT-PCR and IFAT assay. The nucleotide sequence and phylogenetic analysis indicated that the PPRV obtained were clustered genetically with Lineage IV isolates of the virus.

Conclusion

The successful isolation of the virus and molecular findings of this study confirmed active lineage IV PPRV infections among populations of sheep and goats in eastern Amhara, suggesting risks for potential spread of the disease to currently free areas. Thus, we recommend systematic vaccination to contain outbreaks in affected districts and geographically linked surrounding districts to which the disease could potentially spread due to different epidemiological linkages.

First serological and molecular evidence of PPRV occurrence in Ghardaïa district, center of Algeria

In February 2012, an outbreak of peste des petits ruminants (PPR) was suspected in Ghardaïa district at the center of Algeria. Clinical, serological, and molecular investigations were performed to confirm the occurrence of PPRV. The overall morbidity, mortality, and case fatality rates of the ten flocks investigated were 12.2, 2.5, and 20.3 %, respectively. At the flock level, positivity to PPR was 100, 90, and 100 % by competitive ELISA (c-ELISA), RT-PCR of blood samples, and oculo-nasal swabs, respectively. At the individual levels, the present study showed that out of 186 samples collected from the same animals 17/62 (27.41 %), 14/62 (22.85 %), and 36/62 (58.06 %) were positive by c-ELISA, RT-PCR of blood samples, and RT PCR of oculo-nasal swabs, respectively. The positivity of PPR was significantly higher using RT-PCR of oculo-nasal swabs than c-ELISA and RT-PCR of blood samples. The N gene partial sequence of five PPRV-positive amplicons revealed 100 % homology among them and phylogenetically belonged to lineage IV. The sequences also showed similarity range of 97-99 % with the strains implicated in the Moroccan and Tunisian outbreaks, however, suggesting that a similar strain is circulating across this area of the Maghreb and highlighting the need for a regional control approach.

Partial genetic characterization of peste des petits ruminants virus from goats in northern and eastern Tanzania

Peste des petits ruminants (PPR) is an acute viral disease of small ruminants. The disease was first reported in Tanzania in 2008 when it was confined to the Northern Zone districts bordering Kenya. The present study was carried out to confirm the presence of PPR virus (PPRV) in Tanzania and to establish their phylogenetic relationships. Samples (oculonasal swabs, tissues and whole blood) were obtained from live goats with clinical presentation suggestive of PPR and goats that died naturally in Ngorongoro (Northern Tanzania) and Mvomero (Eastern Tanzania) districts. The clinical signs observed in goats suspected with PPR included fever, dullness, diarrhea, lacrimation, matting of eye lids, purulent oculonasal discharges, cutaneous nodules, erosions on the soft palate and gums and labored breathing. Post mortem findings included pneumonia, congestion of the intestines, and hemorrhages in lymph nodes associated with the respiratory and gastrointestinal systems. PPRV was detected in 21 out of 71 tested animals using primers targeting the nucleoprotein (N) gene. Phylogenetic analysis, based on the N gene, indicated that PPRV obtained from Northern and Eastern Tanzania clustered with PPRV strains of Lineage III, together with PPRV from Sudan and Ethiopia. The findings of this study indicate that there are active PPRV infections in Northern and Eastern Tanzania, suggesting risks for potential spread of PPR in the rest of Tanzania.

Experimental infection of sheep and goats with a recent isolate of peste des petits ruminants virus from Kurdistan

Peste des petits ruminants (PPR) is a contagious viral disease of sheep and goats common in Africa and Asia. Its high morbidity and mortality has a devastating impact on agriculture in developing countries. As an example, an Asian lineage IV strain of PPRV was responsible for mass fatalities among wild goats in Kurdistan in 2010/2011. In separate experiments, three sheep and three goats of German domestic breeds were subcutaneously inoculated with the Kurdish virus isolate; three uninfected sheep and goats were housed together with the inoculated animals. All inoculated animals, all in-contact goats and two in-contact sheep developed high fever (up to 41.7 °C), depression, severe diarrhea, ocular and nasal discharge as well as ulcerative stomatitis and pharyngitis. Infected animals seroconverted within a few days of the first detection of viral genome. Clinical signs were more pronounced in goats; four out of six goats had to be euthanized. Necropsy revealed characteristic lesions in the alimentary tract. Peste des petits ruminants virus (PPRV) RNA was detected in blood as well as nasal, oral and fecal swabs and tissues. The 2011 Kurdish strain of PPRV is highly virulent in European goats and spreads easily to in-contact animals, while disease severity and contagiosity in sheep are slightly lower. PPRV strains like the tested recent isolate can have a high impact on small ruminants in the European Union, and therefore, both early detection methods and intervention strategies have to be improved and updated regularly.