Regional epidemiology and associated risk factors of PPR in Asia-A Review

Peste des Petits Ruminants (PPR) is a world organization for animal health (OIE) notifiable and economically important transboundary, highly contagious and acute viral disease of small ruminants. The disease is caused by the PPR Virus (PPRV). PPRV belongs to the genus Morbillivirus of the family Paramyxoviridae. The recent epidemiological and molecular characterization of PPR virus isolates subdivides them into four genetically distinct lineages (I, II, III and IV). The disease is endemic across Asia, the Middle East and African regions and is considered to be a major obstacle to the development of sustainable agriculture across the developing world due to a huge burden on the economy and development of the affected countries and has recently been targeted by the Food and Agriculture Organization (FAO) and the OIE for global eradication by 2030. PPR-endemic countries should join the regional force, and implement regional roadmaps for the progressive and successful control and elimination of PPRV. In this review, the regional epidemiology of PPR outbreaks and overall regional associated risk factors including animal factors (age, species, sex), environmental factors (season, spatial distribution of disease in various locations) and trade associated factors with special reference to the PPR-affected countries in South, Central and East Asia is comprehensively discussed.

Pheno- and genotypic characterization and identification of novel subtypes of Peste des Petits Ruminants virus in domestic and captive wild goats in Northern Iraq

Background Peste des Petits Ruminants (PPR) is an acute or peracute contagious transboundary viral disease that mainly affects caprine and ovine and causes significant economic impact in developing countries. After two PPR virus outbreaks in 2011 and 2014, an investigation, from August 2015 to September 2016, was carried out in Northern Iraq when an increased morbidity and mortality rates were reported in the domestic and captive wild goats. In the present study, ten domestic goat farms and seven captive wild goat herds located in seven geographical areas of Northern Iraq were clinically, pathologically, serologically and genotypically characterized to determine the prevalence and potential cause of PPR virus outbreak. Results The outbreak occurred with rate of morbidity (26.1%) and mortality (11.1%) in domestic goat farms as compared to captive wild goat herds where relatively high mortality (42.9%) and low morbidity (10.9%) rates were recorded. Based on the clinical symptoms (mucopurulent nasal discharges, ulceration and erosion of oral mucosa, profuse watery diarrhea) and necropsy (hemorrhage and congestion on mucous membranes of the colon and rectum with zebra stripes lesions) results, overall, the serological test findings revealed a high frequency (47.9%) of positive samples for anti-PPRV nucleoprotein antibodies. Furthermore, the nucleoprotein (N) gene was detected in 63.2 and 89.1% of samples using conventional and reverse transcription real-time quantitative PCR assays. A phylogenetic analysis of N gene amino acid sequences clustered with the reference strain revealed lineage IV similar to the strains isolated in 2011 and 2014, respectively. However, two sub-types of lineage IV (I and II), significantly distinct from the previous strains, were also observed. Conclusion The phylogenetic analysis suggests that movements of goats are possible cause and one of the important factors responsible for the spread of virus across the region. The study results would help in improving farm management practices by establishing a PPR virus eradication program using regular monitoring and vaccination program to control and mitigate the risk of re-emergence of PPR virus infection in domestic and captive wild goats in Iraq.

Cytopathic Effect of Vero Cells Adapted Bangladeshi Strain of Peste Des Petits Ruminants (PPR) Virus in Cell Culture

The present study described the cytopathic effect of PPR virus presently being used in serial passages at level of 60th in Vero cells and infected tissue culture fluid was used in this study as viral inoculum. Vero cells were grown on cover slip & were infected with tissue culture fluid at a fixed multiplicity of infection (MOI) 0.01. The infected cover slip along with control were stained with H&E stain at periodic intervals and cytopathic effect was studied with microscope. The cytopathic effect (CPE) was visible at first from 24 hpi and the Vero cells showed initial cell rounding, aggregation and syncytial development. Development of inclusion bodies and cell degradation was noticed by 72 hpi. Complete detachment of the cell monolayer was observed by 84 hpi. It is concluded that, development of numerous inclusion bodies is the indication of well adaptation & extensive multiplication of PPRV in Vero cells.

F Gene and N Gene based Reverse Transcription PCR for Molecular Characterization of Peste des Petits Ruminants Virus

Present investigation was undertaken to detect and characterize the PPR virus from different clinical tissue samples of 14 sheep and 17 goats with respiratory disease from Maharashtra, India. All animals were tested by Sandwich ELISA, of which 70.96% were found positive carrying high PPR virus inwhich 12 were sheep and 10 were goats respectively. For confirmation of PPR, molecular detection was performed with RT-PCR using F gene and N gene specific primers. Intestine samples accounted for highest percent positivity (75%) followed by blood (66.66%) and lymph node (62.5%) for presence of virus. Unusually higher positivity was observed in heart, liver and Kidney (60%, each) than normal predilection sites such as lungs (57.84%) and spleen (50%). While nasal swabs and blood were individually processed with F gene and N gene specific PCR, the triturated organs were pooled for processing into ‘Sample A’ comprised of heart, kidney, liver and intestine combined together and ‘Sample B’ comprising of lung, spleen and lymph nodes combined for the molecular detection of PPR yielding the products each of 372bp and 463bp sizes, respectively. Out of total 40 samples tested, 09/12 each from both sample A and B, while 02/10 nasal swabs resulted positive, respectively and all 06 blood samples remained negative. (F as well as N gene PCR methods were found best suitable for detection of PPR virus from tissue samples of small ruminants).

Trehalose improves PPR vaccine virus stability in diluent

Background: Specialized freeze-drying process is being used in the field for different thermostable vaccine preparation worldwide. The thermostability remains only in undiluted conditions. If dilution is made at the morning and used for the whole day, the vaccine efficacy is compromised at high ambient temperature. In this study, trehalose based specialized vaccine diluent was used to improve the stability of Peste des Petits Ruminants (PPR) vaccine in diluted condition. Methods: The available PPR vaccine was reconstituted with conventional diluent and with trehalose based test diluent. The diluted vaccine was kept at ambient temperature without maintaining any cool chain. Stability of diluted vaccine virus was further assessed in vivo and in vitro at different temperatures. Goats were vaccinated and Vero cells were infected with reconstituted vaccines and were assessed at 0, 3, 6, 9 and 24 hours post dilution. Antibody titer was measured and virus infectivity titer was determined in both cultured cell lysate and supernatant. The presence of the virus particles in Vero cell was confirmed by standard RT-PCR targeting Fusion (F) gene of PPR virus. Results: In vivo results revealed that the number of goats possessed antibodies to PPR virus was higher in trehalose based vaccine formulation than the conventional PBS based diluent. Reconstituted vaccine virus (using PBS and trehalose diluent) infected Vero cells produced 70-80% cytopathic effect (CPE) in 5th days of post infection. Both diluents produced and maintained infectivity titer from log10 TCID50 5.5 to log10 TCID50 3.6, until the use of vaccines incubated for 9 hours after dilution. On the other hand, at 24 hours of post dilution only trehalose formulated vaccine produced log10 TCID502.5 whereas no infectivity titer was observed at the same time using conventional one. Conclusion: The present study suggests that trehalose preserves the quality of reconstituted vaccine in terms of infectivity titers. Trehalose can be a diluent of choice for reconstitution of PPR vaccine in field.

Seroprevalence study of peste des petits ruminants in sheep and goats in the northern region of India

Background and Aim: Peste des petits ruminants (PPR) is a contagious, World Organization for Animal Health notifiable, economically important, transboundary morbilliviral disease of sheep and goats. Studying seroprevalence of PPR from different geographical areas under varying agro-climatic conditions may help in formulating effective and appropriate disease control strategies under the ongoing national PPR control program. The present cross-sectional study describes the prevalence of PPR virus antibodies in sheep and goats in the various epidemiological units in different states (Haryana, Himachal Pradesh [HP], Jammu and Kashmir [J&K], Punjab, Uttarakhand [UK], and Uttar Pradesh [UP]) of the northern region of India. Materials and Methods: A total of 5843 serum samples (sheep [n=2463] and goats [n=3380]) were collected by stratified random sampling method from 322 epidemiological units in the studied region during 2017-2018 and tested for PPR virus (PPRV) antibodies by competitive ELISA. Results: The results revealed that an overall seroprevalence of 44.05% (2574/5843) with 57.32%, 55.22%, 65.69%, 37.09%, 32.73%, and 29.35% prevalence of PPRV antibodies in small ruminants in Haryana, Punjab, UP, HP, J&K, and UK states, respectively. Further, Chi-squared test revealed an association of PPRV antibodies in goats (χ2=252.28, p<0.01) and sheep (χ2=192.12, p<0.01) across different states in the region. Conclusion: The seroprevalence in majority of the epidemiological units (n=130) in sheep and goats in the studied region had <30%. This necessitates comprehensive, rigorous, continuous vaccination and active surveillance programs for few more years to achieve the desired 70% seroprevalence level of PPRV antibodies in population and to make the northern region of India, as PPR free zone.