Temporal and Spatial Epidemiological Analysis of Peste Des Petits Ruminants Outbreaks from the Past 25 Years in Sheep and Goats and Its Control in India

Recapitulation of Peste des Petits Ruminants (PPR) Prevalence in Small Ruminant Populations of Pakistan from 2004 to 2023: A Systematic Review and Meta-Analysis

Peste des petits ruminants (PPR) is an extremely transmissible viral disease caused by the PPR virus that impacts domestic small ruminants, namely sheep and goats. This study aimed to employ a methodical approach to evaluate the regional occurrence of PPR in small ruminants in Pakistan and the contributing factors that influence its prevalence. A thorough search was performed in various databases to identify published research articles between January 2004 and August 2023 on PPR in small ruminants in Pakistan. Articles were chosen based on specific inclusion and exclusion criteria. A total of 25 articles were selected from 1275 studies gathered from different databases. The overall pooled prevalence in Pakistan was calculated to be 51% (95% CI: 42-60), with heterogeneity I2 = 100%, τ2 = 0.0495, and p = 0. The data were summarized based on the division into five regions: Punjab, Baluchistan, KPK, Sindh, and GB and AJK. Among these, the pooled prevalence of PPR in Sindh was 61% (95% CI: 46-75), I2 = 100%, τ2 = 0.0485, and p = 0, while in KPK, it was 44% (95% CI: 26-63), I2 = 99%, τ2 = 0.0506, and p < 0.01. However, the prevalence of PPR in Baluchistan and Punjab was almost the same. Raising awareness, proper surveillance, and application of appropriate quarantine measures interprovincially and across borders must be maintained to contain the disease.

Flock level socio-economic and other associated risk factors for Peste des petits ruminants (PPR) exposure in sheep and goats in Madhya Pradesh state, India

To effectively control and eradicate PPR, the comprehensive understanding of risk factors associated with PPR exposure is vital. Hence, this study investigated socioeconomic and other associated risk determinants for PPR exposure at flock level in sheep and goats in a non-vaccination programme implemented Madhya Pradesh state India. A total of 410 sheep and goat flocks, comprised mostly of goats but also some mixed flocks, were surveyed during 2016 using a multistage random sampling procedure. Further, 230 blood samples were also collected from the farmers-reported PPR affected flocks and sera were tested using c-ELISA to confirm PPR exposure. The primary data on socioeconomic factors, farm management factors, health status, vaccination details and other epidemiological risk factors were collected from flock owners and descriptive statistics, chi-square analysis and logistic regression models were fitted to identify the significant risk factors for PPR incidence. The farmer's education, flock size, rearing pattern, and awareness of PPR vaccination were found to be significant pre-disposing risk factors for PPR exposure in the flocks. Hence, the control and eradication strategy need to be designed comprehensively considering the key social factors like education and vaccination awareness along with other flock level risk factors to eradicate PPR by 2030 in consonance with the global plan.

Post-Vaccination Sero-Monitoring of Peste des Petits Ruminants in Sheep and Goats in Karnataka: Progress towards PPR Eradication in India

Peste des petits ruminants (PPR) presents economic challenges in enzootic countries impacting small ruminant productivity. The state of Karnataka, India, implemented a mass vaccination campaign in alignment with the PPR-Global Eradication Programme (GEP) and the National Strategic Plan for PPR eradication. This study was conducted from January to March 2023 to assess seroconversion in post-vaccinated goats and sheep at the epidemiological unit (epi-unit) level, aligning with the World Organisation for Animal Health (WOAH) and the Food and Agriculture Organization (FAO) guidelines in the PPR Global Control and Eradication Strategy (GCES). Before vaccination, 3466 random serum samples were collected from small ruminants of three age groups (6-12 months, 1-2 years, and >2 years) across 116 epi-units, spanning 82 taluks in 28 districts. Post-vaccination sero-monitoring included 1102 serum samples collected from small ruminants of the 6-12-month age group only, across 111 epi-units covering 64 taluks in 23 districts. The PPRV antibody status was determined using an indigenous hemagglutinin (H) protein monoclonal antibody-based competitive ELISA kit. Pre-vaccination, the PPR seropositivity rates were 55%, 62%, and 66% in the age groups of 6-12 months, 1-2 years, and >2 years, respectively, with a 61% PPRV antibody prevalence across all the age groups. Notably, 41% of the epi-units exhibited antibody prevalence rates of ≥70%, indicating a substantial population immunity, possibly attributed to the previous vaccination program in the state since 2011. In contrast, only 17% of the epi-units had below 30% seroprevalence rates, emphasizing the need for intensified vaccination. Statistical analysis of the data revealed significant correlations (p < 0.05) between the presence of PPRV antibodies and host factors such as species, breed, and sex. Post-vaccination seroprevalence in the 6-12 months age group was found to be 73.4%, indicating the use of an efficacious vaccine. On the evaluation of vaccination immunity in the 6-12 months age group, it was revealed that over 69% of the epi-units achieved a response surpassing ≥70%, indicating a significant improvement from 42% of the epi-units in pre-vaccination. For active PPR eradication, a mass vaccination campaign (>95% coverage) targeting small ruminant populations aged >4 months is advocated, aiming to achieve the desired herd immunity of >80%. This study offers crucial insights into PPR baseline seroprevalence/immunity status and vaccine efficacy, guiding national strategies towards a PPR-free India and further supporting the global eradication initiative.

The Global Evolutionary History of Orf Virus in Sheep and Goats Revealed by Whole Genomes Data

Orf virus (ORFV) belongs to the genus Parapoxvirus (Poxviridae family). It is the causative agent of contagious ecthyma (CE) that is an economically detrimental disease affecting small ruminants globally. Contagious ecthyma outbreaks are usually reported in intensive breeding of sheep and goats but they have also been reported in wildlife species. Notably, ORFV can infect humans, leading to a zoonotic disease. This study aims to elucidate the global evolutionary history of ORFV genomes in sheep and goats, including the first genomes from Central America in the analyses. In comparison to the last study on ORFV whole genomes, the database now includes 11 more sheep and goat genomes, representing an increase of 42%. The analysis of such a broader database made it possible to obtain a fine molecular dating of the coalescent time for ORFV S and G genomes, further highlighting the genetic structuring between sheep and goat genomes and corroborating their emergence in the latter half of 20th century.

Assessment of Peste des Petits Ruminants Antibodies in Vaccinated Pregnant Ewes of Kazakh Breed Fine-Fleeced and Determination of the Decreasing Trend of Maternal Immunity in Their Lambs

In this article, we first assessed peste des petits ruminants (PPR) antibodies in vaccinated pregnant ewes of Kazakh breed fine-fleeced immunized with the PPR vaccine and the duration of maternal immunity in their lambs. Ewes in the last trimester of pregnancy and gestation were immunized with a vaccine from the Nigeria 75/1 strain of the PPR virus (PPRV) produced by the Research Institute of Biological Safety Problems (RIBSP), Kazakhstan. Serum samples from lambs born from vaccinated and unvaccinated ewes were collected a week after birth and at intervals of 7 days for 18 weeks after birth. Serum samples collected from lambs were tested for PPR antibodies using competitive ELISA and virus neutralization test (VNT). Maternal antibodies (MAs) in lambs born from vaccinated ewes were detected for up to 18 weeks, with a tendency to decrease starting at week 14, and by the end of the experiment receded below the protective level (<1:8). In the blood serum of a 14-week-old lamb with MAs (1:8), post vaccination with a field dose (103 TCID50) of the vaccine against PPR, the titers of protective antibodies against PPRV increased to 1:16 on day 14 post vaccination, and the lamb was protected from infection with the field PPRV. A lamb of the same age with MAs in the 1:8 titer was 100% protected from infection with the field PPRV. Therefore, it is recommended that lambs of the Kazakh fine-wool breed be immunized from the age of 14 weeks or older to avoid a period of susceptibility.

Potential diagnostic application of the baculovirus-expressed recombinant truncated nucleocapsid protein of peste des petits ruminants in ELISA

The study describes the expression of recombinant truncated nucleocapsid protein (NP) of peste des petits ruminants (PPR) virus in the baculovirus system (PPRV-rBNP) and its potential application as a diagnostic antigen in ELISA for diagnosis of PPR in sheep and goats. The PPRV N-terminal immunogenic region (1-266 aa) of the NP coding sequence was amplified and cloned into the pFastBac HT A vector. The PPRV-rBNP with a molecular weight of ~30 kDa was expressed in an insect cell system using generated recombinant baculovirus through Bac-to-Bac® Baculovirus Expression System. The crude PPRV-rBNP or Ni-NTA affinity-purified NP was characterized by SDS-PAGE and immunoblot using standard PPRV-specific sera. The PPRV-rBNP reacted well with PPRV anti-N specific monoclonal and polyclonal antibodies and PPRV-specific antiserum, suggesting that the expressed PPRV-rBNP is in its native form. The crude PPRV-rBNP as a diagnostic antigen was evaluated either as a coating antigen or standard positive control antigen in the Avidin-Biotin ELISA using the known standard panel reagents. The results showed that the expressed PPRV-rBNP can be an alternative diagnostic antigen to E. coli expressed recombinant PPRV-NPN and the utility of PPRV-rBNP avoids the need to use live PPRV antigen in the diagnostic ELISA. Hence, this allows scope in the future for large-scale field application of the recombinant antigen-based assays for diagnosis/surveillance and monitoring of PPR at the eradication as well as post-eradication phases in endemic or non-endemic countries.

Towards Eradication of PPR: Disease Status, Economic Cost and Perception of Veterinarians in Karnataka, India

In this study, we assessed the PPR disease status, its economic cost, the financial viability of vaccination, and the perspectives of field veterinarians on the PPR vaccination programme implemented in Karnataka state, India. In addition to secondary data, cross-sectional surveys undertaken during 2016-17 (survey I) and 2018-19 (survey II) from 673 sheep and goat flocks and data collected from 62 veterinarians were analysed. The economic costs and perceptions of veterinarians were analysed using deterministic models and the Likert scale, respectively, and the financial viability of vaccination programmes under the best (15%), base (20%), and worst-case (25%) PPR incidence scenarios, considering two different vaccination plans (plan I and plan II), was assessed. The disease incidence in sheep and goats was found to be 9.8% and 4.8% in survey I and survey II, respectively. In consonance with the increased vaccination coverage, the number of reported PPR outbreaks in the state declined significantly. The estimated farm-level loss of PPR varied between the surveyed years. Even under the best-incidence scenario, under vaccination plan-I and plan-II, the estimated benefit-cost ratio (18.4:1; 19.7:1), the net present value (USD 932 million; USD 936 million) and the internal rate of return (412%) implied that the vaccination programmes were financially viable and the benefits outweighed the cost. Though the majority of veterinarians perceived that the control programme was well planned and rolled out in the state, a few of them disagreed or were neutral towards the plan per se, towards the coordination between functionaries, the availability of funding, and the programme acceptance by farmers. Despite many years of vaccination, PPR still persists in the Karnataka state for various reasons and in order to eradicate the disease, a review of the existing control programme with strong facilitation from the federal government is needed.

Comparative diagnostic efficacy of Avidin-Biotin recombinant nucleoprotein competitive ELISA for serosurveillance and monitoring of peste des petits ruminants in sheep and goats

In this study extensive evaluation of Avidin-Biotin recombinant nucleoprotein competitive ELISA (ABrC-ELISA) was carried out by mass screening of a large number of sera to make use of this assay for serosurveillance and seromonitoring of peste des petits ruminants (PPR) in sheep and goats to evaluate its diagnostic efficacy value and strengthen findings associated with the assay. The recombinant PPR virus (PPRV) nucleoprotein was over-expressed in E. coli, Ni-NTA affinity-purified, and characterized and used as coating diagnostic antigen in ABrC-ELISA, and evaluated using the field sera from animals. On evaluation of the diagnostic performance or efficacy of this assay using the pre-vaccinated and post-vaccinated sera of sheep and goats (n = 1437), the ABrC-ELISA showed a relative diagnostic sensitivity of 87.2% (95% CI: 84.1-90%) and diagnostic specificity of 92.0% (95% CI: 90-93.7%), against well-established existing indigenous H protein-specific PPR competitive ELISA kit with an accuracy of 90.1% (95% CI: 88.5-91.7%) and good or substantial agreement of Cohen's Kappa value of 0.79 ± 0.017 SE (95% CI: 0.76 to 0.82). These findings suggest that the ABrC-ELISA is a potential additional diagnostic tool of a rapid, sensitive, and specific assay for the detection of the PPRV nucleoprotein antibodies in sera of sheep and goats. This PPR Ab Chek kit can be used extensively under field conditions for serosurveillance, and seromonitoring of PPR in sheep and goats at the eradication /post-eradication phase in disease-controlled countries or PPR non-enzootic countries.

Assessment of post-vaccination immune response to peste des petits ruminants virus in small ruminants in the central and western regions of India

The cross-sectional serosurvey for post-vaccination assessment of peste des petits ruminants (PPR) virus (PPRV) antibodies in sheep and goats was carried out in different states in the central and western regions of India after the implementation of vaccination under the PPR control programme. The serum samples (n = 4687) were collected from sheep (n = 1539) and goats (n = 3148) from August 2017 to March 2018 at various epidemiological units (n = 301) of the studied regions using a stratified random sampling method and PPR competitive ELISA kit was employed to detect PPRV antibodies. The results revealed 34, 21, 52, 74, 68, and 65% of prevalence of PPRV antibodies in small ruminants in Madhya Pradesh, Goa, Chhattisgarh, Maharashtra, Gujarat, and Rajasthan states, respectively, with a difference in seropositivity in sheep and goats across the states in sheep (p < 0.01) and goats (p < 0.01). Further, this serosurvey revealed that 60% of the epi-units (n = 185) had > 50% prevalence of post vaccination PPRV antibodies across states due to variations in vaccination rates and patterns. The vaccination coverage and the reported outbreaks varied between the states in the studied regions. Due to continuous vaccination under the control program, the reported PPR outbreaks have progressively declined in most of the studied states, and the PPR risk areas are confined to a few districts and sporadically, outbreaks are reported indicating the effectiveness of vaccination. These findings provide valuable information on potential PPRV episystems, and will assist with activities regarding intensive surveillance, vaccination, biosecurity, and modification of policy decisions towards designing and implementing control and eradication measures. Further, the present situation necessitates continuous mass vaccination and active surveillance programs to make these regions free from PPR in consonance with the PPR Global Control and Eradication Strategy under the PPR Global Eradication Program.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-022-00796-6.

Epidemiologic and import risk analysis of Peste des petits ruminants between 2010 and 2018 in India

BACKGROUND

Peste des petits ruminants (PPR) is a serious disease that affects goats, sheep and other small ruminants. As one of the earliest and most serious countries, PPR has seriously threatened India's animal husbandry economy.

RESULTS

In this study, the spatiotemporal characteristics of the PPR in India outbreaks were analyzed. Between 2010 and 2018, the epidemic in India broke out all over the country in a cluster distribution. Epidemic clusters in northern and southern India are at higher risk, and the outbreak time of PPR has significant seasonality. The results of the analysis of the development and transmission of PPR under the natural infection conditions showed that the PPR outbreak in India reached a peak within 15 days. Finally, the quantitative risk analysis results based on scenario tree show showed that the average probability of infecting PPRV in live sheep exported from India was 1.45 × 10^-4.

CONCLUSIONS

This study analyzed the prevalence of PPR in India. The analysis of transmission dynamics on the development of the epidemic provides a reference for the prevention and control of the epidemic. At the same time, it provides risk analysis and suggestions on trade measures for the trading countries of India.

Epidemiology, risk factors and molecular characterization of small ruminant morbillivirus in Haryana, India

Peste des petitis ruminants is an economically important transboundary and notifiable viral disease of sheep and goats. In this study, 14 PPR suspected outbreaks among sheep and goats were investigated in four districts of Haryana, India, during July 2020 to October, 2021. The causative agent of the disease; small ruminant morbillivirus was detected by Reverse Transcription Polymerase Chain Reaction targeting full gene sequences of fusion protein gene and confirmed by sequencing. The overall morbidity and cumulative mortality in these outbreaks were 37.56% and 12.09%, respectively. Risk factor analysis identified significant difference in mortality based on age with higher mortality in young ones; 21% as compared to adults; 7.55%. Analysis of the vaccination status revealed significant difference in morbidity and mortality with higher morbidity and mortality in un-vaccinated animals as compared to vaccinated ones. The sequencing and phylogenetic analysis of representative samples revealed that the strains of the present study fall in lineage IV (96.6-99.1%) along with other Indian isolates but made a separate cluster (sub-lineage). The comparison of deduced amino acid (aa) sequence analysis of fusion protein of circulating field strains with reference vaccine strain and other lineage IV strains revealed four N-linked glycosylation sites instead of three. The findings of the present study revealed changes in fusion protein of some of the circulating field strains of SRMV in Haryana, India. Further detailed studies are warranted to delineate the molecular details of these circulating field strains and to evaluate the effectiveness of currently used vaccine against these mutated strains.

Spatiotemporal characteristics analysis and potential distribution prediction of peste des petits ruminants (PPR) in China from 2007-2018

Peste des petits ruminants (PPR) is a highly infectious disease that mainly infects small ruminants. To date, PPR has been confirmed in more than 70 countries. In China, PPR has occurred in more than 20 provinces and cities. In this study, based on geographic information system (GIS), spatial analysis was used to examine the occurrence of PPR in China from 2007 to 2018. The results showed that PPR first occurred in Tibet and gradually spread to other provinces. The outbreaks of PPR were concentrated in 2014, 2015 and 2018. Combining climate factors with the maximum entropy (MaxEnt), the results also suggested that the potential risk areas of PPR outbreaks in China were mainly Jiangsu, Yunnan and Anhui in Southeast China. Finally, a phylogenetic tree was used to analyse the evolutionary relationship between the peste des petits ruminants virus (PPRV) in China and the global ones, and it was found that the one in China had a close genetic relationship with the one in Mongolia, India and Bangladesh. Understanding and forecasting the distribution of PPR in China will help policymakers develop targeted monitoring plans. Likewise, analysing the global PPRV epidemic trends will play an important role in the elimination and prevention of PPR.

Peste Des Petits Ruminants in Atypical Hosts and Wildlife: Systematic Review and Meta-Analysis of the Prevalence between 2001 and 2021

Peste des petits ruminants (PPR) or goat plague is considered a leading, highly contagious, and most lethal infectious viral disease of small ruminants affecting the worldwide livestock economy and international animal trade. Although sheep and goats are the primarily affected, the PPR Virus (PPRV) host range has expanded to other livestock (large ruminants) and wildlife animals over the last few decades, resulting in serious concern to the ongoing PPR global eradication program, which is primarily optimized, designed, and targeted towards accessible sheep and goat population. A systematic review and meta-analysis study was conducted to estimate the prevalence and spill-over infection of PPRV in large ruminants (bovine and camel) and wildlife. Published articles from 2001 to October 2021 on the "PPR" were searched in four electronic databases of PubMed, Scopus, Science direct, and Google Scholars. The articles were then selected using inclusion criteria (detection/prevalence of PPRV in bovine, camel, and wildlife population), exclusion criteria (only sheep or goats, lack of prevalence data, experimental trial, test evaluation, and reviews written in other languages or published before 2001), and the prevalence was estimated by random effect meta-analysis model. In the current study, all published articles belonged to Africa and Asia. The overall pooled prevalence of PPR estimates was 24% (95% CI: 15-33), with 30% in Asia (95% CI: 14-49) and 20% in Africa (95% CI: 11-30). The overall estimated pooled prevalence at an Africa-Asia level in bovine and camel was 13% (95% CI: 8-19), and in wildlife, it was 52% (95% CI: 30-74) with significant heterogeneity (I² = 97%) in most pooled estimates with a high prevalence in atypical hosts and wildlife across Asia and Africa. Over the last two decades, the host range has increased drastically in the wildlife population, even for prevalent PPR in the unnatural hosts only for a short time, contributing to virus persistence in multi-host systems with an impact on PPR control and eradication program. This observation on the epidemiology of the PPRV in unnatural hosts demands appropriate intervention strategies, particularly at the livestock-wildlife interface.

Avidin-Biotin recombinant nucleoprotein competitive ELISA for the detection of peste des petits ruminants virus antibodies in sheep and goats

The present study describes the development of a truncated recombinant peste des petits ruminants virus (PPRV) nucleoprotein (rPPRV-NPN) and its polyclonal antibodies-based immuno-diagnostic assay, Avidin-Biotin (AB) recombinant nucleoprotein competitive ELISA (ABrC-ELISA) for the detection of PPRV antibodies in the sheep and goats. The PPRV N-terminal immunogenic region (1-266 aa) of nucleoprotein (NPN) coding sequence was amplified and cloned into the pETite vector. The rPPRV-NPN with a molecular weight of ∼ 30 kDa was expressed in E. coli, purified, and characterized by SDS-PAGE and immunoblot using standard PPRV specific sera. The Ni-NTA affinity-purified rPPRV-NPN as coating antigen and its hyperimmune serum as competitive antibodies raised in guinea pigs were evaluated as diagnostic reagents in ABrC-ELISA using the known standard panel of sera. The threshold (cut-off) Percentage Inhibition (PI) value was determined as 45 (mean ± 3 SD) based on the reactivity of the known sheep and goats sera to PPRV antibodies [negative (n = 140) and positive (n = 98)] and the assay had a sensitivity of 97 % (95 % Confidence Interval (CI): 91.3-99.4 %) and specificity of 100 % (95 % CI: 97.4-100 %) with an excellent Area under curve (AUC) of 0.997 (95 % CI: 0.99-1.0). On evaluation of diagnostic performance of the assay using the sheep and goats sera (n = 391) from vaccinated, infected, and non-vaccinated animals, the ABrC-ELISA showed the relative diagnostic sensitivity of 95.88 % (95 % CI: 92.56-98.01 %) & 98.77 % (95 % CI: 96.43-99.74 %) and diagnostic specificity of 97.97 % (95 % CI: 94.19-99.58 %) & 90.54 % (95 % CI: 84.64-94.73 %) against indigenous PPR competitive ELISA kit & IDvet Screen® PPR Competition kit, respectively. The study showed that ABrC-ELISA is rapid, sensitive, and specific and can be a better alternative assay for the detection of the PPRV antibodies in the sera of small ruminants for serosurveillance / seromonitoring of PPR not only at the eradication and post-eradication phases in the disease-controlled endemic countries but also in the PPR non-endemic countries.