Pathological, serological, and virological findings in sheep infected simultaneously with Bluetongue, Peste-des-petits-ruminants, and Sheeppox viruses

Epidemiological, Pathological, and Molecular Studies on Sheeppox Disease Outbreaks in Karnataka, India

An epidemiological study spanning twelve years has revealed that sheeppox disease is both widespread and endemic, predominantly surging during the winter and summer seasons. This investigation focused on sheeppox across 11 field outbreaks, involving 889 animals from non-migratory flocks across six districts in Karnataka, in the southern peninsula of India. Among these, 105 animals exhibited clinical signs suggestive of sheeppox, such as lesions on the body, and 95 cases were confirmed through PCR testing. The overall positivity rate for sheeppox stood at 10.68% (95 out of 889 animals). The incidence of sheeppox was notably higher in animals aged between 1 and 2 years and was more prevalent in females. Affected animals displayed symptoms including respiratory distress, weakness, fever, loss of appetite, depression, and various skin lesions ranging from papular to pock lesions across their bodies. There was a significant increase in total leukocyte count, while hemoglobin levels, red blood cell counts, and hematocrit values significantly decreased. On gross examination, sheeppox lesions, varying from vesicular to nodular forms, were predominantly found on hairless areas of the body. Microscopic examination of skin lesions revealed extensive changes, such as hyperkeratosis, parakeratosis, acanthosis, hydropic degeneration, and necrosis of epithelial cells, along with characteristic intracytoplasmic viral inclusions. The lungs exhibited type-II pneumocyte hyperplasia and proliferative bronchiolitis, also with intracytoplasmic inclusions. Confirmation of the sheeppox virus was achieved through PCR and subsequent sequence analysis. Phylogenetic analysis of the full-length P32 and RPO30 gene demonstrated homology with sheeppox isolates from various parts of India and neighboring countries, indicating that Indian sheeppox viruses are highly lineage-specific and correlate with the host of origin. Based on these findings, it is recommended to implement a homologous vaccination strategy, utilizing selective host/viral strains to enhance protection in susceptible animals.

Cytokine profile in lambs naturally infected with sheeppox virus

In this study, in order to reveal the immune response against the disease in naturally infected sheep with SPPV, the expressions of various pro- or anti-inflammatory cytokines such as tumour necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), interleukin-1beta (IL-1β), interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10) and interleukin-12 (IL-12) were evaluated immunohistochemically. The material of this study consisted of tissue samples taken from 24 sheep, which were brought as dead for routine histopathological examination to the Department of Pathology. Avidin-biotin-peroxidase method was used for immunohistochemistry. Characteristic pox lesions were observed in the skin, lungs and kidneys. In histopathological examinations, pox cells, which are very characteristic for the diagnosis of the disease, were observed in all three tissues. Capripoxvirus nucleic acid was detected in 8 of the 24 tissues. Samples were sequenced, and a phylogenetic tree was constructed with reference strains from GenBank. Strains from the study clustered with sheeppox virus references. In conclusion, the levels of pro-inflammatory cytokines such as TNF-α, IFN-γ, IL-1β, IL-2, IL-8 and IL12 (Th1) were much more dominant compared to the levels of anti-inflammatory cytokines: IL-10 and IL-6 (Th2). This supported the fact that the cellular immune response is much more effective than the humoral immune response in sheeppox.

Spatiotemporal Distributions of Sheep and Goat Pox Disease Outbreaks in the Period 2013-2019 in Eastern Amhara Region, Ethiopia

Sheep and goat pox is highly contagious viral infection of sheep and goats caused by the genus Capripox virus. Clinically, the disease is characterized by fever, macules developing into papules, and necrotic lesions in the skin and nodular lesions in internal organs. In Ethiopia, there are seroprevalence epidemiological studies on the disease. However, the spatiotemporal clustering of sheep and goat pox incidence has not been investigated. A retrospective study design using the outbreak reported data from Kombolcha Regional Laboratory for the years from September 2013 to December 2019 was performed to determine the temporal and spatial distribution of sheep and goat pox outbreaks. A total of 663 sheep and goat pox disease outbreaks were reported in all major parts of Eastern Amhara region between 2013 and 2019. In this period, sheep and goat pox was reported in all administrative zones of Eastern Amhara region (n = 5). The average incidence of sheep and goat pox outbreaks at the district level was 8.61 per 7 years. The incidence differed between areas, being the lowest in hot dry month and highest in warm and cold moist months. Sheep and goat pox outbreaks generally have a peak in November followed by August and a low in May. There is a significant difference in the occurrence of sheep and goat pox disease outbreaks between months and years (p < 0.001). The forecast for the period 2020-2026 revealed that a high number of sheep and goat pox disease outbreaks will occur than the previous one. Therefore, all stakeholders should work cooperatively to combat this disease occurrence, and there should be capacity development for participatory disease search, risk analysis, laboratory diagnosis, and information management in order to respond properly to outbreak of sheep and goat pox disease; thereby, it enhances the prevention and control the disease.

Peste des petits ruminants (PPR) in Africa and Asia: A systematic review and meta-analysis of the prevalence in sheep and goats between 1969 and 2018

BACKGROUND

Peste des petits ruminants (PPR) is a prevalent viral disease of sheep and goats that impacts productivity and international animal trade. Despite the substantial economic consequences related to PPR, little is known about the prevalence of this disease at the broad geographical levels.

OBJECTIVE

The present study aimed to use a systematic approach to assess the regional prevalence of PPR in sheep and goats, and the associated factors that contribute to prevalence estimates.

METHODS

Published articles on PPR in sheep and goats were searched in PubMed, Web of Science, Scopus, Google Scholar and the reference lists of articles reporting the prevalence from 1 January 1969 to 31 December 2018. Articles were selected using inclusion and exclusion criteria. Since the heterogeneity among the studies was significant, pooled prevalences were estimated by a random effect meta-analysis model.

RESULTS

Data on the prevalence of PPR were obtained from Africa and Asia, where the pooled prevalence estimates were 40.99% (95% CI: 37.20%-44.79%) and 38.43% (95% CI: 35.64%-41.22%) respectively. Overall, the estimated pooled prevalence at Africa-Asia level in sheep was 39.31% (95% CI: 35.75%-42.88%) and in goats was 39.57% (95% CI: 36.66%-42.48%). Significant heterogeneity (I²  > 80%) was noted in most pooled estimates.

CONCLUSION

The results on the regional prevalence estimates of PPR presented here will be useful in raising awareness and advocating for Governments to engage in initiatives to eradicate PPR and prevent it from spreading to other continents.

Development of vaccines for prevention of peste-des-petits-ruminants virus infection

Peste des petits ruminants (PPR) is a highly contagious and fatal disease of small ruminants, particularly sheep and goats. This disease leads to high morbidity and mortality of small ruminants, thus resulting in devastating economic loss to the livestock industry globally. The severe disease impact has prompted the Food and Agriculture Organization of the United Nations (FAO) and the World Organization for Animal Health (OIE) to develop a global strategy for the control and eradication of PPR by 2030. Over the past decades, the control of PPR is mainly achieved through vaccinating the animals with live-attenuated vaccines, e.g., rinderpest vaccines. As a closely related disease to PPR of large ruminants, rinderpest was eradicated in 2011 and its vaccines subsequently got banned in order to keep rinderpest-free zones. Consequently, it is desirable to develop homologous PPR vaccines to control the disease. The present review summarizes the objectives of PPR control and eradication by focusing on the homologous PPR vaccines.

Peste Des Petits Ruminants (PPR) in Dromedary Camels and Small Ruminants in Mandera and Wajir Counties of Kenya

A study was conducted to determine the presence of Peste des petits ruminants (PPR) in camel population kept together with small ruminants in Isiolo, Mandera, Marsabit, and Wajir counties of Kenya. This was done in the wake of a disease with unknown etiology “Camel Sudden Death Syndrome” camels in the horn of Africa. Thirty-eight (38) samples, 12, 8, 15, and 3 samples, were collected from Mandera, Wajir, Isiolo, and Marsabit, respectively, from 25 camels, 7 goats, and 4 sheep. One camel in Mandera and one goat in Wajir were confirmed positive for PPR virus (PPRV) through reverse Polymerase Chain Reaction. The analysis of sequences revealed closest nucleotide identities of obtained sequences from both goat and camel to the lineage III of PPRV albeit with 60.29% of nucleotide identity. This study establishes that camels in the study area suffer with PPR manifest clinical signs that are mainly characterized by inappetence, loss of body condition, and general weakness terminally leading to diarrhea, conjunctivitis, and ocular nasal discharges preceding death. These clinical signs are similar to those observed in small ruminants with slight variations of manifestations such as keratoconjunctivitis as well as edema of the ventral surface of the abdomen. This shows that camels could be involved in the epidemiology of PPR in the region and that PPRV could be involved in the epidemics of Camel Sudden Death syndrome. There is therefore a need for resources to be dedicated in understanding the role camels play in the epidemiology of PPR and the role of the disease in Camels Sudden death syndrome.

Isolation and Characterization of Bluetongue Virus Recovered from Blood Samples by Immunoaffinity Purification

An immunoaffinity chromatography (IAC) method was optimized for the selective capture of bluetongue virus (BTV) from blood samples and isolation of the virus in cell culture. The antibody against BTV core particles (lacking the outer capsid proteins VP2 and VP5) was used for the optimization of IAC technique. The antibody against BTV core particle was conjugated with Protein A-virus complex and the complex was dissociated using elution buffer (4 M MgCl₂ with 75 mM HEPES, pH 6.5). The optimized IAC method specifically purified the BTV without capturing other commonly infecting small ruminant's viruses like gaotpox virus (GTPV), sheeppox virus (SPPV), Peste des petits ruminants virus (PPRV) and Foot and mouth disease virus (FMDV). The blood samples (n = 22), positive for BTV antigen in sandwich-ELISA were attempted for virus isolation in the BHK-21 cell using the optimized IAC method. A total of seven BTV were isolated by selective capturing of the virion particles. The isolated viruses were characterized by RNA-PAGE, sequence analysis and serum neutralization test (SNT). Electropherotypic analysis of viral dsRNA in the RNA-PAGE revealed the presence of ten dsRNA segments characteristic of BTV. Out of seven isolates, four isolates were identified as BTV-1 and three isolates were identified as BTV-16 based on nucleotide sequences of segment-2. Phylogenetic analysis of segment-2 nucleotide sequence segregated BTV-1 and BTV-16 isolates to monophyletic cluster at close proximity to other eastern topotype. In SNT, hyperimmune serum (HIS) against BTV-1 neutralized the four BTV-1 isolates up to a titer > 256 and HIS against BTV-16 neutralized the three BTV-16 isolates up to a titer > 128. The IAC technique will be useful for the selective capture of BTV from mixed infection (BTV with other small ruminant's viruses) and isolation from blood sample having low viral load by enrichment.

Future research to underpin successful peste des petits ruminants virus (PPRV) eradication

Peste des petits ruminants virus (PPRV) is a significant pathogen of small ruminants and is prevalent in much of Africa, the Near and Middle East and Asia. Despite the availability of an efficacious and cheap live-attenuated vaccine, the virus has continued to spread, with its range stretching from Morocco in the west to China and Mongolia in the east. Some of the world's poorest communities rely on small ruminant farming for subsistence and the continued endemicity of PPRV is a constant threat to their livelihoods. Moreover, PPRV's effects on the world's population are felt broadly across many economic, agricultural and social situations. This far-reaching impact has prompted the Food and Agriculture Organization of the United Nations (FAO) and the World Organisation for Animal Health (OIE) to develop a global strategy for the eradication of this virus and its disease. PPRV is a morbillivirus and, given the experience of these organizations in eradicating the related rinderpest virus, the eradication of PPRV should be feasible. However, there are many critical areas where basic and applied virological research concerning PPRV is lacking. The purpose of this review is to highlight areas where new research could be performed in order to guide and facilitate the eradication programme. These areas include studies on disease transmission and epidemiology, the existence of wildlife reservoirs and the development of next-generation vaccines and diagnostics. With the support of the international virology community, the successful eradication of PPRV can be achieved.

One-Step Multiplex RT-qPCR Assay for the Detection of Peste des petits ruminants virus, Capripoxvirus, Pasteurella multocida and Mycoplasma capricolum subspecies (ssp.) capripneumoniae

Respiratory infections, although showing common clinical symptoms like pneumonia, are caused by bacterial, viral or parasitic agents. These are often reported in sheep and goats populations and cause huge economic losses to the animal owners in developing countries. Detection of these diseases is routinely done using ELISA or microbiological methods which are being reinforced or replaced by molecular based detection methods including multiplex assays, where detection of different pathogens is carried out in a single reaction. In the present study, a one-step multiplex RT-qPCR assay was developed for simultaneous detection of Capripoxvirus (CaPV), Peste de petits ruminants virus (PPRV), Pasteurella multocida (PM) and Mycoplasma capricolum ssp. capripneumonia (Mccp) in pathological samples collected from small ruminants with respiratory disease symptoms. The test performed efficiently without any cross-amplification. The multiplex PCR efficiency was 98.31%, 95.48%, 102.77% and 91.46% whereas the singleplex efficiency was 93.43%, 98.82%, 102.55% and 92.0% for CaPV, PPRV, PM and Mccp, respectively. The correlation coefficient was greater than 0.99 for all the targets in both multiplex and singleplex. Based on cycle threshold values, intra and inter assay variability, ranged between the limits of 2%-4%, except for lower concentrations of Mccp. The detection limits at 95% confidence interval (CI) were 12, 163, 13 and 23 copies/reaction for CaPV, PPRV, PM and Mccp, respectively. The multiplex assay was able to detect CaPVs from all genotypes, PPRV from the four lineages, PM and Mccp without amplifying the other subspecies of mycoplasmas. The discriminating power of the assay was proven by accurate detection of the targeted pathogen (s) by screening 58 viral and bacterial isolates representing all four targeted pathogens. Furthermore, by screening 81 pathological samples collected from small ruminants showing respiratory disease symptoms, CaPV was detected in 17 samples, PPRV in 45, and PM in six samples. In addition, three samples showed a co-infection of PPRV and PM. Overall, the one-step multiplex RT-qPCR assay developed will be a valuable tool for rapid detection of individual and co-infections of the targeted pathogens with high specificity and sensitivity.

Peste des petits ruminants

Peste des petits ruminants virus causes a highly infectious disease of small ruminants that is endemic across Africa, the Middle East and large regions of Asia. The virus is considered to be a major obstacle to the development of sustainable agriculture across the developing world and has recently been targeted by the World Organisation for Animal Health (OIE) and the Food and Agriculture Organisation (FAO) for eradication with the aim of global elimination of the disease by 2030. Fundamentally, the vaccines required to successfully achieve this goal are currently available, but the availability of novel vaccine preparations to also fulfill the requisite for differentiation between infected and vaccinated animals (DIVA) may reduce the time taken and the financial costs of serological surveillance in the later stages of any eradication campaign. Here, we overview what is currently known about the virus, with reference to its origin, updated global circulation, molecular evolution, diagnostic tools and vaccines currently available to combat the disease. Further, we comment on recent developments in our knowledge of various recombinant vaccines and on the potential for the development of novel multivalent vaccines for small ruminants.

Genetic characterization of peste des petits ruminants virus, Turkey, 2009-2013

Peste des petits ruminants is an endemic disease of small ruminants in Turkey and vaccination has been the method of control but sporadic outbreaks have been reported. This study was carried out to characterize the local peste des petits ruminants virus (PPRV) by sequencing fusion (F) protein and nucleoprotein (N) gene segments and phylogenetic analysis, so as to focus on genetic variation in the field viruses. Samples were collected from sheep and goats clinically suspected of having PPRV infection in Central and Mediterranean regions of Turkey during 2009-2013. Phylogenetic analysis based on the F gene sequences showed that the field isolates in the present study belong to lineage 4 with other Middle East isolates. While N gene sequences revealed a different pattern, the field isolates in the present study clustered with previous Turkish isolates, which probably represents the true picture of molecular epidemiology for PPRV.

A sheeppox outbreak in Morocco: isolation and identification of virus responsible for the new clinical form of disease

Background

Sheeppoxvirus (SPPV) is a member of the Capripoxvirus genus of the Poxviridae family, which causes significant economic losses in Morocco. The resurgence of the sheeppox disease during 2010 was characterized by an emergence of a classical nodular form for the first time in Morocco. However, little is known about the virus strain responsible for nodular form. In this study, thirty three sheep, from the eastern region of Morocco, clinically infected were examined and dead animals were autopsied.

A rapid diagnostic assay for SPPV using different type of clinical samples would be useful for outbreak management. The aim of this work was to isolate the virus strain responsible for nodular form and we identified and compared by phylogenetic analysis the field strain with Moroccan vaccine strain targeting the thymidine kinase (TK) gene and the chemokine analogue receptor of interleukin (IL8) gene. Further, it was important to investigate and validate a real-time PCR using different clinical and post-mortem samples to manage epidemic sheeppox disease.

Results

The nodular form of sheeppox disease observed in Morocco was clinically characterized by fever, depression, lacrimation, diarrhea in lambs and nodule. At necropsy, the most affected organ was the lung. The etiological strain was successfully isolated from lung nodule in a dead lamb and was identified by using real-time PCR that has been tested and validated on different types of clinical and post mortem samples from naturally infected animals. Sequence and phylogenetic analysis of TK and IL8 gene showed that there was a very close relationship between field and vaccine strain. They were clustered within other SPPV strains.

Conclusion

In the current study, we show for the first time the nodular form of sheeppox in Morocco. We demonstrate a robust real-time PCR-based diagnostic assay to detect the sheeppox virus in multiple sample that can be implemented to efficiently manage the disease outbreak. Our study also offers the prospect for future molecular studies to understand the clinical forms.

Molecular detection of a mixed infection of Goatpox virus, Orf virus, and Mycoplasma capricolum subsp. capripneumoniae in goats

The current study investigated an outbreak of mixed infection with Goatpox virus (GTPV), Orf virus (ORFV), and Mycoplasma capricolum subsp. capripneumoniae (MCCP) that occurred on a Chinese goat farm, with a case fatality rate of 60.2%. The observed clinical signs were ecthyma and accelerated respiration with frequent coughing. Specific fragments of the p32 gene of GTPV, B2L gene of ORFV, and 16S ribosomal RNA gene of MCCP were synchronously amplified by polymerase chain reaction (PCR) from the tissues of 12 dead goats. The PCR products were cloned, sequenced, and aligned with related reference sequences in GenBank for further identification of the pathogens. The present study reports a mixed infection with GTPV, ORFV, and MCCP in goats.

First serological investigation of peste-des-petits-ruminants and Rift Valley fever in Tunisia

This study, carried out between September 2006 and January 2007, is the first cross-sectional serological investigation of peste-des-petits-ruminants (PPR) and Rift Valley fever (RVF) in Tunisia. The objective was to assess the potential need to develop a dual, recombinant PPR-RVF vaccine and how such a vaccine might be utilised in Tunisia. An overall PPR seroprevalence of 7.45% was determined, a finding supported by the high specificity (99.4%) and sensitivity (94.5%) of the ELISA used. On assessment of the diversity and density of mosquitoes in the sampling area, four species of RVF-vectors of the genus Aedes and Culex were identified. However, no serological evidence of RVF was found despite the use of a highly sensitive ELISA (99-100%). Larger scale investigations are underway to confirm these findings and the continuation of the emergency vaccination program against these two diseases remains valid.