Use of the polymerase chain reaction in differentiating rinderpest field virus and vaccine virus in the same animals

Ribavirin inhibits peste des petits ruminants virus proliferation in vitro

Peste des petits ruminants virus (PPRV), a member of the family Paramyxoviridae, belongs to the genus Morbillivirus. It causes devastating viral diseases in small ruminants and has been rapidly spreading over various regions in Africa, the Middle East, and Asia. Although vaccination is thought to be an effective management strategy against PPR infections, the heat sensitivity of PPRV vaccines severely restricts their use in regions with hot climates. In this research, we studied the antiviral activities of ribavirin and aimed to understand the potential mechanisms of action of ribavirin in the African green monkey kidney cells (Vero cells). In brief, the adsorption, intrusion, replication, and release of PPRV, as well as the mRNA expression level of RNA-dependent RNA polymerase (RdRp), were significantly inhibited in the ribavirin-treated Vero cells compared to those in the PPRV-infected cells that were not treated with ribavirin. Additionally, ribavirin has potential as an antiviral drug against PPRV, and its antiviral activity is mediated by the Janus kinase signal transducer and activator of transcription (JAK/STAT) and PI3K/AKT pathways.

Development of an Enzyme-Linked Immunosorbent Assay Based on CD150/SLAM for the Detection of Peste des Petits Ruminant Virus

Peste des petits ruminant (PPR) is an economically important severe viral disease of small ruminants that affects primarily the respiratory and digestive tract. Specific detection of the PPR virus (PPRV) antigen plays an important role in the disease control and eradication program. In this study, an indirect enzyme-linked immunosorbent assay (ELISA) based on the recombinant goat signaling lymphocyte activation molecule (SLAM) as the capture ligand was successfully developed for the detection of the PPRV antigen (PPRV SLAM-iELISA). The assay was highly specific for PPRV with no cross-reactions among foot and mouth disease virus, Orf virus, sheep pox virus, and goat pox virus and had a sensitivity with a detection limit of 1.56 × 10¹ TCID₅₀/reaction (50 μl). Assessment of 136 samples showed that the developed PPRV SLAM-iELISA was well correlated with real-time RT-qPCR assays and commercially available sandwich ELISA for detection of PPRV and showed relative sensitivity and specificity of 93.75 and 100.83%, respectively. These results suggest that the developed PPRV SLAM-iELISA is suitable for specific detection of the PPRV antigen. This study demonstrated for the first time that the goat SLAM, the cellular receptor for PPRV, can be used for the development of a diagnostic method for the detection of PPRV.

Host Cellular Receptors for the Peste des Petits Ruminant Virus

Peste des Petits Ruminant (PPR) is an important transboundary, OIE-listed contagious viral disease of primarily sheep and goats caused by the PPR virus (PPRV), which belongs to the genus Morbillivirus of the family Paramyxoviridae. The mortality rate is 90–100%, and the morbidity rate may reach up to 100%. PPR is considered economically important as it decreases the production and productivity of livestock. In many endemic poor countries, it has remained an obstacle to the development of sustainable agriculture. Hence, proper control measures have become a necessity to prevent its rapid spread across the world. For this, detailed information on the pathogenesis of the virus and the virus host interaction through cellular receptors needs to be understood clearly. Presently, two cellular receptors; signaling lymphocyte activation molecule (SLAM) and Nectin-4 are known for PPRV. However, extensive information on virus interactions with these receptors and their impact on host immune response is still required. Hence, a thorough understanding of PPRV receptors and the mechanism involved in the induction of immunosuppression is crucial for controlling PPR. In this review, we discuss PPRV cellular receptors, viral host interaction with cellular receptors, and immunosuppression induced by the virus with reference to other Morbilliviruses.

Peste des petits ruminants in Africa: Meta-analysis of the virus isolation in molecular epidemiology studies

Peste des petits ruminant (PPR) is a highly contagious, infectious viral disease of small ruminant species which is caused by the peste des petits ruminants virus (PPRV), the prototype member of the Morbillivirus genus in the Paramyxoviridae family. Peste des petits ruminant was first described in West Africa, where it has probably been endemic in sheep and goats since the emergence of the rinderpest pandemic and was always misdiagnosed with rinderpest in sheep and goats. Since its discovery PPR has had a major impact on sheep and goat breeders in Africa and has therefore been a key focus of research at the veterinary research institutes and university faculties of veterinary medicine in Africa. Several key discoveries were made at these institutions, including the isolation and propagation of African PPR virus isolates, notable amongst which was the Nigerian PPRV 75/1 that was used in the scientific study to understand the taxonomy, molecular dynamics, lineage differentiation of PPRV and the development of vaccine seeds for immunisation against PPR. African sheep and goat breeds including camels and wild ruminants are frequently infected, manifesting clinical signs of the disease, whereas cattle and pigs are asymptomatic but can seroconvert for PPR. The immunisation of susceptible sheep and goats remains the most effective and practical control measure against PPR. To carry out PPR vaccination in tropical African countries with a very high temperature, a thermostable vaccine using the rinderpest lyophilisation method to the attenuated Nigeria 75/1 PPR vaccine strain has been developed, which will greatly facilitate the delivery of vaccination in the control, prevention and global eradication of PPR. Apart from vaccination, other important questions that will contribute towards the control and prevention of PPR need to be answered, for example, to identify the period when a susceptible naïve animal becomes infectious when in contact with an infected animal and when an infectious animal becomes contagious.

Molecular Detection of Circovirus and Adenovirus in Feces of Fur Seals (Arctocephalus spp.)

In some regions, little is known about exposure to viruses in coastal marine mammals. The present study aimed to detect viral RNA or DNA in 23 free-ranging fur seals on the northern coastline of Rio Grande do Sul State, Brazil. Polymerase chain reaction was used to detect nucleic acids of circoviruses, adenoviruses, morbilliviruses, vesiviruses, and coronaviruses in the feces from twenty-one South American fur seals (Arctocephalus australis) and two Subantarctic fur seals (A. tropicalis). Adenovirus DNA fragments were detected in two South American fur seals; nucleotide sequences of these fragments revealed a high degree of similarity to human adenovirus type C. Circovirus DNA fragments were detected in six animals of the same species. Two were phylogenetically similar to the Circovirus genus, whereas the other four nucleotide fragments showed no similarity to any of the known genera within the family Circoviridae. RNA fragments indicating the presence of coronavirus, vesivirus, and morbillivirus were not detected. These findings suggest that adenoviruses and circoviruses are circulating in fur seal populations found along the coast of Rio Grande do Sul State, Brazil.

Diagnosis and control of peste des petits ruminants: a comprehensive review

Peste des petits ruminants (PPR) is an acute, highly contagious, world organization for animal health (OIE) notifiable and economically important transboundary viral disease of sheep and goats associated with high morbidity and mortality and caused by PPR virus. PPR is considered as one of the main constraints in augmenting the productivity of small ruminants in developing countries and particularly severely affects poor farmer's economy. The disease is clinically manifested by pyrexia, oculo-nasal discharges, necrotizing and erosive stomatitis, gastroenteritis, diarrhoea and bronchopneumonia. The disease can be diagnosed from its clinical signs, pathological lesions, and specific detection of virus antigen/antibodies/genome in the clinical samples by various serological tests and molecular assays. PPR is the one of the priority animal diseases whose control is considered important for poverty alleviation in enzootic countries. Availability of effective and safe live attenuated cell culture PPR vaccines and diagnostics have boosted the recently launched centrally sponsored control programme in India and also in other countries. This review article primarily focus on the current scenario of PPR diagnosis and its control programme with advancement of research areas that have taken place in the recent years with future perspectives.

The detection of rinderpest virus RNA extracted from a rapid chromatographic strip-test by RT-PCR

The Global Rinderpest Eradication Program (GREP) aimed to eradicate rinderpest by 2010 and it is widely believed to have been successful. An integral part of the program was the submission of samples from suspect rinderpest positive animals to a local Reference Laboratory for final confirmation. Confirmation of rinderpest in field samples is often hampered because of poor quality of the sample upon receipt. As part of GREP a rapid diagnostic strip test for the detection of rinderpest virus (RPV) in the field was developed allowing a rapid response to suspect outbreaks. The feasibility of extracting viral RNA from the used rapid diagnostic rinderpest devices for final confirmation in the laboratory is described. Viral material contained within used rinderpest devices was stable enough after storage for one week at 21°C to extract RNA from five different RPV strains and amplify it by reverse transcriptase polymerase chain reaction (RT-PCR). Temperature did not affect adversely the extraction and amplification of the viral RNA but humidity impaired RNA extraction and amplification. Used rinderpest devices from field diagnosed rinderpest-positive animals could represent an ideal additional sample for submission to the Reference Laboratories for confirmation of preliminary diagnosis in the field.

Sequence analysis of the haemagglutinin and fusion protein genes of peste-des-petits ruminants vaccine virus of Indian origin

The amino acid composition of the two surface proteins of peste-des-petits ruminants vaccine virus belonging to lineage four from India were deduced from the nucleotide sequence. The fusion (F) protein gene of PPRV Sungri/96 is 2405 nucleotides long and in relation to the length, it is 80 nucleotides longer than that of PPRV Nigeria/75/1 which are found to be present at the 5'UTR of this virus. The complete F gene alignment with other morbillivirus reveals a homology of 89% with PPRV/Nigeria/75/1 and 48-51% with other morbilliviruses. The F protein of PPRV Sungri/96 exhibited characteristics similarity to those of other morbillivirus F proteins. The overall amino acid similarity with its counterpart PPRV Nigeria/75/1 was 96%; with other morbilliviruses it is 65-74%. The PPRV Sungri/96 haemagglutinin (H) protein gene is 1954 nucleotides long and showed a sequence homology of 90.7% with PPRV/Nigeria/75/1 and with other morbilliviruses it ranged from 33% to 45%. At amino acids level, PPRV Sungri/96 showed a homology of 92.3% with PPRV/Nigeria/75/1 and 34-49% with other morbilliviruses. The phylogenetic tree constructed for F and H gene reveals four separate groups which is very similar to that found in other genes. To the best of our knowledge this is the first report describing the F and H genes of an Indian isolate.

Comparative nucleotide sequence analysis of the phosphoprotein gene of peste des petits ruminants vaccine virus of Indian origin

The nucleotide sequences of the phosphoprotein (P) gene of peste des petits ruminants (PPRV) vaccine virus (PPRV Sungri/96) belongs to Asian lineage have been determined and the deduced amino acid sequences were compared with another vaccine strain PPRV/Nigeria75/1 and with those of the other morbilliviruses. The 1652 nucleotides of the P gene encode a phosphoprotein of 509 amino acid residues (from nucleotide numbers 60 to 1587), which is 91% identical to that of PPRV/Nigeria75/1. The C protein consists of 177 amino acid residues and is 91% identical with that of PPRV/Nigeria75/1. The conserved mRNA editing site (5'TTAAAAGGGCACAG) was present at positions 742-756 in the P gene, which is conserved in all other morbilliviruses. The CTT trinucleotide sequence is present at the N/P and P/M intergenic region, which is totally conserved in morbilliviruses. This will be the third sequence for the P gene of PPRV since that of the vaccine strain and a wild-type Turkish isolate has been published already.

Comparative sequence analysis of the large polymerase protein (L) gene of peste-des-petits ruminants (PPR) vaccine virus of Indian origin

The complete nucleotide sequence of the large polymerase (L) protein of the peste-des-petits ruminants (PPR) vaccine virus (PPRV Sungri/96) belonging to the Asian lineage was determined. The gene was 6643 nucleotides in length from the gene-start to the gene-end and encoded a polypeptide of 2183 amino acids. The PPRV Sungri/96 has a nucleotide homology of 94.1% for PPRV Nigeria 75/1 to 64.4% for Canine distemper virus. At amino acid level PPRV Sungri/96 has an amino acid identity of 96.2% with PPRV Nigeria 75/1 and 70.4% to 74.8% with other morbilliviruses. All the established domains in L protein characteristic of paramyxoviruses were also found to be present in PPRV Sungri/96. Phylogenetic analysis of different L proteins of morbilliviruses revealed five well-defined clusters as observed previously. The 3' trailer sequence of PPRV Sungri/96 is of 37 nucleotides long which is very similar to that of other morbilliviruses. To the best of our knowledge this is the first report describing the polymerase gene sequence of PPRV Indian isolate.

Rinderpest virus lineage differentiation using RT-PCR and SNAP-ELISA

An RT-PCR/ELISA system has been developed that detects and differentiates Rinderpest virus (RPV) from the other closely related morbillivirus of ruminants, Peste des petits Ruminants virus (PPRV). In addition, using lineage specific probes, it is possible to determine whether the virus sample is wild-type or vaccine, and the likely origin of the outbreak if it is wild-type. It involves carrying out a RT-PCR with one digoxygenin (Dig)-labelled primer followed by a hybridisation step with a virus-specific, biotin-labelled, probe. The hybridisation step is carried out in an ELISA format on a streptavidin-coated plate. The DIG-labelled products are detected using a specific anti-DIG monoclonal antibody and an anti-mouse horseradish peroxidase conjugate. The hybridisation step replaces nucleotide sequencing or nested PCR for confirmation of the identity of DNA product. The assay is fast and easy to carry out and can give semi-quantitative estimates of the virus content of samples.

The use of antigen-capture enzyme-linked immunosorbent assay (ELISA) for the diagnosis of rinderpest and peste des petits ruminants in ethiopia

Rinderpest had been reported in most parts of Ethiopia when the Pan African Rinderpest Campaign (PARC) was launched. As a result of intensive disease investigation and strategic vaccination, most parts of the country are now considered provisionally free, and widespread vaccination has been replaced by clinical and serological surveillance. Details of any episodes of disease are recorded and followed up after laboratory confirmation of suspected cass using antigen-capture ELISA. This paper is based on observations on the performance of the antigen detection ELISA compared to the agar gel immunodiffusion (AGID) test, which also differentiates rinderpest from peste des petits ruminants (PPR). The stability of the specific viral antigen was monitored for 4 days, and rinderpest and PPR antigens were still detected, depending on the type of specimen. Antigen capture ELISA is more rapid, sensitive and virus specific than the AGID. Even if the cold chain of the specimen is compromised for a day or two during sample collection and submission, the specimen may still be suitable for testing by ELISA.

Rinderpest: the disease and its impact on humans and animals

Rinderpest is an ancient plague of cattle and other large ruminants, with descriptions of its effects dating back to Roman times. It is caused by a morbillivirus closely related to human measles virus. Although a very effective vaccine is available, it is heat labile, and logistical and financial problems hamper its delivery to the remote areas of Africa and Asia where enzootic foci remain. Periodic epizootics emerge from these foci and spread into neighboring areas, mainly as a result of uncontrolled livestock movement and trading. This is particularly true during wars or civil disturbances when normal veterinary controls do not operate. The disease continues to cause devastating economic losses in domestic livestock in areas of the world where it remains endemic.

Morbillivirus infections, with special emphasis on morbilliviruses of carnivores

Morbilliviruses infections cause significant mortality in human beings and animals. Measles virus is responsible for up to two million childhood deaths annually in the developing world, while rinderpest and peste des petits ruminants cause severe epizootics in domestic and wild ruminants in areas of the world where they remain endemic. Canine distemper virus (CDV) is a cause of fatal disease in many species of carnivores. Distemper is controlled by vaccination in domestic dogs and farmed mink, but it may be impossible to eradicate the virus because of its global distribution and wide variety of susceptible host species, which includes both freshwater and marine seals. Research is currently under way to develop new recombinant vaccines, since the currently available live attenuated vaccines for CDV are not safe for use for all species and many valuable zoo animals need to be protected from CDV. New morbilliviruses with potentially disastrous ecological consequences for marine mammals have been discovered in the past decade; phocid distemper virus (PDV) in seals and the cetacean morbillivirus (CMV) has been found in dolphins, whales and porpoises. Reverse transcription, coupled with the polymerase chain reaction (RT/PCR) and nucleic acid sequencing, has been used to characterise the morbilliviruses and has given insights into the evolution of this virus genus.

A rapid chromatographic strip test for the pen-side diagnosis of rinderpest virus

Rinderpest is a contagious viral disease of cloven-hoofed domestic and wild animals. Eradication of the virus following outbreaks depends on rapid and accurate diagnosis of infection and the implementation of control measures. Reporting and confirmatory diagnosis precede the implementation of control measures. A number of techniques have been used for diagnosis such as agar gel immunodiffusion, enzyme-linked immunosorbent assay (ELISA), molecular biological techniques such as polymerase chain reaction (PCR) and virus isolation in tissue culture. Many of these methods are both time consuming and require skilled personnel. The development of a rapid pen-side test for the detection of rinderpest virus (RPV) antigen in lachrymal fluid of cattle is described using the Clearview chromatographic strip test technology (Unipath, Bedford). Optimum conditions for binding monoclonal antibody to nitrocellulose and latex microspheres were determined and a prototype device was developed. The device detected viral antigen in lachrymal fluids from experimentally and naturally infected cattle and showed no cross-reactivity with other related viruses. A field trial was carried out at the Landhi Cattle Colony (LCC), Pakistan, to assess the performance of the rinderpest test under field conditions. Ninety-seven animals, some of which were showing various clinical signs, at LCC and neighbouring colonies were sampled and tested at the pen-side by Clearview and later by immunocapture ELISA (IC-ELISA) at IAH, Pirbright. Nineteen animals were positive by Clearview and/or IC-ELISA. Seventeen out of 19 rinderpest positive animals were positive by Clearview and 15 out of 19 were positive by IC-ELISA. Reverse transcription polymerase chain reaction (RT-PCR) confirmed the 19 animals to be rinderpest positive. This simple, rapid, specific test allows for the first time, accurate pen-side diagnosis of rinderpest.

Molecular epidemiology of animal virus diseases

In this review the application of methods of molecular epidemiology, particularly the combined approach of amplifying defined fragments of viral genomes using the polymerase chain reaction and subsequent nucleotide sequencing analysis, is described. Emphasis is put on examples of a few important diseases (e.g. those caused by morbilliviruses, rhabdoviruses, pestiviruses and aphthoviruses) to demonstrate the impact of this methodology. Molecular epidemiology is already an important and very sensitive tool to study the evolution of viruses at a level superior to previous methodologies and providing a better understanding of epidemiological relationships.

Detection of animal pathogens by using the polymerase chain reaction (PCR)

The polymerase chain reaction (PCR) is a nucleic acid-based technique that enables the rapid and sensitive detection of specific micro-organisms. Although this technique is widely used in veterinary research, it has not yet found applications in routine microbiological analysis of veterinary clinical samples. However, advances in sample preparation together with the increasing availability of specific gene sequences will probably lead to the more widespread diagnostic use of PCR in the future. PCR is likely to have a strong impact in the epidemiology, treatment and prevention of animal infectious diseases.

Rinderpest and other animal morbillivirus infections: comparative aspects and recent developments

The genus morbillivirus presently comprises measles virus of man, rinderpest virus (RPV), peste des petits ruminants virus (PPRV), and canine distemper virus (CDV). 'Emerging' morbilliviruses, such as phocid distemper virus (PDV) of seals, dolphin (DMV) and porpoise morbillivirus (PMV) have probably been present for a long period of time and outbreaks are possibly related to introduction into a highly susceptible population and/or be the result of interspecies transmission. In this review some comparative aspects of morbillivirus infections, particularly with respect to rinderpest and canine distemper viruses, are presented. Topics include pathogenesis, epidemiology, molecular phylogeny, diagnosis and prophylaxis. Recent developments in molecular biology have created tools which have enabled us to achieve a better understanding of morbillivirus infections at the nucleic acid level ('molecular epidemiology') while recombinant DNA technology has allowed new bivalent recombinant vaccines with improved heat stability to be produced.

Geographic distribution and epidemiology of peste des petits ruminants virus

Peste des petits ruminants (PPR) is an important viral disease of goats and sheep prevalent in West Africa and the Middle East. In recent years, PPR has emerged in India, first in the South India and later in North India. To study the genetic relationships between viruses of distinct geographical origin we have sequenced a 322 nucleotide cDNA fragment of the fusion protein gene generated using reverse transcription followed by polymerase chain reaction (PCR) amplification. Viruses from nineteen independent PPR outbreaks were compared; these included the prototype African strain from Senegal and viruses from disease outbreaks which have occurred at different times and locations across Africa, Arabia, the Near East and the Indian subcontinent. Four separate lineages of the virus were identified and the virus isolates from Asia over the past 2 years were all of one lineage which had not previously been identified in Africa or Asia.

Evaluation of polymerase chain reaction for the detection and characterisation of rinderpest and peste des petits ruminants viruses for epidemiological studies

The high sequence variability found in RNA viruses makes it difficult to design primers for reverse transcription-polymerase chain reaction amplification which will be certain to work with all new field isolates. To overcome this problem for the detection and differential diagnosis of rinderpest (RP) and peste des petits ruminants (PPR) viruses (V), we have designed several sets of primers, based on well-conserved sequences in the P and F genes. Analysis of a large number of field isolates from every region of the world where RPV and PPRV are found showed that no sample failed to react with more than one of the primer sets. To facilitate the multiple analyses, the reverse transcription step was performed using random hexanucleotide primers and aliquots of the cDNA were then amplified using a panel of primer sets to identify and differentiate between the virus nucleic acids in the samples. Evaluation of the method was carried out using eye swabs collected from cattle experimentally infected with RPV and goats infected with PPRV during the course of vaccine trials and on field samples such as whole blood, mouth swabs, lung, spleen and other tissues submitted to the laboratory for diagnosis. Sequencing the PCR products enabled us to examine the genetic relationships between new and previous field isolates from different geographical areas.