A rapid RT-LAMP assay for the detection of all four lineages of Peste des Petits Ruminants Virus

Long-term trial of protection provided by adenovirus-vectored vaccine expressing the PPRV H protein

A recombinant, replication-defective, adenovirus-vectored vaccine expressing the H surface glycoprotein of peste des petits ruminants virus (PPRV) has previously been shown to protect goats from challenge with wild-type PPRV at up to 4 months post vaccination. Here, we present the results of a longer-term trial of the protection provided by such a vaccine, challenging animals at 6, 9, 12 and 15 months post vaccination. Vaccinated animals developed high levels of anti-PPRV H protein antibodies, which were virus-neutralising, and the level of these antibodies was maintained for the duration of the trial. The vaccinated animals were largely protected against overt clinical disease from the challenge virus. Although viral genome was intermittently detected in blood samples, nasal and/or ocular swabs of vaccinated goats post challenge, viral RNA levels were significantly lower compared to unvaccinated control animals and vaccinated goats did not appear to excrete live virus. This protection, like the antibody response, was maintained at the same level for at least 15 months after vaccination. In addition, we showed that animals that have been vaccinated with the adenovirus-based vaccine can be revaccinated with the same vaccine after 12 months and showed an increased anti-PPRV antibody response after this boost vaccination. Such vaccines, which provide a DIVA capability, would therefore be suitable for use when the current live attenuated PPRV vaccines are withdrawn at the end of the ongoing global PPR eradication campaign.

Comparative study of HA and HNB staining RT-LAMP assays for peste des petits ruminants virus detection in West African Dwarf goats

Peste des petits ruminants (PPR) cause severe economic losses to many countries of the world where the disease is endemic. It has been targeted for global eradication by 2030 following the successful eradication of rinderpest in 2011. The proposed eradication program would benefit from efficient and relatively reliable diagnostic tools for early PPR virus (PPRV) detection. A total of 33 eight to 12 months old West African Dwarf (WAD) goats were used. Nineteen goats infected by commingling with two PPR virus-positive animals formed the infected group (PPRV-infected goats) while 14 non-infected goats formed the control group (CTG). The suitability of hydroxyl naphthol blue (HNB) staining of reverse transcription loop-mediated isothermal amplification (RT-LAMP) and haemagglutination (HA) assays was compared for their sensitivity to detect the PPRV in PPRV-infected goats and non-infected CTG. PPR disease severity in WAD goats at different days post infection (dpi) was evaluated by clinical scoring and haemagglutination titre (HAT). HNB staining RT-LAMP reaction and HA showed sensitivities of 100% and 73.68%, respectively, for PPRV detection. Expression of PPR clinical signs began from 3 dpi, attained peak at 5 dpi, thereafter showed irregular patterns till 24 dpi. Evaluation of HAT in PPRV-infected goats at 12 dpi ranged from 2 to 64 haemagglutination units (HAU), while CTG goats had 0 HAU. In conclusion, HA could be a good tool for rapid diagnosis of PPRV in a developing country setting. However, HNB staining RT-LAMP assay demonstrated high sensitivity for accurate diagnoses of PPRV and as an important diagnostic tool when precise phenotyping is desired.

Diagnosis of Ruminant Viral Diseases with Loop-Mediated Isothermal Amplification

Infectious diseases in livestock industry are major problems for animal health, food safety, and the economy. Zoonotic diseases from farm animals are significant threat to human population as well. These are notifiable diseases listed by the World Organization for Animal Health (OIE). Rapid diagnostic methods can help keep infectious diseases under control in herds. Loop-mediated isothermal amplification (LAMP) is a simple and rapid nucleic acid amplification method that is studied widely for detection of many infectious diseases in the field. LAMP allows biosensing of target DNA or RNA under isothermal conditions with high specificity in a short period of time. An untrained user can analyze results based on color change or turbidity. Here we review LAMP assays to diagnose OIE notifiable ruminant viral diseases in literature highlighting properties of LAMP method considering what is expected from an efficient, field usable diagnostic test.

Development of gold nanoparticles-lateral flow test as a novel field diagnostic assay for detecting foot-and-mouth disease and lumpy skin disease viruses

Background and Objectives

Rapid diagnosis is a cornerstone for controlling and preventing viral disease outbreaks. The present study is aimed to develop a rapid field diagnostic test based on gold nanoparticles for the detection of lumpy skin diseases (LSD), and foot and mouth diseases (FMD) in animals with high sensitivity and specificity.

Materials and Methods

FMD and LSD vaccines were used as a source of viruses' antigens for preparing monoclonal antibodies and conjugated with gold nanoparticles that characterized using various techniques such as UV-visible spectrometry, and transmission electron microscopy (TEM). Monoclonal antibodies (mAbs) for each serotype produced in experimental rats and used to capture antibodies for FMDV and/or LSDV. ELISA was used to screen 469 milk samples and 1165 serum samples from naturally infected cattle, buffaloes, sheep, and goats for validation of the lateral flow test (LFT). LSDV DNA was extracted from 117 blood and skin biopsy samples collected from naturally infected cattle during the 2019 outbreak.

Results

The specificity and sensitivity of GNP-LFT were evaluated and compared to Ag-ELISA, Western blot tests (WB), and PCR. A total of 95 FMDV positives out of 469 (20.25%) milk samples and 268 FMDV positives out of 1165 (23.3%) serum samples from natural infected cattle, buffaloes, sheep, and goats examined by ELISA to valid GNPS-LFT Viral LSDV DNA was detected in 60/117 (51.5%) and 31/60 (52.9%). While the GNPS-LFT assay results were 49/117 (41.9%) and 29/60 (48.3%) blood and skin biopsy samples, respectively. The diagnostic sensitivity and specificity of the GNP-LFT test were 72% and 82%, respectively. All vesicular fluid and epithelium samples collected from infected animals were identified as positive by the GNP-LFT and Ag-ELISA. Ag-ELISA, on the other hand, was 90% and 100%. While the developed GNP-LFT used LSDV polyclonal antibodies were similar to ELISA and IgG-WB with a sensitivity of 72.8% and a specificity of 88.8%, respectively.

Conclusion

The GNPS-LFT is a novel immunoassay based on mono or polyclonal antibodies conjugated with gold nanoparticles that provides an accurate, rapid, specific, and sensitive tool for field rapid diagnosis of FMDV and LSDV.

Epidemiology of Peste des Petits Ruminants in Nigeria: A Review

Peste des petits ruminants (PPR) is a major constraint to the productivity of small ruminants in Nigeria. Understanding of the current epidemiological status of PPR is crucial to its effective control. A review of the epidemiology of PPR in Nigeria was performed and research gaps were identified. Thirty-seven eligible articles were reviewed: these presented information from 30 of the 36 states of Nigeria. Most studies focused on goats and/or sheep (n = 33) but camels (n = 4), cattle (n = 1) and wild ruminants (n = 2) were also considered. Fourteen (37.8%) of the articles reported seroprevalence in small ruminants, which varied from 0.0% to 77.5% where more than 10 animals were sampled. Molecular characterization and phylogenetic analysis were performed in 6 studies, with lineages II and IV, detected in sheep and goats. In one study in small ruminants, sequences clustering into lineage I showed a similarity to the vaccine strain, Nigeria 75/1, based on phylogenetic analysis of F gene sequences. However, if the preferred method of sequencing the N gene had been performed, this isolate would have been grouped into lineage II. According to N gene phylogenetic analysis in the other studies, sequences were identified that clustered with clade II-NigA, II-NigB (closely related to the Nigeria 75/1 vaccine strain), and others which were well separated, suggesting a high diversity of PPRV in Nigeria. Five articles reported the detection of lineage IV in 22/36 states, with IV-NigA and IV-NigB detected, highlighting its widespread distribution in Nigeria. Risk factors for PPRV seropositivity were reported in 10/37 (27.0%) articles, with a higher seroprevalence observed in female animals, although differing results were observed when considering species and age separately. There were inconsistencies in study design and data reporting between studies which precluded conduct of a meta-analysis. Nevertheless, several research gaps were identified including the need to investigate the low uptake of PPRV vaccine, and the economic benefits of PPR control measures to small ruminant farmers. Such data will inform PPR control strategies in Nigeria and subsequently contribute to the global 2030 PPR eradication strategy.

Development and Evaluation of Molecular Pen-Side Assays without Prior RNA Extraction for Peste des Petits Ruminants (PPR) and Foot and Mouth Disease (FMD)

Animal diseases such as peste des petits ruminants (PPR) and foot and mouth disease (FMD) cause significant economic losses in endemic countries and fast, accurate in-field diagnostics would assist with surveillance and outbreak control. The detection of these pathogens is usually performed at reference laboratories, tested using assays that are recommended by The World Organisation for Animal Health (OIE), leading to delays in pathogen detection. This study seeks to demonstrate a proof-of-concept approach for a molecular diagnostic assay that is compatible with material direct from nasal swab sampling, without the need for a prior nucleic acid extraction step, that could potentially be applied at pen-side for both PPR and FMD. The use of such a rapid, low-cost assay without the need for a cold chain could permit testing capacity to be established in remote, resource limited areas and support the surveillance activities necessary to meet the goal of eradication of PPR by 2030. Two individual assays were developed that detect > 99% of PPR and FMD sequences available in GenBank, demonstrating pan-serotype FMD and pan-lineage PPR assays. The ability for the BioGene XF reagent that was used in this study to lyse FMD and PPR viruses and amplify their nucleic acids in the presence of unprocessed nasal swab eluate was evaluated. The reagent was shown to be capable of detecting the viral RNA present in nasal swabs collected from naïve and infected target animals. A study was performed comparing the relative specificity and sensitivity of the new assays to the reference assays. The study used nasal swabs collected from animals before and after infection (12 cattle infected with FMDV and 5 goats infected with PPRV) and both PPR and FMD viral RNA were successfully detected two to four days post-infection in all animals using either the XF or reference assay reagents. These data suggest that the assays are at least as sensitive as the reference assays and support the need for further studies in a field setting.

Point of care diagnostics and non-invasive sampling strategy: a review on major advances in veterinary diagnostics

The use of point of care diagnostics (POCD) in animal diseases has steadily increased over the years since its introduction. Its potential application to diagnose infectious diseases in remote and resource limited settings have made it an ideal diagnostic in animal disease diagnosis and surveillance. The rapid increase in incidence of emerging infectious diseases requires urgent attention where POCD could be indispensable tools for immediate detection and early warning of a potential pathogen. The advantages of being rapid, easily affordable and the ability to diagnose an infectious disease on spot has driven an intense effort to refine and build on the existing technologies to generate advanced POCD with incremental improvements in analytical performance to diagnose a broad spectrum of animal diseases. The rural communities in developing countries are invariably affected by the burden of infectious animal diseases due to limited access to diagnostics and animal health personnel. Besides, the alarming trend of emerging and transboundary diseases with pathogen spill-overs at livestock-wildlife interfaces has been identified as a threat to the domestic population and wildlife conservation. Under such circumstances, POCD coupled with non-invasive sampling techniques could be successfully deployed at field level without the use of sophisticated laboratory infrastructures. This review illustrates the current and prospective POCD for existing and emerging animal diseases, the status of non-invasive sampling strategies for animal diseases, and the tremendous potential of POCD to uplift the status of global animal health care.

Development and Evaluation of a Nested PCR for Improved Diagnosis and Genetic Analysis of Peste des Petits Ruminants Virus (PPRV) for Future Use in Nascent PPR Eradication Programme

Peste des petits ruminants (PPR) is a highly contagious viral disease of small ruminants caused by PPR virus (PPRV). PPR is endemic in Asia, the Middle East and across large areas of Africa and is currently targeted for global eradication by 2030. The virus exists as four different lineages that are usually limited to specific geographical areas. However, recent reports of spread of PPRV, in particular of lineage IV viruses to infection-free countries and previously PPR endemic areas are noteworthy. A rapid and accurate laboratory diagnosis and reports on its epidemiological linkage for virus spread play a major role in the effective control and eradication of the disease. Currently, molecular assays, including conventional reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR (RT-qPCR) are usually used for diagnosis of PPR while the sequencing of part of the nucleocapsid gene is usually carried out for the viral lineage identification. However, it is difficult to diagnose and sequence the genetic material if the animal excreted a low level of virus at the initial stage of infection or if the PPRV is degraded during the long-distance transportation of samples to the reference laboratories. This study describes the development of a novel nested RT-PCR assay for the detection of the PPRV nucleic acid by targeting the N-protein gene, compares the performance of the assay with the existing conventional RT-PCR and also provides good-quality DNA suitable for sequencing in order to identify circulating lineages. The 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. This assay provides a solution with an easy, accurate, rapid and cost-effective PPR diagnostic and partial genome sequencing for use in resource-limited settings.

Development of a Novel Loop Mediated Isothermal Amplification Assay (LAMP) for the Rapid Detection of Epizootic Haemorrhagic Disease Virus

Epizootic haemorragic disease (EHD) is an important disease of white-tailed deer and can cause a bluetongue-like illness in cattle. A definitive diagnosis of EHD relies on molecular assays such as real-time RT-qPCR or conventional PCR. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is a cost-effective, specific, and sensitive technique that provides an alternative to RT-qPCR. We designed two sets of specific primers targeting segment-9 of the EHD virus genome to enable the detection of western and eastern topotypes, and evaluated their performance in singleplex and multiplex formats using cell culture isolates (n = 43), field specimens (n = 20), and a proficiency panel (n = 10). The limit of detection of the eastern and western RT-LAMP assays was estimated as ~24.36 C_T and as ~29.37 C_T in relation to real-time RT-qPCR, respectively, indicating a greater sensitivity of the western topotype singleplex RT-LAMP. The sensitivity of the western topotype RT-LAMP assay, relative to the RT-qPCR assay, was 72.2%, indicating that it could be theoretically used to detect viraemic cervines and bovines. For the first time, an RT-LAMP assay was developed for the rapid detection of the EHD virus that could be used as either a field test or high throughput screening tool in established laboratories to control the spread of EHD.

A Review of the Current Status of Peste des Petits Ruminants Epidemiology in Small Ruminants in Tanzania

Peste des petits ruminants (PPR) is a highly contagious viral disease of sheep and goats with high mortality. The disease is of considerable economic importance in countries such as Tanzania, where small ruminant products are important for sustainable livelihoods. This review assesses current knowledge regarding the epidemiology of PPRV in Tanzania, highlighting the challenges with respect to control and suggesting possible interventions. Thirty-three articles were identified after literature searches using Google Scholar and PubMed. Studies revealed that PPRV is endemic in sheep and goats in Tanzania, although seropositivity has also been reported in cattle, camels, buffalo, Grant's gazelle, wildebeest and impala, but with no clinical manifestation. Three lineages (lineage II to IV) of PPRV have been identified in Tanzania, implying at least two separate introductions of the virus. Diagnosis of PPR in Tanzania is mostly by observation of clinical signs and lesions at post mortem. Risk factors in Tanzania include age, sex, species, and close contact of animals from different farms/localities. Although there is an efficacious vaccine available for PPR, poor disease surveillance, low vaccine coverage, and uncontrolled animal movements have been the bane of control efforts for PPR in Tanzania. There is need for collaborative efforts to develop interventions to control and eradicate the disease. The establishment of a national reference laboratory for PPR, conduct of surveillance, the development of high-quality DIVA vaccines, as well as execution of a carefully planned national vaccination campaign may be key to the control and subsequent eradication of PPR in Tanzania and achieving the global goal of eradicating PPR by 2030.

The potential of diagnostic point-of-care tests (POCTs) for infectious and zoonotic animal diseases in developing countries: Technical, regulatory and sociocultural considerations

Remote and rural communities in low‐ and middle‐income countries (LMICs) are disproportionately affected by infectious animal diseases due to their close contact with livestock and limited access to animal health personnel). However, animal disease surveillance and diagnosis in LMICs is often challenging, and turnaround times between sample submission and diagnosis can take days to weeks. This diagnostic gap and subsequent disease under‐reporting can allow emerging and transboundary animal pathogens to spread, with potentially serious and far‐reaching consequences. Point‐of‐care tests (POCTs), which allow for rapid diagnosis of infectious diseases in non‐laboratory settings, have the potential to significantly disrupt traditional animal health surveillance paradigms in LMICs. This literature review sought to identify POCTs currently available for diagnosing infectious animal diseases and to determine facilitators and barriers to their use and uptake in LMICs. Results indicated that some veterinary POCTs have been used for field‐based animal disease diagnosis in LMICs with good results. However, many POCTs target a small number of key agricultural and zoonotic animal diseases, while few exist for other important animal diseases. POCT evaluation is rarely taken beyond the laboratory and into the field where they are predicted to have the greatest impact, and where conditions can greatly affect test performance. A lack of mandated test validation regulations for veterinary POCTs has allowed tests of varying quality to enter the market, presenting challenges for potential customers. The use of substandard, improperly validated or unsuitable POCTs in LMICs can greatly undermine their true potential and can have far‐reaching negative impacts on disease control. To successfully implement novel rapid diagnostic pathways for animal disease in LMICs, technical, regulatory, socio‐political and economic challenges must be overcome, and further research is urgently needed before the potential of animal disease POCTs can be fully realized.

"FastCheckFLI PPR-like"-A Molecular Tool for the Fast Genome Detection of PPRV and Differential Diagnostic Pathogens

To assist the global eradication of peste des petits ruminants virus (PPRV), a molecular test for the rapid and reliable detection of PPRV was developed which additionally enables the detection of pathogens relevant for differential diagnostics. For this purpose, the necessary time frame of a magnetic bead-based nucleic acid extraction protocol was markedly shortened to 7 min and 13 s. The optimized extraction was run on a BioSprint 15 platform. Furthermore, a high-speed multi-well RT-qPCR for the genome detection of PPRV and additional important pathogens such as Foot-and-mouth disease virus, Parapoxvirus ovis, Goatpox virus, and Mycoplasma capricolum subsp. capripneumoniae was established and combined with suitable internal control assays. The here-described qPCR is based on a lyophilized master mix and takes only around 30 to 40 min. Several qPCR cyclers were evaluated regarding their suitability for fast-cycling approaches and for their diagnostic performance in a high-speed RT-qPCR. The final evaluation was conducted on the BioRad CFX96 and also on a portable Liberty16 qPCR cycler. The new molecular test designated as "FastCheck^FLI PPR-like", which is based on rapid nucleic acid extraction and high-speed RT-qPCR, delivered reliable results in less than one hour, allowing its use also in a pen-side scenario.

A Rapid, Simple, Inexpensive, and Mobile Colorimetric Assay COVID-19-LAMP for Mass On-Site Screening of COVID-19

To control the COVID-19 pandemic and prevent its resurgence in areas preparing for a return of economic activities, a method for a rapid, simple, and inexpensive point-of-care diagnosis and mass screening is urgently needed. We developed and evaluated a one-step colorimetric reverse-transcriptional loop-mediated isothermal amplification assay (COVID-19-LAMP) for detection of SARS-CoV-2, using SARS-CoV-2 isolate and respiratory samples from patients with COVID-19 (n = 223) and other respiratory virus infections (n = 143). The assay involves simple equipment and techniques and low cost, without the need for expensive qPCR machines, and the result, indicated by color change, is easily interpreted by naked eyes. COVID-19-LAMP can detect SARS-CoV-2 RNA with detection limit of 42 copies/reaction. Of 223 respiratory samples positive for SARS-CoV-2 by qRT-PCR, 212 and 219 were positive by COVID-19-LAMP at 60 and 90 min (sensitivities of 95.07% and 98.21%) respectively, with the highest sensitivities among nasopharyngeal swabs (96.88% and 98.96%), compared to sputum/deep throat saliva samples (94.03% and 97.02%), and throat swab samples (93.33% and 98.33%). None of the 143 samples with other respiratory viruses were positive by COVID-19-LAMP, showing 100% specificity. Samples with higher viral load showed shorter detection time, some as early as 30 min. This inexpensive, highly sensitive and specific COVID-19-LAMP assay can be useful for rapid deployment as mobile diagnostic units to resource-limiting areas for point-of-care diagnosis, and for unlimited high-throughput mass screening at borders to reduce cross-regional transmission.