Rapid detection of equine infectious anaemia virus nucleic acid by insulated isothermal RT-PCR assay to aid diagnosis under field conditions

Development and evaluation of a test strip for the rapid detection of antibody against equine infectious anemia virus

Equine infectious anemia (EIA) is a contagious disease of horses caused by the equine infectious anemia virus (EIAV). The clinical signs at the acute phase include intermittent high fever, thrombocytopenia, hemorrhage, edema, and anemia. The clinical signs at chronic and relapsing subclinical levels include emaciation and progressive weakness. Surviving horses become lifelong carriers because of the integration of the viral genome into that of the host, and these horses can produce and transmit the virus to other animals. This increases the difficulty of imposing practical control measures to prevent epidemics of this disease. Serological tests measuring the antibodies in equine sera are considered to be a reliable tool for the long-term monitoring of EIA. However, the standard serological tests for EIV either have low sensitivity (e.g., agar gel immunodiffusion test, AGID) or are time consuming to perform (e.g., ELISA and western blotting). The development of a rapid and simple method for detecting the disease is therefore critical to control the spread of EIA. In this study, we designed and developed a colloidal gold immunochromatographic (GICG) test strip to detect antibodies against EIAV based on the double-antigen sandwich. Both the p26 and gp45 proteins were used as the capture antigens, which may help to improve the positive detection rate of the strip. We found that the sensitivity of the test strip was 8 to 16 times higher than those of two commercially available ELISA tests and 128 to 256 times higher than AGID, but 8 to 16 times lower than that of western blotting. The strip has good specificity and stability. When serum samples from experimental horses immunized with the attenuated EIAV vaccine (n = 31) were tested, the results of the test strip showed 100% coincidence with those from NECVB-cELISA and 70.97% with AGID. When testing clinical serum samples (n = 1014), the test strip surprisingly provided greater sensitivity and a higher number of "true positive" results than other techniques. Therefore, we believe that the GICG test strip has demonstrated great potential in the field trials as a simple and effective tool for the detection of antibodies against EIAV. KEY POINTS: • A colloidal gold immunochromatographic (GICG) fast test strip was developed with good specificity, sensitivity, stability, and repeatability • The test strip can be used in point-of-care testing for the primary screening of EIAV antibodies • Both the p26 and gp45 proteins were used as the capture antigens, giving a high positive detection rate in the testing of experimentally infected animal and field samples.

Development and evaluation of a real-time quantitative PCR for the detection of equine infectious anemia virus

IMPORTANCE

Equine infectious anemia (EIA) has a worldwide distribution and causes significant losses to the equine industry worldwide. A reliable detection method is necessary to control the transmission of EIA virus (EIAV). Currently, most of the available real-time PCR assays, including the qPCR of recommended by WOAH, are developed according to the sequences of European or American EIAV strains; however, the primers and probe sequences have low homology with Asian EIAV strains. To the best of our knowledge, no qPCR method capable of the well detection of Asian EIAV strains, especially Chinese EIAV strains, has been published to date. The development of a sensitive, specific, and rapid qPCR assay for the detection of the EIAV strains is therefore of great importance.

Rapid detection methods and modelling simulations provide new insights into cyanobacteria detection and bloom management in a tropical reservoir

The increasing occurrence of cyanobacteria blooms is of global concern, and is often associated with environmental and socio-economic problems, such as degenerated ecosystems and aquaculture impairment. The diazotrophic cyanobacterium Raphidiopsis raciborskii (R. raciborskii) grows rapidly in the tropics, and produces the toxin, cylindrospermopsin (CYN), which has harmful effects on aquatic organisms. Thus, to protect water quality and ecosystem, it is essential to have rapid and reliable methods for cyanobacteria and R. raciborskii detection and prediction so that early warning can be provided for management. Molecular assays, such as PCR, real-time quantitative PCR (qPCR), two-step PCR assays are accurate and widely used, but still require several hours from sample preparation to data analysis. In this study, insulated isothermal PCR (iiPCR) assays in conjunction with fast DNA extraction method, were developed and verified as a rapid detection assay in detecting cyanobacteria and R. raciborskii within 50 min, and also with high detection accuracy (98.8%) and the overall high agreement level (98.8%, k = 97.5%)) comparing to conventional qPCR assay. However, the limitation of the iiPCR assay is that it only generates qualitative results. Therefore, the quantified iiPCR assay, named as A-iiPCR, by coupling iiPCR device with fluorescence signal catching and interpretation instrument (Andor spectrometer with Solis spectroscopy software) was developed and verified with in situ environmental samples. The fluorescence intensity decreased accordingly with the drop of DNA concentration until reaching 1.32 ng/μL. Also, Delft 3D modelling was established to simulate R. raciborskii change in predicting spatial and temporal variabilities for reservoir management, as the simulated R. raciborskii concentration was the highest at sampling site 1, as well as temporally highest in April and October, posing as the most high-risk location and time periods for R. raciborskii bloom-forming requiring corresponding governance measures.

Isothermal Nucleic Acid Amplification Technologies for the Detection of Equine Viral Pathogens

Simple Summary

Equine viral diseases remain a prominent concern for human and equine health globally. Many of these viruses are of primary biosecurity concern to countries that import equines where these viruses are not present. In addition, several equine viruses are zoonotic, which can have a significant impact on human health. Current diagnostic techniques are both time consuming and laboratory-based. The ability to accurately detect diseases will lead to better management, treatment strategies, and health outcomes. This review outlines the current modern isothermal techniques for diagnostics, such as loop-mediated isothermal amplification and insulated isothermal polymerase chain reaction, and their application as point-of-care diagnostics for the equine industry.

Abstract

The global equine industry provides significant economic contributions worldwide, producing approximately USD $300 billion annually. However, with the continuous national and international movement and importation of horses, there is an ongoing threat of a viral outbreak causing large epidemics and subsequent significant economic losses. Additionally, horses serve as a host for several zoonotic diseases that could cause significant human health problems. The ability to rapidly diagnose equine viral diseases early could lead to better management, treatment, and biosecurity strategies. Current serological and molecular methods cannot be field-deployable and are not suitable for resource-poor laboratories due to the requirement of expensive equipment and trained personnel. Recently, isothermal nucleic acid amplification technologies, such as loop-mediated isothermal amplification (LAMP) and insulated isothermal polymerase chain reaction (iiPCR), have been developed to be utilized in-field, and provide rapid results within an hour. We will review current isothermal diagnostic techniques available to diagnose equine viruses of biosecurity and zoonotic concern and provide insight into their potential for in-field deployment.

Molecular detection of equine infectious anemia virus in clinically normal, seronegative horses in an endemic area of Mexico

Equine infectious anemia (EIA) is a highly infectious disease in members of the Equidae family, caused by equine infectious anemia virus (EIAV). The disease severity ranges from subclinical to acute or chronic, and causes significant economic losses in the equine industry worldwide. Serologic tests for detection of EIAV infection have some concerns given the prolonged seroconversion time. Therefore, molecular methods are needed to improve surveillance programs for this disease. We attempted detection of EIAV in 6 clinical and 42 non-clinical horses in Nuevo Leon State, Mexico, using the agar gel immunodiffusion (AGID) test for antibody detection, and nested and hemi-nested PCR for detection of proviral DNA. We found that 6 of 6, 5 of 6, and 6 of 6 clinical horses were positive by AGID, nested PCR, and hemi-nested PCR, respectively, whereas 0 of 42, 1 of 42, and 9 of 42 non-clinical horses were positive by these tests, respectively. BLAST analysis of the 203-bp 5'-LTR/tat segment of PCR product revealed 83-93% identity with EIAV isolates in GenBank and reference strains from other countries. By phylogenetic analysis, our Mexican samples were grouped in a different clade than other sequences reported worldwide, indicating that the LRT/tat region represents an important target for the detection of non-clinical horses.

Viral Diseases that Affect Donkeys and Mules

Simple Summary

Donkeys have been neglected and threatened by abandonment, indiscriminate slaughter, and a lack of proper sanitary management. They are often treated as “small horses.” However, donkeys and horses have significant genetic, physiological, and behavioral differences. Specific knowledge about viral infectious diseases that affect donkeys and mules is important to mitigate disease outbreaks. Thus, the purpose of this review is to provide a brief update on viral diseases of donkeys and mules and ways to prevent their spread.

Abstract

Donkeys (Equus asinus) and mules represent approximately 50% of the entire domestic equine herd in the world and play an essential role in the lives of thousands of people, primarily in developing countries. Despite their importance, donkeys are currently a neglected and threatened species due to abandonment, indiscriminate slaughter, and a lack of proper sanitary management. Specific knowledge about infectious viral diseases that affect this group of Equidae is still limited. In many cases, donkeys and mules are treated like horses, with the physiological differences between these species usually not taken into account. Most infectious diseases that affect the Equidae family are exclusive to the family, and they have a tremendous economic impact on the equine industry. However, some viruses may cross the species barrier and affect humans, representing an imminent risk to public health. Nevertheless, even with such importance, most studies are conducted on horses (Equus caballus), and there is little comparative information on infection in donkeys and mules. Therefore, the objective of this article is to provide a brief update on viruses that affect donkeys and mules, thereby compromising their performance and well-being. These diseases may put them at risk of extinction in some parts of the world due to neglect and the precarious conditions they live in and may ultimately endanger other species’ health and humans.