Equine infectious anemia virus in China

Key Factors and Parameter Ranges for Immune Control of Equine Infectious Anemia Virus Infection

Equine Infectious Anemia Virus (EIAV) is an important infection in equids, and its similarity to HIV creates hope for a potential vaccine. We analyze a within-host model of EIAV infection with antibody and cytotoxic T lymphocyte (CTL) responses. In this model, the stability of the biologically relevant endemic equilibrium, characterized by the coexistence of long-term antibody and CTL levels, relies upon a balance between CTL and antibody growth rates, which is needed to ensure persistent CTL levels. We determine the model parameter ranges at which CTL and antibody proliferation rates are simultaneously most influential in leading the system towards coexistence and can be used to derive a mathematical relationship between CTL and antibody production rates to explore the bifurcation curve that leads to coexistence. We employ Latin hypercube sampling and least squares to find the parameter ranges that equally divide the endemic and boundary equilibria. We then examine this relationship numerically via a local sensitivity analysis of the parameters. Our analysis is consistent with previous results showing that an intervention (such as a vaccine) intended to control a persistent viral infection with both immune responses should moderate the antibody response to allow for stimulation of the CTL response. Finally, we show that the CTL production rate can entirely determine the long-term outcome, regardless of the effect of other parameters, and we provide the conditions for this result in terms of the identified ranges for all model parameters.

Exploring the determinants of influenza A/H7N9 control intervention efficacy in China: disentangling the effect of the "1110" policy and poultry vaccination

: The influenza A virus of the H7N9 subtype (FLUAV H7N9) emerged in Eastern China provinces in 2013 causing illness in both poultry and humans. Most reported FLUAV H7N9 human cases were related to those associated with the live poultry market chain. From 2013 to 2017, there were five epidemic waves of human infections, and from the end of 2016, the number of human cases increased sharply. To control FLUAV H7N9 in the market chain, the so-called "1110" policy at live poultry markets and a national vaccination programme were implemented. The relative efficacy of these two measures on the number of poultry and human infections has not been quantified and compared. To explore their efficacy, a cross-sectional study was conducted in six provinces of China, and the vaccination and surveillance data of H7N9 were analysed. Our survey data showed that poultry vendors were not widely aware of and did not accept the "1110" policy. For subjective and objective factors, some measures of the "1110" policy were not implemented in live bird markets (LBMs). However, the national vaccination programme achieved good immune effects and sharply decreased poultry FLUAV H7N9 infections. The detection rates of FLUAV H7N9 in LBMs and farms gradually decreased since the vaccination programme was implemented. Our analysis also indicated that human infections were closely related to poultry virus carriage rates; therefore, controlling FLUAV H7N9 circulation in poultry was an effective measure to control FLUAV H7N9 infections in humans. Although LBMs play a significant role in human infections, the management measures may not be implemented efficiently; hence, we need to conduct more investigations before developing related policies. This article is protected by copyright. All rights reserved.

Modelling Mutation in Equine Infectious Anemia Virus Infection Suggests a Path to Viral Clearance with Repeated Vaccination

Equine infectious anemia virus (EIAV) is a lentivirus similar to HIV that infects horses. Clinical and experimental studies demonstrating immune control of EIAV infection hold promise for efforts to produce an HIV vaccine. Antibody infusions have been shown to block both wild-type and mutant virus infection, but the mutant sometimes escapes. Using these data, we develop a mathematical model that describes the interactions between antibodies and both wild-type and mutant virus populations, in the context of continual virus mutation. The aim of this work is to determine whether repeated vaccinations through antibody infusions can reduce both the wild-type and mutant strains of the virus below one viral particle, and if so, to examine the vaccination period and number of infusions that ensure eradication. The antibody infusions are modelled using impulsive differential equations, a technique that offers insight into repeated vaccination by approximating the time-to-peak by an instantaneous change. We use impulsive theory to determine the maximal vaccination intervals that would be required to reduce the wild-type and mutant virus levels below one particle per horse. We show that seven boosts of the antibody vaccine are sufficient to eradicate both the wild-type and the mutant strains. In the case of a mutant virus infection that is given infusions of antibodies targeting wild-type virus (i.e., simulation of a heterologous infection), seven infusions were likewise sufficient to eradicate infection, based upon the data set. However, if the period between infusions was sufficiently increased, both the wild-type and mutant virus would eventually persist in the form of a periodic orbit. These results suggest a route forward to design antibody-based vaccine strategies to control viruses subject to mutant escape.

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.

On the irrationality of rational design of an HIV vaccine in light of protein intrinsic disorder

The lack of progress in finding an efficient vaccine for a human immunodeficiency virus (HIV) is daunting. In fact, this search has spanned nearly four decades without much success. There are several objective reasons for such a failure, which include the highly glycosylated nature of HIV-1, the presence of neotopes, and high mutation rates. This article argues that the presence of highly flexible and intrinsically disordered regions in both human anti-HIV-1 antibodies and the major HIV-1immunogen, its surface glycoprotein gp120, represent one of the major causes for the lack of success in utilization of structure-based reverse vaccinology.

Shell disorder and the HIV vaccine mystery: lessons from the legendary Oswald Avery

The search for a human immunodeficiency virus (HIV) vaccine has spanned nearly four decades without much success. A much needed paradigm shift can be found in the abnormally high levels of intrinsic disorder in the outer shells of HIVs, the hepatitis C virus (HCV), and herpes simplex viruses (HSVs), for which successful vaccines have not been established. On the other hand, this feature (high levels of intrinsic disorder in the outer shells) is completely absent in classic viruses for which effective vaccines are found, such as the rabies virus. The motions arising from the disordered outer shell result in the inability of antibodies to bind tightly to the polysaccharides on the viral surface proteins, and, therefore, induce inadequate immune response. Experiments conducted by the legendary Avery Oswald in the 1920s form the theoretical underpinning of this new model. Failures of the vaccines based on the HIV glycoprotein Gp120 and other vaccines can be traced back to the lack of understanding of the important roles of shell disorder in a "Trojan-horse" immune evasion mechanism utilized by the virus.Communicated by Ramaswamy H. Sarma.

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.

Surveillance of the equine infectious anemia virus in Eastern and Central Saudi Arabia during 2014-2016

Background

Equine infectious anemia virus (EIAV) is one of the most important threats to the equine industry globally. This is due to the poor performance of the affected horses, which requires euthanization of the infected animals upon the infection confirmation. Infected animals remain carriers throughout their life. EIAV infection has been reported in many parts of the world, including North America, Europe, Asia, and Africa. However, the EIAV status is never assessed in horses in the Gulf area, especially in the Kingdom of Saudi Arabia (KSA).

Aim

This study aimed to perform molecular and serological surveillance among some horse populations in Eastern and Central Saudi Arabia.

Materials and Methods

Sera and whole blood were collected from 361 horses and 19 donkeys from the eastern and central regions of Saudi Arabia during January 2014-December 2016. Sera were tested by the commercial EIAV enzyme-linked immunosorbent assay kits. Moreover, the collected blood samples were tested by the commercial real-time polymerase chain reaction kits.

Results

Our serological surveillance revealed the absence of any antibodies against EIAV in the tested animals. Similar results were reported for the tested horses' plasma. This study confirms the absence of EIAV in horses and donkeys from Eastern and Central Saudi Arabia during the tenure of the current study. However, careful monitoring of the EIAV is highly recommended to avoid the emergence of such a virus in the horse population in Saudi Arabia.

Conclusion

To the best of our knowledge, this is the first EIAV surveillance conducted not only in Saudi Arabia but also in the Gulf area. This study confirms the absence of EIAV in the tested equine population in the eastern and central regions of Saudi Arabia during 2014-2016.