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Nipah virus is a new type of zoonotic virus. It is an RNA virus belonging to the Paramyxoviridae family. It can cause widespread vasculitis. Infected people have symptoms such as fever, severe headache, meningitis, etc., which bring serious harm to humans and animals. Nipah virus disease (NVD) is another zoonosis that has attracted widespread attention and panic from countries around the world after mad cow disease in the UK, foot-and-mouth disease in pigs in Taiwan Province, and avian influenza in Hong Kong. From the perspective of public health, this disease should be highly valued by domestic medical and animal husbandry veterinary professionals.
Physical and Chemical Characteristics: Nipah virus is polymorphic through negative staining technique. The virus particle size is 120-500nm. It is composed of envelope and filamentous nucleocapsid. The envelope contains two transmembrane proteins: cell receptor binding protein, and a separate fusion protein. The virus is quite unstable in vitro and has low resistance to heat and disinfectants. It is destroyed by heating at 56℃ for 30 minutes. It is easily inactivated by detergents such general disinfectants.
Molecular Biological Characteristics: The Malaysian isolates from laryngeal secretions and cerebrospinal fluid have been sequenced. The genome is 18246bp long. The genome structure is shown in Figure 1. It has 12 more nucleotides than Hendra virus (HV), and the nucleotide consistency between the two is 70% to 78%. This similarity fully demonstrates that the two are closely related, but different viruses.
The use of immunohistochemistry to study the pathogenicity and infectiousness of this disease found that
the virus is tropistic for vascular endothelial cells, causing edema, interstitial pneumonia (pulmonary edema), meningitis, glomerular atrophy and placental infection. As the course of the disease prolongs, endothelial cells develop into multinucleated giant cells, and the clinical manifestations are acute respiratory diseases and obvious neurological diseases. The virus is tropistic for the interstitial and outer membranes, causing vascular diseases, but there are no obvious clinical features. The virus is tropistic for neurons, and the viral nucleocapsid is concentrated in glial cells, cerebral cortex, brainstem, and extends to the parenchymal tissue, showing diffuse vasculitis, accompanied by sparse necrosis in large areas, thus causing serious neurological diseases. Extensive vasculitis manifestations, most of the endothelial damage runs through the cerebral cortex and subcutaneous tissue, and the virus replicates actively in the cerebrospinal fluid. These three factors are associated with increased mortality.
Figure 3. Epidemiology of the Nipah virus.( Deka, M. A, et al., 2018)
The clinical symptoms of this disease are: fever, severe headache, myalgia, and meningitis. The incubation period of pigs infected with this disease is about 7 to 14 days. The clinical symptoms of pigs of different ages are different. Generally, it manifests as neurological symptoms and respiratory symptoms, with high morbidity and low mortality. Weaned piglets and meat pigs have high fever, dyspnea accompanied by mild or severe cough, coarse breath sounds, and severe cases can see hemoptysis. Pregnant sows have more obvious symptoms, pneumonia, purulent secretions, and even miscarriage. At the same time, they die due to severe dyspnea, local muscle spasms, and paralysis.
After human infection, the incubation period is about 1 to 3 weeks. Neck and abdominal spasms are symptoms with diagnostic significance that distinguish them from other encephalitis viruses. Fever and headache begin, followed by drowsiness and disorientation. After 24 to 48 hours, it can further develop into a coma. One-third of patients will die in a coma, and patients who survive the coma will have permanent brain damage. A few patients have respiratory symptoms, and some patients are accompanied by hypertension and tachycardia.
The virus multiplies in the tonsils, respiratory epithelial tissues and infected respiratory cell fragments of pigs, and is more likely to be transmitted through throat and tracheal secretions. There are also reports that encephalitis and pulmonary edema limit the spread of the virus, and the excretion route may be through the urinary system or contact with virus-infected body fluids.
Transmission within the same pig farm may also be caused by direct contact with the urine of sick pigs. Body fluids, tracheal secretions, etc., in addition, it may also be transmitted by using the same needle and artificial insemination equipment. Pigs play a key role in the way Nipah virus infects humans. Patients are mainly infected through contact with wounds and secretions, excretions and exhaled gases of infected pigs.
To improve knowledge about Nipah virus pathology and treatment researchers developed multiple animal models including Syrian hamsters, African green monkeys, pigs and guinea pigs. Scientists use animal models to replicate human Nipah virus pathology including respiratory diseases and encephalitis. African green monkey models were utilized in a study to assess Ribavirin's antiviral effects which demonstrated its potential to prevent fatal Nipah virus infections. Research demonstrated that the monoclonal antibody m102.4 provides effective disease protection for hamsters infected with Nipah virus[1].
Virus isolation is the most important and basic diagnostic method. For a new case, virus isolation is the most ideal. Further identification of virus isolates requires strict quality control experiments such as electron microscopy or immunoelectron microscopy, specific antiserum neutralization test, and PCR.
| Diagnostic method | Description |
| Indirect ELISA Method | The main problem is specificity. The purification loss of viral antigens is large. Genetically engineered antigens have been developed. Recombinant G and M protein antigens synthesized by baculovirus expression system have been used in experiments, but have not been used for daily diagnosis. The success of this technology can not only solve the problem of antigen dosage, but also solve the problem of quality specificity. Although the specificity of ELISA is greater than 95%, there is also a false positive problem. Despite this, ELISA can still be used as a very effective screening tool for daily monitoring. |
| PCR technology | Although it has been developed for a short time, this technology has a very wide range of applications. Any gene segment can be tested by PCR technology. The Nipah virus N gene region is highly conserved. Primers are designed in this region and RNA is detected using RT-PCR technology, which is not easy to miss. This method is highly sensitive and can detect RNA viruses before the body produces immune antibodies or when they are very small, so problems can be discovered early and prevented before they occur. |
| Immunohistochemistry | Anti-rabbit and anti-mouse polydextran linked alkaline phosphatase replaces the biotin-avidin peroxidase detection system, which is economical and convenient. |
| Immunoelectron Microscopy Technology | Although cumbersome, it is the most suitable for studying pathogenic mechanisms and pathological changes. |
| Serum Neutralization Test | It has been reported that serum may cause cytotoxicity, but the quality requirements for serum are low, and it is a reliable experimental method. |
Extensive mosquito control and clearing of stagnant water to eliminate mosquito breeding grounds are also important measures to prevent the spread of pathogens. Pay attention to daily management and regularly quarantine and monitor pigs. Prevention is better than cure to reduce harm to humans and animals.
Healthcare professionals diagnose Nipah virus infection through a combination of patient's epidemiological background and clinical presentation together with laboratory testing outcomes. Since there is no effective treatment for Nipah virus medical care remains focused on supportive measures which consist of rehydration along with antipyretic use sedation and mechanical ventilation. Research is ongoing to determine the effectiveness of antiviral drugs like ribavirin and monoclonal antibody m102.4 to treat Nipah virus infection. Research is actively ongoing for vaccines development which includes both recombinant parainfluenza virus vectors and rabies-based vaccines.
Nipah virus is a zoonotic virus that causes human and animal diseases. There is no specific treatment. Nipah virus can be effectively controlled by developing measures in the field of public health, developing a vaccine and drug. There are also other issues need to be solved in the research on Nipah virus, such as the mechanisms of the pathogenicity of Nipah virus and the establishment of measures in public health for the prevention and control of Nipah virus.
References
| Cat. No. | Product Name | Size | Target | Species | |
| DAG-P2865 | PIV type 3 Nucleocapsid (aa 0-0) | / | PIV | Inquiry | |
| DAG-WT381 | Recombinant Nipah Virus (NiV) VLP | 1 mg | Nipah Virus | / | Inquiry |
| DAGA-1004 | Recombinant Nipah Virus G Protein | 1 mg | / | / | Inquiry |
| DAG-WT633 | Recombinant Nipah Virus F Protein [His] | 50 g, 500 g | Nipah Virus | / | Inquiry |
| DAG-WT634 | Recombinant Nipah Virus G Protein [His] | 50 g, 500 g | Nipah Virus | / | Inquiry |
| DAG-WT1059 | Recombinant Nipah Virus Glycoprotein G | 1 mg | Nipah virus G protein | / | Inquiry |
| DAG-WT271 | Recombinant Nipah Virus G Protein [Fc] | 100 g | Glycoprotein G | / | Inquiry |
| DAG-WT272 | Recombinant Nipah Virus F Protein [Fc] | 100 g | Glycoprotein F | / | Inquiry |
| DAG-WT273 | Recombinant Nipah Virus Nucleoprotein [His] | 100 g | Nucleoprotein | / | Inquiry |
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