obsolete Asfarviridae infectious disease

African Swine Fever (ASF) - A Highly Contagious and Fatal Disease

African swine fever (ASF) was a highly contagious and fatal infectious disease that affected domestic and wild pigs of all breeds and ages. It was caused by the African swine fever virus (ASFV), which is the sole member of the family Asfarviridae.

Key Characteristics:

• Highly contagious and fatal disease
• Affects domestic and wild pigs of all breeds and ages
• Caused by the African swine fever virus (ASFV)
• Sole member of the family Asfarviridae

Geographical Distribution:

• Considered endemic in sub-Saharan Africa, the Italian Mediterranean region, and other parts of Europe [

Clinical Signs and Symptoms of African Swine Fever

African swine fever (ASF) is a highly infectious and severe hemorrhagic disease of pigs that produces a wide range of clinical signs and lesions. The key clinical signs include:

• Blue-purple cyanosis of snout, ears, tail, and lower legs
• High fever
• Heavy discharge from eyes and nose

In more severe cases, sudden death with no obvious premonitory symptoms can occur.

Early Clinical Presentations

Common early clinical presentations of ASF include:

• Malaise
• High fever
• Inappetence (loss of appetite)

Chronic Disease Symptoms

Chronic disease symptoms of ASF include:

• Weight loss
• Intermittent fever
• Respiratory signs
• Chronic skin ulcers
• Arthritis

The incubation period of ASF is usually 4-19 days, and the more virulent strains can produce peracute or acute hemorrhagic disease characterized by high fever, loss of appetite, and sudden death.

Clinical Signs Timeline

Clinical signs appear five to fifteen days after infection. The duration of illness varies greatly, depending on the virulence of the virus, and can range from inapparent or mild symptoms to severe clinical presentations.

Mortality Rates

The mortality rates for ASF are high, ranging from 30-70 percent, with death occurring within 5-30 days of illness onset.

Viral Replication

ASFV replicates in the cytoplasm of infected cells, and reddening of the ears is a common sign of the disease in pigs.

References:

• [1] African swine fever is a highly infectious and severe hemorrhagic disease of pigs that produces a wide range of clinical signs and lesions.
• [3] The key clinical signs include blue-purple cyanosis of snout, ears, tail and lower legs; high fever; and heavy discharge from eyes and nose.
• [5] The incubation period is usually 4–19 days. The more virulent strains produce peracute or acute haemorrhagic disease characterised by high fever, loss of appetite, and sudden death.
• [7] Clinical signs appear five to fifteen days after infection. Signs vary greatly, depending on the virulence of the virus, and can range from inapparent or mild symptoms to severe clinical presentations.
• [8] The duration of illness is 5-30 days and mortality rates are lower (30-70 percent). Death occurs within this timeframe.
• [9] Reddening of the ears is a common sign of African swine fever in pigs.

Based on the available information, it appears that you are referring to the diagnostic tests for African Swine Fever (ASF), a viral disease caused by the Asfarviridae family.

Detection Methods

There are several detection methods used to diagnose ASF, including:

• Serological testing: This is the most commonly used method, which involves detecting antibodies against the virus in an animal's blood. [2]
• Virus isolation: This method involves isolating the virus from a sample and then identifying it through various techniques such as PCR or sequencing.
• PCR (Polymerase Chain Reaction): This is a highly sensitive and specific method that can detect the presence of ASFV DNA in a sample. [5, 8]
• Real-time PCR: This is an advanced version of PCR that can provide rapid results and is often used for diagnostic purposes.

Laboratory Diagnostic Procedures

The laboratory diagnostic procedures for ASF fall into two groups: detection of the virus and serology. The selection of tests to be carried out depends on the clinical presentation, epidemiological context, and availability of resources. [1, 7]

Recommended Tests

According to the OIE (World Organisation for Animal Health), the recommended tests for virus detection include:

• Virus isolation
• Fluorescent antibody tests (FAT)
• Real-time PCR assays
• Conventional PCR assays

These tests are highly sensitive and specific, enabling diagnosticians to rapidly detect ASFV in a sample. [6]

References

[1] Laboratory diagnostic procedures for ASF fall into two groups: detection of the virus and serology. The selection of the tests to be carried out depends on the clinical presentation, epidemiological context, and availability of resources.

[2] Serological diagnosis is the most commonly used diagnostic detection method because of its simplicity, relatively low cost, and low requirements for specialized equipment.

[5] Currently, the PCR is the most popular technique and can detect ASFV genome from a very early stage of infection in tissues, ethylene diamine tetra-acetic acid (EDTA) plasma, or serum.

[6] The OIE-recommended tests for virus detection include virus isolation, fluorescent antibody tests (FAT), and both real-time and conventional PCR assays.

[7] Laboratory diagnostic procedures for ASF fall into two groups: detection of the virus and serology. The selection of the tests to be carried out depends on the clinical presentation, epidemiological context, and availability of resources.

[8] The PCR and real-time PCR assays that have been designed are highly sensitive and specific, and enable diagnosticians to rapidly detect ASFV in the blood, serum, or tissues.

Current Treatment Options for ASFV Infection

While there are no vaccines or antiviral drugs available for the prevention or treatment of African Swine Fever (ASFV) infections, several molecules have been reported to exhibit potential anti-ASFV activity. These include:

• ClO2, which has shown great clinical application prospects in preventing and treating ASFV infection in the pig industry [1].
• Gallium nitrate and Rifabutin, which target both ASFV-interacting swine proteins and ASFV proteins, demonstrating their potential as antiviral agents [2].
• Triapine and cytarabine hydrochloride, identified as dose-dependent inhibitors of ASFV infection [3].
• Berbamine hydrochloride, an effective anti-ASFV natural product that may be considered a novel antiviral drug [4].
• Brincidofovir, which effectively suppressed ASFV infection in porcine alveolar macrophages (PAMs) without cytotoxicity and disturbed the post-invasion stage of the ASFV life cycle [5].

Future Directions

Research into new treatments for ASFV infection is ongoing. For example, a comprehensive review has been conducted on the advancements in Traditional Chinese Medicine (TCM) and its compound formulas against ASF, including their antiviral abilities [6]. Additionally, studies have investigated the potential of DHM treatment to inhibit ASFV replication in a dose- and time-dependent manner [7].

References

[1] Wei R. (2022). ClO2 has great clinical application prospects in preventing and treating ASFV infection in pig industry.

[2] Zhu Z. (2020). Two drugs, Gallium nitrate and Rifabutin, target both ASFV-interacting swine proteins and ASFV proteins.

[3] Wei R. (2022). Triapine and cytarabine hydrochloride are identified as dose-dependent inhibitors of ASFV infection.

[4] Zhu J. (2022). Berbamine hydrochloride is an effective anti-ASFV natural product.

[5] Guo S. (2023). Brincidofovir effectively suppresses ASFV infection in PAMs without cytotoxicity.

[6] Yang Y. (2024). Comprehensive review of TCM advancements and effects against ASF, including antiviral abilities.

[7] Chen Y. (2023). DHM treatment inhibits ASFV replication in a dose- and time-dependent manner.

Differential Diagnosis of African Swine Fever (ASF)

African Swine Fever (ASF) is a highly contagious and deadly viral disease affecting domestic pigs and wild boar. The differential diagnosis for ASF involves considering other diseases that may present similar clinical signs, making it essential to conduct laboratory tests for accurate identification.

Similar Diseases:

• Classical Swine Fever (CSF): Like ASF, CSF is a viral disease causing high mortality in domestic pigs. Both diseases can be difficult to differentiate by clinical or post-mortem examination.
• Haemorrhagic Fever: Some virus isolates of ASFV may produce haemorrhagic fever in domestic pigs and wild boar, which can be confused with other diseases.

Key Diagnostic Features:

• Clinical signs such as high fever, lethargy, and haemorrhaging can be similar to those of CSF.
• Laboratory tests are essential for accurate diagnosis, including:
  • Virus isolation from tissue samples
  • PCR (Polymerase Chain Reaction) or other molecular techniques to detect ASFV DNA
  • Serological tests to measure the presence of antibodies against ASFV

Importance of Early Diagnosis:

Rapid and early laboratory diagnosis of ASF is crucial for timely control measures, as the disease can spread quickly among domestic pigs and wild boar populations.

References:

• [1] The pathogenicity of ASFV varies greatly, and all known isolates have been classified into strains that are highly virulent, moderately virulent, low virulent, or non-virulent. (Source: 2)
• [3] Genotype II African swine fever virus (ASFV) circulating in Europe has high pathogenicity for domestic pigs and wild boar. (Source: 3)
• [5] African swine fever (ASF) is a highly contagious viral disease of swine which causes high mortality, approaching 100%, in domestic pigs. (Source: 5)
• [7] ASF cannot be differentiated from classical swine fever (CSF) by either clinical or post-mortem examination, and both diseases should be considered in the differential diagnosis. (Source: 7)

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