Murray Valley encephalitis

Murray Valley encephalitis (MVE) is a rare but potentially serious infection of the brain caused by the Murray Valley encephalitis virus. It is a mosquito-borne flavivirus endemic to northern Australia and Papua New Guinea.

Causes and Transmission

The MVE virus is transmitted through the bite of an infected mosquito, specifically Culex annulirostris mosquitoes. The virus is maintained in enzootic foci in the Top End, Katherine, and Barkly regions of the Northern Territory (NT) and northern Western Australia (WA).

Symptoms

The symptoms of MVE can vary from person to person but may include:

• Severe headache
• Neck stiffness
• Sensitivity to bright lights (photophobia)
• Drowsiness and confusion
• Coma
• Seizures
• Loss of consciousness

In severe cases, some individuals may experience lifelong neurological complications or even death.

Diagnosis and Reporting

Laboratories diagnosing cases of MVE must notify the local public health unit. Once confirmed, public health unit staff will collect detailed information about where the person has recently traveled and where they are likely to have been exposed to infected mosquitoes.

Geographical Distribution

Most reported cases of MVE have occurred in northern Australia or Papua New Guinea. The virus may also be present in other regions, but its distribution is limited.

References

• [1] Murray Valley encephalitis virus (MVEV) is a zoonotic flavivirus endemic to northern Australia and Papua New Guinea.
• [2] It is the causal agent of Murray Valley encephalitis (MVE; previously known as Australian encephalitis or Australian X disease).
• [3] In humans, it can cause permanent neurological disease or death. MVEV is related to Kunjin virus, which has a similar ecology, but a lower morbidity rate.
• [4] Murray Valley encephalitis (MVE) is a rare disease in humans caused by the Murray Valley encephalitis virus.
• [5] This infection has the capacity to cause acute and severe illness in humans and can be fatal.

Symptoms of Murray Valley Encephalitis

Murray Valley encephalitis (MVE) can cause a range of symptoms, from mild to severe. Here are some of the common signs and symptoms:

• Severe headache: A severe headache is one of the most common symptoms of MVE, often accompanied by neck stiffness [1].
• Neck stiffness: Neck stiffness or rigidity is another symptom that may occur in people with MVE [2].
• Sensitivity to bright lights (photophobia): People with MVE may experience sensitivity to bright lights, which can be a sign of increased intracranial pressure [3].
• Drowsiness and confusion: As the infection progresses, people with MVE may become drowsy or confused, which can progress to coma in severe cases [4].
• Seizures: Seizures are another possible symptom of MVE, especially in infants [5].
• Delirium, coma, and death: In severe cases, MVE can lead to delirium, coma, and even death [6].

Mild symptoms

Some people with MVE may experience mild symptoms, including:

• Fever: A high fever is a common symptom of MVE, often accompanied by headache and other systemic symptoms [7].
• Headache: Headache is another possible symptom of MVE, which can range from mild to severe [8].

Important note

It's essential to seek medical attention immediately if you or someone you know is experiencing any of these symptoms. There is no specific treatment available for Murray Valley encephalitis, and prompt medical attention is crucial in preventing complications and improving outcomes.

References:

[1] Context 2 [2] Context 2 [3] Context 7 [4] Context 5 [5] Context 6 [6] Context 11 [7] Context 9 [8] Context 10

Diagnostic Tests for Murray Valley Encephalitis

Murray Valley encephalitis (MVE) can be diagnosed through various tests, which are crucial in confirming the infection and ruling out other conditions. Here are some of the diagnostic tests used to detect MVE:

• Blood tests: Blood tests are the main way to confirm infection by the MVE virus. These tests look for antibodies against the virus, which appear in the blood after 4-9 days of symptoms starting [1].
• Lumbar puncture (spinal tap): A lumbar puncture can also help diagnose MVE by testing a sample of fluid from around the spinal cord [6].
• Urine tests: Urine tests may be used to detect the presence of the virus or its antibodies in the urine [13].
• Direct viral detection by NAAT (Nucleic Acid Amplification Test): This method is useful for detecting clinically relevant viruses like MVE, and can provide a diagnostic result [2].
• PCR (Polymerase Chain Reaction) analysis: PCR analysis of cerebrospinal fluid (CSF) can detect the presence of viral DNA, which helps in diagnosing MVE [5, 9].

Key Diagnostic Features

The key diagnostic features of MVE include:

• Foci of susceptibility artifact due to hemorrhage and necrosis
• Presence of virus-specific IgM antibody
• Viral isolation on permissive cell lines
• PCR analysis of CSF for viral DNA

These tests can help confirm the diagnosis of MVE, but it's essential to note that repeat testing is usually required to diagnose the infection accurately [13].

References

[1] Murray Valley encephalitis (MVE) is a viral disease spread by mosquitoes. Like other types of encephalitis, it is characterised by brain inflammation.

[2] Direct viral detection by NAAT is a useful method for detecting clinically relevant such as encephalitis.

[3] Murray Valley encephalitis virus (MVEV) is a notifiable mosquito-borne virus endemic to northern Australia during wet seasons.

[4] Diagnosis of Murray Valley encephalitis​​ Diagnosis is made by a blood test or detecting the virus in CSF (cerebrospinal fluid: the fluid surrounding the brain and spinal cord).

[5] PCR (Polymerase Chain Reaction) analysis of cerebrospinal fluid can detect the presence of viral DNA.

[6] A lumbar puncture can also help diagnose MVE by testing a sample of fluid from around the spinal cord.

[9] PCR in conjunction with serological tests can increase the sensitivity of WNV diagnostic tests to 94% compared with 45% for serological tests alone.

[13] Diagnosis of Murray Valley encephalitis. MVE can be diagnosed through testing the blood, by doing a lumbar puncture (also known as a spinal tap), and/or testing the urine.

Treatment for Murray Valley Encephalitis

Murray Valley encephalitis (MVE) is a rare and serious disease caused by a mosquito-borne virus, with no specific treatment available to cure it. However, treatment focuses on supporting the patient's body while it fights the infection.

• Supportive therapy: Treatment aims to ease symptoms and support the patient's body, as there is no effective treatment to cure MVE [1][3][9].
• No antiviral drugs: Currently, no antiviral drugs have been trialed in the treatment of humans with MVEV, and there are few in-vitro or animal-model data available [13][14].
• Supportive care in ICU: Severe cases involve supportive therapy in intensive care units, as development of an effective drug targeting the MVEV serine protease is still being researched [14].

It's essential to note that some people who recover from MVE may experience ongoing problems such as deafness or epilepsy. There is no specific treatment for Murray Valley encephalitis.

References:

[1] Context 1 [3] Context 3 [9] Context 9 [13] Context 13 [14] Context 14

Differential Diagnosis of Murray Valley Encephalitis

Murray Valley encephalitis (MVE) is a serious viral disease caused by the Murray Valley encephalitis virus, which is spread by infected mosquitoes. When diagnosing MVE, it's essential to consider other possible causes of similar symptoms. The differential diagnosis for MVE includes:

• Toxic leukoencephalopathy: A condition characterized by damage to cerebral white matter, often caused by exposure to toxic substances.
• Eastern equine encephalitis: A rare and dangerous virus spread by mosquitoes in the eastern and Gulf Coast regions of the United States.
• Japanese encephalitis: A mosquito-borne flavivirus that is closely related to MVEV and can cause similar symptoms.
• Herpes Simplex Virus (HSV): A viral infection that can cause encephalitis, particularly in individuals with weakened immune systems.
• Varicella-zoster virus (VZV): The same virus responsible for chickenpox and shingles, which can also cause encephalitis in rare cases.
• Enteroviruses: A group of viruses that can cause a range of symptoms, including encephalitis.

Clinical Features to Consider

When considering the differential diagnosis for MVE, clinicians should look out for the following clinical features:

• Altered mental state
• Seizures
• Tremor
• Weakness or paralysis

These symptoms are often present in patients with MVE and can also be seen in individuals with other viral encephalitides.

Laboratory Tests

To confirm a diagnosis of MVE, laboratory tests such as:

• Blood tests to detect the presence of MVEV antibodies
• Cerebrospinal fluid (CSF) analysis to detect the virus or other pathogens

are essential. However, these tests may not always be conclusive, and a combination of clinical features and laboratory results is often necessary for an accurate diagnosis.

References:

[1] Murray Valley encephalitis virus (MVEV) is a mosquito-borne virus that is found across Australia, Papua New Guinea and Irian Jaya. ... It remains difficult to establish an early diagnosis of MVEV infection, and there is a lack of proven therapeutic options. ... Enterovirus PCR (differential diagnosis for meningoencephalitis) During [2]

[3] The differential diagnosis for travel-associated encephalitis should include MVEV, particularly during outbreak years. Keywords: Murray Valley encephalitis virus, viruses, Murray Valley [4]

[5] Differential diagnoses include other viral encephalitides (e.g., eastern equine encephalitis). [6]

[7] A review of the laboratory-confirmed cases of Murray Valley encephalitis (MVE) from Western Australia between 2009 and 2011 was conducted to describe the clinical, laboratory, and radiological features of the disease. The nine encephalitis patients presented with altered mental state and seizures, tremor, weakness, or paralysis. [8]

[9] Murray Valley encephalitis (MVE) is caused by infection with a flavivirus belonging to the Japanese encephalitis (JE) antigenic complex, which also includes ... Eastern equine encephalitis. [10]

[11] The differential diagnosis of Murray Valley encephalitis includes: Toxic leukoencephalopathy, which is characterized by confluent and symmetrical white matter abnormalities involving the corpus callosum and splenium on MRI findings. [12]

[13] The Japanese encephalitis virus (JEV) serocomplex, which also includes Murray Valley encephalitis virus (MVEV), is a group of antigenically closely related, mosquito-borne flaviviruses that are ... Eastern equine encephalitis. [14]

[15] A review of the laboratory-confirmed cases of Murray Valley encephalitis (MVE) from Western Australia between 2009 and 2011 was conducted to describe the clinical, laboratory, and radiological features of the disease. The nine encephalitis patients presented with altered mental state and seizures, tremor, weakness, or paralysis. [16]