Rabies and West Nile Virus Quiz

Viral Pathogens of the CNS/Encephalitis

• This presentation covers viral pathogens causing central nervous system (CNS) infections, specifically meningitis and encephalitis.
• Meningitis is inflammation of the meninges (membranes surrounding the brain and spinal cord).
• Encephalitis is inflammation of the brain parenchyma (the actual brain tissue).
• Meningoencephalitis is a condition where both the meninges and the brain parenchyma are inflamed.
• Viral meningitis is more common than bacterial meningitis.
• Viral encephalitis is variable, ranging from benign to deadly, impacting morbidity and mortality depending on the pathogen and host interaction.

Learning Outcomes

• Differentiate between meningitis and encephalitis
• Understand the causes, routes of infection, clinical presentation, diagnosis, and management of viral meningitis (mostly enteroviruses).
• Learn about viral encephalitis: HSV, WNV, Tick-borne encephalitis, Japanese encephalitis, Polio, and Rabies
• Discuss other important viruses (polio, Zika, measles, JC, HIV) causing CNS manifestations.
• Understand the aetiology of Transmissible Spongiform Encephalopathy (TSE).
• Contrast sporadic and variant CJD, and outline CJD prevention strategies.

Difference Between Meningitis & Encephalitis

• Meningitis: Inflammation of the meninges. Symptoms often include fever, stiff neck, headache, etc
• Encephalitis: Inflammation of the brain parenchyma. Symptoms often include altered mental status, motor/sensory deficits, seizures, etc.
• If both meninges and brain are inflamed, it’s meningoencephalitis.

Viral Infections of the CNS

• Viral infections can be part of a generalized infection (e.g., polio) or affect the CNS directly.
• CNS infections may be evident some time after the initial infection.
• Measles can cause subacute sclerosing panencephalitis (SSPE).

Viruses Causing CNS Infection

• Meningitis: Enteroviruses, Herpes Viruses (HSV, VZV, HHV6), Mumps
• Encephalitis: Herpes Viruses (HSV, VZV, HHV6), Enteroviruses, Mosquito-borne (West Nile, Japanese encephalitis, flaviviruses), Tick-borne flaviviruses, Rabies
• Paralysis: Enteroviruses (esp. polio virus), WNV, JE, Zika, measles (post-infectious encephalitis, SSPE), VZV (vasculitis, arteritis, stroke)

Viral Meningitis in Ireland (2019)

• Data from the HPSC shows trends in viral meningitis cases.
• Enteroviruses and herpes simplex viruses frequently reported contributors.

Viral Encephalitis in Ireland (2019)

• Data tracked the prevalence of viral encephalitis.
• Herpes simplex virus type 6 and varicella-zoster virus were common contributors.

Infectious Disease Notifications (Ireland 2019-2023)

• Reports of viral encephalitis, hemorrhagic fevers, and meningitis trends.

Congenital Infections and CNS Damage

• Certain viruses, like rubella, cytomegalovirus, and Zika virus, can cause congenital damage to the CNS.

Viral Meningitis

• More common than bacterial meningitis.
• Many viral causes, including: Enteroviruses (echoviruses, coxsackie B, enterovirus 71), Herpesviruses (herpes simplex, VZV), Mumps, Arboviruses (e.g., West Nile virus, Japanese encephalitis virus).
• Route of infection: typically via the bloodstream or nerve pathways, but some viruses (e.g., enterovirus, can replicate in and spread from the GI tract).
• HSV (Herpes Simplex Virus) infections are sometimes treated with antiviral medication like acyclovir. Note, differentiating between HSV meningitis and encephalitis is crucial

How Do Viruses Cause CNS Damage?

• Pathology is multifactorial, including virus multiplication, cellular damage, and the host's immune response (cellular+cytokines).
• Common symptoms include fever, headache, neck stiffness, vomiting, and photophobia.
• Symptoms usually unfold more slowly than in bacterial meningitis..

Non-Polio Enteroviruses

• Common cause of viral meningitis, especially subtypes like echoviruses, coxsackie B, and enterovirus 71.
• Primarily impacts infants and young children, usually with mild, self-limiting symptoms.
• Can be severe in neonates
• Peak activity typically occurs in late spring and autumn.
• Primarily a human-only reservoir
• Transmission: faecal-oral route. Viruses often multiply in the gastrointestinal tract and can enter the bloodstream to seed other organs, including the CNS

Non-Polio Enteroviruses: Other CNS Manifestations

• Enterovirus 71: associated with encephalitis (especially in East and Southeast Asia).
• Enterovirus D68: potentially linked to acute flaccid paralysis after respiratory illness.
• Enteroviral infections frequently produce other syndromes (not involving the CNS), including fever, rash, myocarditis, pericarditis, hand, foot, and mouth disease.

CSF Findings in Viral Meningitis

• In viral meningitis analysis the CSF typically displays normal glucose levels, high protein levels and elevated lymphocytes
• Differentiating viral meningitis from other conditions requires careful analysis of CSF characteristics such as the presence of specific microbes

Diagnosis: CSF findings in Viral Meningitis (differential diagnosis)

• A lymphocytic response in CSF is seen in several other conditions, including Leptospirosis, Syphilis, Lyme Disease, Cryptococcosis, Toxoplasmosis, TB, malignant infiltration of the meninges or connective tissue diseases.

Viral Meningitis: Treatment

• Generally self-limiting, especially outside the neonatal period.
• Supportive care (rest, hydration, antipyretics) is usually sufficient.
• Seizure management might be required.

Viral Encephalitis

• Self-limiting viral meningitis is generally benign, but viral encephalitis can have substantial morbidity and mortality, depending on specific pathogen and host interaction..
• Important examples include herpes simplex virus (HSV), varicella-zoster virus (VZV), rabies, West Nile virus, Japanese encephalitis, and tick-borne encephalitis.

Herpes Simplex Encephalitis

• Common in Northern Europe; HSV-1 type is more common than HSV-2
• Human-restricted virus
• Route of infection occurs from (primary or reactivation latent sites in cranial nerve ganglia) to frontal or temporal lobes in the brain
• Neonatal Herpes simplex encephalitis typically associated with primary infection acquired around the time of delivery. Usually affects the entire brain and has high mortality.
• Adults and children over 3 months of age often experience HSV encephalitis restricted to the CNS and have a higher chance of recovery from the infection but still a very high mortality rate without treatment

HSV Encephalitis: Clinical Features

• Symptoms include an acute neurological syndrome, such as behavioral disturbance, hemiparesis, aphasia, focal seizures.
• Diagnosis relies on MRI to identify temporal lobe changes, EEG, and detection of HSV in CSF via PCR.
• Treatment involves prompt intravenous (IV) acyclovir (acyclovir).

HSV Encephalitis: Neonatal

• HSV usually transmitted from the mother to infant during childbirth
• Typically disseminated infection, affecting the entire brain
• High mortality rate.
• Treatment involves IV acyclovir.
• Preventing maternal transmission is crucial, with focus on genital herpes management during pregnancy.

VZV Encephalitis

• Complication of either primary (chickenpox) or reactivation (shingles) of varicella-zoster virus (VZV).
• Symptoms are similar to HSV encephalitis.
• Diagnosis involves detection of VZV DNA in CSF through PCR.
• Treatment usually includes high-dose IV acyclovir.
• Prevention includes childhood chickenpox vaccination and shingles vaccinations for older adults.

Rabies

• Viral zoonotic disease causing acute encephalitis.
• High global mortality rates are observed.
• The majority of human cases stem from dog bites.
• Incubation time depends on distance the virus needs to travel to reach the CNS.
• No effective antiviral treatment exists and is mostly fatal

West Nile Virus (WNV)

• Arbovirus transmitted by the bite of infected mosquitoes.
• Birds are the primary reservoir hosts.
• Primarily affecting temperate zones (e.g., Northern North America) during late summer and early autumn.
• Often asymptomatic cases, but can lead to severe neurological symptoms including encephalitis and/or meningitis.
• Diagnosis is usually reliant on detecting West Nile IgM in blood or CSF.

Japanese Encephalitis (JE)

• Arbovirus, closely related to WNV, found in Asia.
• Humans are incidental hosts to the virus.
• Infection cycle involves mosquitos and vertebrate host (pigs are most common).
• Prevalent in agricultural areas (e.g., rice paddy fields).
• The disease is often asymptomatic, but can cause severe neurological complications (encephalitis).
• Prevention is largely dependent on immunization measures

Tick-Borne Encephalitis (TBE)

• Caused by RNA flaviviruses within the arbovirus family.
• Transmission occurs via infected Ixodes ticks.
• Typically found in forest regions of Central and Eastern Europe, Russia, Mongolia, and China.
• 3 subtypes exist. Distribution varies geographically.
• Symptoms include fever, headache, mild to severe neurological complications.
• Diagnosed from testing for viral RNA and TBEV in blood or CSF
• Prevention includes avoiding tick bites, protective clothing, and vaccination.

Other Causes of Viral Encephalitis

• Enteroviruses (including polio virus): often cause meningitis but sometimes encephalitis.
• Other arboviruses affect specific regions worldwide.

Poliovirus

• Important cause of paralysis before vaccination.
• Human-only reservoir (fecal-oral).
• Now significantly less prevalent despite cases occurring globally
• Prevention is through vaccination programs.
• WHO polio eradication campaign has reduced wild polio outbreaks.
• Wild poliovirus type 1 is now exceedingly uncommon despite cases persisting in certain parts of globe.
• Polio presents with varying degrees of disease and paralysis,

Paralytic Polio

• Spinal (80%): asymmetrical lower limb paralysis—damage to motor neurons in spinal cord
• Bulbar: cranial nerve nuclei in brainstem—tongue/pharyngeal muscles, resulting in weakness/paralysis.
• Bulbospinal: combination of the two.
• Post-Polio Syndrome: years after infection, characterized by weakness, muscle pain, and further neurological issues.

Polio Re-emergence

• Waning vaccine coverage and disruptions to vaccination campaigns contribute to polio re-emergence in previously eradicated locations

Zika Virus

• RNA virus (Flaviviridae family) transmitted primarily by Aedes mosquitoes.
• Can infect CNS and peripheral nervous system.
• Congenital Zika syndrome (severe microcephaly and brain damage in newborns) highly correlated
• Linked to Guillain-Barre syndrome (post-infectious paralysis).

Chronic CNS Viral Infections

• Subacute sclerosing panencephalitis (SSPE): a lingering measles infection, develops years after initial disease.
• HIV encephalopathy; causes neurological dysfunction in HIV-positive patients.
• Progressive multifocal leukoencephalopathy (PML): a rare opportunistic infection mostly impacting immune-compromised individuals.

TSE (Transmissible Spongiform Encephalopathy) = Prion Diseases

• Fatal degenerative brain diseases (e.g., Creutzfeldt-Jakob Disease (CJD)).
• Caused by abnormal prion proteins that accumulate in the brain; these proteins are resistant to conventional sterilization.
• Various subtypes of CJD (sporadic, inherited, variant).
• Variant CJD is often linked to consuming BSE-contaminated products.

CJD: Sporadic vs. Variant

• Sporadic CJD has a late-onset (typically in the 60s) and relatively rapid progression.
• Variant CJD often affects younger individuals and has a slower progression

CJD: Diagnosis

• Diagnosis relies heavily on post-mortem histological examinations.

CJD: Treatment & Prevention

• No effective treatment exists.
• Prevention focuses mostly on protecting the blood supply and food chain with policies like barring feeding bone meal to livestock and properly sterilizing surgical instruments to prevent transmission.

Additional Topics (not in Summary)

• Prescribing Safety Assessment (details not explicitly summarized).
• Sample PSA MCQ (details not explicitly summarized).

Test your knowledge on rabies exposure management and West Nile Virus characteristics. This quiz covers important preventive measures, host information, and the prevalence of asymptomatic cases. Perfect for students and professionals in health-related fields.