Osmosis High-Yield Notes
This Osmosis High-Yield Note provides an overview of Rhabdoviruses essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Rhabdoviruses:
Chapter 2 Acyanotic Defects NOTES RHABDOVIRUSES MICROBE OVERVIEW ▪ Diseases ▫ Rabies encephalitis, vesicular diseases ▪ Genera: Lyssavirus, Vesiculovirus, Sigmavirus, Varicosavirus, Spirivivirus, etc. Genetic material ▪ Rod-shaped, single-stranded RNA virus Morphology ▪ Enveloped, bullet-shaped, with helical nucleocapsids, linear genomes Taxonomy ▪ Order: Mononegavirales ▪ Family: Rhabdoviridae Transmission ▪ Via bite (infected host’s saliva) RABIES VIRUS osms.it/rabies-virus PATHOLOGY & CAUSES ▪ Serious central nervous system (CNS) viral zoonotic infection ▪ Virus spreads via nerves (retrograde axoplasmic transport) ▪ Muscle tissue inoculation → incubation (1–3 months), local multiplication → acetylcholine receptor binding → nerve entry → travel via spinal cord axons → brain infection (found in cerebellum Purkinje cells, hippocampal neurons) → encephalitis Advanced-stage ▪ CNS → other organs (salivary glands, cornea, skin, gastrointestinal, etc.) via parasympathetic nervous system CAUSES ▪ Caused by genus Lyssavirus (multiple species, Rhabdoviridae family) Transmission ▪ Saliva in virus-infected host bite (dogs, bats, cats, raccoon, foxes, skunks, monkeys, etc.) ▪ Rabies-infected organ/tissue transplantation (rare) ▪ Aerosol transmission (e.g. bat caves) possible RISK FACTORS Animal exposure (bite risk) Travel (rabies-endemic Asian/African areas) Age < 15 years Deep bite Head wound (virus → brain transmission risk ↑ ) ▪ No post-exposure prophylaxis ▪ Occupational (laboratory, veterinarian) ▪ Recreational (spelunking → ↑ bat exposure risk) ▪ ▪ ▪ ▪ ▪ OSMOSIS.ORG 511
COMPLICATIONS ▪ ▪ ▪ ▪ ▪ Encephalopathy Increased intracranial pressure Coma Permanent neurological deﬁcits Often fatal SIGNS & SYMPTOMS Prodromal stage ▪ Non-speciﬁc symptoms (ﬁrst week) ▫ Headache; low grade fever, chills; myalgia, weakness, fatigue; malaise, anorexia; nausea/vomiting; sore throat; photophobia (sometimes) ▪ Wound site pain/tenderness/paresthesia/ tingling/itching Encephalitic rabies ▪ AKA furious rabies ▪ Most common form ▪ Involuntary pharyngeal spasms → hydrophobia (fear of water); aerophobia ▪ Fever ▪ Muscle spasms → opisthotonus position ▪ Seizure ▪ ↑ autonomic stimulation ▫ Excess salivation; lacrimation; sweating; mydriasis; impaired temperature homeostasis; tachycardia ▪ Dysphagia ▪ Aggressiveness, agitation, hallucination, confusion ▪ Respiratory distress → coma → respiratory arrest → death Paralytic stage ▪ AKA dumb rabies ▪ Ascending ﬂaccid paralysis ▪ Sphincter atony ▪ Hydrophobia (rare) ▪ Neck stiffness ▪ Cranial nerves palsy ▪ Fasciculations/deep tendon reﬂex loss ▪ Pharyngeal, diaphragm muscle paralysis → death 512 OSMOSIS.ORG DIAGNOSIS ▪ Clinical Presentation ▫ History of rabid animal bite, rabies infection symptoms/signs DIAGNOSTIC IMAGING CT scan ▪ Cerebral edema LAB RESULTS Reverse transcription PCR (RT-PCR) ▪ Saliva ▫ Detects rabies virus RNA Skin punch biopsy ▪ RT-PCR; immunoﬂuorescence staining for viral antigen Cerebrospinal ﬂuid (CSF) ▪ Indirect immunoﬂuorescence, virus neutralization assay ▪ CSF analysis ▫ Pleocytosis, ↑ protein Serum ▪ Anti-rabies virus antibodies in serum appear after ﬁrst week (if individual not immunized) OTHER DIAGNOSTICS Post mortem ▪ Brain tissue/other neural tissue examination ▫ Negri bodies, eosinophilic cytoplasmic inclusions in nerve cell cytoplasm (often) TREATMENT MEDICATIONS ▪ Antivirals ▪ Rabies vaccine ▫ Both post-, pre-exposure prophylaxis ▫ Immunocompetent people: four injections (day 0, 3, 7, 14) ▫ Immunocompromised people: ﬁfth injection (day 28)
Chapter 94 Rhabdoviruses ▫ Previously immunized people: two injections (day 0, 3) ▪ Human rabies immune globulin (HRIG) ▫ Single dose (20 units/kg) injected in, around wound ▫ Remainder administered intramuscular at distant site (e.g. other deltoid) OTHER INTERVENTIONS Post-exposure prophylaxis (rapid) ▪ Wound cleaning ▫ Water/soap, povidone iodine ▪ Antibiotics/tetanus prophylaxis Figure 94.1 Multiple Negri bodies in the brain of an individual infected with the rabies virus. The negri bodies form in the Purkinje cells of the cerebellum. Management ▪ Respiratory (supplemental oxygen, mechanical ventilation), cardiovascular support (ﬂuids) Prevention ▪ Exposed population may receive preexposure prophylaxis ▪ Domestic animal vaccination (especially dogs, cats) OSMOSIS.ORG 513
Osmosis High-Yield Notes
This Osmosis High-Yield Note provides an overview of Rhabdoviruses essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Rhabdoviruses by visiting the associated Learn Page.