Rabies Causative agent: Rabies virus Lyssavirus Enveloped ssRNA Spiked bullet shaped virus Virus multiplies in brain forming Negri bodies

Signs & Symptoms Pain and itching at site of infection Fever, headache, myalgia, sore throat, fatigue Progress rapidly to secondary symptoms Encephalitis, agitation, confusion, hallucinations, seizure, increased sensitivity to light and touch, coma Increased salivation and difficulty swallowing Results in frothing of mouth Hydrophobia occurs in 50% of cases About 50% of patients die within 4 days

Virus enters through bite Attaches to skeletal muscle cells triggering endocytosis Pathogen moves across neuromuscular junction into nerve cell and travels to CNS Slow moving so long incubation period 1-2 months up to several years Viruses travel back to the salivary glands and are secreted in saliva

Epidemiology Zoonotic Skunks, raccoons and bats considered chief reservoir 75% of human cases linked to bat bites 0 to 4 reported cases in US annually

Prevention Treatment Vaccination of domestic animals and Vets Wash wound immediately and thoroughly apply antiseptic Treatment Risk lowered if vaccine administered as soon as possible Interferon may be applied to wound No effective treatment for rabies Only six known survivors of disease

Viral Encephalitis Causative agent Arboviruses Zoonotic diseases mosquitoes Zoonotic diseases Horses, birds and rodents West Nile encephalitis, LaCrosse encephalitis, WEE, EEE, VEE, St. Louis encephalitis

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Signs & Symptoms 3-7 day incubation period Characterized by mild flu-like symptoms Fever; headache; vomiting One or more nervous system abnormalities Disorientation, localized paralysis, deafness, seizures or coma

Only minority infected develop encephalitis Others may develop viral meningitis Most reported human cases in immunosuppressd individuals Elderly and very young Healthy immune system typically fights off virus with only mild flu-like symptoms

Viruses multiply at site of bite and in local lymph nodes viremia Virus crosses blood-brain barrier Damages neurons Causes extensive damage to brain tissue in severe cases Progression of disease halted by neutralizing antibody Mortality ranges from 2% to 50% depending of type of infecting agent and host

Epidemiology Disease are all zoonoses Maintained naturally in birds and rodents Humans are accidental hosts LaCrosse encephalitis usually causes most reported cases

West Nile an emerging disease in US Appeared in New York in 1999

Prevention Treatment Eliminate vector habitat Avoiding outdoor activities at night Windows and porches properly screened Use insect repellents and insecticides Vaccine available for horses Treatment No proven antiviral therapy