Neuro Presentation

Rabies

RabiesLisa Port

overview of rabiesRabies is a zoonotic disease meaning it is transmitted from infected animals to humansIt is caused by the rabies virus which belongs to the genus Lyssavirus Rabies is 100% preventable with the vaccineOnce it travels to the brain, it is deadly and causes a variety of neurological symptoms

It is endemic within 150 countriesIt is found on all continents excluding Antarctica95% of human deaths involving Rabies occur in Asia and AfricaCauses 26,000 to 55,000 deaths worldwide per year

Important Reservoirs for the disease

Natural reservoirs stats More than 90% of all animal cases reported occur in wildlifeWildlife: raccoons, skunks, foxes, batsDomestic animals such as dogs, cats, ferrets, rodents (very rare), rabbits, etc. can also be carriers of rabiesRabid dogs around the world is the cause of over 90% of human exposure to rabies, and accounts for 99% of their deathsIn the United states, bat bites are the most common source of rabies

Transmitted and IncubationVirus is spread through saliva of infected animalsIt can also be transmitted when infected saliva gets into an open wound or the mucous membranes (eyes or mouth)The rabies virus can not go through unbroken skinRabies has an incubation period of 1-3 months, but could vary from less to one week to over a year (longest was 6 years)

SymptomsInitial symptoms includes flu-like symptoms and pain or unexplained tingling at the wound siteAs virus spread, it causes and inflammation of the brain and spinal cordThis causes abnormal behavior, hallucinations, insomnia, hydrophobiaOnce symptoms appear Rabies is always deadly lead to paralysis of heart and lungsOnly two documented survival cases that did not have pro- or post exposure prophylaxisStages Prodromal PhaseVirus first starts to replicate in CNS, characterized by nervousness and variable fever.Furious PhaseVirus spread to peripheral and cranial nerves to enter salivary glands and other tissues; there is also CNS Inflammation. It is characterized by irritability, viciousness, development of phobias, etc.Paralytic PhaseGlobal nerve cell apoptosis occurs, characterized by paralysis of muscles, inability to swallow, etc. How does rabies travel?The virus enters the peripheral nervous system It is then transported to the central nervous system via retrograde axoplasmic flowIn the brain it multiples, causes symptoms, and is transferred to the salivary glands

Paper published in 2014 explains how rabies travels to the brainRabies uses a route normally reserved for nerve growth factorsTherefore, when Rabies enters a neuron in the PNS it binds to the a nerve growth factor receptor called p75Once inside, the virus enters a vesicle and is moved along microtubules through the neurons axon and onto its cell body (located in the spinal cord) This allows the virus to travel much more quickly, and it can dump fuel to further speed up the process

Diagnosis for animals Rabies must be detected from at least two locations in the brain (usually in brain stem and cerebellum)Animals are usually euthanizedBrain samples are taken and tested using a direct fluorescent antibody (DFA) test (gold standard

Histopathologic sign of Rabies includes:Negri bodies, which are cytoplasmic aggregates of substances such as proteins Negri bodies are only present in 50% of samplesMost frequently found in pyramidal cells of Ammons horn of the hippocampus, and the Purkinje cells of the cerebellumUsually not used in diagnosis

Diagnosis for HumansNo single test is sufficientTherefore, a variety of tests are performed on samples of saliva, spinal fluid, and skin biopsies of hair follicles at the nape of the neckTreatment Post-exposure ProphylaxisGiven a series of injections over a period of two weeksFirst injection is a fast-acting shot containing rabies immune globulin (HRIG), which is given near the area of animal biteFour rabies vaccinations follow this prior injectionThese shots help the body fight the virusThere is also the Milwaukee Protocol for patients exhibiting symptoms; stirred some controversyPrevention Get your pets vaccinatedLimit your pets interaction with wildlifeLimit your own interaction with wildlife that is behaving abnormally Washing your wound from an animal efficiently Works Citedhttp://www.sciencedaily.com/releases/2014/08/140828142736.htmhttp://www.who.int/mediacentre/factsheets/fs099/en/http://www.cdc.gov/rabies/index.html