Zoonosis - ViralZoonosis AnOverview Definition Zooneses are...

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    Viral Zoonosis An Overview
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Definition Zooneses are diseases of vertebrate animals that can be transmitted to man: either directly or indirectly through an insect vector. When an insect vector is involved, the disease is also known as an arboviral disease. However, not all arboviral diseases are zoonosis: where the transmission cycle takes place exclusively between insect vector and human e.g. dengue and urban yellow fever. Examples of viral zoonoses that can be transmitted to man directly include rabies, hantaviruses, lassa and ebola fevers.
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Rabies Virus member of the Lyassavirus of the Rhabdoviridae. ssRNA enveloped virus, characteristic bullet-shaped appearance with 6-7 nm spike projections. virion 130-240nm * 80nm -ve stranded RNA codes for 5 proteins; G, M, N, L, S Exceedingly wide range of hosts. There are 5 other members of Lyassavirus : Mokola, Lagosbat, Duvenhage, EBL-1, and EBL-2. Duvenhage and EBL-2 have been associated with human rabies.
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Rabies Virus Structure of rabies virus (Source: CDC) Rabies virus particles
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Epidemiology Rabies is a zoonosis which is prevalent in wildlife. The main animals involved differs from continent to continent.   Europe fox, bats Middle East wolf, dog Asia dog Africa dog, mongoose, antelope N America foxes, skunks, raccoons, insectivorous bats S America dog, vampire bats
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Pathogenesis The commonest mode of transmission in man is by the bite of a rabid animal, usually a dog. Rabies is an acute infection of the CNS which is almost invariably fatal. Following inoculation, the virus replicates in the striated or connective tissue at the site of inoculation and enters the peripheral nerves through the neuromuscular junction. It then spreads to the CNS in the endoneurium of the Schwann cells. Terminally, there is widespread CNS involvement but few neurons infected with the virus show structural abnormalities. The nature of the profound disorder is still not understood.
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Laboratory Diagnosis Histopathology - Negri bodies are pathognomonic of rabies. However, Negri bodies are only present in 71% of cases. Rapid virus antigen detection - in recent years, virus antigen detection by IF had become widely used. Corneal impressions or neck skin biopsy are taken. The Direct Fluorescent Antibody test (DFA) is commonly used. Virus cultivation - The most definitive means of diagnosis is by virus cultivation from saliva and infected tissue. Cell cultures may be used or more commonly, the specimen is inoculated intracerebrally into infant mice. Because of the difficulties involved, this is rarely offered by diagnostic laboratories. Serology - circulating antibodies appear slowly in the course of infection but they are usually present by the time of onset of clinical symptoms.
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Negri Body in neuron cell (source: CDC) Positive DFA test (Source: CDC Diagnosis of Rabies
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Management and Prevention Pre-exposure prophylaxis - Inactivated rabies vaccine
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This note was uploaded on 12/27/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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Zoonosis - ViralZoonosis AnOverview Definition Zooneses are...

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