RHABDO VIRUSPrepared by: Presentation with:SAgun PAudel o Samjhana gurungHealth Assistant o Sabita timilshinaStudent of BPH @ LA GRANDEE International o Sarala kumal college, Simalchour o Samjhana gurung Pokhara, Nepal
INTRODUCTION:The name is derived from the Greek “rhabdos’’meaning rod referring to the shape of the viralparticles.They contain a negative stranded RNA genomeand are very stable to drying.This group of viruses has a broad host range butthere is only one that affects humans. The virusesare generally introduced through a bite wound.
CHARACTERISTICS: Rhabdoviruses carry their genetic material in theform of negative-sense single-stranded RNA.They typically carry genes for five proteins: large protein (L) glycoprotein (G)nucleoprotein (N)phosphoprotein (P) andmatrix protein (M). Rhabdoviruses that infect vertebrates are bullet-shaped.
CHARACTERISTICS : Animal rhabdo viruses infect insects, fish, andmammals, including humans. Present in saliva and transmitted by animal bite. The most common virus of this family is rabies virus.
CLASSIFICATION: Group: Group V (-)ssRNA Order: Mononegavirales Family: Rhabdoviridae Genera: Vesiculovirus Lyssavirus Nucleorhabdovirus Nucleorhabdovirus Novirhabdovirus
MORPHOLOGYElectronmicrograph ofthe rhabdovirusat 64,000Xmagnification:Notice the bullet-shaped virionssurrounding thecell. The darkcircle in the cellis the Negribody:
MORPHOLOGY: o The most outstanding characteristic of the rhabdovirus is the bullet-shaped virion. o Such a shape is caused by a lipid envelope, embedded with glycoprotein peplomers, surrounding a helically wound nucleocapsid. o The virions tend to be approximately 70 nm wide and 170 nm long. oMatrix proteins can also be found under the lipoprotein envelope.
REPLICATION: Replication of many rhabdoviruses occurs in thecytoplasm, although several of the plant infectingviruses replicate in the nucleus. In order for replication, both the L and P proteinmust be expressed to regulate transcription.Transcription results in five monocistronic mRNAsbeing produced because the intergenic sequencesact as both termination and promoter sequences foradjacent genes
REPLICATION: During their synthesis the mRNAs are processed tointroduce a 5 cap and a 3’ polyadenylated tail to each of themolecules. This structure is homologous to cellular mRNAs and canthus be translated by cellular ribosomes to produce bothstructural and non-structural proteins.Genomic replication requires a source of newlysynthesized N protein to encapsidate the RNA.This occurs during its synthesis and results in theproduction of a full length anti-genomic copy.
REPLICATION: This in turn is used to produce more negative- sense genomic RNA. Replication characteristically occurs in an inclusion body within the cytoplasm, from where they bud through various cytoplasmic membranes and the outer membrane of the cell. This process results in the acquisition of the M + G proteins, responsible for the characteristic bullet- shaped morphology of the virus.
PATHOGENESIS: Rhabdoviruses generally enter via a bite or a wound infected with saliva. Initially, the virus replicates at the site and then infects CNS tissue.Incubation period: 6 days up to 1 year average 30-70 days. virus spreads rapidly via the nerves. CNS damage produces the symptoms of disease. Neurons accumulate ribonucleoprotein as intracytoplasmic inclusions. Infection of the thalamus, hypothalamus or pons may occur.
CLINICAL PRESENTATION: Most cases go through three stages. [classical rabies]:I. Prodromal Stage : lasts from 2-10 days and presents in the form of fever, headache, malaise, fatigue, and also localized pain around area of initial infection.I. Sensory Excitation: hyperactivity, hallucinations, disorientation, seizur es and bizarre behavior.
CLINICAL PRESENTATION: Also about 50% of infected individuals developed painful spasms of the pharynx and larynx resulting in a fear to eat or drink. Because of this fear they drool rather than swallow. Increased salivation is another symptom of the disease, thus adding to the drooling problem. This phase persists for 2-7 days.III. Coma and Paralysis Phase: as the disease persists deterioration of CNS tissue leads to paralysis and respiratory problems.
CLINICAL PRESENTATION:About 20% of cases have only two phases [dump rabies]:patient skips the sensory excitation phase and progresses right to the coma and paralysis phase.Dumb rabies is almost 100% fatal with only three known cases of survival.In each of these cases the patients had high titers of antibody in the CSF.
LABORATORY DIAGNOSIS: Diagnosis is perform best by FA staining or RT-PCR of infected cells or tissues. Animals are diagnosed through histological examination of the CNS for Negri bodies. The cytoplasmic Negri body is a diagnostic of rabies encephalitis. size (7 micrometers) and color as a mature RBC. brain biopsy. Indirect immunofluorescence is most often used to detect rabies antigen [impression smear, oronasal mucosa scrapings, or hair follicles of the neck].
CONTROL Sanitary : cleansing of a bite wound to reduce the number of viral particles can help to prevent disease. Use of the vaccine for all dogs (a modified live vaccine) and cats (a dead virus suspension) is important in preventing spread to humans. Immunological : Both active and passive vaccination may be used to prevent human disease. The active vaccines are inactivated virus grown in human diploid cell cultures (HDCV) while the passive vaccine uses immunoglobulin. There is no any chemotherapeutical control available.
TREATMENT: Immediate First Aid :The virus remains localized at the site of the wound for a period of time. To help recovery, wash the wound with soap and water as soon as possible, and follow with application of an antiseptic. Vaccine : Human Diploid Cell Vaccine :HDCV should be given intramuscularly on days 0, 3, 7, 14, and 28, followed by a booster dose on day 90. nervous tissue vaccine, or duck embryo vaccine. Human Rabies Immune Globulin.
PREVENTION: Rabies is the only human disease that can be prevented by active immunization after infection. This is possible due to the long incubation period of the virus. Pre-Exposure Immunization:Anyone at high risk of contact with rabid animals may seek pre-exposure prophylaxis.