Introduction

Rabies is a rapidly progressive, acute, fulminant, and fatal encephalitis in humans and animals that is caused by infection with rabies virus.

-Rabies virus is usually transmitted to humans by the bite of an infected animal.

-Live virus enters the nerve tissue at the time of the bite, multiplies at the site, and then spreads centripetally along peripheral nerves toward the spinal cord or brain stem via retrograde fast axonal transport. It replicates in gray matter and then spreads  to the salivary glands, adrenal glands, and heart. 

Symptoms & Signs 

-The average incubation period is one to three months. 

-The clinical spectrum can be divided into three phases

1.Prodromal phase: 

-The first symptom is usually the paresthesia at the bite site 

-Patient later develops malaise, headache, photophobia, fever, anorexia, nausea, vomiting and sore throat 

2.Acute neurologic phase: 

–Hydrophobia (fear of water), Aerophobia (fear when feeling a breeze) 

-Sympathetic overactivity (Increased salivation, ‘foaming at the mouth’, perspiration, lacrimation, pupillary dilatation, nervousness)

-Psychotic symptoms (hallucinations, delusions, bizarre behavior)

-Two acute neurologic forms of rabies are seen in humans: 

the encephalitic (furious) form in 80% and

the paralytic form in 20%.

3.Coma: Convulsive seizures, coma and death

-The major cause of death is cardiorespiratory arrest. 

Diagnosis 

1.Rabies antigens: diagnosis by rabies specific antigens 

2.Serology: Diagnosis by rabies specific antibodies,  detected by immunofluorescence or neutralization tests. 

3.Viral isolation: Isolation of the virus in the brain neurons. 

Negri bodies: the most characteristic pathologic finding in rabies; They are eosinophilic cytoplasmic inclusions in the brain or the spinal cord. They are composed of rabies virus proteins and viral RNA 

4.Animal observation: 

‘Rabid or suspected rabid’ animals: should be killed humanely immediately after the bite and sent for laboratory examination of neural tissues 

‘Normal’ animals: should be held for observation for 10 days 

If they appear abnormal during or after 10 days: kill humanely and send tissues to laboratory 

If they appear normal during or after 10 days: individualized treatment 

Prevention

–Avoid contact with any unfamiliar domestic animals and wild animals 

–Immunize all household dogs and high risk pets 

–Vaccination: Four 1-mL doses of rabies vaccine should be given IM in the deltoid area. 

Post-Exposure Prophylaxis 

It involves wound cleaning, vaccination and passive immunity 

Wound cleaning: 

-Thoroughly clean the wound with soap and antiseptics 

-Animal bite wounds should not be sutured

Vaccination: Four doses of rabies vaccine over a 14 day period 

-Give the vaccine only in deltoid region in adults or anterolaterial thigh in children 

–Never administer the vaccine in the gluteal area because antibody responses have been lower after administration at this site 

-Pregnancy is not a contraindication for immunization.

Passive immunity: One dose of HRIG along with the first dose of the vaccine 

-HRIG is not indicated beyond the 7th day after vaccination is begun, because an antibody response is most likely occurred 

-HRIG should never be administered in the same syringe or into the same injection site as the vaccine, because the antibody and vaccine will neutralize each other.

-HRIG should not be given to those with immunoglobulin A deficiency, because small amounts of immunoglobulin A present in HRIG might cause a severe allergic reaction.

Treatment 

-There is no successful treatment for clinical rabies. 

-Symptomatic and Palliative treatment using sedatives, antipsychotics, anxiolytics, and pain killers