Rabies
Instructional Objectives: At the end of the lecture the student would be able to: 1-Define the main clinical characteristics of Rabies and Streptococcal disease. 2-Point out the occurrence of the disease. 3-List the causative agent, mode of transmission, incubation period, and period of communicability of Rabies and Streptococcal disease. 4-List the main preventive measures of Rabies and Streptococcal disease. 5-Describe the control measures of Rabies and Streptococcal disease.Fatal acute viral encephalomyelitis Characterized by Sense of apprehension, headache ,fever, malaise &indefinite sensory changes referred to the site of preceding animal bite. Excitability &aerophobia are frequent symptoms. Spasm of swallowing muscles leads to fear of water (hydro phobia) Delirium &convulsions follow The usual duration is 2-6 days Death due to respiratory paralysis
Infectious agent:- Rabies virus (Rhabdovirus). Occurrence:- World wide with an estimated 35.000-40,000 deaths/ year almost in developing countries It is a disease primarily of animals The only areas currently free of rabies in the animal population include: Australians, Newzeland, New guniea, Japan, Hawaii ,Taiwan , Uk, Iceland , Norway, Sweden , Finland, Portugal, Greece , west Indies &Atlantic islands.
Reservoir: Many wild &domestic canidae dogs, foxes, wolves,& other biting animals Infected population of bats. Rabbits ,rats &mice are rarely infected &their bites rarely , if ever call for rabies prophylaxis.
Mode of transmission:- Direct by bite of rabid animal (most common) Air borne spread in caves where millions of bats were present &in lab. Settings Person-to-person is theoretically possible Organ transplants (corneal)
Incubation period : Usually : 3 -8 weeks Rarely :as short as 9 days or as long as 7 years Severity of wound Site of the wound Strain of virus introduced Protection provided by clothing Prolonged I.P have occurred in prepubertal individuals
Period of communicability : In dogs &cats usually 3-7 days before the onset of illness &throughout the course of the disease.
Susceptibility & resistance: All mammals are susceptible to varying degree which may be influenced by virus strain Humans are more resistant to infection
Prevention: Prevention in animals Register, license &immunize all dogs , collect &kill ownerless animals. Immunize all cats Active surveillance for rabies in animals Detain and observe for 10 days any healthy appearing dogs or cats known to have bitten a person (unwanted dogs &cats may be killed immediately &examined for rabies by fluorescent microscopy) (Viral antigen, Negri bodies).
Prevention in human ( Individuals at high risk) A.. Pre-exposure prophylaxis Human diploid cell vaccine (HDCV) in inactivated vaccine grown on human diploid cell culture Rabies vaccine adsorbed (RVA) Purified check embryo cell vaccine (PCEC) an inactivated grown in primary cultures of chicken fibroblasts
Each vaccine 3 doses 1ml IM on days 0,7 & 21 or 28 If risk of exposure continues , either booster doses are given or serum is tested for neutralizing antibodies every 2 years
B.. Prevention of rabies after animal bites (post exposure prophylaxis) consist of the following: a. Treatment of bite wound: Clean &flush the wound immediately Thorough wound cleaning under medical supervision No suture or wound closure advised unless unavoidable Rabies immune globulin &/or vaccine as indicated Tetanus prophylaxis &antibacterial Rx when required
b. specific immunologic protection 10 IU( wounds)+ 10 IU (IM) human rabies immune globulin (HRIG) OR 20 IU (wound)+ 20 IU (IM) purified equine immune globulin (ERIG) modern cell culture vaccines given FIVE IM doses in the deltoid region 0,3,7,14 &28 days after the first dose
If the person has had previous full course immunization Or developed neutralizing antibodies After pre exposure immunization Or after post exposure regimen only 2 doses need (0,3) with severe exposure a third dose may be given on day 7 . HRIG is not used with this regimen
control
Reporting :obligatoryIsolation: contact isolationDisinfection: of saliva &articles soiled with Immunization of contacts who have an open wound or exposure to the pt’s saliva should receive anti rabies specific treatment No specific Rx :intensive supportive medical careStreptococcal disease
Group A (Beta hemolytic)1.Strept. Sore Throat: Presented with sudden onset fever, exudative tonsils or pharynx, tender enlarged ant. Cervical LN, absence of cough or rhinorrhea . Subsequent OM or peritonsillar abscess may occur. AGN can occur within1-5 weeks (mean 10days) RF can occur within 3 weeks (mean 19 days)
2.Strept. Skin infection : (pyoderma, impetigo). usually superficial may proceed to vesicular, pustular, and encrusted stage. RF is not an important complication, however AGN may occur later usually 3 weeks after skin infection.
3.Scarlet fever : It occurs when the infecting strain of Strept. Produces pyrogenic exotoxine (erythrogenic toxin) & the patient is sensitized but not immuned to the toxin. It present with fever, nausea, vomiting, fine erythema punctate blanch on pressure (sandpaper) sparing the face
4.Erysipelas and acute cellulites : Red, Tender, edematous spreading lesion with definite raised border
Infection agent: Streptococcus Pyogenes, (group A). Of approximately 130 serologically distinct types. Group A Strept. producing skin infection Are usually of different serologic types from those associated with throat infection.
Occurrence : Strept. sore throat &scarlet fever are common in temperate zones. In apparent infection is common Strept. Sore throat is unusual <2-3 years. peak incidence in the age group 6-12 years &declines there after .
Reservoir : Human Mode of transmission : Direct contact with patient or carriers Large droplets Indirect through contaminated articles (rare) Nasal carriers are particularly likely to transmit diseases
Incubation period : 1-3 days Period of communicability: Untreated :10-21 days Treated: 24 hours The contagiousness of the carriers decreased sharply in 2-3 weeks after onset of infection.
There is maternal immunity There is tendency for repeated attack of RF with further cardiac damage following each attack of Strept. Group A infection. Recurrence of AGN is unusual One attack of erysipelas predispose to subsequent attacks.
Prevention: mode of transmission 1. Public education relation to AGN &RF prompt Dx complete course of antibiotic Provide easily accessible lab. facilities for recognition of group A Strept. Milk pasteurization Safe preparation of food Exclusion of people with skin infection for food handling Secondary prevention of complication
Control
Reporting is not necessary except at time of epidemic. Isolation Disinfection of discharge Search and treat carriers among contacts Specific Rx penicillin is drug of choice for 10 days (oral or IM) (no resistance) and erythromycin if there is penicillin allergy