Description of Rabies and its Spread, Clinical finding, Prevention and Control

 

Description of Rabies and its Spread, Clinical finding, Prevention and Control



Introduction:

Rabies is an acute viral zoonotic disease (a disease that is transmitted to human from animal) characterized by sign of abnormal behavior, nervous disturbance ascending paralysis and death. All warm blooded mammals are susceptible to infection by the rabies virus. The virus is present in the saliva of the infected animal and is transmitted to the other animal and to human through saliva.

Causative agent:

Rabies is caused by RNA virus belongs to family Rhabdoviridae and genus  lyssavirus. The virus is bullet shape and measure about 180-250 nm in length by 75nm in diameter.





Spread of rabies:

·       Rabies is transmitted through direct contact between the virus (e.g. in contaminated saliva) and mucus membrane or wound.

·       Human infection most frequently occurs following a transdermal bite or scratch from an infected animal.

·       Very rare, rabies has been contracted by inhalation of virus containing aerosol (eg. In caves inhabited by bats)

·       Human –human transmission has never been confirmed. With the exception of organ transplant from rabid patient.

·       
Transmission through the consumption of milk and cooked meat has not been reported to date but the consumption of milk and meat from rabid animal is discouraged.




Rabies exist in 2 cycle: urban and sylvatic. In urban cycle, dog are the main reservoir where as in sylvatic cycle, wild animal are main reservoir.

Many European countries and North America have already eliminated rabies as a public health problem through mandatory vaccination of dog and good access to post exposure prophylaxis for human beings.

More than 95% of human death occurs in Asia/ Africa. And 99% of human rabies cases came from dogs. There is a small proportion of human rabies reported due to transmission via wild life (such as fox, wolves, jackels, raccoon, bats). Rabies kills more than 60,000 people each year (that is one death in every 9 minute) over 150 countries. Some countries like Australia, Switzerland, Netherland, rabies are eliminated.


WHO (world health organization)

OIE (world organization for animal health)

FAO (food agricultural organization)

GARC (global alliance for rabies control)

Mission 

 

Global Eradication of dog mediated rabies by 2030. (zero by thirty project) 0.30


How virus travels:



Rabid dog            virus enter through saliva            Travel via Peripheral Nervous System to Central Nervous System.


Many people think that rabies is transmitted through only dog. But its not true, rabies is transmitted through not only dog, but also spread through bite or scratch from rabies infected animal like dog, bats, raccons, fox, monkeys etc.. Any open wound exposed saliva of infected animal can be potential source of infection.

Clinical findings:

In dog:

1.    Furious form

This is classic “mad dog syndrome”. There is rarely evidence of paralysis during this stage. This form can be divided into stage of melancholy and stage of excitation.

 

Stage of melancholy: In this stage, dog may show bite inanimate or animate objects. It may show unusual violence and frenzy behavior.  Rabid dog may move from one village to other a long distance in a circular way and thus spread the disease over wide areas. The animal may lick water and attempt to drink but due to obvious paralysis of pharyngeal and laryngeal muscle does not succeed to drink water. The above period last for 1 to 3 days.

 

Stage of excitement: in this form dog may become very aggressive. Dog may hide in dark place due to photophobia. The voice may be change due to the paralysis of vocal cord. Animal may lick their genital area its show that the sign of heat. In the fag end, the dog will lose its ability to bark. The lower jaw will hang, tongue will protrude and head will drop down. The dog will develop dyspnea, ascending paralysis, coma and death. This period may last for 1 to 7 days.

 

2.    Dumb form: This form is also called paralytic form. In this form there is paralysis of lower jaw, tongue, larynx, and hind quarter.  The dog is unable to close the mouth (open mouth condition). In fair percentage of cases, the owner is suspicious that  a bone or some other object might have stuck in the neck and owner may try to open the mouth for examination and thus prone them to the possibility of contracting the infection. The entire clinical course of the disease up to the death takes 1 to 7 days.

10 day confinement and observation period:

Clinically course usually less than 7 days animal dead before end of 10 days.

In general if a biting dog does not die within 10 days rabies is unlikely.





In human:

Initial symptoms: pain or paraesthesia at the wound site

Later: hyperactivity, hallucination, hydrophobia, paralysis and coma and death

Furious form:

·       Hydrophobia, photophobia, aerophobia

·       Excitation and confusion

·       Excessive sweating/ salivation’

·       Dehydration and death in 2 to 5 days

 

Paralytic form:

·       Gradual ascending paralysis

·       Hydrophobia is not seen

·       Coma, death in 1-2 weeks

 

Approximately 80% of patient present with classical (furious) rabies and 20% present with paralytic rabies.

40 to 50% of people who are bitten by suspected rabid animal are children under 15 years age. In Nepal less than 100 people have been died each year due to rabies.

 

How long will it take to show symptoms in human?

Generally between 1 to 3 month to more than 1 year.. But it may be short as 4 days or long or may be many years. It depends upon location of bite and how deep the wound


WHO classification of Exposure:

Category of exposure

Type of contact

 

Category:1

Touching or feeding of animal, animal lick on intact skin

(no exposure)

Category:2

Nibbling of uncovered skin

Minor scratches or abrasion without bleeding

(exposure)

Category:3

Single or multiple transdermal bites or scratches

Contamination of mucus membrane or broken skin with saliva from animal kicks

(Severe exposure)

 

Post exposure prophylaxis (PEP):

Category:1 exposure

Category:2 exposure

Category:3 exposure

NO PEP required

Wound washing and immediate vaccination

Wound washing+ immediate vaccination+ RABIES IMMUNOGLOBULIN (RIG) administration

 

Diagnosis:

Diagnosis can only be confirmed by laboratory test preferably conducted postmortem on CNS tissue removed from cranium.

Diagnosis technique for rabies:

1.    Direct fluorescent antibody test (DFA)

2.    Mouse inoculation technique (MIT)

3.    Polymer chain reaction (PCR)

4.    Tissue culture infection technique (TCIT)

 

Can we treat after appearance of symptoms?

No treatment of rabies after the appearance of symptoms. Fatal after symptoms begin.

 

Prevention and control:

·       Rabies in human can be prevented, after exposure by PEP. Proper wound management combine with PEP is close to 100% effective in preventing rabies.

·       Immunize all dog and cat owned by an individual or by the community

·       Immunize any person with proven or probable exposure to rabies and administer rabies immunoglobulin in case of severe exposure

·       Wild animal should not be kept as pets

·       Strict quarantine regulation

·       Human as high risk (eg. Veterinarian, vet technician, lab person, volunteer, etc.. ) much received pre exposure immunization.

·       Pre exposure prophylaxis : 0,7, 21 or 28 days

·       Post exposure prophylaxis:0,3,7, 14, 21 days

·       Vaccine should never be administered in Gluteal region.

·       Rabies awareness and vaccination program




Local wound management:

·       Through washing and flushing of the wound for approximately 15 minutes with soap or detergent and plenty of water is required.

·       If local irritant like herbs, oil, chilli or turmetic powder have been applied, there should be removed by through washing of the wound

·       After wound has been washed, local antiseptics like Povidine iodine should be applied on the wound.

·       Whenever necessary, tetanus prophylaxis should be administered.

              Dr. Manoj karki (B.V.Sc & A.H) 

                   2020/09/28


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