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Rabies Diagnosis:Opinion and Editorial Print E-mail
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Post by Prof.Henry Wilde   
, 31 Ҥ 2009

 

The Jakarta Post. January 22, 2009

 

The article titled "Let experts examine your pets," (The Jakarta Post, Jan. 16) may leave readers confused.
It does not clearly explain that the tests discussed are carried out on the brain tissue of killed animals. A diagnosis of rabies in a living dog or cat (or other mammal) is first made by ob-servation of symptoms and signs by an experienced veterinarian and may not be easy as other infections of the central nervous system such as canine distemper may appear similar.

 

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Tests on saliva can be done through the polymerase chain reaction (PCR), a molecular test done only by experts in laboratories. However, secretion of virus in saliva is intermittent. Thus PCR is diagnostic only if positive.
Serum antibody to rabies is rarely positive at the onset of rabies symptoms in a dog (and man). It is positive if the animal (or man) have been immunized and thus presumably immune to rabies.
Furthermore, there is no method to diagnose incubating rabies; infection that is not manifesting itself clinically, in animals and humans. A dog may look and act perfectly normal for days or months, yet it is incubating rabies which will manifest at some future date.
Response to the rabies outbreak in Bali was delayed and not in accordance with World Health Organization recommendations on how best to prevent dissemination of the virus to the rest of the island.
Owners with dogs that behave abnormally therefore must be encouraged to bring the animal to a veterinary testing center as soon as possible, and in a manner that does not endanger humans by being exposed during capture or transport.
The veterinarian will then have to make a decision whether the dog should be simply caged and observed or there is justification for euthanizing it and examining brain tissue immedi-ately.
The reliable method to diagnose rabies from brain tissue is microscopy by using the fluorescent antibody test for which a reagent called "rabies conjugate" is needed. This reagent is available internationally and the very expensive concentrated vial is diluted as directed to make it quite affordable and widely used worldwide.
The other test (looking for Negri bodies), mentioned in The Jakarta Post, is notoriously unreliable and rarely if ever used in expert laboratories.
The only reliable and cost-effective manner to contain a rabies outbreak and make an island again rabies-free is to vaccinate all dogs in a sustainable manner as soon as possible.
Killing of dogs without sustained vaccination of survivors was tried in a similar outbreak on Flores Island some years ago and failed to make that island again rabies-free.

 

HENRY WILDE
Professor of Medicine
Chulalongkorn University
Bangkok

Last Updated ( , 31 Ҥ 2009 )
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