An introduction to Rabies (Hydrophobia)
|
Dr Asem Suresh Kumar Meitei
Contd from last Saturday
A common clinical sign is a characteristic abnormal bellowing, which may continue intermittently until shortly before death.
Horses and other equine species frequently show evidence of distress and extreme agitation. They show mania. Their uncontrolled actions are often violent and dangerous and include blind charges, sudden falling and rolling and, in many cases, chewing of the skin also observed. Lastly, Paralysis and death ensued. These clinical signs, especially when accompanied by rolling, may be misinterpreted as evidence of colic.
As in other species, horses may bite or strike viciously and, because of their size and strength, become unmanageable in a few hours. People have been killed outright by such animals. These animals frequently have self-inflicted wounds.
Sheep: Affected sheep becomes excited and restless, behave abnormality, bite at the wool of their associates, fall down exhausted to the ground when handled, exhibit an abnormal sexual desire continually mounting each other, dyspnea, twitching of the lips and a wild stare. Bleating is not a symptom, and there is no evidence of itching at the site of wound. Attacking humans or each other, vigorous wool pulling, sudden falling after violent exertion, muscle tremor and salivation are characteristic.
Pigs: Pigs run around in all direction root up the litter of the ground and gnaw or bite at the site of injury. They also become very aggressive. Affected sows show twitching of the nose, excessive salivation and clonic convulsions. They may walk backwards. Terminally, there is paralysis and death occurs 12 to 48 hours after onset of signs.
Fowls: Fowls become very nervous; look frightened run about with the feathers ruffled. They generally emit hoarse cries and attack other fowls, and even man.
Others: Some animals affected with rabies suddenly die without showing any definite symptoms. Others are seized with a convulsive fit during which they may die. As a rule, the disease usually lasts from four to seven days and the mortality is just about 100 %.
Rabid foxes and coyotes often invade yards or even enter houses, attacking dogs and humans. In this state, sometimes an animal will attack a porcupine; finding a fox or another animal with porcupine quills is otherwise considered abnormal and can, in many cases, raise the index of suspicion for rabies.
Rabid raccoons, foxes, and skunks typically show no fear of humans and are ataxic, frequently aggressive, and active during the day, despite their often crepuscular nature. In urban and suburban areas especially, they may attack domestic pets.
In general, rabies should be suspected in wildlife acting abnormally. The same is true of bats that can be observed flying in the daytime; resting on the ground, paralyzed and unable to fly; attacking humans or other animals; or fighting.
Rodents and lagomorphs rarely constitute a risk of exposure to rabies virus. However, each incident should be evaluated individually. Reports of laboratory-confirmed rabies in woodchucks and beavers are not uncommon in association with the raccoon rabies virus variant epizootic in the eastern United States.
When, an animal, especially a carnivores, shows acute nervous symptoms associated with irritability, aggressiveness, and later with paralysis, it should be treated as a case of suspected rabies. The suspected animal should be captured, confined in custody and kept under observation for about 10 days so that the disease can be allowed to run its course. Premature killing will reduce the accuracy of a laboratory diagnosis, as the development of NEGRI BODIES related directly to the length of the clinical illness.
Negri bodies, first reported by Negri in 1903, are the CYTOPLASMIC INCLUSION BODIES in the nerve cells produced by the STREET VIRUS. They are considered to be AGGLOMERATIONS of virus particles and are acidophilic, stain magenta of bright red colour and the basophilic inner corpuscles stain dark blue to black. Negri bodies are specific for rabies and their presence is of high diagnostic value.They occur only rarely or not at all in infections due to FIXED VIRUS. Fixed virus produces another type, known as LENTZ BODIES (first reported by Lentz in 1909). They occur extracellularly between the ganglion cells in the central nervous system. Another type of inclusion bodies, LYSSA BODIES, which may be mistaken for Negri bodies. They are devoid of basophilic granules and may be found normally in cats and mice and also other animals that are not infected with rabies.
As soon as clinical symptoms are well established the animal should be killed without damaging the brain. If animal dies of suspected rabies, the brain should be removed, one half should be submitted in 10% formalin, and the other half in 50% glycerine saline. The better the state in which the specimen arrives at the laboratory the easier will be the diagnosis. Speed and accuracy are essential in carrying out the test.
(To be contd)
Contd from last Saturday
A common clinical sign is a characteristic abnormal bellowing, which may continue intermittently until shortly before death.
Horses and other equine species frequently show evidence of distress and extreme agitation. They show mania. Their uncontrolled actions are often violent and dangerous and include blind charges, sudden falling and rolling and, in many cases, chewing of the skin also observed. Lastly, Paralysis and death ensued. These clinical signs, especially when accompanied by rolling, may be misinterpreted as evidence of colic.
As in other species, horses may bite or strike viciously and, because of their size and strength, become unmanageable in a few hours. People have been killed outright by such animals. These animals frequently have self-inflicted wounds.
Sheep: Affected sheep becomes excited and restless, behave abnormality, bite at the wool of their associates, fall down exhausted to the ground when handled, exhibit an abnormal sexual desire continually mounting each other, dyspnea, twitching of the lips and a wild stare. Bleating is not a symptom, and there is no evidence of itching at the site of wound. Attacking humans or each other, vigorous wool pulling, sudden falling after violent exertion, muscle tremor and salivation are characteristic.
Pigs: Pigs run around in all direction root up the litter of the ground and gnaw or bite at the site of injury. They also become very aggressive. Affected sows show twitching of the nose, excessive salivation and clonic convulsions. They may walk backwards. Terminally, there is paralysis and death occurs 12 to 48 hours after onset of signs.
Fowls: Fowls become very nervous; look frightened run about with the feathers ruffled. They generally emit hoarse cries and attack other fowls, and even man.
Others: Some animals affected with rabies suddenly die without showing any definite symptoms. Others are seized with a convulsive fit during which they may die. As a rule, the disease usually lasts from four to seven days and the mortality is just about 100 %.
Rabid foxes and coyotes often invade yards or even enter houses, attacking dogs and humans. In this state, sometimes an animal will attack a porcupine; finding a fox or another animal with porcupine quills is otherwise considered abnormal and can, in many cases, raise the index of suspicion for rabies.
Rabid raccoons, foxes, and skunks typically show no fear of humans and are ataxic, frequently aggressive, and active during the day, despite their often crepuscular nature. In urban and suburban areas especially, they may attack domestic pets.
In general, rabies should be suspected in wildlife acting abnormally. The same is true of bats that can be observed flying in the daytime; resting on the ground, paralyzed and unable to fly; attacking humans or other animals; or fighting.
Rodents and lagomorphs rarely constitute a risk of exposure to rabies virus. However, each incident should be evaluated individually. Reports of laboratory-confirmed rabies in woodchucks and beavers are not uncommon in association with the raccoon rabies virus variant epizootic in the eastern United States.
When, an animal, especially a carnivores, shows acute nervous symptoms associated with irritability, aggressiveness, and later with paralysis, it should be treated as a case of suspected rabies. The suspected animal should be captured, confined in custody and kept under observation for about 10 days so that the disease can be allowed to run its course. Premature killing will reduce the accuracy of a laboratory diagnosis, as the development of NEGRI BODIES related directly to the length of the clinical illness.
Negri bodies, first reported by Negri in 1903, are the CYTOPLASMIC INCLUSION BODIES in the nerve cells produced by the STREET VIRUS. They are considered to be AGGLOMERATIONS of virus particles and are acidophilic, stain magenta of bright red colour and the basophilic inner corpuscles stain dark blue to black. Negri bodies are specific for rabies and their presence is of high diagnostic value.They occur only rarely or not at all in infections due to FIXED VIRUS. Fixed virus produces another type, known as LENTZ BODIES (first reported by Lentz in 1909). They occur extracellularly between the ganglion cells in the central nervous system. Another type of inclusion bodies, LYSSA BODIES, which may be mistaken for Negri bodies. They are devoid of basophilic granules and may be found normally in cats and mice and also other animals that are not infected with rabies.
As soon as clinical symptoms are well established the animal should be killed without damaging the brain. If animal dies of suspected rabies, the brain should be removed, one half should be submitted in 10% formalin, and the other half in 50% glycerine saline. The better the state in which the specimen arrives at the laboratory the easier will be the diagnosis. Speed and accuracy are essential in carrying out the test.
(To be contd)