An Uncommon Cause of Fatal Paralysis.

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Pathology

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Diagnosis

Rabies virus infection
Human Rabies, paralytic type
(dumb rabies).

Electron microscopy is the accepted method for the diagnosis of many viral diseases including the rhabdoviridae.

The Ultrastructure.

We identified virions in necrotic neurons.We had demonstrated that Negri bodies consist in a compacted mass of viral nucleocapsid surrounded by numerous bullet-shaped viral particles budding from intracytoplasmic membranes. The virions replicated in the cytoplasm of the cell. The nuclear inclusion in fig 5 is uncommon in rabies and is the first case demonstrated (2).

Virion Structure

Rhadoviruses typically have a rod or bacillary shape with dimensions of 130-380 x 60-95 nm. They have single, negative stranded RNA genome. The nucleocapsid is infectious. They are sensitive to lipid solvents (1).

Virus enters the body through the bite of an animal. Human rabies takes two forms, furious or irritable rabies and a dumb or paralytic rabies (3, 4).

The paralytic form of rabies in humans is often indistinguishable from that of most viral encephalitides, except for the fact that a patient suffering from rabies remains conscious during the course of the disease (3,4).

Paralytic rabies is less common in humans, this form is thought to be 100% fatal in humans and commonly occurs after being bitten by a bat (4). The bite marks found on the back of this patient resulted in retrospective questioning of the patients relatives. The bite marks on the skin of the patient's back were those of a vampire bat. The patient lived in a palm house and slept on a palm bed (catre). Vampire bats are known to infest this type of living quarters. Although the rabies control program in Mexico requires vaccination of domestic pets, there is no efficient method for controlling enzootic rabies in the vampire bat population. The incidence of rabies in Nayarit is approximately one case per year.

References:

1. Johnson HN, Emmons RW. Rabies virus. Chapter 26 Laboratory Diagnosis of Viral Infection. Marcel Dekker; New York. 1985. pp 425.
   
2. Gonzalez AA. The ultrastructure of Negri bodies in purkinje neurons in human rabies. Neurology (min)1970; 20: 323.
   
3. Heffner RR. Rabies. Pathology of tropical and extraordinary diseases. AFIP 1976. Vol I chapter 7 pp 44.
   
4. Chopra JS, BanerjeeAK et.al. Paralytic rabies a clinico-pathological study. Brain 1980; 103: 789.