RABIES VIRUS / LYSSAVIRUS GENOTYPE 1
The virus isolated from an infected animal is named street virus : it has a very long incubation period and replicates also in extranervous tissues. After multiple passages on rabbit brain ("fixation") it becomes a fixed virus / virus fixé (remain fixed during further transmission; used for inoculating animals from which rabies vaccine is prepared), with a 4-7 days incubation period and replicating only in nervous tissues.

Table of contents :


  • Epidemiology
  • Proteomics
  • Transmission
  • Pathogenesis
  • Symptoms & signs
  • Laboratory examinations
  • Prevention
  • Therapy
  • Prognosis
  • Web resources

  • Epidemiology : mortality worldwide is estimated to be 40,000-70,000 people annually, half of which are in childrenref

    In a 1995 PAHO document vampire bat rabies (derriengue) is identified as an important public health and economic concern in Latin America, French Guinea, Guyana, Suriname and Trinidad and Tobagoref. From 1989 to 1995, 73 human deaths were attributed to rabies transmitted by vampire bats. It is likely that both vampire and insectivorous bats play a role in the maintenance of rabies infection in Venezuela and in other Latin American countries. The increased number of human attacks may be linked to a change in the bats' migration pattern due to deforestation : such attacks usually occur when bats are deprived of their usual source of food, such as domestic pigs and cattle. Elsewhere (Australia, Chile, Europe, and North America), insectivorous bats are usually associated with transmission of rabies virus to humans. Vampire bats pose a significant problem also in the remote Mosquitia area of Honduras and Nicaragua, especially in the middle and upper ranges of the Coco River. Children represent 60-70% of the cases; most common sites affected were the great toe, the foot, the scalp and the tip of the nose. This empirical observation seems to contradict some studies that have shown increased vampire bite prevalence in adult (mostly male) humans. The discrepancy could be due to a number of reasons, including the demographics of the population studied (some of these surveys have done in mining areas of the Brazilian and Venezuelan Amazon region, where the population at risk would be expected to be predominantly adult and male); the food-seeking behavior pattern of the animals, which locate and recognize their hosts by detection of radiating body heat by means of special receptors in their noseleaf, as well as by the sense of smell and by echolocation: perhaps young children, having higher metabolic rates than adults, present an easier-to-find source for a bloodmeal. Children also have a thinner corneal layer in their epidermis and more superficial and larger number of capillary vessels in their skin, all of which would make the bite more "productive" from the bat's perspective. Lastly, there could be differences in bloodmeal-seeking behavior between northern (e.g. Central American) and southern (South American) bats, even belonging to the same species (probably the common vampire, Desmodus rotundus). Finally, it is important to remember that most people (adults or children) do not realize they have been bitten until they wake up then next morning, usually with a moderate amount of blood surrounding the lesion, due to the anticoagulant effect of the bat's saliva. Vampire bats bites are typically painless, and one wonders if, in addition to the known anticoagulants, the animal's saliva also contains some compound which acts as a form of topical anestheticref1, ref2, ref3
    Proteomics : Transmission : Pathogenesis : replication in skeletal muscle cells (Negri bodies) => peripheral nerves => salivary glands, pancreas and adrenal glandsref. Rabies did not permanently damage any brain structure. Instead, death comes because the virus seems to cause temporary dysfunction of brain centers that control critical functions like breathing and swallowing.
    => rabies (a.k.a. lissa in Italy) after > 10 days (one reliably recorded case of rabies in a human had an incubation period >6 years) : the development of rabies generally takes 10 to 90 days when the virus is transmitted through a biteref. Laboratory examinations : antemortem diagnostic samples consist of a full-thickness skin biopsy (4 to 6 mm in diameter) from the nape of the neck, fresh saliva, serum, and CSF. Although postmortem rabies diagnosis can be performed on formalin-fixed brain material, fresh brain material provides the optimal sample for maximum sensitivity, specificity, and time efficiency. Rabies virus antigen is detected by a modification of the direct fluorescent antibody testref
    Preventionref : Therapy : behavioural or histopathological examination of the vector for > 10 days, cleaning wound with water & soap, ethanol 40-70%, benzalchonium chloride 0.1%, therapeutical killed vaccine. The approach to management of the rabies normally should be palliative. In unusual circumstances, a decision may be made to use an aggressive approach to therapy for patients who present at an early stage of clinical disease. No specific course of treatment for rabies in humans has been demonstrated to be effective, but a combination of treatments, which might include killed rabies vaccine, homologous immune antiserum, monoclonal antibodies, ribavirin, IFN-a, or ketamine, has been proposed. Corticosteroids should not be usedref.
    Prognosis : historically, the mortality rate among previously unvaccinated rabies patients has been 100% once symptoms developref. Only 6 cases of human recovery after rabies infection and onset of symptoms have been described : Web resources : RABNET at WHO

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