Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: syhprum on 18/01/2019 11:29:44
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Rabies is one of the most lethal viral infections known is there any treatment on the horizon once symptom show?,
How does it compare with Ebola ?
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Rabies is carried by wild, feral and domestic animals and transmitted to humans through skin-penetrating inoculation (most usually biting or scratching by dogs and cats, and occasionally bats) or mucous membrane contact with body fluids from an infectious case.
The incubation period is quite long, averaging more than a month, during which the virus first replicates at the site of initial infection before it invades the nervous system, first locally and then centrally.
Once the agent gains access to the central nervous system the victim becomes progressively more unwell and dies a short while later. There are almost no survivors. I say almost none, because there are one or two isolated case reports of rabies victims receiving treatment and recovering, although these are definitely the exception rather than the rule. There is therefore no standard, documented management for acute rabies, or any specific antiviral indicated.
However, the long incubation period provides an ample window of opportunity within which to intervene with post-exposure prophylaxis, which is the mainstay of rabies prevention in the UK.
Depending upon prior vaccination status, victims of potential rabies exposure are given a rapid sequence of vaccination which is sometimes accompanied by anti-rabies antibodies (HRIg) designed to mop up virus and block local replication at the exposure site.
Although costly, this strategy is extremely effective and if followed correctly will prevent rabies infection and is widely used in the majority of western countries.
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How does (Rabies) compare with Ebola ?
- Ebola has a much shorter incubation period.
- Ebola causes the blood vessels to become leaky. This is very different from rabies, which affects the nervous system.
- Ebola is easily passed from person to person by bodily contact or contact with body fluids. Rabies requires really close contact (eg biting) for transmission
In terms of re-emergence, rabies is carried by a variety of wild animals in many countries, while Ebola is carried mainly by monkeys in equatorial Africa. so there is a big difference in natural reservoirs.
- Rabies is mostly transmitted by animals biting humans
- Ebola has mostly reappeared when humans bite animals
Lyssavirus is in the same family as rabies, and is carried by bats in Australia. Horses have been infected by eating bat droppings (and some of their human handlers have been infected too).
see: https://en.wikipedia.org/wiki/Rabies
https://en.wikipedia.org/wiki/Ebola_virus_disease
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There is evidence that opening the blood-brain barrier helps increase survival rates of rabies-infected mice: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1951307/
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Are anti-viral drugs any use against rabies?
Viruses are very diverse in their operation, and an anti-viral drug that is effective against one type of virus is unlikely to have any affect on a different type of virus.
For example, there has been considerable success in blocking the spread of HIV in an individual (and the population) by blocking the incorporation of the viral genome in the human DNA, which is in the cell nucleus. (This process is called "Reverse Transcription", because normally DNA is normally transcribed into RNA.)
However, rabies does not use reverse transcription, but it's viral RNA is duplicated in the cytoplasm of the cell, a totally different process.
Undoubtedly, anti-viral drugs could be developed against rabies, but the cost of development would be very high, and the leadtime would be at least 10 years.
See: https://en.wikipedia.org/wiki/Antiviral_drug#Anti-viral_targeting
It may be easier to inoculate pets and humans against rabies - vaccines are already available. Pet vaccination is compulsory in a number of countries where rabies is endemic.
see: https://en.wikipedia.org/wiki/Rabies_vaccine