The Transmission and Transfer Process and Effects the Rabies Virus Has on Humans By: Heather Totheroh May 17, 2011 ABSTRACT: The rabies virus has many factors that set it apart from other viruses. Though the effects may be similar to other viruses in the beginning stages of development, this proves to be a deadly virus. Rabies virus is transferred from the saliva of a host through broken skin via a bite or in contact with a mucous membrane. From the infected site, the virus then makes its way to the Central Nervous System and eventually to the brain where it begins to destroy the host body while this parasitic virus thrives. Unfortunately, by the time the virus reaches the brain the immune system is too far behind to catch up with a response to stop the virus from taking over the body. Infection of the rabies virus results in overswelling of the brain, or encephalitis, which is fatal. INTRODUCTION: The Rabies virus is part of the Lyssavirus genus and the Rhabdovirdae family (Tortora, 622). Rabies virus is transferred from carnivore hosts and the virus attacks the central nervous system (CNS), eventually targeting the brain. Although the exact effect the rabies virus has on the neural cells is still unknown by researchers, through lab experiments, we can deduce once the viral infection reaches the brain the symptoms from the rabies virus will begin. However, the pathway the virus travels to the brain is clear. The virus affects the human body in five stages, or phases, inevitably ending in death, except in rare cases. We need to continue to study and research the methods the rabies virus targets the neurons so we can learn how to stop the transmission of the virus through out the body. I became interested in the rabies virus out of curiosity. I never really understood what caused rabies and what impacts it has on the world. Through this research paper I have learned that this is a deadly virus that can affect domestic animals as well as even humans. I now know why my own pets get vaccinated each year, to prevent them and my own family from being exposed and eventually dying from this fatal disease induced virus. DISCUSSION: Rabies is a deadly viral infection that is passed on from host to host. Once exposed to this “bullet-shaped enveloped” (Barlough, 1) virus, rabies works its way from the exposed site to the nerves and then to the central nervous system by “binding of its external glycoprotein to cellular receptors” (Ugolini, 3). This virus has the ability to get past the innate immune response system not because its ability to “shut off of host gene expression,” but because of its P proteins on the outer shell that inhibits the production of the innate response gene (Finke, 5). The “mutant strains develop rapidly” making it hard for immune responses to catch up with the virus (Tortora, 622). From there the virus can travel up the nerves to the spinal cord and into the brain. Rabies then begins to infect various tissues of the brain and other organs. In most of all cases reported, death is inevitable. http://spot.pcc.edu/~jvolpe/b/bi234/lec/11_viruses/images/fig13.5d_RabiesVirus.jpg The transmission of this fatal virus has various options from host to host. In “Rabies in Animals and Man” research has proved that the most common transmission method of the rabies virus “to man and domestic animals is undoubtedly by the bite of a rabid animal” (West, 90). Because the virus is contained in the saliva of a rabid animal, the puncture from the bite gives the virus direct access to the body of a new host. The saliva of a rabid animal is the vector that we need to watch out for. One way that humans can be infected with the rabies virus is not only by a bite to the skin, but a lick on any part of the body where the virus can come in contact with a “mucous membrane” (West, 91). The rabies virus is able to “penetrate intact mucous membrane” which includes areas of the “mouth, lips, nose, eyelids as well as the digestive tract” (West, 91). There have been reported cases of humans getting infected by the virus simply because a rabid dog licked a man’s face. Also, eating contaminated “meat from a carcasses’ of rabid animals” has also shown to infect the next hosts (West, 92). There have even been some reported cases where people have been infected with rabies by exploring bat infested caves. The rabid bats transmitted the virus through “aerosol transmission” from their saliva, breath, or urine that was then inhaled by the explorers, where the virus then developed in their “lungs and trachea” (West, 94). In some cases, Rabies can be a latent response and be passive until a trigger such as stress activates the virus (West, 95). This type of infection normally only occurs when the amount of transmitted virus was in low concentration (West, 95). In 1971, there was no evidence that the rabies virus transmission could occur from insects to mammals or birds according to West (97). By being aware of the ways of transmission of the rabies virus we can protect ourselves early before the virus carries on its pathway to killing us. As previously state, the rabies virus targets the CNS and the Brain. This disease, rabies, “almost always results in fatal encephalitis” or swelling of the brain (Tortora, 622). So how is it that this virus can cause those infected to die from encephalitis from just a single bite? The pathway by which the rabies virus travels is vaguely understood, but the basics can be examined in Tortora’s book “Microbiology. An Introduction”. Here, he displays that the first step of the pathology of a rabies infection is that “the virus enters the tissue from saliva of a biting animal” (Tortora, 623). Through fluorescent microscopy researchers discovered the virus gathers in “in regions of high density acetylcholine receptors” (Burrage, 1). The frequency of human’s being infected with the rabies virus normally happens from dogs. Unlike other opportunistic pathogens, rabies then “multiplies in skeletal muscle and connective tissue” and because this virus is transmitted in such low doses, there are not enough signals to trigger the immune system to attack the intruder (Tortora, 623). Also, while most virus and bacteria enter into the bloodstream or the lymphatic system, the immune system can access these pathogens easier. But, because the rabies virus is harvested in the muscle tissue, the immune system cannot recognize it as easily. Once the virus has multiplied, it moves through the tissues at about “15 to 100 mm per day”, “up [the] peripheral nervous system to CNS” (Tortora, 623). When the rabies virus reaches the nerves the immune system can not access the virus until it begins to damage the CNS by which time an immune response is “belated and ineffective” (Tortora, 623). Rapidly the virus shoots up the spinal cord until it reaches the brain. Once in the brain, the infection of the virus triggers the onset of symptoms, one of them being encephalitis. The viruses last location in this host is located in the victims “salivary glands and other organs” (Tortora, 623). The next step in the transfer process is from host to host and the cycle re-circulates. The pathway the rabies virus takes effects the host in multiple ways. http://alternativehealthcarenews.blogspot.com/2010/01/fitness-tips-facts-rabies-virus.html The effects the rabies virus has on the body causes various symptoms once it enters the brain. A host that is infected can expect these symptoms and can be categorized in five separate stages. Each stage contains particular symptoms. The first stage is the incubation phase (Tortora, 623). This is after the host has been exposed to the rabies virus. There are no symptoms in this stage because the virus not in the brain yet. The length of the incubation period varies depending on the location of the exposed site (Barlough, 1). The closer the site of the bite is to the CNS the shorter the incubation stage. The next stage of effects is the “prodome” or prodomal meaning beginning symptoms of a disease (Department of Health Services [DHS], 3). In this clinical phase of the rabies virus symptoms consist of “nonspecific” symptoms like fever, fatigue, headaches, nausea, and sore throat (DHS, 3). The next phase that follows the prodomal stage is “acute neurologic period” (DHS, 3) that can result in “alternation between periods of agitation and intervals of calm” (Tortora, 3). While the rabies virus is attacking the CNS system in this acute phase, hosts can feel anxious and hallucinate while also having trouble swallowing. This is when the “spasms of the muscles in the mouth and pharynx” begins and are onset by stress of swallowing water. “The mere sight of water can set off the spasms” a severe case of hydrophobia. The rabies virus has now reached the salivary glands, causing them to over-salivate so they can jump to the next host easier, hence the phrase associated with rabies: “foaming at the mouth”. The fourth stage of effects the rabies virus has on the host body is a coma. The coma can last for “hours to months” (DHS, 3). This eventually results in the fifth stage of death caused by encephalitis. Except for the one rare case that Carly McCready will discuss, rabies is 100 percent fatal once symptoms begin. The fatal disease caused by the rabies virus still has a lot of wholes and gaps in understanding that researchers need to continue to try and solve. By learning more about the transmission and transfer process of this disease we can recognize rabies in the early stages of development so hopefully we can stop the virus before it kills more hosts. LITERATURE CITED: Barlough, Jeffrey E., Fred W. Scott, and James R. Richards. "Rabies." Welcome To Max's House Animal Rescue - Feline Health, Behavior & Nutrition. Web. 16 May 2011. <http://maxshouse.com/rabies.htm>. Burrage, TG, GH Tignor, and AL Smith. "Rabies Virus Binding at Neuromuscular Junctions." NCBI. PubMed, 1985. Web. 15 May 2011. <http://www.ncbi.nlm.nih.gov/pubmed/3890406>. Finke, Stefan, and Karl-Klaus Conzelmann. "Replication Strategies of Rabies Virus." Virus Research 111.2 (2005): 120-31. Science Direct. 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