Rabies Transmission and Attempts at Control
Rabies is a virus that has a fatal outcome if it is not treated in humans. In the US, most states have laws that make it mandatory to have cats, dogs, and ferrets to be vaccinated for rabies each year. In some cases, they can use the three-year vaccine but the pet needs to receive a booster if they come in contact with a rabid animal.
The rabies virus infects the central nervous system, ultimately causing disease in the brain and later death. This fatal viral zoonotic disease is found in the saliva of rabid animals and usually spread through a bite. It can also be spread through the infected saliva coming in contact with open wounds or mucous membranes.
In humans, the incubation period may last for weeks to months but there is a way to stop this virus in humans by making use of rabies postexposure prophylaxis (RPEP), before the onset of clinical illness. People who have never been vaccinated will require human rabies immune globulin and four or five doses of the vaccine; this is improved from the 17 shots that used to be needed-all given in the abdomen around the belly button.
In Kansas, skunks are the primary reservoirs for ground rabies. This has spillover into other animals and domestic animals as well. A separate rabies virus is also found in the bats. In fact, in US bat-related rabies is the most common virus variant responsible for human cases of rabies. Evaluating exposure to bats and the need for RPEP can be complicated. This is why it is recommended the people consult with state and local health departments (NSSP, 2018).
This study conducted in China found four recipients of organ transplants developed rabies. Rabies is acute and fatal viral encephalitis caused by viruses of the Lyssavirus family. It is acquired from infected animals via bites, scratches or other exposures. The virus attacks the central nervous system. After the brain is infected by the virus then it spreads to the peripheral and autonomic nervous systems, eventually moving on to the glands and organs. The virus claims approximately 59,000 human lives annually; mostly among underserved populations in Africa and Asia.
Of these, 95% of rabies deaths in humans are the result of dog bites. Transmission from infected animals including foxes, raccoons, skunks, jackals or mongoose. Since the development of organ transplantation, transmission of rabies through those transplants has become a notable problem. In the US, in 2004, there were reported three cases of rabies from transplanted organs. Then again, in 2013, another person was reported to have developed rabies from organ transplantation. Since 2015 in China this has become a huge problem. Transmission of rabies through solid organ transplantation is a life-threatening and notable problem.
The mortality rate is extremely high after developing the virus. Serological testing and etiological diagnosis are recommended for donors with a high risk of rabies or clinically suspected of rabies. Organs should be discarded when rabies is confirmed or suspected. This is especially if the donor is diagnosed with encephalitis of unknown cause. And when rabies-infected organs are inadvertently transplanted, recipients must receive PEP in a timely manner. This is only possible and effective method of preventing the transmission of rabies to the recipients (Zhang, J. 2018).
Princeton University has revealed that the rabies virus moves differently compared to other neuron-invading viruses and that its journey can be blocked by a drug commonly used to treat amoebic dysentery. Most viruses only infect the nervous system accidentally when the immune system is compromised. But this study found some viruses have evolved to target neurons as part of the normal infectious cycle. The rabies virus, for example, is transmitted through the saliva of an infected animal. And while rabies infections in the US it has killed over 17,000 people worldwide in 2015. This study investigates how the rabies virus engages the neuronal transport machinery. The researchers infect neurons with a virulent strain with a fluorescent tag so they could track the viral transport in real-time by live-cell fluorescence microscopy. From their study, they found a substance that acts as a protein synthesis inhibitor called emetine efficiently blocked rabies virus transport to the cell body. And because other protein synthesis inhibitors did not, the researchers felt that the emetine works by inhibiting a different process. This substance is usually used with amoebic dysentery. This study and others have shown emetine has anti-viral effects that could inhibit the rabies virus invasion of the nervous system. More research is needed to explore how emetine disrupts the rabies virus (MacGibney, 2018).
Rabies is easily one of the oldest recognized diseases affecting all warm-blooded animals. It is an acute, progressive and almost always fatal form of encephalomyelitis caused by the rabies virus. Rabies occurs in more than 150 countries and territories. Unfortunately, most deaths from rabies occur in developing countries that have inadequate preventative treatment. This is because dog rabies is endemic with a dog to dog transmission then a dog to human from their saliva. Being rabies is a preventable disease some possible disease some possible prevention and control components including making responsible pet ownership, routine veterinary care and vaccination.
Rabies is one of the 17 major neglected tropical diseases. Its control is more difficult because it is a neglected zoonotic disease. The challenges of controlling this disease include the availability of many free-roaming dogs, limited access to control and lack of public and legislative awareness. Rabies can be prevented in domesticated animals by vaccination. And even though historically dogs have been associated with the spread of rabies cats are more often reported as rabid in the US. It is felt because cats come in close contact with rabies. This disease is invariably fatal once clinical signs appear and is of great concern to people having frequent contact with animals such as animal owners and veterinarians (Barecha, 2017).
In 2015 Hamilton Ontario was notified that a locally trapped raccoon was positive for rabies. The raccoon was tested as it had fought two unvaccinated dogs. This was the first case in this area had been documented since 2005. Raccoon rabies first emerged in Florida in the 1940s spreading to the Mid-Atlantic States in the 1970s and has since spread throughout the eastern seaboard of the US. It reached the Canada-US border in the 1990s and first detected in Ontario in 1999.
In Canada, responsibility for rabies control is shared across multiple jurisdictions and reflects a concept that recognizes the relationships between public health, animal health, and the environment. Local public health units are responsible for all activities and providing the PEP as needed. And while the study found the majority of cases were raccoons, they did find some species transmission into striped skunks, as well as some other species including two cats, red fox, and a llama.
And while New York, the problem has been endemic since the late 1990s, the Canadian authorities tested New York states rabies virus and found it was very different from what Canada was dealing with. The study found a great concentration of affected animals located in densely populated urban areas. This made the distribution of oral vaccine baits targeting the wild animals very difficult. In addition, this urban rabies outbreak had a lot of opportunities for species transmission such as dog and cats increasing the risk of transmission to humans.
Initially, the introduction of raccoon rabies into Canada was from across the border with the US; however, further testing proved that the virus around Hamilton was not the same virus. Previous outbreaks have been eradicated from Canada. It is going to take longer as this time it is focused in urban areas but decreasing members being reported is promising (Logo, 2018).
Barecha, C.B.; Girzaw, F.; Kandi, V.; Pal, M. (2017). Epidemiology and Public Health Significance of Rabies. Perspectives in Medical Research, 5(1). http://www.pimc.org.in
Lobo, D. et al. (2018). Raccoon Rabies Outbreak in Hamilton, Ontario: A Progress Report. Canada Communicable Disease Report, 44(5). https://doi.org/10.14745/ccdr.v44i5a05
MacGibney, M.A.; Koyincu, O.O.; Wirblich, C.; Schnell, M.J.; Enquist, L. W. (2018). How Rabies Virus Moves Through Nerve Cells and How it Might be Stopped. PLoS Pathogens,14(7).doi:10.1327/journal.ppat.1007188
National Syndromic Surveillance Program (NSSP)(2018). Kansas Local Health Department Uses Syndromic Surveillance Data to Direct Public Education on Rabies. The community of Practice Updates. https://www.cdc.gov/rabies
Zhang, J et al. (2018). Transmission of Rabies Through Solid Organ Transplantation: A Notable Problem in China. BMC Infectious Diseases, 18(273). https://doi.org/10.1186/s12879-018-3112-y