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Managing Rabies in Humans and Dogs Globally (Epidemiology (Transmission…
Managing Rabies in Humans and Dogs Globally
Epidemiology
Clinical signs
General symptoms start as a feverish illness, followed by itching and burning (if bitten). An over reaction of the autonomic nervous system can then lead to hypersalivation, excessive sweating, hydrophobia and paralysis of muscles. These symptoms can relate to both humans and animals (Kaplan
et al
., 1986)
The rabies virus travels to the brain via the peripheral nerves and multiplies before travelling to the peripheral organs and reaching almost every tissue within the victim's body (Macdonald, 1980)
Transmission
Rabies is not controlled within bats. Can still be transmitted to humans and animals (Macpherson
et al
., 2012)
Total cases of humans transmitting rabies from bats is minimal, apart from vampire bat rabies which is particularly common in Brazil and Peru within the amazon rainforest (Macpherson
et al
., 2012).
Direct contact with infected animal., through either a bite or virus-laden saliva. Other routes of transmission include oral (ingestion), inhalation and other mucosal exposure. Transmission after death is possible (Macpherson
et al
., 2012)
Rabies in wildlife is not as common as in dogs, although plays an important role in the epidemiology and can further the spread. For example in Kirgiz Republic (Central Asia) the red fox is considered a major wildlife reservoir (Sing, 2015).
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Zoonotic. Can be transmitted to any mammal with the major threat to wildlife and livestock. Also present in the bat population (Hampson
et al
., 2008).
Incubation period
On average clinical signs will show around 37 days. However this is an average and can be anywhere between 4 days and 200 days (Li-mei
et al
., 2006)
Diagnosis
In humans a fluorescent antibody test will determine if the viral antigen is present, however rabies is often diagnosed from its clinical symptoms, especially with the history of an animal bite or absence of vaccination (Menezes, 2008)
Post-mortem diagnosis:
The viral antigen can be detected using a Direct Fluorescent Antibody test on brain biopsy, corneal touch impressions or a full thickness nuchal skin biopsy from the hairy nape of the neck, for examination of Negri bodies (Madhusudana and Sukumaran, 2008)
In dogs a latex agglutination test can be carried out using saliva, this is a quick and cost-effective method that can be carried out before death (Kasempimolporn
et al
., 2000)
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There are seven genotypes of the lyssavirus, the majority occur within the canine species and wildlife in Africa and Asia. Some are being maintained in bats throughout Australia and Europe (Macpherson et al., 2012).
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Treatment
No treatment. Cull the animal and dispose of effectively to prevent further spread. Death will occur within 1-5 days without intensive care and is inevitably fatal (WHO, 2005)
:check: All dead animals must be incinerated in order to prevent further spread after death (Garg, 2013)
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Isolation of dog until further testing confirms rabies virus. Can be confirmed by fluorescent antibody testing, rabies tissue culture test or by a hemi-nested reverse-transcription PCR (Whitby
et al
., 2000)
:green_cross: In some cases culling positive animals has not proved effective, which may be due to the virus still transmitting from a dead animal (WHO, 2005)
Post-exposure prophylaxis can prevent the onset of rabies in humans, therefore if bitten or scratched from an animal in Africa or Asia the patient should seek medical help immediately, as rapid diagnosis is essential to prevent the spread throughout the body (Hampson
et al
., 2008)
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This involves local wound treatment, passive immunization with rabies immunoglobulins and active immunization with rabies vaccine (Madhusudana and Sukumaran, 2008).
Post-exposure prophylaxis has proved costly, therefore by preventing the risks of contracting rabies will reduce the use of post-exposure prophylaxis (Dessain, 2008)
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Prevention and Control Methods
Control of Wildlife
:green_cross: Elimination of bat rabies is not possible due to the widespread of it, eliminating this would have a dramatic effect on their global ecology including seed dispersal, pollination and arthropod predation (WHO, 2005)
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Although the consequences may be severe, any method that indiscriminately destroys bats should be avoided, they are also protected in a lot of countries, therefore an alternative control method may prove difficult, therefore should instead focus on preventing its spread to humans by vaccinating those at high risk (WHO, 2005).
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Control of wildlife rabies can be done by hunting, poisoning, quarantine, vaccination or topography (Macdonald, 1980)
:green_cross: Controlling rabies in the wildlife populations has proved ineffective and costly in some countries. Where Denmark spent £80,000 in control of rabies in wildlife, although treatment would mean extermination of an animal species in a large territory (Macdonald, 1980).
:check: Studies have shown success in conducting bait vaccinations within wildlife to control the spread of disease throughout wild animals, however could prove costly and it is difficult to determine which have had the vaccination without causing further stress to the animal (Holmala and Kauhala, 2006)
To promote the success of this programme long term it should consist of two phases, the elimination phase and the maintenance phase. After mass vaccinating, the maintenance includes general surveillance and monitoring of neighbouring areas (WHO, 2005)
An attractive bait method can also help trained professionals to carry out a routine check for clinical symptoms (WHO, 2005)
DEFRA current plan
Due to being a notifiable disease there current plan would involve eradicating the disease, protect public health and safety, safeguard the health of those directly involved, minimise the burden of the tax payer, keep animals destroyed to a minimum and minimise adverse impacts on animal welfare (DEFRA, 2014).
Use of Vaccines
:green_cross: After vaccination some pets may not show the full antibody titre adequate to meet the UK Pet Travel Scheme. Therefore could be at risk of contracting rabies (Mansfield
et al
., 2004)
:check: It is recommended that the titres of neutralising antibodies in all immunocompromised, rabies exposed patients determined 14 and 28 days after vaccination to ensure an adequate response. Therefore should also be carried out on pets if departing to a country where rabies is endemic (Thisyakorn
et al
., 2000).
:green_cross: In some cases developing countries are using nerve tissue vaccinations as post exposure treatment for rabies due to its low cost. However studies have showed that this type of vaccine will only prove effective on around 35% of people (Tantawichien, 2001).
:check: The use of cell or avian cultured vaccines is recommended by the WHO, this is due to them generally being well tolerated , where chances of neurological problems arising are rare and any reactions are easily managed (Tantawichien, 2001).
:check: By setting up a mass vaccination programme of dogs for developing countries funded by charities and funding agencies then humans and dogs are more likely to get vaccinated (Hampson
et al
., 2015)
:check: A mass vaccination programme in dogs has previously been effective in decreasing mortality rates in both humans and canines (WHO, 2014).
:check: Oral vaccinations have proved the most effective method for vaccinating stray dogs, due to their lack of interaction with humans (WHO, 2005)
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:check: Strict licensing and vaccination of pets could prove an effective method to prevent further spread (Menezes, 2008)
:check: This would not tackle the over population of feral dogs, therefore a trap neuter vaccinate programme could be implemented which will have a long term affect on feral dog populations and the incidences of canine rabies (Matter
et al
., 2000).
Thailand implemented a trap, neuter and vaccinate programme which did not prove as successful as hoped due to the lack of veterinary professionals available, however it has proven successful in other countries when the sources were available (Jackman and Rowan, 2007).
Developing countries
:check: Setting up educational programmes, particularly in developing countries could promote dog ownership and raise awareness of preventing the on set of rabies with post exposure prophylaxis and prevention, including wound care and vaccinations (Menezes, 2008)
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:check: In many countries rabies is not a notifiable disease, by making steps to make this notifiable it may prevent further spread when symptoms arise (Menezes, 2008)
This will require the help of major stakeholders such as the FAO, OIE and WHO. Funding may also be available from the Global Alliance of Rabies Control (WHO, 2014)
Cost Value
Globally canine rabies causes approximately 59,000 human deaths and over £6.8 billion in economic losses (Hampson
et al
., 2015)
:green_cross: Between 1996 and 2008 human rabies was becoming more prevalent in China. Although it is not a developing country, it was found that this link was highly related to canine rabies and mass population. The rate of tranmission was at a fast rate due to the free roaming of dogs where approximately 70% weren't vaccinated against rabies (Song
et al
., 2009)
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:check: By using more preventive methods for the developing countries, the incidences and economic losses could be reduced dramatically on a global level (Davlin and VonVille, 2012)
Further spread to livestock will bring further financial loss. Therefore must control the spread throughout wildlife (Meltzer and Rupprecht, 1998)
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:check: Protect livestock to prevent further economic loss by vaccinating and appropriate use of fencing to prevent exposure to wildlife (Menezes, 2008).
:green_cross: Vampire bat rabies has led to higher livestock mortality rates in Mexico, however bat control is not possible, therefore vaccination of livestock can prevent further financial losses (Anderson
et al
., 2012)
:check: By increasing the use of vaccines it can prevent the costs and use of post-exposure prophylaxis by up to 84% (Quiambao
et al
., 2005)
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Africa and Asia lose livestock productivity due to contracting rabies from dogs. They lose the equivalent of £9.3 million a year (WHO, 2005)
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The current canine rabies vaccination prices are $20 in the USA, $0.52 in Thailand, $1.19 in Philippines and $2.70 in Malawi. Some owners may not see the vaccination as an essential and therefore would rather save their money (Meltzer and Rupprecht, 1998)
Environmental Needs
The rabies virus is inactivated by elevated temperatures, UV light, detergents, organic solvents and at extreme pH levels, therefore the organs of rabies positive animals become inactivated within a few days (Macpherson
et al
., 2012)
Due to developing countries having the majority of dogs as strays rather than companions, this means the stray dog population is increasingly growing along with the rate of rabies transmission between dogs (Matter
et al
., 2000).
:green_cross: Euthanise feral dogs could act as a solution, however this could raise ethical considerations. Many of these programmes have been unsuccessful due to complaints from animal welfarists and around 80% of feral population would have to be euthanised before it takes an effect (Menezes, 2008)
:green_cross: Large scale culling campaigns have proved difficult due to human, ecological and economical aspects (WHO, 2005)
:check: Alternative to euthanising, is mass vaccination and implimenting a neutering programme to control the feral dog population. Although similarly, this has to be carried out on 70% of the feral population before it will have an effect (Menezes, 2008)
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:green_cross: Developing countries have a severe lack of veterinary sources, along with epidemiological restraints and insufficient knowledge (Bogel and Meslin, 1990).
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:green_cross: Habitat destruction and extermination has been used previously for stray dogs but has proved less effective and a threat to the public (Dessain, 2008)
Children under 15 years of age are most likely to contract rabies, due to more interaction with animals (WHO, 2005)
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:check: The UK currently has a Pet Travel Scheme where all pets must be vaccinated against rabies using an inactivated vaccine or recombinant vaccine that is approved in that country of travel. The scheme has proved effective in keeping the UK free from rabies (DEFRA, 2017)
:check: Limiiting animal restrictions to and from specific countries where rabies is endemic, especially Africa and Asia (Machperson
et al
., 2012)
:green_cross: Although limiting animal restrictions may not be effective in all cases. Where in 1998 20 people caught rabies after returning from Africa, therefore must implement a safe human movement method (Peigue- Lafeuille
et al
., 2004)
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:check: If travelling to a country where rabies is endemic, vaccination should be essential (Menezes, 2008)
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May lead to a bad reputation of a country if a controlled disease breaks out. Including trustworthiness, stakeholder relationships and lower population levels (Cairns
et al
, 2013)
Risks to public health
:green_cross: Vaccinations for dogs and humans rarely used. More commonly used if animal is travelling and with veterinarians and laboratory workers (Davlin and VonVille, 2012)
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In 99% of cases of human rabies was transmitted by a dog, therefore by decreasing incidences in dogs this will decrease the incidences in humans (WHO, 2005)
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Transmission can still take place with a dead animal, laboratory workers at risk from infection from tissues of infected animal. Also at risk includes rabies researchers, those who work in vaccine production, responsible authorities and owners of rabies-positive animals (Macdonald, 1980)
:check: All laboratory workers that may come in contact with the rabies virus must wear personal protective clothing and have a pre-exposure vaccination (WHO, 2005)
:check: Hospital staff should wear gowns, goggles masks and gloves when dealing with a patient with suspected rabies. They should have a pre-exposure vaccination and strictly barrier nurse (WHO, 2005)