RABIES: AN OVERVIEW

~Dr. Pallabi Thakuria, Dr. Biraj K. Sharma, Dr. Anjan Jyoti Nath and Dr. Mousumi Hazarika and Dr. Dhirashree Choudhury.

     Rabies is a vaccine preventable zoonotic viral disease which occurs in more than 150 countries and territories. Every year almost 59,000 people die and more than 150 million people worldwide receive post-bite vaccination, the major cause of transmission(99%) for which is considered to be dogs (WHO, 2018), apart from which the other major reservoirs being bats, raccoons, skunks, and foxes. Almost 95% of human deaths due to rabies are accounted for in Asian and African regions. Yet, in recent times, India seems to have accounted for fewer human deaths, as the total sum up of human deaths (2014, 2015 and 2016) due to rabies as per the figures given by Union Health Ministry and published by the Times Of India in 2017 was 324, which might be due to prolonged Animal Birth Control programmes and other vaccination programmes.
Transmission:
Rabies virus i.e,lyssavirus are highly neurotropic and transmission almost always occurs via introduction of virus-laden saliva into tissues, usually by the bite of a rabid animal(Merck Veterinary Manual, 11th ed). This virus is also reported to transmit via licking, in case of open or punctured skin, through scratch or even through intact mucous membranes, whereas there is no evidence of hematogenous spread and very rare reports of aerosol transmission. Reports prove that the virus has got a long incubation period, one recorded case in USA having an incubation period of more than 8 years and another case in India having an incubation period of 11 years.
Clinical signs: Clinical signs are variable, although CNS signs are common in almost all species.

Some of the common clinical signs are:
a) Dogs:
(i) Prodromal period: it lasts for 1-3 days, where animals show only vague nonspecific signs, which intensify rapidly.
(ii) Furious form: this symptom is also known as the ‘mad-dog syndrome’. In this stage, the animal becomes highly aggressive and is easily provoked. The animal remains alert and anxious with pupils dilated and noise may invite attack. The dogs suffering from this form of rabies if roaming freely, attacks other animals or humans without provocation and becomes a major cause of transmission of this disease. They commonly swallow and chew foreign objects and frequently attempts to bite. There are prominent vocal changes (eg. hoarse barking or growling sounds).Young pups often seek companionship and attempt to bite when petted. In an episode lasting about 10 days, the dog will develop dyspnea, ascending paralysis, coma leading to death.
(iii) Paralytic form: This sign is manifested by profuse salivation and inability to swallow due to paralysis of throat and masseter muscle. A common sign in dogs is dropping of the lower jaw. In this form, dogs are not vicious and rarely attempt to bite. The dog used to seek solitude and appear sluggish and morrosed.The paralysis progresses to all parts of the body and it may progress to coma and death.

b) Cattle: Cattle with furious rabies tends to attack other animals and humans and there is abrupt cessation of lactation in dairy cattle. The animal remains quite alert and there is a characteristic abnormal bellowing intermittently till death.

c) Humans: The clinical signs in humans are principally manifested in two ways:
i) Furious (classical or encephalitic) form: it is considered to be more common with almost 80% of the total number of human cases, the signs mainly manifested being hyperactivity, hypersalivation, hydrophobia and sometimes aerophobia. Death usually occurs after coma due to cardio-respiratory arrest.
ii) Paralytic or dumb form: this form runs a longer course and is less common. There is
gradual paralysis followed by coma and death.

Treatment:
According to WHO, prompt local treatment of all potentially contaminated bite wounds and scratches with immediate, thorough flushing and washing of the wound for a minumum of 15 minutes with soap and water, detergent, povidone iodine or other substances with virucidal activity is an effective means of protection. If there are any wounds, they are not suggested to be sutured within 24 hours of bite, as it may produce additional trauma and give the virus access to deeper tissues.

The recommended post-exposure prophylaxis depends on the category of exposure to suspected or confirmed rabid animals as given below:
Category of exposure to suspect rabid animal Post-exposure measures
Category I – touching or feeding animals, licks on intact skin (i.e. no exposure) None
Category II – nibbling of uncovered skin, minor scratches or abrasions without bleeding Immediate vaccination and local treatment of the wound
Category III – single or multiple transdermal bites or scratches, licks on broken skin; contamination of mucous membrane with saliva from licks, exposures to bats. Immediate vaccination and administration of rabies immunoglobulin; local treatment of the wound

Post exposure prophylaxis:
The general post-exposure prophylaxis followed in dogs is post bite vaccination schedule of 0,3,7,14 and 28 days. The efficacy of two commercial vaccines given intramuscularly according to this schedule has been reported by Manickama et al., (2008). Other reported post-bite vaccination schedules are-0,3,7,14 and 35 (Hanlon et al., 2002) and 0,3and 35(Manickama et al., 2008). Also, the use of immunoglobulin and monoclonal antibody (mAb) have been reported in dogs by Hanlon et al., (2002), who used purified heat treated equine rabies immunoglobulin and mAb along with vaccines.
In cattle, post-bite vaccination schedule of 0,3,7,14,28 and 90 days proved to be effective in controlling rabies (Basheer et al., 1997). With regards to eliciting satisfactory immune response to protect animals exposed to virulent rabies virus, tissue culture rabies vaccine was found to be superior to nervous tissue vaccine.
In case of humans, if there is a wound of category III exposure, administration of rabies immunoglobulin (RIG) to the wound is of utmost importance (WHO, 2014). The RIG is infiltrated around the wound as much as possible and remaining is injected intramuscularly away from the vaccine inoculation site. If RIG is not currently available, there can be a delay of maximum of 7 days from the first dose of vaccine administration. The post-bite vaccination schedule most commonly followed is 0,3,7,14 and 28.

According to Centres for Disease Control and Prevention,
a) if an animal exposed to rabies has an up to date vaccination schedule, the post bite vaccination schedule is to be followed and the animal should be observed for 45 days.
b) on the other hand, if an animal has never been vaccinated against rabies, it should be euthanized immediately by a licensed animal health professional. If the owner is unwilling to euthanize the animal, post-bite vaccination schedule is to be followed and the animal is to be kept in quarantine and under observation for 4 months in case of dogs and cats and 6 months in case of livestock.

Prevention:
i) Pre-exposure prophylaxis (PrEP): it is recommended for anyone who is at continual, frequent or increased risk for exposure to the rabies virus, as a result of their occupation or residence. One intramuscular dose is administered to humans on days of 0, 7 and 21 or 28. In case of dogs, the first vaccine is usually started at the age of 12 weeks.

ii) Vaccination of dogs: Different case studies have demonstrated that mass vaccination
of dogs have reduced both human and canine rabies cases. OIE suggests mass
vaccination of dogs including oral vaccination as the effective way to control rabies.
Moreover, public health information campaigns and the access of improved
human medical care are also suggestive factors for controlling rabies and human
deaths.

iii) Animal Birth Control: The Animal Birth Control programme under Animal Welfare
Board of India has been quite successful in controlling the rabies menace. Also, the
British-funded non-profit Mission Rabies project has vaccinated more than 2,65,000
dogs in India.

The recent strategy with regards to rabies is to reach ‘Zero by 30’, which is the strategic plan taken together by OIE, WHO, FAO and GARC to eradicate rabies by 2030.

Source: OIE

Some of the objectives undertaken by FAO to reach the global goal of eradication of rabies are:
1. Support massive dog vaccination campaigns
2. Promote responsible dog ownership
3. Support response to rabies outbreaks
4. Awareness
5. Promote the use of existing tools (SARE, DGREP) and OIE vaccine bank
6. Contribute to designing and implementing M&E activities
7. Support capacity building on rabies surveillance
8. Support the preparation and implementation of vaccine pilot plans in “FAO GHSA countries” as a follow up of national stakeholder meetings
9. Support governments (esp. non FAO GHSA countries) for resource mobilization
10. Sensitize donors and the private sector
11. Participate in M&E activities

Thus, we can strive towards making India rabies free by spreading awareness
of rabies amongst masses and encouraging people for responsible ownership of pets.

References:
Basheer, A.M., Ramakrishna, J and Manickam, R. (1997). Evaluation of post-exposure vaccination against rabies in cattle. The New Microbiologica. 20(3): 289-94.
Hanlon, C.A., Michael Niezgoda, M.S and Rupprecht, C.E. (2002). Post-exposure prophylaxis for prevention of rabies in dogs. AJVR. 63(8): 1096-1100.
Manickama, R., Basheer, M.D and Jayakumar, R. (2008). Post-exposure prophylaxis of rabies-infected Indian dogs. Vaccine. 26(51): 6564-8.

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AUTHORS: Dr. Pallabi Thakuria, Dr. Biraj K. Sharma, Dr. Anjan Jyoti Nath and Dr. Mousumi Hazarika and Dr. Dhirashree Choudhury.
Lakhimpur College of Veterinary Science, AAU, Joyhing, North Lakhimpur

Editor’s Note: Republished from the Compendium on Rabies Awareness Week, held at LCVSc, AAU, Joyhing on 22-28 Sept, 2018, with due consent from the author.

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