FAQs ON RABIES (1-155) FOR VETERINARIANS
by-DR RAJESH KUMAR SINGH ,JAMSHEDPUR,JHARKHAND, INDIA,
9431309542,rajeshsinghvet@gmail.com
All veterinarians, from those who work with farm animals to pets to wild animals, play a crucial role in protecting human health as well by managing crises such as diseases and zoonoses and foodborne diseases. Cross-border collaboration, communication and cooperation between veterinarians, represented by various vet org, and the various animal and human health-focussed agencies and industries they work with, such as the OIE, FAO and WHO, are important parts of global health initiatives-ONE WORLD ONE HEALTH..
The work these veterinarians undertake has been integral to the containment and eradication of several major diseases that have harmful effects on both human and animal health. One of the most well-known cases is rabies, which can be deadly in both humans and animals. The responsibility for controlling rabies and preventing transmission of this deadly viral disease is associated with vets. Vets are being asked several questions from the common people of society about Rabies.By providing detail knowledge about rabies , we can make our people aware about the deadly Rabies. On the occasion of the WORLD RABIES DAY i.e 27TH OCTOBER , I thought to post some most crucial informations which are not only useful to common people but also to vets.In this post I have compiled 155 faqs on behalf of common people from vets, It is not possible to post all at a times so it will be posted subsequently.
1.What is Rabies?
• Rabies is acute viral encephalitis caused by a RNA virus (Genus: Lyssavirus, Family: Rhabdoviridae). The genus name derives from lyssa, the Greek goddess of frenzy. The virus is bullet shaped and can be seen through an electron microscope only. Rabies is a zoonotic disease (i.e., transmitted by animals) that affects all mammals and is endemic in India.
2.Why is Rabies an important disease?
• Rabies is one of the oldest and most feared zoonotic diseases, and has been a threat to human health for more than 4000 years. Rabies is a neglected and severely under-reported disease killing each year worldwide (WHO 2007) an estimated 55,000people (24,000 to 90,000 deaths). All mammals, but mainly carnivores and bats, are susceptible and can transmit rabies virus. Human exposures are most frequently associated with bites by rabid dogs and transmission of virus from dogs’ saliva. The Association for the Prevention and Control of Rabies in India (APCRI) estimated in 2004 that in India, there were 20,565 reported human deaths every year. Rabies is practically 100% fatal even today but easily preventable.
About half of the world’s population lives in areas in which rabies is enzootic.
3.What are the important features of Rabies Virus?
• The virus is bullet shaped and can be seen through an electron microscope only. These viruses have a phospholipids envelope with glycoprotein surface spikes and a negative polarity strand; single chain RNA. The rabies virus genome encodes five proteins: the nucleoprotein, the matrix protein, the glycoprotein, the phosphorylated protein and a large polymerase protein.
The existence of lyssaviruses that are closely related to rabies virus and that can also cause clinical disease (Duvenhage virus, Lagos bat virus, Mokola virus, Shimoni bat virus, and Ikoma virus) has been known for several decades.
4.What is a street virus?
• Street virus is a type of rabies virus which is virulent, having a long and variable incubation period of about 3 weeks to 3 months.
When first isolated from natural human or animal hosts, rabies virus preserves its natural properties and is referred to as street virus. Most of the street virus isolates generally cause a lethal CNS infection.
5.What is a fixed virus?
• It is a rabies virus that has been passaged in tissue culture or animals. The term fixed indicates only that the incubation period and virulence has been stabilized. It is least virulent, and has a fixed short incubation period of 5-9 days. It is used as seed
6.How can rabies virus be inactivated?
• Rabies virus is inactivated:-
(1)By heat (1 hour at 50°C)
(2)On exposure to ultraviolet radiation
(3)By exposure to 70% ethanol, phenol, formalin, trypsin, ß-propiolactone
(4)Detergents
(5)By lipid solvents
(6)At pH below 3 or above 11
(7)Rabies virus is inactivated rapidly in sunlight and does not survive for long periods out of the host (in dried blood and secretions) as it is susceptible to sunlight and desiccation
(8)X-rays
7.Is rabies virus resistant to anything?
• Rabies virus is resistant to cold and freeze drying.
8.Are there any survivors of human rabies?
• Till date only seven survivors have been recorded. These patients survived not due to any specific anti-rabies therapy but following intensive life support and excellent nursing care. These patients survived for variable periods with residual neurological deficits. All the survivors had paralytic form of rabies and majority had history of some anti-rabies vaccination in the past
9.Name rabies-free countries
•
REGION COUNTRIES
Africa Cape Verde, Libya, Mauritius, Réunion, São Tomé and Príncipe, and Seychelles
Americas North: Bermuda, St. Pierre and Miquelon
Caribbean: Antigua and Barbuda, Aruba, The Bahamas, Barbados, Cayman Islands, Dominica, Guadeloupe, Jamaica, Martinique, Montserrat, Netherlands Antilles, Saint Kitts (Saint Christopher) and Nevis, Saint Lucia, Saint Martin, Saint Vincent and Grenadines, Turks and Caicos, and Virgin Islands (UK and US)
Asia and the Middle East Hong Kong, Japan, Kuwait, Lebanon, Malaysia (Sabah), Qatar, Singapore, United Arab Emirates
Europe Austria, Belgium, Cyprus, Czech Republic,2 Denmark,2 Finland, Gibraltar, Greece, Iceland, Ireland, Isle of Man, Luxemburg, Netherlands,2 Norway, Portugal, Spain2 (except Ceuta and Melilla), Sweden, Switzerland.
Oceania3 Cook Islands, Fiji, French Polynesia, Guam, Hawaii, Kiribati, Micronesia, New Caledonia, New Zealand, Northern Mariana Islands, Palau, Papua New Guinea, Samoa, and Vanuatu.
1. Bat rabies may exist in some areas that are reportedly free of rabies in other mammals.
2. Bat lyssaviruses are known to exist in these areas that are reportedly free of rabies in other mammals.
3. Most of Pacific Oceania is reportedly “rabies-free.”
In India the islands of Andaman and Nicobar and Lakshadweep are free of rabies.
10.How is rabies transmitted?
• Rabies is transmitted by infected secretions. Most commonly, transmission to humans takes place through exposure to saliva following a bite by an infected animal. Rabies virus can be excreted in saliva, urine, nasal discharge and respiratory secretions.
11.What are the factors responsible for rabies transmission in man from rabid animals?
• 1. Rabies is most commonly transmitted to humans via the bite of a rabies-infected animal.
2. Humans usually contract rabies through bite wounds from rabid animals (bite exposure) because the rabies virus is highly concentrated in the saliva of infected animals.
3. The amount of virus reaching the lesion is also a factor in transmission; for example, when a bite has to penetrate clothing, the saliva may be retained in the fabric and be prevented from entering the wound.
4. It can also be transmitted through non-bite exposure, although this rarely occurs. Airborne infections, such as inhaling an aerosol of infected animal brain tissue in virus laboratories, or of contaminated air in bat-inhabited caves, have been reported.
5. Iatrogenic rabies cases have occurred in patients who received cornea, kidney, liver, or blood vessel graft transplantation from donors who had undiagnosed rabies.
6. To date, the only medically verified cases of human-to-human rabies transmission are the cases infected through organ transplantation from undiagnosed rabies patients
7. Potential non-bite modes of transmission include contamination of a pre-existing wound, contact of mucous membrane or respiratory tract with the saliva of an infected animal, exposure to aerosolized rabies virus in the laboratory (or from bats), or via organ transplantation from an infected donor.
12.How common are animal bites?
• Animal bites are very common in India.
The annual incidence of animal bites is high, 1.7% and it was more in rural areas (1.8%), children (2.6%) and poor/low income group (75%). The main biting animal was dog (91.5%), mostly stray (63%), followed by cat (4.7%).
13.Can rabies infection be transmitted through environment?
• Rabies infection can be transmitted through aerial (by aerosol) route. Airborne infections, such as inhaling an aerosol of infected animal brain tissue in virus laboratories, or of contaminated air in bat-inhabited caves, have been reported.
14.Can rabies be transmitted from man to man?
• Man-to-man transmission of rabies is possible. Rabies can be transmitted following bite by a rabies patient.
In 2004, three cases of human rabies were reported in U.S. following liver and kidney transplantation from rabies patients.
Transplantation of rabies infected cornea can cause rabies in recipient. Therefore a careful neurological history of donor must be taken before cornea transplantation.
15.Can rabies be transmitted to doctor/assistants conducting postmortem of a person died of rabies?
• As per Centre for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR), no confirmed case of rabies has ever been reported in persons who performed a postmortem examination of people or animals, although contact with decedents with confirmed or suspected rabies can cause anxiety. Even from living patients with rabies, human-to-human transmission has been documented only rarely, (in cases of organ or tissue transplantation).
Both CDC and the World Health Organization (WHO) have stated that the infection risk to health-care personnel from human rabies patients is no greater than from patients with other viral or bacterial infections. In addition, rabies post-exposure prophylaxis (PEP) is available for exposed personnel. Nevertheless, because of the nearly universal fatal outcome from rabies, both CDC and WHO recommend that all personnel working with rabies patients or decedents adhere to recommended precautions. Even the minimal risk for rabies virus transmission at autopsy can be reduced by using careful dissection techniques and appropriate personal protective equipment, including an N95 or higher respirator, full face shield, goggles, gloves, complete body coverage by protective wear, and heavy or chain mail gloves to help prevent cuts or sticks from sharp instruments or bone fragments.
Participation in the autopsy should be limited to persons directly involved in the procedure and collection of specimens. Previous vaccination against rabies is not required for persons performing such autopsies. PEP of autopsy personnel is recommended only if contamination of a wound or mucous membrane with patient saliva or other potentially infectious material (e.g., neural tissue) occurs during the procedure.
16.What are the common animal reservoirs of Rabies?
• Rabies exists in two forms:-
(1) Urban Rabies, propagated chiefly by unimmunized dogs.
(2) Sylvatic rabies, propagated by skunks, foxes, raccoons, mongooses, wolves, bats etc.
Worldwide the most common cause by far of human rabies infections is dog bites. The host animals of the rabies virus differ among regions, even though almost every mammal is capable of contracting rabies. The main vectors are foxes in Europe and Canada, raccoons, skunks, and fruit-eating and insectivorous bats in the United States, dogs in Asia, mongooses, jackals, and dogs in Africa, and dogs and vampire bats in Latin America.
In India, the animals commonly responsible for transmission of rabies are dogs and cats (97%) followed by wild animals like mongoose, foxes & jackals (2%) and occasionally by horses, donkeys, monkeys, cows, goats, sheep and pigs.
17.What is the dog population of India?
• India has approximately 25 million dogs, with an estimated dog: man ratio of 1:36.2. The dogs fall into 4 broad categories: pets (restricted and supervised); family dogs (partially restricted, wholly dependent); community dogs (unrestricted, partially dependent); and undomesticated stray dogs (unrestricted, independent). Most dogs in India, perhaps 80%, would fall into the last 3 categories. The majority of the stray dog population is found in rural areas.
18.Do rat bite cases require rabies vaccination?
• In India most rodents, rats, squirrel, rabbits, birds and bats have been found to be free of rabies. However, following exposure to mongoose, PEP is recommended. Rat bite cases do not require rabies vaccination but this is a right opportunity to start pre-exposure vaccination
19.What are the most common modes of exposures of rabies virus?
• Human exposures to rabies can generally be categorized as bite, open wound, mucous membrane, or other types of exposure:
Bite exposure: Any penetration of the skin of a person by the teeth of a rabid or potentially rabid animal.
Open wound exposure: Introduction of saliva or other potentially infectious material (cerebrospinal fluid, spinal cord, or brain tissue) from a rabid or potentially rabid animal into an open wound (e.g., broken skin that bled within the past 24 hours).
Mucous membrane exposure: Introduction of saliva or other potentially infectious material (cerebrospinal fluid, spinal cord, or brain tissue) from a rabid or potentially rabid animal onto any mucous membrane (eyes, nose, mouth).
Other exposure: Any interaction with a rabid or potentially rabid animal where a bite, open wound, or mucous membrane exposure cannot be definitively ruled out.
20.Why a person does not acquire immunity against natural rabies infection, as it occurs in other viral infections?
• A person does not acquire immunity against natural rabies infection, as it occurs in other viral infections because there is no viremia in rabies and the virus is not accessible to the normal immune mechanism of the body. The antibody production starts only after travelling efferently from CNS via mostly autonomic nerves to different target organs. But by that time, the neuronal cells of patient`s brain stem are affected.
21.What is the best known clinical feature of rabies?
• Hydrophobia and aerophobia are pathognomonic for rabies and occur in 50% of patients. Attempting to drink or having air blown in the face produces severe laryngeal or diaphragmatic spasms and a sensation of asphyxia. This may be related to a violent response of the airway irritant mechanisms. Even the suggestion of drinking may induce hydrophobic spasm. Hydrophobia is typically unique to human beings.
22.What is the incubation period of rabies in humans?
• The incubation period of rabies that is the time interval between the exposure to virus and the onset of symptoms, is usually from 03 weeks to 03 months (rarely 04 days to 02 years). An incubation period as long as 19 years has been reported. Children are at an increased risk of a shorter incubation period because of their short stature and bites are often closer to CNS. Multiple bites to the head and neck are associated with very short incubation periods less than 1 month.
The incubation period varies with the amount of virus transmitted, virus strain, site of inoculation (bites closer to the head have a shorter incubation period), host immunity and nature of the wound.
During most of the long incubation period of rabies, the virus likely remains close to the site of viral entry. Centripetal spread to the central nervous system and spread within the central nervous system occur by fast axonal transport.
People who are immuno-compromised will most likely be more susceptible to rabies. Rabies is usually undetectable during the incubation period, and infections can also be difficult to diagnose when the clinical signs first appear.
23.What are the initial (prodromal) symptoms of Rabies?
• 1.Pain or paraesthesiae at the site of the bite is well known as a diagnostically useful prodromal symptom occurring in one-third to two-thirds of cases.
2. In Thailand, however, a specific type of paraesthesiae-itching-was the earliest symptom in >40% of cases. Itching occurred at the site of the healed bite wound or involved the whole bitten limb and was sometimes so intense as to provoke frenzied scratching and excoriation of the skin. The explanation for local paraesthesiae may be the multiplication of virus in the dorsal root ganglion of the sensory nerve supplying the area of the bite.
3. Pain behind the grafted eye was an early symptom in three of the four patients who developed rabies following corneal transplants.
4. Priapism with frequent spontaneous orgasms was the first symptom in one Thai patient.
5. Fever, malaise, nausea and vomiting.
6. The skin becomes sensitive to changes of temperature, especially air currents.
24.What are the types of Rabies?
• There are mainly two types of rabies:-
a) Two-third of rabies patients suffer from typical furious (encephalitic) type of rabies. The virus replicates in portions of the brain including the hippocampus, amygdala, anterior thalamic nuclei and limbic cortex. Furious rabies has three cardinal signs:-
1. Fluctuating consciousness, episodes of excitement and hallucinations.
2. Phobic spasms – Aerophobia, Hydrophobia and Photophobia.
3. Autonomic dysfunctions like increased salivation, excessive sweating, priapism & pupillary abnormalities.
It is typically believed that salivation and vomiting are linked, and contribute to the apparent hydrophobia (fear of water) in patients. These symptoms can last for few days, after which the patient may suffer from the second type of rabies, or may slip into a coma and die. It is when suffering from furious rabies that a person or animal is likely to attack those near them, and spread the disease.
b) Dumb (paralytic) type which is characterized by flaccid muscle weakness, constipation, urinary retention, stupor, coma. Hydrophobia is usually absent in these cases. This is a condition resembling Guillain Barre Syndrome. Dumb Rabies occurs as the result of the virus replicating in the brain’s neocortex. It is much harder for a doctor to diagnose rabies in its “dumb” form than it is in its “furious” form, because the symptoms are less indicative of a specific medical issue.
Both forms are progressive and will lead to death, usually within 7 days in patients with encephalitic rabies and 3 weeks in those with paralytic rabie
25.What should be done if there is a human rabies case?
• A study on management of human rabies concluded that the dismal outcome of patients with rabies provides little optimism for heroic efforts. Palliative therapy is of paramount importance in this fatal disease.——-
(TO BE CONTINUED)
