Rabies infection kills 20,000 people in India and 55,000 worldwide.In India, the disease is reported throughout the year and in all parts of the country. Estimates suggest that 175 lakh bites occur annually in India, 95% of which are inflicted by domestic dogs. In human, it is often fatal.

 

 

 

 

 

 

---

When physicians encounter a patient presenting with an animal-to-human exposure, a proper history should be taken in order to generate a preliminary risk assessment.As the incubation period is long, prophylaxis can be started as soon as possible in order to avoid serious signs and symptoms. Before starting prophylaxis following things should be considered

What type of animals was involved in exposure?

This is important as depending upon the animal prophylaxis is given. For example wild animal bite comes under category III contact so prophylaxis is given as per WHO’s suggestion for this category. Bite by rodents does not require prophylaxis.

The WHO rabies exposure categories are:

• Category I: Touching or feeding animals, licks on intact skin;
• Category II: Nibbling of uncovered skin, minor scratches or abrasions without bleeding;
• Category III: Single or multiple transdermal bites or scratches, contamination of mucous membrane or broken skin with saliva from animal licks, exposures due to direct contact with bats .

Why did the exposure occur?

Unprovoked bites are characteristics of rabid animals. So it is important to know if the dog bite was a provoked one or an unprovoked one. However, even provoked bites should be treated as an exposure and given prophylaxis as soon as possible.

Who was the owner of the animal?

Owner details are important for tracking the animals and for observational study. For cats and dogs observation period is 10 days. For other mammals observation period is not applicable as the history in them is not understood completely.

Was the dog vaccinated?

Vaccination status of the animal should be confirmed. However, even a vaccinated animal can also transmit rabies due to vaccine failure.

---

The PEP (post exposure prophylaxis) consists the following steps. 

• Wound toilet: Immediate washing of the wound(s) should be carried out with soap and water. Since the rabies virus can persist and even multiply at the site of bite for a long time, wound(s) toilet must be performed even if the patient reports late.
• Application of antiseptics: After thorough washing and drying the wound(s), any one of the available chemical viricidal agents should be applied, such as povidone iodine, alcohol, etc.
• Local infiltration of rabies immunoglobulin: In category III exposures rabies immunoglobulin should be infiltrated in the depth and around the wound(s) to neutralize the locally present virus.
• Suturing of wound(s) should be avoided as far as possible. If surgically unavoidable, after adequate cleansing, rabies immunoglobulin should be infiltrated in the depth and around the wound(s) and suturing should be delayed by a few hours. The delay in suturing allows diffusion of antibodies in the tissues. Minimum loose sutures should be applied for arresting the bleeding in life threatening situations.
• Cauterization of the wound(s) is no longer recommended as it leaves a bad scar, and does not confer any additional advantage over washing the wound(s) with water and soap.
• Tetanus and antibiotic prophylaxis should be given if required. To prevent sepsis in the wound(s), a suitable course of an antibiotic may be recommended.
• DO NOT touch the wound(s) with the bare hand and /or apply irritants like soil, chilies, oil, lime, herbs, chalk, betel leaves, etc.

---

Rabies prophylaxis

Rabies can be prevented to a large extent if animal bites are managed appropriately and in time.Prophylaxis has been shown to markedly reduce the likelihood of rabies. Prophylaxis for rabies as per national guidelines is as follows:

I) Pre-exposure prophylaxis: Pre-exposure vaccination is given to people who are at a high risk of getting infected by rabies like laboratory staff handling the virus and infected material, clinicians and persons attending to human rabies cases, veterinarians, animal handlers etc. Vaccines can be given by intramuscular route or intradermal route.

Dose and schedule: If a vaccine is given by intramuscular route, it is administered as one full dose and if given by intradermal route the dose is 0.1 ml. It can be given on any day (counted as day 0) followed by the administration on day 7 and either day 21 or 28 counted from day 0.People who are at a high risk of continuous exposure should check neutralizing antibody titer every 6 months. If it is less than 0.5 IU/ml a booster dose of vaccine should be administered.

II) Post-exposure prophylaxis:The incubation period of rabies is long in human, so in order to immunize the patient before virus reaches the central nervous system, post exposure prophylaxis should be given as soon as possible.

In rabies endemic country like India, where every animal bite is potentially suspected as a rabid animal bite the treatment should be started immediately. For this purpose, prophylaxis is suggested by WHO depending on the type of contact.

 

Category	Type of contact	Recommended post-exposure prophylaxis
I	Touching or feeding animals, licks on intact skin	None
II	Nibbling of uncovered skin, minor scratches without bleeding	Vaccination and wound management
III	Single or multiple bites, licks and contaminated mucous membrane	Wound management, immunization with rabies immunoglobulins and vaccination

 

Post exposure prophylaxis can be done in three steps:

1. Management of animal bite wound
2. Passive immunisation: Rabies Immunoglobulins (RIG)
3. Active immunisation: Anti-Rabies Vaccines (ARV)

All the three steps are important and they should be done simultaneously as per the category.

---

A) Post-exposure prophylaxis for non-immunised individuals

Management of animal bite wound: The wounds should be cleaned with water and soap immediately. The wound should be disinfected with povidone-iodine, alcohol, chloroxylenol etc. Irritants and sutures should be avoided.

Passive immunization with Rabies Immunoglobulins

Rabies immunoglobulin contains readymade anti-rabies antibody, which binds to virus resulting in neutralizing the infectivity of the virus. Two types of rabies immunoglobulins are present

Type	Dose (IU/per kg of body weight)
Equine Rabies Immunoglobulins	40 (max:3000)
Human Rabies Immunoglobulins	20 (max: 1500)

 

Sensitivity test should be performed before administration of equine rabies immunoglobulins as due to equine origin anaphylactic shock can be experienced. The maximum dose should be infiltrated into the or around the wound; remaining volume should be given by intramuscular route at a site different from vaccine administration.

The recommended dose should not be exceeded as RIG can suppress antibody production.

Active immunisation with anti-rabies vaccines

Active immunisation is achieved by administering cell culture vaccines, as they are least reactogenic of all the available rabies vaccine. Earlier nervous tissue vaccine (NTV) was used, as it was reactogenic it was banned in 2004. Vaccines can be administered by intramuscular or intradermal route.

• Intramuscular route: Vaccines by intramuscular route is administered using Essen regimen. It consists of 5 injections on day 0 (day of first injection), 3, 7, 14 and 28. Sixth injection should be considered in immunosuppressed patients. In adults, it should be given in deltoid area (arm) and in children anterolateral aspect of thigh. Gluteal area should be avoided as it does not generate optimum immune response.
• Intradermal route: Vaccines by intradermal route is administered using Thai Red Cross Schedule. 0.1 ml of reconstituted vaccines is injected per site. Injection sites are both deltoid areas. It is given on days 0, 3, 7 and 28.

B) Post-exposure prophylaxis for previously immunized individuals

Managing re-exposure following post-exposure treatment with tissue culture vaccine (TCV)

If a person who has previously received post-exposure prophylaxis either by intramuscular route or intradermal route is re-exposed then only two booster doses are given on day 0 and 3. For intramuscular administration the dose is 0.5ml/1ml and for intradermal administration, it is 0.1ml at 1 site. Rabies Immunoglobulins are not required

Managing exposure following pre-exposure prophylaxis with TCV

If after pre-exposure prophylaxis, a person is exposed to rabies then after cleaning wound two dose of cell culture vaccine either by intramuscular or intradermal route should be administered on day 0 and 3. Rabies Immunoglobulins are not required

Managing re-exposure following post-exposure treatment with NTV

Patients who have received post-exposure treatment with NTV are considered as a new case.

---

Contraindications

There is no contraindication to PEP. Pregnancy, lactation, infancy, old age and concurrent illness are no contraindications for rabies PEP in the event of an exposure. PEP against rabies takes preference over any other consideration as it is a lifesaving treatment. Moreover, rabies vaccine does not have any adverse effect on pregnant woman, course of pregnancy, fetus or lactating mother. Hence, complete PEP should be given depending on the category of the exposure. People taking chloroquine for malaria treatment or prophylaxis may have a reduced response to ID rabies vaccination. These patients should receive the rabies vaccine intramuscularly.

---

Rabies is a fatal infection but it can be prevented by giving the post-exposure prophylaxis as soon as possible and by giving pre-exposure prophylaxis to the people with high-risk groups. Fortunately, animal bites, if managed appropriately and timely the disease is preventable to a large extent. 

Source:

1.National Guidelines on Rabies Prophylaxis.National Rabies Control Programme Document.

2.WHO webpage: WHO announces new rabies recommendations.