Rabies Vaccine, When Should Rabies Vaccine Be Given?

Rabies is a 100% fatal viral disease caused by bites of rabid animals. Rabies has global distribution, but countries like Japan, Ireland, UK, Spain, Norway, Portugal, Norway, and Sweden are considered to be free from rabies. It is prevalent in African, South American, some of Asian countries like India, Thailand, Philippines, Vietnam and Cambodia.Dog is considered to be the primary vector for rabies transmission.

Rabies Virus

Rabies virus is a neurotropic virus belonging to the family of rhabdovirus (serotype lyssa virus). This virus is sensitive to heat, ultraviolet radiation and lipid solvents. Drying and cold have very little effect on the virus and the virus can stay alive for a very long time.

Transmission

Rabies virus can be transmitted to human beings in any of the following ways:

a.Exposure through bites.

The main transmission of virus to humans is through transdermal bite from an infected animal.99% of cases are due to canines (96% dog bites, 2% due to cats and 1% by any other warm blooded animal which is supposed to be susceptible to this disease and can transmit it). Bites by domestic rats, lizards, birds and hares are not considered to be by rabid animals.

b.Exposure without bites.

This can only happen if there is evidence that mucous membrane or skin has given away or was broken so that there is contact with the saliva of the infected animal even without a bite.

c.Person-to-person.

This may occur during organ transplantation.

Local wound (Bite) Management

* Wash the wound with plenty of soap and water.

* Apply antiseptic or alcohol. Apply only povidone iodine, do not use tincture iodine. Ethyl alcohol can also be applied. Don't use carbolic acid and other irritant chemicals.

* Tetanus prophylaxis should be done in every bite case if the patient has had no tetanus prophylaxis in the recent past.

* Do not apply chillies, mustard oil, carbolic acid to the wound.

* Avoid suturing. If suturing is essential, infiltrate with RIG first.

* Do not cover the wound, it should be left open.

Pathogenesis

When an animal bites a person, the virus gets implanted at the site of bite. It stays their for sometime(eclipse period). The virus then ascends along the motor nerves to reach the spinal cord and the brain; the virus proliferates in the brain and then descends and spreads to other parts of the body like salivary glands, heart, reproductive organs and kidneys.

The following are the stages found:

* Incubation period ; 20 to 90 days

* Prodromal period : 2 to 10 days

* Acute neurological stage : 2 to 10 days

* Coma :0 to 14 days

* Death

Once the symptoms appear, no drug, vaccine or immunoglobulin can help and death is inevitable.

Clinical Findings

Rabies may present as either:

* Furious form (80% cases)

*Dumb (or paralytic) form

In the dumb form, patient presents with ascending paralysis involving the lower limbs, which then spreads to the upper limb and the urinary bladder. The patient may then become hyper-active or hyper-excited as in the furious form. The patient may show features of aerophobia or hydrophobia in both forms. The jaw muscles get paralyzed and the patient may not be able to swallow the secretions. The virus may spread from the salivary to respiratory secretions also. Coma then sets in and the patient dies because of cardio-respiratory arrest.

Management

Rabies is very effectively preventable and is the only known disease where vaccination given to an exposed person provides protection. The management is as under:

* wound treatment

* active immunization(vaccine)

* passive immunization (rabies immunoglobulin or anti rabies serum)

Wound Treatment.

Flush the wound with running tap water for at least 10 minutes, also wash with plenty of soap and water. Do not scrub the wound too hard. Suturing should be avoided, at least for 48 hours. In case suturing cannot be avoided, (as in facial bite or profuse bleeding), infiltrate the wound with rabies immunoglobulin and apply minimal sutures to stop the bleeding and approximate the wound edges.

Active Immunization

Currently available vaccines:

* Human Diploid Cell Vaccine (HDCV)

* Purified Chick Embryo Cell Vaccine (PCECV)

* Purified Duck Embryo Cell Vaccine

* Purified Verocell Rabies Vaccine (PVRV)

Passive Immunization

Two types of (RIG) rabies immunoglobulin are available:

* Equine rabies immunoglobulin (ERIG)

* Human rabies immunoglobulin (HRIG)

There are 3 categories of exposure:

Class I: This includes licks of animals on healthy skin with no mucous membrane exposure. No treatment is required for these cases. But most often, to allay the patients anxiety and apprehension, one may give 3 doses of tissue culture vaccine if the patient can afford it. Never give nerve tissue vaccine because of its complications.

Class II: Scratches, licks on broken skin where only the epidermis has been breached leaving the dermis intact, come under this category. Tissue culture vaccine or nerve tissue vaccine should be administered in such cases. there is no need for rabies immunoglobulin.

Class III: Any single or multiple transdermal bite, anywhere on the body, including scratches, or licks over mucous membrane are considered class lll exposures.These cases should be treated with both tissue culture vaccine and rabies immunoglobulin.

Standard Post-Exposure Regimen.

Any of the active immunization vaccine is given IM (deltoid) on days 0, 3, 7, 14, 28, 90. The day 90 dose is optional.

Pregnancy and Lactation.

Pregnancy and lactation are not contraindication to tissue culture vaccine(TCV). They are completely safe during pregnancy. If a pregnant women get exposed to rabies, she should be given full anti-rabies vaccination.

Re-exposure.

If (TCV) has been taken(5 doses) in the past 1 year and the patient is again exposed to a bite, he requires just 2 doses of TCV, on day 0 and day 3- there is no need to give rabies immunoglobulin.