MANAGEMENT OF DOG BITE

Important steps in the management of a dog bite include: (a) local wound care, (b) evaluation of exposure,

(c) passive immunization with anti-rabies immuno­globulin and (d) active immunization.

Step I. Local wound care is essential in all cases pre­senting soon after bite, to kill the virus by mechanical and virucidal action. Proper wound care reduces risk of rabies by 80% and includes:

• Cleaning, i.e. immediate washing of wounds/licks and adjoining area with soap and running-water for at least for 5-10 minutes.

• Irrigation of deep wounds with virucidal agents, e.g. povidone iodine or alcohol. Cauterization with carbolic acid is no longer recommended.

• Avoidance of suturing, as further trauma increases local vascularity and facilitates spread of virus in deep tissues. If essential, it should be deferred as long as possible and done after local infiltration of Rabies immunoglobulin (RIG).

Step II. Evaluation of exposure: A dog bite is considered as potential risk for rabies if:

• Bite by a stray, domestic but unvaccinated, untraceable, or abnormally aggressive dog,

• Bite was unprovoked, and

• Severity of bite involved actual bite/scratch with skin penetration or licks over previous scratch, abrasion, mucous membrane or open wound.

A classification system, depending on the severity of exposure and risk of disease is frequently used to decide the need for post-exposure prophylaxis (Table 10.45).

Step III. Passive immunization aims to prevent imme­diate attachment of virus to the nerve endings, till vaccine-mediated immunity develops.

Presently, there are two options for passive immuniza­tion-human rabies immunoglobulin (HRIG), and

TABLE 10.45: WHO categories for exposure risk and post­exposure ARV prophylaxis

monoclonal antibodies, e.g. Rabishield® or Twintab®.

WHO as well as IAP encourages use of monoclonal antibodies instead of RIG due to easier availability, lower cost, lesser side effects, and possibly greater effectiveness. These antibodies bind ectodomain of G glycoprotein of the virus to block its entry into neighboring cells, both products (Rabishield^® or Twintab^®) are nearly comparable in efficacy and cost. Rabishield^® is avail­able 40 IU/ml, with recommended dose of 3.3 IU/kg, Twinrab® is available as 300 or 600 IU/ml with recom­mended dose of 40 IU/kg.

Passive immunization, is most effective when given immediately after exposure, but may be given till 7^th day of first vaccine dose, by which the active immune response to vaccine is expected to develop. These antibodies must be infiltrated locally at the time of the first vaccine dose or upto 7^th day of first dose. If the calculated dose is insufficient to infiltrate all the wounds, it may be diluted in sterile normal saline to get a volume enough to be infiltrated around all the wounds.

Step IV. Active immunization: Two types of anti-rabies vaccines are available in India—(a) cell-culture vaccines,

e. g. purified chick-embryo vaccine (PCEV), human diploid-cell vaccine (HDCV), purified Vero-cell vaccines (PVRV), and (b) embryonated egg-based vaccines, e.g. purified duck-embryo vaccine (PDEV). All are safe, stable and equally effective with gt;99% protective efficacy. All these vaccines contain minimum 2.5 IU antigen/ dose, available in lyophilized form with sterile water as diluents and must be stored at 2-8°C. Side effects are rare and insignificant, e.g. local pain, fever or malaise, though a few cases resembling Guillain-Barre syndrome are reported with HDCV. PCEV should be avoided in children with history of egg-allergy.

Post-exposure prophylaxis (PEP): All vaccines are given as 1.0 ml/dose (0.5 ml for PVRV) over deltoid or anterolateral thigh region as total four doses intra­muscularly on day 0, 3, 7 and 14-28, as recommended by WHO and IAP, though 5 doses (0, 3, 7, 14 and 28 days) are used in National Rabies Prophylaxis Programme.

Intradermal (ID) vaccination is cost-effective alternative to intramuscular vaccination due to lesser dose require­ment (0.1 ml/dose), when large number of vaccines are available simultaneously, as in major public health centers. Government of India provides ID vaccination (under National Rabies Control Programme, given as two ID doses on both deltoids on days 0, 3, 7 and 28). ID vaccination is not recommended for individual practice or in immunocompromised cases.

Re-exposure prophylaxis in previous vaccinated children needs only two IM/ID doses on day 0 and 3, if the last dose was received 3 months back. Rabies immunoglobulin is not required in these cases.

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