Q: I am myself a doctor and I am writing on behalf of my brother who is a third year dental student. He happened to come in physical contact with a cat. A small area of skin on his right index finger showed a scratch. Initially he ignored it. He did not confine the cat and did not observe it for 10 days (as is generally the rule). But he could not say whether the cat was rabid. He washed the area with soap and water. At present, he is fine. After opening the pages of Harrison's Principles of Internal Medicine (part 1, pg. 1149, 15th. edn.) to know about the pathogenesis of rabies, he found that the incubation period is of invariably long duration, (from less than a year to 7 years). In such circumstances, he is worried and anxious. He constantly fears that he will get rabies at any time of its long incubation period (in the event of rabies virus entering through the scratch). If he takes post-exposure prophylaxis now, can it prevent rabies? If it is indicated, should he go for both active and passive immunisation or only active immunisation will do? Please give us your valuable advice.

A:Rabies has a variable incubation period, as rightly said, from few days to upto 7 years. If the cat (as in this case) is not observed for 10 days / is untraceable, it is necessary to take Post Exposure Treatment as per the category of exposure. Post Exposure Treatment, as per WHO and National Guidelines, should be started as soon as possible after exposure. However, it should not be denied to individuals who have reported late (taking advantage of its long incubation period). In this case it was a scratch by a cat on a finger. If it did not bleed it would be categorized as Category II and the person needs to wash the area with soap and water. (Already done as stated). Take full course (5 doses) of active immunization with available Tissue Culture Vaccine (Rabipur/ Verorab/ Human Diploid Cell Culture vaccine). If there was bleeding (Category III), then the person, in addition to above, should also take Passive Immunisation with Rabies Immunoglobulins. I hope this clears all the raised concerns.