Scrub Typhus fast spreading in cities

Risk of getting the infection is more where rat population is high. The disease is spread by harvest mite, a microscopic parasite of rodents (mice, rats and bandicoots) and humans.

Besides mosquito-borne diseases such as malaria and viruses like dengue and chikungunya, there is an infection caused by an intra-cellular bacteria, which is a cause for concern for people living in urban centres. The infection is called Scrub Typhus or Bush Typhus, and there is a growing incidence of it in cities.

The disease is spread by harvest mite, a microscopic parasite of rodents (mice, rats and bandicoots) and humans.

There is a danger of people getting the infection where the rat population is high. Since the infection is relatively rare, the testing kits are not available at all diagnostic laboratories. Since the symptoms of the disease are fever, headache, muscle pain, cough, vomiting and diarrhoea, it is not diagnosed in time. Without treatment, the disease may turn fatal.

With the use of antibiotics, fatalities have come down from 40 per cent to less than 2 per cent.

Surprisingly, there are currently no licensed vaccines available for this infection. Attempts to manufacture a vaccine failed as it is now learnt that there is an enormous antigenic variation in Orientia tsutsugamushi strains, and immunity to one strain does not give immunity to another. Any Scrub Typhus vaccine should give protection to all the strains present locally to give an acceptable level of protection. A vaccine developed for one locality may not be protective in another locality, because of antigenic variations. 

Senior physician T.V. Narayana Rao who has been tracing the growing incidence of Scrub Typhus says clinical diagnosis was the best, as it is timely and cheap. This, however, involves careful examination of the patient’s entire body in pursuit of the black scab formed at the point where the Microscopic Harvest Mite bites. The scab is nearly one centimetre in diameter.

Testing of the patient’s blood for anti-bodies of Orientia tsutsugamushi, the bacteria, is a costly affair. While diagnosis is generally made on clinical grounds alone, it may be confirmed by laboratory testing.

For Scrub Typhus there is no particular season, and it is, therefore, essential for physicians to be alert throughout the year.