Four persons with fever, a rash over the body and muscle pain that refused to respond to routine antibiotics, were treated at three hospitals in the city a month ago. One of the patients had a black scar, like a cigarette burn, on his thigh.

A blood test diagnosed them with scrub typhus fever, a type of mite–borne (rickettsial) infectious disease. Doctors said that one or two cases of rickettsial infections crop up in the city every month.

Also known as ‘tsutsugamushi fever’ (derived from two Japanese words: tsutsuga, meaning something small and dangerous, and mushi, meaning creature), scrub typhus is curable only if a particular type of antibiotic is used, but it can get out of hand when diagnosis is delayed or routine antibiotics are used.

It spreads when chiggers, which are mites found in forests, and now in urban shrubs, bite the person and inject a microorganism called rickettsia tsutsugamushi into the blood. A blood test can confirm the infection.

“Farmers, shepherds and mountaineers are usually at high risk of catching this infection which is transmitted from animals to humans. The disease epidemiology has been changing with increasing urbanisation. The vectors of this disease, ticks and mites have now found their residence in urban bushes with increasing transport, influx of people and city limits extending into nearby rural areas. Hence, we see scrub typhus cases,” infectious disease expert Bharat Purandare said. He has treated four patients with the infection last month.

More cases are being diagnosed than before because of increasing awareness among physicians and easier availability of the diagnostic test, Purandare said.

Physicians, who have been trained in internal medicine, usually do not have difficulty in identifying this infection. The level of awareness among other, particularly primary–care physicians too is improving, Purandare said.

The gold standard test for diagnosis of rickettsial infections (including scrub typhus) is direct fluoroscent antigen. “This test is not available widely. Christian Medical College, Vellore has been doing this test. The other test, which is widely available in Pune, is Weil–Felix test,” Purandare said.

Weil–Felix test can diagnose the infection with good sensitivity, but sometimes may be falsely positive due to urinary tract infection.

At Golwilkar Metropolis laboratory, one of the few accredited labs in Pune, Weil–Felix test was carried out on 267 samples between January 2011 and January 2012. “Of them, 86 samples tested positive. More samples — almost 10 to 12 per month — tested positive for the infection between August and December. While there were sporadic cases during March and April,” pathologist Aditi Golwilkar–Mehendale said.

Western countries use rickettsial polymeras chain reaction test. “We don't have access to this test except in some rare research setting,” Purandare said. Solapur district and large areas of interior Marathwada are the endemic areas in Maharashtra state. The disease has been endemic also in large areas of south India, particularly Tamil Nadu. Northern areas of India are less affected.

Physician R B Kulkarni of Deenanath Mangeshkar Hospital confirmed cases of typhus fever in Pune. “Tick typhus — another form of rickettsial infections is common. Cases of typhus fever usually come from Shreerampur belt in Ahmednagar district and Satara district. The history indicates contact with cattle. The cases of tick typhus which we usually come across in Pune have a contact history of dogs. Besides, body louse–borne typhus infection is also seen among people from lower socio–economic strata.”

Patient can be clinically diagnosed with rickettsial infection if there is fever not responding to routine antibiotics and rash all over body especially palms and soles.

“If closely examined, many patients do have a black necrotic mark or eschar (classically described as cigarette burn mark) on mainly lower limbs due to the tick or mite's bite which marks the entry point of the infecting organisms,” Purandare said. Sometimes the eschar may be present on genitals and may be missed. Many patients do not remember any insect bite and lack of such a history or eschar mark does not rule out possibility of rickettsial infection, he added.

“Late diagnosis of this infection is common particularly if patients do not have the typical rash and delay may be fatal in some cases. Routine antibiotics do not work in this infection. The disease can rarely be self resolving,” Purandare said.

A case of scrub typhus, most common of the rickettsial diseases in India, has high grade fever, measles like rash all over body particularly on palms and soles, eschar at mite bite site, regional lymph node enlargement, increased white cell count, decreased platelet count and affection of the liver and kidney function tests.

“Routine antibiotics do not help. Patients can die of brain involvement (encephalitis), heart involvement (myocarditis), liver or kidney failure, disseminated intravascular coagulation or lung failure,” said intensivist Prasad Rajhans.

At Ruby Hall Clinic, there were three clinically diagnosed cases of scrub typhus in the last four months. “Scrub typhus is a one of the forms of ricketsial infection and such Weil–Felix positive cases could be about 12 to 15 per year,” said intensivist Prachee Sathe, director, ICU at Ruby Hall Clinic.

“There are some other tropical illnesses manifesting in similar manner involving the same organs (malaria , dengue, viral fevers, leptosprosis). So it becomes difficult to diagnose immediately. Besides, we do not have specific tests. Serological tests take some time .So it is not unusual to miss the diagnosis in the early stages," said Sathe.

Only tetracycline group of antibiotics or chloramphenicol work in these cases. If diagnosed early, seven days of oral treatment is sufficient. Very rapid response with resolution of fever in 48 hours of starting therapy is characteristic. Treatment of complicated disease and treatment of pregnant patients is challenging and requires multidisciplinary approach.

• It is caused by microorganism Rickettsia tsutsugamushi (RT). Mites that live in shrubs carry it in their salivary gland and inject it into humans.

• Once transmitted , RT incubates for about 10–12 days. After that the infected person gets headaches, conjunctival infection, high–grade fever or fatigue and muscle pains.

• Difficult to diagnose through clinical symptoms. In most cases, doctors look for a scab or a black scar caused by flea bite. A simple blood test can confirm infection

• Scrub typhus is seen commonly in Southeast Asia and Japan where the disease was first described in 1899. Scrub typhus can also be prevalent in sandy beaches, mountain deserts, and equatorial rain forests

• If detected early, the disease can be treated with simple drugs, usually the one used to treat rat fever (doxycycline). But if undiagnosed, complications such as pneumonitis, encephalitis and circulatory failure can kill the patient

• Rickettsial diseases are some of the most covert reemerging infections of the present times.
• They are generally incapacitating and notoriously difficult to diagnose; untreated cases can have fatality rates as high as 30–35% but when diagnosed properly, they are often easily treated.
• These are one of the most difficult infections to diagnose in their early course and high index of suspicion is the key to early diagnosis.
• Epidemiological features and history of exposure to vector are crucial for diagnosis.
• Failure of early diagnosis is associated with significant mortality and morbidity
• Doxycycline is the drug of choice and it can be used safely even in chldren below 8 years

• Rickettsial diseases can be easily confused with a variety of viral (measles, enteroviral exanthems, dengue, infectious mononucleosis), protozoal (malaria), bacterial (meningococcemia, typhoid, leptospirosis, toxic shock syndrome, scarlet fever) and collagen vascular (Kawasaki disease, other vasculitis) diseases, and adverse drug reactions

• Napoleon's retreat from Moscow was forced by rickettsial disease breaking out among his troops. Russian leader Ivan Lenin, referring to rickettsial disease rampant during Russian revolution, said that, "Either socialism will defeat the louse or the louse will defeat the socialism." Tickborne rickettsial diseases continue to cause severe illnesses and death in healthy individual.

If closely examined, many patients do have a black necrotic mark or eschar (classically described as cigarette burn mark) due to the tick or mite's bite which marks the entry point of the infecting organisms