A Clinical Study of Rickettsial Fever and Factors Affecting Its Outcome

Rickettsiae comprise a family of obligate intracellular short gram-negative coco-bacilli and are transmitted by insects, mites, fleas, louse, and tick vectors. Scrub typhus, north-Asian tick typhus, rickettsia pox, and boutonniere fevers are common in India and Asia. In the early phase of illness during the initial five days, all these are indistinguishable among themselves; also, they mimic any other self-limiting viral fever. Patients usually present with fever, headache, myalgia, malaise, nausea, vomiting, and anorexia. Rarely do patients present with rash, or give a history of exposure to animals or tick bite. Thus, rickettsial diseases are missed in the early phase, when they are easily treatable, due to lack of suspicion.

To study clinical features, investigations, outcomes, and factors affecting the outcome of rickettsial fever.

This was an observational study conducted from December 2012 to November 2014 in a tertiary care hospital. The study population consisted of patients above the age of 13 years with a history of any one or more of the following: fever, headache, jaundice, altered sensorium, renal dysfunction, tick bite, a farmer by occupation, exposure to cattle or sheep or dog, multiorgan failure; with serological evidence of rickettsial infection by Weil-Felix test (ox-19/ox-2/ox-k ≥ 1:320) or rickettsial antibody IgM ≥ 1.1) or PCR positive. A sample size of 40 was considered for the final analysis of this study. Statistical analysis was done using inferential statistical tests such as the chi-square test and odds ratio (OR).

The most common presenting symptom was fever (100%) seen in almost every patient followed by body aches (72.5%), joint pain (62.5%), and jaundice (62.5%). General examination showed icterus (37.5%), hypotension (30%), edema (22.5%), lymphadenopathy (22.5%), and pallor (15%). On the day of admission, 17 patients were found to have the Weil-Felix test positive with an OR of 0.538462 (CI = 0.151-1.917), while the Weil-Felix test done in the second week was positive in 37 patients with an OR of 5.4 (CI = 0.439-63.11). Rickettsial antibodies were positive only in three patients on the day of admission with an OR of 0.381 (CI = 0.0317-4.58), while in the second week, rickettsial antibodies were positive in 27 patients with an OR of 16.25. The rickettsial PCR test was positive in 13 patients with an OR of 1.48 (CI = 0.3857-5.722). The mortality rate was significantly high in patients presenting with breathlessness and respiratory complications like pneumonia, pulmonary edema, and acute respiratory distress syndrome. Similarly, patients presented with hypotension and required Ionotropic support had a high mortality rate.

While the clinical presentation of rickettsia infection is similar, the causative species and epidemiology can vary depending on the region. It is important to recognize both the typical symptoms and the epidemiology of a given region to correctly diagnose and treat these infections promptly, as they can be associated with significant morbidity and mortality. Through this study, we attempt to bring awareness about this disease which would help clinicians to suspect and start treatment at the earliest before complications set in.