Scrub Typhus is often not considered as a differential of acute febrile illness. Historically, this is attributed to a lack of interest in rickettsial diseases after the discovery of Chloramphenicol in 1940, despite extensive research during World War 2. The non-specific presentation of rickettsial infections, coupled with difficulty in lab diagnosis are among cited factors that discourage clinicians from considering scrub typhus as a differential [3]. Moreover, acute dengue fever is given more prominence and often associated with a deep public stigma in endemic areas, further dissuading considerations of Scrub Typhus [4].

The consequences of a missed diagnosis are significant as 20% of rickettsial patients may present with a qSOFA score > 2, with a corresponding 10% mortality rate. As a result, scrub typhus is now considered a neglected tropical disease that is gradually making a comeback [3]. A local paper has since described its prevalence 8% when studied in the context of acute febrile illness, with increased incidence during rainy seasons [2].

In clinical practice, apt suspicion is important as serological confirmation is time consuming: a raised IgG level on immunofluorescent assay takes 2 weeks, which is not practical when dealing with acutely ill patients in whom diagnosis is suspected [5]. PCR is a useful tool for diagnosis, allowing for early and sensitive detection of bacteremia before antibody responses become detectable [2]. However, in resource limited setting such as ours, cost of transportation of samples to a tertiary center with PCR facilities posits an issue and, in many places, PCR testing might be available at all. Eschar, while traditionally attributed to scrub typhus, is absent in areas with high typhus endemicity due to acquired immunity from previous exposure [1]. Besides complicating the diagnostic process, its absence signifies a lack of biopsy samples for molecular diagnostics for scrub typhus, which often results if 100% specificity [6]. A therapeutic trial with Doxycycline PO with resolution of fever within 48 hours is expected. A failure to respond should prompt clinicians to consider other forms of tick infections, treatment resistance or other diagnosis. Alternatives for pregnant ladies or children include PO Azithromycin or Rifampicin [1].

To differentiate between dengue & scrub typhus, the Clinical Score to Differentiate Scrub Typhus and Dengue (CSSD score) may be utilized. This simple scoring system incorporates mental status, pulse oximetry, hemoglobin level, white cell count, SGOT (Alanine transferase) and serum bilirubin level. Our patient's CSSD score is 16, favoring dengue. This combined with a positive Dengue IgM, most certainly alludes to the diagnosis. However, the timing of rash, as well as respiratory complains generally points against this [4].

In dengue, fever is typically resolved as the patient enters the critical phase, most commonly around the 5th day of illness. The classical rash, typically described as ‘isles of white in a sea of red’ does not blanch with pressure [3]. Patients with typhus, regardless of severity, typically present with a blanchable maculopapular rash that coincides with the presence of fever, originating at the trunk (Image 1), that spreads to the axilla, sparing the face, palms, and soles [1]. Furthermore, respiratory complaints are a noteworthy manifestation that is more specific to scrub typhus. Cough is present in 40% of patients, in contrast with Dengue (19%). Interstitial pneumonitis and acute respiratory distress syndrome (ARDS) are manifestation more inclined towards scrub typhus [2]. These clinical features were seen in our patient. As such, CSSD scoring, while helpful needs to be interpreted with regards to the patient’s overall presentation. Additionally, the role of Dengue IgM has recently been called into question as it is known to persist for at least 60 days and caution must be utilized in interpretation [8].