Discussion
The case illustrates the acute multi-bacterial infection ofSalmonella typhi and Orientia tsutsugamushi in patient with Dengue fever. All the diagnosis was made on the basis of rapid serology test kit. Rapid serology kits can be questioned for their accuracy, but due to lack of resources in the settings and deteriorating condition of patient, the need for quick diagnostic approach was needed. Clinical laboratory parameters also played a vital role for taking the medical decision in addition to rapid serological tests. Other tests such as ELISA and/or polymerase chain reaction would lead to more confirmatory identification but were not accessible.
Dengue infection was diagnosed based on IgM positivity. Manufacturer (SD Bioline™ Dengue Duo, Abbott, Santa Clara, USA) reported sensitivity of 94.2% and specificity of 96.4% for diagnosis of acute IgM dengue infection. Salmonella typhi IgG/IgM (Bioline Diagnostics LLP, Delhi, India) was also identified based on IgM positivity with sensitivity and specificity of 91% and 99.3% respectively. Suspecting the possible cross-reactivity of Rapid Salmonella typhi IgM in dengue fever, which is also concluded with the study performed by Bhatti et al, follow-up test was requested5. Three to four days following the initial test, a follow-up test showed that both the IgG/IgM tests for S. typhi and dengue were IgG positive. The study performed by Bhatti et al concluded cross-reactivity based on positive S. typhi IgM but negative IgG on dengue patients using rapid kits but our test showed positive IgM-Ab on initial test and subsequent IgG positivity on follow-up5. ImmuneMed Scrub Typhus Rapid test kit was used for qualitative detection of IgM/IgG Ab specific to Orientia tsutsugamushi. The sensitivity and specificity was 97.3% and 99.7% respectively.
Our patient works primarily in agricultural fields in Dang district of Nepal. Her work may have had her be exposed to ticks and mites. Furthermore, climatic condition as well as seasonal factors also played a role in co-infection4. Various studies and case reports have been documented regarding co-infection of Dengue virus and scrub typhus 6, scrub typhus and enteric fever7 as well as dengue and enteric fever 8 in Nepal. Few cases of all three i.e. dengue, scrub typhus and S. typhi co-infection was reported in India9. A study conducted by Murdoch DR et aldid not observe any eschar in patient with scrub typhus-typhoid co-infection which is also consistent with our non-finding of eschar7. Thrombocytopenia, transaminitis, hyperbilirubinemia along with subsequent hypoalbuminemia was seen in our patient which is also consistent with dengue-scrub infection as conducted by Basheer A et al10. Another study in scrub- typhoid and dengue- typhoid co-infection revealed low hemoglobin level, thrombocytopenia, and increase in transaminases level11,12.