Abstract
Rickettsial diseases are among the most common cause of febrile illness in Southeast Asia and sub-Saharan Africa. There remain several unanswered questions, including prevalence and risk factors for infection in countries where they are endemic. Laboratory diagnosis of rickettsial diseases remains complex, with a ≥four-fold in antibody titre to relevant antigens by immunofluorescence antibody (IFA) test on paired sera the reference standard. Interpretation of results from IFA testing of single acute samples is fraught, due to both lack of sensitivity early in disease and the difficult of setting single serum cut offs in areas of high endemicity.
There has been little research on rickettsial diseases in Myanmar since World War II. We sought to estimate the prevalence of, and risk factors for, scrub typhus, murine typhus, and spotted fever group rickettsioses (SFGR) among febrile patients presenting to hospital in Yangon, Myanmar. Consenting patients aged >12 years with fever from among those seeking care at Yangon General Hospital, October 2015 through October 2016 were recruited. A standardised clinical and risk factor assessment was done. Multivariable logistic regression was used to identify associations between confirmed infection, defined as a positive PCR or ≥four-fold in antibody titre to Orientia tsutsugamushi or Rickettsia typhi or R. honei/R. conorii respectively, or probable infection defined as titre ≥1:400 to O. tsutsugamushi, ≥1:800 to R. typhi and ≥1:200 to R. honei/R. conorii. Among 944 participants, 38 (4.0%) and 63 (6.7%) had confirmed or probable scrub typhus, respectively, and eight (0.8%) and 15 (1.6%) had confirmed or probable murine typhus, respectively. No SFGR infections were identified. The odds of confirmed or probable scrub typhus were lower among females than males (adjustedOR 0.5, p=0.014) and higher among agricultural workers compared with others (aOR 3.9, p<0.001). Scrub typhus was common among patients presenting with fever in Yangon. Empiric treatment of severe febrile illness should include an antimicrobial with activity against rickettsial diseases.
There are gaps in knowledge as it relates to SFGR in sub-Saharan Africa. We sought to identify risk factors for both acute SFGR and SFGR exposure in participants presenting to hospital in Kilimanjaro Region, Tanzania. We recruited patients presenting with fever at two hospitals in Moshi, Tanzania, from February 2012 through May 2014. A standardised clinical and risk factor questionnaires was done. Multivariable logistic regression was used to identify associations between acute SFGR, defined as a ≥four-fold in antibody titre to R. africae, or SFGR exposure, defined as a titre ≥1:64. For acute SFGR, being younger than two years, living rurally (aOR 4.1, p=0.007), and in an area with a maximum daily temperature below 26°C were all identified as risk factors for disease. For SFGR exposure being older than two years, working in the garden (aOR 1.8, p=0.010), and seeing a dog in the village (aOR 1.5, p=0.010) were risk factors. Female sex (aOR 0.62, p<0.001) and being from Chaga tribe (aOR 0.68, p=0.003) were protective. Clinicians in Kilimanjaro Region should be aware of SFGR as a common cause of fever among infants and young children. Public health prevention efforts could be targeted to males, those who live rurally, or who work in a garden.