Incidence Estimates of Acute Q Fever and Spotted Fever Group Rickettsioses, Kilimanjaro, Tanzania, from 2007 to 2008 and from 2012 to 2014.

Sruti Pisharody,Manuela Carugati,Wilbrod Saganda,Matthew P Rubach,Holly M Biggs,Julian T Hertz,Jo E B Halliday,Sarah Cleaveland,William L Nicholson,Bingileki F Lwezaula,Michael J Maze,Jamie L Perniciaro,Venance P Maro,Rudovick R Kazwala,Kathryn J Allan,Blandina T Mmbaga,John A Crump

doi:10.4269/ajtmh.20-1036

Abstract

ABSTRACT.Q fever and spotted fever group rickettsioses (SFGR) are common causes of severe febrile illness in northern Tanzania. Incidence estimates are needed to characterize the disease burden. Using hybrid surveillance—coupling case-finding at two referral hospitals and healthcare utilization data—we estimated the incidences of acute Q fever and SFGR in Moshi, Kilimanjaro, Tanzania, from 2007 to 2008 and from 2012 to 2014. Cases were defined as fever and a four-fold or greater increase in antibody titers of acute and convalescent paired sera according to the indirect immunofluorescence assay of Coxiella burnetii phase II antigen for acute Q fever and Rickettsia conorii (2007–2008) or Rickettsia africae (2012–2014) antigens for SFGR. Healthcare utilization data were used to adjust for underascertainment of cases by sentinel surveillance. For 2007 to 2008, among 589 febrile participants, 16 (4.7%) of 344 and 27 (8.8%) of 307 participants with paired serology had Q fever and SFGR, respectively. Adjusted annual incidence estimates of Q fever and SFGR were 80 (uncertainty range, 20–454) and 147 (uncertainty range, 52–645) per 100,000 persons, respectively. For 2012 to 2014, among 1,114 febrile participants, 52 (8.1%) and 57 (8.9%) of 641 participants with paired serology had Q fever and SFGR, respectively. Adjusted annual incidence estimates of Q fever and SFGR were 56 (uncertainty range, 24–163) and 75 (uncertainty range, 34–176) per 100,000 persons, respectively. We found substantial incidences of acute Q fever and SFGR in northern Tanzania during both study periods. To our knowledge, these are the first incidence estimates of either disease in sub-Saharan Africa. Our findings suggest that control measures for these infections warrant consideration.

Highlights

Among the 589 participants residing in the catchment area, 344 (58.4%) and 307 (52.1%) had paired sera tested for Q fever and spotted fever group rickettsioses (SFGR), respectively
We found moderate incidence point estimates for acute Q fever in Moshi Municipal and Moshi Rural Districts in the Kilimanjaro Region of Tanzania during both the 2007 to 2008 and 2012 to 2014 study periods
We found a high incidence point estimate of SFGR during the 2007 to 2008 study period, and a moderate incidence point estimate of SFGR during the 2012 to 2014 study period in the same region

Summary

Introduction

Q fever and spotted fever group rickettsioses (SFGR) are common zoonotic causes of febrile illness in sub-Saharan Africa, and both diseases can cause substantial morbidity.[1,2] In Tanzania, despite both diseases being common causes of fever, awareness among healthcare providers remains low, and little attention has been focused on measures for disease control or prevention.[3,4] Both diseases often have nonspecific presentations, such as fever, myalgia, headache, and fatigue.[5,6] An accurate diagnosis is difficult, in resource-limited areas where appropriate diagnostic testing is seldom available.[7,8] Under-recognition and underreporting of cases make it difficult to calculate the reliable disease incidence, which is a key component of disease burden estimates.[9] To our knowledge, there are no estimates of the incidences of Q fever or SFGR in sub-Saharan Africa, and there are no estimates of global disease burden for either disease

Methods

Results

Conclusion