Evidence of Rickettsia and Orientia Infections Among Abattoir Workers in Djibouti

Abstract

Abstract. Of 49 workers at a Djiboutian abattoir, eight (16%, 95% confidence interval [CI]: 9-29) were seropositive against spotted fever group rickettsiae (SFGR), two (4%, 95% CI: 1-14) against typhus group rickettsiae, and three (6%, 95% CI: 2-17) against orientiae. One worker (9%, 95% CI: 2-38) seroconverted against orientiae during the study period. This is the first evidence of orientiae exposure in the Horn of Africa. SFGR were also identified by polymerase chain reaction in 32 of 189 (11%, 95% CI: 8-15) tick pools from 26 of 72 (36%) cattle. Twenty-five (8%, 95% CI: 6-12) tick pools were positive for Rickettsia africae, the causative agent of African tick-bite fever. Health-care providers in Djibouti should be aware of the possibility of rickettsiae infections among patients, although further research is needed to determine the impact of these infections in the country.Rickettsiae, obligate intracellular Gram-negative bacteria primarily transmitted to vertebrate hosts by arthropod vectors, are divided into four groups, two of which were examined in this study: spotted fever group rickettsiae (SFGR) and typhus group rickettsiae (TGR).1 The closely related Orientia spp. causes scrub typhus, a disease similar to rickettsioses. 2Although rickettsiae are found globally, orientiae are mainly endemic in the Asia-Australia-Pacific region, with limited evidence of infections in Africa, 3 the Middle East, 4 and South America. 5 As part of a broader study examining exposure to vector-borne and zoonotic pathogens in a high-risk environment in Djibouti, human samples were analyzed for evidence of exposure to and infection with rickettsiae and orientiae, and tick samples were examined for infection with rickettsiae.Before study initiation, the research protocol was reviewed by the institutional review boards (IRBs) and Institutional Animal Care and Use Committees at U. IRB protocol no. 911) and the U.S. Centers for Disease Control and Prevention (IRB protocol no. 5901), and by the Ministry of Health (MOH) and the Ministry of Agriculture, Livestock and the Sea in Djibouti. Samples were then collected at the Abattoir Frigorifique de Djibouti.In September 2010, participating abattoir workers completed baseline questionnaires and provided blood samples. Every 4 weeks, for a total of 20 weeks, an additional blood sample and questionnaire were collected from workers who self-reported a recent history of acute febrile illness (AFI); no subsequent samples were collected from workers who did not report recent AFI. Serum was stored at −20°C at MOH, transferred to NAMRU-3 in Cairo, Egypt, on dry ice, and stored at −40°C. Aliquots of 49 baseline and 11 follow-up samples were sent to the Naval Medical Research Center (NMRC) in Silver Spring, Maryland, on dry ice. Serum samples were screened for IgG antibodies against whole-cell antigens of SFGR, TGR, and orientiae by enzyme-linked immunosorbent assays (ELISAs), as described previously. 6,7 An ELISA titer procedure was performed on all screenpositive samples. Western blot assays us...

A Concise Review of the Epidemiology and Diagnostics of Rickettsioses: Rickettsia and Orientia spp

“…Orientia agents may have a wider global presence, with O. chuto isolated from patient blood in the United Arab Emirates and scrub typhus-seropositive results recognized in patients from Chile (15). Evidence is emerging that scrub typhus may be widely distributed in Africa and is causing disease with reports from Djibouti and Cameroon (16,17). The trombiculid mite is the sole vector for Orientia spp.…”

Tick-, Flea-, and Louse-Borne Diseases of Public Health and Veterinary Significance in Nigeria

“…However, louse-borne typhus remains on the WHO epidemic threat list for Africa and the continuing political instability and health crisis in many African countries may be a classic background for new outbreaks in conflict areas, as previously happened in Burundi in 1995–1997 [ 168 ] and Rwanda in 2012 [ 169 ]. One other rickettsial disease, scrub typhus, has recently received more attention in the context of the diagnosis of scrub-typhus-like cases outside of its classic endemic area [ 170 , 171 ], evidence for human exposure during passive surveillance [ 154 , 172 ], and molecular detection of Orientia DNA in these areas [ 173 , 174 ], so it may have been overlooked in Nigeria as well. Furthermore, circulation of emerging pathogens such as Candidatus Neoehrlichia mikurenis [ 25 ], potential human pathogenicity of E. ruminantium [ 175 ], and other yet unidentified pathogens is likely to contribute to the list of febrile illnesses.…”

Invasive plants facilitated by socioeconomic change harbor vectors of scrub typhus and spotted fever

“…Scrub typhus is an acute, potentially lethal febrile disease transmitted by chigger mites (Trombiculidae) infected with the rickettsia Orientia tsutsugamushi (OT) and has long been thought confined to Asia and northern Australia [16]. However, this disease has recently been identified in South America (Chile and Peru [17][18][19]) and Africa (Kenya and Djibouti [20][21][22]), and is also emerging in some endemic regions, such as China and Korea [23][24][25][26][27]. The life cycle of chigger mites include the egg, larva, nymph, and adult; only the larval stage (chiggers thereafter) is parasitic.…”