Rickettsial infection among military personnel deployed in Northern Sri Lanka

Abstract

BackgroundMilitary personnel deployed in field actvities report on frequent tick bites. Therefore they may run the risk of exposure to rickettsial organisms.MethodsIn order to assess the risk of exposure to rickettsial organisms, two groups of military personnel who were deployed in field activities of Nothern Sri Lanka were investigated. The first group was studied in order to assess the sero-prevalence of rickettsioses and consisted of soldiers who were admitted following injuries during field activities. The second group was studied to identify the incidence of acute rickettsioses during their acute febrile presentations. They were tested with IFA-IgG against spotted fever group rickettsioses (SFG), scrub typhus (ST) and murine typhus.ResultsIn the first group, 48/57 (84%) military personnel had serological evidence of exposure to rickettsioses (in all, IFA-IgG titer ≥ 1:128): 33/50 (66%) to SFG rickettsioses, 1/50 (2%) to ST and 14/50 (28%) had mixed titers for both (in all, titers were higher for SFG). While all of them were in military uniform most of the time and frequently slept on scrub land, 35/57 (61.4%) had never used insect repellents and none were on doxycycline prophylaxis. 48/57 (84%) had experienced tick bites during field activity.In the second group, there were 49 who presented with acute febrile illness with a mean duration of 8.5 days (SD 3.2). 33/49 (67.3%) were serologically positive for acute rickettsioses (IgG ≥1:256); 26 (79%) due to ST and 7 (21%) due to SFG rickettsioses,ConclusionsExposure to rickettsial disease was common among soldiers who were deployed in Northern Sri Lanka. Scrub typhus was the predominent species accounting for acute febrile illness. Further studies are needed to understand the reasons for very high sero-prevalence for SFG rickettsioses with no anticedent febrile illness. Use of preventive measures was not satisfactory. The high sero-prevelence of SFG rickettsioses is likely to interfere with serological diagnosis of acute SFG rickettsioses in this population.

Rickettsial Infections and Q Fever Amongst Febrile Patients in Bhutan

“…STG was the most commonly identified rickettsiosis in this study, similar to reports from Sri Lanka [ 36 ] and south India [ 37 ]. An eschar was seen in 44.3% (31/70) of STG patients in this study, compared to 93% (243/261) in a study in Taiwan [ 38 ], 40% (59/146) in Thailand [ 33 ], and 10% (2/21) in an Indian study [ 39 ].…”

A review of the global epidemiology of scrub typhus

“…The reported seroprevalence of O . tsutsugamushi for each country is shown in Table 1 [ 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 ]. The reports of outbreaks of scrub typhus are summarized in Table 2 [ 43 , 94 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , …”

Diagnosis of spotted fever groupRickettsiainfections: the Asian perspective

“…In the case of seroprevalence studies, the application of a consistent regional cut off will more readily reflect true endemicity and enable comparability between countries and regions. In Southeast, South and East Asia, studies have used reasonably consistent cut-off titers of ⩾1:64 in Philippines [86], Sri Lanka [87], Thailand [3] and Bangladesh [88] and in South Korea and Taiwan, a cut-off of 1:40 is considered as positive [89, 90]. However, different cut-off values have been reported for IgM and IgG isotypes, such as ⩾1:128 for IgG and ⩾1:64 for IgM in Thailand [3].…”