Seroepidemiology of rickettsioses in Sri Lanka: a patient based study

Clinical characteristics of and antibody response to spotted fever group rickettsial infections in South India: Case series and serological cohort study

OBJECTIVE

The clinical and serological characteristics of spotted fever group rickettsial (SFGR) infections in South Asia are poorly understood. We studied the clinical presentation and the IgM/IgG response in cases enrolled at two health care centres in South India.

METHOD

We enrolled 77 patients. Fifty-seven of these patients were recruited at a tertiary care centre, the remaining 20 at a community hospital (secondary care level). Diagnostic tests included IgM and IgG enzyme-linked immunosorbent assay and polymerase chain reaction. Over a period of 1 year, 41 cases were followed up for repeated sero-analysis.

RESULTS

Median age was 9 years (range 1-79). A rash was present in 74% of cases (57/77). In cases aged <15 years, rash was present in 94% (44/47) vs. 43% (13/30) in cases aged ≥15 years. An eschar was found in two cases (3%). Severe infection or complications occurred in 10 cases (13%). These included central nervous system infection (6/77, 8%), kidney injury (3/77, 4%), shock (3/77, 4%), lung involvement (2/77, 3%) and peripheral gangrene (2/77, 3%). IgM antibody levels increased faster after fever onset than IgG antibodies, peaking at 50 and 60 days, respectively. After the peak, IgM and IgG levels showed a slow decline over one year with less than 50% of cases showing persistent IgG antibody levels.

CONCLUSION

Spotted fever group rickettsial infections in South India may be under-diagnosed, as many cases may not develop a rash. The proportion of cases developing severe infection seems lower than for scrub typhus in this region. IgG seroprevalence may substantially underestimate the proportion in a population with past SFGR infection.

High initial IgG antibody levels against Orientia tsutsugamushi are associated with an increased risk of severe scrub typhus infection

BACKGROUND

Scrub typhus is a dominant cause of febrile illness in many parts of Asia. Immunity is limited by the great strain diversity of Orientia tsutsugamushi. It is unclear whether previous infection protects from severe infection or enhances the risk.

METHODS/PRINCIPAL FINDINGS

We studied IgG antibody levels against O. tsutsugamushi at presentation in 636 scrub typhus patients using enzyme-linked immunosorbent assays (ELISA). The association between ELISA optical density (OD) and risk of severe infection was modelled using Poisson regression. OD was categorised as low (<1.0), intermediate (1.0 to 2.9), and high (≥3.0). OD was also modelled as a continuous variable (cubic spline). Median age of cases was 41 years (range 0-85), with 37% having severe infection. Compared to the low category, the age-adjusted risk of severe infection was 1.5 times higher in the intermediate category (95%CI 1.2, 1.9), and 1.3 times higher in the high category (95%CI 1.0, 1.7). The effect was stronger in cases <40 years, doubling the risk in the intermediate and high categories compared to the low category. The effect was more pronounced in cases tested within 7 days of fever onset when IgG ODs are more likely to reflect pre-infection levels.

CONCLUSIONS/SIGNIFICANCE

Intermediate and high IgG antibody levels at the time of diagnosis are associated with a higher risk of severe scrub typhus infection. The findings may be explained by severe infection eliciting an accelerated IgG response or by previous scrub typhus infection enhancing the severity of subsequent episodes.

Antibody response following scrub typhus infection: clinical cohort study

OBJECTIVE

Scrub typhus is a common cause of fever in Asia. The antibody response to infection and its effect on subsequent infection are unclear. We studied the IgM and IgG antibody response after infection, accounting for clinical severity.

METHOD

We studied 197 scrub typhus patients for up to 2 years post-infection. Overall, 501 blood samples were analysed for scrub typhus antibodies using ELISA. IgM and IgG ELISA optical densities (OD) were analysed using quantile regression. OD values of 1.0 (IgM) and 1.5 (IgG) were used to define seropositivity.

RESULTS

IgM OD values fell rapidly from an initial peak after infection. 50% of cases were IgM seronegative after 82 days. About 2 years after fever onset, 50% of cases had fitted IgG OD values of <1.5. Patients with high initial IgG OD values (≥2.5, used as a proxy for probable previous scrub typhus infection) had a more sustained IgG response than those with a low initial IgG OD, and more often presented with complications (18/36 = 50% vs. 28/91 = 30.8%, risk ratio = 1.63, 95% CI 1.04, 2.55, P = 0.035). This association was robust to adjusting for age (risk ratio 1.50, 95% CI 0.96, 2.33, P = 0.072).

CONCLUSION

Cross-sectional IgG seroprevalence data substantially underestimate the proportion in a population ever infected with scrub typhus. A high initial IgG as a potential marker for previous scrub typhus infection may be associated with long-term IgG persistence and a higher risk of complicated scrub typhus.

Bilateral Sensorineural Deafness in a Young Pregnant Female Presenting with a Fever: A Rare Complication of a Reemerging Disease-Spotted Fever Group Rickettsioses

Background

Rickettsial illnesses are a group of arthropod-borne remerging diseases. They are subdivided into three groups as typhus, spotted fever, and scrub typhus group. Complications such as reversible bilateral deafness due to spotted fever rickettsioses are infrequently reported in the literature.

Case Presentation

We present a young pregnant female who developed bilateral sensorineural deafness on the fifth day of an acute febrile illness with a maculopapular rash. Rickettsia conorii IgG (>1/450) became highly positive, and she received oral azithromycin for ten days with complete resolution of fever and rash. The sensorineural deafness slowly improved over several months.

Conclusion

Sensorineural deafness is a rare complication of spotted fever group rickettsioses. Since usage of doxycycline is controversial in pregnancy, azithromycin gave a favourable recovery of fever. Sensorineural deafness took several months to resolve after completion of antibiotics.

Spotted fever rickettsioses causing myocarditis and ARDS: a case from Sri Lanka

Background

Spotted fever group of rickettsial infections are emerging in Sri Lanka. We describe a patient with rapidly progressing ARDS and myocarditis secondary to spotted fever caused by Rickettsia conorii. ARDS and myocarditis are rare complications of Rickettsia conorii infections and only a few cases are reported to date.

Case presentation

A 53 years old manual worker presented with fever for 5 days and a skin rash. He was in circulatory failure on admission and developed severe hypoxaemia with gross changes in chest radiograph by next day requiring assisted ventilation. He had myocarditis causing left ventricular failure and acute respiratory distress syndrome. He was confirmed to have spotted fever rickettsial infection with rising titre of indirect immunofluorescence antibodies to Ricketssia conorii and made a complete recovery with appropriate antibiotic therapy and supportive care.

Conclusion

Rickettsial infections can present with diverse manifestations. Even the patients with severe organ involvements such as myocarditis and ARDS can be completely cured if timely identified and treated.

Canine seroprevalence to Orientia species in southern Chile: A cross-sectional survey on the Chiloé Island

Background

Scrub typhus is a potentially life-threatening vector-borne infection caused by Orientia species. It occurs mainly in the Asian-Pacific region, where it causes significant morbidity and mortality. Recently, an endemic focus of scrub typhus has been described in South America, on Chiloé Island in southern Chile. Dogs have been used as sentinel hosts to determine the presence and spatial distribution of various vector-borne infections. Their suitability to gain insight into human exposure to Orientia tsutsugamushi has been suggested in studies from Asia.

Methodology

In January 2016, we conducted a cross-sectional study, which included the two main cities on Chiloé Island. Canine blood samples were obtained in households, chosen by double stratified random sampling in urban and by convenience in rural locations. Specimens were tested by ELISA for IgG antibodies against whole-cell antigen preparations from three strains of O. tsutsugamushi. Data were further analyzed for factors associated with seropositivity including spatial clustering.

Results

Serum samples from 202 dogs (104 urban, 98 rural) were tested for IgG against O. tsutsugamushi, of which 43 (21.3%) were positive. Seroprevalence rates were higher in rural than in urban settings (p<0.01) and in older compared to younger dogs (p<0.01). Spatial analysis by LISA indicated the presence of four localities of highly grouped cases.

Conclusions

The detected seroprevalence supports the endemicity of scrub typhus in southern Chile and suggests a wide exposure of household dogs to the infected, yet unknown vector(s). The spatial data will be used for future research identifying further human cases as well as the local vector(s)/reservoirs for scrub typhus in southern Chile. The study reinforces that dogs are useful sentinels for Orientia spp. in regions of uncertain endemicity and distribution.

Under-diagnosis of rickettsial disease in clinical practice: A systematic review

BACKGROUND

Rickettsial diseases present as acute febrile illnesses, sometimes with inoculation eschars.

METHODS

We performed a systematic review of studies published between 1997 and 2017 to assess the underestimation of non-eschar rickettsial disease (NERD) relative to eschar rickettsial disease (ERD), as a cause of acute fever in patients with rickettsial diseases that commonly present with eschar(s): scrub typhus (ST), Mediterranean spotted fever (MSF), and African tick-bite fever. We compared ERD/NERD ratios according to study design: 'complete approach' studies, with testing performed in all patients with 'unspecified febrile illness'; versus 'clinical judgement' studies, with testing performed if patients presented with specific symptoms.

RESULTS

In 'complete approach' studies, ERD/NERD ratios were significantly lower, suggesting a considerable under-diagnosis of NERD in 'clinical judgement' studies. Based on these results, we estimate that the diagnosis of rickettsial disease was missed in 66.5% of patients with ST, and in 57.9% of patients with MSF.

CONCLUSIONS

Study design influences the reported eschar rates in ST and MSF significantly. NERD is likely to be a vastly underdiagnosed entity, and clinicians should consider and test for the disease more often.

PROSPERO REGISTRATION NUMBER

CRD 42016053348.

A review of the global epidemiology of scrub typhus

Scrub typhus is a serious public health problem in the Asia-Pacific area. It threatens one billion people globally, and causes illness in one million people each year. Caused by Orientia tsutsugamushi, scrub typhus can result in severe multiorgan failure with a case fatality rate up to 70% without appropriate treatment. The antigenic heterogeneity of O. tsutsugamushi precludes generic immunity and allows reinfection. As a neglected disease, there is still a large gap in our knowledge of the disease, as evidenced by the sporadic epidemiologic data and other related public health information regarding scrub typhus in its endemic areas. Our objective is to provide a systematic analysis of current epidemiology, prevention and control of scrub typhus in its long-standing endemic areas and recently recognized foci of infection.

Situation of Sri Lanka, where autochthonous malaria is no longer a problem, and other infections dominate, such as dengue, leptospirosis and rickettsioses

PURPOSE OF REVIEW

Sri Lanka achieved a major milestone in communicable disease control in 2012 by reporting zero incidence of autochthonous malaria. However, reduction of malaria was associated with concurrent increase of several tropical diseases. This review looks into the time trends and epidemiology of these communicable diseases in Sri Lanka.

RECENT FINDINGS

Reduction of malaria cases coincides with an increase of dengue, leptospirosis and rickettsioses in Sri Lanka. Although the case fatality rate of dengue has reduced and maintained below 1%, leptospirosis in clinical management is questionable. Despite having national focal points for control and prevention, these emerging diseases are completely out of control. Whether the holding back of vector control activities of malaria after a successful control programme is having an effect on emergence of other vector-borne diseases should be studied.

SUMMARY

The communicable disease control programme in Sri Lanka should be further strengthened with availability of proper and rapid diagnostic facilities. Malaria control could not be considered as a great achievement due to the fact that other emerging infectious diseases are replacing malaria.

Revisiting clinico-epidemiological pattern of human rickettsial infections in the central region of Sri Lanka: a hospital based descriptive study

Background

This study revisits the clinico-epidemiology and serological patterns of rickettsioses in the central region of Sri Lanka and highlights the need of advanced diagnostics for precise identification of species responsible for rickettsioses.

Methods

The patients treated for rickettsioses between November 2009 and October 2011 were recruited for the study from Teaching Hospital, Peradeniya. Clinical characteristics and serology results were used for diagnosis.

Results

Study included 210 patients (mean age 44 years ± 3.2) and of them 188 (90%) had positive IgG and/or IgM sero-reactivity for spotted fever group (SFG). Of them, 134 had IgG titre ≥1/256 for SFG and presented with fever and skin rash. They also had headache [n = 119 (89%)], myalgia [n = 103 (77%)], arthralgia [n = 89 (66%)] of large joints, conjunctival injections [n = 83 (62%)], thrombocytopenia (n = 78.58%), anaemia (n = 14.10%), leukocytosis [n = 35 (26%)], leucopenia [n = 17 (13%)], elevated aspartate transaminase [n = 69 (52%)] and alanine transaminase [n = 73 (55%)].

Conclusions

Predominance of SFG rickettsioses are reiterated, possibly transmitted by ticks. Joint disease is common with occasional fern leaf skin necrosis. Changing socio-economic conditions, vegetations, contact with domestic and wild animals, abundance of vectors would have contributed for emergence and sustenance of SFG in the region. Further research is needed to identify the causative agents and the mode of transmission.

Seroepidemiology of Spotted Fever Rickettsiosis in Uttar Pradesh: A Prospective Study

INTRODUCTION

Spotted Fever Rickettsiosis (SFR), an acute febrile illness caused by Rickettsia rickettsii, R. conorii and R. akari which is associated with considerable morbidity and mortality. SFR is one of the most covert emerging infections of the present time which is prevalent in various parts of India as shown by the increase in the number of clinically diagnosed patients in various states except Uttar Pradesh.

AIM

To diagnose SFR in clinically suspected patients using serological tests and recognition of common epidemiologic situations and clinical manifestations of SFR in the state of Uttar Pradesh.

MATERIALS AND METHODS

Patients of all age groups presented with a diagnosis of Pyrexia of Unknown Origin (PUO) from May 2013 to February 2015 were evaluated. Testing was done using a nonspecific Weil felix test followed by more specific Enzyme Linked Immunosorbent Assay (ELISA) and a gold standard Immunofluorescence Assay (IFA) test for specific IgM antibodies against Rickettsia conorii. The data was statistically analysed on Graph Pad Prism (5.0) software by using Chi-square test.

RESULTS

Of the 432 patient samples tested by non specific Weil felix test, 200 (46.29 %) samples showed titre 1:80 or more and were taken as positive. Similarly out of the 432 blood samples tested by both ELISA and IFA based test against Rickettsiaconorii IgM antibody, only 115 (26.62%) samples were found to be positive and these samples were also positive by Weil felix. The common symptoms noted were fever, hepatomegaly, thrombocytopenia, lymphadenopathy and rashes, nausea followed by icterus, cyanosis, headache, oedema and abdominal pain. Eschar was found in only four (3.4%) patients. We also found that 31 patients with SFR also had associated co-infections like typhoid, malaria, dengue and hepatitis.

CONCLUSION

Our findings demonstrated that Weil Felix test can fill in as an underlying yet not sole strategy to perceive and analyse rickettsial ailments, as it needs specificity. So, it may be used to assess the burden in the area and later on other tests like ELISA or IFA can be added, as these are more specific diagnostic tests. Further, our results also showed that if a patient tests positive for the more common endemic infections, we must test for rickettsiosis so that appropriate treatment could be administered.

Widespread subcutaneous necrosis in spotted fever group Rickettsioses from the coastal belt of Sri Lanka- a case report

BACKGROUND

Spotted fever group rickettsioses (SFGR) transmitted mostly by ticks are increasingly discovered around the World and some of them are either re-emerging or emerging in Sri Lanka. Accidental human infections caused by these vector borne zoonotic diseases generally give rise to nonspecific acute febrile illnesses which can be complicated by multi organ involvement carrying high morbidity and mortality. Nonspecific clinical features and non-availability of early diagnostic facilities are known to result in delay in the diagnosis of rickettsial infections. Therefore, awareness of their prevalence and more importantly their clinical features would be help in the early diagnosis and institution of appropriate therapy.

CASE PRESENTATION

A 39-year-old otherwise healthy female presented with an acute febrile illness complicated by severe small joint and large joint arthritis, jaundice, acute kidney injury and disseminated intravascular coagulation (DIC) mimicking palindromic rheumatism or severe sepsis. She later developed a widespread fern-leaf pattern necrotic skin rash with evidence of vasculitis on the palms and soles, aiding the clinical diagnosis of SFGR. She had very high antibody titres against R. conorii antigen confirming the diagnosis and recovered completely with anti-rickettsial therapy.

CONCLUSION

We feel that clinicians should be aware of the unusual clinical presentations such as purpura fulminans and 'fern-leaf' pattern necrotic skin rash of SFGR infection. Such knowledge would not only benefit those who practice in tropics with limited diagnostic facilities but also would improve the management of acute febrile illness in returning travelers who visit endemic areas.

Rickettsial infection among military personnel deployed in Northern Sri Lanka

Background

Military personnel deployed in field actvities report on frequent tick bites. Therefore they may run the risk of exposure to rickettsial organisms.

Methods

In 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.

Results

In 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,

Conclusions

Exposure 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.

Emerging scrub typhus infection in the northern region of Sri Lanka

Background

There is an increasing trend in rickettsioses or typhus fevers in the island of Sri Lanka. The seroepidemiological mapping previously published did not include the northern region of the island. This study was conducted to demonstrate the presence of scrub typhus (ST) and to characterise the clinical presentation of ST in this region.

Findings

Serum samples from patients (n = 64) with clinical symptoms suspected of typhus fever following exclusion of other common febrile illnesses commonly seen in the northern region of Sri Lanka were selected and screened for ST using specific IgM and IgG ELISA (ImBios, USA). ST was confirmed by serology in 54 patients, with typical eschar being found in 49 of cases positive for ST. Fever was the sole presenting complaint of these patients with the duration of febrile illness varying from 2–14 days. Of these patients 44.4% had regional lymphadenopathy, 18.5% hepatomegaly, 12.9% pneumonitis and 9.3% splenomegaly. None of the patients had a rash.

Conclusions

This study confirms the presence of high numbers of patients with ST in northern Sri Lanka. It was found that 84.4% of the patients presenting with clinical features of rickettsioses (54 of the 64) were seropositive for ST with a significant majority having a typical eschar. This data provided will enable clinicians to be vigilant of ST in this region and provide appropriate therapy and also facilitate planning for preventive measures aimed at reducing the burden of ST.

Cutaneous manifestations of spotted fever rickettsial infections in the Central Province of Sri Lanka: a descriptive study

BACKGROUND

Characteristic skin lesions play a key role in clinical diagnosis of spotted fever group rickettsioses and this study describes these cutaneous manifestations along with basic histological features.

METHODS AND FINDINGS

Study was conducted at Medical Unit, Teaching Hospital, Peradeniya, from November 2009 to October 2011, where a prospective data base of all rickettsial infections is maintained. Confirmation of diagnosis was made when IgM and IgG immunofluorescent antibody titre of 1/32 and >1/256 respectively. Of the 210 clinical cases, 134 had cutoff antibody titers for Rickettsia conorii antigen for confirmation. All these 134 patients had fever and skin rash, and of them 132(98%) had discrete maculopapular rash while eight (6%) had fern leaf type skin necrosis. Eight patients (6%) had healed tick bite marks. Average size of a skin lesion was 5 mm and rash involved 52% of body surface, distributed mainly in limbs and back of the chest. Generally the facial and leg skin was slightly oedematous particularly in old aged patients. Sixteen patients (12%) had pain and swelling of ankle joints where swelling extended to feet and leg. Biopsies from skin rash of six patients showed evidence of cutaneous vasculitis and of them, 247 bp region of the 17-kDa spotted fever group specific protein antigen was amplified using PCR.

CONCLUSIONS

A discrete maculopapular rash and occasional variations such as fern leaf shape necrosis and arthritis are found in spotted fever group. Histology found vasculitis as the pathology of these lesions.

Serological evidence for exposure of dogs to Rickettsia conorii, Rickettsia typhi, and Orientia tsutsugamushi in Sri Lanka

Vector-borne rickettsial infection is a major cause of febrile illnesses throughout the world. Although vertebrates hosting the vectors play a vital role in the natural cycle of rickettsiae, studies have not been conducted on them in Sri Lanka. Therefore, the present study was designed to determine the exposure of dog population in Rajawatta, Thambavita, and areas of the Western Slopes and Unawatuna of Sri Lanka to rickettsial pathogens. A total of 123 dog blood samples were collected from those areas. Samples were tested for antibodies against Rickettsia conorii (RC) of the spotted fever group (SFG), Rickettsia typhi (RT) of the typhus group (TG), and Orientia tsutsugamushi (OT) of the scrub typhus group (ST) of rickettsiae by indirect immunofluorescence antibody test (IFA). Samples with titers ≥ 1:64 were considered as positive in this study. Collectively, 49% dogs were found to have antibodies against the rickettsial agents. Of the dogs, 42%, 24%, and 2% had antibodies against RC, OT, and RT, respectively. The seropositive rate of 100% was observed in areas of the Western Slopes, whereas the lowest rate of 20% was in Unawatuna. Among the positive samples, antibody titers against RC and OT ranged from 1/64 to 1/8192. In contrast, the few dogs that tested positive for RT showed very low titers of 1/64 and 1/128. Results of this study show the extent of exposure to the pathogen and its dispersion in the natural ecology. We suggest that dogs could be acting as reservoirs in the rickettsial transmission cycle or could be effective tracer animals that can be used to detect areas with potential for future outbreaks.