Characteristics of the initial dengue outbreaks in a region without dengue prior to mid-2009 in a dengue-endemic country.

INTRODUCTION: The present study evaluated the characteristics of the initial dengue outbreaks in the Jaffna peninsula, a region without dengue prior to mid-2009 in dengue-endemic Sri Lanka, a tropical island nation. METHODOLOGY: This is a cross-sectional study conducted using a total of 765 dengue patients' clinical data and samples collected from the Teaching Hospital, Jaffna during the initial dengue outbreaks. Clinical, non-specific, and specific virological laboratory characteristics including the platelet count, NS1 antigen, and anti-DENV IgM/IgG were evaluated as correlates of dengue virus (DENV) infection in the two initial outbreaks of 2009/2010 and 2011/2012 in Northern Sri Lanka. RESULTS: Firstly, affected age and clinical characteristics were significantly different between the outbreaks (p < 0.005). Secondly, NS1 antigen detection in patients with fever days < 5 was statistically significant (p < 0.005). Thirdly, platelet count, detection of NS1 antigen, and anti-DENV IgM/IgG profiles were adequate to diagnose 90% of the patients; hepatomegaly and platelet count of < 25,000/mm3 were identified as predictors of severe disease. Fourthly, secondary DENV infections were detected in the early stages of the illness in many patients. Finally, infecting DENV serotypes were different between the two outbreaks. CONCLUSIONS: Clinical and non-specific laboratory characteristics and the infecting DENV serotypes between the two initial outbreaks in Northern Sri Lanka were significantly different. NS1 antigen, anti-DENV IgM/IgG, and platelet counts were identified 90% of the dengue patients. Hepatomegaly and platelet count of < 25,000/mm3 were able to predict the disease severity in this study.

Comparison of a rapid immuno-chromatography assay with a standard ELISA for the detection of IgM and IgG antibodies against dengue viruses.

A total of 765 blood samples collected from dengue suspected patients admitted to a Teaching Hospital in Sri Lanka were used to compare a rapid ICT assay with a standard ELISA for the detection of anti-dengue virus (DENV) IgM and IgG. Detection accuracy indices including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), Chi square and Cohen's kappa values were determined for the ICT assay using the ELISA as a comparator for the detection of anti-DENV IgM and IgG. The rapid ICT assay showed a sensitivity of 64%, specificity of 75%, NPV of 68% and PPV of 72% for anti-DENV IgM detection. However, all the accuracy indices were relatively higher for the anti-DENV IgG detection by the ICT assay than those for anti-DENV IgM detection. Despite the low sensitivity for anti-DENV IgM detection by the ICT assay, considering the limitations in using ELISAs in resource limited regions, rapid ICT assays would be useful for the detection of more recent DENV infections. As many patients present after fever days 5 in the study area, anti-DENV IgM/IgG would be the suitable marker to be detected by rapid ICT assays in such areas.

Blood group AB is associated with severe forms of dengue virus infection.

Several viral and host factors are believed to contribute to the development of severe forms of dengue such as dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) following a dengue virus (DENV) infection. The pathogenesis of DHF/DSS is not fully understood, however, host factors like ABO blood groups have been shown to contribute to the severity of DENV infection. The present study investigated the association of blood groups with severity of DENV infection in the northern region of Sri Lanka. The blood-groups of 405 patients positive for DENV NS1 antigen and anti-DENV IgM/IgG were determined using the standard haemagglutination assay recommended by the national blood bank/s. The occurrence of severe dengue in patients with certain blood groups was significantly different (p < 0.001) to those with other blood groups. Patients with AB blood group had more than 2.5 times higher risk of developing DHF than those with other blood groups. On the other hand, patients with blood group O were significantly under represented for DHF relative to the proportion of this blood group in the general population. Thus dengue patients with blood group O appear to have a low risk of developing DHF than those with other blood groups.

In ovo delivery of CpG DNA reduces avian infectious laryngotracheitis virus induced mortality and morbidity.

Endosomal toll-like receptor-21 and -9 sense CpG DNA activating production of pro-inflammatory mediators with antimicrobial effects. Here, we investigated the induction of antiviral response of in ovo delivered CpG DNA against infectious laryngotracheitis virus (ILTV) infection. We found that in ovo delivered CpG DNA significantly reduces ILTV infection pre-hatch correlating with the expression of IL-1ß and increase of macrophages in lungs. As assessed in vitro, CpG DNA stimulated avian macrophages could be a potential source of IL-1ß and other pro-inflammatory mediators. Since we also found that in ovo CpG DNA delivery maintains increased macrophages in the lungs post-hatch, we infected the chickens on the day of hatch with ILTV. We found that in ovo delivered CpG DNA significantly reduces mortality and morbidity resulting from ILTV infection encountered post-hatch. Thus, CpG DNA can be a candidate innate immune stimulant worthy of further investigation for the control of ILTV infection in chickens.

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.