Geographical distribution of primary & secondary dengue cases in India – 2017: A cross-sectional multicentric study

Background & objectives: Dengue virus infection is endemic in India with all the four serotypes of dengue virus in circulation. This study was aimed to determine the geographic distribution of the primary and secondary dengue cases in India. Methods: A multicentre cross-sectional study was conducted at Department of Health Research / Indian Council of Medical Research (DHR)/(ICMR) viral research and diagnostic laboratories (VRDLs) and selected ICMR institutes located in India. Only laboratory-confirmed dengue cases with date of onset of illness less than or equal to seven days were included between September and October 2017. Dengue NS1 antigen ELISA and anti-dengue IgM capture ELISA were used to diagnose dengue cases while anti-dengue IgG capture ELISA was used for identifying the secondary dengue cases. Results: Of the 1372 dengue cases, 897 (65%) were classified as primary dengue and 475 (35%) as secondary dengue cases. However, the proportion varied widely geographically, with Theni, Tamil Nadu; Tirupati, Andhra Pradesh and Udupi-Manipal, Karnataka reporting more than 65 per cent secondary dengue cases while Srinagar, Jammu and Kashmir reporting as low as 10 per cent of the same. The median age of primary dengue cases was 25 yr [interquartile range (IQR 17-35] while that of secondary dengue cases was 23 yr (IQR 13.5-34). Secondary dengue was around 50 per cent among the children belonging to the age group 6-10 yr while it ranged between 20-43 per cent among other age groups. Interpretation & conclusions: Our findings showed a wide geographical variation in the distribution of primary and secondary dengue cases in India. It would prove beneficial to include primary and secondary dengue differentiation protocol in the national dengue surveillance programme.

Acute and chronic toxicity of copper on aquatic insect Chironomus ramosus from Assam, India.

Acute toxicity of copper (Cu) on Chironomus ramosus was determined by exposing third-instar larvae to graded concentrations of copper sulphate (CuSO4. 5H2O). Median lethal concentrations (LC50) of Cu as CuSO4 at 24, 48, 72 and 96 hr were determined as 3280, 1073.33, 780, and 183 μg l-1, respectively. For determining the effects of chronic toxicity, small first-instar larvae were individually exposed to sublethal concentrations of copper sulphate (1.0-18.0 μg l-1) for a period of 21 days. Discoloration and thinning of body were detected at 1 μg l-1 and ventilation movements, pupation and adult emergence were significantly affected at 1.8 μg l-1. At 10 μg l-1 CuSO 4 concentration, growth and tube-building activities of the larva were significantly different from the control.

Acute toxicity of endosulfan and malathion on Chironomus ramosus (Insecta : Diptera : Chironomidae) from north Cachar hills, Assam, India.

Acute toxicity tests for the pesticides endosulfan and malathion on the larvae of Chironomus ramosus were conducted. Median Lethal Concentration (LC50 ) values of endosulfan were 0.55 x 10-2, 0.16 x 10-2, 0.089 x 10-2 and 0.036 x 10-2 ppb respectively, while those for malathion were 0.139 x 10-2, 0.054 x 10-2, 0.019 x 10-2 and 0.0032 x 10-2 ppb respectively, at 24 , 48, 72 and 96 hr. Thus Chironomus ramosus larvae were more sensitive to malathion at all hours of toxicity tests than endosulfan.

Role of virulence plasmid of Aeromonas hydrophila in the pathogenesis of ulcerative disease syndrome in Clarias batrachus.

Pathogenic Aeromonas hydrophila (strain VB21), a multiple-drug resistance strain contains a plasmid of about 21 kb. After curing of plasmid, the isolates became sensitive to antimicrobials, to which they were earlier resistant. The cured bacteria exhibited significant alterations in their surface structure, growth profile and virulence properties, and failed to cause ulcerative disease syndrome (UDS) when injected into the Indian catfish Clarias batrachus. Routine biochemical studies revealed that the plasmid curing did not alter the biochemical properties of the bacteria. After transformation of the plasmid into cured A. hydrophila the bacterium regained its virulence properties and induced all the characteristic symptoms of UDS when injected into fish. Thus, the plasmid plays a pivotal role in the phenotype, growth and virulence of A. hydrophila and pathogenesis of aeromonad UDS.