ABSTRACT
BACKGROUND AND OBJECTIVES: During the first week of July 2003, suspected cases of dengue fever were reported from three villages in Kanyakumari district in Tamil Nadu. Since the fever outbreak occurred for the first time in these villages, serological, virological and entomological investigations were carried out to confirm the aetiology of outbreak. METHODS: A total of 76 plasma samples were collected from suspected cases of dengue fever and screened for the presence of IgM antibodies by Pan Bio ELISA kit. Toxo-IFA system was used for the isolation of dengue virus from the plasma samples. Vector survey employing ovitraps and adult landing collection were carried out in the study villages. Pooled samples of Aedes mosquito were screened for dengue virus antigen by an in-house antigen capture ELISA test employing dengue virus specific monoclonal antibodies. RESULTS: Of the 76 samples tested, 15 (20%) were found positive for dengue virus specific IgM antibodies. Dengue virus serotype-3 was detected from a plasma sample by Toxo-IFA test using virus specific monoclonal antibodies. Entomological survey revealed the abundance of Aedes albopictus (Skuse) mosquitoes in the study area. One pool consisting of 12 Ae. albopictus males were found positive for dengue virus infection. INTERPRETATION AND CONCLUSION: Based on the IgM antibody capture ELISA results, it was evident that the current infection was caused by dengue virus in the affected areas. All the age groups were affected during this outbreak. Detection of dengue virus serotype-3 in plasma samples further confirmed the aetiology of this outbreak. The high prevalence of the mosquito vector Ae. albopictus (Skuse) was observed. Detection of dengue virus antigen in the male mosquitoes confirms that the virus is maintained in wild populations of Ae. albopictus in these areas.
Subject(s)
Adolescent , Adult , Animals , Antibodies, Viral/blood , Child , Child, Preschool , Dengue/epidemiology , Dengue Virus/immunology , Disease Outbreaks , Female , Humans , Immunoglobulin M/blood , India/epidemiology , Infant , MaleABSTRACT
Out of 5357 wild-caught mosquitoes in 163 pools tested for virus using antigen capture ELISA and an insect-bioassay (inoculation into Toxorhynchites splendens larvae and identification by IFA using JE virus-specific monoclonal antibody), 16 flavivirus isolations were made of which 12 (75%) were identified as JE virus. Of the 12 JE virus isolations, 7 were from Culex tritaeniorhynchus, 3 from Mansonia uniformis and 1 each from Ma. indiana and Anopheles subpictus. Four isolations from Mansonia species for the first time reported here are noteworthy.
Subject(s)
Animals , Antibodies, Monoclonal/diagnosis , Disease Outbreaks , Encephalitis Virus, Japanese/isolation & purification , Encephalitis, Japanese/epidemiology , Enzyme-Linked Immunosorbent Assay , Fluorescent Antibody Technique, Direct , Humans , India/epidemiologyABSTRACT
Entomological studies showed that due to outdoor resting by the vector Anopheles culicifacies as well as poor spray coverage, indoor residual spraying with malathion was ineffective in malarious villages of the Thenpennai riverine tract in Tamil Nadu. Over a 4 yr period during which residual spraying was supplemented with ground applications of malathion space spraying, the slide positivity among patients with fever fell from 21.04 to 1.1 per cent. In mass blood surveys 0.7 per cent persons surveyed at the beginning of the study were positive for the malarial parasite, but no positives were detected in the last survey, in 1984. There was a rising trend in malaria incidence in riverine villages outside the programme.