Volume 23, Issue 6
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



Exposure to infection with was studied for 1 year in a suburb of Calcutta, India, and correlated with parasitological and clinical observations on the human study population. Blood surveys at the beginning and end of the study showed microfilaremia rates of 12.4% and 14.8%, respectively. The median microfilarial density remained constant at 18 per 20 mm of blood. A clinical survey at the end of the study revealed little severe filarial disease. However, between 30% and 40% of the males in the age groups above 20 years had milder symptoms suggestive of filariasis, mostly small hydroceles and cord abnormalities. Exposure to infection with stage III larvae was very heavy and continuous throughout the year. It was estimated that a person sleeing indoors during the year of this study would have been bitten by 1,850 “infective” mosquitoes carrying a total of 5,904 infective larvae. A person sleeping outdoors during the same period would have been bitten by 1,352 “infective” mosquitoes carrying 4,056 larvae. This heavy exposure was shown to be primarily due to the extremely high mosquito biting density of over 115,000 bites per person per year in the study area. The reasons for the discrepancy between the relatively moderate microfilaremia rates and lack of severe filarial disease which suggest low exposure to infection and the epidemiological data which suggests very high exposure to infection are discussed.


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