The impact of housing structures on filarial infection

A study was undertaken to correlate the impact of housing and patterns of house construction on the vector density and transmission of filaria among the inhabitants of these houses. Three different types of houses in ecologically similar hamlets of Hariharpur village in Varanasi were selected for determining the density of Culex quinquefasciatus, the vector of Wuchereria bancrofti and its infectivity. The maximum per man hour density of the vector was recorded during March (31.66, 40.33 and 41.33) while minimum was recorded during June (1.3, 2.6 and 0.33) in all the three types of houses. Infection rate in the vectors collected from poorly constructed houses was observed during April, May, October and January of the following year, whereas in moderately constructed houses, infection was observed only in September and in the well constructed houses dissection results did not reveal any infection during the months of the study. Infectivity rate was observed to be 10.0% in moderately constructed houses (group B) during the month of September and 14.2% in poorly constructed houses (group C) during the month of October. Parasitological observations of the population showed a 12.2% microfilaria (mf) rate and 6.7% disease rate among the residents of poorly constructed houses, 5.8% mf rate and 2.9% disease rate among residents of moderately constructed houses. Among residents of well built houses (Group A), none were found to be positive with mf, but disease rate was observed to be 2.7%. Throughout the year the relative humidity was observed to be higher in the poorly constructed houses and ambient temperatures were found to be lower during the summer but higher during the winter than to those of the better constructed houses. The study made evident that the construction of houses plays an important role in the vector's resting preference, leading to a higher density in poorly constructed houses, thereby increasing the possibility of infection within them, and thus maintaining a higher potential for filarial transmission among its inhabitants.