House Structure Is Associated with Malaria among Febrile Patients in a High-Transmission Region of Zambia

Since the late nineteenth century, the importance of house structure as a determinant of malaria risk has been recognized. Few studies to date have examined the association of housing and malaria in clinical populations. We conducted a cross-sectional study of febrile patients (n = 282) at two rural health clinics in a high malaria-transmission area of northern Zambia. Participants underwent testing for Plasmodium falciparum infection by PCR. Demographic and other risk factors including house structure, indoor residual spraying (IRS), bed net use, education level, and household income were collected. Data were fitted to logistic regression models for relational and mediation analyses. Residing in a house with a thatch roof was associated with higher odds of malaria than residing in a house with corrugated metal (odds ratio: 2.6; 95% CI: 1.0–6.3, P = 0.04). Lower income and educational attainment were also associated with greater odds of malaria. Living under a thatch roof accounted for 24% (95% CI: 14–82) of the effect of household income on malaria risk, and income accounted for 11% (95% CI: 8–19) of the effect of education. Neither IRS nor bed net use was associated with malaria risk despite large, local investments in these vector control interventions. The findings testify to malaria as a disease of rural poverty and contribute further evidence to the utility of housing improvements in vector control programs.

Roof Runoff Water as Source of Pollution: A Case Study of Some Selected Roofs in Orlu Metropolis, Imo State, Nigeria

Samples collected from different runoffs; AR, GMR, TR, ASR, and DR for aluminum roof, galvanized metal roof, thatch roof, asbestos roof and ambient rainfall respectively were analyzed for pH, conductivity, turbidity, TDS, TSS, NO3-, PO43-, Cd, Cu, Fe, Zn and Pb. The result indicates that the mean concentration of the parameters analyzed ranged from 5.8± 0.39 –7.10±0.70, 22.25±11.70-79.99± 3.40μScm-1, 1.47±0.43 - 46.53±1.60mg/l, 11.90±0.93 - 59.83±1.62NTU,15.53±0.70 - 204.53±5.08mg/l, 0.93±0.06 - 2.55±0.13 mg/l, 1.33±0.22 - 7.30±0.57mg/l respectively for pH, conductivity, TDS, turbidity, TSS, PO43-and NO3-, and the levels of the heavy metals (in mg/l); Cd, Cu, Fe, Zn and Pb ranged from 0.0023±0.001– 0.0521±0.004, 0.052±0.01–0.2483±0.02, 0.0348±0.01–1.1120±0.07, 0.0161±0.01-0.8093±0.02 and 0.0106±0.01-0.0499±0.002 respectively. Ranking of the heavy metal in roof runoff is in the order; Fe>Zn>Cu>Cd>Pb. The result compared with WHO standard showed elevated level of the parameters analyzed with Cd and Pb exceeding the limit. Though the result of this study showed some variability which is an indication of the type of roofing material; air quality of the environment and industrial activity going on in the area. It could be deduced from the result that roof runoff may be a non point source of environmental pollution owning to the release of heavy metals and other pollutants into the environment, and increased concentration of some of the pollutants as reported by this study suggests that roof runoff water could impact negatively to the environment and if consumed without being treated may be injurious to human health.

Observations on Mosquito Behaviour in Native Huts

Mosquitos continue to enter occupied, untreated native huts throughout the night, with peak periods of entry at dusk and dawn. Early morning mosquito catches do not give a true picture of the numbers entering and leaving huts during the night.In a series of catches 63 per cent. of 5,576 mosquitos and 79 per cent. of 506 Anopheles gambiae were caught resting on the underside of the thatch roof.By using five traps inserted in apertures one foot below the top of the wall, the numbers of mosquitos attempting to leave a hut were determined. Of 1,014 mosquitos entering huts before 10 p.m., 63 per cent. remained inside until 6.30 a.m., that is for 8½ hours. Catches to estimate numbers entering and leaving at different times during the night were also made.Treatment of huts with DDT wettable powder and DDT-kerosene solution did not interfere with the normal behaviour of mosquitos as far as entry was concerned. Biting occurred in the treated huts.The DDT wettable powder appeared to be more effective than the DDT-kerosene solution.Some mosquitos entered the treated huts, fed and then left before acquiring a lethal dose. After making contact with treated surfaces mosquitos became restless but, under the conditions existing in the huts during the experiments, activation did not result in more leaving the treated huts than the untreated one. Unfortunately there were few A. gambiae and the predominant species entering the huts was Taeniorhynchus fuscopennatus.Some of the female A. gambiae released into unoccupied DDT-treated huts escaped into the traps before acquiring a lethal dose. Although there was a tendency for more to enter the traps of a DDT-treated hut than those of an untreated hut, the data are insufficient to show a significant difference.The majority of mosquitos entering the traps did so within one hour of their release.No mosquitos were still alive 12 hours after their release in huts treated 17 weeks previously with DDT wettable powder or DDT-kerosene solution, or in the hut treated 12 weeks previously with "“Gammexane” wettable powder.