Bio-efficacy of deltamethrin based durable wall lining against wild populations of Anopheles gambiae s.l. in Northern Tanzania.

BACKGROUND: Indoor residual spraying (IRS) is one of the preferred tools used for control of malaria in many settings in the world. However, this control tool still faces challenges that include lack of long lasting active ingredient, limited number of well-trained personal, and need of repeated treatment which increases operational costs and reduces acceptability by residents. As a result there is need to develop and validate other methods which can complement the existing controls. The current study compared the bio-efficacy of durable wall lining (DL) (treated with deltamethrin 265 mg/m2) and IRS (with deltamethrin 5% WP at 20 mg/m2) on indoor mosquitoes densities and biting behaviour of mosquitoes in comparison with control houses without either DL or IRS. METHODS: A study with two treatment arms and a control was conducted in Magugu ward, Northern Tanzania. Overall, a total of 60 houses were selected for the study with 20 houses per treatment arm and control. From each arm and control five houses were selected for mosquitoes trapping. Mosquitoes were sampled from 18:00 to 07:00 hourly every month for a period of 6 months. Mosquitoes were sampled using CDC miniature light traps. RESULTS: A total of 14,400 female wild mosquitoes were used for contact bioassays in the control arm. 20 houses were sprayed, additionally walls of 20 houses were installed with wall liners, and walls of 20 unsprayed houses were used as control. Also, a total of 946 mosquitoes were sampled with traps in 60 houses during the hourly sampling for 6 months. A total of 3000 unfed females of An. gambiae s.l. wild population raised from larvae were collected from natural habitats in the same village for bioassays. The decline in indoor mosquitoes densities observed in this study did not lead to a shift in the biting cycles (P = 0.712). The number of mosquitoes caught indoors in houses with DL and IRS was significantly lower (P < 0.001) compared to control houses. When the comparisons were done between DL and IRS houses, the densities were significantly lower in DL houses compared to IRS houses (P = 0.021). In the DL installed houses, indoor mosquito density declined notably and sustained throughout the 6 months of the study. However, in those houses sprayed with deltamethrin 5% WP (PALI™5 WP), the density noted to start to increase within four months after spraying(do you mean to say that the densities declined up to 4 months post spraying and thereafter increased. CONCLUSIONS: Considering the efficacy duration of DL against IRS with deltamethrin 5% WP on mosquito densities decline indoors. The results of this study suggest that DL is more effective in malaria control as its efficacy lasted more than that of IRS.

Effect of Deforestation and Land Use Changes on Mosquito Productivity and Development in Western Kenya Highlands: Implication for Malaria Risk.

BACKGROUND: African highlands were known to be free of malaria for the past 50 years. However, the ever growing human population in the highlands of Africa has led to the deforestation and land coverage changes to create space for more land for cultivation, grazing, and house construction materials needs. This has lead to the creation of suitable breeding habitats, which are in open places. Decrease of canopy and forest cover has led to increased temperature both in outdoors and indoors in deforested areas. This increased temperature has resulted in the shortening of developmental stages of aquatic stages of mosquitoes and sporogony development in adult mosquitoes. METHOD: Assessment of the effects of deforestation and land coverage changes (decrease), which leads to temperature changes and subsequently increases survivorship of adults and sporogony development in adult mosquitoes' body was gathered from previous data collected from 2003 to 2012 using different analysis techniques. Habitats productivity, species dynamics and abundance, mosquitoes feeding rates, and sporogony development are presented in relation to temperature changes. RESULTS: The effects of temperature rise due to land cover changes in highlands of western Kenya on larval developmental rates, adult sporogony developments, and malaria risk in human population were derived. Vector species dynamics and abundance in relation to land use changes have been found to change with time. CONCLUSION: This study found that, land cover changes is a key driver for the temperature rise in African highlands and increases the rate of malaria vectors Anopheles gambiae ssp., An. Funestus, and An. arabiensis colonizing the highlands. It has also significantly enhanced sporogony development rate and adult vector survival and therefore the risk of malaria transmission in the highlands.

Social economic factors and malaria transmission in Lower Moshi, northern Tanzania.

BACKGROUND: For many years social economic status has been used as an indicator to characterize malaria treatment seeking behaviors of communities and their adherence to malaria control programs. The present study was therefore conducted to assess the influence of household social economic status, knowledge, attitude and practice on treatment seeking behaviors, distance to health facilities and vector control measures in the Lower Moshi area, northern Tanzania. METHODS: A cross-sectional household survey was carried out, a quantitative method was used to collect information from the households, and the household socio-economic status was estimated by employing a household asset-based approach. The structured questionnaire also collected information on malaria knowledge, attitudes and treatment seeking behaviors. RESULTS: A total of 197 (68.8% were female) household heads were interviewed. Distance to the health centers influenced malaria treatment seeking behaviors especially for children (P = 0.001) and the number of visits to the health facilities made by the household members (P = 0.001). The head of the households' level of education had an influence on bed-net retreatment (P < 0.001) and acceptability of larval control programmes (P <0.001). Similarly, a significant association was observed between bed-net retreatment, larval control and occupation of the head of the household . CONCLUSION: Distance to the health centre influenced malaria treatment seeking behaviors, and the number of visits made by the household members. In addition, the education level of the household heads played a role in understanding and in the selection of malaria interventions for the households. Increasing the number of health facilities close to rural areas will improve malaria treatment seeking behavior, case management and hence reduce malaria-associated morbidities, especially in high risk groups.

Low sensitivity of ParaHIT-f rapid malaria test among patients with fever in rural health centers, Northern Tanzania.

INTRODUCTION: Several rapid diagnostic tools for malaria are currently available in local markets. However, diagnostic accuracy varies widely. The present study was conducted to evaluate a cheaply and easily available rapid diagnostic malaria test (ParaHIT-f) in rural Tanzania. METHODOLOGY: Participants presenting with fever at health centers in the Kilimanjaro and Manyara regions were eligible. Parasitological thin and thick smears were examined from finger-prick blood samples and compared to ParaHIT-f test results. Sensitivity, specificity and predictive values were calculated using microscopic parasitological examination as the gold standard. RESULTS: In total, 236/743 (31.8%) individuals had a positive malaria microscopy, and 25/715 (3.4%) were positive in the rapid diagnostic test. The sensitivity of ParaHIT-f was 10.7% (95% CI, 6.7-14.7) and specificity was 100% (95% CI, 97.4-102), with positive and negative predictive values (PPV and NPV) of 100% (95% CI, 99.1-100.2) and 70.9% (95% CI, 66.9-74.9) respectively. Sensitivity of ParaHIT-f increased with increasing P. falciparum density (P > 0.003) from 5.8% (95% CI, 0-12.9) at < 100 parasites/µl to 20.5% (95% CI, 13.5-27) at ≥ 100 parasites/µl. CONCLUSIONS: Sensitivity of the ParaHIT-f rapid test was very low in this setting, therefore concomitant use of rapid diagnostic tests and microscopy is recommended. In the case of positive test results, confirmation by parasitological techniques is not necessary. Further monitoring of ParaHIT-f in various epidemiological settings in Tanzania is warranted. 

Is aging raw cattle urine efficient for sampling Anopheles arabiensis Patton?

BACKGROUND: To ensure sustainable routine surveillance of mosquito vectors, simple, effective and ethically acceptable tools are required. As a part of that, we evaluated the efficiency of resting boxes baited with fresh and aging cattle urine for indoor and outdoor sampling of An. arabiensis in the lower Moshi rice irrigation schemes. METHODS: A cattle urine treatment and re-treatment schedule was used, including a box with a piece of cloth re-treated with urine daily, and once after 3 and 7 day. Resting box with piece of black cloth not treated with urine was used as a control. Each treatment was made in pair for indoor and outdoor sampling. A 4 by 4 Latin square design was used to achieve equal rotation of each of the four treatments across the experimental houses. Sampling was done over a period of 6 months, once per week. RESULTS: A total of 7871 mosquitoes were collected throughout the study period. 49.8% of the mosquitoes were collected from resting box treated with urine daily; 21.6% and 20.0% were from boxes treated 3 and 7 days respectively. Only 8.6% were from untreated resting box (control). The proportion collected indoors was approximately 2 folds greater than the outdoor. Of all mosquitoes, 12.3% were unfed, 4.1% full fed, 34.2% semi-gravid and 49.4% gravid. CONCLUSION: Fresh and decaying cattle urine odour baited resting boxes offer an alternative tool for sampling particularly semi-gravid and gravid An. arabiensis. Evaluation in low density seasons of An. arabiensis in different ecological settings remains necessary. This sampling method may be standardized for replacing human landing catch.

A resting box for outdoor sampling of adult Anopheles arabiensis in rice irrigation schemes of lower Moshi, northern Tanzania.

BACKGROUND: Malaria vector sampling is the best method for understanding the vector dynamics and infectivity; thus, disease transmission seasonality can be established. There is a need to protecting humans involved in the sampling of disease vectors during surveillance or in control programmes. In this study, human landing catch, two cow odour baited resting boxes and an unbaited resting box were evaluated as vector sampling tools in an area with a high proportion of Anopheles arabiensis, as the major malaria vector. METHODS: Three resting boxes were evaluated against human landing catch. Two were baited with cow odour, while the third was unbaited. The inner parts of the boxes were covered with black cloth materials. Experiments were arranged in latin-square design. Boxes were set in the evening and left undisturbed; mosquitoes were collected at 06:00 am the next morning, while human landing catch was done overnight. RESULTS: A total of 9,558 An. arabiensis mosquitoes were collected. 17.5% (N = 1668) were collected in resting box baited with cow body odour, 42.5% (N = 4060) in resting box baited with cow urine, 15.1% (N = 1444) in unbaited resting box and 24.9% (N = 2386) were collected by human landing catch technique. In analysis, the house positions had no effect on the density of mosquitoes caught (DF = 3, F = 0.753, P = 0.387); the sampling technique had significant impact on the caught mosquitoes densities (DF = 3, F 37. 944, P < 0.001). CONCLUSION: Odour-baited resting boxes have shown the possibility of replacing the existing traditional method (human landing catch) for sampling malaria vectors in areas with a high proportion of An. arabiensis as malaria vectors. Further evaluations of fermented urine and longevity of the urine odour still need to be investigated.

Insecticides Susceptibility Status of the Bedbugs (Cimex lectularius) in a Rural Area of Magugu, Northern Tanzania.

The recent spread of bedbugs, Cimex lectularius L. (Heteroptera: Cimicidae), has received attention of the public health sector for designing of effective plan of action for control. Several studies have focused on determining the distribution and abundance of bedbug populations in tropical areas. This study establishes baseline information on deltamethrin, permethrin, alphacypermethrin, lambdacypermethrin and K-O tab susceptibility status in a bedbug population collected from Magugu area in northern Tanzania. The evolution of insecticide resistance could be a primary factor in explaining this resurgence of bedbugs in many areas, both rural and urban. Evaluation of the bedbug population from houses in Magugu indicates that the population of bedbugs is susceptible to pyrethroid insecticides, which are commonly used. Without the development of new tactics for bedbug resistance management, further escalation of this public health problem should be expected when resistant gene spreads within the population. These results suggest that although all concentrations kill bedbugs, more evaluations should be done using WHO kits and mechanisms involved in pyrethroid resistance should be evaluated, such as metabolic and knockdown resistance gene, to have a broad picture for better design of control methodologies.