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. 

Oviposition Deterrence Induced by Ocimum kilimandscharicum and Ocimum suave Extracts to Gravid Anopheles gambiae s.s (Diptera: Culicidae) in Laboratory.

BACKGROUND: In most of the past decades, mosquito control has been done by the use of indoor residual spray and insecticides-treated bed nets. The control of mosquitoes by targeting the breeding sites (larval habitat) has not been given priority. Disrupting the oviposition sensory detection of mosquitoes by introducing deterrents of plant origin, which are cheap resources, might be add value to integrated vector control. Such knowledge is required in order to successfully manipulate the behavior of mosquitoes for monitoring or control. MATERIALS AND METHODS: Twenty gravid mosquitoes were placed in a cage measuring 30 × 30 × 30 cm for oviposition. The oviposition media were made of different materials. Experiments were set up at 6:00 pm, and eggs were collected for counting at 7:30 am. Mosquitoes were observed until they died. The comparisons of the number of eggs were made between the different treatments. RESULTS: There was significant difference in the number of eggs found in control cups when compared with the number of eggs found in water treated with Ocimum kilimandscharicum (OK) (P=0.02) or Ocimum suave (OS) (P=0.000) and that found in water with debris treated with OK (P=0.011) or OS (P=0.002). There was no significant difference in the number of eggs laid in treated water and the number of eggs laid in water with debris treated either with OK (P=0.105) or OS (P=0.176). Oviposition activity index for both OS and OK experiments lay in a negative side and ranged from -0.19% to -1%. The results show that OS and OK deter oviposition in An.gambiae s.s. CONCLUSIONS: Further research needs to be done on the effect of secondary metabolites of these plant extracts as they decompose in the breeding sites. In the event of favorable results, the potential of these plant extracts can be harnessed on a larger scale.

Longitudinal evaluation of Ocimum and other plants effects on the feeding behavioral response of mosquitoes (Diptera: Culicidae) in the field in Tanzania.

BACKGROUND: The use of repellent materials from plants against nuisance insects is common with great potential to compliment existing malaria control programmes and this requires evaluation in the field. Ocimum plant species, Ocimum suave (Willd) and O. kilimandscharicum (Guerke) materials and their essential oils extracted by steam distillation were evaluated in the field and experimental huts for repellence, exophily and feeding inhibition effects against three mosquito species, Anopheles arabiensis (Patton), An. gambiae ss (Giles) and Culex quinquefasciatus (Say). The protective effect of essential oils from Ocimum plants were compared with N, N-diethly-3- methylbenzamide (DEET), a standard synthetic repellent. Also, the protective effect of fumigation by burning of repellent plants; Ocimum suave, Ocimum kilimandscharicum, Azadirachta indica, Eucalyptus globules and Lantana camara were tested in experimental huts and selected local houses. RESULTS: In the field, protection by Ocimum plants from mosquito bites was high and there was small variation among different mosquito species. Protection efficiency was 93.4%, 91.98% and 89.75% for An. arabiensis while for Cx. quinquefaciatus it was 91.30%, 88.65% and 90.50% for DEET, Ocimum suave and O. kilimandscharicum respectively. In the experimental hut, deterrence induced by burning of Ocimum and other plants ranged from 73.1.0% to 81.9% for An. arabiensis and 56.5% to 67.8% for Cx. quinquefaciatus, while feeding inhibition was 61.1% to 100% for An. arabiensis and 50% to 100% for Cx. quinquefaciatus. Evaluations under field conditions confirmed high protective efficacy, enhanced feeding inhibition and house entry inhibition (Deterrence). CONCLUSION: This study shows the potential of Ocimum suave and Ocimum kilimandscharicum crude extracts and whole plants of Ocimum suave, Ocimum kilimandscharicum, Azadirachta indica, Eucalyptus globules and Lantana camara for use in protecting against human biting while the burning of plants reduces significantly the indoor resting mosquitoes.

Ethnobotanical study of some of mosquito repellent plants in north-eastern Tanzania.

BACKGROUND: The use of plant repellents against nuisance biting insects is common and its potential for malaria vector control requires evaluation in areas with different level of malaria endemicity. The essential oils of Ocimum suave and Ocimum kilimandscharicum were evaluated against malaria vectors in north-eastern Tanzania. METHODOLOGY: An ethnobotanical study was conducted at Moshi in Kilimanjaro region north-eastern Tanzania, through interviews, to investigate the range of species of plants used as insect repellents. Also, bioassays were used to evaluate the protective potential of selected plants extracts against mosquitoes. RESULTS: The plant species mostly used as repellent at night are: fresh or smoke of the leaves of O. suave and O. kilimandscharicum (Lamiaceae), Azadirachta indica (Meliaceae), Eucalyptus globules (Myrtaceae) and Lantana camara (Verbenaceae). The most popular repellents were O. kilimandscharicum (OK) and O. suave (OS) used by 67% out of 120 households interviewed. Bioassay of essential oils of the two Ocimum plants was compared with citronella and DEET to study the repellence and feeding inhibition of untreated and treated arms of volunteers. Using filter papers impregnated with Ocimum extracts, knockdown effects and mortality was investigated on malaria mosquito Anopheles arabiensis and Anopheles gambiae, including a nuisance mosquito, Culex quinquefasciatus. High biting protection (83% to 91%) and feeding inhibition (71.2% to 92.5%) was observed against three species of mosquitoes. Likewise the extracts of Ocimum plants induced KD90 of longer time in mosquitoes than citronella, a standard botanical repellent. Mortality induced by standard dosage of 30 mg/m2 on filter papers, scored after 24 hours was 47.3% for OK and 57% for OS, compared with 67.7% for citronella. CONCLUSION: The use of whole plants and their products as insect repellents is common among village communities of north-eastern Tanzania and the results indicate that the use of O. suave and O. kilimandscharicum as a repellent would be beneficial in reducing vector biting. The widespread use of this approach has a potential to complement other control measures.

Mosquito abundance, bed net coverage and other factors associated with variations in sporozoite infectivity rates in four villages of rural Tanzania.

BACKGROUND: Entomological surveys are of great importance in decision-making processes regarding malaria control strategies because they help to identify associations between vector abundance both species-specific ecology and disease intervention factors associated with malaria transmission. Sporozoite infectivity rates, mosquito host blood meal source, bed net coverage and mosquito abundance were assessed in this study. METHODOLOGY: A longitudinal survey was conducted in four villages in two regions of Tanzania. Malaria vectors were sampled using the CDC light trap and pyrethrum spray catch methods. In each village, ten paired houses were selected for mosquitoes sampling. Sampling was done in fortnight case and study was undertaken for six months in both Kilimanjaro (Northern Tanzania) and Dodoma (Central Tanzania) regions. RESULTS: A total of 6,883 mosquitoes were collected including: 5,628 (81.8%) Anopheles arabiensis, 1,100 (15.9%) Culex quinquefasciatus, 89 (1.4%) Anopheles funestus, and 66 (0.9%) Anopheles gambiae s.s. Of the total mosquitoes collected 3,861 were captured by CDC light trap and 3,022 by the pyrethrum spray catch method. The overall light trap: spray catch ratio was 1.3:1. Mosquito densities per room were 96.5 and 75.5 for light trap and pyrethrum spray catch respectively. Mosquito infectivity rates between villages that have high proportion of bed net owners and those without bed nets was significant (P < 0.001) and there was a significant difference in sporozoite rates between households with and without bed nets in these four villages (P < 0.001). CONCLUSION: Malaria remains a major problem in the study areas characterized as low transmission sites. Further studies are required to establish the annual entomological inoculation rates and to observe the annual parasitaemia dynamics in these communities. Outdoor mosquitoes collection should also be considered.