Impact of MiraNet® long-lasting insecticidal net against Anopheles arabiensis wild population of Northern Tanzania.

Despite high levels of pyrethroid resistance reported in malaria vectors, long-lasting insecticidal nets (LNs) still play a key role in controlling malaria transmission. This study tested the efficacy of MiraNet®, a pyrethroid-based LN against a wild population of Anopheles arabiensis in northern Tanzania. DuraNet® was used as a positive control in this evaluation. Standard WHO laboratory bioefficacy evaluations of MiraNet and DuraNet that were unwashed or had been washed 20 times indicated optimal knockdown and mortality for both net types against a susceptible strain of Anopheles gambiae s.s. Standard experimental hut evaluations were conducted to evaluate the efficacy of both nets against a wild population of An. arabiensis. The killing effect of MiraNet was 54.5% for unwashed and 50% for 20 times washed while DuraNet achieved 44.4% mortality for unwashed and 47.4% for 20 times washed against wild An. arabiensis. Both DuraNet and MiraNet exhibited significantly higher killing effects (> 44.4%). There was no significant difference in deterrence or induced exophily detected between the treatment arms for either net. Additionally, there were no adverse effects reported among hut sleepers. The results of this study indicate that the pyrethroid net MiraNet can be used effectively against wild populations of An. gambiae s.l. of low to moderate resistant levels from Northern Tanzania.

The Impact of Insecticide Pre-Exposure on Longevity, Feeding Succession, and Egg Batch Size of Wild Anopheles gambiae s.l.

BACKGROUND: Insecticide resistance among the vector population is the main threat to existing control tools available. The current vector control management options rely on applications of recommended public health insecticides, mainly pyrethroids through long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Regular monitoring of insecticide resistance does not provide information on important factors that affect parasite transmission. Such factors include vector longevity, vector competence, feeding success, and fecundity. This study investigated the impacts of insecticide resistance on longevity, feeding behaviour, and egg batch size of Anopheles gambiae s.l. METHOD: The larval sampling was conducted in rice fields using a standard dipper (350 ml) and reared to adults in field insectary. A WHO susceptibility test was conducted using standard treated permethrin (0.75%) and deltamethrin (0.05%) papers. The susceptible Kisumu strain was used for reference. Feeding succession and egg batch size were monitored for all survivors and control. RESULTS: The results revealed that mortality rates declined by 52.5 and 59.5% for permethrin and deltamethrin, respectively. The mortality rate for the Kisumu susceptible strain was 100%. The survival rates of wild An. gambiae s.l. was between 24 and 27 days. However, the Kisumu susceptible strain blood meal feeding was significantly higher than resistant colony (t = 2.789, df = 21, P=0.011). Additionally, the susceptible An. gambiae s.s. laid more eggs than the resistant An.gambiae s.l. colony (Χ2 = 1366, df = 1, P ≤ 0.05). CONCLUSION: It can, therefore, be concluded that the wild An. gambiae s.l. had increased longevity, blood feeding, and small egg batch size compared to Kisumu susceptible colonies.

Anopheline Mosquito Species Composition, Kdr Mutation Frequency, and Parasite Infectivity Status in Northern Tanzania.

The scaling-up of malaria control interventions in northern Tanzania has resulted in a decline in malaria prevalence and vector species composition. Despite this achievement, residual malaria transmission remains a concern in the area. The main aim of this study was to investigate malaria vector species composition, parasite infectivity rates, and the presence of insecticide knockdown resistance (kdr) mutations in three sites that have experienced a significant decline in malaria in northern Tanzania. Adult mosquitoes were sampled using light traps in houses and hand-aspirators in cowsheds, whereas the standard dipping method was used for sampling mosquito larvae. Adult mosquitoes identified as Anopheles gambiae s.l. and An. funestus s.l. and larval stages III and IV of An. gambiae s.l. were stored in absolute ethanol for further laboratory molecular identification. The identified species in the An. gambiae complex were An. gambiae s.s., An. merus, An. quadriannulatus, and An. arabiensis, whereas the An. funestus group comprised An. funestus s.s., An. rivulorum, and An. leesoni. For An. gambiae s.s. analyzed from Zeneth, 47.6% were kdr-East homozygous susceptible, 35.7% kdr-East heterozygous resistant, 9.6% kdr-East homozygous resistant, and 7.1% undefined, whereas specimens from Kwakibuyu were 45.5% kdr-East homozygous susceptible, 32.7% kdr-East heterozygous resistant, 16.3% kdr-East homozygous resistant, and 5.5% undefined. There were no kdr-West alleles identified from any specimen. The overall malaria parasite infectivity rate was 0.75%. No infections were found in Moshi. The findings indicate that populations of the major malaria vector mosquitoes are still present in the study area, with An. funestus taking a lead in malaria transmission.

Bio-efficacy and wash resistance of MAGNet long-lasting insecticidal net against wild populations of Anopheles funestus in experimental huts in Muheza, Tanzania.

BACKGROUND: The decline in malaria cases and vectors is major milestone in fighting against malaria. The efficacy of MAGNet long-lasting insecticidal nets (MAGNet LLIN), an alpha-cypermethrin incorporated long-lasting net, with the target dose ± 25% of 5.8 g active ingredient (AI)/kg (4.35-7.25 g AI/kg) was evaluated in six veranda-trap experimental huts in Muheza, Tanzania against freely flying wild population of Anopheles funestus. METHODS: MAGNet LLINs were tested against wild, free-flying, host-seeking An. funestus mosquitoes over a period of 6 weeks (total of 36 nights in the huts). MAGNet LLIN efficacy was determined in terms of mosquito mortality, blood-feeding inhibition, deterrence, induced exiting, personal protection, and insecticidal killing over 20 washes according to WHO standardized procedures. Efficacy was compared with reference to a WHOPES recommended approved LLINs (DuraNet) and to a net conventionally treated (CTN) treated with alpha-cypermethrin at WHO-recommended dose and washed to just before cut-off point. The efficacy of MAGNet was evaluated in experimental huts against wild, free-flying, pyrethroid-resistant An. funestus. The WHO-susceptibility method was used to detect resistance in wild Anopheles exposed to 0.75% permethrin. Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets and standard LLINs. Blood-feeding rates were recorded and compared between the 20 times washed; blood-feeding rates between 20 times washed MAGNet LLIN and 20 times washed WHOPES-approved piperonyl butoxide (PBO)/pyrethroid were not statistically different (p > 0.05). RESULTS: The results have evidently shown that MAGNet LLIN provides similar blood-feeding inhibition, exophily, mortality, and deterrence to the standard approved LLIN, thus meeting the WHOPES criteria for blood feeding. The significantly high feeding inhibition and personal protection over pyrethroid-resistant An. funestus recorded by both unwashed and 20 times washed MAGNet compared to the unwashed DuraNet, the WHOPES-approved standard pyrethroid-only LLIN provides proof of MAGNet meeting Phase II WHOPES criteria for a LLIN. CONCLUSION: Based on this study, MAGNet has been shown to have a promising impact on protection when 20 times washed against a highly resistant population of An. funestus.

Bio-efficacy of DuraNet® long-lasting insecticidal nets against wild populations of Anopheles arabiensis in experimental huts.

BACKGROUND: Mosquitoes have developed resistance to multiple classes of insecticides for malaria vector control. A new generation of long-lasting insecticidal bed nets (LLINs) has been developed with increased efficacy against these resistant mosquitoes. The present study therefore evaluated the efficacy of the pyrethroid-based LLINs, DuraNet versus PermaNet 3.0, in an Eastern Africa hut design in Magugu in northern Tanzania where mosquitoes' population higher proportion (69.3%) has been identified as Anopheles gambiae s.l. METHODS: Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area with high populations of Anopheles arabiensis. All nets used were subjected to laboratory cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition, and personal protection rate were compared between untreated nets, unwashed LN, and LN that were washed 20 times. RESULTS: Standard WHO laboratory bioefficacy evaluations of DuraNet and PermaNet® 3.0 which were untreated, washed, or 20 times washed showed optimal knockdown and mortality for both net types against a susceptible strain of An. arabiensis. In standard experimental hut evaluations, the blood feeding inhibition for PermaNet® 3.0 unwashed and washed was 82.4% (76.3-88.6%) to 91.5% (84.1-98.8%) while for DuraNet was 98.3% (97.0-99.5%) to 96.0% (94.1-88.2%) respectively. The DuraNet LLINs showed a significantly higher killing effect than the other treatment of 90.0% (86.1-94.2%) and 94.0% (90.2-97.9%) for unwashed and washed nets respectively. No significant difference in deterrence or induced exophily was detected between the treatment arms. There were no adverse effects reported among sleepers in the experimental huts. CONCLUSION: The findings of this study indicate that the pyrethroid-based net DuraNet LLINs attained required efficacy when evaluated against wild population of An. arabiensis from Northern Tanzania. This adds value to the existing vector control tool box which gives community wider choice for vector control.

The influence of age on insecticide susceptibility of Anopheles arabiensis during dry and rainy seasons in rice irrigation schemes of Northern Tanzania.

BACKGROUND: Insecticide resistance is the major emerging challenge facing the malaria vector control programmes in Tanzania. Proper monitoring and detection is of paramount importance guiding the vector control programmes. This paper presents the effect of mosquito aging on insecticide resistance status in Anopheles arabiensis populations in dry and rainy seasons in northern Tanzania. METHODS: Anopheles gambiae s.l. larvae were sampled from rice fields in both dry and rainy seasons and reared in the insectary to adults. The emerged females in batches of 2, 3, 5, and 10 days old were exposed to six insecticides (deltamethrin, permethrin, lambda-cyhalothrin, DDT, bendiocarb and pirimiphos-methyl) to see the effects of age on insecticide resistance. Mosquitoes were exposed to insecticides using WHO standard susceptibility test kits. Knockdown was recorded during the 1-h exposure, while mortality and resistance ratio were recorded 24 h later. Mosquito specimens were identified to species level using the polymerase chain reaction (PCR) method. RESULTS: Among the 326 specimens processed by PCR, 323 (99.1%) were identified as Anopheles arabiensis. There was reduced mortality (ranging from 61 to 97.7%) when adults reared from larvae were exposed to all pyrethroids and bendiocarb in both dry and rainy seasons, while they were fully susceptible to DDT and pirimiphos-methyl. There was a significant increase in mortality rate with increase in mosquito's age in both dry and rainy seasons following exposure to pyrethroids (DF = 1, P < 0.05). Mosquitoes showed significantly higher mortality rates in the rainy season than in the dry season after being exposed to pyrethroids (DF = 1, P < 0.05). Higher mortality rates (94.0-99.8%) were observed in all ages and seasons when mosquitoes were exposed to bendiocarb compared with pyrethroids. Pirimiphos-methyl was only tested in the rainy season so no comparison with dry season mosquitoes could be made. CONCLUSIONS: Results showed that An. arabiensis were resistant to pyrethroids in both seasons and that the young age groups exhibited higher levels of resistance compared with the older age groups. Mosquitoes were full susceptible to DDT and pirimiphos-methyl irrespective of the season and age.

Efficacy of PermaNet® 3.0 and PermaNet® 2.0 nets against laboratory-reared and wild Anopheles gambiae sensu lato populations in northern Tanzania.

BACKGROUND: Mosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs). The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet® 3.0 LLIN versus the pyrethroid-only PermaNet® 2.0 LLIN, in an East African hut design in Lower Moshi, northern Tanzania. In this setting, resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes. METHODS: Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An. arabiensis mosquitoes. All nets used were subjected to cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition and personal protection rate were compared between untreated nets, unwashed LLINs and LLINs that were washed 20 times. RESULTS: Both washed and unwashed PermaNet® 2.0 and PermaNet® 3.0 LLINs had knockdown and mortality rates of 100% against a susceptible strain of An. gambiae sensu stricto. The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet® 3.0 and PermaNet® 2.0 nets was found to be higher than after use of the washed PermaNet® 2.0 and PermaNet® 3.0 nets. CONCLUSIONS: Given the increasing incidence of pyrethroid resistance in An. gambiae mosquitoes in Tanzania, we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan.

Direct and indirect effect of predators on Anopheles gambiae sensu stricto.

The increased insecticides resistance by vectors and the ecological harm imposed by insecticides to beneficial organisms drawback mosquitoes chemical control efforts. Biological control would reduce insecticides tolerance and yet biodiversity friend. The predatory and non-predatory effects of Gambusia affinis and Carassius auratus on gravid Anopheles gambiae sensu strict and larvae survivorship were assessed. In determining predation rate, a single starved predator was exposed to third instar larvae of An. gambiae s.s. in different densities 20, 60 and 100. Six replicates in each of the densities for both predators, G. affinis and C. auratus, were set up. The larvae densities were monitored in every 12 and 24 h. In assessing indirect effects: An. gambiae s.s. first instar larvae of three densities 20, 60 and 100 were reared in water from a predator habitat and water from non-predator habitat. Larvae were monitored until they emerged to adults where larval survivorship and sex ratio (Female to total emerged mosquitoes) of the emerged adult from both water habitats were determined. Oviposition preference: twenty gravid females of An. gambiae s.s. were provided with three oviposition choices, one containing water from predator habitat without a predator, the second with water from a predator with a predator and the third with water from non-predatory habitat. The number of eggs laid on each container was counted daily. There were 20 replicates for each predator, G. affinis and C. auratus. Survivorship of An. gambiae s.s. larvae reared in water from non-predator habitat was higher than those reared in water from the predator habitats. Many males emerged in water from non-predatory water habitats while more females emerged from predator's habitats water. More eggs laid in tap water than in water from predator habitat and water from predator habitat with live predator. In 24 h, a starved C. auratus and G. affinis were able to consume 100% of the 3rd instar larvae. The findings from this study suggest that G. affinis and C. auratus may be useful in regulating mosquito populations in favour of beneficial insects. However, a small scale trial shall be needed in complex food chain system to ascertain the observed predation and kairomones effects.

Protective efficacy of menthol propylene glycol carbonate compared to N, N-diethyl-methylbenzamide against mosquito bites in Northern Tanzania.

BACKGROUND: The reduction of malaria parasite transmission by preventing human-vector contact is critical in lowering disease transmission and its outcomes. This underscores the need for effective and long lasting arthropod/insect repellents. Despite the reduction in malaria transmission and outcomes in Tanzania, personal protection against mosquito bites is still not well investigated. This study sought to determine the efficacy of menthol propylene glycol carbonate (MR08), Ocimum suave as compared to the gold standard repellent N, N-diethyl-methylbenzamide (DEET), either as a single dose or in combination (blend), both in the laboratory and in the field against Anopheles gambiae s.l and Culex quinquefasciatus. METHODS: In the laboratory evaluations, repellents were applied on one arm while the other arm of the same individual was treated with a base cream. Each arm was separately exposed in cages with unfed female mosquitoes. Repellents were evaluated either as a single dose or as a blend. Efficacy of each repellent was determined by the number of mosquitoes that landed and fed on treated arms as compared to the control or among them. In the field, evaluations were performed by human landing catches at hourly intervals from 18:00 hr to 01:00 hr. RESULTS: A total of 2,442 mosquitoes were collected during field evaluations, of which 2,376 (97.30%) were An. gambiae s.l while 66 (2.70%) were Cx. quinquefaciatus. MR08 and DEET had comparatively similar protective efficacy ranging from 92% to 100 for both single compound and blends. These findings indicate that MR08 has a similar protective efficacy as DEET for personal protection outside bed nets when used singly and in blends. Because of the personal protection provided by MR08, DEET and blends as topical applicants in laboratory and field situations, these findings suggest that, these repellents could be used efficiently in the community to complement existing tools. Overall, Cx. quinquefasciatus were significantly prevented from blood feeding compared to An. gambiae s.l. CONCLUSION: The incorporation of these topical repellents for protection against insect bites can be of additional value in the absence or presence of IRS and ITNs coverage. However, a combination of both the physical (bed nets) and the repellent should be used in an integrated manner for maximum protection, especially before going to bed. Additional research is needed to develop repellents with longer duration of protection.

Knockdown Resistance, rdl Alleles, and the Annual Entomological Inoculation Rate of Wild Mosquito Populations from Lower Moshi, Northern Tanzania.

AIM: Understanding vector behavioral response due to ecological factors is important in the control of disease vectors. This study was conducted to determine the knockdown resistance (kdr) alleles, dieldrin resistance alleles, and entomological inoculation rates (EIRs) of malaria vectors in lower Moshi irrigation schemes for the mitigation of disease transmission. MATERIALS AND METHODS: The study was longitudinal design conducted for 14 months. Mosquitoes were collected fortnightly by using a CDC miniature light trap in 20 houses. Mosquitoes were identified morphologically in the field, of which 10% of this population was identified to species level by using molecular techniques. Samples from this study population were taken for kdr and resistance to dieldrin (rdl) genes detection. RESULTS: A total of 6220 mosquitoes were collected by using a light trap, of which 86.0% (n=5350) were Anopheles gambiae sensu lato and 14.0% (n=870) were Culex quinquefasciatus. Ten percent of the An. gambiae s.l. (n=535) collected were taken for species identification, of which 99.8% (n=534) were identified as An. arabiensis while 0.2% (n=1) were An. gambiae sensu stricto. Of the selected mosquitoes, 3.5% (n=19) were sporozoite positive. None of the mosquitoes tested had the kdr gene. The rdl resistant allele was detected at a frequency of 0.48 throughout the year. EIR was determined to be 0.54 ib/trap/year. CONCLUSION: The findings of this study suggest that the homozygous and the heterozygous resistance present in rdl genes demonstrated the effect of pesticide residues on resistance selection pressure in mosquitoes. A better insecticide usage protocol needs to be developed for farmers to use in order to avoid excessive use of pesticides.

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.

The role of cow urine in the oviposition site preference of culicine and Anopheles mosquitoes.

BACKGROUND: Chemical and behavioural ecology of mosquitoes plays an important role in the development of chemical cue based vector control. To date, studies available have focused on evaluating mosquito attractants and repellents of synthetic and human origins. This study, however, was aimed at seasonal evaluation of the efficiency of cow urine in producing oviposition cues to Anopheles gambiae s.l. and Culex quinquefasciatus in both laboratory and field conditions. METHODS: Oviposition response evaluation in laboratory conditions was carried out in mosquito rearing cages. The oviposition substrates were located in parallel or in diagonal positions inside the cage. Urine evaluation against gravid females of An. arabiensis and Cx. quinquefasciatus was carried out at Day 1, Day 3 and Day 7. Five millilitres (mls) of cow urine was added to oviposition substrate while de-chlorinated water was used as a control. In field experiments, 500 mls of cow urine was added in artificial habitats with 2500 mls of de-chlorinated water and 2 kgs of soil. The experiment was monitored for thirty consecutive days, eggs were collected daily from the habitats at 7.00 hrs. Data analysis was performed using parametric and non-parametric tests for treatments and controls while attraction of the oviposition substrate in each species was presented using Oviposition Activity Index (OAI). RESULTS: The OAI was positive with ageing of cattle urine in culicine species in both laboratory and field experiments. The OAI for anopheline species was positive with fresh urine. The OAI during the rainy season was positive for all species tested while in the dry season the OAI for culicine spp and Anopheles gambiae s.l., changed with time from positive to negative values.Based on linear model analysis, seasons and treatments had a significant effect on the number of eggs laid in habitats, even though the number of days had no effect. CONCLUSION: Oviposition substrates treated with cow urine in both laboratory and field conditions have shown that cow urine left to age from 1-7 days has an influence on oviposition behavioural response in mosquitoes. The analysis of microbial colonies for decaying urine should be investigated along with its associated by-products.

Durability associated efficacy of long-lasting insecticidal nets after five years of household use.

BACKGROUND: Long-lasting insecticidal nets (LLINs) have been strongly advocated for use to prevent malaria in sub-Saharan Africa and have significantly reduced human-vector contact. PermaNet® 2.0 is among the five LLINs brands which have been given full approval by the WHO Pesticide Evaluation Scheme (WHOPES). The LLINs are expected to protect the malaria endemic communities, but a number of factors within the community can affect their durability and efficacy. This study evaluated the durability, efficacy and retention of PermaNet® 2.0 after five years of use in a Tanzanian community. METHOD: Two to three day- old non blood-fed female mosquitoes from an insectary susceptible colony (An. gambiae s.s, this colony was established at TPRI from Kisumu, Kenya in 1992) and wild mosquito populations (An. arabiensis and Culex quinquefasciatus) were used in cone bioassay tests to assess the efficacy of mosquito nets. FINDINGS: The knockdown effect was recorded after three minutes of exposure, and mortality was recorded after 24 hours post-exposure. Mortality of An. gambiae s.s from insectary colony was 100% while An. arabiensis and Cx.quinquefasciatus wild populations had reduced mortality. Insecticide content of the new (the bed net of the same brand but never used before) and used PermaNet® 2.0 was determined using High Performance Liquid Chromatography (HPLC). CONCLUSION: The results of this study suggest that, in order to achieve maximum protection against malaria, public health education focusing on bed net use and maintenance should be incorporated into the mass distribution of nets in communities.

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.

Optimization of odour-baited resting boxes for sampling malaria vector, Anopheles arabiensis Patton, in arid and highland areas of Africa.

BACKGROUND: Odour baited resting boxes are simple, reliable and important tools for sampling malaria vector mosquitoes in surveillance and control programmes in different parts of Africa. To optimize the use of cow urine baited resting boxes for sampling An. arabiensis, a community-based study was conducted in Mabogini hamlet in the Lower Moshi irrigation scheme area. METHOD: Experimental designs using 3 by 3 Latin square were conducted for twenty days to evaluate the following: i) the effect of different parameters in the sampling of mosquitoes using odour baited resting boxes; ii) the performance of odour baited traps under indoor and outdoor conditions and the effect of people sleeping indoors on mosquito density; iii) the effect of position in the placement of traps on collection of mosquitoes; and, iv) the efficiency of the trap outdoors at three different distances from the house wall. One extra house served as the sentinel house to monitor species abundance using a CDC-miniature light trap. RESULTS: 8581 mosquitoes were sampled by odour baited resting boxes of which, 8051 (93.82%) were An. arabiensis and 530 (6.18%) Cx. quinquefasciatus. The light trap collected 12,420 mosquitoes, of which 9442 (76.02%) were An. arabiensis, 126 (1.01%) An. funestus group, 230 (1.85%) An. rufipes and 2622 (21.11%) Cx. quinquefasciatus. The best height for outdoor mosquitoes sampling was 15 cm and 220 cm while indoors was 105 cm. The difference in mosquito collection between different outdoor and indoor heights was statistically significant (p < 0.0001). The optimal outdoor location of odour baited resting boxes from the wall of the house was 3 m. CONCLUSIONS: The results of these studies demonstrate an optimal method for sampling during surveillance and control programmes in rural villages of highlands and arid areas of Africa using inexpensive baits and boxes.

Effect of Different Hosts on Feeding Patterns and Mortality of Mosquitoes (Diptera: Culicidae) and their Implications on Parasite Transmission.

AIM: The host-response to hematophagus insects is still an important parameter in understanding disease transmission patterns. We investigated the feeding and mortality rates of three mosquito species, namely Culex quinquefasciatus, Aedes aegypti and Anopheles arabiensis against three different hosts. MATERIALS AND METHODS: Unfed three to five-day-old female mosquitoes were released in a tunnel box that had a rabbit or guinea pig or mice as a host. The feeding succession patterns of mosquitoes in different hosts were An. arabiensis, Cx. quinquefasciatus and A. aegypti. RESULTS: Mosquito mortality rate was 54.9% for mosquitoes introduced in mice as a host, 34.3% in the Guinea pig and 10.8% for those that introduced in the rabbit. CONCLUSION: The presence of defensive and tolerable hosts in environment emphasizes the relevance of studying epidemiological impact of these behaviors in relation to diseases transmission.

Field Evaluation of the Bio-Efficacy of Three Pyrethroid Based Coils against Wild Populations of Anthropophilic Mosquitoes in Northern Tanzania.

AIMS: This study aims to assess the feeding inhibition and repellency effect of three brands of mosquito coils in experimental huts (East African design). Evaluated products were all pyrethroid-based mosquito coils-Kiboko(R), Total(R) and Risasi(R). Mosfly (0.1% D-allethrin) was a positive control. Indoor resting behavior, feeding inhibition and induced exophily were measured as responses of burnt coil smoke in huts. MATERIALS AND METHODS: Resting mosquitoes were collected inside the huts, in window traps and verandah traps using mechanical aspirators. Identified to species level and sex. RESULTS: A total of 1460 mosquitoes were collected, 58.9% (n=860) were Anopheles gambiae s.l while 41.1% (n=600) Culex quinquefasciatus. Indoor resting mosquitoes in all treated huts were significantly reduced than in negative control (DF=4, F=18.6, P < 0.001). Species found to rest indoors were not statistical different between the positive control (Mosfly coil) and other three treated huts (DF=3, F=1.068, P=0.408). Cx.quinquefasciatus had significantly higher induced exophily in all treatments comparing to An.gambiae s./ (DF=1, F=5.34, P=0.050). Comparison between species (An.gambiae s.l and Cx. quinquefasciatus) for the feeding inhibition among treated huts was not statistically significant (DF=1, F=0.062, P=0.810). CONCLUSION: Introduction of several personal protection measures will be ideal to supplement the existing gap in reducing the man vector contacts hence lowering the disease transmission.

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.