26 research outputs found
Molecular community surveillance of Plasmodium falciparum in 6 sites of different malaria endemicity in Tanzania
Get PDFMalaria prevalence estimates in Tanzania have been documented to decline in the recent years. National malaria data shows prevalence rates have been reduced by half from 18% in 2008 to 9% in 2012 (THMIS 2009; 2013). This decline has been attributed to countrywide implementation of malaria interventions, including indoor residual spraying (IRS), mass distribution of insecticide treated nets (ITNs), long-lasting ITNs and the use of artemisinin combination therapy (ACT), which aim at transmission reduction. Monitoring and evaluation of malaria interventions requires accurate information on the remaining malaria burden in the community. The rapid diagnostic tests (RDTs) and light microscopy (LM) are the commonly used diagnostic tools for parasite detection and estimation of parasite prevalence rates in many resource-limited areas such as Tanzania. However, owing to the low detection limit of LM and RDTs of about 50-100 parasites/µL, their ability to capture low density infections is limited (Moody 2002; MalEra 2011). The use of molecular techniques to detect malaria parasites has been advocated to improve the accuracy of parasite prevalence estimates, especially in moderate to low endemic settings. This is because in areas of reduced endemicity, most infections occur at low densities and cannot be detected by the routine diagnostic tools. With a detection limit of about 0.034 parasites/µL of blood, molecular diagnostics are more reliable for parasite detection. In Tanzania, most of the parasites prevalence estimates have been performed by LM and RDTs, hence the most of the low density infections may remain undetected. Thus this thesis aimed to assess the usefulness of diagnostic methods for epidemiological studies by comparing the performance of routine and molecular diagnostics in parasite and gametocytes detection in community samples from Tanzania. Furthermore, the thesis investigated the occurrence of submicroscopic infections at different endemic sites in Tanzania.
For the above aims we conducted community surveys at 6 sites in Tanzania between 2011 and 2013. These sites were classified as low (Iringa), low urban (Dar-Es Salaam), moderate (coastal Tanga and Lugoba) and high (Rufiji and Morogoro) endemic sites according to district prevalence data recorded by the Tanzania HIV and Malaria indicator surveys of 2008 (THMIS 2009): A total of 2046 volunteers of all ages with signed consent forms were recruited. Finger prick blood was drawn from all individuals for parasite detection by LM, RDT and 18S rRNA qPCR. Gametocytes were detected by both LM and qRT-PCR targeting transcripts of the gametocyte specific expressed marker pfs25.
Generally, high P. falciparum Prevalence rates of 20% (416/2046; 95% CI 18-22%) by 18S rRNA qPCR, 17% (349/2046; 95% CI 15.4-18.7%) by RDT and 11% (229/2046; 95% CI 9.8-12%) by LM were recorded in Tanzania. A substantial variation in molecular prevalence rates from geographically different sites was observed varying from 50% in the high endemic site, Rufiji, to 0.6% in the low endemic site, Iringa. These observed differences highlight the heterogeneity of transmission patterns in Tanzania attributed to geographical differences. Molecular parasite diagnostics unveiled that more than a half, 60% (249/416) of P. falciparum positive samples carried submicroscopic infections. Submicroscopic carriage was prevalent in all endemic settings. However, very few positive samples from areas of low and moderate endemicity impede a firm conclusion on the association of endemicity and submicroscopic carriage to be drawn from our samples. Molecularly determined Gametocyte prevalence was 15.3% (312/2046; 95% CI 13.6-16.8%) when data from all sites were combined. On the other hand, LM detected only 0.88% (18/2046; 95% CI 0.47-1.2%) of all samples implying only about 5% of the total gametocytes detected by molecular assay.
In conclusion molecular parasite detection revealed high parasite prevalence in Tanzania, such precise point prevalence molecular data obtained from community sampling may provide a more reliable basis of planning new tools of interventions or monitoring and evaluating the performance of existing tools in the country. Furthermore, high submicroscopic carriage of >50% in Tanzania, particularly in adults is key indicator of transmission potential of asymptomatic infections in Tanzania community and thus it is relevant for control strategies to focus on identifying submicroscopic carriers in order to successfully interrupt transmission
Olfactory mediation of oviposition in Anopheles mosquitoes : A new strategy for malaria vector control
No full textMosquito-borne diseases are among the most serious infectious diseases in the world caused by parasites and pathogens. The African mosquito Anopheles gambiae transmits malaria parasites as well as filarial worms. The mosquitoes feed on humans inside and outside houses, which complicates control strategies. Current control strategies focus mostly on reducing contact with host-seeking mosquitoes through the use of long-lasting insecticide-impregnated nets (LLINs) and indoor residual spraying (IRS). Despite the fact that these tools have lowered the burden of malaria in many parts of the world, transmission is sustained by vectors that bite outdoors. This thesis proposes a new strategy for malaria vector control to be added to existing control tools. It goes beyond blood-feeding processes and it targets all mosquitoes which are feeding indoors and outdoors. The proposed strategy is based on manipulation of oviposition behaviour using chemical cues that mimic olfactory cues emitted by breeding sites. Mosquitoes are attracted to lay their eggs on selected water bodies with specific biotic and abiotic factors. Organic chemical cues, emitted by these sites, are presumed to act as infochemicals enabling these mosquitoes to find suitable breeding sites. Identification of the odours that mediate the site-seeking behaviour of mosquitoes can lead to the development of novel intervention methods for mosquito-borne disease control. My study marked an important progress in the development of mosquito surveillance and control strategies using infochemicals by: (1) generating knowledge on the biology and ecology of immature stages of Anopheles mosquitoes in the study area, (2) providing evidence that mosquitoes select breeding sites preferentially and lay eggs on suitable sites while avoiding unsuitable ones, (3) identifying and characterizing volatile organic chemicals that mediate oviposition behaviour in mosquitoes, (4) generating evidence that oviposition infochemicals can be used to divert oviposition activities to specific breeding sites, which can be targeted by an environmentally safe larvicide: a lure-and-kill method. The research aimed to understand the reasons that prevent early and late larval stages from sharing breeding sites, and also why breeding sites with late stage larvae are not immediately succeeded by early stage larvae (Chapter 5). Several studies have indicated a possible role of habitat materials in the production of volatiles chemicals which either attract or deter egg-laying mosquitoes. A review of recently published studies showed that oviposition attractants and deterrents are produced by biotic factors present in breeding sites (Chapter 2). In my study it was found that breeding sites which are occupied by larvae play an important role in the production of odours that mediate oviposition behaviour of mosquitoes (Chapter 3). These infochemicals can potentially be used for manipulation of mosquito behaviour by making protected resources unsuitable for mosquitoes, while luring them towards attractive sources. Such push and pull strategies using ovipostion infochemicals for other mosquitoes were reviewed in order to develop similar surveillance and control strategies for malaria vectors. Among other larviciding products reviewed, bacterial products such as Bacillus sphaericus (Bs) and Bacillus thuringiensis israelensis (Bti) emerged with the potential to be combined with attractive infochemicals in the development of a lure and kill strategy (Chapter 2). To understand the factors influencing oviposition behaviour of Anopheles mosquitoes, a series of dual-choice behavioural experiments were conducted in the laboratory using larval habitats materials. Results show that the presence of larvae in breeding sites mediates oviposition behaviour of Anopheles mosquitoes (Chapter 3). The presence of early-stage larvae in oviposition cups attracted conspecific gravid mosquitoes to lay eggs, whereas the presence of late-stage larvae in the cups deterred conspecific gravid mosquitoes to lay eggs. The response was density dependent: as larval density increased so did the response, until reaching a threshold. Moreover, this behaviour was manifested more profoundly in the presence of larvae than larval-conditioned water. To test whether larval habitats produce volatiles that mediate oviposition behaviour, the oviposition cups containing larvae were covered by a filter paper to prevent gravid females from seeing the larvae in the cups. Results show that both olfactory and visual cues are involved in mediating the oviposition behaviour of anopheline mosquitoes. To confirm the findings that larval habitats emit infochemicals that mediate oviposition behaviour of gravid mosquitoes, larval habitats containing early- or late-stage larvae were placed in containers in the laboratory. Headspace volatiles of the larval microcosm were entrained and analyzed by gas chromatography - mass spectrometry (GC-MS). Analysis of the volatiles emitted by larvae in-vitro led to the identification of 16 compounds, and four of them, when tested with An. gambiae, had an effect on oviposition behaviour (Chapter 4). Volatile chemicals extracted from headspace collections of larvae mediated similar behaviour; volatiles entrapped from young larvae attracted conspecific gravid mosquitoes, whereas those from late-stage larvae deterred conspecific gravid mosquitoes to lay eggs. Nonane and 2,4-pentenedione, which were isolated from headspace collection of larvae, enhanced the attractiveness of a synthetic solution and could be used to increase mosquito egg deposition for monitoring or vector control purposes. Dimethyldisulphide (DMDS) and dimethyltrisulphide (DMTS), which were isolated from headspace collection of late-stage larvae only, decreased mosquito egg deposition in a synthetic solution and may act as a spatial deterrent. Laboratory and semi-field experiments in Tanzania showed similar results and suggested that nonane and 2,4-pentanedione can be used as mid-range cues for oviposition. The study described in Chapter 5 provided ecological characteristics of the field site where observations on the behaviour and distribution pattern of larvae were done. This is the field site where initial observations on succession of larvae in breeding sites and the actual testing of infochemicals took place. The factors influencing the selection of breeding sites by gravid females and distribution patterns of mosquito larvae were explored. Human activities such as brick-making and rice production were found to influence oviposition site selection and hence constitute a risk factor for malaria and other mosquito-borne diseases. The presence of larvae of Anopheles mosquitoes in breeding sites was associated with vegetation, presence of culicine larvae, shallowness and sunlight. The association between anopheline and culicine larvae is a vital finding that suggests that gravid mosquitoes of the two species use similar cues in selecting suitable breeding sites. Moreover, results from the study suggested that productivity of anopheline larvae in the field can be reduced by introducing larval predators, water management, or water pollution with rotting vegetation. The findings obtained after careful observation of the field site helped to design surveillance and larval control strategies using synthetic infochemicals identified in Chapter 4. Field experiments in east-central Tanzania showed results similar to the laboratory and semi-field studies and suggested that larval habitat volatiles also attract other disease vectors (Chapter 6). This study showed that infochemicals from selected sites can induce an oviposition response in mosquitoes under natural conditions, and that soil from a breeding site and nonane both induced oviposition in An. gambiae and Cx. quinquefasciatus with a synergistic effect caused by nonane + soil in An. gambiae. Therefore, the study also revealed that the oviposition-site-selection process of gravid mosquitoes is mediated by a combination of infochemicals derived from natural breeding sites. This knowledge can be exploited to develop a control strategy based on the push-pull or attract-and-kill concept. Furthermore, the knowledge can be utilized to develop other surveillance tools for mosquito vectors of human and animal diseases. In order to explore the potential of using a push-pull system for mosquito control, the attractants were combined with environmentally friendly biolarvicides in order to achieve more effective control of their aquatic larval offspring (Chapter 7). As an attractant for gravid mosquitoes, nonane, which originated from An. gambiae larvae, was selected. As toxicant for mosquito larvae, Bacillus thuringiensis var israeliensis (Bti) and Temephos were selected. Mosquitoes were successfully attracted to lay eggs in water-filled clay pots treated with attractants and combined with larvicides. Therefore, a lure-and-kill system was successfully implemented; mosquitoes were attracted to lay eggs in intervention pots containing toxicants, consequently, all emerged larvae died before reaching the pupal stage. The results presented in this thesis create new opportunities for applied research, especially on the development of novel vector-borne disease control strategies using infochemicals (Chapter 8). The volatiles produced by the larval habitats play an important role in the site-selection behaviour of An. gambiae and Cx. quinquefasciatus mosquitoes. The attractiveness of the synthetic chemicals identified in this study may be improved by making blends of attractants or in combination with other infochemicals identified elsewhere. Identified compounds can be used in push-pull and/or lure-and-kill strategies for the manipulation of mosquitoes; thereby reducing the abundance of mosquitoes, the human-biting frequency, and the intensity of pathogen transmission. Research on the role of oviposition-based infochemicals in the site-seeking behaviour of mosquitoes may lead to a better understanding of vector behaviour and contribute to the fight against vector-borne diseases. The main conclusions from this thesis can be summarized as follows: Volatiles produced by larval habitats play an important role in the mediation of oviposition behaviour of An. gambiae and in the dispersal of mosquito species. The analysis of the headspace from larval microcosms led to the identification of 16 compounds. Out of these, four (DMDS, DMTS, nonane and 2,4-pentanedione) had behavioural effects on An. gambiae. Nonane acts as an oviposition cue for Cx. quinquefasciatus as well. Mosquitoes are governed by multiple cues in the selection of suitable breeding sites, thus further research on the role of combined infochemicals to optimize selection of breeding sites should be initiated. These infochemicals can be used in push-pull or attract–and-kill strategies for surveillance and control of malaria mosquito larvae. Thus, odour-based technologies can improve the surveillance, sampling and control strategies for disease vectors. In this way the burden resulting from mosquito-borne diseases such as morbidity, mortality and economic losses will be decreased
Evaluation of the Long-Lasting Insecticidal Net Interceptor LN: Laboratory and Experimental Hut Studies against Anopheline and Culicine Mosquitoes in Northeastern Tanzania
Get PDFLong lasting insecticidal nets (LN) are a primary method of malaria prevention. Before new types of LN are approved they need to meet quality and efficacy standards set by the WHO Pesticide Evaluation Scheme. The process of evaluation has three phases. In Phase I the candidate LN must meet threshold bioassay criteria after 20 standardized washes. In Phase II washed and unwashed LNs are evaluated in experimental huts against wild, free flying anopheline mosquitoes. In Phase III the LN are distributed to households in malaria endemic areas, sampled over three years of use and tested for continuing insecticidal efficacy. Interceptor® LN (BASF Corporation, Germany) is made of polyester netting coated with a wash resistant formulation of alpha-cypermethrin. Interceptor LN was subjected to bioassay evaluation and then to experimental hut trial against pyrethroid-susceptible Anopheles gambiae and An. funestus and resistant Culex quinquefasciatus. Mosquito mortality, blood feeding inhibition and personal protection were compared between untreated nets, conventional alpha-cypermethrin treated nets (CTN) washed 20 times and LNs washed 0, 20 and 30 times. In Phase I Interceptor LN demonstrated superior wash resistance and efficacy to the CTN. In the Phase II hut trial the LN killed 92% of female An. gambiae when unwashed and 76% when washed 20 times; the CTN washed 20 times killed 44%. The LN out-performed the CTN in personal protection and blood-feeding inhibition. The trend for An. funestus was similar to An. gambiae for all outcomes. Few pyrethroid-resistant Cx. quinquefasciatus were killed and yet the level of personal protection (75-90%) against Culex was similar to that of susceptible An. gambiae (76-80%) even after 20 washes. This protection is relevant because Cx. quinquefasciatus is a vector of lymphatic filariasis in East Africa. After 20 washes and 60 nights’ use the LN retained 27% of its initial insecticide dose. Interceptor LN meets the approval criteria set by WHO and is recommended for use in disease control against East African vectors of malaria and filariasis. Some constraints associated with the phase II evaluation criteria, in particular the washing procedure, are critically reviewed
Synergism between nonane and emanations from soil as cues in oviposition‐site selection of natural populations of Anopheles gambiae and Culex quinquefasciatus
No full textBackground: Olfactory cues have been shown to have an important role in guiding gravid mosquito females to selected sites for egg laying. The objective of this study was to determine the influence of emanations from soil from a breeding site and the putative oviposition pheromone nonane on oviposition-site selection of natural populations of Anopheles gambiae sensu lato (s.l.) and Culex quinquefasciatus. Methods: This field-based study was conducted in Mvomero District in East-central Tanzania. In a dual-choice experimental set up, clay bowls were dug into the ground and filled with one of the following treatments: (i) distilled water + autoclaved soil (control), (ii) distilled water + soil from a natural mosquito breeding site, (iii) distilled water + nonane and (iv) distilled water + nonane + soil from a natural breeding site. Soil was dried and autoclaved or dried only before use. After five days of incubation, larvae were collected daily for 10 days. The median number of larvae per bowl per day was used as outcome measure. Results: Autoclaved soil had a significant attractive effect on oviposition behaviour of Cx. quinquefasciatus (median values ± s.e: 8.0 ± 1.1; P < 0.005) but no effect on An. gambiae (median value ± s.e: 0.0 ± 0.2; P = 0.18). Nonane and emanations from untreated soil significantly and positively influenced the selection of oviposition sites by both An. gambiae s.l. (median values ± s.e.: 12.0 ± 2.0 and 4.5 ± 1.5, respectively; P < 0.0001) and Cx. quinquefasciatus (median values ± s.e.: 19.0 ± 1.3 and 17.0 ± 2.0, respectively; P < 0.0001). A mixture of nonane and untreated soil caused a synergistic effect on oviposition behaviour in An. gambiae s.l. (median value ± s.e.: 23.5 ± 2.5; P < 0.0001) compared to either nonane (median values ± s.e.: 12.0 ± 2.0; P < 0.0001) or untreated soil alone (median value ± s.e.: 4.5 ± 1.5; P < 0.0001). A synergistic effect of nonane mixed with untreated soil was also found in Cx. quinquefasciatus (median value ± s.e.: 41.0 ± 2.1; P < 0.0001) compared to either nonane (median value ± s.e. 19.0 ± 1.3; P < 0.0001) or untreated soil alone (median value ± s.e.: 17.0 ± 2.0; P < 0.0001). The oviposition activity index for An. gambiae was 0.56 (P < 0.001) and for Cx. quinquefasciatus 0.59 (P < 0.0001). Conclusions: The larval pheromone nonane and emanations from breeding-site soil both induced oviposition in wild An. gambiae s.l. and Cx. quinquefasciatus, with a synergistic effect when both stimuli were present simultaneously. This is the first study in which nonane is shown to cause oviposition under natural conditions, suggesting that this compound can potentially be exploited for the management of mosquito vectors
Mpoto Fables and Folktales (Tanzania)
No full textLIST OF RECORDINGS — FABLES:
1) Ndava Linyaunyau liyenda nyatanyata wichu — "Why Spider moves very fast" (recorded 2/13/14); 2) Ndava Kapecha ayii ni nkela uyipi — "Why Hare has a short tail" (recorded 10/8/13); 3) Ndava Kapecha ni Lwiha hiyii hee ni ukocha — "Why Hare and Chameleon are not friends" (recorded 11/12/13); 4) Ndava Kapecha ni Liyani hikalekana ukochi wavi — "Why Hare and Monkey broke off their friendship" (recorded 2/13/14); 5) Ndava Liyani livenga Kapecha — "Why Monkey chases Hare" (recorded 10/16/13); 6) Cha Kapecha kanketikihi Litombele — "How Hare tricked Monkey" (recorded 3/13/14); 7) Cha Lihogho linketikihi Kapecha — "How Hyena tricked Hare" (recorded 10/1/13); 8) Cha Lihogho lihovitayi makakala ghaki — "How Hyena lost his power" (recorded 3/13/14); FOLKTALES: 9) Muhana nkata ni ndomi waki nkata — "The lazy wife and her lazy husband" (recoded 12/10/13); 10) Muhavi ni ling’wina — "The witch and the crocodile" (recorded 9/3/13); 11) Ndomi yaa ahokiti muhana — "The husband who wronged his wife" (recorded 10/2/13); 12) Cha nchokolo atowili — "How grandchild got married" (recoded 9/18/13)The Mpoto are a Bantu people located along the shores of Lake Nyasa in the Ruvuma Region, Mbinga District, of southwestern Tanzania. Fables and folktales, as recalled by the first author, were recorded in 2013-2014 at Indiana University. Each text has been linguistically analyzed and glossed, providing readers the opportunity to compare the broad translation with specific words used in the texts. This is the first published collection on oral literature of the Mpoto people. The following recordings correspond with the book Mpoto Fables and Folktales (Tanzania), available at https://www.koeppe.de/titel_mpoto-fables-and-folktales-tanzania
Exploiting the chemical ecology of mosquito oviposition behavior in mosquito surveillance and control: a review
No full textVector control is an important component of the interventions aimed at mosquito-borne disease control. Current and future mosquito control strategies are likely to rely largely on the understanding of the behavior of the vector, by exploiting mosquito biology and behavior, while using cost-effective, carefully timed larvicidal and high-impact, low-volume adulticidal applications. Here we review the knowledge on the ecology of mosquito oviposition behavior with emphasis on the potential role of infochemicals in surveillance and control of mosquito-borne diseases. A search of PubMed, Embase, Web of Science, Global Health Archive, and Google Scholar databases was conducted using the keywords mosquito, infochemical, pheromone, kairomone, allomone, synomone, apneumone, attractant, host-seeking, and oviposition. Articles in English from 1974 to 2019 were reviewed to gain comprehensive understanding of current knowledge on infochemicals in mosquito resource-searching behavior. Oviposition of many mosquito species is mediated by infochemicals that comprise pheromones, kairomones, synomones, allomones, and apneumones. The novel putative infochemicals that mediate oviposition in the mosquito subfamilies Anophelinae and Culicinae were identified. The role of infochemicals in surveillance and control of these and other mosquito tribes is discussed with respect to origin of the chemical cues and how these affect gravid mosquitoes. Oviposition attractants and deterrents can potentially be used for manipulation of mosquito behavior by making protected resources unsuitable for mosquitoes (push) while luring them towards attractive sources (pull). In this review, strategies of targeting breeding sites with environmentally friendly larvicides with the aim to develop appropriate trap-and-kill techniques are discussed
The Influence of Larval Stage and Density on Oviposition Site-Selection Behavior of the Afrotropical Malaria Mosquito Anopheles coluzzii (Diptera: Culicidae)
No full textIn the selection of oviposition sites female mosquitoes use various cues to assess site quality to optimize survival of progeny. The presence of conspecific larvae influences this process. Interactive effects of oviposition site selection were studied in the malaria mosquito Anopheles coluzzii Coetzee & Wilkerson in dual- and no-choice assays, by exposing single gravid mosquitoes to oviposition cups containing 1) larvae of different developmental stages, 2) larvae-conditioned water (LCW), and 3) cups where visual cues of conspecific larvae were absent. Early-stage conspecific larvae had a positive effect on the oviposition response. By contrast, late stages of conspecific larvae had a negative effect. Oviposition choice was dependent on larval density. Moreover, in oviposition cups where larvae were hidden from view, late-stage larvae had a significant negative effect on oviposition suggesting the involvement of olfactory cues. LCW had no effect on oviposition response, indicating involvement of chemicals produced by larvae in vivo. It is concluded that the presence of larvae in a breeding site affects the oviposition response depending on the development stage of the larvae. These responses appear to be mediated by olfactory cues emitted by the larval habitat containing live larvae, resulting in the enhanced reproductive fitness of the females
Aedes albopictus invasion across Africa: the time is now for cross-country collaboration and control
Get PDFThe distribution of Aedes albopictus across west Africa is well documented. However, little has been done to synthesise data and establish the current distribution of this invasive vector in central and east Africa. In this Viewpoint, we show that A albopictus is establishing across Africa, how this is potentially related to urbanisation, and how establishment poses risks of near-term increases in arbovirus transmission. We then use existing species distribution maps for A albopictus and Aedes aegypti to produce consensus estimates of suitability and make these estimates accessible. Although urban development and increased trade have economic and other societal gains, the resulting potential changes in Aedes-borne virus epidemiology require a discussion of how cross-country collaboration and mitigation could be facilitated. Failure to respond to species invasion could result in increased transmission of Aedes-associated pathogens, including dengue, chikungunya, and Rift Valley fever viruses.</p
Will mass drug administration eliminate lymphatic filariasis? Evidence from northern coastal Tanzania
Get PDFCopyright @ 2012 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and 85 reproduction in any medium, provided the original author and source are credited. The article was made available through the Brunel University Open Access Publishing Fund.This article documents understandings and responses to mass drug administration (MDA) for the treatment and prevention of lymphatic filariasis among adults and children in northern coastal Tanzania from 2004 to 2011. Assessment of village-level distribution registers, combined with self-reported drug uptake surveys of adults, participant observation and interviews, revealed that at study sites in Pangani and Muheza districts the uptake of drugs was persistently low. The majority of people living at these highly endemic locations either did not receive or actively rejected free treatment. A combination of social, economic and political reasons explain the low uptake of drugs. These include a fear of treatment (attributable, in part, to a lack of trust in international aid and a questioning of the motives behind the distribution); divergence between biomedical and local understandings of lymphatic filariasis; and limited and ineffective communication about the rationale for mass treatment. Other contributory factors are the reliance upon volunteers for distribution within villages and, in some locations, strained relationships between different groups of people within villages as well as between local leaders and government officials. The article also highlights a disjuncture between self-reported uptake of drugs by adults at a village level and the higher uptake of drugs recorded in official reports. The latter informs claims that elimination will be a possibility by 2020. This gives voice to a broader problem: there is considerable pressure for those implementing MDA to report positive results. The very real challenges of making MDA work are pushed to one side - adding to a rhetoric of success at the expense of engaging with local realities. It is vital to address the kind of issues raised in this article if current attempts to eliminate lymphatic filariasis in mainland coastal Tanzania are to achieve their goal.This work is funded from the Bill and Melinda Gates Foundation
Significant geographical differences in prevalence of mutations associated with Plasmodium falciparum and Plasmodium vivax drug resistance in two regions from Papua New Guinea
Get PDFDrug resistance remains a major obstacle to malaria treatment and control. It can arise and spread rapidly, and vary substantially even at sub-national level. National malaria programmes require cost-effective and timely ways of characterizing drug-resistance at multiple sites within their countries.; An improved multiplexed post-PCR ligase detection reaction-fluorescent microsphere assay (LDR-FMA) was used to simultaneously determine the presence of mutations in chloroquine resistance transporter (crt), multidrug resistance 1 (mdr1), dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes in Plasmodium falciparum (n = 727) and Plasmodium vivax (n = 574) isolates collected in 2006 from cross-sectional community population surveys in two geographically distinct regions (Madang and East Sepik) of Papua New Guinea (PNG) where strong regional differences in in vivo aminoquinoline and antifolate therapeutic efficacy had previously been observed. Data were compared to those of a follow-up survey conducted in 2010.; Despite some very low parasite densities, the assay successfully amplified all P. falciparum and P. vivax loci in 77 and 69 % of samples, respectively. In 2006, prevalences of pfdhfr (59R-108 N) double mutation/wild type pfdhps haplotype, pfcrt SVMNT haplotype (72S-76T double mutation), and 86Y pfmdr1 mutation all exceeded 90 %. For P. vivax, 65 % carried at least two pvdhfr mutations, 97 % the 647P pvdhps mutation and 54 % the 976F pvmdr1 mutation. Prevalence of mutant haplotypes was higher in Madang than East Sepik for pfcrt SVMNT (97.4 vs 83.3 %, p = 0.001), pfdhfr (59R-108 N) (100 vs 90.6 %, p = 0.001), pvdhfr haplotypes (75.8 vs 47.6 %, p = 0.001) and pvmdr1 976F (71.2 vs 26.2 %, p < 0.001). Data from a subsequent Madang survey in 2010 showed that the prevalence of pfdhps mutations increased significantly from <5 % to >30 % (p < 0.001) as did the prevalence of pvdhfr mutant haplotypes (from 75.8 to 97.4 %, p = 0.012).; This LDR-FMA multiplex platform shows feasibility for low-cost, high-throughput, rapid characterization of a broad range of drug-resistance markers in low parasitaemia infections. Significant geographical differences in mutation prevalence correlate with previous genotyping surveys and in vivo trials and may reflect variable drug pressure and differences in health-care access in these two PNG populations
