scholarly journals Widespread zoophagy and detection of Plasmodium spp. in Anopheles mosquitoes in southeastern Madagascar

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Micaela Finney ◽  
Benjamin A. McKenzie ◽  
Bernadette Rabaovola ◽  
Alice Sutcliffe ◽  
Ellen Dotson ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Vector Control ◽  
Plasmodium Vivax ◽  
Malaria Control ◽  
Feeding Behaviour ◽  
Enzyme Linked Immunosorbent Assay ◽  
Habitat Gradient ◽  
Blood Meals ◽  
Feeding Behaviours ◽  
Southeastern Madagascar

Abstract Background Malaria is a top cause of mortality on the island nation of Madagascar, where many rural communities rely on subsistence agriculture and livestock production. Understanding feeding behaviours of Anopheles in this landscape is crucial for optimizing malaria control and prevention strategies. Previous studies in southeastern Madagascar have shown that Anopheles mosquitoes are more frequently captured within 50 m of livestock. However, it remains unknown whether these mosquitoes preferentially feed on livestock. Here, mosquito blood meal sources and Plasmodium sporozoite rates were determined to evaluate patterns of feeding behaviour in Anopheles spp. and malaria transmission in southeastern Madagascar. Methods Across a habitat gradient in southeastern Madagascar 7762 female Anopheles spp. mosquitoes were collected. Of the captured mosquitoes, 492 were visibly blood fed and morphologically identifiable, and a direct enzyme-linked immunosorbent assay (ELISA) was used to test for swine, cattle, chicken, human, and dog blood among these specimens. Host species identification was confirmed for multiple blood meals using PCR along with Sanger sequencing. Additionally, 1,607 Anopheles spp. were screened for the presence of Plasmodium falciparum, P. vivax-210, and P. vivax 247 circumsporozoites (cs) by ELISA. Results Cattle and swine accounted, respectively, for 51% and 41% of all blood meals, with the remaining 8% split between domesticated animals and humans. Of the 1,607 Anopheles spp. screened for Plasmodium falciparum, Plasmodium vivax 210, and Plasmodium vivax 247 cs-protein, 45 tested positive, the most prevalent being P. vivax 247, followed by P. vivax 210 and P. falciparum. Both variants of P. vivax were observed in secondary vectors, including Anopheles squamosus/cydippis, Anopheles coustani, and unknown Anopheles spp. Furthermore, evidence of coinfection of P. falciparum and P. vivax 210 in Anopheles gambiae sensu lato (s.l.) was found. Conclusions Here, feeding behaviour of Anopheles spp. mosquitoes in southeastern Madagascar was evaluated, in a livestock rich landscape. These findings suggest largely zoophagic feeding behaviors of Anopheles spp., including An. gambiae s.l. and presence of both P. vivax and P. falciparum sporozoites in Anopheles spp. A discordance between P. vivax reports in mosquitoes and humans exists, suggesting high prevalence of P. vivax circulating in vectors in the ecosystem despite low reports of clinical vivax malaria in humans in Madagascar. Vector surveillance of P. vivax may be relevant to malaria control and elimination efforts in Madagascar. At present, the high proportion of livestock blood meals in Madagascar may play a role in buffering (zooprophylaxis) or amplifying (zoopotentiation) the impacts of malaria. With malaria vector control efforts focused on indoor feeding behaviours, complementary approaches, such as endectocide-aided vector control in livestock may be an effective strategy for malaria reduction in Madagascar.

scholarly journals The epidemiology of Plasmodium falciparum and Plasmodium vivax in East Sepik Province, Papua New Guinea, pre- and post-implementation of national malaria control efforts

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Johanna H. Kattenberg ◽  
Dulcie L. Gumal ◽  
Maria Ome-Kaius ◽  
Benson Kiniboro ◽  
Matthew Philip ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Plasmodium Vivax ◽  
Papua New Guinea ◽  
Malaria Control ◽  
New Guinea

scholarly journals Host-feeding Preference of Anopheles Species under Prolonged Use of Insecticide-treated Bed Nets in Kamuli District, Uganda: Implications for Vector Control

2020 ◽  
pp. 16-25
Author(s):  
Fredrick G. Kabbale ◽  
Anne M. Akol ◽  
John B. Kaddu ◽  
Enock Matovu ◽  
Anne Kazibwe ◽  
...  
Keyword(s):  
Vector Control ◽  
Blood Meal ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Enzyme Linked Immunosorbent Assay ◽  
Host Feeding ◽  
Bed Net ◽  
Insecticide Treated Bed Nets ◽  
Intervention Zone ◽  
Blood Meals

Background: The blood-feeding patterns are crucial in incriminating disease vectors as well as facilitating the design and consolidation of effective vector control interventions in an area.  Objective: This study aimed to establish if prolonged use of insecticide-treated bed nets (ITNs) caused a shift in the preferred hosts of the common malaria vectors as the hosts were under the bed net. Such a shift would render ITNs less effective and would probably explain the continued morbidity and mortality due to malaria in the highly endemic Kamuli district. Methods: A total of 3,519 indoor and outdoor human biting female Anopheles gambiae sensu lato and An. funestus mosquitoes were collected from 48 households using human-baited bed net traps. All 187 indoor resting blood-fed anophelines collected were tested by direct enzyme-linked immunosorbent assay (ELISA) for blood meal host identification. Of these, 73 mid guts came from 24 households in villages with a 69% ITNs coverage, while 114 mid guts were from 24 households in non-ITN villages. Results: Blood meal hosts were identified in only 10.96% (n = 8) and 14.91% (n = 17) of the Anopheles blood meals from the intervention and non-intervention zones, respectively. Other blood meals could not be clearly identified.  Eight (100%) blood meals in the intervention zone were from humans, while in the non-intervention zone, 15 (88.24%), one (5.88%) and one (5.88%) came from humans, cattle and goat, respectively. These findings demonstrated that the malaria vectors in Kamuli district are anthropophilic, with nearly all the mosquitoes collected from both zones feeding on humans during every blood meal (p = 0.82). This indicated high vector-human contacts, and thus implicating these species as important in the transmission of Plasmodium species and probably other infections. Conclusion: The use of insecticide-treated bed nets is effective for controlling malaria vectors inside houses, evoking universal coverage of houses in the area.

scholarly journals Adaptation of ELISA detection of Plasmodium falciparum and Plasmodium vivax circumsporozoite proteins in mosquitoes to a multiplex bead-based immunoassay

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Alice C. Sutcliffe ◽  
Seth R. Irish ◽  
Eric Rogier ◽  
Micaela Finney ◽  
Sarah Zohdy ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Plasmodium Vivax ◽  
Lower Limit ◽  
Limit Of Detection ◽  
Enzyme Linked Immunosorbent Assay ◽  
Limits Of Detection ◽  
Sporozoite Rate ◽  
The Impact ◽  
Lower Limits ◽  
Multiplex Bead

Abstract Background Plasmodium spp. sporozoite rates in mosquitoes are used to better understand malaria transmission intensity, the relative importance of vector species and the impact of interventions. These rates are typically estimated using an enzyme-linked immunosorbent assay (ELISA) utilizing antibodies against the circumsporozoite protein of Plasmodium falciparum, Plasmodium vivax VK210 (P. vivax210) or P. vivax VK247 (P. vivax247), employing assays that were developed over three decades ago. The ELISA method requires a separate assay plate for each analyte tested and can be time consuming as well as requiring sample volumes not always available. The bead-based multiplex platform allows simultaneous measurement of multiple analytes and may improve the lower limit of detection for sporozoites. Methods Recombinant positive controls for P. falciparum, P. vivax210 and P. vivax247 and previously developed circumsporozoite (cs) ELISA antibodies were used to optimize conditions for the circumsporozoite multiplex bead assay (csMBA) and to determine the detection range of the csMBA. After optimizing assay conditions, known amounts of sporozoites were used to determine the lower limit of detection for the csELISA and csMBA and alternate cut-off measures were applied to demonstrate how cut-off criteria can impact lower limits of detection. Sporozoite rates from 1275 mosquitoes collected in Madagascar and 255 mosquitoes collected in Guinea were estimated and compared using the established csELISA and newly optimized csMBA. All mosquitoes were tested (initial test), and those that were positive were retested (retest). When sufficient sample volume remained, an aliquot of homogenate was boiled and retested (boiled retest), to denature any heat-unstable cross-reactive proteins. Results Following optimization of the csMBA, the lower limit of detection was 25 sporozoites per mosquito equivalent for P. falciparum, P. vivax210 and P. vivax247 whereas the lower limits of detection for csELISA were found to be 1400 sporozoites for P. falciparum, 425 for P. vivax210 and 1650 for P. vivax247. Combined sporozoite rates after re-testing of samples that initially tested positive for Madagascar mosquitoes by csELISA and csMBA were 1.4 and 10.3%, respectively, and for Guinea mosquitoes 2% by both assays. Boiling of samples followed by csMBA resulted in a decrease in the Madagascar sporozoite rate to 2.8–4.4% while the Guinea csMBA sporozoite rate remained at 2.0%. Using an alternative csMBA cut-off value of median fluorescence intensity (MFI) of 100 yielded a sporozoite rate after confirmational testing of 3.7% for Madagascar samples and 2.0% for Guinea samples. Whether using csMBA or csELISA, the following steps may help minimize false positives: specimens are appropriately stored and bisected anterior to the thorax-abdomen junction, aliquots of homogenate are boiled and retested following initial testing, and an appropriate cut-off value is determined. Conclusions The csMBA is a cost-comparable and time saving alternative to the csELISA and may help eliminate false negatives due to a lower limit of detection, thus increasing sensitivity over the csELISA. The csMBA expands the potential analyses that can be done with a small volume of sample by allowing multiplex testing where analytes in addition to P. falciparum, P. vivax210 and P. vivax247 can be added following optimization.

scholarly journals Monitoring of Plasmodium falciparum and Plasmodium vivax using microsatellite markers indicates limited changes in population structure after substantial transmission decline in Papua New Guinea

2019 ◽  
Author(s):  
Johanna Helena Kattenberg ◽  
Zahra Razook ◽  
Raksmei Keo ◽  
Cristian Koepfli ◽  
Charlie Jennison ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Population Structure ◽  
Microsatellite Markers ◽  
Plasmodium Vivax ◽  
Papua New Guinea ◽  
Malaria Control ◽  
New Guinea ◽  
Parasite Population ◽  
Parasite Populations ◽  
The Impact

ABSTRACTMonitoring the genetic structure of malaria parasite populations has been proposed as a novel and sensitive approach to quantify the impact of malaria control and elimination efforts. Here we describe the first population genetic analysis of sympatric Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) populations following nationwide distribution of long-lasting insecticide treated nets (LLIN) in Papua New Guinea (PNG). Parasite isolates from serial cross-sectional studies pre-(2005-6) and post-LLIN (2010-2014) were genotyped using microsatellite markers. Despite parasite prevalence declining substantially in these communities (East Sepik: Pf=54.9-8.5%, Pv=35.7-5.6%, Madang: Pf=38.0-9.0%, Pv: 31.8-19.7%), genetically diverse and intermixing parasite populations remained. P. falciparum diversity declined modestly post-LLIN relative to pre-LLIN (East Sepik: Rs = 7.1-6.4, He = 0.77-0.71; Madang: Rs= 8.2-6.1, He = 0.79-0.71). Unexpectedly, population structure present in pre-LLIN populations was lost post-LLIN, suggesting that more frequent human movement between provinces may have contributed to higher gene flow between provinces. P. vivax prevalence initially declined but increased again in one province, yet diversity remained high throughout the study period (East Sepik: Rs=11.4-9.3, He=0.83-0.80; Madang: Rs=12.2-14.5, He=0.85-0.88). Although genetic differentiation values increased between provinces over time, no significant population structure was observed at any time point. For both species, the emergence of clonal transmission and significant multilocus linkage disequilibrium (mLD) due to increased focal inbreeding post-LLIN was a strong indicator of impact on the parasite population using these markers. After eight years of intensive malaria control in PNG and substantial prevalence decline the impact on parasite population diversity and structure detectable by microsatellite genotyping was limited.

scholarly journals On multifactorial drivers for malaria rebound in Brazil: a spatio-temporal analysis

2021 ◽  
Author(s):  
Mario JC Ayala ◽  
Leonardo S Bastos ◽  
Daniel A.M. Villela
Keyword(s):  
Plasmodium Falciparum ◽  
Plasmodium Vivax ◽  
Malaria Control ◽  
Amazon Basin ◽  
Malaria Incidence ◽  
Control Program ◽  
Brazilian Amazon ◽  
Temporal Analysis ◽  
Control Programs ◽  
Spatio Temporal

Background: Malaria incidence in Brazil reversed its decreasing trend when cases from recent years, as recent as 2015, exhibited an increase in the Brazilian Amazon basin, the area with highest transmission of Plasmodium vivax and Plasmodium falciparum. In fact, an increase of more than 20% in the years 2016 and 2017 revealed possible vulnerabilities in the national malaria-control program. Methods: We studied factors that are potentially associated with this reversal, including migration, economical activities, and deforestation, and weakening of investment in control programs. We analyze past incidences of malaria cases due to Plasmodium vivax and Plasmodium falciparum with a spatio-temporal Bayesian model using more than 5 million individual records of malaria cases from January of 2003 to December of 2018 in the Brazilian Amazon to establish the municipalities with unexpected increases in cases. Results: We observe an increase in imported cases from border countries in Roraima state and found small effects due to deforestation and change of occupations. Also, an overall funding reduction from 2013 to 2016 happened before an increase in malaria cases in five regions in Amazon basin, markedly for P. vivax incidence and especially, in Pará and Roraima States. Conclusion: Urban developments, discontinued funding for control programs, migration from border areas, deforestation activities, and different economic activities such as mining and agriculture appear linked to the rebound on malaria incidence. These multifactorial drivers show that malaria control programs require permanent attention towards elimination.

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