ABSTRACT
Introduction: Seasonal malaria chemoprevention (SMC) with Sulfadoxine pyrimethamine plus amodiaquine (SP + AQ) consist of a monthly administration of therapeutic dose to children under five years of age during the high risk of malaria in area where malaria is highly seasonal. According to SMC recommendation, both non-infected and asymptomatic Plasmodium falciparum infected children will receive similar treatment. The gap in our knowledge is how the effect of asymptomatic infection on the efficacy of SMC in preventing clinical malaria over a four-week period. Thus, this study aimed to assess the risk of clinical malaria and its association with children's infection status when SMC treatment is given. Methodology: The study was carried out in the Koulikoro health district in Mali and concerned children under 10 years of age. A total of 726 and 1452 children were randomly selected and followed over the SMC campaign in the years 2019 and 2020 respectively. Prevalence of asymptomatic P. falciparum infection was determined each round by microscopy before SMC drugs intake. Children were passively followed over a four-week period to determine incidence of clinical malaria. R-Studio software was used for analysis. The risk of clinical malaria by infection status was estimated using a logistic regression. A Kaplan-Meier curve was used to determine the survival time between infected and uninfected children. The Pearson Chi-square test was used to compare proportions with the significant level at p< 0.05. Results: The average prevalence of asymptomatic infection was 11.0% both years, and it was higher among children aged 5 to 9 years old in 2019 (p<0.001) and 2020 (p=0.016). The risk of clinical malaria was significantly higher among asymptomatic infected children 2019: (RR=3.05, CI [2.04-4.72]) and 2020 (RR=1.43, CI [1.04-1.97]) transmission seasons. Likewise, the time of the first malaria occurrence was statistically lower among infected children regardless the year (p<0.001 in 2019 and p=0.01 in 2020). Conclusion: Results show a high risk of clinical malaria in asymptomatic infected children during SMC delivery. Screening for P. falciparum infection before the SMC treatment could significantly enhance the impact of the strategy on malaria morbidity in endemic areas.
ABSTRACT
BACKGROUND: In Africa, the relationship between childhood nutritional status and malaria remains complex and difficult to interpret. Understanding it is important in the improvement of malaria control strategies. This study aimed to assess the influence of nutritional status on the occurrence of multiple malaria episodes in children aged 6 to 59 months between 2013 and 2017 living in the village of Dangassa, Mali. METHODS: A community-based longitudinal study was conducted using cross-sectional surveys (CSSs) at the beginning (June) and end (November) of the malaria transmission season associated with passive case detection (PCD) at the Dangassa Community Health Centre. Children with asymptomatic malaria infection during cross-sectional surveys were selected and their malaria episodes followed by PCD. Malaria indicators in person-months were estimated using an ordinal-logistic model repeated on subjects during follow-up periods. RESULTS: The incidence rate (IR) during the period of high transmission (June to October), for 1 episode and for 2 + episodes peaked in 2013 with 65 children (IR = 95.73 per 1000 person-months) and 24 cases (IR = 35.35 per 1000 person-months), respectively. As expected, the risk of multiple episodes occurring during the period of high transmission was 3.23 compared to the period of low transmission after adjusting for other model parameters (95% CI [2.45-4.26], p = 0.000). Children with anaemia were at high risk of having multiple episodes (OR = 1.6, 95% CI [1.12-2.30], p = 0.011). However, the risk of having 2 + episodes for anemic children was higher during the period of low transmission (RR = 1.67, 95% CI [1.15-2.42], p = 0.007) compared to the period of high transmission (RR = 1.58, 95% CI [1.09-2.29], p = 0.016). The trend indicated that anemic and underweight children were significantly associated with multiple malaria episodes during the period of low transmission (p < 0.001). CONCLUSION: Results show that multiple episodes of malaria are significantly related to the nutritional status (anaemia and underweight) of the child during the two transmission seasons and more pronounced during the dry season (period of low transmission). Further research including other malnutrition parameters will be needed to confirm these findings.
Subject(s)
Malaria , Nutritional Status , Humans , Mali/epidemiology , Infant , Child, Preschool , Male , Female , Malaria/epidemiology , Longitudinal Studies , Cross-Sectional Studies , Incidence , PrognosisABSTRACT
Diagnostics for febrile illnesses other than malaria are not readily available in rural sub-Saharan Africa. This study assessed exposure to three mosquito-borne arboviruses-dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV)-in southern Mali. Seroprevalence for DENV, CHIKV, and ZIKV was analyzed by detection of IgG antibodies and determined to be 77.2%, 31.2%, and 25.8%, respectively. Among study participants, 11.3% were IgG-positive for all three arboviruses. DENV had the highest seroprevalence rate at all sites; the highest seroprevalence of CHIKV and ZIKV was observed in Bamba. The seroprevalence for all three arboviruses increased with age, and the highest seroprevalence was observed among adults older than 50 years. The prevalence of Plasmodium spp. in the cohort was analyzed by microscopy and determined to be 44.5% (N = 600) with Plasmodium falciparum representing 95.1% of all infections. This study demonstrates the co-circulation of arboviruses in a region hyperendemic for malaria and highlights the needs for arbovirus diagnostics in rural sub-Saharan Africa.
Subject(s)
Chikungunya Fever , Dengue Virus , Humans , Mali/epidemiology , Seroepidemiologic Studies , Adult , Middle Aged , Male , Female , Adolescent , Young Adult , Chikungunya Fever/epidemiology , Chikungunya Fever/blood , Dengue Virus/immunology , Child , Child, Preschool , Chikungunya virus/immunology , Dengue/epidemiology , Arboviruses/immunology , Arboviruses/isolation & purification , Antibodies, Viral/blood , Malaria/epidemiology , Arbovirus Infections/epidemiology , Arbovirus Infections/virology , Zika Virus Infection/epidemiology , Zika Virus Infection/blood , Zika Virus Infection/diagnosis , Zika Virus/immunology , Endemic Diseases , Immunoglobulin G/blood , Aged , Infant , PrevalenceABSTRACT
Objectives: Following the scaling-up of malaria control strategies in Mali, understanding the changes in age-specific prevalence of infection and risk factors associated with remains necessary to determine new priorities to progress toward disease elimination. This study aimed to estimate the risk of clinical malaria using longitudinal data across three different transmission settings in Mali. Methods: Cohort-based longitudinal studies were performed from April 2018 to December 2022. Incidence of malaria was measured through community health center-based passive case detection. Generalized estimation equation model was used to assess risk factors for clinical malaria. Results: A total of 21,453 clinical presentations were reported from 4500 participants, mainly from July to November. Data shows a significant association between malaria episodes, sex, age group, season, and year. Women had lower risk, the risk of clinical episode increased with age up to 14 years then declined, and in both sites, the dry-season risk of clinical episode was significantly lower compared to the rainy season. Conclusion: Determining factors associated with the occurrence of clinical malaria across different ecological settings across the country could help in the development of new strategies aiming to accelerate malaria elimination in an area where malaria transmission remains intense.
ABSTRACT
Background: In Africa, the relationship between nutritional status and malaria remains complex and difficult to interpret in children. Understanding it is important in the development of malaria control strategies. This study evaluated the effect of nutritional status on the occurrence of multiple malaria episodes in children aged 6 to 59 months between 2013 and 2017 living in the village of Dangassa, Mali. Methods: A community-based longitudinal study was conducted using cross-sectional surveys (SSCs) at the beginning (June) and end (November) of the malaria transmission season associated with passive case detection (PCD) at the Dangassa Community Health Center. Children with asymptomatic malaria infection during cross-sectional surveys were selected and their malaria episodes followed by PCD. Palustrine indicators in person-months were estimated using an ordinal-logistic model repeated on subjects during follow-up periods. Results: The incidence rate (IR) during the period of high transmission (June to October), for 1 episode and for 2 + episodes peaked in 2013 with 65 children (IR = 95.73 per 1000 person-months) and 24 cases (IR = 35.35 per 1000 person-months), respectively. As expected, the risk of multiple episodes occurring during the period of high transmission was 3.23 compared to the period of low transmission after adjusting for other model parameters (95% CI = [2.45-4.26], p = 0.000). Children with anemia were at high risk of having multiple episodes (OR = 1.6, 95% CI [1.12-2.30], p = 0.011). However, the risk of having 2 + episodes for anemic children was higher during the period of low transmission (RR = 1.67, 95% CI [1.15-2.42], p = 0.007) compared to the period of high transmission (RR = 1.58, 95% CI [1.09-2.29], p = 0.016). The trend indicated that anemic and underweight children were significantly associated with multiple malaria episodes during the period of low transmission (p < = 0.001). Conclusion: Our results indicate that multiple episodes of malaria are significantly related to the nutritional status (anemia and underweight) of the child during the two transmission seasons and more pronounced during the dry season (period of low transmission). Further research including other malnutrition parameters will be needed to confirm our findings.
ABSTRACT
In Mali, malaria vector control relies mostly on long-lasting insecticidal nets and indoor residual spraying (IRS). From 2008 to 2016, an IRS program was implemented in the district of Koulikoro. After a significant reduction in malaria indicators, IRS was stopped in 2016. This study evaluated the effect of IRS withdrawal on entomological parameters of malaria transmission and incidence in children aged 6 months to 10 years in the district of Koulikoro. Entomological parameters of malaria transmission during the last year of IRS implementation in 2016 were compared with those obtained 2 years after IRS withdrawal in 2018 in two villages of Koulikoro. Mosquito vectors were collected by mouth aspiration and pyrethrum spray catches in the villages to monitor these transmission parameters. A sharp increase (10.8 times higher) in vector abundance after IRS withdrawal was observed. The infection rate of Anopheles gambiae sensu lato to Plasmodium falciparum increased from zero during IRS implementation to 14.8% after IRS withdrawal. The average entomological inoculation rate, which was undetectable before, was 1.22 infected bites per person per month 2 years after IRS was withdrawn, and the cumulative malaria incidence rate observed after IRS was 4.12 times (15.2% versus 3.7%) higher than that observed in 2016 in the villages before IRS withdrawal. This study showed a resurgence of malaria transmission and incidence in the Koulikoro health district after IRS was withdrawn. Thus, to manage the potential consequences of malaria transmission resurgence, alternative approaches are needed when stopping successful malaria control interventions.
Subject(s)
Anopheles , Insecticides , Malaria , Animals , Child , Humans , Incidence , Insecticides/pharmacology , Malaria/epidemiology , Malaria/prevention & control , Mali/epidemiology , Mosquito Control , Mosquito Vectors , Infant , Child, PreschoolABSTRACT
Distinct cytomegaloviruses (CMVs) are widely distributed across their mammalian hosts in a highly host species-restricted pattern. To date, evidence demonstrating this has been limited largely to PCR-based approaches targeting small, conserved genomic regions, and only a few complete genomes of isolated viruses representing distinct CMV species have been sequenced. We have now combined direct isolation of infectious viruses from tissues with complete genome sequencing to provide a view of CMV diversity in a wild animal population. We targeted Natal multimammate mice (Mastomys natalensis), which are common in sub-Saharan Africa, are known to carry a variety of zoonotic pathogens, and are regarded as the primary source of Lassa virus (LASV) spillover into humans. Using transformed epithelial cells prepared from M. natalensis kidneys, we isolated CMVs from the salivary gland tissue of 14 of 37 (36â%) animals from a field study site in Mali. Genome sequencing showed that these primary isolates represent three different M. natalensis CMVs (MnatCMVs: MnatCMV1, MnatCMV2 and MnatCMV3), with some animals carrying multiple MnatCMVs or multiple strains of a single MnatCMV presumably as a result of coinfection or superinfection. Including primary isolates and plaque-purified isolates, we sequenced and annotated the genomes of two MnatCMV1 strains (derived from sequencing 14 viruses), six MnatCMV2 strains (25 viruses) and ten MnatCMV3 strains (21 viruses), totalling 18 MnatCMV strains isolated as 60 infectious viruses. Phylogenetic analysis showed that these MnatCMVs group with other murid viruses in the genus Muromegalovirus (subfamily Betaherpesvirinae, family Orthoherpesviridae), and that MnatCMV1 and MnatCMV2 are more closely related to each other than to MnatCMV3. The availability of MnatCMV isolates and the characterization of their genomes will serve as the prelude to the generation of a MnatCMV-based vaccine to target LASV in the M. natalensis reservoir.
Subject(s)
Cytomegalovirus Infections , Cytomegalovirus , Animals , Humans , Mice , Phylogeny , Base Sequence , MurinaeABSTRACT
Despite a significant reduction in the burden of malaria in children under five years-old, the efficient implementation of seasonal malaria chemoprevention (SMC) at large scale remains a major concern in areas with long malaria transmission. Low coverage rate in the unattainable areas during the rainy season, a shift in the risk of malaria to older children and the rebound in malaria incidence after stopping drug administration are mainly reported in these areas. These gaps represent a major challenge in the efficient implementation of SMC measures. An open randomized study was conducted to assess the effect of a fifth additional round to current regime of SMC in older children living in Dangassa, a rural malaria endemic area. Poisson regression Model was used to estimate the reduction in malaria incidence in the intervention group compared to the control group including age groups (5-9 and 10-14 years) and the use of long-lasting insecticidal nets (LLINs; Yes or No) with a threshold at 5%. Overall, a downward trend in participation rate was observed from August (94.3%) to November (87.2%). In November (round 4), the risk of malaria incidence was similar in both groups (IRR = 0.66, 95%CI [0.35-1.22]). In December (round 5), a decrease of 51% in malaria incidence was observed in intervention group compared to control group adjusted for age groups and the use of LLINs (IRR = 0.49, 95%CI [0.26-0.94]), of which 17% of reduction is attributable to the 5th round in the intervention group. An additional fifth round of SMC resulted in a significant reduction of malaria incidence in the intervention group. The number of SMC rounds could be adapted to the local condition of malaria transmission.
ABSTRACT
The Mali National Malaria Control Program (NMCP) recently established a phased set of goals for eliminating malaria in Mali by 2030. Over the past decade, the scale-up of NMCP-led malaria control interventions has led to considerable progress, as evidenced by multiple malariometric indicators. The West Africa International Center of Excellence in Malaria Research (WA-ICEMR) is a multidisciplinary research program that works closely with the NMCP and its partners to address critical research needs for malaria control. This coordinated effort includes assessing the effectiveness of control interventions based on key malaria research topics, including immune status, parasite genetic diversity, insecticide and drug resistance, diagnostic accuracy, malaria vector populations and biting behaviors, and vectorial capacity. Several signature accomplishments of the WA-ICEMR include identifying changing malaria age demographic profiles, testing innovative approaches to improve control strategies, and providing regular reporting on drug and insecticide resistance status. The NMCP and WA-ICEMR partnership between the WA-ICEMR and the NMCP offers a comprehensive research platform that informs the design and implementation of malaria prevention and control research programs. These efforts build local expertise and capacity for the next generation of malaria researchers and guide local policy, which is crucial in sustaining efforts toward eliminating malaria in West Africa.
Subject(s)
Anopheles , Insecticides , Malaria , Animals , Anopheles/parasitology , Chlorphentermine/analogs & derivatives , Humans , Insecticides/therapeutic use , International Cooperation , Malaria/drug therapy , Mali/epidemiology , Mosquito Vectors , PolicyABSTRACT
This article highlights over a decade of signature achievements by the West Africa International Centers for Excellence in Malaria Research (WA-ICEMR) and its partners toward guiding malaria prevention and control strategies. Since 2010, the WA-ICEMR has performed longitudinal studies to monitor and assess malaria control interventions with respect to space-time patterns, vector transmission indicators, and drug resistance markers. These activities were facilitated and supported by the Mali National Malaria Control Program. Research activities included large-scale active and passive surveillance and expanded coverage of universal long-lasting insecticide-treated bed nets and seasonal malaria chemoprevention (SMC). The findings revealed substantial declines in malaria occurrence after the scale-up of control interventions in WA-ICEMR study sites. WA-ICEMR studies showed that SMC using sulfadoxine-pyrimethamine plus amodiaquine was highly effective in preventing malaria among children under 5 years of age. An alternative SMC regimen (dihydroartemisinin plus piperaquine) was shown to be potentially more effective and provided advantages for acceptability and compliance over the standard SMC regimen. Other findings discussed in this article include higher observed multiplicity of infection rates for malaria in historically high-endemic areas, continued antimalarial drug sensitivity to Plasmodium falciparum, high outdoor malaria transmission rates, and increased insecticide resistance over the past decade. The progress achieved by the WA-ICEMR and its partners highlights the critical need for maintaining current malaria control interventions while developing novel strategies to disrupt malaria transmission. Enhanced evaluation of these strategies through research partnerships is particularly needed in the wake of reported artemisinin resistance in Southeast Asia and East Africa.
Subject(s)
Antimalarials , Artemisinins , Malaria, Falciparum , Malaria , Amodiaquine/therapeutic use , Antimalarials/therapeutic use , Artemisinins/therapeutic use , Child , Child, Preschool , Drug Combinations , Humans , Malaria/drug therapy , Malaria/epidemiology , Malaria/prevention & control , Malaria, Falciparum/drug therapy , Malaria, Falciparum/epidemiology , Malaria, Falciparum/prevention & control , Mali/epidemiologyABSTRACT
Little is known about the temporal patterns of infection and transmission of Lassa virus (LASV) within its natural reservoir (Mastomys natalensis). Here, we characterize infection dynamics and transmissibility of a LASV isolate (Soromba-R) in adult lab-reared M. natalensis originating from Mali. The lab-reared M. natalenesis proved to be highly susceptible to LASV isolates from geographically distinct regions of West Africa via multiple routes of exposure, with 50% infectious doses of < 1 TCID50. Postinoculation, LASV Soromba-R established a systemic infection with no signs of clinical disease. Viral RNA was detected in all nine tissues examined with peak concentrations detected between days 7 and 14 postinfection within most organs. There was an overall trend toward clearance of virus within 40 days of infection in most organs. The exception is lung specimens, which retained positivity throughout the course of the 85-day study. Direct (contact) and indirect (fomite) transmission experiments demonstrated 40% of experimentally infected M. natalensis were capable of transmitting LASV to naïve animals, with peak transmissibility occurring between 28 and 42 days post-inoculation. No differences in patterns of infection or transmission were noted between male and female experimentally infected rodents. Adult lab-reared M. natalensis are highly susceptible to genetically distinct LASV strains developing a temporary asymptomatic infection associated with virus shedding resulting in contact and fomite transmission within a cohort.
ABSTRACT
BACKGROUND: Over the past decade, three strategies have reduced severe malaria cases and deaths in endemic regions of Africa, Asia and the Americas, specifically: (1) artemisinin-based combination therapy (ACT); (2) insecticide-treated bed nets (ITNs); and, (3) intermittent preventive treatment with sulfadoxine-pyrimethamine in pregnancy (IPTp). The rationale for this study was to examine communities in Dangassa, Mali where, in 2015, two additional control strategies were implemented: ITN universal coverage and seasonal malaria chemoprevention (SMC) among children under 5 years old. METHODS: This was a prospective study based on a rolling longitudinal cohort of 1401 subjects participating in bi-annual smear surveys for the prevalence of asymptomatic Plasmodium falciparum infection and continuous surveillance for the incidence of human disease (uncomplicated malaria), performed in the years from 2012 to 2020. Entomological collections were performed to examine the intensity of transmission based on pyrethroid spray catches, human landing catches and enzyme-linked immunosorbent assay (ELISA) testing for circumsporozoite antigen. RESULTS: A total of 1401 participants of all ages were enrolled in the study in 2012 after random sampling of households from the community census list. Prevalence of infection was extremely high in Dangassa, varying from 9.5 to 62.8% at the start of the rainy season and from 15.1 to 66.7% at the end of the rainy season. Likewise, the number of vectors per house, biting rates, sporozoites rates, and entomological inoculation rates (EIRs) were substantially greater in Dangassa. DISCUSSION: The findings for this study are consistent with the progressive implementation of effective malaria control strategies in Dangassa. At baseline (2012-2014), prevalence of P. falciparum was above 60% followed by a significant year-to-year decease starting in 2015. Incidence of uncomplicated infection was greater among children < 5 years old, while asymptomatic infection was more frequent among the 5-14 years old. A significant decrease in EIR was also observed from 2015 to 2020. Likewise, vector density, sporozoite rates, and EIRs decreased substantially during the study period. CONCLUSION: Efficient implementation of two main malaria prevention strategies in Dangassa substantially contribute to a reduction of both asymptomatic and symptomatic malaria from 2015 to 2020.
Subject(s)
Insecticide-Treated Bednets , Malaria, Falciparum , Malaria , Adolescent , Child , Child, Preschool , Humans , Malaria/epidemiology , Malaria/prevention & control , Malaria, Falciparum/epidemiology , Malaria, Falciparum/prevention & control , Mali/epidemiology , Prospective StudiesABSTRACT
Seasonal malaria chemoprevention (SMC) was adopted in Mali in 2012 for preventing malaria in children younger than 5 years. Although this strategy has been highly effective in reducing childhood malaria, an uptick in malaria occurrence has occurred in children 5 to 15 years of age. This study aimed to investigate the feasibility of providing SMC to older children. A cohort of 350 children age 5 to 14 years were monitored during the 2019 transmission season in Dangassa, Mali. The intervention group received five monthly rounds of sulfadoxine-pyrimethamine plus amodiaquine, whereas the control group consisted of untreated children. Community acceptance for extending SMC was assessed during the final round. Logistic regression models were applied to compare the risk of Plasmodium falciparum malaria infection, anemia, and fever between the intervention and control groups. Kaplan-Meier survival analyses were used to compare the time to P. falciparum parasitemia infection between the groups. The community acceptance rate was 96.5% (139 of 144). Significant declines were observed in the prevalence of P. falciparum parasitemia (adjusted odds ratio, 0.22; 95% CI, 0.11-0.42) and anemia (adjusted odds ratio, 0.15; 95% CI, 0.07-0.28) in the intervention group compared with the control group. The cumulative incidence of P. falciparum infections was significantly greater (75.4%, 104 of 138) in the control group compared with the intervention group (40.7%, 61 of 143, P = 0.001). This study reveals that expanding SMC to older children is likely feasible, has high community acceptance, and is in reducing uncomplicated malaria and anemia in older children.
Subject(s)
Antimalarials/therapeutic use , Chemoprevention/standards , Malaria/prevention & control , Patient Acceptance of Health Care , Public Health/methods , Seasons , Adolescent , Chemoprevention/methods , Child , Child, Preschool , Cohort Studies , Female , Humans , Incidence , Malaria/drug therapy , Male , Mali/epidemiology , Prevalence , Public Health/standards , Risk FactorsABSTRACT
Mali had 2 reported introductions of Ebola virus (EBOV) during the 2013-2016 West Africa epidemic. Previously, no evidence for EBOV circulation was reported in Mali. We performed an EBOV serosurvey study in southern Mali. We found low seroprevalence in the population, indicating local exposure to EBOV or closely related ebola viruses.
Subject(s)
Ebolavirus , Hemorrhagic Fever, Ebola , Antibodies, Viral , Humans , Immunoglobulin G , Mali , Seroepidemiologic StudiesABSTRACT
BACKGROUND: Insecticide-based vector control is responsible for reducing malaria mortality and morbidity. Its success depends on a better knowledge of the vector, its distribution, and resistance status to the insecticides used. In this paper, we assessed Anopheles gambiae sensu lato (A gambiae s.l.) population resistance to pyrethroids in different ecological settings. METHODS: The World Health Organization standard bioassay test was used to assess F0A gambiae s.l. susceptibility to pyrethroids. Biochemical Synergist assays were conducted with piperonyl butoxide (PBO), S,S,S-tributyl phosphotritioate, and diethyl maleate. L1014F, L1014S, and N1575Y knockdown resistance (kdr) mutations were investigated using TaqMan genotyping. RESULTS: Anopheles gambiae sensu lato was composed of Anopheles arabienisis, Anopheles coluzzii, and A gambiae in all study sites. Anopheles gambiae sensu lato showed a strong phenotypic resistance to deltamethrin and permethrin in all sites (13% to 41% mortality). In many sites, pre-exposure to synergists partially improved the mortality rate suggesting the presence of detoxifying enzymes. The 3 kdr (L1014F, L1014S, and N1575Y) mutations were found, with a predominance of L1014F, in all species. CONCLUSIONS: Multiple resistance mechanisms to pyrethroids were observed in A gambiae s.l. in Mali. The PBO provided a better partial restoration of susceptibility to pyrethroids, suggesting that the efficacy of long-lasting insecticidal nets may be improved with PBO.
Subject(s)
Anopheles/drug effects , Insecticides/pharmacology , Mosquito Control/methods , Pyrethrins/pharmacology , Animals , Anopheles/genetics , Insecticide Resistance/drug effects , Insecticide Resistance/genetics , Mali , Mosquito Vectors/geneticsABSTRACT
Mastomys natalensis are a ubiquitous and often dominant rodent across sub-Saharan Africa. Importantly, they are a natural reservoir for microbial pathogens including Lassa virus (LASV), the etiological agent of Lassa fever in humans. Lassa-infected rodents have been documented across West Africa and coincide with regions where annual outbreaks occur. Zoonotic transmission to humans most often occurs directly from infected rodents. Little is known about LASV infection kinetics and transmissibility in M.natalensis, primarily due to available animals. Here, we describe the establishment of a laboratory breeding colony of genetically confirmed M.natalensis from wild-captured rodents. This colony will provide a convenient source of animals to study LASV and other emerging pathogens that utilize M. natalensis in their enzootic lifecycles.
Subject(s)
Animals, Wild/genetics , Murinae/genetics , Selective Breeding , Africa, Western , Animals , Animals, Wild/virology , Female , Lassa Fever/transmission , Lassa virus/pathogenicity , Male , Models, Animal , Murinae/physiology , Murinae/virologyABSTRACT
BACKGROUND: Implementation and upscale of effective malaria vector control strategies necessitates understanding the multi-factorial aspects of transmission patterns. The primary aims of this study are to determine the vector composition, biting rates, trophic preference, and the overall importance of distinguishing outdoor versus indoor malaria transmission through a study at two communities in rural Mali. METHODS: Mosquito collection was carried out between July 2012 and June 2016 at two rural Mali communities (Dangassa and Koïla Bamanan) using pyrethrum spray-catch and human landing catch approaches at both indoor and outdoor locations. Species of Anopheles gambiae complex were identified by polymerase chain reaction (PCR). Enzyme-Linked -Immuno-Sorbent Assay (ELISA) were used to determine the origin of mosquito blood meals and presence of Plasmodium falciparum sporozoite infections. RESULTS: A total of 11,237 An. gambiae sensu lato (s.l.) were collected during the study period (5239 and 5998 from the Dangassa and Koïla Bamanan sites, respectively). Of the 679 identified by PCR in Dangassa, Anopheles coluzzii was the predominant species with 91.4% of the catch followed by An. gambiae (8.0%) and Anopheles arabiensis (0.6%). At the same time in Koïla Bamanan, of the 623 An. gambiae s.l., An. coluzzii accounted for 99% of the catch, An. arabiensis 0.8% and An. gambiae 0.2%. Human Blood Index (HBI) measures were significantly higher in Dangassa (79.4%; 95% Bayesian credible interval (BCI) [77.4, 81.4]) than in Koïla Bamanan (15.9%; 95% BCI [14.7, 17.1]). The human biting rates were higher during the second half of the night at both sites. In Dangassa, the sporozoite rate was comparable between outdoor and indoor mosquito collections. For outdoor collections, the sporozoite positive rate was 3.6% (95% BCI [2.1-4.3]) and indoor collections were 3.1% (95% BCI [2.4-5.0]). In Koïla Bamanan, the sporozoite rate was higher indoors at 4.3% (95% BCI [2.7-6.3]) compared with outdoors at 2.4% (95% BCI [1.1-4.2]). In Dangassa, corrected entomological inoculation rates (cEIRs) using HBI were 13.74 [95% BCI 9.21-19.14] infective bites/person/month (ib/p/m) at indoor, and 18.66 [95% BCI 12.55-25.81] ib/p/m at outdoor. For Koïla Bamanan, cEIRs were 1.57 [95% BCI 2.34-2.72] ib/p/m and 0.94 [95% BCI 0.43-1.64] ib/p/m for indoor and outdoor, respectively. EIRs were significantly higher at the Dangassa site than the Koïla Bamanan site. CONCLUSION: The findings in this work may indicate the occurrence of active, outdoor residual malaria transmission is comparable to indoor transmission in some geographic settings. The high outdoor transmission patterns observed here highlight the need for additional strategies to combat outdoor malaria transmission to complement traditional indoor preventive approaches such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) which typically focus on resting mosquitoes.
Subject(s)
Anopheles/physiology , Malaria, Falciparum/transmission , Mosquito Vectors/physiology , Plasmodium falciparum/isolation & purification , Adult , Animals , Biodiversity , Environment , Feeding Behavior , Female , Humans , Male , Mali , Rural Population , Sporozoites/isolation & purification , Young AdultABSTRACT
Laboratory-controlled physiological data for the multimammate rat (Mastomys natalensis) are scarce, despite this species being a known reservoir and vector for zoonotic viruses, including the highly pathogenic Lassa virus, as well as other arenaviruses and many species of bacteria. For this reason, M. natalensis is an important rodent for the study of host-virus interactions within laboratory settings. Herein, we provide basic blood parameters for age- and sex-distributed animals in regards to blood counts, cell phenotypes and serum chemistry of a specific-pathogen-monitored M.natalensis breeding colony, to facilitate scientific insight into this important and widespread rodent species.
Subject(s)
Blood Cell Count/veterinary , Blood Chemical Analysis/veterinary , Hematocrit , Murinae/blood , Animals , Animals, Laboratory , Erythrocyte Count/veterinary , Female , Hemoglobins/analysis , Leukocyte Count/veterinary , Male , Platelet Count/veterinary , Reference ValuesABSTRACT
Malaria vector control in Mali relies heavily on the use of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) in selected districts. As part of strengthening vector control strategies in Koulikoro district, the National Malaria Control Programme (NMCP) through the support from the US President's Malaria Initiative (PMI) has strategically driven the implementation of IRS, with the LLINs coverage also rising from 93.3% and 98.2%. Due to the increased reports of vector resistance to both pyrethroid and carbamates, there was a campaign for the use of pirimiphos-methyl, an organophosphate at Koulikoro between 2015 and 2016. In this study, the effect of IRS on malaria transmission was assessed, by comparing some key entomological indices between Koulikoro, where IRS was implemented and its neighboring district, Banamba that has never received IRS as vector control intervention. The study was conducted in two villages of each district (Koulikoro and Banamba). Pyrethrum spray catches and entry window trapping were used to collect mosquitoes on a monthly basis. WHO tube tests were carried out to assess mosquito susceptibility to insecticides. Mosquitoes were identified to species level by PCR and their infection to P. falciparum was detected by Enzyme Linked-Immuno-Sorbent Assay (ELISA). Of the 527 specimens identified, An. coluzzii was the most frequent species (95%) followed by An. gambiae (4%) and An. arabiensis (1%). Its density was rainfall dependent in the no-IRS area, and almost independent in the IRS area. The infection rate (IR) in the no-IRS area was 0.96%, while it was null in the IRS area. In the no-IRS area, the entomological inoculation rate (EIR) was 0.21 infective bites /person month with a peak in September. High resistance to pyrethroids and carbamates and susceptibility to organophosphates was observed at all sites. The introduction of pirimiphos-methyl based IRS for vector control resulted in a significant decrease in malaria transmission. An. gambiae s.l., the main malaria vector in the area, was resistant to pyrethroids and carbamates but remained susceptible to the organophosphate pirimiphos-methyl.
Subject(s)
Anopheles/drug effects , Anopheles/parasitology , Carbamates/pharmacology , Malaria/prevention & control , Malaria/transmission , Organothiophosphorus Compounds/pharmacology , Pyrethrins/pharmacology , Animals , Anopheles/genetics , Disease Vectors , Female , Humans , Insect Bites and Stings/parasitology , Insecticide Resistance , Insecticides/pharmacology , Mali , Molecular Typing , Mosquito Control/methods , Mosquito Vectors/drug effects , Mosquito Vectors/genetics , Polymerase Chain ReactionABSTRACT
Mali aims to reach the pre-elimination stage of malaria by the next decade. This study used functional regression models to predict the incidence of malaria as a function of past meteorological patterns to better prevent and to act proactively against impending malaria outbreaks. All data were collected over a five-year period (2012-2017) from 1400 persons who sought treatment at Dangassa's community health center. Rainfall, temperature, humidity, and wind speed variables were collected. Functional Generalized Spectral Additive Model (FGSAM), Functional Generalized Linear Model (FGLM), and Functional Generalized Kernel Additive Model (FGKAM) were used to predict malaria incidence as a function of the pattern of meteorological indicators over a continuum of the 18 weeks preceding the week of interest. Their respective outcomes were compared in terms of predictive abilities. The results showed that (1) the highest malaria incidence rate occurred in the village 10 to 12 weeks after we observed a pattern of air humidity levels >65%, combined with two or more consecutive rain episodes and a mean wind speed <1.8 m/s; (2) among the three models, the FGLM obtained the best results in terms of prediction; and (3) FGSAM was shown to be a good compromise between FGLM and FGKAM in terms of flexibility and simplicity. The models showed that some meteorological conditions may provide a basis for detection of future outbreaks of malaria. The models developed in this paper are useful for implementing preventive strategies using past meteorological and past malaria incidence.