Nigatu N E G A S H Demeke | Dilla University (original) (raw)
Uploads
Papers by Nigatu N E G A S H Demeke
Background Endemic African malaria vectors are poorly adapted to typical urban ecologies. Howeve... more Background
Endemic African malaria vectors are poorly adapted to typical urban ecologies. However, Anopheles stephensi, an urban malaria vector formerly con ned to South Asia and the Persian Gulf, was recently detected in Africa and may change the epidemiology of malaria across the continent. Little is known about the public health implications of An. stephensi in Africa. This study is designed to assess the contribution of An. stephensi to malaria transmission in urban settings in Sudan and Ethiopia.
Methods
Case-control studies will be conducted in 3 urban settings (2 in Sudan, 1 in Ethiopia) to assess the association between presence/absence of An. stephensi in and around households and malaria cases. Cases, dened as individuals aged between 6 months and 12 years (in Sudan) and greater than 6 months (in Ethiopia), positive for Plasmodium falciparum and/or P. vivax by microscopy/rapid diagnostic test (RDT), and controls, dened as age-matched individuals negative for P. falciparum and/or P. vivax by microscopy/RDT, will be recruited from public health facilities. Entomological surveillance for adult and immature mosquitoes, and household surveys will be conducted at participant homes within 48 hours of enrolment. Both adult and immature mosquitoes will be identi ed by PCR. Conditional logistic regression will be used to estimate the association between presence/absence of An. stephensi and malaria status, adjusted for co-occurrence of other malaria vectors and participant gender.
Conclusions
Findings from this study will provide evidence of the relative importance of An. stephensi for malaria burden in urban African settings, shedding light on the need for future intervention planning and policy development.
Background The efficacy of vector control tools depends on the behaviors of vector species. Many... more Background
The efficacy of vector control tools depends on the behaviors of vector species. Many studies have sought to determine the blood meal origin of Anopheles mosquitoes in different settings of Ethiopia. This systematic review aims to generate the overall and species-speci c source of blood meal of Anopheles mosquitoes in Ethiopia.
Method
A comprehensive search was conducted between March 11 and April 2, 2024, to locate studies that met predetermined selection criteria. After exhaustive screening, evaluation and critical appraisal of the selected studies, data were extracted using a pre-prepared template in Excel. Data were analyzed using STATA-14 software to produce a descriptive statistical summary of the overall and species-speci c blood meal sources of Anopheles mosquitoes in Ethiopia. The study was conducted based on preferred reporting items for systematic reviews and meta-analysis guidelines. The protocol of this study was registered on international prospective register of systematic reviews, registration no. CRD42024515725.
Result
Of the 2,431 studies located, 27 met the inclusion criteria. In a total of 215 data points, 18,771 Anopheles mosquitoes that belonged to 23 species or species complex were tested for blood meal source. The dominant blood meal sources were bovine, 36.0% (n = 6,758) and human, 29.4% (n = 5,520). Anopheles arabiensis accounted for 67.9% (n = 12,741) followed by An. pharoensis, An. demeilloni and An. stephensi with 10.0%, 5.6% and 4.4% of the tested anophelines, respectively. Overall, there is no difference in mean proportion of An. arabiensis detected with domestic animals’ blood, 33.4% (95% CI, 32.4–34.4%), when compared with human blood, 31.8% (95% CI, 30.9–32.8%). However, higher proportion of outdoor collected An. arabiensis were found to feed on bovine, 47.9 (95% CI, 35.3, 60.6) when compared to human, 12.9 (95% CI, 0.8, 24.9, P < 0.01). The foraging ratio, which accounts for host availability, was high for bovine (FR = 0.7) when compared to human (FR = 0.2) for An. arabiensis indicating preferential feeding on bovine hosts. This host preference was supported by the host preference index (human: bovine = 0.4).
Conclusion
Bovine and human hosts were the common sources of blood meal for Anopheles mosquitoes. When considering host availability into account, An. arabiensis showed a preferential feeding on bovine/cattle. Targeting domestic animals, bovines and ovine with endectocides could supplement the current vector control interventions.
Background: Ticks are the second most common vector of human infectious diseases after mosquitoes... more Background: Ticks are the second most common vector of human infectious diseases after mosquitoes. Their transovarial transmission contributes to the maintenance of environmental diseases. This study evaluates the phytochemical screening and in vitro efficacy of Calpurnia aurea against the adult survival and egg hatchability of two transovarial transmission vectors: Amblyomma variegatum and Rhipicephalus microplus.
Methods: Plant material was extracted using maceration techniques, and concentrated solutions of 12.5, 25, 50, 100, 200, and 400 ppm were prepared. Distilled water and diazinon were used as negative and positive controls, respectively. Ten adult ticks were exposed for 10 minutes, and dead ticks were counted after 24 hours of recovery. Twenty 15-day-old eggs were immersed for 10 minutes, and after 15 days of incubation, hatched and unhatched eggs were tallied. Preliminary phytochemical constituents were screened. A one-way analysis of variance and the probit regression model determined mean mortality and hatchability and estimated
lethal and inhibitory concentrations, respectively.
Results: The ethanolic and aqueous leaf extracts caused 10±0.0% mortality in adult A.variegatum and R. microplus. The effective dose was LC50 of 27 and 29 ppm and LC50 of 37 and 41 ppm, respectively. At 400 ppm, the leaf ethanolic and aqueous extracts showed 18.7±0.9% and 18.3±1.7%; 18.3±1.2% and 19.7±0.3% egg hatching inhibition, respectively. The effective dose had an IC50 of 50 ppm and IC50s of 91 and 79 ppm, respectively. Flavonoids and saponins were found in both leaf and pod extracts.
Conclusion: C. aurea extracts showed a more promising effect on tick survival and hatchability than synthetic diazinon. The susceptibility test indicated that the leaf extract could control vectors and contribute to environmental disease maintenance.
Complex phytochemicals, especially phenolic compounds, are additional evidence of effectiveness in vector control. Further investigation of in vivo efficacy and advanced fractionation of phytochemicals is needed.
Keywords: hatchability, mortality, transovarial, phytochemical, vector control
Parasites & vectors, Mar 31, 2024
Research Square (Research Square), Feb 14, 2024
Background Endemic African malaria vectors are poorly adapted to typical urban ecologies. Howeve... more Background
Endemic African malaria vectors are poorly adapted to typical urban ecologies. However, Anopheles stephensi, an urban malaria vector formerly con ned to South Asia and the Persian Gulf, was recently detected in Africa and may change the epidemiology of malaria across the continent. Little is known about the public health implications of An. stephensi in Africa. This study is designed to assess the contribution of An. stephensi to malaria transmission in urban settings in Sudan and Ethiopia.
Methods
Case-control studies will be conducted in 3 urban settings (2 in Sudan, 1 in Ethiopia) to assess the association between presence/absence of An. stephensi in and around households and malaria cases. Cases, dened as individuals aged between 6 months and 12 years (in Sudan) and greater than 6 months (in Ethiopia), positive for Plasmodium falciparum and/or P. vivax by microscopy/rapid diagnostic test (RDT), and controls, dened as age-matched individuals negative for P. falciparum and/or P. vivax by microscopy/RDT, will be recruited from public health facilities. Entomological surveillance for adult and immature mosquitoes, and household surveys will be conducted at participant homes within 48 hours of enrolment. Both adult and immature mosquitoes will be identi ed by PCR. Conditional logistic regression will be used to estimate the association between presence/absence of An. stephensi and malaria status, adjusted for co-occurrence of other malaria vectors and participant gender.
Conclusions
Findings from this study will provide evidence of the relative importance of An. stephensi for malaria burden in urban African settings, shedding light on the need for future intervention planning and policy development.
Background The efficacy of vector control tools depends on the behaviors of vector species. Many... more Background
The efficacy of vector control tools depends on the behaviors of vector species. Many studies have sought to determine the blood meal origin of Anopheles mosquitoes in different settings of Ethiopia. This systematic review aims to generate the overall and species-speci c source of blood meal of Anopheles mosquitoes in Ethiopia.
Method
A comprehensive search was conducted between March 11 and April 2, 2024, to locate studies that met predetermined selection criteria. After exhaustive screening, evaluation and critical appraisal of the selected studies, data were extracted using a pre-prepared template in Excel. Data were analyzed using STATA-14 software to produce a descriptive statistical summary of the overall and species-speci c blood meal sources of Anopheles mosquitoes in Ethiopia. The study was conducted based on preferred reporting items for systematic reviews and meta-analysis guidelines. The protocol of this study was registered on international prospective register of systematic reviews, registration no. CRD42024515725.
Result
Of the 2,431 studies located, 27 met the inclusion criteria. In a total of 215 data points, 18,771 Anopheles mosquitoes that belonged to 23 species or species complex were tested for blood meal source. The dominant blood meal sources were bovine, 36.0% (n = 6,758) and human, 29.4% (n = 5,520). Anopheles arabiensis accounted for 67.9% (n = 12,741) followed by An. pharoensis, An. demeilloni and An. stephensi with 10.0%, 5.6% and 4.4% of the tested anophelines, respectively. Overall, there is no difference in mean proportion of An. arabiensis detected with domestic animals’ blood, 33.4% (95% CI, 32.4–34.4%), when compared with human blood, 31.8% (95% CI, 30.9–32.8%). However, higher proportion of outdoor collected An. arabiensis were found to feed on bovine, 47.9 (95% CI, 35.3, 60.6) when compared to human, 12.9 (95% CI, 0.8, 24.9, P < 0.01). The foraging ratio, which accounts for host availability, was high for bovine (FR = 0.7) when compared to human (FR = 0.2) for An. arabiensis indicating preferential feeding on bovine hosts. This host preference was supported by the host preference index (human: bovine = 0.4).
Conclusion
Bovine and human hosts were the common sources of blood meal for Anopheles mosquitoes. When considering host availability into account, An. arabiensis showed a preferential feeding on bovine/cattle. Targeting domestic animals, bovines and ovine with endectocides could supplement the current vector control interventions.
Background: Ticks are the second most common vector of human infectious diseases after mosquitoes... more Background: Ticks are the second most common vector of human infectious diseases after mosquitoes. Their transovarial transmission contributes to the maintenance of environmental diseases. This study evaluates the phytochemical screening and in vitro efficacy of Calpurnia aurea against the adult survival and egg hatchability of two transovarial transmission vectors: Amblyomma variegatum and Rhipicephalus microplus.
Methods: Plant material was extracted using maceration techniques, and concentrated solutions of 12.5, 25, 50, 100, 200, and 400 ppm were prepared. Distilled water and diazinon were used as negative and positive controls, respectively. Ten adult ticks were exposed for 10 minutes, and dead ticks were counted after 24 hours of recovery. Twenty 15-day-old eggs were immersed for 10 minutes, and after 15 days of incubation, hatched and unhatched eggs were tallied. Preliminary phytochemical constituents were screened. A one-way analysis of variance and the probit regression model determined mean mortality and hatchability and estimated
lethal and inhibitory concentrations, respectively.
Results: The ethanolic and aqueous leaf extracts caused 10±0.0% mortality in adult A.variegatum and R. microplus. The effective dose was LC50 of 27 and 29 ppm and LC50 of 37 and 41 ppm, respectively. At 400 ppm, the leaf ethanolic and aqueous extracts showed 18.7±0.9% and 18.3±1.7%; 18.3±1.2% and 19.7±0.3% egg hatching inhibition, respectively. The effective dose had an IC50 of 50 ppm and IC50s of 91 and 79 ppm, respectively. Flavonoids and saponins were found in both leaf and pod extracts.
Conclusion: C. aurea extracts showed a more promising effect on tick survival and hatchability than synthetic diazinon. The susceptibility test indicated that the leaf extract could control vectors and contribute to environmental disease maintenance.
Complex phytochemicals, especially phenolic compounds, are additional evidence of effectiveness in vector control. Further investigation of in vivo efficacy and advanced fractionation of phytochemicals is needed.
Keywords: hatchability, mortality, transovarial, phytochemical, vector control
Parasites & vectors, Mar 31, 2024
Research Square (Research Square), Feb 14, 2024