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We detected malaria vector Anopheles stephensi mosquitoes in the Al Hudaydah governorate in Yemen by using DNA sequencing. We report 2 cytochrome c oxidase subunit I haplotypes, 1 previously found in Ethiopia, Somalia, Djibouti, and Yemen. These findings provide insight into invasive An. stephensi mosquitoes in Yemen and their connection to East Africa.

Background Yemen has witnessed several dengue fever outbreaks coincident with the social unrest and war in the country. The aim of the present study was to describe the knowledge, attitudes and practices (KAPs) of at-risk urban populations residing in Taiz, southwest of Yemen. In addition, factors possibly associated with poor preventive practices were investigated. Methods A household-based, cross-sectional survey was conducted in three urban districts encompassing 383 households. Data on the socio-demographic characteristics and KAPs of the participating household heads were collected using a pre-designed, structured questionnaire. The association of socio-demographic characteristics, knowledge and attitudes of the population with poor preventive practices against dengue fever was then analyzed using logistic regression. Results More than 90.0 % of respondent household heads had correct knowledge about fever, headache and joint pain as common signs and symptoms of dengue fever. Moreover, muscular pain and bleeding were perceived by more than 80.0 % of the respondents as being associated with dengue fever; however, only 65.0 % of the respondents reported skin rash as a sign of dengue fever. More than 95.0 % of respondents agreed about the seriousness and possible transmission of dengue fever; however, negative attitudes regarding the facts of being at risk of the disease and that the infection is preventable were expressed by 15.0 % of respondents. Despite the good level of knowledge and attitudes of the respondent population, poor preventive practices were common. Bivariate analysis identified poor knowledge of dengue signs and symptoms (OR = 2.1, 95 % CI = 1.24–3.68; P =  0.005) and its vector (OR = 2.1, 95 % CI = 1.14–3.84; P =  0.016) as factors significantly associated with poor preventive practices. However, multivariable analysis showed that poor knowledge of the vector is an independent predictor of poor preventive practices of the population (adjusted OR = 2.1, 95 % CI = 1.14–3.84; P  = 0.018). Conclusion The majority of people in urban communities of Taiz have a clear understanding of most signs/symptoms of dengue fever as well as positive attitudes towards the seriousness and possible transmissibility of dengue fever. However, negative attitudes regarding their perception of the risk and possible prevention of the infection are prevailing among a small proportion of the population and need to be targeted by educational campaigns. It appears that the good level of the population knowledge of the signs/symptoms of dengue fever and the factors contributing to the spread and control of its vectors did not translate into good practices.

Background Anopheles stephensi  is an efficient vector of both  Plasmodium falciparum  and  Plasmodium vivax  in South Asia and the Middle East. The spread of  An. stephensi  to countries within the Horn of Africa threatens progress in malaria control in this region as well as the rest of sub-Saharan Africa. Methods The available malaria data and the timeline for the detection of An. stephensi was reviewed to analyse the role of  An. stephensi  in malaria transmission in Horn of Africa of the Eastern Mediterranean Region (EMR) in Djibouti, Somalia, Sudan and Yemen. Results Malaria incidence in Horn of Africa of EMR and Yemen, increased from 41.6 in 2015 to 61.5 cases per 1000 in 2020. The four countries from this region, Djibouti, Somalia, Sudan and Yemen had reported the detection of An. stephensi as of 2021. In Djibouti City, following its detection in 2012, the estimated incidence increased from 2.5 cases per 1000 in 2013 to 97.6 cases per 1000 in 2020. However, its contribution to malaria transmission in other major cities and in other countries, is unclear because of other factors, quality of the urban malaria data, human mobility, uncertainty about the actual arrival time of An. stephensi and poor entomological surveillance. Conclusions While An. stephensi may explain a resurgence of malaria in Djibouti, further investigations are needed to understand its interpretation trends in urban malaria across the greater region. More investment for multisectoral approach and integrated surveillance and control should target all vectors particularly malaria and dengue vectors to guide interventions in urban areas.

Background Universal coverage of the targeted malaria-endemic areas with long-lasting insecticidal nets (LLINs) is implemented as one of the key interventions for malaria control and elimination in Yemen. In 2013, through a mass campaign, LLINs were distributed to the targeted communities in Al Hudaydah governorate. This study aimed to assess the ownership of, access to, and use of LLINs. It also aimed to identify factors associated with not using LLINs in malaria-endemic areas of Al Hudaydah in the Tihama region, west of Yemen. Methods A cross-sectional survey was conducted in four districts (Ad Durayhimi, Al Marawi’ah, Al Mansuriyah and Bayt Al Faqiah) in Al Hudaydah during February 2016. A total of 701 households were included in this study. Data on socio-demographic characteristics and availability of LLINs were collected by interview and observation. Four indicators for malaria prevention using LLINs; proportion of households with at least one LLIN, proportion of households with at least one LLIN for every two people, proportion of population with access to LLINs in the surveyed households and proportion of population who slept under LLINs the previous night of the survey were calculated as indicated by Roll Back Malaria Monitoring and Evaluation Reference Group. Use to access ratio was assessed. Factors associated with not using LLINs among people with access were also investigated. Results Of 701 households with 4900 de facto population, ownership of at least one LLIN was 90.6%, while 24.1% owned at least one for every two people during the survey in 2016. The overall proportion of people with access to LLINs was 51.5% (95% CI 50.1–52.9). Only 19.0% (95% CI 17.9–20.1) slept under LLINs the night before the survey and the overall use to access ratio was 0.37. The proportions of children under 5 years of age with access to and use of LLINs were 13.7 and 42.5%, respectively. On the other hand, the proportions of pregnant women with access to and use of LLINs were 16.4 and 20.0%, respectively. Multivariable analysis identified that people living in Al Mansuriyah district [adjusted odds ratio (AOR) = 3.29, 95% confidence interval (CI)  1.35–8.01; P  = 0.009)], having three or more damaged LLINs in the house (AOR = 2.76, 95% CI 1.79–4.25; P  < 0.001), aged between 16 and 45 years old (AOR = 2.17, 95% CI 1.26–3.75; P  = 0.005) or older (AOR = 2.17, 95% CI 1.09–4.29; P  = 0.026) and living in huts (AOR = 1.59, 95% CI 1.09–2.32; P  = 0.015) were significantly less likely to use LLINs. Conclusions This study shows a low LLIN access rate among local communities targeted for universal LLIN coverage in Al Hudaydah, a malaria-endemic area of high transmission. This finding necessitates additional distribution channels following mass campaigns to maintain the universal coverage. Reduced use of LLINs among people with access in these communities together with the identified risks of non-use highlight the importance of conducting behaviour change communication campaigns to enhance using LLINs in areas with universal coverage.

Onchocerciasis in Yemen is one of the most neglected diseases, where baseline estimates of onchocerciasis and monitoring of the impact of ivermectin regularly administered to the affected individuals on its transmission are lacking. Therefore, this study aimed to determine the anti-Ov16 IgG4 seroprevalence among local communities of Hodeidah and Al-Mahwit governorates of Tihama Region. The factors possibly associated with previous exposure to infection were also studied. This cross-sectional study was conducted in two ivermectin-targeted districts endemic for onchocerciasis in Hodeidah and Al-Mahwit and two untargeted districts with unknown previous endemicity in Hodeidah between February and July 2017. For 508 residents sampled by a multi-stage random approach, data were collected and blood specimens were screened for anti-Ov16 IgG4 using the SD BIOLINE Onchocerciasis IgG4 rapid tests. The study revealed an overall anti-Ov16 IgG4 rate of 18.5% (94/508) in all surveyed districts, with 10.2% (12/118) of children aged ≤10 years being seropositive. Moreover, rates of 8.0% (4/50) and 6.1% (4/66) were found in districts not officially listed as endemic for the disease. Multivariable analysis confirmed the age of more than ten years and residing within a large family as the independent predictors of exposure to infection. Onchocerciasis transmission is still ongoing as supported by the higher anti-Ov16 IgG4 seroprevalence rate among children aged ≤10 years compared to that (<0.1%) previously set by the World Health Organization as a serologic criterion for transmission interruption. Further large-scale studies combining serologic and entomologic criteria are recommended for the mapping of O. volvulus in human and blackfly populations in endemic foci and their neighboring areas of uncertain endemicity. In addition, ivermectin distribution, coverage and impact on disease transmission need to be continually assessed.

Background The Republic of Yemen has the highest incidence of malaria in the Arabian Peninsula, yet little is known of its vectors or transmission dynamics. Methods A 24-month study of the vectors and related epidemiological aspects of malaria transmission was conducted in two villages in the Taiz region in 2004–2005. Results Cross-sectional blood film surveys recorded an overall malaria infection rate of 15.3 % (250/1638), with highest rates exceeding 30 % in one village in May and December 2005. With one exception, Plasmodium malariae , all infections were P. falciparum. Seven Anopheles species were identified among 3407 anophelines collected indoors using light traps (LT) and pyrethrum knockdown catches (PKD): Anopheles arabiensis (86.9 %), An. sergentii (9 %), An. azaniae , An. dthali , An. pretoriensis , An. coustani and An. algeriensis . Sequences for the standard barcode region of the mitochondrial COI gene confirmed the presence of two morphological forms of An. azaniae , the typical form and a previously unrecognized form not immediately identifiable as An. azaniae . ELISA detected Plasmodium sporozoites in 0.9 % of 2921 An. arabiensis (23 P. falciparum , two P. vivax ) confirming this species as the primary malaria vector in Yemen. Plasmodium falciparum sporozoites were detected in An. sergentii (2/295) and a single female of An. algeriensis , incriminating both species as malaria vectors for the first time in Yemen. A vector in both wet and dry seasons, An. arabiensis was predominantly anthropophilic (human blood index = 0.86) with an entomological inoculation rate of 1.58 infective bites/person/year. Anopheles sergentii fed on cattle (67.3 %) and humans (48.3; 20.7 % mixed both species), but only 14.7 % were found in PKDs, indicating predominantly exophilic behaviour. A GIS analysis of geographic and socio-economic parameters revealed that An. arabiensis were significantly higher (P < 0.001) in houses with televisions, most likely due to the popular evening habit of viewing television collectively in houses with open doors and windows. Conclusions The predominantly indoor human biting vectors recorded in this study could be targeted effectively with LLINs, indoor residual spraying and/or insecticide-treated window/door curtains reinforced by education to instil a perception that effective and affordable malaria prevention is achievable.

The invasion of Anopheles stephensi in Africa warrants investigation of neighboring countries. In this study, genetic analysis was applied to determine the status of An. stephensi in southern Yemen. Cytochrome c oxidase subunit I ( COI ) and internal transcribed spacer 2 (ITS2) were sequenced in An. stephensi collected in Dar Sa’ad (Aden City), Tuban, Rodoom, Al Mukalla, and Sayhut, and phylogenetic analysis confirmed An. stephensi identity. Our analyses revealed that the ITS2 sequences were identical in all An. stephensi , while COI analysis revealed two haplotypes, one previously reported in northern Horn of Africa and one identified in this study for the first time. Overall, these findings revealed low levels of mitochondrial DNA diversity, which is consistent with a more recent population introduction in parts of southern Yemen relative to the Horn of Africa. Further, whole genomic analysis is needed to elucidate the original connection with invasive populations of An. stephensi in the Horn of Africa. Graphical Abstract

Systems for disease vector control should be effective, efficient, and flexible to be able to tackle contemporary challenges and threats in the control and elimination of vector-borne diseases. As a priority activity towards the strengthening of vector control systems, it has been advocated that countries conduct a vector-control needs assessment. A review was carried out of the perceived needs for disease vector control programs among eleven countries and subnational states in South Asia and the Middle East. In each country or state, independent teams conducted vector control needs assessment with engagement of stakeholders. Important weaknesses were described for malaria, dengue and leishmaniases regarding vector surveillance, insecticide susceptibility testing, monitoring and evaluation of operations, entomological capacity and laboratory infrastructure. In addition, community mobilization and intersectoral collaboration showed important gaps. Countries and states expressed concern about insecticide resistance that could reduce the continued effectiveness of interventions, which demands improved monitoring. Moreover, attainment of disease elimination necessitates enhanced vector surveillance. Vector control needs assessment provided a useful planning tool for systematic strengthening of vector control systems. A limitation in conducting the vector control needs assessment was that it is time- and resource-intensive. To increase the feasibility and utility of national assessments, an abridged version of the guidance should focus on operationally relevant topics of the assessment. Similar reviews are needed in other regions with different contextual conditions.

Visceral leishmaniasis (VL) is a debilitating, often fatal disease caused by Leishmania donovani complex; however, it is a neglected tropical disease. L. donovani complex comprises two closely related species, L. donovani that is mostly anthroponotic and L. infantum that is zoonotic. Differentiation between these two species is critical due to the differences in their epidemiology and pathology. However, they cannot be differentiated morphologically, and their speciation using isoenzyme-based methods poses a difficult task and may be unreliable. Molecular characterization is now the most reliable method to differentiate between them and to determine their phylogenetic relationships. The present study aims to characterize Leishmania species isolated from bone marrows of Yemeni pediatric patients using sequence analysis of the ribosomal internal transcribed spacer-1 (ITS1) gene. Out of 41 isolates from Giemsa-stained bone marrow smears, 25 isolates were successfully amplified by nested polymerase chain reaction and sequenced in both directions. Phylogenetic analysis using neighbor joining method placed all study isolates in one cluster with L. donovani complex (99% bootstrap). The analysis of ITS1 for microsatellite repeat numbers identified L. infantum in 11 isolates and L. donovani in 14 isolates. These data suggest the possibility of both anthroponotic and zoonotic transmission of VL-causing Leishmania species in Yemen. Exploring the possible animal reservoir hosts is therefore needed for effective control to be achieved.

Insecticides have played a major role in the prevention, control, and elimination of vector-borne diseases, but insecticide resistance threatens the efficacy of available vector control tools. A global survey was conducted to investigate vector control insecticide use from 2010 to 2019. Out of 140 countries selected as sample for the study, 87 countries responded. Also, data on ex-factory deliveries of insecticide-treated nets (ITNs) were analyzed. Insecticide operational use was highest for control of malaria, followed by dengue, leishmaniasis and Chagas disease. Vector control relied on few insecticide classes with pyrethroids the most used overall. Results indicated that IRS programs have been slow to react to detection of pyrethroid resistance, while proactive resistance management using insecticides with unrelated modes of action was generally weak. The intensive use of recently introduced insecticide products raised concern about product stewardship regarding the preservation of insecticide susceptibility in vector populations. Resistance management was weakest for control of dengue, leishmaniasis or Chagas disease. Therefore, it will be vital that vector control programs coordinate on insecticide procurement, planning, implementation, resistance monitoring, and capacity building. Moreover, increased consideration should be given to alternative vector control tools that prevent the development of insecticide resistance.