Introduction to the special issue: challenges and opportunities in the fight against neglected tropical diseases: a decade from the London Declaration on NTDs

Neglected Tropical Diseases (NTDs) in Saudi Arabia: Systematic Review and Meta-analysis

Neglected tropical diseases (NTDs) pose a significant public health challenge in tropical and subtropical regions, particularly in the Kingdom of Saudi Arabia (KSA), where epidemiological data remain scarce. These diseases disproportionately affect vulnerable populations, leading to chronic morbidity and economic burdens. Understanding their distribution and burden is crucial for effective public health interventions. This study aimed to systematically evaluate the prevalence, distribution, and etiological patterns of NTDs in KSA, identifying key research gaps and informing future policy directions. A systematic review and meta-analysis were conducted on peer-reviewed studies published between 1950 and 2024 that investigated NTDs in humans in KSA. Ninety-four articles met the inclusion criteria. The majority (69.15%, n = 65) were published after 2010, with most studies concentrated in the western (n = 35, 37.23%) and southwestern (n = 15, 15.96%) regions, areas known for environmental and socioeconomic factors that may contribute to disease transmission. Protozoal NTDs were the most frequently reported (n = 28, 29.78%), followed by viral (n = 26, 27.66%), helminthic (n = 18, 19.15%), and ectoparasitic (n = 9, 9.57%) infections. Bacterial (n = 5, 5.32%), fungal (n = 4, 4.26%), and venom-related (n = 4, 4.26%) NTDs were less commonly reported. Meta-analysis yielded pooled prevalence estimates of leishmaniasis at 0.59 (95% CI: 0.38-0.77, I² = 94.2%) and dengue at 0.20 (95% CI: 0.05-0.53, I² = 98.8%), highlighting a substantial disease burden and high heterogeneity among studies. The findings emphasize the urgent need for strengthened national surveillance, improved diagnostic capacity, and region-specific interventions to control NTDs in KSA. Future research should focus on underrepresented regions, expand community-based epidemiological studies, and integrate cross-border surveillance strategies to mitigate disease importation risks. By addressing these gaps, KSA can enhance its preparedness and contribute to global NTD elimination efforts.

Development and Assessment of a Multiple-Analysis System for Diagnosing Malaria and Other Blood Parasite Infections in Humans and Non-Human Primates

Background/Objectives: Many tropical diseases such as malaria, Chagas, human African Trypanosomiasis, and Lymphatic filariasis coexist in endemic countries, affecting more than 1 billion people worldwide, and are recognised as major global vector-borne diseases. Tackling this disease requires an accurate diagnosis that is sensitive, specific, and rapid. This study aimed to describe and validate a new highly sensitive and specific multiple-analysis system that can effectively detect numerous etiological agents in a single test. Methods: A total of 230 human blood samples were assessed retrospectively for parasite characterisation, as well as 58 stool samples from non-human primates. Primers and probes were designed in the small subunit ribosomal RNA gene, except for Plasmodium spp., for which the novel target was Cytochrome Oxidase Subunit 1. Results: The analytical specificity of the presented method was 100%, with no unspecific amplifications or cross-reactions with other blood parasitic diseases. The detection limit obtained was between 0.6 and 3.01 parasites/µL for Plasmodium species, 1.8 parasites/mL for Trypanosomatidae, and 2 microfilariae/mL in the case of Filariae. The sensitivity, specificity, predictive values, and kappa coefficient reached almost 100%, except for Filariae, whose sensitivity dropped to 93.9% and whose negative predicted value dropped to 89.5%. The operational features described a turnaround and a hands-on time shorter than the compared methods with a lower cost per essay. Conclusions: This work presents a cost-effective and highly sensitive multiplexed tool (RT-PCR-bp) capable of performing simultaneous detection for blood parasitic diseases using specific fluorescence probes, enabling the diagnosis of low parasite loads and coinfections.

Exploring healthcare professionals' perspectives on neglected tropical diseases in Eastern Uganda: a qualitative study with a focus on schistosomiasis and soil-transmitted helminths

BACKGROUND

Neglected tropical diseases (NTDs), including soil-transmitted helminths (STHs) and schistosomiasis, continue to impose a heavy burden, especially in sub-Saharan Africa and Uganda, despite being preventable. Integration of NTD management into primary healthcare has been inadequate. While researchers have explored community perspectives, there is a notable gap in understanding the viewpoints of healthcare workers (HCW), which is crucial for effective NTD control strategies. This study explores HCW' perspectives in Eastern Uganda, highlighting challenges in schistosomiasis and STH prevention and management.

METHODS

In this qualitative descriptive study, we conducted semistructured interviews with 10 key informants who were HCW in Eastern Uganda with experience in managing STHs and schistosomiasis. Participants were selected purposively and interviewed through Zoom guided by a comprehensive interview guide. The data were transcribed, coded and analyzed thematically.

RESULTS

We identified five key themes regarding the impact and management of NTDs: (i) the burden of NTDs, where schistosomiasis and STHs were notably prevalent among children and communities adjacent to water bodies; (ii) transmission of NTDs, emphasizing water bodies and poor sanitation as primary routes of disease spread; (iii) clinical manifestations of NTDs, detailing the symptomatic presentations that complicate diagnosis and management; (iv) challenges in managing and diagnosing NTDs, highlighting the shortages of essential medications and diagnostic tools, along with the under-prioritization of NTDs within healthcare systems; and (v) fatalities and complications arising from NTDs, reporting on the severe outcomes and under-reporting of deaths associated with NTDs due to misdiagnosis, delayed treatment and traditional healing preferences.

CONCLUSION

The interviewed Ugandan HCW demonstrated sufficient knowledge of schistosomiasis and STHs, but faced challenges due to inadequate diagnostic tools and medication shortages. The study underscores the need for NTD prioritization with direct funding and government involvement, alongside strategies that integrate continuous medical training, effective community outreach and an enhanced healthcare system response to reduce the burden of NTDs.

Worldwide absence of canonical benzimidazole resistance-associated mutations within β-tubulin genes from Ascaris

BACKGROUND

The giant roundworm Ascaris is an intestinal nematode, causing ascariasis by infecting humans and pigs worldwide. Recent estimates suggest that Ascaris infects over half a billion people, with chronic infections leading to reduced growth and cognitive ability. Ascariasis affects innumerable pigs worldwide and is known to reduce production yields via decreased growth and condemnation of livers. The predominant anthelminthic drugs used to treat ascariasis are the benzimidazoles. Benzimidazoles interact with β-tubulins and block their function, and several benzimidazole resistance-associated mutations have been described in the β-tubulins of ruminant nematodes. Recent research on ascarids has shown that these canonical benzimidazole resistance-associated mutations are likely not present in the β-tubulins of Ascaris, Ascaridia or Parascaris, even in phenotypically resistant populations.

METHODS

To further determine the putative absence of key β-tubulin polymorphisms, we screened two β-tubulin isotypes of Ascaris, highly expressed in adult worms. Using adult and egg samples of Ascaris obtained from pigs and humans worldwide, we performed deep amplicon sequencing to look for canonical resistance-associated mutations in Ascaris β-tubulins. Subsequently, we examined these data in closer detail to study the population dynamics of Ascaris and genetic diversity within the two isotypes and tested whether genotypes appeared to partition across human and pig hosts.

RESULTS

In the 187 isolates, 69 genotypes were found, made up of eight haplotypes of β-tubulin isotype A and 20 haplotypes of isotype B. Single nucleotide polymorphisms were seen at 14 and 37 positions for β-tubulin isotype A and isotype B, respectively. No evidence of any canonical benzimidazole resistance-associated mutations was found in either human- or pig-derived Ascaris isolates. There was, however, a difference in the genetic diversity of each isotype and distribution of β-tubulin genotypes between human- and pig-derived Ascaris. Statistical tests of population differentiation show significant differences (p < 0.001) between pig- and human-derived worms; however, more diversity was seen between worms from different populations than worms from different hosts.

CONCLUSIONS

Our work suggests an absence of canonical β-tubulin mutations within Ascaris, but alternative modes of anthelminthic resistance may emerge necessitating continued genetic scrutiny alongside monitoring of drug efficacy.

Privileged small molecules against neglected tropical diseases: A perspective from structure activity relationships

Neglected tropical diseases (NTDs) comprise diverse infections with more incidence in tropical/sub-tropical areas. In spite of preventive and therapeutic achievements, NTDs are yet serious threats to the public health. Epidemiological reports of world health organization (WHO) indicate that more than 1.5 billion people are afflicted with at least one NTD type. Among NTDs, leishmaniasis, chagas disease (CD) and human African trypanosomiasis (HAT) result in substantial morbidity and death, particularly within impoverished countries. The statistical facts call for robust efforts to manage the NTDs. Currently, most of the anti-NTD drugs are engaged with drug resistance, lack of efficient vaccines, limited spectrum of pharmacological effect and adverse reactions. To circumvent the issue, numerous scientific efforts have been directed to the synthesis and pharmacological development of chemical compounds as anti-infectious agents. A survey of the anti-NTD agents reveals that the majority of them possess privileged nitrogen, sulfur and oxygen-based heterocyclic structures. In this review, recent achievements in anti-infective small molecules against parasitic NTDs are described, particularly from the SAR (Structure activity relationship) perspective. We also explore current advocating strategies to extend the scope of anti-NTD agents.

Accelerating Progress Towards the 2030 Neglected Tropical Diseases Targets: How Can Quantitative Modeling Support Programmatic Decisions?

Over the past decade, considerable progress has been made in the control, elimination, and eradication of neglected tropical diseases (NTDs). Despite these advances, most NTD programs have recently experienced important setbacks; for example, NTD interventions were some of the most frequently and severely impacted by service disruptions due to the coronavirus disease 2019 (COVID-19) pandemic. Mathematical modeling can help inform selection of interventions to meet the targets set out in the NTD road map 2021-2030, and such studies should prioritize questions that are relevant for decision-makers, especially those designing, implementing, and evaluating national and subnational programs. In September 2022, the World Health Organization hosted a stakeholder meeting to identify such priority modeling questions across a range of NTDs and to consider how modeling could inform local decision making. Here, we summarize the outputs of the meeting, highlight common themes in the questions being asked, and discuss how quantitative modeling can support programmatic decisions that may accelerate progress towards the 2030 targets.

Getting around the roundworms: Identifying knowledge gaps and research priorities for the ascarids

The ascarids are a large group of parasitic nematodes that infect a wide range of animal species. In humans, they cause neglected diseases of poverty; many animal parasites also cause zoonotic infections in people. Control measures include hygiene and anthelmintic treatments, but they are not always appropriate or effective and this creates a continuing need to search for better ways to reduce the human, welfare and economic costs of these infections. To this end, Le Studium Institute of Advanced Studies organized a two-day conference to identify major gaps in our understanding of ascarid parasites with a view to setting research priorities that would allow for improved control. The participants identified several key areas for future focus, comprising of advances in genomic analysis and the use of model organisms, especially Caenorhabditis elegans, a more thorough appreciation of the complexity of host-parasite (and parasite-parasite) communications, a search for novel anthelmintic drugs and the development of effective vaccines. The participants agreed to try and maintain informal links in the future that could form the basis for collaborative projects, and to co-operate to organize future meetings and workshops to promote ascarid research.