Frontiers in Tropical Diseases
EISSN : 2673-7515
Published by: Frontiers Media SA (10.3389)
Total articles ≅ 122
Latest articles in this journal
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.824484
Background: Human African trypanosomiasis (HAT) has caused social–economic burden in remote rural communities mostly in sub-Saharan Africa for over a century. The World Health Organization had targeted the year 2020 for the elimination of HAT caused by Trypanosoma brucei rhodesiense, which is mainly endemic in Malawi, Uganda, Tanzania, and Zambia. Significant progress has been made in reducing reported HAT cases in some countries. Area-specific updated epidemiological and clinical data may facilitate in understanding the progress of such efforts as well as the development of new intervention strategies.Methods: We analyzed HAT prevalence and demographics from epidemiological surveys carried out from 2012 to 2020 obtained from the Ministry of Health, Malawi. In addition, we analyzed blood samples and clinical profiles of HAT patients surveyed between 2016 and 2020 from Rumphi and Nkhotakota districts. From the blood samples, parasite observations and speciation were carried out, whereas disease staging and severity were ascertained from the clinical profiles.Results: Malawi reported 315 HAT cases from 2012 to 2020. The majority of HAT cases were men (70.2%), and the mean age was 29.9 ± 15.3 with all HAT fatalities resulting from stage 2 disease. Clinical symptoms were not significantly associated with disease outcome; however, swollen lymph nodes (p = 0.004), weight loss (p = 0.010), headache (p = 0.019), and sleep disturbance (p = 0.032) were significantly associated with the HAT stage of patients. About 50% of all HAT patients were reported within 2 years from 2019 to 2020, suggesting a HAT outbreak in Malawi.Conclusion: This study has highlighted the current epidemiological insights of the rHAT trend in Malawi. We have shown that rHAT clinical phenotypes in Malawi are focus-dependent and that there has been a steady increase in rHAT cases compared to all countries with incidences of rHAT. We have also highlighted an outbreak of rHAT that occurred in Malawi from 2019 to 2020 with almost 50% of the total rHAT cases that we have presented in this study reported within 2 years of the outbreak. These should call for a review of Malawi’s rHAT control and elimination strategies. A One-Health approach with the inclusion of key stakeholders such as the department of parks and wildlife may also be considered.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.957109
Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) have resulted in a major decrease in malaria transmission. However, it has become apparent that malaria can be effectively transmitted despite high coverage of LLINs/IRS. Residual transmission can occur due to Plasmodium-carrying Anopheles mosquitoes that are insecticide resistant and have feeding and resting behavior that reduces their chance of encountering the currently deployed indoor malaria control tools. Residual malaria transmission is likely to be the most significant hurdle to achieving the goal of malaria eradication and research and development towards new tools and strategies that can control residual malaria transmission is therefore critical. One of the most promising strategies involves biological agents that are part of the mosquito microbiome and influence the ability of Anopheles to transmit Plasmodium. These differ from biological agents previously used for vector control in that their primary effect is on vectoral capacity rather than the longevity and fitness of Anopheles (which may or may not be affected). An example of this type of biological agent is Microsporidia MB, which was identified in field collected Anopheles arabiensis and caused complete inhibition of Plasmodium falciparum transmission without effecting the longevity and fitness of the host. Microsporidia MB belongs to a unique group of rapidly adapting and evolving intracellular parasites and symbionts called microsporidia. In this review we discuss the general biology of microsporidians and the inherent characteristics that make some of them particularly suitable for malaria control. We then discuss the research priorities for developing a transmission blocking strategy for the currently leading microsporidian candidate Microsporidia MB for malaria control.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.874727
Culex quinquefasciatus is responsible for the transmission of filarial worms and several arboviruses. Olfaction plays a crucial role in disease transmission as it influences behaviors that are essential for the survival and reproduction of the mosquito, such as the host-seeking behavior, courtship, and oviposition. Understanding the molecular events that coordinate how mosquitoes find their host may lead to alternative methods to reduce diseases transmission. Our aim was to investigate the differential expression profile of odorant receptor (ORs) and odorant-binding proteins (OBPs) genes in Cx. quinquefasciatus field females compared with CqSLab laboratory mosquito colony. Seventeen genes of interest were evaluated for their qualitative and specific expression by RT-PCR on RNAs extracted from female antennae, female legs, complete male bodies, incomplete female bodies (no head and no legs), and L4 larvae. The general expression mapping of olfactory genes revealed that all analyzed genes were expressed in antennae. Some genes showed different qualitative expression profiles, such as CquiOR2, CquiOR64, CquiOR93, CquiOBP11, and CquiOBP16, which were expressed exclusively in female antennae. On the other hand, CquiOR37, CquiOBP2, and CquiOBP43 are expressed in all sample types, and CquiOBP10 was expressed in female antennae and legs and in the complete male bodies. The expression of CquiOBP5 was detected in the female’s antennae and body, but it was absent in the legs. The quantitative differential expression analysis of six of the 17 genes by RT-qPCR was performed from RNA samples from antenna pools collected in three physiological states, post-emergence, post-mating, and post-blood feeding of the field females and CqSLab. A total of 3,600 antennae were analyzed, in pools containing 100 pairs. Most genes screened showed a higher expression level in field mosquitoes when compared with the laboratory strain CqSLab. The expression of CquiOBP5 and CquiOBP10 genes was significantly different between the post-mating and post blood-meal samples of laboratory females (p < 0.05). Our results suggest specialization of the function of the genes studied and divergence in the expression pattern of field mosquitoes compared with laboratory mosquitoes, and therefore, caution should be exercised in the interpretation of data from laboratory mosquito studies.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.953061
Onchocerciasis affects predominantly rural communities in Africa, and with small foci in South America and the Yemen. The disease is a major cause of blindness and other significant morbidity and mortality. Control programs have achieved a major impact on the incidence and prevalence of onchocerciasis by interrupting transmission with vector control programs, and treatment with mass drug administration using the microfilaricide ivermectin. Over the last few decades, several microfilaricides have been developed. This initially included diethylcarbamazine, which had significant side effects and is no longer used as such. Ivermectin which is a safe and highly effective microfilaricide and moxidectin which is a longer acting microfilaricide are presently recognized therapies. Suramin was the first effective macrofilaricide but was prohibitively toxic. Certain antibiotics including doxycycline can help eliminate adult worms by targeting its endosymbiont bacteria, Wolbachia pipientis. However, the dosing regimens may make this difficult to use as part of a mass disease control program in endemic areas. It is now widely recognized that treatments that are able to kill or permanently sterilize adult filarial worms should help achieve the elimination of this disease. We summarize in detail the historic drug development in onchocerciasis, including prospective future candidate drugs.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.822566
Background: Key populations (KP) are defined groups with an increased risk of HIV due to specific higher risk behaviours. KP who use substances engage in risky behaviors that may play a co-active role in HIV transmission and acquisition in Nigeria. This qualitative study explored the 'syndemics' of substance use, sexual risk behavior, violence and HIV infection among KP who use substances.Methods: Nineteen sexually active men who have sex with men [MSM] and 18 female sex workers [FSW] aged 16 years and older who use substances were purposively selected to participate in sixteen in-depth interviews and two focus groups. We utilized a syndemic framework to explore the interaction of socio-economic factors, substance use and high-risk sexual practices. The interviews were audio-recorded, transcribed, organized in NVIVO 11 and analyzed using thematic analysis.Results: Majority (95%) were non-injection substance users (primarily alcohol and marijuana); a few KP also used cocaine and heroin. Sixty percent of participants were between 16-24 years. Substance use utilities and trajectories were heavily influenced by KP social networks. They used substances as a coping strategy for both physical and emotional issues as well as to enhance sex work and sexual activities. Key HIV/STI risk drivers in the settings of substance use during sexual intercourse that emerged from this study include multiple sexual partnerships, condom-less sex, transactional sex, intergenerational sex, double penetration, rimming, and sexual violence. Poverty and adverse socio-economic conditions were identified as drivers of high-risk sexual practices as higher sexual risks attracted higher financial rewards.Conclusions and Recommendations: Findings indicate that KP were more inclined to engage in high-risk sexual practices after the use of substances, potentially increasing HIV risk. The syndemic of substance use, high-risk sexual behavior, adverse socio-economic situations, and violence intersect to limit HIV prevention efforts among KP. The behavioural disinhibition effects of substances as well as social and structural drivers should be considered in the design of targeted KP HIV prevention programs. HIV intervention programs in Nigeria may yield better outcomes if they address the nexus of sexual risk behavior and substance use as well as knowledge and appropriate use of HIV prophylaxis.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.902211
Ecological upheavals resulting from uncontrolled urbanization can lead to significant changes in vector borne diseases’ profiles, thus requiring a thorough revision of their prevention and control strategies. The current study aimed at characterizing malaria vector populations in the Simbock neighborhood of Yaoundé-city (Cameroon), in relation to its urbanization scheme. Adult mosquitoes were captured by human landing catches (HLC) in- and outdoors prior to (2000–2006) and during infrastructural development (2014–2016). Anophelines were morphologically identified and analyzed for Plasmodium (P.) falciparum circumsporozoite protein detection using the ELISA technique. Species of the Anopheles (An.) gambiae complex were identified using SINE-PCR. Adult An. gambiae s.l. from larvae collected between 2014 and 2017 were tested for susceptibility to insecticides (0.1% bendiocarb, 4% DDT, 0.75% permethrin and 0.05% deltamethrin) with or without piperonyl butoxide (PBO) synergist, using WHO standard bioassays. The Hot Oligonucleotide Ligation Assay was used to detect the knockdown resistance (kdr) L995F/S mutations. Overall, nine malaria vector species were identified in 2000-2006, mostly An. moucheti (49%), An. nili (13.5%) and An. gambiae s.l. (12%); the six remaining species were represented at less than 3% each. However, only three species were found in 2014-2016, with increasing proportions of An. gambiae s.l. (67%) and An. funestus (32%) (P 85%) and An. gambiae (<15%) species during the two study periods. Plasmodium falciparum infection rates were 2.1% and 1.0% in 2000-2006 and 2014-2016 respectively (P=0.4), with decreasing entomological inoculation rates (EIR) from 0.34 infective bites per man per night (ib/m/n) to 0.02 ib/m/n (P<0.0001). Anopheles gambiae s.l. was resistant to DDT and permethrin [<40% mortality rates (MR)], and deltamethrin (65-89% MR), but fully susceptible to bendiocarb (100% MR). Pre-exposure of mosquitoes to PBO resulted in 90-100% MR to deltamethrin but not to permethrin. Furthermore, the two kdr L995F/S resistance alleles were recorded at 0.64 and 0.006 frequencies respectively. This study highlights a shift from rural to urban malaria transmission in Simbock, coupled with DDT and pyrethroid resistance in An. gambiae s.l. Combination vector control interventions, e.g., PBO nets and bendiocarb indoor residual spraying are needed in such areas.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.951380
This article presents a concise mini review about human monkeypox (MPX), in response to the current outbreak in non-endemic countries. MPX is one of the viral zoonotic diseases which is attributed to monkeypox virus (MPXV) and causes a smallpox-like disease. Despite its ability to infect various mammals, the animal reservoir for MPXV is still unconfirmed. The disease usually lasts for an average of 2-4 weeks before complete recovery. The incubation period for MPXV ranges from 5-21 days and the illness starts with prodromal phase, which is characterized by fever, chills, muscle pain, back pain, general malaise, lymph node enlargement, and headache, followed by rash. MPX is a self-limited illness with spontaneous recovery in most cases. In the middle of May 2022, an outbreak of human MPX has been declared by the World Health Organization (WHO) across various WHO regions, and in countries that are not endemic for the disease. As of June 08, 2022, the number of confirmed MPX cases that were reported across 18 countries of European Union/European Economic Area (EU/EEA) has reached 704 cases. Worldwide, and as of June 08, 2022, a total of 1285 confirmed MPX cases were reported in non-endemic countries across four WHO regions. Exportation of MPXV from Africa to other continents has been increasingly reported. Lacking travel connections to Africa among most current reported cases in 2022 raises an alarm about the changing epidemiology of the disease which warrants a stringent epidemiological surveillance to prevent further escalation of the current outbreak in non-endemic countries.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.893653
Leprosy is a public health issue, and early detection is critical to avert disability. Despite the global attempt to eradicate this disease as a public health problem, it remains an important cause of global neurological disability. India, Brazil and Indonesia share more than 70% of the cases. The reduction of new cases is a priority in the WHO global strategy 2021-2030 which aims to reduce disease transmission in the community by diagnosing cases and identifying subclinical infection. The clinical manifestations of leprosy range from a few to several lesions. The identification remains difficult due to the limited sensitivity of traditional approaches based on bacillary counts of skin smears and histology. To aid in the diagnosis of this disease, molecular biology, and biotechnological technologies have been applied, each with its own set of benefits and downsides despite providing an essential tool to validate the clinical diagnosis of leprosy. Because of this, it is strongly recognized that specific, inexpensive point of care technologies should be developed, particularly to identify asymptomatic M. leprae infections or leprosy nearer to the suspected cases seeking medical attention. Thus, this review will provide an overview of the advancements in leprosy diagnosis over the world. The purpose of this review is to improve our understanding of the outcomes of current tests and technologies used in leprosy diagnosis and to emphasize critical aspects concerning the detection of leprosy bacilli.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.843509
Background: The Global Point Prevalence Study (PPS) provides a platform for institutions to register and add clinical information on antimicrobial usage and determine variables related to proper antimicrobial stewardship.Objective: To assess the trends in antimicrobial usage and quality indicators in antimicrobial prescriptions at our hospital.Method: We retrospectively compared data collected at Komfo Anokye Teaching Hospital (KATH) during the Global PPS in 2015 and 2019. Both surveys took place on a day in September of the respective year. Medical records of all in-patients on admission at 0800 hours on a specific day were reviewed for antimicrobial use in the survey. Data on antibiotic use, including indications for use and the presence of quality indicators, were recorded.Results: The total number of patients on admission in 2015 and 2019 were 386 and 630, respectively. The proportion of patients on at least one antimicrobial was 64% (247/386) and 58.4% (368/630) in 2015 and 2019, respectively. Pneumonia was the most common medical condition for which antimicrobial was prescribed for 2015, 30(16.9%) and 2019, 44(23.0%), respectively. There was a decrease in Hospital-acquired infections from 2015, 6.2% (24/386) to 4.8% (30/630) in 2019. The use of biomarkers increased from 4.9% (12/247) to 7.6% (28/368).Conclusion: Over 50% of hospitalised patients were on antimicrobials for both years. The inauguration of the antimicrobial stewardship committee at KATH will improve these quality indicators.
Frontiers in Tropical Diseases, Volume 3; https://doi.org/10.3389/fitd.2022.924719
Traditionally, pathogen-associated molecular patterns (PAMPs) were described as structural molecular motifs shared by different classes of microorganisms. However, it was later discovered that the innate immune system is also capable of distinguishing metabolically active microbes through the detection of a special class of viability-associated PAMPs (vita-PAMPs). Indeed, recognition of vita-PAMPs triggers an extra warning sign not provoked by dead bacteria. Bacterial RNA is classified as a vita-PAMP since it stops being synthesized once the microbes are eliminated. Most of the studies in the literature have focused on the pro-inflammatory capacity of bacterial RNA on macrophages, neutrophils, endothelial cells, among others. However, we, and other authors, have shown that microbial RNA also has down-modulatory properties. More specifically, bacterial RNA can reduce the surface expression of MHC class I and MHC class II on monocytes/macrophages and help evade CD8+ and CD4+ T cell-mediated immune surveillance. This phenomenon has been described for several different bacteria and parasites, suggesting that microbial RNA plays a significant immunoregulatory role in the context of many infectious processes. Thus, beyond the pro-inflammatory capacity of microbial RNA, it seems to be a crucial component in the intricate collection of immune evasion strategies. This review focuses on the different facets of the immune modulating capacity of microbial RNA.