Hosts and transmission of Mycobacterium ulcerans: a systematic review

The control of Buruli ulcer (BU), a debilitating neglected tropical disease, is hampered by the inadequate understanding of the mode of transmission of its causative agent, Mycobacterium ulcerans (M. ulcerans). The DNA of M. ulcerans has been detected in some living organisms and non-living environmental samples of both aquatic and terrestrial sources. However, it is unclear whether the identified organisms support in vivo multiplication of the bacterium or play any role in its transmission. This paper identifies hosts of M. ulcerans, reviews progress made in unravelling the exact mode of transmission of M. ulcerans and identifies research gaps in this aspect of BU epidemiology. Using the search terms, ‘niche, Mycobacterium ulcerans’ and ‘mode of transmission, Mycobacterium ulcerans’ as well as defined inclusion criteria, information was obtained from the PubMed database and reviewed to assess their importance to the research question. Aquatic bugs of the genera Appasus and Diplonychus as well as Naucoris cimicoides and possums were identified to support in vivo multiplication of the bacterium. Bite of M. ulcerans contaminated Aedes notoscriptus, bite of aquatic bugs harboring or contaminated with M. ulcerans, and M. ulcerans contaminated skin-puncturing materials present in nature create opportunity for its transmission and infection. Appropriate protective measures may be useful to reduce the risk of exposure to M. ulcerans in BU endemic areas, and incorporation of trophic interactions of aquatic organisms known to support in vivo multiplication of M. ulcerans is needed in future research for better understanding of the spread of M. ulcerans in nature. French title: Hôtes et transmission de Mycobacterium ulcerans: une revue systématique   Le contrôle de l'ulcère de Buruli (UB), une maladie tropicale négligée débilitante, est entravé par la compréhension insuffisante du mode de transmission de son agent causal, Mycobacterium ulcerans (M. ulcerans). L'ADN de M. ulcerans a été détecté dans certains organismes vivants et des échantillons environnementaux non vivants de sources aquatiques et terrestres. Cependant, il n'est pas clair si les organismes identifiés favorisent la multiplication in vivo de la bactérie ou jouent un rôle dans sa transmission. Cet article identifie les hôtes de M. ulcerans, passe en revue les progrès réalisés pour démêler le mode exact de transmission de M. ulcerans et identifie les lacunes de la recherche dans cet aspect de l'épidémiologie de l'UB. À l'aide des termes de recherche « niche, Mycobacterium ulcerans » et « mode de transmission, Mycobacterium ulcerans » ainsi que des critères d'inclusion définis, des informations ont été obtenues à partir de la base de données PubMed et examinées pour évaluer leur importance pour la question de recherche. Des punaises aquatiques des genres Appasus et Diplonychus ainsi que Naucoris cimicoides et possums ont été identifiées pour soutenir la multiplication in vivo de la bactérie. La piqûre d'Aedes notoscriptus contaminé par M. ulcerans, la piqûre d'insectes aquatiques hébergeant ou contaminés par M. ulcerans et les matériaux de perforation de la peau contaminés par M. ulcerans présents dans la nature créent une opportunité de transmission et d'infection. Des mesures de protection appropriées peuvent être utiles pour réduire le risque d'exposition à M. ulcerans dans les zones d'endémie UB, et l'incorporation d'interactions trophiques d'organismes aquatiques connus pour favoriser la multiplication in vivo de M. ulcerans est nécessaire dans les recherches futures pour une meilleure compréhension de la propagation de M. ulcerans dans la nature. &nbsp

Anthelmintic Effect of Moringa oleifera Lam. in Wild-caught Achatina achatina Linnaeus, 1758 from the Sefwi Wiawso District, Ghana

Parasitic infection in edible snail species such as Achatina achatina has the potential of reducing growth and requires investigation.This study assessed the anthelmintic effect of Moringa oleifera in A. achatina. Using dissecting and microscopic techniques, the proportion of parasitic infection in A. achatina group fed with M. oleifera was significantly lower than that of the control group (χ²(1) = 14.97; P = 0.0001). The mean parasite intensity recorded for the kidney of both treated (2.17) and control (3.33) groups of snails were significantly different (bootstrap t = 2.31; P = 0.041). Similar observation was made in the lung of treated (1.43) and control (3.14) snail groups (bootstrap t = 3.54; P = 0.005). However, no significant mean parasite intensity in the spermoviduct of treated (1.80) and control (1.96) snail groups was observed (bootstrap t = 0.475; P = 0.627). The results generally highlight anthelmintic value of M. oleifera in the control of parasites in A. achatina. Fresh foliage of M. oleifera may serve as useful addition to the feed of reared edible snails

Assessment of Helminth Infections in Goats Slaughtered in an Abattoir in a suburb of Accra, Ghana

A cross-sectional study to evaluate parasitic infections in small ruminants was conducted in an abattoir in a suburb of Accra from January to March 2015. Samples from various sections of the gut of 35 goats, either reared in Ghana or imported from Burkina Faso, were analyzed using the Kato-Katz technique. The overall prevalence was 100%. The proportions of goats infected with each parasite type were 100%, 94.4%, 88.6%,80.5%, 68.6 62.8% and 44.4% respectively for Strongyloides sp., tapeworms, Ascaris sp., Fasciola hepatica, Trichuris sp., Haemonchus contortus and Schistosoma haematobium. The proportion of animals infected with Haemonchus contortus was significantly higher in imported goats than those reared locally (p<0.05). The mean intensity of infection was low for all the parasites. However, high diversity of parasites with 80% of goats having at least four parasite types was observed. The data show high multiple infections in the goats brought to the slaughter house and suggest the need to institute appropriate measures to curb the problem

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Background: Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. Methods: The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model—a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates—with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality—which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. Findings: The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2–100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1–290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1–211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4–48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3–37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7–9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. Interpretation: Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. Funding: Bill & Melinda Gates Foundation