Factors influencing the re-emergence of plague in Madagascar

Malagasy flea microbiota results from a combination of vertically transmitted and environmentally acquired microbes

Fleas (Insecta, Siphonaptera) are the known vectors of serious bacterial pathogens, such as Yersinia pestis and Rickettsia typhi. The microbiota of fleas has been poorly investigated although it has a known influence on vector competence. Here, we report and analyse the microbiota of 577 flea specimens from Madagascar, a hotspot of plague transmission. Importantly, endemic Malagasy fleas show low host specificity, allowing addressing the importance of vertebrate host species in microbiota composition, as well as that of abiotic variables. We describe through Illumina sequencing of 2 hypervariable regions of 16 S rDNA the bacterial composition of 577 flea specimens of Madagascar. We address the importance of biotic (mammalian host and flea species) and abiotic (season and sampling site) variables on bacterial community composition. Bacterial composition appears driven by flea species and season, but interestingly not by the flea's vertebrate hosts. These results suggest that the flea microbiota is at least in part acquired before they become adult, possibly in the immature off-host stages. Taken together, our results suggest that the microbiota of sampled fleas are composed of bacterial taxa with vertical transmission, such as Wolbachia which are prevalent in the present dataset, together with several bacterial taxa for which the occurrence is driven by environment factors, especially season and habitat. Given the importance of the microbiota in vector competence, we discuss the epidemiological consequences of environmentally-driven acquisition of microbiota in fleas on plague transmission in Madagascar.

Insecticide Resistance of Xenopsylla cheopis in Madagascar: Revision of Diagnostic Doses for Bioassay and Exploration of Biochemical Mechanisms

The Oriental rat flea, Xenopsylla cheopis, is known worldwide as an efficient plague vector, including in Madagascar, where the disease remains a public health concern. Chemical control is the primary response method against X. cheopis in Madagascar. Previous bioassays focusing on different flea populations from Madagascar showed phenotypic resistance to various insecticides, including deltamethrin and fenitrothion, which, respectively, represent the previous and current chemicals for flea vector control. Despite apparent insecticide resistance, the associated mechanisms of this resistance remain poorly known. The aims of this study were to adjust diagnostic doses of deltamethrin and fenitrothion and to investigate the metabolism-based insecticide resistance of X. cheopis in Madagascar. Five available laboratory-reared flea strains of X. cheopis were selected, and their susceptibility statuses to deltamethrin and fenitrothion were determined using the WHO standard bioassay. Diagnostic doses of each insecticide were determined by the probit method, in accordance with concentration gradients. Biochemical microplate-based assays were performed to detect overproduction of cytochrome P450, alpha-/beta-esterases, and glutathione S-transferase (GST), which are signatures of metabolic resistance. The five tested strains showed different susceptibility statuses against deltamethrin and fenitrothion. The diagnostic doses were estimated to be 0.07% for deltamethrin and 1.56% for fenitrothion. Increased activities of cytochrome P450, beta-esterase, and GST enzymes in the resistant strains were revealed in comparison with those of the susceptible strain. In conclusion, readjusted diagnostic doses will help to better understand the susceptibility status of X. cheopis to deltamethrin and fenitrothion. The overproduction of cytochrome P450, beta-esterase, and GST observed on deltamethrin-resistant flea strains suggests metabolic resistance.

Applicability of TB-LAMP test for diagnosis of pulmonary TB among HIV-positive individuals

BACKGROUND

The loop-mediated isothermal amplification for TB (TB-LAMP) assay is more cost-effective and accessible than the Xpert® MTB/RIF assay. This study aimed to evaluate the diagnostic performance of the TB-LAMP assay in individuals with and without HIV infection.

METHODS

Patients aged ≥15 years presenting with symptoms of TB were included in the study. The TB-LAMP assay was performed alongside routine TB diagnostic methods, including the Xpert assay and smear microscopy, to evaluate discrepancies in test results and associated factors.

RESULTS

A total of 903 patients were enrolled in the study. The positive percentage agreement for smear microscopy and TB-LAMP compared with the Xpert assay was respectively 54.3% (95% CI 46.6-61.8) and 76.6% (95% CI 69.9-82.6). Among HIV-positive individuals, the positive percentage agreement was 42.5% (95% CI 32.9-52.4) for smear microscopy and 68.9% (95% CI 59.1-77.5) for TB-LAMP. Factors such as age >60 years (adjusted OR 3.29, 95% CI 0.32-33.83), loss of appetite (aOR 0.30, 95% CI 0.13-0.70), and HIV-positive status (aOR 3.29, 95% CI 1.12-9.63) were associated with discrepancies between TB-LAMP and Xpert results.

CONCLUSIONS

TB-LAMP demonstrated better agreement with the Xpert assay compared with smear microscopy in detecting TB among HIV-positive patients, suggesting that TB-LAMP could effectively replace smear microscopy.

Madagascar's Plague: One Health Research Aims to Slow Its Spread

The integrated approach tackles a perfect storm of poverty, invasive rats, deforestation, and climate change that is contributing to the increase in bubonic plague cases.

Imaging analysis of pneumonic plague infection in Xizang, China: a case report and literature review

BACKGROUND

Plague is an acute infectious disease caused by the Yersinia pestis. Historically, it has been a major pandemic with high mortality rates, known as the "Black Death" in the 14th century, which resulted in millions of deaths in Europe. With increasing economic prosperity, more and more people are traveling to Xizang. However, this trend also hides significant safety hazards. Currently, there are few recent reports on plague, especially those with imaging manifestations available. In this study, we report the detailed clinical and radiological data of the patient with pneumonic plague in Xizang, China, in 2023.

CASE PRESENTATION

We report a case of pneumonic plague in Xizang, which occurred in a herdsman living in an area where dead marmots were found. The patient presented with symptoms such as fever, hemoptysis, dyspnea and coma. Chest computed tomography (CT) scans showed multiple nodules distributed in the central regions of lung lobes, consolidation distributed in secondary pulmonary lobules, and had a gravity-dependent distribution pattern. These imaging findings were consistent with pulmonary hemorrhage and diffuse alveolar damage. Despite emergency treatment, the patient died within 48 h of admission. Through retrospective medical history investigation, laboratory examination and autopsy, the final diagnosis was confirmed as pneumonic plague.

CONCLUSION

Pneumonic plague is the most deadly infectious disease, and its pathological features mainly include damage to the alveoli, pulmonary hemorrhage, and pulmonary edema. Corresponding to CT, it manifests as acute and rapidly progressing pneumonia, alveolar damage, and pulmonary hemorrhage. The value of this article lies in the completeness and typicality of the imaging data, vivid hand-drawn illustrations of transmission pathways, and comprehensive literature review, all of which serve to enhance public understanding of plague and play an important warning role.

Recombinant YopE and LcrV vaccine candidates protect mice against plague and yersiniosis

No licensed vaccine exists for the lethal plague and yersiniosis. Therefore, a combination of recombinant YopE and LcrV antigens of Yersinia pestis was evaluated for its vaccine potential in a mouse model. YopE and LcrV in formulation with alum imparted a robust humoral immune response, with isotyping profiles leaning towards the IgG1 and IgG2b subclasses. It was also observed that a significantly enhanced expression of IFN-γ, TNF-α, IL-6, IL-2, and IL-1β from the splenic cells of vaccinated mice, as well as YopE and LcrV-explicit IFN-γ eliciting T-cells. The cocktail of YopE + LcrV formulation conferred complete protection against 100 LD50Y. pestis infection, while individually, LcrV and YopE provided 80 % and 60 % protection, respectively. Similarly, the YopE + LcrV vaccinated animal group had significantly lower colony forming unit (CFU) counts in the spleen and blood compared to the groups administered with YopE or LcrV alone when challenged with Yersinia pseudotuberculosis and Yersinia enterocolitica. Histopathologic evidence reinforces these results, indicating the YopE + LcrV formulation provided superior protection against acute lung injury as early as day 3 post-challenge. In conclusion, the alum-adjuvanted YopE + LcrV is a promising vaccine formulation, eliciting a robust antibody response including a milieu of pro-inflammatory cytokines and T-cell effector functions that contribute to the protective immunity against Yersinia infections. YopE and LcrV, conserved across all three human-pathogenic Yersinia species, provide cross-protection. Therefore, our current vaccine (YopE + LcrV) targets all three pathogens: Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica. However, the efficacy should be tested in other higher mammalian models.

Socioenvironmental determinants as indicators of plague risk in the central highlands of Madagascar: Experience of Ambositra and Tsiroanomandidy districts

BACKGROUND

Human plague cases are reported annually in the central highland regions of Madagascar, where the disease is endemic. The socioenvironmental characteristics and lifestyles of the populations of the central highland localities could be linked to this endemicity. The aim of this study was to determine socioenvironmental determinants that may be associated with plague risk and explain this variation in epidemiological contexts.

METHODS

The current study was based on the distribution of plague cases between 2006 and 2015 that occurred in localities of districts positioned in the central highlands. Household surveys were performed from June to August 2017 using a questionnaire and direct observations on the socioenvironmental aspects of households in selected localities. Bivariate and multivariate analyses were performed to highlight the socioenvironmental parameters associated with plague risk in both districts.

RESULTS

A total of 503 households were surveyed, of which 54.9% (276/503) were in Ambositra and 45.1% (227/503) were in Tsiroanomandidy. Multivariate analyses showed that thatched roofs [adjusted odds ratio (AOR): 2.63; 95% confidence interval (95% CI): 1.78-3.88] and ground floor houses [AOR: 2.11; 95% CI: 1.3-3.45-] were significantly associated with the vulnerability of a household to plague risk (p value<0.05).

CONCLUSIONS

Plague risk in two districts of the Malagasy central highlands is associated with human socioenvironmental characteristics. Socioenvironmental characteristics are parameters expressing spatial heterogeneity through the difference in epidemiological expression of the plague in Ambositra and Tsiroanomandidy. These characteristics could be used as indicators of vulnerability to plague risk in plague-endemic areas.

Genomic diversity of Yersinia pestis from Yunnan Province, China, implies a potential common ancestor as the source of two plague epidemics

Plague, caused by Yersinia pestis, is a zoonotic disease that can reemerge and cause outbreaks following decades of latency in natural plague foci. However, the genetic diversity and spread pattern of Y. pestis during these epidemic-silent cycles remain unclear. In this study, we analyze 356 Y. pestis genomes isolated between 1952 and 2016 in the Yunnan Rattus tanezumi plague focus, China, covering two epidemic-silent cycles. Through high-resolution genomic epidemiological analysis, we find that 96% of Y. pestis genomes belong to phylogroup 1.ORI2 and are subdivided into two sister clades (Sublineage1 and Sublineage2) characterized by different temporal-spatial distributions and genetic diversity. Most of the Sublineage1 strains are isolated from the first epidemic-silent cycle, while Sublineage2 strains are predominantly from the second cycle and revealing a west to east spread. The two sister clades evolved in parallel from a common ancestor and independently lead to two separate epidemics, confirming that the pathogen responsible for the second epidemic following the silent interval is not a descendant of the causative strain of the first epidemic. Our results provide a mechanism for defining epidemic-silent cycles in natural plague foci, which is valuable in the prevention and control of future plague outbreaks.

One Health: navigating plague in Madagascar amidst COVID-19

BACKGROUND

Africa sees the surge of plague cases in recent decades, with hotspots in the Democratic Republic of Congo, Madagascar, and Peru. A rodent-borne scourge, the bacterial infection known as plague is transmitted to humans via the sneaky bites of fleas, caused by Yersinia pestis. Bubonic plague has a case fatality rate of 20.8% with treatment, but in places such as Madagascar the mortality rate can increase to 40-70% without treatment.

MAIN TEXT

Tragedy strikes in the Ambohidratrimo district as three lives are claimed by the plague outbreak and three more fight for survival in the hospitals, including one man in critical condition, from the Ambohimiadana, Antsaharasty, and Ampanotokana communes, bringing the total plague victims in the area to a grim to five. Presently, the biggest concern is the potential plague spread among humans during the ongoing COVID-19 pandemic. Effective disease control can be achieved through training and empowering local leaders and healthcare providers in rural areas, implementing strategies to reduce human-rodent interactions, promoting water, sanitation and hygiene practices (WASH) practices, and carrying out robust vector, reservoir and pest control, diversified animal surveillance along with human surveillance should be done to more extensively to fill the lacunae of knowledge regarding the animal to human transmission. The lack of diagnostic laboratories equipped represents a major hurdle in the early detection of plague in rural areas. To effectively combat plague, these tests must be made more widely available. Additionally, raising awareness among the general population through various means such as campaigns, posters and social media about the signs, symptoms, prevention, and infection control during funerals would greatly decrease the number of cases. Furthermore, healthcare professionals should be trained on the latest methods of identifying cases, controlling infections and protecting themselves from the disease.

CONCLUSIONS

Despite being endemic to Madagascar, the outbreak's pace is unparalleled, and it may spread to non-endemic areas. The utilization of a One Health strategy that encompasses various disciplines is crucial for minimizing catastrophe risk, antibiotic resistance, and outbreak readiness. Collaboration across sectors and proper planning ensures efficient and consistent communication, risk management, and credibility during disease outbreaks.

Plague Prevention and Therapy: Perspectives on Current and Future Strategies

Plague, caused by the bacterial pathogen Yersinia pestis, is a vector-borne disease that has caused millions of human deaths over several centuries. Presently, human plague infections continue throughout the world. Transmission from one host to another relies mainly on infected flea bites, which can cause enlarged lymph nodes called buboes, followed by septicemic dissemination of the pathogen. Additionally, droplet inhalation after close contact with infected mammals can result in primary pneumonic plague. Here, we review research advances in the areas of vaccines and therapeutics for plague in context of Y. pestis virulence factors and disease pathogenesis. Plague continues to be both a public health threat and a biodefense concern and we highlight research that is important for infection mitigation and disease treatment.