Acta tropica最新文献

The performance of Aedes aegypti was evaluated under natural winter nutritional and thermal conditions in the temperate region of Argentina. Immature stages were reared using leaf litter as a food source. The rearing was structured in three cohorts, the first started in late-fall, the second in early-winter and the last in mid-winter, and in each cohort two treatments were arranged according to solar exposure (sun and shade). The mean monthly temperature during the experiment ranged from 10.1 °C in July to 14.3 °C in the early days of October. Survival in the experiment was low (average 16.2 %), with a maximum (33 %) in mid-winter cohort. Development time from first instar larva to adult emergence varied between 24 and 103 days, was affected by cohort, treatment and their interaction, and showed an inverse relationship with temperature, particularly in the sun treatment. Individuals from the sun treatments of mid-winter and late-fall cohorts had shorter development times. Adult longevity was very low and was only affected by sex, being higher in females (4.5 days) than in males (3.1 days). The results of this work suggest that although immature stages may complete their development and reach the adult stage during the winter in temperate Argentina, females may not survive long enough to reproduce successfully.

Molossus molossus is a widely distributed neotropical bat species in the Americas, often found in urban areas. This study evaluated climate change effects on the potential geographic distribution of M. molossus, a natural host of zoonotic pathogens such as Orthohantavirus, in the Neotropical region. Using ecological niche modeling (ENM), models were generated for current (1970-2000) and future (2070) climate scenarios based on two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5) and two Global Circulation Models (MPI-ESM1-2-LR and IPSL-CM6A-LR). Results indicated that in the current scenario, warm and coastal areas of the Neotropics are suitable for M. molossus occurrence. Risk areas for Orthohantavirus transmission were mapped by overlapping the probability of urban expansion with projections of climatic suitability for the bat. For both future scenarios (2070), projections indicate an expansion of suitable climatic areas for M. molossus over urban expansion zones, specifically in Brazil, Paraguay, Peru, Ecuador, Costa Rica, Honduras, El Salvador, Guatemala, Belize, Mexico, the United States, Cuba, Haiti, the Dominican Republic, and Puerto Rico. However, projections also indicate the Lesser Antilles under climate threat, considering that no climatic suitability areas will remain. These findings provide important information for planning surveillance and mitigation actions for zoonotic risks associated with M. molossus, considering climate change impacts on its geographic distribution in the Neotropical region.

Ixodid ticks are significant vectors of pathogens affecting both humans and animals. Biological control with natural enemies represents a sustainable tool for managing ticks. However, there is a substantial lack of knowledge about the natural enemies of ticks. Wasps of the genus Ixodiphagus (Encyrtidae) are currently the only known tick-specific parasitoids. While these wasps have been sporadically recorded worldwide, their presence in Eastern Asia is poorly documented. In this study, we investigated the occurrence of Ixodiphagus wasps in field-collected ticks reared on rabbits under laboratory conditions. Ticks were collected from the Hokkaido, Hokuriku, Chugoku, Shikoku, and Kyushu regions in Japan. Out of 1,933 Haemaphysalis ticks infested on rabbits, adult wasps emerged from 15 engorged ticks. All the ticks from which wasps emerged were morphologically and molecularly identified as Haemaphysalis flava. Additionally, wasp DNA was detected in unfed H. flava nymphs using a newly designed Ixodiphagus-specific PCR assay. Among nine experimental sites in the Chugoku region, Ixodiphagus wasps were detected at three sites, with parasitism rates ranging from 1.8 % to 8.1 %. Finally, the mitochondrial COI gene sequences of four wasp and two tick samples were characterized using shotgun sequencing, direct sequencing, and in-fusion cloning approaches. Multiple intra-individual polymorphisms were observed in all the tested samples. Further studies are needed to investigate the relationship between Ixodiphagus wasps and Ixodid ticks. An increased understanding of these parasitoid wasps could contribute to future biological control measures against ticks.

The establishment of West Nile Virus (WNV) competent vectors continues to pose a major public health challenge in Canada, especially in the south. While studies have examined the association between weather conditions and the abundance of mosquitoes over trap weeks, there is limited research on the effects of weather conditions on the abundance of Culex tarsalis (Cx. tarsalis) mosquitoes for a lapse of time beyond the trap week in Saskatchewan, Western Canada. To address this gap, we analyzed provincially available weekly mosquito trap and co-incident meteorological station data in Saskatchewan from 2010 to 2021 using a bi-dimensional distributed lag and nonlinear model. Data indicate that 171,141 Cx. tarsalis mosquitoes were trapped across much of Saskatchewan, from 2010 to 2021. Cx. tarsalis were found to be most abundant between weeks 26 and 35 (July and August) and peaked in weeks 30 and 31. Based on the WNV-positive pools, mosquito infection rates increased from week 23 to 36. While weekly average maximum air temperatures between 20 °Cand 30 °C were associated with more Cx. tarsalis across all lags (0 - 8 weeks), higher weekly average minimum air temperatures had a strong and immediate effect that diminished over longer lags. Higher weekly average rainfall amounts (> 20 mm) were associated with fewer Cx. tarsalis mosquitoes across all lags, while average weekly rainfall between 8 and 20 mm was strongly associated with a high abundance of Cx. tarsalis mosquitoes over longer lags (5 -7 weeks). Additionally, increasing wind speed was associated with lower abundance of Cx. tarsalis across all lags. Findings identified nonlinear lag associations for weekly average maximum air temperature and rainfall, but linear associations for weekly average minimum air temperature and wind speed. Identified lags and thresholds for temperature, rainfall, and wind speed at which mosquito abundance peaked could help to inform public health authorities in timing of vector control measures to prevent WNV transmission.

Given the rapid increase in climate change, investigating the impact of climate change on the transmission mechanism of tick-borne diseases is imperative. In order to fully capture the influence of the seasonal variation of temperature, environmental disturbances and the co-feeding transmission on the spread of tick-borne diseases, we propose a novel stochastic dynamical model that couples the mean-reverting Ornstein-Uhlenbeck temperature equation with periodic input to the tick-borne disease model. Through theoretical analysis, we derive sufficient conditions for the extinction of tick populations and the eradication of tick-borne diseases, as well as the stochastic persistence conditions of the system. In numerical simulations, we find that the periodic Ornstein-Uhlenbeck temperature equation can effectively fit the actual temperature data in low, medium, and high latitude regions of China. In risk assessment, we find that at the spatial perspective, low-latitude areas have a higher risk of tick-borne diseases, requiring enhanced control measures; from a temporal perspective, compared to the past, the current stage presents a greater risk of tick-borne diseases when preventive measures are not implemented. Additionally, we observe that larger noise of environment for tick populations favors the extinction of tick populations, while smaller temperature fluctuations, noise on infected hosts and ticks, as well as higher temperature regression rate, are more likely to lead to the extinction of tick-borne diseases. These findings provide crucial insights into understanding the impact of climate change on the transmission mechanism of tick-borne diseases.

Bartonella spp. are gram-negative bacteria recognized as zoonotic pathogens of wide spectrum mammals. Rodents are recognized as a natural reservoir of pathogens, and many Bartonella species transmitted by various blood-sucking arthropods have been detected in various rodents populations. In Guangxi Zhuang Autonomous Region, humans have a habit of preying on rodents, however, data on the genetic diversity of Bartonella are still absent. Investigating the epidemiological characteristics of Bartonella infection in rodents is of great significance for the prevention and control of human Bartonellosis. In this study, rodents were captured to monitor the prevalence of Bartonella in four cities in Guangxi Zhuang Autonomous Region, Southwestern China. Six species of Bartonella, including three confirmed zoonotic species, were detected based on the rrs gene with an overall prevalence of 11.5 % (32/278) in rodents. Bartonella tribocorum (21/32, 65.6 %) was the predominant species among the three zoonotic Bartonella species. In addition, phylogenetic and genetic analyses of the rrs, gltA, and rpoB genes indicated that the strains were divided into distinct clade within the same rodent, suggesting the co-circulating of diverse genetic genotypes of Bartonella species. These results provide insights into the prevalence and genetic diversity of Bartonella species circulating in rodents in Guangxi Zhuang Autonomous Region, and also urged the surveillance of rodent-associated Bartonella species in these areas.

Introduction: The WHO aims to eliminate schistosomiasis as a public health problem by 2030. Based on the Global Burden of Disease 2021 (GBD 2021), this study assesses the global distribution of schistosomiasis burden to guide policy and resource allocation.

Methods: Schistosomiasis burden and social-demographic indexes (SDIs) data were extracted from GBD 2021 study. Smoothing spline models were used to examine the relationship between age-standardized prevalence rates (ASPR), DALY rates, mortality rates (ASMR), and SDI. Future burden predictions till 2030 were made using a Bayesian age-period-cohort model. Predictions and their 95 % certainty intervals were used to determine whether the region can meet the target by 2030.

Results: Globally, the burden of schistosomiasis was substantial (prevalence: 151.38 million; DALYs: 1,746,333.31; deaths: 12,857.57) in 2021. Africa accounted for most burden (Prevalence: 84.25 %; DALYs: 87.92 %; Deaths: 87.28 %). Among all age groups, individuals aged 15 to 24 years old bear the heaviest burden in 2021. The ASPR, Age-standardized DALY rate and ASMR were inversely correlated to the SDIs across different super regions (r = -0.72, P < 0.00; r = -0.71, P < 0.00; r = -0.71, P < 0.00) and countries and territories (r = 0.02, P = 0.85; r = -0.48, P < 0.00; r = -0.72, P < 0.00). According to model results, the burden of schistosomiasis in most regions will continue to decline in the future, while it in regions with high-income presented slightly rising.

Conclusions: Despite significant progress, further effects are needed to achieve the 2030 goal across the world. Additionally, the rising ASR of DALY of schistosomiasis in regions with high-income warrants attentions.

Schistosomiasis presents a significant public health challenge, especially in regions with inadequate sanitation. Current diagnostic methods, including the Kato-Katz technique, often lack sensitivity in detecting low parasite loads, prompting the search for more precise alternatives. This study introduces the Sm1-7-qPCR system as a highly sensitive and specific diagnostic tool for identifying S. mansoni infections. The 15 female Swiss Webster mice were infected with S. mansoni cercariae, and the data were compared with those of the nested PCR assay and Kato-Katz technique. The analytical sensitivity of the Sm1-7-qPCR system was tested using genomic DNA extracted from S. mansoni worms, which demonstrated excellent detection capability. For the analytical specificity, different parasites did not show amplification. The Sm1-7-qPCR system detected S. mansoni genomic DNA in 86.7 % of the stool samples from infected mice, surpassing the Kato-Katz method. The system showed high sensitivity and specificity, accurately quantifying parasite load in infected samples, showing promise in identifying patients with low parasite loads, and contributing to disease control efforts. In conclusion, the Sm1-7-qPCR system exhibited outstanding performance as a diagnostic tool for S. mansoni, surpassing traditional methods for detecting and quantifying parasite load. Further validation studies in low endemicity areas are recommended to enhance its integration into control and management strategies for S. mansoni infections.

Endocarditis is a very rare complication of Burkholderia pseudomallei infection and prosthetic valve endocarditis rarer still. We present, to our knowledge, the first confirmed Australian case of prosthetic valve endocarditis in a patient with melioidosis. Blood cultures were persistently positive for B. pseudomallei, a transoesophageal echocardiogram demonstrated a mobile vegetation on his bioprosthetic aortic valve, and computed tomography and magnetic resonance imaging identified no other focus of infection. Infection of prosthetic material appears to be rare in cases of melioidosis, however, if present, its removal should be strongly considered to effect cure. Fortunately, in our case, clinical response to 8 weeks of intravenous therapy and 6 months of high-dose oral co-trimoxazole obviated the requirement for valve replacement surgery. However, sadly, the patient died from complications of a stroke 4 months after cessation of his antibiotic treatment. The stroke was not felt to be directly related to his infection; however, his clinical course highlights the importance of aggressively addressing the comorbidities that predispose an individual to melioidosis and which also increase their risk of premature death.