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1.
Different models have been proposed to elucidate the origins of the founding populations of America, along with the number of migratory waves and routes used by these first explorers. Settlements, both along the Pacific coast and on land, have been evidenced in genetic and archeological studies. However, the number of migratory waves and the origin of immigrants are still controversial topics. Here, we show the Australasian genetic signal is present in the Pacific coast region, indicating a more widespread signal distribution within South America and implicating an ancient contact between Pacific and Amazonian dwellers. We demonstrate that the Australasian population contribution was introduced in South America through the Pacific coastal route before the formation of the Amazonian branch, likely in the ancient coastal Pacific/Amazonian population. In addition, we detected a significant amount of interpopulation and intrapopulation variation in this genetic signal in South America. This study elucidates the genetic relationships of different ancestral components in the initial settlement of South America and proposes that the migratory route used by migrants who carried the Australasian ancestry led to the absence of this signal in the populations of Central and North America.  相似文献   
2.
Temperature constrains the transmission of many pathogens. Interventions that target temperature-sensitive life stages, such as vector control measures that kill intermediate hosts, could shift the thermal optimum of transmission, thereby altering seasonal disease dynamics and rendering interventions less effective at certain times of the year and with global climate change. To test these hypotheses, we integrated an epidemiological model of schistosomiasis with empirically determined temperature-dependent traits of the human parasite Schistosoma mansoni and its intermediate snail host (Biomphalaria spp.). We show that transmission risk peaks at 21.7 °C (Topt), and simulated interventions targeting snails and free-living parasite larvae increased Topt by up to 1.3 °C because intervention-related mortality overrode thermal constraints on transmission. This Topt shift suggests that snail control is more effective at lower temperatures, and global climate change will increase schistosomiasis risk in regions that move closer to Topt. Considering regional transmission phenologies and timing of interventions when local conditions approach Topt will maximize human health outcomes.

Temperature is important to the transmission of most infectious diseases, but the effects of temperature variability on parasite and host traits and their interactive effects on infection dynamics are poorly understood across many host–parasite systems (13). The variable responses of host and parasite traits to altered thermal regimes (i.e., thermal trait variation) could also impact intervention efficacy if the mortality of temperature-sensitive life stages is greater than the relative contribution of natural, temperature-dependent constraints on parasite transmission. For example, anthelminthic drugs decrease parasite transmission but likely have little effect on temperature-dependent transmission dynamics because adult parasites are buffered from environmental temperature in endothermic hosts. In contrast, vector control measures and water sanitation cause vector and parasite mortality, respectively, that is independent of ecophysiological constraints and irrespective of environmental temperature (46).If interventions override natural temperature-dependent constraints on transmission, they could cause shifts in the thermal optimum (Topt) of parasite transmission, which could theoretically alter seasonal disease dynamics and render interventions less effective at certain times of the year and with global warming. This, in turn, would affect risk assessments and intervention planning for various disease systems (7, 8), especially under global climate change. Nevertheless, the hypotheses of intervention-related shifts to the Topt of transmission and the resulting knock-on effects on disease phenology and intervention efficacy have never been proposed or tested.Human schistosomiasis, which affects more than 200 million people worldwide, is a major source of human morbidity and mortality in sub-Saharan Africa (9) and represents an ideal system to test these hypotheses. Schistosoma mansoni, an important causative parasite species, is transmitted through two aquatic larval stages (Fig. 1). Miracidia infect intermediate snail hosts (Biomphalaria spp.), and cercariae are released from snails to infect humans (10). Because free-living parasite larvae and snails are ectotherms, aquatic transmission is influenced by temperature (11, 12), with warm temperatures decreasing miracidial (13, 14) and cercarial survival (15) and reducing the odds of infection (13, 16). Although several Schistosoma parasite and snail traits are temperature-dependent (1721), many models assume temperature-invariant transmission (12, 22, 23). Additionally, schistosomiasis interventions either target temperature-sensitive transmission stages, such as molluscicides, snail removal, and water sanitation, or temperature-insensitive stages, such as anthelmintic drugs provided to endothermic hosts. These interventions might impact Topt differently and thus transmission phenology in areas where S. mansoni is endemic.Open in a separate windowFig. 1.The schistosomiasis transmission cycle spans the endothermic human body and aquatic environment. Parameters representing temperature-dependent traits investigated in this study are highlighted in purple. Parameters pertaining to disease control interventions are highlighted in orange. Parameter definitions are given in the main text and SI Appendix, Table S6.The objectives of this study were to: 1) quantify temperature-dependent S. mansoni and Biomphalaria spp. traits; 2) derive temperature-specific R0 (i.e., estimated number of secondary cases from one infected human) predictions and thus a Topt for schistosome transmission; 3) evaluate how R0 and Topt are affected by three interventions targeting distinct components of the parasite life cycle; and 4) explore the effects of temperature and interventions on transmission with regard to spatial and temporal surface water temperature variation.We predicted that 1) parasite and snail traits would exhibit unimodal responses to temperature, allowing for the identification of a Topt for each trait; 2) transmission (i.e., R0) would decrease in response to all interventions; 3) Topt of R0 would only change in response to interventions targeting ectothermic parasite and host life stages; and 4) this in turn would alter transmission phenology in geographically and temporally dependent manners based on the proximity of local conditions to Topt.  相似文献   
3.
4.
Tropical regions receive a significant part of the traveling population. It is very important that health professionals are familiar with the main tropical skin diseases and able to advice patients appropriately. This article reviews the main tropical diseases of travelers, with an emphasis on diagnosis, management, and prevention. Among others, cutaneous larva migrans, myiasis, tungiasis, Chagas disease, Dengue fever, African trypanosomiasis, filariasis, and leishmaniasis are discussed. Increasing awareness among travelers and health care professionals can help reduce morbidity and mortality. Continued research on new drugs and vaccines is needed to reduce the risks of tropical diseases.  相似文献   
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6.
《Vaccine》2016,34(26):2992-2995
A number of leishmaniasis vaccine candidates are at various stages of pre-clinical and clinical development. Leishmaniasis is a vector-borne neglected tropical disease (NTD) caused by a protozoan parasite of the genus Leishmania and transmitted to humans by the bite of a sand fly. Visceral leishmaniasis (VL, kala-azar) is a high mortality NTD found mostly in South Asia and East Africa, while cutaneous leishmaniasis (CL) is a disfiguring NTD highly endemic in the Middle East, Central Asia, North Africa, and the Americas. Estimates attribute 50,000 annual deaths and 3.3 million disability-adjusted life years to leishmaniasis. There are only a few approved drug treatments, no prophylactic drug and no vaccine. Ideally, an effective vaccine against leishmaniasis will elicit long-lasting immunity and protect broadly against VL and CL. Vaccines such as Leish-F1, F2 and F3, developed at IDRI and designed based on selected Leishmania antigen epitopes, have been in clinical trials. Other groups, including the Sabin Vaccine Institute in collaboration with the National Institutes of Health are investigating recombinant Leishmania antigens in combination with selected sand fly salivary gland antigens in order to augment host immunity. To date, both VL and CL vaccines have been shown to be cost-effective in economic modeling studies.  相似文献   
7.
《Vaccine》2022,40(17):2476-2477
The United States Indo-Pacific Command Surgeon Office had the opportunity to participate in the Pacific Eclipse workshop in December 2019. This paper discusses the value of the exercise in pandemic and disaster planning for the US Indo-Pacific Command.  相似文献   
8.
The analysis of human population variation is an area of considerable interest in the forensic, medical genetics and anthropological fields. Several forensic single nucleotide polymorphism (SNP) assays provide ancestry-informative genotypes in sensitive tests designed to work with limited DNA samples, including a 34-SNP multiplex differentiating African, European and East Asian ancestries. Although assays capable of differentiating Oceanian ancestry at a global scale have become available, this study describes markers compiled specifically for differentiation of Oceanian populations. A sensitive multiplex assay, termed Pacifiplex, was developed and optimized in a small-scale test applicable to forensic analyses. The Pacifiplex assay comprises 29 ancestry-informative marker SNPs (AIM-SNPs) selected to complement the 34-plex test, that in a combined set distinguish Africans, Europeans, East Asians and Oceanians. Nine Pacific region study populations were genotyped with both SNP assays, then compared to four reference population groups from the HGDP-CEPH human diversity panel. STRUCTURE analyses estimated population cluster membership proportions that aligned with the patterns of variation suggested for each study population’s currently inferred demographic histories. Aboriginal Taiwanese and Philippine samples indicated high East Asian ancestry components, Papua New Guinean and Aboriginal Australians samples were predominantly Oceanian, while other populations displayed cluster patterns explained by the distribution of divergence amongst Melanesians, Polynesians and Micronesians. Genotype data from Pacifiplex and 34-plex tests is particularly well suited to analysis of Australian Aboriginal populations and when combined with Y and mitochondrial DNA variation will provide a powerful set of markers for ancestry inference applied to modern Australian demographic profiles. On a broader geographic scale, Pacifiplex adds highly informative data for inferring the ancestry of individuals from Oceanian populations. The sensitivity of Pacifiplex enabled successful genotyping of population samples from 50-year-old serum samples obtained from several Oceanian regions that would otherwise be unlikely to produce useful population data. This indicates tests primarily developed for forensic ancestry analysis also provide an important contribution to studies of populations where useful samples are in limited supply.  相似文献   
9.
Theoretical models have been used to argue that seasonal mean monsoons will shift abruptly and discontinuously from wet to dry stable states as their radiative forcings pass a critical threshold, sometimes referred to as a “tipping point.” Further support for a strongly nonlinear response of monsoons to radiative forcings is found in the seasonal onset of the South Asian summer monsoon, which is abrupt compared with the annual cycle of insolation. Here it is shown that the seasonal mean strength of monsoons instead exhibits a nearly linear dependence on a wide range of radiative forcings. First, a previous theory that predicted a discontinuous, threshold response is shown to omit a dominant stabilizing term in the equations of motion; a corrected theory predicts a continuous and nearly linear response of seasonal mean monsoon strength to forcings. A comprehensive global climate model is then used to show that the seasonal mean South Asian monsoon exhibits a near-linear dependence on a wide range of isolated greenhouse gas, aerosol, and surface albedo forcings. This model reproduces the observed abrupt seasonal onset of the South Asian monsoon but produces a near-linear response of the mean monsoon by changing the duration of the summer circulation and the latitude of that circulation’s ascent branch. Thus, neither a physically correct theoretical model nor a comprehensive climate model support the idea that seasonal mean monsoons will undergo abrupt, nonlinear shifts in response to changes in greenhouse gas concentrations, aerosol emissions, or land surface albedo.Monsoons deliver water to billions of people, so catastrophe would likely result if a gradual and small change in a forcing produced a comparatively abrupt and large change in monsoon strength. Previous studies (1, 2) used theoretical models to argue that monsoons will undergo exactly this sort of abrupt transition if anthropogenic or natural forcings exceed a critical threshold, which they referred to as a “tipping point” (3). Changes in land use or atmospheric aerosols sufficient to increase local top-of-atmosphere albedo to 0.5 have been predicted to cause a shift in the Indian summer monsoon from its current wet state to a dry state (1). The idea that anthropogenic climate forcings might produce an abrupt shutdown of some monsoons has become prominent (3, 4), even though some argue that this is unlikely to occur in the next century (5).Paleoclimate records contain abundant evidence for abrupt changes in various measures of monsoon strength (6, 7). However, such records typically measure variations at a particular location and so may not distinguish between a nonlinear response of the entire monsoon and a more gradual, linear shift of a spatial pattern with sharp horizontal gradients. It is also unclear whether mechanisms that govern monsoon changes on orbital to geological time scales are relevant for the response to anthropogenic forcings. However, even if proxy records of past monsoons are ambiguous, the modern seasonal cycle contains evidence for the abrupt response of monsoons to a radiative forcing: South Asian summer monsoon onset occurs more rapidly than can be explained by a linear response to the annual cycle of insolation (8, 9). Although the cause of this nonlinear seasonal evolution is the subject of active research (10, 11), it seems plausible that the same mechanism might produce an abrupt response of the seasonal mean monsoon to an imposed seasonal mean forcing.These results motivate our examination of how monsoon strength scales with a range of forcings. In particular, we use a simple energetic theory and an ensemble of global climate model (GCM) integrations to determine whether the summer mean strength of tropical monsoons will change discontinuously in response to a large range of radiative forcings.  相似文献   
10.
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