Translational repression of messenger RNAs (mRNAs) plays an important role in sexual differentiation and gametogenesis in multicellular eukaryotes. Translational repression and mRNA turnover were ...shown to influence stage-specific gene expression in the protozoan PLASMODIUM: The DDX6-class RNA helicase, DOZI (development of zygote inhibited), is found in a complex with mRNA species in cytoplasmic bodies of female, blood-stage gametocytes. These translationally repressed complexes are normally stored for translation after fertilization. Genetic disruption of pbdozi inhibits the formation of the ribonucleoprotein complexes, and instead, at least 370 transcripts are diverted to a degradation pathway.
On 6 December 2013, two laboratory-confirmed cases of chikungunya without a travel history were reported on the French part of the Caribbean island of Saint Martin, indicating the start of the first ...documented outbreak of chikungunya in the Americas. Since this report, the virus spread to several Caribbean islands and French Guiana, and between 6 December 2013 and 27 March 2014 more than 17,000 suspected and confirmed cases have been reported. Further spread and establishment of the disease in the Americas is likely, given the high number of people travelling between the affected and non-affected areas and the widespread occurrence of efficient vectors. Also, the likelihood of the introduction of the virus into Europe from the Americas and subsequent transmission should be considered especially in the context of the next mosquito season in Europe. Clinicians should be aware that, besides dengue, chikungunya should be carefully considered among travellers currently returning from the Caribbean region.
UIS4 is a key protein component of the host-parasite interface in the liver stage of the rodent malaria parasite Plasmodium berghei and required for parasite survival after invasion. In the ...infectious sporozoite, UIS4 protein has variably been shown to be translated but also been reported to be translationally repressed. Here we show that uis4 mRNA translation is regulated by the P. berghei RNA binding protein Pumilio-2 (PbPuf2 or Puf2 from here on forward) in infectious salivary gland sporozoites in the mosquito vector. Using RNA immunoprecipitation we show that uis4 mRNA is bound by Puf2 in salivary gland sporozoites. In the absence of Puf2, uis4 mRNA translation is de-regulated and UIS4 protein expression upregulated in salivary gland sporozoites. Here, using RNA immunoprecipitation, we reveal the first Puf2-regulated mRNA in this parasite.
Many variant proteins encoded by Plasmodium-specific multigene families are exported into red blood cells (RBC). P. falciparum-specific variant proteins encoded by the var, stevor and rifin multigene ...families are exported onto the surface of infected red blood cells (iRBC) and mediate interactions between iRBC and host cells resulting in tissue sequestration and rosetting. However, the precise function of most other Plasmodium multigene families encoding exported proteins is unknown. To understand the role of RBC-exported proteins of rodent malaria parasites (RMP) we analysed the expression and cellular location by fluorescent-tagging of members of the pir, fam-a and fam-b multigene families. Furthermore, we performed phylogenetic analyses of the fam-a and fam-b multigene families, which indicate that both families have a history of functional differentiation unique to RMP. We demonstrate for all three families that expression of family members in iRBC is not mutually exclusive. Most tagged proteins were transported into the iRBC cytoplasm but not onto the iRBC plasma membrane, indicating that they are unlikely to play a direct role in iRBC-host cell interactions. Unexpectedly, most family members are also expressed during the liver stage, where they are transported into the parasitophorous vacuole. This suggests that these protein families promote parasite development in both the liver and blood, either by supporting parasite development within hepatocytes and erythrocytes and/or by manipulating the host immune response. Indeed, in the case of Fam-A, which have a steroidogenic acute regulatory-related lipid transfer (START) domain, we found that several family members can transfer phosphatidylcholine in vitro. These observations indicate that these proteins may transport (host) phosphatidylcholine for membrane synthesis. This is the first demonstration of a biological function of any exported variant protein family of rodent malaria parasites.
Abstract Objectives In the context of public health, risk governance (or risk analysis) is a framework for the assessment and subsequent management and/or control of the danger posed by an identified ...disease threat. Generic frameworks in which to carry out risk assessment have been developed by various agencies. These include monitoring, data collection, statistical analysis and dissemination. Due to the inherent complexity of disease systems, however, the generic approach must be modified for individual, disease-specific risk assessment frameworks. Study design The analysis was based on the review of the current risk assessments of vector-borne diseases adopted by the main Public Health organisations (OIE, WHO, ECDC, FAO, CDC etc…). Methods Literature, legislation and statistical assessment of the risk analysis frameworks. Results This review outlines the need for the development of a general public health risk assessment method for vector-borne diseases, in order to guarantee that sufficient information is gathered to apply robust models of risk assessment. Stochastic (especially spatial) methods, often in Bayesian frameworks are now gaining prominence in standard risk assessment procedures because of their ability to assess accurately model uncertainties. Conclusions Risk assessment needs to be addressed quantitatively wherever possible, and submitted with its quality assessment in order to enable successful public health measures to be adopted. In terms of current practice, often a series of different models and analyses are applied to the same problem, with results and outcomes that are difficult to compare because of the unknown model and data uncertainties. Therefore, the risk assessment areas in need of further research are identified in this article.
As a result of numerous successful invasions by both Aedes albopictus (Skuse) and Ades aegypti (L.), the current worldwide distributions of these mosquito species overlap. Shared larval habitats and ...shifts in the distribution and abundance of resident A. albopictus or A. aegypti after the establishment of the other species suggest that competitive displacement occurs. Experiments on larval competition between North American populations of the two species showed that A. albopictus has the competitive advantage under local field conditions, which apparently accounts for displacement of A. aegypti from much of the United States after the invasion of A. albopictus. The role of competition, and potential shifts of competitive advantage in different parts of their worldwide ranges are unknown, but variation due to intraspecific or environmental differences is possible. In the current study, we measured the performance of larvae of Brazilian populations of A. albopictus and A. aegypti competing under field conditions in Rio de Janeiro, Brazil. Finite rates of increase for each species were estimated and the effects of species composition, larval density, and leaf litter resource levels were determined. A. albopictus maintained positive population growth at higher combined densities and lower per capita resource availability than did A. aegypti. A. albopictus showed higher survivorship than A. aegypti under all treatments and leaf litter resource levels. These results indicate that in Brazil, just as in North America, A. albopictus is a superior larval competitor to A. aegypti when exploiting leaf litter resources. Our results further suggest that this competitive advantage for A. albopictus is likely to be independent of mosquito population origin, local environmental conditions, and local differences in the types of leaves that form the resource base of the aquatic habitats of larvae.
Two patients from Eritrea, recently arrived in the Netherlands, presented with fever and were investigated for malaria. Bloodfilms showed spirochetes but no blood parasites. Louse-borne relapsing ...fever caused by Borrelia recurrentis was diagnosed. Treatment was complicated by severe Jarisch-Herxheimer reactions in both patients. Physicians should be aware of the possibility of B. recurrentis infection in migrant populations who travel under crowded conditions, especially after passing through endemic areas such as Ethiopia and neighbouring countries.
Translational repression (TR) plays an important role in post-transcriptional regulation of gene expression and embryonic development in metazoans. TR also regulates the expression of a subset of the ...cytoplasmic mRNA population during development of fertilized female gametes of the unicellular malaria parasite, Plasmodium spp. which results in the formation of a polar and motile form, the ookinete. We report the conserved and sex-specific regulatory role of either the 3′- or 5′-UTR of a subset of translationally repressed mRNA species as shown by almost complete inhibition of expression of a GFP reporter protein in the female gametocyte. A U-rich, TR-associated element, identified previously in the 3′-UTR of TR-associated transcripts, played an essential role in mediating TR and a similar region could be found in the 5′-UTR shown in this study to be active in TR. The silencing effect of this 5′-UTR was shown to be independent of its position relative to its ORF, as transposition to a location 3′ of the ORF did not affect TR. These results demonstrate for the first time in a unicellular organism that the 5′ or the 3′-UTR of TR-associated transcripts play an important and conserved role in mediating TR in female gametocytes.
Various arthropod vectors are responsible for the transmission of pathogens that cause serious diseases in humans. Some important pathogens are transmitted by mosquitoes during blood-feeding, for ...example the well-known parasite causing malaria, and viruses-causing diseases such as dengue, chikungunya, and Zika virus fever. In contrast, very little is known about the potential of mosquitoes to transmit pathogenic bacteria. Hitherto, only a few bacteria have occasionally been suggested to be spread by mosquitoes, but this is not widely known nor accepted, and literature on this topic is limited. The aim of this study was to review the literature about the possible role of mosquitoes in the transmission of the bacterium
F. tularensis
, the causal agent of tularaemia, which has been proposed by several experts. Available primary articles investigating this possible vector role of mosquitoes were analysed and evaluated based on four vector incrimination criteria. This demonstrated that several studies had indeed found indications of a correlation between mosquito bites and tularaemia, and that the results of some other studies suggested that such a vector role for mosquitoes might exist. However, conclusive evidence of a causal relationship was not found, nor irrefutable proof that mosquitoes can actually transmit this bacterium during blood-feeding. This literature review has provided an overview of the current relevant literature, shows that future studies should focus on gaining more insight into other explanations for the correlation between mosquito bites and tularaemia, and that the certainty with which some authors write about the vector role of mosquitoes is not entirely justified.
Background & objectives: The first chikungunya (CHIK) epidemic in the Americas was reported in December 2013. Chikungunya virus (CHIKV) causes an acute febrile illness and is transmitted to humans by ...Aedes mosquitoes. Although earlier studies have described long-term clinical manifestations of CHIK patients infected with the East/Central/South African (ECSA) genotype, little is known about persistent manifestations in the Caribbean region, for which the Asian genotype is responsible. The objective of this study was to describe the presence of persisting clinical manifestations, specifically arthralgia, in CHIKV-infected patients on the Caribbean Island, Sint Maarten, 15 months after onset of the disease.
Methods: This retrospective cohort study included confirmed CHIK patients that were recorded by the participating general practitioners (GPs) during the chikungunya outbreak in 2014 in Sint Maarten. Between March and July 2015, 15 months after the onset of disease, patients were interviewed via telephone about the presence, duration and impact of clinical CHIKV manifestations.
Results: In total, 56 patients were interviewed (median age 47 yr), of which 30 (54%) were females. Out of the total interviewed patients, 52 (93%) reported arthralgia for the first three months after the disease onset, of which 23 (44%) patients reported to have persistent arthralgia, 15 months after the disease onset. Pain intensity of persistent arthralgia was perceived as mild in the majority of patients (n = 14; 60%), moderate in 7 (30%) patients and severe in 2 (9%) patients. During the acute phase of disease, most patients had to miss school or work (n = 39; 72%) due to clinical CHIKV manifestations and reported a negative impact on daily activities (n = 36; 57%).
Interpretation & conclusion: Results suggested that persisting arthralgia is a frequent complication in CHIK patients included in the study. Future research on strain-specific clinical long-term manifestations and on their impact on daily life of patients, in the form of a comparative study between patients and controls, is recommended.
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