Engineered mosquitoes to fight mosquito borne diseases: not a merely technical issue

Malaria, dengue and other mosquito-borne diseases pose dramatic problems of public health, particularly in tropical and sub-tropical countries. Historically, vector control has been one of the most successfully strategies to eradicate some mosquito-borne diseases, as witnessed by malaria eradication in Mediterranean regions such as Italy and Greece. Vector control through insecticides has been used worldwide; unfortunately, it is losing effectiveness due to spread of resistances. Control of mosquito-borne diseases through field-releases of genetically engineered mosquitoes is an innovative and now feasible approach. Genetically modified mosquitoes have already been released into the wild in some regions, and protocols for this release are on hand in others. Local authorities are vigilant that transgenic insects in the field are safe for human and animal populations, and the public engagement in every control program is assuming a central role

Microbial symbiosis in mosquito vectors

n/

Ned-19 inhibition of parasite growth and multiplication suggests a role for NAADP mediated signalling in the asexual development of plasmodium falciparum

BACKGROUND: Although malaria is a preventable and curable human disease, millions of people risk to be infected by the Plasmodium parasites and to develop this illness. Therefore, there is an urgent need to identify new anti-malarial drugs. Ca2+ signalling regulates different processes in the life cycle of Plasmodium falciparum, representing a suitable target for the development of new drugs. RESULTS: This study investigated for the first time the effect of a highly specific inhibitor of nicotinic acid adenine dinucleotide phosphate (NAADP)-induced Ca2+ release (Ned-19) on P. falciparum, revealing the inhibitory effect of this compound on the blood stage development of this parasite. Ned-19 inhibits both the transition of the parasite from the early to the late trophozoite stage and the ability of the late trophozoite to develop to the multinucleated schizont stage. In addition, Ned-19 affects spontaneous intracellular Ca2+ oscillations in ring and trophozoite stage parasites, suggesting that the observed inhibitory effects may be associated to regulation of intracellular Ca2+ levels. CONCLUSIONS: This study highlights the inhibitory effect of Ned-19 on progression of the asexual life cycle of P. falciparum. The observation that Ned-19 inhibits spontaneous Ca2+ oscillations suggests a potential role of NAADP in regulating Ca2+ signalling of P. falciparum

Microbial symbionts : a resource for the management of insect-related problems

Microorganisms establish with their animal hosts close interactions. They are involved in many aspects of the host life, physiology and evolution, including nutrition, reproduction, immune homeostasis, defence and speciation. Thus, the manipulation and the exploitation the microbiota could result in important practical applications for the development of strategies for the management of insect-related problems. This approach, defined as Microbial Resource Management (MRM), has been applied successfully in various environments and ecosystems, as wastewater treatments, prebiotics in humans, anaerobic digestion and so on. MRM foresees the proper management of the microbial resource present in a given ecosystem in order to solve practical problems through the use of microorganisms. In this review we present an interesting field for application for MRM concept, i.e. the microbial communities associated with arthropods and nematodes. Several examples related to this field of applications are presented. Insect microbiota can be manipulated: (i) to control insect pests for agriculture; (ii) to control pathogens transmitted by insects to humans, animals and plants; (iii) to protect beneficial insects from diseases and stresses. Besides, we prospect further studies aimed to verify, improve and apply MRM by using the insectsymbiont ecosystem as a model

Mosquito/microbiota interactions: from complex relationships to biotechnological perspectives.

To date around 3500 different species of mosquito have been described, several tens of which are vectors of pathogens of remarkable interest in public health. Mosquitoes are present all around the world showing a great ability to adapt to very different types of habitats where they play relevant ecological roles. It is very likely that components of the mosquito microbiota have given the mosquito a great capacity to adapt to different environments. Current advances in understanding the mosquito-microbiota relationships may have a great impact in a better understanding of some traits of mosquito biology and in the development of innovative mosquito-borne disease-control strategies aimed to reduce mosquito vectorial capacity and/or inhibiting pathogen transmission

Horizontal transmission of the symbiotic bacterium Asaia sp. in the leafhopper Scaphoideus titanus Ball (Hemiptera: Cicadellidae)

<p>Abstract</p> <p>Background</p> <p>Bacteria of the genus <it>Asaia</it> have been recently recognized as secondary symbionts of different sugar-feeding insects, including the leafhopper <it>Scaphoideus titanus</it>, vector of Flavescence dorée phytoplasmas. <it>Asaia</it> has been shown to be localized in <it>S. titanus</it> gut, salivary glands and gonoducts and to be maternally transmitted to the progeny by an egg smearing mechanism. It is currently not known whether <it>Asaia</it> in <it>S. titanus</it> is transmitted by additional routes. We performed a study to evaluate if <it>Asaia</it> infection is capable of horizontal transmission <it>via</it> co-feeding and venereal routes.</p> <p>Results</p> <p>A Gfp-tagged strain of <it>Asaia</it> was provided to <it>S. titanus</it> individuals to trace the transmission pathways of the symbiotic bacterium. Co-feeding trials showed a regular transfer of bacterial cells from donors to recipients, with a peak of frequency after 72 hours of exposure, and with concentrations of the administrated strain growing over time. Venereal transmission experiments were first carried out using infected males paired with uninfected females. In this case, female individuals acquired Gfp-labelled <it>Asaia</it>, with highest infection rates 72-96 hours after mating and with increasing abundance of the tagged symbiont over time. When crosses between infected females and uninfected males were conducted, the occurrence of “female to male” transmission was observed, even though the transfer occurred unevenly.</p> <p>Conclusions</p> <p>The data presented demonstrate that the acetic acid bacterial symbiont <it>Asaia</it> is horizontally transmitted among <it>S</it>. <it>titanus</it> individuals both by co-feeding and venereal transmission, providing one of the few direct demonstrations of such a symbiotic transfer in Hemiptera. This study contributes to the understanding of the bacterial ecology in the insect host, and indicates that <it>Asaia</it> evolved multiple pathways for the colonization of <it>S</it>. <it>titanus</it> body.</p

Molecular Diagnosis of Malaria Infection: A Survey in a Hospital in Central Italy

Malaria is a dramatic disease caused by the protozoan parasites Plasmodium. The diagnosis is mainly based on microscopy and rapid diagnostic tests (RDT). Molecular approaches based on PCR techniques may be an alternative tool particularly favourable in regions with declining prevalence. This work aimed to assess pros and cons of molecular diagnosis of malaria in a district of Central Italy were several tens of imported malaria cases are diagnosed every year. Thirty-three blood samples were analysed by microscopy, RDT and molecular techniques to monitor the relative efficiency in malaria diagnosis. Molecular analysis and microscopy diagnosed 32 out of 33 samples as positive for malaria, while RDT only 29. More differences concerned the diagnosis of mixed infections. Our findings remark the importance of the molecular approach in supporting and improving malaria diagnosis. In the cases here presented, the molecular analysis was particularly useful to unveil parasites presence in infections not detectable by blood smear analysis and to additionally solve real and/or presumed mixed infections

Intra-instar larval cannibalism in Anopheles gambiae (s.s.) and Anopheles stephensi (Diptera: Culicidae)

BACKGROUND: Cannibalism has been observed in a wide range of animal taxa and its importance in persistence and stability of populations has been documented. In anopheline malaria vectors the inter-instar cannibalism between fourth- and first-instar larvae (L4-L1) has been shown in several species, while intra-instar cannibalism remains poorly investigated. In this study we tested the occurrence of intra-instar cannibalism within larvae of second-, third- and fourth-instar (L2, L3 and L4) of Anopheles gambiae (s.s.) and An. stephensi. Experiments were set up under laboratory conditions and the effects of larval density, duration of the contact period among larvae and the presence of an older larva (i.e. a potential cannibal of bigger size) on cannibalism rate were analysed. Cannibalism was assessed by computing the number of missing larvae after 24 and 48 h from the beginning of the experiments and further documented by records with a GoPro videocamera. RESULTS: Intra-instar cannibalism was observed in all larval instars of both species with higher frequency in An. gambiae (s.s.) than in An. stephensi. In both species the total number of cannibalistic events increased from 0-24 to 0-48 h. The density affected the cannibalism rate, but its effect was related to the larval instar and to the presence of older larvae. Interestingly, the lower cannibalism rate between L4 larvae was observed at the highest density and the cannibalism rate between L3 larvae decreased when one L4 was added. CONCLUSIONS: The present study provides experimental evidence of intra-instar cannibalism in the malaria vectors An. gambiae (s.s.) and An. stephensi and highlights the possible occurrence of complex interactions between all larval instars potentially present in the breeding sites. We hypothesize that the high density and the presence of a potential cannibal of bigger size could affect the readiness to attack conspecifics, resulting into low risk larval behavior and lower cannibalism rate. The understanding of cannibalistic behavior and the factors affecting it is of utmost importance for malaria vectors, as nutrition during larval development can strongly affect the fitness of adult female mosquitoes and ultimately their vector ability

De novo genome assembly of the invasive mosquito species Aedes japonicus and Aedes koreicus

Background: Recently, two invasive Aedes mosquito species, Ae. japonicus and Ae. koreicus, are circulating in several European countries posing potential health risks to humans and animals. Vector control is the main option to prevent mosquito-borne diseases, and an accurate genome sequence of these mosquitoes is essential to better understand their biology and to develop efective control strategies. Methods A de novo genome assembly of Ae. japonicus (Ajap1) and Ae. koreicus (Akor1) has been produced based on a hybrid approach that combines Oxford Nanopore long-read and Illumina short-read data. Their quality was ascertained using various metrics. Masking of repetitive elements, gene prediction and functional annotation was performed. Results Sequence analysis revealed a very high presence of repetitive DNA and, among others, thermal adaptation genes and insecticide-resistance genes. Through the RNA-seq analysis of larvae and adults of Ae. koreicus and Ae. japonicus exposed to diferent temperatures, we also identifed genes showing a diferential temperature-dependent activation. Conclusions The assembly of Akor1 and Ajap1 genomes constitutes the frst updated collective knowledge of the genomes of both mosquito species, providing the possibility of understanding key mechanisms of their biol ogy such as the ability to adapt to harsh climates and to develop insecticide-resistance mechanisms