Parasites & Vectors最新文献

Background: Anopheles stephensi is a competent malaria vector mainly present in southern Asia and the Arabian Peninsula. Since 2012, it has invaded several countries of eastern Africa, creating an emerging risk of urban transmission. Urgent efforts are required to develop novel and more efficient strategies for targeted vector control. CRISPR/Cas9-based homing gene drives have been proposed as attractive alternative strategies. Gene drives have the potential to spread a desired trait through a population at higher rates than via normal Mendelian inheritance, even in the presence of a fitness cost. Several target genes have been suggested and tested in different mosquito vector species such as Anopheles gambiae and Aedes aegypti. Several promising suppression drives have been developed in An. gambiae that target the sex determination gene doublesex (dsx).

Methods: In this study, a geographically confineable gene drive system targeting dsx was developed (dsx^gRNA). Here, a transgenic line which expresses Cas9 under the control of the endogenous zpg promoter was generated. Separately a transgenic line which expresses a gRNA targeting the female specific exon of dsx was inserted into that same target site. The reproductive fitness of males and females heterozygous and homozygous for this element was determined. A series of experimental crosses was performed to combine the two elements and assess the homing rate of the dsx element in a split drive system.

Results: The drive was able to home in a super-Mendelian rate comparable to those obtained by an autonomous drive in this species. Although inheritance rates as high as 99.8% were observed, potentially providing very potent gene drive, dominant effects on male and female fertility were observed, which would be sufficient to hinder spread of such a drive. Molecular analysis indicated that the gRNA expressing insertion disrupted normal splicing of dsx.

Conclusions: These results should be considered when proposing the viability of dsx as a target gene for a population suppression gene drives in Anopheles stephensi. Although high homing rates were observed, the fitness defects found in both males and females carrying the transgene would likely prohibit this drive from functioning in the field.

White-tailed deer (Odocoileus virginianus) are a ubiquitous species in North America. Their high reproductive potential leads to rapid population growth, and they exhibit a wide range of biological adaptations that influence their interactions with vectors and pathogens. This review aims to characterize the intricate interplay between white-tailed deer and the transmission cycles of various tick- and mosquito-borne pathogens across their range in the eastern United States and southeastern Canada. The first part offers insights into the biological characteristics of white-tailed deer, their population dynamics, and the consequential impacts on both the environment and public health. This contextual backdrop sets the stage for the two subsequent sections, which delve into specific examples of pathogen transmission involving white-tailed deer categorized by tick and mosquito vectors into tick-borne and mosquito-borne diseases. This classification is essential, as ticks and mosquitoes serve as pivotal elements in the eco-epidemiology of vector-borne diseases, intricately linking hosts, the environment, and pathogens. Through elucidating these associations, this paper highlights the crucial role of white-tailed deer in the transmission dynamics of tick- and mosquito-borne diseases. Understanding the interactions between white-tailed deer, vectors, and pathogens is essential for effective disease management and public health interventions.

Background: The intestinal protozoa Entamoeba spp. can infect humans and various animals, including donkeys, causing diarrhea and malabsorption and presenting significant risks to animal husbandry and public health. Most Entamoeba species are not pathogenic except for Entamoeba histolytica. China has among the highest rates of donkey farming worldwide. Donkey (Equus asinus) farming is increasingly important in China because of their draft and medicinal value; however, epidemiological data on Entamoeba spp. in donkeys remains limited globally. This study aimed to investigate the prevalence of Entamoeba in donkeys in Shanxi Province, North China, and assess associated risk factors using a molecular approach.

Methods: Fecal samples of 815 donkeys from three representative geographical locations in Shanxi Province were collected to investigate the presence of Entamoeba spp. A portion of the small-subunit rRNA gene (SSU rRNA) was amplified and sequenced to determine the prevalence and species/genotypes of Entamoeba spp. Statistical analysis of possible risk factors was performed using Statistical Product and Service Solutions (SPSS) 26.0 software. The phylogenetic relationship of Entamoeba spp. was reconstructed using the neighbor-joining (NJ) method in Molecular Evolutionary Genetics Analysis (Mega) 7.0 software.

Results: The overall prevalence of Entamoeba spp. in donkeys in Shanxi Province was 7.12% (58/815). Two species (Entamoeba sp. RL9 and Entamoeba equi) were identified by sequence analysis; of these, Entamoeba sp. RL9 was the most prevalent species in donkeys in this study. Statistical analysis revealed that the donkeys' sex, region, age, and altitude are the risk factors associated with Entamoeba spp. prevalence (P < 0.05). Phylogenetic analysis indicated that the sequences of Entamoeba sp. RL9 and E. equi isolated from donkeys in this study were clustered with previously reported animal-derived Entamoeba sp. RL9 and E. equi sequences, respectively.

Conclusions: This study reports the occurrence and prevalence of Entamoeba spp. in donkeys worldwide for the first time to our knowledge. This not only expands the geographical distribution but also broadens the host range of Entamoeba spp., addressing the knowledge gap regarding the prevalence of Entamoeba spp. in donkeys, providing baseline data for carrying out prevention and control of Entamoeba spp. in donkeys in China.

Background: Jingmen tick virus (JMTV) is a novel tick-borne virus detected for the first time in Rhipicephalus (Boophilus) microplus in China. To date, there is no information regarding the circulation of JMTV in ticks collected from livestock in Cameroon. As part of the surveillance for arboviral circulation, this study aimed to assess the presence of JMTV in ticks collected from livestock (cattle and sheep) in an area of the Akonolinga health district, Center Region, Cameroon.

Methods: A cross sectional study was carried out during the dry season between 5 and 14 March 2024. Ticks were collected from cattle and sheep in six sampling sites in an area approximately 30 km long and 18 km wide along the Nyong River, in central Cameroon. Ticks were identified morphologically and molecularly. Total RNA/DNA was extracted from tick pools and screened for JMTV RNA using a segment 2 RT-qPCR system. Positive JMTV pools were sequenced for partial JMTV-Segment 1 and full genome analyses.

Results: A total of 622 ticks, organized into 251 pools were collected from 155 cattle and nine sheep. They consisted of five species covering three genera: R. (B.) microplus (472; 75.9%), Amblyomma variegatum (118; 19.0%), Hyalomma truncatum (13; 2.1%), Hyalomma rufipes (2; 0.3%), and other Rhipicephalus spp. (17; 2.7%). The quantitative reverse transcription polymerase chain reaction (qRT-PCR) screening of 251 tick pools yielded 61 JMTV-positive pools, of which 58 corresponded to R. (B.) microplus. Multiple sequence analysis revealed that JMTV from the Akonolinga area shared > 95% identity with strains from Guinea, and that these strains clustered phylogenetically together.

Conclusions: We provide molecular evidence of the presence of JMTV in R. (B.) microplus and A. variegatum collected from cattle and sheep from an area not yet recognized as endemic for this virus, confirming its wide geographical distribution.

Background: Sugar feeding is an essential aspect of mosquito biology that may be exploited for mosquito control by adding insecticides to sugar attractants, so-called 'attractive targeted sugar baits' (ATSBs). To optimize their effectiveness, ATSB products need to be maximally attractive at both short and long range and induce high levels of feeding. This study aimed to assess the attractiveness and feeding success of Anopheles mosquitoes exposed to attractive sugar baits (ASBs).

Method: Experiments were conducted in 2 × 5 × 2-m cages constructed within the semi-field systems (SFS) at Ifakara Health Institute, Bagamoyo, Tanzania. Male and female Anopheles gambiae s.s. and An. funestus s.s. mosquitoes were exposed to either 20% sucrose or different ASB station prototypes produced by Westham Co. in either (1) no-choice experiments or (2) choice experiments. Mosquitoes were exposed overnight and assessed for intrinsic or relative olfactory attraction using fluorescent powder markers dusted over the ASB stations and 20% sucrose and for feeding using uranine incorporated within the bait station and food dye in 20% sucrose controls.

Results: Both male and female An. gambiae and An. funestus mosquitoes were attracted to the ASBs, with no significant difference between the sexes for each of the experiments conducted. Older mosquitoes (3-5 days) were more attracted to the ASBs (OR = 8.3, [95% CI 6.6-10.5] P < 0.001) than younger mosquitoes (0-1 day). Similarly, older mosquitoes responded more to 20% sucrose (OR = 4.6, [3.7-5.8], P < 0.001) than newly emerged Anopheles. Of the four prototypes tested, the latest iteration, ASB prototype v1.2.1, showed the highest intrinsic attraction of both Anopheles species, attracting 91.2% [95% CI 87.9-94.5%]. Relative to ATSB v1.1.1, the latest prototype, v.1.2.1, had higher attraction (OR = 1.19 [95% CI 1.07-1.33], P < 0.001) and higher feeding success (OR = 1.71 [95% CI 1.33-2.18], P < 0.001).

Conclusions: Data from these experiments support using ASBs v1.2.1, deployed in large-scale epidemiological trials, as it is the most attractive and shows the highest feeding success of the Westham prototypes tested. The findings indicate that future bioassays to evaluate ATSBs should use mosquitoes of both sexes, aged 3-5 days, include multiple species in the same cage or chamber, and utilize both non-choice and choice tests with a standard comparator.

Background: Aedes albopictus, the Asian tiger mosquito, which is listed among the world's 100 most dangerous invasive species, is the main vector of chikungunya, dengue and Zika viruses. This mosquito species has rapidly dispersed and invaded much of the globe assisted by its life history traits and high propagule pressure driven by human activities. Aedes albopictus is currently widespread across mainland Europe and the Mediterranean region, including the islands. Cyprus remained free of Ae. albopictus until October 2022, when specimens were recorded for the first time in Limassol district, including the port area. Understanding the processes associated with the introduction, expansion and establishment of this vector in Cyprus is of primary importance to mitigate its dispersal on the island, and to implement control methods to prevent disease outbreaks. A genetic analysis of these invasive specimens collected in Limassol district and in areas from the Central Mediterranean was performed to obtain a genetic portrait of the demographic history of the invasive mosquitoes on Cyprus.

Methods: We applied highly polymorphic simple sequence repeat (SSR) markers to the Ae. albopictus mosquitoes collected in Cyprus and to specimens from Italy, France, Switzerland, the Balkans, Greece and Turkey to construct an SSR individual genotype dataset that would enable the invasion pattern of Ae. albopictus in Cyprus to be traced. Bayesian clustering analyses using STRUCTURE and BayesAss version 3 were employed to derive information on the degree of ancestry among Cypriot and Mediterranean mosquitoes and on recent mosquito movements both within Cyprus and between Cyprus and the Central Mediterranean areas.

Results: The Cypriot mosquitoes appear to be highly polymorphic with no signs of genetic drift due to recent founder effects. An ongoing mosquito dispersal within the Limassol district was detected, suggesting the presence of established, hidden adventive populations. These mosquitoes share a high degree of ancestry with those in the Balkans and parts of northern Italy that border the Adriatic Sea.

Conclusions: Considering the trade connections of Limassol port, Cyprus with the Balkans and the Adriatic Italian region, we hypothesise that these areas may be involved in the incursion of Ae. albopictus into Cyprus. As the Balkan and Italian mosquitoes display high competence for CHIKV, questions arise about possible arbovirus outbreaks in Cyprus and highlight the need to implement surveillance and control measures.

Background: Schistosomiasis, which is caused by the parasite Schistosoma mansoni as well as other species of the trematode genus Schistosoma, leads to chronic inflammation and finally to liver fibrosis. If untreated, the disease can cause life-threatening complications. The current treatment of schistosomiasis relies on a single drug, praziquantel (PZQ). However, there is increasing concern about emerging resistance to PZQ due to its frequent use.

Methods: To identify potential alternative drugs for repurposing, the Open Global Health Library (OGHL) was screened in vitro, using two different screening workflows at two institutions, against adult S. mansoni couples and newly transformed schistosomula. This was followed by confirmation of the effects of the lead structures against adult worms.

Results: In vitro screening at one of the institutions identified two fast-acting substances affecting worm physiology (OGHL00022, OGHL00121). The effects of the two lead structures were investigated in more detail by confocal laser scanning microscopy and 5-ethynyl 2´-deoxyuridine (EdU) assays to assess morphological effects and stem cell effects. Both substances showed negative effects on stem cell proliferation in S. mansoni but no further morphological changes. The EC₅₀values of both compounds were determined, with values for compound OGHL00022 of 5.955 µM for pairing stability, 10.88 µM for attachment, and 18.77 µM for motility, while the values for compound OGHL00121 were 7.088 µM for pairing stability, 8.065 µM for attachment, and 6.297 µM for motility 24 h after treatment. Furthermore, S. mansoni couples were treated in vitro with these two lead structures simultaneously to check for additive effects, which were found with respect to reduced motility. The second in vitro screening, primarily against newly transformed schistosomula and secondarily against adult worms, identified four lead structures in total (OGHL00006, OGHL00022, OGHL00169, OGHL00217). In addition, one of the tested analogues of the hits OGHL00006, OGHL00169, and OGHL00217 showed effects on both stages.

Conclusions: In two independent in vitro screening approaches against two stages of S. mansoni one common interesting structure with rapid effects was identified, OGHL00022, which provides opportunities for further development.

Background: Tick hemolymph is a sterile fluid that carries nutrients to maintain tick health. The hemolymph creates a hostile environment for invaders including the destruction of microorganisms by its circulating hemocytes. However, Babesia parasites escape and disseminate to other organs through the hemolymph to continue their transmission life cycle. Still, it is unknown how tick hemocytes respond to B. bovis or B. bigemina infection. In this study, we conducted a transcriptomic analysis of hemocytes from female Rhipicephalus microplus ticks infected with Babesia parasites to understand how gene expression changes during parasite infection.

Methods: During Babesia acute infection, female R. microplus ticks were fed on bovines to acquire parasites. Engorged females were collected and incubated to develop Babesia kinetes in tick hemolymph. The hemolymph was examined to identify ticks that were highly infected with Babesia kinetes. Hemocyte cells were collected from replete female ticks infected with Babesia bovis or Babesia bigemina to perform high-throughput RNA-sequencing (RNA-Seq) analysis.

Results: This study identified major changes in the gene profile of tick hemocytes during Babesia infection. The main groups of hemocyte genes that were altered during Babesia infection were associated with metabolism, immunity, and cytoskeletal rearrangement. Upregulated genes were mainly involved in defense mechanisms, while downregulated genes were related to cell proliferation and apoptosis. However, the expression of hemocyte genes varied among Babesia species' infections, and it reflected the changes that occurred in the tick's physiology, including growth, reproduction, and skeletal muscle development.

Conclusions: The differential gene expression of R. microplus hemocytes revealed that genes highly regulated upon Babesia infection were related to metabolism, tick immunity, cell growth, apoptosis, development, metabolism, and reproduction. Additional research is necessary to further define the genes that exhibited varying expression levels in hemocytes during the infection. The findings of this study will enhance our understanding on how Babesia parasites survive in the hostile environment of ticks and perpetuate their transmission cycle, ultimately contributing to the spread of bovine babesiosis.

Background-objective: Trichinella spiralis drug development and control need an objective high throughput system to assess first stage larvae (L1) viability. YOLOv5 is an image recognition tool easily trained to count muscular first stage larvae (L1) and recognize morphological differences. Here we developed a semi-automated system based on YOLOv5 to capture photographs of 96 well microplates and use them for L1 count and morphological damage evaluation after experimental drug treatments.

Material and methods: Morphological properties were used to distinguish L1 from debris after pepsin muscle digestion and distinguish healthy (serpentine) or damaged (coiled) L1s after 72 h untreated or treated with albendazole or mebendazole cultures. An AxiDraw robotic arm with a smartphone was used to scan 96 well microplates and store photographs. Images of L1 were manually annotated, and augmented based on exposure, bounding, blur, noise, and mosaicism.

Results: A total of 1309 photographs were obtained that after L1 labeling and data augmentation gave 27478 images. The final dataset of 12571 healthy and 14907 affected L1s was used for training, testing, and validating in a ratio of 70/20/10 respectively. A correlation of 92% was found in a blinded comparison with bare-eye assessment by experienced technicians.

Conclusion: YOLOv5 is capable of accurately counting and distinguishing between healthy and affected L1s, thus improving the performance of the assessment of meat inspection and potential new drugs.