Parasites & Vectors最新文献

Background: Acute undifferentiated febrile illness (AUFI) is a challenging clinical condition in tropical regions, caused by a broad range of pathogens. In Villeta municipality, Colombia, data on neglected bacterial causes remain scarce, highlighting the need to expand understanding of the local etiological spectrum. Thus, the aim of the present study was to explore the presence of the neglected pathogens, Bartonella, Borrelia, and Coxiella burnetii, as potential causes of AUFI in Villeta.

Methods: DNA was extracted from whole-blood samples from febrile patients. Quality and purity were assessed spectrophotometrically and by conventional polymerase chain reaction (PCR). Bartonella, Borrelia, and C. burnetii were detected using genus- and species-specific quantitative PCR (qPCR) assays. Bartonella-positive samples were further analyzed by multigene PCRs and sequencing for species identification. Anti-Bartonella and anti-C. burnetii immunoglobulin G (IgG) antibodies were evaluated by indirect immunofluorescence to assess recent or past exposure to these agents.

Results: A total of 41 febrile patients were evaluated. Bartonella DNA was detected in 9.8% (4/41) of samples. No Borrelia or C burnetii DNA was detected. Phylogenetic analysis revealed two distinct clades, although none could be assigned to species level. Serological analysis showed anti-Bartonella IgG antibodies in 29.3% (12/41) of cases, with 9.8% (4/41) exhibiting seroconversion. One patient presented both molecular and seroconversion evidence of recent Bartonella infection. None of the patients were seropositive for C. burnetii.

Conclusions: This study provides the first molecular and serological evidence of Bartonella circulation among febrile patients in Villeta, Colombia, revealing genetically distinct lineages and indicating both active and past infections, underscoring its potential role in AUFI.

Background: Mosquitoes are vectors of diseases globally, making development of models that better explain mosquito abundance imperative. Mosquito population dynamics are particularly sensitive to local weather conditions, and mosquito-borne disease outbreaks can be spatially concentrated. There is a need for improved modeling studies to address whether spatial variation in disease outbreaks is driven by spatial variation in weather conditions, especially in dry and hot environments. In the present study, we built a climate-driven model of mosquito population dynamics and compared whether predictions of mosquito abundance at the county scale were improved by accounting for subcounty weather variation.

Methods: Using a 5-year time series of weekly Culex quinquefasciatus abundance data collected for each zip code in Maricopa County, USA, we assessed how local variation in weather could explain and predict mosquito population dynamics. We built a mechanistic model of mosquito population dynamics influenced by daily maximum temperature and 30-day accumulated precipitation. We grouped zip codes on the basis of similar patterns of temperature and precipitation using functional clustering. We compared two approaches: one using county-level average weather and another using data from the identified weather clusters. We used Markov chain Monte Carlo simulations to fit the mechanistic model using averaged weather data in each cluster, then compared the model fit with observed data between the county-level model and the model on the basis of weather-based clusters.

Results: Simple, weather-forced modeling accurately estimated detailed Cx. quinquefasciatus abundance trajectories throughout the 5-year period. Modeling mosquito abundances in the subcounty spatial clusters demonstrated that the same effects of temperature and precipitation on population growth rates could explain small-scale changes in mosquito abundances. However, when we aggregated the subcounty model fits to the county-scale, the resulting fits were more precise but sometimes overly confident, leading to lower overall accuracy and predictive performance.

Conclusions: Our study demonstrated the importance of collecting fine-scale mosquito abundance data to improve our understanding and the predictability of mosquito population dynamics. The strong performance of both the cluster-based and county-level models illustrated the value of spatially sensitive modeling in this application. We anticipate that such modeling efforts will aid in using weather forecasts to predict increases in mosquito populations, thereby aiding in efforts to control the spread of infectious disease.

Background: Land-use change can influence parasite transmission by reshaping ecological interactions among parasites, vectors, and hosts. In particular, deforestation and agricultural expansion modify habitat structure and resource availability, potentially altering the prevalence and distribution of vector-borne diseases.

Methods: Fieldwork was conducted on São Tomé Island (Gulf of Guinea, Central Africa) across a land-use gradient from the core of an oil palm plantation to adjacent native forest. Culicoides biting midges and birds were sampled across four habitat types (village, oil palm plantation, at the border between the plantation and the forest, and forested areas) using Centers for Disease Control (CDC) traps and mist nets, respectively. DNA extracted from Culicoides and bird blood was used to screen for Plasmodium, Haemoproteus, and Leucocytozoon using nested polymerase chain reaction (PCR). Blood-fed Culicoides collected in the traps were analyzed by PCR to identify the host species. Linear models were used to assess differences in vector diversity, abundance, host-feeding preferences, and haemosporidian prevalence among habitats.

Results: Culicoides species richness did not differ significantly between habitats, but species abundances did vary. Overall abundance was lower in the oil palm plantation than in border and forest areas. Mammophilic Culicoides were more abundant in the village, whereas ornithophilic species were predominated in the forest. We screened 432 bird blood samples and 452 parous Culicoides for haemosporidian infections. Haemosporidian parasites were most frequently detected in Culicoides pools from the border area. Among birds, Plasmodium prevalence was significantly higher in the oil palm plantation than in border and forest habitats, while Leucocytozoon infections were completely absent in plantation birds.

Conclusions: Anthropogenic habitat disturbance modifies vector communities and host-parasite associations, influencing the transmission dynamics of Haemoproteus parasites. These findings highlight the ecological consequences of agricultural expansion and the importance of preserving natural habitats to mitigate disease emergence under land-use change scenarios.

Background: Both Simparica® and Simparica TRIO® chewable tablets are efficacious within 12 h against existing Ixodes scapularis infestations and within 24 h against re-infestations for 1 month. It is therefore expected that treatment with either product prevents Lyme infections due to their efficacy against I. scapularis ticks before the anticipated transmission of Borrelia burgdorferi by infected ticks.

Methods: In total, four laboratory studies were conducted in which dogs were randomly allocated to two treatment groups of 10 dogs each. On day 0, dogs were either administered a placebo treatment (Pet-Tabs® Palatable Vitamin-Mineral Supplement for Dogs), Simparica TRIO tablets at the minimum dose of 1.2 mg/kg sarolaner, 24 μg/kg moxidectin and 5 mg/kg pyrantel (study 1 and 2) or Simparica at the minimum dose of 2 mg/kg sarolaner (study 3 and 4). On post-treatment day 28, each dog was infested with approximately 50 unfed, wild-caught adult I. scapularis ticks with a high B. burgdorferi infection rate. Blood samples were collected from each prior dog to treatment and on post-treatment days 27, 49, 63, 77, 91 and 104, and qualitatively tested for B. burgdorferi antibodies using the SNAP® 4Dx Plus and Lyme Quant C6® antibody tests. Four skin biopsies from each dog were collected on day 104 from the most common areas of tick attachment and tested by PCR for the quantitative presence of B. burgdorferi.

Results: In all studies, at least nine out of 10 placebo-treated dogs were infected with B. burgdorferi before the end of the study. In study 1, one Simparica Trio-treated dog tested positive, whereas in the other studies none of the dogs treated with sarolaner tested positive at any time point during the study.

Conclusions: Both Simparica and Simparica Trio at the minimum label dose prevent the transmission of B. burgdorferi infections as a direct result of killing the I. scapularis vector ticks.

Mosquito-borne diseases cause millions of deaths every year, imposing a heavy burden on global public health systems and socioeconomic development. In China, mosquito-borne diseases exhibit a pattern of imported cases leading to localized transmission, and in recent years, periodic outbreaks of related diseases have continued to erupt, posing a serious threat to public health security. Additionally, due to global warming, the suitable living range for mosquitoes is continuously expanding, increasing the frequency of outbreaks and the affected areas. Although substantial global resources have been invested in prevention and control research, a definitive solution to completely eradicate mosquito-borne transmission has not yet been established. This review systematically summarizes the three principal mosquito control strategies-mechanical, biological, and chemical-with a particular emphasis on chemical repellents. It delineates the structure-activity relationships, efficacy profiles, mechanisms of action, and toxicological evaluation results of major synthetic repellents. It also elaborates on the active constituents and action mechanisms of plant-based natural repellents, exploring how emerging formulation technologies can enhance the stability and duration of repellents. Moreover, together with China's practical experience in mosquito-borne disease prevention and control, this review examines domestic research achievements and policy standards, ultimately constructing a theoretical framework to support the development of efficient, safe, and environmentally sustainable mosquito control solutions, thereby contributing to both national and global efforts in mosquito-borne disease prevention and control.

Background: Infections with Sarcocystis spp. in sheep (Ovis aries) are globally prevalent and pose significant health and economic concerns. Nine Sarcocystis taxa, comprising seven identified species and two unclassified entities, are known to form sarcocysts in sheep. Macroscopic sarcocysts with elongated villar protrusions are rare, having been reported only twice: as S. mihoensis in Japan and as an S. mihoensis -like organism in Spain. This study reports the first identification of this morphological type in China.

Methods: Muscle samples were collected from 83 domestic sheep in Kunming City, China, between March and September 2025. Sarcocysts were characterized morphologically using light microscopy (LM) and transmission electron microscopy (TEM). For molecular analysis, genomic DNA was extracted from individual sarcocysts isolated from different sheep. Five genetic markers-the nuclear 18S rDNA, 28S rDNA, and ITS-1 regions, the mitochondrial cox1 gene, and the apicoplast rpoB gene-were amplified, sequenced, and analyzed.

Results: A novel sarcocyst type was detected via LM in 6 out of 83 (7.2%) domestic sheep. These macroscopic sarcocysts measured up to 6230 μm in length and 341 μm in width, and possessed a thick cyst wall with numerous sloping villar protrusions (VPs) measuring 6.9-11.9 μm in length. Ultrastructurally, the VPs were 5.8-9.3 μm long and 0.8-1.1 μm wide, lined by an electron-dense layer, and contained scattered microtubules that extended from the apex to the base. Sequence comparisons with GenBank entries revealed the highest sequence similarities with S. buffalonis for 18S rDNA (97.6-98.0%), S. miescheriana for 28S rDNA (92.1-92.3%), S. japonica for cox1 (81.2-81.8% identity), and S. arctica for rpoB (88.5-88.8% identity). No significant matches were found for the ITS-1 region. Genetic divergence analysis against other sheep-infecting species indicated the smallest distances with S. medusiformis at 18S rDNA (0.0582), S. gigantea at 28S rDNA (0.0556), and S. gigantea at cox1 (0.2922). Given the distinct morphological features and the unique molecular characteristics, this organism is proposed as a new species, Sarcocystis chenggongensis n. sp.

Conclusions: The discovery of this new species marks the third global report of macroscopic sarcocysts with elongated villar protrusions, confirming a broad geographical distribution for this rare morphotype. Persistent taxonomic uncertainties, due to inconsistent data, require future research to resolve the group's evolution and life cycles.

Background: Documented changes in spatial and seasonal tick distribution highlight the importance of continuous surveillance. This paper documents results of a year-round sampling campaign in France, including identification of ticks and associated pathogens recovered from dogs and cats, as part of the European project "Protect Our Future Too."

Methods: Ticks were collected from dogs and cats presented to 35 veterinary practices from 27 administrative French departments between April 2021 and July 2022. DNA extracted from each tick sample was amplified by polymerase chain reaction (PCR) for simultaneous detection of 18 types of protozoan or bacterial microorganisms.

Results: Among 777 collected ticks, 6 species were morphologically identified in descending prevalence order as: Ixodes ricinus (58.3%), Dermacentor reticulatus (24.2%, mainly on dogs), I. hexagonus (7.2%, mainly on cats), Rhipicephalus sanguineus sensu lato (3.6%, mainly on dogs), I. canisuga (one tick collected from a cat), and Haemaphysalis punctata (one tick from a dog). Geographical distribution varied by tick species: I. ricinus and D. reticulatus were more frequent in northeast France, whereas R. sanguineus (s.l.) was predominant in southeast France. Ticks were collected throughout the study period but peaked in spring and early summer for I. ricinus and late winter and spring for D. reticulatus. The ticks R. sanguineus (s.l.) were collected only during summer. In total, 71.0% of the ticks were positive for DNA of at least one microorganism. Anaplasma bacteria were most frequent (up to 75.3% in I. ricinus) followed by Rickettsia (up to 49.5% in D. reticulatus). Piroplasm DNA (Babesia/Theileria/Cytauxzoon spp.) was found in 6.4% of I. ricinus, 5.3% of D. reticulatus, and 3.6% of both I. hexagonus and R. sanguineus (s.l). Borrelia burgdorferi sensu lato DNA was detected in 10.2% of I. ricinus. Mycoplasma haemominutum/haematoparvum DNA was detected in 21.8% of D. reticulatus, whereas M. turicensis DNA was detected in 14.3% of I. hexagonus.

Conclusions: Results of this study show that ticks are a year-round risk for dogs and cats in France, and tick-borne pathogens are present as mono- or coinfections at high frequencies. Tick control recommendations for veterinarians and dog and cat owners should incorporate these risks.

Background: The global burden of tick-borne viral diseases (TBVDs) has significantly increased in recent decades, emerging as a critical public health priority due to their diverse pathogenic profiles, severe disease outcomes, and therapeutic challenges. Within the expanding landscape of tick-borne pathogens, the Orthonairovirus genus has gained particular scientific attention for its members' zoonotic capacity and clinical virulence. Orthonairoviruses are arboviruses that infect humans and animals, posing a serious threat for the spread of zoonotic diseases. Huangpi tick virus 1 (HpTV-1), a member of the genus Orthonairovirus, has been detected in ticks.

Methods: Haemaphysalis longicornis collected in 2023 from Central China were pooled for RNA-seq and reverse transcription quantitative polymerase chain reaction (RT-qPCR) screening. Genomes were assembled and viruses isolated in suckling mice and Vero E6. Replication kinetics, mouse pathogenesis, and 223 livestock sera were assessed.

Results: In the present study, we isolated HpTV-1 from Haemaphysalis longicornis in Central China. Viral genome and phylogenetic analyses placed HpTV-1 in a distinct clade close to the Songling and Tamdy viruses within the Nairoviridae family. In vitro experiments demonstrated that HpTV-1 infects a wide range of animal and human cell lines. Importantly, all infected C57BL/6 mice survived without overt signs of severe disease while developing only minor pathological lesions in specific organs (liver, spleen, and lungs). Serological surveys revealed HpTV-1 antibodies, including neutralizing antibodies, in 16.1% of the goats, suggesting that HpTV-1 can infect livestock.

Conclusions: These findings suggest that HpTV-1 is an Orthonairovirus capable of infecting animals, highlighting its potential risk and the need for enhanced surveillance and research, particularly in Central China and other endemic regions.

Background: Canine leishmaniosis caused by Leishmania infantum remains a major zoonotic concern in the Mediterranean basin, where native breeds may have evolved adaptive immune mechanisms under long-term endemic exposure. The Fonni dog, indigenous to Sardinia, may represent a model of such adaptation. This study aimed to compare cytokine and growth factor profiles between Fonni dogs and German Shepherd dogs exposed to L. infantum and other vector-borne pathogens, to investigate potential breed-associated immune regulatory patterns.

Methods: Fifty-nine clinically healthy dogs (Fonni and German Shepherds) living in endemic areas were included. Serum samples were tested for antibodies against Anaplasma phagocytophilum, Ehrlichia canis, Leptospira spp., Leishmania infantum, and Rickettsia spp. Concentrations of eleven cytokines and growth factors were measured using a multiplex bead-based immunoassay. Statistical analyses evaluated differences between breeds, associations with serological status and age, as well as correlation matrices and principal component analysis to explore clustering patterns among immune mediators.

Results: Fonni dogs showed significantly higher serum concentrations of IL-10, NGF-β, IFN-γ, TNF-α, and VEGF-α compared with German Shepherds. Seropositive dogs for L. infantum and Rickettsia spp. exhibited increased levels of IL-10, NGF-β, and TNF-α. Age influenced cytokine expression, with young Fonni dogs displaying the highest IL-10 and NGF-β values, whereas TNF-α and MCP-1 concentrations increased with age. Correlation and principal component analyses revealed distinct breed-specific clustering, highlighting coordinated regulation of pro-inflammatory and angiogenic mediators, particularly IL-6, TNF-α, MCP-1, and VEGF-α.

Conclusions: The elevated levels of several cytokines and growth factors in Fonni dogs suggest a breed-associated immune phenotype characterized by a regulatory/pro-inflammatory balance consistent with a tolerance-like response under endemic exposure. These findings support the hypothesis that native breeds such as the Fonni dog may have developed adaptive immunological mechanisms that limit immunopathology while maintaining effective responses in areas endemic for canine vector-borne pathogens.