Current research in parasitology & vector-borne diseases最新文献

A crucial factor to predict the persistence and spread of infections in natural systems is the capacity of reservoir hosts to maintain the infection and transmit it to others. This is known to greatly vary within and between species and through time, although the latter part of the variation is often less well understood in the wild. Borrelia garinii is one of the causal agents of Lyme disease in humans and is transmitted among avian hosts by the hard tick Ixodes ricinus. Great tits are known to be a reservoir in Europe for B. garinii. For tick-borne pathogens like B. garinii, infectiousness or host-to-vector transmission can be measured using xenodiagnosis where pathogen-free vectors are fed on a host, and the blood-fed vectors are subsequently tested for the pathogen. Here we describe and evaluate a methodology to quantify infectiousness for tick-borne pathogens in individual wild great tits (Parus major), involving captures and recaptures of targeted individuals. The methodology can potentially be applied to other species where recapturing is sufficiently guaranteed. We successfully recaptured most of the infested great tits two to three days after initial infestation (i.e. just before ticks have fully fed) with sufficient numbers of I. ricinus larval ticks, which were subsequently screened for B. garinii using a newly developed B. garinii-specific real-time PCR assay. Higher larval tick numbers were recovered from birds during the breeding seasons than during the winter months. Our novel B. garinii-qPCR performed well, and greatly reduced the amount of Sanger sequencing needed. Preliminary results suggest both seasonal and individual variation in infectiousness; heterogeneity that needs to be unravelled to further understand the contribution of resident birds to the epidemiology of B. garinii.

This study aimed to genotype isolates of Toxoplasma gondii obtained from samples of brain, diaphragm and heart of goats and sheep intended for human consumption in the State of Paraíba, Brazil. Tissue samples from 14 animals, goats (n = 5) and lambs (n = 9), were sourced from public slaughterhouses in seven cities and bio-assayed in mice. The brains of the mice were utilized for DNA extraction. Genotyping was carried out by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) using 10 markers (SAG1, SAG2, SAG3, BTUB, c22-8, PK1, GRA6, L358, c-29-2 and Apico). A total of 10 isolates were fully genotyped (i.e. at all loci), three from goats and seven from sheep, revealing five distinct genotypes: #13 (n = 4); #48 (n = 3); #57 (n = 1); #273 (n = 1); and one new genotype that had not been previously described. Genotype #13 is frequently found in the Northeast of Brazil and represents a clonal lineage circulating in this region and was the most prevalent genotype identified (n = 4). Moreover, in the present study genotypes #13, #48, #57, and #273 were documented for the first time in sheep from Brazil, and the novel genotype was isolated from a goat. Our findings align with previous studies on T. gondii from Brazil, where new genotypes are continuously being identified, highlighting a high level of genetic diversity of T. gondii isolates in the country.

Cryptosporidium parvum is a causative agent of cryptosporidiosis, an infectious gastroenteritis in neonatal ruminants, which can be fatal in severe cases. The aim of this study was to determine the prevalence of infections in dairy cattle/calves during the early stages of a calving season and the species/genotypes of the Cryptosporidium present. Faecal samples collected from pre- and post-partum dams (n = 224) as well as calves from age ∼1 day onwards (n = 312) were examined. Oocysts were concentrated, DNA extracted and tested by Cryptosporidium 18S rRNA gene PCR and sequencing, while genotypes of C. parvum were determined by gp60 and VNTR analysis. Results showed that 31.3% and 30.4% of pre- and post-partum dams tested positive for Cryptosporidium, respectively. In the adults, C. parvum (n = 52), C. bovis (n = 4) and C. andersoni (n = 19) were identified, while in the calves 248 out of 312 (79.5%) were PCR-positive for C. parvum. The proportion of positive calf samples was significantly higher (P < 0.0001) than the proportion of positive adult cattle during the first seven weeks of the calving season. In adult cattle, three distinct gp60 genotypes were identified, a predominant genotype IIaA15G2R1 (n = 36) and genotypes IIaA15R1 (n = 2) and IIaA14G2R1 (n = 1). In the calves, only genotype IIaA15G2R1 was detected (n = 125). Although C. parvum was observed in adult cattle two weeks after the start of the calving season, the predominant genotypes were not detected until Week 4 in both adults and calves, meaning it is still unclear whether adult cattle are the initial source of C. parvum infections on the farm. Historically calves on this dairy farm demonstrated the IIaA19G2R1 genotype, which, has now clearly been replaced with the IIaA15G2R1 genotype that is now found in both adults and calves. During the study season, significantly higher levels of neonatal calf mortality were observed compared to the seasons before (P = 0.046) and after (P = 0.0002). This study has shown comparable levels of C. parvum infection in both pre- and post-partum dams but higher levels of infection in neonatal calves.

Approximately 80% of the global cattle population is at risk of infestation and infection by ticks and tick-borne diseases (TTBDs). The economic losses from animal mortality, reduced production, vector control costs and animal treatment are very substantial, hence there is an urgent need to develop and deploy alternative vector control strategies. Breeding for host tick resistance has the potential for sustainable large-scale TTBD control especially in cattle. The gold standard method for phenotyping tick resistance in cattle is by counting ticks on the body but is very laborious and subjective. Better methods for phenotyping tick resistance more objectively, faster and at scale, are essential for selecting host genetic resistance to ticks. This study investigated the correlation between haematological cellular profiles and immunological responses (immunoglobulin E, IgE) and full body tick counts in herds of Bos indicus and Bos taurus following artificial tick challenge with Rhipicephalus decoloratus larvae. Fifty-four Friesian and Ayrshire (Bos taurus) and 52 East African Zebu (Bos indicus) calves were each infested with ∼2500 larvae. Near-replete adult female ticks (≥ 4.5 mm) were counted daily from Day 20–25. Blood and serum samples were obtained from each animal on Days 0 and 23 for cellular blood and IgE titre analysis, respectively. The indicine cattle were refractory to R. decoloratus infestation in comparison with the taurine breed (P < 0.0001). Repeated measurements of blood components pre-infestation revealed a significant (P < 0.05) association with tick count in IgE and red blood cells, haematocrit, and haemoglobin post-infestation. There was also a strong positive correlation between the tick counts and red blood cell numbers, haemoglobin, haematocrit, and IgE concentration (P < 0.0001) following tick challenge. The application of this approach to phenotype host resistance needs to be assessed using higher cattle numbers and with different tick species or genera.

Spatial repellents are volatile or volatilized chemicals that may repel arthropod vectors in free space, preventing bites and reducing the potential for pathogen transmission. In a 21-week field study, we investigated the efficacy of passive transfluthrin-impregnated diffusers placed in two-person United States (US) military tents located in canopy and open field habitats in north Florida to prevent mosquitoes from entering. Mosquito collections with US Centers for Disease Control and Prevention traps baited with light and carbon dioxide were conducted weekly for weeks 0–4, every two weeks for weeks 5–10, and monthly for weeks 11–21. Our results demonstrated that these transfluthrin-impregnated devices did not function as spatial repellents as expected and did not create a mosquito-free zone of protection. Instead, we observed consistently higher collections of mosquitoes from tents with transfluthrin-impregnated diffusers, and higher rates of mosquito mortality in collections from tents with transfluthrin diffusers, compared to untreated control tents. Based on these findings we do not recommend the use of passive transfluthrin-impregnated diffusers for mosquito protection in two-person US military tents in warm-temperate environments similar to north Florida.

The genus Mansonella Faust, 1929 includes 29 species, mainly parasites of platyrrhine monkeys in South America and anthropoid apes in Africa. In Malaysia, Mansonella (Tupainema) dunni (Mullin & Orihel, 1972) was described from the common treeshrew Tupaia glis Diard & Duvaucel (Scandentia). In a recent classification of the genus Mansonella, seven subgenera were proposed, with M. (Tup.) dunni as a monotypic species in the subgenus Tupainema. In this study, we collected new material of M. (Tup.) dunni from common treeshrews in Peninsular Malaysia and redescribed the morphological features of this species. We found that M. (Tup.) dunni differs from M. (Cutifilaria) perforata Uni et al., 2004 from sika deer Cervus nippon (Cetartiodactyla) in Japan, with regards to morphological features and predilection sites in their respective hosts. Based on multi-locus sequence analyses, we examined the molecular phylogeny of M. (Tup.) dunni and its Wolbachia genotype. Species of the genus Mansonella grouped monophyletically in clade ONC5 and M. (Tup.) dunni was placed in the most derived position within this genus. Mansonella (Tup.) dunni was closely related to M. (M.) ozzardi (Manson, 1897) from humans in Central and South America, and most distant from M. (C.) perforata. The calculated p-distances between the cox1 gene sequences for M. (Tup.) dunni and its congeners were 13.09% for M. (M.) ozzardi and 15.6–16.15% for M. (C.) perforata. The molecular phylogeny of Mansonella spp. thus corroborates their morphological differences. We determined that M. (Tup.) dunni harbours Wolbachia endosymbionts of the supergroup F genotype, in keeping with all other Mansonella species screened to date.

Female genital schistosomiasis (FGS) caused by Schistosoma haematobium is a neglected chronic parasitic disease. Diagnosis relies mainly on a colposcopy, which reveals non-specific lesions. This study aimed to assess the performance of two sampling methods for the molecular diagnosis of FGS in the uterine cervix. We conducted a descriptive cross-sectional study in women of reproductive age in Saint Louis, Senegal, who presented for cervical cancer screening. Cotton swab and cytobrush samples were collected from the cervix and examined by real-time PCR. The PCR results obtained using the cotton swabs were compared with those obtained using cytobrush. Of the 189 women recruited, 56 (30%) were found to be positive for S. haematobium infection via real-time PCR. Women aged 40–54 years were predominantly infected (45%) followed by those aged 25–39 years (36%). Numerically more PCR-positive specimens were identified using cytobrush sampling. Of the 89 women who underwent both cytobrush and cotton swab sampling, 27 were PCR-positive in the cytobrush sampling vs 4 in the swab sampling. The mean Ct-value was 31.0 ± 3.8 for cytobrush-based PCR vs 30.0 ± 4.4 for swab-based PCR. The results confirm that real-time PCR can detect Schistosoma haematobium DNA in the uterine cervix. The next step will be to compare PCR with the other diagnostic methods of FGS.

Mosquito-borne viruses are leading causes of morbidity and mortality in many parts of the world. In recent years, modelling studies have shown that climate change strongly influences vector-borne disease transmission, particularly rising temperatures. As a result, the risk of epidemics has increased, posing a significant public health risk. This review aims to summarize all published laboratory experimental studies carried out over the years to determine the impact of temperature on the transmission of arboviruses by the mosquito vector. Given their high public health importance, we focus on dengue, chikungunya, and Zika viruses, which are transmitted by the mosquitoes Aedes aegypti and Aedes albopictus. Following PRISMA guidelines, 34 papers were included in this systematic review. Most studies found that increasing temperatures result in higher rates of infection, dissemination, and transmission of these viruses in mosquitoes, although several studies had differing findings. Overall, the studies reviewed here suggest that rising temperatures due to climate change would alter the vector competence of mosquitoes to increase epidemic risk, but that some critical research gaps remain.

Several human pathogens vectored by the blacklegged tick (Ixodes scapularis Say; Acari: Ixodidae) are endemic in the state of New Jersey. Disease incidence data suggest that these conditions occur disproportionately in the northwestern portion of the state, including in the county of Hunterdon. We conducted active surveillance at three forested sites in Hunterdon County during 2020 and 2021, collecting 662 nymphal and adult I. scapularis. Ticks were tested for five pathogens by qPCR/qRT-PCR: Anaplasma phagocytophilum, Babesia microti, Borrelia burgdorferi, Borrelia miyamotoi, and Powassan virus (POWV) lineage 2. Over 2 years, 25.4% of nymphs and 58.4% of adults were found infected with at least one pathogen, with 10.6% of all ticks infected with more than one pathogen. We report substantial spatial and temporal variability of A. phagocytophilum and B. burgdorferi, with high relative abundance of the human-infective A. phagocytophilum variant Ap-ha. Notably, POWV was detected for the first time in Hunterdon, a county where human cases have not been reported. Based on comparisons with active surveillance initiatives in nearby counties, further investigation of non-entomological factors potentially influencing rates of tick-borne illness in Hunterdon is recommended.