Parasites & Vectors最新文献

Background: The house fly, Musca domestica L., is a global insect pest that poses serious health risks by carrying pathogens to humans and animals. Pyrethroid (PYR) insecticides have been widely used to control agricultural pests and disease vectors. Multiple reports have documented house fly resistance to PYR insecticides.

Methods: In this study, we assessed the resistance levels of M. domestica populations collected from slaughterhouses in Riyadh, Jeddah, and Taif, Saudi Arabia, against the PYR insecticide deltamethrin (DM). We also examined the genetic mutations in the voltage-sensitive sodium channel (Vssc) and P450 genes of the collected field flies and analyzed the correlation between these detected genetic mutations and the levels of DM resistance.

Results: The house fly field populations showed very high levels of resistance to DM, with resistance ratio (RR) values of 625-, 256-, and 107-fold for Jeddah, Taif, and Riyadh, respectively. Three VSSC resistance alleles, kdr (T929 + 1014F), kdr-his (T929 + 1014H), and 1B (929I + 1014F), along with the susceptible allele (T929 + L1014) were identified in the Saudi house fly populations. The super-kdr allele (918 T + 1014F) and type N (D600N + M918T + L1014F) were not detected in Saudi house fly populations. Type 1B was the most dominant VSSC resistance allele, followed by kdr and kdr-his, in both field populations and the surviving flies exposed to DM. The resistance CYP6D1v1 allele of P450 was detected in slaughterhouse house fly populations of Riyadh, Jeddah, and Taif, with frequencies of 71%, 58%, and 60%, respectively. The VSSC resistance alleles exhibited a positive correlation with the resistance levels to DM; conversely, the CYP6D1v1 displayed a negative correlation with DM resistance levels.

Conclusions: In general, the Saudi house fly populations exhibited high genetic diversity, with three VSSC resistance alleles identified in slaughterhouse populations. The Vssc mutations appear to be the principal mechanism of DM resistance in Saudi house fly field populations. This study is the first report on the Vssc and CYP6D1 mutations associated with PYR resistance in M. domestica field populations from Saudi Arabia.

Background: In vector-borne diseases, invertebrate hosts are exposed to highly variable quantities of parasites during their blood meal. This heterogeneity may partly explain the overdispersed distribution of parasites within the vector population and the variability in the extrinsic incubation period (EIP) of the parasite. Indeed, the quantity of parasites ingested is often considered as a good predictor of the quantity of parasites that will develop within the vectors, as well as the speed at which they will develop (i.e. EIP). However, density-dependent processes can influence the relationship between parasite burden in the vertebrate host and in vectors, making this relationship unclear at times.

Methods: Here, we used an avian malaria system to investigate whether the proportion of red blood cells infected by sexual and/or asexual stages of Plasmodium relictum influences the intensity of infection and the EIP within vectors. For this purpose, we experimentally infected 12 birds in order to generate a range of infection intensity. More than 1000 mosquitoes took a blood meal on these hosts, and the development of Plasmodium within the vectors was followed for more than 20 days.

Results: Our study reveals a negative relationship between the intensity of infection in birds and the time until 10% of mosquitoes become infectious (EIP₁₀). A period of only 4 days was sufficient to detect sporozoites in at least 10% of mosquitoes fed on the most infected hosts. However, the number of sporozoites did not vary significantly according to the vertebrate host intensity of infection, but was positively correlated to the oocyst burden (parasitic stage preceding the sporozoite stage).

Conclusions: While the quantity of ingested parasites had no impact on oocyst and sporozoite burden in infectious mosquitoes, the EIP₁₀ was affected. Studies have demonstrated that small changes in the EIP can have a significant effect on the number of mosquitoes living long enough to transmit parasites. Here, we observed a difference of 4-6 days in the detection of the first sporozoites, depending on the intensity of infection of the bitten vertebrate host. Considering that a gonotrophic cycle lasts 3-4 days, the shortened EIP may have significant effects on Plasmodium transmission.

Background: Second only to mosquitoes, ticks (Acari: Ixodida) are significant blood-feeding ectoparasites and vectors of numerous pathogens affecting both animals and humans. Despite bats serving as hosts to various tick species, they remain relatively understudied due to their nocturnal behavior and laborious capture procedures. Soft ticks in particular display diverse ecological behaviors, inhabiting bat roosts, caves, and occasionally human dwellings. This overlap in habitats suggests soft ticks may play a critical role as vectors of zoonotic pathogens. In Southeast Asia, research on soft ticks has primarily focused on island nations, with limited studies on bat-associated ticks in Thailand. This study aimed to examine the identity and distribution of bat ticks in Thailand.

Methods: Bats were captured across ten provinces in Thailand between 2018 and 2023. Ticks were removed from the bats' skin and identified through morphological examination using a stereomicroscope, with molecular confirmation. Scanning electron micrographs were recorded. Prevalence, mean abundance, and mean intensity of tick infestations were calculated. The mitochondrial genomes of the ticks were sequenced, annotated, and subjected to phylogenetic analysis.

Results: A total of 1031 bats, representing 7 families, 11 genera, and 28 species, were captured. Tick infestations were found in 34 bats (3.30%), specifically in two species: Craseonycteris thonglongyai (33/139, 23.74%) and Eonycteris spelaea (1/2, 50%). All ticks were in the larval stage. Basic local alignment search tool for nucleotide (BLASTN) searches using 16S rRNA (425 bp) and COI (825 bp) sequences, along with Barcode of Life Database (BOLD) database queries, revealed the highest similarity to tick in the genus Reticulinasus found on bats in Zambia. The mitochondrial genomes of ticks collected from C. thonglongyai and E. spelaea were 14,433 bp and 14,439 bp in length, respectively, and contained 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes. Phylogenetic analysis placed these ticks within the Reticulinasus clade, with strong support indicated by high bootstrap values.

Conclusions: This study identified Reticulinasus sp. infestations on C. thonglongyai and E. spelaea bats, marking the first report of soft ticks in bats from Thailand, with potential implications for zoonotic disease transmission.

Background: The liver fluke Fasciola hepatica is one of the most important endoparasites in domestic ruminants worldwide and can cause considerable economic losses. This study presents the first population genetic analysis of F. hepatica in Germany and aims at providing new insights into genetic diversity and population structure.

Methods: A total of 774 liver flukes, collected from 60 cows of 17 herds and 13 cows of unknown herd origin, were subjected to comparative analysis of two mitochondrial genes (cox1 and nad1), one nuclear region (internal transcribed spacer (ITS)-1) and eight nuclear microsatellite markers. In addition, individual fluke measurements allowed comparison of morphometric differences between genotypes.

Results: The nuclear ITS-1 region showed minimal variability, with 772 of 774 flukes having identical sequences, while the mitochondrial sequences revealed a high genetic diversity, with 119 distinct haplotypes, a mean haplotype diversity (Hd) of 0.81 and a mean nucleotide diversity (π) of 0.0041. Mitochondrial phylogenetic analysis identified two clusters with no clear association with the host or farm of origin. In the microsatellite analysis, all eight loci were highly polymorphic, with a mean allele frequency of 19.0 and a mean genotype frequency of 73.5 per locus. A total of 500 unique multilocus genotypes (MLGs) were found across all fluke samples, indicating that 68.5% of all genotypes were unique. A mean expected heterozygosity of 0.71 suggested a high potential for adaptability and the number of migrants (Nm = 3.5) indicated high gene flow between farms. Population structure analysis based on microsatellite data revealed that flukes from two farms differed genetically from the others. Linear mixed model results revealed that fluke length differed significantly between the two mitochondrial clusters, although it should be noted that fluke age could not be considered in the analyses.

Conclusions: Fasciola hepatica in German dairy farms showed high genetic diversity and gene flow. The differences in population structure identified by mitochondrial sequences compared with microsatellite loci highlight the benefits of analysing genetic markers of different origins. This is the first study to correlate fluke morphometry measurements with genetic markers, indicating that the identified markers can influence fluke size.

Background: The great gerbil (Rhombomys opimus), whose ectoparasitic fleas significantly influence the transmission and prevalence of plague, was the dominant rodent species in the Junggar Basin in Northwestern China. However, the distribution pattern of fleas parasitizing the great gerbils and whether that pattern affected the intensity of plague prevalence in different regions remains unclear.

Methods: A total of 17,780 fleas were collected from 2258 great gerbils throughout 90 investigations. This study focused on analyzing the rate of flea infestation and the flea indices of species that parasitized the great gerbils. The aggregation patterns of fleas parasitizing the great gerbils were measured using the parameter b of Taylor's power law, and the differences in the aggregation index of plague epidemic areas were compared.

Results: We observed an aggregated distribution of ectoparasitic fleas in the great gerbils. The aggregation degree of combined fleas was higher (P > 0.05) in the eastern area of the Junggar Basin than in the western area. The primary species of ectoparasitic fleas of the great gerbils were Xenopsylla skrjabini, Xenopsylla minax, Xenopsylla hirtipes, and Nosopsyllus laeviceps laiveceps. X. skrjabini exhibited the highest (P < 0.01) degree of aggregation in the eastern zone (III), with an aggregation index of 1.61. In addition, in the middle zone (II), the aggregation index of X. minax and X. hirtipes reached their peak, with values of 1.53 and 1.56, respectively. Conversely, the degree of aggregation of N. laeviceps was more pronounced in the eastern zone than in the western zone of the Junggar Basin. Notably, the aggregation degree of the combined fleas of the great gerbils during the low-intensity plague epidemic period, with an index of 1.93, was significantly higher (P < 0.001) than during the high-intensity epidemic period, with an index of 1.50.

Conclusions: Fleas exhibited an aggregated distribution within the great gerbil population. The levels of flea aggregation varied across zones characterized by differing intensities of plague epidemics. In addition, the degree of flea aggregation was significantly correlated with the intensity of plague prevalence.

Ticks are well-known vectors of pathogens, including filarial nematodes, which can affect animal and human health. This review synthesizes current knowledge of filarial nematodes that utilize ticks as vectors, focusing on the Onchocercidae. Five genera of onchocercid filarial nematodes (Cercopithifilaria, Cherylia, Cruorifilaria, Monanema, and Yatesia) have demonstrated vector-parasite relationships with ticks, while Acanthocheilonema has only demonstrated molecular detection without confirmed vector competence. Vector competence has been experimentally proven for several species through documented development to infective stages. However, our understanding of tick-borne filarial nematodes remains limited owing to insufficient detection efforts and methodological challenges. Detection methods include traditional dissection, advanced imaging techniques such as microcomputed tomography (micro-CT), and molecular approaches, each with distinct advantages and limitations. To address knowledge gaps, future research should focus on conducting large-scale surveys of tick populations and wildlife to investigate vector competence, health impacts, and coinfection dynamics. Multi-disciplinary collaboration and community involvement in tick surveillance will advance our understanding of tick-borne filarial nematode ecology and epidemiology. Future research priorities include confirming vector competence where only molecular detection exists, investigating natural transmission patterns, and understanding the mechanisms influencing successful development in tick vectors. By addressing these knowledge gaps through systematic surveillance and experimental studies, we can better understand these complex host-parasite-vector relationships and their implications for animal health.

Background: Neospora caninum is an intracellular parasitic protozoon that can infect pregnant animals and cause symptoms such as miscarriage, stillbirth and mummified fetuses. It is one of the main causes of miscarriage in bovines. Apical membrane antigen (AMA) and dense granule protein (GRA) are two major antigenic proteins of N. caninum.

Methods: In this study, NcGRA9 recombinant subunit vaccine and Ad5-NcAMA1 recombinant adenovirus vaccine were prepared and used to immunize C57BL/6 mice and Yanbian yellow cattle.

Results: IgG, IgG1, IgG2a, IgG2b, IgA and IgE antibodies and interferon (IFN-γ), interleukin (IL-4) and tumor necrosis factor (TNF-α) cytokines were significantly higher in immunized mice than in the control group (P < 0.0001). The biochemical indexes showed that vaccination had no effect on hepatic and renal functions. The survival rate was 70% in mice immunized with NcGRA9 vaccine, 75% in mice immunized with Ad5-NcAMA1 vaccine, 85% in the combined immunization group and 10% in the control group. The parasite load in the brain and liver tissues of the immunized groups was significantly lower than in the control group, as detected by fluorescence quantitative PCR (P < 0.0001). In cattle, IgG, IgG2a, IgG2b, IgA, IgM and IgE antibodies and IFN-γ, IL-4 and TNF-α cytokines were significantly higher in the immunized groups than in the control group (P < 0.0001). Combined immunization with NcGRA9 + Ad5-NcAMA1 was significantly better than immunization with either vaccine alone.

Conclusions: The biochemical indexes showed that the vaccine had no effect on the liver and kidney functions of cattle. Our results indicate that combined immunization with NcGRA9 + Ad5-NcAMA1 may be a candidate for bovine neosporosis vaccination.

Background: Phlebotomine sand flies are the key vectors for phleboviruses (order Hareavirales and family Phenuiviridae), of which some are associated with febrile diseases and nervous system infections. In the Mediterranean Basin, Toscana virus (TOSV; Phlebovirus toscanaense) and sandfly fever Sicilian viruses (SFSV; Phlebovirus siciliaense) are important human pathogens, and their endemicity has been known for decades, particularly in the Balkan countries. While the circulation of both viruses is highly evident among humans and livestock in the Central Balkan country Kosovo, data from companion animals are scarce; however, it might help to further assess the distribution of both viruses in the country.

Methods: Sera of dogs from all seven districts of Kosovo were screened for TOSV and SFSV antibodies by seroneutralization assays.

Results: Altogether, 45 of 288 (15.6%) samples showed anti-Phlebovirus antibodies, of which 36 (12.5%) were against TOSV, 11 (3.8%) were against SFSV, and 2 (0.7%) were positive for antibodies against both viruses.

Conclusions: Phlebovirus seroprevalence was observed in all seven districts of the country, generally being higher for TOSV compared with SFSV. Our study presents the first assessment of neutralization-based seroprevalence of two medically important phleboviruses among dogs in the Republic of Kosovo. Although healthy dogs are unsusceptible to Phlebovirus infection, dogs with leishmaniasis can be potential amplifying hosts. Given the high number of stray dogs, frequent uncontrolled spreading of phleboviruses in dogs, and potential spillover in populated regions of the country, these findings should be taken into consideration.

Background: The detection of Angiostrongylus spp. larvae in intermediate host snails is a critical epidemiological investigation, essential for the effective control of disease outbreaks. Compared to molecular biological detection methods, lung microscopy, a traditional pathogen morphological detection approach, is susceptible to oversights and exhibits relatively lower sensitivity. However, we posit that lung microscopy offers irreplaceable advantages in the context of large-scale field surveys and can serve as a vital foundation for use in conjunction with other diagnostic technologies.

Methods: In this study, 348 Achatina fulica samples were examined using lung microscopy, PCR, and AcanITS1 qPCR. Statistical analysis was conducted to compare detection rates and sensitivities among these methods. DNA from a snail confirmed positive by lung microscopy was diluted and tested using PCR and AcanITS1 qPCR to assess the diagnostic efficacy of the molecular assays. Finally, we combined the highly sensitive AcanITS1 qPCR with lung microscopy for identifying Angiostrongylus spp. larvae in Achatina fulica for the first time to our knowledge and compared its diagnostic efficacy with that of individual testing methods.

Results: The lung microscopy, PCR, AcanITS1 qPCR, and combined test yielded detection rates of 29.31%, 32.18%, 38.22%, and 38.51%, respectively. These differences were statistically significant (X² = 9.565, p < 0.05). Notably, AcanITS1 qPCR demonstrated superior sensitivity with a detection threshold of 10 pg/μl, outperforming the PCR with a threshold of 10 ng/μl. When PCR was utilized as the gold standard, the sensitivities for lung microscopy, AcanITS1 qPCR, and the combined test were determined to be 88.39%, 97.32%, and 98.21%, respectively. Correspondingly, the specificities were 98.73%, 89.83%, and 89.83%, respectively.

Conclusions: This novel straregy, the combined test for the detection of Angiostrongylus spp. larvae in Achatina fulica exhibited superior positive detection rates and sensitivity compared to each of the three individual methods. We believe that this novel strategy is not only applicable to large-scale field investigations of Achatina fulica and Pomacea canaliculata but also has potential application value for monitoring the infection of these snails sold at the local farmers' markets with Angiostrongylus spp. larvae. Of course, while qPCR is exceptionally sensitive, the potential for false negatives remains a consideration. Repeated experimentation is also essential to maximize the reliability and accuracy of the outcomes.

Background: Malaria is the parasitic disease with the highest morbidity and mortality worldwide. Angola is one of the five sub-Saharan African countries with the highest malaria burden. Real-time PCR diagnosis in endemic areas has not been implemented due to its high cost and the need for adequate infrastructure. Dried blood spots (DBSs) are an alternative for collecting, preserving, and transporting blood samples to reference laboratories. The objective of the study was to assess the efficacy of DBS as a sampling method for malaria research studies employing real-time PCR.

Methods: The study was divided into two phases: (i) prospective study at the Hospital Universitario Vall d'Hebron (HUVH) to compare real-time PCR from whole blood or DBS, including 12 venous blood samples from patients with positive real-time PCR for Plasmodium spp. and 10 quality control samples (nine infected samples and one negative control). Samples were collected as DBSs (10, 20, 50 µl/circle). Samples from both phases of the study were analyzed by generic real-time PCR (Plasmodium spp.) and the subsequent positive samples underwent species-specific real-time PCR (Plasmodium species) and (ii) cross-sectional study conducted at the Hospital Nossa Senhora da Paz, Cubal (Angola), including 200 participants with fever. For each patient, a fresh capillary blood specimen [for thin and thick blood films and rapid diagnostic test (RDT)] and venous blood, collected as DBSs (two 10-µl circles were combined for a total volume of 20 µl of DBS), were obtained. DBSs were sent to HUVH, Barcelona, Spain.

Results: (i) Real-time PCR from whole blood collection was positive for 100% of the 21 Plasmodium spp.-infected samples, whereas real-time PCR from DBSs detected Plasmodium spp. infection at lower proportions: 76.19% (16/21) for 10 µl, 85.71% (18/21) for 20 µl, 88.24% (15/17) for 50 µl and 85.71% (18/21) for 100 µl DBSs. (ii) Field diagnosis (microscopy and/or RDT) showed a 51.5% (103/200) positivity rate, while 50% (100/200) of the DBS samples tested positive by real-time PCR. Using field diagnosis as the reference method, the sensitivity of real-time PCR in DBS samples was 77.67% with a specificity of 79.38%. Plasmodium species were identified in 86 samples by real-time PCR: 81.40% (16/86) were caused by Plasmodium falciparum, 11.63% (10/86) were coinfections of P. falciparum + P. malariae, 4.65% (4/86) were P. falciparum + P. ovale, and 2.33% (2/86) were triple coinfections.

Conclusions: The DBS volume used for DNA extraction is a determining factor in the performance of real-time PCR for Plasmodium DNA detection. A DBS volume of 50-100 µl appears to be optimal for malaria diagnosis and Plasmodium species determination by real-time PCR. DBS is a suitable method for sample collection in Cubal followed by real-time PCR analysis in a reference laboratory.