Medical and Veterinary Entomology最新文献

The ‘oviposition preference-offspring performance’ hypothesis (PPH) proposes that females select oviposition sites that optimise offspring performance. For Aedes aegypti L. (Diptera: Culicidae), the main vector of dengue in the Americas, it is expected that females prefer to lay eggs in containers with high nutritional quality, where developmental success is maximised. In this study we aimed to test the PPH in relation to three detritus decomposition time treatments (3, 14 and 42 days). Oviposition was studied during 1 week in three contiguous ovitraps (one per decomposition time treatment) at 18 sites. Immature development in the three treatments was studied at constant densities (20 larvae) or at realistic densities (eggs/treatment in the oviposition study). The number of eggs from the oviposition study and a performance index based on development time, wing length and survival in the immature development study were compared between treatments. Both the oviposition site selection and the subsequent larval development were affected by the detritus decomposition time. Females laid fewer eggs in the 3-day treatment (mean: 16 eggs) than in the 14- and 42-day treatments (mean: 65 and 62 eggs respectively). Immature developmental performance was inversely related to decomposition time at constant densities, and at realistic densities, immatures performed even worse in the longer decomposition time treatments due to higher larval densities. Thus, the effects of detritus decomposition time seem to act in opposite directions for oviposition site selection and immature development success, which does not align with the PPH. One possible explanation for this apparent contradiction is that containers with short detritus decomposition times could indicate a frequent replacement of water, and that females might be selecting signals associated with habitat permanence to ensure the completion of development of their offspring.

The biting midges, Culicoides peregrinus Kieffer and Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) are the most significant vector species of bluetongue virus (BTV) in the Oriental region, including India. Rearing of these vector species was cumbersome; previous researchers supplemented the rearing substrates primarily with cattle dung (the habitat), yeast and nutrient broth. Other investigations reiterated that an enriched milieu of live bacteria is required for the oviposition and developmental progression of the immatures as they failed to develop in sterile medium. Therefore, bacteria-based approaches provide novel opportunities for artificial rearing. This investigation tries to simplify and create a cleaner version of rearing based on different bacterial strains. The substrate bacterial strains were biochemically characterised, and their influence on oviposition, hatching and larval development was analysed and evaluated under laboratory conditions. We artificially reared two vector species by utilising three different strains of Bacillus cereus and one strain of Alcaligenes faecalis retrieved from the substrates. The results demonstrated that gravid females select their oviposition substrates based on stimuli derived from live microorganisms that indicate the suitability of the developmental substrate for immature development. Bacillus cereus 1B stimulated the greatest extent of egg hatching (>99%), larval survivability (>74%), pupae formation (>83%) and adult emergence (>98%) in both species. This present investigation proposes to utilise B. cereus 1B as an alternative approach to artificially rear and establish laboratory colonies of these vector species.

The study of population dynamics in a vertical forest gradient provides basic information on the aspects of insect vector natural history that influence the rate of pathogen transmission. In Mexico, these studies are remarkably limited for sand flies recognised as Leishmania vectors. This study analyses the temporal dynamics of sand fly species (Diptera: Psychodidae) along vertical strata of a tropical dry forest in Yucatán, Mexico, an area previously identified as a transmission hotspot for Leishmania mexicana. Bimonthly samplings were conducted over 1 year by using six CDC light traps in the understory and six traps in the canopy. During the collection period, forest attributes and environmental data (temperature and relative humidity) were recorded for each ecotope. In total, 630 individuals were sampled, of which 68% were collected in the understory and 32% in the canopy. No significant differences in species diversity and abundance were detected between the two ecotopes. Psathyromyia shannoni (Dyar) and Dampfomyia deleoni (Fairchild and Hertig) were the only species structured in the vertical dimension. Observed diversity in both strata responds similarly across both monthly and seasonal time scales. Data analyses indicated that relative humidity influenced the vertical distribution of P. shannoni and D. deleoni, although the magnitude and direction of this effect varied by species. Psathyromyia shannoni exhibited contrasting responses to relative humidity between the canopy and the understory, independent of sex, suggesting that additional environmental factors not assessed in this study may modulate its vertical distribution. Despite the limitations of our work, these findings contribute to the knowledge on the population dynamics of sand flies in the tropical forests of the Yucatán Peninsula.

Fleas (Insecta: Siphonaptera) are recognised vectors of bacteria that affect human and other animal health, whose reservoirs are in the majority mammals. Among these, some species of the genera Rickettsia (Rickettsiales: Rickettsiaceae) and Bartonella (Rhizobiales: Bartonellaceae) are emerging and re-emerging throughout the world; however, their circulation across vast regions of Argentina and numerous animal species, particularly wild species remains largely unknown. The study of wild animal roadkill provides valuable insights into parasitic associations and the presence of pathogenic microorganisms, allowing the generation of a health alert in certain ecosystems. The aim of this study was to describe the diversity of fleas associated with roadkilled wild native meso-mammals in the extreme northeast of Argentinian Patagonia, and to detect the presence of Rickettsia and Bartonella bacteria. Five host species were examined, including Chaetophractus villosus Desmarest (Cingulata: Chlamyphoridae); Didelphis albiventris Lund (Didelphimorphia: Didelphidae); Lagostomus maximus Desmarest (Rodentia: Chinchillidae); Leopardus geoffroyi d'Orbigny and Gervais (Carnivora: Felidae) and Lycalopex gymnocercus Fischer (Carnivora: Canidae). A total of 248 fleas were recovered, identified as Hectopsyllidae: Hectopsylla broscus Jordan and Rothschild and Hectopsylla cypha Jordan; Malacopsyllidae: Phthiropsylla agenoris Rothschild and Malacopsylla grossiventris Weyenbergh; Pulicidae: Ctenocephalides felis Bouché and Pulex irritans Linnaeus. Molecular analysis detected two flea-borne pathogenic bacteria: Rickettsia felis (Bouyer et al.), found in C. felis from D. albiventris, and Bartonella rochalimae (Eremeeva et al.), reported here for the first time in Argentina, detected in P. agenoris from C. villosus, and in P. irritans from L. maximus and L. gymnocercus. The results contribute to knowledge of flea diversity in Argentinian Patagonia and provide new information about flea-borne pathogens circulating in the wildlife of this region. Furthermore, this study is the first in Argentina to investigate ectoparasites and their associated bacteria in roadkilled animals, making a pioneering contribution to the field. The interesting findings highlight the importance of implementing and expanding road ecology studies, which could easily be replicated in other regions where information gaps on flea and flea-borne bacteria diversity still exist.

Tick-borne rickettsiosis has posed a significant threat to Egypt, with various pathogenic Rickettsia species being reported. In this study, 134 ticks were collected from camels in Esna City, Luxor, Egypt and all were identified as Hyalomma dromedarii through both morphological and molecular techniques. Using specific primers targeting the citrate synthase (gltA), outer membrane protein A (ompA) and 17 kD antigen (17 kDa) genes, Rickettsia japonica was detected via conventional and nested PCR assays. Remarkably, two samples tested positive for R. japonica across all three genes, indicating a prevalence of 1.5%. Phylogenetic analysis based on the gltA, ompA and 17 kDa genes confirmed the presence of R. japonica within H. dromedarii ticks. This is the first reported detection of R. japonica in Egypt. These findings highlight the urgent need to investigate the origin and spread of R. japonica in the country and underscore the importance of continuous surveillance and data collection on lesser-known pathogens circulating in ticks as part of Egypt's public health efforts to manage tick-borne diseases.

Rodents represent the most diverse mammalian group and are considered important hosts for different groups of parasites serving as vectors for some zoonotic agents. Although there have been numerous studies conducted on occurrence records of ectoparasites on rodents, there is a paucity of knowledge regarding the biogeographical patterns of ectoparasites on this group of small mammals. In this study, a quantitative approach was employed to identify patterns of distributional congruence (PDCs) of ectoparasites of rodents in Iran. A total of 121 occurrence records for 37 species of ectoparasites (ticks, mites, lice and fleas) in Iran were analysed using endemicity analysis NDM/VNDM. Twelve consensus areas, characterised by 30 species, were found which were grouped into three PDCs. The PDCs showed that the highest endemicity values were primarily linked to the Zagros Mountains and central Persian areas. The patterns as a whole showed a clear tendency of the Zagros Mountains, forest steppe and central Persian desert basins ecoregions to provide possible areas of endemism. The current study extends the knowledge on the distribution patterns of four main groups of ectoparasites in association with rodent species in Iran and emphasises the significance of endemic zones in controlling management of reservoirs and vectors and conservation efforts.

Climate change is expected to expand the geographic ranges of ectoparasites, increasing the transmission of vector-borne diseases and necessitating a better understanding of ectoparasite–host trophic dynamics. Haematophagous ectoparasites can serve as valuable subsamples of their hosts, retaining isotopic values that reflect dietary information in both their blood meals and tissues. However, differences in the life histories and feeding strategies of lice, fleas and ticks may influence how host isotopic composition is preserved. Here, stable isotope values of carbon (δ¹³C) and nitrogen (δ¹⁵N) were used to investigate trophic interactions between ectoparasites and their mammalian hosts in three pairings: lice (Anoplura: Polyplacidae; n = 101) from Eurasian red squirrels Sciurus vulgaris L. (Rodentia: Sciuridae), fleas (Siphonaptera: Ceratophyllidae; n = 92) from fat dormice Glis glis L. (Rodentia: Gliridae) and ticks (Ixodida: Ixodidae; n = 16) from European hedgehogs Erinaceus europaeus L. (Eulipotyphla: Erinaceidae). Our findings indicate that ectoparasites reflect the dietary patterns of their hosts, with lice exhibiting the closest isotopic values, followed by fleas and ticks. All parasites had significantly higher δ¹⁵N values than their hosts, indicative of trophic enrichment, but their δ¹³C values varied. Notably, we found that the presence of a blood meal did not significantly affect the isotopic values found in lice and fleas, while ticks showed a significant difference between exoskeleton and blood meal in δ¹³C values. This study highlights the importance of understanding how the life histories of parasite species influence the preservation of isotopic host signals in order to be able to utilise stable isotope analyses of ectoparasites to infer host dietary niches and preferences, with broader implications for understanding host–parasite dynamics and disease transmission pathways.

Species belonging to the genus Lipoptena have received limited attention and have historically been subject to misidentifications. Recent records of L. fortisetosa in Europe have rekindled interest in these hippoboscids, leading to the discovery of a new species in Spain in 2024, which has been named L. andaluciensis. During an opportunistic sampling conducted in March 2023 and October 2024 on the Italian red deer (Cervus elaphus italicus), an Italian endemic subspecies, within the ancient relict lowland forest of the Bosco della Mesola Nature Reserve, hippoboscids morphologically identical to L. andaluciensis were collected and examined. This represents the first record of this species in Italy. In total, 257 specimens of Lipoptena were collected and analysed (161 in 2023 and 94 in 2024), all identified as L. andaluciensis. Additionally, Lipoptena specimens collected from fallow deer in 2007 within the same nature reserve, which had remained unidentified until now, were re-examined. A total of 66 specimens were reassessed, of which 63 were morphologically identified as L. andaluciensis and 3 as L. cervi. Morphological identification of the 2023 and 2024 specimens was further confirmed through molecular analysis using COI as a barcode marker. Molecular analysis also revealed the presence of a nuclear copy of the COI gene (NUMTs) in the nuclear genome of L. andaluciensis. The discovery of L. andaluciensis in Spain and in Italy since 2007 raises the possibility that this species has a much broader distribution, particularly at lower altitudes and within a Mediterranean climatic zone. It is plausible that its presence has so far gone unnoticed or has been misidentified.

Ticks are significant vectors of pathogens affecting both animals and humans, with the climate and environment of Sub-Saharan Africa providing ideal conditions for their growth. However, there are limited data on ticks and tick-borne pathogens (T&TBPs) in cattle in The Gambia. This study aimed to identify tick species on cattle and conduct molecular screening for T&TBPs. A total of 92 ticks were collected from 306 indigenous cattle. Ticks were first identified morphologically using taxonomic keys and then confirmed molecularly through DNA sequencing. DNA was extracted from the right fourth leg of six representative ticks for species confirmation, while 77 whole adult ticks were used for screening T&TBPs. Screening polymerase chain reaction (PCR) assays targeted Anaplasma marginale msp1β gene, Ehrlichia spp. dsb gene and hemotropic Mycoplasma spp. 16S rRNA gene. Ehrlichia-positive samples underwent additional assays targeting the sodB, 16S rRNA and groEL genes, followed by Sanger sequencing and phylogenetic analyses. A total of 92 (53 M, 37 F and two nymphs) ticks were collected from 30/306 (9.8%; 95% confidence interval [CI]: 5.6%–12.2%) cattle. Adult ticks were identified as Hyalomma marginatum (73/92; 79.3%; 45 M and 28 F), Amblyomma variegatum (8/92; 8.7%; 8 M), Hyalomma rufipes (4/92; 4.3%; 4 F) and Rhipicephalus evertsi (1/92; 1.1%; one F). The 16S rRNA sequences of six (four engorged female and two nymphs) ticks showed 98.6–100% identity with reference sequences from Rhipicephalus geigyi. Twelve out of 77 (15.6%) ticks tested positive for at least one TBP. Eight H. marginatum (six M and two F) (10.4%) were positive for Ehrlichia spp. dsb gene, three H. marginatum (two M and one F) (3.9%) for A. marginale and two (one H. marginatum F and one A. variegatum M) (2.6%) for hemotropic Mycoplasma spp. All Ehrlichia-positive samples showed 100% detection for the 16S rRNA gene and 62.5% for the sodB gene. BLASTn analysis revealed 99.3%–99.7% identity with Ehrlichia sp. from Brazil and 98.2%–99.3% identity with E. minasensis from Panama and Pakistan. Phylogenetic analysis grouped the sequences from this study with Ehrlichia spp. and E. minasensis from ticks in the Czech Republic and Brazil. This study identified various tick species and pathogens in cattle from The Gambia, including the first report of E. minasensis, A. marginale and hemotropic Mycoplasma spp. in the country. These findings highlight the importance of ongoing surveillance and research on tick-borne diseases in the region.

Bluetongue virus (BTV) is an arthropod-borne virus that is transmitted between ruminants by Culicoides (Order Diptera, Family Ceratopogonidae) midges. In September 2023, BTV serotype 3 (BTV-3/NET2023) emerged in the Netherlands, causing a devastating epidemic in sheep and cattle. The aim of this study was to determine which midge species contributed to the spread of BTV-3 and to what extent the virus is present in local midge populations. Midges were collected using Onderstepoort UV-light suction traps on BTV-affected farms in the centre of the Netherlands, from October 2023 till March 2024. Species, sex and parity of the midges were morphologically determined. Pooled female parous and gravid midges were subjected to pan-BTV and BTV-3 real-time polymerase chain reaction (PCR) testing. Pool prevalence, minimum infection rate (MIR) and infection rate (IR) were calculated. In total, 33,093 midges were morphologically identified, all being indigenous Culicoides species. Of these, 10,835 parous or gravid female midges were selected and pooled in 383 pools (mean 28.3 midges per pool, range 1–115). A total of 155 pools (40.5%) tested BTV positive, with a mean MIR/100 of 1.4 and an IR of 2.2 (95% confidence interval: 1.9–2.6). All positive pools were from batches that were collected in October 2023 (week 40 and 41). BTV-RNA was detected in the Culicoides species C. obsoletus Meigen, C. scoticus Downes and Kettle, C. chiopterus Meigen, C. dewulfi Goetghebuer and C. punctatus Meigen. The high proportion of BTV-PCR positive midge pools is indicative of a high vector competence for BTV-3/NET2023 of Dutch indigenous midges present on farms; it could potentially partly explain the rapid spread of the virus throughout the Netherlands.