Medical and Veterinary Entomology最新文献

The diversity and abundance of vectors are essential parameters in the transmission dynamics of West Nile virus (WNV) between its avian reservoirs and clinically susceptible mammalian species. Knowing the determinants of vector abundance could be thus useful in preventing West Nile fever (WNF) cases and associated socio-economic impact. We designed a survey at the wildlife-livestock interface to test the hypothesis that variations in environmental favourability between anthropized and wild scenarios modulate WNV vector abundance and transmission risk. In a continental Mediterranean region where WNF has recently emerged, we selected nine sampling sites and allocated three areas to every site with a decreasing gradient of wildlife-livestock interaction: A₁-a horse farm where interaction is maximal; A₂-a zone of intermediate interaction 500-1000 m from the farm; and A₃-an entirely wild zone of low interaction 1-5 km from the farm. At a fortnightly frequency, we estimated mosquito abundance at each of the 27 study sites in May-December 2018 and April-July 2019. We estimated bird and mammal abundance, collected meteorological information and characterised mosquito habitat at the site scale. Thereafter, we studied the determinants of Culex spp., Culex pipiens sensu lato (s.l.) Linnaeus, 1758 (Diptera: Culicidae) and Culex theileri  Theobald, 1903 abundance by constructing negative binomial generalised linear mixed models. We identified 20 mosquito species, with a notable predominance of Culex spp. and, particularly, of Cx. pipiens s.l. We found differences in the spatiotemporal distribution of Culex spp. abundance and confirmed our hypothesis by finding important effects of local environmental variations in abundance. The accumulated rainfall in fortnights 4-14 and the mean temperature of the two fortnights before sampling were positively and statistically significantly associated with the abundance of Cx. pipiens s.l. (Z = 13.09, p < 0.001, and Z = 9.91, p < 0. 001, respectively) and Culex spp. (Z = 13.35, p < 0.001, and Z = 6.99, p < 0.001, respectively), while the mean temperature of the two previous fortnights was a positive statistically significant predictor (Z = 14.69, p < 0.001) of the abundance of Cx. theileri. The farm environment was the most conducive predictor to hosting Culex spp. compared with wild settings. Our results indicate that continental Mediterranean environments are favourable for WNV circulation and maintenance, especially the environment of anthropized rural settings such as farms. These results will have an impact on the spatiotemporal risk prediction of WNF emergence in continental Mediterranean environments.

This study aimed to assess the presence of Anaplasma, Ehrlichia and Rickettsia species infecting wild birds and their associated ticks in two localities: Moconá Provincial Park (MPP) and Piñalito Provincial Park (PPP), within the Atlantic rainforest ecoregion of Argentina. A total of 142 birds were captured representing 34 species, 28 genera, 15 families and five orders. Ticks were collected from 33 of these birds, comprising 19 species, 14 genera and one order. A total of 59 ticks were collected and identified as Amblyomma calcaratum (13 larvae and four nymphs), Amblyomma longirostre (31 larvae and four nymphs), Amblyomma ovale (one larva and one nymph) and Haemaphysalis leporispalustris (five larvae). All samples were screened for detection of Anaplasma, Ehrlichia and Rickettsia DNA by polymerase chain reaction (PCR) assay. Four bird species tested positive for Anaplasmataceae, with three closely related to Anaplasma and Ehrlichia species previously reported in A. calcaratum adults from a site 15 km away from MPP. The fourth Anaplasmataceae agent was phylogenetically related to Ehrlichia strains reported in Amblyomma triste from the Delta and Parana Islands ecoregion. Additionally, two Rickettsia species were detected and molecularly identified within ticks collected from birds: Rickettsia amblyommatis in A. longirostre larvae and Rickettsia rhipicephali in H. leporispalustris larvae. These findings suggest that birds may play a significant role in the spread of ticks and their associated tick-borne pathogens across diverse biomes.

Culicoides biting midges (Diptera: Ceratopogonidae) are known vectors of multiple arboviruses of veterinary and medical importance, as well as avian haemosporidian parasites. Despite their significant role as vectors, the distribution of Culicoides species in non-farmland habitats remains largely unknown. We conducted a study to assess the species community composition, abundance, and host feeding patterns of Culicoides biting midges in urban ecosystems in northern Spain. Light-baited suction traps were operated biweekly for 6 months across six urban landscapes (three cemeteries and three green areas). In total, 181 Culicoides specimens of 18 species were morphologically identified, with the Obsoletus complex being predominant (43.% of the total catches), followed by Culicoides kibunensis (21.5%). Culicoides midges peaked in early June in green areas and in May in cemeteries. Host feeding patterns revealed avian preferences (mainly Turdus spp.) in four Culicoides species. Despite the low overall number of specimens collected, a high diversity of biting midge species was recorded. These findings offer critical insights into Culicoides ecology and their interactions with hosts in urban settings, which are vital for disease surveillance and management strategies.

Vector-borne diseases pose a significant threat to human and animal health worldwide, with arthropods, including fleas and lice, acting as key vectors for transmitting various pathogens. In Uzbekistan, where millions of domestic dogs coexist with humans, the diversity of vector-borne pathogens carried by ectoparasites remains largely unexplored. This study aimed to investigate the diversity and prevalence of lice and pathogens carried by fleas and lice collected from domestic dogs in Uzbekistan. Ectoparasites were collected from 77 dogs across five regions and subjected to morphological identification and molecular analysis. The 47 lice collected were identified as Trichodectes canis Fabricius, 1780 (Psocodea: Trichodectidae), Linognathus africanus Kellogg and Paine, 1911 (Psocodea: Linognathidae) and Bovicola bovis Linnaeus, 1758 (Phthiraptera: Trichodectidae), alongside with 197 fleas. Notably, L. africanus was detected for the first time on dogs worldwide. Molecular screening detected Rickettsia spp. in 27.9% fleas and 44.7% lice, Dipylidium caninum Linnaeus, 1758 (Cyclophyllidea: Dipylidiidae) in 1.5% of fleas and Bartonella spp. in 0.5% of fleas. Sequencing confirmed Rickettsia asembonensisMaina et al., 2016 (Rickettsiales: Rickettsiaceae), Rickettsia helvetica Beati et al., 1993 (Rickettsiales: Rickettsiaceae), Rickettsia monacensis Simser et al., 2019 (Rickettsiales: Rickettsiaceae), D. caninum and Bartonella clarridgeiae Lawson and Collins, 1996 (Hyphomicrobiales: Bartonellaceae). These findings highlight the potential role of dogs as reservoirs for vector-borne pathogens and emphasises the need for further research to inform effective disease control strategies.

The cattle tick Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Ixodida, Ixodidae) is responsible for significant economic losses in bovine production in tropical and subtropical regions worldwide. Control of this tick predominantly involves the use of chemical acaricides; however, their indiscriminate use has led to the selection of resistant populations. A survey on tick populations was conducted in the state of Rio Grande do Sul, in Brazil, to assess the prevalence of multiple resistance to acaricides in cattle farms. Additionally, questionnaires were administered to identify potential risk factors associated with multiple resistance to acaricides. In total, 176 farms with a bovine population of ≥40 cattle were randomly assigned for tick sampling. The resistance to six acaricidal compounds was investigated by bioassays. A larval packet test was performed for amitraz, chlorpyrifos, cypermethrin, fipronil and ivermectin. Fluazuron was screened using an adult immersion test. Multiple resistance to acaricides (i.e., resistance to three or more compounds) was detected in 173 samples, representing 98% of the total samples. Among these samples, 125 (71%) showed resistance to all six compounds tested. Additionally, we classified the resistance intensity into four levels (I to IV) based on the quartile distribution of the bioassay data. Ten samples (6%) showed high and very high levels (III and IV) of resistance to all six compounds tested. Three variables were significantly associated with multiple resistance to the six acaricides tested: (i) use of injectable acaricides to control ticks, (ii) application of more than five acaricide treatments per year, and (iii) farms with larger herds (≥232 animals). These results regarding widespread resistance and the emergence of multiple resistance to acaricides ticks are alarming and highlight the significant challenge of tick control in southern Brazil.

In Mexico, Triatoma pallidipennis is a major vector of Trypanosoma cruzi, the causative agent of Chagas disease. Current efforts are focused on developing attractants to control these vectors, using volatile substances derived from vertebrate hosts or compounds known to attract hematophagous insects. However, the efficacy of these compounds in attracting parasite-infected triatomines remains to be evaluated. In this study, we assessed the attractant activity of octenol (1-octen-3-ol), nonanal and a mixture of odorants consisting of ammonium hydroxide, lactic acid and hexanoic acid (in a ratio of 1:0.2:0.4 respectively), at concentrations of 1, 10 and 100 ng on the N3, N4 and N5 nymphal stages of T. pallidipennis, both infected and non-infected with T. cruzi. We also evaluated the synergistic effect of the most effective compounds and doses. All experiments were performed in a laboratory using a Y-type glass olfactometer. We found that both infected and non-infected N3 and N4 nymphs were attracted to low doses of octenol, nonanal and the odorant mixture. Particularly noteworthy was the synergistic effect observed between the odorant mixture and nonanal, which significantly increased attraction of T. cruzi-infected individuals. These findings contribute to the development of baited traps utilising these compounds for monitoring triatomines in epidemiological studies or for mass trapping to control these vectors.

The ability to determine when ticks last fed and assign them to a specific feeding cohort is important in attempts to explain their population dynamics; the biochemical measurement of stored lipid, has been widely used for this purpose. However, when relating feeding history to behaviour or infection status, a non-destructive approach to its assessment would be of value and, to this end, previous studies have attempted to use morphometric indices. Within any instar, the sclerotised scutal components of the body will not vary with increasing starvation while the alloscutal components will, and the resulting ratio should provide a measure of time since feeding. Here, the aim was to determine whether such a morphological ratio (described here as the hunger index) changed predictably with starvation in Ixodes ricinus L. (Ixodida: Ixodidae). For this a cohort of 300 I. ricinus nymphs was collected from the field in February 2021 and starved in a humidified incubator at 15°C and 80% relative humidity (RH). Every 2 weeks, 50 nymphs selected at random were removed and killed by freezing; morphometric measurement was followed by the measurement of lipid using a standard spectrophotometric approach. Both hunger index and stored lipid changed significantly with increasing starvation and were positively correlated with each other. However, the change in morphometric ratio was relatively slight (11%) over 9 weeks and the variation was high. The data suggest therefore that morphological measurements could be used to provide, at best, only broad categorisation of the hunger status of individual I. ricinus ticks in the field.

Wildlife forensic science is a growing research field globally with application in criminal cases of illegal hunting requiring an estimate of time of death based on insect fauna. The techniques and procedures of forensic entomology acquired over the last 40 years, used in legal cases relating to human remains, can be adapted to decomposing wildlife. Research on carrion utilising the rate of development of insect immatures provides a biological clock from which a minimum post-mortem interval (minPMI) can be derived. The following study concerns 19 rhinoceros that were illegally killed and dehorned in the Republic of South Africa between 2014 and 2021. The paper details 74 samples of insect evidence collected from these rhinoceros remains from which an accurate estimate of their PMI was calculated. The specimens comprised 18 species from 12 families belonging to three insect orders. Many Dipteran and Coleopteran species were found on and around each carcass. The species of fly larvae (family Calliphoridae) used in each case to estimate the PMI are as follows: Chrysomya marginalis (Wiedemann) (13 cases), Chrysomya chloropyga (Wiedemann) (2 cases), Chrysomya albiceps (Wiedemann) (1 case) and Chrysomya megacephala (Fabricius) (1 case). Two species of Coleoptera from the family Dermestidae and Silphidae involved Dermestes maculatus (DeGeer) and Thanatophilus micans (Fabricius), respectively, also were involved in one PMI estimation each. The paper highlights opportunities for improving our global understanding of gaps in procedures and training related to wildlife criminal cases.

The Borrelia burgdorferi sensu lato (s.l.) complex includes a group of spirochete bacteria that are involved in transmission cycles with vertebrates and the ticks associated with them. Rodents play an essential role in the ecoepidemiology of Borrelia, acting as reservoirs for the bacteria and hosts for ticks. To identify potential reservoir vertebrate hosts of Borrelia spirochetes in Argentina, we conducted molecular analyses on tissues obtained from a population of Sigmodontinae rodents inhabiting the Delta and Parana Islands ecoregion. We report the presence of B. burgdorferi s.l. complex genotypes infecting Akodon azarae and Oxymycterus rufus in this ecoregion. Phylogenetic analysis revealed at least three flaB haplotypes related to 'Candidatus Borrelia paulista' and Borrelia sp. strain Pampa from Brazil and to several Borrelia haplotypes from Uruguay. Additionally, we identified different alleles of the plasmid-borne gene ospC in B. burgdorferi s.l. infecting A. azarae and Ox. rufus. The ospC allele present in Borrelia from Ox. rufus was also detected in Borrelia from Oligoryzomys mattogrossae, indicating the ability of Borrelia harbouring this ospC allele to infect multiple Sigmodontinae species, whereas the ospC allele from Borrelia infecting A. azarae represents a novel variant. Further research is needed to determine host specificity of ospC alleles present in South America.

We explored how the ratio of blood-feeding behaviour—nonfeeding, bird feeding (ornithophily) and mammal feeding (mammalophily)—and voltinism (univoltine and multivoltine) vary over a latitudinal gradient from Alaska to Florida. These two fixed species traits were divided into five mutually exclusive combinations of trait states—nonfeeding/univoltine, ornithophilic/univoltine, mammalophilic/univoltine, ornithophilic/multivoltine and mammalophilic/multivoltine—within each of three datasets (north, east and west). We found a significant association between location (north, east and west) and trait state, which was driven by the large percentage of nonfeeding females in the north. When this trait state was removed, no significant differences were found for the remaining trait states and locations. Although the distribution of trait states did not differ between east and west datasets, the distribution with relation to 1° changes in latitude within each of these datasets showed distinct differences. In the east, both ornithophilic/univoltine and mammalophilic/univoltine species significantly increased with latitude, in proportion to the total species present. In contrast, the proportion of mammalophilic/multivoltine species decreased as latitude increased. Ornithophilic/multivoltine species in the east and the trait states in the west did not show any significant relationship to latitude.