Medical and Veterinary Entomology最新文献

Pyrethroid-resistance is an emergent trait in populations of various insect species. For Triatoma infestans (Klug, 1834) (Heteroptera: Reduviidae), the major vector of Chagas disease in the southern part of South America, hotspot areas of pyrethroid-resistance have recently been found in the Chaco Province of Argentina. Resistant condition can reduce fitness of individuals in the absence of insecticide exposure, that is, fitness costs. We evaluated the existence of developmental and/or reproductive costs in T. infestans collected from two areas of pyrethroid-resistance in Chaco Province, Argentina. Three toxicological groups were defined from field-collected insects: susceptible (survival <20%), moderately resistant (survival between 20% and 80%) and highly resistant (survival >80%). Cohorts of the three toxicological groups were followed-up to study life cycle and reproductive parameters. Additionally, we parameterized matrix population growth models. First and IV nymphal stages of the resistant groups exhibited a longer stage duration than susceptible ones. The reproductive days and hatching success showed significant lower values revealing reproductive costs for the resistant groups. Matrix analysis showed lower population growth rates for the resistant groups. Our results support developmental and reproductive costs for pyrethroid-resistant individuals. This trait could be interpreted as lower population recovery ability for pyrethroid-resistant individuals compared to susceptible insects after alternative vector control actions.

Sand flies have expanded their areas of distribution, thereby increasing the risk of pathogen transmission in non-endemic areas. To establish efficient prevention and control strategies for the transmission of vector-borne pathogens, it is important to understand seasonal dynamics of their vectors. In Mexico, there are several areas where the contact between sand flies, hosts and reservoirs favours the transmission of the pathogen. We compared sand fly communities in a forest management area and a conserved area in Noh-Bec, Quintana Roo, Mexico. The analysis included species diversity, activity peaks and molecular detection of pathogens. Sand flies were collected from November to December 2021 and April to May 2022, during 84 night-traps. The conserved area showed higher numbers and greater species heterogeneity of sand flies as compared with the other sites. The β-diversity analysis revealed that sites disturbed by logging (S1, S2, S3) had greater similarity (90%) in their sand fly species composition than a conserved area (S4) (similarity = 36%). Although none of the specimens were infected with Leishmania, we detected Wolbachia (19.4%) in all four sites, as well as Bartonella (3.25%) only in the disturbed sites. Further studies on the dynamics of sand fly populations and their association with pathogens are necessary.

Sand flies (Diptera: Psychodidae, Phlebotominae; Newstead, 1911) are widespread in Europe, being particularly common in the Mediterranean region but rare north of the Alps. Thus, Switzerland is an opportune place to investigate the sand fly fauna on both sides of the Alpine crest, in southern sub-Mediterranean climate and northern oceanic temperate climate. We reinvestigated the Swiss sand fly fauna with the aim to assess changes in composition, altitudinal distribution, abundance and seasonality. Thirty-eight sites were investigated with light traps and/or interception sticky traps in 4 years. Ninety and 380 specimens were caught by light traps and sticky traps, respectively, at 15 collecting sites. Four species were identified. Phlebotomus mascittii (Grassi, 1908), Phlebotomus perniciosus (Newstead, 1911) and Sergentomyia minuta (Rondani, 1843) were confirmed in Ticino, and P. mascittii for the first time in neighbouring Grisons. Also, Phlebotomus neglectus (Tonnoir, 1921) is for the first time reported, though at a very low density compared to P. perniciosus at the same site. Its presence in Ticino supports the northward spread observed in Italy. Sand flies were detected north of the Alps at one site only, endorsing a historical report. Overall, the low density of P. perniciosus and very low density of P. neglectus suggest that canine leishmaniosis may not be an important disease risk in Switzerland.

Aedes koreicus Edwards, 1917 (Hulecoetomyia koreica) is a mosquito (Diptera: Culicidae) from Northeast Asia with a rapidly expanding presence outside its original native range. Over the years, the species has been discovered in several new countries, either spreading after first introduction or remaining localised to limited areas. Notably, recent studies have demonstrated the ability of the species to transmit zoonotic parasites and viruses both in the field and in laboratory settings. Combined with its invasive potential, the possible role of Ae. koreicus in pathogen transmission highlights the public health risks resulting from its invasion. In this study, we used a recently established population from Italy to investigate aspects of biology that influence reproductive success in Ae. koreicus: autogeny, mating behaviour, mating disruption by the sympatric invasive species Aedes albopictus Skuse, 1894, and the presence of the endosymbiont Wolbachia pipientis Hertig, 1936. Our laboratory population did not exhibit autogenic behaviour and required a bloodmeal to complete its ovarian cycle. When we exposed Ae. koreicus females to males of Ae. albopictus, we observed repeated attempts at insemination and an aggressive, disruptive mating behaviour initiated by male Ae. albopictus. Despite this, no sperm was identified in Ae. koreicus spermathecae. Wolbachia, an endosymbiotic bacterium capable of influencing mosquito reproductive behaviour, was not detected in this Ae. koreicus population and, therefore, had no effect on Ae. koreicus reproduction.

Lucilia sericata is one of the most studied species in forensic entomology due to its widespread distribution, forensic importance as well as medical use. The growth and development stage of maggots is often used to determine the post-mortem interval in forensic cases. L. sericata can cause myiasis in humans who are not able to maintain personal hygiene due to age or medical condition and can therefore be used to determine the time period of neglect. The influence of the temperature on the maggot development has been examined in various studies. Different examinations on the effects of toxic substances on the maggot development and survival have been conducted in order to test the influence and resulting deviations. In this study, the effects of different therapeutical doses of the antibiotics ceftriaxone and levofloxacin were examined on L. sericata in order to determine and compare deviations in maggot development and survival. The used antibiotics did not significantly influence the maggot weight and length. A significant delay in the time of pupation has been determined in the treatments with high concentrations of levofloxacin. The mortality was significantly increased in all treatments with antibiotics compared to the control, whereby the survivability of all treatments remained over 80%. Because of the high doses needed to produce an effect, we concluded that an overestimation of the post-mortem interval is unlikely but higher antibiotic concentrations or possible interactions with other medications could increase the maggot development time.

Ticks are efficient vectors for transmitting pathogens that negatively affect livestock production and pose a risk to public health. In this study, Babesia and Theileria species were identified in ticks collected from cattle, sheep and goats from the Kassena-Nankana Districts of Ghana between February and December 2020. A total of 1550 ticks were collected, morphologically identified, pooled and screened for pathogens using primers that amplify a 560 bp fragment of the ssrRNA gene and Sanger sequencing. Amblyomma variegatum (62.98%) was the predominant tick species. From the 491 tick pools screened, 12/15 (2.44%) positive pools were successfully sequenced. The pathogen DNA identified were Theileria ovis in eight (15.38%) pools of Rhipicephalus evertsi evertsi, Theileria velifera in two (0.78%) pools of A. variegatum and Babesia occultans and Babesia sp. Xinjiang in one (1.72%) pool each of Hyalomma truncatum. It was further observed that T. ovis occurred in ticks collected from only sheep (p < 0.001) which were females (p = 0.023) and < =1 year old (p = 0.040). This study reports the first identification of these pathogens in ticks within Kassena-Nankana. With the constant trade of livestock, there is a need for effective tick control measures to prevent infection spread.

Targeted vector surveillance informed by data on mosquito biting patterns can help limit arboviral zoonotic diseases. To characterise host-biting networks in rural and urban equestrian facilities from temperate Argentina, adult resting mosquitoes were collected (December 2018–April 2019) with a battery-powered aspirator. Engorged females were sorted to species, and their blood source was identified using molecular techniques. Bipartite network analysis was performed for rural and urban matrices. A total of 177 bloodmeals from 11 mosquito species of Aedes and Culex were identified, with seven mammal and 17 bird species recognised as hosts. Mammals represented 61% of the total feeds, mainly horse, dog and sheep; the best represented avian hosts were Columbiformes. Aedes species and Culex maxi fed only on mammals, while most other Culex species presented a wide range of hosts. The rural network had more nodes and interactions than its urban counterpart, both with some degree of host selection and aggregated patterns according to network indices. Culex quinquefasciatus was the strongest species in both networks, whereas Culex apicinus and Culex dolosus had a prominent role in the rural network. Bipartite network analysis will contribute to understanding the effects of urbanisation in the dynamics of vector-borne diseases.

In Argentina, the distribution of Aedes albopictus (Skuse) is limited to two provinces with a subtropical climate and few records. This study aims to describe and compare assemblies of Culicidae that breed in artificial containers in two areas with different degrees of urbanisation where Ae. albopictus is present and to evaluate possible biotic interactions. We sampled container larval habitats of an urban (Eldorado city) and a rural environment (Colonia Aurora village). We performed generalized linear mixed models to evaluate which variables (containers characteristics or environment) are associated with the presence and abundance of Ae. albopictus, Aedes aegypti Linneaus and Culex quinquefasciatus Say, and the presence of mosquito predators (Lutzia bigoti (Bellardi) and Toxorhynchites spp.). Also, the relationship between the most abundant species was quantified in each environment using Hurlbert's C8 association coefficient. Ae. aegypti was the most abundant species in the urban environment, while Cx. quinquefasciatus and Ae. albopictus were the most abundant in the rural area. Predators were more present in the rural environment and affected the abundance of Aedes mosquitoes. Regarding the C8 index, Ae. aegypti was negatively associated with Ae. albopictus in the urban area, whereas in the rural area these species presented a significantly positive relationship. These results show that in urban environments the high abundance of Ae. aegypti could be affecting the Asian tiger mosquito as evidenced by local studies of food larval competition. Also a greater presence of predators could be affecting Ae. albopictus in rural environments.

Visceral leishmaniasis (VL, kala azar), caused by Leishmania donovani, transmitted by Phlebotomus orientalis, is a serious systemic disease that causes high morbidity and mortality rates in Sudan and other parts of East Africa and the world. Despite progress in understanding the epidemiology of the disease in East Africa, little is known about the host preference of P. orientalis in kala azar endemic villages of Sudan, which have some of the highest VL incidence rates in the world. The present study used host choice experiments and blood-meal identification approaches to determine the host preference of P. orientalis in kala azar endemic villages in Gedarif state, eastern Sudan. In the host choice experiment, tent traps were used to compare the attractiveness of cows, donkeys, sheep and goats for host-seeking P. orientalis. In the blood-meal identification study, blood-fed P. orientalis females, captured inside houses and peri-domestic habitats, were subjected to molecular typing using cytochrome b gene (cyt b) amplification and sequence analysis. Cows and donkeys were the most attractive to blood-seeking P. orientalis, followed by goats. Similarly, the blood-meal analysis of P. orientalis showed that the vector preferentially feeds on cows, followed by donkeys, humans and goats. The human blood index of P. orientalis was 19.4% (42/216), indicating a high zoophilic habit of the vector, both inside and outside the houses. Although the order of host preference varied by location, it was clear that cows are the most preferred host of P. orientalis in the area. Results are discussed in relation to the role of domestic/livestock animals in VL zoopotentiation and zooprophylaxis. Inference is made on the potential impact of insecticide treatment of cows in control of the vector and the transmission of VL in Sudan and other parts of East Africa.

In medical, veterinary and forensic entomology, the ease and affordability of image data acquisition have resulted in whole-image analysis becoming an invaluable approach for species identification. Krawtchouk moment invariants are a classical mathematical transformation that can extract local features from an image, thus allowing subtle species-specific biological variations to be accentuated for subsequent analyses. We extracted Krawtchouk moment invariant features from binarised wing images of 759 male fly specimens from the Calliphoridae, Sarcophagidae and Muscidae families (13 species and a species variant). Subsequently, we trained the Generalized, Unbiased, Interaction Detection and Estimation random forests classifier using linear discriminants derived from these features and inferred the species identity of specimens from the test samples. Fivefold cross-validation results show a 98.56 ± 0.38% (standard error) mean identification accuracy at the family level and a 91.04 ± 1.33% mean identification accuracy at the species level. The mean F1-score of 0.89 ± 0.02 reflects good balance of precision and recall properties of the model. The present study consolidates findings from previous small pilot studies of the usefulness of wing venation patterns for inferring species identities. Thus, the stage is set for the development of a mature data analytic ecosystem for routine computer image-based identification of fly species that are of medical, veterinary and forensic importance.