Medical and Veterinary Entomology最新文献

Defecation is one of the posterior-station transmission routes for pathogens in haematophagous insects. Culicoides peregrinus Kieffer and Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) are the proven vectors of many arboviruses, most importantly bluetongue virus, protozoa, and filarial nematodes of livestock. Duration of blood feeding and defecation vary according to species. Culicoides females take blood from their hosts to acquire additional protein to develop their eggs. This study investigates the bacterial communities in defecated contents and gut of the field-collected post-defecated females of C. peregrinus and C. oxystoma. To observe the defecation period and pathogenic bacteria in their defecated contents, engorged females of both species were investigated. The females were transferred to the glass vials containing moistened cotton beds at the bottom and kept in an environmental test chamber. The females defecated within 48 h of post-blood meal intake. The defecated contents discharged by C. peregrinus contained the following bacterial species: Bacillus cereus, Bacillus flexus, Enterococcus faecium, Proteus vulgaris, and C. oxystoma: B. cereus, E. faecium, and Alcaligenes faecalis. Bacillus cereus, B. flexus, Paenibacillus sp., E. faecium, A. faecalis, and Brevundimonas sp. were obtained from the gut of post-defecated females of C. peregrinus, and B. cereus, Lysinibacillus sp., and Paenibacillus sp. were identified from the gut contents of post-defecated females of C. oxystoma. Within the defecated contents, the following pathogenic bacteria, B. cereus, P. vulgaris, and A. faecalis, were detected, which raises the chances of zoonotic posterior transmission to their hosts that should be investigated.

The house fly (Musca domestica Linnaeus, 1758) has developed resistance to several pesticides, necessitating innovative approaches for effective control. This study explores the synergistic effects of benzyl alcohol (BA) on the toxicity of deltamethrin (D) against various life stages of M. domestica larvae, pupae and adults. Additionally, molecular docking analyses were conducted to investigate interactions with the acetylcholinesterase enzyme (AChE) and voltage-sensitive sodium channel (Vssc). Two formulations of deltamethrin were tested: deltamethrin + benzyl alcohol (DBA) mix (D 5% dissolved in ethyl alcohol, then mixed with BA at its LC₅₀ concentration) and DBA combination (D 5% dissolved directly in pure BA). In vitro testing revealed significant synergistic effects. For larvae, the LC₅₀ of deltamethrin alone was 0.95 mg/mL, while the DBA mix reduced it to 0.09 mg/mL, yielding a synergism factor of 10.56. For pupae, deltamethrin's LC₅₀ was 1.32 mg/mL, compared with 0.104 mg/mL for the DBA mix, with a synergism factor of 12.69. The DBA combination also exhibited notable toxicity, with LC₅₀ values of 0.14 mg/mL for larvae and 0.16 mg/mL for pupae, corresponding to synergism factors of 6.79 and 8.80, respectively. Against adult flies, the DBA mix and DBA combination demonstrated high fumigant toxicity, with LC₅₀ values of 0.08 mg/L and 0.09 mg/L air, respectively, and synergism factors of 9.31 and 8.11. Docking analyses showed that deltamethrin exhibited a strong binding affinity to AChE, forming two hydrogen bonds with Lys480 and a pi-sigma interaction with Met351. BA occupied a separate binding pocket in AChE, forming two hydrogen bonds with Met309 and Lys335. Both compounds demonstrated strong, distinct binding affinities, confirming their synergistic inhibition of AChE. Against Vssc, deltamethrin (ΔG = -5.90 kcal/mol) formed a pi-pi interaction with Phe78 and a hydrogen bond with Lys79, while BA (ΔG = -3.79 kcal/mol) interacted with a different pocket via hydrophobic interactions. These findings highlight the potential of combining BA with deltamethrin to overcome insecticide resistance in house fly populations, offering a promising strategy to enhance pest control effectiveness.

The monoxenous Ixodid tick Rhipicephalus microplus is an economically important pest infesting cattle populations worldwide. Apart from being a vector of various diseases, they cause substantial production losses. The control against this tick is mostly through chemical acaricides, which have been undermined by problems of resistance as well as toxic residues in the environment and living beings. In spite of the development of two commercial vaccines against the tick way back in the 1990s, the anticipated results were not recorded in field conditions. The search for vaccine antigens has led to the identification of subolesin, serpins, lipocains and proteoses showing protective immune response. The efficacy of these candidate antigens is mostly assessed by the mortality of adult and larval stages and effect on reproductive performance. Similarly, the use of plant extracts, nano encapsulation of plant extracts and entomopathogenic fungi have been widely subjected to in vitro and in vivo trials to offer a cost-effective and green solution to tick infestation. In recent years, the use of modern technologies like RNA interference, in silico docking and CRISPR technology have accelerated the identification of potent antigens and active fractions of plant extracts. Integrated tick management is a good option for the eradication of R. microplus. However, the integration of chemical and non-chemical control strategies still remains a challenge. The present review article is focused on the ongoing and emerging control strategies against the tick that will help researchers evolve a sustainable solution against R. microplus infestation.

Aedes aegypti L. (Diptera, Culicidae), the key vector of viral diseases to humans in the tropics, is susceptible to infection by entomopathogenic fungi. Self-grooming behaviour, which remains largely unstudied for mosquitoes, may possibly interfere with fungal infection through the cuticle. In this study, self-grooming by A. aegypti adults exposed to Metarhizium humberi Luz, Rocha & Delalibera 2019 (Hypocreales, Clavicipitaceae) conidia supplemented or not with micronized carnauba wax (MCW) led to a decrease of non-germinated conidia and of early germinative stages from their body surface up to 24 h after exposure to a fungus-treated surface. Self-grooming behaviours by adults distinctly showed increased low-level, spontaneous and stimulus-independent self-grooming after exposure to conidia with or without added MCW or only to MCW. The first pair of legs simultaneously scraped the proboscis, antennae and wings; in three separate actions, the third pair of legs scraped (a) each other, (b) the first and second legs and (c) the gonapophyses. Immediately after exposure, conidia, a conidial/MCW mixture or MCW (without fungus) was readily detectable on tarsi, tibias and femurs (especially of the first and second leg pairs), gonapophyses, proboscis, antennae and wings. In mobile adults, mean conidial numbers dropped approximately fivefold during the 24 h immediately after exposure, but especially during the first 6 h, regardless of the conidial preparation and then, to a lesser extent, in the remaining 18 h. For cold-immobilized adults, during the first day post-exposure, conidial losses were distinctly lower or insignificant. MCW neither increased the number nor enhanced the retention time of conidia on the cuticle during the time tested. These findings strengthen the importance of considering self-grooming of mosquitoes – particularly regarding A. aegypti, the vector examined here – when developing specific fungal formulations for use in biological control.

The Aedes aegypti mosquito is generally associated with arboviruses that cause yellow fever, dengue, zika and chikungunya. The most efficient way to control their populations is through application in breeding sites of highly toxic insecticides that can also impact non-target organisms and generate resistant populations. Therefore, the use of compounds is desirable. Morin hydrate has broad pharmacological applications based on its antioxidant potential, in addition to not having negative effects on mammals. Therefore, the objective of the present study was to investigate the effects of morin hydrate on A. aegypti survival, pupation rate, egg laying, triacylglycerol reserves and expression of proteins related to lipid metabolism 24 h after exposure of larvae. For this, rearing media containing A. aegypti larvae with different concentrations of morin hydrate were formulated to evaluate the lethal concentration. Calculation of the expected lethal concentrations showed LC₂₅ of 52.692 μM, LC₄₀ of 111.121 μM, LC₅₀ of 174.775 μM, LC₇₅ of 575.083 μM and LC₉₀ of 1685.936 μM. Twenty-four hours after treatment with morin hydrate, surviving larvae were transferred to morin-free water with food, and their pupation rate and fertility were evaluated. We observed that an increase in the concentration of morin hydrate induced a dose-dependent reduction in survival, doubled pupation time in survivors and reduced the number of eggs laid by treated females during the larval stage by approximately 30% at concentrations exceeding 100 μM. From this, the impact of 24 h on the triacylglycerol (TAG) stock was evaluated, in addition to evaluating the expression of proteins involved in lipid metabolism. Larvae 24 h after treatment with 100 μM morin showed a reduction in TAG reserves of approximately 17%, while at 175 μM, there was a reduction of more than 33% in stocks, and at 500 μM there was a reduction of 61%. Furthermore, the lipolytic proteins TAGL1 and HSL were upregulated, while the lipogenic proteins FAS1, DGAT1 and GPAT1 were downregulated. Insulin-like receptors were also downregulated, unlike AKHr, which was also upregulated. These data demonstrate that morin hydrate reduces the survival and fertility of A. aegypti by affecting its lipid metabolism. Morin hydrate did not exhibit toxicity toward non-target organisms, demonstrating interesting potential for the control of mosquito populations.

The Amblyomma cajennense (Fabricius) complex (Acari: Ixodidae) is represented by six species of hard ticks widely distributed from southern Texas in the United States to northern Argentina. Species within the complex feed on a variety of vertebrate hosts, primarily mammals, including humans. These ticks are the main vector of the bacterium Rickettsia rickettsii (Brumpt; Rickettsiales: Rickettsiaceae) and have been associated with the transmission of several arboviruses. In Colombia, one of the most ecologically diverse countries of the Neotropics, two species of the complex have been recorded with sympatric distribution in the northwestern part of the country: Amblyomma mixtum (Koch) and Amblyomma patinoi (Labruna, Nava & Beati). The latter is of medical importance as it has been confirmed as a competent vector of R. rickettsii in inter-Andean valleys of Colombia. Here, we assessed the current distribution of A. patinoi and predicted changes in its distribution over the century under different climate change scenarios. Additionally, we incorporated new records, delved deeper into the distribution of A. patinoi and interpreted model results using the climate classification and ecoregions for the Neotropical region. The results showed the presence of A. patinoi in 79 localities distributed across 34 municipalities and seven departments of the Caribbean and Andean regions of Colombia. In addition, new records were identified in two additional departments (Valle del Cauca and Caquetá) of the Andean and Amazon regions, as well as additional records in the department of Cundinamarca, especially in the inter-Andean Magdalena River basin. A. patinoi has been recorded in five ecoregions (Cauca Valley Dry Forests, Guajira-Barranquilla Moist Forests, Magdalena Valley Dry Forests and Magdalena-Urabá Moist Forests) and is associated with horses, cattle, dogs and humans. Its elevational range extends from 8 to 645 m a.s.l. in the Caribbean region and from 497 to 1712 m a.s.l. in the Andean region and inter-Andean valleys. The potential distribution models suggest that A. patinoi presents high climatic suitability in the Caribbean areas and inter-Andean valleys. Under climate change scenarios a possible expansion of the species distribution is observed in areas currently not recorded in the Neotropics, in countries such as Brazil, Peru and Venezuela. However, geographical conditions, such as elevation, could limit its distribution at higher elevations.

The aim of this study was to analyse the prevalence and distribution of Bartonella species in companion animals, wildlife and their associated fleas in different landscapes of the Atlantic Forest ecoregion of Argentina, and to analyse the phylogenetic relationships between the Bartonella species identified in this study in addition to those found in other regions available in GenBank. A total of 257 mammals, including rodents, opossums, dogs and cats, were examined to detect the presence of Bartonella in both fleas and host tissues. The study revealed the presence of Bartonella in rodent fleas (47.7%), opossum fleas (7.8%), rodent spleens (6.5%) and cat blood (10%). Analysis of 15 gltA gene fragments revealed the existence of at least three different genotypes and eight haplotypes. Genetic analysis has established a close association between Bartonella species from mammals and fleas in both the Atlantic Forest of Brazil and the Costanera Sur Reserve in Argentina. Bartonella henselae (Regnery et al.) Brenner et al. (Hyphomicrobiales: Bartonellaceae) was identified in three rodent species: Rattus rattus (L.; Muridae), Akodon montensis Thomas (Cricetidae) and Calomys tener Winge (Cricetidae). This marks the first report of B. henselae in R. rattus in Argentina, as well as the initial documentation of its association with A. montensis and C. tener. Additionally, Bartonella clarridgeiae Lawson and Collins (Hyphomicrobiales: Bartonellaceae) was identified in feline blood and in fleas from dogs and cats. These findings are particularly relevant in the context of areas undergoing deforestation, where interactions between wild and domestic hosts increase the risk of zoonotic disease transmission. A One Health approach is crucial to understand transmission dynamics and to address the challenges posed by fleas as infection amplifiers and spillover phenomena. These present significant challenges for public health and biodiversity conservation.

Parasite relationships are influenced by host size, behaviour, population density and location and can affect the ecological dynamics of their hosts. Urban environments provide new contexts for host–parasite interactions, often leading to changes in infection dynamics when compared with the natural environment. This study focuses on the relationship between five genera of haemoparasites (Anaplasma Theiler, Ehrlichia Moshkovski, Hepatozoon Miller, haemotropic Mycoplasma Nowak and Neorickettsia Philip) found in the South American coati Nasua nasua Linnaeus (Carnivora: Procyonidae), a carnivore highly adaptable to urban areas. Here, we used network analysis to verify the interaction between N. nasua and haemoparasites. We also used a General Linear Model to investigate the influence of biotic and abiotic variables and haemoparasite infections on the functional roles of N. nasua individuals, considering weight, age, sex and tick infestation (number of immature ticks collected). The network revealed low modularity, and none of the biotic variables, immature stages of ticks and location of sampling had any influence on the functional role of N. nasua. The most important haemoparasite in the network was haemotropic Mycoplasma, identified as a key non-hub connector, probably spreading efficiently through frequent agonistic social interactions from N. nasua. These findings underscore the complex interplay between host behaviour, environmental factors and parasite ecology in urban environments, offering insights into managing urban wildlife diseases.

The spread of the West Nile (WNV) and Usutu (USUV) flaviviruses in Europe in recent decades highlights the urgent need to understand the transmission networks of these pathogens as a basis for effective decision-making. These viruses are part of a complex disease cycle that involves birds as principal hosts and humans and horses as dead-end hosts. Our study aims to uncover the intricate relationships between the main mosquito vector of these viruses, Culex pipiens L. (Diptera: Culicidae) and its feeding preferences based on the forage ratio among several host species, primarily birds in a land-use gradient. We estimated the bird host potential to act as a host for flavivirus, the reservoir capacity index, based on forage ratios and potential host competence based on molecular prevalence. We sampled mosquitoes and, at the same time, conducted bird censuses in the Camargue region in southern France, where co-circulation of these viruses has been reported. Several localities were sampled along a land-use gradient in peri-urban, agricultural and natural areas from May to November 2021. We identified 55 vertebrate species in 110 engorged Cx. pipiens by PCR amplification and sequencing of mitochondrial 12S and 16S Ribosomal DNA genes. Culex pipiens feeds primarily on 51 bird species and secondarily on two mammals, one amphibian and one reptile. Based on forage ratios, we found a preference of Cx. pipiens in the Camargue for the order Passeriformes and, more specifically, for Columba livia domestica L. (Columbiformes: Columbidae) in agricultural areas, and for Passer domesticus/montanus L. (Passeriformes: Passeridae), in agricultural and peri-urban areas. The natural habitats had significantly higher forage ratio values than agricultural and peri-urban areas. We suggest that certain key species, such as Passer sp., Columba livia and Turdus sp., might be potentially considered locally relevant hosts for transmission in this area, as they are important for mosquito feeding and also potentially important hosts for flavivirus amplification. These data will be beneficial in understanding host–vector interactions and the relationships between bird communities, mosquito feeding preferences and emerging mosquito-borne diseases.

We studied geographic patterns of functional and phylogenetic niche breadth of 194 flea species. Niche breadth was measured as the functional and phylogenetic diversity and uniqueness of the assemblages of small mammal hosts exploited by these fleas.We asked (a) whether the relationships between niche breadth and geographic range size conform to the ‘niche breadth hypothesis’, predicting positive correlations, and (b) whether variation of niche breadth along the latitudinal position of geographic range conforms to the ‘niche breadth-latitude hypothesis’, predicting narrower niche breadth at lower latitudes. We found that the functional and phylogenetic diversity, but not the functional and phylogenetic uniqueness, of the host assemblages demonstrated patterns conforming to the prediction of the ‘niche breadth hypothesis’. Host assemblages exploited by broadly distributed fleas tended to be functionally and phylogenetically more diverse than those of fleas with a restricted geographic distribution, but the functional and phylogenetic uniqueness of hosts decreased in more broadly distributed fleas. The phylogenetic diversity of hosts exploited by a flea did not vary with the latitudinal position of the flea's geographic range. In contrast, the functional diversity and both the functional and phylogenetic uniqueness of hosts decreased from south to north, thus contradicting the predictions of ‘the niche breadth-latitude hypothesis’. Comparing these and earlier results on the geographic patterns of flea niche breadth, we conclude (a) that compositional, functional and phylogenetic diversity could be similarly driven by some factors and differently by other factors and (b) that these diversity facets are not always good surrogates for each other.