{"title":"What happens when the insecticide does not kill? A review of sublethal toxicology and insecticide resistance in triatomines.","authors":"Gastón Mougabure-Cueto, Georgina Fronza, Julieta Nattero","doi":"10.1111/mve.12753","DOIUrl":"https://doi.org/10.1111/mve.12753","url":null,"abstract":"<p><p>Chagas disease is considered one of the most important human parasitosis in the United States. This disease is mainly transmitted by insects of the subfamily Triatominae. The chemical vector control is the main tool for reducing the incidence of the disease. However, the presence of triatomines after pyrethroids spraying has been reported in some regions, as in the case of Triatoma infestans in Argentina and Bolivia. The presence of insects can be explained by the colonization from neighbouring areas, the reduction of insecticide dose to sublethal levels due to environmental factors, and/or by the evolution of insecticide resistance. In the last two scenarios, a proportion of the insects is not killed by insecticide and gives rise to residual populations. This article focuses on the toxicological processes associated with these scenarios in triatomines. Sublethal doses may have different effects on insect biology, that is, sublethal effects, which may contribute to the control. In addition, for insect disease vectors, sublethal doses could have negative effects on disease transmission. The study of sublethal effects in triatomines has focused primarily on the sequence of symptoms associated with nervous intoxication. However, the effects of sublethal doses on excretion, reproduction and morphology have also been studied. Rhodnius prolixus and T. infestans and pyrethroids insecticides were the triatomine species and insecticides, respectively, mainly studied. Insecticide resistance is an evolutionary phenomenon in which the insecticide acts as a selective force, concentrating on the insect population's pre-existing traits that confer resistance. This leads to a reduction in the susceptibility to the insecticide, which was previously effective in controlling this species. The evolution of resistance in triatomines received little attention before the 2000s, but after the detection of the first focus of resistance associated with chemical control failures in T. infestans from Argentina in 2002, the study of resistance increased remarkably. A significant number of works have studied the geographical distribution, the resistance mechanisms, the biological modifications associated with resistance, the environmental influences and the genetic of T. infestans resistant to pyrethroid insecticides. Currently, studies of insecticide resistance are gradually being extended to other areas and other species. The aim of this article was to review the knowledge on both phenomena (sublethal effects and insecticide resistance) in triatomines. For a better understanding of this article, some concepts and processes related to insect-insecticide interactions, individual and population toxicology and evolutionary biology are briefly reviewed. Finally, possible future lines of research in triatomine toxicology are discussed.</p>","PeriodicalId":18350,"journal":{"name":"Medical and Veterinary Entomology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142017932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Isolation and comparative analysis of culturable bacterial communities associated with life stages, breeding and rearing substrates of Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) vector of bluetongue virus","authors":"Ankita Sarkar, Paramita Banerjee, Abhijit Mazumdar","doi":"10.1111/mve.12754","DOIUrl":"10.1111/mve.12754","url":null,"abstract":"<p><i>Culicoides oxystoma</i> Kieffer (Diptera: Ceratopogonidae) has been vectoring several arboviruses, protozoa and nematodes, leading to mortality and morbidity of livestock and wild ruminants in the tropics and subtropics. Insight into the bacterial communities associated with the vector species must be worked out. This work tries to inventorize the bacterial communities associated with this important vector species. Acquisition of gut microbiota may be the parental origin, while some are obtained through feeding during larval stages. <i>Culicoides oxystoma</i> possesses semi-aquatic life cycle strategies for egg-laying and larval survival. The bacteria associated with <i>C. oxystoma</i> were compared throughout (i) life stages: egg, larval instars, pupa, adult: male and female obtained from laboratory colony; (ii) field-collected adult: male and age-graded females; and (iii) natural breeding substrate and artificial rearing substrate. The culture-dependent bacteria were identified by Sanger sequencing of 16S rRNA, and haemolytic bacteria were screened on blood agar. Results show that Firmicutes and Proteobacteria are the predominant Phyla, of which <i>Bacillus</i> spp. was the most abundant across the life stages. Across the life history, <i>Bacillus cereus</i>, <i>Bacillus pumilus</i>, <i>Bacillus tropicus</i>, <i>Lysinibacillus</i> sp. and <i>Paenibacillus</i> sp. were retrieved routinely. <i>Bacillus cereus</i> and <i>Alcaligenes faecalis</i> were detected in the lab-reared specimens and shared between the natural breeding site and rearing medium. From the adults trapped across two locations, <i>B. cereus</i>, <i>Bacillus flexus</i>, <i>A. faecalis</i>, <i>Enterococcus faecium</i> and <i>Pseudomonas</i> sp. were isolated. The bacterial species associated with this vector may influence various physiological traits, such as vectorial capacity, digestion and larval development, which need further investigation.</p>","PeriodicalId":18350,"journal":{"name":"Medical and Veterinary Entomology","volume":"38 4","pages":"542-551"},"PeriodicalIF":1.9,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142017931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Survival of Calliphora vicina (Diptera: Calliphoridae) embryos under cold temperature conditions: forensic implications","authors":"Jaime López-García, Daniel Martín-Vega","doi":"10.1111/mve.12749","DOIUrl":"10.1111/mve.12749","url":null,"abstract":"<p>Most blow flies (Diptera: Calliphoridae) species are sarcosaprophagous during the larval stage, primarily feeding on the soft tissues of carcasses during the early stages of decomposition, making them valuable forensic indicators for minimum post-mortem interval (minPMI) estimations. Like other insects, their developmental rates are strongly influenced by the environmental temperature. Although several studies have examined the influence of temperature on the development of different blow fly species, the impact of cold temperatures remains largely unstudied, despite its potential forensic implications. The present study investigates the effect of three cold temperatures (0, −2.5 and −5°C) on the survival of <i>Calliphora vicina</i> embryos of five different ages (0%, 20%, 40%, 60% and 80% of the total embryonic development) and two exposure times (6 and 24 h). Our results revealed significant differences in egg survival at the earliest embryonic stages (0% and 20% of the total embryonic development), resulting in high mortality rates. While at 20% of the total embryonic development high mortality was only observed under −5°C, at 0% of the total embryonic development high mortality rates were observed at all the temperatures tested. Although <i>C. vicina</i> embryos demonstrate tolerance to cold temperatures once they have completed the first 20% of the total embryonic development, potentially mitigating the impact of cold weather events, the possibility of minPMI underestimations due to the death of the first egg batches should not be disregarded. Additionally, considering that the embryonic development stages may last for several days under low temperatures, caution should be taken in the analysis of entomological evidence if a cadaver is discovered following cold weather episodes.</p>","PeriodicalId":18350,"journal":{"name":"Medical and Veterinary Entomology","volume":"39 1","pages":"33-40"},"PeriodicalIF":1.9,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/mve.12749","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142004540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Culicoides biting midges feeding behaviour as a key for understanding avian Haemoproteus transmission in Lithuania","authors":"Margarita Kazak, Kristina Valavičiūtė-Pocienė, Simona Kondrotaitė, Mélanie Duc, Dovilė Bukauskaitė, Carolina Hernández-Lara, Rasa Bernotienė, Carolina Romeiro Fernandes Chagas","doi":"10.1111/mve.12752","DOIUrl":"10.1111/mve.12752","url":null,"abstract":"<p>Investigations of host feeding behaviour in haematophagous insects are critical to assess transmission routes of vector-borne diseases. Understanding if a certain species has ornithophilic or mammalophilic feeding behaviour can facilitate future studies focused on pathogens transmission to and from certain host species. <i>Culicoides</i> Latreille (Diptera: Ceratopogonidae) are vectors of several pathogens, which include arboviruses, bacteria and parasites to a considerable diversity of vertebrate hosts. However, most of the studies focused on feeding habits target <i>Culicoides</i> species that could transmit the Bluetongue virus, consequently with a mammalophilic feeding behaviour, leaving aside the <i>Culicoides</i> species that are involved in the transmission of vector-borne parasites to birds, such as <i>Haemoproteus</i> Kruse (Haemosporida: Haemoproteidae). This study aimed to investigate the source of blood meals of wild-caught <i>Culicoides</i> using molecular-based methods and to correlate our findings with the reports of <i>Haemoproteus</i> parasites in <i>Culicoides</i> species. Engorged <i>Culicoides</i> females were collected using ultraviolet (UV)-light traps at seven different localities in Lithuania in 2021–2023. Biting midges were dissected, and the abdomens of engorged females were used for molecular investigation of the blood meal source. A polymerase chain reaction (PCR) protocol that amplifies a fragment of the <i>Cytochrome B</i> gene of vertebrates was used. Obtained sequences were compared to available information in GenBank database to confirm the source of the blood meal. In total, 258 engorged <i>Culicoides</i> females, representing nine different species, were analysed. The source of blood meal was identified in 29.1% of them with most of the insects having fed on birds (74.7%) and the remaining on mammals (25.3%). <i>Culicoides segnis</i> Campbell, Pelham-Clinton was the only species to feed exclusively on birds; <i>Culicoides</i> from the Obsoletus group, <i>C. pallidicornis</i> Kieffer and <i>C. punctatus</i> Latreille were found to feed exclusively on mammals; <i>C. festivipennis</i> Kieffer, <i>C. kibunensis</i> Tokunaga and <i>C. pictipennis</i> Staeger had an opportunistic feeding behaviour, with the first two preferably feeding on birds. Due to their feeding behaviour and the presence of <i>Haemoproteus</i> parasites reported in the literature, <i>C. festivipennis</i>, <i>C. kibunensis</i>, <i>C. pictipennis,</i> and <i>C. segnis</i> play an important role in the transmission of those avian vector-borne parasite in the wild. These <i>Culicoides</i> species were already confirmed as being able to support the development of several <i>Haemoproteus</i> species and lineages. Future studies focused on understanding the epidemiology of avian pathogens transmitted by <i>Culicoides</i> should target these species.</p>","PeriodicalId":18350,"journal":{"name":"Medical and Veterinary Entomology","volume":"38 4","pages":"530-541"},"PeriodicalIF":1.9,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141988238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Melissa Florencio, Francisco Romulo Oilveira Magalhães, Aline Araujo Zuma, Cinara Lima Oliveira Lugathe, Dayana Rosa, Karina Riguete, Maria Cristina Machado Motta, Aparecida Alves do Nascimento, Jacenir Reis dos Santos Mallet, Georgia Correa Atella, Patrícia Fampa
{"title":"Morphological analysis and lipid composition of the stable fly Stomoxys calcitrans salivary glands reinforce important features of feeding behaviour\u0000 Análises morfológicas e composição lipídica das glândulas salivares de Stomoxys calcitrans, a mosca-dos-estábulos, reforçam importantes características de seu comportamento alimentar","authors":"Melissa Florencio, Francisco Romulo Oilveira Magalhães, Aline Araujo Zuma, Cinara Lima Oliveira Lugathe, Dayana Rosa, Karina Riguete, Maria Cristina Machado Motta, Aparecida Alves do Nascimento, Jacenir Reis dos Santos Mallet, Georgia Correa Atella, Patrícia Fampa","doi":"10.1111/mve.12751","DOIUrl":"10.1111/mve.12751","url":null,"abstract":"<p><i>Stomoxys calcitrans</i> L. (Diptera: Muscidae), the stable fly, is a hematophagous insect of great veterinary importance, because it is a mechanical vector of diverse pathogens in livestock. The saliva of blood-feeding insects presents important pharmacologically active molecules that impair blood clotting, promote vasodilation and modulate the host immune system response, crucial processes for successful feeding. These properties also enable pathogens' transmission. In the present work, we describe an efficient protocol to dissect <i>S. calcitrans</i> salivary glands, their morphological characteristics and lipid profile. The mean length of the tubular gland is 3.23 mm with a bulbous posterior end and a narrow anterior end. Histological analysis revealed a monolayer of large polygonal epithelial cells with voluminous nuclei and high lipid content in their cytoplasm. Ultrastructural analysis showed that the epithelium is rich in mitochondria, free ribosomes, Golgi complex cisternae, presenting a great extension of rough endoplasmic reticulum that contains an electron-dense material. Lipid analysis by thin-layer chromatography showed that neutral fatty acids and phosphatidylcholine are predominant in the fly salivary glands. Lysophosphatidylcholine, an important signalling biomolecule involved in different metabolic processes, including host's immunomodulation and pathogens proliferation and differentiation, is also present.</p>","PeriodicalId":18350,"journal":{"name":"Medical and Veterinary Entomology","volume":"38 4","pages":"508-517"},"PeriodicalIF":1.9,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141976068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}