Screening of olfactory genes related to blood-feeding behaviors in Culex pipiens quinquefasciatus and Culex pipiens molestus by transcriptome analysis

The antennal transcriptome of Triatoma infestans reveals substantial expression changes triggered by a blood meal

BACKGROUND

Triatoma infestans is the main vector of Chagas disease in the Americas, currently transmitting it in Argentina, Paraguay, and Bolivia. Many T. infestans populations present insecticide resistance, reducing the efficiency of control campaigns. Alternative vector control methods are needed, and molecular targets mediating fundamental physiological processes can be a promising option to manipulate kissing bug behavior. Therefore, it is necessary to characterize the main sensory targets, as well as to determine whether they are modulated by physiological factors. In order to identify gene candidates potentially mediating host cue detection, the antennal transcripts of T. infestans fifth instar larvae were sequenced and assembled. Besides, we evaluated whether a blood meal had an effect on transcriptional profiles, as responsiveness to host-emitted sensory cues depends on bug starvation.

RESULTS

The sensory-related gene families of T. infestans were annotated (127 odorant receptors, 38 ionotropic receptors, 11 gustatory receptors, 41 odorant binding proteins, and 25 chemosensory proteins, among others) and compared to those of several other hemipterans, including four triatomine species. Several triatomine-specific lineages representing sensory adaptations developed through the evolution of these blood-feeding heteropterans were identified. As well, we report here various conserved sensory gene orthogroups shared by heteropterans. The absence of the thermosensor pyrexia, of pickpocket receptor subfamilies IV and VII, together with clearly expanded takeout repertoires, are revealed features of the molecular bases of heteropteran antennal physiology. Finally, out of 2,122 genes whose antennal expression was significantly altered by the ingestion of a blood meal, a set of 41 T. infestans sensory-related genes (9 up-regulated; 32 down-regulated) was detected.

CONCLUSIONS

We propose that the set of genes presenting nutritionally-triggered modulation on their expression represent candidates to mediate triatomine host-seeking behavior. Besides, the triatomine-specific gene lineages found represent molecular adaptations to their risky natural history that involves stealing blood from an enormously diverse set of vertebrates. Heteropteran gene orthogroups identified may represent unknown features of the sensory specificities of this largest group of hemipteroids. Our work is the first molecular characterization of the peripheral modulation of sensory processes in a non-dipteran vector of human disease.

Oral feeding skills in premature infants: A concept analysis

Background

The delay in developing oral feeding skills becomes a problem experienced by premature infants. One of the reasons for the delay may be related to inconsistent definitions of oral feeding skills, which can cause discrepancies in the provision of nursing care.

Objective

This study aimed to clarify the concept of oral feeding skills in premature infants.

Methods

The Walker and Avant concept analysis method was used. A literature search was also conducted from five databases: CINAHL, PubMed, ProQuest, EMBASE, and Google Scholar, to find articles between January 2020 and December 2022.

Results

The literature search obtained 20 articles on oral feeding skills from various disciplines. Five attributes were developed from the concept analysis, including (1) coordination ability to suck, swallow, and breathe, (2) the ability to regulate oral-motor functions, (3) the ability to regulate sensory functions, (4) the ability to maintain the stability of physiology function, and (5) the ability to regulate feeding behavior. Antecedents to oral feeding skills include immaturity of the nervous system, gestational age, feeding intolerance, increased length of stay and cost of care, increased rehospitalization, stress on parents, and increased morbidity and mortality. Consequences include optimization of growth and development, reduction of length of stay and cost of hospitalization, increased bonding attachment, increased self-efficacy of parents in caring for premature infants, and improvement of the quality of life of premature infants.

Conclusion

The concept analysis provides five comprehensive attributes and their antecedents and consequences. However, this concept can be used to provide nursing care to premature infants, assess the criteria for discharge, and optimize nutrition for the growth and development of premature infants.

The chemical code for attracting Culex mosquitoes

Mosquitoes use chemical codes to locate and discriminate among vertebrate hosts to obtain a blood meal. Recent advances have allowed for the identification of the chemical codes used by mosquitoes to locate and discriminate humans from other vertebrate hosts. Humans are incidental “dead-end” hosts for the West Nile virus, which is maintained in an enzootic cycle, primarily through its transmission between infected birds by Culex mosquitoes. Host-seeking Culex mosquitoes are attracted to the odor of chicken, which are used in sentinel traps to monitor West Nile virus transmission. Using combined gas chromatography and electroantennography and mass spectrometry we identify a blend of volatile organic compounds present in chicken emanates, including mostly salient bioactive compounds previously identified in human emanates. When released at their identified ratios, this blend elicits behavioral responses of Culex pipiens molestus and Culex quinquefasciatus similar to that to the natural chicken odor. Tested under field conditions, this blend attract Culex spp. and other species of mosquitoes using birds among their hosts. This study provides evidence for conserved chemical codes for resource location by mosquitoes, and highlights the intricate role of CO2 for host-seeking mosquitoes. The identification of conserved chemical codes, which drive innate preference behaviors that are fundamental for survival and reproduction, provides important substrates for future control interventions targeting disease vector mosquitoes.

Elevated expression of odorant receptors and odorant-binding proteins genes detected in antennae of Culex quinquefasciatus field females

Culex quinquefasciatus is responsible for the transmission of filarial worms and several arboviruses. Olfaction plays a crucial role in disease transmission as it influences behaviors that are essential for the survival and reproduction of the mosquito, such as the host-seeking behavior, courtship, and oviposition. Understanding the molecular events that coordinate how mosquitoes find their host may lead to alternative methods to reduce diseases transmission. Our aim was to investigate the differential expression profile of odorant receptor (ORs) and odorant-binding proteins (OBPs) genes in Cx. quinquefasciatus field females compared with CqSLab laboratory mosquito colony. Seventeen genes of interest were evaluated for their qualitative and specific expression by RT-PCR on RNAs extracted from female antennae, female legs, complete male bodies, incomplete female bodies (no head and no legs), and L4 larvae. The general expression mapping of olfactory genes revealed that all analyzed genes were expressed in antennae. Some genes showed different qualitative expression profiles, such as CquiOR2, CquiOR64, CquiOR93, CquiOBP11, and CquiOBP16, which were expressed exclusively in female antennae. On the other hand, CquiOR37, CquiOBP2, and CquiOBP43 are expressed in all sample types, and CquiOBP10 was expressed in female antennae and legs and in the complete male bodies. The expression of CquiOBP5 was detected in the female’s antennae and body, but it was absent in the legs. The quantitative differential expression analysis of six of the 17 genes by RT-qPCR was performed from RNA samples from antenna pools collected in three physiological states, post-emergence, post-mating, and post-blood feeding of the field females and CqSLab. A total of 3,600 antennae were analyzed, in pools containing 100 pairs. Most genes screened showed a higher expression level in field mosquitoes when compared with the laboratory strain CqSLab. The expression of CquiOBP5 and CquiOBP10 genes was significantly different between the post-mating and post blood-meal samples of laboratory females (p < 0.05). Our results suggest specialization of the function of the genes studied and divergence in the expression pattern of field mosquitoes compared with laboratory mosquitoes, and therefore, caution should be exercised in the interpretation of data from laboratory mosquito studies.

Nanoemulsions containing some plant essential oils as promising formulations against Culex pipiens (L.) larvae and their biochemical studies

The chemical composition of cypress, lavender, lemon eucalyptus, and tea tree oils has been investigated using gas chromatography/mass spectrometry (GC/MS). These oils were tested for larvicidal activity against Culex pipiens alongside their nanoemulsions (NEs) and conventional emulsifiable concentrates (ECs). Oil-in-water (O/W) NEs preparation was based on a high-energy ultra-sonication technique. The effect of independent variables of preparation on the different outputs was studied using the response surface method to obtain the optimum preparation technique. The droplet sizes of prepared NEs were significantly different (71.67, 104.55, 211.07, and 70.67 for cypress, lavender, lemon eucalyptus, and Tea tree NEs, respectively). The zeta potentials of NEs were recorded to have a high negatively charge (-28.4, -22.2, -23.6, and - 22.3 mV for cypress, lavender, lemon eucalyptus, and tea tree NEs, respectively). The results showed that the tea tree oil has the most significant effect with LC₅₀ = 60.02 and 57.10 mg/L after 24 and 48 h of exposure, respectively. In comparison, cypress oil proved the lowest toxicity with LC₅₀ values of 202.24 and 180.70 mg/L after 24 and 48 h, respectively. However, lavender oil does not show any effect against larvae at tested concentrations. In addition, pure oil exhibited the lowest larvicidal activity. However, the EC of all tested insecticides slightly improved the toxic action against the larvae. While the NEs showed significantly high toxicity compared to the EO and EC. An in vivo assessment of acetylcholine esterase (AChE), adenosine triphosphatase (ATPase), and gamma-aminobutyric acid transaminase (GABA-T) revealed that the NEs exhibited higher activity than the pure oils and ECs. This work describes these oils with potential use against C. pipiens larvae as eco-friendly products.