Artificial blood feeding for Culicidae colony maintenance in laboratories: does the blood source condition matter?

Comparative analysis of midgut bacterial communities in Chikungunya virus-infected and non-infected Aedes aegypti Thai laboratory strain mosquitoes

Chikungunya virus (CHIKV) poses a significant global health threat, re-emerging as a mosquito-transmitted pathogen that caused high fever, rash, and severe arthralgia. In Thailand, a notable CHIKV outbreak in 2019-2020 affected approximately 20,000 cases across 60 provinces, underscoring the need for effective mosquito control protocols. Previous studies have highlighted the role of midgut bacteria in the interaction between mosquito vectors and pathogen infections, demonstrating their ability to protect the insect from invading pathogens. However, research on the midgut bacteria of Aedes (Ae.) aegypti, the primary vector for CHIKV in Thailand remains limited. This study aims to characterize the bacterial communities in laboratory strains of Ae. aegypti, both infected and non-infected with CHIKV. Female mosquitoes from a laboratory strain of Ae. aegypti were exposed to a CHIKV-infected blood meal through membrane feeding, while the control group received a non-infected blood meal. At 7 days post-infection (dpi), mosquito midguts were dissected for 16S rRNA gene sequencing to identify midgut bacteria, and CHIKV presence was confirmed by E1-nested RT-PCR using mosquito carcasses. The study aimed to compare the bacterial communities between CHIKV-infected and non-infected groups. The analysis included 12 midgut bacterial samples, divided into three groups: CHIKV-infected (exposed and infected), non-infected (exposed but not infected), and non-exposed (negative control). Alpha diversity indices and Bray-Curtis dissimilarity matrix revealed significant differences in bacterial profiles among the three groups. The infected group exhibited an increased abundance of bacteria genus Gluconobacter, while Asaia was prevalent in both non-infected and negative control groups. Chryseobacterium was prominent in the negative control group. These findings highlight potential alterations in the distribution and abundance of gut microbiomes in response to CHIKV infection status. This study provides valuable insights into the dynamic relationship between midgut bacteria and CHIKV, underscoring the potential for alterations in bacterial composition depending on infection status. Understanding the relationships between mosquitoes and their microbiota holds promise for developing new methods and tools to enhance existing strategies for disease prevention and control. This research advances our understanding of the circulating bacterial composition, opening possibilities for new approaches in combating mosquito-borne diseases.

New artificial hematophagy system with attractive polymeric biofilm for maintenance of Culex quinquefasciatus (Diptera: Culicidae) in the laboratory

BACKGROUND

Maintaining mosquito colonies in the laboratory requires a blood supply so that females' oocytes can mature and oviposition can take place. In this study, a new artificial hematophagy system for colonization and maintenance of Culex quinquefasciatus in the laboratory was developed and tested.

METHODS

We developed an attractive polymeric biofilm including 25% L-lactic acid for use as a membrane in an artificial hematophagy system and compared the feeding rate of females with Parafilm-M®. We also evaluated the oviposition rate, larval survival and adult emergence of females fed through the attractive biofilm.

RESULTS

The average percentage of female Cx. quinquefasciatus fed through the attractive biofilm was 87%, while only 20% became engorged with Parafilm-M® (p < 0.0001). Feeding through the attractive biofilm developed in this study produced high levels of evaluated biological parameters; the percentage of egg laying by females that underwent artificial hematophagy through the biofilm was 90%, with an average of 158 eggs per raft. From these eggs, 97% of the larvae hatched, of which 95% reached the pupal stage. The adult emergence rate corresponded to 93% of pupae.

CONCLUSIONS

Insects fed with attractant through the biofilm system had a higher engorgement rate compared to those fed through Parafilm-M®. Our study is preliminary and suggests that polymeric biofilm has great potential for artificially feeding mosquitoes in the laboratory. Based on this research, new studies will be carried out with biofilm and different systems.

The effects of human and rhesus macaque blood meal sources on mosquito reproduction and adult survival under laboratory conditions

Mass rearing of mosquitoes as required to fulfil research studies is a technically challenging endeavor. Blood meal source has been recognized as a key consideration in mass rearing of mosquitoes that affects colony health and fecundity. Four species of laboratory-colonized mosquitoes from the Department of Entomology, US Army Medical Directorate - Armed Forces Research Institute of Medical Sciences (USAMD-AFRIMS); Anopheles cracens, An. dirus, An. minimus and An. sawadwongporni were fed blood meals from human and rhesus macaque sources using an artificial membrane feeder. The effects of different blood meal sources were evaluated concerning blood-feeding, survival and reproduction (fecundity and hatching rates). Adult survival was monitored at days 7, 14 and 21 post blood-feeding. Although the mosquitoes fed on human blood exhibited higher rates of engorgement, there were no significant differences in blood-feeding rates in An. cracens (P = 0.08) and An. dirus (P = 0.91) between rhesus macaque and human blood sources. Twenty-one days post-feeding, no significant differences were observed in the survival rates of mosquitoes fed on human versus rhesus macaque blood. Except for An. dirus, which had better survival rates with human blood (97.5%) than after feeding on rhesus macaque blood (95.4%). All mosquito species fed on human blood produced significantly more eggs when compared to those fed on rhesus macaque blood. However, there was no statistical difference in hatching rates between blood sources, except for An. dirus, which had better hatching rates with human blood. These results indicate that human and rhesus macaque blood may be a viable alternative for maintaining Anopheles mosquitoes in colony.

Membrane Feeding Devices to Blood Feed Mosquitoes in the Laboratory

Husbandry protocols for medically important mosquito species in the laboratory have the blood feeding procedure as an inherent step in the maintenance routine for egg production. Artificial feeders have become the main solution for delivering blood meals to these hematophagous insects, circumventing the need for vertebrate hosts. Mimicking the skin, these devices both heat the blood and hold a membrane through which the blood can be ingested by mosquitoes. Several commercial and noncommercial artificial mosquito feeders are available, but obstacles like high cost and complex assembly can restrict their routine use. To address this issue, a number of feeders have been designed that can be built with common materials found in the laboratory. They are cheaper and more accessible, but the absence of built-in temperature control and heating units can limit their efficacy. One of the most accessible mosquito feeders is the Glytube. It consists of a 50-mL conical centrifuge tube with heated glycerol that delivers blood through a membrane. The Glytube has been used successfully to model mosquito blood feeding. Recently, 3D printing has emerged as an alternative method to create customized artificial feeders. This technology is expected to facilitate access to and reduce the cost of these devices with open-source 3D model files that can be shared among laboratories maintaining mosquitoes worldwide.

Life History Metrics for Culex tarsalis (Diptera: Culicidae) and Culicoides sonorensis (Diptera: Ceratopogonidae) Are Not Impacted by Artificial Feeding on Defibrinated Versus EDTA-treated Blood

Artificial blood feeding is a common practice for the study and maintenance of blood-feeding arthropod colonies. Commercially purchased blood is often treated to prevent clot-formation using either mechanical or chemical means. For many hematophagous insects, the effect that different anticoagulation methods may have on life history metrics is unclear. In the current study, Culex tarsalis Coquillett and Culicoides sonorensis Wirth & Jones were fed blood treated with either mechanical (defibrination) or chemical (K2 EDTA) anticoagulation methods. Several blood feeding and life history metrics were evaluated between treatment groups including proportion blood feeding, fecundity, fertility, and mortality. No significant differences were found for any of the measured life history metrics for either species. For experiments measuring aspects of these blood feeding and life history traits, blood treated using either defibrination or K2 EDTA anticoagulants should not impact experimental outcomes.

A standardised low-cost membrane blood-feeder for Aedes aegypti made using common laboratory materials

Blood feeding is a necessary part of laboratory studies involving mosquitoes and other hematophagous arthropods of interest in medical and ecological research. However, methods involving hosts may present serious risks, require ethics approvals and can be expensive. Here we describe an insect blood feeder made using common laboratory materials, which is low cost (<US$100) and can be constructed and operated with little technical expertise. We compared the blood feeder containing an artificial blood diet, Skitosnack, to direct human arm feeding for Aedes aegypti (Diptera: Culicidae), in terms of engorgement rate, fecundity and hatch rate. No significant difference in fecundity between the two approaches was found, (mean ± SD); direct human arm: 56 ± 26 eggs/female, artificial method: 47 ± 25 eggs/female, P = 0.569. Engorgement rates (direct human arm: 97.8 ± 4%, artificial: 64.1 ± 23%, P < 0.05) and hatch rates (direct human arm: 75 ± 12%, artificial: 59 ± 14%, P < 0.05) were lower in the artificially fed mosquitoes. Despite these differences, we maintained a healthy mosquito colony for 10 generations using the artificial feeding approach. Results from this comparison are within the range of other studies which compared direct host feeding with an artificial feeding method. We anticipate that the blood feeder presented here could substantially reduce costs usually required to establish a standardised and effective blood feeding method for maintaining mosquito colonies or conducting experiments, extending the capability of laboratories especially where research resources are limited, but vector-borne diseases common.

The Use of Frozen, Food-Grade Blood to Successfully Maintain Colonies of Four Species of Mosquitoes (Diptera: Culicidae)

An essential component of all mosquito-rearing activities is the act of blood-feeding the mosquitoes (Diptera: Culicidae). Many options exist for this purpose including live host animals and a diverse array of artificial-feeding methods. Most of the published artificial-feeding methods involve expensive materials, custom-built devices, or are labor-intensive. All of the previously published methods utilize blood sources, which are either expensive, or difficult to obtain. Additionally, much of the research into artificial blood-feeding methods for mosquitoes has focused on two species: Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse). This article presents a modified artificial blood-feeding method that uses affordable and easily sourced materials, does not require any technical knowledge to assemble, and requires minimal time and effort. The combination of inexpensive aluminum plates, Parafilm and polytetrafluoroethylene tape membranes, an electric germination mat, and frozen, food-grade blood produces exceptional feeding rates and abundant egg production. The method has been used for 2 yr at the Lee County Mosquito Control District to successfully maintain laboratory colonies of four species of mosquito: Ae. aegypti, Ae. albopictus, Aedes taeniorhynchus (Wiedemann), and Culex quinquefasciatus (Say). Variations of this method are reported, which can be used for wild and laboratory colonies of multiple species. This modified method is highly accessible for any small-scale mosquito rearing facility with labor or budgetary constraints.

The type of blood used to feed Aedes aegypti females affects their cuticular and internal free fatty acid (FFA) profiles

Aedes aegypti, the primary vector of various arthropod-borne viral (arboviral) diseases such as dengue and Zika, is a popular laboratory model in vector biology. However, its maintenance in laboratory conditions is difficult, mostly because the females require blood meals to complete oogenesis, which is often provided as sheep blood. The outermost layer of the mosquito cuticle is consists of lipids which protects against numerous entomopathogens, prevents desiccation and plays an essential role in signalling processes. The aim of this work was to determine how the replacement of human blood with sheep blood affects the cuticular and internal FFA profiles of mosquitoes reared in laboratory culture. The individual FFAs present in cuticular and internal extracts from mosquito were identified and quantified by GC-MS method. The normality of their distribution was checked using the Kolmogorov-Smirnov test and the Student's t-test was used to compare them. GC-MS analysis revealed similar numbers of internal and cuticular FFAs in the female mosquitoes fed sheep blood by membrane (MFSB) and naturally fed human blood (NFHB), however MFSB group demonstrated 3.1 times greater FFA concentrations in the cuticular fraction and 1.4 times the internal fraction than the NFHB group. In the MFSB group, FFA concentration was 1.6 times higher in the cuticular than the internal fraction, while for NFHB, FFA concentration was 1.3 times lower in the cuticular than the internal fraction. The concentration of C18:3 acid was 223 times higher in the internal fraction than the cuticle in the MHSB group but was absent in the NFHB group. MFSB mosquito demonstrate different FFA profiles to wild mosquitoes, which might influence their fertility and the results of vital processes studied under laboratory conditions. The membrane method of feeding mosquitoes is popular, but our research indicates significant differences in the FFA profiles of MFSB and NFHB. Such changes in FFA profile might influence female fertility, as well as other vital processes studied in laboratory conditions, such as the response to pesticides. Our work indicates that sheep blood has potential shortcomings as a substitute feed for human blood, as its use in laboratory studies may yield different results to those demonstrated by free-living mosquitoes.

Assessment of Synthetic Membranes for Artificial Blood Feeding of Culicidae

Potential pathogen transmission through hematophagy in Culicidae is a major public-health problem, and several studies have been performed to better understand this phenomenon. Research on these insects often requires the maintenance of colonies in the laboratory. Due to the hematophagic habits of these organisms, blood must be provided in order to guarantee the reproduction of individuals that constitute the colonies. Some species of mammals and birds are used as a direct blood source in many laboratories. Due to current bioethical parameters, the direct use of animals has been replaced by artificial blood feeding by using synthetic membranes to simulate animal skin. In this study, the efficiency of collagen and latex in the artificial feeding of mosquitoes of the Aedes aegypti and Culex quinquefasciatus species was evaluated and compared with Parafilm^®, a standard membrane that is frequently used for this purpose. Important aspects of the feeding and reproduction of these insects were considered. For both species, latex showed the poorest performance. Collagen membrane performed well in most parameters, but was not as efficient as Parafilm^® for fecundity in Aedes aegypti, and for the percentage of engorged females in Culex quinquefasciatus. We concluded that, although collagen is more resistant and easier to handle, Parafilm^® was the most efficient among the three evaluated membranes for the artificial blood feeding of mosquitoes.

Heparin Administered to Anopheles in Membrane Feeding Assays Blocks Plasmodium Development in the Mosquito

Innovative antimalarial strategies are urgently needed given the alarming evolution of resistance to every single drug developed against Plasmodium parasites. The sulfated glycosaminoglycan heparin has been delivered in membrane feeding assays together with Plasmodium berghei-infected blood to Anopheles stephensi mosquitoes. The transition between ookinete and oocyst pathogen stages in the mosquito has been studied in vivo through oocyst counting in dissected insect midguts, whereas ookinete interactions with heparin have been followed ex vivo by flow cytometry. Heparin interferes with the parasite's ookinete-oocyst transition by binding ookinetes, but it does not affect fertilization. Hypersulfated heparin is a more efficient blocker of ookinete development than native heparin, significantly reducing the number of oocysts per midgut when offered to mosquitoes at 5 µg/mL in membrane feeding assays. Direct delivery of heparin to mosquitoes might represent a new antimalarial strategy of rapid implementation, since it would not require clinical trials for its immediate deployment.

Does membrane feeding compromise the quality of Aedes aegypti mosquitoes?

Modified Aedes aegypti mosquitoes are being mass-reared for release in disease control programs around the world. Releases involving female mosquitoes rely on them being able to seek and feed on human hosts. To facilitate the mass-production of mosquitoes for releases, females are often provided blood through artificial membrane feeders. When reared across generations there is a risk that mosquitoes will adapt to feeding on membranes and lose their ability to feed on human hosts. To test adaptation to membrane feeding, we selected replicate populations of Ae. aegypti for feeding on either human arms or membrane feeders for at least 8 generations. Membrane-selected populations suffered fitness costs, likely due to inbreeding depression arising from bottlenecks. Membrane-selected females had higher feeding rates on membranes than human-selected ones, suggesting adaptation to membrane feeding, but they maintained their attraction to host cues and feeding ability on humans despite a lack of selection for these traits. Host-seeking ability in small laboratory cages did not differ between populations selected on the two blood sources, but membrane-selected females were compromised in a semi-field enclosure where host-seeking was tested over a longer distance. Our findings suggest that Ae. aegypti may adapt to feeding on blood provided artificially, but this will not substantially compromise field performance or affect experimental assessments of mosquito fitness. However, large population sizes (thousands of individuals) during mass rearing with membrane feeders should be maintained to avoid bottlenecks which lead to inbreeding depression.