Comparison between precipitin and ELISA tests in the bloodmeal detection of Aedes aegypti (Linnaeus) and Aedes fluviatilis (Lutz) mosquitoes experimentally fed on feline, canine and human hosts

Rapid assessment of the blood-feeding histories of wild-caught malaria mosquitoes using mid-infrared spectroscopy and machine learning

BACKGROUND

The degree to which Anopheles mosquitoes prefer biting humans over other vertebrate hosts, i.e. the human blood index (HBI), is a crucial parameter for assessing malaria transmission risk. However, existing techniques for identifying mosquito blood meals are demanding in terms of time and effort, involve costly reagents, and are prone to inaccuracies due to factors such as cross-reactivity with other antigens or partially digested blood meals in the mosquito gut. This study demonstrates the first field application of mid-infrared spectroscopy and machine learning (MIRS-ML), to rapidly assess the blood-feeding histories of malaria vectors, with direct comparison to PCR assays.

METHODS AND RESULTS

Female Anopheles funestus mosquitoes (N = 1854) were collected from rural Tanzania and desiccated then scanned with an attenuated total reflectance Fourier-transform Infrared (ATR-FTIR) spectrometer. Blood meals were confirmed by PCR, establishing the 'ground truth' for machine learning algorithms. Logistic regression and multi-layer perceptron classifiers were employed to identify blood meal sources, achieving accuracies of 88%-90%, respectively, as well as HBI estimates aligning well with the PCR-based standard HBI.

CONCLUSIONS

This research provides evidence of MIRS-ML effectiveness in classifying blood meals in wild Anopheles funestus, as a potential complementary surveillance tool in settings where conventional molecular techniques are impractical. The cost-effectiveness, simplicity, and scalability of MIRS-ML, along with its generalizability, outweigh minor gaps in HBI estimation. Since this approach has already been demonstrated for measuring other entomological and parasitological indicators of malaria, the validation in this study broadens its range of use cases, positioning it as an integrated system for estimating pathogen transmission risk and evaluating the impact of interventions.

Blood feeding habits of mosquitoes: hardly a bite in South America

Mosquito blood feeding plays a key role in epidemiology. Despite its importance and large number of studies worldwide, less attention has been paid in South America. We summarized some general concepts and methodological issues related to the study of mosquito blood feeding habits, and compiled and analyzed all published information regarding the subject in the continent until 2020. Available literature comprised 152 scientific studies, that pursued different approaches: human landing catches (102 studies), baited trap (19), and blood meal analyses of collected specimens (38). Among the latter, 23 used serological and 15 molecular techniques. Species most frequently studied were those incriminated in malaria transmission, whereas relevant vectors such as Aedes aegypti, Ae. albopictus, and Haemagogus janthinomys were surprisingly neglected. Brazil was the leading country both in number of works and species studied. For over 70% of the species and three out of 13 South American countries there is no single information on mosquito blood feeding habits. Data from baited traps included 143 mosquito species, 83.9% of which were attracted to humans, either exclusively (10.5%) or in combination with other vertebrates (73.4%). Host blood identification of field collected specimens provided data on 102 mosquito species, and 60.8% of these fed on humans (55.9% combined with other vertebrates). Only 17 of the 73 species assessed by both methods yielded similar feeding patterns. Finally, supplementary tables are provided in a comprehensive summary of all information available and information gaps are highlighted for future research in the continent.

Blood meal profile and positivity rate with malaria parasites among different malaria vectors in Sudan

Background

Malaria is a life-threatening public health problem globally with particularly heavy burden in the sub-Saharan Africa including Sudan. The understanding of feeding preference of malaria vectors on different hosts is a major challenge for hindering the transmission cycle of malaria. In this study, blood meals taken by blood-fed Anopheles mosquitoes collected from the field in malaria endemic areas of Sudan were analysed for source of blood meal and malaria parasite presence.

Methods

Anopheles mosquitoes were collected from different regions in Sudan: Khartoum state, Sennar state, Northern state, and El Gedarif state between September 2020 and February 2021. Anopheles mosquitoes were collected using the standard pyrethrum spray catch and back-pack aspirator. Mosquito samples were sorted and morphologically identified to species level using international identification keys. Morphologically identified mosquito species were also confirmed using PCR. Genomic DNA was extracted from mosquitoes for molecular identification of blood meal source and parasite detection. The presence of Plasmodium species DNA in each mosquito sample was investigated using semi-nested PCR. Frequency of each blood meal source, Anopheles mosquito vector, and malaria parasite detected was calculated. Positivity rate of each fed female Anopheles mosquito was calculated for each species.

Results

A total of 2132 Anopheles mosquitoes were collected. 571 (26.8%) were males and 1561 (73.2%) were females classified based on their abdominal status into 1048 (67.1%) gravid, 274 (17.6%) fed, and 239 (15.3%) unfed females. Among the blood fed Anopheles mosquitoes, 263 (96.0%) were morphologically identified and confirmed using PCR to Anopheles arabiensis, 9 (3.3%) to Anopheles stephensi, and 2 (0.7%) to Anopheles rufipes. Of 274 blood-fed An. arabiensis, 68 (25.9%) fed on mixed blood meals from human and cattle, 8 (3.0%) fed on cattle and goat, and 13 (4.8%) fed on human, cattle and goat. For single blood meal sources, 70 (26.6%) fed on human, 95 (36.1%) fed on cattle, 8 (3.0%) fed on goat, and 1 (0.4%) fed on dog. While An. rufipes and An. stephensi fed on dog (2; 0.75%) and cattle (9; 3.3%), respectively. Plasmodium parasite detection in the blood meals showed that 25/274 (9.1%) An. arabiensis meals were positive for Plasmodium vivax and 19/274 (6.9%) An. arabiensis meals were positive for Plasmodium falciparum. The rate of positivity of An. arabiensis with any Plasmodium species was 16.7%. However, the positivity rate with P. falciparum only was 7.2%, while P. vivax was 9.5%. Both An. rufipes and An. stephensi were having positivity rates of 0.0% each.

Conclusions

This study which was mainly on blood-fed Anopheles mosquitoes showed a diversity in the type of diet from human, cattle, and goat. Anopheles mosquitoes especially An. arabiensis in Sudan, are opportunistic blood feeders and can feed broadly on both human and cattle. The application of blood meal identification is not only important in malaria vector epidemiological surveillance but also is very useful in areas where arthropods exhibit zoophilic feeding behaviour for mammals.

Vertebrate-Aedes aegypti and Culex quinquefasciatus (Diptera)-arbovirus transmission networks: Non-human feeding revealed by meta-barcoding and next-generation sequencing

Background

Aedes aegypti mosquito-borne viruses including Zika (ZIKV), dengue (DENV), yellow fever (YFV), and chikungunya (CHIKV) have emerged and re-emerged globally, resulting in an elevated burden of human disease. Aedes aegypti is found worldwide in tropical, sub-tropical, and temperate areas. The characterization of mosquito blood meals is essential to understand the transmission dynamics of mosquito-vectored pathogens.

Methodology/principal findings

Here, we report Ae. aegypti and Culex quinquefasciatus host feeding patterns and arbovirus transmission in Northern Mexico using a metabarcoding-like approach with next-generation deep sequencing technology. A total of 145 Ae. aegypti yielded a blood meal analysis result with 107 (73.8%) for a single vertebrate species and 38 (26.2%) for two or more. Among the single host blood meals for Ae. aegypti, 28.0% were from humans, 54.2% from dogs, 16.8% from cats, and 1.0% from tortoises. Among those with more than one species present, 65.9% were from humans and dogs. For Cx. quinquefasciatus, 388 individuals yielded information with 326 (84%) being from a single host and 63 (16.2%) being from two or more hosts. Of the single species blood meals, 77.9% were from dogs, 6.1% from chickens, 3.1% from house sparrows, 2.4% from humans, while the remaining 10.5% derived from other 12 host species. Among those which had fed on more than one species, 11% were from dogs and humans, and 89% of other host species combinations. Forage ratio analysis revealed dog as the most over-utilized host by Ae. aegypti (= 4.3) and Cx. quinquefasciatus (= 5.6) and the human blood index at 39% and 4%, respectively. A total of 2,941 host-seeking female Ae. aegypti and 3,536 Cx. quinquefasciatus mosquitoes were collected in the surveyed area. Of these, 118 Ae. aegypti pools and 37 Cx. quinquefasciatus pools were screened for seven arboviruses (ZIKV, DENV 1–4, CHIKV, and West Nile virus (WNV)) using qRT-PCR and none were positive (point prevalence = 0%). The 95%-exact upper limit confidence interval was 0.07% and 0.17% for Ae. aegypti and Cx. quinquefasciatus, respectively

Conclusions/significance

The low human blood feeding rate in Ae. aegypti, high rate of feeding on mammals by Cx. quinquefasciatus, and the potential risk to transmission dynamics of arboviruses in highly urbanized areas of Northern Mexico is discussed.

Elucidating arbovirus-vector-host contact networks is critical to understand and control mosquito-borne virus transmission, including pathogens such as ZIKV, DENV 1–4, CHIKV, and WNV. Here, we report the results of metabarcoding of blood meals of two primary pathogen mosquito vectors, Aedes aegypti and Culex quinquefasciatus. We found limited human blood feeding by Ae. aegypti and high preference for feeding on mammals by Cx. quinquefasciatus. Interestingly, blood meal analysis revealed dogs as the most utilized host for both vector species suggesting the potential for zooprophylaxis for human-amplified urban arboviruses. Pools of these vector species were tested for seven arboviruses and all were negative. We calculated vectorial capacity to discuss the potential risk and transmission dynamics of pathogens transmitted by these two important vectors in an urban location in Northern Mexico.

Studies of host preferences of wild-caught Phlebotomus orientalis and Ph. papatasi vectors of leishmaniasis in Sudan

Introduction

Understanding the feeding behavior and host choice of sand flies provides valuable information on vector-host relationships and elucidates the epidemiological patterns of leishmaniasis transmission. Blood meal analysis studies are essential for estimating the efficiency of pathogen transmission, assessing the relative human disease risk, and assist in identifying the other potential hosts of leishmaniasis. In Sudan and most of East Africa, there are large remaining gaps in knowledge regarding the feeding habits of phlebotomine vectors. The study aimed to identify the blood meal sources and, therefore, the host preferences of the principal vectors Phlebotomus orientalis and Ph. papatasi in leishmaniasis endemic areas of eastern and central Sudan.

Materials and methods

Sand flies were collected from two endemic villages in eastern and central Sudan using CDC light traps and sticky traps. The phlebotomine sand flies were morphologically and then molecularly identified. The source of blood meal of the engorged females was determined using a multiplex PCR methodology and specific primers of cytochrome b gene of mitochondrial DNA for human, goat, cow, and dog. The detection of the Leishmania parasite was done using PCR.

Results

The total number of collected female phlebotomine sand flies was 180. Morphological identification revealed the abundance of Ph. orientalis 103 (57.2%), Ph. papatasi 42 (23.3%), Ph. bergeroti 31 (17.2%), Ph. rodhaini 2 (1.1%) and Ph. duboscqi 2 (1.1%) in the study sites. Out of the 180 collected, 31 (17%) were blood-fed flies. Three species were blood-fed and molecularly identified: Ph. papatasi (N = 7, 22.6%), Ph. bergeroti (N = 9, 26%), and Ph. orientalis (N = 15, 48.4%). Blood meal analysis revealed human DNA in two Ph. orientalis (6.4%), hence, the anthropophilic index was 13.3%.

Conclusions

Multiplex PCR protocol described here allowed the identification of blood meal sources of many vertebrate species simultaneously. The results indicate that wild-caught Ph. orientalis are anthropophilic in the study areas. Further studies on larger blood-fed sample size are required to validate the potential applications of this technique in designing, monitoring and evaluating control programs, particularly in investigating the potential non-human hosts of leishmaniasis.

Using mid-infrared spectroscopy and supervised machine-learning to identify vertebrate blood meals in the malaria vector, Anopheles arabiensis

BACKGROUND

The propensity of different Anopheles mosquitoes to bite humans instead of other vertebrates influences their capacity to transmit pathogens to humans. Unfortunately, determining proportions of mosquitoes that have fed on humans, i.e. Human Blood Index (HBI), currently requires expensive and time-consuming laboratory procedures involving enzyme-linked immunosorbent assays (ELISA) or polymerase chain reactions (PCR). Here, mid-infrared (MIR) spectroscopy and supervised machine learning are used to accurately distinguish between vertebrate blood meals in guts of malaria mosquitoes, without any molecular techniques.

METHODS

Laboratory-reared Anopheles arabiensis females were fed on humans, chickens, goats or bovines, then held for 6 to 8 h, after which they were killed and preserved in silica. The sample size was 2000 mosquitoes (500 per host species). Five individuals of each host species were enrolled to ensure genotype variability, and 100 mosquitoes fed on each. Dried mosquito abdomens were individually scanned using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectrometer to obtain high-resolution MIR spectra (4000 cm-1 to 400 cm-1). The spectral data were cleaned to compensate atmospheric water and CO2 interference bands using Bruker-OPUS software, then transferred to Python™ for supervised machine-learning to predict host species. Seven classification algorithms were trained using 90% of the spectra through several combinations of 75-25% data splits. The best performing model was used to predict identities of the remaining 10% validation spectra, which had not been used for model training or testing.

RESULTS

The logistic regression (LR) model achieved the highest accuracy, correctly predicting true vertebrate blood meal sources with overall accuracy of 98.4%. The model correctly identified 96% goat blood meals, 97% of bovine blood meals, 100% of chicken blood meals and 100% of human blood meals. Three percent of bovine blood meals were misclassified as goat, and 2% of goat blood meals misclassified as human.

CONCLUSION

Mid-infrared spectroscopy coupled with supervised machine learning can accurately identify multiple vertebrate blood meals in malaria vectors, thus potentially enabling rapid assessment of mosquito blood-feeding histories and vectorial capacities. The technique is cost-effective, fast, simple, and requires no reagents other than desiccants. However, scaling it up will require field validation of the findings and boosting relevant technical capacity in affected countries.

Molecular identification of blood meals in mosquitoes (Diptera, Culicidae) in urban and forested habitats in southern Brazil

The study of host associations of mosquitoes (Diptera, Culicidae) provides valuable information to assist in our understanding of a variety of related issues, from their life-history to the entomological surveillance of pathogens. In this study, we identified and characterized mosquito blood meals from both urban and forested areas in the city of Paranaguá, state of Paraná, Brazil, by analyzing the amplification of host DNA ingested by mosquitoes under different storage conditions and digestion levels. Host DNA preservation was evaluated in fresh blood meals according to storage duration (30 to 180 days) and temperature (-20°C / -80°C) and, in digested blood, according the degree of digestion classified on the Sella scale. Molecular analysis of blood meals was based on DNA extraction and amplification of a fragment of the mitochondrial COI gene. We determined that, up to180 days of storage, the evaluated temperatures did not influence the preservation of fresh blood meals DNA, whereas the amplification success was increasingly reduced over the course of the digestion process. The species Anopheles cruzii, Aedes fluviatilis, Aedes scapularis, Psorophora ferox, Culex quinquefasciatus, Culex mollis, and Culex intrincatus, together with specimens representing four subgenera and one genus of Culicidae [Ae. (Ochlerotatus), Cx. (Culex), Cx. (Melanoconion), Cx. (Microculex), and Limatus, respectively] had their blood meals identified. Their diverse host use was evidenced by the identification of 19 species of vertebrate host, namely two amphibians, three mammals and 14 birds. Birds were the most commonly identified host in blood meals. These results not only show the diversity of mosquito hosts, but also underscore the challenges involved in monitoring arboviruses of public health importance, given potential combinations of host use for each mosquito species.

Blood Meal Source Characterization Using Illumina Sequencing in the Chagas Disease Vector Rhodnius pallescens (Hemiptera: Reduviidae) in Panamá

Accurate blood meal identification is critical to understand hematophagous vector-host relationships. This study describes a customizable Next-Generation Sequencing (NGS) approach to identify blood meals from Rhodnius pallescens (Hemiptera: Reduviidae) triatomines using multiple barcoded primers and existing software to pick operational taxonomic units and match sequences for blood meal identification. We precisely identified all positive control samples using this method and further examined 74 wild-caught R. pallescens samples. With this novel blood meal identification method, we detected 13 vertebrate species in the blood meals, as well as single and multiple blood meals in individual bugs. Our results demonstrate the reliability and descriptive uses of our method.

MALDI-TOF MS identification of Anopheles gambiae Giles blood meal crushed on Whatman filter papers

BACKGROUND

Identification of the source of mosquito blood meals is an important component for disease control and surveillance. Recently, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) profiling has emerged as an effective tool for mosquito blood meal identification, using the abdomens of freshly engorged mosquitoes. In the field, mosquito abdomens are crushed on Whatman filter papers to determine the host feeding patterns by identifying the origin of their blood meals. The aim of this study was to test whether crushing engorged mosquito abdomens on Whatman filter papers was compatible with MALDI-TOF MS for mosquito blood meal identification. Both laboratory reared and field collected mosquitoes were tested.

MATERIAL AND METHODS

Sixty Anopheles gambiae Giles were experimentally engorged on the blood of six distinct vertebrate hosts (human, sheep, rabbit, dog, chicken and rat). The engorged mosquito abdomens were crushed on Whatman filter papers for MALDI-TOF MS analysis. 150 Whatman filter papers, with mosquitoes engorged on cow and goat blood, were preserved. A total of 77 engorged mosquito abdomens collected in the Comoros Islands and crushed on Whatman filter papers were tested with MALDI-TOF MS.

RESULTS

The MS profiles generated from mosquito engorged abdomens crushed on Whatman filter papers exhibited high reproducibility according to the original host blood. The blood meal host was correctly identified from mosquito abdomens crushed on Whatman filter papers by MALDI-TOF MS. The MS spectra obtained after storage were stable regardless of the room temperature and whether or not they were frozen. The MS profiles were reproducible for up to three months. For the Comoros samples, 70/77 quality MS spectra were obtained and matched with human blood spectra. This was confirmed by molecular tools.

CONCLUSION

The results demonstrated that MALDI-TOF MS could identify mosquito blood meals from Whatman filter papers collected in the field during entomological surveys. The application of MALDI-TOF MS has proved to be rapid and successful, making it a new and efficient tool for mosquito-borne disease surveillance.

Attraction of mosquitoes to domestic cats in a heartworm enzootic region

Heartworm disease is caused by a mosquito-borne parasite that can affect many different mammalian species and has worldwide distribution. The agent, Dirofilaria immitis (Leidy 1856), infect mainly dogs but feline infection have been frequently reported in the last decade. Feline heartworm infection is difficult to detect, therefore, low reported prevalence could reflect true low prevalence or poor diagnostic efficiency. As mosquitoes are known to be attracted differently by different mammalian species, mosquitoes were collected from both a cattery and a contiguous home located in a canine heartworm enzootic area in Niterói, state of Rio de Janeiro, Brazil. For 14 months, mosquitoes were collected weekly for genus identification, speciation when possible, and for individual blood meal identification. Culex species mosquitoes were the most captured and those most frequently found with feline blood meal, followed by Aedes species that, although captured in lower numbers, also fed on feline blood. While Culex species mosquitoes have been reported as potential secondary heartworm vectors for dogs and primary vectors for cats, the present results suggest that Aedes species mosquitoes may also be involved in feline heartworm transmission in a larger proportion than previously thought.

Onchocerciasis transmission in Ghana: the human blood index of sibling species of the Simulium damnosum complex

Background

Vector-biting behaviour is important for vector-borne disease (VBD) epidemiology. The proportion of blood meals taken on humans (the human blood index, HBI), is a component of the biting rate per vector on humans in VBD transmission models. Humans are the definitive host of Onchocerca volvulus, but the simuliid vectors feed on a range of animals and HBI is a key indicator of the potential for human onchocerciasis transmission. Ghana has a diversity of Simulium damnosum complex members, which are likely to vary in their HBIs, an important consideration for parameterization of onchocerciasis control and elimination models.

Methods

Host-seeking and ovipositing S. damnosum (sensu lato) (s.l.) were collected from seven villages in four Ghanaian regions. Taxa were morphologically and molecularly identified. Blood meals from individually stored blackfly abdomens were used for DNA profiling, to identify previous host choice. Household, domestic animal, wild mammal and bird surveys were performed to estimate the density and diversity of potential blood hosts of blackflies.

Results

A total of 11,107 abdomens of simuliid females (which would have obtained blood meal(s) previously) were tested, with blood meals successfully amplified in 3,772 (34 %). A single-host species was identified in 2,857 (75.7 %) of the blood meals, of which 2,162 (75.7 %) were human. Simulium soubrense Beffa form, S. squamosum C and S. sanctipauli Pra form were the most anthropophagic (HBI = 0.92, 0.86 and 0.70, respectively); S. squamosum E, S. yahense and S. damnosum (sensu stricto) (s.s.)/S. sirbanum were the most zoophagic (HBI = 0.44, 0.53 and 0.63, respectively). The degree of anthropophagy decreased (but not statistically significantly) with increasing ratio of non-human/human blood hosts. Vector to human ratios ranged from 139 to 1,198 blackflies/person.

Conclusions

DNA profiling can successfully identify blood meals from host-seeking and ovipositing blackflies. Host choice varies according to sibling species, season and capture site/method. There was no evidence that HBI is vector and/or host density dependent. Transmission breakpoints will vary among locations due to differing cytospecies compositions and vector abundances.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1703-2) contains supplementary material, which is available to authorized users.

Determination of the foraging behaviour and blood meal source of malaria vector mosquitoes in Trincomalee District of Sri Lanka using a multiplex real time polymerase chain reaction assay

Background

Studies of host preference patterns in blood-feeding anopheline mosquitoes are crucial to incriminating malaria vectors. However, little information is available on host preferences of Anopheles mosquitoes in Sri Lanka.

Methods

Adult Anopheles mosquitoes were collected from five selected sentinel sites in Trincomalee District during June–September 2011. Each blood-fed mosquito was processed on filter papers. DNA was extracted using the dried blood meal protocol of the QIAmp DNA mini kit. A multiplexed, real-time PCR assay targeting eight animals was developed for two panels to identify the host meal of Anopheles. Human blood index (HBI), forage ratio (FR) and host feeding index (HFI) were calculated.

Results

A total of 280 field-caught, freshly engorged female mosquitoes belonging to 12 anopheline species were analysed. The overall HBI and HFI in the present study were low indicating that humans were not the preferred host for the tested anopheline species. Nevertheless, a small proportion engorged Anopheles aconitus, Anopheles culicifacies, Anopheles barbirostris, Anopheles annularis, Anopheles subpictus, Anopheles peditaeniatus, Anopheles pseudojamesi, and Anopheles barbumbrosus contained human blood.

Conclusion

The presence of human blood in mosquito species indicates the possibility of them transmitting malaria. Further studies on vector competence are needed to determine the role of each of the above anopheline species as efficient vectors of malaria.

Feeding Patterns and Xenomonitoring of Trypanosomes among Tsetse Flies around the Gashaka-Gumti National Park in Nigeria

In order to understand the epidemiology of trypanosomoses in Gashaka-Gumti National Park, Nigeria, we determined the density, infection rates, and feeding patterns of tsetse flies using biconical traps, ITS, and mitochondrial cytochrome b PCRs. A total of 631 tsetse flies were captured, of which 531 (84.2%) and 100 (15.8%) were analyzed for trypanosomes and blood meals, respectively. Tsetse distribution varied significantly (p < 0.05) across study sites with average trap and daily catches of 4.39 and 26.34, respectively. Overall tsetse infection rate was 5.08% and ranged between 3.03% and 6.84% across study sites. We identified 10 T. brucei, 3 T. congolense savannah, 2 T. congolense forest, and 2 mixed infections among the 13 pools made from the 27 flies positive for trypanosomes with light microscopy. The distribution of vertebrate blood meals in tsetse flies varied significantly (p < 0.05) and ranged between 6.0% and 45% across hosts. We also observed dual feeding patterns involving at least 2 hosts in 24% and multiple feeding involving at least 3 hosts in 17% of the flies. We observed predominance of G. palpalis which also recorded higher infection rate. T. brucei was more prevalent among tsetse flies. Tsetse flies fed predominantly on cattle and less frequently on humans and also showed mixed feeding habits.

Feeding patterns of Culex quinquefasciatus (Diptera: Culicidae) from eastern Santa Catarina state, Brazil

Blood-feeding sources of Culex quinquefasciatus Say (Diptera: Culicidae) collected in the eastern region of the Brazilian state of Santa Catarina were analyzed by precipitin technique. One hundred fifty-four female mosquitoes collected by CDC traps in the Navegantes municipality 13-15 February 2005 reacted to one or more of eight antisera, including chicken, dog, goat, sheep, horse, opossum, human and rodent antisera. One hundred thirty-seven specimens (89%) reacted to only one source, and 17 (11%) specimens reacted to two sources. Among the 137 specimens reacting to only one source, reactions to rodent (50.4%), sheep (5.8%), chicken (5.1%), goat (5.1%), dog (2.2%), horse (3.6%), and human (3.6%) antisera were observed. The analyzed species demonstrated a high degree of opportunistic feeding behavior in relation to host preference. Results are compared with results from similar studies, and the low proportion of reactions to human antisera is discussed.

Identification of bloodmeals in wild caught blood fed Phlebotomus argentipes (Diptera: Psychodidae) using cytochrome b PCR and reverse line blotting in Bihar, India

Identification of the source of bloodmeals in vectors plays an important role in epidemiological studies by determining the host preferences of wild sand flies in natural habitat. The anthropophilic index is a crucial component in human leishmaniasis. Bloodmeal analysis can identify the reservoir hosts of vector borne diseases. The amplification of the mitochondrial cytochrome b gene, followed by reverse line blot analysis, helps to identify the bloodmeal ingested by the wild caught sand flies. In the current study, blood fed sand flies were collected from three different villages in Bihar, India, by using Centers for Disease Control mini traps with incandescent light. Traps were placed in five different sites in the villages. Whole genome DNA was extracted from the blood fed sand flies and was amplified for the cytochrome b region, followed by reverse line blot analysis. In total, 442 blood fed sand flies were analyzed out of which 288 (65%) were positive to cytochrome b polymerase chain reaction. Humans, cattle, buffalo, and goats were the major bloodmeals identified, followed by chickens. In some of the blood fed sand flies, multiple bloodmeals were identified. In the current study, sand flies mostly fed on humans, followed by cattle, buffalo, and goats. In this regard, it is necessary to also consider cattle, buffalo, and goats when addressing vector control in Bihar, India.

Development of an enzyme-linked immunosorbent assay to identify host-feeding preferences of Phlebotomus species (Diptera: Psychodidae) in endemic foci of visceral leishmaniasis in Nepal

Anthroponotic visceral leishmaniasis, transmitted by Phlebotomus argentipes Annandale & Brunetti (Diptera: Psychodidae) sand flies, is regarded as a major problem of public health importance in the Indian subcontinent. Understanding the feeding behavior of the vector can be used to investigate changes in human-vector contact during intervention programs. An enzyme-linked immunosorbent assay (ELISA) was modified to make it suitable to identify the origin of P. argentipes and Phlebotomus papatasi Scopoli (Diptera: Psychodidae) blood meals. The sensitivity and specificity of the precipitin ring test and ELISA were compared, as well as the stability of the tests across different stages of blood meal digestion. The ELISA was more sensitive and specific than the precipitin test for identifying the sources of blood meals. When using the ELISA method with a plate reader, it was possible to obtain 100% sensitivity and specificity. When comparing the techniques across digestion stages, it was found that there was a drop in sensitivity, 48 and 72 h postblood meal for precipitin and visually read ELISA, respectively. However, the sensitivity of the ELISA using a plate reader was not altered by the digestion time. The feeding habits of P. argentipes and P. papatasi from the Terai region of Nepal, determined by the ELISA developed, showed P. papatasi to be highly anthropophilic, and P. argentipes appeared to feed both on humans and animals, in particular bovines.

Blood meal identification of selected mosquitoes in Rio de Janeiro, Brazil

ABSTRACT. The blood meal sources of 5 species (Mansonia titillans, Aedes scapularis, Culex quinquefasciatus, Coquillettidia shannoni, and Anopheles peryassui) collected in Conceição do Macacu, in the southeastern Brazilian state of Rio de Janeiro, were examined with the precipitin test. Of the 1,128 mosquitoes collected, 907 (80.4%) reacted to some antisera. Although all 5 species were eclectic in their feeding habits, Ma. titillans and Ae. scapularis fed mostly on birds, while Cx. quinquefasciatus, Cq. shannoni, and An. peryassui fed mostly on bovines. Proportions of mosquitoes feeding on 1 source varied from 60.0% (Ae. scapularis) to 87.7% (Ma. titillans), while that of mosquitoes feeding on > 1 source varied from 12.2% (Ma. titillans) to 34.4% (Ae. scapularis). Epidemiological implications of the feeding and their potential involvements in the transmission of arboviruses are commented upon.

Identification of blood meals imbibed by phlebotomine sand flies using cytochrome b PCR and reverse line blotting

Blood meal identification is important for determining the host preferences and the vectorial capacity of hematophagous arthropods. In the past, mostly serological techniques using host-specific antibodies were used, but in recent years more sensitive and accurate polymerase chain reaction (PCR)-based molecular approaches for identifying blood meals have been developed. Here, a vertebrate-specific PCR is combined with reverse line blot analysis for identifying blood meals ingested by female phlebotomine sand fly vectors of leishmaniasis. Species-specific oligonucleotides were covalently linked to nylon membranes, and biotinylated PCR products of the mitochondrial cytochrome b gene were used as probes in a hybridization reaction revealed using colorimetric or enhanced chemiluminescent detection systems. This combination identified blood meals up to 96 hours after ingestion containing minimal amounts of DNA (>0.1 pg). The specific probes discriminated between putative host species in several study areas. The source of blood was identified in 68 of 89 wild-caught sand flies tested (76%). Mixed blood meals were identified in 15 (17%) of those. The advantages and limitations of this method are discussed.

Influence of hosts on the ecology of arboviral transmission: potential mechanisms influencing dengue, Murray Valley encephalitis, and Ross River virus in Australia

Ecological interactions are fundamental to the transmission of infectious disease. Arboviruses are particularly elegant examples, where rich arrays of mechanisms influence transmission between vectors and hosts. Research on host contributions to the ecology of arboviral diseases has been undertaken within multiple subdisciplines, but significant gaps in knowledge remain and multidisciplinary approaches are needed. Through our multidisciplinary review of the literature we have identified five broad areas where hosts may influence the ecology of arboviral transmission: host immunity; cross-protective immunity and antibody-dependent enhancement; host abundance; host diversity; and pathogen spillover and dispersal. Herein we discuss the known and theoretical roles of hosts within these topics and then apply this knowledge to three epidemiologically important mosquito-borne arboviruses that occur in Australia: dengue virus (DENV), Murray Valley encephalitis virus (MVEV), and Ross River virus (RRV). We argue that the underlying mechanisms by which hosts influence arboviral activity are numerous and attempts to delineate these mechanisms further are needed. Investigations that focus on hosts of vector-borne diseases are likely to be rewarding, particularly where the ecology of vectors is relatively well understood. From an applied perspective, enhanced knowledge of host influences upon vector-borne disease transmission is likely to enable better management of disease burden. Finally, we suggest a framework that may be useful to identify and determine host contributions to the ecology of arboviruses.

Blood meal identification and parasite detection in laboratory-fed and field-captured Lutzomyia longipalpis by PCR using FTA databasing paper

The phlebotomine sand fly Lutzomyia longipalpis takes blood from a variety of wild and domestic animals and transmits Leishmania (Leishmania) infantum chagasi, etiological agent of American visceral leishmaniasis. Blood meal identification in sand flies has depended largely on serological methods but a new protocol described here uses filter-based technology to stabilise and store blood meal DNA, allowing subsequent PCR identification of blood meal sources, as well as parasite detection, in blood-fed sand flies. This technique revealed that 53.6% of field-collected sand flies captured in the back yards of houses in Teresina (Brazil) had fed on chickens. The potential applications of this technique in epidemiological studies and strategic planning for leishmaniasis control programmes are discussed.

Stable isotope analysis can potentially identify completely-digested bloodmeals in mosquitoes

Background

Vertebrate bloodfeeding is a critical component of a mosquito's ability to transmit pathogens that cause diseases such as malaria, dengue fever and viral encephalitis. Due to degradation by the digestive process, current methods to identify mosquito bloodmeal sources are only useful for approximately 36 hours post-feeding. A critical need exists for technologies to extend this window and gain a more complete picture of mosquito feeding behavior for epidemiological studies. Stable isotopes are useful for investigating organism feeding behavior because the isotopic ratio of an organism's tissues reflects that of the material it ingests.

Methodology/Principal Findings

Proof-of-principle data indicates that after bloodfeeding, Aedes albopictus mosquitoes acquire diagnostic Carbon and Nitrogen stable isotope profiles from their vertebrate hosts that can be accurately identified one week post-feeding, approximately 4 days after the entire bloodmeal has been digested. Total C/N ratio served as a biomarker marker for bloodfeeding (P<0.02), while δN was the most informative variable which could distinguish between unfed, chicken-fed and human-fed mosquitoes (P<0.01). By plotting C/N vs. δN, all feeding treatments could be identified in a double-blind analysis.

Conclusions/Significance

These proof-of-principle experiments indicate that analysis of stable isotopes can be used to distinguish bloodfed from unfed mosquitoes, and also distinguish between different vertebrate bloodmeal sources even after all blood has been digested. The development of stable isotope-based assays for mosquito bloodmeal identification may be a powerful tool to investigate mosquito feeding ecology and the dynamics of vector-borne pathogens.

Identification of mosquito bloodmeals using polymerase chain reaction (PCR) with order-specific primers

A polymerase chain reaction (PCR) protocol was developed to identify host bloodmeals from mosquitoes. Primers for the cytochrome b gene were designed to distinguish between mammalian and avian bloodmeals and further differentiate among four avian orders: passeriformes, falconiformes, columbiformes, and galliformes. The assay was validated by testing tissues from 18 species of passeriformes, three species of falconiformes, three species of columbiformes, and two species of galliformes. American crows were distinguished from other passeriformes by restriction enzyme digestion. Host bloodmeals from engorged mosquitoes collected in New York State were identified to avian order level. PCR was able to detect the mosquito bloodmeal for up to 3 d after feeding on a quail. Significantly, these studies use order-specific primers in a single PCR test to identify mosquito bloodmeals.