The significance of the advance lies partly in the mosquito genus involved. Culex species have received far less attention from spectroscopy-based methods than Anopheles mosquitoes, which dominate malaria research, despite the fact that Culex vectors are increasingly important players in the transmission of orthoflaviviruses and filarial parasites. Because these pathogens typically infect multiple host species, including birds, mammals and humans, mapping the feeding patterns of Culex mosquitoes is essential for predicting where and when spillover into human populations is likely to occur. Traditional blood meal identification relies on techniques such as PCR-based assays or sequencing, which are accurate but costly, time-consuming and progressively less reliable as the blood meal is digested inside the mosquito. A method that is rapid, inexpensive and robust to digestion time could transform the scale at which blood meal surveillance is feasible, particularly in the low-resource settings where mosquito-borne disease burdens are often highest.

The experimental design was straightforward but rigorous. The team reared Culex quinquefasciatus mosquitoes in the laboratory and fed them blood from six different host species: human, pig, chicken, cattle, dog and horse. This panel deliberately spans the range of hosts that matter most for multi-host pathogens in many endemic regions, from domestic animals that amplify viruses to humans who suffer the consequences. At four time points after feeding, namely 6, 12, 24 and 30 hours, the researchers rolled the abdominal contents of the mosquitoes onto filter paper to create dried bloodspots, a simple and field-friendly way of preserving samples without refrigeration or elaborate cold chains. Each bloodspot was then scanned using a Bruker ALPHA Fourier-transform infrared spectrometer, an instrument that measures how the sample absorbs mid-infrared light across a spectrum of wavelengths.

The underlying physics is what gives the method its power. Mid-infrared light interacts with the vibrational modes of chemical bonds in proteins, lipids, carbohydrates and nucleic acids, producing a complex absorption spectrum that acts as a molecular fingerprint of the sample. Because the blood of different host species differs subtly in its biochemical composition, those fingerprints carry enough information to distinguish a chicken blood meal from a dog blood meal, or a human meal from a horse meal. The raw spectra, however, are far too intricate for visual interpretation, which is where machine learning enters. The researchers trained a multilayer perceptron, a type of artificial neural network, on the spectra from laboratory mosquitoes with known blood meal origins, allowing the algorithm to learn the spectral patterns that discriminate between host species and then apply that learned knowledge to unknown samples.

The results were striking. On laboratory-reared mosquitoes, the trained model predicted host species with 93.6 percent accuracy, a dramatic improvement over the 16.7 percent expected from random classification among six host species. Even more importantly for real-world application, accuracy declined only modestly with digestion time, falling by just 6 percent at the 30-hour mark. This resilience matters because mosquitoes caught in surveillance traps are rarely fresh; they may have fed a day or more earlier, and conventional molecular methods lose accuracy as digestive enzymes break down the host DNA they rely on. A technique that remains reliable across a full day of digestion therefore captures a much larger and more representative fraction of the blood meals collected in the field, reducing the bias that plagues traditional approaches.

The true test came with field-collected mosquitoes. When the laboratory-trained model was applied to bloodspots from wild-caught Culex mosquitoes, accuracy dropped to 67.9 percent. The authors attribute this gap to differences between laboratory and field conditions rather than any fundamental flaw in the approach. Wild mosquitoes feed directly on living hosts, whereas the laboratory mosquitoes were fed through artificial feeders, and the blood used in the laboratory was treated with anticoagulants that wild blood meals naturally lack. Wild blood meals also reflect the true biochemical diversity of free-ranging animals, whose diet, health and physiology vary far more than those of the standardized blood sources used in the laboratory. In other words, the model was trained on a simplified version of the world and then asked to interpret a messier one, and the performance drop is an expected consequence of that mismatch.

Crucially, the team found a practical way to manage this uncertainty. By applying a probability threshold to the model’s predictions, accepting only classifications in which the algorithm expressed high confidence, accuracy on field samples rose to 78 percent, at the cost of discarding 21 percent of samples that the model could not confidently assign. This trade-off is a familiar one in applied machine learning, and for surveillance purposes it is often the right one. A public health programme that needs to know which hosts are driving transmission can afford to leave a fifth of samples unclassified if the remaining classifications are substantially more trustworthy. The threshold approach effectively lets users dial between coverage and confidence depending on the question at hand, a flexibility that rigid molecular assays do not offer.

The economic and logistical implications are considerable. Once the spectrometer is in place, the marginal cost of scanning a bloodspot is minimal, and the analysis requires no reagents, no cold chain and no highly specialized molecular biology laboratory. Filter paper bloodspots can be collected in remote villages, shipped at ambient temperature and analysed centrally, which makes the method particularly attractive for large-scale surveillance programmes in low-resource settings. The study’s field collections in the Philippines, supported by the Department of Health and local partners, alongside work in Australia’s Northern Peninsula Area, demonstrate that the sampling workflow is feasible in exactly the kinds of environments where Culex-borne pathogens impose their greatest burden. The work was funded by the Wellcome Trust, the European Research Council and several university and institutional grants, reflecting a collaboration spanning the University of Glasgow, the University of Sydney, NSW Health Pathology and the Ifakara Health Institute.

There are, of course, limits to what the current model can do. The laboratory training set covered only six host species, whereas real mosquitoes bite a far wider menagerie, including wild birds, rodents, bats and marsupials, and the model cannot classify hosts it was never taught to recognize. Expanding the library of host species, incorporating spectra from wild-fed mosquitoes into the training data, and refining the preprocessing of spectra to correct for the chemical differences introduced by anticoagulants and artificial feeders are all obvious next steps. The authors note that further development using samples from field-collected mosquitoes could enhance classification accuracy and broaden the range of identifiable hosts, and the open-access publication of the work should accelerate those efforts across the research community.

Even in its present form, however, the study marks a meaningful shift in how blood meal analysis could be conducted. By demonstrating that a benchtop infrared spectrometer and a neural network can recover host identities from a day-old blood meal with near-laboratory accuracy, the researchers have opened a path toward blood meal surveillance at a scale that PCR-based methods could never economically achieve. For diseases that move between animals and humans along cryptic transmission chains, that scale is precisely what has been missing. If subsequent studies confirm and extend these results across more host species and more field settings, the humble dried bloodspot, read by a beam of infrared light, may become one of the standard tools of vector-borne disease intelligence, helping health authorities see not just which mosquitoes are present, but whose blood they are carrying and which transmission pathways need to be interrupted first.

Subject of Research: Mid-infrared spectroscopy and machine learning for identifying host species of Culex mosquito blood meals

Article Title: Rapid host species identification from dried bloodspots of Culex mosquito blood meals using mid-infrared spectroscopy

Article References: Rapid host species identification from dried bloodspots of Culex mosquito blood meals using mid-infrared spectroscopy. (n.d.). https://doi.org/10.1186/s13071-026-07703-8

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07703-8

Keywords: Culex mosquitoes, blood meal analysis, mid-infrared spectroscopy, machine learning, multilayer perceptron, vector-borne disease, orthoflaviviruses, lymphatic filariasis, dried bloodspots, disease surveillance, one health, entomology

Leishmania parasites are transmitted to humans and other mammals through the bites of phlebotomine sand flies, tiny insects belonging to the order Diptera and the family Psychodidae. Among the various Leishmania species, L. infantum is particularly consequential: it is the causative agent of both visceral leishmaniasis, the potentially fatal form of the disease that attacks internal organs, and cutaneous leishmaniasis, which produces disfiguring skin lesions. In the eastern Mediterranean basin, several sand fly species are known or suspected to transmit L. infantum, including Phlebotomus perfiliewi, Phlebotomus tobbi, and Phlebotomus neglectus. Yet the identity and relative importance of vector species vary considerably from one geographic area to another, and in many places the picture remains incomplete.

Israel presents a particularly complex epidemiological landscape. Multiple Leishmania species are endemic in the country, and L. infantum causes both visceral and cutaneous disease in humans, with dogs serving as the main reservoir of the parasite. Despite decades of surveillance, the precise sand fly vectors responsible for transmitting L. infantum in different regions of Israel have remained uncertain. Phlebotomus syriacus, a member of the subgenus Larroussius, has been a common species in the country and a long-standing suspect, but without molecular confirmation its actual role in the transmission cycle could only be speculated upon. Closing that gap was the central aim of the new study.

The research team, led by Liora Studentsky of the Hebrew University of Jerusalem and the Public Health Laboratories Jerusalem of the Israeli Ministry of Health, together with colleagues including corresponding author Oscar David Kirstein, conducted an intensive three-year field campaign between 2021 and 2023. Sand flies were collected using CDC miniature light traps at two villages where leishmaniasis is endemic: Aderet in central Israel and Kahal in the north. The choice of two ecologically distinct sites allowed the researchers to compare vector communities and infection patterns across different parts of the country, providing a more nuanced picture of the transmission system than a single-site study could offer.

The scale of the collection effort was substantial. In total, 20,634 sand flies were captured, of which 13,676, or 66.3 percent, were females, the sex responsible for blood feeding and therefore for parasite transmission. From this pool, the researchers analyzed 4,635 samples representing 5,050 individual female sand flies. Male specimens were identified by morphological examination, while females, which are harder to distinguish by morphology alone, were identified using molecular methods. In all, fourteen sand fly species were identified across the two sites, with species of the subgenus Larroussius dominating the catches at both locations.

The species composition differed markedly between the two villages, underscoring the heterogeneity of the transmission system. In Aderet, in central Israel, Phlebotomus syriacus was the prevalent species, accounting for 27.5 percent of the catch. In Kahal, in northern Israel, the community was structured differently: Phlebotomus galilaeus predominated at 54.1 percent, followed by Phlebotomus tobbi at 24.9 percent. This geographic variation in vector communities is epidemiologically significant because it means that different sand fly species may be responsible for maintaining transmission in different parts of the country, complicating any one-size-fits-all approach to vector control.

To detect the parasite, the researchers screened both unfed and blood-fed female sand flies using a technique known as real-time PCR with high-resolution melting analysis, or PCR-HRM, targeting the internal transcribed spacer 1 (ITS1) region of the parasite’s genome. This approach not only detects Leishmania DNA but also allows differentiation between Leishmania species based on the melting profiles of the amplified DNA. Three samples tested positive for L. infantum DNA: two individual unfed female Phlebotomus syriacus specimens collected in Aderet, and one pooled sample from Kahal. The detection in unfed females is particularly meaningful, since it reduces the likelihood that the DNA merely represented a recent, undigested blood meal from an infected host rather than a genuine infection of the fly itself.

These detections represent the first species-resolved identification of L. infantum DNA in Phlebotomus syriacus both in Israel and worldwide. While the finding stops short of proving that the species is a fully competent vector, since demonstrating vectorial capacity requires additional evidence such as the presence of infective parasite stages in the fly and experimental or epidemiological confirmation of transmission, it provides the first molecular evidence supporting Phlebotomus syriacus as a putative vector of L. infantum in central Israel. For a species that has been on the suspect list for years, this is a crucial step toward formal recognition of its role in the transmission cycle.

Blood-meal analysis added another important layer to the epidemiological picture. By sequencing the blood meals of engorged female sand flies, the researchers identified vertebrate hosts in 74.2 percent of the fed females examined. The results showed a strong dominance of cattle, which accounted for 84.8 percent of identified blood meals, followed by canids at 5.8 percent, with other mammals making up the remainder. The canid finding is especially relevant because dogs and other canids are the main reservoir hosts of L. infantum. Notably, Phlebotomus syriacus females were found to feed on canids in 16.7 percent of cases, a proportion that supports the species’ potential epidemiological relevance as a bridge between the animal reservoir and humans.

The combined findings paint a picture of a heterogeneous transmission system in which multiple sand fly species, different blood-feeding preferences, and geographically varying vector communities all interact to sustain L. infantum circulation. The authors conclude that these results have important implications for targeted surveillance and vector-focused control strategies. Rather than assuming a single vector species across the country, public health authorities may need to tailor monitoring and intervention efforts to the specific vector communities and reservoir dynamics of each region. The identification of cattle as the dominant blood-meal source also raises questions about the role of livestock in the ecology of the transmission system, whether as dead-end hosts that divert flies from reservoir animals or as contributors to sustaining large sand fly populations.

The study was supported by the public health laboratories of the Israeli Ministry of Health in Jerusalem, with fieldwork assistance from inspectors of the Israeli Ministry of Environmental Protection. The research was co-funded by the European Commission under grant 101057690 and by UKRI grants 10038150 and 10039289, as part of the CLIMOS project, one of six Horizon Europe initiatives forming the Climate Change and Health Cluster alongside BlueAdapt, CATALYSE, HIGH Horizons, IDAlert, and TRIGGER. This funding context reflects a growing recognition in Europe and beyond that climate change is altering the distribution and dynamics of vector-borne diseases, making detailed knowledge of local transmission systems increasingly urgent.

For Israel, the confirmation of L. infantum DNA in Phlebotomus syriacus fills a long-standing gap in the map of leishmaniasis transmission. For the broader eastern Mediterranean region, where Phlebotomus syriacus is also present, the finding suggests that this species may deserve closer attention in surveillance programs elsewhere as well. As the authors emphasize, understanding which sand fly species carry which Leishmania parasites, and under what ecological conditions, is fundamental to designing effective interventions, whether through insecticide spraying, reservoir dog management, or environmental modification. The first molecular evidence implicating Phlebotomus syriacus in L. infantum transmission marks a meaningful advance toward that goal, and it signals that the full complexity of leishmaniasis transmission in the region is only now beginning to come into focus.

Subject of Research: First molecular detection of Leishmania infantum DNA in the sand fly Phlebotomus syriacus and its implications for leishmaniasis transmission in Israel

Article Title: First detection of Leishmania infantum DNA in Phlebotomus (Larroussius) syriacus and its epidemiological implications in Israel

Article References: Studentsky, L., Kirstein, O. D., Diaz, D., Elbaz, S. L., Ben Avi, I., Shalan, R., Okla, H., Shilo, S., Kalmus, S., Davidovich-Cohen, M., Orshan, L., & Baneth, G. (2026). First detection of Leishmania infantum DNA in Phlebotomus (Larroussius) syriacus and its epidemiological implications in Israel. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07623-7

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07623-7

Keywords: Leishmania infantum, Phlebotomus syriacus, sand flies, leishmaniasis, vector-borne disease, PCR-HRM, blood meal analysis, Israel, visceral leishmaniasis, cutaneous leishmaniasis, Parasites & Vectors, vector surveillance