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Background The ocular manifestations of cat scratch disease (CSD) are diverse. We report a rare case of isolated choroidal granuloma with serous retinal detachment (SRD) secondary to Bartonella henselae infection in a patient without feline exposure. Case presentation A retrospective analysis of a 38-year-old female presenting in March 2024 with unilateral visual impairment and metamorphopsia. Diagnostic evaluations included multimodal imaging (spectral-domain optical coherence tomography [SD-OCT], fluorescein angiography [FA], indocyanine green angiography [ICGA]), and serologic testing. Ocular examination revealed a yellowish-white subretinal lesion with associated SRD superotemporal to the optic disc. SD-OCT demonstrated a dome-shaped choroidal elevation with homogeneous hyporeflectivity and subretinal fluid. FA showed late hyperfluorescence of the lesion, while ICGA revealed persistent hypofluorescence. Serologic testing confirmed elevated Bartonella henselae IgG titers (1:256). The patient had no systemic symptoms or history of feline contact and initially received systemic steroids, topical anti-inflammatory/antibiotic agents, and traditional Chinese medicine. All treatments were discontinued after 24 h, and the lesion subsequently resolved with complete resolution of subretinal fluid and best-corrected visual acuity (BCVA) recovery to 20/20. Conclusion Ocular bartonellosis may manifest as an isolated choroidal granuloma with vision-threatening SRD, even in the absence of feline exposure. Multimodal imaging and serologic testing are critical for diagnosis. The condition may resolve spontaneously without targeted antimicrobial therapy for Bartonella infection, even in the absence of anti-inflammatory therapy.

Bartonellosis is a vector-borne zoonotic disease with worldwide distribution that can infect humans and a large number of mammals including small companion animals (cats and dogs). In recent years, an increasing number of studies from around the world have reported Bartonella infections, although publications have predominantly focused on the North American perspective. Currently, clinico-pathological data from Europe are more limited, suggesting that bartonellosis may be an infrequent or underdiagnosed infectious disease in cats and dogs. Research is needed to confirm or exclude Bartonella infection as a cause of a spectrum of feline and canine diseases. Bartonella spp. can cause acute or chronic infections in cats, dogs and humans. On a comparative medical basis, different clinical manifestations, such as periods of intermittent fever, granulomatous inflammation involving the heart, liver, lymph nodes and other tissues, endocarditis, bacillary angiomatosis, peliosis hepatis, uveitis and vasoproliferative tumors have been reported in cats, dogs and humans. The purpose of this review is to provide an update and European perspective on Bartonella infections in cats and dogs, including clinical, diagnostic, epidemiological, pathological, treatment and zoonotic aspects.

Background Species of the genus Bartonella are facultative intracellular alphaproteobacteria with zoonotic potential. Bartonella infections in humans range from mild with unspecific symptoms to life threatening, and can be transmitted via arthropod vectors or through direct contact with infected hosts, although the latter mode of transmission is rare. Among the small mammals that harbour Bartonella spp., rodents are the most speciose group and harbour the highest diversity of these parasites. Human–rodent interactions are not unlikely as many rodent species live in proximity to humans. However, a surprisingly low number of clinical cases of bartonellosis related to rodent-associated Bartonella spp. have thus far been recorded in humans. Methods The main purpose of this review is to determine explanatory factors for this unexpected finding, by taking a closer look at published clinical cases of bartonellosis connected with rodent-associated Bartonella species, some of which have been newly described in recent years. Thus, another focus of this review are these recently proposed species. Conclusions Worldwide, only 24 cases of bartonellosis caused by rodent-associated bartonellae have been reported in humans. Possible reasons for this low number of cases in comparison to the high prevalences of Bartonella in small mammal species are (i) a lack of awareness amongst physicians of Bartonella infections in humans in general, and especially those caused by rodent-associated bartonellae; and (ii) a frequent lack of the sophisticated equipment required for the confirmation of Bartonella infections in laboratories that undertake routine diagnostic testing. As regards recently described Bartonella spp., there are presently 14 rodent-associated Candidatus taxa. In contrast to species which have been taxonomically classified, there is no official process for the review of proposed Candidatus species and their names before they are published. This had led to the use of malformed names that are not based on the International Code of Nomenclature of Prokaryotes. Researchers are thus encouraged to propose Candidatus names to the International Committee on Systematics of Prokaryotes for approval before publishing them, and only to propose new species of Bartonella when the relevant datasets allow them to be clearly differentiated from known species and subspecies. Graphical Abstract

In this review, we explore the state-of-the-art of sand fly relationships with microbiota, viruses and Leishmania, with particular emphasis on the vector immune responses. Insect-borne diseases are a major public health problem in the world. Phlebotomine sand flies are proven vectors of several aetiological agents including viruses, bacteria and the trypanosomatid Leishmania, which are responsible for diseases such as viral encephalitis, bartonellosis and leishmaniasis, respectively. All metazoans in nature coexist intimately with a community of commensal microorganisms known as microbiota. The microbiota has a fundamental role in the induction, maturation and function of the host immune system, which can modulate host protection from pathogens and infectious diseases. We briefly review viruses of public health importance present in sand flies and revisit studies done on bacterial and fungal gut contents of these vectors. We bring this information into the context of sand fly development and immune responses. We highlight the immunity mechanisms that the insect utilizes to survive the potential threats involved in these interactions and discuss the recently discovered complex interactions among microbiota, sand fly, Leishmania and virus. Additionally, some of the alternative control strategies that could benefit from the current knowledge are considered.

Pathogenic bacteria of the genus Bartonella can induce vasoproliferative lesions during infection. The underlying mechanisms are unclear, but involve secretion of an unidentified mitogenic factor. Here, we use functional transposon-mutant screening in Bartonella henselae to identify such factor as a pro-angiogenic autotransporter, called BafA. The passenger domain of BafA induces cell proliferation, tube formation and sprouting of microvessels, and drives angiogenesis in mice. BafA interacts with vascular endothelial growth factor (VEGF) receptor-2 and activates the downstream signaling pathway, suggesting that BafA functions as a VEGF analog. A BafA homolog from a related pathogen, Bartonella quintana , is also functional. Our work unveils the mechanistic basis of vasoproliferative lesions observed in bartonellosis, and we propose BafA as a key pathogenic factor contributing to bacterial spread and host adaptation. Pathogenic bacteria of the genus Bartonella can induce vasoproliferative lesions during infection. Here, Tsukamoto et al. show that this effect is caused by a secreted protein that induces cell proliferation and angiogenesis by acting as an analog of the host’s vascular endothelial growth factor (VEGF).

Blood-sucking phlebotomine sand flies (Diptera: Psychodidae) transmit leishmaniasis as well as arboviral diseases and bartonellosis. Sand fly females become infected with Leishmania parasites and transmit them while imbibing vertebrates’ blood, required as a source of protein for maturation of eggs. In addition, both females and males consume plant-derived sugar meals as a source of energy. Plant meals may comprise sugary solutions such as nectar or honeydew (secreted by plant-sucking homopteran insects), aswell as phloem sap that sand flies obtain by piercing leaves and stems with their needle-like mouthparts. Hence, the structure of plant communities can influence the distribution and epidemiology of leishmaniasis. We designed a nextgeneration sequencing (NGS)–based assay for determining the source of sand fly plant meals, based upon the chloroplast DNA gene ribulose bisphosphate carboxylase large chain (rbcL). Here, we report on the predilection of several sand fly species, vectors of leishmaniasis in different parts of the world, for feeding on Cannabis sativa. We infer this preference based on the substantial percentage of sand flies that had fed on C. sativa plants despite the apparent “absence” of these plants from most of the field sites. We discuss the conceivable implications of the affinity of sand flies for C. sativa on their vectorial capacity for Leishmania and the putative exploitation of their attraction to C. sativa for the control of sand fly-borne diseases.

Sandflies are vectors for several tropical diseases such as leishmaniasis, bartonellosis, and sandfly fever. Moreover, sandflies exhibit species-specificity in transmitting particular pathogen species, with females being responsible for disease transmission. Thus, effective classification of sandfly species and the corresponding sex identification are important for disease surveillance and control, managing breeding/populations, research and development, and conducting epidemiological studies. This is typically performed manually by observing internal morphological features, which maybe an error-prone tedious process. In this work, we developed a deep learning artificial intelligence system to determine the gender and to differentiate between three species of two sandfly subgenera (i.e., Phlebotomus alexandri , Phlebotomus papatasi , and Phlebotomus sergenti ). Using locally field-caught and prepared samples over a period of two years, and based on convolutional neural networks, transfer learning, and early fusion of genital and pharynx images, we achieved exceptional classification accuracy (greater than 95%) across multiple performance metrics and using a wide range of pre-trained convolutional neural network models. This study not only contributes to the field of medical entomology by providing an automated and accurate solution for sandfly gender identification and taxonomy, but also establishes a framework for leveraging deep learning techniques in similar vector-borne disease research and control efforts.

Bartonella is a vector-borne zoonotic pathogen, which could also be transmitted directly and cause a variety of clinical illnesses. This study aimed to investigate the prevalence of Bartonella in countries in the WHO Eastern Mediterranean Region (WHO-EMR) region. We searched using the keywords Bartonella and the name of each country in the WHO-EMR in databases such as PubMed, ISI (Web of Science), Scopus, and Google Scholar, with a publication date range of 1990–2022 and limited to English articles. We evaluated the quality of the studies using the STROBE 6-item checklist and used the random effects model to integrate the findings of the included studies. A total of 45 papers out of 240 were included in the analysis. The results showed the prevalence of Bartonella infection among endocarditis patients was 3.8% (95% CI: 0.2–7.4) and the seroprevalence of Bartonella among other people was 27.5% (95% CI: 13.5–41.5). The overall prevalence of Bartonella spp. among animals, as determined by molecular, serological, and culture methods, was 11.9% (95% CI: 5.7–18.2), 38.9% (95% CI: 27.5–50.2), and 1.7% (95% CI: 0.5–2.9), respectively. Furthermore, the prevalence of Bartonella spp. in ectoparasites was 3.9% (95% CI: 3.5–5.2), with fleas (6.2%) showing a higher prevalence compared to lice (4.9%) and ticks (1.0%). The detection of Bartonella in all animal and ectoparasites species and human populations in the WHO-EMR with prevalence ranging from 0.3% to 23% is concerning, emphasizes the importance of conducting more comprehensive studies to gain a deeper understanding of the spread of Bartonella in these areas.

Companion vector-borne diseases (CVBDs) are an important threat for pet life, but may also have an impact on human health, due to their often zoonotic character. The importance and awareness of CVBDs continuously increased during the last years. However, information on their occurrence is often limited in several parts of the world, which are often especially affected. Latin America (LATAM), a region with large biodiversity, is one of these regions, where information on CVBDs for pet owners, veterinarians, medical doctors and health workers is often obsolete, limited or non-existent. In the present review, a comprehensive literature search for CVBDs in companion animals (dogs and cats) was performed for several countries in Central America (Belize, Caribbean Islands, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Puerto Rico) as well as in South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana (British Guyana), Paraguay, Peru, Suriname, Uruguay, Venezuela) regarding the occurrence of the following parasitic and bacterial diseases: babesiosis, heartworm disease, subcutaneous dirofilariosis, hepatozoonosis, leishmaniosis, trypanosomosis, anaplasmosis, bartonellosis, borreliosis, ehrlichiosis, mycoplasmosis and rickettsiosis. An overview on the specific diseases, followed by a short summary on their occurrence per country is given. Additionally, a tabular listing on positive or non-reported occurrence is presented. None of the countries is completely free from CVBDs. The data presented in the review confirm a wide distribution of the CVBDs in focus in LATAM. This wide occurrence and the fact that most of the CVBDs can have a quite severe clinical outcome and their diagnostic as well as therapeutic options in the region are often difficult to access and to afford, demands a strong call for the prevention of pathogen transmission by the use of ectoparasiticidal and anti-feeding products as well as by performing behavioural changes.

Vector-borne diseases account for nearly 20% of all globally recognised infectious diseases. Within the spectrum of flea-borne pathogens, Bartonella and Rickettsia bacteria are prominent, contributing to the emergence and resurgence of diseases on a global scale. This study investigates the presence of species of Bartonella and Rickettsia harboured by fleas collected from wild rodents in northwestern Argentina (NWA). A total of 28 fleas from three genera and seven species were assessed. DNA of Bartonella and Rickettsia spp. was found in 12 fleas (42.8%). Phylogenetic analysis of concatenated sequences of gltA and rpoB genes showed the presence of Bartonella quintana in eight fleas of two species, Craneopsylla minerva minerva and Polygenis acodontis . Phylogenetic analysis of concatenated sequences of gltA , ompA and ompB genes identified Rickettsia felis in ten fleas of five species, C. m. minerva , P. acodontis , Polygenis bohlsi bohlsi , Polygenis byturus and Tiamastus palpalis . These bacterial species mark the first report in all flea species studied. This study represents the first survey of flea-borne bacteria for NWA. The results provide information to address strategies for the control and prevention of bartonellosis and rickettsiosis that could have an impact on public health in one of the geographical areas of Argentina with the highest incidence of infections transmitted to humans by ectoparasites.