Enzootic Cycle Research Articles

Positive feedback regulation between RpoS and BosR in the Lyme disease pathogen.

In Borrelia burgdorferi, the causative agent of Lyme disease, differential gene expression is primarily governed by the alternative sigma factor RpoS (σS). Understanding the regulation of RpoS is crucial for elucidating how B. burgdorferi is maintained throughout its enzootic cycle. Our recent studies have shown that the homolog of Fur/PerR repressor/activator BosR functions as an RNA-binding protein that controls the rpoS mRNA stability. However, the mechanisms regulating BosR, particularly in response to host signals and environmental cues, remain largely unclear. In this study, we uncovered a positive feedback loop between RpoS and BosR, wherein RpoS post-transcriptionally regulates BosR levels. Specifically, mutation or deletion of rpoS significantly reduced BosR levels, whereas artificial induction of rpoS resulted in a dose-dependent increase in BosR levels. Notably, RpoS does not affect bosR mRNA levels but instead modulates the turnover rate of the BosR protein. Moreover, we demonstrated that environmental cues do not directly influence bosR expression but instead induce rpoS transcription and RpoS production, thereby enhancing BosR protein levels. These findings reveal a new layer of complexity in the RpoN-RpoS regulatory pathway, challenging the existing paradigm and suggesting a need to re-evaluate the factors and signals previously implicated in regulating RpoS via BosR. This study provides new insights into the intricate regulatory networks underpinning B. burgdorferi's adaptation and survival in its enzootic cycle.IMPORTANCELyme disease is the most prevalent arthropod-borne infection in the United States. The etiological agent, Borreliella (or Borrelia) burgdorferi, is maintained in nature through an enzootic cycle involving a tick vector and a mammalian host. RpoS, the master regulator of differential gene expression, plays a crucial role in tick transmission and mammalian infection of B. burgdorferi. This study reveals a positive feedback loop between RpoS and a Fur/PerR homolog. Elucidating this regulatory network is essential for identifying potential therapeutic targets to disrupt B. burgdorferi's enzootic cycle. The findings also have broader implications for understanding the regulation of RpoS and Fur/PerR family in other bacteria.

West Nile and Usutu viruses: current spreading and future threats in a warming northern Europe

Climate change heavily threatens planetary and human health. Arboviral infections are best studied using the One Health concept, due to their reliance on complex interactions between environmental factors, arthropod vectors and vertebrate hosts. This review focuses on two arboviruses, namely West Nile Virus (WNV) and Usutu Virus (USUV), both causing emerging public health issues in northern Europe. They are both maintained in an enzootic cycle involving birds and Culex spp mosquitoes. WNV has demonstrated its sensitivity to the consequences of climate change and there is already evidence that global warming contributes to its expansion in Europe. Future WNV indigenous transmission in northern Europe is therefore plausible. Usutu is a lesser known arbovirosis, sharing similar vectors and hosts as WNV. USUV has a similar geographic expansion to WNV, exhibiting some level of co-circulation. It is therefore crucial to monitor these viruses in the hitherto relatively spared regions of northern Europe.

Borrelia burgdorferi tolerates alteration to P66 porin function in a murine infectivity model.

Borrelia burgdorferi exists in a complex enzootic life cycle requiring differential gene regulation. P66, a porin and adhesin, is upregulated and essential during mammalian infection, but is not produced or required within the tick vector. We sought to determine whether the porin function of P66 is essential for infection. Vancomycin treatment of B. burgdorferi cultures was used to screen for P66 porin function and found to generate spontaneous mutations in p66 (bb0603). Three novel, spontaneous, missense P66 mutants (G175V, T176M, and G584R) were re-created by site-directed mutagenesis in an infectious strain background and tested for infectivity in mice by ID50 experiments. Two of the three mutants retained infectivity comparable to the isogenic control, suggesting that B. burgdorferi can tolerate alteration to P66 porin function during infection. The third mutant exhibited highly attenuated infectivity and produced low levels of P66 protein. Interestingly, four isolates that were recovered for p66 sequencing from mouse tissues revealed novel secondary point mutations in genomic p66. However, these secondary mutations did not rescue P66 porin function. New structural modeling of P66 is presented and consistent with these experimental results. This is the first work to assess the contribution of P66 porin function to B. burgdorferi pathogenesis.

There Goes the Neighbourhood-A Multi-City Study Reveals Ticks and Tick-Borne Pathogens Commonly Occupy Urban Green Spaces.

Humans acquire tick-borne pathogens (TBPs) from infected ticks contacted during outdoor activities. Outdoor activity is at its highest in urban green spaces, where the presence of tick populations has increasingly been observed. Consequently, more insight into factors influencing the presence of ticks therein is needed. Here, we assess the occurrence of ticks and several TBPs in urban green spaces in Finland, estimate related human hazard and assess how landscape features influence tick and TBP occurrence therein. Ticks collected from five cities during 2019-2020 were utilised. Borrelia, Rickettsia, Neoehrlichia mikurensis, Anaplasma phagocytophilum, Babesia and TBEV were screened from ticks using qPCR. Various landscape features were calculated and utilised in generalised linear mixed models to assess their contribution towards tick and TBP occurrence in green spaces. Finally, human population density proximate to each study site was calculated and used to create population-weighted risk indices. Borrelia were the most common pathogens detected, with 22% of nymphs and 43% of adults infected. Increasing forest cover had a positive effect on the densities of nymphs and adults, whereas forest size had a negative effect. Middling percentages of artificial surfaces predicted higher nymph densities than low or high values. Human population-weighted risk estimates were highly varied, even within cities. A positive correlation was observed between total city population and risk indices. Ticks and TBPs are commonplace in urban green spaces in Finland. Enzootic cycles for Borrelia and Rickettsia appear to be well maintained within cities, leading to widespread risk of infection therein. Our results suggest that nymph densities are highest in urban forests of medium size, whereas small or large forests show reduced densities. Green spaces of roughly similar risk can be found in cities of different sizes, emphasising that the identification of areas of particularly high hazard is important for effective mitigation actions.

MCP5, a methyl-accepting chemotaxis protein regulated by both the Hk1-Rrp1 and Rrp2-RpoN-RpoS pathways, is required for the immune evasion of Borrelia burgdorferi.

Borrelia (or Borreliella) burgdorferi, the causative agent of Lyme disease, is a motile and invasive zoonotic pathogen adept at navigating between its arthropod vector and mammalian host. While motility and chemotaxis are well known to be essential for its enzootic cycle, the role of each methyl-accepting chemotaxis proteins (MCPs) in the infectious cycle of B. burgdorferi remains unclear. In this study, we show that mcp5, a gene encoding one of the most abundant MCPs in B. burgdorferi, is differentially expressed in response to environmental signals and at distinct stages of the pathogen's enzootic cycle. Notably, mcp5 expression is regulated by the Hk1-Rrp1 and Rrp2-RpoN-RpoS pathways, two key regulatory pathways that are critical for the spirochete's colonization of the tick vector and mammalian host, respectively. Infection experiments with an mcp5 mutant revealed that spirochetes lacking MCP5 were unable to establish infections in either C3H/HeN mice or Severe Combined Immunodeficiency (SCID) mice, which are deficient in adaptive immunity, underscoring MCP5's critical role in mammalian infection. However, the mcp5 mutant was able to establish infection and disseminate in NOD SCID Gamma (NSG) mice, which are deficient in both adaptive and most innate immune responses, suggesting that MCP5 plays an important role in evading host innate immunity. Moreover, NK cell depletion in C3H and SCID mice restored the infectivity of the mcp5 mutant, further highlighting MCP5's role in evading NK cell-associated immunity. Co-culture assays with NK cells and macrophages revealed that the mcp5 mutant enhanced interferon-gamma production by NK cells. In the tick vector, the mcp5 mutants survived feeding but failed to transmit to mice. These findings reveal that MCP5, regulated by both the Rrp1 and Rrp2 pathways, is critical for establishing infection in mammalian hosts by evading NK cell-mediated host innate immunity and is important for the transmission of spirochetes from ticks to mammalian hosts. This work provides a foundation for further elucidation of chemotactic signals sensed by MCP5 that facilitate B. burgdorferi in evading host defenses.

Eastern Equine Encephalitis Virus: The Importance of Metabolism and Aging.

Eastern equine encephalitis virus (EEEV) is a mosquito-transmitted alphavirus that, among humans, can cause a severe and often fatal illness. The zoonotic EEEV enzootic cycle involves a cycle of transmission between Culiseta melanura and avian hosts, frequently resulting in spillover to dead-end vertebrate hosts such as humans and horses. Interestingly, it has been described that the W132G mutation of the very low-density lipoprotein receptor (VLDLR), the receptor of EEEV, significantly enhanced the VLDLR-mediated cell attachment of EEEV. The patient's metabolism plays a pivotal role in shaping the complex landscape of viral zoonosis. EEEV represents a significant public health concern due to its severe clinical outcomes, challenging epidemiological characteristics, and certain risk factors that heighten susceptibility among specific populations or age groups. Age is one of several predictors that can impact the outcome of EEEV infection; juvenile animals appear to be particularly vulnerable to severe disease. This has also been observed in natural infections, as children are often the most severely impacted humans. The aim of this piece is to shed light on the intricate relationship between human metabolism and the Eastern equine encephalitis virus.

Molecular Identification of Host Blood Meal from Phlebotomine Sandflies (Diptera: Psychodidae) from Kerala, India.

Female phlebotomine sandflies serve as vectors for the transmission of Leishmania parasites, perpetuating an enzootic cycle by disseminating between sylvatic and domestic animals. Humans form a part of this cycle because the sandflies search for a blood source required for egg development. The present study aimed to identify the feeding preferences of different sandfly fauna from six districts of Kerala, India, using molecular tools. An entomological survey was conducted during 2021-2023 in Kollam, Kottayam, Thiruvananthapuram, Thrissur, Malappuram, and Palakkad. Both indoor and outdoor habitats were targeted from sandfly collection using different standard tools and methods. Sandflies were identified using standard taxonomic keys, and DNA was extracted from blood meal collected from sandflies. A total of 7366 sandfly specimens were collected during the study period, which belonged to three different genera and 19 species. Blood source was successfully identified from 119 sandflies revealing that the Sergentomyia genus preferably fed on small reptiles and amphibians, whereas Phlebotomus genus was found to mainly feed on mammalian and avian blood. Sergentomyia zeylanica was an exception, as it primarily fed on mammalian blood sources. Interestingly, humans were the second feeding source for Phlebotomus species, which are the proven vectors. Comprehending the feeding patterns of sandflies is crucial, not just for public health but also for obtaining insights into the ecological dynamics between vectors and hosts, ultimately enabling more efficient strategies for disease control and prevention.

Broadly conserved FlgV controls flagellar assembly and Borrelia burgdorferi dissemination in mice

Flagella propel pathogens through their environments, yet are expensive to synthesize and are immunogenic. Thus, complex hierarchical regulatory networks control flagellar gene expression. Spirochetes are highly motile bacteria, but peculiarly, the archetypal flagellar regulator σ28 is absent in the Lyme spirochete Borrelia burgdorferi. Here, we show that gene bb0268 (flgV) in B. burgdorferi, previously and incorrectly annotated to encode the RNA-binding protein Hfq, is instead a structural flagellar component that modulates flagellar assembly. The flgV gene is broadly conserved in the flagellar superoperon alongside σ28 in many Spirochaetae, Firmicutes and other phyla, with distant homologs in Epsilonproteobacteria. We find that B. burgdorferi FlgV is localized within flagellar basal bodies, and strains lacking flgV produce fewer and shorter flagellar filaments and are defective in cell division and motility. During the enzootic cycle, flgV-deficient B. burgdorferi survive and replicate in Ixodes ticks but are attenuated for infection and dissemination in mice. Our work defines infection timepoints when spirochete motility is most crucial and implicates FlgV as a broadly distributed structural flagellar component that modulates flagellar assembly.

Modeling of the Habitat Characteristics and Ecological Niche of the Asian Tiger Mosquito in a Fine-Scale Area of a Primate Research Center Using the Maximum Entropy Model.

Aedes-borne diseases, such as Zika and Chikungunya, originate from an enzootic cycle in which non-human primates (NHPs) function as reservoirs. This study aimed to analyze the characteristic habitat and ecological niche models of Aedes albopictus within the confines of a Primate Research Center (PRC), to assess its potential as a site for zoonotic arbovirus transmission. Additionally, this study aimed to construct a comprehensive map to delineate the risks of arbovirus transmission. A 1-year direct field survey was conducted from January to December 2022 in the PRC to obtain comprehensive data on the presence of larvae, including their conditions, habitat types, and physicochemical characteristics. Larval collection was meticulously performed at potential breeding sites using a 350 ml dipper and pipette. Information on the ecological niche was compiled based on a combination of general environmental variables and mosquito presence data obtained from direct field surveys using the Maximum Entropy (MaxEnt) model. In total, 120 presence points for Ae. albopictus larvae were obtained from the PRC area, with 23.02% of the larvae found in buckets as artificial habitats, and 18.25% found in bromeliad plants as natural habitat types. Larvae of Ae. albopictus occupy artificial habitats that are not turbid, exposed to direct sunlight, and devoid of predators. The abundances and occurrences of Ae. albopictus larvae was found to be significantly influenced by pH and total dissolved solids. This study showed that the PRC was a suitable habitat for breeding Ae. albopictus larvae, with the distance to buildings emerging as a significant environmental variable in the species distribution model CONCLUSIONS: The fine-scale empirical model developed for Ae. albopictus and its habitat characteristics not only provide insights into the suitability of vector habitats, but can also be used assess the risk of arbovirus transmission, potentially informing strategies for controlling mosquito breeding sites within the PRC.

Exposure to live saprophytic Leptospira before challenge with a pathogenic serovar prevents severe leptospirosis and promotes kidney homeostasis

Previous studies demonstrated that Leptospira biflexa, a saprophytic species, triggers innate immune responses in the host during early infection. This raised the question of whether these responses could suppress a subsequent challenge with pathogenic Leptospira. We inoculated C3H/HeJ mice with a single or a double dose of L. biflexa before challenge with a pathogenic serovar, Leptospira interrogans serovar Copenhageni FioCruz (LIC). Pre-challenge exposure to L. biflexa did not prevent LIC dissemination and colonization of the kidney. However, it rescued weight loss and mouse survival thereby mitigating disease severity. Unexpectedly, there was correlation between rescue of overall health (weight gain, higher survival, lower kidney fibrosis marker ColA1) and higher shedding of LIC in urine. This stood in contrast to the L. biflexa unexposed LIC challenged control. Immune responses were dominated by increased frequency of effector T helper (CD4+) cells in spleen, as well as significant increases in serologic IgG2a. Our findings suggest that exposure to live saprophytic Leptospira primes the host to develop Th1 biased immune responses that prevent severe disease induced by a subsequent challenge with a pathogenic species. Thus, mice exposed to live saprophytic Leptospira before facing a pathogenic serovar may withstand infection with far better outcomes. Furthermore, a status of homeostasis may have been reached after kidney colonization that helps LIC complete its enzootic cycle.

Exposure to live saprophytic Leptospira before challenge with a pathogenic serovar prevents severe leptospirosis and promotes kidney homeostasis.

Previous studies demonstrated that Leptospira biflexa, a saprophytic species, triggers innate immune responses in the host during early infection. This raised the question of whether these responses could suppress a subsequent challenge with pathogenic Leptospira. We inoculated C3H/HeJ mice with a single or a double dose of L. biflexa before challenge with a pathogenic serovar, Leptospira interrogans serovar Copenhageni FioCruz (LIC). Pre-challenge exposure to L. biflexa did not prevent LIC dissemination and colonization of the kidney. However, it rescued weight loss and mouse survival thereby mitigating disease severity. Unexpectedly, there was correlation between rescue of overall health (weight gain, higher survival, lower kidney fibrosis marker ColA1) and higher shedding of LIC in urine. This stood in contrast to the L. biflexa unexposed LIC challenged control. Immune responses were dominated by increased frequency of effector T helper (CD4+) cells in spleen, as well as significant increases in serologic IgG2a. Our findings suggest that exposure to live saprophytic Leptospira primes the host to develop Th1 biased immune responses that prevent severe disease induced by a subsequent challenge with a pathogenic species. Thus, mice exposed to live saprophytic Leptospira before facing a pathogenic serovar may withstand infection with far better outcomes. Furthermore, a status of homeostasis may have been reached after kidney colonization that helps LIC complete its enzootic cycle.

Circulation of West Nile virus and Usutu virus in birds in Germany, 2021 and 2022

Background Usutu virus (USUV) and West Nile virus (WNV) are zoonotic arthropod-borne orthoflaviviruses. The enzootic transmission cycles of both include Culex mosquitoes as vectors and birds as amplifying hosts. For more than 10 years, these viruses have been monitored in birds in Germany by a multidisciplinary network. While USUV is present nationwide, WNV used to be restricted to the central-east. Methods In 2021 and 2022, over 2300 live bird blood samples and organs from over 3000 deceased birds were subjected to molecular and serological analysis regarding the presence of WNV and USUV. The samples were collected at sites all over Germany. Results Circulation of both viruses increased in 2022. For USUV, the nationwide presence of lineages Africa 3 and Europe 3 reported in previous years was confirmed. Lineage Europe 2, formerly restricted to the German east, was able to expand westward. Nonetheless, USUV neutralizing antibody (nAb) detection rates remained low (< 9%). Years 2021 and 2022 were characterized by stable enzootic circulation of WNV lineage 2, dominated by one previously identified subcluster (95% of generated sequences). In 2022, >20% of birds in the endemic region in eastern Germany carried nAb against WNV. Serological data also indicate expanding WNV circulation west and south of the known hotspots in Germany. Conclusions USUV circulates enzootically nationwide. Emergence of WNV at several new locations in Germany with a potential increase in human infections may be imminent. In this context, wild bird monitoring serves as a capable early warning system in a One Health setting.

Spatiotemporal dynamics of rabies virus detected in rabid dogs in Cameroon, 2010–2021

Rabies is a viral zoonosis that causes an estimated 60,000 human deaths each year, mainly in Africa and Asia. The etiological agent of rabies, the Rabies Lyssavirus or Rabies Virus (RABV) has been characterized in dog populations in Cameroon, in previous studies. However, the dynamics of RABV maintenance and propagation in dogs are still to be documented in Cameroon. This study thus, aimed at investigating the spatial and temporal dynamics of RABV variants in Cameroon. Long genomic sequences of about 4893 nucleotides, encompassing the N, P, M and G genes as well as part of the G-L intergenic region (Ψ), were determined from 56 RABV strains recovered from dog populations in Cameroon from 2010 to 2021. Temporal and spatial dynamics of RABV circulation in Cameroon were investigated by Bayesian analyses with the BEAST 1.10.4 package from extended RABV genomic sequences data combined with their collection dates and the geographical coordinates of their sampling areas. This revealed a genetic evolution rate of 3.14 × 10−4 substitutions/site/year among Africa-1a and Africa-2 clades of RABV from Cameroon. The most recent common ancestor (MRCA) of the studied strains of the Africa-1a lineage was estimated to have emerged between 1880 and 1906 (95 % HPD; mean 1894), while that of the strains of the Africa-2 clade had a slightly later estimated origin between 1907 and 1928 (95 % HPD, mean 1918). Overall, phylogeographic analyses suggested RABV spread in Cameroon between sub-national regions. Our data provides substantial support to previous findings from similar epidemiological settings, indicating human mediated movements of infected dogs between distant cities may be a key factor in the maintenance of the enzootic cycle of rabies among dogs in Cameroon.

Integrating indicator-based and event-based surveillance data for risk mapping of West Nile virus, Europe, 2006 to 2021.

BackgroundWest Nile virus (WNV) has an enzootic cycle between birds and mosquitoes, humans being incidental dead-end hosts. Circulation of WNV is an increasing public health threat in Europe. While detection of WNV is notifiable in humans and animals in the European Union, surveillance based on human case numbers presents some limitations, including reporting delays.AimWe aimed to perform risk mapping of WNV circulation leading to human infections in Europe by integrating two types of surveillance systems: indicator-based and event-based surveillance.MethodsFor indicator-based surveillance, we used data on human case numbers reported to the European Centre for Disease Prevention and Control (ECDC), and for event-based data, we retrieved information from news articles collected through an automated biosurveillance platform. In addition to these data sources, we also used environmental data to train ecological niche models to map the risk of local WNV circulation leading to human infections.ResultsThe ecological niche models based on both types of surveillance data highlighted new areas potentially at risk of WNV infection in humans, particularly in Spain, Italy, France and Greece.ConclusionAlthough event-based surveillance data do not constitute confirmed occurrence records, integrating both indicator-based and event-based surveillance data proved useful. These results underscore the potential for a more proactive and comprehensive strategy in managing the threat of WNV in Europe by combining indicator- and event-based and environmental data for effective surveillance and public health response.

The plasmid-encoded members of paralogous gene family 52 are dispensable to the enzootic cycle of Borrelia burgdorferi.

Lyme disease, the leading vector-borne disease in the United States and Europe, develops after infection with Borrelia burgdorferi sensu lato bacteria. Transmission of the spirochete from the tick vector to a vertebrate host requires global changes in gene expression that are controlled, in part, by the Rrp2/RpoN/RpoS alternative sigma factor cascade. Transcriptional studies defining the B. burgdorferi RpoS regulon have suggested that RpoS activates the transcription of paralogous family 52 (PFam52) genes. In strain B31, PFam52 genes (bbi42, bbk53, and bbq03) encode a set of conserved hypothetical proteins with >89% amino acid identity that are predicted to be surface-localized. Extensive homology among members of paralogous families complicates studies of protein contributions to pathogenicity as the potential for functional redundancy will obfuscate findings. Using a sequential mutagenesis approach, we generated clones expressing a single PFam52 paralog, as well as a strain deficient in all three. The single paralog expressing strains were used to confirm BBI42, BBK53, and BBQ03 surface localization and RpoS regulation. Surprisingly, the PFam52-deficient strain was able to infect mice and complete the enzootic cycle similar to the wild-type parental strain. Indeed, the presence of numerous pseudogenes that contain frameshifts or internal stop codons among the PFam52 genes suggests that they may be subjected to gene loss in B. burgdorferi's reduced genome. Alternatively, the lack of phenotype might reflect the limitations of the experimental mouse infection model.

Positive feedback regulation between RpoS and BosR in the Lyme disease pathogen.

Lyme disease is the most prevalent arthropod-borne infection in the United States. The etiological agent, Borreliella (or Borrelia ) burgdorferi , is maintained in nature through an enzootic cycle involving a tick vector and a mammalian host. RpoS, the master regulator of differential gene expression, plays a crucial role in tick transmission and mammalian infection of B. burgdorferi . This study reveals a positive feedback loop between RpoS and a Fur/PerR homolog. Elucidating this regulatory network is essential for identifying potential therapeutic targets to disrupt B. burgdorferi 's enzootic cycle. The findings also have broader implications for understanding the regulation of RpoS and Fur/PerR family in other bacteria.

Japanese encephalitis in swine in San Jose, Tarlac, Philippines

ObjectivesA systematic review of multidisciplinary studies on Japanese encephalitis (JE) in the Philippines indicated that endemic foci may be found in all 17 administrative regions in the country. MethodsTo establish the etiology of the disease, virus detection and seroprevalence surveys in 198 pigs were conducted in 2010–2011 in four barangays (villages) in the Municipality of San Jose, Tarlac. Prior to the present study, JE virus genotype III (JEV GIII) was recovered from the mosquito, Culex tritaeniorhynchus, in the same municipality where backyard hog-raising and wet rice cultivation were common practices among households located within 1 km radius from the paddies. ResultsJEV GIII was detected from serum and nasal swabs from pigs, 3 to 5-month-old, from barangays Pao, Moriones, and Villa Aglipay. Immunoglobulin (Ig) M and IgG were measured by enzyme-linked immunosorbent assay in pigs < 4 to > 8 months old, with an overall total of 17.2 % and 62.1 %, respectively. The presence of these antibodies in all pigs during four observation periods indicated year-round transmission starting with the rainy season, which encompasses the months of July and September 2010. IgM represented new infections. IgG increased correspondingly with age with repeated infections in older pigs. IgG levels remained high in all barangays. The number of households with any one of the markers: IgM, IgG, reverse transcription-polymerase chain reaction averaged out at 82.5 %, reflecting as it were, vulnerability to JE in barangays where all 198 pigs were examined. This report contributes to knowledge on JE, whereby incidence in humans may be linked to its epizootic spillover from pigs. ConclusionsThe study has shown that four barangays, representing a rice-farming community, supported the enzootic cycle of JE in swine, with mosquitoes previously found to be infected with JEV GIII in San Jose. Thus, infected pigs, rainfall, and proximity of human habitation to breeding sites of vector mosquitoes constituted the risk factors for JE, as it were in other endemic countries in Asia. The finding of viral RNA in nasal swabs suggests the possibility of direct transmission among pigs via the oronasal route. From the standpoint of public health, JE immunization of children and periodic surveillance of swine are recommended.

DnaA modulates the gene expression and morphology of the Lyme disease spirochete.

All bacteria encode a multifunctional DNA-binding protein, DnaA, which initiates chromosomal replication. Despite having the most complex, segmented bacterial genome, little is known about Borrelia burgdorferi DnaA and its role in maintaining the spirochete's physiology. In this work we utilized inducible CRISPR-interference and overexpression to modulate cellular levels of DnaA to better understand this essential protein. Dysregulation of DnaA, either up or down, increased or decreased cell lengths, respectively, while also significantly slowing replication rates. Using fluorescent microscopy, we found the DnaA CRISPRi mutants had increased numbers of chromosomes with irregular spacing patterns. DnaA-depleted spirochetes also exhibited a significant defect in helical morphology. RNA-seq of the conditional mutants showed significant changes in the levels of transcripts involved with flagellar synthesis, elongation, cell division, virulence, and other functions. These findings demonstrate that the DnaA plays a commanding role in maintaining borrelial growth dynamics and protein expression, which are essential for the survival of the Lyme disease spirochete.

Transovarial transmission of Yersinia pestis in its flea vector Xenopsylla cheopis

Yersinia pestis, the causative agent of plague, is endemic in certain regions due to a stable transmission cycle between rodents and their associated fleas. In addition, fleas are believed to serve as reservoirs that can occasionally cause enzootic plague cycles and explosive epizootic outbreaks that increase human exposure. However, transmission by fleas is inefficient and associated with a shortened lifespan of the flea and rodent hosts, indicating that there remain significant gaps in our understanding of the vector-animal cycle of Y. pestis. Here, we show that laboratory-reared, infected fleas (Xenopsylla cheopis) can transmit viable Y. pestis from adults to eggs, and the bacteria can be passed through all subsequent life stages of the flea. Thus, our data raise the possibility that transovarial transmission in fleas might contribute to the persistence of Y. pestis in the environment without detectable plague activity in mammals.

A Systematic Assessment of Leishmania donovani Infection in Domestic and Wild Animal Reservoir Hosts of Zoonotic Visceral Leishmaniasis in India

Leishmaniasis is a neglected disease with a global spread that affects both domestic and wild animals in addition to people. Leishmania donovani is the suspected anthroponotic cause of visceral leishmaniasis (VL) in India, where it is an endemic disease. The reservoir hosts play a crucial role in the life cycle of the Leishmania parasite. The complicated connection between the pathogen, vector, and reservoir exhibits geographical and temporal diversity. Human-to-human and, to a lesser extent, human-to-animal transmission are the principal mechanisms for the maintenance of anthroponotic diseases. A number of animals were examined for the presence of Leishmania parasites and the findings were reviewed in order to examine the role of animal reservoirs in domestic transmission of cutaneous leishmaniasis in endemic regions of India. The analysis objective was to assess the research conducted on domestic animals’ propensity to spread L. donovani in endemic areas, with a particular emphasis on how proximity and animal density may impact the prevalence of human leishmaniasis. Species of the L. donovani complex have distinct enzootic, zoonotic, and anthroponotic life cycles that depend on the environment. The majority of Leishmania spp. are zoonotic, spreading from non-human mammals to humans. Many nations have leishmaniasis as an endemic disease, and the Indian subcontinent (ISC) has an estimated two to three lakh people who are at risk. This systematic review evaluates the gaps in our understanding of disease transmission that contradict conventional wisdom about the reservoir(s) of visceral leishmaniasis and efforts to manage it on the Indian subcontinent. Fundamental concerns in VL epidemiology and ecology will be clarified by a better understanding of L. donovani infection in domestic animals and its transfer to sandflies. A deliberate, systematic search was conducted on PubMed, Science Direct, and Google Scholar using keywords such as “Leishmania donovani”, “zoonotic visceral leishmaniasis”, and “wild animal reservoir for Leishmania donovani”. A total of 530 potentially relevant references were obtained from these databases, and 507 were not considered due to copy avoidance, irrelevant titles, research publications from nations other than India, or modified compositions. Among the remaining 23 investigations, 20 were rejected, and only 3 were included in the present study. Finally, three research papers with 867 goats, 161 cattle, 106 chickens, 26 sheep, three buffaloes, 406 dogs, and 309 rats were reported. Along with these data, studies across Asian and African countries that are considered VL-endemic areas have been discussed. According to the review, goats are the epidemic’s primary host and possible reservoir in several regions of India. In the endemic regions of the disease, some species of rodents, along with the canines, appear to be maintaining the L. donovani transmission cycle.