Biology subjects

Levy, M. Z.

Publications and source records attributed to Levy, M. Z..

9 recordsLinked to original sources

bioRxiv2025

Cave dogs around major urban areas threaten rabies elimination program

BackgroundIn the city of Arequipa, Peru, the government has implemented control measures against dog rabies virus since the detection of its reintroduction in 2015. The city was previously considered free of animal reservoirs other than owned and stray dogs within its urban boundaries. However, multiple reports from peri-urban residents have suggested the presence of feral dogs living in caves on the citys outskirts. We aim to document the presence and dietary patterns of feral dogs adjacent to the city margins. MethodsWe conducted monthly field visits to four peri-urban localities in eastern Arequipa, an area where the presence of feral dogs had been previously reported. Dog caves were identified by tracking footprints and other field signs left by dogs, and their locations were georeferenced. Each cave was revisited monthly three times to record the presence of live and dead dogs, and puppies. Fecal samples collected around the caves were analyzed to assess dietary patterns. ResultsWe observed that feral dogs use caves for resting, hiding, and reproduction-- some of which appear to be constructed by the dogs themselves. The high number of puppies and dead adult dogs indicates a high population turnover. Dietary analysis revealed that these dogs feed on local fauna, including birds, rodents, cats, sheep, and, notably, other dogs. ConclusionsThese unowned, cave-dwelling dogs are not reached by mass rabies vaccination or sterilization programs. Moreover, they exist outside the jurisdiction of health inspectors responsible for rabies surveillance, resulting in a lack of data on rabies infection in this subpopulation. Our findings highlight the need for integrated One Health strategies to address the challenges posed by feral dog populations in rabies elimination efforts.

ecology↗

bioRxiv2025

Highly Dynamic Population of Owned Dogs and Implications for Zoonosis Control

BackgroundDomestic dogs are known carriers of a variety of zoonotic pathogens significant to public health including leishmaniasis, echinococcosis, and, the most lethal, rabies. Control efforts for rabies and other diseases focus on the removal of infected individuals and mass treatment or vaccination to reduce incidence and raise immunity in the susceptible population. However, the complex population dynamics surrounding free-roaming dogs in many developing countries complicate these control methods. While rabies vaccination coverage of 70% or higher, of the dog population at risk, performed annually, should be sufficient to maintain coverage above the critical threshold, rapid population turnover and growth could reduce effective coverage. Our objective was to investigate the impact of dog population dynamics on rabies control activities in a rabies-endemic city. MethodologyUsing data from annual door-to-door surveys in urban and periurban areas, we collected household information (e.g., number of residents), respondent characteristics (e.g., education level), and dog-related data (e.g., vaccination status). These variables were analyzed to evaluate changes in the dog population and vaccination coverage. A compartmental Susceptible - Exposed - Infectious - Vaccinated (SEIV) mathematical model was utilized to estimate the effects of population dynamics on herd immunity against rabies. FindingsWe found that the highly dynamic dog population in Arequipa and its rapid expansion hampers herd immunity, counteracting the efforts made in yearly vaccination campaigns and leading to underestimates of the human to dog ratios ([~]4:1 vs 6:1). Moreover, there are significant differences in dog population trends within urban and periurban areas indicating that different strategies or coverage vaccination targets might be needed. This study also introduces an important variable of interest: transient dogs, a population with extremely high turnover (less than one year), which causes an important drop in vaccination coverage that has thus far gone undetected. ConclusionsStabilizing the free-roaming domestic dog population by lowering both mortality and birth rates may help improve the efficacy of current mass vaccination programs. Additionally, the population dynamic parameters, on which we base our models, must be regularly refined to best represent the current status of disease risk and population immunity. By using a One Health approach we can understand and address the dynamics of dog populations, and better control zoonotic diseases like rabies, ultimately improving public health.

ecology↗

bioRxiv2024

Genomic Characterization of a Dog-Mediated Rabies Outbreak in El Pedregal, Arequipa, Peru

BackgroundRabies, a re-emerging zoonosis with the highest known human case fatality rate, has been largely absent from Peru, except for endemic circulation in the Puno region on the Bolivian border and re-emergence in Arequipa City in 2015, where it has persisted. In 2021, an outbreak occurred in the rapidly expanding city of El Pedregal near Arequipa, followed by more cases in 2022 after nearly a year of epidemiological silence. While currently under control, questions persist regarding the origin of the El Pedregal outbreak and implications for maintaining rabies control in Peru. MethodsWe sequenced 25 dog rabies virus (RABV) genomes from the El Pedregal outbreak (n=11) and Arequipa City (n=14) from 2021-2023 using Nanopore sequencing in Peru. Historical genomes from Puno (n=4, 2010-2012) and Arequipa (n=5, 2015-2019), were sequenced using an Illumina approach in the UK. In total, 34 RABV genomes were analyzed, including archived and newly obtained samples. The genomes were analyzed phylogenetically to understand the outbreaks context and origins. ResultsPhylogenomic analysis identified two genetic clusters in El Pedregal: 2021 cases stemmed from a single introduction unrelated to Arequipa cases, while the 2022 sequence suggested a new introduction from Arequipa rather than persistence. In relation to canine RABV diversity in Latin America, all new sequences belonged to a new minor clade, Cosmopolitan Am5, sharing relatives from Bolivia, Argentina, and Brazil. ConclusionGenomic insights into the El Pedregal outbreak revealed multiple introductions over a 2-year window. Eco-epidemiological conditions, including migratory worker patterns, suggest human-mediated movement drove introductions. Despite outbreak containment, El Pedregal remains at risk of dog-mediated rabies due to ongoing circulation in Arequipa, Puno, and Bolivia. Human-mediated movement of dogs presents a major risk for rabies re-emergence in Peru, jeopardizing regional dog-mediated rabies control. Additional sequence data is needed for comprehensive phylogenetic analyses.

genomics↗

bioRxiv2020

Elucidating the mechanism of Trypanosoma cruzi acquisition by triatomine insects: evidence from a large field survey of Triatoma infestans

Blood-sucking triatomine bugs transmit the protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas disease. We measured the prevalence of T. cruzi infection in 58,519 Triatoma infestans captured in residences in and near Arequipa, Peru. Among bugs from infected colonies, T. cruzi prevalence increased with stage from 12% in second instars to 36% in adults. Regression models demonstrated a linear relationship between infection prevalence and developmental stage. Prevalence increased by 5.4 percentage points with each additional stage. We postulate that the probability of acquiring the parasite may be related to the number of feeding events. Transmission of the parasite does not appear to be correlated with the amount of blood ingested during feeding. Similarly, other hypothesized transmission routes such as coprophagy fail to explain the observed pattern of prevalence. Our results could have implications for the feasibility of late-acting control strategies that preferentially kill older insects.

ecology↗

bioRxiv2020

A real-time search strategy for finding urban disease vector infestations

Containing domestic vector infestation requires the ability to swiftly locate and treat infested homes. In urban settings where vectors are heterogeneously distributed throughout a dense housing matrix, the task of locating infestations can be challenging. Here, we present a novel stochastic compartmental model developed to help locate infested homes in urban areas. We designed the model using infestation data for the Chagas disease vector species Triatoma infestans in Arequipa, Peru. Our approach incorporates disease vector counts at each observed house, and the vectors complex spatial dispersal dynamics. We used a Bayesian method to augment the observed data, estimate the insect population growth and dispersal parameters, and determine posterior infestation probabilities of households. We investigated the properties of the model through simulation studies, followed by field testing in Arequipa. Simulation studies showed the model to be accurate in its estimates of two parameters of interest: the growth rate of a domestic triatomine bug colony and the probability of a triatomine bug successfully invading a new home after dispersing from an infested home. When testing the model in the field, data collection using model estimates was hindered by low household participation rates, which severely limited the algorithm and in turn, the models predictive power. While future optimization efforts must improve the models capabilities when household participation is low, our approach is nonetheless an important step toward integrating data with predictive modeling to carry out evidence-based vector surveillance in cities.

bioinformatics↗

bioRxiv2019

Dispersal patterns of Trypanosoma cruzi in Arequipa, Peru

Anthropogenic environmental alterations such as urbanization can threaten native populations as well as create novel environments that allow human pests and pathogens to thrive. As the number and size of urban environments increase globally, it is more important than ever to understand the dispersal dynamics of hosts, vectors and pathogens of zoonotic disease systems. For example, a protozoan parasite and the causative agent of Chagas disease in humans, Trypanosoma cruzi, recently colonized and spread through the city of Arequipa, Peru. We used population genomic and phylogenomic tools to analyze whole genomes of 123 T. cruzi isolates collected throughout Arequipa to determine patterns of T. cruzi dispersal. The data show significant population genetic structure within city blocks-parasites in the same block tend to be very closely related - but no population structure among blocks within districts - parasites in neighboring blocks are no more closely related to one another than to parasites in distant districts. These data suggest that T. cruzi dispersal within a block occurs regularly and that occasional long-range dispersal events allow the establishment of new T. cruzi populations in distant blocks. Movement of domestic animals may be the primary mechanism of inter-block and inter-district T. cruzi dispersal. Author SummaryUrbanization creates environments that are ideal for some human pests and pathogens. As the number and size of urban environments increases globally, it is becoming vital to understand how human disease-causing pathogens, their vectors, and their non-human hosts disperse through urban landscapes. Here we study a population of Trypanosoma cruzi - the protozoan parasite and causative agent of Chagas disease in humans - that recently colonized the city of Arequipa, Peru. We use population genomic and phylogenomic tools to understand how this parasite population dispersed through the city to achieve its current distribution and abundance. We show that T. cruzi collected from the same city block tend to be very closely related, while those from neighboring blocks are often as distantly related as those from blocks in distant districts. The data suggest that vectors facilitate frequent within-block dispersal of the parasite, while domestic animal movement may facilitate the relatively infrequent inter-block and interdistrict dispersal.

evolutionary biology↗

bioRxiv2019

Movement patterns of urban free-roaming dogs: implications for rabies control in Arequipa, Peru

In 2015, a case of canine rabies in Arequipa, Peru indicated the re-emergence of rabies virus in the city. Despite mass dog vaccination campaigns across the city and reactive ring vaccination and other control activities around positive cases (e.g. elimination of unowned dogs), the outbreak has spread. Here we explore how the urban landscape of Arequipa affects the movement patterns of free-roaming dogs, the main reservoirs of the rabies virus in the area. We tracked 23 free-roaming dogs using Global Positioning System (GPS) collars. We analyzed the spatio-temporal GPS data using the time- local convex hull method. Dog movement patterns varied across local environments. We found that water channels, an urban feature of Arequipa that are dry most of the year, promote movement. Dogs that used the water channels move further, faster and more directionally than dogs that do not. Our findings suggest that water channels can be used by dogs as highways to transverse the city and have the potential to spread disease far beyond the radius of control practices. Control efforts should focus on a robust vaccination campaign attuned to the geography of the city, and not limited to small-scale rings surrounding cases.

ecology↗

bioRxiv2019

Socio-spatial heterogeneity in participation in mass dog vaccination campaigns, Arequipa, Peru

To control and prevent rabies in Latin America, mass dog vaccination campaigns (MDVC) are implemented mainly through fixed-location vaccination points: owners have to bring their dogs to the vaccination points where they receive the vaccination free of charge. Dog rabies is still endemic in some Latin-American countries and high overall dog vaccination coverage and coverage evenness are desired attributes of MDVC to halt rabies virus transmission. In Arequipa, Peru, we conducted a door-to-door post-campaign survey on >6,000 houses to assess the placement of vaccination points on these two attributes. We found that the odds of participating in the campaign decreased by 16% for every 100 m from the owners house to the nearest vaccination point (p=0.041) after controlling for potential covariates. We found social determinants associated with participating in the MDVC: for each child under 5 in the household the odds of participating in the MDVC decreased by 13% (p=0.032), and for every ten more years living in the area, the odds of participating in the MDVC increased by 9% (p<0.001), after controlling for distance and other covariates. We also found significant spatial clustering of unvaccinated dogs over 500m from the vaccination points, which created pockets of unvaccinated dogs that may sustain rabies virus transmission. Understanding the barriers to dog owners participation in community-based dog-vaccination programs will be crucial to implement effective zoonotic disease preventive activities. Spatial and social elements of urbanization play an important role in coverage of MDVCs and should be considered during their planning and evaluation.

epidemiology↗

bioRxiv2019

Immigration and establishment of urban Trypanosoma cruzi populations

Changing environmental conditions, including those caused by human activities, reshape biological communities through both loss of native species and establishment of non-native species in the altered habitats. Dynamic interactions with the abiotic environment impact both immigration and initial establishment of non-native species into these altered habitats. The repeated emergence of disease systems in urban areas worldwide highlights the importance of understanding how dynamic migratory processes affect the current and future distribution and abundance of pathogens in urban environments. In this study, we examine the pattern of invasion of Trypanosoma cruzi--the causative agent of human Chagas disease--in the city of Arequipa, Peru. Phylogenetic analyses of 136 T. cruzi isolates from Arequipa and other South American locations suggest that only one T. cruzi immigrant established a population in Arequipa as all T. cruzi isolated from vectors in Arequipa form a recent monophyletic group within the broader South American phylogeny. We discuss several hypotheses that may explain the limited number of established T. cruzi lineages despite multiple introductions of the parasite.\n\nAuthor SummaryHuman-associated pests and pathogens, who benefit from the abundance of humans and human-associated hosts or vectors, commonly invade environments altered by human activities. As the number and size of human-disturbed environments increase, so does the importance of identifying ecological and environmental factors that affect the probability that disease systems immigrate to, subsequently establish populations in, urban environments. We examined the number and timing of immigration and establishment events of Trypanosoma cruzi, the causative agent of Chagas disease, in a currently endemic area. Phylogenetic analyses of 136 T. cruzi isolates suggests that the current population descended from a single, recent immigration event. We discuss historical and ecological hypotheses that can explain the limited T. cruzi diversity in this region.

evolutionary biology↗