RESUMEN
Few studies have been able to provide experimental evidence of the ability of fleas to maintain rodent-associated Bartonella infections and excrete these bacteria. These data are important for understanding the transmission cycles and prevalence of these bacteria in hosts and vectors. We used an artificial feeding approach to expose groups of the oriental rat flea (Xenopsylla cheopis Rothschild; Siphonaptera, Pulicidae) to rat blood inoculated with varying concentrations of Bartonella elizabethae Daly (Bartonellaceae: Rhizobiales). Flea populations were maintained by membrane feeding on pathogen-free bloodmeals for up to 13 d post infection. Individual fleas and pools of flea feces were tested for the presence of Bartonella DNA using molecular methods (quantitative and conventional polymerase chain reaction [PCR]). The threshold number of Bartonellae required in the infectious bloodmeal for fleas to be detected as positive was 106 colony-forming units per milliliter (CFU/ml). Individual fleas were capable of harboring infections for at least 13 d post infection and continuously excreted Bartonella DNA in their feces over the same period. This experiment demonstrated that X. cheopis are capable of acquiring and excreting B. elizabethae over several days. These results will guide future work to model and understand the role of X. cheopis in the natural transmission cycle of rodent-borne Bartonella species. Future experiments using this artificial feeding approach will be useful for examining the horizontal transmission of B. elizabethae or other rodent-associated Bartonella species to naïve hosts and for determining the viability of excreted bacteria.
Asunto(s)
Bartonella/fisiología , ADN Bacteriano/análisis , Insectos Vectores/microbiología , Xenopsylla/microbiología , Animales , Heces/químicaRESUMEN
Rodent fleas from northwestern Chihuahua, Mexico, were analyzed for the presence of Bartonella and Yersinia pestis. In total, 760 fleas belonging to 10 species were tested with multiplex polymerase chain reaction analysis targeting the gltA (338-bp) and pla genes (478-bp) of Bartonella and Y. pestis, respectively. Although none was positive for Y. pestis, 307 fleas were infected with Bartonella spp., resulting in an overall prevalence of 40.4%. A logistic regression analysis indicated that the presence of Bartonella is more likely to occur in some flea species. From a subset of Bartonella-positive fleas, phylogenetic analyses of gltA gene sequences revealed 13 genetic variants clustering in five phylogroups (IV), two of which were matched with known pathogenic Bartonella species (Bartonella vinsonii subsp. arupensis and Bartonella washoensis) and two that were not related with any previously described species or subspecies of Bartonella. Variants in phylogroup V, which were mainly obtained from Meringis spp. fleas, were identical to those reported recently in their specific rodent hosts (Dipodomys spp.) in the same region, suggesting that kangaroo rats and their fleas harbor other Bartonella species not reported previously. Considering the Bartonella prevalence and the flea genotypes associated with known pathogenic Bartonella species, we suggest that analysis of rodent and flea communities in the region should continue for their potential implications for human health. Given that nearby locations in the United States have reported Y. pestis in wild animals and their fleas, we suggest conducting larger-scale studies to increase our knowledge of this bacterium.
Asunto(s)
Bartonella/aislamiento & purificación , Roedores/parasitología , Siphonaptera/microbiología , Yersinia pestis/aislamiento & purificación , Animales , Bartonella/genética , GenotipoRESUMEN
Early-phase transmission (EPT) of Yersinia pestis by unblocked fleas is a well-documented, replicable phenomenon with poorly defined mechanisms. We review evidence demonstrating EPT and current knowledge on its biological and biomechanical processes. We discuss the importance of EPT in the epizootic spread of Y. pestis and its role in the maintenance of plague bacteria in nature. We further address the role of EPT in the epidemiology of plague.
Asunto(s)
Insectos Vectores/microbiología , Peste/transmisión , Siphonaptera/microbiología , Yersinia pestis , Animales , Brotes de Enfermedades , Humanos , Peste/epidemiologíaRESUMEN
If a parasite is not detected during a survey, one of two explanations is possible: the parasite was truly absent or it was present but not detected. We fit occupancy models to account for imperfect detection when combing fleas (Siphonaptera) from black-tailed prairie dogs (Cynomys ludovicianus) during June-August 2012 in the Vermejo Park Ranch, New Mexico, USA. With the use of detection histories from combing events during monthly trapping sessions, we fit occupancy models for two flea species: Oropsylla hirusta (a prairie dog specialist) and Pulex simulans (a generalist). Detection probability was <100% for both species and about 21% lower for P. simulans. Pulex simulans may be especially difficult to detect because it is about half the size of O. hirusta. Monthly occupancy (prevalence) for P. simulans was estimated at 24% (June, 95% confidence intervalâ=â19-30), 39% (July, 32-47), and 56% (August, 49-64) in new prairie dog colonies, and 43% (32-54), 61% (49-71), and 79% (70-87) in old colonies. These results suggest P. simulans can attain high prevalence on prairie dogs, especially in old colonies. If P. simulans is highly prevalent on prairie dogs, it may serve as a "bridge vector" between Cynomys and other mammalian hosts of the plague bacterium Yersinia pestis, and even function as a reservoir of Y. pestis between outbreaks.
Asunto(s)
Infestaciones por Pulgas/veterinaria , Sciuridae , Siphonaptera/clasificación , Animales , Infestaciones por Pulgas/epidemiología , Insectos Vectores/microbiología , Modelos Biológicos , New Mexico/epidemiología , Peste/epidemiología , Peste/transmisión , Peste/veterinaria , Siphonaptera/microbiología , Especificidad de la Especie , Yersinia pestis/fisiologíaRESUMEN
Socioeconomic indicators associated with temporal changes in the distribution of human plague cases in New Mexico were investigated for 1976-2007. In the 1980s, cases were more likely in census block groups with poor housing conditions, but by the 2000s, cases were associated with affluent areas concentrated in the Santa Fe-Albuquerque region.
Asunto(s)
Peste/epidemiología , Factores Socioeconómicos , Censos , Vivienda , Humanos , New Mexico , Peste/microbiología , Pobreza , Estaciones del Año , Estados Unidos , Yersinia pestisRESUMEN
Within the United States, the majority of human plague cases are reported from New Mexico. We describe climatic factors involved in intra- and inter-annual plague dynamics using animal-based surveillance data from that state. Unlike the clear seasonal pattern observed at lower elevations, cases occur randomly throughout the year at higher elevations. Increasing elevation corresponded with delayed mean time in case presentation. Using local meteorological data (previous year mean annual precipitation, total degrees over 27 degrees C 3 years before and maximum winter temperatures 4 years before) we built a time-series model predicting annual case load that explained 75% of the variance in pet cases between years. Moreover, we found a significant correlation with observed annual human cases and predicted pet cases. Because covariates were time-lagged by at least 1 year, intensity of case loads can be predicted in advance of a plague season. Understanding associations between environmental and meteorological factors can be useful for anticipating future disease trends.
Asunto(s)
Clima , Peste/epidemiología , Vigilancia de la Población , Animales , Gatos , Perros , Humanos , New Mexico/epidemiología , Estaciones del AñoRESUMEN
Yersinia pestis, the causative agent of plague, has been detected in fleas and mammals throughout the western United States. This highly virulent infection is rare in humans, surveillance of the disease is expensive, and it often was assumed that risk of exposure to Y. pestis is high in most of the western United States. For these reasons, some local health departments in these plague-affected regions have hesitated to undertake surveillance and other prevention activities. To aid in targeting limited public health resources, we created a fine-resolution human plague risk map for New Mexico, the state reporting more than half the human cases in the United States. Our GIS-based model included three landscape features-a nonlinear relationship with elevation, distance to water, and distance to the ecotone between Rocky Mountain/Great Basin open and closed coniferous woodlands-and yielded an overall accuracy of approximately 80%. The model classified 17.25% of the state as posing significant risk of exposure to humans on privately or tribally owned land, which suggests that resource requirements for regular surveillance and control of plague could be effectively focused on < 20% of the state.