Defining New Pathways to Manage the Ongoing Emergence of Bat Rabies in Latin America.

Rabies transmitted by common vampire bats (Desmodus rotundus) has been known since the early 1900s but continues to expand geographically and in the range of species and environments affected. In this review, we present current knowledge of the epidemiology and management of rabies in D. rotundus and argue that it can be reasonably considered an emerging public health threat. We identify knowledge gaps related to the landscape determinants of the bat reservoir, reduction in bites on humans and livestock, and social barriers to prevention. We discuss how new technologies including autonomously-spreading vaccines and reproductive suppressants targeting bats might manage both rabies and undesirable growth of D. rotundus populations. Finally, we highlight widespread under-reporting of human and animal mortality and the scarcity of studies that quantify the efficacy of control measures such as bat culling. Collaborations between researchers and managers will be crucial to implement the next generation of rabies management in Latin America.

MAMMALIAN HOSTS, VECTORS, AND BACTERIAL PATHOGENS IN COMMUNITIES WITH AND WITHOUT BLACK-TAILED PRAIRIE DOGS ( CYNOMYS LUDOVICIANUS) IN NORTHWESTERN MEXICO.

: The presence of keystone species can influence disease dynamics through changes in species diversity and composition of vector and host communities. In this study, we compared 1) the diversity of small mammals; 2) the prevalence, abundance, and intensity of arthropod vectors; and 3) the prevalence of Yersinia pestis, Francisella tularensis, and Bartonella spp. in vectors, between two grassland communities of northern Sonora, Mexico, one with (La Mesa [LM]) and one without (Los Fresnos [LF]) black-tailed prairie dogs ( Cynomys ludovicianus). The mammal community in LF exhibited higher species richness and diversity than LM, and species composition was different between the two communities. Flea species richness, prevalence, abundance, and intensity, were higher in LM than in LF. The most abundant fleas were Oropsylla hirsuta and Pulex simulans, and C. ludovicianus was the host with the highest flea intensity and richness. There was no serologic evidence for the presence of Y. pestis and F. tularensis in any community, but Bartonella spp. was present in 18% of the total samples. Some specificity was observed between Bartonella species, flea species, and mammal species. Although prairie dogs can indirectly affect the diversity and abundance of hosts and vectors, dynamics of vector-borne diseases at these spatial and temporal scales may be more dependent on the vector and pathogen specificity.

Molecular Survey of Bartonella Species and Yersinia pestis in Rodent Fleas (Siphonaptera) From Chihuahua, Mexico.

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.

Prevalence and genetic diversity of Bartonella strains in rodents from northwestern Mexico.

Bartonella infections were investigated in wild rodents from northwestern Chihuahua, Mexico. A total of 489 rodents belonging to 14 species were surveyed in four areas. Bartonella bacteria were cultured from 50.1% of rodent samples (245/489). Infection rates ranged from 0% to 83.3% per rodent species, with no significant difference between sites except for Cynomys ludovicianus. Phylogenetic analyses of the citrate synthase gene (gltA) of the Bartonella isolates revealed 23 genetic variants (15 novel and 8 previously described), clustering into five phylogroups. Three phylogroups were associated with Bartonella vinsonii subsp. vinsonii, B. vinsonii subsp. arupensis, and B. washoensis, respectively. The other two phylogroups were not genetically related to any known Bartonella species. The genetic variants and phylogenetic groups exhibited a high degree of host specificity, mainly at the genus and family levels. This is the first study that describes the genetic diversity of Bartonella strains in wild rodents from Mexico. Considering that some variants found in this study are associated with Bartonella species that have been reported as zoonotic, more investigations are needed to further understand the ecology of Bartonella species in Mexican wildlife and their implications for human health.

Responses of small mammals to habitat fragmentation: epidemiological considerations for rodent-borne hantaviruses in the Americas.

Rodent-borne hantaviruses are a group of zoonotic agents that cause hemorrhagic fever in humans. The transmission of hantaviruses among rodent hosts may be higher with the increase of reservoir host abundance in a given area (density-dependent transmission) and with the decrease of small mammal diversity (dilution effect phenomenon). These population and community parameters may be modified by habitat fragmentation; however, studies that focus on fragmentation and its effect on hantavirus infection risk are scarce. To further understanding of this issue, we assessed some population and community responses of rodents that may increase the risk for hantavirus transmission among wildlife hosts in the Americas. We conducted a meta-analysis of published studies to assess the responses of small mammals to fragmentation of native habitats, relative to patch size. Our analyses included five countries and 14 case studies for abundance of reservoir hosts (8 species) and 15 case studies for species richness. We found that a reduction of patch area due to habitat fragmentation is associated with increased reservoir host abundances and decreased small mammal richness, which is mainly due to the loss of non-host small mammals. According to these results, habitat fragmentation in the Americas should be considered as an epidemiological risk factor for hantavirus transmission to humans. These findings are important to assess potential risk of infection when fragmentation of native habitats occurs.

Orthopoxvirus antibodies in grey squirrels (Sciurus aureogaster) in Mexico City, Mexico.

Serum from Mexican grey squirrels (Sciurus aureogaster) from Mexico City reacted to Orthopoxvirus by enzyme-linked immunosorbent assay. Real-time PCR based on oral swabs and scabs did not detect viral DNA. Antibody prevalence was 30% (n=366), providing the first evidence of Orthopoxvirus antibodies in Mexican wild rodents.

Morphometric differences in testicular tissue of tadarida brasiliensis bats from the urban area of Mexico City during summer, autumn, and winter / Diferencias morfométricas en parenquima testicular de murcielagos tadarida brasiliensis del área urbana de la Ciudad de México en verano, otoño e invierno

Most of the neotropical bats reproduce in a seasonal fashion. The purpose of this study was to assess changes in testicular tissue by morphometry, in Tadarida brasiliensis bat, in a south urban zone of Mexico City during summer, autumn, and winter. Three sample collections (February, June, and September) from T. brasiliensis were carried out (n=6). Testicle fragments were obtained for histological studies. Diameter of the seminiferous tubules and interstitial space were measured, cellular populations were identified and counted. June samples showed smaller diameter of seminiferous tubules and larger interstitial space between tubules; also there were less number of germinal epithelium cells and spermatids were absent. Tissues from September and February showed a significant increase (p 0.05) in tubule diameter, germinal epithelium thickness, and number of germinal epithelium cells when compared to June samples. Only February samples showed presence of spermatids. Our results suggest the existence of seasonal variations in the reproductive activity of T. brasiliensis, under conditions in which the study was conducted.

La mayoría de los murciélagos neotropicales se reproducen de manera estacional. El objetivo de este estudio fue determinar los cambios morfométricos en el parénquima testicular del murciélago Tadarida brasiliensis que habita en un área urbana del sur de la Ciudad de México durante las estaciones de verano, otoño e invierno. Se obtuvieron fragmentos de tejido testicular para su estudio histológico. Se midió el diámetro de los túbulos seminíferos y el espacio interstisial y se identificaron y contaron distintos tipos celulares. En las muestras de junio se encontró un menor diámetro de los túbulos seminíferos y un mayor espacio intersticial entre los túbulos; también hubo un menor número de células del epitelio germinal y no hubo presencia de espermátides. En las muestras de tejido obtenidas en el mes de septiembre y febrero se observó un incremento significativo en el diámetro del túbulo, grosor del epitelio germinal y número de células del epitelio germinal cuando fueron comparadas con las muestras de junio (p 0.05). Solo en las muestras de febrero hubo presencia de espermátides. En conjunto, nuestros resultados sugieren la existencia de variaciones estacionales en la actividad reproductiva de T. brasiliensis, bajo las condiciones en que se realizó el estudio.