Extensive surveillance in bat populations in response to recent emerging diseases has revealed that this group of mammals acts as a reservoir for a large range of viruses. However, the oldest known association between a zoonotic virus and a bat is that between rabies virus and the vampire bat. Vampire bats are only found in Latin America and their unique method of obtaining nutrition, blood-feeding or haematophagy, has only evolved in the New World. The adaptations that enable blood-feeding also make the vampire bat highly effective at transmitting rabies virus. Whether the virus was present in pre-Columbian America or was introduced is much disputed, however, the introduction of Old World livestock and associated landscape modification, which continues to the present day, has enabled vampire bat populations to increase. This in turn has provided the conditions for rabies re-emergence to threaten both livestock and human populations as vampire bats target large mammals. This review considers the ecology of the vampire bat that make it such an efficient vector for rabies, the current status of vampire-transmitted rabies and the future prospects for spread by this virus and its control.

Blood-feeding arthropods play a major role in the transmission of several flaviviruses, which represent an important problem for human health. Currently, dengue is one of the most important arboviral emerging diseases worldwide. Furthermore, some previous studies have reported the presence of viral nucleic acids and antibodies against dengue virus (DENV) in wild animals. Our knowledge of the role played by wildlife reservoirs in the sylvatic transmission and maintenance of DENV remains limited. Our objective was to screen blood-feeding ectoparasites (bat flies) and their common vampire bat (Desmodus rotundus) hosts, for flaviviruses in Hidalgo, Mexico. We detected Flavivirus sequences in 38 pools of ectoparasites (Diptera: Streblidae, Strebla wiedemanni and Trichobius parasiticus) and 8 tissue samples of D. rotundus by RT-PCR and semi-nested PCR using FlaviPF1S, FlaviPR2bis, and FlaviPF3S primers specific for NS5, a gene highly conserved among flaviviruses. Phylogenetic inference analysis performed using the maximum likelihood algorithm implemented in PhyML showed that six sequences clustered with DENV (bootstrap value = 53.5%). Although this study supports other reports of DENV detection in bats and arthropods other than Aedes mosquitoes, the role of these ectoparasitic flies and of hematophagous bats in the epidemiology of DENV still warrants further investigation.

Although emerging nonviral pathogens remain relatively understudied in bat populations, there is an increasing focus on identifying bat-associated bartonellae around the world. Many novel Bartonella strains have been described from both bats and their arthropod ectoparasites, including Bartonella mayotimonensis, a zoonotic agent of human endocarditis. This cross-sectional study was designed to describe novel Bartonella strains isolated from bats sampled in Mexico and evaluate factors potentially associated with infection. A total of 238 bats belonging to seven genera were captured in five states of Central Mexico and the Yucatan Peninsula. Animals were screened by bacterial culture from whole blood and/or polymerase chain reaction of DNA extracted from heart tissue or blood. Bartonella spp. were isolated or detected in 54 (22.7%) bats, consisting of 41 (38%) hematophagous, 10 (16.4%) insectivorous, and three (4.3%) phytophagous individuals. This study also identified Balantiopteryx plicata as another possible bat reservoir of Bartonella. Univariate and multivariate logistic regression models suggested that Bartonella infection was positively associated with blood-feeding diet and ectoparasite burden. Phylogenetic analysis identified a number of genetic variants across hematophagous, phytophagous, and insectivorous bats that are unique from described bat-borne Bartonella species. However, these strains were closely related to those bartonellae previously identified in bat species from Latin America.

In pre-Hispanic Mexico, dogs were not identified as an important source of rabies. We know from codexes and chronicles of the conquerors that at that time, rabies cases in humans and domestic animals were caused by local wildlife species such as bats. Canine-rabies virus variant seems to have arrived with Europeans. The first documented case of canine rabies in the Americas is found in Mexico in the Annals of the Holy Inquisition (16th century). During Mexico's independence, cases were frequently reported. In the 19th century the first attempts to control human rabies were made through sanitary measures such as elimination of rabid dogs and applying postexposure vaccination. During the first half of the 20th century, the efficacy of canine vaccination to prevent human rabies was established. However, in Mexico, despite reports of numerous human cases (>70/year), canine vaccination did not have enough coverage. It was only during the 1990s that Mexico made a serious commitment to eliminate dog-transmitted human rabies. Since the beginning, vaccination campaigns have been free and massive. Coverage increased from 7,100,000 doses in 1990 to more than 18,000,000 since 2017. This culminated in the elimination of dog-mediated human rabies cases since 2006. Subsequently, the epidemiology of rabies had changed. Nowadays, it is wildlife species (mainly bats and skunks) that are the source of human rabies. As a mega-biodiverse country Mexico has numerous wildlife species with potential to transmit rabies virus. Thus it is paramount to remain vigilant with respect to canine vaccination campaigns and to promote rabies research in wildlife.

Hepatitis E virus (HEV; family Hepeviridae ) infections cause >40,000 human deaths annually. Zoonotic infections predominantly originate from ungulates and occasionally from rats, highlighting the zoonotic potential of rodent-associated hepeviruses. We conducted host genomic data mining and uncovered two genetically divergent rodent-associated hepeviruses, and two bat-associated hepeviruses genetically related to known bat-associated strains. We thus analyzed 2,565 liver specimens from 108 rodent and shrew species sampled from globally understudied regions and hosts in Africa, Asia, and Latin America during 2011-2018 for hepeviruses by RT–PCR. We detected 63 positive field samples (2.5%, 95% CI 1.9-3.1) from 14 animal species, including two coinfections with genetically divergent strains and significant variation ( X ² , P < 0.001) in detection rates between study sites. Strain-specific qRT–PCR assays showed virus concentrations between 9.2 × 10 ² and 3.2 × 10 ⁹ copies/g. We recovered 24 near-complete hepeviral genomes from rodents, shrews, and bats, all showing three partially overlapping open reading frames (ORFs), some including putative late domains that may be associated with quasi-envelopment. Rodent-derived hepeviruses grouped into five clades clustering in basal sister relationship to human- (31 to 84% distance in translated ORF1-3) and rat-associated HEV. Parsimony-based analyses and cophylogenetic reconciliations revealed that rodents were predominant sources of hepeviral cross-order host shifts. Bayesian ancestral state reconstructions substantiated a direct origin of human-associated HEV in ungulates such as swine and camelids (posterior probability 0.8), whereas the nonrecent evolutionary origins of human- and ungulate-associated HEV were projected to rodent hosts (posterior probability > 0.9). Our results elucidate the genealogy of human HEV and warrant increased surveillance and experimental risk assessments for rodent-associated hepeviruses.