Dengue Virus in Bats from Córdoba and Sucre, Colombia

Microbial community dynamics in blood, faeces and oral secretions of neotropical bats in Casanare, Colombia

Bats are known reservoirs for a wide range of pathogenic microorganisms, including viruses, bacteria, fungi, helminths, and protozoa, which can be transmitted and infect other zoonotic organisms. Various studies have utilised next-generation sequencing (NGS) to describe the pathogens associated with bats. Although most have characterised microbial communities in specific body fluids, few have analysed the composition and diversity of these microbial communities across different body fluids at the individual level. In this study, we employed two next-generation sequencing techniques: amplicon-based sequencing of the V4 hypervariable region of the 16S- and 18S-rRNA genes and viral metagenomics, to describe the prokaryotic, eukaryotic, and viral communities present in blood, faeces, and oral swab samples collected from two genera of bats (Carollia and Phyllostomus) in the department of Casanare, eastern Colombia. A total of 60 samples corresponding to the three bodily fluids were processed and analysed. The results indicated that the microbial communities across the body fluids were mainly composed of bacteria, fungi, protozoa, and various DNA and RNA viruses, showing a variability of microbial genera and species. The abundances, diversity metrics, and correlations of these microorganisms displayed patterns associated with bat genus and body fluids, suggesting that the ecological characteristics of these microbial communities may be influenced by the ecological and physiological traits of the bats. Additionally, we found similar community compositions of bacteria, some fungal genera, and viruses in the three body fluids, indicating a possible circulation of these microbes within the same bat. This could be due to microbial movement from the gut microbiota to other physiological systems or transmission via blood-feeding vectors. Furthermore, our results revealed the presence of various microbes of public health concern, including Bartonella spp., Mannheimia haemolytica, Rhodotorula spp., Piroplasmida spp., Toxoplasma gondii, Alphacoronavirus spp., and Bat circovirus. The abundance of these pathogenic microbial species across the three bodily fluids suggests potential transmission routes from bats to other organisms, which may contribute to the emergence of zoonotic disease outbreaks. These findings highlight the variability of microorganisms present within the same bat and the different pathogen-host interactions that may regulate the presence and transmission of these zoonotic microbes. Further research is required to elucidate the genomic features, ecological interactions, and biological activities of these microbial communities in bats.

Serological and molecular detection of dengue virus in animals: A systematic review and meta-analysis

Introduction

Dengue is a vector-borne disease, especially important in tropical and subtropical areas. The first presentation of many arboviral diseases occurred mainly in animals, including multiple Alphaviruses and Flaviviruses, such as dengue.

Objective

To determine the serological and molecular frequency of the dengue virus in animals.

Methods

A systematic literature review was carried out in five databases for the proportion of animals infected with dengue, defined by molecular and serological tests. A meta-analysis was performed using a random-effects model to calculate the pooled prevalence and 95% confidence intervals (CI). Cochran?s Q test and the I2 statistic were used to assess the heterogeneity between the two studies.

Results

The presence of dengue in bats, primates, birds, sheep, horses, cattle, pigs, rodents and buffaloes, according to serological methods, had a prevalence of 10%, 29%, 8%, 1%, 11%, 0%, 49%, 2%, 7%, respectively. According to molecular methods, the presence of dengue in bats had a seroprevalence of 6.0%.

Conclusion

The present study confirms the presence of the Dengue virus in a large group of animal species, with potential implications as possible reservoirs of this virus, raising the possibility of zoonotic transmission.

Experimental infection of Artibeus lituratus bats and no detection of Zika virus in neotropical bats from French Guiana, Peru, and Costa Rica suggests a limited role of bats in Zika transmission

Bats are important natural reservoir hosts of a diverse range of viruses that can be transmitted to humans and have been suggested to play an important role in the Zika virus (ZIKV) transmission cycle. However, the exact role of these animals as reservoirs for flaviviruses is still controversial. To further expand our understanding of the role of bats in the ZIKV transmission cycle in Latin America, we carried out an experimental infection in wild-caught Artibeus lituratus bats and sampled several free-living neotropical bats across three countries of the region. Experimental ZIKV infection was performed in wild-caught adult bats (4 females and 5 males). The most relevant findings were hemorrhages in the bladder, stomach and patagium. Significant histological findings included inflammatory infiltrate consisting of a predominance of neutrophils and lymphocytes, in addition to degeneration in the reproductive tract of males and females. This suggests that bat reproduction might be at some level affected by ZIKV. Leukopenia was also observed in some inoculated animals. Hemorrhages, genital alterations, and leukopenia are suggested to be caused by ZIKV; however, since these were wild-caught bats, we cannot exclude other agents. Detection of ZIKV by qPCR was observed at low concentrations in only two urine samples in two inoculated animals. All other animals and tissues tested were negative. Finally, no virus-neutralizing antibodies were found in any animal. To determine ZIKV infection in nature, the blood of a total of 2056 bats was sampled for ZIKV detection by qPCR. Most of the sampled individuals belonged to the genus Pteronotus sp. (23%), followed by the species Carollia sp. (17%), Anoura sp. (14%), and Molossus sp. (13.7%). No sample of any tested species was positive for ZIKV by qPCR. These results together suggest that bats are not efficient amplifiers or reservoirs of ZIKV and may not have an important role in ZIKV transmission dynamics.

Genome sequencing of dengue virus serotype 4 in a bat brain sample (Platyrrhinus helleri) from the Brazilian Amazon

The existence of sylvatic transmission of dengue virus in communities of neotropical bats remains uncertain. In this work we present a near-complete genome of dengue virus serotype 4 obtained from the brain sample of a bat from Platyrrhinus helleri specie collected in the Brazilian Amazon region. The presence of the virus in the brain sample may indicate a possible tropism for the central nervous system in bats, which may justify negative results in previous studies that focused on analysis of other tissues, such as liver and spleen. Besides the duration of dengue virus circulation in the Americas (circa 40 years) may be too short for an implementation of a sylvatic dengue virus cycle. Our findings suggest that continued monitoring is needed to confirm with the neotropical bats could potentially act as a natural reservoir of dengue in the region.

The one health perspective to improve environmental surveillance of zoonotic viruses: lessons from COVID-19 and outlook beyond

The human population has doubled in the last 50 years from about 3.7 billion to approximately 7.8 billion. With this rapid expansion, more people live in close contact with wildlife, livestock, and pets, which in turn creates increasing opportunities for zoonotic diseases to pass between animals and people. At present an estimated 75% of all emerging virus-associated infectious diseases possess a zoonotic origin, and outbreaks of Zika, Ebola and COVID-19 in the past decade showed their huge disruptive potential on the global economy. Here, we describe how One Health inspired environmental surveillance campaigns have emerged as the preferred tools to monitor human-adjacent environments for known and yet to be discovered infectious diseases, and how they can complement classical clinical diagnostics. We highlight the importance of environmental factors concerning interactions between animals, pathogens and/or humans that drive the emergence of zoonoses, and the methodologies currently proposed to monitor them-the surveillance of wastewater, for example, was identified as one of the main tools to assess the spread of SARS-CoV-2 by public health professionals and policy makers during the COVID-19 pandemic. One-Health driven approaches that facilitate surveillance, thus harbour the potential of preparing humanity for future pandemics caused by aetiological agents with environmental reservoirs. Via the example of COVID-19 and other viral diseases, we propose that wastewater surveillance is a useful complement to clinical diagnosis as it is centralized, robust, cost-effective, and relatively easy to implement.

Animals as potential reservoirs for dengue transmission: A systematic review

Dengue is a rapidly spreading mosquito-borne flavivirus infection that is prevalent in tropical and sub-tropical regions. Humans are known to be the main reservoir host maintaining the epidemic cycles of dengue but it is unclear if dengue virus is also maintained in a similar enzootic cycle. The systematic review was conducted in accordance to Cochrane's PRISMA recommendations. A search was done on PubMed, EMBASE, Scopus and Cochrane Library. Key data on animal dengue positivity was extracted and classified according to animal type and diagnostic modes. Of the 3818 articles identified, 56 articles were used in this review. A total of 16,333 animals were tested, 1817 of which were positive for dengue virus by RT-PCR or serology. Dengue positivity was detected in bats (10.1%), non-human primates (27.3%), birds (11%), bovid (4.1%), dogs (1.6%), horses (5.1%), pigs (34.1%), rodents (3.5%), marsupials (13%) and other small animals (7.3%). While majority of dengue positivity via serology suggests potential enzootic transmission, but regular dengue virus spillback cannot be excluded. With the exception of bats, acute infection among animals is limited. Further investigation on animals is critically required to better understand their role as potential reservoir in dengue transmission.

Two Cases of Natural Infection of Dengue-2 Virus in Bats in the Colombian Caribbean

Dengue, a mosquito-borne zoonotic disease, is the most common vector-borne disease in tropical and subtropical areas. In this study, we aim to demonstrate biological evidence of dengue virus infection in bats. A cross-sectional study was carried out in the departments of Cordoba and Sucre, Colombia. A total of 286 bats were captured following the ethical protocols of animal experimentation. The specimens were identified and euthanized using a pharmacological treatment with atropine, acepromazine and sodium pentobarbital. Duplicate samples of brain, heart, lung, spleen, liver, and kidney were collected with one set stored in Trizol and the other stored in 10% buffered formalin for histopathological and immunohistochemical analysis using polyclonal antibodies. Brain samples from lactating mice with an intracranial inoculation of DENV-2 were used as a positive control. As a negative control, lactating mouse brains without inoculation and bats brains negative for RT-PCR were included. Tissue sections from each specimen of bat without conjugate were used as staining control. In a specimen of Carollia perspicillata captured in Ayapel (Cordoba) and Phylostomus discolor captured in San Carlos (Cordoba), dengue virus was detected, and sequences were matched to DENV serotype 2. In bats RT-PCR positive for dengue, lesions compatible with viral infections, and the presence of antigens in tissues were observed. Molecular findings, pathological lesions, and detection of antigens in tissues could demonstrate viral DENV-2 replication and may correspond to natural infection in bats. Additional studies are needed to elucidate the exact role of these species in dengue epidemics.

Current Knowledge and Ecological and Human Impact Variables Involved in the Distribution of the Dengue Virus by Bats in the Americas

Dengue fever, caused by the dengue virus (DENV), is one of the most important reemerging viral diseases transmitted by arthropods worldwide. DENV is maintained in nature in two transmission cycles: urban and sylvatic. The latter has only been recorded in Africa and Asia and involves nonhuman primates as natural hosts, although it has been suggested that other mammals may play a secondary role as potential reservoir host, including bats. The objective of this article is to review the current state of knowledge about DENV-positive bats in the Americas and to determine what ecological and human impact variables could favor DENV infection in bats. We performed a search of published studies on natural and experimental DENV infection in bats. From 1952 to 2019, 14 studies have been carried out (71.4% in the last decade) examining DENV infection in bats in seven countries of the Americas. DENV infection was examined in 1884 bats of 63 species and DENV was detected in 19 of these species. Clench's model estimated that more than 75 species could be carriers of DENV; therefore, considering that at least 350 species of bats are distributed in the Americas, to detect 95% of the DENV-bearing species, it would be necessary to examine about 10,206 bats of ∼287 species that have not been analyzed until 2019. The species with the highest number of positive cases were Molossus sinaloae and Artibeus jamaicensis. Species, colony size, mean annual temperature, mean annual precipitation, human population size, and bat collection site (site inhabited by humans, vegetation cover, and caves) contributed to explain the variation in DENV detection in bats in the Americas. These results provide evidence on the exposure of bats to DENV in different geographic areas of the Americas and a bat sylvatic transmission cycle is very likely to be occurring, where bats may be either accidental hosts, dead-end hosts, or potential reservoir hosts for DENV.

Bats in ecosystems and their Wide spectrum of viral infectious potential threats: SARS-CoV-2 and other emerging viruses

Bats have populated earth for approximately 52 million years, serving as natural reservoirs for a variety of viruses through the course of evolution. Transmission of highly pathogenic viruses from bats has been suspected or linked to a spectrum of potential emerging infectious diseases in humans and animals worldwide. Examples of such viruses include Marburg, Ebolavirus, Nipah, Hendra, Influenza A, Dengue, Equine Encephalitis viruses, Lyssaviruses, Madariaga and Coronaviruses, involving the now pandemic Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Herein, we provide a narrative review focused in selected emerging viral infectious diseases that have been reported from bats.

An Experimental and Theoretical Approach to Understand Fever, DENF & its Cure

Fever is a response of a human body, due to an increase in the temperature, against certain stimuli. It may be associated with several reasons and one of the major causes of fever is a mosquito bite. Fever due to dengue virus (DENV) infection is being paid most attention out of several other fever types because of a large number of deaths reported worldwide. Dengue virus is transmitted by biting of the mosquitoes, Aedes aegypti and Aedes albopictus. DENV1, DENV2, DENV3 and DENV4 are the four serotypes of dengue virus and these serotypes have 65% similarities in their genomic structure. The genome of DENV is composed of single-stranded RNA and it encodes for the polyprotein. Structural and non-structural proteins (nsP) are the two major parts of polyprotein. Researchers have paid high attention to the non-structural protease (nsP) of DENV like nsP1, nsP2A, nsP2B, nsP3, nsP4A, nsP4B and nsP5. The NS2B-NS3 protease of DENV is the prime target of the researchers as it is responsible for the catalytic activity. In the present time, Dengvaxia (vaccine) is being recommended to patients suffering severely from DENV infection in few countries only. Till date, neither a vaccine nor an effective medicine is available to combat all four serotypes. This review describes the fever, its causes, and studies to cure the infection due to DENV using theoretical and experimental approaches.

Human Urban Arboviruses Can Infect Wild Animals and Jump to Sylvatic Maintenance Cycles in South America

The present study shows that the most prominent human arboviruses worldwide (dengue viruses 1, 2, 3, and 4, Chikungunya virus, and Zika virus) can infect wild animals and transfer from urban to sylvatic maintenance cycles in South America, as did the yellow fever virus (YFV) in the past. All these viruses are transmitted by the anthropophilic mosquito Aedes aegypti and cause epidemics throughout Brazil. The YFV is the oldest example of an urban arbovirus that became sylvatic in South America. Currently, the disease is a zoonosis of non-human primates that moves like a wave through the forests of the Brazilian countryside, traveling thousands of kilometers, killing many animals and eventually infecting man. However, since 2016, this zoonotic wave has reached the highly populated areas of Southeast Brazil, producing the largest human outbreak in the past 60 years. As with the YFV, sylvatic cycles may occur with dengue, Chikungunya, and Zika. In order to become sylvatic, arboviruses require an apparently unlikely conjunction of factors to unexpectedly take place. These arboviruses could start to infect sylvatic primates and be transmitted by Haemagogus mosquitoes that inhabit tree canopies. We mention here publications reporting evidence of sylvatic cycles of dengue, Chikungunya, and Zika virus in South America. Indeed, it is almost unfeasible to control these cycles of arboviruses since it is impossible to know where, when or why an arboviral spill-over would occur in wild animals. The sylvatic maintenance cycle could preclude the eradication of an arbovirus. Moreover, an arbovirus in a sylvatic cycle could re-emerge anytime, infecting humans and producing outbreaks. In case of the reemergence of an arbovirus, it is crucial to prevent the occurrence of an urban cycle as a spill-back from the sylvatic cycle.