Epizootiological and epidemiological study of hantavirus infection in Japan

Region-Specific Genetic Diversity of Black Rats (Rattus rattus Complex) in Southeast and East Asia Shaped by Rapid Population Expansion Events

Among the six mitochondrial DNA lineages of the black rat (Rattus rattus Complex; RrC), lineages II and IV are widespread in Southeast and East Asia. This study explored their demographic history using 17 new sequences from the Miyako Islands in the Ryukyu archipelago, together with 178 publicly available cytochrome b sequences. We defined six and two haplotype groups showing rapid population expansion signals in Lineages II and IV, respectively. The six haplotype groups of Lineage II were represented by haplotypes from 1) Myanmar/Bangladesh/Northeast India, 2) Laos, 3) Thailand, 4) Indonesia/Philippines, 5) Vietnam/southern China, and 6) the Ryukyu archipelago. These expansion times were estimated using time-dependent evolutionary rates to be 115,300 years ago (ya), 128,500 ya, 9600 ya, 10,600 ya, 7200 ya, and 1400 ya, respectively, although all had large confidence intervals. The two groups of Lineage IV were recovered from the mainland and islands of Southeast Asia with predicted expansion times of 197,000 ya and 5800 ya, respectively. These results suggest that climatic fluctuations during the last 200,000 years of the Quaternary, affected the population dynamics in subtropical areas at different times. Furthermore, the results of the younger rapid expansion events of RrC suggest the possibility of agricultural advancement and dispersal of Neolithic farmers to different areas within the mainland and islands of Southeast Asia during the Holocene. A subset of rats from the Miyako Islands were found to have the same lineage IV haplotypes as those in Southeast Asia, suggesting a recent introduction of these new lineages.

Hantavirus: an overview and advancements in therapeutic approaches for infection

Hantaviruses are a significant and emerging global public health threat, impacting more than 200,000 individuals worldwide each year. The single-stranded RNA viruses belong to the Hantaviridae family and are responsible for causing two acute febrile diseases in humans: Hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). Currently, there are no licensed treatments or vaccines available globally for HTNV infection. Various candidate drugs have shown efficacy in increasing survival rates during the early stages of HTNV infection. Some of these drugs include lactoferrin, ribavirin, ETAR, favipiravir and vandetanib. Immunotherapy utilizing neutralizing antibodies (NAbs) generated from Hantavirus convalescent patients show efficacy against HTNV. Monoclonal antibodies such as MIB22 and JL16 have demonstrated effectiveness in protecting against HTNV infection. The development of vaccines and antivirals, used independently and/or in combination, is critical for elucidating hantaviral infections and the impact on public health. RNA interference (RNAi) arised as an emerging antiviral therapy, is a highly specific degrades RNA, with post-transcriptional mechanism using eukaryotic cells platform. That has demonstrated efficacy against a wide range of viruses, both in vitro and in vivo. Recent antiviral methods involve using small interfering RNA (siRNA) and other, immune-based therapies to target specific gene segments (S, M, or L) of the Hantavirus. This therapeutic approach enhances viral RNA clearance through the RNA interference process in Vero E6 cells or human lung microvascular endothelial cells. However, the use of siRNAs faces challenges due to their low biological stability and limited in vivo targeting ability. Despite their successful inhibition of Hantavirus replication in host cells, their antiviral efficacy may be hindered. In the current review, we focus on advances in therapeutic strategies, as antiviral medications, immune-based therapies and vaccine candidates aimed at enhancing the body's ability to control the progression of Hantavirus infections, with the potential to reduce the risk of severe disease.

Role of Seaports and Imported Rats in Seoul Hantavirus Circulation, Africa

Seoul orthohantavirus (SEOV) is not considered a major public health threat on the continent of Africa. However, Africa is exposed to rodentborne SEOV introduction events through maritime traffic after exponential growth of trade with the rest of the world. Serologic studies have already detected hantavirus antibodies in human populations, and recent investigations have confirmed circulation of hantavirus, including SEOV, in rat populations. Thus, SEOV is a possible emerging zoonotic risk in Africa. Moreover, the range of SEOV could rapidly expand, and transmission to humans could increase because of host switching from the usual brown rat (Rattus norvegicus) species, which is currently invading Africa, to the more widely installed black rat (R. rattus) species. Because of rapid economic development, environmental and climatic changes, and increased international trade, strengthened surveillance is urgently needed to prevent SEOV dissemination among humans in Africa.

First study of Seoul virus (SEOV) in urban rodents from newly urbanized areas of Gran La Plata, Argentina

Alterations of ecosystems have deep effects on the distribution of parasites. Big cities of Argentina present structural features that favor the presence of synanthropic species, acting as source of zoonotic diseases, for example in urban rodents: the Norway rat (Rattus norvegicus) and the black rat (R. rattus). One of the important zoonotic pathogens related are the RNA virus Hantavirus, with high prevalence rates in South America. The aim of this study was to explore and identify the presence of Hantavirus in urban rodents from Gran La Plata, Argentina. The presence of anti-hantavirus IgG antibodies was determined by the Enzyme-Linked Immunosorbent Assay. Six samples turned out positive for Seoul virus (SEOV, p = 14.3%). These are the first records of SEOV in urban rodents in Gran La Plata. It represents the first report in R. rattus in Argentina, and in America. This situation underscores the inequality and historical forgetfulness of a portion of society, calling for urgent action to be taken in this regard.

Genetic Characterization of Seoul Virus in the Seaport of Cotonou, Benin

Seoul virus is a zoonotic pathogen carried by the brown rat Rattus norvegicus. Information on its circulation in Africa is limited. In this study, the virus was detected in 37.5% of brown rats captured in the Autonomous Port of Cotonou, Benin. Phylogenetic analyses place this virus in Seoul virus lineage 7.

Rodent-Borne Orthohantaviruses in Vietnam, Madagascar and Japan

Hantaviruses are harbored by multiple small mammal species in Asia, Europe, Africa, and the Americas. To ascertain the geographic distribution and virus-host relationships of rodent-borne hantaviruses in Japan, Vietnam, Myanmar, and Madagascar, RNAlater™-preserved lung tissues of 981 rodents representing 40 species, collected in 2011-2017, were analyzed for hantavirus RNA by RT-PCR. Our data showed Hantaan orthohantavirus Da Bie Shan strain in the Chinese white-bellied rat (Niviventer confucianus) in Vietnam, Thailand; orthohantavirus Anjo strain in the black rat (Rattus rattus) in Madagascar; and Puumala orthohantavirus Hokkaido strain in the grey-sided vole (Myodes rufocanus) in Japan. The Hokkaido strain of Puumala virus was also detected in the large Japanese field mouse (Apodemus speciosus) and small Japanese field mouse (Apodemus argenteus), with evidence of host-switching as determined by co-phylogeny mapping.

Hantavirus RNA Prevalence in Myomorph Rodents on Bolshoy Ussuriysky Island at the Sino-Russian Border

OBJECTIVE

To understand the distribution and infection status of hantavirus in Myomorph rodents on Bolshoy Ussuriysky Island (Heixiazi Island) at the Sino-Russian border, and to provide data for the safe development and utilization of Bolshoy Ussuriysky Island.

METHODS

In 2013 and 2014, Myomorph rodents were trapped on Bolshoy Ussuriysky Island. Total RNA was extracted from rodent tissue, and it was screened for hantavirus RNA by using reverse transcription-polymerase chain reaction. Univariate and multivariate nonconditional logistic regression analysis was used to analyze the RNA prevalence rates in eight species of rodents, in relation to species, sex, age, habitat, and season. In addition, PCR amplicons were sequenced and phylogenetic analysis was performed by using Mega 5.1 software.

RESULTS

Six hundred forty-four rodents belonging to three orders, five families, and eight genera were trapped. Fifty-two rodents were infected with hantavirus, and the rate of RNA detection was 8.07%. The infection rates of rodents in different habitats (χ² = 14.853, p < 0.05) and different seasons (χ² = 16.990, p < 0.05) showed significant differences. A logistic regression analysis showed that habitat and trapping season were risk factors of hantavirus infection (p < 0.05). Phylogenetic analysis showed that the gene sequences of positive samples were Hantaan virus and Khabarovsk virus.

CONCLUSION

There are two types of hantaviruses, such as HTNV (in Apodemus agrarius, Clethrionomys rutilus, Microtus fortis, Rattus norvegicus) and KHAV (in C. rutilus), among the rodents on Bolshoy Ussuriysky Island, and season and habitat are risk factors of hantavirus infection.

Rodent Species Distribution and Hantavirus Seroprevalence in Residential and Forested areas of Sarawak, Malaysia

Rodents belong to the order Rodentia, which consists of three families in Borneo (i.e., Muridae, Sciuridae and Hystricidae). These include rats, mice, squirrels, and porcupines. They are widespread throughout the world and considered pests that harm humans and livestock. Some rodent species are natural reservoirs of hantaviruses (Family: Bunyaviridae) that can cause zoonotic diseases in humans. Although hantavirus seropositive human sera were reported in Peninsular Malaysia in the early 1980s, information on their infection in rodent species in Malaysia is still lacking. The rodent populations in residential and forested areas in Sarawak were sampled. A total of 108 individuals from 15 species of rodents were collected in residential (n = 44) and forested ( n = 64) areas. The species diversity of rodents in forested areas was significantly higher (H = 2.2342) compared to rodents in residential areas (H = 0.64715) (p < 0.001 of Zar-t test based on the Shannon index). Rattus rattus and Sundamys muelleri were present at high frequencies in both localities. An enzyme-linked immunosorbent assay (ELISA) showed that hantavirus-targeting antibodies were absent from 53 tested serum samples. This is the first report of hantavirus seroprevalence surveillance in rodent populations in Sarawak, East Malaysia. The results suggested that hantavirus was not circulating in the studied rodent populations in Sarawak, or it was otherwise at a low prevalence that is below the detection threshold. It is important to remain vigilant because of the zoonotic potential of this virus and its severe disease outcome. Further studies, such as molecular detection of viral genetic materials, are needed to fully assess the risk of hantavirus infection in rodents and humans in this region of Malaysia.

Hantavirus infection: a global zoonotic challenge

Hantaviruses are comprised of tri-segmented negative sense single-stranded RNA, and are members of the Bunyaviridae family. Hantaviruses are distributed worldwide and are important zoonotic pathogens that can have severe adverse effects in humans. They are naturally maintained in specific reservoir hosts without inducing symptomatic infection. In humans, however, hantaviruses often cause two acute febrile diseases, hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). In this paper, we review the epidemiology and epizootiology of hantavirus infections worldwide.

Seroepidemiological survey of hantavirus infection in healthy people in Vallès Occidental, Barcelona

INTRODUCTION

Hantaviruses are the etiological agents of hemorrhagic fever with renal syndrome in Europe and Asia, and hantavirus pulmonary syndrome in America. Approximately 150,000 cases are reported annually worldwide. In Spain, some hantavirus infection cases have been described. Besides, rodents that have been described as hantavirus reservoirs are present. The aim of the present study was to determinate the seroprevalence of hantavirus in humans in the northeast of Spain.

MATERIALS AND METHODS

During a 5-month period, 217 serum samples were collected. The study population was stratified by age, gender, and residential area. Age, gender, residential area, contact with pets, contact with wild animals, contact with farm animals, and occupation were surveyed. Immunoglobulin G antibodies to Hantaan virus, Seoul virus, or Puumala virus were examined by immunofluorescence assay. Titles ≥1/32 against any of the hantavirus were considered positive.

RESULTS

Four (1.8%) positive samples were detected. Age ranged from 14 to 67 years. Two subjects were male. Three samples reacted to both Puumala virus and Hantaan virus. The other one reacted against all three hantavirus surveyed. Titles ranged from 32 to 1024. The highest titles were found against Seoul virus.

CONCLUSIONS

Our data show serological evidence about hantavirus infection among population of Catalonia, northeast of Spain. Seroprevalence rate was (around 2%) similar to other regions of Spain.

Ecology of hantavirus in a changing world

Hantavirus is a genus of virus represented by 45 different species and is hosted by small mammals, predominantly rats and mice. Roughly, half of all hantaviruses cause diseases in humans that vary in morbidity from mild to severe. The natural and anthropogenic changes occurring in the environment appear to be impacting the ecology of hantaviruses and their natural hosts as well as the incidence of hantaviral diseases in humans. Although such studies are limited at this time, there is evidence that natural climate cycles such as El Niño as well as anthropogenic climate change enhance hantavirus prevalence when host population dynamics are driven by food availability. Climate appears to have less of an effect on hantavirus when host populations are controlled by predators. Human alteration to the landscape also appears to enhance hantavirus prevalence when the disturbance regime enriches the environment for the host, for example, agriculture. More long-term studies on multiple species of hantavirus are needed to accurately predict the outcome of changing environmental conditions on prevalence in hosts as well as disease incidence in humans.

Serological and genetic evidence for the presence of Seoul hantavirus in Rattus norvegicus in Flanders, Belgium

Seoul hantavirus (SEOV), carried by Rattus rattus (black rat) and R. norvegicus (Norway, brown rat), was reported to circulate as well as cause HFRS cases in Asia. As Rattus sp. are present worldwide, SEOV has the potential to cause human disease worldwide. In Europe however, only SEOV prevalence in rats from France was reported and no confirmed cases of SEOV infection were published. We here report genetic and serological evidence for the presence of SEOV virus in brown rat populations in Belgium. We also serologically screened an at-risk group that was in contact with R. norvegicus on a daily basis and found no evidence for SEOV infection.

Prevalence of hantavirus infection in wild Rattus norvegicus and R. rattus populations of Buenos Aires City, Argentina

OBJECTIVE

To determine the prevalence of infection with hantaviruses in wild Rattus norvegicus and R. rattus populations in areas of Buenos Aires city.

METHODS

Norway rats and black rats were trapped from 2003 to 2005 at 10 sites throughout Buenos Aires city. Blood samples for serological analysis were collected by cardiac puncture from all individuals captured and tested by enzyme-linked immunosorbent assay for Seoul hantavirus- and Andes virus-specific IgG antibodies.

RESULTS

Hantavirus seroprevalence was 11.9% in R. norvegicus (n = 151), varying between 0% and 26.1% depending on the site. Bigger sexually active males were more likely to be infected with Seoul virus than females or juvenile individuals. No antibody-reactive rodents were detected among 33 R. rattus analysed.

CONCLUSION

Hantavirus infections are geographically widespread in Buenos Aires city and confirm that they have been enzootic there for at least 20 years.

Hantavirus infection in East Asia

Hantaviruses are enveloped RNA viruses that belong to the Hantavirus genus of the family Bunyaviridae. These viruses persistently infect their rodent reservoirs without causing disease. The virus is transmitted to humans via the inhalation of infectious aerosols generated from contaminated animal secretions or through the contaminated saliva of animal bites. Hantaviruses cause haemorrhagic fever with renal syndrome in Euro-Asia, and hantavirus pulmonary syndrome (HPS) in North and South America. Here, we review the epidemiology and epizootiology of hantavirus infection in Asian countries.

Seaport as a source of hantavirus: a study on isolated isles

Since small mammals from seaports have relative higher seroprevalences of hantavirus, this seroepidemiologic study was conducted on the isles in Kinmen and Lienchiang Counties along the coast of southern mainland China to determine whether seaport may play the role as a source of hantavirus. Among six species of small mammals trapped in Kinmen County, only male Mus musculus (6.7%) and Rattus losea (5.3%) were found to be positive. In Lienchiang County, five species of small mammals were trapped and positive findings were obtained only in male R. norvegicus (9.3%), male M. musculus (7.7%), and female R. losea (1.6%). There was no significant difference in the seroprevalence between the two counties (Kinmen 3.8% vs. Lienchiang 3.9%). The positive rate in Liaolo (17.9%) of Kinmen County was significantly higher than the remaining trapping stations and those in Matsu Distillery (10.3%) and Fushing (5.8%) of Lienchiang County were significantly higher than the remaining ones. Moreover, a significant inverse correlation was found between the seropositive rate and the distance of small mammal sampling sites to the seaport (p < 0.01). These findings suggest the role of seaport as a source of hantavirus.

Preliminary genetic characterization of two lineages of black rats (Rattus rattus sensu lato) in Japan, with evidence for introgression at several localities

We conducted a pilot survey of genetic diversity among 37 karyotyped individuals of the black rat Rattus rattus (sensu lato) from six localities on the Japanese Islands, using complete gene sequences of mitochondrial cytochrome b (cyt b) and nuclear interphotoreceptor retinoid binding protein (IRBP). Our sampling included two previously documented karyotypic groups: 'Oceanian' with 2n = 38 and 'Asian' with 2n = 42. Cyt b sequences for most individuals clustered according to their karyotypic groups, with an average between-group divergence of 3.8%. One exception was that individuals from Kagoshima (Kyushu Island) showed 'Asian' karyotypes combined with a cyt b haplotype that differed by a single nucleotide substitution from the haplotype of the 'Oceanian' karyotypic group. Six IRBP haplotypes were identified. They belonged to three distinct IRBP lineages (I-III), with an average inter-lineage divergence of 1%. Among homozygous individuals, these lineages showed good association with the karyotypic groups: IRBP lineage I occurred only with 'Oceanian' karyotypes, while IRBP lineages II and III both occurred with 'Asian' karyotypes. Individuals from Kagoshima all possessed IRBP of 'Asian' lineages, despite the presence of an 'Oceanian' mitochondrial type. The Chichijima population (Ogasawara Islands) featured exclusively 'Asian' karyotypes and cyt b sequences, but various combinations of all three IRBP lineages. The Kagoshima and Chichijima populations thus provide strong evidence of viable hybridization and genetic introgression between the two karyotypic groups, but with variable genetic outcomes. Our results demonstrate the potential of combined analysis of karyotypes and mitochondrial and nuclear gene sequences to elucidate the complex dispersal and population history of the black rat.