Prevalence and molecular characterizations of Toxoplasma gondii and Babesia microti from small mammals captured in Gyeonggi and Gangwon Provinces, Republic of Korea

Investigation of Viral, Bacterial and Parasitic Zoonotic Diseases in Rodents in Turkey

BACKGROUND

Rodents are reservoir hosts for zoonotic pathogens that cause tropical diseases, many of which have been overlooked.

OBJECTIVES

The aim of this study was to investigate the presence of viral lymphocytic choriomeningitis and hantavirus infections, bacterial tularaemia and leptospirosis, and parasitic leishmaniasis and toxoplasmosis in rodents that are likely to carry and spread zoonotic agents, by using molecular methods.

METHODS

A total of 498 voles collected from 20 counties of Erzurum province. Conventional PCR was used for pathogen search. PCR-positive samples were subjected to sequence analysis.

RESULTS

Hantavirus (4.8%, 24/498) and tularaemia (0.8%, 4/498) positivity were detected. However, no positivity was detected for other selected pathogens.

CONCLUSIONS

Rodents, which are pathogen carriers and potential risk factors, are thought to may act as reservoirs for hantavirus and tularaemia in the study area. A preliminary study has been carried out at the point of detection of these diseases of global importance. The extent of the distribution of the infections, alternative hosts and the consequences of human exposure needs to be clarified through further studies.

Current Status of Trypanosoma grosi and Babesia microti in Small Mammals in the Republic of Korea

Small mammals, such as rodents and shrews, are natural reservoir hosts of zoonotic diseases, including parasitic protozoa. To assess the risk of rodent-borne parasitic protozoa in the Republic of Korea (ROK), this study investigated the status of parasitic protozoa, namely Trypanosoma, Babesia, and Theileria, in small mammals. In total, 331 blood samples from small mammals were analyzed for parasites using PCR and sequenced. Samples were positive for Trypanosoma grosi (23.9%; n = 79) and Babesia microti (10%; n = 33) but not Theileria. Small mammals from Seogwipo-si showed the highest infection rate of T. grosi (48.4%), while the highest B. microti infection rate was observed in those from Gangneung-si (25.6%). Sequence data revealed T. grosi to be of the AKHA strain. Phylogenetic analysis of B. microti revealed the US and Kobe genotypes. B. microti US-type-infected small mammals were detected throughout the country, but the Kobe type was only detected in Seogwipo-si. To our knowledge, this is the first nationwide survey that confirmed T. grosi and B. microti infections at the species level in small mammals in the ROK and identified the Kobe type of B. microti. These results provide valuable information for further molecular epidemiological studies on these parasites.

Toxoplasma gondii in small mammals in Romania: the influence of host, season and sampling location

BACKGROUND

Toxoplasma gondii is a protozoan parasite that infects a large spectrum of warm-blooded animals, including humans. Small rodents and insectivores play an important role in the epidemiology of T. gondii and may serve as a source of infection for both, domestic and wild definitive felid hosts. Factors influencing the occurrence of T. gondii in wild small mammals are unknown, despite the fact that many intermediate host species are identified. We have used small mammals (Rodentia and Lipotyphla) captured over two years in various habitats, both in urbanised and in natural landscapes. We assessed the importance of land-use, season and host ecology on T. gondii infection.

RESULTS

We examined 471 individuals belonging to 20 small mammal species, collected at 63 locations spread over wide altitude, habitat and land-use ranges from Romania. Heart tissue samples were individually analysed by PCR targeting the 529 bp repetitive DNA fragment of T. gondii. The overall prevalence of infection was 7.3%, with nine species of rodents and two species of shrews being found to carry T. gondii DNA. Five species showed high frequency of infection, with the highest prevalence found in Myodes glareolus (35.5%), followed by Spermophilus citellus (33.3%), Sorex minutus (23.1%), S. araneus (21.7%) and Micromys minutus (11.1%). Adults seemed more often infected than young, however when controlling for season, the difference was not significant, as in spring both adults and young showed higher infection rates, but more adults were sampled. Contrary to our expectations, urban/rural areas (with their implicit high density of domestic feline presence) had no effect on infection prevalence. In addition, neither habitat, nor land-use at sampling sites was important as only geographical location and host species were contributing factors to the infection risk.

CONCLUSIONS

High prevalence of T. gondii infection showed a highly localised, patchy occurrence, with long living and higher mobility host species being the most common carriers, especially during autumn.

High prevalence rates of Toxoplasma gondii in cat-hunted small mammals - Evidence for parasite induced behavioural manipulation in the natural environment?

Toxoplasma gondii causes one of the most frequent parasitic infections in vertebrates on earth. The present study aimed to assess the occurrence of T. gondii infection in cat-hunted wild small mammals, and to determine the circulating T. gondii genotypes in cat prey. There is evidence suggesting that T. gondii may manipulate rodents' behaviour enhancing transmission to their definitive feline host by facilitating predation. Given that most studies focusing on rodent behavior have been performed under laboratory conditions, we tested this hypothesis in the natural environment. We analysed 157 cat-hunted wild small mammals of six different species from Switzerland. Brain and skeletal muscle samples from each animal were tested for T. gondii DNA by PCR, and positive samples were genotyped using a multilocus sequence typing approach, including 10 genetic markers. Additionally, to evaluate exposure to cat faeces, the presence of Taenia taeniaeformis metacestodes was investigated at necropsy. The prevalence of T. gondii in cat-hunted Arvicola amphibius s.l. was 11.1% (7/63), 14.6% (7/48) in Apodemus spp., 13.6% (3/22) in Myodes glareolus, 6.7% (1/15) in Crocidura russula, and 0% in Microtus arvalis (0/8) and Sorex sp. (0/1). All completely genotyped T. gondii parasites, exhibited the ToxoDB #3 genotype, a Type II variant. We additionally analysed 48 trap-captured A. amphibius s.l., which all tested negative for T. gondii infection, contrasting with the higher prevalence in cat-hunted A. amphibius s.l. (0% vs. 11.1%; p = 0.0176). Furthermore, T. taeniaeformis was detected in both groups, indicating widespread contamination with cat faeces in the sampled areas. These results provide evidence that T. gondii infected rodents are at higher risk to be predated by cats and therewith support the behaviour manipulation hypothesis.

Zoonotic Babesia microti infection in wild rodents in Erzurum province, northeastern Turkey

Wild rodents are natural reservoir hosts of various pathogens, including Babesia microti. This study investigated the presence of B. microti in rodents from Erzurum province in Turkey. A total of 498 rodents and 21 rodent-fed ticks were analysed using the polymerase chain reaction (PCR) technique to test for the presence of B. microti. Babesia spp. were detected in three (0.6%) of the 498 rodent spleen samples. The Babesia-positive rodent species were identified as Microtus socialis by means of molecular analysis. The rodent-fed ticks comprised 15 Ixodes laguri and 6 Rhipicephalus sanguineus, none of which tested positive for Babesia spp. A sequence analysis of the 18S PCR amplicons confirmed the three Babesia-positive samples to be B. microti. The Erzurum isolates were 100% identical to the zoonotic Jena strain. The results of this study indicate the existence of zoonotic B. microti strains that may constitute a potential public health risk in Erzurum province. Future studies should determine the tick vector and other reservoir rodent species of B. microti in Erzurum.

A Review of Zoonotic Babesiosis as an Emerging Public Health Threat in Asia

Zoonotic babesiosis poses a serious health risk in many parts of the world. Its emergence in Asia is thus a cause for significant concern, demanding that appropriate control measures are implemented to suppress its spread in this region. This study focuses on zoonotic Babesia species reported in Asia, offering an extensive review of those species reported in animals and humans. We reported 11 studies finding zoonotic Babesia species in animals and 16 in humans. In China, the most prevalent species was found to be Babesia microti, reported in both humans (n = 10) and wild and domesticated animals (n = 4). In Korea, only two studies reported human babesiosis, with a further two studies reporting Babesia microti in wild animals. Babesia microti was also reported in wild animal populations in Thailand and Japan, with evidence of human case reports also found in Singapore, Mongolia and India. This is the first review to report zoonotic babesiosis in humans and animals in Asia, highlighting concerns for future public health in this region. Further investigations of zoonotic species of Babesia in animal populations are required to confirm the actual zoonotic threat of babesiosis in Asia, as well as its possible transmission routes.

The Global Emergence of Human Babesiosis

Babesiosis is an emerging tick-borne disease caused by intraerythrocytic protozoa that are primarily transmitted by hard-bodied (ixodid) ticks and rarely through blood transfusion, perinatally, and organ transplantation. More than 100 Babesia species infect a wide spectrum of wild and domestic animals worldwide and six have been identified as human pathogens. Babesia microti is the predominant species that infects humans, is found throughout the world, and causes endemic disease in the United States and China. Babesia venatorum and Babesia crassa-like agent also cause endemic disease in China. Babesia divergens is the predominant species in Europe where fulminant cases have been reported sporadically. The number of B. microti infections has been increasing globally in recent decades. In the United States, more than 2000 cases are reported each year, although the actual number is thought to be much higher. In this review of the epidemiology of human babesiosis, we discuss epidemiologic tools used to monitor disease location and frequency; demographics and modes of transmission; the location of human babesiosis; the causative Babesia species in the Americas, Europe, Asia, Africa, and Australia; the primary clinical characteristics associated with each of these infections; and the increasing global health burden of this disease.

Molecular evidence of zoonotic Babesia species, other than B. microti, in ixodid ticks collected from small mammals in the Republic of Korea

The occurrence of tick‐borne infectious diseases, including zoonotic babesiosis, has become a serious concern in recent years. In this study, we detected Babesia spp. using polymerase chain reaction (PCR) amplification of the 18S rRNA of the parasites isolated from ixodid ticks collected from small mammals in the Republic of Korea (ROK). Sequence analysis of the PCR amplicon revealed the presence of B. duncani, B. venatorum, B. capreoli/divergens, and, the most prevalent, B. microti in the ticks. The molecular phylogenetic analysis showed that the four species‐specific18S rRNA sequences clustered in four distinct clades. This is the first study to provide molecular evidence for the presence of zoonotic Babesia spp. other than B. microti in ticks in the ROK.

Animal reservoirs of zoonotic Babesia species: A global systematic review and meta-analysis of their prevalence, distribution and species diversity

Zoonotic babesiosis caused by Babesia divergens, B. microti and B. venatorum is a vector-borne protozoan zoonosis of increasing public health importance worldwide. A complex system of animal reservoirs including a wide range of mammals and a limited number of birds play a central role in maintaining the infection. Governed by the PRISMA guidelines, we conducted a systematic review and meta-analysis to determine the global prevalence, distribution and the diversity of zoonotic Babesia species in animal reservoirs. We pooled data using the random-effects model and determined quality of individual studies, heterogeneity and across study bias using the Joanna Briggs Institute critical appraisal instrument for prevalence studies, Cochran's Q-test and Egger's regression test respectively. Seventy nine studies from 29 countries reported a total 9311 positive cases of zoonotic Babesia infections from 46,649 animal reservoirs, yielding an overall estimated prevalence of 12.45% (95% CI: 10.09-15.27). Continental prevalence ranged between 8.55 (95% CI: 1.90-31.11) in Africa and 27.81% (95% CI: 21.25-35.48) in North America. Estimated prevalence in relation to country income levels, methods of diagnosis, study periods, sample sizes and reservoir categories ranged between 4.97 (95% CI: 1.80-13.00) and 30.12% (95% CI: 22.49-39.04). B. divergens was the most prevalent (12.50%, 95% CI: 8.30-18.39) of the 3 species of zoonotic Babesia reported in animal reservoirs. Zoonotic Babesia infections are prevalent in animal reservoirs across the world with the highest prevalence in North America and domestic animals. B. microti had the widest geographic distribution. We recommend tick control as well as strategic and prophylactic treatment against these parasites in animal reservoirs to curtail the economic losses associated with zoonotic Babesia species and possible transmission to humans.

Modelling Toxoplasma gondii infection in human cerebral organoids

Pluripotent stem cell-derived cerebral organoids have the potential to recapitulate the pathophysiology of in vivo human brain tissue, constituting a valuable resource for modelling brain disorders, including infectious diseases. Toxoplasma gondii, an intracellular protozoan parasite, infects most warm-blooded animals, including humans, causing toxoplasmosis. In immunodeficient patients and pregnant women, infection often results in severe central nervous system disease and fetal miscarriage. However, understanding the molecular pathophysiology of the disease has been challenging due to limited in vitro model systems. Here, we developed a new in vitro model system of T. gondii infection using human brain organoids. We observed that tachyzoites can infect human cerebral organoids and are transformed to bradyzoites and replicate in parasitophorous vacuoles to form cysts, indicating that the T. gondii asexual life cycle is efficiently simulated in the brain organoids. Transcriptomic analysis of T. gondii-infected organoids revealed the activation of the type I interferon immune response against infection. In addition, in brain organoids, T. gondii exhibited a changed transcriptome related to protozoan invasion and replication. This study shows cerebral organoids as physiologically relevant in vitro model systems useful for advancing the understanding of T. gondii infections and host interactions.

Epidemiological Significance of Toxoplasma Gondii Infections in Wild Rodents: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. Rodents are one of the most important intermediate hosts for T. gondii because they are preyed on by cats, who in turn excrete the environmentally resistant oocysts in their feces and thus spread the infection. Information on T. gondii infections is spread in numerous reports and is not easily accessible to readers. Here, we review prevalence, persistence of infection, clinical disease, epidemiology, and genetic diversity of T. gondii infections in wild rodents worldwide. Data are tabulated by country, by each rodent species alphabetically, and chronologically. Recent genetic diversity of T. gondii strains in rodents is critically evaluated.

Toxoplasma gondii infection in Colombia with a review of hosts and their ecogeographic distribution

Toxoplasma gondii is one of the most prevalent zoonotic protozoan parasites among warm-blooded animal populations (humans included) around the world, causing multiple clinic manifestations including death in the most severe cases of infection. Due to the versatile life cycle of T. gondii and its diversity of potential hosts, there is a common perception that natural areas and wildlife are highly prevalent reservoirs for the parasite; however, information and reports of the parasite on wildlife populations in Colombia are scarce. Using PRC-based detection analyses of the B1 gene, we evaluated the presence of T. gondii in 49 native small mammal species (10% of the mammal species of Colombia) from 4 different undisturbed natural habitats. Additionally, to understand the ecogeographical distribution of the parasite in Colombia, we developed a literature search of infection reports including information on the host species, density of records and occurrence patterns (using landcover and ecoregions) in natural, rural and urban areas. Our literature review showed a total of 8,103 reports of T. gondii for Colombia of which 86% were related to humans, and 14% to non-human mammals and other categories, with just a single report associated to wildlife; additionally, 82% of all reports were associated to urban areas whereas only 18% to rural sites. Based on the negative results for the presence of T. gondii in our PCR-based analyses and our literature search, we suggest that T. gondii has a synanthropic distribution in Colombia occurring in ecoregions as variable as the xeric scrubs in the northern lowlands and humid montane Andean forests, also we show a lack of information on the parasite relationship with wildlife, a concerning fact given that zoonoses are the leading mechanism for the emergence of infectious diseases.

Global Status of Toxoplasma gondii Seroprevalence in Rodents: A Systematic Review and Meta-Analysis

Toxoplasmosis is one of the most prevalent infections in humans and animals caused by the intracellular protozoan parasite Toxoplasma gondii (T. gondii). Rodents, as intermediate and reservoir hosts, play a key role in the maintenance and transmission of T. gondii. They can be contaminated and maintain the parasite in the form of cysts in their bodies, demonstrating an infection source for their offsprings, predators (particularly felids), and other animals. Therefore, the present systematic review and meta-analysis study was carried out to evaluate the global seroprevalence of T. gondii in these mammals. For achieving the purpose of the current study, six English databases (PubMed, Science Direct, Web of Science, Scopus, ProQuest, and Google Scholar) were systematically searched for related studies from 1970 to 2018. Finally, a total of 52,372 records were screened, 105 records including 26,221 rodents were incorporated in the present study. By random effect models, the overall seroprevalence was calculated at 6% (95% CI = 6-7%), with the highest amount was observed in Africa (24%) and South America (18%), and the lowest amount in Europe (1%). The subgroup data analysis by gender manifested that the prevalence of Immunoglobulin G antibodies did not differ between genders (P > 0.05). Due to the significant heterogeneity, meta-regression models were applied based on serological techniques and continental regions; however, the obtained values were not statistically significant (P = 0.480 and P = 0.295, respectively). The present study revealed a relatively low level of T. gondii seroprevalence in rodents; however, if they were the main food source for their predators, they would cause high transmission of T. gondii.

Detection and characterization of an emerging type of Babesia sp. similar to Babesia motasi for the first case of human babesiosis and ticks in Korea

Babesiosis is a tick-transmitted intraerythrocytic zoonosis. In Korea, the first mortalities were reported in 2005 due to Babesia sp. detection in sheep; herein we report epidemiological and genetic characteristics of a second case of babesiosis. Microscopic analysis of patient blood revealed polymorphic merozoites. To detect Babesia spp., PCR was performed using Babesia specific primers for β-tubulin, 18S rDNA, COB, and COX3 gene fragments. 18S rDNA analysis for Babesia sp., showed 98% homology with ovine Babesia sp. and with Babesia infections in Korea in 2005. Moreover, phylogenetic analysis of 18S rDNA, COB, and COX3 revealed close associations with B. motasi. For identifying the infectious agent, Haemaphysalis longicornis (296) and Haemaphysalis flava (301) were collected around the previous residence of the babesiosis patient. Babesia genes were identified in three H. longicornis: one sample was identified as B. microti and two samples were 98% homologous to B. motasi. Our study is the first direct confirmation of the infectious agent for human babesiosis. This case most likely resulted from tick bites from ticks near the patient house of the babesiosis patient. H. longicornis has been implicated as a vector of B. microti and other Babesia sp. infections.

Geographical distribution of Toxoplasma gondii genotypes in Asia: A link with neighboring continents

Defining the pattern of genetic diversity of Toxoplasma gondii is important to understand its worldwide distribution. During the last decades, a large number of studies have been published on Toxoplasma genotypes circulating in Europe, in North and South America. Two continents are still largely unexplored, Africa and, to a less extent, Asia. In this last continent, an increasing number of publications reported genotypes circulating in diverse provinces of China, but very few data are available for other Asian countries. After a systematic database search, 47 papers related to T. gondii genotypes in Asia were analyzed. Genetic characterization of DNA was performed by microsatellite markers, or more usually by a multiplex PCR using 11 PCR-RFLP markers, allowing data comparison to draw a first global picture of the population structure of this parasite throughout Asia. Overall, 390 isolates or DNA extracts were completely typed by PCR-RFLP and/or microsatellite marker methods, revealing 36 different PCR-RFLP or equivalent microsatellite genotypes: 15 genotypes identified by a ToxoDB number and 21 atypical or unique genotypes. The most common genotype found in Asia is the genotype ToxoDB#9 (Chinese 1). The clonal types I, II and II variant, and III were also commonly found in Asia. The geographical distribution of these genotypes across Asia may reflect either a continuum with Europe for the western part of Asia (presence of Type II), or the circulation of strains through animal migration or human activities between Africa and the Southwestern part of Asia (Africa 1 genotype in Turkey or ToxoDB#20 both I Sri-Lanka and in Ethiopia or Egypt). Although there are some indications of a genetic population structure in Southeast Asian countries different from the rest of Asia, more studies in this tropical part of Asia will be necessary for a region which represent as well as Africa one of the missing links of the T. gondii genetic diversity.

Serological and Molecular Detection of Toxoplasma gondii and Babesia microti in the Blood of Rescued Wild Animals in Gangwon-do (Province), Korea

Infections of Toxoplasma gondii and Babesia microti are reported in many wild animals worldwide, but information on their incidence and molecular detection in Korean wild fields is limited. In this study, the prevalence of T. gondii and B. microti infection in blood samples of 5 animal species (37 Chinese water deer, 23 raccoon dogs, 6 roe deer, 1 wild boar, and 3 Eurasian badgers) was examined during 2008–2009 in Gangwon-do (Province), the Republic of Korea (=Korea) by using serological and molecular tests. The overall seropositivity of T. gondii was 8.6% (6/70); 10.8% in Chinese water deer, 4.3% in raccoon dogs, and 16.7% in roe deer. PCR revealed only 1 case of T. gondii infection in Chinese water deer, and phylogenic analysis showed that the positive isolate was practically identical to the highly pathogenetic strain type I. In B. microti PCR, the positive rate was 5.7% (4/70), including 2 Chinese water deer and 2 Eurasian badgers. Phylogenetic analysis results of 18S rRNA and the β-tubulin gene showed that all positive isolates were US-type B. microti. To our knowledge, this is the first report of B. microti detected in Chinese water deer and Eurasian badger from Korea. These results indicate a potentially high prevalence of T. gondii and B. microti in wild animals of Gangwon-do, Korea. Furthermore, Chinese water deer might act as a reservoir for parasite infections of domestic animals.

Toxoplasma gondii B1 Gene Detection in Feces of Stray Cats around Seoul, Korea and Genotype Analysis of Two Laboratory-Passaged Isolates

The increasing prevalence of Toxoplasma gondii infection in the human population in the Republic of Korea (= Korea) is due to various reasons such as an increase in meat consumption. However, the importance of cats in transmitting T. gondii infection through oocysts to humans has seldom been assessed. A total of 300 fecal samples of stray cats captured around Seoul from June to August 2013 were examined for T. gondii B1 gene (indicating the presence of oocysts) using nested-PCR. Fourteen (4.7%) of 300 cats examined were positive for B1 gene. Female cats (7.5%) showed a higher prevalence than male cats (1.4%). Cats younger than 3 months (5.5%) showed a higher prevalence than cats (1.5%) older than 3 months. For laboratory passage of the positive samples, the fecal suspension (0.2 ml) of B1 gene positive cats was orally inoculated into experimental mice. Brain tissues of the mice were obtained after 40 days and examined for the presence of tissue cysts. Two isolates were successfully passaged (designated KNIH-1 and KNIH-2) and were molecularly analyzed using the SAG5D and SAG5E gene sequences. The SAG5D and SAG5E gene sequences showed high homologies with the ME49 strain (less virulent strain). The results indicated the importance of stray cats in transmitting T. gondii to humans in Korea, as revealed by detection of B1 gene in fecal samples. T. gondii isolates from cats were successfully passaged in the laboratory for the first time in Korea.