Publications by authors named "Benjamin M Rosenthal"

64 Publications

Polymorphism of Antifolate Drug Resistance in From Local Residents and Migrant Workers Returned From the China-Myanmar Border.

Front Cell Infect Microbiol 2021 24;11:683423. Epub 2021 Jun 24.

Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, China.

Drug-resistant  malaria impedes efforts to control, eliminate, and ultimately eradicate malaria in Southeast Asia. resistance to antifolate drugs derives from point mutations in specific parasite genes, including the dihydropteroate synthase (), dihydrofolate reductase (), and GTP cyclohydrolase I () genes. This study aims to investigate the prevalence and spread of drug resistance markers in populating the China-Myanmar border. Blood samples were collected from symptomatic patients with acute infection. Samples with single-clone infections were sequenced for and genesand genotyped for 6 flanking microsatellite markers. Copy number variation in the gene was also examined. Polymorphisms were observed in six different codons of the  gene (382, 383, 512, 549, 553, and 571) and six different codons of the  gene (13, 57, 58, 61, 99, 117) in two study sites. The quadruple mutant haplotypes 57I/L/58R/61M/117T of gene were the most common (comprising 76% of cases in Myitsone and 43.7% of case in Laiza). The double mutant haplotype 383G/553G of  gene was also prevalent at each site (40.8% and 31%). Microsatellites flanking the gene differentiated clinical samples from wild type and quadruple mutant genotypes ( = 0.259-0.3036), as would be expected for a locus undergoing positive selection. The lack of copy number variation of suggests that SP-resistant may harbor alternative mechanisms to secure sufficient folate.
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http://dx.doi.org/10.3389/fcimb.2021.683423DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8265503PMC
July 2021

Genetic evidence substantiates transmission of Trichinella spiralis from one swine farm to another.

Parasit Vectors 2021 Jul 9;14(1):359. Epub 2021 Jul 9.

European Union Reference Laboratory for Parasites, Istituto Superiore Di Sanità, Rome, Italy.

Background: Trichinella spiralis ranks seventh in the risk posed by foodborne parasites. It causes most human cases of trichinellosis and is the most frequent cause of Trichinella outbreaks on pig farms and in wild boar, worldwide. Veterinary inspectors seek the source of outbreaks in hopes of limiting the spread. Established molecular tools are inadequate for distinguishing among potential T. spiralis infection sources because genetic variability in these zoonotic pathogens is limited in Europe. Microsatellite markers proved successful in tracing an outbreak of T. britovi, a related parasite harboring much more genetic variation. Here, we successfully employed microsatellite markers to determine the genetic structure of T. spiralis isolates from two pig outbreaks, discovering notable uniformity among parasites within each farm and discovering an epidemiological link between these two outbreaks.

Methods: The individual larvae from five isolates of T. spiralis from two pig farms and from ten wild boars were genotyped using nine microsatellite markers to examine their genetic structure.

Results: Notably uniform parasite populations constituted each farm outbreak, and the parasites from the first and second outbreaks resembled each other to a notable degree, indicating an epidemiological link between them. Wild boar harbored more genetically variable larval cohorts, distinguishing them from parasites isolated from domestic pigs.

Conclusions: Microsatellite markers succeeded in distinguishing isolates of the highly homogeneous T. spiralis, aiding efforts to track transmission. Each outbreak was composed of a homogenous group of parasites, suggesting a point source of contamination.
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http://dx.doi.org/10.1186/s13071-021-04861-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8268521PMC
July 2021

Loop-mediated isothermal amplification (LAMP) assays targeting 18S ribosomal RNA genes for identifying P. vivax and P. ovale species and mitochondrial DNA for detecting the genus Plasmodium.

Parasit Vectors 2021 May 24;14(1):278. Epub 2021 May 24.

Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, 650500, Yunnan, People's Republic of China.

Background: Loop-mediated isothermal amplification (LAMP) has been widely used to diagnose various infectious diseases. Malaria is a globally distributed infectious disease attributed to parasites in the genus Plasmodium. It is known that persons infected with Plasmodium vivax and P. ovale are prone to clinical relapse of symptomatic blood-stage infections. LAMP has not previously been specifically evaluated for its diagnostic performance in detecting P. ovale in an epidemiological study, and no commercial LAMP or rapid diagnostic test (RDT) kits are available for specifically diagnosing infections with P. ovale.

Methods: An assay was designed to target a portion of mitochondrial DNA (mtDNA) among Plasmodium spp., the five human Plasmodium species and two other assays were designed to target the nuclear 18S ribosomal DNA gene (18S rDNA) of either P. vivax or P. ovale for differentiating the two species. The sensitivity of the assays was compared to that of nested PCR using defined concentrations of plasmids containing the target sequences and using limiting dilutions prepared from clinical isolates derived from Chinese workers who had become infected in Africa or near the Chinese border with Myanmar.

Results: The results showed that 10 copies of the mitochondrial target or 10 and 10 copies of 18S rDNA could be detected from Plasmodium spp., P. vivax and P. ovale, respectively. In 279 clinical samples, the malaria Pan mtDNA LAMP test performed well when compared with a nested PCR assay (95% confidence interval [CI] sensitivity 98.48-100%; specificity 90.75-100%). When diagnosing clinical cases of infection with P. vivax, the 18S rDNA assay demonstrated an even great sensitivity (95.85-100%) and specificity (98.1-100%). The same was true for clinical infections with P. ovale (sensitivity 90.76-99.96%; specificity 98.34-100%). Using plasmid-positive controls, the limits of detection of Malaria Pan, 18S rDNA P. vivax and 18S rDNA P. ovale LAMP were 100-, 100- and tenfold lower than those of PCR, respectively.

Conclusion: The novel LAMP assays can greatly aid the rapid, reliable and highly sensitive diagnosis of infections of Plasmodium spp. transmitted among people, including P. vivax and P. ovale, cases of which are most prone to clinical relapse.
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http://dx.doi.org/10.1186/s13071-021-04764-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8147439PMC
May 2021

Zoonotic Sarcocystis.

Res Vet Sci 2021 May 19;136:151-157. Epub 2021 Feb 19.

Animal Parasitic Disease Laboratory, United States Department of Agriculture- Agricultural Research Service, 10300, Baltimore Avenue, Beltsville, MD 20705, United States of America. Electronic address:

Apicomplexan species in the genus Sarcocystis form tissue cysts, in their intermediate hosts, similar to those established in chronic toxoplasmosis. More than 200 species are known, but just a few are known to threaten human health owing to infection in livestock species. Intestinal sarcocystosis occurs when people consume raw or undercooked beef contaminated with Sarcocystis hominis or S. heydorni or undercooked pork contaminated with S. suihominis. Those infections may cause mild enteritis, but most infections are thought to be asymptomatic. People also become dead-end (intermediate) hosts for non-human Sarcocystis spp. after accidentally ingesting sporocysts, leading to extraintestinal sarcocystosis. The clinical spectrum may range from asymptomatic muscle cysts to a severe, acute, eosinophilic myositis associated with systemic symptoms with peripheral eosinophilia. Most human cases have been described from Southeast Asia, but Sarcocystis parasites have a worldwide distribution, especially where livestock is raised, and human infections in other areas have been described but may be underrecognized.
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http://dx.doi.org/10.1016/j.rvsc.2021.02.008DOI Listing
May 2021

Divergence at mitochondrial and ribosomal loci indicates the split between Asian and European populations of Trichinella spiralis occurred prior to swine domestication.

Infect Genet Evol 2021 03 6;88:104705. Epub 2021 Jan 6.

United States Department of Agriculture, Agricultural Research Service, Animal Parasitic Diseases Laboratory, Beltsville, MD 20705, USA.

Available evidence suggests that Trichinella spiralis first originated in Asia and subsequently spread to the rest of the world. Notably limited genetic diversity in European T. spiralis isolates indicates that the parasite went through a dramatic genetic bottleneck at some point in its history. Did this genetic bottleneck result from the transport of a limited number of T. spiralis infected pigs from Asian centers of domestication, or was the parasite resident in Europe far earlier than the domestication of pigs there? In order to explore this hypothesis, we generated complete mitochondrial genomes and ribosomal DNAs from seventeen European T. spiralis isolates, six North American isolates and seven Asian isolates using next generation sequencing. A total of 13,858 base pairs of mitochondrial DNA and 7431 nucleotides of the nuclear ribosomal DNA sequence from each isolate were aligned and subjected to phylogenetic analysis using T. nelsoni as an outgroup. We confirmed that North American and European isolates were tightly clustered within a single "western clade" and all Chinese T. spiralis isolates were placed within a well-supported sister clade. These results indicate that European T. spiralis did not directly descend from extant Chinese parasite populations. Furthermore, the amount of nucleotide divergence between the two clades suggests that they diverged before pigs were domesticated. Over evolutionary time periods, Chinese and European T. spiralis were likely maintained as separate populations. The data presented here indicates the genetic bottleneck observed in European T. spiralis did not result from a small number of founders introduced with Chinese pigs in the recent past, but derives from an earlier bottleneck in host populations associated with the end of the last glacial maximum.
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http://dx.doi.org/10.1016/j.meegid.2021.104705DOI Listing
March 2021

Assessing the evolutionary persistence of ecological relationships: A review and preview.

Infect Genet Evol 2020 10 1;84:104441. Epub 2020 Jul 1.

USDA-Agricultural Research Service, Animal Parasitic Diseases Lab, Beltsville, MD 20705 USA. Electronic address:

Species interactions, such as pollination, parasitism and predation, form the basis of functioning ecosystems. The origins and resilience of such interactions therefore merit attention. However, fossils only occasionally document ancient interactions, and phylogenetic methods are blind to recent interactions. Is there some other way to track shared species experiences? "Comparative demography" examines when pairs of species jointly thrived or declined. By forging links between ecology, epidemiology, and evolutionary biology, this method sheds light on biological adaptation, species resilience, and ecosystem health. Here, we describe how this method works, discuss examples, and suggest future directions in hopes of inspiring interest, imitators, and critics.
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http://dx.doi.org/10.1016/j.meegid.2020.104441DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7327472PMC
October 2020

Hiding in plain sight: discovery and phylogeography of a cryptic species of Trichinella (Nematoda: Trichinellidae) in wolverine (Gulo gulo).

Int J Parasitol 2020 04 24;50(4):277-287. Epub 2020 Mar 24.

Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N 5B4, Canada.

Understanding parasite diversity and distribution is essential in managing the potential impact of parasitic diseases in animals and people. Imperfect diagnostic methods, however, may conceal cryptic species. Here, we report the discovery and phylogeography of a previously unrecognized species of Trichinella in wolverine (Gulo gulo) from northwestern Canada that was indistinguishable from T. nativa using the standard multiplex PCR assay based on the expansion segment 5 (ESV) of ribosomal DNA. The novel genotype, designated as T13, was discovered when sequencing the mitochondrial genome. Phylogenetic analyses of the mitochondrial genome and of 15 concatenated single copy orthologs of nuclear DNA indicated a common ancestor for the encapsulated clade is shared by a subclade containing Trichinella spiralis and Trichinella nelsoni, and a subclade containing T13 and remaining taxa: T12 + (T2 + T6) + [(T5 + T9) + (T3 + T8)]. Of 95 individual hosts from 12 species of mammalian carnivores from northwestern Canada from which larvae were identified as T. nativa on multiplex PCR, only wolverines were infected with T13 (14 of 42 individuals). These infections were single or mixed with T. nativa and/or T6. Visual examination and motility testing confirmed that T13 is encapsulated and likely freeze-tolerant. We developed a new Polymerase Chain Reaction-Restriction Fragment Length Polymorphism which unequivocally distinguishes between T13 and T. nativa. We propose Trichinella chanchalensis n. sp. for T13, based on significant genetic divergence from other species of Trichinella and broad-based sampling of the Trichinella genome. Exploration of Alaskan and Siberian isolates may contribute to further resolution of a phylogeographically complex history for species of Trichinella across Beringia, including Trichinella chanchalensis n. sp. (T13).
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http://dx.doi.org/10.1016/j.ijpara.2020.01.003DOI Listing
April 2020

Hepatitis E Virus in Pigs from Slaughterhouses, United States, 2017-2019.

Emerg Infect Dis 2020 02;26(2):354-357

Hepatitis E virus (HEV) RNA was detected in 6.3% and HEV IgG in 40% of 5,033 serum samples from market-weight pigs at 25 slaughterhouses in 10 US states. The prevalent HEV genotype was zoonotic genotype 3, group 2. Blood of HEV-viremic pigs from slaughterhouses may contaminate pork supply chains.
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http://dx.doi.org/10.3201/eid2602.191348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6986846PMC
February 2020

Widespread resistance mutations to sulfadoxine-pyrimethamine in malaria parasites imported to China from Central and Western Africa.

Int J Parasitol Drugs Drug Resist 2020 04 29;12:1-6. Epub 2019 Nov 29.

Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, 650500, Yunnan, PR China. Electronic address:

Background: Imported cases of infectious disease provide invaluable information about epidemiological conditions abroad, and should guide treatment decisions at home and abroad. Here, we examined cases of malaria imported from Africa to China for mutations eroding the efficacy of sulfadoxine-pyrimethamine (SP), sometimes used as an intermittent preventive treatment during for pregnant women and infants.

Methods: A total of 208 blood samples were collected from P. falciparum-infected workers who had returned from Western and Central Africa to Guangxi Province Frequency distribution. Samples were analyzed for the mutations in dhfr and dhps genes by PCR -sequencing. The prevalence of dhfr and dhps polymorphisms was analyzed. Among the isolates, polymorphisms were detected in mutants N51I, C59R, S108N and I164L of Pfdhfr and I431V, S436 A/F, A437G, K540 E/N, A581G and A613T of pfdhps.

Results: Mutations promoting drug resistance were widespread in this cohort. For pfdhfr and pfdhps, wild types were equally rare among patients returned from Western Africa and Central Africa. A triple-mutant dhfr haplotype was most prevalent (>70%). We report for the first time mutation I164L-dhfr and I431V-dhps in Ghana, and for the first time we found A581G to exceed a clinically-relevant threshold that may counter-indicate current clinical practices. For Pfdhps, the double-mutant IAGKAA was high prevalent haplotype in Ghana, Western Africa. The single-mutant ISGKAA was a majority haplotype in Cameroon. Alarmingly, a "super resistance" quintuple mutant was detected, for the first time, in parasites of West African origin (defined by IAGKAA/IRNI in combination with pfdhps 581G and dhfr I164L). This may limit the efficacy of this drug combination for even intermittent clinical applications.

Conclusions: These data are cause for great concern and call for continued surveillance of the efficacy of SP in source and recipient populations, and should be considered when developing treatment policy for imported malaria cases in China and elsewhere.
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http://dx.doi.org/10.1016/j.ijpddr.2019.11.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6909128PMC
April 2020

Comparative demography elucidates the longevity of parasitic and symbiotic relationships.

Proc Biol Sci 2018 10 3;285(1888). Epub 2018 Oct 3.

US Department of Agriculture, Agricultural Research Service, 10300 Baltimore Avenue, Beltsville, MD 20705, USA

Parasitic and symbiotic relationships govern vast nutrient and energy flows, yet controversy surrounds their longevity. Enduring relationships may engender parallel phylogenies among hosts and parasites, but so may ephemeral relationships when parasites colonize related hosts. An understanding of whether symbiont and host populations have grown and contracted in concert would be useful when considering the temporal durability of these relationships. Here, we devised methods to compare demographic histories derived from genomic data. We compared the historical growth of the agent of severe human malaria, , and its mosquito vector, , to human and primate histories, thereby discerning long-term parallels and anthropogenic population explosions. The growth history of , a zoonotic parasite disseminated by swine, proved regionally specific, paralleling distinctive growth histories for wild boar in Asia and Europe. Parallel histories were inferred for an anemone and its algal symbiont ( and ). Concerted growth in potatoes and the agent of potato blight ( and ) did not commence until the age of potato domestication. Through these examples, we illustrate the utility of comparative historical demography as a new exploratory tool by which to interrogate the origins and durability of myriad ecological relationships. To facilitate future use of this approach, we introduce a tool called C-PSMC to align and evaluate the similarity of demographic history curves.
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http://dx.doi.org/10.1098/rspb.2018.1032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6191686PMC
October 2018

Histopathological, morphological, and molecular characterization of Sarcocystis species in elk (Cervus elaphus) from Pennsylvania, USA.

Parasitol Res 2018 Oct 17;117(10):3245-3255. Epub 2018 Aug 17.

United States Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Animal Parasitic Diseases Laboratory, Beltsville, MD, 20705-2350, USA.

Sarcocystis sarcocysts are common in many species of domestic and wild animals. Here, we report sarcocystosis in muscles from 91 free range elk (Cervus elaphus) from Pennsylvania, USA, tested by histopathology, transmission electron microscopy (TEM), and DNA sequencing. Sarcocysts were detected in hematoxylin and eosin (HE)-stained sections from 83 of 91 (91.2%) elk, including 83/91 (91.2%) tongues and 15/17 (88.2%) hearts. With respect to age, sarcocysts were found in 0/5 calves, 8/9 (88.8%) yearlings, and 75/77 (97.4%) adults. Sarcocysts were identified in 62/69 (89.4%) females and 21/22 (91.2%) males. Associated lesions were mild and consisted of inflammatory foci around degenerate sarcocysts. There were two morphologically distinct sarcocysts based on wall thickness, thin (< 0.5 μm) and thick-walled (> 4.0 μm). Thin-walled sarcocysts had a TEM "type 2" and villar protrusions (vps), identical to Sarcocystis wapiti previously described from elk in western USA. This species was present both in tongue and heart samples and was detected in all infected elk. Thick-walled sarcocysts consisted of three morphologic variants, referred to herein as subkinds A, B, C. Subkind A sarcocysts were rare; only four sarcocysts were found in three elk. Histologically, they had a 5-8-μm thick wall with tufted vp. By TEM, the sarcocyst wall was "type 12" and appeared similar to Sarcocystis sybillensis, previously described from elk in USA. Subkind B, Sarcocystis sp.1 sarcocysts were also rare, found in only 1 elk. These sarcocysts had 6.7-7.3-μm-thick wall with TEM "type 15b" vp. Subkind C Sarcocystis sp.2 sarcocysts were more common (22/91). Morphologically, the sarcocyst wall was 6.1-6.8 μm thick and contained "type 10b" vp. Comparisons of ribosomal DNA loci with published sequences indicated all sarcocysts were similar to what has previously been isolated from cervid hosts across the northern hemisphere. Phylogenetic analysis placed the thin-walled S. wapiti within a strongly supported clade with S. linearis and S. taeniata, while the thick-walled cysts were very closely related to S. truncata, S. elongata, S. silva, and S. tarandi. Further sequencing is needed to produce molecular diagnostics to distinguish among these species. North American elk are hosts to multiple Sarcocystis species with diverse morphology, deriving from two separate evolutionary lineages.
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http://dx.doi.org/10.1007/s00436-018-6024-2DOI Listing
October 2018

Human impact on the diversity and virulence of the ubiquitous zoonotic parasite .

Proc Natl Acad Sci U S A 2018 07 2;115(29):E6956-E6963. Epub 2018 Jul 2.

Department of Microbiology, The University of Tennessee, Knoxville, TN 37996;

A majority of emerging infectious diseases in humans are zoonoses. Understanding factors that influence the emergence and transmission of zoonoses is pivotal for their prevention and control. is one of the most widespread zoonotic pathogens known today. Whereas only a few genotypes of dominate in the Northern Hemisphere, many genotypes coexist in South America. Furthermore, strains from South America are more likely to be virulent than those from the Northern Hemisphere. However, it is not clear what factor(s) shaped modern-day genetic diversity and virulence of Here, our analysis suggests that the rise and expansion of farming in the past 11,000 years established the domestic cat/mouse transmission cycle for , which has undoubtedly played a significant role in the selection of certain linages of Our mathematical simulations showed that within the domestic transmission cycle, intermediately mouse-virulent genotypes have an adaptive advantage and eventually become dominant due to a balance between lower host mortality and the ability to superinfect mice previously infected with a less virulent strain. Our analysis of the global type II lineage of suggests its Old World origin but recent expansion in North America, which is likely the consequence of global human migration and trading. These results have significant implications concerning transmission and evolution of zoonotic pathogens in the rapidly expanding anthropized environment demanded by rapid growth of the human population and intensive international trading at present and in the future.
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http://dx.doi.org/10.1073/pnas.1722202115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6055184PMC
July 2018

A partition of Toxoplasma gondii genotypes across spatial gradients and among host species, and decreased parasite diversity towards areas of human settlement in North America.

Int J Parasitol 2018 07 23;48(8):611-619. Epub 2018 Mar 23.

Department of Microbiology, The University of Tennessee, Knoxville, TN 37996, USA. Electronic address:

Toxoplasma gondii counts among the most consequential food-borne parasites, and although the parasite occurs in a wide range of wild and domesticated animals, farms may constitute a specific and important locus of transmission. If so, parasites in animals that inhabit agricultural habitats might be suspected of harbouring genetically distinct parasite types. To better understand habitat effects pertinent to this parasite's transmission, we compiled and analysed existing genotypic data of 623 samples from animals across a proximity gradient from areas of human settlement to the wilderness in North America. To facilitate such analysis, T. gondii isolates were divided into three groups: (i) from farm-bound animals (with the most limited home ranges on farms); (ii) from free-roaming animals (with wider home ranges on or near farms); and (iii) from wildlife. In addition, parasite genotype distribution in different animal species was analysed. We observed no absolute limitation of any of five major genotypes to any one habitat; however, the frequency of four genotypes decreased across the gradient from the farm-bound group, to the free-roaming group, then the wildlife, whereas a fifth genotype increased along that gradient. Genetic diversity was greater in free-roaming than in farm-bound animals. The genotypic composition of parasites in wildlife differed from those in farm-bound and free-roaming animals. Furthermore, parasite genotypes differed among host species. We conclude that T. gondii genotype distributions are influenced by the spatial habitat and host species composition, and parasite diversity decreases towards areas of human settlement, elucidating facts which may influence transmission dynamics and zoonotic potential in this ubiquitous but regionally variable parasite.
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http://dx.doi.org/10.1016/j.ijpara.2018.01.008DOI Listing
July 2018

Morphological and molecular characteristics of Sarcocystis bertrami from horses and donkeys in China.

Vet Parasitol 2018 Mar 2;252:89-94. Epub 2018 Feb 2.

Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, Yunnan Province 650500, China. Electronic address:

While Sarcocystis parasites from the muscles of donkey and horse have been characterized as different species, similarities between the parasites in these host raises questions about this assignment (Levine and Tadros, 1980; Matuschka, 1983; Odening et al., 1995b). To resolve this, we examined the tissue cysts of Sarcocystis collected from donkeys and horses were studied by morphological and molecular methods. Morphological studies performed by light microscopy (LM) revealed that each of two types of cysts were present in samples from each host type. Under LM, villar protrusions (VP) were sometimes observed on the larger (Type I) and smaller (Type II) of these cyst types; when present, these were sometimes short and sometimes long. By electron microscopy (EM), VPs from both horse and donkey cysts were found to share similar structures, appearing to be typical of 'type 11a' VPs found on the Sarcocystis wall of Sarcocystis fayeri as described by Dubey et al., 1977. The VP of cysts in both horses and donkeys contained microtubules extending from the villar tips to the ground substance (GS). Ovoid, osmiophilic bodies (OB) were found along the length of the microtubules within the villi, but this feature was not found in all VP. To understand the phylogeny of the parasites, a portion of the coxI gene was sequenced from 22 isolated cysts (9 from donkeys and 13 from horses). Phylogenetic relationships were reconstructed from these sequences and the closest homologues available in GenBank, revealing that all of the samples, regardless of host origin or morphological appearance under LM, grouped in one clade. Ours is the first attempt to combine morphological measurements with coxI sequences in assessing such equine parasites; the results confirm a close relationship of the parasites from horse and donkey with S. fayeri. Further, the data suggest that the cysts in each host likely belong to the same species. As the first named species was Sarcocystis bertrami, we propose S. bertrami (syn. Sarcocystis fayeri) as the descriptor for this parasite of both horses and donkeys. Ultimately, this finding will only be validated by cross-transmission infection experiments that score the ability of parasite isolates from one Equus to infect the other.
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http://dx.doi.org/10.1016/j.vetpar.2018.01.024DOI Listing
March 2018

Sarcocystis cymruensis: discovery in Western Hemisphere in the Brown rat (Rattus norvegicus) from Grenada, West Indies: redescription, molecular characterization, and transmission to IFN-γ gene knockout mice via sporocysts from experimentally infected domestic cat (Felis catus).

Parasitol Res 2018 Apr 19;117(4):1195-1204. Epub 2018 Feb 19.

United States Department of Agriculture, Agricultural Research Service, Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Beltsville, MD, 20705-2350, USA.

Rodents are intermediate hosts for many species of Sarcocystis. Little is known of Sarcocystis cymruensis that uses the Brown rat (Rattus norvegicus) as intermediate hosts and the domestic cat (Felis catus) as experimental definitive host. Here, we identified and described Sarcocystis cymruensis in naturally infected R. norvegicus from Grenada, West Indies. Rats (n = 167) were trapped in various locations in two parishes (St. George and St. David). Microscopic, thin (< 1 μm) walled, slender sarcocysts were found in 11 of 156 (7.0%) rats skeletal muscles by squash examination. A laboratory-raised cat fed naturally infected rat tissues excreted sporocysts that were infectious for interferon gamma gene knockout (KO) mice, but not to Swiss Webster outbred albino mice. All inoculated mice remained asymptomatic, and microscopic S. cymruensis-like sarcocysts were found in the muscles of KO mice euthanized on day 70, 116, and 189 post inoculation (p.i.). Sarcocysts from infected KO mice were infective for cats at day 116 but not at 70 days p.i. By transmission electron microscopy, the sarcocyst wall was "type 1a." Detailed morphological description of the cyst wall, metrocytes, and bradyzoites is given for the first time. Additionally, molecular data on S. cymruensis are presented also for the first time. Molecular characterization of sarcocysts 18S rDNA and 28S rDNA, ITS-1, and cox1 loci showed the highest similarity with S. rodentifelis and S. muris. In conclusion, the present study described the natural infection of S. cymruensis in Brown rat for the first time in a Caribbean country and provided its molecular characteristics.
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http://dx.doi.org/10.1007/s00436-018-5799-5DOI Listing
April 2018

Bobcats (Lynx rufus) are natural definitive host of Besnoitia darlingi.

Vet Parasitol 2017 Dec 14;248:84-89. Epub 2017 Nov 14.

United States Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Animal Parasitic Diseases Laboratory, Building 1001, Beltsville, MD 20705-2350, USA. Electronic address:

Bovine besnoitiosis, caused by Besnoitia besnoiti, is an economically important disease of cattle in many countries but its transmission remains a mystery. Wild felids are suspected to be its definitive hosts. The domestic cat (Felis catus) is known experimental definitive host for Besnoitia species of rodents. Here, we report for Besnoitia darlingi the first identification of a natural definitive host, the bobcat (Lynx rufus). Oocysts resembling Toxoplasma gondii (unsporulated; 10.9±0.8×12.1±0.2μm; n=5) were detected microscopically in the feces of two of 25 free ranging wild bobcats from Mississippi, USA. After detailed investigation, we identified these oocysts as B. darlingi and not T. gondii. The IFN-γ gene knockout (KO) mice fed oocysts from bobcats died of acute besnoitiosis and tachyzoites were found in their tissues. Oocysts were also mildly pathogenic to outbred Swiss Webster mice (SW) (Mus musculus). The SW mice fed oocysts became ill but generally survived and developed characteristic thick-walled Besnoitia tissue cysts in their tongue and heart muscles and brains. Two laboratory-raised domestic cats (Felis catus) excreted B. darlingi oocysts after ingesting murine tissues infected with bobcat-derived oocysts. The parasite was successfully cultivated in African green monkey kidney fibroblast cells (CV-1 cell line) seeded with infected murine tissue homogenate. The multilocus PCR-DNA sequencing (18S rDNA, 28S rDNA, and ITS-1) from culture-derived tachyzoites confirmed the parasite as B. darlingi. Our results suggest that bobcats may be an important link in the sylvatic cycle of Besnoitia species and bioassay or molecular tests are needed to differentiate Toxoplasma gondii-like oocysts in feces of felids, both domestic and wild cats.
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http://dx.doi.org/10.1016/j.vetpar.2017.10.013DOI Listing
December 2017

Long-read sequencing improves assembly of Trichinella genomes 10-fold, revealing substantial synteny between lineages diverged over 7 million years.

Parasitology 2017 Sep 6;144(10):1302-1315. Epub 2017 Jun 6.

USDA,Agricultural Research Service,Animal Parasitic Diseases Laboratory,Beltsville Agricultural Research Center,10300 Baltimore Avenue,Beltsville,MD 20705,USA.

Genome assemblies can form the basis of comparative analyses fostering insight into the evolutionary genetics of a parasite's pathogenicity, host-pathogen interactions, environmental constraints and invasion biology; however, the length and complexity of many parasite genomes has hampered the development of well-resolved assemblies. In order to improve Trichinella genome assemblies, the genome of the sylvatic encapsulated species Trichinella murrelli was sequenced using third-generation, long-read technology and, using syntenic comparisons, scaffolded to a reference genome assembly of Trichinella spiralis, markedly improving both. A high-quality draft assembly for T. murrelli was achieved that totalled 63·2 Mbp, half of which was condensed into 26 contigs each longer than 571 000 bp. When compared with previous assemblies for parasites in the genus, ours required 10-fold fewer contigs, which were five times longer, on average. Better assembly across repetitive regions also enabled resolution of 8 Mbp of previously indeterminate sequence. Furthermore, syntenic comparisons identified widespread scaffold misassemblies in the T. spiralis reference genome. The two new assemblies, organized for the first time into three chromosomal scaffolds, will be valuable resources for future studies linking phenotypic traits within each species to their underlying genetic bases.
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http://dx.doi.org/10.1017/S0031182017000348DOI Listing
September 2017

Morphological and molecular characterization of Sarcocystis arctica-like sarcocysts from the Arctic fox (Vulpes lagopus) from Alaska, USA.

Parasitol Res 2017 Jul 15;116(7):1871-1878. Epub 2017 May 15.

Agricultural Research Service, Animal Parasitic Diseases Laboratory, United States Department of Agriculture, Beltsville Agricultural Research Center, Building 1001, Beltsville, MD, 20705-2350, USA.

The muscles of herbivores commonly harbor sarcocysts of parasites belonging to species in the genus Sarcocystis, but such muscle parasites are rare in carnivores. Here, we report Sarcocystis arctica-like sarcocysts in muscles of Arctic foxes (Vulpes lagopus) from Alaska, USA, for the first time. The tongues of 56 foxes were examined for Sarcocystis infection using several methods. Sarcocystis bradyzoites were detected in pepsin digests of 13 (23.2%), and sarcocysts were found in histological sections stained with hematoxylin and eosin (HE) of 9 (16.0%). By light microscopy, sarcocysts were up to 4 mm long and up to 245 μm wide. In HE-stained sections, the sarcocyst wall appeared smooth and up to 1.5 μm thick without visible protrusions. By transmission electron microscopy, the sarcocyst wall had a wavy parasitophorous vacuolar membrane (pvm) folded as pleomorphic villar protrusions (vp), sometimes with anastomoses of villar tips. The vp and the ground substance (gs) layer were smooth and without microtubules. The gs was up to 2.0 μm thick. The total width of the wall including vp and the gs was up to 4.0 μm. The vp were up to 3.0 μm long and most closely resembled "type 9c." All sarcocysts were mature and contained numerous 8.1 × 2.1 μm sized bradyzoites. Molecular characterization (at 18S rDNA, 28S rDNA, ITS-1, and cox1) showed the highest affinity for S. arctica of the Arctic fox (V. lagopus) from Norway. In the present investigation, we provide evidence that sarcocysts are common in tongues of Alaskan Arctic foxes suggesting that these carnivores are serving as intermediate hosts, and we also provide ultrastructure of S. arctica from the Arctic fox for the first time.
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http://dx.doi.org/10.1007/s00436-017-5462-6DOI Listing
July 2017

Ancient, globally distributed lineage of Sarcocystis from sporocysts of the Eastern rat snake (Pantherophis alleghaniensis) and its relation to neurological sequalae in intermediate hosts.

Parasitol Res 2016 Jul 30;115(7):2697-704. Epub 2016 Apr 30.

United States Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Animal Parasitic Diseases Laboratory, Building 1001, Beltsville, MD, 20705-2350, USA.

There is an emerging concern that snakes are definitive hosts of certain species of Sarcocystis that cause muscular sarcocystosis in human and non-human primates. Other species of Sarcocystis are known to cycle among snakes and rodents, but have been poorly characterized in the USA and elsewhere. Although neurological sequalae are known for certain species of Sarcocystis, no such neurological symptoms are known to typify parasites that naturally cycle in rodents. Here, sporocysts of a species of Sarcocystis were found in the intestinal contents of a rat snake (Pantherophis alleghaniensis) from Maryland, USA. The sporocysts were orally infective for interferon gamma gene knockout (KO) mice, but not to Swiss Webster outbred mice. The KO mice developed neurological signs, and were necropsied between 33 and 52 days post-inoculation. Only schizonts/merozoites were found, and they were confined to the brain. The predominant lesion was meningoencephalitis characterized by perivascular cuffs, granulomas, and necrosis of the neuropil. The schizonts and merozoites were located in neuropil, and apparently extravascular. Brain homogenates from infected KO mice were infective to KO mice and CV-1 cell line. DNA extracted from the infected mouse brain, and infected cell cultures revealed the highest identity with Sarcocystis species that employ snakes as definitive hosts. This is the first report of Sarcocystis infection in the endangered rat snake (P. alleghaniensis) and the first report of neurological sarcocystosis in mice induced by feeding sporocysts from a snake. These data underscore the likelihood that parasites in this genus that employ snakes as their definitive hosts constitute an ancient, globally distributed monophyletic group. These data also raise the possibility that neurological sequalae may be more common in intermediate hosts of Sarcocystis spp. than has previously been appreciated.
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http://dx.doi.org/10.1007/s00436-016-5086-2DOI Listing
July 2016

Coccidian parasites of fish encompass profound phylogenetic diversity and gave rise to each of the major parasitic groups in terrestrial vertebrates.

Infect Genet Evol 2016 06 19;40:219-227. Epub 2016 Feb 19.

Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Hungária krt. 21, H-1143 Budapest, Hungary.

Fish are the oldest and most diverse group of vertebrates; it therefore stands to reason that fish may have been the original hosts for many types of extant vertebrate parasites. Here, we sought to determine whether coccidian parasites of fish are especially diverse. We therefore sampled such parasites from thirty-nine species of fish and tested phylogenetic hypotheses concerning their relationships, using 18S rDNA. We found compelling phylogenetic support for distinctions among at least four lineages of piscine parasites presently ascribed to the genus Goussia. Some, but not all parasites attributed to Eimeria were confirmed as such. Major taxonomic revisions are likely justified for these parasites of fish, which appear to have given rise to each of the major lineages of coccidian parasites that subsequently proliferated in terrestrial vertebrates, including those such as Toxoplasma gondii that form tissue cysts in intermediate hosts.
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http://dx.doi.org/10.1016/j.meegid.2016.02.018DOI Listing
June 2016

Local admixture of amplified and diversified secreted pathogenesis determinants shapes mosaic Toxoplasma gondii genomes.

Nat Commun 2016 Jan 7;7:10147. Epub 2016 Jan 7.

Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.

Toxoplasma gondii is among the most prevalent parasites worldwide, infecting many wild and domestic animals and causing zoonotic infections in humans. T. gondii differs substantially in its broad distribution from closely related parasites that typically have narrow, specialized host ranges. To elucidate the genetic basis for these differences, we compared the genomes of 62 globally distributed T. gondii isolates to several closely related coccidian parasites. Our findings reveal that tandem amplification and diversification of secretory pathogenesis determinants is the primary feature that distinguishes the closely related genomes of these biologically diverse parasites. We further show that the unusual population structure of T. gondii is characterized by clade-specific inheritance of large conserved haploblocks that are significantly enriched in tandemly clustered secretory pathogenesis determinants. The shared inheritance of these conserved haploblocks, which show a different ancestry than the genome as a whole, may thus influence transmission, host range and pathogenicity.
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http://dx.doi.org/10.1038/ncomms10147DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4729833PMC
January 2016

Hybridization is limited between two lineages of freeze-resistant Trichinella during coinfection in a mouse model.

Infect Genet Evol 2016 Mar 23;38:146-151. Epub 2015 Dec 23.

Animal Parasitic Diseases Laboratory, USDA-Agricultural Research Service, BARC-East, Building 1180, Beltsville, MD 20705, USA. Electronic address:

Hybridization between two closely related but distinct genetic lineages may lead to homogenization of the two lineages with potentially novel phenotypes, or selective pressure to avoid hybridization if the two lineages are truly distinct. Trichinella nativa and Trichinella T6 are zoonotic nematode parasites which can be distinguished genetically despite occasional hybridization. Here, using an experimental murine model, we attempt to determine whether there are barriers to hybridization when sizeable numbers of each lineage are allowed to coinfect a host. Two mice were independently infected with equal numbers of T. nativa and T6. The offspring of these coinfections were genotyped at two microsatellite loci and one mitochondrial locus capable of distinguishing T. nativa from T6 genotypes. Among larvae in the F1 generation, offspring of every possible mating were encountered. Most larvae (63.6%) derived from T. nativa×T. nativa matings, while 21.1% of offspring were the product of T6×T6 matings, and only 15.3% were hybrid offspring of T. nativa×T6 crosses, differing markedly from null expectations. In this experimental model, T. nativa and Trichinella T6 were able to mate, but ratios of offspring indicated pre- or post-zygotic barriers to hybridization that may include assortative mating, genetic incompatibilities, and/or differences in the fitness of offspring. These barriers would limit gene flow between these two lineages in a natural setting, serving as a barrier to their homogenization and promoting their persistence as distinct and separate entities.
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http://dx.doi.org/10.1016/j.meegid.2015.12.016DOI Listing
March 2016

Sarcocystis cruzi infection in wood bison (Bison bison athabascae).

Vet Parasitol 2015 May 20;210(1-2):102-5. Epub 2015 Mar 20.

Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, United States Department of Agriculture, Beltsville 20705-2350, MD, USA. Electronic address:

Endangered wood bison (Bison bison athabascae) is the largest terrestrial mammal in the American continent. Animal health is an important issue in their conservation, and Sarcocystis cruzi may be a cause of clinical disease in Bovidae. Hearts of eight wood bison from Alaska, USA were examined for sarcocysts by histology, transmission electron microscopy, pepsin digestion, and molecularly. Sarcocystis bradyzoites were found in pepsin digests of all eight and sarcocysts were found in histologic sections of myocardium of four bison. Sarcocysts were thin-walled and ultrastructurally consistent with S. cruzi. Characterization of DNA obtained from lysis of pepsin liberated bradyzoites by PCR-RFLP and subsequent phylogenetic analyses matched with that previously reported for S. cruzi infecting cattle in the USA. Collectively, data indicate that wood bison is a natural intermediate host for S. cruzi.
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http://dx.doi.org/10.1016/j.vetpar.2015.03.007DOI Listing
May 2015

Reply to Italiano et al.

Clin Infect Dis 2015 Apr 23;60(7):1135-6. Epub 2014 Dec 23.

Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia Department of Medicine, Division of Infectious Diseases, Emory University, Atlanta, Georgia.

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http://dx.doi.org/10.1093/cid/ciu1165DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4620924PMC
April 2015

NextGen sequencing reveals short double crossovers contribute disproportionately to genetic diversity in Toxoplasma gondii.

BMC Genomics 2014 Dec 23;15:1168. Epub 2014 Dec 23.

Department of Molecular Microbiology, Washington University School of Medicine, Campus Box 8230, 660S, Euclid Ave,, St, Louis, Mo 63110, USA.

Background: Toxoplasma gondii is a widespread protozoan parasite of animals that causes zoonotic disease in humans. Three clonal variants predominate in North America and Europe, while South American strains are genetically diverse, and undergo more frequent recombination. All three northern clonal variants share a monomorphic version of chromosome Ia (ChrIa), which is also found in unrelated, but successful southern lineages. Although this pattern could reflect a selective advantage, it might also arise from non-Mendelian segregation during meiosis. To understand the inheritance of ChrIa, we performed a genetic cross between the northern clonal type 2 ME49 strain and a divergent southern type 10 strain called VAND, which harbors a divergent ChrIa.

Results: NextGen sequencing of haploid F1 progeny was used to generate a genetic map revealing a low level of conventional recombination, with an unexpectedly high frequency of short, double crossovers. Notably, both the monomorphic and divergent versions of ChrIa were isolated with equal frequency. As well, ChrIa showed no evidence of being a sex chromosome, of harboring an inversion, or distorting patterns of segregation. Although VAND was unable to self fertilize in the cat, it underwent successful out-crossing with ME49 and hybrid survival was strongly associated with inheritance of ChrIII from ME49 and ChrIb from VAND.

Conclusions: Our findings suggest that the successful spread of the monomorphic ChrIa in the wild has not been driven by meiotic drive or related processes, but rather is due to a fitness advantage. As well, the high frequency of short double crossovers is expected to greatly increase genetic diversity among progeny from genetic crosses, thereby providing an unexpected and likely important source of diversity.
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http://dx.doi.org/10.1186/1471-2164-15-1168DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4326188PMC
December 2014

Geographic separation of domestic and wild strains of Toxoplasma gondii in French Guiana correlates with a monomorphic version of chromosome1a.

PLoS Negl Trop Dis 2014 Sep 18;8(9):e3182. Epub 2014 Sep 18.

Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America.

Background: Previous studies have stressed the genetic divergence and high pathogenicity of strains of T. gondii from French Guiana. Although strains from coastal, human adapted environments (so called anthropized) resemble those found in other regions of the Caribbean, strains collected from inland jungle environment are genetically quite diverse. To better understand the composition of these distinct strain types, we undertook a more in depth analysis of T. gondii strains from French Guiana including profiling of chromosome 1a (Chr1a), which is often shared as a single monomorphic haplotype among lineages that are otherwise genetically distinct.

Methodology/principal Findings: Comparison of intron sequences from selectively neutral genes indicated that anthropized strains were most closely related to clonal type III strains from North America, although wider RFLP analysis revealed that they are natural hybrids. In contrast, strains isolated from the jungle were genetically very diverse. Remarkably, nearly all anthropized strains contained the monomorphic version of Chr1a while wild stains were extremely divergent. The presence of the monomorphic Chr1a strongly correlated with greater transmission in domestic cats, although there were several exceptions, indicating that other factors also contribute. Anthropized strains also varied in their virulence in laboratory mice, and this pattern could not be explained by the simple combination of previously identified virulence factors, indicating that other genetic determinants influence pathogenicity.

Conclusions/significance: Our studies underscore the marked genetic separation of anthropized and wild strains of T. gondii in French Guiana and provide additional evidence that the presence of Chr1a is associated with successful expansion of widely different lineages within diverse geographic areas. The predominance of Chr1a among strains in the anthropized environment suggests that it may confer an advantage for transmission in this environment, and thus potentially contribute to the spread of pathogenecity determinants.
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http://dx.doi.org/10.1371/journal.pntd.0003182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4169257PMC
September 2014

European mustelids occupying pristine wetlands in the Danube Delta are infected with Trichinella likely derived from domesticated swine.

J Wildl Dis 2014 Oct 14;50(4):972-5. Epub 2014 Aug 14.

1  Department of Parasitology and Parasitic Diseases, University of Agricultural Sciences and Veterinary Medicine, Calea Mănăştur 3-5, Cluj-Napoca 400372, Romania.

Abstract We analyzed 32 specimens from nine species of Mustelidae for Trichinella; six infections from two Trichinella species were observed from three host species. This provides documentation of Trichinella in Mustela erminea and Martes foina in Romania and Trichinella spiralis in a mustelid host from Europe. Trichinella spiralis continues to be a public challenge characterized by a wide host range and geographical distribution ( Pozio 2007 ). During the past 20 yr, Romania has had the most reported human cases of trichinellosis in the world ( Blaga et al. 2007 ). Transmission occurs among domesticated swine, rats, and wild mammals that feed by scavenging or predation ( Pozio 2000 ). Trichinella transmission to humans may occur by consumption of meat of livestock infected after exposure to wildlife ( Pozio et al. 2009 ).
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http://dx.doi.org/10.7589/2013-12-335DOI Listing
October 2014

Acute muscular sarcocystosis: an international investigation among ill travelers returning from Tioman Island, Malaysia, 2011-2012.

Clin Infect Dis 2014 Nov 4;59(10):1401-10. Epub 2014 Aug 4.

Background: Through 2 international traveler-focused surveillance networks (GeoSentinel and TropNet), we identified and investigated a large outbreak of acute muscular sarcocystosis (AMS), a rarely reported zoonosis caused by a protozoan parasite of the genus Sarcocystis, associated with travel to Tioman Island, Malaysia, during 2011-2012.

Methods: Clinicians reporting patients with suspected AMS to GeoSentinel submitted demographic, clinical, itinerary, and exposure data. We defined a probable case as travel to Tioman Island after 1 March 2011, eosinophilia (>5%), clinical or laboratory-supported myositis, and negative trichinellosis serology. Case confirmation required histologic observation of sarcocysts or isolation of Sarcocystis species DNA from muscle biopsy.

Results: Sixty-eight patients met the case definition (62 probable and 6 confirmed). All but 2 resided in Europe; all were tourists and traveled mostly during the summer months. The most frequent symptoms reported were myalgia (100%), fatigue (91%), fever (82%), headache (59%), and arthralgia (29%); onset clustered during 2 distinct periods: "early" during the second and "late" during the sixth week after departure from the island. Blood eosinophilia and elevated serum creatinine phosphokinase (CPK) levels were observed beginning during the fifth week after departure. Sarcocystis nesbitti DNA was recovered from 1 muscle biopsy.

Conclusions: Clinicians evaluating travelers returning ill from Malaysia with myalgia, with or without fever, should consider AMS, noting the apparent biphasic aspect of the disease, the later onset of elevated CPK and eosinophilia, and the possibility for relapses. The exact source of infection among travelers to Tioman Island remains unclear but needs to be determined to prevent future illnesses.
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http://dx.doi.org/10.1093/cid/ciu622DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4624310PMC
November 2014

Traditional goat husbandry may substantially contribute to human toxoplasmosis exposure.

J Parasitol 2015 Feb 8;101(1):45-9. Epub 2014 Jul 8.

University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, Parasitology and Parasitic Diseases Department, 3-5 Mănăştur Street, cod 400372, Cluj-Napoca, Romania.

Raising goats in settings that are highly contaminated with oocysts of Toxoplasma gondii may contribute significantly to human exposure to this zoonotic parasite. Increasing consumption of young goats in countries where goats are frequently reared in backyards that are also homes to cats (the definitive host of this parasite) elevates such concern. To date, there has been little attention to either the prevalence or genotypic characteristics of T. gondii isolates in young ruminant food animals in Europe. Here, we estimated the prevalence of T. gondii goat-kids raised in backyards and slaughtered for human consumption during Easter. We collected 181 paired samples of serum and diaphragm. Serum samples were analyzed by enzyme-linked immunosorbent assay for antibodies against T. gondii , and muscle tissues were analyzed by polymerase chain reaction to detect T. gondii DNA. Thirty-two diaphragm samples were also bioassayed in mice, and the isolates were genotyped using microsatellite markers. The overall seroprevalence of T. gondii infection in goat-kids was 33.1% (60/181; 95% confidence interval [CI] 26.3-40.5%), and T. gondii DNA was found in 6.1% (11/181; 95% CI 3.1-10.6) of the diaphragm samples. We isolated the parasite from 2 of 32 goat-kids, and the T. gondii strains belonged to genotype II. The results showed that 1/3 of 3-mo-old goats may be infected with T. gondii, and their consumption during Easter (as barbecue) may seriously compromise food safety as a result.
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http://dx.doi.org/10.1645/13-483.1DOI Listing
February 2015

Hybridization between previously isolated ancestors may explain the persistence of exactly two ancient lineages in the genome of the oyster parasite Perkinsus marinus.

Infect Genet Evol 2014 Jun 28;24:167-76. Epub 2014 Mar 28.

University of Maryland, Department of Biology, 1210 Biology-Psychology Bldg, College Park, MD 20742, USA.

Theory predicts that neutral genetic variation accumulates within populations to a level determined by gains through mutation and losses by genetic drift. This balance results in a characteristic distribution of allelic variation with the maximum allelic difference determined by effective population size. Here, we report a striking departure from these expectations in the form of allelic dimorphism, observed at the majority of seven loci examined in Perkinsus marinus, an important oyster parasite that causes Dermo disease. DNA sequences were collected from five loci flanking microsatellite repeats and two loci coding for superoxide dismutase enzymes that may mediate the parasite's interaction with its host. Based on 474 sequences, sampled across 5000 km of the eastern United States coastline, no more than two alleles were observed at each locus (discounting singletons). Depending on the locus, the common allele ranged in overall frequency from 72% to 92%. At each locus the two alleles differed substantially (3.8% sequence difference, on average), and the among-locus variance in divergences was not sufficient to reject a simultaneous origin for all dimorphisms using approximate Bayesian methods. Dimorphic alleles were estimated to have diverged from a common ancestral allele at least 0.9 million years ago. Across these seven loci, only five other alleles were ever observed, always as singletons and differing from the dimorphic alleles by no more than two nucleotides. Free recombination could potentially have shuffled these dimorphisms into as many as 243 multilocus combinations, but the existence of only ten combinations among all samples strongly supports low recombination frequencies and is consistent with the observed absence of intragenic recombination. We consider several demographic and evolutionary hypotheses to explain these patterns. Few can be conclusively rejected with the present data, but we advance a recent hybridization of ancient divergent lineages scenario as the most parsimonious.
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http://dx.doi.org/10.1016/j.meegid.2014.03.003DOI Listing
June 2014
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