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A previous population genetics study of Opisthorchis viverrini from a locality in an endemic area in Thailand found little genetic variation over time and second intermediate fish host species. Since a similar comparative analysis is not available for Lao PDR, we conducted a study of O. viverrini from different endemic foci in Vientiane Province, Lao PDR, based on spatial, temporal and fish host species. A total of 620 adult O. viverrini originating from the Nam Ngum River wetland were analysed at five previously defined polymorphic enzyme loci. Of these worms, 252 were from six different localities (spatial samples), 162 worms from different years (temporal samples) and 206 worms from four different cyprinid fish species. Significant heterozygote deficiency was found in most O. viverrini populations with levels of genetic differentiation ranging between F ST 0.0000 and 0.0197 suggesting that gene flow occurred at a variable rate. The role of temporal factors and fish host species had little influence on the level of genetic differentiation. As for O. viverrini from Thailand, these findings indicate that self-fertilization and/or a clonal distribution of O. viverrini occurs in Lao PDR. Unlike the results for O. viverrini from Thailand, spatial population substructuring may be the underlying population processes for O. viverrini in Lao PDR. These findings indicate that geographical variation may contribute to the transmission dynamics of the parasite with implications for parasite control. However, other host factors, such as snail intermediate hosts and mammal reservoir hosts, as well as human beings, may also play significant roles.

Species and subspecies of the Oncomelania hupensis species complex are recognized as intermediate hosts of Schistosoma japonicum. Of these species and subspecies, O. quadrasi is distributed throughout the Philippines. This study used 12S ribosomal RNA sequences to explore the genetic structure of O. quadrasi populations in the Philippines. Three subspecies, O. h. hupensis, O. h. formosana, and O. h. chiui of this group were also examined. The phylogenetic tree and haplotypes network showed that O. quadrasi separated from the subspecies. Ten O. quadrasi haplotypes (Oq1-Oq10) clustered in relation to their geographic origin. Genetic differentiation (FST) and estimated gene flow (Nm) among populations showed significant differences, ranging from 0.556-1.000 to 0.00-0.74, respectively. Genetic differences among groups (FCT = 0.466), populations within a group (FSC = 0.727), and populations (FST = 0.854) were observed. These results indicate that the O. quadrasi populations in the Philippines have a substructure associated with their geographic origin., (© The American Society of Tropical Medicine and Hygiene.)

Zoonotic diseases are major causes of infection related morbidity and mortality worldwide. Of the various arthropods capable of transmitting pathogens that cause such diseases to humans, ticks, which are vectors of more kinds of pathogens than any other group of invertebrate, have become an increasing focus of attention. This is particularly the case in the temperate northern hemisphere where they are a significant vector of human disease. Here, we provide an overview of the complex ecological systems defining the various epidemiological cycles of tick-borne diseases. We highlight the abiotic and biotic factors influencing the establishment and persistence of tick populations and their associated pathogens. Furthermore, we emphasize the dynamic nature of such systems, especially when they are under the influence of both small and large-scale anthropogenic changes to the environment. Although a great deal of work has been done on ticks and the diseases which they transmit, the very dynamism of the system means that new factors are continually arising which shift the epidemiological pattern within specific areas. We therefore consider that more detailed, long-term (i.e. at least 10 years), multidisciplinary studies need to be carried out to define why and how these pattern shifts take place and to determine their public health significance., (Copyright © 2013 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

Clonorchis sinensis, Opisthorchis felineus and Opisthorchis viverrini are the three most important liver flukes involved in human health, infecting more than 45 million people worldwide. Both C. sinensis and O. viverrini, and possibly O. felineus, can induce human cholangiocarcinoma as well as inducing other hepatobiliary pathology. Although the life cycles of all three species are similar, only that of O. felineus in Europe remains predominantly zoonotic, while O. felineus in Asia and C. sinensis have a stronger mixture of zoonotic and anthroponotic components in their life cycles. Opisthorchis viverrini from the Mekong area of southeastern Asia is predominantly anthroponotic. Here we discuss the comparative epidemiology of these three taxa comparing in detail the use of first, second and final animal hosts, and consider the potential role of humans in spreading these pathogens. In addition we discuss the genetic structure of all three species in relation to potentially cryptic species complexes., (Copyright © 2013 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

Patterns of host-parasite association are poorly understood in tropical forests. While we typically observe only snapshots of the diverse assemblages and interactions under variable conditions, there is a desire to make inferences about prevalence and host-specificity patterns. We studied the interaction of ticks with non-volant small mammals in forests of Borneo. We inferred the probability of species interactions from individual-level data in a multi-level Bayesian model that incorporated environmental covariates and advanced estimates for rarely observed species through model averaging. We estimated the likelihood of observing particular interaction frequencies under field conditions and a scenario of exhaustive sampling and examined the consequences for inferring host specificity. We recorded a total of 13 different tick species belonging to the five genera Amblyomma, Dermacentor, Haemaphysalis, Ixodes, and Rhipicephalus from a total of 37 different host species (Rodentia, Scandentia, Carnivora, Soricidae) on 237 out of 1,444 host individuals. Infestation probabilities revealed most variation across host species but less variation across tick species with three common rat and two tree shrew species being most heavily infested. Host species identity explained ca. 75 % of the variation in infestation probability and another 8-10 % was explained by local host abundance. Host traits and site-specific attributes had little explanatory power. Host specificity was estimated to be similarly low for all tick species, which were all likely to infest 34-37 host species if exhaustively sampled. By taking into consideration the hierarchical organization of individual interactions that may take place under variable conditions and that shape host-parasite networks, we can discern uncertainty and sampling bias from true interaction frequencies, whereas network attributes derived from observed values may lead to highly misleading results. Multi-level approaches may help to move this field towards inferential approaches for understanding mechanisms that shape the strength and dynamics in ecological networks.

Human–wildlife interactions have reached unprecedented levels, and humans are influencing the earth’s ecosystems more rapidly and extensively than ever before. This situation is cause for serious concern, especially since disease interactions between wildlife and humans have been recognized as major conservation threats. In this study, long-tailed macaques, Macaca fascicularis, from 2 forest parks located in north-eastern Thailand were investigated to determine the influence of habitat modification by humans on helminth parasite associations in non-human primates. Macaque populations with contact to anthropogenically modified environments were compared with sylvatic groups in nearby natural environments. In order to test for human–non-human primate transmission of parasites, the local human populations were also examined. Humans were infected with a number of potentially pathogenic parasites, including Opisthorchis viverrini and Strongyloides stercoralis. However, eggs of these helminths were not detected in macaque feces. Thus, no direct parasite transfer from humans to non-human primates could be confirmed. However, macaque groups with more frequent contact with human modified habitats, and a higher portion of human-provided food in their diet, had significantly higher prevalences and intensities of Strongyloides fuelleborni and of an intestinal fluke (probably Haplorchis sp.) than sylvatic groups. Positive correlations were found between the time foraging on the ground and infection with S. fuelleborni, and the amount of human-provided food and intestinal fluke infection. Human alteration of habitat and associated modifications in nonhuman primate behaviour are likely to play a role in determining the occurrence, prevalence and intensity of zoonotic helminth infection of wild non-human primates.

Bithynia snails are important hosts of the human liver fluke, Opisthorchis viverrini. Allozyme markers were used to examine genetic variation and the systematics of Bithynia snails from different geographical localities in Thailand and Lao PDR. Our results show that Bithynia siamensis goniomphalos contains two major evolutionary clades with at least nine morphologically similar but genetically distinct "cryptic" species (taxa). Clade A consists of snails from the Chi and the Mun River wetlands, Thailand and clade B consists of snails from the Nam Ngum River wetland, Lao PDR, as well as snails from some localities in the Songkram River wetland, Thailand. There is an association between O. viverrini cryptic taxa with B. s. goniomphalos cryptic taxa within the defined wetlands. Bithynia species are the critical amplifying component of O. viverrini and they control transmission from humans to fish second intermediate hosts. These findings are particularly important for understanding the transmission dynamics of O. viverrini. They are, in addition, a link in the life cycle of O. viverrini which can be used for developing and implementing programs to eliminate and control opisthorchiasis and its associated cholangiocarcinoma., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Genetic differentiation between two synonymous echinostomes species, Artyfechinostomum malayanum and Artyfechinostomum sufrartyfex was determined by using the first and second internal transcribed spacers (ITS1 and ITS2), the non-coding region of rDNA as genetic makers. Of the 699 bp of combined ITS1 and ITS2 sequences examined, 18 variable nucleotide positions (2.58 %) were observed. Of these, 17 positions could be used as diagnostic position between these two sibling species, whereas the other one variation was intraspecific variation of A. malayanum. A clade of A. malayanum was closely aligned with A. sufrartyfex and clearly distance from the cluster of other echinostomes. Our results may sufficiently suggest that the current synonymy of these species is not valid.

Throughout Southeast Asia and China, eating raw and or partially cooked cyprinid fish causes liver (hepatobiliary) disease and cancer (cholangiocarcinoma) due to fishborne zoonotic trematodes (FZT), in particular Clonorchis sinensis and Opisthorchis viverrini. The primary source of transmission is by native fish, but aquaculture fish are also reported to have high infective potential. Here, a cross-sectional survey of FZT in fish farms was conducted in an endemic area in Khon Kaen Province, Thailand. By using conventional and polymerase chain reaction (PCR) methods, we detected O. viverrini and FZT metacercariae (Centrocestus formosanus and Haplorchis taichui) in two popular fish species, Barbonymus gonionotus (silver barb) and Cirrhinus mrigala (mrigal), from aquaculture farms. Both species were infected in five of six farms examined by PCR but not by conventional methods, yet the prevalence of FZT metacercariae in aquaculture fish was high (46.9%). In addition to O. viverrini (17.1%), the native fish Cyclocheilichthys armatus and Hampala dispar had a prevalence of FZT of 81.4%, which included 5.7% for C. formosanus and 17.1% for H. taichui by conventional method. To our knowledge, this is the first discovery of O. viverrini in aquaculture fish in Thailand. More comprehensive studies are required to determine if human-induced disease transmission coupled with natural transmission cycle occurs throughout the aquaculture industry in the region. This has significant impact on food quality and safety, and provides the basis for the development of an effective strategy for the prevention and control of foodborne diseases.

Domestic dogs, Canis lupus, have been one of the longest companions of humans and have introduced their own menagerie of parasites and pathogens into this relationship. Here, we investigate the parasitic load of 212 domestic dogs with fleas (Siphonaptera) chewing lice (Phthiraptera), and ticks (Acarina) along a gradient from rural areas with near-natural forest cover to suburban areas in Northern Borneo (Sabah, Malaysia). We used a spatially-explicit hierarchical Bayesian model that allowed us to impute missing data and to consider spatial structure in modelling dog infestation probability and parasite density. We collected a total of 1,968 fleas of two species, Ctenocephalides orientis and Ctenocephalides felis felis, from 195 dogs (prevalence, 92 %). Flea density was higher on dogs residing in houses made of bamboo or corrugated metal (increase of 40 % from the average) compared to timber or stone/compound houses. Host-dependent and landscape-level environmental variables and spatial structure only had a weak explanatory power. We found adults of the invasive chewing louse Heterodoxus spiniger on 42 dogs (20 %). The effect of housing conditions was opposite to those for fleas; lice were only found on dogs residing in stone or timber houses. We found ticks of the species Rhipicephalus sanguineus as well as Haemaphysalis bispinosa gp., Haemaphysalis cornigera, Haemaphysalis koenigsbergi, and Haemaphysalis semermis on 36 dogs (17 %). The most common tick species was R. sanguineus, recorded from 23 dogs. Tick infestations were highest on dogs using both plantation and forest areas (282 % increase in overall tick density of dogs using all habitat types). The infestation probability of dogs with lice and ticks decreased with elevation, most infestations occurred below 800 m above sea level. However, the density of lice and ticks revealed no spatial structure; infestation probability of dogs with these two groups revealed considerable autocorrelation. Our study shows that environmental conditions on the house level appeared to be more influential on flea and lice density whereas tick density was also influenced by habitat use. Infestation of dogs with Haemaphysalis ticks identified an important link between dogs and forest wildlife for potential pathogen transmission.

Together with host and environmental factors, the systematics and population genetic variation of Opisthorchis viverrini may contribute to recorded local and regional differences in epidemiology and host morbidity in opisthorchiasis and cholangiocarcinoma (CCA). In this review, we address recent findings that O. viverrini comprises a species complex with varying degrees of population genetic variation which are associated with specific river wetland systems within Thailand as well as the Lao PDR. Having an accurate understanding of systematics is a prerequisite for a meaningful assessment of the population structure of each species within the O. viverrini complex in nature, as well as a better understanding of the magnitude of genetic variation that occurs within different species of hosts in its life cycle. Whether specific genotypes are related to habitat type(s) and/or specific intermediate host species are discussed based on current available data. Most importantly, we focus on whether there is a correlation between incidence of CCA and genotype(s) of O. viverrini. This will provide a solid basis for further comprehensive investigations of the role of genetic variation within each species of O. viverrini sensu lato in human epidemiology and genotype related morbidity as well as co-evolution of parasites with primary and secondary intermediate species of host., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Opisthorchis viverrini is one of the most common and medically important food-borne parasites in the Lower Mekong area of Southeast Asia. As we learn more about its ecology, pathology and epidemiology we see the need to consider more deeply the socio-cultural dynamics with which food-borne species complexes are associated. This paper argues that the Mekong region is characterized by strong livelihoods and life-style associations within wetland ecosystems, which are inseparable from human eating habits ("raw attitudes"). Within the fish-rice economies of the region there are many long-cherished food cultures based on eating raw, semi-cooked and fermented fish dishes, which are known to lead to opisthorchiasis, and potentially cholangiocarcinoma. This paper examines evidence from northeast Thailand showing that dedicated health outreach campaigns do help to reduce prevalence of opisthorchiasis over time. For disease prevention and health education approaches to be most effective, they must be sensitive to culture, livelihood economics, gender, and age. Further integrative, inter-disciplinary and international research must incorporate the complex dynamics of parasite ecology, human behavior, socio-economics, and public health awareness., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

The carcinogenic liver fluke, Opisthorchis viverrini, requires Bithynia snail intermediate hosts in its life cycle. However, the prevalence of O. viverrini in snail intermediate hosts is typically low (< 1%). Here, we examined B. siamensis goniomphalos from 48 localities in Thailand and The Lao People's Democratic Republic (Lao PDR) and reported high-prevalence levels of O. viverrini. The highest-prevalence levels per locality were 6.93% (mean = 3.04%) in Thailand and 8.37% (mean = 2.01%) in Lao PDR; 4 of 13 localities examined showed prevalence higher than any prevalence previously recorded. The number of cercariae infecting snails and their prevalence were positively correlated with the size of the snails. High prevalence occurred in the Songkram River wetland (Thailand) and the Nam Ngum River wetland (Lao PDR). Our results show that transmission of O. viverrini from humans as well as animal reservoir hosts to snail intermediate hosts is ongoing and potentially increasing in endemic areas across Thailand and Lao PDR.

Khon Kaen Province in northeast Thailand is known as a hot spot for opisthorchiasis in Southeast Asia. Preliminary allozyme and mitochondrial DNA haplotype data from within one endemic district in this Province (Ban Phai), indicated substantial genetic variability within Opisthorchis viverrini. Here, we used microsatellite DNA analyses to examine the genetic diversity and population structure of O. viverrini from four geographically close localities in Khon Kaen Province. Genotyping based on 12 microsatellite loci yielded a mean number of alleles per locus that ranged from 2.83 to 3.7 with an expected heterozygosity in Hardy-Weinberg equilibrium of 0.44-0.56. Assessment of population structure by pairwise F(ST) analysis showed inter-population differentiation (P<0.05) which indicates population substructuring between these localities. Unique alleles were found in three of four localities with the highest number observed per locality being three. Our results highlight the existence of genetic diversity and population substructuring in O. viverrini over a small spatial scale which is similar to that found at a larger scale. This provides the basis for the investigation of the role of parasite genetic diversity and differentiation in transmission dynamics and control of O. viverrini.

We echo the viewpoints presented in the recent editorials and forums in ecohealth in 2009 and 2010 that understanding the links between water and health using biogeography can provide insights into the patterns of and the processes that give rise to the distribution of disease prevalence. In particular, we underscore the need to integrate disease ecology and biogeography using landscape ecological approaches. We use opisthorchiasis, a major public health problem in Southeast Asia, to illustrate our opinions.

Snails are the critical amplifying hosts of the liver fluke Opisthorchis viverrini, the causative agent of hepatobiliary disease and cholangiocarcinoma in the Mekong area of Southeast Asia. Bithynia funiculata, B. siamensis goniomphalos and B. s. siamensis are the first intermediate hosts of O. viverrini in Thailand. Morphological similarity between Bithynia species and subspecies creates problems for their taxonomic identification and an understanding of Bithynia systematics. In this study, multilocus enzyme electrophoresis (MEE) was applied to define genetic markers that could prove useful for investigating the systematics and population genetics of this genus in Thailand. Of the 34 enzymes examined, 20 encoding a presumptive 24 loci showed sufficient staining intensity and resolution for genetic interpretation. Of these, three loci were monomorphic and eight loci were diagnostic among the three Bithynia taxa. The remaining 13 loci were diagnostic between combinations of the three taxa. Fixed genetic differences were detected at 67-73% of loci among these taxa which in turn differed from a closely related species, Hydrobioides nassa, at 88% of loci. Seventy three percent fixed genetic differences were detected between B. funiculata and the two sub-species B. s. siamensis and B. s goniomphalos. Our data reveals similarly large genetic divergence, 67% fixed genetic differences, between B. s. siamensis and B. s. goniomphalos, which may well represent different species rather than subspecies as currently defined. The genetic markers detected will form the basis for subsequent comprehensive studies on the systematics and population genetics of Bithynia snails as well as for their role in the transmission of O. viverrini and opisthorchiasis., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A total of 314 individual Echinostoma revolutum were collected at different locations and times from domestic ducks from Khon Kaen Province, Thailand and Vientiane Province, the Lao People's Democratic Republic (PDR). Genetic variation of these parasites was analyzed using multilocus enzyme electrophoresis at three polymorphic loci namely, glucose-6-phosphate dehydrogenase (G6pd), malic enzyme (Me) and peptidase valine-leucine (PepA). High levels of genetic variability were found within and between populations. Significant heterozygote deficiencies compared with the predictions under Hardy-Weinberg equilibrium were detected in populations from Thailand and the Lao PDR for all loci except G6pd-1. Significant genetic differentiation was observed between spatially separated populations from Thailand and the Lao PDR. This as also true for some samples collected at different times in Thailand. The variability found may be consistent with a Wahlund effect, genetic drift and/or other factors such as the population structure of snail hosts. Our data provide further insight into the process of genetic divergence within and among geographically and temporally isolated populations of E. revolutum, and potentially other medically important echinostomes in Southeast Asia., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Multilocus enzyme electrophoresis (MEE) and DNA sequencing of the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene were used to genetically compare four species of echinostomes of human health importance. Fixed genetic differences among adults of Echinostoma revolutum, Echinostoma malayanum, Echinoparyphium recurvatum and Hypoderaeum conoideum were detected at 51-75% of the enzyme loci examined, while interspecific differences in CO1 sequence were detected at 16-32 (8-16%) of the 205 alignment positions. The results of the MEE analyses also revealed fixed genetic differences between E. revolutum from Thailand and Lao PDR at five (19%) of 27 loci, which could either represent genetic variation between geographically separated populations of a single species, or the existence of a cryptic (i.e. genetically distinct but morphologically similar) species. However, there was no support for the existence of cryptic species within E. revolutum based on the CO1 sequence between the two geographical areas sampled. Genetic variation in CO1 sequence was also detected among E. malayanum from three different species of snail intermediate host. Separate phylogenetic analyses of the MEE and DNA sequence data revealed that the two species of Echinostoma (E. revolutum and E. malayanum) did not form a monophyletic clade. These results, together with the large number of morphologically similar species with inadequate descriptions, poor specific diagnoses and extensive synonymy, suggest that the morphological characters used for species taxonomy of echinostomes in South-East Asia should be reconsidered according to the concordance of biology, morphology and molecular classification., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Echinostomatidae are common, widely distributed intestinal parasites causing significant disease in both animals and humans worldwide. In spite of their importance, the taxonomy of these echinostomes is still controversial. The taxonomic status of two species, Echinostoma revolutum and Echinoparyphium recurvatum, which commonly infect poultry and other birds, as well as human, is problematical. Previous phylogenetic analyses of Southeast Asian strains indicate that these species cluster as sister taxa. In the present study, the first internal transcribed spacer (ITS1) sequence was used for genetic characterization and to examine the phylogenetic relationships between an isolate from Thailand with other isolates available from GenBank database. Interspecies differences in ITS1 sequence between E. revolutum and E. recurvatum were detected at 6 (3%) of the 203 alignment positions. Of these, nucleotide deletion at positions 25, 26, and 27, pyrimidine transition at 50, 189, and pyrimidine transversion at 118 were observed. Phylogenetic analysis revealed that E. recurvatum from Thailand clustered as a sister taxa with E. revolutum and not with other members of the genus Echinoparyphium. Interestingly, this result confirms a previous report based on allozyme electrophoresis and mitochondrial DNA that E. revolutum and E. recurvatum in Southeast Asia are sister species. Hence, the taxonomic status of E. recurvatum in Thailand, as well as in Southeast Asian countries needs to be confirmed and revised using more comprehensive analyses based on morphology and other molecular techniques.

Recent systematic studies of Opisthorchis viverrini based on multilocus enzyme electrophoresis (MEE) have shown that there are at least five genetic groups and possibly two cryptic species occurring in Thailand and Lao PDR each associated with a specific wetland system. A study based on mitochondrial DNA (mtDNA) gene analyses of an O. viverrini population from Savannakhet (SV, Lao PDR) clustered with several isolates from Thailand and Lao PDR although they originated from different river wetland systems. We used MEE to re-examine whether O. viverrini from SV was similar genetically to isolates from Thailand and Lao PDR. The allelic profiles of O. viverrini from SV and five different wetlands representing defined genetic groups of O. viverrini were recorded at 24 enzyme loci as opposed to only two loci of mtDNA. Contrary to previous studies, O. viverrini from SV was found to have fixed genetic differences at six to eight of the 24 loci examined (24.50-35.42%). Allelic data indicated that O. viverrini from SV differed from isolates in the Nam Ngum River wetland in Lao PDR (29.33% fixed genetic differences) and clustered with O. viverrini from Nakhon Phanom and Sakon Nakhon within the Songkram River wetland in Thailand but had fixed genetic differences from these at 24.5% of loci examined. Our data confirm the association between genetic groups of O. viverrini and specific wetland systems, and raise important questions regarding the significance of the genetic differences and relationships of O. viverrini from these wetlands.

An important question in many parasitological studies is the assessment of differences in parasite numbers between samples of hosts. This is not always an easy problem with which to deal. While almost everyone will agree that the main task consists in deciding whether the values in one sample tend to be higher than the values of another sample, there is considerable disagreement about what higher (or lower) should mean. In most cases, dissimilarity measures are differences between mean values, medians, geometric means, prevalence rates, relative effects, and more. In general, different measures can lead to different conclusions. However, a debate as to which measure is superior is fruitless; it depends on goals and circumstances of the respective study. In our opinion, it is more important to identify situations in which most of the above measures coincide, and, hence, one can confidently claim that the values in one sample are higher than in another. This is the case when one sample is stochastically larger than a second. Roughly speaking, a random variable X is stochastically larger than a second random variable Y, when X assumes large values with a higher probability than Y. In this paper, we review this concept using distributional and data examples, and we propose the use of graphical tools for detecting stochastic dominance. Our method provides a relatively easy, visual way of fully justifying general statements that the number of parasites in one sample is larger than in another.

Although there is a growing recognition that the transfer of diseases between humans and non-human primates can be of great significance for conservation biology, there have been only a few studies focusing on parasites. In this study, saddleback (Saguinus fuscicollis) and moustached tamarin (Saguinus mystax) from the rainforest of the Peruvian lowlands were used as models to determine helminth parasite associations between canopy-dwelling primate species and a nearby human settlement. The human population showed high prevalences of infestation with a number of nematodes, including Ascaris lumbricoides (88.9%), Trichuris trichiura (37%) and hookworms (55.6%). However, the ova of these geohelminths were not detectable in tamarin faeces. Thus, no direct parasite transfer from humans to non-human primates could be documented. However, tamarin groups with more frequent contact to humans and their facilities had significantly higher prevalences and egg output of Prosthenorchis elegans, an important primate pathogen, than a forest group. In contrast, a cestode was significantly more common with more egg output in sylvatic than in human-associated groups. Human alteration of the habitat is likely to play a major role in determining the occurrence, prevalence and intensity of helminth infestation of wild non-human primates.

The palaeacanthocephalan Plagiorhynchus cylindraceus is a common intestinal parasite of passerine birds, which can also occur parenterally or in the intestinal tract of mammals, often as an invading species in many countries worldwide. In this survey, introduced hedgehogs (Erinaceus europaeus, n = 183) killed in New Zealand during a biocontrol campaign and conspecifics (n = 174) that had died in hedgehog rehabilitation centers in Germany and Britain were examined for this parasite. In New Zealand, P. cylindraceus is recorded for the first time here, in the vicinity of Auckland. In Europe, prevalences ranged from 4.2% up to 47.6%, while in New Zealand, only 1.6% (Auckland 7.9%). Most of the worms occurred inside the peritoneal cavity where they had partly degenerated. Since hedgehogs are seldom preyed upon in continental Europe but often become traffic victims, we hypothesize that the worms inside them, whether extra- or intraperitoneally, contribute to the abundance and persistence of the parasite by being ingested by scavenging birds. Accordingly, we consider P. cylindraceus as a "modern parasite" taking advantage of two aspects of global change: anthropogenic promoted transmission (road kills) and the transcontinental spread of infected intermediate and/or final hosts caused by humans.

Previous molecular genetic analyses indicate that Opisthorchis viverrini is a complex of at least 2 cryptic species in Thailand and the Lao People's Democratic Republic (PDR). Opisthorchis viverrini sensu lato (s.l.) populations can be divided into 6 genetic groups, which correlate with 5 different river wetlands systems. The present study examines the infectivity, growth, fecundity, and body size of O. viverrini s.l. isolates from these systems. Worm recovery was lowest in the Songkhram River, which differed significantly from all other wetland systems. In addition, the Chi River and Nam Ngum River populations also differed significantly. A similar pattern was found for fecundity. These results support the genetic/molecular data indicating a subdivision of O. viverrini populations on the basis of watershed and that propose the existence of cryptic species in Thailand and the Lao PDR.

There are numerous discrepancies in recent published lists of the ticks of the world. Here we review the controversial names, presenting evidence for or against their validity and excluding some altogether. We also address spelling errors and present a list of 17 species described or resurrected during the years 2003-2008. We consider the following 35 tick species names to be invalid: Argas fischeri Audouin, 1826, Ornithodoros boliviensis Kohls and Clifford, 1964, Ornithodoros steini (Schulze, 1935), Amblyomma acutangulatum Neumann, 1899, Amblyomma arianae Keirans and Garris, 1986, Amblyomma bibroni (Gervais, 1842), Amblyomma colasbelcouri (Santos Dias, 1958), Amblyomma concolor Neumann, 1899, Amblyomma cooperi Nuttall and Warburton, 1908, Amblyomma curruca Schulze, 1936, Amblyomma cyprium Neumann, 1899, Amblyomma decorosum (Koch, 1867), Amblyomma nocens Robinson, 1912, Amblyomma perpunctatum (Packard, 1869), Amblyomma striatum Koch, 1844, Amblyomma superbum Santos Dias, 1953, Amblyomma testudinis (Conil, 1877), Amblyomma trinitatis Turk, 1948, Dermacentor confractus (Schulze 1933), Dermacentor daghestanicus Olenev, 1928, Haemaphysalis himalaya Hoogstraal, 1966, Haemaphysalis vietnamensis Hoogstraal and Wilson, 1966, Hyalomma detritum Schulze, 1919, Ixodes apteridis Maskell, 1897, Ixodes donarthuri Santos Dias, 1980, Ixodes kempi Nuttall, 1913, Ixodes neotomae Cooley, 1944, Ixodes rangtangensis Teng, 1973, Ixodes robertsi Camicas, Hervy, Adam and Morel, 1998, Ixodes serrafreirei Amorim, Gazetta, Bossi and Linhares, 2003, Ixodes tertiarius Scudder, 1885, Ixodes uruguayensis Kohls and Clifford, 1967, Ixodes zealandicus Dumbleton, 1961, Ixodes zumpti Arthur, 1960 and Rhipicephalus camelopardalis Walker and Wiley, 1959. We consider the following 40 names valid: Argas delicatus Neumann, 1910, Argas vulgaris Filippova, 1961, Ornithodoros aragaoi Fonseca, 1960, Ornithodoros dugesi Mazzoti, 1943, Ornithodoros knoxjonesi Jones and Clifford, 1972, Ornithodoros marocanus Velu, 1919, Ornithodoros nattereri Warburton, 1927, Amblyomma beaurepairei Vogelsang and Santos Dias, 1953, Amblyomma crassipes (Neumann, 1901), Amblyomma echidnae Roberts, 1953, Amblyomma fuscum Neumann, 1907, Amblyomma orlovi (Kolonin, 1995), Amblyomma parkeri Fonseca and Aragão, 1952, Amblyomma pseudoconcolor Aragão, 1908, Bothriocroton oudemansi (Neumann, 1910), Bothriocroton tachyglossi (Roberts, 1953), Dermacentor abaensis Teng, 1963, Dermacentor confragus (Schulze 1933), Dermacentor ushakovae Filippova and Panova, 1987, Haemaphysalis anomaloceraea Teng, 1984, Haemaphysalis filippovae Bolotin, 1979, Haemaphysalis pavlovskyi Pospelova-Shtrom, 1935, Hyalomma excavatum Koch, 1844, Hyalomma isaaci Sharif, 1928, Hyalomma rufipes Koch, 1844, Hyalomma turanicum Pomerantzev, 1946, Ixodes arabukiensis Arthur, 1959, Ixodes boliviensis Neumann, 1904, Ixodes columnae Takada and Fujita, 1992, Ixodes maslovi Emel'yanova and Kozlovskaya, 1967, Ixodes sachalinensis Filippova, 1971, Ixodes siamensis Kitaoka and Suzuki, 1983, Ixodes sigelos Keirans, Clifford and Corwin, 1976, Ixodes succineus Weidner, 1964, Rhipicephalus aurantiacus Neumann, 1907, Rhipicephalus cliffordi Morel, 1965, Rhipicephalus pilans Schulze, 1935, Rhipicephalus pseudolongus Santos Dias, 1953, Rhipicephalus serranoi Santos Dias, 1950 and Rhipicephalus tetracornus Kitaoka and Suzuki, 1983.

The population genetics of 317 individual Opisthorchis viverrini from Khon Kaen Province Thailand, from 4 different years and 4 cyprinid fish species was examined using multilocus enzyme electrophoresis of enolase (Enol), phosphoglucomutase (Pgm) and triose phosphate isomerase (Tpi). Allele and genotype frequencies for Enol and Pgm were consistent irrespective of year or host species. No heterozygote deficiency was detected for Enol. Significant heterozygote deficiencies were detected in 3 of 4 years for Pgm. For Tpi, allele frequencies of the most common allele and genotype frequency varied between years and among individuals from different host species. Heterozygote deficiencies for Tpi were detected in 2 years. No significant heterozygous deficiencies were detected among O. virerrini from different fish species in 2005, except at Pgm and Tpi from Puntioplites protozsron. There was no statistical significance in pairwise FST values between O. viverrini from Cyclocheilichthys armatus in different years or different host species in 2005. Significant departures from Hardy-Weinberg expectations and a high rate of gene flow in a population of O. viverrini are discussed in terms of self- and cross-fertilisation, natural selection, non-random mating, the Wahlund effect, presence of null alleles, intensity of infection, biology and ecology of their intermediate cyprinid hosts.

Genetic variation among 231 individuals of Opisthorchis viverrini from the Ban Phai District, Khon Kaen Province (Thailand) was examined at three polymorphic enzymes: enolase (ENOL), phosphoglucomutase (PGM), and triose phosphate isomerase (TPI). Four alleles were detected for TPI and PGM, whereas only two alleles were detected for ENOL. The inferred genotype frequencies for both TPI and ENOL were not significantly different from Hardy-Weinberg equilibrium. In contrast, the inferred genotype frequencies for PGM showed a significant departure from Hardy-Weinberg equilibrium, with a lack of heterozygous individuals. This heterozygote deficiency suggests non-random mating and/or potentially high self fertilization.

Infection with Opisthorchis viverrini and its associated cholangiocarcinoma (CCA) is an underestimated problem in the Mekong region of Southeast Asia, despite the widespread use of praziquantel and health education measures for parasite control. Although data from Cambodia, Laos and Vietnam are rare, data from Thailand often show wide-ranging variability in epidemiological parameters, including human morbidity and the prevalence and incidence of CCA. The recent discovery of high levels of population genetic variability in O. viverrini in different wetlands in Thailand and Laos, which indicates the presence of sibling species, suggests that we have underestimated the complexity of this epidemiological situation. Future research should determine the relationship between the genetic variability of O. viverrini and patterns of opisthorchiasis-related disease.

The present study compared the genetic variation among 14 different geographical isolates of Opisthorchis viverrini sensu lato from Thailand and Lao PDR using sequence data for 2 mitochondrial DNA genes, the subunit 1 of NADH dehydrogenase gene (nad1) and cytochrome c oxidase gene (cox1). Four different nad1 haplotypes were detected among isolates, all of which were identical at the amino acid sequence level. Nucleotide sequence variation among 14 isolates ranged from 0 to 0.3% for nad1. Two different cox1 haplotypes were detected among isolates. These two haplotypes differed at 2 nucleotide positions, one of which resulted in a change in the amino acid sequence. Nucleotide sequence variation among isolates for cox1 ranged from 0 to 0.5%. Comparison of cox1 sequences of O. viverrini to those of other trematodes revealed nucleotide differences of 13-31%. A phylogenetic analysis of the cox1 sequence data revealed strong statistical support for a clade containing O. viverrini and 2 other species of opisthorchid trematodes; O. felineus and Clonorchis sinsensis.

Our knowledge of the species of ticks present in Southeast Asia is good, particularly due to the vast amount of work from the 1960s to the 1980s by Hoogstraal and colleagues. Unfortunately, this knowledge is scattered throughout the specialist literature, and there is currently no synopsis available. In addition, our knowledge of the tick fauna of several countries, for example Cambodia, Laos, and Myanmar, is very limited.

The food-borne trematodes, Opisthorchis viverrini, O. felineus and Clonorchis sinensis, have long been recognized as the cause of major human health problems, with an estimated 40 million infected persons. Of the three species of liver fluke, only O. viverrini is classified as a type 1 carcinogen because of its role as an initiator of chronic inflammation and the subsequent development of cholangiocarcinoma. At present, there are no techniques for the early diagnosis of cholangiocarcinoma and it is fatal for most patients. There is considerable variation in parasite prevalence and disease presentation in different geographical areas, the latter of which may be associated with genetic differences among parasites. In the present study, multilocus enzyme electrophoresis was used to provide a comprehensive genetic characterization of O. viverrini from different geographical localities in Thailand and the Peoples' Democratic Republic of Laos. Parasites from different localities were compared genetically at 32 enzyme loci. The results of the genetic analyses are sufficient to reject the null hypothesis that O. viverrini represents a single species. Therefore, O. viverrini consists of at least two genetically distinct, yet morphologically similar (i.e. cryptic) species. Moreover, there was also separation of the different populations of snails (i.e. the first intermediate hosts) into two distinct genetic groups that corresponded with the delineation of O. viverrini into two species. This suggests that there may be a history of co-evolution in this host-parasite lineage. Additionally, five distinct genetic groups of parasites were detected, each of which occurred within a different and independent river wetland system. Our findings have major implications for the implementation of effective control and surveillance programs targeted to these medically important food-borne parasites.

Genetic variation in Opisthorchis viverrini adults originating from different locations in northeast Thailand and Laos, People's Democratic Republic (PDR), was examined using random amplified polymorphic DNA (RAPD) analyses. In an initial analysis, the genomic DNA of one fluke from each of ten localities was amplified using 15 random primers (10-mers); however, genetic variation among O. viverrini specimens was detected reliably for only four primers. A more detailed RAPD analysis using these four primers was conducted on ten individuals from nine localities. Considerable genetic variation was detected among O. viverrini from different geographical areas and among some individuals from the same collecting locality. Comparison of the RAPD profiles revealed that O. viverrini adults from Laos PDR were genetically distinct from those from northeast Thailand. The taxonomic significance of this finding needs to be explored in more detail. The RAPD markers established in the present study provide opportunities to examine the biology and epidemiology of O. viverrini and fish-borne trematodes within the region. Additionally, application of these markers in such studies could have important implications in relation to the prevalence of cholangiocarcinoma in different regions of Asia.

The liver fluke, Opisthorchis viverrini, is one of the major food borne trematodes in Southeast Asia, where infection causes hepatobiliary disease and subsequent development of cholangiocarcinoma. In Thailand, O. viverrini is most prevalent in the northeast where there is marked regional variation in the rate of infection in humans at provincial, district and village levels. To date, the roles of genetic variation of O. viverrini on this observed variability in infection, transmission and associated disease are not known. We have applied multilocus enzyme electrophoresis (MEE), specifically allozyme electrophoresis, to isolates of O. viverrini from Thailand and Laos to establish genetic markers to examine its systematics and population structure. Forty-six enzymes commonly found useful for genetic characterisation in parasitic helminths were screened, and of these, 33 enzymes gave sufficient staining and resolution to act as potential genetic markers. Sixteen enzymes were monomorphic and 17 enzymes were polymorphic in the pools of worms examined. Whether they are indicative of different enzyme loci, heterozygosity or unique genotypes within the pools of worms examined remains to be determined. Preliminary investigations examining five individual worms at enzyme loci where pools of worms showed multiple bands have confirmed the diagnostic value of the enzyme loci established as well as providing evidence of potential population sub structuring and heterozygosity. For the first time, we have established at least 17 enzymes that provide the basis to undertake comprehensive genetic analyses of the systematics and population structure of O. viverrini, a medically important food borne trematode in Southeast Asia.

We conducted an allozyme electrophoretic study to explore potential enzyme markers to distinguish Opisthorchis viverrini in Thailand and Lao PDR. Twenty-eight enzymes encoding presumptive 32 loci were established. The enzymes glucose-6-phosphate dehydrogenase and pyruvate kinase were diagnostic between two geographically separate isolates from Thailand. Twelve enzymes, ie, aconitate hydratase, aldolase, creatine kinase, enolase, esterases, fumarate hydratase, aspartate aminotransferase, glucose-phosphate isomerase, alanine aminotransferase, isocitrate dehydrogenase, malic enzyme, and pyruvate kinase, also provided diagnostic markers for these two isolates from Thailand and one isolate from Lao PDR.

Striped mice, Rhabdomys pumilio, were trapped over a period of 17 months in the Thomas Baines Nature Reserve, and placed in cages, over water, until all the ticks they harboured had detached. The mice were then returned to the reserve. Four ixodid tick species were recovered from the mice of which the larvae and nymphs of Rhipicephalus follis and Rhipicephalus simus were the most numerous. Most larvae of R. follis detached from mice trapped from March to July, and most nymphs in March and from June to September. Most larvae of R. simus detached from mice trapped from December to March, and most nymphs from January to March and during May and June. Seven ixodid tick species were collected from striped mice, house rats, Rattus rattus, vlei rats, Otomys spp. and Praomys sp. captured in the vicinity of human dwellings or animal holding facilities in the Grahamstown district. The striped mice captured in the Thomas Baines Reserve harboured considerably larger numbers of ticks than any of the rodent species in the more urbanized localities.

The status of Argas persicus in Australia has been a matter of controversy for over 25 years. Although early records of A. persicus sensu stricto are common, a major revision of the genus indicated that these records refer to A. robertsi, first described in 1968 from northern Australia, and to an "undescribed" member of the complex occurring in the south. Here, we show that A. persicus sensu stricto does occur in southern Australia and is the only species of Argas in the area recorded from poultry. Another undescribed species belonging to the A. persicus complex, from crows' nests near Lake Eyre in South Australia, was also discovered. This information is of considerable epidemiological significance, as A. persicus sensu stricto is a major vector for a number of highly pathogenic diseases of poultry, not all of which have yet been recorded from Australia., (Copyright 2004 Springer-Verlag)

The changes taking place within the societies, cultures and the environments in which we live are massive and complex. By referring to simple epidemiological models it is possible to build an objective framework with which to look at these changes in terms of their likely impact on the epidemiology of parasitic diseases within human communities. These parameters are listed for hosts and both micro- and macroparasites, as are epidemiologically significant cultural, social and environmental variables. Changes in these variables may be either detrimental or beneficial to human health and may, in addition, interact in complex ways. Examples of the complexity of changes which can influence epidemiology are provided for a cultural template of the population living in the north-east of Thailand.

The cleaning of ixodid ticks for microscopy can be achieved quickly and efficiently using a combination of a wax solvent and an ultrasonic cleaner. The technique involves minimum handling of specimens, produces no detectable damage and is suitable for cleaning many specimens at the same time.

The risk of Borrelia burgdorferi infection and the value of antibiotic prophylaxis after tick bite are controversial. In this study, performed in two areas of southwestern Germany, ticks were collected from 730 patients and examined by the polymerase chain reaction (PCR) for B. burgdorferi. To assess whether transmission of B. burgdorferi occurred, the patients were clinically and serologically examined after tick removal and during follow-up examinations. Data from all tick bites gave a total transmission rate of 2.6% (19 patients). Eighty-four ticks (11.3%) were PCR positive. Transmission occurred to 16 (26.7%) of 60 patients who were initially seronegative and could be followed up after the bite of an infected tick. These results indicate that the transmission rate from infected ticks in Europe is higher than previously assumed. Examination of ticks and antibiotic prophylaxis in the case of positivity appears to be indicated.

Individual humans and animals are subject to infection by a variety of parasites (broadly defined to include viruses, bacteria and other non-protozoan microparasites) at any one time. Multiple parasite infections occur frequently in populations of wild animals as well as in humans from developing countries. In some species and regions, hosts with multiple infections are more common than hosts with either no infection or a single infection. Studies, predominantly on animals, show that a wide variety of environmental and host-dependent factors can influence the structure and dynamics of the communities of parasites that make up these multiple infections. In addition, synergistic and competitive interactions can occur between parasite species, which can influence the likelihood of their successful transmission to other hosts and increase or decrease their overall pathogenic impact. This review summarises aspects of our current knowledge on the frequency of multiparasite infections, the factors which influence them, and their pathogenic significance.

The control of arthropods of veterinary importance represents a disturbance for the ecosystem and its animal community. This disturbance can influence the densities of target and non-target organisms and their associated indirect interactions in the food web, leading to reductions in the species richness and diversities in the communities involved. Finely tuned control affecting the target organism alone can have unexpected consequences, depending on the relationships between the target and other organisms within the food web. Broad-spectrum control methods will have more wide ranging and less predictable consequences. Modifications within the community caused by arthropod control can take place over generations and may not be immediately apparent. Most modern techniques of control are designed to minimize environmental impact by concentrating specifically on the target organism. The effects of control of arthropod pests of domestic and production stock must be seen against a background of more general effects caused by rural development which acts to modify the environment continuously over a long time span.

A total of 4803 domestic and wild animals which were presented for examination at a veterinary clinic in north Baden, Germany over a period of 1 year were examined for tick infestation. A total of 434 nymphal and adult ticks were collected from 175 hosts. Ticks found belonged to the species Ixodes ricinus (385), Ixodes hexagonus (48), and Ixodes ventalloi (one). The polymerase chain reaction was used to examine 132 I. ricinus and 21 I. hexagonus for the presence of Borrelia burgdorferi. Twenty-two per cent of adult I. ricinus were infected as were one female and one larval I. hexagonus.

PCR was used to compare urinary bladder and ear biopsy samples from four European species of wild rodents for the presence of Borrelia burgdorferi sensu lato. From 60 paired comparisons of bladder and ear biopsy samples, the PCR results were concordantly positive or negative in 43 samples (71.7%). Of the 17 which differed, 14 bladder samples were positive and ear samples were negative while the converse occurred for three samples. Thus ear biopsy samples led to a significantly lower estimate of infection than bladder biopsy samples. This suggests that the use of ear biopsy samples in epidemiological studies of B. burgdorferi in Central European rodents is likely to lead to underestimates of the prevalence.