Untangling the Complexity of Liver Fluke Infection and Cholangiocarcinoma in NE Thailand Through Transdisciplinary Learning

This study demonstrates how a transdisciplinary learning approach provided new insights for explaining persistent Opisthorchis viverrini infection in northern Thailand, as well as elucidating problems of focusing solely on the parasite as a means of addressing high prevalence of cholangiocarcinoma. Researchers from diverse backgrounds collaborated to design an investigative homestay program for 72 Singaporean and Thai university students in five northeast Thai villages. The students explored how liver fluke infection and potential cholangiocarcinoma development are influenced by local landscape dynamics, aquatic ecology, livelihoods, food culture and health education. Qualitative fieldwork was guided daily by the researchers in a collaborative, co-learning process that led to viewing this health issue as a complex system, influenced by interlinked multidimensional factors. Our transdisciplinary experience has led us to believe that an incomplete understanding of these linkages may reduce the efficacy of interventions. Further, viewing liver fluke infection and cholangiocarcinoma as the same issue is inadvisable. Although O. viverrini infection is an established risk factor for the development of cholangiocarcinoma, multiple factors are known to influence the likelihood of acquiring either. Understanding the importance of the current livelihood transition, landscape modification and the resulting mismatch between local cultures and new socio-ecological settings on cholangiocarcinoma initiation and liver fluke transmission is of critical importance as it may help readjust our view of the respective role of O. viverrini and other socioeconomic risk factors in cholangiocarcinoma etiology and refine intervention strategies. As demonstrated in this study, transdisciplinary approaches have the potential to yield more nuanced perspectives to complex diseases than research that focuses on specific aspects of their epidemiology. They may therefore be valuable when designing effective solutions to context-sensitive diseases such as liver fluke infection and cholangiocarcinoma.

Distributions of the paralysis ticks Ixodes cornuatus and Ixodes holocyclus in south-eastern Australia

OBJECTIVE

To describe the actual and potential geographic distributions of Ixodes cornuatus and I holocyclus in south-eastern Australia.

PROCEDURE

Examination of ticks from museum collections and trapped animals were made. (Bioclimatic analysis BIOCLIM) was used to predict potential distributions.

RESULTS

I holocyclus was collected from rodents (Rattus fuscipes, R lutreolus, R rattus), wombats (Vombatus ursinus), cats and dogs in Gippsland and I cornuatus was collected from rodents (R fuscipes), wombats, cats and dogs in central Victoria. All life-cycle stages of both species were collected during the warmer months of the year. The known distribution of the two species was established from specimens in museum collections and suggested that a boundary between the two may exist in eastern Gippsland. BIOCLIM suggested that the area immediately to the east of Melbourne was climatically suitable for I holocyclus, although no endemic foci of infection are currently known from this region. The potential distribution of I cornuatus included east Gippsland and the Otway Ranges, areas in which the tick is not currently known to occur.

CONCLUSIONS

I holocyclus and I cornuatus have more restricted distributions than current collections suggest and therefore may have the possibility to extend their geographical ranges in the future.

Argas persicus sensu stricto does occur in Australia

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.

Cysticercoids of five species of Raillietina Fuhrmann, 1920 (Cestoda: Davaineidae) in ants, Pheidole sp., from emu farms in Australia

Cysticercoids of five species of Raillietina, R. australis (Krabbe, 1869) Fuhrmann, 1924, R. beveridgei O'Callaghan, Davies & Andrews, 2000, R. chiltoni O'Callaghan, Davies & Andrews, 2000, R. dromaius O'Callaghan, Davies & Andrews, 2000 and R. mitchelli O'Callaghan, Davies & Andrews, 2000, parasitic in the emu Dromaius novaehollandiae Latham, are described. Each species was identified on the basis of the number and size of the rostellar hooks, which correspond to those of adult worms. Cysticercoids were recovered from the haemocoele of the gaster of ants belonging to the genus Pheidole (Hymenoptera: Formicidae) in Australia. There was a trend towards an inverse relationship between the size of the cysticercoids and the parasite burden in the intermediate host.

Genetic variation within the ticks Ixodes holocyclus and Ixodes cornuatus from south-eastern Australia

Ticks from mainland Australia (Victoria, New South Wales and Queensland) and Tasmania, identified morphologically as either Ixodes holocyclus or Ixodes cornuatus, were compared genetically using 24 enzyme loci. The results showed that ticks from three localities in Victoria were genetically similar to I. cornuatus in Tasmania, but both groups had fixed genetic differences at >45% of loci compared with other ticks on the mainland. In addition, there were fixed genetic differences at 0-60% of loci among I. holocyclus from different localities on the mainland. Ixodes holocyclus samples could be divided into four distinct clusters (with fixed genetic differences >15%), three of which were represented by one or two specimens. Nonetheless, these electrophoretic data suggest that I. holocyclus represents a species complex. The results also showed that the morphological criteria used to identify specimens were not always accurate because several specimens had been mis-identified morphologically. Despite limitations with the morphological identification, this study has demonstrated that I. cornuatus can be distinguished from the I. holocyclus species complex using six enzyme loci, providing the foundation for a re-examination of morphological characteristics. The present study has shown that I. cornuatus and the I. holocyclus complexes have a greater distribution than previously reported, with both occurring in sympatry at Cape Patterson, on the southern coastline of Victoria.

Influence of temperature and relative humidity on the moulting success of Amblyomma limbatum and Aponomma hydrosauri (Acari: Ixodidae) larvae and nymphs

This study compared the duration of the moulting periods of engorged larvae and nymphs of the ixodid ticks, Amblyomma limbatum and Aponomma hydrosauri, at different temperature/relative humidity regimes, and examined the relationships between the engorged weight of ticks and their weights after moulting. The results showed that for each species, there was a significant relationship between the weights of unfed nymphs and engorged larvae, and the weights of unfed adults and engorged nymphs. The weight of engorged nymphs was also a good indicator of their sex, with female ticks having heavier weights as engorged nymphs. Temperature and relative humidity had a marked effect on the moulting success of engorged ticks of both species. Aponomma hydrosauri larvae and nymphs were able to moult at lower temperatures than Amb. limbatum but most ticks, except Ap. hydrosauri larvae, failed to moult at 13 degrees C. Additionally, there was a marked decrease in the pre-moult times of ticks at higher temperatures, with larvae taking less time to moult than nymphs. At temperatures greater than 21 degrees C, Amb. limbatum took less time to moult than Ap. hydrosauri but this interspecific difference was less marked for nymphs. The interspecific differences in the responses of engorged larvae and nymphs to different temperatures and relative humidities correlated with interspecific differences in off-host behaviour and with the different climates the two species experience throughout most of their distributional range.

A simplified method of cleaning ixodid ticks for microscopy

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.

Molecular systematics of the parasitic protozoan Giardia intestinalis

The long-standing controversy regarding whether Giardia intestinalis is a single species prevalent in both human and animal hosts or a species complex consisting of morphologically similar organisms that differ in host range and other biotypic characteristics is an issue with important medical, veterinary, and environmental management implications. In the past decade, highly distinct genotypes (some apparently confined to particular host groups) have been identified by genetic analysis of samples isolated from different host species. The aim of this study was to undertake a phylogenetic analysis of G. intestinalis that were representative of all known major genetic groups and compare them with other Giardia species, viz. G. ardeae, G. muris, and G. microti. Segments from four "housekeeping" genes (specifying glutamate dehydrogenase, triose phosphate isomerase, elongation factor 1 alpha, and 18S ribosomal RNA) were examined by analysis of 0.48-0.69-kb nucleotide sequences determined from DNA amplified in polymerase chain reactions from each locus. In addition, isolates were compared by allozymic analysis of electrophoretic data obtained for 21 enzymes representing 23 gene loci. The results obtained from these independent techniques and different loci were essentially congruous. Analyses using G. ardeae and/or G. muris as outgroups supported the monophyly of G. intestinalis and also showed that this species includes genotypes that represent at least seven deeply rooted lineages, herein designated assemblages A-G. Inclusion of G. microti in the analysis of 18S rRNA sequence data demonstrated the monophyly of Giardia with the same median body morphology but did not support the monophyly of G. intestinalis, instead placing G. microti within G. intestinalis. The findings support the hypothesis that G. intestinalis is a species complex and suggest that G. microti is a member of this complex.

Multilocus enzyme electrophoresis: a valuable technique for providing answers to problems in parasite systematics

The aim of this review is to highlight the effectiveness of the technique of multilocus enzyme electrophoresis in answering questions relating to the systematics of parasites and to highlight errors in the way the technique has been used and the results interpreted. We have approached this topic by answering specific questions that we have been asked by colleagues and students not necessarily familiar with the technique, the method of data analysis and its application. Although the technique has been applied to provide answers for taxonomic and population genetics studies, it remains under-utilised, perhaps because of recent advances in newer molecular technology. Rather than not acknowledge or dismiss the value of more traditional technology, we suggest that researchers examine problems in the systematics of parasites by the comparison of data derived from morphological, biochemical and molecular techniques.

Comparison of the levels of intra-specific genetic variation within Giardia muris and Giardia intestinalis

The extent of intra-specific genetic variation between isolates of Giardia muris was assessed by allozyme electrophoresis. Additionally, the levels of allozymic variation detected within G. muris were compared with those observed between members of the two major assemblages of the morphologically distinct species Giardia intestinalis. Four isolates of G. muris were analysed. Three (Ad-120, -150, -151) were isolated from mice in Australia, while the fourth (R-T) was isolated from a golden hamster in North America. The 11 isolates of G. intestinalis (Ad-1, -12, -2, -62, representing genetic Groups I and II of Assemblage A and BAH-12, BRIS/87/HEPU/694, Ad-19, -22, -28, -45, -52, representing genetic Groups III and IV of Assemblage B) were from humans in Australia. Intra-specific genetic variation was detected between G. muris isolates at four of the 23 enzyme loci examined. Similar levels of variation were found within the genetic groups that comprise Assemblages A and B of G. intestinalis. These levels of intra-specific variation are similar to those observed within other morphologically-distinct species of protozoan parasites. We suggest that the magnitude of the genetic differences detected within G. muris provides an indication of the range of genetic variation within other species of Giardia and that this can be used as a model to delineate morphologically similar but genetically distinct (cryptic) species within this genus.

Molecular epidemiology: assumptions and limitations of commonly applied methods

An understanding of the epidemiology of a disease (i.e. its aetiology, transmission patterns) is crucial for the development and implementation of effective management practices. This requires sound epidemiological data. It is therefore important that scientists understand the assumptions and limitations of the methods used to gather such data. The aim of this paper is to discuss some of the assumptions and limitations of PCR-based methods used in studies of epidemiology. Since its development, PCR has had a major impact in the biological sciences. The ability to selectively amplify a specific region of the genome from a small amount of DNA makes this technique particularly useful as a diagnostic tool. A variety of PCR-based methods are available which can be used to identify strains and species of parasites. Some of these methods, such as random amplification of polymorphic DNA, have intrinsic properties which can limit their application. Other methods, such as PCR-restriction fragment length polymorphism, require the availability of a sound taxonomic or genetic framework for the development of any diagnostic system for a particular organism. The problems encountered developing diagnostic probes in the absence of such a framework will be discussed using Giardia intestinalis as an example.

Paradigms and expectations: the nature of research and diagnostics

Researchers are judged by their best work. No matter what disasters happen at the researcher's bench, there is time to repeat experiments, discard ambiguous data and work steadily toward a clearer understanding of the research problem. The work practices of researchers are matters of personal choice, because the process of peer review prior to publication considers only the work that is reported and not all work done by the researcher. On the other hand, the diagnostician's credibility is directly linked to every experiment performed, because a customer is waiting for the result. This paper contrasts aspects of the work of researchers and diagnosticians and concludes that researchers could benefit from understanding the framework within which diagnosticians operate.

Multiparasite communities in animals and humans: frequency, structure and pathogenic significance

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.

Novel lineages of Giardia intestinalis identified by genetic analysis of organisms isolated from dogs in Australia

Infection of suckling mice with Giardia trophozoites recovered from the intestines of 11 dogs autopsied in Central and Southern Australia in each case produced an established isolate. In contrast, only 1 isolate was obtained by inoculation of faecal cysts. The organisms grew poorly in comparison with isolates from humans or non-canine animal hosts. Light microscopy revealed that the trophozoites had median bodies with the 'claw hammer' appearance typical of G. intestinalis (syn. G. duodenalis, G. lamblia) but that they differed in shape and nuclear morphology from axenic isolates of human or canine origin. Allozymic analysis of electrophoretic data representing 26 loci and phylogenetic analysis of nucleotide sequences obtained from DNA amplified from the glutamate dehydrogenase locus showed that the 11 isolates examined from Australian dogs were genetically distinct from all isolates of G. intestinalis that have been established previously from humans and animals, and also from G. muris. Both analytical methods placed 10 of the Australian canine isolates into a unique genetic lineage (designated Assemblage C) and the eleventh into a deep-rooted second branch (designated Assemblage D), each well separated from the 2 lineages (Assemblages A and B) of G. intestinalis that encompass all the genotypes known to infect humans. In contrast, 4 axenic isolates derived from dogs in Canada and Europe (the only other isolates to have been established from dogs) have genotypes characteristic of genetic Assemblages A or B. The findings indicate that the novel Giardia identified in these rural Australian dogs have a restricted host range, possibly confined to canine species. The poor success rate in establishing Giardia from dogs in vitro suggests, further, that similar genotypes may predominate as canine parasites world-wide. The absence of such organisms among isolates of Giardia that have been established from humans by propagation in suckling mice indicates that they are unlikely to infect humans. However, infection of humans by those dog-derived genotypes that grow in vitro cannot be excluded.

Genetic analysis of Giardia from hoofed farm animals reveals artiodactyl-specific and potentially zoonotic genotypes

Thirty one Giardia isolates, established from six species of hoofed livestock by axenic culture or growth in suckling mice, were compared genetically by analysis of DNA amplified from loci encoding variant surface proteins or the enzyme glutamate dehydrogenase and by allozyme analysis. The isolates were heterogeneous, but all showed affinity with genetic Assemblage A--one of two major assemblages defined previously by analysis of Giardia from humans. Three distinct genotypes were evident. Ten isolates (eight axenic and two established in suckling mice) from an alpaca, pig, horse, cattle and sheep were indistinguishable from human-derived G. intestinalis belonging to a previously designated genetic group (Group I). This genotype seems to have broad host specificity, including a zoonotic potential for humans. Five isolates (two axenic and three established in suckling mice) from an alpaca, a horse and sheep had close affinity with human-derived Group I and Group II G. intestinalis genotypes. The other 16 isolates (comprising both axenic and suckling mouse-propagated cultures derived from cattle, sheep, alpaca, a goat and pigs in Australia and Europe) differed from all other Giardia with "duodenalis" morphology that have been examined by these methods and they segregated as a highly distinct sublineage (referred to herein as 'Novel livestock') within genetic Assemblage A. The predominance of 'Novel livestock' genotypes in the test panel and their apparent exclusive association with artiodactyl hosts indicates that they may be confined to this group of mammals. Assemblage B genotypes, which are prevalent in humans and some other animal species, were not detected.

An electrophoretic analysis of patterns of speciation in Cloacina clarkae, C. communis, C. petrogale and C. similis (Nematoda:Strongyloidea) from macropodid marsupials

An electrophoretic study was conducted on Cloacina clarkae, C. communis, C. petrogale and C. similis based on 19 enzyme loci. C. communis was widely distributed in Macropus robustus, showing some genetic variation among populations but occasionally switching to other macropodid hosts (M. agilis, M. antilopinus). C. similis occurred in members of the Petrogale penicillata complex, Macropus dorsalis and Thylogale billardierii, but showed no evidence of genetic differentiation in spite of its occurrence in different host species and in geographically distinct regions of Australia. C. clarkae from Macropus eugenii was genetically indistinguishable from C. similis and was considered synonymous with it. C. petrogale occurred in a similarly diverse range of hosts and geographical regions to C. similis, but was represented electrophoretically as 4 distinct genetic species, 1 in Petrogale assimilis, a second in P. lateralis purpureicollis, a third in Macropus parryi in Queensland and a fourth in M. eugenii in South Australia. Although the host and geographical ranges of C. similis and C. petrogale are analogous, the genetic uniformity of the former and diversity of the latter illustrate the incomplete understanding we have of the immediate causes of speciation in nematodes.

Genetic relationship among isolates of Helicobacter pylori: evidence for the existence of a Helicobacter pylori species-complex

We investigated the population genetics of 23 isolates of H. pylori by allozyme electrophoresis using 16 enzyme loci. Isolates were obtained from adult patients of whom 48% were of Greek extraction. Eight patients (35%) had an active duodenal ulcer. Allelic variation per loci ranged from 2 to 11 alleles. Four major genetic clusters were apparent, having > 75% fixed genetic differences. There was no distinct clustering (clonal structure) on the basis of the geographical origin of the persons from whom isolates were obtained, indicating that this bacterium has not recently jumped a species barrier into humans. Isolates associated with ulcer disease were not monophyletic, with isolates from ulcer patients being found in phylogenetically diverse branches of the dendogram derived from the data. Based on the genetic diversity of H. pylori isolates, we propose that isolates should be classified as belonging not to a single species but to a 'Helicobacter pylori species-complex'.

Effect of advanced cardiac life support training on resuscitation efforts and survival in a rural hospital

STUDY OBJECTIVE

To determine the impact of an Advanced Cardiac Life Support (ACLS) training program on resuscitation and survival in a rural hospital.

METHODS

Retrospective review of arrests in a 119-bed rural community hospital before, during, and after organization of an ACLS teaching program. ICU logs, death logs, and code review sheets were used to determine resuscitation efforts and outcomes; these were cross-checked with medical and administrative records. From 1980 through 1984, resuscitation attempts were conducted only in the ICU. By 1985, after the training program was instituted, resuscitation efforts were conducted throughout the hospital. Data are presented on resuscitations in the ICU only and on total hospital resuscitations. To assess effort, resuscitation attempts and successes were compared with total death events (ie, total number of hospital deaths plus total number surviving a resuscitation effort).

RESULTS

From 1980 through 1984, before ACLS training was instituted, 42 patients were resuscitated and 15 (36%) survived to discharge. From 1985 through 1987, 113 ICU patients were resuscitated and 29 (26%) survived. From 1988 through 1990, after ACLS protocol and code review procedures were established, 81 ICU patients were resuscitated and 23 (28%) survived. The number of attempted resuscitations throughout the hospital increased from 42 in the early period to 179 in the final period, with 15 (36%) and 52 (29%) survivors, respectively. Rates of ICU or hospital-wide resuscitation success were not significantly different over time (P > .3). There were 893 total death events in the early period and 485 in the final period. The percentage of death events with an intervention rose from 5% to 37% (P < .001), and the percentage reversed by intervention increased from 2% to 11% (P < .001).

CONCLUSION

After widespread ACLS training and code team organization, there was a significant increase in resuscitation efforts and reversal of death events despite a slight decline in the percentage of patients surviving resuscitation attempts. An ACLS training program in a rural hospital can contribute to increased overall survival.

Investigations of the taxonomy and systematics of Fusobacterium nucleatum using allozyme electrophoresis

Fusobacterium nucleatum forms part of the resident microbiota in both oral and extraoral sites in humans and animals. It is also involved in infections in such sites. Despite the genetic heterogeneity within the species, it has been divided into five subspecies, the validities of which have been questioned. In the present study, 44 F. nucleatum isolates were examined at 21 enzyme loci by using the allozyme electrophoretic technique to establish an accurate genetic framework for taxonomic purposes. Three distinct genetic clusters were identified; one cluster consisted exclusively of extraoral isolates, another cluster consisted predominantly of human oral isolates, and the third cluster consisted of a single human oral isolate. Our results highlight the urgent need for extensive biochemical, immunological, and epidemiological studies to accurately define the systematics of the genus fusobacterium based on the framework derived in this study by using 21 independent genetic characteristics.

The use of allozyme electrophoresis to assess genetic heterogeneity among previously subspeciated isolates of Fusobacterium nucleatum

Fusobacterium nucleatum has been implicated in the pathogenesis of periodontal diseases. Five subspecies have previously been proposed. The validity of these subdivisions was investigated using allozyme electrophoresis for 21 enzyme mobilities. The 18 F. nucleatum isolates tested had previously been subspeciated and included type strains as well as isolates from both oral and extraoral sites. The results showed 2 distinct genetic groups with fixed differences at 82.5% of the test loci, indicative of a species complex with a number of subspecies within each of the 2 groups. There was also evidence of a correlation between the 2 major groups of isolates and the site from which they were taken. It was concluded that there is a high degree of genetic heterogeneity within the species F. nucleatum and that its current subspeciation is of questionable validity.

Molecular genetic analysis of Giardia intestinalis isolates at the glutamate dehydrogenase locus

Samples of DNA from a panel of Giardia isolated from humans and animals in Europe and shown previously to consist of 2 major genotypes--'Polish' and 'Belgian'--have been compared with human-derived Australian isolates chosen to represent distinct genotypes (genetic groups I-IV) defined previously by allozymic analysis. Homologous 0.52 kilobase (kb) segments of 2 trophozoite surface protein genes (tsa417 and tsp11, both present in isolates belonging to genetic groups I and II) and a 1.2 kb segment of the glutamate dehydrogenase (gdh) gene were amplified by the polymerase chain reaction (PCR) and examined for restriction fragment length polymorphisms (RFLPs). Of 21 'Polish' isolates that were tested, all yielded tsa417-like and tsp11-like PCR products that are characteristic of genetic groups I or II (15 and 6 isolates respectively) in a distinct assemblage of G. intestinalis from Australia (Assemblage A). Conversely, most of the 19 'Belgian' isolates resembled a second assemblage of genotypes defined in Australia (Assemblage B) which contains genetic groups III and IV. RFLP analysis of gdh amplification products showed also that 'Polish' isolates were equivalent to Australian Assemblage A isolates (this analysis does not distinguish between genetic groups I and II) and that 'Belgian' isolates were equivalent to Australian Assemblage B isolates. Comparison of nucleotide sequences determined for a 690 base-pair portion of the gdh PCR products revealed > or = 99.0% identity between group I and group II (Assemblage A/'Polish') genotypes, 88.3-89.7% identity between Assemblage A and Assemblage B genotypes, and > or = 98.4% identity between various Assemblage B/'Belgian' genotypes. The results confirm that the G. duodenalis isolates examined in this study (inclusive of G. intestinalis from humans) can be divided into 2 major genetic clusters: Assemblage A (= 'Polish' genotype) containing allozymically defined groups I and II, and Assemblage B (= 'Belgian' genotype) containing allozymically defined groups III and IV and other related genotypes.

Division of Giardia isolates from humans into two genetically distinct assemblages by electrophoretic analysis of enzymes encoded at 27 loci and comparison with Giardia muris

Giardia that infect humans are known to be heterogeneous but they are assigned currently to a single species, Giardia intestinalis (syn. G. lamblia). The genetic differences that exist within G. intestinalis have not yet been assessed quantitatively and neither have they been compared in magnitude with those that exist between G. intestinalis and species that are morphologically similar (G. duodenalis) or morphologically distinct (e.g. G. muris). In this study, 60 Australian isolates of G. intestinalis were analysed electrophoretically at 27 enzyme loci and compared with G. muris and a feline isolate of G. duodenalis. Isolates of G. intestinalis were distinct genetically from both G. muris (approximately 80% fixed allelic differences) and the feline G. duodenalis isolate (approximately 75% fixed allelic differences). The G. intestinalis isolates were extremely heterogeneous but they fell into 2 major genetic assemblages, separated by fixed allelic differences at approximately 60% of loci examined. The magnitude of the genetic differences between the G. intestinalis assemblages approached the level that distinguished the G. duodenalis isolate from the morphologically distinct G. muris. This raises important questions about the evolutionary relationships of the assemblages with Homo sapiens, the possibility of ancient or contemporary transmission from animal hosts to humans and the biogeographical origins of the two clusters.

Improved detection of fetal cells from maternal blood with polymerase chain reaction

OBJECTIVE

The objective was to test the reliability of new deoxyribonucleic acid primers that have previously been used very efficiently by this laboratory with amniolysate samples to amplify a 248 bp Y-specific, repeated sequence from maternal blood during pregnancy.

STUDY DESIGN

Blood samples were obtained from 50 women during weeks 11 and 16 of pregnancy and were analyzed for the presence of the Y chromosome-specific sequences.

RESULTS

Y-specific fragments were identified in 19 of 24 (79.2%) women after one complete amplification. A second amplification of these samples negative for Y-specific fragments revealed three additional samples positive for the Y chromosome-specific fragment. Only two male fetuses remained unidentified. Overall, 91.7% male fetuses and 96% of all fetuses (48/50) in these women were correctly identified.

CONCLUSIONS

The primers described in this study provide an additional or alternative tool for the determination, by means of the polymerase chain reaction, of Y chromosome-bearing cells in maternal circulation.

Giardia intestinalis: detection of major genotypes by restriction analysis of gene amplification products

The polymerase chain reaction (PCR) has been used to amplify a 0.52 kb segment of Giardia intestinalis DNA, using primers specific for nucleotide sequences conserved within two genes (tsp11 and tsa417) that encode homologous, cysteine-rich trophozoite surface proteins. Using products amplified from axenic isolates belonging to genetic groups I and II (defined on the basis of allozyme electrophoresis data), restriction endonuclease analysis revealed both tsp11-like and tsa417-like fragments within all samples. The study also identified among the amplification products of group II organisms an additional fragment, containing a novel PstI site, that is not detected in the reaction products of group I isolates. The recovery of three distinct PCR products from each group II isolate was verified by cloning the fragments into the plasmid vector pGEM-7. Fragments containing the new PstI site possess the ClaI site common to both tsp11 and tsa417-like fragments, but they lack the HindIII site which characterizes tsp11-like fragments and also lack the PstI and KpnI sites which characterize tsa417-like fragments. Spot-blot analyses using cloned fragments of all three types as probes showed strong homologous hybridization but weak heterologous hybridization, indicating that each type differs substantially in nucleotide sequence from the others. Because the samples of Giardia DNA used in the PCR were purified from cultures that had been established from single trophozoites, the data indicate that individual trophozoites belonging to genetic group II possess three homologous genes defined by these related fragments. The presence of a PstI site in the amplified segment of the newly-discovered third gene of group II organisms provides a simple diagnostic means of differentiating group I and II isolates.

Differentiation of major genotypes of Giardia intestinalis by polymerase chain reaction analysis of a gene encoding a trophozoite surface antigen

The polymerase chain reaction (PCR) has been used to amplify in vitro a semi-conserved region of a gene encoding an M(r) 68-72,000 surface antigen of Giardia intestinalis trophozoites. Using primers specific for conserved nucleotide sequences identified within the promoter-distal portion of two homologous genes (tsp11 and tsa417) cloned previously from the G. intestinalis isolates Ad-1 (from Australia) and WB (from Afghanistan), a single PCR-amplified DNA fragment of the expected size (0.52 kilobases) was obtained in high yield from either purified DNA or whole trophozoites of the Ad-1 isolate and from every 1 to 9 other axenic G. intestinalis isolates belonging to genetic groups I and II (defined previously on the basis of allozyme electrophoresis data--Andrews et al. 1989). Discernible product was recovered from as few as 2-4 trophozoites. In contrast, 6 G. intestinalis isolates that were assigned by allozymic analysis to genetic groups III/IV yielded small amounts of a 0.37-kilobase (kb) amplification product (with evidence in some samples of an additional 0.4 or 0.18 kb fragment) but no 0.52 kb product. Two animal-derived isolates of G. duodenalis (one from an Australian native rodent, Notomys alexis, the other from a domestic cat) also yielded a single 0.37 kb PCR-amplified fragment, whereas an isolate from another cat produced a 0.34 kb fragment. No product was recovered from G. muris, a morphologically distinct species of Giardia. The results demonstrate that different genotypes of G. duodenalis can be distinguished using this assay and that it is diagnostic for isolates belonging to two major clusters (groups I/II and III/IV) of G. intestinalis. The amplified DNA segment appears to be relatively conserved among group I and group II isolates of G. intestinalis. A related but clearly distinct sequence seems to be conserved among group III/IV isolates of G. intestinalis and some isolates of G. duodenalis.

Distinct genetic groups of Giardia intestinalis distinguished by restriction fragment length polymorphisms

The taxonomic status of the parasitic protozoal species Giardia intestinalis depends on the morphological similarity of all Giardia isolated from humans and the presumption that Giardia are host-specific. On the basis of electrophoretic data derived from examination of 26 enzyme loci in Australian isolates, it has been proposed that G. intestinalis is a species complex comprising three or four genetically distinct (but morphologically cryptic) species. These received the tentative designations of genetic groups I-IV (R. H. Andrews, M. Adams, P. F. L. Boreham, G. Mayrhofer & B. P. Meloni. International Journal for Parasitology 19, 183-190, 1989). In the present study, two unrelated DNA probes (one specific for a gene encoding a trophozoite surface protein, the other detecting a non-coding repetitive sequence within the G. intestinalis genome) were used in Southern hybridization analyses to examine 10 axenic isolates of G. intestinalis, established from diverse geographical regions in Australia, together with the Portland-1 isolate from the USA. Both probes identified every isolate unambiguously as belonging to one or other of two genetic clusters. Electrophoretic analysis of the same samples indicated that these clusters correspond to the previously defined genetic groups I and II. No heterogeneity was apparent within the seven group I isolates using either probe. However, when probed with the repetitive sequence, the four isolates belonging to group II exhibited small differences in banding patterns, suggesting that this group may be less homogeneous than group I.(ABSTRACT TRUNCATED AT 250 WORDS)

Sibling species within Macropostrongyloides baylisi (Nematoda: Strongyloidea) from macropodid marsupials

Macropostrongyloides baylisi from four different species or subspecies of host were analysed electrophoretically at 27 enzyme loci. The results revealed the existence of two species, one in Macropus giganteus and the other in M. robustus robustus, M.r. erubescens and M.r. parryi, that had fixed genetic differences at 33% of loci. Populations of nematodes from two subspecies of M. robustus, M.r. robustus from Queensland and M.r. erubescens from South Australia, had fixed genetic differences at two (7.4%) of 27 loci and were considered to belong to the same species. No fixed genetic differences were detected between nematodes from M. parryi and M.r. robustus. A discriminant function analysis of morphological data assigned 96% of specimens to groups defined on the basis of the host species or subspecies from which they were obtained. This separation of Ma. baylisi into host-specific groups did not, however, totally correlate with the electrophoretic data. The species of M. baylisi in M. giganteus was genetically more distinct from the sibling species in M. robustus/M. parryi than to a related but morphologically dissimilar nematode, Ma. yamagutii from M. fuliginosus. This suggests an evolutionary parallel between host and parasite at the genetic level which is not reflected by morphological differences.

Selection of specific genotypes of Giardia intestinalis by growth in vitro and in vivo

This study examined whether allelic changes observed when clinical isolates of Giardia intestinalis made in suckling mice were adapted to in vitro growth occurred as a result of gene switching (alternate isoenzymes) or through selection of organisms with different genotypes from mixed infections. Samples were compared electrophoretically at 20 enzyme loci. Marked allelic differences were detected between the uncloned clinical isolates grown in mice and the axenic cultures established from them. Furthermore, the allelic profiles of the uncloned isolates changed during the course of in vivo or in vitro growth. In contrast, all clones produced from each isolate retained identical allelic profiles, regardless of whether they were grown in vivo or in vitro. These findings argue against gene switching as an explanation for the observed allozyme changes and support preferential selection of organisms with specific genotypes by growth conditions. The data indicate the presence of at least 2 and possibly up to 4 distinct genotypes within each clinical isolate. The genetic differences detected between clinical isolates in suckling mice were of similar magnitude to those that separate different axenic isolates of G. intestinalis into cryptic species. Conversely, the genetic differences between the isolates were limited when sampled after establishment in vitro. These findings have significant implications for research on Giardia and other medically important parasites and raise the possibility that culture may exert a similar selective bias on the genotypes isolated from infections with other parasitic protozoa.

Apparent lack of genetic variation within Pelecitus roemeri (Nematoda: Filarioidea) from three Australian species of macropodid marsupial

An electrophoretic study of Pelecitus roemeri from Macropus robustus, M. giganteus and Wallabia bicolor revealed no genetic differences at 23 enzyme loci. The genetic data support the existing morphological evidence that P. roemeri from these three hosts represents a single species. The data show no genetic variation between nematodes from the same or different host species collected in northern and southern Australia. This result is discussed briefly in relation to Price's model of parasite speciation.

The use of suckling mice to isolate and grow Giardia from mammalian faecal specimens for genetic analysis

A simple technique is described for preparation of Giardia cysts from faecal samples, the growth of trophozoites in suckling mice and the isolation of trophozoites for genetic analysis by allozyme electrophoresis. In total, 125 new isolates of Giardia have been collected from human and animal sources over a wide geographical area of South Australia and the Northern Territory of Australia. A number of long-established axenized isolates of G. intestinalis belonging to Groups I and II also adapted to grow in suckling mice. These findings indicate that suckling mice are permissive hosts for a variety of genetically dissimilar but morphologically similar organisms of the G. duodenalis type and that this in vivo technique may be less selective than isolation by in vitro culture. The use of suckling mice has revealed that infections can be composed of mixed genotypes and that isolation and purification techniques can be selective. Allozymic interpretation is essential to reveal the genetic complexity of such mixtures.

Detection by allozyme electrophoresis of cryptic species of Hypodontus macropi (Nematoda: Strongyloidea) from macropodid marsupials

Allozyme electrophoresis of 98 Hypodontus macropi from eight different species of hosts using 24 enzymes revealed a complex of at least six sibling species, with 15-50% fixed genetic differences between taxa. Except for the taxon parasitizing Macropus rufus/M. robustus, pairs of parasite taxa were, in each case, sympatric at each locality examined, thus supporting the conclusion that they represent valid species. The existence of a series of host-specific nematode taxa explains many of the inconsistencies noted previously in the host distribution of H. macropi. Comparison of parasite allozyme phenograms with host phylogeny suggests that four of the speciation events could be attributable to cospeciation and two to host switching. A clear case of host switching between M. rufus/M. robustus and M. fuliginosus was found.

Changes in allozyme pattern of the protozoan parasite Giardia intestinalis

The present study compares the allelic profiles of Giardia intestinalis grown in vivo and in vitro. Three clinical isolates of G. intestinalis were established in suckling mice and subsequently adapted to in vitro culture to test the null hypothesis that samples of the same clinical isolate grown in different culture conditions have identical allelic profiles. For each isolate, a mouse-derived and an axenically cultured sample were analysed electrophoretically at 11 enzyme loci. In each case, the axenically cultured sample of each isolate showed marked allelic differences from its corresponding in vivo sample. These data suggest that there may be either regulated expression of alternative genes encoding distinct isozymes (i.e. gene switching) or selection by different growth conditions of specific genotypes from a mixture present within the original clinical isolate. Although these hypotheses are not tested in this study, the data highlight the importance of confirming that allozymes (or isozymes) are stable genetic characters for the identification and characterization of protozoan taxa.

Interspecific differences in the movements of female ticks on reptiles

Movements of females of two reptile ticks, Amblyomma limbatum and Aponomma hydrosauri were studied to determine whether the behaviour of the species on hosts was similar or different. Experiments were conducted to determine if the movement of females on hosts prior to mating was influenced by the delayed attachment of conspecific males. A field experiment was also undertaken to determine whether data obtained during laboratory experiments reflected the behaviour of females on hosts in the field. Both in laboratory and field experiments, a significantly greater proportion of Ap. hydrosauri females changed their site of attachment prior to mating. Individual Ap. hydrosauri females made significantly more positional changes than Amb. limbatum females. These interspecific differences occurred irrespective of the absence of conspecific males or presence of non-conspecific adults on hosts. These data may have important ecological implications in relation to the success of colonizing females at their parapatric boundary.

Apparent absence of genetic differences among species of Teladorsagia (Nematoda: Trichostrongylidae)

The technique of allozyme electrophoresis was applied to three species of Teladorsagia present in sheep to determine the extent of genetic variation among species. Thirty-four enzyme loci were established of which 22 were invariant and 12 were shown to be polymorphic. No fixed allelic differences were detected among the species and the level of polymorphism was within the range found commonly between populations of a single species. Therefore, the genetic data support breeding data and existing morphological evidence that T. circumcincta, T. davtiani and T. trifurcata as currently recognized do in fact belong to a single species.

A genetic approach to species criteria in the amoeba genus Naegleria using allozyme electrophoresis

The present study employs allozyme electrophoresis to characterize and inter-relate 61 isolates of Naegleria. Diploidy was confirmed, with heterozygotes observed at 29 of the 33 loci established and in all but two isolates. With a single exception, isolates clustered at two levels of similarity, either below 21% or above 52%. It is argued that such a major discontinuity provides a sound biological basis for a species concept in Naegleria. On this basis the present species-level taxonomy does not reflect the genetic diversity of the genus. The study recognized 18 genetic groups of species rank. The subspecies N. australiensis italica deserves specific rank; additional thermophilic species not closely related to N. fowleri and N. lovaniensis are recognized; and N. gruberi as currently conceived is a complex of 10 species, at least five of which are represented in the formal culture collections. Most species are genetically too different for relationships to be elucidated by allozyme electrophoresis, supporting the view that some of the times of divergence within the genus are extremely ancient.

Genetic characterization of three strains of Hymenolepis diminuta at 39 enzyme loci

The technique of allozyme electrophoresis was applied to three strains of Hymenolepis diminuta to distinguish between three hypotheses [(1) multiple species, (2) genetically distinct founder stocks and (3) response to differential selection among similar stocks] proposed to account for metabolic differences among strains. There was no evidence from the 39 enzyme loci established that the three strains represented more than one species. In the absence of knowledge of the population structure of H. diminuta in the wild, electrophoretic data herein could not distinguish between the latter hypotheses. Nevertheless, all three strains were distinguishable on electrophoretic profiles and allelic similarities between strains question the view of their proposed origins.

Genetic characterization of three species of Onchocerca at 23 enzyme loci

The technique of allozyme electrophoresis was applied to species of Onchocerca from cattle to increase the number of enzyme loci established and therefore provide a genetic basis for a rational species-level taxonomy. Twenty-three enzyme loci were established and provided unequivocal genetic evidence for the taxonomic validity of Onchocerca gibsoni, O. gutturosa and O. lienalis. Furthermore, the diagnostic enzyme markers detected form the basis for identification of life-cycle stages, individuals and species and population structure analyses.

Giardia intestinalis: electrophoretic evidence for a species complex

The technique of allozyme electrophoresis was applied to 29 Australasian stocks and 48 clones of Giardia intestinalis from humans as a means of increasing the number of genetic markers currently available for identification and classification. Fifty different enzymes were examined and of these 26 loci were found to be suitable for use as genetic markers. The data indicate the presence of four discrete genetic groups within the sample of G. intestinalis examined. The groups had fixed genetic differences at 23-69% of loci established. The evidence suggests that G. intestinalis is a species complex. The results have important implications for the systematics of human isolates of Giardia, as well as for studies on the epidemiology and demography of giardiasis in Australia and elsewhere.

Identification of life cycle stages of the nematode Echinocephalus overstreeti by allozyme electrophoresis

Data presented in this study highlight the potential of allozyme electrophoresis in providing unequivocal genetic evidence for the identification of life cycle stages, particularly where species have complex life cycles. Adults of the nematode Echinocephalus overstreeti parasitize the elasmobranch Heterodontus portusjacksoni. The putative larval form which is morphologically dissimilar is found in two species of marine molluscs, Chlamys bifrons and Pecten albus. Electrophoretic analysis indicated that the adult and larval forms shared alleles at all of the 34 enzyme loci established. Furthermore, there were no fixed allelic differences between larval forms from different mollusc species.

Correspondence between MMPI PTSD measures and clinical diagnosis

Correspondence of the Minnesota Multiphasic Personality Inventory (MMPI) posttraumatic stress disorder (PTSD) subscale and the clinical scale decision rules reported by Keane, Malloy, and Fairbank (1984) with clinical diagnoses of PTSD was measured on a sample of 595 veterans. The measures demonstrated good sensitivity and selectivity, but the false-positive rate was high. It is suggested the MMPI measures be used to rule out, but not to establish, the diagnosis of PTSD. The construct validity of the PTSD subscale was supported by the finding of a higher mean score in combat than noncombat veterans.