Infectivity of Swiss Giardia isolates to jirds and mice, and in vitro cultivation of trophozoites originating from sheep

The application of a polymerase chain reaction (PCR)-based capillary electrophoretic technique provides detailed insights into Eimeria populations in intensive poultry establishments

Intestinal coccidiosis, caused by one or multiple species of Eimeria (Protozoa: Apicomplexa), is one of the most important infectious diseases affecting chickens. In this study, we used a polymerase chain reaction (PCR)-based capillary electrophoresis (CE) approach to conduct an epidemiological survey of Eimeria species in seven Australian broiler flocks, varying in age from 18 to 42 days. We confirmed that all seven recognized Eimeria species of poultry were present. Eimeria acervulina and E. maxima were the most common, followed by E. mitis (i.e., 89%, 87% and 64% of chickens, respectively). E. praecox was present in 44% of birds, whereas E. brunetti and E. tenella were uncommon, being found in 36% and 26%, respectively. E. necatrix was rarely detected (10%). Even the least common species were present in more than 70% of sheds. The prevalence of individual species was higher in older than in younger chickens. Most of the chickens sampled were simultaneously infected with multiple Eimeria species (mean=3.6). The number of Eimeria oocysts excreted per gram of faeces reached a peak at 36 days of age, before declining to a considerably lower level by 42 days. As anticoccidial drugs were permanently withdrawn at 36 days, the decreasing Eimeria oocyst excretion rates indicated the development of protective immunity in the chickens. The present study showed that even healthy chickens usually harbour numerous species of Eimeria. The CE technique proved to be a time and cost-effective means of investigating the epidemiology of Eimeria in commercial establishments.

Investigating a persistent coccidiosis problem on a commercial broiler–breeder farm utilising PCR-coupled capillary electrophoresis

In the present study, we utilised a polymerase-chain-reaction-coupled capillary electrophoresis (CE) approach to investigate the epidemiology of Eimeria species on a broiler-breeder farm in Victoria, Australia. The Eimeria populations of two flocks vaccinated against coccidiosis were followed over an 11-week period. All seven recognised Eimeria species of chickens were detected in both flocks. One flock suffered increased morbidity and mortality in its eighth week and had consistently higher Eimeria oocyst counts, species prevalences and rates of co-infections. Four Eimeria species included in the vaccine administered occurred at higher prevalences before the disease outbreak in the flock. Using the CE approach, two new, previously undescribed Eimeria genotypes were discovered in both chicken flocks, one of which dominated toward the end of the study period. The molecular approach proved versatile and capable of providing useful epidemiological data which could be used to investigate and interpret coccidiosis outbreaks.

Cloning and nucleotide sequencing of the second internal transcribed spacer of ribosomal DNA for three species of Eimeria from chickens in Taiwan

Coccidiosis of chickens caused by protozoan parasites of the genus Eimeria (Coccidia: Eimeriidae) is an enteric disease that results in great economic losses throughout the world, including Taiwan. Using polymerase chain reaction (PCR) with primers specific for the second internal transcribed spacer (ITS-2) of ribosomal DNA (rDNA), three species of Eimeria, E. tenella, E. maxima, and E. acervulina have been successfully characterised from chickens in Taiwan. The sizes of PCR products from various isolates representing these three species were between 370 and 580 base pairs (bp). After cloning and sequencing of the PCR products, high nucleotide sequence identity (96.8-100%) was observed within a species. In addition, ITS-2 nucleotide sequences for E. tenella had higher homology (98.5-99.3%) than E. maxima (81.6-96.5%) when compared with appropriate sequences deposited in GenBank. To our knowledge, this is the first report of a 412-bp ITS-2 sequence for E. acervulina from chickens.

Reproductive characteristics of a precocious vaccine line (Rt3+15) of Eimeria tenella in embryonating chicken eggs

Coccidiosis of chickens, caused by species of Eimeria (Protozoa, Apicomplexa), is an intestinal disease of major economic importance worldwide. In the present study, the reproductive characteristics of a precocious line (designated E. tenella Rt3+15) from Australia were investigated in chicken embryos and the implications of the findings briefly discussed.

High-throughput capillary electrophoresis for the identification and differentiation of seven species ofEimeria from chickens

A capillary electrophoretic approach has been evaluated for the identification of seven currently recognised species of Eimeria infecting chickens. The second internal transcribed spacer of ribosomal DNA is PCR-amplified from any of the seven species using a single set of oligonucleotide primers (one of which is fluorescently labelled). The amplicons are heat-denatured and subjected to capillary electrophoresis in a MegaBACE 1000 (Amersham). The chromatograms captured are stored electronically and then analysed using MegaBACE Fragment Profiler software. Using control DNA samples representing monospecific lines of Eimeria, specific peaks in the chromatograms were defined for the unequivocal identification of each of the seven species and their differentiation. Electrophoretic reading and analysis are carried out automatically, thus making it a time- and cost-effective method. This procedure should find applicability as a tool for the quality control of Eimeria vaccines, the monitoring of coccidiosis outbreaks and the high-throughput analysis of oocyst samples for epidemiological surveys.

Giardia infection in farm animals

Giardia infection is prevalent in farm animals from an early age. Despite the wide occurrence of the infection and recent understanding of its epidemiology, many aspects of giardiasis of farm animals remain unclear. In this article, Lihua Xiao discusses the prevalence, patterns, sources and clinical importance of Giardia infection in a variety of farm animals.

Cryptosporidium and Giardia-zoonoses: fact or fiction?

Giardia and Cryptosporidium are enteric protozoan parasites that infect a wide range of vertebrate hosts. Both are transmitted either by direct faecal/oral contact or by the ingestion of contaminated food or water. The discovery of morphologically similar organisms infecting humans and a variety of mammals and birds has led to the proposal that both Cryptosporidium and Giardia are zoonotic (i.e. transmitted in nature between humans and animals). Transmission between humans and animals has been supported by cross-infection studies. However, closer examination of many of these studies reveals limitations in the methodologies utilised. More recent molecular genetic studies have demonstrated considerable genetic diversity among isolates of the same species of Giardia and Cryptosporidium, suggesting that these species are in fact species complexes and that some of these novel species may be host-specific. This paper will critically examine the evidence for the zoonotic transmission of these parasites.

Automated, fluorescence-based approach for the specific diagnosis of chicken coccidiosis

We have established a fluorescence-based electrophoretic approach for the specific identification of all seven currently recognised species of Eimeria infecting chickens. The second internal transcribed spacer (ITS-2) of ribosomal DNA is amplified by polymerase chain reaction (PCR) from any of the seven species using a single set of oligonucleotide primers (of which the reverse one is fluorescently labelled). The amplicons are heat-denatured, subjected to denaturing polyacrylamide gel electrophoresis in a 377 DNA sequencer (ABI). The chromatograms produced are stored electronically and then analysed using GeneScan 3.1 software. Using control DNA samples representing monospecific lines of Eimeria, regions in the chromatograms have been defined for the specific identification of each of the seven species, although some variation in the chromatograms (reflecting population variation) was detectable within two species. Electrophoretic reading and analysis is carried out automatically using a computer imaging system, thus making it a time- and cost-effective approach. It is well suited for high-throughput diagnostic screening of oocyst samples and should find applicability as a tool for prevalence studies, monitoring of coccidiosis outbreaks and the quality control of vaccines.

High-resolution electrophoretic procedures for the identification of five Eimeria species from chickens, and detection of population variation

To overcome limitations of conventional approaches for the identification of Eimeria species of chickens, we have established high resolution electrophoretic procedures using genetic markers in ribosomal DNA. The first and second internal transcribed spacer (ITS-1 and ITS-2) regions of ribosomal DNA were amplified by polymerase chain reaction (PCR) from genomic DNA samples representing five species of Eimeria (E. acervulina, E. brunetti, E. maxima, E. necatrix and E. tenella), denatured and then subjected to denaturing polyacrylamide gel electrophoresis (D-PAGE) or single-strand conformation polymorphism (SSCP) analysis. Differences in D-PAGE profiles for both the ITS-1 and ITS-2 fragments (combined with an apparent lack of variation within individual species) enabled the unequivocal identification of the five species, and SSCP allowed the detection of population variation between some isolates representing E. acervulina, which remained undetected by D-PAGE. The establishment of these approaches has important implications for controlling the purity of laboratory lines of Eimeria, for diagnosis and for studying the epidemiology of coccidiosis.

Single-strand restriction fragment length polymorphism analysis of the second internal transcribed spacer (ribosomal DNA) for six species of Eimeria from chickens in Australia

Species of Eimeria from chickens from Australia were characterised using a polymerase chain reaction-linked restriction fragment length polymorphism (PCR-RFLP) approach. The ribosomal DNA region spanning the second internal transcribed spacer (ITS-2) was amplified from genomic DNA by PCR, digested separately with three restriction endonucleases (CfoI, Sau3AI and TaqI) and the fragments separated by denaturing gel electrophoresis. The PCR products amplified from the six species varied from approximately 70 to 620 bp on agarose gels, with differences in size and number of bands among species, but no apparent variation within a species. The PCR-RFLP analysis of ITS-2 amplicons on denaturing gels gave characteristic profiles for individual species (except for minor variation in profiles within some species). The results indicate that ITS-2 contains useful genetic markers for the identification of six Eimeria species occurring in Australia.

Experimental giardiasis in goat kids

The clinical, pathological and parasitological features of giardiasis resulting from experimental inoculation with 3 x 10(6) Giardia cysts were studied in goat kids. All experimentally inoculated goat kids given Giardia cysts became infected. Three of the eight inoculated kids had decreased appetite, formless feces and become slightly depressed beginning 7 or 8 days post inoculation. The mean duration of the appearance of abnormal feces was 6 days. Irregular and intermitted cysts shedding started after prepatent periods of 6-10 days and lasted throughout this study (10 weeks). The evidence of high infectivity and fast transmission of Giardia were observed under standard zoohygienic conditions. The characteristics of intestinal lesions were similar to those found in other hosts infected with Giardia. The most severe lesions were seen in the duodenum and proximal jejunum, and consisted of moderate villus atrophy, villus blunting, crypt hyperplasia and inflammatory infiltration in the lamina propria. Scanning electron microscopy revealed ultrastructural alterations in the microvillus border of enterocytes. Mucosal smears and histological sections of the gall bladder displayed Giardia trophozoites and gall bladder epithelium hyperplasia together with bile ductular proliferation in the liver tissue in two kids.

Comparison of genetic groups determined by molecular and immunological analyses of Giardia isolated from animals and humans in Switzerland and Australia

Nine axenic isolates of Giardia originating from four different host species in Switzerland were subjected to genetic analysis using the polymerase chain reaction (PCR) to amplify segments of genes encoding different trophozoite variant surface proteins (VSPs). Three genotypes were identified on the basis of product yield, size, and restriction-fragment-length polymorphisms (RFLPs). Five G. duodenalis isolates (O1, B1, B2, B3-1A1 and C1--from a sheep, three calves and a dog, respectively) were classified as belonging to genetic group I of Andrews et al. (1989). DNA amplified from the VSP genes tsp11, tsa417 and vsp1267 of these isolates was indistinguishable in size and restriction characteristics from that amplified from group-I Giardia isolated from humans in Australia. One human-derived Swiss isolate (H2-17A1), typed as belonging to genetic group II, yielded a vsp1267-specific PCR product that was indistinguishable by size or restriction sites from the equivalent 1.6-kb product amplified from human-derived Australian group-II organisms. This isolate also yielded 1.8-kb tsp11 and 0.52-kb tsa417/tsp11-like PCR products possessing RFLPs typical of group-II organisms. Three isolates (O2-4A1, O3 and H3-15K2--originating from two sheep and a human, respectively) represent a novel genotype that is closely related to genetic groups I and II. These three isolates exhibited identical RFLPs in their tsp11 PCR products and failed to yield a vsp1267 PCR product. An antiserum specific for the 90-kDa VSP of the sheep-derived clone O2-4A1 reacted strongly by immunofluorescence and on Western blots with surface proteins from the O2, O3 and H3 isolates only--consistent with the genetic classification determined above. The data provide no evidence for the occurrence of host-specific genotypes.

Quantitation of Giardia cysts and Cryptosporidium oocysts in fecal samples by direct immunofluorescence assay

The lack of quick, simple, and sensitive quantitative tests has impeded studies on infection patterns and treatment of Giardia spp. and Cryptosporidium spp. A quantitative direct immunofluorescence assay (FA) using a commercial FA kit was developed and evaluated. Recovery rates of the FA for Cryptosporidium oocysts in calf feces seeded with 1,000, 10,000, 100,000, and 1,000,000 oocysts per g were 14.8, 40.8, 84.2, and 78.2%, respectively. Interassay coefficients of variation were 10.6 to 47.1%. Recovery rates of the FA for Giardia cysts in feces seeded with 1,000, 10,000, and 100,000 cysts per g were 76.4, 96.9, and 89.6%, respectively. Interassay coefficients of variation were 7.4 to 22.1%. By comparison, recovery rates of Giardia cyst by sucrose gradient flotation were only 20.5, 51.2, and 42.9%, respectively. Counts of cysts-per-gram obtained by sucrose gradient flotation with samples from calves, lambs, and ewes were only 49.1 to 54.8% of those obtained by the FA. Zinc sulfate flotation detected only 36.4% of infections when there were < or = 1,000 cysts per g. The quantitative FA offers a useful technique for epidemiological and control studies of these two parasites.

Molecular variation in Giardia

Molecular characterisation of species within the genus Giardia has revealed that much of the phenotypic heterogeneity, particularly within the species G. duodenalis, has a genetic basis. The source of this genetic variation appears to arise from predominantly asexual, clonal reproduction, although occasional bouts of sexual reproduction cannot be ruled out. Genetic variation is extensive with some clones widely distributed and others seemingly unique and localised to a particular endemic focus. Little attention has been given to the molecular epidemiology of Giardia infections. Future studies should be directed at studying the ecology and dynamics of transmission of Giardia clones, particularly in localised areas, and to evaluating the factors that serve to maintain genetic diversity between clones, especially the role of inter-clonal competition. Future research using molecular techniques should aim to identify and follow Giardia clones in nature and correlate genetic typing with important clinical and epidemiological characteristics such as virulence, drug sensitivity and zoonotic potential.

Comparative studies on the growth dynamics of two genetically distinct isolates of Giardia duodenalis in vitro

The in vitro growth behaviour of the intestinal protozoan Giardia duodenalis was studied in detail and comparisons were made between two genetically and biologically distinct cloned isolates. Replicates of each clone were grown at six different initial cell concentrations and in culture media at four different pH values. Significant differences in in vitro growth were found between the two isolates, BAH12 and P1. BAH12 had a specific narrow pH requirement, with satisfactory growth only obtained at pH 6. The mean generation time of BAH12 at pH 6 between days 1 and 3 was 10.8 h, compared to an average of 6 h for the same period for P1, both at pH 6 and pH 7. Comparative health of cultures was assessed during both the pH and growth experiments using a suite of six variables. Consistent changes in the health of cultures over time were found to reflect growth behaviour over time. These results provide the first detailed evidence that genetically different isolates of Giardia may differ in such fundamental biological parameters as growth rate and pH requirements. These differences may have important epidemiological and taxonomic implications.

Critical comparison of Giardia duodenalis from Australia and Switzerland using isoenzyme electrophoresis

Isoenzyme electrophoresis using 13 enzyme systems was applied to 31 Australian and 7 Swiss isolates of Giardia of human, cat, cattle, dog, sheep and rat origin. The Portland (ATCC No. 30888) reference strain was also included. The 39 isolates were divided into 22 different zymodemes. These consisted of 19 zymodemes containing the P1 and Australian isolates and three zymodemes containing Swiss isolates only. Differences in enzyme profiles between zymodemes was measured by euclidean distance and it was found that Australian isolates of Giardia exhibited more variation than the Swiss isolates. Relationships between zymodemes determined by clustering analysis are discussed with particular reference to the zoonotic potential of Giardia.

Immunohistochemical labeling of Giardia trophozoites spp. in formalin fixed paraffin embedded tissues

An immunoperoxidase method using rabbit anti human Giardia lamblia serum for the demonstration of giardia in paraffin embedded intestinal animal tissue is described. Specificity was tested against other protozoal parasites.

Growth, activities of enzymes in the small intestine, and ultrastructure of microvillous border in gerbils infected with Giardia duodenalis

The aim of this study was to assess and correlate changes in weight gain, food intake, small intestinal disaccharidase activities and microvillous border surface area over the course of a primary Giardia duodenalis infection in weanling Mongolian gerbils (Meriones unguiculatus). Weight gain in infected animals was significantly impaired between days 8 and 20 postinoculation when compared to age- and weight-matched controls. No difference in food intake was observed between groups. Trophozoite population in the small intestine was maximal on day 4 and 6 of infection, and colonization persisted in the duodenum throughout the experiment (30 days). In infected gerbils, mucosal sucrase and maltase activities were significantly depressed in the duodenum and jejunum on day 4 and in all areas of the small intestine by day 6. Eight and 25 days postinoculation, disaccharidase activities had recovered in the jejunum and distal small intestine but remained depressed in the duodenum, the area where trophozoite colonization persisted. Diffuse loss of microvillous border surface area was observed in the duodenum and jejunum after 6 days of infection. Eight days postinoculation, microvillus surface area had returned to normal in the jejunum, but not in the duodenum. Our findings demonstrate that acute giardiasis in weanling gerbils impairs weight gain, depresses disaccharidase activities, and diffusely reduces mucosal microvillous border surface area.(ABSTRACT TRUNCATED AT 250 WORDS)

New aspects of parasitic zoonoses

Selected parasitic zoonoses are discussed with emphasis on epidemiological, diagnostic and some chemotherapeutic aspects. Pneumocystosis, toxoplasmosis, cryptosporidiosis and microsporidiosis are briefly reviewed as "AIDS-related zoonoses". Up to now 5 genera of Microsporidia have been identified as causative agents of human infections, including Encephalitozoon cuniculi, Enterocytozoon bieneusi and Pleistophora sp. which were found in AIDS patients. From the many "other parasitic zoonoses", giardiasis, echinococcosis and taeniosis/cysticercosis are discussed as examples. Significant advances in the understanding of transmission dynamics, in strain characterisation and diagnosis of the diseases have been achieved.