Experimental giardiasis in goat kids

Prevalence and multilocus genotyping of Giardia duodenalis in Tan sheep (Ovis aries) in northwestern China

Giardia duodenalis is a common intestinal protozoa, which can cause the occurrence of diarrhea, weight loss, and even death in animals or human, this threatens the husbandry industry and public health. It can infect virtually humans and all domestic animals including sheep. Tan sheep is one of the most important sheep breeds, which is short-tailed indigenous sheep breed used for production of high quality meat and pelts in China. However, there are no report regarding the occurrence and multilocus genotyping of G. duodenalis in Tan sheep in northwestern China. Thus, the objective of the present study was to investigate the prevalence and multilocus genotypes of G. duodenalis in Tan sheep. 1014 fecal samples were collected from Tan sheep from Ningxia Hui Autonomous Region, and three loci (β-giardin (bg), glutamate dehydrogenase (gdh) and triosephosphate isomerase (tpi) genes) were amplified by nested PCR. The prevalence of G. duodenalis in Tan sheep was 14.5% (147/1014), two assemblages (assemblage A, n = 43; and E, n = 90) were detected, including one novel assemblage A at bg locus, one novel assemblage A at tpi locus, and 10 and 11 novel subtypes of assemblage E were detected at the bg and gdh loci, respectively. One MLGs was formed based on sequence variation among the three loci. Moreover, 9 Tan sheep were infected with two assemblages (A and E) based on the three loci. These findings expand the host range of G. duodenalis and revealed genetic diversity of G. duodenalis assemblages in Tan sheep.

Delayed development of the protective IL-17A response following a Giardia muris infection in neonatal mice

Giardia is an intestinal protozoan parasite that has the ability to infect a wide range of hosts, which can result in the clinical condition 'giardiasis'. Over the years, experimental research has shown the crucial involvement of IL-17A to steer the protective immune response against Giardia. The development of the protective response, as reflected by a significant drop in cyst secretion, typically takes around 3 to 4 weeks. However, early-life infections often have a more chronic character lasting for several weeks or months. Therefore, the aim of the current study was to investigate the dynamics of a Giardia muris infection and the subsequent host immune response in neonatal mice infected 4 days after birth. The outcome of the study showed that a G. muris infection in pre-weaned mice failed to trigger a protective IL-17A response, which could explain the prolonged course of infection in comparison to older mice. Only after weaning, a protective intestinal immune response started to develop, characterized by an upregulation of IL-17A and Mbl2 and the secretion of parasite-specific IgA.

The course of experimental giardiasis in Mongolian gerbil

Fifteen Mongolian gerbils were inoculated with 10 × 10⁶ viable trophozoites of Giardia intestinalis. Their faeces were examined daily by flotation method and the number of shed cysts was counted. Two animals (male and female) were euthanised at 4- to 5-day intervals (9, 14, 18 days post-infection (DPI)). The remaining nine gerbils were sacrificed and dissected at the end of the experiment (23 DPI). Their small intestinal tissues were processed for examination using histological sectioning and scanning electron microscopy and their complete blood count (CBC) was examined. The highest number of trophozoites at the total was observed in the duodenum in gerbils sacrificed on 14 DPI. Number of shed cysts was positively correlated with number of trophozoites rinsed from the intestine. Infected gerbils had lower body weight gain in comparison with control group and in three male gerbils; diarrhoea occurred during infection. Cyst shedding was negatively correlated with values of mean corpuscular haemoglobin concentration. Females showed another pattern in cyst shedding than males. This information needs to be taken into account while planning the experiments.

Prevalence and risk factors associated with Giardia duodenalis infection in dairy cattle of Chitwan, Nepal

Livestock farming has been an integral part of Nepalese agriculture systems since time immemorial. Giardia duodenalis is a cosmopolitan intestinal parasite present in a wide range of hosts. Very little or no information is reported on the prevalence of giardiasis in livestock of Nepal. This study was done during Jan 18 to July 19, 2014 to determine the prevalence and associated risk factors of Giardia duodenalis infection in dairy cattle of Chitwan, Nepal. A total of 96 fresh fecal samples were collected from various dairy pocket areas and were transferred to collection bottles with 10% formalin. Wet smears of the samples were prepared, stained with lugol's iodine and then viewed under microscope at 400× magnification. The overall prevalence was found to be 44.79% (43/96). Based on the risk factors assessment survey, age was found to be significantly associated with the prevalence of Giardia duodenalis. The prevalence was found significantly (P < 0.05) higher in 1-6 months age group compared to > 3 years. Similarly, higher prevalence was found in diarrheic animals compared to their counterparts (P < 0.05). Though higher prevalence was recorded in unhygienically housed animals, it was statistically non-significant (P < 0.05). Giardiasis should be considered as an important cause of diarrhea and further advanced diagnostic approaches should be employed for the confirmation of giardiasis in dairy cattle.

Immunological interaction between Giardia cyst extract and experimental toxoplasmosis

Toxoplasmosis is mostly associated with other intestinal parasitic infections especially Giardia due to shared mode of peroral infection. Toxoplasma and Giardia induce a strong T-helper 1- immune response. Our aim was to induce a protective immune response that results in significant impact on intestinal and extra-intestinal phases of Toxoplasma infection. This study was conducted in experimental animals and assessment of Giardia cyst extract effect on Toxoplasma infection was investigated by histopathological examination of small intestine and brain, Toxoplasma cyst count and iNOS staining of the brain, measurement of IFN-γ and TGF-β in intestinal tissues. Results showed that the brain Toxoplasma cyst number was decreased in mice infected with Toxoplasma then received Giardia cyst extract as compared to mice infected with Toxoplasma only. This effect was produced because Giardia cyst extract augmented the immune response to Toxoplasma infection as evidenced by severe inflammatory reaction in the intestinal and brain tissues, increased levels of IFN-γ and TGF-β in intestinal tissues and strong iNOS staining of the brain. In conclusion, Giardia cyst extract generated a protective response against T. gondii infection. Therefore, Giardia antigen will be a suitable candidate for further researches as an immunomodulatory agent against Toxoplasma infection.

Zoonotic Cryptosporidium and Giardia shedding by captured rangeland goats

Faecal shedding of Cryptosporidium and Giardia by captured rangeland goats was investigated using a longitudinal study with four faecal samples collected from 125 male goats once monthly for four months, commencing immediately after capture and transport to a commercial goat depot (feedlot). Goats were composite breed and aged approximately 9-12months on arrival. Faecal samples were screened for Cryptosporidium and Giardia presence and concentration using quantitative PCR and sequencing at the 18S ribosomal RNA locus (Cryptosporidium), and glutamate dehydrogenase and β-giardin loci (Giardia). Longitudinal prevalence for Cryptosporidium was 27.2% (point prevalence range 3-14%) with 3 species identified: C. xiaoi (longitudinal prevalence 13.6%), C. ubiquitum (6.4%) and C. parvum (3.2%). Sub-typing at the gp60 locus identified C. ubiquitum XIIa, C. parvum IIaA17G2R1 and C. parvum IIaA17G4R1. This is the first report of the zoonotic C. parvum subtype IIaA17G4R1 in goats. The pattern of genotypes shed in faeces changed over the duration of study with C. ubiquitum identified only at the first and second samplings, and C. parvum identified only at the fourth sampling. Longitudinal prevalence for Giardia duodenalis was 29.6% (point prevalence range 4-12%) with all positives sub-typed as assemblage E. Only 2/125 goats were identified to be shedding Cryptosporidium or Giardia on more than one occasion. This is the first report of Cryptosporidium and Giardia genotypes in captured rangeland goats. Faecal shedding of zoonotic Cryptosporidium spp. and potentially zoonotic G.duodenalis has implications for food safety and effluent management. Keywords: Cryptosporidium; Giardia; Rangeland goats; zoonotic.

Microarray analysis of the intestinal host response in Giardia duodenalis assemblage E infected calves

Despite Giardia duodenalis being one of the most commonly found intestinal pathogens in humans and animals, little is known about the host-parasite interactions in its natural hosts. Therefore, the objective of this study was to investigate the intestinal response in calves following a G. duodenalis infection, using a bovine high-density oligo microarray to analyze global gene expression in the small intestine. The resulting microarray data suggested a decrease in inflammation, immune response, and immune cell migration in infected animals. These findings were examined in more detail by histological analyses combined with quantitative real-time PCR on a panel of cytokines. The transcription levels of IL-6, IL-8, IL-13, IL-17, and IFN-γ showed a trend of being downregulated in the jejunum of infected animals compared to the negative controls,.No immune cell recruitment could be seen after infection, and no intestinal pathologies, such as villus shortening or increased levels of apoptosis. Possible regulators of this intestinal response are the nuclear peroxisome proliferator-activated receptors alpha (PPARα), and gamma (PPARγ) and the enzyme adenosine deaminase (ADA), all for which an upregulated expression was found in the microarray and qRT-PCR analyses.

Intestinal growth and pathology of Giardia duodenalis assemblage subtype A(I), A(II), B and E in the gerbil model

This study investigated the significance of the genetic differences between assemblages A, B and E on intestinal growth and virulence. Intestinal growth and virulence were studied in 2 laboratory (A(I): WB and B: GS/M-83-H7) and 6 field isolates of assemblage subtype A(I), A(II), B and E(III). Intestinal trophozoite burdens, body weight and faecal consistency were monitored until day 29 post-infection (p.i.), morphological (mucosal architecture and inflammation) and functional (disaccharidase and alkaline phosphatase enzyme activity) damage to the small intestine were evaluated on days 7 and 18 p.i. The assemblage subtypes A(I) and B were more infectious and produced higher trophozoite loads for a longer period compared to the subtypes A(II) and E(III). The body weight of infected gerbils was significantly reduced compared to uninfected controls, but did not differ between the assemblage subtypes. Consistent softening of the faeces was only observed with assemblage B. Assemblage B next to assemblage subtype A(I) elicited relatively higher pathogenicity, characterized by more extensive damage to mucosal architecture, decreased brush-border enzyme function and infiltration of inflammatory cells. Assemblage E(III) and A(II) isolates showed relatively low virulence. The Giardia assemblage subtypes exhibit different levels of growth and virulence in the gerbil model.

The effect of a fenbendazole treatment on cyst excretion and weight gain in calves experimentally infected with Giardia duodenalis

A total of 28 Holstein-Friesian calves were experimentally infected with 10(5)Giardia duodenalis cysts. Eleven days later, all animals were allocated into two groups of 14 animals each, based on the average pre-treatment cyst counts. Treatment was randomly assigned to one of the two groups, and all animals in the treatment group received a daily oral dosage of 15mg fenbendazole per kg bodyweight during 3 consecutive days. The calves in the control group received a placebo (water). From 3 days after treatment onwards, cyst excretion was determined three times a week during 4 consecutive weeks. The faecal consistency and general health were recorded on a daily basis, and all animals were weighed prior to treatment and weekly thereafter. At the end of the experimental period, there was a significant (P<0.001) reduction (98%) of the cumulative cyst excretion. There were no significant differences in general health between both groups, but faecal consistency was significantly lower (P<0.002) in the control group compared to the treatment group, although none of the animals displayed overt gastro-intestinal symptoms. Prior to treatment the weight did not differ between both experimental groups. At the end of the 4-week experimental period however, the animals in the treatment group gained on average 2.86kg (=102g per day) more than the animals in the control group (P<0.031). This study demonstrates for the first time a significant difference in weight gain between fenbendazole treated and untreated calves experimentally infected with G. duodenalis, although additional data need to confirm the need for treatment in natural conditions.

Is Giardia a significant pathogen in production animals?

Although Giardia duodenalis is recognised worldwide as the most important parasitic cause of gastro-intestinal disorder in human patients, the relevance of infection in production animals is prone to debate. Since the 1980s, clinical disease has been associated with giardiasis in production animals, both in natural conditions and in experimental studies. However, most Giardia research is focussed on the relevance of production animals as a reservoir for zoonotic transmission. In this study, the current knowledge on clinical relevance of giardiasis in production animals is reviewed, along with the diagnosis, treatment and control of infection. Furthermore, future research objectives are discussed.

Molecular and immunohistochemical detection of assemblage E, Giardia duodenalis in scouring North Dakota calves

Despite many reports on the shedding of Giardia parasites by scouring calves, the role of Giardia as a cause of calf diarrhea is still controversial. To elucidate the role of Giardia duodenalis in calf scours, diagnostic samples from 189 scouring calves were tested by different assays during a 1-year-study period. Giardia antigens were detected in 22/189 scouring calves by a fecal-based enzyme-linked immunosorbent assay and 10 of these were positive for assemblage E, G. duodenalis by polymerase chain reaction. Giardia trophozoites were demonstrated by immunohistochemistry in intestinal sections from five calves in which the parasites were spatially distributed in areas of microscopically detectable enteritis. Our data suggest that under certain circumstances, Giardia may cause intestinal lesions leading to calf scours. Gnotobiotic calf-based infectivity studies are needed if the pathogenicity of Giardia in calves is to be definitively determined.

The public health and clinical significance of Giardia and Cryptosporidium in domestic animals

Giardia and Cryptosporidium are common enteric parasites of domestic animals, particularly dogs, cats and livestock. Their occurrence is of potential significance from both clinical and public health perspectives yet, until recently, confusion over the taxonomy of these organisms prevented a clear understanding of the epidemiology of infections with both Giardia and Cryptosporidium. The recent application of molecular epidemiological tools has helped to resolve taxonomic issues, allowing cycles of transmission to be determined. In addition, advances have been made in elucidating mechanisms associated with pathogenesis, whereas only limited progress has been achieved in the areas of chemotherapy and prophylaxis.

Giardiasis and cryptosporidiosis in ruminants

Although they differ considerably with respect to their biology, both Giardia duodenalis and Cryptosporidium parvum are common in ruminants, whereas Cryptosporidium andersoni is not. G. duodenalis infections are acquired during the first few months of life, tend to be chronic, and may be a production-limiting disease of ruminants. C. parvum infections remain an important cause of diarrhea in neonatal ruminants. Abomasal cryptosporidiosis, caused by C. andersoni, is an emerging disease of cattle that may affect both beef and dairy herds. This article reviews the life cycles, production impacts, treatments, controls, and zoonotic potentials of these important ruminant parasites.

Recent insights into the mucosal reactions associated with Giardia lamblia infections

Giardia lamblia is an intestinal protozoan parasite infecting humans and various other mammalian hosts. The most important clinical signs of giardiasis are diarrhoea and malabsorption. Giardia lamblia is able to undergo continuous antigenic variation of its major surface antigen, named VSP (variant surface protein). While intestinal antibodies, and more specifically anti-VSP IgA antibodies, were proven to be involved in modulating antigenic variation of the parasite the participation of the local antibody response in control of the parasite infection is still controversial. Conversely, previous studies based on experimental infections in mice showed that cellular immune mechanisms are essential for elimination of the parasite from its intestinal habitat. Furthermore, recent data indicated that inflammatory mast cells have a potential to directly, or indirectly, interfere in duodenal growth of G. lamblia trophozoites. However, this finding was challenged by other reports, which did not find a correlation between intestinal inflammation and resistance to infection. Since intestinal infiltration of inflammatory cells and/or CD8+T-cells were demonstrated to coincide with villus-shortening and crypt hyperplasia immunological reactions were considered to be a potential factor of pathogenesis in giardiasis. The contribution of physiological factors to pathogenesis was essentially assessed in vitro by co-cultivation of G. lamblia trophozoites with epithelial cell lines. By using this in vitro model, molecular (through surface lectins) and mechanical (through ventral disk) adhesion of trophozoites to the epithelium was shown to be crucial for increased epithelial permeability. This phenomenon as well as other Giardia-induced intestinal abnormalities such as loss of intestinal brush border surface area, villus flattening, inhibition of disaccharidase activities, and eventually also overgrowth of the enteric bacterial flora seem to be involved in the pathophysiology of giardiasis. However, it remains to be elucidated whether at least part of these pathological effects are causatively linked to the clinical manifestation of the disease.

Immunopathology of giardiasis: the role of lymphocytes in intestinal epithelial injury and malfunction

T lymphocyte-mediated pathogenesis is common to a variety of enteropathies, including giardiasis, cryptosporidiosis, bacterial enteritis, celiac's disease, food anaphylaxis, and Crohn's disease. In giardiasis as well as in these other disorders, a diffuse loss of microvillous brush border, combined or not with villus atrophy, is responsible for disaccharidase insufficiencies and malabsorption of electrolytes, nutrients, and water, which ultimately cause diarrheal symptoms. Other mucosal changes may include crypt hyperplasia and increased infiltration of intra-epithelial lymphocytes. Recent studies using models of giardiasis have shed new light on the immune regulation of these abnormalities. Indeed, experiments using an athymic mouse model of infection have found that these epithelial injuries were T cell-dependent. Findings from further research indicate that that the loss of brush border surface area, reduced disaccharidase activities, and increase crypt-villus ratios are mediated by CD8+ T cells, whereas both CD8+ and CD4+ small mesenteric lymph node T cells regulate the influx of intra-epithelial lymphocytes. Future investigations need to characterize the CD8+ T cell signaling cascades that ultimately lead to epithelial injury and malfunction in giardiasis and other malabsorptive disorders of the intestine.

Giardia duodenalis trophozoites isolated from a parrot (Cacatua galerita) colonize the small intestinal tracts of domestic kittens and lambs

This study examines the ability of Giardia duodenalis trophozoites, isolated from a wild bird, to colonize the intestinal tracts of companion animals (kittens) and domestic ruminants (lambs). Trophozoites colonized the intestinal tracts of intraduodenally inoculated animals as demonstrated by increasing parasite burdens within the duodenum and jejunum and by fecal passage of cysts within 4 days post-inoculation. The pathogenesis of the trophozoites was further investigated in kittens. In these animals, infection significantly reduced jejunal brush border microvillous length and density, which resulted in a loss of overall epithelial brush border surface area. This injury was associated with the production of diarrhea in four of five infected kittens. These findings indicate that some bird species may carry G. duodenalis that represent a possible health threat to companion animals and livestock. Our results describe the first successful colonization of avian-derived G. duodenalis trophozoites in the small intestines of domestic kittens and lambs.

Giardiasis in dairy calves: effects of fenbendazole treatment on intestinal structure and function

Twelve Giardia duodenalis-infected Holstein dairy calves were allocated into a treatment (n=6) and placebo group (n=6) according to pre-study faecal cyst counts. Calves in the treatment group received an oral dose of 5 mg/kg fenbendazole once daily for 3 days, while placebo calves received a sterile saline solution. Calves were euthanised 7 days following the initiation of treatment and intestinal were collected and prepared for trophozoite quantitation, histology, electron microscopy, and disaccharidase assays. In all calves treated with fenbendazole, intestinal trophozoites were below detection limits, while in saline-treated calves, trophozoites were observed in all intestinal segments. Histologically, no significant difference was observed between treatment groups with respect to intestinal villus height or crypt depth. However, a significant decline in the number of intraepithelial lymphocytes (IEL) was observed in fenbendazole-treated calves when compared with placebo-treated calves in the duodenum (13.9+/-1.2 vs. 17.0+/-1.1 IEL/100 enterocytes) and jejunum (21.6+/-0.8 vs. 30.7+/-1.0 IEL/100 enterocytes). In addition, measurements from TEM micrographs demonstrated a significant increase in microvillus surface area in the jejunum of fenbendazole-treated calves compared with saline-treated calves (31.2+/-10.2 vs. 22.8+/-7.6 microm(2)). This increase in microvillus surface area was also associated with an increase in jejunal maltase activity in fenbendazole-treated calves compared with calves treated with saline. These results demonstrate that fenbendazole is an effective treatment for giardiasis in calves. fenbendazole treatment eliminated Giardia trophozoites from the small intestine of calves resulting in increased microvillus surface area and greater intestinal enzyme activity. This study also demonstrates that the pathogenesis of giardiasis in calves is similar to that observed in humans and laboratory animals, and provides further evidence that Giardia is a pathogen of cattle with potential economic importance.