Performance of microscopy and ELISA for diagnosing Giardia duodenalis infection in different pediatric groups

Infectious etiology and indicators of malabsorption or intestinal injury in childhood diarrhea

INTRODUCTION

The multifactorial etiology of gastroenteritis emphasizes the need for different laboratory methods to identify or exclude infectious agents and evaluate the severity of diarrheal disease.

OBJECTIVE

To diagnose the infectious etiology in diarrheic children and to evaluate some fecal markers associated with intestinal integrity.

MATERIALS AND METHODS

The study group comprised 45 children with diarrheal disease, tested for enteropathogens and malabsorption markers, and 76 children whose feces were used for fat evaluation by the traditional and acid steatocrit tests.

RESULTS

We observed acute diarrhea in 80% of the children and persistent diarrhea in 20%. Of the diarrheic individuals analyzed, 40% were positive for enteropathogens, with rotavirus (13.3%) and Giardia duodenalis (11.1%) the most frequently diagnosed. Among the infected patients, occult blood was more evident in those carrying pathogenic bacteria (40%) and enteroviruses (40%), while steatorrhea was observed in infections by the protozoa G. duodenalis (35.7%). Children with diarrhea excreted significantly more lipids in feces than non-diarrheic children, as determined by the traditional (p<0.0003) and acid steatocrit (p<0.0001) methods. Moreover, the acid steatocrit method detected 16.7% more fecal fat than the traditional method.

CONCLUSIONS

Childhood diarrhea can lead to increasingly severe nutrient deficiencies. Steatorrhea is the hallmark of malabsorption, and a stool test, such as the acid steatocrit, can be routinely used as a laboratory tool for the semi-quantitative evaluation of fat malabsorption in diarrheic children.

Detection of IgG Anti-Giardia duodenalis Antibodies in Sera by Indirect Immunofluorescence and Western Blotting Assays

INTRODUCTION

Serological assays are alternative laboratory tools for the diagnosis of parasitic infections. The aim of this work was to evaluate the performance of the indirect fluorescent antibody test (IFAT) and Western blotting (WB) for the detection of IgG anti-Giardia antibodies in human sera.

METHODOLOGY

Sera from individuals infected with Giardia duodenalis, other parasites or non-parasitized were selected for serological assays. Ninety-seven sera were tested by IFAT at 1:20 and 1:40 dilutions and of these, 40 samples were also analyzed by WB.

RESULTS

The sensitivity and specificity of the IFAT was 97% and 46.9% at 1:20 sera dilution, and 39.4% and 59.4% at 1:40 sera dilution. The low molecular weight polypeptides fractions of 25 kDa, 27-31 kDa and 45-55 kDa were the most frequently identified by the sera of individuals infected with G. duodenalis, along with low cross-reactivity, presenting an individual sensitivity of 42.8%, 50.0% and 57.1%, and specificity of 83.3%, 83.3% and 91.7%, respectively. The highest overall sensitivity of WB (85.7%) was based on the immunoreactivity of sera with at least one of those proteins. The concordance between the detection of G. duodenalis in feces by microscopy and the WB results was considered substantial (Kappa = 0.61).

CONCLUSION

Constant exposure to Giardia infection throughout a lifetime can maintain high levels of specific antibodies in serum, even without active infection. Moreover, proteins found in intestinal amoebas may hinder the serological diagnosis of giardiasis in endemic areas due to cross-reactivity, which can be partially solved using Giardia low molecular weight proteins.

Systematic Review of Diagnostic Approaches for Human Giardiasis: Unveiling Optimal Strategies

Giardiasis, caused by the protozoan Giardia intestinalis, affects around 400 million people worldwide, emphasizing the critical need for accurate diagnosis to enhance human health, especially in children. Prolonged giardiasis in childhood can lead to intellectual deficits and other complications. A variety of diagnostic tools, including microscopic, immunological, and molecular methods, are available for detecting G. intestinalis infection. Choosing the most suitable method can be challenging due to the abundance of options. This systematic review assesses the reliability and applicability of these diagnostic modalities. Utilizing the Dimensions and Wordart platforms for data analysis, we focus on relevant literature addressing diagnostic methods for human giardiasis. Microscopic techniques, particularly Ritchie's method, emerge as the primary choice, followed by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). PCR's limited use is attributed to its high cost and infrastructure challenges in developing nations. In conclusion, our analysis supports microscopic methods as the gold standard for giardiasis diagnosis. However, in cases where symptoms persist despite a negative diagnosis, employing more sensitive diagnostic approaches is advisable.

Parasitic infections in hematopoietic stem cell transplant recipients

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) is a vital treatment for various hematological disorders. However, HSCT recipients face increased risks of infectious complications due to immunosuppression. Parasitic infections are a significant concern in this vulnerable population and can lead to substantial morbidity and mortality. This review examines parasitic infections in HSCT recipients, focusing on major infections affecting different organ systems, including intestinal parasites (Giardia spp., Entamoeba histolytica, and Cryptosporidium spp.), hematologic parasites (Plasmodium spp. and Babesia spp.), and tissue/visceral parasites (Toxoplasma gondii, Leishmania spp., and Trypanosoma cruzi).

METHODS

A systematic search of relevant literature was conducted and included studies up to August 2023. Databases included PubMed, Google Scholar, were queried using specific keywords related to parasitic infections in HSCT patients. The epidemiology, risk factors, clinical presentation, diagnostic methods, and treatment approaches for each infection were evaluated.

RESULTS AND CONCLUSION

Knowing the epidemiology, risk factors, and clinical presentations are crucial for timely intervention and successful management. By emphasizing early detection, effective therapies, and the unique challenges posed by each of these infections, this review highlights the importance of tailored strategies for HSCT recipients. Future research can further refine management protocols to enhance care and outcomes for these patients.

Giardia duodenalis and dysentery in Iron Age Jerusalem (7th-6th century BCE)

The aim of this study was to determine if the protozoa that cause dysentery might have been present in Jerusalem, the capital of the Kingdom of Judah, during the Iron Age. Sediments from 2 latrines pertaining to this time period were obtained, 1 dating from the 7th century BCE and another from the 7th to early 6th century BCE. Microscopic investigations have previously shown that the users were infected by whipworm (Trichuris trichiura), roundworm (Ascaris lumbricoides), Taenia sp. tapeworm and pinworm (Enterobius vermicularis). However, the protozoa that cause dysentery are fragile and do not survive well in ancient samples in a form recognizable using light microscopy. Enzyme-linked immunosorbent assay kits designed to detect the antigens of Entamoeba histolytica, Cryptosporidium sp. and Giardia duodenalis were used. Results for Entamoeba and Cryptosporidium were negative, while Giardia was positive for both latrine sediments when the analysis was repeated three times. This provides our first microbiological evidence for infective diarrhoeal illnesses that would have affected the populations of the ancient near east. When we integrate descriptions from 2nd and 1st millennium BCE Mesopotamian medical texts, it seems likely that outbreaks of dysentery due to giardiasis may have caused ill health throughout early towns across the region.

Meta-analysis of the prevalence of Giardia duodenalis in sheep and goats in China

Giardia duodenum (G. duodenalis) can cause giardiasis and infect a variety of hosts. So far, there have been no detailed data regarding the positive rate of G. duodenalis in sheep and goats in China. Here, a systematic literature review was carried out to investigate the epidemiology of G. duodenalis in sheep and goats in China. To perform the meta-analysis, the databases CNKI, VIP, WanFang, PubMed, Web of science and ScienceDirect were employed for screening studies related to the prevalence of G. duodenalis in sheep and goats in China. The total prevalence of G. duodenalis in sheep and goats was estimated to be 7.00% (95% CI: 4.00-10.00). In the age subgroup, the prevalence of G. duodenalis in sheep and goats of >12 months (11.29%; 95% CI: 8.08-14.97) was higher than that in sheep and goats of ≤12 months (7.57%; 95% CI: 3.95-12.24). An analysis based on seasons showed that the prevalence of G. duodenalis in sheep and goats was higher in summer (11.90%; 95% CI: 0.50-35.05) than that in other seasons. The prevalence of G. duodenalis in sheep and goats after 2016 was 8.57% (95% CI: 5.34-11.79), which was higher than others. The highest prevalence of G. duodenalis in sheep and goats was 13.06% (95% CI: 6.26-19.86) recorded in Southwestern China. The prevalence of Giardia infection in sheep (7.28%; 95% CI: 2.30-14.73) was higher than that in goats (5.43%; 95% CI: 2.73-8.98). The NOAA's National Center for Environmental Information (https://gis.ncdc.noaa.gov/maps/ncei/cdo/monthly) was used to extract relevant geoclimatic data (latitude, longitude, elevation, temperature, precipitation, humidity, and climate). By analyzing the data of each subgroup, it was shown that region, genetype, and climate were potential risk factors for giardiasis prevalence in sheep and goats. Based on the analysis of common factors and geographical factors, it is recommended to strengthen effective management measures (e.g. ventilation and disinfection in warm and humid areas) and formulate relevant policies according to local conditions. Breeders should strengthen the detection of G. duodenalis in sheep and goats, customize corresponding control measures according to the diet and living habits of sheep and goats, and strengthen the protection of sheep and lamb calves, so as to reduce the incidence rate and reduce the economic loss of China's animal husbandry.

Meta-Analysis of the Prevalence of Giardia duodenalis in Cattle in China

Giardia duodenum (G. duodenalis) can cause giardiasis and infect a variety of hosts. So far, there have been no detailed data regarding the positive rate of G. duodenalis in cattle in China. Here, a systematic literature review was carried out to investigate the epidemiology of bovine G. duodenalis in China. To perform the meta-analysis, the databases China National Knowledge Infrastructure, VIP Chinese Journal Databases, WanFang Databases, PubMed, and ScienceDirect were employed for screening studies related to the prevalence of G. duodenalis in cattle in China. The total prevalence of G. duodenalis in cattle was estimated to be 8.00% (95% confidence interval [CI]: 5.51-11.62). In the age subgroup, the prevalence of G. duodenalis in calves (11.72%; 95% CI: 7.75-17.73) was significantly higher than that in cattle of other age groups. An analysis based on seasons showed that the prevalence of G. duodenalis in cattle was higher in summer (9.69%; 95% CI: 2.66-35.30) than that in other seasons. The prevalence of G. duodenalis in cattle in 2016 or later was 11.62% (95% CI: 6.49-20.79), which was significantly higher than that before 2016 (3.65%; 95% CI: 2.17-6.12). The highest prevalence of G. duodenalis in cattle was 74.23% (95% CI: 69.76-78.45) recorded in South China. The NOAA's National Center for Environmental Information (https://gis.ncdc.noaa.gov/maps/ncei/cdo/monthly) was used to extract relevant geoclimatic data (latitude, longitude, elevation, temperature, precipitation, humidity, and climate). By analyzing the data of each subgroup, it was shown that age of cattle, sampling year, province, region, temperature, and climate were potential risk factors for giardiasis prevalence in cattle. Based on the analysis of common factors and geographical factors, it is recommended to strengthen effective management measures (e.g., ventilation and disinfection in warm and humid areas) and formulate relevant policies according to local conditions. Breeders should pay more attention to the detection of G. duodenalis in calves, to prevent giardiasis prevalence in cattle of different ages, thereby reducing the economic losses of animal husbandry in China.

Role of anti-Giardia recombinant cyst wall protein IgG polyclonal antibodies in diagnosis and protection

Giardia duodenalis (G. duodenalis) is an infectious protozoan that has a global distribution especially in the hot climate. Around 200 million people are infected worldwide annually by Giardia, but infection is not always accompanied by symptoms, especially in endemic countries. Using traditional microscopy techniques in diagnosis, both in stool and water samples were less sensitive when compared to immunological methods; and the need for new diagnostic methods was necessary. Also, protection from infection is required in endemic areas. Therefore, the study aimed to produce anti- G. duodenalis IgG polyclonal antibodies (pAbs) by immunizing rabbit by G. duodenalis cyst recombinant protein. The produced antibodies were evaluated in the detection of G. duodenalis antigens in patients' stool and water samples from endemic areas across River Nile; where pAbs were used as a coating and a peroxidase conjugate antibody in sandwich ELISA. Moreover, pAbs were tested for the protection of mice from giardiasis. Sandwich ELISA using pAb has succeeded in the detection of G. duodenalis coproantigens in stool samples by a sensitivity of 97% and a specificity of 92.72%. Moreover, G. duodenalis cyst was detected in only seven water samples by ordinary microscopy; while sandwich ELISA revealed nineteen positive results. IgG pAb (1/200 µg/ml) protected mice from giardiasis; which was evident from the reduction in cysts and trophozoites numbers. We recommended the use of sandwich ELISA to monitor water quality, investigate environmental contamination and diagnosis in patients' stools. The pAbs can be prepared in large amount and used in field diagnosis and protection. This will help in the early diagnosis of G. duodenalis in water, which in turn can control outbreaks in rural areas.

Cryptosporidium diagnosis in different groups of children and characterization of parasite species

Background:

Microscopy and enzyme-linked immunosorbent assay (ELISA) are routinely used for Cryptosporidium diagnosis, without differentiating the parasite species.

Methods:

Children’s feces were analyzed by modified Ziehl-Neelsen (mZN) and ELISA for Cryptosporidium diagnosis and by polymerase chain reaction-restriction fragment length polymorphism for species identification.

Results:

Cryptosporidium frequency was 2.6%. The sensitivity and specificity of ELISA were 85.7% and 99.7%, respectively, with excellent concordance with mZN (kappa=0.854). Parasite species were characterized as Cryptosporidium hominis (78.3%), Cryptosporidium felis (17.4%), and Cryptosporidium parvum (4.3%).

Conclusions:

Coproantigen ELISA is as efficient as mZN for Cryptosporidium diagnosis. Cryptosporidium genotyping suggests anthroponotic and zoonotic transmission to children.

Global epidemiology of Giardia duodenalis infection in cancer patients: a systematic review and meta-analysis

Background

Application of chemotherapeutics in cancer patients may provide an immunosuppressive milieu, favourable for parasitic infections. Giardia duodenalis is an important zoonotic intestinal parasite responsible for diarrhoea in humans worldwide.

Methods

The present systematic review and meta-analysis was conducted to estimate the prevalence of G. duodenalis and respective odds ratios (ORs) in cancer patients around the globe. Four online databases—PubMed, Scopus, Web of Science and Google Scholar—were carefully explored for relevant literature without time limitation until 28 November 2020. Meta-analysis was done based on a random effects model to pool the estimations and define 95% confidence intervals (CIs).

Results

The overall weighted prevalence of G. duodenalis infection in cancer patients was calculated to be 6.9% (95% CI 0.5 to 9.3) globally, based on data from 32 studies. Although not statistically significant, eight case–control studies revealed that cancer patients were 1.24 times (95% CI 0.66 to 2.31; p=0.501) more exposed to G. duodenalis infection than healthy controls. Moreover, the prevalence of infection was not significantly associated with quantitative variables, including publication year (regression coefficient −0.0135, p=0.578), sample size (regression coefficient −0.0007, p=0.074) and human development index (regression coefficient −1.6263, p=0.419). Also, subgroup analysis of the pooled G. duodenalis infection was performed for publication year, World Health Organization regions, countries, continents, cancer types and country income.

Conclusions

Altogether, the epidemiology of G. duodenalis infection and its associated risk factors in immunocompromised individuals, especially cancer patients, is still open to question and deserves comprehensive investigations.

Prevalence of intestinal parasites in children from public preschool in the Triple Border Brazil, Argentina, and Paraguay

Introduction: The prevalence of parasitosis in children from Brazilian border cities is unknown. Objective: To identify the prevalence of intestinal parasites in children from public pre-school on the Brazilian border and their socioeconomic and health profile. Methods: Fecal samples were obtained from 178 children from public early childhood educational center (CMEI) in Brazilian border municipalities in Foz do Iguaçu, Brazil. Samples were processed by Hoffman sedimentation and zinc sulfate centrifugation and flotation methods. A questionnaire was administered to children´s parents or guardians regarding parasitic diseases, socioeconomic status, and sanitary habits. Results: The prevalence of intestinal parasites was 26.9% (n=48). A high prevalence of Giardia duodenalis was found (16.3%), followed by Endolimax nana (8.4%), Enterobius vermiculares (1.7%), Ascaris lumbricoides, and Entamoeba coli (0.5%). Forty-seven children (26.4%) presented monoparasitism. The percentage of parasitosis was significantly higher among male children (33.7% - p<0.036) who exhibited weight loss (50.0%), were from low-income families (35.4%- p=0.05), and had mothers with a low education (54.0%-p=0.0001). The highest percentage of Giardia was in children who exhibited weight loss (42.9% - p<0.05) and had mothers with low education (35.0%- p=0.0001). Multivariate analysis indicated that in the variable gender (male gender), weight loss and low maternal education contributed to the variability of parasitosis in children from the surveyed MCEC. Conclusion: The higher prevalence of Giardia was due to child and family variables. The detection of Enterobius vermiculares and Ascaris lumbricoides, despite the low frequency, indicates the need for better basic sanitation policies.   Keywords: child; parasites; prevalence; border areas; giardiasis.

Specific IgG and IgA Antibody Reactivities in Sera of Children by Enzyme-Linked Immunoassay and Comparison With Giardia duodenalis Diagnosis in Feces

Background

Giardia duodenalis is conventionally diagnosed in fecal samples using parasitological methods. However, sensitivity is poor when only a single sample is analyzed, due to intermittent excretion of cysts in feces. Alternatively, the serum antibodies to G. duodenalis can be used for parasite diagnosis and epidemiological studies to determine previous exposure. We compared the rate of G. duodenalis infection between serum anti-Giardia IgG and IgA antibodies and fecal examination in Brazilian children.

Methods

Fecal and serum samples were tested from 287 children at a clinical laboratory and from 187 children at daycare centers. Fecal samples were processed using conventional parasitological methods and coproantigen detection for Giardia diagnosis. Serum samples were tested using an in-house ELISA for detection of anti-Giardia IgG and IgA.

Results

G. duodenalis was found in 8.2% (N=39) of the 474 children analyzed. The sensitivity and specificity of ELISA were 80.0% and 90.0% for IgG and 80.0% and 83.3% for IgA, respectively. The total positivity rate of anti-Giardia IgG and IgA in the sera was 13.9% (N=66) and 23.6% (N=112). The agreement between the positivity of specific antibodies and the detection of G. duodenalis in feces was moderate for ELISA-IgG, kappa index (95% CI)=0.543 (0.422–0.664), and mild for ELISA-IgA, kappa index (95% CI)=0.283 (0.162–0.404). Among the children infected with other enteroparasites, 11.6% (N=10) and 24.4% (N=21) showed reactivity to anti-Giardia IgG and to IgA, respectively. This cross-reactivity was more frequent in samples from children infected with Endolimax nana and Entamoeba coli.

Conclusions

The higher frequency of specific antibody reactivity compared with G. duodenalis diagnosis in feces could reflect continuous exposure of children to G. duodenalis infection, resulting in long-lasting immunological memory and/or cross-reactivity with other intestinal amoebas.

Intestinal Schistosomiasis and Giardiasis Co-Infection in Sub-Saharan Africa: Can a One Health Approach Improve Control of Each Waterborne Parasite Simultaneously?

Both intestinal schistosomiasis and giardiasis are co-endemic throughout many areas of sub-Saharan Africa, significantly impacting the health of millions of children in endemic areas. While giardiasis is not considered a neglected tropical disease (NTD), intestinal schistosomiasis is formally grouped under the NTD umbrella and receives significant advocacy and financial support for large-scale control. Although there are differences in the epidemiology between these two diseases, there are also key similarities that might be exploited within potential integrated control strategies permitting tandem interventions. In this review, we highlight these similarities and discuss opportunities for integrated control of giardiasis in low and middle-income countries where intestinal schistosomiasis is co-endemic. By applying new, advanced methods of disease surveillance, and by improving the provision of water, sanitation and hygiene (WASH) initiatives, (co)infection with intestinal schistosomiasis and/or giardiasis could not only be more effectively controlled but also better understood. In this light, we appraise the suitability of a One Health approach targeting both intestinal schistosomiasis and giardiasis, for if adopted more broadly, transmission of both diseases could be reduced to gain improvements in health and wellbeing.

Giardia lamblia mimicking acute graft versus host disease after allogeneic hematopoietic stem cell transplantation: A case report

RATIONALE

As the major complications post allogeneic hematopoietic stem cell transplantation (allo-HSCT), gastrointestinal disorders were most commonly ascribed to acute graft-versus-host disease (aGVHD) and opportunistic infections. Though Giardia lamblia (G lamblia) is the most common waterborne parasite of intestinal infection worldwide, seldom has it been reported in a patient with acute severe aplastic anemia after allo-HSCT.

PATIENT CONCERNS

A 23-year-old male with severe aplastic anemia developed diarrhea, abdominal cramps, bloating, nausea, vomiting, fever, weight loss, and fatigue after allo-HSCT.

DIAGNOSIS

Stool examinations for ova and parasites showed Giardia trophozoites and cysts.

INTERVENTIONS

Methylprednisolone was stopped and the patient was intravenously treated with a 7-day course of metronidazole (500 mg, tid.). Simultaneously, cyclosporine (5 mg/kg) was continually utilized for suspicious gut GVHD.

OUTCOMES

The Giardia lamblia in stool turned negative and his symptoms were resolved after the 7-day course.

LESSONS

Incorporating non-invasive monitoring of stool examination for ova and parasites in the follow-up algorithm for post-HSCT patients can expedite clinical decision-making in the differential diagnoses for aGVHD even in the non-endemic area. Metronidazole therapy can be well-tolerated in HSCT patients with giardiasis.

Association between Cryptosporidium infection and cancer: A systematic review and meta-analysis

The link between cryptosporidiosis and cancer has been suggested by some epidemiological studies. This systematic review and meta-analysis was conducted to further understand this relationship. In the current study, six electronic databases were reviewed for Cryptosporidium infection in cancer patients. We used random effects model and 95% confidence intervals (CI) to determine the overall odds ratio (OR). Heterogeneity was calculated with Cochran's Q test and I²statistic. In total, 19 studies involving 3562 individuals with case-control (nine) and cross-sectional (ten) designs were included in our project. The pooled overall random effect favored a statistically significant increased risk of Cryptosporidium infection in cancer patients compared with non-cancer individuals [OR = 3.3; 95% CI: 2.18-4.98]. The overall heterogeneity was medium (χ² = 25.77; I² = 30.2%, P = .11). The pooled ORs in case-control and cross-sectional studies were [OR = 5.60; 95% CI: 3.43-9.13; χ² = 5.51; I² = 0.00%, P = .70] and [OR = 2.08; 95% CI: 1.18-3.67; χ² = 13.69; I² = 34.3, P = .13], respectively. T-value and P-value were 0.54 and 0.57 based on the results of Harbord's modified's regression test. In summary, this meta-analysis demonstrates that Cryptosporidium infection is associated with cancer. Also, it found that study design and year of publication are the specific sources of heterogeneity. Further studies should be carried out to investigate the impact of Cryptosporidium infection in the onset or development of cancer in the future.

A Cross-Sectional Study of Entamoeba histolytica/dispar/moshkovskii Complex in Salvador, Bahia, Brazil

Epidemiological studies on species-specific Entamoeba infections are scarce due to the morphological similarity of pathogenic Entamoeba histolytica and nonpathogenic E. dispar and E. moshkovskii. The diagnosis of E. histolytica is frequently based on coproantigen (E. histolytica-Gal/GalNAc lectin specific) detection by immunoassays. However, specific E. histolytica-lectin is not expressed in cysts, which are eliminated by asymptomatic individuals leading to false-negative results and an underestimation of amebiasis prevalence. Molecular techniques based on the amplification of parasite DNA have been shown to be a highly sensitive and specific method that allows the detection of different Entamoeba species. This study aimed to assess the frequency of the species from E. histolytica/dispar/moshkovskii complex by molecular and immunological techniques in individuals attended at a public health system in Salvador-Bahia, Brazil. A cross-sectional study involving 55,218 individuals was carried out. The diagnosis was based on microscopy revealing E. histolytica/dispar/moshkovskii complex. The species differentiation was performed by E. histolytica-specific antigen, serological evaluation and by molecular technique. The overall prevalence of E. histolytica/dispar/moshkovskii complex determined by microscopy was approximately 0.49% (273/55,218). E. histolytica-specific antigen detection and molecular characterization returned 100% negativity for E. histolytica. However, serological evaluation returned an 8.9% positivity (8/90). In the stool samples analysed by PCR, it was not possible to identify E. histolytica and E. moshkovskii, although circulating IgG anti-E. histolytica has been detected.

Assessment of the diagnostic performance of four methods for the detection of Giardia duodenalis in fecal samples from human, canine and feline carriers

Enteric parasitic diseases including giardiasis are of public health concern. Different methods are available for the diagnosis of this parasitic infection in fecal samples such as the identification of protozoan cysts and trophozoites by light microscopy, detection of specific antigens by ELISA, and amplification of DNA fragments by PCR. The present study aimed at assessing the performance of four laboratory tests for the detection of Giardia duodenalis in fecal specimens from three different host species with a previous diagnosis of giardiasis; canine, feline and human patients provided new stool samples to be retested for Giardia before initiating treatment with antiprotozoal drugs. For this purpose, triplicate fecal specimens from 54 humans, 24 dogs and 18 cats living in the city of Niterói, RJ, southeast Brazil, were analysed by light microscopy, ELISA, immunochromatography, and nested PCR. The centrifugal-flotation method detected Giardia cysts in 89.6% (86/96) of the fecal samples. The protozoan parasite was detected via immunochromatography in 87.5% (84/96) of these samples. Giardia was detected by ELISA in 69.8% (67/96) of the stool specimens from carriers with a previous diagnosis of Giardia infection. Giardia was detected by PCR in only 39.6% (38/96) of the fecal specimens. Based on these findings, we suggest that, among the four assays that were used in this study, the zinc sulphate flotation technique (Faust et al., 1939) is the best diagnostic assay in terms of sensitivity and specificity to detect G. duodenalis on serially collected samples from dogs, cats and humans.

Stool antigen immunodetection for diagnosis of Giardia duodenalis infection in human subjects with HIV and cancer

Human infection with the protozoan parasite Giardia duodenalis is one the most common parasitic diseases worldwide. Higher incidence rates of giardiasis have been reported from human subjects with multiple debilitating chronic conditions, including hypogammaglobulinemia and common variable immunodeficiency (CVID). In the current study, stool specimens were collected from 199 individuals diagnosed with HIV or cancer and immunocompetent subjects. The sensitivity of microscopy-based detection on fresh stool preparations, trichrome staining and stool antigen immunodetection for the diagnosis of G. duodenalis were 36%, 45.5% and 100%, respectively when compared with a highly sensitive stool-based PCR method as the gold standard. Further multilocus molecular analyses using glutamate dehydrogenase (gdh) and triose phosphate isomerase (tpi) loci demonstrated that the AI genotype of G. duodenalis was the most prevalent, followed by the AII genotype and mixed (AI+B) infections. We concluded that stool antigen immunodetection-based immunoassays and stool-based PCR amplification had comparable sensitivity and specificity for the diagnosis of G. duodenalis infections in these populations. Stool antigen detection-based diagnostic modalities are rapid and accurate and may offer alternatives to conventional microscopy and PCR-based diagnostic methods for the diagnosis of G. duodenalis in human subjects living with HIV or cancer.