High prevalence of Strongyloides stercoralis infection among the elderly in Brazil

Frequency of strongyloidiasis and associated factors: Analysis of 13 years of laboratory results in a tertiary referral hospital in Honduras, 2010-2022

INTRODUCTION

The frequency of detected strongyloidiasis is affected by the selected laboratory method in the studied population. Considering that Honduras has few community-based studies, the analysis of the laboratory record data can provide information helping to understand this parasitosis.

OBJECTIVE

To estimate the frequency and to identify the factors associated with strongyloidiasis, analyzing the laboratory records of the Servicio de Parasitología at Hospital Escuela in Tegucigalpa (Honduras) between 2010 and 2022.

MATERIALS AND METHODS

We carried out a descriptive, cross-sectional, analytical study. The laboratory diagnosis consisted of stool samples' examination by direct smear and modified Baermann technique. We estimated frequencies and percentages. The statistical association was calculated with prevalence ratios and a 95% confidence interval. Software R, version 4.2.0, and epiR package, version 2.0.46, were used to perform the analysis.

RESULTS

The frequency of strongyloidiasis was 0.29% (112/38,085). It was higher with the modified Baermann technique (0.87%; 40/4,575) among male patients (0.44%; 70/15,758). Regarding the age, strongyloidiasis was higher in the 20-40 years old group (0.41%; 28/6,886) with direct smear and 41-61 years old (1.14%; 14/1,232) group with the modified Baermann technique. Among the factors associated with strongyloidiasis were age between 20 and 61 years old (PR=2.26, CI 95%=1.53-3.31), male patients (PR=2.34, CI 95%=1.60‑3.44), mucus (PR=1.86, CI 95%=1.22-2.83) and Charcot-Leyden crystals in stool (PR=8.47, CI 95%=5.14-13.96); watery stool (PR=2.39, CI 95%=1.55-3.68), and other helminthiases (PR=6.73, CI 95%=3.98-11.38). Associated factors to cases detected with the modified Baermann technique were outpatient consultation (PR=4.21, CI 95%=1.91-9.28) and formed stools (PR=3.99, CI 95%=1.94-8.19).

CONCLUSIONS

The modified Baermann technique increased the detection of strongyloidiasis almost four times. Most cases were distributed among male adults. The cases diagnosed exclusively with the modified Baermann technique have differences from those with observed larvae in the direct smear. It is necessary to develop community-based population studies.

Current prevalence and geographic distribution of helminth infections in the parasitic endemic areas of rural Northeastern Thailand

BACKGROUND

Helminth infection is a global health issue that not only causes acute helminthiasis but long-term infection may lead to complicated symptoms as well as severe complications. The World Health Organization cooperated with the Ministry of Public Health in many countries, particularly where high prevalence, spending a lot of resources for limiting the infection. In Thailand, the incidence of parasitic helminth infections was continuously declined in the last few decades according to several campaigns for parasitic elimination. However, the rural community in the northeast of Thailand where the highest prevalence of the country still needs to be monitored. This present study aims to report the current prevalence of parasitic helminth infections in Nakhon Ratchasima and Chaiyaphum provinces where sharing a huge area of the northeastern region of Thailand but only a few studies have been published.

METHODS

The stool specimens were collected from 11,196 volunteers and processed by modified Kato-Katz thick smear, PBS-ethyl acetate concentration techniques, and PCR. The epidemiological data were collected, analyzed, and used for generating of parasitic hotspots.

RESULTS

The results indicated that O. viverrini remains the major parasite in this area with a total prevalence of 5.05% followed by Taenia spp., Hookworms, T. trichiura, and Echinostoma spp., respectively. Mueang district of Chaiyaphum province has the highest prevalence especially O. viverrini with a prevalence of 7.15% that higher than the latest national surveillance. Interestingly, the prevalence of O. viverrini was hugely reported (more than 10%) in five subdistricts. The geographic localization of O. viverrini infections revealed that a lot of water reservoirs such as the lakes or branches of the river in the two-most prevalent subdistricts. Our finding indicated that gender and age were insignificantly different.

CONCLUSION

This finding suggested that the parasitic helminth infection in the rural areas of northeast of Thailand remains high and the housing location is a major contributing factor for the parasitic infection.

Opisthorchis viverrini and Strongyloides stercoralis mono- and co-infections: Bayesian geostatistical analysis in an endemic area, Thailand

Parasitic infections caused by Opisthorchis viverrini and Strongyloides stercoralis remain a major public health threat in the Greater Mekong Sub-region. An understanding of climate and other environmental influences on the geographical distribution and emergence of parasitic diseases is a crucial step to guide targeted control and prevention programs. A parasitological survey was conducted from 2008 to 2013 and included 12,554 individuals (age between 20 and 60 years) from 142 villages in five districts in Khon Kaen Province, Thailand. Geographical information systems, remote sensing technologies and a Bayesian geostatistical framework were used to develop models for O. viverrini and S. stercoralis mono- and co-infections in areas where both parasites are known to co-occur. The results indicate that male sex, increased age, altitude, precipitation, and land surface temperature have influenced the infection rate and geographical distribution of mono- and co-infections of O. viverrini and S. stercoralis in this area. Males were 6.69 times (95% CrI: 5.26-8.58) more likely to have O. viverrini - S. stercoralis co-infection. We observed that O. viverrini and S. stercoralis mono-infections display distinct spatial pattern, while co-infection is predicted in the center and southeast of the study area. The observed spatial clustering of O. viverrini and S. stercoralis provides valuable information for the spatial targeting of prevention interventions in this area.

Age range implications of rats over Strongyloides venezuelensis infection

OBJECTIVE

To evaluate the dynamics of S. venezuelensis infection in Wistar rats of different age ranges.

DESIGN

Thirty-five (n = 35, 7 per group) male Wistar rats were distributed according to age into five groups: 2, 3, 6, 12 and 18 months old (mo). The rats were infected by S. venezuelensis and eggs per gram of feces (EPG) were measured at 3, 9, 15 and 21 days post-infection (dpi). All animals were killed at 21 dpi, thymus, lungs and small intestines were removed, and relative weight calculated. The adult worms recovered from the small intestines and blood cells were counted.

RESULTS

Rats in advanced age presented higher parasite oviposition at 9 dpi and posterior reduction of EPG, while young rats still showed higher oviposition at 15 dpi and 21 dpi. At 12 and 18 mo, the rats had greater number of adult worms, which with low fecundity, eosinophilia and least concentration of monocytes. The fecundity of worms was more expressive in young rats. A strong correlation was observed between age and EPG at 9 dpi (R = 0.72, p < 0.0001), at 15 (R = -0.66, p < 0.0001) and at 21 dpi (R = -0.65, p < 0.0001), as well as age and numbers of worms at 21 dpi (R = 0.74, p < 0.0001). The relative weight of the thymus, lungs and small intestines were higher in rats at 2 and 3 mo in comparison to the older groups of rats.

CONCLUSIONS

Aging process interfered on host-parasite relationship and changed the dynamics of infection of S. venezuelensis in Wistar rats.

Design, Expression and Purification of Strongyloides stercoralis IgG4 Immunoreactive Protein (NIE) in Escherichia coli

Background

Strongyloidiasis is a public health concern in northern regions of Iran, caused by Strongyloides stercoralis. Auto-infection cycle can be resulted in high parasitic load, especially in immunocompromised hosts. Because of low sensitivity of stool culture and stool-based microscopy techniques, detection of antibodies in patient's sera can be an alternative diagnostic technique for detection of the nematode. In the present study, as the first step of the development of an ELISA kit for the detection of antibodies against the nematode, IgG4 immunoreactive protein (NIE) was expressed in Escherichia coli expression system, purified and verified.

Methods

The NIE gene sequence was retrieved from the GenBank. This sequence was codon-optimized for the expression in E. coli BL21 (DE3). The sequence was inserted into the expression vector pET-30b (+). The recombinant vector was then transferred into competent E. coli BL21 (DE3). Transformed colonies were selected and verified by colony PCR. NIE gene expression was induced with IPTG induction. The protein production was evaluated by SDS-PAGE and verified using Western blotting.

Results

The codon-optimized NIE gene had required parameters for expression in E. coli. NIE protein was proved and verified by SDS-PAGE and Western blotting.

Conclusion

NIE recombinant protein was successfully expressed in E. coli expression system in appropriate amounts. The recombinant protein can be used for developing ELISA kit in diagnosis of S. stercoralis.

Strongyloides stercoralis Infection at Different Altitudes of the Cusco Region in Peru

Strongyloides stercoralis affects 30-100 million people worldwide. The burden is underestimated because of the paucity of studies, limited geographical areas surveyed, and poor quality of diagnostic tests. This study aimed at determining the epidemiology of strongyloidiasis using sensitive microscopy testing in rural populations living at different altitudes in Cusco, Peru. Data were collected from subjects aged > 3 years living in Quellouno (elevation 2,600 ft) and Limatambo (elevation 8,379 ft) districts. Subjects provided one fresh stool sample and answer a standardized questionnaire. Fresh stool was tested on site using the Baermann's test and agar plate culture. Formalin-preserved stool was tested by rapid sedimentation. Eighty percent (585/715) of eligible subjects consented to participate; after excluding subjects with missing data, 65% (462/715) were included. Fifty-five percentage were female; the median age was 33 years (interquartile range 13-52), and 72% had government health insurance. Half had intestinal parasites, and Strongyloides was the most common (24.5%) followed by Giardia (15.5%), Blastocystis (14.9%), and hookworm (11.5%). The agar plate culture detected more cases of Strongyloides than Baermann's or sedimentation tests. Strongyloides infection was more common at low altitude (26.4%) than at high altitude (18.6%), but the difference was not statistically significant (P = 0.08). Older age, walking barefoot, bathing in rivers/streams, and using municipal sewage were associated with strongyloidiasis. Strongyloides was the most prevalent parasite in the areas studied and was associated with demographic, socioeconomic, and sanitary factors.

Helminth infections and immunosenescence: The friend of my enemy

Age-associated alterations of the immune system, which known as "immunosenescence", is characterized by a decline in innate and adaptive immunity, which leading to increased susceptibility to age-associated diseases, such as infectious diseases, rheumatic disease and malignancies. On the other hand, helminth infections are among the most prevalent infections in older individuals, especially in the nursing homes. Most of helminth infections have minor clinical symptoms and usually causing chronic infections without treatment. Nevertheless, chronic helminthiasis alters immune responses somewhat similar to the immunosenescence. Some similarities also exist between helminth infections and immunosenescence: 1) both of them led to declining the immune responses; 2) undernutrition is a consequence of immunosenescence and helminthiasis; 3) vaccine efficacy declines in aging and individuals with helminth infections; 4) increase incidence and prevalence of infectious diseases in the elder individuals and patients with helminth infections; and 5) both of them promote tumorigenesis. Hence, it is probable that helminth infections in the elderly population can intensify the immunosenescence outcomes due to the synergistic immunoregulatory effects of each of them. It would be suggested that, diagnosis, treatment and prevention of helminth infections should be more considered in older individuals. Also, it would be suggested that helminths or their antigens can be used for investigation of immunosenescence because both of them possess some similarities in immune alterations. Taken together, this review offers new insights into the immunology of aging and helminth infections.

scFv against HSP60 of Strongyloides sp. and Its Application in the Evaluation of Parasite Frequency in the Elderly

The present study is aimed at evaluating serological method using scFv anti-Strongyloides sp. and reporting the frequencies of the results with conventional parasitological technique (faeces) in elderly individuals. Among 112 elderly individuals (≥60 years of age), 14.28% were positive for at least one enteroparasite, with one individual positive for S. stercoralis. Sera were evaluated for the presence of anti-Strongyloides sp. antibodies using total or detergent fraction extracts of Strongyloides venezuelensis, which presented positivity rates of 19.64% and 10.71%, respectively. An anti-HSP60 single-chain variable fragment from Strongyloides sp. was used to detect parasite antigens, with 5.36% (6 individuals) of ELISA-positive individuals returning a positive result. While the serological test indicates previous or recent infection and may be limited by antigen purification, the anti-HSP60 method reflects the presence of Strongyloides sp. immune complexes and exhibits greater sensitivity and specificity. Our results demonstrate the variable occurrence of enteroparasites in elderly individuals residing in long-term nursing homes and validate a novel epidemiological tool to describe infection cases by Strongyloides sp.

Highly specific and sensitive anti-Strongyloides venezuelensis IgY antibodies applied to the human strongyloidiasis immunodiagnosis

Due to the epidemiological problem of the neglected condition of human strongyloidiasis, rapid and effective diagnosis is extremely important, with the development of new diagnostic tools being essential to reduce infections and chronic cases. Avian immunoglobulin Y (IgY) technology is an alternative for antibody production that has high specificity and profitability. This study aimed to produce and fractionate IgY antibodies from the egg yolks of hens that were immunized with the total antigenic extracts of Strongyloides venezuelensis infectious filariform larvae (iL3) and parthenogenetic females (pF). IgY antibodies were then evaluated by their recognition of antigenic proteins, evolutive helminth forms, and serological diagnosis of human strongyloidiasis by the detection of immune complexes in serum samples. Egg yolks were fractionated to obtain IgY antibodies by thiophilic interaction chromatography. Immune complex detection in serum samples showed diagnostic values for anti-iL3 IgY and anti-pF IgY antibodies at 95.56% and 88.89% sensitivity and 95.56% and 91.11% specificity, respectively. Therefore, IgY technology is a promising tool for the detection of blood circulating Strongyloides antigens, with possible application as a serological diagnostic method.

Solid organ transplantation in older adults. Infectious and other age-related considerations

In the U.S., older adults aged 65 or above comprise nearly one quarter of the solid organ transplant (SOT) waitlists, and the number of transplants performed in this age group continues to increase. There are no specific guidelines for the assessment and follow up of the older SOT candidate or recipient. Older adults are at increased risk of infectious complications after SOT. Despite these complications and even with the use of suboptimal donors, overall outcomes are favorable. We provide an overview to specific consideration as they relate to the older SOT candidate and recipient.

Prevalence of intestinal parasitosis and associated factors among the elderly

Abstract Objective: To identify the prevalence of intestinal parasitosis and associated factors in elderly persons resident in the community. Methods: A cross-sectional study was performed involving 236 elderly persons in Aiquara, in the state of Bahia, Brazil, in 2015. Data were collected through a coprological survey and a questionnaire for information relating to sociodemographic characteristics, health and lifestyle. The presence of parasites in stools was verified by the Hoffman method. Results: The prevalence of intestinal parasites among the elderly was 30.5%. Among infected elderly persons, 26.3% had monoparasitism, 3.8% biparasitism and 0.4% polyparasitism. There was a predominance of protozoa (80.8%) over helminths (19.2%). The most prevalent parasites were Entamoeba coli (44.6%); Endolimax nana (21.7%) and Iodamoeba bütschlii (14.5%). In the population studied, the independent variables analyzed were not associated (p>0.05) with the presence of intestinal parasites. Conclusion: the prevalence of intestinal parasitic infections in elderly people living in the urban area of the municipal region of Aiquara, Bahia, was high and there was no association between intestinal parasites and sociodemographic characteristics, lifestyle or health.

Strongyloidiasis: A Disease of Socioeconomic Disadvantage

Strongyloidiasis is a disease caused by soil transmitted helminths of the Strongyloides genus. Currently, it is predominately described as a neglected tropical disease. However, this description is misleading as it focuses on the geographical location of the disease and not the primary consideration, which is the socioeconomic conditions and poor infrastructure found within endemic regions. This classification may result in misdiagnosis and mistreatment by physicians, but more importantly, it influences how the disease is fundamentally viewed. Strongyloidiasis must be first and foremost considered as a disease of disadvantage, to ensure the correct strategies and control measures are used to prevent infection. Changing how strongyloidiasis is perceived from a geographic and clinical issue to an environmental health issue represents the first step in identifying appropriate long term control measures. This includes emphasis on environmental health controls, such as better infrastructure, sanitation and living conditions. This review explores the global prevalence of strongyloidiasis in relation to its presence in subtropical, tropical and temperate climate zones with mild and cold winters, but also explores the corresponding socioeconomic conditions of these regions. The evidence shows that strongyloidiasis is primarily determined by the socioeconomic status of the communities rather than geographic or climatic conditions. It demonstrates that strongyloidiasis should no longer be referred to as a "tropical" disease but rather a disease of disadvantage. This philosophical shift will promote the development of correct control strategies for preventing this disease of disadvantage.

Strongyloidiasis with emphasis on human infections and its different clinical forms

Strongyloidiasis (caused by Strongyloides stercoralis, and to a lesser extent by Strongyloides fuelleborni) is one of the most neglected tropical diseases with endemic areas and affecting more than 100 million people worldwide. Chronic infections in endemic areas can be maintained for decades through the autoinfective cycle with the L3 filariform larvae. In these endemic areas, misdiagnosis, inadequate treatment and the facilitation of the hyperinfection syndrome by immunosuppression are frequent and contribute to a high mortality rate. Despite the serious health impact of strongyloidiasis, it is a neglected disease and very little is known about this parasite and the disease when compared to other helminth infections. Control of the disease is difficult because of the many gaps in our knowledge of strongyloidiasis. We examine the recent literature on different aspects of strongyloidiasis with emphasis in those aspects that need further research.