This study demonstrates that strongyloidiasis is a common parasitic disease that affects 15.1% of patients undergoing haemodialysis in the city of Cochabamba. These results confirm the high prevalence (15.3%) found by Getaz et al. in other patients at high risk of complications living in the Cochabamba region (4).
As previously mentioned, SS is a complication with high mortality risk (7, 8). Its incidence is likely underestimated due to the lack of recognition of this syndrome. According to Buonfrate et al., given the considerable number of case reports of SS published in non-endemic countries, it is likely that fatal cases of SS are also common in endemic countries but, unfortunately, not published (8). In addition, between 7% and 12% of cases are diagnosed only at the time of autopsy, which is rarely performed in low and middle income countries (8, 9).
Although haemodialysis or end-stage renal disease as specific risk factors for severe strongyloidiasis have never been investigated, these patients have a weakened immune system and infections represent their second leading cause of death (13). In particular, sepsis is a very common complication in dialysis patients, with a cumulative incidence of up to 11.7% and a risk 26 to 50 times higher than in the general population (15, 18, 19). Similarly, septic shock is a complication present in up to 57.3% of patients with SS due to the massive penetration of larvae into the intestinal mucosa that can promote bacterial translocation (9, 24).
In addition, nine (6%) patients received corticosteroid treatment during the three months before recruitment, a major risk factor for SS (7, 20, 21). Diabetes was identified in 48 (32%) patients, another risk factor although of lesser importance (22, 23).
In view of the high prevalence found in our study and the fatal consequences of delayed diagnosis, it is essential to systematically screen for and treat SS in the event of sepsis or respiratory and/or gastrointestinal symptoms. Furthermore, prevention of SS is of paramount importance in the management of S. stercoralis. In groups of patients at high risk for SS and with a prevalence greater than 10%, experts advise presumptive treatment with ivermectin to prevent the life-threatening consequences of strongyloidiasis and in light of this drug’s proven safety (4, 25).
Considering both the chronic immunodeficiency associated with end-stage renal disease and the actual prevalence of 15.1% found in our study, treatment at regular intervals seems to be an appropriate strategy for haemodialysis patients living in an endemic area, such as Bolivia; however, to date, no prospective study has been carried out to validate this approach.
Transplantation, particularly kidney transplantation, is a major risk factor for severe strongyloidiasis (7, 26). For the aforementioned reasons, any transplant patient living in or coming from Bolivia should benefit from prophylactic treatment with ivermectin before a transplant and then again at regular intervals to prevent a potentially fatal complication.
Our study has several strengths. To our knowledge, this is the first study to determine the prevalence of S. stercoralis in haemodialysis patients. Another strength is the high participation rate in the serological study, with only 11 refusals amongst the 164 patients invited to participate. In contrast, our study has also several limitations. First, due to the limited sample size, risk factors of S. stercoralis infection may have been missed, such as those identified in previous studies: living in a rural area, walking barefoot, having a low level of education, or having gastrointestinal symptoms (4, 27–29). Second, collecting stool samples was very difficult in our study, due to low acceptance of this test amongst patients and despite full cost coverage. In addition, these techniques require obtaining fresh stool, which must be sent in to the laboratory for analysis no more than four hours after collection for living larvae to be detectable therein. Most of the patients in our cohort lived more than two hours from their dialysis centre, making the delivery of fresh stool samples difficult or even impossible. The high discrepancy between the actual and the coproparasitological prevalence (15.1% vs. 1.9%) could be linked to a delay in the delivery of numerous samples and to the known limited sensitivity of coproparasitological techniques. Finally, serological testing is a diagnostic tool with suboptimal performance, which is why an actual prevalence calculation is presented. The sensitivity reported in the literature was measured in populations that were predominantly not immunosuppressed. It is possible that the sensitivity of serological testing is even lower in dialysis patients, whose ability to synthesise antibodies could be reduced, similar to their altered response to hepatitis B or influenza virus vaccines (30). Thus, this potential bias could lead to an underestimation of the real prevalence of strongyloidiasis in the study population.
These limitations related to diagnostic tests are important to consider and reinforce the proposition for presumptive prescription of antiparasitic treatment to all patients at high risk of complications.