Opportunistic parasitoses among Egyptian hemodialysis patients in relation to CD4+ T-cell counts: a comparative study

Renal failure is an immunosuppressive condition that makes patients more prone to infections, including those caused by opportunistic protozoan parasites. Patients undergoing hemodialysis (HD) suffer from humoral and cell-mediated immune defects and have disturbances in acquired immune response to a variety of antigens [1, 2]. End-stage renal failure (ESRF) leads to impaired cell-mediated immunity as a result of lymphopenia and dysfunction of cluster of differentiation 4 (CD4+) T cells [1]. Moreover, uremia-associatedpro-inflammatory conditions developed in ESRD patients can lead to irreversible premature aging of T-cell compartment that contributes to the cell-mediated defects and susceptibility to infectious agents [3, 4]. On the other hand, HD induces apoptosis of T cells, decreased phagocytic capacity of neutrophils and monocytes along with abnormal production of pro-inflammatory cytokines by monocytes because of their direct contact with artificial membranes in HD machines [5‐8]. In addition, frequent blood transfusions to patients with chronic renal failure (CRF) can lead to the development of antibodies against human leukocyte antigens, which can form immune complexes that interfere with cellular immune responses [9, 10].

Opportunistic parasitic infections, including those with Cryptosporidium species, Cystoisospora belli, Cyclospora cayetanensis, Blastocystis hominis, Toxoplasma gondii and microsporidia, have been documented to cause serious complications or even death among immunocompromized patients, including those undergoing HD [11‐13]. In this context, humoral and cell-mediated immunosuppression can increase the susceptibility to and worsen the outcome of parasitic infections through increasing the acquisition of infection and the clinical severity of disease [14].

In Egypt, ESRD has been estimated to affect 264 to 414 per million population [15]. Despite the availability of a number of reports on opportunistic parasitoses among HD patients in Egypt [16‐18], there is a paucity of data on the association of CD4+ counts with such infections. Therefore, the present study was conducted to determine the prevalence of intestinal parasites and T. gondii among HD patients in Alexandria governorate, Egypt in relation to CD4+ counts compared to apparently healthy individuals.

Opportunistic parasitic infections are a major cause of morbidity and mortality in immunocompromized patients, particularly those with low CD4+ counts [11‐13]. Increased blood urea levels in patients with ESRD could lead to a weakened immune system and increased risk of morbidity and mortality associated with such opportunistic infections [30]. On the other hand, HD patients are more prone to such opportunistic infections, where repeated HD decreases CD4+ counts compared to predialysis and healthy controls [31]. Up to the best of our knowledge, the present study is the first to compare infection rates with intestinal parasites and T. gondii between HD patients and apparently healthy individuals in relation to CD4+ counts in Alexandria, Egypt.

The overall prevalence rate of intestinal parasitoses among HD patients was significantly higher than their apparently healthy counterparts (52.5% vs. 12.0%, respectively). Lower infection rates among HD patients were reported from Brazil (45.1%), Turkey (43.7%) and Iran (11.9–30.7%) [13, 32‐34]. Compared to the finding of the present study, higher infection rates with Cryptosporidium species (40.0%), E. histolytica (14.0%) and G. lamblia (12.0%) have been recently reported among CRF patients undergoing HD in Upper Egypt [16]. The differences in the prevalence rates of infections between HD patients in the present study (north of Egypt) and those in the latter study (south of Egypt) could be attributed, among others, to differences in environmental, sanitary and hygienic factors. However, the reasons for such geographical differences in the prevalence of parasites among HD patients require further investigations.

In line with the findings of the present study, Cryptosporidiumspecies (26.4%) and B. hominis (24.5%) were the most prevalent intestinal parasites among Brazilian HD patients [12]. Among the controls, however, B. hominis was the most prevalent species while Cryptosporidiumspecies was not detected [12]. Another Brazilian study also reported B. hominis as the most prevalent parasite species among HD patients (20.1%) followed by Endolimax nana(16.3%), while Cryptosporidium species was reported among 4.7% of patients [31]. Similarly, B. hominis(4.2–14.1%) and Cryptosporidium species (11.5%) were the most common parasite species among Iranian HD patients [13, 34‐36]. In addition, B. hominis (23.9%) followed by G. lamblia (8.5%) were the most prevalent parasite species among Turkish ESRF patients undergoing HD, while low rates of Cryptosporidium species, E. histolytica and microsporidia (2.1% each) were detected among patients but not the controls [33]. The variations in the prevalence of intestinal parasitoses among HD patients could be partly explained by the differences in the geographical distribution of parasites at the community level as a result of environmental, climatic and sanitary differences in addition to differences in hygienic and behavioral factors at the individual level. In addition, the role of the immune status and duration of HD as well as the method of stool examination in infection rate differences could not be ruled out.

In the present study, approximately a third of HD patients infected with the opportunistic parasites (Cryptosporidium species, B. hominis or microsporidia) had diarrhea, even though with no statistically significant association. Although the role of B. hominis in human disease is controversial [37], it can be a cause of diarrhea in patients on regular HD and renal transplant recipients [38, 39]. The lack of a statistically significant association between individual parasite species and presentation with diarrhea among HD patients in the present study is in contrast to the recent finding among CRF patients undergoing HD in Upper Egypt, where a statistical significance was found between Cryptosporidium species and diarrhea [16]. It also disagrees with that reported among Saudi patients undergoing HD [40], where Cryptosporidium species, microsporidia and G. lamblia were significantly higher among diarrheic patients compared to diarrheic controls. However, it is in agreement with that reported among Brazilian HD patients, where no association was found among individual parasite species and diarrhea [32]. In fact, the lack or presence association of HD with diarrhea among patients from different countries could be explained by differences in the level of immunosuppression, which determines the presence and severity of diarrhea. It is noteworthy that the differences in the incidence of gastrointestinal symptoms, including diarrhea, among CRF patients undergoing dialysis could be largely attributed to a number of factors such as the levels of uremic toxins, presence of metabolic co-morbidities, intake of medications and psychosocial factors [41, 42]. On the other hand, absence of helminths among HD patients in the present study is consistent with an earlier study among immunocompromized patients from Alexandria [43].

The overall T. gondii seroprevalence rate among approximately a third of HD patients in the present study is lower than those previously reported among HD patients (61.7%) and renal transplant recipients (70.0%) in Alexandria [17]. Similarly, it is lower than the rates reported from Turkey (56.0–76.5%) [44, 45], Mexico (56.7%) [46] and Iran (56.7–73.7%) [47‐49]. The anti-Toxoplasma IgM seroprevalence among HD patients in the present study (3.3%) is lower than those reported among Egyptian patients on regular HD (16.7%) and renal transplant recipients (24.1%) [50]. In addition, it is lower than those (7.8–13.5%) reported among Iranian patients undergoing regular HD [49, 51]. In general, the seroprevalence rate of anti-Toxoplasma IgM among HD patients in the present study is somewhat close to the rates reported from Turkey (1.7%) and Iran (2.0%) [44, 47]. However, comparisons can be difficult due to a number of factors such as the duration of HD and the severity of renal damage. Because of the difficulty in adopting molecular techniques for the diagnosis of T. gondii infection in resource-limited countries, serological detection of anti-Toxoplasma antibodies is still the most commonly used approach for the screening of the infection among immunocompromized patients [52]. However, a major limitation of the present study is the inability to confirm whether the three cases seropositive for both IgM and IgG were acute infections because IgM may persist for years [53, 54]. A good approach to the real-time serodiagnosis of T. gondii infection that distinguishes between acute and chronic infections is the measurement of IgG avidity [55]. In this regard, the low avidity of specific anti-Toxoplasma IgG indicates a recent primary infection [56]. In addition, development of kits using immunoreactive proteins and multi-epitope antigens has been suggested for improving the diagnosis of T. gondii infection [57‐59]. The high T. gondiiseronegativity rate among HD patients in the present study indicates that the majority of HD patients had not been exposed to infection and are susceptible to the risk of acute infection.

In the present study, 40.0% of HD patients had CD4+ counts < 200 cells/μl compared to > 500 cells/μl in all apparently healthy individuals. It is noteworthy that CD4+ count of < 200/μl is categorized as a severe level of immunosuppression [29]. Such low CD4+ counts among HD patients were significantly associated with the infection with opportunistic parasites Cryptosporidium species, B. hominis, microscopridia and T. gondii. The significant association between low CD4+ count and infection with Cryptosporidium species in the present study is consistent with that reported from Saudi Arabia, where a significantly higher rate of infection with Cryptosporidiumspecies was found among HD patients with CD4+ counts of < 500 cells/μl compared to those with CD4+ counts of > 500 cells/μl (66.7% vs. 29.6%) [39]. In another context, CD4+ counts of < 200 cells/μl were significantly associated with infection with Cryptosporidium species, C. belli and microsporidia among HIV-infected patients on antiretroviral therapy from Cameroon [60]. On the other hand, the significant association between low CD4+ count and T. gondii seropositivity in the present study is in line with that reported among Indian HIV-infected patients [61, 62], where a significant difference was found between the mean CD4+ counts in Toxoplasma-seropositive and -seronegative patients and that most IgG-seropositive patients had CD4+ counts of < 100/μl. Similarly, CD4+ counts of ≤100/μl were also found to be significantly associated with IgG seropositivity among HIV-positive patients without neurological complication from Nigeria [63].

One of the primary limitations of the present study comes from its observational design and that the prevalence of intestinal parasitoses was determined at a single point in time. The temporal relationship of the duration of HD with CD4+ counts and, hence, prevalence of parasites was not studied in the present study. However, this study reveals an absence of helminthic parasites that are usually detected by routine stool examinations as well as a high prevalence of Cryptosporidium species, B. hominis and microsporidia that are only detected after staining with specialized stains. This, in turn, necessitates the importance of considering the special request for such staining procedures by physicians as part of the routine diagnostic tests for HD patients. Another limitation is the inability to confirm serodiagnosis because no IgG avidity testing was done and single serum samples were tested.

Intestinal parasitoses and T. gondii infection rates are significantly higher among Egyptian HD patients compared to apparently healthy individuals. Moreover, Cryptosporidium species, B. hominis, microsporidia and T. gondii are the most frequently detected opportunistic parasites among HD patients. The significantly higher past exposure to T. gondii infection among HD patients compared to their counterparts can pose these patients to the risk of infection reactivation because of their immunocompromized state. In addition, the high rate of T. gondiiseronegativity can threaten their lives as a result of the possibility of exposure to infection during HD. CD4+ cell counts < 200 cells/μl can be significantly associated with a higher infection rate with Cryptosporidium species, microsporidia and T. gondii among Egyptian HD patients. Therefore, regular screening of HD patients for opportunistic intestinal parasites using specialized staining techniques and serological testing for T. gondii are recommended as part of the overall healthcare of such patients. Further large-scale studies on parasitic infections and associated risk factors among HD patients and other categories of immunocompromized patients are recommended.