Strongyloides stercoralis in Alcoholic Patients: Implications of Alcohol Intake in the Frequency of Infection and Parasite Load.

Strongyloides stercoralis infection in immunocompromised subjects, including chronic alcoholics, can lead to a severe disease. Moreover, its prevalence in alcoholic patients seems to be higher than that in the general population. The aims of this study were to evaluate the frequency of S. stercoralis infection in alcoholic patients and to investigate the influence of alcohol intake on the parasite load, as well as to evaluate the sensitivity of three different parasitological methods according to the larval output. Fecal samples of 1290 chronic alcoholic patients were examined by spontaneous sedimentation, Baermann-Moraes, and agar plate culture (APC) methods. S. stercoralis was the most frequent parasite found (14.5%; n = 187). Alcoholic individuals infected with Strongyloides stercoralis had a higher daily consumption of alcohol than those who were not infected, 528.6 and 403.0 g/day, respectively (p < 0.05). In addition, individuals with higher alcohol intake presented an increase in parasite load. The S. stercoralis diagnostic method with the highest sensitivity was APC, 97.9% (183/187). In conclusion, S. stercoralis seems to be the most frequent parasite found in alcoholic individuals from endemic areas and alcohol intake is positively associated with S. stercoralis larvae output. In addition, this study confirms that APC is the most sensitive parasitological method used for Strongyloides diagnosis.

Association between Strongyloides stercoralis infection and cortisol secretion in alcoholic patients.

A higher prevalence of Strongyloides stercoralis infections has been reported in alcoholic patients compared to nonalcoholic patients living in the same area. Excessive alcohol consumption increases the levels of endogenous corticosteroids that subsequently enhance the fecundity of S. stercoralis parthenogenetic females. These corticosteroids also enhance the transformation of rhabditiform larvae into infective filariform larvae by mimicking the effect of the ecdysteroid hormones produced by the parasite, thus leading to autoinfection. In addition, alterations in the intestinal barrier and host immune response contribute to the development of hyperinfection and severe strongyloidiasis in alcoholic patients. The aim of this study was to evaluate the frequency of S. stercoralis infections in alcoholic patients and to determine the association between S. stercoralis infection and endogenous cortisol levels. The frequency of infection was evaluated in 332 alcoholic and 92 nonalcoholic patients. The parasitological diagnosis was carried out by agar plate culture, the modified Baermann-Moraes method and spontaneous sedimentation. The immunological diagnosis was performed using an ELISA with anti-S. stercoralis IgG. The cortisol levels were measured in serum samples by ELISA. The frequency of S. stercoralis infection in alcoholic patients was 23.5% (78/332), while in nonalcoholic patients, it was 5.4% (5/92) (p<0.05). The cortisol levels were higher in alcoholic than in nonalcoholic patients (p<0.05). However, among the alcoholic patients, the cortisol levels did not differ between S. stercoralis-infected and uninfected patients (p>0.05). As demonstrated in this work, 81.3% (26/32) of patients with a high parasite load, considered as more than 11 larvae per gram of feces, presented serum cortisol levels above the normal reference value (24 mg/dL). High endogenous cortisol levels in alcoholic patients were not associated to susceptibility to S. stercoralis infection, however once infected, this may lead to a high parasite load.

Strongyloides stercoralis Infection in Alcoholic Patients.

The course of Strongyloides stercoralis infection is usually asymptomatic with a low discharge of rhabditoid larva in feces. However, the deleterious effects of alcohol consumption seem to enhance the susceptibility to infection, as shown by a fivefold higher strongyloidiasis frequency in alcoholics than in nonalcoholics. Moreover, the association between S. stercoralis infection and alcoholism presents a risk for hyperinfection and severe strongyloidiasis. There are several possible mechanisms for the disruption of the host-parasite equilibrium in ethanol-addicted patients with chronic strongyloidiasis. One explanation is that chronic ethanol intake stimulates the hypothalamic-pituitary-adrenal (HPA) axis to produce excessive levels of endogenous cortisol, which in turn can lead to a deficiency in type 2 T helper cells (Th2) protective response, and also to mimic the parasite hormone ecdysone, which promotes the transformation of rhabditiform larvae to filariform larvae, leading to autoinfection. Therefore, when untreated, alcoholic patients are continuously infected by this autoinfection mechanism. Thus, the early diagnosis of strongyloidiasis and treatment can prevent serious forms of hyperinfection in ethanol abusers.

Efficacy of parasitological methods for the diagnosis of Strongyloides stercoralis and hookworm in faecal specimens.

To compare the efficacy of stool examination for the detection of Strongyloides stercoralis and hookworm, a total of 634 stool samples from the routine laboratory service of the Pharmacia Faculty, Federal University of Bahia, Brazil, were examined by agar plate culture (APC), Baermann-Moraes and spontaneous sedimentation. The sensitivity of agar plate culture, calculated by combining results of all 3 methods, was 95% for S. stercoralis and 77.6% for hookwoorm. Moreover, APC had superior accuracy than Baermann-Moraes and spontaneous sedimentation for S. stercoralis and hookworm diagnosis, respectively. The S. stercoralis and hookworm positive samples from the laboratory routine, obtained after the previous analysis, along with those initially selected, were used to evaluate the concordance between microscopic examination and both the type of furrows left by larvae and the time for culture positivity using the APC method. Of 115 stool samples positive for S. stercoralis and 92 positive for hookworm, 110 (95.7%) and 89 (96.7%), respectively, had concordant results for furrows and morphological characteristics. The cumulative percentage of positivity increased to 94% by the third day of observation; at this time, only 19.6% of hookworm-positive samples had positive culture plates. Analyses of 74 S. stercoralis-positive stool samples stored at 4°C for 24, 48 and 72h showed the presence of larvae in 48.6%, 28.4% and 23% of samples, respectively when re-examined by the APC. As a definitive diagnosis of strongyloidiasis depends on the microscopic demonstration of parasites, increasing the sensitivity of the detection requires the use of different parasitological methods, including APC.