Evaluation of the role of Ancylostoma caninum in humans as a cause of acute and recurrent abdominal pain

Ancylostoma caninum is responsible for cases with eosinophilic enteritis (EE) and unexplained abdominal pain with peripheral eosinophilia in man. Ninety-five patients with obscure acute or recurrent abdominal pain and ten asymptomatic healthy parasite free were subjected to thorough history taking, clinical examination, sonography, routine laboratory investigations and serotesting by IgG ELISA to detect antibodies to excretory/secretory (ES) antigens of adult A. caninum and by IgG and IgG4 Western blot (W.B.) to detect antibodies to Ac68 antigen. Eleven male patients (11.6%) (5 with acute abdomen, 3 diagnosed as appendicitis and 3 had recurrent mild to moderate abdominal pain) fulfilled the criteria of case definition of human enteric infection with A. caninum (G.I). The study also detected human hookworm infection in 14 patients (G.IIb) other parasites in 34 patients (GIIc) and 36 patients had no parasites (G.IIa). Although 3 patients from group I were diagnosed as appendicitis and were dealt with surgically, the pain recurred and mebendazole only put an end to the patient's complaints. The obtained appendices of these operated cases showed marked eosinophilic infiltration but no adult canine hookworms were detected. IgG ELISA was positive in 72.7%, 8.3%, 100%, 23.5% and 0% in groups and control respectively. IgG and IgG4 W.B. did not increase the sensitivity but IgG4 W.B. elevated specificity to 100% excluding those with HH infection (Group Iib) who showed 100% cross-reactions. Stool analysis was the only differentiation between these two types of hookworms. These findings confirmed the presence of human enteric infection with A. caninum as clinical entity in the study community and referred to its value in differential diagnosis of the obscure abdominal pain.

Evaluation of circulating Fasciola antigens in specific diagnosis of fascioliasis

Ninety-eight individuals were included in this study, 60 of them were passing Fasciola eggs, 20 were infected with other parasites but not Fasciola (infected control group) and 18 individuals were free from parasite infection (normal control group). Circulating Fasciola antigens (CFAg) and anti-Fasciola IgG were estimated by ELISA technique among all groups. Highly significant increased level of CFAg was observed among Fasciola-infected cases when compared with normal control group. The percentage positivity of CFAg was 95% among Fasciola-infected cases. Solid specificity was observed by the test. Moreover, a highly significant increase in the antigen level was detected among moderately infected patients compared with lightly infected group. The level of CFAg was significantly higher in the hepatomegalic cases than those without organomegaly. Anti-Fasciola IgG antibodies were detected in only 35% of Fasciola infected cases, which indicates much lower sensitivity of the antibody detection than antigens. No correlation between the level of the circulating antibodies and either the intensity of infection or the clinical presentations was observed.

Immunity to schistosomiasis before puberty: humeral or cell mediated

To determine if the cell mediated immunity, induced by T-helper type-1 lymphocytes (Th1) response, during schistosomiasis mansoni has the potential to protect against infection, intensities of infections and re-infections, reflected in the egg count were followed up to 20 months among 119 individuals aged 5-22 years (Ys) with different number of previous infections whose yearly levels and pattern of water contact were similar. They were classified into 5 groups. Delayed hypersensitivity skin tests (DHT) to adult schistosome excretory-secretary antigens (ESAgs) and anti-schistosomula (ESAgs) isotypes were measured on detecting re-infection. The group with a mean age of (8.6 +/- 2.6 Ys) and infected less than 5 times showed only 6.5 percentage reduction of the egg count (PREC) and low cellular and humoral responses. Th1-associated cellular (DHT) and antibody responses (IgG2, IgG3) to the five infections were significantly higher in the (13.5 +/- 1.4 Ys) than in (18 +/- 2.2 Ys) age group. This was reflected in significant difference in PREC; being 41.5% among the first and 13.5% among the second. Th2-associated antibody responses (IgG1, IgG4, IgE) went on rising as patients allowed for age and number of infections increased over 5, being significantly higher in the (19 +/- 1.8 Ys) than in (14 +/- 1.1 Ys) age groups with PREC 45.5% and 12.9% respectively. These results imply a substantial protective role for cell mediated immunity in the pre-puberty stage and provide evidence that Th1-based vaccination strategy can work if augmented.

Diagnosis of early pre-patent schistosomiasis by cystatin capture enzyme-linked immunosorbent assay

To test the efficacy of detecting anti-Schistosoma mansoni cysteine proteinase antibodies (CP Abs) by cystatin capture (CC) ELISA in the diagnosis of prepatent schistosomiasis (before egg passing); 253 schistosome negative individuals were selected and divided into two groups. The first comprised 118 children whose first water contact occurred in March and April 1999 (primarily infected), and the second 135 individuals were previously treated for schistosomasis (re-infected). All the individuals were followed up triweekly by stool for detecting schistosome eggs and by serological tests for detecting antibodies against CP and anti-soluble egg antigens (SEA) by ELISA technique. CP seropositivity was detected in 92 from all examined individuals, out of them 38 were primarily infected (PI) children (20 of them were pre-patently treated), the rest; 54 were re-infected patients (28 out of them were pre-patently treated). The untreated (44) individuals from both groups were followed up till they passed eggs within 4 weeks and then were treated (post-patent). CP Abs were reassessed for the 92 patients after treatment, only 11 (12%) were still seropositive with marked decrease in optical density (O.D.) level than before treatment. Anti-SEA IgM Abs were sought in the 92 CP seropositive sera, and the seropositivity rate was lower in 38 PI children (5.3%) than in the 54 re-infected individuals (92.6%). The anti-SEA seropositivity rate in the PI children was 5% in the pre-patent and was 94.4% in the post-patent. None of the 161 CP seronegative individuals passed eggs up to 12 weeks.

Relationship between circulating antigen level and morbidity in Schistosoma mansoni-infected children evaluated by ultrasonography

Ninety-eight Schistosoma mansoni-infected children from an endemic area in Sharkia Governorate, Egypt were evaluated by abdominal ultrasonography to determine liver and spleen sizes, grade of periportal fibrosis, and splenic vein diameter. Circulating antigen levels were measured using a double sandwich ELISA in which the sensitivity was 91.8% and specificity was > 99%, with no evidence of cross-reactivity with other parasites. No significant relationship was observed between antigen level and clinical stages of the disease as assessed by physical examination (P > 0.05). When ultrasound was used to stage disease, the mean antigen level was significantly higher among hepatosplenic cases than intestinal cases (P < 0.05). No difference in mean antigen levels were found between the splenic and hepatic cases. Furthermore, a direct correlation (P < 0.01) was observed between antigen level and disease severity as monitored by ultrasonography. Antigen level showed a positive correlation with the degree of periportal fibrosis (P < 0.05). Moreover, a significant increase in the percent of children who were antigen positive (> 80 ng/ml) was found in those with more severe periportal fibrosis (P < 0.001). The findings suggest that ultrasonography along with measurement of circulating antigen levels predict morbidity in schistosomiasis mansoni.

Role of ELISA in early detection of Fasciola copro-antigens in experimentally infected animals

An immunodiagnostic sandwich enzyme-linked immunosorbent assay (ELISA) was performed for the detection of F. hepatica antigens in stool sample (copro-antigens) of experimentally infected animals (mice, rats and rabbits) over a period of 18 weeks using affinity-purified polyclonal antibodies raised against the whole adult F. gigantica. The test demonstrated fascioliasis in mice earlier than in rats or rabbits (4, 6 and 7 weeks post infection respectively) by detection of copro-antigens in stool samples. In all experimentally infected models, F. hepatica copro-antigens concentration showed continuous increase and mice samples had higher antigen concentration than rats and rabbits. Sensitivity of ELISA was significantly higher in mice (83.3%) than in rats and rabbits (75% and 66.7% respectively) and its specificity showed nearly similar results to sensitivity. From the previously obtained data, it could be concluded that ELISA proved to be a rapid, easy and sensitive test for diagnosing fascioliasis by detection of F. hepatica copro-antigens earlier than routine stool examination of Fasciola eggs.

Evaluating the detection of circulating filarial antigen in diagnosis of bancroftian filariasis and filarial hydrocele

Four groups of patients were selected: 16 patients with clinical evidence of obstructive filarial lymphangiopathy without microfilaraemia; 12 patients with clinical evidence of obstructive filarial lymphangiopathy with microfilaraemia and 9 patients with microfilaraemia. Two control groups were also included. Blood films, sera and hydrocele fluid samples were collected from all subjects. Polyclonal antibody against Dirofilaria immitis worm homogenate was prepared, fractionated and conjugated with HRP. Both polyclonal antibody and monoclonal antibody (AD12) were used in a sandwich ELISA. Using polyclonal antibody, both microfilaraemic groups (groups 2 and 3) had a significantly higher mean O.D. readings than that of control groups (P < 0.05), whereas, the mean O.D. readings of patients with symptomatic amicrofilaraemia had no significant difference than control groups. Symptomatic microfilaraemic group had the highest percentage of antigen positivity 7/12 (58.3%) among all groups while symptomatic amicrofilaraemic group had the least antigen positivity 2/16 (12.5%). Patients presented with elephantiasis only or with hydrocele had no antigen positive levels 0/12 (0%) in their serum or hydrocele fluid samples. On the other hand, 2 out of 4 cases represented with hydrocele (50%) had positive antigen levels in their hydrocele fluid samples. Using monoclonal antibody, all groups had a highly significant higher mean optical density readings than control groups. Asymptomatic microfilaraemic group had the highest percentage of antigen positivity 8/9 (88.9%), followed by symptomatic microfilaraemic 8/12 (66.7%), then symptomatic amicrofilaraemic group 4/16 (25%). The same 2 patients (amicrofilaraemia) and 7 (microfilaraemia) represented with hydrocele had positive antigen levels in their hydrocele fluid samples.

Parasitic causes of hepatomegaly in children

Three hundred children with hepatomegaly were selected. They were subjected to full clinical and laboratory examinations. Also serum samples were examined to detect IgG using ELISA against SEA, chromatography purified hydatid cyst antigen, commercially available Toxoplasma antigen, partially purified adult Fasciola antigen and second-stage larvae Toxocara canis antigen. IFAT was used to detect IgG against Toxoplasma and T. canis. A commercially available IHAT kit for leishmaniasis was used. Based on immunological assays, 125 cases were suffering from various parasitic infections. Thirty cases with schistosomiasis (10%), 26 cases fascioliasis (8.7%), 18 toxocariasis (6%), 35 toxoplasmosis (11.7%), 3 cases hydatidosis (1%) and 13 cases mixed parasitic infections. No parasitic causes could be found in 175 cases (58.3%). Moderate or marked hepatomegaly favours the presence of schistosomiasis. Whereas, most cases with other parasites and those with non-parasitic infections fall in the category of mild hepatic enlargement. There was no associated splenomegaly in cases with Fasciola, Toxocara, hydatid disease and/or the non-parasitic group. Most of hepatomegalic cases with non-parasitic causes were found to be associated with fever (88.5%). Fever was found in nearly 50% of cases with either Toxoplasma or Toxocara infections. Mild eosinophilia was found in all cases with parasitic causes. Only 24 cases of non-parasitic group (13.7%) had easinophilia. Moderate and high eosinophilia were found in cases with fascioliasis and toxocariasis. Cases with fascioliasis had a statistically significant increase in enzymes activities specially alkaline phosphatase. It was concluded that parasitic infections should be considered as an important cause of liver enlargement in children. Serological methods using purified antigenic fractions are an important tool for diagnosis.

Prevalence of Fasciola infection among school children in Sharkia Governorate, Egypt

This study was performed on 1350 school children from 9 different villages in Sharkia Governorate to investigate the real situation of endemicity of fascioliasis in the area. Stool examination using modified Kato thick smear method was performed to detect Fasciola infection and other parasites. Those with negative stool samples were examined serologically by ELISA test to detect anti-Fasciola IgG. All cases with positive anti-Fasciola IgG were further examined by circum-oval precipitin test (COPT) against viable S. mansoni eggs to exclude the crossly reacted Schistosoma infections. Sixty nine cases were found to pass Fasciola eggs in their stool samples (5.1%). Anti-Fasciola IgG was detected in the sera of 231 children (17.1%) using ELISA test. Eighty four out of the 231 children were found positive by COPT and were considered as schistosomal cases. The remaining 147 who gave negative COPT were considered as Fasciola infections. All of the 69 Fasciola positive stool cases were found positive by ELISA test and negative by COPT test. The sensitivity of stool analysis was 47% versus 100% sensitivity of ELISA, whereas the specificity of ELISA was 63%. The total number of Fasciola positive cases by ELISA and stool analysis were 147 cases among 1350 children indicating a prevalence of 10.9% among school children in Sharkia Governorate. This results highlighting the importance of health education and snail control in decreasing the high prevalence.