Fluke egg characteristics for the diagnosis of human and animal fascioliasis by Fasciola hepatica and F. gigantica

In trematodiases, shape and size of the fluke eggs shed with faeces are crucial diagnostic features because of their typically reduced intraspecific variability. In fascioliasis, the usual diagnosis during the biliary stage of infection is based on the classification of eggs found in stools, duodenal contents or bile. The aim of the present study is to validate the identification of Fasciola species based on the shape and size of eggs shed by humans, characterizing their morphometric traits using a computer image analysis system (CIAS). The influence of both the geographical location and of the host (human and livestock) has been analysed. Coprological studies were carried out in fascioliasis human endemic areas, where only F. hepatica is present (the northern Bolivian Altiplano and the Cajamarca valley in Peru), and where F. hepatica and F. gigantica coexist (the Kutaisi region of Georgia, the Nile Delta in Egypt, and the Quy Nhon province in Vietnam). Classically, it is considered that at the abopercular end of the shell of Fasciola eggs there is often a roughened or irregular area. Nevertheless, results show that the frequency of the presence of this feature in F. hepatica is population-dependent, and therefore is not a pathognomonic criterion in diagnosis. The study reveals that eggs shed by humans show morphological traits different from eggs shed by animals. In humans, F. hepatica eggs are bigger and F. gigantica eggs are smaller than reported to date from livestock, and their measurements overlap when compared. The material analysed in this study shows that the size of eggs shed by humans from Georgia and Egypt corresponds to the F. hepatica morph, while the size of eggs shed by humans from Vietnam corresponds to the F. gigantica morph. Measurements of F. hepatica and F. gigantica eggs originating from humans and animals from sympatric areas overlap, and, therefore, they do not allow differential diagnosis when within this overlapping range. In this sense, the new results should aid clinicians since the application of the classic egg size range in human samples may lead to erroneous conclusions. Fasciolid egg size in human stool samples ought to be corrected in books and monographs related to medical parasitology and/or tropical medicine as well as in guides for clinicians and parasitic disease diagnosis analysts.     

Confutation of the existence of sequence-conserved cytochrome P450 enzymes in Plasmodium falciparum

A cross-sectional survey on bovine fasciolosis was conducted in the Binh Dinh province of Central Vietnam that was previously identified as hyperendemic for human fasciolosis. In Vietnam, both pure Fasciola gigantica and hybrid and/or introgressed populations of liverflukes bearing genetic material from both Fasciola hepatica and F. gigantica infect humans and animals. In this study, 825 cattle were randomly selected from 8 of the 11 provincial districts for faecal collection; blood samples were taken from 400 of these animals. Fasciola eggs and antibodies against Fasciola were detected by a quantitative sedimentation method and an Enzyme Linked Immunosorbent Assay, respectively. Overall, 54.9% of the animals were shedding Fasciola eggs while 72.2% were Fasciola seropositive. Animals under two years showed lower Fasciola infection rates than older animals. There were no differences in infection rates between districts. These results indicate a very high prevalence of Fasciola infections in cattle in Binh Dinh province. It is concluded that a fasciolosis control programme should be designed in this region aiming at reducing infection in both cattle and humans.     

The immune response of regional lymph nodes during the early stages of Fasciola hepatica infection in cattle

In this study we examined regional immune responses to Fasciola hepatica infection in the natural ruminant host. Naïve cattle and those pre‐exposed to a drug‐abbreviated infection were subsequently challenged and lymph nodes extracted at slaughter. In vitro proliferation and cytokine production by mononuclear cells isolated from hepatic and mesenteric lymph nodes were measured after culture with whole fluke antigen (WFA). Hepatic lymph node cells had a significantly greater response to parasite antigen than mesenteric lymph node cells (P < 0·02), although there was no difference in the magnitude of the proliferative response between naïve and pre‐exposed challenged cattle. Mononuclear cells from hepatic lymph nodes produced interferon gamma, interleukin 2 and interleukin 4 after culture with parasite antigen, indicative of a mixed, T helper type 0, response. Comparison of the hepatic node response to a variety of F. hepatica antigens showed that proliferation was lower after culture with cathepsin‐L, than with a high molecular weight fraction, WFA or excretory–secretory antigen. Cell culture supernatant fluid from unstimulated hepatic lymph node cells showed an IgG1 response to antigens of 48, 52–70, 82, 96 and 120–190 kDa on Western blot in pre‐exposed, but not naïve, challenged animals.     

Neutralization of the activity of a Fasciola hepatica cathepsin L proteinase by anti-cathepsin L antibodies

Fasciola hepatica secretes a cathepsin L proteinase that is suggested to play an in vivo role in immunoprotection since the enzyme can cleave host immunoglobulin. In the present report, rabbit anti-cathepsin L IgG was shown to bind to the cathepsin L enzyme and inhibit its ability to cleave IgG molecules. Cathepsin L can prevent the antibody-mediated attachment of eosinophils to newly excysted juveniles in in vitro assays; however, if anti-cathepsin L IgG are mixed with the cathepsin L prior to the addition of the enzyme to the assay, eosinophils attach to the newly excysted juveniles. Thus it is possible to prepare antibodies that can bind and disrupt the biological activity of the F. hepatica cathepsin L.     

Assessment of a 27‐kDa antigen in Enzyme‐Linked Immunosorbent Assay for the diagnosis of fasciolosis in Vietnamese patients

Fasciolosis has emerged as an important zoonotic disease in many parts of the world. In recent years, an increasing number of human cases were reported in Vietnam. In this study, the 27‐kDa component protein from the excretory/secretory production of adult Fasciola gigantica, purified by high performance liquid chromatography, was assessed in an enzyme‐linked immunosorbent assay (ELISA) to detect antibodies against Fasciola spp. for diagnosis of human fasciolosis. The ELISA showed a high sensitivity (100%) and specificity (97.67%) when tested on patients with fasciolosis, other parasitic infections, cholangiocarcinoma and on healthy controls. The assay was applied for diagnosis on 143 patients in the Viet Duc‐Hanoi hospital who presented with clinical signs of liver disease and lesions in their livers as shown by imaging techniques. Antibodies were found in 37 (25.9%) of these patients, of whom only 3 shed Fasciola eggs in their stools (2.1%). The excellent response to triclabendazole treatment of 37 sero‐positive patients confirmed the diagnosis of fasciolosis. This study demonstrated the diagnostic potential for human fasciolosis of the 27‐kDa antigen ELISA. Fasciolosis should be considered in the differential diagnosis of hepatic disease in Vietnam.     

Effect of heavy metal emission on the immune response of sheep with experimental fasciolosis

The effect of industrial heavy metal emission on immune reactions was studied in lambs subsequently infected with Fasciola hepatica. The heavy metal emission (Cu,Hg,Pb,Cd,Cr,Zn) was collected from grass at 5km distance from a mercury plant. Administration of the emission for 28 days prior to infection of the animals reduced the percent circulating T- and B-cell populations when compared with untreated animals and animals infected with F. hepatica only. The administration of emission had no suppressive effects on the levels of circulating antibodies to F. hepatica following infection. The intensity of liver infection with mature F. hepatica in the emission-fed and infected lamb group increased by 21·5%. This difference in comparison with control infected animals was not significant.     

Differential expression and localization of saposin-like protein 2 of Fasciola hepatica

FhSAP2 is a novel antigen isolated from the adult fluke of Fasciola hepatica. Based on sequence similarity with amoebapores and other related proteins, it belongs to the saposin-like protein (SAPLIP) family. FhSAP2 has been shown to be highly immunogenic and capable of inducing protective immune responses in mice and rabbits challenged with F. hepatica. Moreover, FhSAP2 is also reactive with sera from humans with chronic fascioliasis. In the present study, we investigated the expression of FhSAP2 in various developmental stages of F. hepatica by qPCR and demonstrated that FhSAP2–mRNA species are up-regulated in undeveloped eggs, newly excysted juveniles, and adults, but down-regulated in the miracidium stage. Monoclonal antibodies against FhSAP2 were produced, and two clones that are positive to F. hepatica whole-body extract, but not reactive with extracts from other trematodes, were selected, expanded and used for histolocalization studies. Confocal immunofluorescence revealed the presence of native FhSAP2 in epithelial cells surrounding the gut, toward the outermost part of the tegument, and toward the tegumental cells of both adults and newly excysted juveniles.     

Immune responses directed at egg proteins during experimental infection with the liver fluke Fasciola hepatica

Fasciola hepatica is responsible for human disease and economic livestock loss on a global scale. Unlike the well characterized schistosomes, only the adult and juvenile stages of F. hepatica are implicated in disease, whereas the freely voided egg is not thought to contribute to host–parasite interactions. We investigated specific immune responses to soluble F. hepatica egg proteins (SFHEP), during a 14‐week experimental infection, demonstrating significant increases in anti‐SFHEP IgG1 (P = 0·001), transforming growth factor beta‐1 (P = 0·008) and IL‐10 (P < 0·001) titres at the onset of egg production. Western blot analysis of soluble SFHEP demonstrates that protein bands migrating at 61·6, 54·8 and 44 kDa become sero‐reactive before the appearance of eggs within host faeces. Therefore, expression of some egg‐associated proteins indicates progression to chronic disease. Antigenic bands were investigated through mass spectrometry, identifying a protein disulphide isomerase (PDI) (61·6 kDa), an enolase and ferritin‐related proteins (54·8 kDa), and a cocktail of dehydrogenases (44 kDa). Biochemical analysis of egg secretions reveals proteolytic activity, which increases over time, indicating that proteases may be continually secreted during the course of egg maturation. The implications of egg‐specific immune responses and proteolytic secretions are further discussed.     

Seroprevalence of fascioliasis in the eastern region of Turkey: an eight-year investigation

Background/AimsFascioliasis is a zoonotic disease and one of the most neglected infectious diseases in humans. Its prevalence has been increasing significantly during the last decades. This study aimed to investigate the prevalence of fascioliasis using direct microscopy and indirect hemagglutination (IHA) technique in a region in Eastern Anatolia of Turkey.Material and MethodsThis study was conducted on the serum samples obtained from 817 patients (372 male and 445 female) between 2011 and 2018, who were suspected to have fascioliasis. IHA was used to investigate anti-Fasciola hepatica antibodies in the serum samples. Stool specimens were obtained from the seropositive patients and were examined with the native-Lugol method to identify the parasites.ResultsIt was determined that 5.5% (45/817) of all the patients were F. hepatica seropositive and 6.4% (52/817) were borderline positive. Positivity was 5.7% (21/372) among males and 5.4% (24/445) among females, and the difference in the infection rates between these groups was not significant (p=0.913). The highest number of patients who applied to the clinic was in the “45 and over” age group (317 patients); 270 patients were in the 25–44 age group. A maximum positivity of 10.3% was observed in the 7–14 age group.ConclusionPreviously, fascioliasis was considered a rare infection in humans; however, it has emerged as an important public health problem in the world. Considering fascioliasis in patients with clinical symptoms, not only with direct observation but also using serological methods, would be effective in early diagnosis and treatment of the disease.     

High prevalence of large trematode eggs in schoolchildren in Cambodia

Large trematode eggs (LTE) resembling Fasciola spp. eggs were reportedly found in the stools of schoolchildren in Kandal province, Cambodia. This study aimed to assess the prevalence of LTE in the stools of children attending the affected school, identify potential risk factors for infection and ascertain the trematode species. We performed a cross-sectional study involving an in-depth questionnaire administered to schoolchildren at the affected school, and examined cattle droppings in the surrounding area and the livers of slaughtered cattle. Three stool samples were examined per child, using Kato–Katz and formalin–ether concentration techniques. In addition, blood serum enzyme-linked immunosorbent assay (ELISA) and coprological polymerase chain reaction (PCR) was conducted for species clarification. Cattle droppings were examined by cup sedimentation and coprological ELISA. LTE were observed in the stools of 106 schoolchildren (46.5%). Two blood serum samples from schoolchildren were positive for Fasciola hepatica in a first ELISA but were negative in a confirmation immunofluorescence antibody test. Out of 221 PCR samples, only one tested positive for Fasciola spp. and none for Fasciolopsis buski. The consumption of raw aquatic plants (odds ratio (OR) = 3.3) and fermented fish sauce (OR = 2.1) were significantly associated with LTE in the stool. Fasciola spp. flukes were observed in 18.3% of 191 cattle livers. The prevalence of fascioliasis in cattle droppings was 88.8%. The low prevalence of schoolchildren that tested positive for Fasciola spp. with specific molecular diagnostics and who had no diagnostic evidence of F. buski strongly indicates that the majority of microscopically observed LTE are from Echinostoma spp. Fasciola spp. transmission from cattle to human is possible and public health services need to be alerted accordingly.     

High fascioliasis infection in children linked to a man-made irrigation zone in Peru

We detected 10 protozoan and nine helminth species in surveys of 338 5-15 year-old Quechua schoolchildren in three communities of the Asillo zone of the Puno region, located at a very high altitude of 3910 m in the Peruvian Altiplano. The area proved to be hyperendemic for human fascioliasis with a 24.3% overall mean prevalence of Fasciola hepatica, local prevalences ranging between 18.8 and 31.3%, and infection intensities of up to 2496 eggs per gram of faeces (epg), with 196-350 epg (mean: 279 epg) and 96-152 epg (123 epg) as arithmetic and geometric means, respectively. Prevalences did not significantly vary between schools and in relation to sex. No statistical differences were found in intensities between schools, nor according to sex or age groups between and within schools, although the highest overall egg counts were detected in girls and in the youngest age group. Asillo zone is a man-made irrigation area built only recently to which both liver fluke and lymnaeid snails have quickly adapted. The region appears to be isolated from the Northern Bolivian Altiplano natural endemic area. Such man-made water resources in high altitude areas of Andean countries pose a high fascioliasis risk. Significant positive association of F. hepatica with protozooses following a one host life cycle, such as Giardia intestinalis, suggests that human infection mainly occurs through drinking water. This is supported by additional evidence such as the absence of typical aquatic vegetation in the drainage channels inhabited by lymnaeid snails, the absence of aquatic vegetables in the traditional nutrition habits of the Quechua inhabitants, and the lack of potable water systems inside dwellings, which requires inhabitants to obtain water from irrigation canals and drainage channels.     

Fascioliasis in Eosinophilic Patients in the Isparta Region of Turkey

Background: The aim of this study was to investigate fascioliasis in a group of eosinophilic and non-eosinophilic patients in the Isparta region of Turkey. Patients and Methods: All cases were examined for antibodies against Fasciola hepatica by the modified ES-ELISA method. Seropositive patients with fascioliasis were investigated by radiological and laboratory evaluations. Results: Of the 756 eosinophilic patients, 6.1% were found to be positive for fascioliasis by ES-ELISA, while the rate was only 0.9% among the non-eosinophilic group (statistically significant, p < 0.001). Among the seropositives, 19 cases were evaluated further. Ultrasonographic findings were found in 14 of the 19 cases. In six of nine cases, computed tomography findings were related to fascioliasis. F. hepatica eggs were found in ine of the 19 cases. Conclusion: Fascioliasis was demonstrated in the Isparta region of Turkey for the first time. The higher prevalence of fascioliasis among patients with eosinophilia indicates the importance of this sign for this infection. Received: May 23, 2002 · Revision accepted: October 5, 2002 M. Demirci (corresponding author)     

Resistance to liver fluke infection in the natural sheep host is correlated with a type-1 cytokine response

Indonesian thin‐tail (ITT) sheep can resist infection with Fasciola gigantica but not F. hepatica and presents an ideal model to investigate the mechanisms of liver fluke resistance in a natural host. This study examines the local and systemic immune responses of sheep during Fasciola infection and demonstrates that different anatomical tissues display distinct cytokine profiles consistent with liver fluke migration. The study also reveals a significant difference in the cytokine and antibody profiles of ITT sheep infected with F. gigantica compared with F. hepatica, with a higher ratio of IL‐4/IFN‐γ mRNA expression and specific IgG1/IgG2 antibodies strongly correlating with pathology. Interestingly, the significant type‐1 cytokine profile occurred in the lymph node closest to the site of infection at a time when the effective immune response against F. gigantica liver flukes is thought to occur. When the same F. gigantica infection in the resistant ITT sheep was compared with the susceptible Merino breed, the resistant type‐1 phenotype against liver fluke infection was only observed in the ITT sheep. These studies provide the first evidence to suggest that the induction of an early type‐1 immune response in this natural sheep host may be responsible for the ability to resist liver fluke infection.     

Fasciola hepatica: A cause of Obstructive Jaundice in an Elderly Man From Iran

Fascioliasis is a zoonotic infection caused by Fasciola hepatica. Humans can become accidental hosts of this parasite by ingesting contaminated drinking water or plants in endemic area. The north of Iran is one of the regions. This disease is rarely seen with jaundice caused by obstruction of the biliary tree. We report a case of human fascioliasis with obstructive jaundice who was diagnosed using endoscopic retrograde cholangiopancreatography (ERCP). This report confirms the diagnostic role of ERCP in patients with obstructive jaundice caused by biliary fascioliasis.     

肝片吸虫组织蛋白酶L基因的克隆、表达和免疫原性分析

目的 克隆和表达肝片吸虫组织蛋白酶 L 基因（FhCL）,分析其免疫原性。 方法 根据GenBank公布的FhCL基因序列设计引物,以肝片吸虫总RNA为模板,通过RT-PCR扩增FhCL基因编码序列,PCR产物经TA克隆,通过EcoRⅠ、HindⅢ双酶切和测序鉴定获得重组质粒pMD18-T/FhCL,并将其亚克隆入原核表达载体pET30a（+）,经PCR,以及BamHⅠ、HindⅢ双酶切和测序鉴定,构建原核表达质粒pET30a（+）-FhCL,转化大肠埃希菌(E. coli)BL21（DE3）pLysS,异丙基-β-D-硫代半乳糖苷（IPTG）诱导表达并获得纯化的重组蛋白FhCL,用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）鉴定,以及蛋白质印迹（Western blotting）分析该重组蛋白对感染肝片吸虫的山羊血清及免疫的SD大鼠血清的免疫反应性。结果 PCR和BamHⅠ、HindⅢ双酶切均可见约1 000 bp的条带,测序结果显示重组质粒pET30a（+）-FhCL构建成功。SDS-PAGE结果表明,重组蛋白相对分子质量约为 Mr 42 000（含6个组氨酸标签）,与目的蛋白相符,以包涵体形式表达。Western blotting分析结果显示,纯化的重组蛋白FhCL可被感染肝片吸虫的山羊血清和免疫的SD大鼠血清识别,在目的条带Mr 42 000处见单一特异性条带,而阴性对照血清则无反应带。 结论 克隆及表达了肝片吸虫组织蛋白酶 L 编码基因,重组蛋白具有良好的免疫原性。     

Indirect evidence of ectopic pancreatic fascioliasis in a human

Fascioliasis is not common in humans and, furthermore, its ectopic migration into the pancreas is extremely rare. A definitive diagnosis of ectopic fascioliasis is based on the demonstration of flukes in the affected organ. If the flukes invade the parenchyma, however, imaging studies are limited in the detection of worms and surgical identification is required. We encountered a clinical case of probable ectopic pancreatic fascioliasis diagnosed through indirect evidence. A 46-year-old Korean woman was admitted with left upper quadrant pain. She had taken praziquantel for hepatic fascioliasis, which had been diagnosed at another hospital, and then developed abdominal pain. Peripheral eosinophilia, hyperamylasemia and hyperlipasemia were documented. Abdominal computed tomography (CT) revealed multiple, hypodense foci which had coalesced, forming irregular nodules in the medial and lateral segments of the left lobe of the liver, and similar 2- to 3-cm sized, hypodense lesions in the body and isthmus of the pancreas. IgG antibody against Fasciola hepatica was positive. Bithionol was given orally, and the patient's symptoms and biochemistry then improved, with reversal of eosinophilia. Radiological studies showed normalization of the liver and pancreas at the 10th week, and the serology for Fasciola hepatica was negative at the fifth month.     

Molecular differentiation of Turkey cattle isolates of <Emphasis Type="Italic">Fasciola hepatica</Emphasis> and <Emphasis Type="Italic">Fasciola gigantica</Emphasis>

The most common and widespread liver flukes of the genus Fasciola are Fasciola hepatica and F. gigantica. Adults of both species occur in many domestic ruminants and in humans and can cause serious disease. The differential diagnosis of these flukes infection is very important because of their different transmission and epidemiological characteristics. A simple and rapid PCR-restriction fragment length polymorphism (RFLP) assay, using the common restriction enzymes AluI and RsaI, is described to distinguish between both fasciolid species. After the digestion of the mitochondrial cytochrome c oxidase 1 (CO1) PCR product with the restriction enzyme AluI, the RFLP profile obtained from F. hepatica revealed two fragments, whereas F. gigantica was not cut. The RsaI digestion generated two fragments from F. gigantica, whereas it did not cut the PCR product from F. hepatica. Results were confirmed with CO1 sequence analysis of both F. hepatica and F. gigantica. The present study suggests that the PCRRFLP method described here can be used for the proper identification of Fasciola species.     

Use of a partially purified Fasciola gigantica worm antigen in the serological diagnosis of human fascioliasis in Egypt

Crude extracts of Fasciola gigantica adult worms, when used as an antigen in indirect hemagglutination (IHA) and counterimmunoelectrophoresis (CIEP) tests, detected all independently diagnosed human F. gigantica and F. hepatica infections but cross-reacted with sera of patients with schistosomiasis and amebiasis. Fractionation of this crude worm extract using Sephadex G-200 chromatography demonstrated four major protein peaks. Antigen from the crest and descending portion of peak II (mol. wt. approximately 20 x 10(3)) and all of peak III (mol. wt. approximately 6 x 10(3)) were pooled and used as a source of partially purified antigen. This partially purified fraction, when used in the CIEP test, reacted with sera from patients with fascioliasis but not those from schistosomiasis or amebiasis patients, whether undiluted or concentrated fivefold, but failed to react by IHA with fascioliasis sera. It reacted with undiluted sera from all individuals passing F. gigantica eggs except one, a possibly spurious infection, and with eight of 20 sera from individuals passing F. hepatica eggs, while the remaining 12 sera became positive after fivefold concentration. It also reacted with two sera from individuals passing eggs of both Fasciola species and with five of 11 sera from individuals negative microscopically but positive serologically with the crude antigen.     

Fasciola hepatica infection reduces Mycobacterium bovis burden and mycobacterial uptake and suppresses the pro‐inflammatory response

Bovine tuberculosis (BTB), caused by Mycobacterium bovis, has an annual incidence in cattle of 0.5% in the Republic of Ireland and 4.7% in the UK, despite long‐standing eradication programmes being in place. Failure to achieve complete eradication is multifactorial, but the limitations of diagnostic tests are significant complicating factors. Previously, we have demonstrated that Fasciola hepatica infection, highly prevalent in these areas, induced reduced sensitivity of the standard diagnostic tests for BTB in animals co‐infected with F. hepatica and M. bovis. This was accompanied by a reduced M. bovis‐specific Th1 immune response. We hypothesized that these changes in co‐infected animals would be accompanied by enhanced growth of M. bovis. However, we show here that mycobacterial burden in cattle is reduced in animals co‐infected with F. hepatica. Furthermore, we demonstrate a lower mycobacterial recovery and uptake in blood monocyte‐derived macrophages (MDM) from F. hepatica‐infected cattle which is associated with suppression of pro‐inflammatory cytokines and a switch to alternative activation of macrophages. However, the cell surface expression of TLR2 and CD14 in MDM from F. hepatica‐infected cattle is increased. These findings reflecting the bystander effect of helminth‐induced downregulation of pro‐inflammatory responses provide insights to understand host‐pathogen interactions in co‐infection.     

Adult worm‐specific IgE/IgG4 balance is associated with low infection levels of Schistosoma mansoni in an endemic area

Field studies have suggested an immune‐mediated mechanism associated with resistance to Schistosoma mansoni infection. Overall, levels of specific IgE have been correlated with resistance to infection, whereas levels of IgG4 have been associated with susceptibility. This study aimed to evaluate serum levels of soluble adult worm antigen preparation (SWAP)‐specific IgE and IgG4 in relation to current infection in a large casuistic of individuals living in an endemic area of schistosomiasis in Bahia, Brazil. The prevalence of S. mansoni infection was 37·7% and the mean parasite burden was 55·4 (0–2100) epg/faeces. There was no significant difference in the levels of SWAP‐specific IgE in individuals with different parasite burden, whereas high producers of parasite‐specific IgG4 presented higher parasite burden when compared to low IgG4 producers. Additionally, S. mansoni parasite load was positively correlated with the levels of specific IgG4 or total IgE. No significant correlation was observed between parasite burden and SWAP‐specific IgE. Nevertheless, SWAP‐specific IgE/IgG4 ratio was higher in uninfected or lightly infected individuals (1–99 epg/faeces) than in heavily infected ones (≥400 epg/feces). These findings highlight the important role of IgE/IgG4 ratio in the resistance to infection, which could be useful for further studies in schistosomiasis vaccine candidates.