Schistosoma mansoni is the main causative agent of intestinal schistosomiasis which affects millions of people worldwide. At the larval stage, miracidia are released into bodies of water where they utilize their motility to successfully infect their intermediate host, snails. Here, we revisit the motility and survival of S. mansoni miracidia throughout its life span. Briefly, miracidia motility was monitored at 30-min and 60-min intervals under the presence/absence of natural/artificial light. Based on a subjective evaluation of activity, body shape and transparency, 6 categories of miracidia activity were established from its fully active stage to its immobile larva stage. The estimated life span of miracidia was 5.8 and 3.5 h in the experiments with 60-min and 30-min observation intervals, respectively. Death was defined by an absence of cilia and body movement. When mobility was used as a proxy for infectivity, infective miracidia were detected at 2.5 and 4.5 h, respectively. The present miracidia motility and survival re-evaluation supports parameters optimization for computational modelling of schistosomiasis transmission dynamics. Target control interventions, especially at late stages next to transmission interruption, may greatly benefit from improved modelling studies.

Assays which enable the detection of schistosome gut-associated circulating anodic (CAA) and cathodic (CCA) antigen in serum or urine are increasingly used as a diagnostic tool for schistosome infection. However, little is known about the production and clearance of these circulating antigens in relation to the sex and reproductive maturity of the parasite. Here we describe CAA and CCA excretion patterns by exploring a mouse model after exposure to 36 male-only, female-only and mixed (male/female) Schistosoma mansoni cercariae. We found that serum and urine CAA levels, analysed at 3 weeks intervals, peaked at 6 weeks post-infection. Worms recovered after perfusion at 14 weeks were cultured ex vivo. Male parasites excreted more circulating antigens than females, in the mouse model as well as ex vivo. In mixed infections (supporting egg production), serum CAA levels correlated to the number of recovered worms, whereas faecal egg counts or Schistosoma DNA in stool did not. No viable eggs and no inflammation were seen in the livers from mice infected with female worms only. Ex vivo, CAA levels were higher than CCA levels. Our study confirms that CAA levels reflect worm burden and allows detection of low-level single-sex infections.

The study aimed to compare the diagnostic performance of the Kato-Katz, formalin ether concentration method (FECM) and FLOTAC using Sheather's sugar solution (FS1), saturated sodium chloride (FS2) and zinc sulfate (FS7) for the diagnosis of intestinal parasites among school children, focusing on Schistosoma mansoni. Ninety fecal samples were examined using the above mentioned techniques. The overall infection rate was 87.7%. Concerning protozoa, FLOTAC (FS1 and FS2) and FECM detected nearly equal infection rates (43.3% and 44.4%, respectively) with very good agreement. Kato-Katz diagnosed the highest helminthic infection rate (57.8%) followed by FLOTAC FS7 (44.4%) and FECM showed the lowest helminthic infection rate (27.7%). As for S. mansoni, Kato-Katz showed an infection rate of 38.8% vs FLOTAC (22.2%) and FECM (11.1%). The three techniques detected the same infection rate (11.1%) with egg counts more than 72 eggs/gram of feces. The FLOTAC sensitivity and accuracy for the diagnosis of protozoa were 97% and 99%, respectively. Regarding helminths diagnosis, FLOTAC technique showed higher sensitivity (77%) and accuracy (87%) compared to FECM (48% sensitivity and 70% accuracy). Therefore, FLOTAC can be used synchronously or in replacement to other diagnostic techniques. This can strategically impact future control programmes of intestinal parasitic infections in limited resources settings.

Schistosomiasis is a neglected tropical parasitic disease caused by different species of genus Schistosoma. Schistosoma mansoni causes a severe intestinal parasitic infection of high public and medical importance in Ethiopia. This study aimed to determine the prevalence of, and risk factors for, S. mansoni infection among the fishermen of Lake Hawassa, southern Ethiopia, using a cross-sectional study design. A total of 243 fishermen were selected from the Hawassa Town Fishermen Association’s list in 2013. Data on socio-demographic characteristics and risk factors were collected from the fishermen using semi-structured questionnaires. Stool samples were collected and processed using the Kato–Katz thick smear technique. The overall prevalence of S. mansoni among the fishermen was 29.21% and the mean intensity of infection was 158.88 eggs per gram (EPG). The overall prevalence of intestinal helminths, including S. mansoni, was 69.54%. Similar prevalences of S. mansoni were recorded in age groups 15–19, 20–24 and 25–29 years: 31.82%, 31.75% and 31.94%, respectively. Fishermen who swam a minimum of once a week in Lake Hawassa were 2.92 times (95% CI: 1.554, 5.502) more likely to have acquired S. mansoni infection than those who swam in the lake less than once a week. The results indicate moderate endemicity of S. mansoni infection among the fishermen of Lake Hawassa. These fishermen could be a potentially high-risk group for S. mansoni infection and might be responsible for the transmission of infection to other segments of the community visiting the lake for recreation. Moreover, a high prevalence of soil-transmitted helminths (STHs) was recorded among the fishermen. Integrated prevention and control strategies for schistosomiasis and STHs by different sectors are needed to tackle this problem.

Acetylcholinesterase (AChE) is present in all stages of the life-cycle of schistosomes and is located in muscle and on the surface of the parasite. Metrifonate is a drug that inhibits AChE. We compared the AChEs from three schistosome species (Schistosoma mansoni, Schistosoma haematobium and Schistosoma bovis) that have different susceptibilities to metrifonate in vivo. Sensitivities to AChE inhibitors were similar. The subunits of AChE were 110 kDa and 76 kDa and the dominant molecular form of AChE was a G2 form in all three species. This was the major form on the tegument while additional molecular forms were associated with the internal tissues. Differences in relative amounts of AChE activity between these species were found in the adults but not in the schistosomula. At the adult stage the major difference between species lay in the relative amounts of AChE activity in their teguments. S. haematobium teguments carried 20 times and S. bovis 6·9 times the activity present on S. mansoni teguments. These quantitative differences associate with the relative sensitivities of these species to metrifonate.

Irrigation for intensive sugar cultivation started in the early 1980s at Richard Toll, some 100 km from the mouth of the Senegal River. Infections with Schistosoma mansoni were first seen in late 1988. This study records quantitative snail surveys for over 3 years from 1992 at sites representing different habitats in and around the irrigation scheme. Populations of both Biomphalaria pfeifferi (the intermediate host of S. mansoni) and Bulinus spp. (mainly B. truncatus, the local host of S. bovis) peaked in late ‘spring' or early ‘summer', depending on the habitat, and then remained low until the following ‘spring'. B. pfeifferi favoured smaller, man-made habitats with most transmission between May and August each year. The less abundant Bulinus spp. favoured larger natural and man-made habitats with most S. bovis transmission between April and July. S. mansoni infections were more, but S. bovis infections were less abundant than other trematodes in their respective snail hosts. Ecological changes in the early 1980s due to sugar irrigation pre-dated similar, more widespread changes in the late 1980s when the completion of dams across the Senegal River prevented seasonal rain fed floods and sea water intrusion. S. mansoni has since spread rapidly around Richard Toll. The incompatibility of the local S. haematobium strains with the dominant bulinid snails has so far prevented an epidemic of urinary schistosomiasis at Richard Toll, but the invasion of similar downstream habitats by susceptible B. globosus is worrying. The principal control measure, chemotherapy, given in the ‘winter' would minimise the rate of reinfection. It could be reinforced by judicious mollusciciding within the sugar irrigation scheme but not elsewhere.

Schistosomiasis remains a serious world-wide public health problem with a still unfulfilled need for routine cost-effective methods of diagnosis. Such methods are required not only for people in endemic areas, but increasingly for tourists who may have become infected during visits to such places. This article reviews the wide range of immunoassays and antigenic preparations that have been shown to have potential for diagnosis of schistosomiasis by the indirect method of antibody detection. Antigens in native form derived from cercariae, adult worms and eggs are considered, as well as schistosome antigens produced by recombinant DNA technology and the schistosome cross-reactive antigen, keyhole limpet haemocyanin (KLH). Respective advantages and disadvantages of antibody detection, circulating antigen detection and parasitological methods of diagnosis are analysed. It is suggested that due to the relative insensitivity of both parasitology and antigen detection, antibody detection methods could find increasing use in situations of low infection intensity.