A seafood risk tool for assessing and mitigating chemical and pathogen hazards in the aquaculture supply chain

Intricate links between aquatic animals and their environment expose them to chemical and pathogenic hazards, which can disrupt seafood supply. Here we outline a risk schema for assessing potential impacts of chemical and microbial hazards on discrete subsectors of aquaculture-and control measures that may protect supply. As national governments develop strategies to achieve volumetric expansion in seafood production from aquaculture to meet increasing demand, we propose an urgent need for simultaneous focus on controlling those hazards that limit its production, harvesting, processing, trade and safe consumption. Policies aligning national and international water quality control measures for minimizing interaction with, and impact of, hazards on seafood supply will be critical as consumers increasingly rely on the aquaculture sector to supply safe, nutritious and healthy diets.

Aquatic contaminants in Solomon Islands and Vanuatu: Evidence from passive samplers and Microtox toxicity assessment

Water Quality issues in many Pacific countries are rising, with the increase in coastal populations and associated urban runoff but management requires contamination issues in the aquatic environment to be identified and prioritised. In Vanuatu and Solomon Islands there are few laboratories and resources to assess for the presence or impact of complex chemical contaminants. The extent and impact of chemical contamination of the marine and coastal environment is poorly described. Passive chemical samplers were used to measure a range of aquatic pollutants around the capital cities, Honiara (Solomon Islands) and Port Vila (Vanuatu). We detected a range of chemicals indicative of agricultural and industrial contamination and a few sites had concerning concentrations of specific hydrocarbons and pesticides. The rapid ecotoxicology test, Microtox, indicated toxic impacts in rivers, coastal sites and urban drains This work provides new data on chemical contamination and possible impacts of that contamination for both countries. The techniques could be applied widely across the region to generate critical data for environmental management, guide monitoring efforts and measure the impact of policy or land-use changes.

Baseline survey of marine sediments collected from the Kingdom of Bahrain: PAHs, PCBs, organochlorine pesticides, perfluoroalkyl substances, dioxins, brominated flame retardants and metal contamination

A baseline survey of sediment contamination was undertaken at 14 locations around the coastline of Bahrain in May 2017, followed by a focused survey of 20 sites, in November 2019. Samples were assessed for industrial pollutants, including metals, PAHs and a suite of organohalogen compounds. The data generated indicated that levels of chemical contaminants were generally low and did not pose a toxicological risk when assessed against commonly applied sediment quality guidelines (SQG). The highest concentrations of PAHs and PCBs were identified in samples collected at coastal sites adjacent to a refinery area known to contain a diverse mix of industry. Tubli Bay, a heavily stressed small bay receiving high loads of sewage effluent, was also identified as an area warranting further investigation with elevated concentrations of BDE209, PFOS and metal contamination. Such data provides a useful baseline assessment of sediment contamination, against which management control measures can be assessed.

Synthetic peptides for the immunodiagnosis of hepatitis A virus infection

VP1, VP2 and VP3 molecules of hepatitis A virus are exposed capsid proteins that have shown to be antigenic and are used for diagnosis in recombinant-antigen commercial kits. In this study, we developed a sequence analysis in order to predict diagnostic peptide epitopes, followed by their spot synthesis on functionalized cellulose paper (Pepscan). This paper with synthetic peptides was tested against a sera pool of hepatitis A patients. Two peptide sequences, that have shown an antigenic recognition, were selected for greater scale synthesis on resin. A dimeric form of one of these peptides (IMT-1996), located in the C-Terminus region of protein VP1, was antigenic with a recognition frequency of 87-100% of anti-IgG antibodies and 100% of anti-IgM antibodies employing the immunological assays MABA and ELISA. We propose peptide IMT-1996, with less than twenty residues, as a cheaper alternative for prevalence studies and diagnosis of hepatitis A infection.

Polychlorinated biphenyl and organochlorine pesticide contamination signatures in deep-sea fish from the Mediterranean Sea

Polychlorinated biphenyl (PCB) and OCP concentrations were determined in the livers of two deep-sea fish species, roughsnout grenadier and hollowsnout grenadier, from the Adriatic Sea. In both species, contaminant concentrations were in the following order: PCBs>DDTs>>HCB. Contaminant load was higher in roughsnout grenadier (PCB: 12,327ngg(-1); DDTs: 5357ngg(-1); HCB: 13.1ngg(-1)) than in hollowsnout grenadier (PCB: 1234ngg(-1); DDTs: 763ngg(-1); HCB 6.3ngg(-1)). PCB patterns were dominated by higher chlorinated congeners (hexa-CBs: 50.3-52.1%, hepta-CBs: 29.6-35.5%, penta-CBs: 8.0-11.1% and octa-CBs :5.2-5.4%). PCBs 138, 153 180 and 187 were the most abundant. Regarding the DDT pattern, p,p'-DDE was prevalent in both species (roughsnout grenadier: 99.7%, hollowsnout grenadier: 90%), suggesting no recent DDT input. In both species, the total 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent (TEQ) concentrations (roughsnout grenadier: mean 43.77pg/g, hollowsnout grenadier: mean 20.49pg/g), calculated from non- and mono-ortho PCBs, reached those encountered in marine organisms at higher levels in the trophic chain.

Detection of schistosomiasis cases in low-transmission areas based on coprologic and serologic criteria The Venezuelan experience

Low and very-low intensities of infection hinder the diagnosis of schistosomiasis. Therefore, new parameters should be established in order to more accurately identify active cases and true infection prevalence, for the adequate implementation of a control program. After the survey and analysis of the epidemiological characteristics of five Venezuelan communities, we propose three criteria for the definition of a "schistosomiasis case", based on different diagnostic methods: stool examination, ELISA-soluble egg antigen with sodium metaperiodate (SMP-ELISA), alkaline phosphatase immunoassay (APIA) and the circumoval precipitin test (COPT). Briefly, criterion I: persons with Schistosoma mansoni eggs in stools; criterion II: persons without eggs in stools, with positive COPT, without previous antischistosome chemotherapy in the last year; and criterion III: persons without eggs in stools, with negative COPT, with two positive immunoenzymatic tests (SMP-ELISA and APIA), and with no previous chemotherapy. The incorporation of serological tests to epidemiologic surveillance in areas of low-transmission tries to compensate the underestimation of prevalence based only on parasitological diagnosis.

Schistosoma: Cross-reactivity and antigenic community among different species

It is not unusual to find common molecules among different species of the genus Schistosoma. When those molecules are antigenic, they may be used in immunodiagnosis and vaccines, but they could also be applied to taxonomic and evolutionary studies. To study cross-reactivity and antigenic community among different species of schistosomes, plasmas from laboratory animals infected with Schistosoma bovis, S. guineensis, S. rodhaini, S. haematobium, and four strains of S. mansoni were evaluated with a crude extract of adult worms of S. mansoni by Western blot. Using the multiple antigen blot assay, plasmas from these infected animals were exposed to a selected group of synthetic peptides from Sm28GST, Sm28TPI, Sm elastase, Sm97, Sm32, Sm31, and Sm Cathepsin L. The results presented herein demonstrate differential cross-reactivity and antigenic community among the Mansoni and Haematobium groups of schistosomes, which is of relevance as an additional new tool for phylogenetic studies of schistosomes as well as for diagnosis and vaccine purposes.

Immunogenicity of polymerizable synthetic peptides derived from a vaccine candidate against schistosomiasis: the asparaginyl endopeptidase (Sm32)

The asparaginyl endopeptidase (Sm32) is expressed in the gastrodermal cells of the schistosome gut and in the head glands of the cercariae. Possibly, Sm32 hydrolyzes pro-proteins involved in the degradation of host hemoglobin [Parasitol. Today 12 (1996) 125]. Preliminary evidences using an Sj32/Sm32 murine vaccine have shown a profound effect on oviposition and worm burden [Chin. J. Schist. Control. 7 (1995) 72; Bull. Human Med. Univ. 24 (1999) 225; Vaccine 20 (2002) 439]. The importance of Sm32 as a novel vaccine candidate is based on the possibility of preventing the maturation of other cathepsins and/or preventing schistosome skin invasion. We studied the immunogenicity of polymerizable peptides derived from Sm32 to select potential protective epitopes. Sm32 prediction of T and B epitopes and homology studies with human legumain were performed. Among the variety of factors that influence the antibody response, we specifically examined the effect of: (i) genetic background of mouse strain, inbred (C57BL/6) versus outbred (Swiss) mice; and (ii) vaccination with a single peptide versus pool of peptides. Swiss mice raised antibodies to three different regions of the Sm32, as tested by the Multiple Antigen Blot Assay (MABA): 182-215 (peptides IMT-70 and 72), 244-273 (IMT-64) and 336-355 (IMT-66). None of these regions were immunogenic for C57BL/6. On the contrary, other peptides, IMT-4 (21-40), IMT-12 (101-120) and IMT-26 (292-313) were highly immunogenic for this inbred strain. Only Swiss mice immunized with a single peptide (IMT-64 and 72) or with three different pools of IMT-peptides (Pool A-II: 14, 16, 18, 70, 72, 89; pool A-III: 22, 64, 24, 26, 28 and pool A-V: 64, 66, 28, 70, 72) recognized the original protein in a crude extract of the worm antigen by Western blot. Peptides IMT-64, 14 and 26 were responsible for this recognition. In general, the vaccination with pool of peptides was more immunogenic for both mouse strains. Predicted B cell epitopes, with hydrophilicity scores over +10 (IMT-12, 64, 26) were always immunogenic after either single or combined peptide vaccination. Sm32 sequences 41-80 (IMT-6 and 8), 141-160 (IMT-16) and 182-215 (IMT-70 and 72) were nearly identical to the corresponding human legumain regions and should be excluded from the human vaccine. We can conclude that the regions of Sm32 that were recognized by antibodies of mice immunized with polymerizable peptides depended on the mice strain and on the hydrophilicity score of the peptides.

Antigenic community between Schistosoma mansoni and Biomphalaria glabrata: on the search of candidate antigens for vaccines

We have previously confirmed the presence of common antigens between Schistosoma mansoni and its vector, Biomphalaria glabrata. Cross-reactive antigens may be important as possible candidates for vaccine and diagnosis of schistosomiasis. Sera from outbred mice immunized with a soluble Biomphalaria glabrata antigen (SBgA) of non-infected B. glabrata snails recognized molecules of SBgA itself and S. mansoni AWA by Western blot. Recognition of several molecules of the SBgA were inhibited by pre-incubation with AWA (16, 30, 36, 60 and 155 kDa). The only specific molecule of AWA, inhibited by SBgA, was a 120 kDa protein. In order to determine which epitopes of SBgA were glycoproteins, the antigen was treated with sodium metaperiodate and compared with non-treated antigen. Molecules of 140, 60 and 24 kDa in the SBgA appear to be glycoproteins. Possible protective effects of the SBgA were evaluated immunizing outbred mice in two different experiments using Freund's Adjuvant. In the first one (12 mice/group), we obtained a significant level of protection (46%) in the total worm load, with a high variability in worm recovery. In the second experiment (22 mice/group), no significant protection was observed, neither in worm load nor in egg production per female. Our results suggest that SBgA constitutes a rich source of candidate antigens for diagnosis and prophylactic studies.

Schistosomiasis mansoni in areas of low transmission: epidemiological characterization of Venezuelan foci

Severe schistosomiasis is a rare event in Venezuela nowadays, after a successful national campaign by the Schistosomiasis Control Program. Unfortunately, this program has practically disappeared, and snail surveillance in field is not a priority, anymore. Thus, schistosomiasis has become a neglected disease in this country. However, surveys in different populations from the endemic area have shown particular epidemiological features described herein. In five communities we evaluated 2,175 persons and searched for the presence of Biomphalaria glabrata snails. Some markers were used for classifying schistosomiasis foci: mean age of the persons with Schistosoma mansoni eggs in the stools, serological tests, presence of B. glabrata snails, and intensity of infection. Places without B. glabrata snails and with few schistosomiasis cases were defined as "past transmission sites"; a site with abundant snails but few cases was defined as "potential risk"; "new transmission" foci were characterized by the presence of infected snails and young people passing eggs in the stools. A "re-emergent" focus has shared these last features, showing in addition a place where schistosomiasis had been reported before. Recent evidences of active transmission with the increasing dispersion of B. glabrata snails, point out the necessity for the re-establishment of the Schistosomiasis Control Program in Venezuela.

Laboratory diagnosis of Schistosomiasis in areas of low transmission: a review of a line of research

After 57 years of successful control of schistosomiasis in Venezuela, the prevalence and intensity of infection have declined. Approximately 80% of the individuals eliminate less than 100 eggs/g of stools, therefore morbidity is mild and the majority are asymptomatic. The sensitivity of Kato-Katz decreases to approximately 60%. Available serological methods for the detection of circulating antigens only reach a 70% of sensitivity. Tests based on the detection of antibodies by immunoenzymatic assays have been improved. The circumoval precipitine test has shown a high sensitivity (97%), specificity (100%), and correlation with oviposition, being considered the best confirmatory diagnostic test. Additionally to the classical immunoenzymatic assays, the development of the alkaline phosphatase immunoassay, allowed to reach a 100% specificity with an 89% sensitivity. Recently, we have developed a modified ELISA in which the soluble egg antigen is treated with sodium metaperiodate (SMP-ELISA) in order to eliminate the glycosilated epitopes responsible for the false positive reactions. The specificity and sensitivity reaches 97% and 99%, respectively. Synthetic peptides from the excretory-secretory enzymes, cathepsin B (Sm31) legumain (Sm32) and cathepsin D (Sm45), have been synthesized. The combination of two peptides derived from the Sm31 have been evaluated, reaching a sensitivity of 96% when analyzed independently and with a 100% specificity. Antibodies raised in rabbits against peptides derived from the Sm31 and Sm32 are currently evaluated in two different antigen-capture-based assays. The development of a simple, cheap and reliable test that correlates with parasite activity is a major goal.

Schistosoma mansoni: immunodiagnosis is improved by sodium metaperiodate which reduces cross-reactivity due to glycosylated epitopes of soluble egg antigen

ELISA with soluble egg antigen (SEA) from Schistosoma mansoni is widely used in the diagnosis of schistosomiasis, but cross-reactivity with other intestinal helminths, overestimating the true prevalence, represents a great limitation. The role of glycoproteins of SEA in cross-reactions was investigated. SEA was oxidized with sodium metaperiodate (SMP) in ELISA and immunoblot. One hundred schistosomiasis-negative individuals sera were submitted to SMP-ELISA improving the specificity from 73% without SMP treatment to 97% with SMP. On the other hand, 94 S. mansoni-positive sera were evaluated showing that 99% were positive in ELISA either with or without SMP treatment, indicating the maintenance of high sensitivity under SMP treatment. By immunoblot, 24 sera from persons with schistosomiasis and 10 sera from schistosomiasis-free persons were assayed under reducing and nonreducing conditions with or without SMP, looking for specific infection markers and cross-reactivity markers. Reactivity from positive sera showed that specific molecules were mainly low-molecular-mass antigens and seem to have predominant proteic epitopes. The unspecific molecules reacting with some schistosomiasis-negative individuals harboring other intestinal parasites (false-positive sera) were mostly larger than 60 kDa and seemed to be basically glycosylated. Glycosylated epitopes have an important role in cross-reaction and SMP can successfully be used to reduce the false reactivity of SEA with no decrease in sensitivity, especially in ELISA as an immunodiagnostic screening surveillance method, which is useful in areas of low schistosomiasis transmission.

Evaluation of alkaline phosphatase immunoassay and comparison with other diagnostic methods in areas of low transmission of schistosomiasis

The alkaline phosphatase immunoassay (APIA) is an antibody detection technique which permits the diagnosis of schistosomiasis using a butanolic extract preparation from adult worms. APIA has demonstrated high sensitivity and specificity in previous reports with well characterized human sera. Its potential as a diagnostic tool for epidemiological surveillance was assessed in comparison with three other diagnostic tests: stool examination, ELISA with soluble egg antigen (SEA) and the circumoval precipitin test (COPT). APIA was 100% specific in an area without Schistosoma mansoni transmission and had 89% sensitivity in an endemic area where 69% of the infected subjects excreted less than 100 eggs g of faeces. It was found to be less sensitive in children under 5 years of age who were positive by the COPT test. APIA can be applied as an initial screening test, based on its high sensitivity, specificity, absence of cross-reactivity with intestinal parasites and the fact that it is a technique suitable for use in epidemiological surveillance.

Do intestinal parasites interfere with the seroepidemiologic surveillance of Schistosoma mansoni infection?

In view of the known cross-reactivity of sera from patients with intestinal parasites to some Schistosoma mansoni antigens, field work was conducted in an area of Venezuela non-endemic for schistosomiasis using the routine immunoenzymatic assay (ELISA) with soluble egg antigen (SEA). False positive reactions represented 15.3% of the total population as determined by SEA-ELISA. SEA-immunoblotting of the false positive sera indicated that protein fractions of 91 and 80 kDa appear to be responsible for cross-reactivity. Sera from hookworm infected individuals produced a higher frequency and intensity of cross-reaction than other sera. SEA-fractions of 105, 54, 46, 42, 32, 25 and 15 kDa were the most specific.

Humoral immune response of children with chronic schistosomiasis. Isotype recognition of adult worm antigens

In areas of low transmission of schistosomiasis, the evaluation of the success of control depends on reliable diagnostic tests. Under such conditions, some of the serological tests better estimate the real prevalence of this parasitosis than the classical stool examinations. On the search of highly sensitive and specific antigenic fractions for use in serological tests, an immunoblot technique with a luminescent substrate was used in order to evaluate, under dissociating and reducing conditions, the Schistosoma mansoni adult worm antigen (AWA). The sera of 30 infected Venezuelan children were assayed for specific recognition of AWA by IgG, IgM, IgE, IgA, and the four IgG subclasses. Eight highly specific polypeptide molecules from the parasite of 118, 114, 105, 74, 71, 45, 36, and 30 kDa were recognized by total IgG. Additionally, IgG1 and IgG2 recognized a molecule of 100 kDa and IgM one of 77 kDa. The present data suggests that certain molecules from the adult worm, specially the 36 kDa, might be relevant in the specific immunodiagnosis of this parasitic disease. The fact that the children antibodies were able to recognize the primary structure of these antigens, will allow us to chemically synthesize the relevant linear epitopes.

Effect of chemotherapy on immune response to egg antigens of Schistosoma mansoni in chronically infected children from areas of low transmission

In an attempt to identify antigenic molecules from Schistosoma mansoni eggs, a serological study was performed on children of a Venezuelan town (Caraballeda) in which the transmission of schistosomiasis had been interrupted two years prior to sera sampling. Infected children received treatment with Praziquantel and, based on the disappearance of eggs in the stools plus negativization of the circumoval precipitin test (COPT) one year after treatment, they were classified as either responders or non-responders to chemotherapy. Western blots of soluble egg antigen (SEA) with a very sensitive chemiluminescent substrate were performed. Sera from responder children recognized a 25 kDa band of SEA which diminished significantly after treatment. This was less frequent in non-responder children. When the sera of responder and non-responder children were compared before treatment, we found that the recognition of the 40 and 41 kDa proteins could be predictive of response to chemotherapy. All these antigens, used in ELISA-type techniques, might be of importance in the evaluation and follow-up of large scale schistosome control programmes.

A calmodulin-activated (Ca(2+)-Mg2+)-ATPase is involved in Ca2+ transport by plasma membrane vesicles from Trypanosoma cruzi

High-affinity Ca(2+)-activated ATPases that do not show any demonstrable dependence on Mg2+ have been reported in the plasma membranes of different trypanosomatids, and it has been suggested [McLaughlin (1985) Mol. Biochem. Parasitol. 15, 189-201; Ghosh, Ray, Sarkar & Bhaduri (1990) J. Biol. Chem. 265, 11345-11351] that these enzymes may have a role in Ca2+ transport by the plasma membrane and in the regulation of intracellular Ca2+ in these parasites. In this report we investigated Ca2+ transport by Trypanosoma cruzi plasma membrane vesicles using Arsenazo III as a Ca2+ indicator. These vesicles accumulated Ca2+ upon addition of ATP only when Mg2+ was present and released it in response to the Ca2+ ionophore A23187, but were insensitive to inositol 1,4,5-trisphosphate. Ca2+ transport was insensitive to antimycin A, oligomycin and carbonyl cyanide p-trifluorophenylhydrazone, ruling out any mitochondrial contamination. Staurosporine and phorbol myristate acetate had no effect on this activity, while low concentrations of vanadate (10 microM) completely inhibited it. In addition, we describe a high-affinity vanadate-sensitive (Ca(2+)-Mg2+)-ATPase in the highly enriched plasma membrane fraction of T. cruzi. Kinetic studies indicated that the apparent Km for free Ca2+ was 0.3 microM. On the other hand, Ca(2+)-ATPase activity and Ca2+ transport were both stimulated by bovine brain calmodulin and by endogenous calmodulin purified from these cells. In addition, trifluoperazine and calmidazolium, at concentrations in the range in which they normally exert anti-calmodulin effects, inhibited the calmodulin-stimulated Ca(2+)-ATPase activity. These observations support the notion that a Mg(2+)-dependent plasma membrane Ca2+ pump is present in these parasites.