Epidemiologia e filodinamica dei genotipi e sottogenotipi di HBV pi\uf9 diffusi in Italia e in Albania

The molecular epidemiology and phylodynamic history of HBV in Italy and Albania was studied on 230 Italian isolates drawn during the period 1980-2007 and 73 Albanian isolates drawn between 2005-2007 from patients living in a homogenous geographical area. Evolutionary rates were estimated and HBV demographic history was reconstructed by using a statistical approach based on coalescent theory. In Italy, the predominant genotype resulted was D (72%) followed by genotype A (20%), F and G (3%) both; among the subgenotypes, D3 was predominant in intravenous drug users (IVDUs) and A2 in men-having-sex-with-men (MSM). In Albania, the only genotype resulted was D, the predominant subgenotypes were D2 (72%), followed by D1 and D3 (14%) both. The evolutionary rates in Albanian D2 and Italian D3 subgenotype were equal. In Italy, the diffusion of D3 subgenotype was identified between 1950 and 1980 probably by use of non safely blood transfusions. In Albania, the entry and diffusion of D2 subgenotype was identified between 1986 and 1995 probably by parenteral transmission of the HBV. The exponential growth rate of D3 epidemic in Italy was significantly lower than that of D2 in Albania

Mapping of poverty and likely zoonoses hotspots

The objective of this report is to present data and expert knowledge on poverty and zoonoses hotspots to inform prioritisation of study areas on the transmission of disease in emerging livestock systems in the developing world, where prevention of zoonotic disease might bring greatest benefit to poor people

ORIGINE, EPIDEMIOLOGIA E FILOGEOGRAFIA DEI GENOTIPI D E A DEL VIRUS DELL'EPATITE B

Hepatitis B virus (HBV) is the leading cause of liver disease and infects an estimated 240 million people worldwide. It is characterized by an high degree of genetic heterogeneity because of the use of a reverse transcriptase during viral replication. The ten genotypes (A-J) that have been described so far further segregate into a number of subgenotypes which have distinct ethno-geographic distribution. Genotypes A and D are ubiquitous and the most prevalent genotypes in Europe (mainly represented by subgenotypes D1-3 and A2); genotypes B and C are restricted to eastern Asia and Oceania; genotype E to central and western Africa; and genotypes H and F (classified into 4 subgenotypes) to Latin America and Alaska. The aim of this study was to determine the HBV genotypes/subgenotypes circulating in Italy and to study their distribution in relation to demographic and risk factors. To this aim, we analyzed the P gene sequences of a total 230 HBsAg-positive Italian patients. Our study showed that the HBV genotype prevalent in Italy was D (72.2%) followed by A (18.7%). In particular in patients infected with HBV-D the subgenotype prevalent was D3 (80.1%); in patients with HBV-A the subgenotype prevalent was A2 (93%). The subgenotype D3 was common among subjects who used injecting drug (69.2%) while the subgenotype A2 was common among subjects having sex with men (66.7%). Furthermore, to reconstruct the spatio-temporal dynamics (origin and geographic dispersion) of the genotypes/subgenotypes widespread in Italy and in Europe, the Italian HBV sequences characterized in this study were aligned with reference sequences obtained in different countries, retrieved from public databases. The study was performed using new methods of phylogenetic analysis based on molecular clocks coalescent theory and the phylogeographic approach. The phylogeographical analysis of HBV-D showed that India had the highest posterior probability of being the location of the tree root, whereas central Asia was the most probable location of the common ancestor of subgenotypes D1-D3. The time of the most recent common ancestor (tMRCA) of the tree root was 128 years ago, which suggests that the common ancestor of the currently circulating subgenotypes existed in the second half of the XIX century. The mean tMRCA of subgenotypes D1-D3 was between the 1940s and the 1950-60s. On the basis of our phylogeographic reconstruction, it seems that HBV-D reached the Mediterranean area in the middle of the XX century by means of at least two routes: the first pathway (mainly due to the spread of subgenotype D1) crossing the Middle East and reaching north Africa and the eastern Mediterranean, and the second pathway (closely associated with D2) that crossed the former Soviet Union and reached eastern Europe and the Mediterranean through Albania. The phylogeographical analysis of HBV-A showed that the common ancestor of the currently circulating A subgenotypes was placed in west-central Africa a mean 1057 years ago. The genotype diverged into two main clades at the beginning of the 13th century: one including all of the west-central African quasi-subgenotypes and the other corresponding to subgenotype A1, originating in east Africa and further segregating into two main subclades: an \u201cAfrican\u201d and a \u201cCosmopolitan\u201d clade. It is likely that the slave trade was the main source the spread of Cosmopolitan HBV-A1, which was exported to Asia in the 17th century as a result of Arab or Portuguese trade, and to Latin America in the 18th centuries through the trans-Atlantic slave trade. The origin of the currently circulating A2 strains dates back to the first decades of the 20th century, and the evolutionary demography analysis suggests an exponential growth of infections, between 1970s and the mid-1990s. This study suggests that the HBV genotypes were dispersed in Europe in different times and through different transmission routes. In particular, some genotypes (such as HBV-D or HBV-A2) spread recently (in the last 100 years), mainly through parenteral or sexual exposure; on the contrary other strains (such as HBV-A1) have been dispersed in more ancient times and are now linked to individuals of particular geographic origin or ethnicity

Improving the monitoring and evaluation of schistosomiasis by determining appropriate targets and utilizing new technologies

The World Health Organization’s framework for the assessment of schistosomiasis morbidity control utilizes the prevalence of heavy-intensity infections in a homogenous ecological zone. The foundational research for the use of heavy-intensity infections is at least 30 years old. Research since then has illuminated the relationship between Schistosoma infection and all morbidity. In addition, severe, chronic, schistosomiasis morbidity is less common due to increasing dissemination of preventive chemotherapy. There are calls for improvements to the monitoring and evaluation framework, especially relating to the measurement of schistosomiasis morbidity. The focus of this thesis was to improve the schistosomiasis monitoring and evaluation framework by evaluating whether those current infection measures are linked to morbidity indicators. For those measures linked to indicators, an attempt was made to calculate programmatic targets linked to morbidity using robust methods. Targets based on microhaematuria prevalence were calculated based on community-level S. haematobium prevalence. For S. mansoni, associations between infection and morbidity were much weaker and it appears unlikely that a reliable target can be found. S. mansoni morbidity control may require changes to accurately measure the S. mansoni morbidity burden in a geographic area. Incorporating new technologies, such as portable, tablet-based ultrasound systems, may allow researchers and control programs to collect schistosomiasis morbidity indicators

Genetic and biological characterization of Toxoplasma gondii from Uganda

Toxoplasma gondii is a widely distributed protozoan parasite, estimated to infect 25-50% of the global human population. While most infections are asymptomatic, AIDS-associated toxoplasmic encephalitis causes a high level of morbidity and mortality and this is a particular problem in sub-Saharan Africa, where HIV affects a substantial part of the population. Despite the scale of the problem, virtually nothing has been known about the T. gondii strains present in Africa. The work presented in this thesis showed for the first time that all the three main clonal lineages of T. gondii are present and cause disease in African HIV-patients, and that genotype II was the most common in Uganda. Subsequent isolation of eight strains revealed that the T. gondii parasites in Uganda are highly similar to the strains found in Europe and North America, but over 1,200 novel mutations were identified and many of these were indicative of positive selection of genes active in the interface with the host. An important finding was the discovery of a rare natural recombinant strain, which possessed genetic elements from both genotype II and III and displayed an intermediate in vivo growth rate, compared with the genuine type II and III strains from the same area. Whole genome sequencing of this isolate revealed that sexual recombination may be more frequent than previously thought, but that selective pressures appear to favour a conserved genetic composition. The studies included in this thesis provide novel insight into the genotype and phenotype of T. gondii strains from Africa, and describe for the first time the genomics of a natural recombinant T. gondii strain

Pathogenesis of Encephalitis

Many infectious agents, such as viruses, bacteria, and parasites, can cause inflammation of the central nervous system (CNS). Encephalitis is an inflammation of the brain parenchyma, which may result in a more advanced and serious disease meningoencephalitis. To establish accurate diagnosis and develop effective vaccines and drugs to overcome this disease, it is important to understand and elucidate the mechanism of its pathogenesis. This book, which is divided into four sections, provides comprehensive commentaries on encephalitis. The first section (6 chapters) covers diagnosis and clinical symptoms of encephalitis with some neurological disorders. The second section (5 chapters) reviews some virus infections with the outlines of inflammatory and chemokine responses. The third section (7 chapters) deals with the non-viral causative agents of encephalitis. The last section (4 chapters) discusses the experimental model of encephalitis. The different chapters of this book provide valuable and important information not only to the researchers, but also to the physician and health care workers

Approche écologique, épidémiologique et génétique de la biodiversité de Toxoplasma gondii en zone tropicale humide : exemples du Gabon et de la Guyane Française

Toxoplasmosis is a zoonosis due to the protozoan Toxoplasma gondii, widely distributed around the world. Some characteristics of the tropical humid zone may favor its circulation, yet very few studies on this parasite in the tropical area are available.We conducted two field studies to clarify the circulation and diversity of Toxoplasma in this humid tropical environment: (i) in Gabon, in urban and rural environments, with different approaches such as the seroprevalence of toxoplasmosis in human and animal analyzed with GIS and multivariate analysis, but also the study of genetic diversity and population structure of Toxoplasma and (ii) in French Guiana with the characterization and genetic comparison of strains circulating in both the "wild" and the "domestic" cycle of Toxoplasma. The population structure analysis was performed using tree distance (Neighbor -joining), the study of Fst and linkage disequilibrium, Bayesian statistical model (STRUCTURE), and multivariate methods (DAPC) incorporating spatial information (sPCA).In Gabon, animal and human seroprevalence was high in an urban as well as in a rural environment, with a predominant telluric risk in relation to the level of hygiene and climatic conditions. The 69 isolates have been characterized genetically and phenotypically through virulence in mice at isolation. Besides the Type III found all over the world, two major haplogroups were defined and proposed as new major haplogroups for T. gondii in Africa. A link with the strains circulating in Central and South America has been highlighted. The analysis of population structure showed increased circulation of the parasite between the main Gabonese cities in relation to human activities.In French Guiana, the 33 isolates obtained mainly from peridomestic animals were compared to 18 previously published strains, mainly from the wild environment. The wild population was far more diverse. In addition to a spatial and genetic structuring in two populations reflecting the two environmental populations, "anthropized" and "wild", a genetic substructure was found, associated to distinct phenotypic traits (virulence in mice) for some groups. These results also suggested the existence of interpenetration between wild and domestic cycles with potential risks for human health.La toxoplasmose est une zoonose due au protozoaire Toxoplasma gondii largement réparti dans le monde. La zone tropicale humide présente des caractéristiques propices à sa circulation, pourtant elle reste peu étudiée vis-à-vis de ce parasite.Nous avons réalisé deux études de terrain afin de préciser la circulation et la diversité du toxoplasme dans cet environnement tropical humide : (i) au Gabon en milieu urbain et rural, avec différentes approches telles que la séroprévalence de la toxoplasmose humaine et animale analysée à l'aide des SIG et d'analyse multivariée, mais aussi l'étude de la diversité génétique et de la structure des populations du toxoplasme et (ii) en Guyane Française avec la caractérisation et la comparaison génétique des souches circulant dans le cycle « sauvage » et le cycle « domestique » du toxoplasme. Dans ces deux études l'analyse de la structure des populations a été réalisée à l'aide d'arbres de distance (Neighbor-joining), de l'étude des FST et du déséquilibre de liaison, de modèle statistique Bayésien (STRUCTURE) et de méthodes multivariées (DAPC) intégrant pour certaines des informations spatiales (sPCA).Au Gabon, la séroprévalence animale et humaine retrouvée est élevée en milieu urbain et rural, avec un risque tellurique prépondérant en relation avec le niveau d'hygiène et les conditions climatiques. Les 69 isolats obtenus ont été caractérisés génétiquement et phénotypiquement au travers de la virulence chez la souris à l'isolement. Outre le Type III que l'on retrouve partout dans le monde, deux principaux haplogroupes ont été caractérisés et proposés comme nouveaux haplogroupes d'importance pour T. gondii en Afrique. Un lien avec les souches circulant en Amérique Centrale et du Sud a été mis en évidence. L'analyse de la structure de la population montre une circulation accrue du parasite entre les principales villes du pays en relation avec les activités humaines.En Guyane Française, les 33 nouveaux isolats obtenus principalement de la faune péri domestique ont été comparés à 18 souches déjà publiées provenant essentiellement de l'environnement sauvage. La population sauvage était la plus diversifiée. En plus d'une structuration spatiale et génétique en deux populations reflétant les deux populations environnementales, « anthropisée » et « sauvage », une sous structuration génétique a été trouvée, confirmée pour certains groupes par des traits phénotypiques distincts (virulence chez la souris). Ces résultats suggèrent aussi l'existence d‟interpénétration entre les cycles sauvage et domestique avec des risques potentiels pour la santé humaine

Hepatitis B and C in Malawi: Epidemiology, Disease Burden and Opportunities for a Public Health Treatment Programme

Abstract In sub-Saharan Africa, hepatitis B virus (HBV) infection is the principal cause of liver cirrhosis and hepatocellular carcinoma (HCC). Mortality from cirrhosis and HCC is projected to rise beyond 2030 unless adult HBV treatment programmes are implemented. Infant HBV vaccination was introduced across sub-Saharan Africa between 1994-2014, and in Malawi in 2002 where it is given at 6, 10 and 14 weeks of life. Hepatitis C virus (HCV) is an important contributor to liver disease globally, with an estimated population prevalence of 1% in sub-Saharan Africa. In Southern Africa there is a paucity of HCV prevalence data, with no previous random probability-sampling community studies. A hospital-based study of cirrhosis and HCC in a tertiary hospital, and seroprevalence studies in an urban township, were conducted in Blantyre, Malawi, to determine HBV and HCV prevalence and HBV vaccine impact. Of 97,386 censused individuals, single stage non-replacement age-stratified probability sampling was used to select 6,073 individuals who were tested for hepatitis B surface antigen (HBsAg) in a community serosurvey. HBsAg-positive individuals aged ≥16 were recruited to assess treatment eligibility. Among individuals aged ≥16 in the serosurvey, 1661 (51%) were randomly selected for HCV antigen/antibody (Ag/Ab) testing with confirmatory HCV RNA PCR. Prevalence estimates were standardised to census age and sex distribution using post-stratification proportional fitting. In the hospital study, the population attributable fraction (PAF) of HBV to cirrhosis and HCC was 23.1% (95% CI 15.7- 29.8) and 71.5% (59.3- 80.1) respectively among 250 consecutively recruited patients. For HCV the PAF was 1.6% (95% CI -0.4 – 3.6) for cirrhosis and 4.8% (-0.1, 9.5) for HCC. Patients with HCC were diagnosed at an advanced stage with a median tumour size of 12.6cm and a median survival of 1.3 months. Six-month survival was 67% (59.0- 73.8) among patients with cirrhosis. Standardised HBsAg prevalence in serosurvey participants born prior to, and after HBV vaccine introduction, was 5.1% (95% CI 4.3- 6.1) and 0.3% (95% CI 0.1- 0.6) respectively. Three-dose vaccination coverage was 97.4% (1141/1171) among 1171/2085 children aged ≤10 years with known vaccine status. By comparison of participants born 5 years before and after vaccine introduction, vaccine impact was 95.9% (95% CI 70.6- 99.4). Treatment eligibility was assessed in 94/150 HBsAg positive people aged ≥16 years from the serosurvey, of whom 24/93 (26%) were HIV positive, and 16/24 (67%) were receiving antiretroviral therapy containing tenofovir, with HBV DNA suppression. Among 69 HIV-negative HBsAg positive individuals, 3,6 and 9% were eligible for HBV treatment by WHO, EASL and AASLD criteria respectively. Standardised HCV Ag/Ab prevalence was 0.78% (95% CI 0.46- 1.33) and HCV RNA prevalence was 0.18% (95% CI 0.06- 0.53). HCV Ag/Ab positive individuals were older than the general population but no differences in sex, educational, employment or marital status were observed. In an urban township in Malawi, HBV prevalence was intermediate at 5.1% among unvaccinated adults. Infant HBV vaccination was associated with a vaccine impact of 96%. Among HBsAg-positive adults, one quarter were HIV-positive and 3-9% of HIV-negative adults were eligible for antiviral therapy. Estimated population HCV RNA prevalence was 0.2%. Future prevalence studies should sample rural communities and specific risk groups. HCC is diagnosed at an advanced stage with a poor prognosis in Malawi, and HBV is an important cause. The burden of HBV and HCV associated liver disease represents both a challenge, and an opportunity to implement public health treatment programmes to reverse rising liver-related mortality in Southern Africa

Seroprevalence and molecular epidemiology of Toxoplasma gondii in the Western Cape of South Africa

Thesis (PhD)--Stellenbosch University, 2016.ENGLISH SUMMARY: Toxoplasmosis is a disease caused by the obligate intracellular parasite Toxoplasma gondii and is one of the most widely occurring infections known to man, causing disease in almost all mammals and warm-blooded birds. Toxoplasma gondii is an opportunistic pathogen, taking advantage of weakened immune systems to cause disease. The disease toxoplasmosis is known to occur in both active and latent or chronic forms. The latent or chronic form of toxoplasmosis is known to be the most common latent infection in man. Currently, the effects of the latent or chronic form of toxoplasmosis is neither properly studied nor understood. In Africa, there is currently no systematic monitoring or reporting of toxoplasmosis incidence or T. gondii prevalence and this leaves health systems at a disadvantage. The United States Centre for disease Control and Prevention (CDC) currently classify toxoplasmosis as a neglected tropical infection. In this series of research projects, the seroprevalence of T. gondii antibodies and the risk factors to infection were investigated. Following that, the molecular epidemiology and population structure of the pathogen was also investigated. The investigations were conducted in opportunistically selected human and animal populations within the Western Cape Province of South Africa. The data obtained was analyzed from a “One World One Health” perspective and conclusions were then documented. The selected human populations were, a cohort of human immunodeficiency virus (HIV) positive and human immunodeficiency virus (HIV) negative post parturient women and their HIV exposed and uninfected (HEU) and HIV unexposed and uninfected (HUU) infants, and a cohort of HIV positive and HIV negative male and female patients presenting with a clinical diagnosis of uveitis at the Tygerberg academic hospital opthalmology clinic. The selected animal populations were a population of feral cats in the greater Cape Town metropole, a population of free ranging sheep on a single farm in Bredasdorp and a population of free ranging caracals in the Cape peninsula region. Toxoplasma gondii seroprevalence was 23.3% in the cohort of post parturient women, whilst the seroprevalence in the infant cohort was 1.02%. The seroprevalence was 24.7% in the cohort of patients presenting with ocular infections. The seroprevalence was not associated with HIV status but was associated with the consumption of unwashed fruits and vegetables. The similarity between the seroprevalence in the post parturient cohort and the ocular cohort points to the lack of regional differences in seroprevalence rates, whilst the low seroprevalence in the infant cohort implies a low rate of congenital toxoplasmosis in the study area and this comforms to what is observed in other parts of Africa, Europe and North America. Seroprevalence was extremely high in the felid populations investigated (Feral cats - 37.1% and Caracals- 69.6%). These justifies considerable attention since these felids were free ranging and therefore have access to domestic human and animal populations. The seroprevalence in the sheep flock was also higher at 8.0% than the five point six percent (5.6%) reported in earlier studies in Cape Town. Current research has established that T. gondii genotypes vary in their geographic distribution, with certain genotypes being more predominant in certain geographic areas than others. To establish the genotypes of T. gondii present in our selected geographic area, we investigated the molecular epidemiology of the pathogen. The molecular epidemiology investigations revealed a predominance of Type II genotypes in both human and animal samples. A Type III genotype was detected in human but not in animal samples. Atypical genotypes were also identified in both human and animal samples. The observed population structure is similar to that of South America and other parts of Africa but differs from that observed in Europe and North America. We have demonstrated the presence of T. gondii as well as its active transmission within selected human and animal populations in the Cape Town metropole of South Africa. The presence of atypical T. gondii genotypes was also demonstrated. The observed seroprevalence rates investigated in this study implies that more attention needs to be paid to the disease as it could have implications for female reproductive health, infant to adolescent ocular health as well as overall economic losses due to an increase in disease burden in humans (reported as disability-adjusted life years) and for agriculture.AFRIKAANSE OPSOMMING: Toksoplasmose is 'n siektetoestand wat veroorsaak word deur die intrasellulêre-gebonde parasiet Toxoplasma gondii is 'n opportunistiese patogeen, wat voordeel trek uit verswakte immuunstelsels om die siekte te veroorsaak Toksoplasmose is een van die mees wyd verspreide infeksies wat bekend is aan die mens, en affekteer baie, indien nie die meeste, soogdierspesies en voëls. Toksoplasmose kom voor in beide aktiewe en latente vorms, en dit is bekend dat die latente vorm van toksoplasmose die mees algemene latente infeksie in die mens is, en die gevolge daarvan is nog nie behoorlik bestudeer of word verstaan nie. In Afrika, is daar tans geen sistematiese monitering of verslagdoening oor die voorkoms van toksoplasmose óf Toxoplasma gondii nie en dit benadeel tans gesondheidbestuur. Die “Centre for Disease Control (CDC)” in die Verenigde State van Amerika klassifiseer toksoplasmose tans as 'n afgeskeepte tropiese infeksiesiekte. In hierdie reeks navorsingsprojekte word die serologiese voorkoms van T. gondii teenliggame en die risikofaktore wat tot infeksie lei, ondersoek. Hierop volg dan ‘n verdere ondersoek na die molekulêre epidemiologie en populasiestrukture van die patogeen. Die navorsing is uitgevoer op opportunisties geselekteerde mens- en dierbevolkings binne Suid-Afrika. Die data wat verkry is, is verwerk vanuit ‘n “One World One Health” perspektief en gevolgtrekkings is hiervolgens gemaak. Die geselekteerde menslike bevolking het bestaan uit 'n groep MIV-positiewe en MIVnegatiewe na-swangerskap vroue-pasiënte met hul MIV-blootgestelde en onbesmette (HEU), en MIV-onblootgestelde en onbesmette (HUU) kinders, asook 'n groep van manlike en vroulike pasiënte met okulêre infeksies gediagnoseer by die Tygerberg Hospitaal oogkliniek. Die geselekteerde dierebevolkings het bestaan uit 'n bevolking van wilde katte in die groter Kaapse metropool, 'n bevolking van vry weiende skape op n enkele plaas, en 'n bevolking van los-lopende rooikatte in die Kaapse skiereiland, almal in die bestek van die Wes-Kaap Provinsie van Suid-Afrika. Seroprevalensie van T. gondii was 23.3% in die groep van na-geboorte vroue terwyl prevalensie 1.02% in die kindergroep was. Die seroprevalensie was ook hoog, teen 24.7%, in die groep van pasiënte met okulêre infeksies. Die seroprevalensie was nie verbind met MIV-status nie, maar wel met die verbruik van ongewaste vrugte en groente. Die ooreenstemming in die seroprevalensie van die na-geboorte groep en die ooginfeksie groep dui op ‘n area-verskil in seroprevalensie tempo, terwyl die lae seroprevalensie in die kinder-groep dui op ‘n lae tempo van aangebore toksoplasmose in die area van studie en dit stem ooreen met waarnemings in ander dele van Afrika, Europa en Noord- Amerika. Seroprevalensie was baie hoog in die wilde kat bevolkings (wildekatte –37.1% en in Rooikatte- 69,6%). Hierdie bevinding vereis verdere aandag omdat die katte vrylopend was en daarom toegang gehad het tot die plaaslike mens- en huisdierbevolkings. Die seroprevalensie in die skaapbevolking was ook hoër teen 8.0% teenoor die 5.6% wat in vorige studies gerapporteer was in Kaapstad. Huidige navorsing het bepaal dat T.gondii genotipies varieër in hul geografiese verspreiding, met sekere genotipes meer dominant in sekere geografiese area’s as ander. Om die genotipes van T.gondii in ons geselekteerde geografiese gebied te bestudeer , het ons die molekulêre epidemiologie van die patogeen bepaal. Die molekulêre epidemiologiese ondersoeke het aangedui op 'n oorheersing van Tipe II genotipes in beide mens- en dier monsters. Tipe III genotipes was gevind in die menslike siektevorm, maar nie in die dier-infeksie monsters nie. Atipiese genotipes is ook waargeneem in beide mens- en dieremonsters. Die waargeneemde bevolkingstruktuur van Toxoplasma gondii is soortgelyk aan dié van Suid-Amerika en ander dele van Afrika, maar verskil van dié wat waargeneem word in Europa en Noord-Amerika. Ons het die teenwoordigheid van T. gondii asook sy aktiewe oordrag binne die geselekteerde mens en dier bevolkings in die Wes-Kaap van Suid-Afrika bewys. Die teenwoordigheid van atipiese T.gondii genotipes word ook beskryf. Die waargeneemde seroprevalensies wat in hierdie studie ondersoek is, dui daarop dat meer aandag gegee moet word aan die siekte, omdat dit ernstige implikasies inhou vir vroulike reproduktiewe gesondheid, baba tot adolessent okulêre gesondheid, asook ‘n hoë lading op die gesondheidstelsel en in die landbou plaas as gevolg van 'n toename in siektelas in die mens

Ultrasensitive detection of toxocara canis excretory-secretory antigens by a nanobody electrochemical magnetosensor assay.

peer reviewedHuman Toxocariasis (HT) is a zoonotic disease caused by the migration of the larval stage of the roundworm Toxocara canis in the human host. Despite of being the most cosmopolitan helminthiasis worldwide, its diagnosis is elusive. Currently, the detection of specific immunoglobulins IgG against the Toxocara Excretory-Secretory Antigens (TES), combined with clinical and epidemiological criteria is the only strategy to diagnose HT. Cross-reactivity with other parasites and the inability to distinguish between past and active infections are the main limitations of this approach. Here, we present a sensitive and specific novel strategy to detect and quantify TES, aiming to identify active cases of HT. High specificity is achieved by making use of nanobodies (Nbs), recombinant single variable domain antibodies obtained from camelids, that due to their small molecular size (15kDa) can recognize hidden epitopes not accessible to conventional antibodies. High sensitivity is attained by the design of an electrochemical magnetosensor with an amperometric readout with all components of the assay mixed in one single step. Through this strategy, 10-fold higher sensitivity than a conventional sandwich ELISA was achieved. The assay reached a limit of detection of 2 and15 pg/ml in PBST20 0.05% or serum, spiked with TES, respectively. These limits of detection are sufficient to detect clinically relevant toxocaral infections. Furthermore, our nanobodies showed no cross-reactivity with antigens from Ascaris lumbricoides or Ascaris suum. This is to our knowledge, the most sensitive method to detect and quantify TES so far, and has great potential to significantly improve diagnosis of HT. Moreover, the characteristics of our electrochemical assay are promising for the development of point of care diagnostic systems using nanobodies as a versatile and innovative alternative to antibodies. The next step will be the validation of the assay in clinical and epidemiological contexts