The taxonomic distinctiveness of Ascaris lumbricoides and A. suum, two of the world’s most significant nematodes, still represents a much-debated scientific issue. Previous studies have described two different scenarios in transmission patterns, explained by two hypotheses: (1) separated host-specific transmission cycles in highly endemic regions, (2) a single pool of infection shared by humans and pigs in non-endemic regions. Recently, A. suum has been suggested as an important cause of human ascariasis in endemic areas such as China, where cross-infections and hybridization have also been reported. The main aims of the present study were to investigate the molecular epidemiology of human and pig Ascaris from non-endemic regions and, with reference to existing data, to infer the phylogenetic and phylogeographic relationships among the samples.
Globally, about 1.5 billion people are infected with at least one species of soil-transmitted helminth (STH). Soil is a critical environmental reservoir of STH, yet there is no standard method for detecting STH eggs in soil. We developed a field method for enumerating STH eggs in soil and tested the method in Bangladesh and Kenya. The US Environmental Protection Agency (EPA) method for enumerating Ascaris eggs in biosolids was modified through a series of recovery efficiency experiments; we seeded soil samples with a known number of Ascaris suum eggs and assessed the effect of protocol modifications on egg recovery. We found the use of 1% 7X as a surfactant compared to 0.1% Tween 80 significantly improved recovery efficiency (two-sided t-test, t = 5.03, p = 0.007) while other protocol modifications-including different agitation and flotation methods-did not have a significant impact. Soil texture affected the egg recovery efficiency; sandy samples resulted in higher recovery compared to loamy samples processed using the same method (two-sided t-test, t = 2.56, p = 0.083). We documented a recovery efficiency of 73% for the final improved method using loamy soil in the lab. To field test the improved method, we processed soil samples from 100 households in Bangladesh and 100 households in Kenya from June to November 2015. The prevalence of any STH (Ascaris, Trichuris or hookworm) egg in soil was 78% in Bangladesh and 37% in Kenya. The median concentration of STH eggs in soil in positive samples was 0.59 eggs/g dry soil in Bangladesh and 0.15 eggs/g dry soil in Kenya. The prevalence of STH eggs in soil was significantly higher in Bangladesh than Kenya (chi-square, χ2 = 34.39, p < 0.001) as was the concentration (Mann-Whitney, z = 7.10, p < 0.001). This new method allows for detecting STH eggs in soil in low-resource settings and could be used for standardizing soil STH detection globally.
The Sabin Vaccine Institute Product Development Partnership is developing a Pan-anthelmintic vaccine that simultaneously targets the major soil-transmitted nematode infections, in other words, ascariasis, trichuriasis and hookworm infection. The approach builds off the current bivalent Human Hookworm Vaccine now in clinical development and would ultimately add both a larval Ascaris lumbricoides antigen and an adult-stage Trichuris trichiura antigen from the parasite stichosome. Each selected antigen would partially reproduce the protective immunity afforded by UV-attenuated Ascaris eggs and Trichuris stichosome extracts, respectively. Final antigen selection will apply a ranking system that includes the evaluation of expression yields and solubility, feasibility of process development and the absence of circulating antigen-specific IgE among populations living in helminth-endemic regions. Here we describe a five year roadmap for the antigen discovery, feasibility and antigen selection, which will ultimately lead to the scale-up expression, process development, manufacture, good laboratory practices toxicology and preclinical evaluation, ultimately leading to Phase 1 clinical testing.
Ascaris sp. is a soil-transmitted helminth (STH) significantly affecting the health of human and swine populations. Health inequities and poverty, with resulting deficiencies in water, sanitation and hygiene, are directly associated with Ascaris lumbricoides prevalence in humans. Resource constraints also lead to small-scale livestock production under unsanitary conditions. Free-ranging pigs, for instance, are exposed to a number of infectious agents, among which Ascaris suum is one of the most common. Under these conditions, close proximity between people and pigs can result in cross-contamination; that is, pigs harbouring human Ascaris and vice versa. Moreover, the potential interbreeding between these two Ascaris species has been demonstrated. The present study analysed Ascaris worms obtained from children and pigs in Honduras. Adult worms were collected from stool samples of children after pharmacological treatment, and from pigs' intestines after slaughter for commercial purposes at a local abattoir. A nuclear ribosomal internal transcribed spacer (ITS) region was amplified by polymerase chain reaction (PCR) and digested with a restriction enzyme in order to separate putative human- and pig-derived Ascaris isolates. PCR products were also sequenced, and cladograms were constructed. All parasites isolated from children showed the typical human-derived genotype of Ascaris, whereas 91% of parasites from pigs showed the expected pig-derived genotype. Cross-infections between hosts were not demonstrated in this study. Nine per cent of pig-derived worms showed a restriction band pattern highly suggestive of a hybrid human-pig Ascaris genotype. These results contribute to the understanding of ascariasis epidemiology and its zoonotic potential in a highly endemic region.
The roundworm Ascaris lumbricoides is one of the most prevalent parasites belonging to the class of the soil-transmitted helminths. Infections are most common in developing countries with a tropical climate where sanitation and hygiene are poor. However, prevalence of ascariasis in industrialized countries is increasing because of immigration and increasing number of refugees.
Biliary ascariasis is still the leading cause of surgical complication of ascariasis, though its incidence has been dramatically reduced. Herein, we report a case of biliary ascariasis for the purpose of enhancing awareness of parasitic infections as a possible cause. A 72-year-old male visited the emergency room of Dankook University Hospital on 12 July 2015, complaining of right-upper-quadrant pain. By endoscopic retrograde cholangiopancreatography (ERCP), a tubular filling defect in the right hepatic duct was detected. The defect was endoscopically removed and diagnosed as an adult female of Ascaris lumbricoides worm, of 30 cm length. Upon removal of the worm, the pain subsided, and the patient was discharged without any complication. When treating cases of biliary colic, physicians should not neglect biliary ascariasis as the possible cause.
The aim of the present study was to determine the association between the presence of Ascaris suum at fattening pig farms, using different serological methods and the percentage of affected livers at slaughter, with performance and management indices. In total, 21 fattening pig farms from the North of Spain were included in the study. Serum samples were collected from pigs at slaughter and analysed for the presence of anti-Ascaris antibodies. For this, two different ELISAs were used. The first was based on the antibody recognition of the A. suum haemoglobin (As-Hb) molecule whereas the second test used the total extract of A. suum lung stage L3. The serological results were subsequently correlated with the percentage of condemned livers at slaughter, management practices and technical performance parameters including average daily gain (ADG) and feed conversion ratio (FCR). According to the data from the slaughterhouse, 12 out of the 21 farms had livers condemned due to liver white spots. A total of 10 farms (48%) had an average optical density ratio (ODr) exceeding the test cutoff when the As-Hb ELISA was used. This number increased to 18 farms (81%) when using the As-Lung-L3 ELISA. The average ODr of the farms on both ELISAs correlated positively with the percentage of affected livers (P<0.01). Only the average ODr values obtained with the As-Lung-L3 ELISA were positively correlated with the FCR (P<0.01). No correlation was found between percentage of affected livers or serology and the ADG. In relation to management practices, farms with greater than or equal to 50% slatted flooring and that applied the 'all-in/all-out' flow system showed a lower percentage of liver condemnations (P<0.01), lower average ODr results on the As-Lung-L3 ELISA (P<0.05) and lower FCR (P<0.01) compared with those with less than 50% slatted flooring. This study emphasizes that serology is a promising diagnostic tool for diagnosing ascariasis at fattening pig farms. It also supports earlier findings that the presence of A. suum can have a significant negative impact on farm productivity and that stable infrastructure or management practices can have a considerable impact on the control of this parasite.
The aim of this study was to evaluate whether serology can be used to measure exposure of piglets to Ascaris suum during the nursery phase. Experimental infection studies were performed in which 7 groups of 10 piglets of 4 weeks of age were orally infected with either 10, 20, 40, 60, 80, 100 and 500 A. suum eggs/day during 7 consecutive weeks, mimicking a nursery phase in an A. suum contaminated environment. Serum was collected on a weekly basis to monitor seroconversion on 2 ELISA tests based on the antibody recognition of either a haemoglobin protein purified from the pseudocoelomic fluid of adult A. suum or a water-soluble complete homogenate of the 3rd stage larvae isolated from the lungs (L3-lung). A dose-dependent seroconversion was measurable with the L3-lung ELISA starting from 4 weeks post-infection onwards, whereas this was not measurable with the haemoglobin-based test. After 7 weeks, equivalent to the end of the nursery phase, the L3-lung ELISA showed a 99% specificity and a 90% sensitivity to detect exposure of piglets to A. suum, with a minimum infection level of 20 A. suum eggs per day. To further evaluate the test under field conditions, a seroprevalence study was performed by sampling 10 piglets on 68 different nursery farms in Belgium. The results showed that for 38% of the farms analysed all piglets tested seronegative, whereas for the remaining 62% of the farms the percentage seropositive piglets ranged from 10 to 100%. This indicates contamination of the nursery facilities with A. suum eggs. In conclusion, the outcome of this study shows that serology can be used to measure exposure of nursery piglets to A. suum, thereby providing an additional tool in the control of this widespread parasite.
Following the Worms: Detection of Soil-Transmitted Helminth Eggs on Mothers' Hands and Household Produce in Rural Kenya
- The American journal of tropical medicine and hygiene
- Published 8 months ago
Approximately one-quarter of the world’s population is infected with at least one species of soil-transmitted helminth (STH). The role of produce and hands in STH transmission is not well understood. We collected and processed mother hand rinse and garden-grown produce rinse samples from 116 rural households in Kakamega, Kenya, in an area previously identified to have high STH egg contamination in household soil. Ascaris was the only STH species detected; 0.9% of hand rinse, 3.5% of leafy produce, and 1.8% of root produce samples had Ascaris eggs. Our results indicate produce and hands can transmit Ascaris eggs. However, due to the low detected prevalence of eggs on hands and produce, and a high prevalence of cooking the produce items tested, these pathways might have a minor contribution to STH transmission in this setting.
Analysis of the internal transcribed spacer region of Ascaris suum and Ascaris lumbricoides derived from free range Tibetan pigs
- Mitochondrial DNA. Part A, DNA mapping, sequencing, and analysis
- Published 11 months ago
Ascaris suum (A. suum) is the most commonly occurring worldwide internal parasite of pigs; however, little is known about this organism in Tibetan pigs in China. A study was carried to isolate and identify the characteristics of internal transcribed spacer region (ITS) gene of A. suum derived from Tibetan pigs. Adult nematodes were collected from Tibetan pigs in 2015-2016. Total genomic DNA of the extracted parasites was performed and a fragment of the ITS of mitochondrial (mt) gene was amplified. The amplicons were cloned into PGEM®-T Easy Vector (Promega, WI) and the positive clones were sequenced by ABI 3730 × 1 sequencer. The sequence and phylogenetic analysis were performed by ClustalWVer. 1.4 and MEGA 6.0 software, respectively. Results indicated that the identity of A. suum isolates was 98.4%-99.9% with previously reported pig isolates, and 99.4%-99.7% with A. lumbricoides isolates. To the best of our knowledge, this is the first report describing the characteristics of ITS gene of A. suum derived from the Tibetan pigs from high and remote areas depicting high identity with the isolates of both A. suum and A. lumbricoides.