Ascaris lumbricoides is a common nematode infecting humans worldwide with increased Here, we present a case of an intestinal ascariasis. Background With one quarter of the world population infected, the intestinal nematode Ascaris lumbricoides is one of the most common. of Ascaris lumbricoides and Necator americanus distributions in Manufahi District , Timor-Leste. Rebecca Wardell1, Archie C. A. Clements1.
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Soil-transmitted helminths STHs infect over one billion people worldwide. Ascariasis may mimic a number of conditions, and individual clinical diagnosis often requires a thorough work-up. Kato-Katz thick smears are the standard detection method for Ascaris and, despite low sensitivity, are often used for mapping and monitoring and evaluation of national control programmes. Antibody-based diagnostics may be a sensitive diagnostic tool; however, their usefulness is limited to assessing transmission in areas aiming for elimination.
Molecular diagnostics are highly sensitive and specific, but high costs limit lumvricoides use to individual diagnosis, drug – efficacy studies and identification of Ascaris suum. Increased investments in research on Ascaris and other STHs are urgently junal for the development of diagnostic assays to support efforts to reduce human suffering caused by these infections. Soil-transmitted helminths STHs infect over 1.
Single- and multi-species infections cause human disease ranging from mild to severe and even fatal cases, as well as increased school absenteeism, although this might not be detectable at a community level [ 2 ].
Most of such neglected tropical diseases NTDs occur in areas with poor sanitation and hygiene; however, increased travel and migration have made STH infections more common also in non-endemic areas. With the scale-up of national STH – control programmes, the associated scientific opportunities and known limitations of the currently recommended techniques, research on Ascaris diagnostics is needed more than ever.
We review the available literature for the diagnosis of A. We cover scenarios ranging from clinical settings to large-scale control programmes, and emphasise the need for integration of diagnosis of multi-species infections.
Infection is often asymptomatic and may occur alongside other diseases. After being swallowed, an A. Unable to cross the capillary network, the parasite penetrates the walls of the alveoli, migrates to the larynx and is swallowed, ending up as an adult worm in the small intestines. The female parasite lays tens of thousands of eggs daily that, through stool excretion, enter the environment and may infect other human hosts.
Differential diagnoses to ascariasis morbidity in humans, grouped by larval and intestinal stages of infection. Similar to a number of parasite infections, individual diagnosis of ascariasis often depends on a thorough investigation that may include travel history or origin from endemic countries when presenting in non-endemic areas and clinical and laboratory examinations, including potentially serological, molecular and image-based diagnostics. Recent findings suggest that ascariasis should be suspected in patients with relevant symptoms even without travel to A.
Clinical findings may include urticaria or other rash, abnormal breath sounds by auscultation and tender hepatomegaly. The leukocyte differential count typically reveals eosinophilia, and the chest X-ray may show pulmonary infiltrates. Serology can aid the diagnosis, especially if egg excretion has not yet started, although cross-reactivity with other parasites is common.
Rarely, Ascaris larvae migrate to ectopic sites, and associated eosinophilia may cause complications [ 8 ]. Light infections are frequently asymptomatic, whereas heavy infections commonly lead to acute abdominal pain and ileus from conditions such as mechanical small bowel obstruction, volvulus and intussusception, especially in children [ 59 ].
In endemic countries, intestinal ascariasis is also a common cause of hepatic, biliary and pancreatic disease, including acute pancreatitis and cholecystitis [ 10 ].
Ultrasonography, abdominal X-ray, computed tomography and magnetic resonance imaging scans may identify the cause [ 11 — 13 ]. Endoscopic retrograde cholangiopancreatography may be both diagnostic and therapeutic, and capsule endoscopy can be considered, even in individuals with negative conventional gastrointestinal endoscopy [ 1415 ].
In endemic countries, Ascaris infection is a common cause of malabsorption, and undernutrition and micronutrient deficiencies may lead to growth failure and cognitive impairment, as well as defective immune regulation and increased risk of other parasitic infections [ 1617 ]. Quantifying the lumrbicoides burden of A. Lumbicoides various microscopy-based techniques are also commonly used for other intestinal parasites.
For intensity of infection, measured as number of eggs per gram of stool Lumbricoidees [ 3 ], Kato-Katz correlates well with worm burden [ lumbticoides ]. However, the high variance of EPG from repeated Kato-Katz sampling, lumbricoiddes non-random egg distribution within the same stool and daily fluctuations in egg detection from different stools from the same person, and potentially from mislabelled stools from different peopleis an important limitation of this technique [ 19 ].
Due to the high variance, probably exacerbated by the small fixed volume of stool used normally In addition, the number of eggs recorded in each smear is multiplied to calculate EPG, but the volume-to-weight ratio is affected by stool density, and actual weights vary considerably [ 23 ]. Finally, the diagnostic accuracy of Kato-Katz depends on sufficiently well-trained laboratory technicians.
Increased sampling from one to multiple slides from stools collected on consecutive days greatly improves the sensitivity of Kato-Katz, often resulting in higher prevalence estimates [ 24 — 26 ]. On the other hand, multiple smears do not always improve sensitivity, may bias results through age-related non-compliance [ 27 ] and require increased human and financial resources. However, cost per detected case increases as prevalence decreases [ 34 ]. Other diagnostic techniques have shown promising results for A.
Further studies are needed to determine the diagnostic value of these tests for Ascaris and other intestinal parasite infections. Kato-Katz has low sensitivity for detection of A. Modified Wisconsin floatation and simple gravity sedimentation are more sensitive for infants than Kato-Katz, formal-ethyl acetate sedimentation or modified formal-ethyl acetate sedimentation [ 44 ].
The gravity sedimentation method is labour-intensive but can distinguish fertilised from unfertilised Ascaris ova and is unaffected by diarrhoeal stool, unlike the Wisconsin method [ 44 ].
Human Ascariasis: Diagnostics Update
Detection jurnzl antibodies or antigens could provide a simpler, more rapid nurnal of Ascaris infection than conventional stool microscopy. Importantly, factors such as age, genetic predisposition, atopy, nutritional status and co-infections may affect the humoral response to Ascaris [ 175354 ]. Total immunoglobulin Ig lumbgicoides are associated with worm burden in individuals living in endemic areas [ 51 ]. In some studies, certain Ig isotypes, such as IgG4, have been found to be sensitive and specific markers of chronic A.
These findings are consistent with other parasite infections [ 57 ], although others have found more variable results for Ascaris [ 52 ]. Cross-reactivity of anti- Ascaris antibodies with epitopes of other helminths is common [ 51 ], and standardisation of Ascaris antigens for research and diagnostic purposes is warranted, including recombinant antigens, Ascaris -associated allergens and antigens of other ascarid species [ 565859 ].
Few studies have evaluated the use of serological diagnosis of Ascaris at the community level. In one study of individuals with high-intensity infections treated repeatedly over several lumbrcioides, anti- Ascaris IgG4 fell to levels equal to negative controls [ 60 ].
Human Ascariasis: Diagnostics Update
In another study, however, antibody titres did not correlate with worm – load expulsion after treatment [ 56 ]. Anti- Ascaris antibody titres have been associated with larval stage ascariasis in particular and may remain elevated for several months, even following treatment, especially in areas where re-infection is frequent [ 760 ]. Anti- Ascaris antibodies are therefore generally not seen as suitable to detect active Ascaris infection and could overestimate the number of individuals in need of treatment in mass control programmes.
A number of commercial diagnostic tests are available for detection of anti- Ascaris lumbricoides IgG and IgM; however, to our knowledge, most are based on somatic A. Interestingly, saliva-based detection of IgG performed well in high-intensity T. Whilst antibody detection could represent past infection or exposure, as well as current infections, antigen detection only represents current infections.
We did not find any studies of detection of antigens in blood or other specimens for A. Detection of schistosome antigen in urine is highly sensitive and is available as a commercialised point-of-care test [ 5062 ].
Similar tools for STHs may be limited by the location of the adult worms in the intestines, rather than in the blood vessels as is the case for schistosomes, and it is possible that coproantigen tests would be more sensitive than urine or blood tests for STHs. As control programmes potentially move towards elimination of STHs, antibodies may provide a good marker of infection in young children, especially in areas where children are frequently exposed to intestinal pathogens [ 6364 ].
Few studies have identified biomedical target markers for A. Fatty acid products of A. Molecular diagnostic tools are highly sensitive and specific, and rapid advances are being made, resulting in reduced costs and improved techniques such as real-time quantitative PCR qPCR and multiplex assays.
The DNA extraction and amplification of the nuclear first internal transcribed spacer region ITS1 from single Ascaris eggs have primarily been optimised for population genetic analyses [ 66 ]. These techniques, used on stool samples, could enable highly sensitive detection of Ascarisparticularly by amplification of DNA from single eggs. Methods to detect small amounts of ancient DNA, such as molecular paleoparasitological hybridization approach [ 67 ], may improve sensitivity for very low infections.
Multiplex PCR enables the detection of multiple parasite species in a single reaction and can simplify diagnostics by replacing several individual tests with one molecular test. Unlike conventional PCR, which can only indicate presence of infection, qPCR enables quantification of amplicon and associated infection intensity.
High intensity reactions result in rapid amplification and early fluorescence. Multiplex qPCR assays have successfully detected A. These findings highlight the importance of multi-species diagnostic tests, even in young children, including common intestinal infections that are often neglected by control programmes. Alternatively, amplicons for several STHs and protozoa can be hybridised to beads for probe-based detection on a Luminex platform providing a high-throughput diagnostic tool with less equipment required than for qPCR [ 73 ].
Further, reverse transcriptase PCR can identify specific stages of schistosomes [ 74 ] and could be useful for distinguishing new and treatment-resistant Ascaris infections. The significantly higher sensitivity of qPCR over stool microscopy typical for a number species is not always observed for Ascaris due to high egg output and technical challenges related to isolating parasite DNA from the resistant, four-layered Ascaris egg shell [ 75 ].
Also, specific multiplex assays are limited to the species targeted in the respective tests, and DNA from high-intensity infections will compete for dNTPs, thereby deterring detection of species of lower infection intensities. Recent studies suggest that A. The zoonotic potential of Ascaris spp.
Additional studies from sympatric populations using multi-locus genotype data are required to determine if cross-transmission is a global issue, and to determine what diagnostics are required.
Detailed comparisons [ 89 ] of the published mitochondrial genome of A. However, the mitochondria vary by only 1.
Lumbricpides choice of diagnostic technique and protocol will vary depending aacaris the research question being addressed. To date, the development of diagnostic tests for ascariasis has been limited by largely insufficient investments and is further complicated by the fact that no true gold standard exists for comparison of tests.
Ideal relationships should be linear, with low variance. Characteristics of the most common current and potential laboratory-based diagnostic ascairs, and their use in national control programmes. Mapping of disease for defining appropriate frequency of MDA is currently done through stool microscopy, most commonly Kato-Katz, with A.
Unlike some common NTDs, questionnaires are not a sensitive tool for identification of communities targeted for STH treatments [ 95 ]. Although current stool-based tests may be sufficient to define mass treatment strategies, especially in moderate- to high-endemic areas, tests with higher sensitivity are needed as infection intensity is reduced [ 4 ]. However, due to the location of STHs in the intestines, it is possible that coproantigen tests will be more sensitive, although research to support this prediction is needed.
Moreover, improved coordination of disease mapping, including specimens lumbricokdes for other NTD surveys, could strengthen cooperation between health and non-health sectors, as well as attract sustainable funding for control programmes . The impact of mass control programmes is currently evaluated through sentinel site surveys [ 3 ]. In some instances, evaluating impact through repeated mapping is conducted, although the value of comparing cross-sectional survey lumbrkcoides, often with differing protocols and techniques, is debatable [ ].
At present, stool-based microscopy, especially Kato-Katz, remains the main diagnostic test to evaluate impact of treatment, and outcomes include binary values of prevalence and cure rate CR; recommended by WHOand numeric values of EPG and egg reduction rates ERRs. Although cost and ease of use have historically been more important than diagnostic sensitivity, especially for prevalence and CR, more sensitive tools may be needed as successful control programmes lead to reduced prevalence and intensity of infection.
As infection intensity decreases, measuring disease transmission becomes increasingly important, and direct markers of infection, including antigens, will be required. As integrated control programmes lumbricoidws, increased precision of diagnostic tests may improve the interpretation of the effect of complementing interventions, such as Jufnal [ ].
As albendazole is used to treat both LF and STH infections, jurnall impact surveys may be coordinated [ ], and collection of the same, conveniently sampled specimens would improve data validity and cost-effectiveness. However, LF surveillance will probably scale down as the disease becomes eliminated ahead of STH programmes, and rapid on-site tools for STH diagnosis are highly required. Ideally, the test would also detect other common tropical diseases, such as malaria, through lumbriocides multi-array platform .