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Clinics in Colon and Rectal Surgery Jun 2015Over one billion people worldwide harbor intestinal parasites. Parasitic intestinal infections have a predilection for developing countries due to overcrowding and poor... (Review)
Review
Over one billion people worldwide harbor intestinal parasites. Parasitic intestinal infections have a predilection for developing countries due to overcrowding and poor sanitation but are also found in developed nations, such as the United States, particularly in immigrants or in the setting of sporadic outbreaks. Although the majority of people are asymptomatically colonized with parasites, the clinical presentation can range from mild abdominal discomfort or diarrhea to serious complications, such as perforation or bleeding. Protozoa and helminths (worms) are the two major classes of intestinal parasites. Protozoal intestinal infections include cryptosporidiosis, cystoisosporiasis, cyclosporiasis, balantidiasis, giardiasis, amebiasis, and Chagas disease, while helminth infections include ascariasis, trichuriasis, strongyloidiasis, enterobiasis, and schistosomiasis. Intestinal parasites are predominantly small intestine pathogens but the large intestine is also frequently involved. This article highlights important aspects of parasitic infections of the colon including epidemiology, transmission, symptoms, and diagnostic methods as well as appropriate medical and surgical treatment.
PubMed: 26034403
DOI: 10.1055/s-0035-1547335 -
Reumatologia Clinica May 2021Uric acid has been related to a tendency to precipitate to form crystals, presenting asymptomatically, until the formation of arthritis, tophi or renal lithiasis....
BACKGROUND
Uric acid has been related to a tendency to precipitate to form crystals, presenting asymptomatically, until the formation of arthritis, tophi or renal lithiasis. Previously, the presence of asymptomatic hyperuricaemia has been associated with the presence of cardiovascular disease.
OBJECTIVES
To determine the association of complex coronary artery disease in patients with asymptomatic hyperuricaemia.
MATERIAL AND METHODS
An observational retrospective, transversal, unicentric study was conducted in a tertiary hospital in Mexico, in the period from June 2017 to March 2019. All patients admitted for coronary angiography were included; patients with gout, use of diuretics and chronic kidney disease were excluded.
RESULTS
During the study period, a total of 300 patients were collected, of which 40% presented hyperuricaemia. The patients with hyperuricaemia were older (59 vs. 63, P = .002). The group of patients with asymptomatic hyperuricaemia had a higher proportion of complex coronary lesions (64 vs. 35%, P ≤ .0001) as well as a higher SYNTAX I score (27 vs. 17, P ≤ .001). There was a higher probability of presenting complex coronary lesions in this group of patients (OR 3.4, P ≤ .0001). In addition, in the group division of uric acid levels, it was related to the presence of complex coronary lesions (Q1 = .5, P = .06), (Q2 = 2, P = .01) and (Q3 = 3, P ≤ .0001).
CONCLUSION
Asymptomatic hyperuricaemia has a higher prevalence and association of presenting complex coronary lesions.
PubMed: 31707094
DOI: 10.1016/j.reuma.2019.08.003 -
Mathematical Biosciences and... Nov 2020Asymptomatic transmission of infectious diseases has been recognized recently in several epidemics or pandemics. There is a great need to incorporate asymptomatic...
Asymptomatic transmission of infectious diseases has been recognized recently in several epidemics or pandemics. There is a great need to incorporate asymptomatic transmissions into traditional modeling of infectious diseases and to study how asymptomatic transmissions shift epidemic dynamics. In this work, we propose a compartmental model with asymptomatic transmissions for waterborne infectious diseases. We conduct a detailed analysis and numerical study with shigellosis data. Two parameters, the proportion $p$ of asymptomatic infected individuals and the proportion $k$ of asymptomatic infectious individuals who can asymptomatically transmit diseases, play major rules in the epidemic dynamics. The basic reproduction number $\mathscr{R}_{0}$ is a decreasing function of parameter $p$ when parameter $k$ is smaller than a critical value while $\mathscr{R}_{0}$ is an increasing function of $p$ when $k$ is greater than the critical value. $\mathscr{R}_{0}$ is an increasing function of $k$ for any value of $p$. When $\mathscr{R}_{0}$ passes through 1 as $p$ or $k$ varies, the dynamics of epidemics is shifted. If asymptomatic transmissions are not counted, $\mathscr{R}_{0}$ will be underestimated while the final size may be overestimated or underestimated. Our study provides a theoretical example for investigating other asymptomatic transmissions and useful information for public health measurements in waterborne infectious diseases.
Topics: Asymptomatic Infections; Basic Reproduction Number; Communicable Diseases; Epidemics; Humans; Pandemics
PubMed: 33525082
DOI: 10.3934/mbe.2021005 -
Frontiers in Cellular and Infection... 2019, or Group A Streptococcus (GAS), is a human-restricted pathogen most commonly found in the posterior oropharynx of the human host. The bacterium is responsible for 600... (Review)
Review
, or Group A Streptococcus (GAS), is a human-restricted pathogen most commonly found in the posterior oropharynx of the human host. The bacterium is responsible for 600 million annual cases of pharyngitis globally and has been found to asymptomatically colonize the pharynxes of 4-30% of the population. As such, many studies have utilized animals as models in order to decipher bacterial and host elements that contribute to the bacterial-pharyngeal interaction and determine differences between acute infection and asymptomatic colonization. The aim of this review is to first describe both bacterial and host factors that are important for the pharyngeal persistence of GAS in humans, then to detail the bacterial and host factors that are important for colonization in murine model, and finally to compare the two in order to evaluate the strength of murine pharyngeal colonization as a model for the human-GAS pharyngeal interaction.
Topics: Animals; Carrier State; Disease Models, Animal; Mice; Pharynx; Streptococcal Infections; Streptococcus pyogenes
PubMed: 31119108
DOI: 10.3389/fcimb.2019.00137 -
Pathogens (Basel, Switzerland) Feb 2022is a commensal fungus that asymptomatically colonizes the skin and mucosa of 60% of healthy individuals. Breaches in the cutaneous and mucosal barriers trigger... (Review)
Review
is a commensal fungus that asymptomatically colonizes the skin and mucosa of 60% of healthy individuals. Breaches in the cutaneous and mucosal barriers trigger candidiasis that ranges from asymptomatic candidemia and mucosal infections to fulminant sepsis with 70% mortality rates. Fungi influence at least several diseases, in part by mechanisms such as the production of pro-carcinogenic agents, molecular mimicking, and triggering of the inflammation cascade. These processes impact the interactions among human pathogenic and resident fungi, the bacteriome in various organs/tissues, and the host immune system, dictating the outcomes of invasive infections, metabolic diseases, and cancer. Although mechanistic investigations are at stages of infancy, recent studies have advanced our understanding of host-fungal interactions, their role in immune homeostasis, and their associated pathologies. This review summarizes the role of and other opportunistic fungi, specifically their association with various diseases, providing a glimpse at the recent developments and our current knowledge in the context of inflammatory-bowel disease (IBD), cancers, and COVID-19. Two of the most common human diseases where fungal interactions have been previously well-studied are cancer and IBD. Here we also discuss the emerging role of fungi in the ongoing and evolving pandemic of COVID-19, as it is relevant to current health affairs.
PubMed: 35215155
DOI: 10.3390/pathogens11020212 -
Antimicrobial Agents and Chemotherapy Aug 2022Malaria control relies on passive case detection, and this strategy fails detecting asymptomatic infections. In addition, infections in endemic areas harbor multiple...
Malaria control relies on passive case detection, and this strategy fails detecting asymptomatic infections. In addition, infections in endemic areas harbor multiple parasite genotypes that could affect case management and malaria epidemiology. Here, we performed AmpSeq genotyping to capture polymorphisms associated with antimalarial resistance and the genetic diversity within natural Plasmodium falciparum infections. Known genetic polymorphisms associated with altered drug susceptibility were screened for the five most common marker genes, , , , , and , and genetic diversity was established from two known AmpSeq markers, and . Relative abundance of the different genotypes within mixed infections was calculated from the number of reads per genotype. Genotyping was performed on 117 samples, 63 from asymptomatic and 54 from symptomatic individuals. We identified up to 15 genotypes within an infection, and the median multiplicity of infection was higher in asymptomatic infections (median MOI = 5 in asymptomatics versus median MOI = 2 in symptomatics, 0.001). No genetic differentiation on parasites from asymptomatic and symptomatic individuals was found. No mutation associated with ART resistance was identified. Prevalence of the P. falciparum chloroquine resistance wild-type genotype (CVMNK) reached 80%, confirming a return to chloroquine (CQ) sensitive parasites in Cameroon. In addition, the CQ-associated resistant genotype (CVIET) was present at very low density in polyclonal infections. Persistence of low-density chloroquine resistant parasites indicates competition-survival trade-offs may contribute to maintaining genetic diversity . Thus, monitoring the expansion of these low-density genotypes in different immune backgrounds will be critical to evaluate drug policy changes.
Topics: Antimalarials; Asymptomatic Infections; Chloroquine; Drug Resistance; Folic Acid Antagonists; Genotype; Humans; Malaria; Malaria, Falciparum; Mutation; Plasmodium falciparum; Protozoan Proteins
PubMed: 35862750
DOI: 10.1128/aac.00188-22 -
Malaria Journal Sep 2021Further reductions in malaria incidence as more countries approach malaria elimination require the identification and treatment of asymptomatic individuals who carry...
BACKGROUND
Further reductions in malaria incidence as more countries approach malaria elimination require the identification and treatment of asymptomatic individuals who carry mosquito-infective Plasmodium gametocytes that are responsible for furthering malaria transmission. Assessing the relationship between total parasitaemia and gametocytaemia in field surveys can provide insight as to whether detection of low-density, asymptomatic Plasmodium falciparum infections with sensitive molecular methods can adequately detect the majority of infected individuals who are potentially capable of onward transmission.
METHODS
In a cross-sectional survey of 1354 healthy children and adults in three communities in western Kenya across a gradient of malaria transmission (Ajigo, Webuye, and Kapsisywa-Kipsamoite), asymptomatic P. falciparum infections were screened by rapid diagnostic tests, blood smear, and quantitative PCR of dried blood spots targeting the varATS gene in genomic DNA. A multiplex quantitative reverse-transcriptase PCR assay targeting female and male gametocyte genes (pfs25, pfs230p), a gene with a transcriptional pattern restricted to asexual blood stages (piesp2), and human GAPDH was also developed to determine total parasite and gametocyte densities among parasitaemic individuals.
RESULTS
The prevalence of varATS-detectable asymptomatic infections was greatest in Ajigo (42%), followed by Webuye (10%). Only two infections were detected in Kapsisywa. No infections were detected in Kipsamoite. Across all communities, children aged 11-15 years account for the greatest proportion total and sub-microscopic asymptomatic infections. In younger age groups, the majority of infections were detectable by microscopy, while 68% of asymptomatically infected adults (> 21 years old) had sub-microscopic parasitaemia. Piesp2-derived parasite densities correlated poorly with microscopy-determined parasite densities in patent infections relative to varATS-based detection. In general, both male and female gametocytaemia increased with increasing varATS-derived total parasitaemia. A substantial proportion (41.7%) of individuals with potential for onward transmission had qPCR-estimated parasite densities below the limit of microscopic detection, but above the detectable limit of varATS qPCR.
CONCLUSIONS
This assessment of parasitaemia and gametocytaemia in three communities with different transmission intensities revealed evidence of a substantial sub-patent infectious reservoir among asymptomatic carriers of P. falciparum. Experimental studies are needed to definitively determine whether the low-density infections in communities such as Ajigo and Webuye contribute significantly to malaria transmission.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Asymptomatic Infections; Child; Child, Preschool; Cross-Sectional Studies; Female; Humans; Infant; Kenya; Malaria, Falciparum; Male; Middle Aged; Prevalence; Rural Population; Young Adult
PubMed: 34535134
DOI: 10.1186/s12936-021-03905-w -
International Journal of Molecular... May 2023, a Gram-positive, coagulase-positive pathogen belonging to the family with a spherical shape that forms grape-like clusters, is a commensal that is often present...
, a Gram-positive, coagulase-positive pathogen belonging to the family with a spherical shape that forms grape-like clusters, is a commensal that is often present asymptomatically on parts of the human body [...].
Topics: Humans; Staphylococcus aureus; Anti-Bacterial Agents; Drug Resistance, Bacterial; Staphylococcal Infections; Coagulase; Microbial Sensitivity Tests
PubMed: 37175886
DOI: 10.3390/ijms24098182 -
PLoS Neglected Tropical Diseases Apr 2020In the Mediterranean basin, Leishmania infantum is the causative agent of visceral leishmaniasis (VL), a zoonosis in which the dog is the primary domestic reservoir,...
BACKGROUND
In the Mediterranean basin, Leishmania infantum is the causative agent of visceral leishmaniasis (VL), a zoonosis in which the dog is the primary domestic reservoir, although wildlife may have a leading role in the sylvatic cycle of the disease in some areas. Infections without disease are very frequent. There is limited information regarding the role that VL patients and asymptomatic infected individuals could be playing in the transmission of L. infantum. Xenodiagnosis of leishmaniasis has been used in this descriptive study to explore the role of symptomatic and asymptomatic infected individuals as reservoirs in a recent focus of leishmaniasis in southwestern Madrid, Spain.
METHODOLOGY AND MAIN FINDINGS
Asymptomatic blood donors (n = 24), immunocompetent patients who were untreated (n = 12) or treated (n = 11) for visceral leishmaniasis (VL), and immunocompromised patients with VL (n = 3) were enrolled in the study. Their infectivity to Phlebotomus perniciosus was studied by indirect xenodiagnosis on peripheral blood samples. Quantitative polymerase chain reaction of blood samples from immunocompetent patients untreated for VL and immunocompromised untreated, treated and under secondary prophylaxis for VL was performed. Antibodies against Leishmania were studied by indirect fluorescent antibody and rK39-immunochromatographic tests. A lymphoproliferative assay with a soluble Leishmania antigen was used to screen for leishmaniasis infection in the healthy population. Sixty-two xenodiagnostic tests were carried out and 5,080 sand flies were dissected. Positive xenodiagnosis was recorded in four patients, with different sand fly infection rates: 1 immunosuppressed HIV / L. infantum coinfected asymptomatic patient, 1 immunosuppressed patient with multiple myeloma and symptomatic active VL, and 2 immunocompetent patients with untreated active VL. All blood donors were negative for both xenodiagnosis and conventional PCR.
CONCLUSIONS / SIGNIFICANCE
There is no consensus amongst authors on the definition of an 'asymptomatic case' nor on the tools for screening; we, therefore, have adopted one for the sake of clarity. Immunocompetent subjects, both infected asymptomatics and those treated for VL, are limited in number and appear to have no epidemiological relevance. The impact is limited for immunocompetent patients with untreated active VL, whilst immunosuppressed individuals undergoing immunosuppressive therapy and immunosuppressed individuals HIV / L. infantum coinfected were the most infectious towards sand flies. It is noteworthy that the HIV / L. infantum coinfected patient with asymptomatic leishmaniasis was easily infectious to sand flies for a long time, despite being under continuous prophylaxis for leishmaniasis. Accordingly, screening for latent Leishmania infection in HIV-infected patients is recommended in scenarios where transmission occurs. In addition, screening for VL in HIV-infected patients who have spent time in VL-endemic areas should also be implemented in non-endemic areas. More research is needed to better understand if some asymptomatic coinfected individuals contribute to transmission as 'super-spreaders'.
Topics: Adult; Animals; Antibodies, Protozoan; Asymptomatic Diseases; DNA, Protozoan; Disease Reservoirs; Disease Transmission, Infectious; Female; Humans; Leishmania infantum; Leishmaniasis, Visceral; Leukocytes, Mononuclear; Male; Middle Aged; Psychodidae; Spain
PubMed: 32324738
DOI: 10.1371/journal.pntd.0008253 -
Clinical Microbiology and Infection :... Feb 2022The role of SARS-Cov-2-infected persons who develop symptoms after testing (presymptomatics) or not at all (asymptomatics) in the pandemic spread is unknown. (Review)
Review
BACKGROUND
The role of SARS-Cov-2-infected persons who develop symptoms after testing (presymptomatics) or not at all (asymptomatics) in the pandemic spread is unknown.
OBJECTIVES
To determine infectiousness and probable contribution of asymptomatic persons (at the time of testing) to pandemic SARS-CoV-2 spread.
DATA SOURCES
LitCovid, medRxiv, Google Scholar, and WHO Covid-19 databases (to 31 March 2021) and references in included studies.
STUDY ELIGIBILITY CRITERIA
Studies with a proven or hypothesized transmission chain based either on serial PCR cycle threshold readings and/or viral culture and/or gene sequencing, with adequate follow-up.
PARTICIPANTS
People exposed to SARS-CoV-2 within 2-14 days to index asymptomatic (at time of observation) infected individuals.
INTERVENTIONS
Reliability of symptom and signs was assessed within contemporary knowledge; transmission likelihood was assessed using adapted causality criteria.
METHODS
Systematic review. We contacted all included studies' corresponding authors requesting further details.
RESULTS
We included 18 studies from a diverse setting with substantial methodological variation (this field lacks standardized methodology). At initial testing, prevalence of asymptomatic cases was 12.5-100%. Of these, 6-100% were later determined to be presymptomatic, this proportion varying according to setting, methods of case ascertainment and population. Nursing/care home facilities reported high rates of presymptomatic: 50-100% (n = 3 studies). Fourteen studies were classified as high risk of, and four studies as at moderate risk of symptom ascertainment bias. High-risk studies may be less likely to distinguish between presymptomatic and asymptomatic cases. Six asymptomatic studies and four presymptomatic studies reported culturing infectious virus; data were too sparse to determine infectiousness duration. Three studies provided evidence of possible and three of probable/likely asymptomatic transmission; five studies provided possible and two probable/likely presymptomatic SARS-CoV-2 transmission.
CONCLUSION
High-quality studies provide probable evidence of SARS-CoV-2 transmission from presymptomatic and asymptomatic individuals, with highly variable estimated transmission rates.
Topics: Bias; COVID-19; Humans; Pandemics; Reproducibility of Results; SARS-CoV-2
PubMed: 34757116
DOI: 10.1016/j.cmi.2021.10.015