Parasitic Source Research Articles

Parasites of Nile tilapia (<i>Oreochromisniloticus</i>) from selected fish farms and Lake Koftuin central Ethiopia

This study was conducted from October 2016 to January 2017 at Lake Koftu, Sebeta ponds and selected private fish farms in Wonchi area, Ethiopia. The main objective was to identify the major parasites of Oreochromis niloticus to the lowest possible Taxa, thereby determine the prevalence, mean intensities and mean abundances of parasites. A total of 302 O. niloticus (101 from Lake Koftu, 127 from Sebeta pond and 72 from selected small scale fish farms) were collected and examined for the presence of parasites.The overall prevalence of all parasites in Lake Koftu, Sebeta ponds and private fish farms were found to be 100%, 71.0% and 82.2% respectively. There was statistically significant difference (p<0.05) between the study sites in overall prevalence. Nine Taxa of parasites were identified in Lake Koftu, the Trematode Tylodelpyes spp. being the most prevalent parasite (93.1%). In Sebeta fish ponds, 11 Taxa of parasites were recovered from O. niloticus with the most prevalent parasite being Trichodina (37.5%) and four Taxa of parasites from small scale fish farms were identified and the highest prevalent parasite being with Trichodina spp (53.25%). The study showed that fingerlings from Lake Koftu had high prevalence of parasitic infestation and hence may be source of parasites for others when used for stocking small scale fish farms requiring intervention measures such as deworming before being stocked to other farms.Keywords: Ethiopia; Fish farms; Lake Koftu; Oreochromis niloticus; Parasites, Prevalence

Prevalence of zoonotic helminths in Italian house dogs.

Dogs may act as potential sources of zoonotic parasites, e.g. intestinal helminths like Toxocara spp., Ancylostoma spp., Echinococcus spp. In particular circumstances, the environment contaminated by parasitic elements represents a source of infection for people and animals. The present study has evaluated the presence of zoonotic helminths in house dogs from central and north-eastern Italy. Stool samples from 493 dogs were examined by a qualitative copromicroscopic technique and differences in prevalence of zoonotic parasites were statistically examined in relation to canine individual data. 48/493 (9.7%) were positive for at least one parasite. Helminths recovered were Trichuris vulpis (5.5%), Toxocara canis (4.3%), Ancylostoma spp. (0.6%) and Eucoleus aerophilus (0.4%), while no cestodes were detected. Age and living with other dogs resulted risk factors for T. canis infection. The health risk associated with the occurrence of parasitic nematodes in privately owned dogs, along with the current anthelmintic treatment plans, are discussed.

Relationships between the weaning period and the introduction of complementary foods in the transmission of gastrointestinal parasitic infections in children in Honduras.

PurposeThis study was to investigate weaning practices used by mothers when transitioning infants from breast milk to complementary foods and to determine the role these foods have in the transmission of gastrointestinal parasites.Participants and methodsOn average, of the 175 mothers extensively interviewed, 93% said they had breast-fed their infants. Approximately 20.8% of mothers had added some other liquid to their infant’s diet at 3 months, while most mothers had added other liquids at 6 months (39.0%) and >6 months (32.1%). Some mothers expanded food offerings to infants before 3 months. The percentage of mothers who had added other liquids to their infants’ diet was reported by age of the infant: as early as 1 day (2.5%), <1 week (1.9%), first month (3.1%), 3 months (20.8%), 6 months (39.0%), and >6 months (32.1%). These foods included fruit, vegetables, meat, and grains. The maximum age a child was found to be still breastfeeding was 13 years.ResultsForty percent of mothers involved in this survey reported that their children were diagnosed and/or treated for gastrointestinal parasitic infection. Routes of infection of protozoan and helminth parasites likely resulted from contaminated complementary foods and water given to infants while still breast-feeding or from contaminated foods after breast-feeding had been completed. Contaminated water is a likely source of protozoan parasites. Contaminated water was fed to infants, mixed with formula or complementary foods, or used to wash bottles for infant feeding. There was an absence of hand-washing by children and mothers before eating or while preparing foods.ConclusionThe major source of soil-transmitted helminth infections was likely the result of unwashed or uncooked pureed fruit or vegetables used as complementary foods, unpasteurized animal milk, insanitary food storage, poor living conditions with exposed dirt floors, and exposure to roaming domestic animals.

Effect of gate–source spacing on parasitic source access resistance in AlGaN/GaN heterostructure field-effect transistors

In this paper, the AlGaN/GaN heterostructure field-effect transistors (HFETs) with different gate–source spacings were fabricated. Using the measured parasitic source access resistance and the scattering theoretical calculation, it is verified that the gate–source spacing can affect the parasitic source access resistance by altering PCF scattering. This paves a possible way to utilize this effect to improve the performance of AlGaN/GaN HFETs by choosing the optimizing gate-source spacing.

Enteric Parasitic Infections among School Children at Rupandehi, Nepal

INTRODUCTION: Soil-transmitted helminths (STHs), are the common intestinal parasites among school age children in Nepal. Periodic epidemiological studies and transmission dynamics in parasitic infections will provide accurate understanding. The aim of this study is to find out the prevalence of intestinal parasitic infections among primary school children at Rupandehi district Nepal.MATERIALS AND METHODS: This is a school based cross-sectional descriptive study including 217 students studying at primary level in two Government School in Rupandehi. The demographic data and anthropometric data was collected. Routine Stool examination was done and concentration techniques were used for maximum recovery of parasites.RESULTS: The prevalence of parasitic infection was 60% (130/217). Statistically significant association was found between parasitic infection and source of drinking water (p&lt;0.05) A. lumbricoides was most common followed by Taenia spp, Hymenolepsis nana and others. Parasitic infection was highest 70% (21/30) in age group 13-15 years and lowest i.e. 38.1% (8/21) in age group 4-6 years. The mean height and weight of children was found to be 1.28 m and 26.5 kg respectively. Among total children 90.8% (197/217) of the children were malnourished (BMI&lt;18.5 kg/m2) and among infected children 90% (117/130) were malnourished.CONCLUSION: The intestinal parasitosis was found comparatively higher in school children in this region. Higher rate of infection was found in malnourished children.Journal of Universal College of Medical Sciences (2016) Vol.04 No.02 Issue 14, page: 30-34

Improved Linearity with Polarization Coulomb Field Scattering in AlGaN/GaN Heterostructure Field-Effect Transistors

The single-tone power of the AlGaN/GaN heterostructure field-effect transistors (HFETs) with different gate widths was measured. A distinct improvement in device linearity was observed in the sample with a larger gate width. The analysis of the variation of the parasitic source access resistance showed that, as the gate bias is increased, the polarization Coulomb field scattering can offset the increased polar optical phonon scattering and improve the device linearity. This approach is shown to be effective in improving the device linearity of AlGaN/GaN HFETs.

Printing Parasites: Hookworm and Public Health Narratives in Southern Fiction.

During the early twentieth century, public health campaigns taught Americans from all strata of society to recognize that a great threat to the health and prosperity of the South was not an enemy abroad, but rather a bloodsucking parasite living underfoot in Southern soil: hookworm. According to the information widely disseminated by these campaigns, hookworm infection was responsible for the physical "backwardness" of Southern men, women, and children. By linking physical and cognitive symptoms to a parasitic source, the public health campaign introduced a new literary tool for constructing characters who are not "quite right" that continues to be employed in contemporary fiction. This paper focuses on the so-called "lazy man's disease" (hookworm) and takes the work of William Faulkner as a case study to demonstrate how authors deployed a figurative form of hookworm to construct disabled, poor, and degenerate characters.

The selective cleaning behaviour of juvenile blue-headed wrasse (Thalassoma bifasciatum) in the Caribbean

Through the removal of parasites, dead skin and mucus from the bodies of visiting reef fish (clients), cleaner fish have a significant ecosystem function in the ecology of coral reefs. Cleaners gain nutrition from these interactions and through offering a ‘service’ are afforded protection from predators. Given these benefits, it is unclear why more fish do not engage in cleaning, and why part-time cleaning strategies exist. On coral reefs, dedicated species clean throughout their life, whereas some species are facultative, employing opportunistic and/or temporary cleaning strategies. Here, we investigate the cleaning behaviour of a facultative species to assess the relative importance of this interaction to the cleaner. Using a combination of focal and event sampling from a coral reef in Tobago, we show that cleaning is not an essential food source for facultative juvenile blue-headed wrasse (Thalassoma bifasciatum), as cleaning rate was unrelated to their foraging rate on the substrate. These wrasse displayed two cleaning strategies: stationary versus wandering cleaning, with cleaning frequency being highest for stationary cleaners. A specific cleaning location facilitated increased cleaning frequency, and wrasse cleaning rate decreased as cleaner or client abundance increased. We also compared juvenile blue-headed wrasse cleaning behaviour to a resident dedicated cleaner, the sharknose goby (Elacatinus evelynae), and showed that, in comparison, juvenile wrasse clean a narrower client range, predominately cleaning three species of gregarious free-ranging surgeonfish (Acanthurus spp.). The wrasse, however, frequently approached these clients without cleaning, which suggests that their selective cleaning strategy may be driven by the acquisition of a particular parasitic food source. Juvenile blue-headed wrasse are generalist foragers, and may thus be limited in their cleaning behaviour by their nutritional requirements, the availability of a suitable cleaning site, and fish density, which ultimately means that they do not adopt more dedicated cleaning roles within the reef community.

Babesia bigemina: Advances in continuous in vitro culture using serum-free medium supplemented with insulin, transferrin, selenite, and putrescine

This study reported that Babesia bigemina (Bbig-SF) was continuously cultured in vitro in a serum-free medium supplemented with a mixture of insulin-transferrin-selenite (M-ITS) and putrescine (Pu). Firstly, the effect of five different types of basal culture media supplemented with 40% bovine serum was evaluated regarding the proliferation of the protozoan parasite. Cultures with the advanced DMEM/F12 medium (A-DMEM/F12) showed the highest percentage of parasitized erythrocytes (PPE) at 8.37%. Using A-DMEM/F12, a strain of B. bigemina (Bbig-SF) was adapted for growth in bovine serum-free medium by a sequential reduction of serum and demonstrated a maximum PPE of 7.18% in the absence of serum. The next study was the evaluation of the effect of adding four different concentrations of M-ITS to the serum-free A-DMEM/F12 medium on Bbig-SF; the optimal concentrations of M-ITS were 2000, 1100, and 1.34mg/L, which yielded a PPE of 7.23%. Next, eight levels of Pu were evaluated on Bbig-SF cultured in serum-free A-DMEM/F12. After the addition of 0.1012mg/L of Pu, the maximum PPE was 7.61%. When the combination of serum-free A-DMEM/F12+M-ITS (2000, 1100, and 1.34mg/L)+Pu (0.1012mg/L) was evaluated, it yielded a maximum PPE of 14.80%. Finally, the combination of M-ITS+Pu in A-DMEM/F12 without serum and incorporation of a perfusion bioreactor yielded a maximum PPE of 33.45%. We concluded these culturing innovations for B. bigemina in vitro allow the optimization of small- and large-scale proliferation as a source of this protozoan parasite for future studies.

Effect of polarization Coulomb field scattering on device linearity in AlGaN/GaN heterostructure field-effect transistors

The power gain for the AlGaN/GaN heterostructure field-effect transistors (HFETs) has been measured, and a distinct difference of device linearity for a single device under two types of direct current quiescent points was observed. Based on the analyses of the variation of the transconductance and the parasitic source access resistance, it is found that polarization Coulomb field scattering can affect the power gain and the device linearity. We show that this is an effective approach to improve the linearity of AlGaN/GaN HFETs.

Parasitic source resistance at different temperatures for AlGaN/AlN/GaN heterostructure field-effect transistors**Project supported by the National Natural Science Foundation of China (Grant Nos. 11174182, 11574182, and 61306113) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110131110005).

The parasitic source resistance (RS) of AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) is studied in the temperature range 300–500 K. By using the measured RS and both capacitance–voltage (C–V) and current-voltage (I–V) characteristics for the fabricated device at 300, 350, 400, 450, and 500 K, it is found that the polarization Coulomb field (PCF) scattering exhibits a significant impact on RS at the above-mentioned different temperatures. Furthermore, in the AlGaN/AlN/GaN HFETs, the interaction between the additional positive polarization charges underneath the gate contact and the additional negative polarization charges near the source Ohmic contact, which is related to the PCF scattering, is verified during the variable-temperature study of RS.

Determination of the strain distribution for the Si3N4 passivated AlGaN/AlN/GaN heterostructure field-effect transistors

A method to determine the strain distribution of the AlGaN barrier layer after the device fabrication and the passivation process has been presented. By fitting the calculated parasitic source access resistance with the measured ones for the AlGaN/AlN/GaN HFETs and using the polarization Coulomb field scattering theory, the strain variation of the AlGaN barrier layer after the passivation process has been quantitatively studied. The results show that the tensile strain in the access regions of the AlGaN barrier layer has been increased by 4.62% for the 250 nm-Si3N4 passivated device, and has been decreased by 2.0% for the 400 nm-Si3N4 passivated device, compared to that of before the passivation, respectively. For the gate region of the two devices, the tensile strain has been decreased by 60.77% and increased by 3.60% after the passivation of different thicknesses, oppositely.

Ball sensor rattle: Experimental and numerical sensitivity study for seatbelt applications

Seatbelt systems are important elements of automotive safety systems. Most seatbelt retractors are equipped with ball sensors, enabling retractors to comply with mandatory vehicle sensitive locking requirements. The functional principle is based on ball inertia plus defined backlash of mating surfaces, which renders seatbelt retractors susceptible to rattle. Sensor ball rattle is considered as the most persistent parasitic noise source in occupant safety industry. The vibration induced noise behavior of the ball sensor is analyzed, both experimentally and by numerical simulation, predicting the sound pressure spectrum up to 5 kHz. Impact forces among mating surfaces are computed in the time domain with flexible multibody system analysis, employing Craig-Bampton modes to approximate the vibrations of acoustically relevant substructures. Acoustic radiation into the sound field is determined in the frequency domain using preprocessed acoustic transfer vectors from boundary element method analysis, significantly reducing computation time. A sensitivity study with variation of sensor mass, gap, and excitation demonstrates excellent correlation between numerical model prediction and experimental result across a large variety of test cases. The presented methodology can predict rattle induced noise, and therefore delivers substantial input for retractor design. Furthermore, other applications beyond seatbelt retractors could equally benefit from using this approach.

Minimally invasive microbiopsies: a novel sampling method for identifying asymptomatic, potentially infectious carriers of Leishmania donovani

Visceral leishmaniasis (VL) is a potentially lethal, sand fly-borne disease caused by protozoan parasites belonging to the Leishmania donovani species complex. There are several adequate methods for diagnosing VL, but the majority of infected individuals remain asymptomatic, comprising potential parasite reservoirs for transmission of the disease. The gold standard for assessing host infectiousness to biting vector insects is xenodiagnosis (i.e. scoring infection rates among insectary-reared insects that had fed on humans suspected of being infected). However, when it comes to sand flies and leishmaniasis, xenodiagnosis is an intricate operation burdened by logistical hurdles and ethical concerns that prevent its effective application for mass screening of widely dispersed communities, particularly in rural regions of underdeveloped countries. Minimally invasive microbiopsy (MB) devices were designed to penetrate the skin to a depth of ∼200µm and absorb blood as well as skin cell lysates, mimicking the mode by which phlebotomine sand flies acquire blood meals, as well as their composition. MBs taken from 137 of 262 volunteers, living in endemic VL foci in Ethiopia, detected Leishmania parasites that could potentially be imbibed by feeding sand flies. Although the volume of MBs was 10-fold smaller than finger-prick blood samples, Leishmania DNA detection rates from MBs were significantly higher, implying that skin, more often than blood, was the source of parasites. Volunteers with histories of VL were almost as likely as healthy volunteers to test positive by MBs (southern Ethiopian focus: 95% CI: 0.35–2.59, P=1.0. northern Ethiopian focus 0.87: 95% CI: 0.22–3.76, P=1), suggesting the importance of asymptomatic patients as reservoirs of L. donovani. Minimally invasive, painless MBs should be considered for reliably and efficiently evaluating both L. donovani infection rates among large numbers of asymptomatic carriers and their infectiousness to blood-feeding sand flies.

On the Source of Oscillatory Behaviour during Switching of Power Enhancement Mode GaN HEMTs

With Gallium Nitride (GaN) device technology for power electronics applications being ramped up for volume production, an increasing amount of research is now focused on the performance of GaN power devices in circuits. In this study, an enhancement mode GaN high electron mobility transistor (HEMT) is switched in a clamped inductive switching configuration with the aim of investigating the source of oscillatory effects observed. These arise as a result of the increased switching speed capability of GaN devices compared to their silicon counterparts. The study identifies the two major mechanisms (Miller capacitance charge and parasitic common source inductance) that can lead to ringing behaviour during turn-off and considers the effect of temperature on the latter. Furthermore, the experimental results are backed by SPICE modelling to evaluate the contribution of different circuit components to oscillations. The study concludes with good design techniques that can suppress the effects discussed.

On the Source of Oscillatory Behaviour during Switching of Power Enhancement Mode GaN HEMTs

With Gallium Nitride (GaN) device technology for power electronics applications being ramped up for volume production, an increasing amount of research is now focused on the performance of GaN power devices in circuits. In this study, an enhancement mode GaN high electron mobility transistor (HEMT) is switched in a clamped inductive switching configuration with the aim of investigating the source of oscillatory effects observed. These arise as a result of the increased switching speed capability of GaN devices compared to their silicon counterparts. The study identifies the two major mechanisms (Miller capacitance charge and parasitic common source inductance) that can lead to ringing behaviour during turn-off and considers the effect of temperature on the latter. Furthermore, the experimental results are backed by SPICE modelling to evaluate the contribution of different circuit components to oscillations. The study concludes with good design techniques that can suppress the effects discussed.

Influence of Different Gate Biases and Gate Lengths on Parasitic Source Access Resistance in AlGaN/GaN Heterostructure FETs

The AlGaN/GaN heterostructure FETs with different gate lengths were fabricated. Under different gate biases or for the devices with different gate lengths, the measured parasitic source access resistance values were different. By the analysis of different scattering mechanisms and polarization charge distribution, it is found that the gate bias and gate length can change the polarization Coulomb field scattering, and then affect the parasitic source access resistance. At last, the systematic scattering theories were adopted and the influence of different gate biases and gate lengths on parasitic source access resistance was further confirmed in theory.

Carriage of sub-microscopic sexual and asexual Plasmodium falciparum stages in the dry season at Navrongo, Ghana.

We investigated the prevalence of sub-microscopic Plasmodium falciparum infections and gametocyte carriage in asymptomatic individuals in Navrongo in northern Ghana, an area of seasonal malaria transmission. A cross sectional study of 209 randomly selected participants of all age-groups was conducted in February and March, 2015. Capillary blood samples collected from these individuals were used for the detection of both asexual and gametocyte stage parasites by microscopy, reverse transcriptase polymerase chain reaction (RT-PCR) and conventional nested PCR methods. The prevalence data as determined by microscopy and molecular methods were compared using chi-square tests. Parasitaemia from these asymptomatic infections ranged from 40 to 3,520 parasites/µl of blood (geometric mean parasitaemia = 732 parasites/µl). The prevalence of asymptomatic P. falciparum carriage was 4.8% (10/209) and 13.9% (29/209) using microscopy and RT-PCR respectively. The overall prevalence of sub-microscopic infections in the total number of samples analysed was 9.1% (19/209) and 66% (19/29) of the asymptomatic infections. P. falciparum gametocytemia detected by microscopy was 1% (2/209) and 3.8% (8/209) by PCR. This is the first report of sub-microscopic asexual and gametocytes infections in the dry season in a seasonal malaria transmission area in Ghana. It has established that persistent latent malaria infections occur and that these could supply the source of parasites for the next transmission season. The findings highlight the presence of sub-microscopic infections and therefore the need for active case detection surveillance to eliminate "asymptomatic reservoir" parasites and consequently break the transmission of the disease in Ghana. Bill and Melinda Gates Foundation grant awarded to Noguchi Memorial Institute for Medical Research Postdoctoral and Postgraduate Training in Infectious Diseases Research (Global Health Grant # OPP52155); National Institutes of Health grant (NIH-NIAID RO1 # 1RO1AI099623) to MDW; European Developing Countries Clinical Trials Partnership (EDCTP)-West African Network of Excellence for Clinical Trials in TB, AIDS and Malaria (WANETAM) (Project code CB.07.41700.007).

Urban Dog Parks as Sources of Canine Parasites: Contamination Rates and Pet Owner Behaviours in Lisbon, Portugal.

Dog parks represent a recent trend in western countries, enabling owners to spend quality time with their pets in a controlled environment. Despite their growing popularity, few studies have been performed to date on these parks to investigate dog intestinal parasitic infections and soil contamination. The present study examined 369 faecal and 18 soil samples collected from 3 dog parks in Greater Lisbon, Portugal. Additionally, 102 interviews were performed with dog owners to assess dog-walking behaviours and parasite risk. In total, 33% of the faecal dog samples were infected with at least one parasitic agent: hookworms (16.5%), Cryptosporidium spp. (11.9%), Giardia spp. (11.4%), Toxascaris leonina (1.1%), Cystoisospora spp. (1.1%), Toxocara spp. (0.5%), and Sarcocystis sp. (0.3%). The soil of all the parks was contaminated with hookworm eggs. This is the first study performed in a European urban area to assess canine faecal contamination and parasitic agents in dog parks. Our results highlight the potential of these parks as a source of transmission for canine parasites, including some with zoonotic potential. Public awareness and effective preventive measures should be promoted to minimise the health-risk impact to both animals and humans, under the scope of environmental and public health.

Dissolved air flotation as a potential treatment process to remove Giardia cysts from anaerobically treated sewage

ABSTRACTControlling Giardia cysts in sewage is an essential barrier for public health protection, reducing possible routes of protozoa transmission. The aim of this study was to evaluate the capability of dissolved air flotation (DAF), on a bench scale, to remove Giardia cysts from anaerobic effluent. Moreover, removals of indicator microorganisms and physical variables were also investigated. Flocculation conditions were studied, associating different flocculation times with different mean velocity gradients. DAF treatment achieved mean log removals in the range of 2.52–2.62 for Giardia cysts, depending on the flocculation condition. No statistical differences were observed among the flocculation conditions in terms of cyst removal. Low levels of turbidity and apparent color obtained from the treated effluent may indicate good treatment conditions for the DAF process in cyst removal. Indicator microorganisms were not able to predict the parasitological quality of the wastewater treated by flotation in terms of cyst concentrations. The DAF process provided an effective barrier to control cysts from sewage, which is an important parasite source.