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PubMed2001

Association of helminth infections with increased gametocyte carriage during mild falciparum malaria in Thailand.

The objective of this study was to determine whether pre-existing helminth infections could affect sexual forms of Plasmodium falciparum. A cross-sectional case record study compared 120 mild P. falciparum malaria cases with patent gametocyte carriage and 187 without gametocytes for helminth exposure. Relevant crude odds ratios and potential confounders were included in a logistic regression model. Helminth infections were associated with the presence of gametocytes with a crude odds ratio of 1.9 (95% confidence interval = 1.1-3.3) (P = 0.01). A positive linear trend was observed between the odds of having patent gametocytemia and the number of different helminth species (P = 0.003). However, when adjusting for hemoglobin concentration the significance of the association between helminths and gametocytes disappeared (P = 0.15). Pre-existing helminth infections may increase the severity of malarial anemia and therefore increase the likelihood of carrying gametocytes. At a population level, helminth infections may thus have a significant influence on malaria transmission.

Adolescent↗
PubMed1996

Gastrointestinal helminths of Arctic foxes (Alopex lagopus) from different bioclimatological regions in Greenland.

Nine species of gastrointestinal helminths were recovered from 254 arctic foxes (Alopex lagopus) from 8 different localities in Greenland. Prevalences of infection with the helminth species differed from area to area: Toxascaris leonina (39-68%), Strongyloides stercoralis (0-14%), Mesocestoides lineatus (0-58%), Diphyllobothrium dendriticum (0-15%), Taenia ovis krabbei (0-70%), Cryptocotyle sp. (0-3%), Plagiorchis elegans (0-6%), and Polymorphus sp. (0-3%). Additionally, a Taenia species, which appears to be different from T. ovis krabbei, had a prevalence of 24% but only on the east coast of Greenland. In general, the composition of the helminth fauna of arctic foxes in Greenland showed distinct differences geographically. Thus, the diversity of helminth species in foxes caught in the northern districts of Greenland seems lower than in the southern districts; only nematode species with direct life cycles were represented equally in all parts of the country. The diversity of the surrounding fauna, and thereby the food items available for the foxes, seems to determine the spectrum of helminth species. Helminths requiring rodents as intermediate hosts were absent on the west coast, even in the areas in northwest Greenland in close proximity to the Canadian Archipelago. Foxes from air bases, which are known to feed intensively on garbage, harbored similar numbers of species compared to foxes from settlements in the same regions. The number of T. leonina in animals less than 1 yr of age was significantly higher than in older individuals. For M. lineatus, the prevalence of infection was found to increase and worm burdens to decrease with increasing host age. Infections with 2 or more helminth species were most frequent in older animals (47% in foxes > or = 4 yr old and 33% in foxes < 4 yr old).

Animals↗
PubMed2005

Can worms defend our hearts? Chronic helminthic infections may attenuate the development of cardiovascular diseases.

The established risk factors for atherosclerosis fail to fully explain the extent and severity of coronary artery diseases in 50% of the patients. Thus, the causative agents and processes, which may be involved in the pathogenesis of atherosclerosis, are being sought. Notoriously, atherosclerosis and cardiovascular event rates are much lower in developing countries. Clinically, severe infections by intracellular pathogens are widespread mostly in developing countries with poor sanitation, nutrition and massive worm infections. A link between atherosclerosis and helminth infections has never been examined. Based on the present knowledge of immune and infectious mechanisms related to atherosclerosis, it is proposed that chronic helminthic infections can have a significant bearing on the epidemiology of cardiovascular diseases. How can helminthic infections affect the cardiovascular risk? (1) Helminths evade or suppress host immune responses, by producing anti-inflammatory and other immunomodulatory molecules. (2) Helminths induce chronic Th2 activation, which can modify cytokine profiles and immunological responses to heat shock proteins, Chlamydia pneumoniae and cytomegalovirus. (3) The chronic Th2 profile may modulate monocyte activation and chemotaxis to inflammatory sites (atherosclerotic plaques). (4) Chronic Th2 activation may lead to a cytokine profile that could be beneficial for attenuation of atherosclerosis development (upregulation of IL-4, IL-10 and IL-13 and downregulation of proinflammatory cytokines). (5) Helminthic infections may reduce plasma LDL level not only by affecting the host nutrition, but also via modulation of naturally occurring antibodies to cholesterol. Studies are needed to clarify these suggestions. If the hypothesis that helminthic infections impact atherosclerosis is correct, it should be taken into consideration in atherosclerosis immunomodulation therapy and especially in the design of vaccines and vaccine trials.

Animals↗
PubMed2001

Atopy, intestinal helminth infection and total serum IgE in rural and urban adult Gambian communities.

BACKGROUND: The rarity of atopy in traditional societies has been attributed to high parasite-driven blocking IgE concentrations. Information is lacking on the relationship between atopy, IgE and intestinal helminth infection in African populations. OBJECTIVE: To determine the prevalence of atopy and intestinal helminth infection and to relate these to wheeze history and serum total IgE in a community sample of adults from an urban (Banjul) and a rural (Farafenni) area of the Gambia. METHODS: Six hundred and ninety-three adults were interviewed about respiratory symptoms using a modified version of the IUTLD questionnaire, and had skin prick testing using four allergens. Stools were examined after formol-ether concentration. Total serum IgE concentration was measured in a subset of participants. RESULTS: The prevalence of atopy (mean weal diameter > or = 3 mm) in the urban and rural area was 35.3% and 22.5% (P = 0.05); D. pteronyssinus and Mold mix being the common sensitizing allergens. Prevalence of wheeze in the previous 12 months was 4.4% and 3.5% for the urban and rural areas, respectively. Wheezing was not significantly associated with atopy. Seventeen per cent of urban and 8.2% of rural subjects had helminths detected in stools. There was an inverse association between atopy and intestinal helminth infection; 7% of atopic subjects had helminths, compared to 13% of non-atopic subjects (unadjusted odds ratio 0.51, 95%CI 0.24-1.1, P = 0.09; adjusted odds ratio 0.37, 95%CI 0.15-0.92, P = 0.03). Non-atopics had total serum IgE concentrations about 2.5 times the upper limit of the reference range in non-atopic Western populations. Geometric mean total serum IgE concentration was significantly higher among atopic subjects (570 IU/mL, IQR 91-833) than non-atopic subjects (259 IU/mL, IQR 274-1303) (P < 0.001). IgE concentration was not associated with the presence of helminth infection. CONCLUSION: Further studies are needed to clarify why asthma is still relatively uncommon in spite of the prevalence of atopy in Gambian adults. Our data are also compatible with the idea that atopy might protect against helminth infection.

Adolescent↗
PubMed2004

Helminth infracommunities of a population of the Gran Canaria giant lizard Gallotia stehlini.

A survey of gastro-intestinal helminth communities of Gallotia stehlini (Sauria: Lacertidae) from Gran Canaria island (Canary Archipelago, Spain), was conducted to determine the prevalence, abundance and species diversity of intestinal parasites in these lizards. Pharyngodonid nematodes were the most common intestinal helminths, three species being Gallotia specialists. Helminth infracommunities of G. stehlini were rich and appear to be closer to the interactive end of the continuum isolationist-interactive helminth communities, according to the high values of helminth diversity. It is the first case of a saurian reptile showing this kind of diverse helminth infracommunity, produced by a large size, a wide-ranging plant diet and exposure to helminths with direct life-cycles.

Animal Feed↗
PubMed2004

Impaired T helper 2 response to aeroallergen in helminth-infected patients with asthma.

Helminthic infections have been shown to inhibit allergy skin-prick tests and to modify the course of asthma. We evaluated Dermatophagoides pteronyssinus-specific immune responses in patients with asthma by measuring levels of T helper 2 (Th2) cytokines in peripheral blood mononuclear cell (PBMC) cultures. PBMCs from Schistosoma mansoni-infected patients with asthma living in an area of polyhelminthic endemicity produced lower levels of interleukin (IL)-5 and IL-4 in response to D. pteronyssinus antigen (Ag) 1 than did PBMCs from helminth-free patients with asthma. In contrast, D. pteronyssinus Ag 1-specific production of IL-10 was higher in helminth-infected patients than in helminth-free patients. The addition of recombinant human IL-10 to D. pteronyssinus Ag 1-stimulated cultures of PBMCs from helminth-free patients led to down-modulation of production of IL-5. After helminth-infected patients with asthma received antihelminthic treatment, there was down-modulation of D. pteronyssinus Ag 1-specific production of IL-10 in vitro. S. mansoni-infected patients with asthma produce lower levels of Th2 cytokines than do helminth-free patients with asthma, and this modulation is likely done by IL-10.

Adolescent↗
PubMed2006

Helminth-derived products inhibit the development of allergic responses in mice.

RATIONALE: Epidemiological studies suggest that infections with helminths protect from the development of asthma. Supporting this view is our published finding that infection with Nippostrongylus brasiliensis decreased ovalbumin-induced Th2 responses in the lung of mice. OBJECTIVES: To evaluate if N. brasiliensis excretory-secretory products also prevent the development of asthma. METHODS: Mice were immunized with ovalbumin/alum intraperitoneally in the absence or presence of helminthic products and then challenged intranasally with ovalbumin. Six days later, we analyzed if the mice developed Th2 responses in the lung. MAIN RESULTS: The application of the helminthic products together with ovalbumin/alum during the sensitization period totally inhibited the development of eosinophilia and goblet cell metaplasia in the airways and also strongly reduced the development of airway hyperreactivity. Allergen-specific IgG1 and IgE serum levels were also strongly reduced. These findings correlated with decreased levels of IL-4 and IL-5 in the airways in product-treated animals. The suppressive effects on the development of allergic responses were independent of the presence of Toll-like receptors 2 and 4, IFN-gamma, and most important, IL-10. Interestingly, suppression was still observed when the helminthic products were heated or treated with proteinase K. Paradoxically, we found that strong helminth product-specific Th2 responses were induced in parallel with the inhibition of ovalbumin-specific responses. CONCLUSION: Our results suggest that helminths suppress the development of asthma by secreting substances that modulate allergic responses without affecting the generation of helminth-specific Th2 immunity. The identification of these products may lead to the design of novel therapeutic intervention strategies for the treatment of asthma.

Animals↗
PubMed2002

Intestinal helminth infections are associated with increased incidence of Plasmodium falciparum malaria in Thailand.

In a prospective study of the total population of 5 hamlets on the western border of Thailand, all subjects were screened for helminth infections; during the following year, the incidence of malaria was recorded. Patients were not treated for helminth infections. Among 731 villagers, helminth-infected subjects were more likely to develop falciparum malaria during the following year (adjusted risk ratio 2.24, range 1.4-3.6; P = 0.001). The risk of developing falciparum malaria increased with the number of helminth species (P =0.036). Whereas in other studies helminths were associated with protection from severe complications of malaria, it seemed here that helminth-infected patients were more likely to develop malaria. It is suggested that a helminth-mediated Th2 shift may have complex consequences on malaria, decreasing antisporozoite immunity, but protecting against severe malaria.

Adolescent↗
PubMed2006

Helminth assemblages of the turtle Emydura macquarii (Pleurodira: Chelidae) Queensland, Australia.

The helminth fauna of 76 Emydura macquarii from 3 river systems in central and northern Queensland was examined. Eleven species were found, including 2 nematodes, 6 trematodes, 1 aspidogastrean, 1 cestode, and 1 monogenean. Analysis of helminth diversity showed that the Fitzroy and Ross River turtles had communities of comparable diversity, but the helminth communities in Proserpine River turtles were much less diverse. The helminth communities in all localities were dominated by trematodes. Polystomoides australiensis was the most prevalent, being found in 60% of the Ross River turtles, 57% of the Fitzroy River turtles, and 46% of the Proserpine River turtles. Notopronocephalus peekayi was the most abundant species, with mean abundances of 5.9 in the Ross River turtles and 9.8 in the Fitzroy River turtles. Species richness, Simpson's Reciprocal Index, was highest, 4.68, for the Ross River helminth community, Sorensen's Qualitative Index showed 95% similarity between the Ross River and Fitzroy River communities, although Sorensen's Quantitative Index indicated only 35% similarity between the 2 sites. Host feeding patterns are likely the most important factor affecting species richness of the helminth infracommunities, as the majority of helminth species are transmitted by food-web interactions involving intermediate hosts.

Animals↗
PubMed2006

Prevalence of soil transmitted helminthes infections among Bangladeshi males seeking job abroad.

This cross-sectional study was undertaken to identify the prevalence of soil transmitted helminthes infections and its relation to socio-demographic characteristics among Bangladeshi males seeking job abroad. The stool sample of each respondent coming for medical check up was collected by code number and examined under microscope to see the presence helminthic ova or larvae. Among 8140 respondents, 68.05% were from rural and 31.95% from urban area. As a whole, helminthic infection was found in 20.22% respondents. Off which rural and urban distribution were 27.58% and 5.22% respectively (p<0.001). Pattern of helminthes as per rural and urban basis were as follows: Ascaris lumbricoides in 12.45% & 2.61%, Trichuris trichurias in 2.61% & 2.50% samples respectively. As per age distribution was concerned, number of positive cases among rural population in all age groups was statistically higher (p<0.001) than that of urban population. Similarly, rate of combined infections among the rural population was also statistically higher (p<0.001). Higher positivity of helminthes was obtained in low-level educated respondents and in the farmers group. Since the study reflected a high proportion of helminthes infections in rural people, so it was recommended to launch regular deworming programme in rural community at national level. Health education activities on proper sanitary practice, safe disposal of excreta and taking safe food-drinks should be meaningful to eradicating helminthes infections. Further study is needed for monitoring the active status in the community.

Adult↗
PubMed2002

Helminth infections are associated with protection from cerebral malaria and increased nitrogen derivatives concentrations in Thailand.

Following a study showing an association between Ascaris and protection from cerebral malaria, we hypothesized helminths may have induced protection through immunoglobulin E (IgE) and the CD23/NO pathway. We compared the prevalence of helminth infections in 67 cerebral malaria patients and 217 hyperparasitemic controls with no complications. For 24 cerebral malaria cases and 56 controls, we compared reactive nitrogen intermediates (RNI) concentrations and their correlations to total IgE and sCD23 concentrations in helminth-infected and noninfected patients. We observed a dose-dependent association between helminth infections and protection from cerebral malaria (adjusted odds ratio [OR] = 0.36, 95% CI = 0.19-0.7, P = 0.002, linear trend P = 0.0007). Helminth-infected controls had higher RNI concentrations than those without helminths: 72 OD +/- 19 SD and 57 OD +/- 20 SD, respectively (P = 0.006). Logistic regression, including interaction terms between RNI and sCD23, showed that an increase of RNI could be both protective and pathogenic depending on the concentration of sCD23. Helminths increasing both the CD23 receptor and its ligand may have a role in the establishment of malaria tolerance through the CD23/NO pathway.

Animals↗
PubMed2001

Associations and interactions among intestinal helminths of the brown trout, Salmo trutta, in northern Italy.

Species co-occurrences and interspecific associations between intensity of infection were studied in helminth communities of three populations of brown trout, Salmo trutta, from northern Italy. Of the eight helminth species, only four were common enough to be included in the analyses: Pomphorhynchus laevis, Acanthocephalus anguillae, Echinorhynchus truttae and Cyathocephalus truncatus. The observed frequencies of co-occurrences of the different species, based on presence/absence data, did not differ from those predicted by a null model derived from prevalence data. However, the intensity of infection (number of individuals per fish) of different helminth species were generally, but not always significantly, negatively correlated in tests of pairwise associations. Variation in fish sizes and its effect on infection levels, and whether or not two helminth species used the same or different intermediate hosts, had no influence on these findings. Of the few significant negative associations found between pairs of helminth species, none was found in more than one fish population. This suggests that interspecific associations may be condition-dependent: even in apparently similar localities, the same combinations of helminth species show different associations. Without evidence of replicability, it is almost impossible to conclude to the consistent role of competition between any pair of helminth species in the field.

Animals↗
PubMed1975

[Evaluation of helminth carrier rates among foreign workers (author's transl)].

The evaluated helminth carrier rate among foreign workers give rise to many problems under socio-economic, hygienic and occupational aspects. The evaluation of helminth infestation is connected with considerable uncertainty. Based on the author's examinations these problems are critically investigated from the point of view of both, the employer and the employee. It is shown in tables that in the Institute of Hygiene and Microbiology of Würzburg during 1973/1974 497/702 respectively faecal examinations were performed among German and foreign employees and workers. No difference was noted in the overall positive rates in both groups. But there were distinct differences in the species of helminths noted: Among the foreign workers mainly Trichuris trichiura, Ascaris lumbricoides and Enterobius vermicularis were noted while among Germans Taenia saginata prevailed. Noteworthy is the fact, that workers from Turkey and Yugoslavia have occasionally three and more species of helminths and pathogenic protozoa in a single specimen. Since the helminth species found are not transmitted from man to man and since usually the circumstances do not permit a transmission via food, such carriers of helminth don't represent a direct danger for man or the contamination of foofdstuff. For hygienic reasons however helminth carriers may not be acceptable in certain occupations. In case of clinical symptoms the treatment of such patients is required for medical reasons. In spite of frequent absence of clinical signs the consequent liberation of the carriers from their intestinal worms and the sanitation of their personal environment should not be neglected.

Adult↗
PubMed2004

Microscopy and the helminth parasite.

Microscopy has a long and distinguished history in the study of helminth parasites and has made a singularly outstanding contribution to understanding how these complex animals organise their lives and relate to their hosts. Increasingly, the microscope has been used as a powerful investigative tool in multidisciplinary approaches to parasitological problems, placing emphasis on functional correlates rather than anatomical detail. In doing so, microscopy has also uncovered a number of attributes of parasites that are of wider significance in the field of biology. Parasite surfaces have understandably demanded most of the attention of microscopists, largely as a result of the pioneering studies using transmission electron microscopy. Their findings focused the attention of physiologists and immunologists on the tegument and cuticle of helminths and in doing so helped unravel the complex molecular exchanges that are fundamental to understanding host-parasite interactions. Scanning electron microscopy succeeded in augmenting these data by revealing novel microtopographical features of the host-parasite relationship, as well as proving invaluable in helminth taxonomy and in assessing the efficacy of test substances in drug screens. Control of helminth parasites has never been more critical: problems of drug resistance demand urgent action to identify exploitable targets for new generation anthelmintics. In this regard, the neuropeptide signalling system of helminths is envisioned as central to nerve-muscle function, and thereby a crucial regulatory influence on their motility, alimentation and reproduction. The use of immunocytochemistry interfaced with confocal scanning laser microscopy has not only been instrumental in discovering the peptidergic system of helminths and its potential for chemotherapeutic exploitation, but through increasingly sophisticated bio-imaging technologies has continued to help dissect and analyse the molecular dynamics of this and other cellular systems within these important parasites.

Animals↗
PubMed2025

Helminth infections affect host immune responses to viral infections and vaccines.

Helminths are highly prevalent in many regions of the world. Due to the chronic nature of most helminth infections, these parasites are proficient immunomodulators of their hosts. This modulation often leads to skewed or even impaired immune responses against unrelated antigens, such as viruses and vaccines, which can be both beneficial and detrimental for the host. The extent of these effects and the impact on the outcomes of viral infection depends on a variety of factors including timing and tropism of both infections, pathological mechanisms, genetic background, and environmental factors. In this review, we dissect these complex interactions between virus and helminths in the context of coinfection and the impact of helminth infection on antiviral vaccine efficacy. We characterize the key contributing mechanisms that have been defined in preclinical models and human trials and describe the immune actors involved in the modulation of the antiviral and vaccine immune response by helminths. Finally, we address the limitations of our current understanding of helminth-virus interactions.

Helminthiasis↗
PubMed2003

A comparison of the structure of helminth communities in the woodmouse, Apodemus sylvaticus, on islands of the western Mediterranean and continental Europe.

We investigated the pattern of helminth species diversity in woodmouse, Apodemus sylvaticus, on western Mediterranean islands. We first performed a survey of the helminth fauna of A. sylvaticus in Sicily. Despite the small sampling effort, parasite species richness in Sicily is large in comparison with parasite species richness on other Mediterranean islands. We tested the nestedness of helminth parasite species from a number of Mediterranean localities using data compiled from epidemiological surveys of the helminth species of A. sylvaticus. We showed a nested pattern for woodmouse helminth species on western Mediterranean islands which suggests that the distribution of parasites on these islands is not the result of a random process. Properties of helminth parasites such as taxonomic group or life cycle and properties of the host population localities such as area size or the stability of the environment (estimated by mammal species diversity) contribute to the nestedness.

Animals↗
PubMed2005

Relationship between diet and helminths in Gallotia caesaris (Sauria: Lacertidae).

Diet and helminth fauna were analysed in Gallotia caesaris, a small lacertid lizard endemic to El Hierro (Canary Islands, Spain) in order to study the evolutionary and functional relationships between the two traits. This species is omnivorous but consumed a high proportion (82.13%) of plant matter including not only seeds but also leaves and other vegetative parts. Helminth fauna included many helminth species typical of herbivorous reptiles. Both herbivory and helminth presence were higher than expected for a lizard of its size. Comparison with other lacertids suggests that both traits result from an adaptation to insular conditions but that some "evolutionary time" to develop them is needed. Canarian Gallotia lizards, a separate lineage evolving for a long time in insularity, constitutes the most advanced lacertid group in this way. Nevertheless, results for G. caesaris indicate that helminth fauna also changes seasonally tracking variation in diet (and herbivory) throughout the year, which suggests a dynamic interaction between diet and helminth parasites.

Analysis of Variance↗
PubMed2001

Interspecific associations among larval helminths in fish.

Various processes can generate associations between the larvae of different helminth species in their fish intermediate or paratenic host. We investigated the pairwise associations among larval helminth species in eight different fish populations, using two different coefficients of associations, in order to determine in what situations they are strongest. All helminth species included use the fish studied as either their second intermediate host or their paratenic host, and are acquired by the fish when it ingests an infected first intermediate host. The intensity of infection correlated positively with fish length for most helminth species. Pairs of species which both exhibited positive correlations with fish length tended to be more strongly associated with one another, although this tendency was not pronounced. Similarity in life cycle had a more important influence on pairwise associations. Among the 62 pairwise associations that could be computed, pairs of helminth species that shared both first intermediate hosts and definitive hosts were the most strongly associated, followed by pairs that shared only one other host, and finally by pairs that did not share other hosts. The results suggest that assemblages of larval helminth parasites in fish are not random collections of locally available species, but rather structured packets of larval parasites that travel together along common transmission routes.

Animals↗