Effects of Gasterophilus pecorum infestation on the intestinal microbiota of the rewilded Przewalski's horses in China

Horse botflies have been a threat to the Przewalski’s horses in the Kalamaili Nature Reserve in Xinjiang of China since their reintroduction to the original range. As larvae of these parasites could infest the intestine of a horse for months, they could interact with and alter the structure and composition of its intestinal microbiota, affecting adversely its health. Nonetheless, there are no such studies on the rewilded Przewalski’s horses yet. For the first time, this study characterizes the composition of the intestinal microbiota of 7 rewilded Przewalski’s horses infected severely by Gasterophilus pecorum following and prior to their anthelmintic treatment. Bioinformatics analyses of the sequence data obtained by amplicon high throughput sequencing of bacterial 16S rRNA genes showed that G. pecorum infestation significantly increased the richness of the intestinal microbial community but not its diversity. Firmicutes and Bacteroidetes were found the dominant phyla as in other animals, and the parasitic infestation decreased the F/B ratio largely by over 50%. Large reduction in relative abundances of the two genera Streptococcus and Lactobacillus observed with G. pecorum infestation suggested possible changes in colic and digestion related conditions of the infected horses. Variations on the relative abundance of the genus groups known to be pathogenic or symbiotic showed that adverse impact of the G. pecorum infestation could be associated with reduction of the symbiotic genera Lactobacillus and Bifidobacterium that are probiotics and able to promote immunity against parasitic infection.

Intestinal helminth co-infection is an unrecognised risk factor for increased pneumococcal carriage density and invasive disease

Infection with Streptococcus pneumoniae is the leading cause of death in children and burden of disease is greatest where helminth infections are also common. We investigated the impact of intestinal helminth co-infection on pneumococcal carriage; a risk factor for invasive disease. We used a mouse co-infection model and clinical data to assess the impact of co-infection on carriage density. Co-infection in mice was associated with increased pneumococcal carriage density and dissemination into lungs. Helminth-infected children also exhibited increased carriage density as compared to uninfected children. Anthelmintic treatment may be a cost-effective method of reducing pneumococcal disease burden in lower-income countries.

Contrasting microbiota profiles observed in children carrying either Blastocystis spp. or the commensal amoebas Entamoeba coli or Endolimax nana

Recent studies have shown how intestinal parasites can modulate gut microbiota. This observation is not surprising since the human intestinal lumen, like any other niche, is a battlefield of microbial competition, and Eukaryotes can affect bacterial populations. Intestinal pathogenic protist has been associated with reshaping the microbial community structure; however, the interactions between the colonic bacterial communities and parasites like Blastocystis spp., Entamoeba coli, and Endolimax nana have been poorly studied. In this work, we studied the distal intestinal bacterial microbiota of 49 children attending 7 public daycare centers in Medellin, Colombia, and compared the bacterial microbiota structure in the presence or absence of the protists Blastocystis spp., E. coli, and E. nana. Parasite colonization was associated with an increase in bacterial richness. Moreover, Blastocystis spp. presented a positive relationship with Prevotella, since this bacterium was selectively enriched in children carrying it. Remarkably, the E. coli colonized children showed a microbial profile that was closer to uninfected controls, although some bacterial taxa displayed to be enriched. This is the case for Akkermansia, which showed to be favored in E. coli colonized individuals, while notably reduced in the Blastocystis spp. parasitized group.

Seasonal intestinal coccidiosis in wild bluegill Lepomis macrochirus is associated with a spring bacterial epizootic

Wild bluegill, Lepomis macrochirus Rafinesque, succumb to seasonal mortality in the early spring during cool water temperatures, shown previously to be related to bacteraemia caused by a psychrotrophic bacterium, Pseudomonas mandelii. In the study herein, intestinal coccidiosis in wild bluegill had seasonal prevalence causing heavy intestinal infections and sloughing of intestinal epithelium occurring in late winter/early spring. Infections were predominantly related to two different species, Goussia washuti n. sp., an epicellular coccidium, and a coccidium closely resembling Goussia desseri Molnár 1996, previously only described in percid fish in Europe. In 2019, co-infections of bacteraemia and intestinal coccidiosis occurred in bluegills. Evaluating coccidium infection intensity by fresh parasite examination and histology, an association was observed in which fish with moderate-to-heavy intestinal coccidiosis were 8-12 times more likely to have bacteraemia compared to fish with no or light coccidiosis. The association of these co-infections suggests that intestinal coccidiosis could contribute to seasonal bacterial epizootics of wild bluegill.

Diarrheal disease outbreak in Gaidatar village of Rautahat District, Nepal

OBJECTIVE

Diarrheal diseases, including cholera, remain a major public health concern in developing countries like Nepal. This study investigated a diarrheal outbreak that affected over 1500 people in Gaidatar village of Rautahat district in central Nepal and sought to identify the source and causation of the disease. Stool samples were collected from individuals with acute diarrheal illness (n = 16) and healthy non-diarrheal children (n = 39), along with samples from local drinking water sources (n = 8) and their sewage system (n = 10). None of the individuals were sampled multiple times. Diarrheic stool and sewage samples were analysed for the presence of Vibrio cholerae, while coliforms were tested in drinking water samples following standard microbiological protocols. Enteric parasites were tested in both diarrheic and non-diarrheic stool samples.

RESULTS

Vibrio cholerae O1 Ogawa serotype was isolated in 18.7% of the diarrheic stool and 20.0% of the sewage. Coliforms were found in all drinking water samples, with 87.5% testing positive for fecal coliform. Additionally, 43.6% of the stool samples (n = 55) had at least one of the intestinal parasites tested, primarily Giardia lamblia (21.8%). However, almost all parasites were found in non-diarrheal stool. Taken together, our results provide evidence that the diarrheal outbreak was associated with V. cholerae O1 Ogawa serotype, possibly transmitted through the drinking water sources contaminated with fecal matters from their sewage (drainage) system. These findings warrant regular surveillance of drinking water sources to help prevent future outbreaks.

The bacterial community associated with the sheep gastrointestinal nematode parasite Haemonchus contortus

Culture-independent methods were used to study the microbiota of adult worms, third-stage larvae and eggs, both in faeces and laid in vitro, of Haemonchus contortus, a nematode parasite of the abomasa of ruminants which is a major cause of production losses and ill-health. Bacteria were identified in eggs, the female reproductive tract and the gut of adult and third-stage larvae (L3). PCR amplification of 16S rRNA sequences, denaturing gradient gel electrophoresis (DGGE) and clone libraries were used to compare the composition of the microbial communities of the different life-cycle stages of the parasites, as well as parasites and their natural environments. The microbiomes of adult worms and L3 were different from those in the abomasum or faeces respectively. The H. contortus microbiota was mainly comprised of members of the phyla Proteobacteria, Firmicutes and Bacteroidetes. Bacteria were localised in the gut, inside eggs and within the uterus of adult female worms using the universal FISH Eub338 probe, which targets most bacteria, and were also seen in these tissues by light and transmission electron microscopy. Streptococcus/Lactococcus sp. were identified within the distal uterus with the probe Strc493. Sequences from the genera Weissella and Leuconostoc were found in all life-cycle stages, except eggs collected from faeces, in which most sequences belonged to Clostridium sp. Bacteria affiliated with Weissella/Leuconostoc were identified in both PCR-DGGE short sequences and clone libraries of nearly full length 16S rRNA bacterial sequences in all life-cycle stages and subsequently visualised in eggs by fluorescent in situ hybridisation (FISH) with group-specific probes. This strongly suggests they are vertically transmitted endosymbionts. As this study was carried out on a parasite strain which has been maintained in the laboratory, other field isolates will need to be examined to establish whether these bacteria are more widely dispersed and have potential as targets to control H. contortus infections.

Infections by human gastrointestinal helminths are associated with changes in faecal microbiota diversity and composition

Investigations of the impact that patent infections by soil-transmitted gastrointestinal nematode parasites exert on the composition of the host gut commensal flora are attracting growing interest by the scientific community. However, information collected to date varies across experiments, and further studies are needed to identify consistent relationships between parasites and commensal microbial species. Here, we explore the qualitative and quantitative differences between the microbial community profiles of cohorts of human volunteers from Sri Lanka with patent infection by one or more parasitic nematode species (H+), as well as that of uninfected subjects (H-) and of volunteers who had been subjected to regular prophylactic anthelmintic treatment (Ht). High-throughput sequencing of the bacterial 16S rRNA gene, followed by bioinformatics and biostatistical analyses of sequence data revealed no significant differences in alpha diversity (Shannon) and richness between groups (P = 0.65, P = 0.13 respectively); however, beta diversity was significantly increased in H+ and Ht when individually compared to H-volunteers (P = 0.04). Among others, bacteria of the families Verrucomicrobiaceae and Enterobacteriaceae showed a trend towards increased abundance in H+, whereas the Leuconostocaceae and Bacteroidaceae showed a relative increase in H- and Ht respectively. Our findings add valuable knowledge to the vast, and yet little explored, research field of parasite—microbiota interactions and will provide a basis for the elucidation of the role such interactions play in pathogenic and immune-modulatory properties of parasitic nematodes in both human and animal hosts.

Helminth infections and gut microbiota - a feline perspective

BACKGROUND

Investigations of the relationships between the gut microbiota and gastrointestinal parasitic nematodes are attracting growing interest by the scientific community, driven by the need to better understand the contribution of parasite-associated changes in the composition of the gut flora to both host malnutrition and immune modulation. These studies have however been carried out mainly in humans and experimental animals, while knowledge of the make-up of the gut commensal flora in presence or absence of infection by parasitic nematodes in domestic animals is limited. In this study, we investigate the qualitative and quantitative impact that infections by a widespread parasite of cats (i.e. Toxocara cati) exert on the gut microbiota of feline hosts.

METHODS

The faecal microbiota of cats with patent infection by T. cati (= Tc+), as well as that of negative controls (= Tc-) was examined via high-throughput sequencing of the V3-V4 hypervariable region of the bacterial 16S rRNA gene, followed by bioinformatics and biostatistical analyses of sequence data.

RESULTS

A total of 2,325,366 useable high-quality sequences were generated from the faecal samples analysed in this study and subjected to further bioinformatics analyses, which led to the identification of 128 OTUs and nine bacterial phyla, respectively. The phylum Firmicutes was predominant in all samples analysed (mean of 53.0%), followed by the phyla Proteobacteria (13.8%), Actinobacteria (13.7%) and Bacteroidetes (10.1%). Among others, bacteria of the order Lactobacillales, the family Enterococcaceae and genera Enterococcus and Dorea showed a trend towards increased abundance in Tc+  compared with Tc- samples, while no significant differences in OTU richness and diversity were recorded between Tc+ and Tc- samples (P = 0.485 and P = 0.581, respectively). However, Canonical Correlation and Redundancy Analyses were able to separate samples by infection status (P = 0.030 and P = 0.015, respectively), which suggests a correlation between the latter and the composition of the feline faecal microbiota.

CONCLUSIONS

In spite of the relatively small number of samples analysed, subtle differences in the composition of the gut microbiota of Tc+ vs Tc- cats could be identified, some of which in accordance with current data from humans and laboratory animal hosts. Nevertheless, the findings from this study contribute valuable knowledge to the yet little explored area of parasite-microbiota interactions in domestic animals.

Small intestinal nematode infection of mice is associated with increased enterobacterial loads alongside the intestinal tract

Parasitic nematodes are potent modulators of immune reactivity in mice and men. Intestinal nematodes live in close contact with commensal gut bacteria, provoke biased Th2 immune responses upon infection, and subsequently lead to changes in gut physiology. We hypothesized that murine nematode infection is associated with distinct changes of the intestinal bacterial microbiota composition. We here studied intestinal inflammatory and immune responses in mice following infection with the hookworm Heligmosomoidespolygyrusbakeri and applied cultural and molecular techniques to quantitatively assess intestinal microbiota changes in the ileum, cecum and colon. At day 14 post nematode infection, mice harbored significantly higher numbers of γ-Proteobacteria/Enterobacteriaceae and members of the Bacteroides/Prevotella group in their cecum as compared to uninfected controls. Abundance of Gram-positive species such as Lactobacilli, Clostridia as well as the total bacterial load was not affected by worm infection. The altered microbiota composition was independent of the IL-4/-13 – STAT6 signaling axis, as infected IL-4Rα^-/- mice showed a similar increase in enterobacterial loads. In conclusion, infection with an enteric nematode is accompanied by distinct intestinal microbiota changes towards higher abundance of gram-negative commensal species at the small intestinal site of infection (and inflammation), but also in the parasite-free large intestinal tract. Further studies should unravel the impact of nematode-induced microbiota changes in inflammatory bowel disease to allow for a better understanding of how theses parasites interfere with intestinal inflammation and bacterial communities in men.

Immunity to the model intestinal helminth parasite Heligmosomoides polygyrus

Heligmosomoides polygyrus is a natural intestinal parasite of mice, which offers an excellent model of the immunology of gastrointestinal helminth infections of humans and livestock. It is able to establish long-term chronic infections in many strains of mice, exerting potent immunomodulatory effects that dampen both protective immunity and bystander reactions to allergens and autoantigens. Immunity to the parasite develops naturally in some mouse strains and can be induced in others through immunization; while the mechanisms of protective immunity are not yet fully defined, both antibodies and a host cellular component are required, with strongest evidence for a role of alternatively activated macrophages. We discuss the balance between resistance and susceptibility in this model system and highlight new themes in innate and adaptive immunity, immunomodulation, and regulation of responsiveness in helminth infection.

Prevalence of intestinal parasitic and bacterial pathogens in diarrhoeal and non-diarroeal human stools from Vhembe district, South Africa

In the present study, a cross-sectional survey of intestinal parasitic and bacterial infections in relation to diarrhoea in Vhembe district and the antimicrobial susceptibility profiles of isolated bacterial pathogens was conducted. Stool samples were collected from 528 patients attending major public hospitals and 295 children attending two public primary schools and were analyzed by standard microbiological and parasitological techniques. Entamoeba histolytica/E. dispar (34.2%) and Cryptosporidium spp. (25.5%) were the most common parasitic causes of diarrhoea among the hospital attendees while Giardia lamblia (12.8%) was the most common cause of diarrhoea among the primary school children (p < 0.05). Schistosoma mansoni (14.4%) was more common in non-diarrhoeal samples at both hospitals (16.9%) and schools (17.6%). Campylobacter spp. (24.9%), Aeromonas spp. (20.8%), and Shigella spp. (8.5%) were the most common bacterial causes of diarrhoea among the hospital attendees while Campylobacter (12.8%) and Aeromonas spp. (12.8%) were most common in diarrhoeal samples from school children. Vibrio spp. was less common (3% in the hospitals) and were all associated with diarrhoea. Antimicrobial resistance was common among the bacterial isolates but ceftriaxone (91%) and ciprofloxacin (88.6%) showed stronger activities against all the organisms. The present study has demonstrated that E. histolytica/dispar, Cryptosporidium, Giardia, and Cyclospora are common parasitic causes of diarrhoea in Vhembe district while Campylobacter spp. and Aeromonas are the most common bacterial causes of diarrhoea in Vhembe district of South Africa.

Frequency of enteric protozoan parasites among patients with gastrointestinal complaints in medical centers of Zahedan, Iran

We investigated the prevalence of intestinal protozoan parasites in patients with gastrointestinal complaints in medical centers in Zahedan, Iran. A total of 1562 stool samples was examined from July 2004 to January 2006 using microscopy (direct smear, formalin-ether concentration), xenic culture and PCR techniques. Four hundred and twenty-seven (27.3%) of the patients were infected with one or more intestinal parasites. Giardia lamblia (10.1%), Entamoeba coli (10%), E. hartmanni (1.7%), Blastocystis hominis (2.2%), Chilomastix mesnili (1.7%), Trichomonas hominis (0.7%), E. histolytica/E. dispar (0.51%) and Iodamoeba butschlii (0.45%) were the most prevalent protozoa detected with microscopy. Of the eight microscopy-positive E. histolytica/E. dispar samples, six were identified as E. dispar by PCR/gel electrophoresis, whereas E. histolytica was not detected at all. Although Zahedan is an area with poor hygiene located in a tropical area near the border of Pakistan and Afghanistan, the prevalence of E. histolytica and E. dispar here compared with other parasites and infectious diseases is unexpectedly low.

Presence of Enterocytozoon bieneusi associated with intestinal coccidia in patients with chronic diarrhea visiting an HIV center in Haiti

This study investigated the presence of Enterocytozoon bieneusi as a possible cause of chronic diarrhea in Haitian patients attending the GHESKIO AIDS clinic in Port-au-Prince, Haiti. Coccidian oocysts were found by polymerase chain reaction (PCR) in the stools of 58/74 patients with chronic diarrhea and included the following agents: 45 (60%) Cryptosporidium spp., 27 (34%) Cyclospora cayetanensis, and 11 (15%) Isospora belli. Four patients (5.5%) were co-infected with E. bieneusi and one (1.4%) had E. bieneusi alone. The PCR-restriction fragment length polymorphism (RFLP) method made it possible to document the presence in human feces of E. bieneusi in Haiti. As in sub-Saharan Africa, the association of E. bieneusi with coccidian parasites found in Haitian patients with diarrhea is probably caused by the high level of fecal contamination of soils and surface waters usually associated with countries with low hygienic standards.

Intestinal helminth co-infection has a negative impact on both anti-Mycobacterium tuberculosis immunity and clinical response to tuberculosis therapy

The impact of intestinal helminth infection on Mycobacterium tuberculosis (MTB)-specific immune responses during active tuberculosis (TB) is not known. We investigated the role of intestinal helminth infection in anti-MTB immunity by evaluating both cellular phenotype and cytokine profiles in patients with TB and patients with concomitant TB and intestinal helminth infection (TB + Helm) during TB therapy. Twenty-seven per cent of TB patients enrolled for the study were co-infected with at least one intestinal helminth. At baseline, absolute frequencies of leucocytes, monocytes and eosinophils from TB and TB + Helm patients differed from healthy subjects. Concomitant intestinal helminth infection in TB + Helm patients had a negative impact (P < 0.05) on absolute frequencies of CD3(+), CD4(+), CD8(+), natural killer (NK) T and CD4(+) CD25(high) T cell subsets when compared to either TB patients or healthy controls. Differences in CD4(+) T cell frequencies were accompanied by lower interferon (IFN)-gamma and elevated and sustained interleukin (IL)-10 levels in whole blood (WB) cultures from TB + Helm compared to TB patients. In addition to a depressed anti-MTB immunity, TB + Helm patients also presented with more severe radiological pulmonary disease, with a significant difference (P = 0.013) in the number of involved lung zones at the end of TB treatment. The above data may indicate that concomitant intestinal helminth infection in patients with newly diagnosed TB skews their cytokine profile toward a T helper 2 response, which could favour persistent MTB infection and a more protracted clinical course of the disease.

Changes in immune-related gene expression and intestinal lymphocyte subpopulations following Eimeria maxima infection of chickens

Coccidiosis, a major intestinal parasitic disease of poultry, induces a cell-mediated immune response against the etiologic agent of the disease, Eimeria. In the current study, the expression levels of gene transcripts encoding pro-inflammatory, Th1, and Th2 cytokines, as well as chemokines were measured in intestinal intraepithelial lymphocytes (IELs) after Eimeria maxima infection. In addition, changes in IEL numbers were quantified following E. maxima infection. Transcripts of the pro-inflammatory and Th1 cytokines IFN-gamma, IL-1beta, IL-6, IL-12, IL-15, IL-17, and IL-18 were increased 66- to 8 x 10(7)-fold following primary parasite infection. Similarly, mRNA levels of the Th2 cytokines IL-3, IL-10, IL-13, and GM-CSF were up-regulated 34- to 8800-fold, and the chemokines IL-8, lymphotactin, MIF, and K203 were increased 42- to 1756-fold. In contrast, IFN-alpha, TGF-beta4, and K60 transcripts showed no increased expression, and only the level of the Th2 cytokine IL-13 was increased following secondary E. maxima infection. Increases in intestinal T cell subpopulations following E. maxima infection also were detected. CD3(+), CD4(+), and CD8(+) cells were significantly increased at days 8, 6, and 7 post-primary infection, respectively, but only CD4(+) cells remained elevated following secondary infection. TCR1(+) cells exhibited a biphasic pattern following primary infection, whereas TCR2(+) cells displayed a single peak in levels. Taken together, these data indicate a global chicken intestinal immune response is produced following experimental Eimeria infection involving multiple cytokines, chemokines, and T cell subsets.

Dioecious Schistosoma mansoni express divergent gene repertoires regulated by pairing

Pairing of adult Schistosoma mansoni parasites initiates a cascade of events including mating and egg production that ultimately leads to immuno-pathological lesions during schistosomiasis. To identify genes associated with this important biological process, we studied parasites isolated from single- versus mixed-sex cercariae-infected mice using DNA microarray analysis to uncover pair-regulated transcriptional profiles. We report that: (i) transcriptomes of parasites isolated from single-sex infections are significantly more complex than their mixed-sex counterparts; (ii) transcriptomes of single-sex males are distinct from mixed-sex males; and (iii) not all transcripts, previously hypothesized to be critical in female egg production, are regulated by pairing.

Clinical and microbiological features of dientamoebiasis in patients suspected of suffering from a parasitic gastrointestinal illness: a comparison of Dientamoeba fragilis and Giardia lamblia infections

OBJECTIVES

To describe the clinical and microbiological features of Dientamoeba fragilis and Giardia lamblia infected patients, and to analyze the genetic variation of D. fragilis strains.

METHODS

For a period of two years, all stool samples collected from patients suspected of having a parasitic gastrointestinal infection were examined according to our specific triple feces test (TFT) protocol. A retrospective case-control study was performed on D. fragilis and G. lamblia infected patients. Furthermore, PCR and genotyping by restriction fragment length polymorphism (RFLP) were performed upon the former.

RESULTS

D. fragilis (6.3%) and G. lamblia (7.1%) were the most common pathogenic protozoa isolated out of 448 patients studied. Symptoms most frequently encountered with D. fragilis and G. lamblia infection were abdominal pain (69.2% and 72.4%, respectively) and diarrhea (61.5% and 79.3%, respectively). However, patients with D. fragilis infections suffered significantly less frequently from nausea and/or vomiting, anorexia and weight loss. After treatment, all D. fragilis and G. lamblia infected patients presenting a negative TFT follow-up also reported a complete resolution of their symptoms. Only genotype 1 could be detected in D. fragilis infected patients.

CONCLUSIONS

D. fragilis and G. lamblia were the most frequently encountered parasites in our study population. Improved diagnostic tests are essential tools to study the prevalence and pathogenesis of D. fragilis.

Comparative efficacy of the nematode-trapping fungus Duddingtonia flagrans against Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis in goat faeces: influence of the duration and of the temperature of coproculture

Amongst the alternative strategies to the use of anthelmintics, the administration of Duddingtonia flagrans spores has already proved its efficacy in reducing the number of developing larvae of several nematode species in goat faeces. In this trial, the efficacy of this fungus against the larvae of the three major nematode species of goats was compared in various conditions of coproculture. Twelve strongyle free goats were experimentally infected with either Trichostrongylus colubriformis, Teladorsagia circumcincta or Haemonchus contortus larvae. Half of the animals received an oral dose of 5x10(5) Duddingtonia chlamydospores/kg BW daily for 27 days, whereas the remaining was kept as control goats. From the 7th day of administration onwards, individual coproscopical examinations as well as coprocultures, which were incubated 4, 7, 10 or 14 days at 21 or 28 degrees C, were performed. The reduction in developing larvae due to the activity of Duddingtonia ranged from 62.8 to 99.5% compared to control. The trapping efficacy depended on temperature (better activity of the fungus at 21 than at 28 degrees C) and on duration (larval reductions lower after 4 days than after 7, 10 and 14 days of coproculture). Teladorsagia larvae were the least trapped, and Haemonchus larvae were the most trapped.

Impact of the nematophagous fungus Duddingtonia flagrans on Muellerius capillaris larvae in goat faeces

The small lungworm Muellerius capillaris is very prevalent in goats and causes production losses. Its control is particularly difficult. The nematophagous fungus Duddingtonia flagrans has been shown to be effective in trapping a large range of gastro-intestinal nematode larvae but its trapping activity against small lungworm remains to be assessed. The purpose of this work was firstly, to evaluate the ability of first-stage larvae of M. capillaris (L1) to induce trap formation in in vitro conditions and secondly, to determine the effect of D. flagrans on the L1 infectivity to snails. In experiments on agar, the presence of L1 failed to induce any D. flagrans traps whereas in the same conditions, gastro-intestinal third-stage larvae induced 44-135 traps/cm(2) depending on the species. Moreover, when the traps were pre-induced by Haemonchus contortus larvae, the L1 of M. capillaris were not trapped. For the in vivo trial, two goats naturally infected with M. capillaris received D. flagrans chlamydospores at the daily dose rate of 5x10(5) spores/kg BW for 8 days. Faeces were collected individually before, during and 11 days after spore administration. On each day of harvest, the initial larval output was determined. The remaining faeces were subjected to coproculture at 21 degrees C for 7 days. At the end of this period, L1 were collected and used to infect snails (30 snails per goat isolate each snail given 40 L1 by direct deposit of the larvae on the foot of the snail). These snails were artificially challenged in contrast to others that were exposed to natural infection by exposure to faeces carrying first-stage M. capillaris larvae. The natural infection used the same number of snails, i.e. 30 snails deposited on the faeces of each goat. After 3 weeks at room temperature, the infective larvae present in the snail foot were counted. There was no difference in the survival of the L1 in faeces after coproculture whether the faeces contained D. flagrans or not. The infectivity of the extracted larvae from the two goats before and after fungal administration was the same. The number of infective larvae per snail obtained after "natural" infection showed variations that were not related to the presence of D. flagrans mycelium in faeces. These trials clearly indicate that D. flagrans was unable to trap or to alter the infectivity of M. capillaris first-stage larvae and thus cannot be considered as a non-chemotherapeutic alternative approach to the control of the small lungworm in goats.

Recent developments in research into the Cyathostominae and Anoplocephala perfoliata

Intestinal helminths are an important cause of equine disease. Of these parasites, the Cyathostominae are the commonest group that infect horses. These nematodes consist of a complex tribe of 51 species, although individual horses tend to harbour 10 or so common species, in addition to a few rarer species. The Cyathostominae can be extremely pathogenic, and high levels of infection result in clinical symptoms ranging from chronic weight loss to colic, diarrhoea and death. As part of their life cycle, immature cyathostomins penetrate the large intestinal wall, where they can enter a state of inhibited larval development. These larvae can exist in this state for months to years, after which they subsequently re-emerge. If larvae re-emerge in large numbers (i.e. several million), severe pathological consequences ensue. The inhibited larvae are also relatively refractory to several of the currently available anthelmintics, so that horses treated previously with anthelmintics can still carry life-threatening burdens of these parasitic stages. Little is known about the cyathostomin larvae during their mucosal phase, and current research efforts are focused on investigating the biology of these stages. Much of the research described here highlights this area of research and details studies aimed at investigating the host immune responses that the mucosal larvae invoke. As part of this research effort, molecular tools have been developed to facilitate the identification of larval and egg stages of cyathostomins. These molecular tools are now proving very useful in the investigation of the relative contributions that individual, common cyathostomin species make to the pathology and epidemiology of mixed helminth infections. At the more applied level, research is also in progress to develop an immunodiagnostic test that will allow numbers of mucosal larvae to be estimated. This test utilises antigen-specific IgG(T) serum antibody responses as markers of infection. As anthelmintic resistance will be the major constraint on the future control of the Cyathostominae, researchers are now actively investigating this area and studies aimed at elucidating the molecular mechanisms of drug resistance are described. Another parasite which has assumed a clinically important role in horses is the tapeworm, Anoplocephala perfoliata. This parasite is prevalent world-wide and has been shown to be a significant cause of equine colic. Because previous methods of estimating the infection intensity of tapeworm were inaccurate, recent research has been directed at developing an immunodiagnostic ELISA for these cestodes. Specific IgG(T) responses to antigens secreted by adult tapeworms have been shown to provide a reasonable indication of infection intensity. An ELISA based on these responses is now commercially available. The steps involved in the development of this ELISA are described here. In addition to these recent advances in research, this review also outlines the principle areas for future research into these important equine parasites.

Human intestinal anisakiosis due to consumption of raw salmon

Anisakiosis is a parasitic infection that follows consumption of raw or insufficiently pickled, salted, smoked, or cooked wild marine fish infected with Anisakis sp. larvae. We report a case of intestinal anisakiosis in a 50-year-old man from Quebec who presented with abdominal pain and peripheral eosinophilia after eating raw wild-caught salmon from the Pacific Ocean off Canada. Abdominal CT scan showed bowel distension proximal to a segmental jejunal wall thickening, which was resected. The jejunum segment showed a localized area of serositis with mucosal edema and a submucosal abscess rich in eosinophils surrounding a parasite consistent with the third larval stage of Anisakis sp. Diagnostic morphologic characteristics included an unpaired excretory gland (renette cell), Y-shaped lateral epidermal cords, no apparent reproductive system, and a ventriculus (glandular esophagus). These features and the absence of lateral alae excluded Ascaris sp. The absence of ventricular appendage and intestinal cecum excluded other anisakids of the genera Pseudoterranova and Contracaecum. As the popularity of eating raw fish is growing in North America, anisakiosis may be diagnosed more frequently in surgical specimens. This parasitic infection should be considered in the differential diagnosis of acute abdominal syndromes and eosinophilic infiltrates of the stomach, small intestine, colon, omentum, and mesentery, especially with a history of raw marine fish consumption.

Pseudobacciger harengulae from the Atlantic herring Clupea harengus: a new host and locality record

During the summer and autumn of 1994, 1995 and 1996, 406 juvenile herring caught off the Swedish west coast were examined for parasites. Amongst those found was the digenean Pseudobacciger harengulae, which represents new host and locality records for this parasite. Pseudobacciger harengulae has been reported from several species of clupeiformes, mostly from tropical and temperate regions of the Atlantic, Pacific and Indian Oceans. The morphology of P. harengulae is described and compared with earlier descriptions of P. harengulae and P. manteri. The possible relationships between P. harengulae and P. manteri are discussed and the validity of the P. manteri is questioned. Most of the specimens (75%) of P. harengulae were found in the pyloric caeca and the remainder (25%) in the intestine.

Pathogenic intestinal parasites and bacterial agents in solid wastes

OBJECTIVE

To determine the profile of potentially pathogenic enteric parasites and bacterial agents in municipal refuse dumps in Ibadan, Nigeria.

DESIGN

A cross-sectional survey.

SETTING

Five major market places refuse dumps in Ibadan municipality, Nigeria.

METHODS

The major market places in Ibadan city were randomly selected by lottery method. The refuse sludge were sampled and examined parasitologically and bacteriologically using the methods as described. Data analysis was done by using chi-square test where applicable.

RESULTS

Cases of multiple intestinal parasites and bacterial agents were commonly encountered in the sludge refuse samples. The commonly found parasitic agents were of both human and veterinary importance. These include Ascaris Lumbricoides (9.3 egp), Entamoeba histolytica (8.07 cyst per gram), Hookworm/strongyle (6.27 egp) and Ascaris suum (1.07 egp). Others were Ascaris vitolorum (1.09 epg), Strongyloides papillosu (0.52 larvae per gram.), Schistosoma suis (0.31 epg) Dicrocoelium dendriticum (0.9 egp). The most commonly found bacterial agents were Klebsiella species, Escherichia Coli, Proteus species, streptococci, and other gram-positive organisms. Climatic conditions affected the distribution of both parasites and bacterial agents in the sludge (P<0.001). More intestinal parasites 2423 (53.4%) and bacterial agents 2150 (27.2%) were encountered at mean air temperature 26.1 +/- 0.6, mean relative humidity of 72 +/- 3.5%. The degree of contamination by market locations varies significantly (P<0.001).

CONCLUSION

A high degree of contamination of solid waste dumpsites with bacterial and parasitic agents was observed in the present study. As a result of the public health importance of the organisms isolated it is opined that well planned waste management and health education programs will go a long way to reduce the potential epidemic risks posed by such sites in Ibadan, Nigeria.

[Co-occurrence of parasites sensu lato in alimentary tract of patients hospitalised in lower Silesia]

Up to now, the co-occurrence of parasites sensu stricto and fungi were confirmed mostly in the oral cavity. The aim of the present parallel parasitological and mycological investigations was to determine co-occurrence of protozoa, helminths and fungi (parasites sensu lato) both in smears from cavity and in stool samples of 93 patients undergoing the non-parasitological treatment in two hospitals of Lower Silesia (Poland). Among the examined patients parasites sensu lato (13 species) were found in 62 cases (63%). Trofozoites of Trichomonas tenax and/or Entamoeba gingivalis as well as fungi (Candida albicans, C. krusei, C. tropicalis and C. pseudotropicalis) occurred in 10% of the examined patients. Almost all infected cases (90%) were joined with infection of common invasion of protozoa and fungi. In stool common invasion of parasites sensu lato (Giardia intestinalis, Entamoeba coli, Ascaris lumbricoides, Taenia sp., Enterobius vermicularis as well as Candida albicans, C. krusei, C. pseudotropicalis, C. guilliermondii and Rhodotorula sp.) were found in 12% of the patiens. The co-occurrence of parasites and fungi was stated in the half of invasions. C. albicans was the most often co-occurring species in alimentary tract.

[The prevalence of enteropathogens in urban day nurseries]

BACKGROUND

Survey on the intestinal pathogens prevalence in a population of preschool children attending to the urban day-nurseries.

METHODS

Samples of faeces of 408 children and 31 adults, in their charge, were collected. The children were classified per sex, age and kind of day-nursery they were to; data on their physical condition and the faeces characteristics were obtained.

RESULTS

Parasites were the enteropathogens, found with the greatest frequency (21% of children and 19% of adults), next were rotavirus (3% of the children's samples and only one case in adults). The cases of a double parasitization only were 0.74% of the total number of the children surveyed (3 children per each case).

CONCLUSIONS

The highest prevalence of enteropathogens in children attending to the urban day-nurseries in our community belongs to the group of parasites; rotavirus are a much smaller group and bacterium are only isolated cases.

Acquired immunodeficiency with intestinal cryptosporidiosis: possible transmission by Haitian whole blood

A 31-year-old Frenchman had an acquired immunodeficiency syndrome (AIDS) with profound depression of cellular immunity and relative sparing of humoral immunity. The clinical picture included intractable secretory diarrhoea, vomiting, abdominal pain, and weight loss. Gastrointestinal cryptosporidiosis was present and a perfusion technique showed profuse secretion of fluid in the proximal small bowel. The patient also had recurrent Salmonella typhimurium septicaemia, cytomegalovirus infection, and cerebral toxoplasmosis and he died within 13 months. This patient did not belong to any of the groups known to be affected by this type of acquired immunodeficiency (homosexuals, drug addicts, haemophiliacs, Haitians) but had been transfused with Haitian blood 4 years before onset of symptoms. This case supports the notion that some forms of AIDS may be transmitted by blood, with a long incubation period.

[The effects of intestinal parasites on enteric bacterial flora]

Intestinal parasites, can cause malabsorption syndromes and shifts in intestinal bacterial flora. In this study 200 cases with parasitic infestations were examined in regard to their intestinal flora. The series included 96 giardiasis. 58 Ascariasis, 20 Oxyuriasis and 17 H. nana 14 T. trichiura, 8 Tenia cases. The stool cultures yielded mainly E. coli, Strep. faecalis and other gram negative enteric bacteria, yeasts along with uncommon species as B. subtilis, Herellea, Shigella at low frequencies. The control group of 50 patients without parasitic infestations had the same distribution ratio for the same species. The observed frequencies of the isolated bacterial species showed no significant differences between the parasite positive and control cases.

[The effect of parasites on enteric bacterial flora]

In this paper, the intestinal bacterial flora is described and the functions of permanent bacterial flora and its individual members is discussed. The pertinent publications about the factors which effects the bacterial flora and specially relations between intestinal parasites and bacterial flora is reviewed. Among these parasites giardia, amoebae, B. coli and Ascaris may change bacterial population by causing malabsorption syndromes. Some drugs used in treatment of parasitic infestations may have harmful effects on normal intestinal bacterial flora. In parasitic diseases the probable floral changes could be looked for and taken into the consideration for a successful treatment of the patients.

High rates of enteric protozoal infections in selected homosexual men attending a venereal disease clinic

Stool specimens from 89 high-risk, sexually active homosexual men were screened for enteric protozoal cysts. Patients whose specimens contained nonpathogenic cysts were investigated further by examination of fresh purged specimens. A total of 27 of the initial specimens (30%) contained protozoal cysts. Twenty-three patients (26%) harbored pathogens. There were 18 cases (20%) of amebiasis and 11 cases (12%) of giardiasis. Six men (7%) had concurrent amebiasis and giardiasis. The presence of infections correlated with a history of anilingus but not with place of birth, travel, or history of symptoms. The exceptionally high rate of prevalence of intestinal protozoal infection in this population suggests that enteric protozoal infections are important among sexually transmitted diseases.

[Infectious agents in diarrhea of hospitalized children in Costa Rica]

Shigella, toxigenic Escherichia coli (stable toxin) and rotaviruses were frequently found among 50 children hospitalized with diarrhea studied during one year. These agents were less common among 45 controls without diarrhea, of comparable age and from the same wards as the cases reported. There was a greater frequency of respiratory symptoms in the diarrhea associated with rotaviruses. These were characterized by frequent bowel movements and vomiting and often fever. The bacterial diarrheas showed, in general, a more severe clinical picture than the viral ones. The rotaviruses had a low endemic level during April-October, but their prevalence increased in December and January; in such months these viruses were found in more than 50 per cent of the diarrheal cases.

Changes in the bacterial cecal flora of mice infected with Trichuris muris (Schrank, 1788)

Cecal microorganisms of mice were categorized and enumerated weekly during the developmental cycle of infection with the whipworm, Trichuris muris. The cecal bacterial population consisted of Escherichia coli, Proteus spp, Acinetobacter lwoffi (Mima polymorpha), aerobic lactobacilli, staphylococci, enterococci, and anaerobes (bacteroides, streptococci, and lactobacilli) in control and T. muris-infected mice. The aerobic lactobacilli and the anaerobes constituted the greatest number of organisms in both groups. In week three there was a decrease in the number of these organisms, and in week four fewer of these and of all other organisms in the worm-infected mice when compared to controls. The most significantly reduced bacterial counts were observed during the period of T. muris self-cure.

Clinical trial methodology in intestinal parasitic diseases

The high prevalence of intestinal parasitic infections as an index of underdevelopment, especially in tropical countries, is related to poverty, poor housing, lack of sanitation, malnutrition, and ignorance. The effects are lowered work capacity, physical and mental retardation, leading to recurrences and exacerbations of the parasitism and malnutrition. The most prevalent parasites, methods of detection by specific tests in patients in clinical trials involving antiparasitic drugs are dealt with. How and by whom investigations of new drugs should be undertaken, the need for a basic knowledge of parasitology and techniques of the discipline, of biostatistics, and use of such controls as randomized allotment to treatment groups, placebo administration, and double-blind assessments are emphasized. The justification for undertaking an evaluation of an antiparasitic drug is predicated on the demonstration of safety in exhaustive in vitro and animal studies and of the drug's potential superiority as to efficacy and lower incidence of unwanted side effects, as compared with existing agents. Tolerance and dose-range studies should be conducted in male adult hospitalized patients under close supervision. The evaluation of amebicides in clinical trials, as well as of anthelmintics, is considered in terms of differentiation and reproductive habits of specific causative agents and tests for detecting their elimination to determine improvement under drug therapy. The problem of reinfection, particuarly of nonhospitalized patients under the adverse conditions of life, is stressed.

Intestinal anisakiasis. First case report from North America

The first case of intestinal anisakiasis in North America is described. This parasitic disease is recognized as a public health hazard in Japan and Europe. Man becomes infected with a larval form of the nematode Anisakis by consuming raw or undercooked fish containing the parasite. Typically, patients present with acute abdominal syndromes. Clinical and reontgenographic features may cause confusion with regional enteritis. Histologically, a striking oesinophilic granulomatous reaction occurs. Anisakiasis is most effectively prevented by discouraging the consumption of raw fish.