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Coccidiosis is caused by protozoa of the genus Eimeria. These are intracellular parasites of enterocytes that rupture the host cell, causing lesions in the intestinal mucosa. The lesions caused by Eimeria reduce nutrient absorption capacity, negatively affecting productive gains in broilers, and representing a gateway for other enteropathogens. The objective of this study was to analyze the correlation between lesions caused by Eimeria and the prevalence of coccidiosis and other alterations found in the gastrointestinal tracts of broilers produced in Brazil from 2017 to 2018. Intestinal health evaluations were performed in 32 integrations (farm) of broilers in Brazil, totaling 726 birds analyzed between the ages of 22 and 40 days. Necropsied chickens were collected at three different points, with at least three birds per shed. We analyzed the following changes in the gastrointestinal tract: presence of cellular desquamation, fluid and mucus excess, ingestion of bedding, small and large intestine lesion, food passage, altered tone, "Turkish towel" lesions, worm infection, enteritis and gizzard erosion. The definition of macroscopic lesion scores caused by Eimeria acervulina, Eimeria maxima, Eimeria tenella followed a specific methodology. Mucosal oocyst counts for E. maxima (E. maxima micro) was performed using an optical microscope with a magnification of 100×. We found that the species E. acervulina had the highest prevalence (5.5%). With respect to E. acervulina, a positive correlation was observed with cellular desquamation, bedding ingestion and passage of food. The second highest prevalence was E. maxima (average of 4%), showing positive correlations with cellular desquamation, fluid excess, bed ingestion, feed passage and E. acervulina. E. tenella represented the lowest prevalence (0.8%) among the species of Eimeria analyzed, showing a positive correlation with altered intestinal tone. On microscopic evaluation, E. maxima was present in 45% of mucosa scrapings, representing subclinical coccidiosis of 1125% (11.25-fold) greater than the rate of clinical coccidiosis. Regarding other alterations that were visualized in the gastrointestinal tract, we have recorded the incidence of altered intestinal tone (0.1%), worm infection (0.4%), small intestine (0.8%), enteritis (1%), duodenitis (1.5%), "Turkish towel" lesions (3.3%), excess fluid (4.5%), bed ingestion (6.9%), excess mucus (8.4%), food passage (10.3%), cellular desquamation (11%) and gizzard erosion (13.4%). We conclude that monitoring is of paramount importance to understand the intestinal health status of poultry lots. Microscopic E. maxima is present in 45%. We identified factors that correlate with reduction in intestinal health, impairing zoo-economic performance., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Helminths, allergens, and certain protists induce type 2 immune responses, but the underlying mechanisms of immune activation remain poorly understood. In the small intestine, chemosensing by epithelial tuft cells results in the activation of group 2 innate lymphoid cells (ILC2s), which subsequently drive increased tuft cell frequency. This feedforward circuit is essential for intestinal remodeling and helminth clearance. ILC2 activation requires tuft-cell-derived interleukin-25 (IL-25), but whether additional signals regulate the circuit is unclear. Here, we show that tuft cells secrete cysteinyl leukotrienes (cysLTs) to rapidly activate type 2 immunity following chemosensing of helminth infection. CysLTs cooperate with IL-25 to activate ILC2s, and tuft-cell-specific ablation of leukotriene synthesis attenuates type 2 immunity and delays helminth clearance. Conversely, cysLTs are dispensable for the tuft cell response induced by intestinal protists. Our findings identify an additional tuft cell effector function and suggest context-specific regulation of tuft-ILC2 circuits within the small intestine., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Fasciola hepatica is the causative agent of fasciolosis, a parasitic zoonosis of global distribution causing significant economic losses in animal production and a human public health problem in low-income countries. Hosts are infected by ingestion of aquatic plants carrying metacercariae. Once ingested, the juvenile parasites excyst in the small intestine and, after crossing it, they follow a complex migratory route that lead the parasites to their definitive location in the bile ducts. Despite being a critical event in the progression of the infection, the available data on the cross-talk relationships between the parasite and the host at an early stage of the infection are scarce. The objective of the present work is to characterize the proteomic changes occurring in both the parasite and the host, through the development of a novel in vitro model, to shed light on the molecular pathways of communication between the newly excysted juveniles (NEJ) from F. hepatica and the host's intestinal epithelium. For this, in vitro excystation of F. hepatica metacercariae was carried out and NEJ were obtained. Additionally, optimal conditions of growth and expansion of mouse primary small intestinal epithelial cells (MPSIEC) in culture were fine-tuned. Tegumentary and somatic parasite antigens (NEJ-Teg and NEJ-Som), as well as host cell protein lysate (MPSIEC-Lys) were obtained before and after 24 h co-culture of NEJ with MPSIEC. We used an isobaric tags for relative and absolute quantitation (iTRAQ)-based strategy to detect 191 and 62 up-regulated, and 112 and 57 down-regulated proteins in the NEJ-Teg and NEJ-Som extracts, respectively. Similarly, 87 up-regulated and 73 down-regulated proteins in the MPSIEC-Lys extract were identified. Taking into account the biological processes in which these proteins were involved, interesting mechanisms related to parasite development, invasion and evasion, as well as manipulation of the host intestinal epithelial cell adhesion, immunity and apoptosis pathways, among others, could be inferred, taking place at the host-parasite interface. The further understanding of these processes could constitute promising therapeutic targets in the future against fasciolosis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Tuft cells are an epithelial cell type critical for initiating type 2 immune responses to parasites and protozoa in the small intestine. To respond to these stimuli, intestinal tuft cells use taste chemosensory signaling pathways, but the role of taste receptors in type 2 immunity is poorly understood. In this study, we show that the taste receptor TAS1R3, which detects sweet and umami in the tongue, also regulates tuft cell responses in the distal small intestine. BALB/c mice, which have an inactive form of TAS1R3, as well as Tas1r3 -deficient C57BL6/J mice both have severely impaired responses to tuft cell-inducing signals in the ileum, including the protozoa Tritrichomonas muris and succinate. In contrast, TAS1R3 is not required to mount an immune response to the helminth Heligmosomoides polygyrus , which infects the proximal small intestine. Examination of uninfected Tas1r3 -/- mice revealed a modest reduction in the number of tuft cells in the proximal small intestine but a severe decrease in the distal small intestine at homeostasis. Together, these results suggest that TAS1R3 influences intestinal immunity by shaping the epithelial cell landscape at steady-state., (Copyright © 2020 The Authors.)

The endogenous life cycle of Eimeria caliginosa was studied in experimentally infected dusky rice rats, Melanomys caliginosus. All endogenous stages were located in the epithelial cells of villi in the small intestine. Both Giemsa-stained mucosal scrapings and histological sections were studied for the diagnosis of all the life-cycle stages. Eimeria caliginosa has 3 generations of meronts (M) that differ by size, shape, and number of merozoites (m), which also differ in their size, shape, and location of their nuclei within the cytoplasm of the meronts. The 3 meront types, M 1 -M 3 , respectively, had 20-33 (m 1 ), 5-9 (m 2 ), and 13-16 (m 3 ) merozoites. Macrogametocytes and microgametocytes, as well as macrogametes and microgametes, completed the sexual cycle, which concludes with the formation of unsporulated oocysts. This parasite's endogenous development produced severe intestinal lesions in the experimentally infected dusky rice rats. In our ongoing work to understand the biodiversity present in plants and animals of the protected Reserva Biológica Alberto Manuel Brenes (ReBAMB) field station in Costa Rica, we now have discovered 3 new Eimeria species, and this is the second complete life cycle in which we document both the asexual and sexual stages.

The lumen-dwelling protozoan Giardia is an important parasitic cause of diarrheal disease worldwide. Infection can persist over extended periods with minimal intestinal inflammation, suggesting that Giardia may attenuate host responses to ensure its survival, although clearance eventually occurs in most cases. IL-10 is an anti-inflammatory regulator critical for intestinal homeostasis and controlling host responses to bacterial exposure, yet its potential role in coordinating antiprotozoal host defense in the intestine is not known. In this study, we found that murine infection with the natural enteric pathogen Giardia muris induced a transient IL-10 response after 2-4 wk at the primary site of infection in the upper small intestine, but parasite colonization and eradication were not affected by the absence of the cytokine in gene-targeted mice. However, IL-10 was critical for controlling infection-associated immunological sequelae in the colon because severe and persistent diarrhea and colitis were observed in IL-10-deficient mice within 1-2 wk postinfection but not in uninfected littermate controls. Inflammation was characterized by epithelial hyperplasia, neutrophil and macrophage expansion, and Th1 induction and could be prevented by blockade of IL-12/IL-23 p40 but not depletion of CD11c + dendritic cells. Furthermore, the intestinal microbiota underwent characteristic shifts in composition and was required for disease because antibiotics and loss of TLR signaling in MyD88-deficient mice protected against colitis. Together, our data suggest that transient infection by a luminal and seemingly noninflammatory pathogen can trigger sustained colitis in genetically susceptible hosts, which has broader implications for understanding postinfectious syndromes and other chronic intestinal inflammatory conditions., (Copyright © 2018 by The American Association of Immunologists, Inc.)

An evaluation of a localized intestinal allergic type-2 response concomitant with consumption of probiotic bacteria is not well documented. This study investigated the effect of feeding probiotic Bifidobacterium animalis subspecies lactis (Bb12) or a placebo in weaned pigs that were also inoculated with Ascaris suum (A. suum) eggs to induce a strong Th2-dependent allergic type 2 immune response. Sections of jejunal mucosa were mounted in Ussing chambers to determine changes in permeability and glucose absorption, intestine and liver samples were collected for analysis of type-2 related gene expression, jejunum examined histologically, and sera and intestinal fluid were assayed for parasite antigen specific antibody. The prototypical parasite-induced secretory response to histamine and reduced absorption of glucose in the jejunum were attenuated by feeding Bb12 without a change in mucosal resistance. Parasite antigen-specific IgA response in the serum and IgG1 and IgG2 response in the ileal fluid were significantly increased in A. suum-infected pigs treated with Bb12 compared to infected pigs given the placebo. Ascaris suum-induced eosinophilia in the small intestinal mucosa was inhibited by Bb12 treatment without affecting the normal expulsion of A. suum 4th stage larvae (L4) or the morphometry of the intestine. Expression of genes associated with Th1/Th2 cells, Treg cells, mast cells, and physiological function in the intestine were modulated in A. suum infected-pigs treated with Bb12. These results suggested that Bb12 can alter local immune responses and improve intestinal function during a nematode infection by reducing components of a strong allergenic type-2 response in the pig without compromising normal parasite expulsion.

Despite increased appreciation for the role of nicotinic receptors in the modulation of and response to inflammation, the contribution of muscarinic receptors to mucosal homeostasis, clearance of enteric pathogens, and modulation of immune cell function remains relatively undefined. Uninfected and Nippostrongylus brasiliensis-infected wild-type and type 3 muscarinic receptor (M3R)-deficient (Chrm3(-/-)) mice were studied to determine the contribution of M3R to mucosal homeostasis as well as host defense against the TH2-eliciting enteric nematode N. brasiliensis Intestinal permeability and expression of TH1/TH17 cytokines were increased in uninfected Chrm3(-/-) small intestine. Notably, in Chrm3(-/-) mice infected with N. brasiliensis, small intestinal upregulation of TH2 cytokines was attenuated and nematode clearance was delayed. In Chrm3(-/-) mice, TH2-dependent changes in small intestinal function including smooth muscle hypercontractility, increased epithelial permeability, decreased epithelial secretion and absorption, and goblet cell expansion were absent despite N. brasiliensis infection. These findings identify an important role for M3R in host defense and clearance of N. brasiliensis, and support the expanding role of cholinergic muscarinic receptors in maintaining mucosal homeostasis.

Background: The intestinal epithelium plays a multifactorial role in mucosal defense. In this sense, augmented epithelial cell turnover appears as a potential effector mechanism for the rejection of intestinal-dwelling helminths., Methods: A BrdU pulse-chase experiment was conducted to investigate the infection-induced alterations on epithelial cell kinetics in hosts of high (mouse) and low (rat) compatibility with the intestinal trematode Echinostoma caproni., Results: High levels of crypt-cell proliferation and tissue hyperplasia were observed in the ileum of infected mice, coinciding with the establishment of chronic infections. In contrast, the cell migration rate was about two times higher in the ileum of infected rats compared with controls, with no changes in tissue structure, indicating that an accelerated cell turnover is associated with worm expulsion., Conclusion: Our results indicate that E. caproni infection induces a rapid renewal of the intestinal epithelium in the low compatible host that may impair the establishment of proper, stable host-parasite interactions, facilitating worm clearance.

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 Heligmosomoides polygyrus bakeri 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.

Toxoplasma gondii infection occurs through the oral route, but we lack important information about how the parasite interacts with the host immune system in the intestine. We used two-photon laser-scanning microscopy in conjunction with a mouse model of oral T. gondii infection to address this issue. T. gondii established discrete foci of infection in the small intestine, eliciting the recruitment and transepithelial migration of neutrophils and inflammatory monocytes. Neutrophils accounted for a high proportion of actively invaded cells, and we provide evidence for a role for transmigrating neutrophils and other immune cells in the spread of T. gondii infection through the lumen of the intestine. Our data identify neutrophils as motile reservoirs of T. gondii infection and suggest a surprising retrograde pathway for parasite spread in the intestine.

Natural infection by Toxoplasma gondii occurs via oral ingestion of tissue cysts that rupture in the small intestine, releasing zoites that infect locally before disseminating throughout the host. The studies presented here used fluorescent parasites combined with flow cytometry and multiphoton microscopy techniques to understand the events associated with parasite replication in the mucosa. At 3 days postinfection with tissue cysts, parasites were localized in small foci and flow cytometry revealed parasites present in macrophages, neutrophils, and monocytes in the lamina propria. By day 6 postinfection, there were large foci of replicating parasites; however, foci unexpectedly varied in the number of villi involved and were associated with the presence of viable tachyzoites within the intestinal lumen. Consistent with the flow cytometry data, neutrophils and monocytes in the lamina propria were preferentially associated with parasite plaques. In contrast, dendritic cells comprised a small fraction of the infected immune cell population and were localized at the periphery of parasite plaques. Together, these findings reveal the formation of localized sites of parasite replication and inflammation early during infection and suggest that sustained replication of T. gondii in the gut may be a function of pathogen luminal spread.

Giardiasis is one of the most common parasitic diseases worldwide, and the disease is an important cause of diarrhoea and malabsorption in children and immunosuppressed individuals. However, there is no evidence that characterises malnutrition as an aggravating factor for this disease. We evaluated changes in villi structures to examine the association between malnutrition and Giardia lamblia infection. We used 32 gerbils, divided into 4 groups: Control (CT) and Control Infected (CTIn), which each received a 20% protein diet, Malnourished (MN) and Malnourished Infected (MNIn), which each received a 5% protein diet. Groups CTIn and MNIn were inoculated with 1×10(6) trophozoites of G. lamblia, while the remaining groups were mock infected. Seven days post-infection, all groups were sacrificed, and the proximal portions of the small intestines were collected for the analysis of villus height, mucus area and extent of Giardia infection. Gerbils fed with a low-protein diet had significantly lower body weights. Malnourished infected animals presented significantly increased production of mucus, suggesting a synergism occurs between malnutrition and Giardiasis, potentially to control the adhesion of Giardia in the mucosa. Villus height was significantly lower in group MNIn compared to CTIn. This work suggests that malnutrition contributes to severity of Giardiasis by decreasing the intestinal absorption capacity via shortening of the villi., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Notch receptor-mediated signaling is involved in the developmental process and functional modulation of lymphocytes, as well as in mast cell differentiation. Here, we investigated whether Notch signaling is required for antipathogen host defense regulated by mast cells. Mast cells were rarely found in the small intestine of wild-type C57BL/6 mice but accumulated abnormally in the lamina propria of the small-intestinal mucosa of the Notch2-conditional knockout mice in naive status. When transplanted into mast cell-deficient W(sh)/W(sh) mice, Notch2-null bone marrow-derived mast cells were rarely found within the epithelial layer but abnormally localized to the lamina propria, whereas control bone marrow-derived mast cells were mainly found within the epithelial layer. After the infection of Notch2 knockout and control mice with L3 larvae of Strongyloides venezuelensis, the abundant number of mast cells was rapidly mobilized to the epithelial layer in the control mice. In contrast, mast cells were massively accumulated in the lamina propria of the small intestinal mucosa in Notch2-conditional knockout mice, accompanied by impaired eradication of Strongyloides venezuelensis. These findings indicate that cell-autonomous Notch2 signaling in mast cells is required for proper localization of intestinal mast cells and further imply a critical role of Notch signaling in the host-pathogen interface in the small intestine.

Giardia is the most prevalent human intestinal parasitic protist in the world, and one of the most common parasite of companion animals and young livestock. Giardia is a major cause of diarrhea in children and in travelers. The host-microbial interactions that govern the outcome of infection remain incompletely understood. Findings available to date indicate that the infection causes diarrhea via a combination of intestinal malabsorption and hypersecretion. Malabsorption and maldigestion mainly result from a diffuse shortening of epithelial microvilli. This enterocytic injury is mediated by activated host T lymphocytes. Pathophysiological activation of lymphocytes is secondary to Giardia-induced disruption of epithelial tight junctions, which in turn increases intestinal permeability. Loss of epithelial barrier function is a result of Giardia-induced enterocyte apoptosis. Recent findings suggest that these effects may facilitate the development of chronic enteric disorders, including inflammatory bowel disease, irritable bowel syndrome, and allergies, via mechanisms that remain poorly understood. A newly discovered SGLT-1 glucose uptake-mediated host cytoprotective mechanism may represent an effective modulator of the epithelial apoptosis induced by this parasite, and, possibly, by other enteropathogens. A better understanding of the pathogenesis of giardiasis will shed light on new potential therapeutic targets.

Rats infected with the larvae of Taenia taeniaeformis harbour the intermediate stage of the parasite Strobilocercus fasciolaris within the liver. Affected animals also develop gastric and intestinal hyperplasia. The pathogenesis of the gastric hyperplasia has been extensively investigated, but few studies have addressed the nature of the intestinal changes. This study characterizes the proliferation of small intestinal epithelial cells by immunohistochemical labelling for proliferating cell nuclear antigen (PCNA) and bromodeoxyuridine (BrdU) uptake. At 6 weeks post-infection (wpi) there was an increase in villous length but crypt depth was normal. At 9 wpi there was evidence of epithelial hyperplasia, increased villous length and crypt depth, and expansion of zones of epithelial proliferation. Immunohistochemical labelling indicated that an increase in the number of proliferating cells produced a greater number of progeny cells. Intestinal hyperplasia during experimental infection with T. taeniaeformis larvae is likely to be related to the associated gastropathy, although the mechanisms underlying both changes remain undefined.

Infection with Giardia duodenalis is one of the most common causes of waterborne diarrheal disease worldwide. Mechanisms of pathogenesis and host response in giardiasis remain incompletely understood. Previous studies have shown that exposure to G. duodenalis products induce apoptosis in enterocytes. We recently discovered that sodium-dependent glucose cotransporter (SGLT)-1-mediated glucose uptake modulates enterocytic cell death induced by bacterial lipopolysaccharide. The aim of this study was to examine whether enhanced epithelial SGLT-1 activity may constitute a novel mechanism of host defense against G. duodenalis-induced apoptosis. SGLT-1-transfected Caco-2 cells were exposed to G. duodenalis products in low (5mM) or high (25mM) glucose media. In low glucose environments, G. duodenalis-induced caspase-3 activation and DNA fragmentation in these cells. These apoptotic phenomena were abolished in the presence of high glucose. A soluble proteolytic fraction of G. duodenalis was found to upregulate SGLT-1-mediated glucose uptake in a dose- and time-dependent manner, in association with increased apical SGLT-1 expression on epithelial cells. Kinetic analysis showed that this phenomenon resulted from an increase in the maximal rate of sugar transport (V(max)) by SGLT-1, with no change in the affinity constant (K(m)). The addition of phloridzin (a competitive inhibitor for glucose binding to SGLT-1) abolished the anti-apoptotic effects exerted by high glucose. Together, the findings indicate that SGLT-1-dependent glucose uptake may represent a novel epithelial cell rescue mechanism against G. duodenalis-induced apoptosis.

To examine the infection kinetics and development of alterations in the small intestine of gerbils (Meriones unguiculatus), 72 gerbils were divided into six groups (A to F), with A serving as control and the others inoculated with increasing doses of trophozoites from Giardia duodenalis human isolate. The infection kinetics and the development of histopathological alterations were monitored by optical scanning electron microscopy (SEM). A 12-day prepatent period was observed, with intermittent elimination up to day 35 after inoculation. Statistically significant differences were found between the mean number of trophozoites recovered, per group, on the days of sacrifice, and a positive correlation between the inoculum dosage and the number of trophozoites recovered. Morphometrically, the villus:crypt ratio showed a drop in all the groups when compared with the control group. SEM revealed an increase in mucus production in the inoculated animals and the presence of trophozoite clusters at the top and base of the villi. The dosage of trophozoite inoculum does not interfere in the ability for infection to occur or in the development of histopathological alterations generated by intestinal colonization.

Mucosal mast cell (MMC) responses and worm recovery rates in rats experimentally infected with Centrocestus caninus were investigated. Metacercariae of C. caninus, procured from goldfish, Carassius auratus, were orally administered to twenty-five male rats (300 metacercariae each rat). The infected rats were sacrificed on days 3, 7, 14, 21 and 28 post-infection (PI) along with the control rats. Worm recovery was performed from each part of small intestine. To investigate MMC, duodenal, jejunal and ileal paraffinized-tissue sections were processed and stained with 1% alcian blue and 0.5% safranin-O. The average worm recovery rates were 42.8, 37.7, 21.2, 12.5 and 3.7% on days 3, 7, 14, 21 and 28 PI, respectively. The majority of the worms (98.9%) were collected from the duodenum and jejunum. The MMC numbers in the infected rats were significantly higher than those of the controls (p<0.05). A peak level was observed on days 14 PI and the numbers gradually decreased thereafter. The results reveal that MMC plays an important role in the expulsion of C. caninus from the host intestine. A more precise description of the role the MMC plays in helminth expulsion is still needed to understand the mechanism of host defense against intestinal helminthic infection, along with other effector cells, such as goblet cells.

To understand the development of the inflammatory responses in the wall of the gut, during the process of expulsion of the parasites from the host, samples of tissues were removed from the small intestines from four groups of naturally infected buffalo calves with Toxocara vitulorum during the beginning of the infection, at the peak of egg output, during the period of expulsion and post-expulsion of the worms, as well as from uninfected calves. Cells (mast cells, eosinophils, intraepithelial lymphocytes - IEL and goblet cells) present in the epithelial layer (intraepithelial) of the small intestine were counted. In the duodenum, jejunum and ileum, the population of mast cells, eosinophils and lymphocytes increased significantly during the peak of the infection. Goblet cell numbers increased also during the beginning and at the peak of the infection. The decline of the number of these cells occurred during the periods of expulsion of the worms reaching to uninfected control counts at the post-expulsion period indicating a role of these cells in the process of expulsion of T. vitulorum by the buffalo calves. The layers of the intestinal wall (villus, crypt, submucosa and muscular) were also measured. Morphological examinations showed a significant vilar atrophy, particularly in the duodenum during the beginning, peak and during the period of expulsion of the worms, but smooth muscle hypertrophy or other alteration was not observed in any period of the infection.

The ultrastructural characterisitics of four types of Toxoplasma gondii schizonts (types B, C, D and E) and their merozoites, microgamonts and macrogamonts were compared in cats killed at days 1, 2, 4 and 6 after feeding tissues cysts from the brains of mice. Schizonts, merozoites and gamonts contained most of the ultrastructural features characteristic of the phylum Apicomplexa. All four types of schizonts developed within enterocytes or intraepithelial lymphocytes. Occasionally, type B and C schizonts developed within enterocytes that were displaced beneath the epithelium into the lamina propria. Type D and E schizonts and gamonts developed exclusively in the epithelium. Tachyzoites occurred exclusively within the lamina propria. Type B schizonts formed merozoites by endodyogeny, whereas types C to E developed by endopolygeny. The parasitophorous vacuoles surrounding type B and C schizonts consisted of a single membrane, whereas those surrounding types D and E schizonts were comprised of two to four electron-dense membranes. The parasitophorous vacuole of type B schizonts had an extensive tubulovesicular membrane network (TMN); the TMN was reduced or absent in type C schizonts and completely absent in types D and E schizonts and gamonts. Type B merozoites were ultrastructurally similar to tachyzoites, except that they were slightly larger. Type C merozoites exhibited a positive periodic acid-Schiff reaction by light microscopy and ultrastructurally contained amylopectin granules. Rhoptries were labyrinthine in type B merozoites but were electron-dense in types C-E. The development of microgamonts, macrogamont and oocysts is also described.

To determine the response of the small intestinal mucosa to environmental conditions, we studied changes in mucosal architecture and function in a longitudinal cohort study in African adults. Over three consecutive years, 238 adults submitted monthly stool samples for parasitologic and bacteriologic analysis and underwent an annual endoscopic jejunal biopsy for mucosal morphometry. Absorption and permeability assays were performed on the same day as the enteroscopy. Variation in mucosal architecture and function was correlated with environmental factors and stool microbiology. The whole cohort had structural and functional evidence of tropical enteropathy, but structure and function were only weakly correlated. There were marked changes over time, and seasonal variation was observed in villous height (16%), xylose recovery (16%), and permeability (28%). Asymptomatic intestinal infections were common. Enteropathy was more severe in participants with Citrobacter rodentium or hookworm ova in the stool sample taken one month before the investigations were performed.

In order to improve our understanding of the host cell-parasite interactions in giardiasis, this study assessed the effects of Giardia lamblia on epithelial permeability and tight junctional ZO-1, determined whether epidermal growth factor (EGF) may affect Giardia-induced epithelial injury, and evaluated if EGF modulates epithelial colonization by live G. lamblia trophozoites. Permeability was assessed in assays of trans-epithelial fluxes of FITC-dextran, and ZO-1 integrity was characterized by confocal laser immunofluorescence microscopy in confluent epithelial cell monolayers. G. lamblia significantly increased paracellular permeability and disrupted tight-junctional ZO-1 of a novel non-transformed human small intestinal epithelial cell line (SCBN). Pre-treatment with EGF prevented the development of these abnormalities and significantly inhibited attachment of live trophozoites to the enterocytes, independently of a direct microbiocidal action. These findings demonstrate that G. lamblia may cause intestinal pathophysiology by disrupting tight junctional ZO-1 and increasing epithelial permeability. Apical administration of EGF prevents these abnormalities, and reduces epithelial colonization by the live parasites.

Intestinal coccidiosis was diagnosed histologically in the small intestine of a spinner dolphin (Stenella longirostris). Numerous intralesional coccidia were present in mucosal epithelial cells. Schizonts, gamonts, and unsporulated oocysts were seen. Schizonts were up to 30 x 20 microm and contained up to 16 merozoites, which measured 10-12 x 2 microm. Unsporulated oocysts were about 9-12 x 8-10 microm. This is the first report of intestinal coccidiosis in a spinner dolphin.

Nitric oxide (NO) possesses potent anti-inflammatory properties; however, an over-production of NO will promote inflammation and induce cell and tissue dysfunction. Thus, the ability to precisely regulate NO production could prove beneficial in controlling damage. In this study, advantage was taken of the well characterized inflammatory response caused by an intestinal parasite, Trichinella spiralis, to study the relationship between intestinal inflammation and the regulation of nitric oxide synthase-type 2 (NOS-2) expression. Our study revealed that a specific gut inflammatory reaction results in inhibition of NOS-2 expression. Characteristics of this inhibition are: 1) local jejunal inflammation induced by T. spiralis systemically inhibits NOS-2 gene transcription, protein expression, and enzyme activity; 2) the inhibition blunts endotoxin-stimulated NOS-2 expression; 3) the inhibition does not extend to the expression of other isoforms of NOS, to paxillin, a housekeeper protein, or to cyclooxygenase-2, another protein induced by proinflammatory cytokines; 4) the inhibition is unlikely related to the formation of specific anti-parasite antibodies; and 5) the inhibition may involve substances other than stress-induced corticosteroids. Elucidation of such potent endogenous NOS-2 down-regulatory mechanisms could lead to the development of new strategies for the therapy of inflammatory conditions characterized by the overproduction of NO.

We recently showed that, in our Trichinella spiralis rat model, first exposure, but not re-exposure to infective-stage larvae evoked heat shock responses in 4 test organs. Our work, however, failed to implicate either early complete clearance of challenge muscle larvae (ML), or rapid elimination of newborn larvae (NBL) in the phenomenon noted in reinfected rats. This study clarifies that issue using 2 established facts in T. spiralis biology and anti-T. spiralis immunology. That is, adult worms injure gut cells and immune destruction of NBL requires release of material also toxic to host cells. To approach the above problem we analysed relevant and irrelevant rat organs for increased heat shock protein (HSP) production at 1, 7, 14, 20 and 27 p.i. during first and second infections. Organs examined were intestines, mesenteric lymph nodes (MLN), heart and lungs. Using densitometric analyses of immunoblots, increased HSP expression was detected on day 7 in intestines from both primary and secondary-infected rats albeit that the change in the latter was just short of significant. Interestingly, MLN only exhibited increased HSP levels in the reinfected rat model with increased HSP levels persisting for 1 week. A lasting shock response was detected in reinfected rats; in contrast, first exposure resulted in shock responses being evident in lungs at either day 7 or day 14, only. These findings suggest that (i) in immune rats, a few challenge ML develop into adults, produce NBL which are trapped within MLN, and (ii) that anti-T. spiralis and/or anti-NBL immunity is associated with an, as yet, uncomprehended stress to host's heart tissues.

The ultrastructure of intracytoplasmic meronts and macrogamonts of Eimeria s.l. boveroi in the small intestine of the gekkonid lizard Hemidactylus mabouia from Belem, Para north Brazil is described. Young meronts, and some of the fully grown macrogamonts, are coated with a glycocalyx which, in cross-section, has the appearance of a series of fine tubules. The wall of the parasitophorous vacuole (PV) is a single membrane, lined on the host-cytoplasm side with an endoplasmic reticulum (ER) which sometimes expands into large cisternae filled with electron-lucent, globular material. The membranal edges of the ER, canaliculi and cisternae have regularly spaced indentations filled with an electron-dense substance. Vesicular mitochondria are present in addition to those of the conventional type. Macrogamonts develop the characteristic type 1 and type 2 wall-forming bodies, and in some zygotes the cisternae containing the latter are grossly expanded. Both types of wall-forming bodies persist in young oocysts that have a distinct oocyst wall.

It has been reported that infection with Nippostrongylus brasiliensis induces villus atrophy with various histological alterations. In N. brasiliensis-infected rats, villus length in the jejunum was reduced significantly at day 10 p.i., when serum levels of rat mast cell protease (RMCP) II had increased significantly. To determine whether the villus atrophy is associated with enhancement of apoptosis, apoptotic nuclei were labelled using the nick end-labelling method. Numbers of labelled cells were markedly increased in the villus epithelium at 7-10 days p.i., while the numbers returned to normal 14 days p.i. when worms were rejected from the intestine and villus length became normal. Examination of the expression of the adhesion molecule E-cadherin showed granular immunoreactivity in the cytoplasm of atrophic villus epithelium with loss of normal localization to epithelial cell borders. In mast cell-deficient Ws/Ws rats, villus length was reduced as significantly as in +/+ counterparts at day 10 p.i. with marked increases in the numbers of apoptotic cells. These results suggested that villus atrophy was closely associated with enhanced apoptosis and loss of adhesion in epithelial cells. Mast cell activation appears not to be involved in these alterations.

In the present study, we investigated the site in the host where protective gut immunity to Fasciola hepatica is induced and expressed, following the infection route of the parasite. Expression of protection was studied in ex vivo gut segments with intact blood and lymph supply that were prepared at different locations along the entire length of the small and large intestine. Four weeks after oral infection, significant protection was detected in the duodenum, upper jejunum, midjejunum, and ileum. Protection at the gut level was expressed as early as 2 wk after oral priming and waned after 27 wk. The possibility that the gut wall plays a role in age-related protection was excluded. The effect of newly excysted juveniles (NEJ) penetrating the gut on the induction of protection was studied by recovering or killing the NEJs of the primary infection immediately after gut migration. Results showed that protection was low (13.9-19.8%). However, when gut migration was by-passed and NEJs of the primary infection were injected into the peritoneal cavity or between the liver lobes, high levels of protection at the gut level were detected (76.5-87.4%). The results indicate that protection expressed at the gut level is induced by the parasite at a young stage, during migration through the peritoneal cavity, or liver, or both and not during penetration of the gut.

To assess the gamma delta TCR T cells in the control of the timing of the mucosal response to enteric parasitic infections, we used C57BL mice, orally infected with 200 viable T. spiralis larvae. The small intestine, spleens and Peyer's patches (PP) were excised on 1, 4, 7, 14, 21 and 29 postinfection days (p.i.) for immunophenotyping and histological studies. Uninfected mice served as control. Characterization of isolated lymphocytes of C57BL control mice, confirmed that T cell immunophenotype differs in spleen, PP and i-IEL. Practically all i-IEL were CD3+ cells (83%). In addition, most of the i-IEL expressed Ly-2 (65%). Among the i-IEL, the level of gamma delta TCR+ cells was significantly higher (29%) than that found in spleen (3%) and PP (3%). The expression was high on CD3+ and Ly-2+ (26 and 21%, respectively) and low on L3T4+ i-IEL (< 1%). During T. spiralis infection alpha beta TCR+ CD3+, gamma delta TCR+ CD3+ and gamma delta TCR+ Ly-2+ i-IEL increased on day 4 and 7. However, infected mice displayed a reduction in i-IEL number from 14 to 29 p.i. day. At the same time the proportion of gamma delta TCR on spleen Ly-2+ and on PP CD3+ and Ly-2+ cells increased on 14 and 21 p.i. day. Adult worms were expelled from the gut by day 14. Thus, the kinetics of gamma delta TCR+ i-IEL, but not spleen and PP gamma delta TCR, corresponded to the kinetics of worm expulsion in C57BL mice. Most murine i-IEL of the gamma delta T cell lineage tend to be cytolytic when activated. We speculated that gamma delta T cells of i-IEL during the early stages of infection recognize and eliminate damaged epithelial cells generated by parasite antigens, simultaneously accelerating the worm expulsion.

Transmission electron microscopy was used to study Toxoplasma gondii infections in the small intestines of Swiss-Webster mice at 2-48 h post-feeding of oocysts (p.f.). Sporozoites passed through intestinal epithelial cells (enterocytes and goblet cells) and infected all cells except red blood cells in the lamina propria. Parasites in intestinal epithelial cells or in cells in the lamina propria were located within a single type of parasitophorous vacuole, which contained exocytosed electron-dense material and well-developed tubulovesicular membranous networks. Sporozoites did not infect intraepithelial lymphocytes (IELs), but at 48 h p.f. IELs had become infected with tachyzoites arising from those that had developed in the lamina propria. At 48 h p.f., the lamina propria contained numerous tachyzoites, much cellular debris, and few intact cells. The intestinal epithelium exhibited limited cytopathological changes except for villar fusion, slight vacuolation, and cell separation at the bases of enterocytes.

Background: AIDS is characterised by small intestinal mucosal damage, but its aetiopathogenesis is poorly understood. Enteric infections in Africa differ from those in northern countries, where protozoan infections have been associated with severe enteropathy in AIDS patients., Aims: To characterise enteropathy in Zambian AIDS patients compared with local controls, and to assess relative contributions of enteric infection, nutritional impairment, and immune dysfunction., Methods: Computer aided mucosal morphometry of small intestinal biopsy specimens from 56 HIV infected Zambians with persistent diarrhoea and 26 diarrhoea free controls, followed by regression modelling., Results: Patients with HIV related diarrhoea had reduced villous height and increased crypt depth compared with controls. There was no difference between HIV positive and negative controls. In regression models applied to AIDS mucosal measurements, villous height and crypt depth were related to nutritional parameters and to serum soluble tumour necrosis factor receptor p55 concentration. Crypt depth was also related to lamina propria plasma cell count. Intestinal infection was found in 79%, which consisted predominantly of microsporidia in 34%, Isospora belli in 24%, and Cryptosporidium parvum in 21%, but detection of these enteropathogens was not related to severity of enteropathy., Conclusions: Nutritional and immune disturbances were associated with enteropathy, accounting for over one third of the variation in mucosal morphometric parameters.

Comparisons were made between microscopic lesion scores (MLSs) and gross lesion scores (GLSs) in sections from small intestine of broilers during three routine coccidiosis screenings. The duodenal and jejunal GLS were determined and recorded by different evaluators. During each screening, 2-cm sections of duodenum and jejunum were collected, and sections of intestine were then scored using a microscopic lesion scoring system. No correlation between MLS and GLS was observed in duodenum in two out of three coccidiosis screenings, and no correlation was observed between MLS and GLS in jejunum in three out of three screenings. Our findings demonstrate that, if used alone in coccidiosis screening, GLSs can underestimate infections and may not provide a true representation of the magnitude of Eimeria maxima infection within broiler flocks.

Mucosal glycoconjugates were examined in C3H mice and in hamster small intestines infected with Echinostoma trivolvis and in uninfected rodents, using periodic-acid Schiff (PAS) and high-iron diamine-alcian blue (HID-AB) staining and three different fluorescein-conjugated lectins: Triticum vulgaris agglutinin (WGA), Helix pomatia agglutinin (HPA) and Griffonia simplicifolia agglutinin (GSA-II). Lectin-labelling by electron microscopy was also undertaken with WGA and HPA lectin-gold probes. HID-AB stain demonstrated that the most mature goblet cells of the mouse villi contain sulfomucins, whereas those of hamsters contain sialomucins. The expression of lectin-binding sites and the intensity of the lectin binding in the small intestines were changed by echinostome infection. Specific differences in the reaction to mucin glycoproteins were clearly observed between the mouse and hamster intestines infected with E. trivolvis; lectin-binding to hyperplastic goblet cells and crypts in the infected mice increased, while no marked increase in the number of goblet cells and reaction to the glycoconjugates were observed in the infected hamsters. These findings indicate that the expression of terminal N-acetyl-D-galactosamine, sialic acid and N-acetyl-D-glucosamine increased in mucins secreted from hyperplastic goblet cells associated with E. trivolvis infection in mice. No marked increase in these glycoconjugates occurred in hamster infections. These findings reflect clear differences in infectivity of E. trivolvis in C3H mice versus hamsters.

Metagonimus yokogawai was found deeply invaded into the submucosa of the small intestine of mice (ICR) when they were immunosuppressed by prednisolone injection. Experimental groups consisted of control, fluke infection (1,800 metacercariae per mouse), and fluke infection plus immunosuppression. In fluke infection group, many worms were found sectioned in the intervillous space of the jejunum and ileum at 6 hrs, 12 hrs, and 1 day after infection, and pathological changes characterized by villous atrophy and crypt hyperplasia were observed. After 3 days, only a few worms were found in intestinal sections, and after 7 days, the pathological changes became minimal. No worm was found penetrated beyond the mucosal layer. On the other hand, in immunosuppressed mice, numerous worms were found sectioned in the duodenum and jejunum, irrespective of the infection period up to 14 days. Pathological changes of the mucosa were minimal until 3 days after infection, but at 5 days marked destruction of the mucosal layer was observed. At this time many flukes were found invaded deeply into the submucosa facing the muscular layer. Despite continuous immunosuppression, the mucosal damage was gradually recovered at 7-21 days post-infection. The results showed that immunosuppression of ICR mice can induce, for a short period of time, severe mucosal damage, and allow deep invasion of M. yokogawai into the submucosa of the small intestine.

Background & Aims: The factors that determine the severity of giardiasis are poorly understood. Host factors are important, but parasite virulence may also play a role. The aim of this study was to compare the apparent virulence of three genotypically different Giardia isolates (PO1, VNB3, and WB)., Methods: Infection rates, parasite loads, structural damage, disaccharidase activity, and water and electrolyte absorption were observed at 10 days after inoculation in a neonatal rat model of infection., Results: DNA fingerprinting showed differences between isolates studied. The infective rate varied between 67% and 100%. There were no differences in intestinal parasite load. Infection with strains PO1 and WB, but not with VNB3, was associated with a reduction in villus height. There was precocious expression of sucrase at 10 days after inoculation in all infected groups. Water absorption of a plasma electrolyte solution was decreased in VNB3-infected animals when compared with PO1- and WB-infected animals and controls. Water absorption and lactose hydrolysis were impaired during perfusion with a lactose-containing solution in all infected groups., Conclusions: Three genotypically different Giardia isolates that infect neonatal rats with the same trophozoite load differ in their ability to cause functional mucosal damage. Infection with Giardia lamblia induced precocious expression of sucrase activity and impaired mucosal absorption.

Mucosal changes associated with anthelmintic treatment in Trichostrongylus colubriformis-infected rabbits were assessed along the entire length of the small intestine. The following groups, each of five rabbits, were compared: infected (group I); infected and treated on day 21 with fenbendazole (group IT); uninfected but given fenbendazole on day 21 (group C, controls). All animals were killed on day 28. In the proximal part of the small intestine of group I rabbits, the worms were associated with shortening of the villi and a significant depletion in alkaline phosphatase activity, which differed significantly from the findings in groups C and IT. In the same region, no difference was found between groups C and IT. In the distal small intestine, hypertrophy of villi and crypts (an adaptive response to the infection), coupled with an increase in enzymic activity, were present in both groups I and IT, in contrast to group C. These results suggest that a complete mucosal restoration occurred within 7 days of anthelmintic treatment in the parasitized part of the intestine. In contrast, the adaptive response observed beyond the main site of parasitism was not abolished by treatment. The functional significance of these findings is discussed in relation to the compensatory growth commonly observed after anthelmintic treatment in ruminants.

Athymic (nude) rats have been used to assess the role of thymus-dependent T cells in the control of the intestinal response following infection with the enteric parasite, Nippostrongylus brasiliensis. Tissues from infected rats were excised on days 4, 7, 10, and 21 postinfection (p-i) for physiological and morphological studies; uninfected (day 0) rats served as controls. In response to the worm burden, jejunal tissues displayed a secretory response, indicated by an elevated baseline short-circuit current (Isc) on days 7 and 10 p-i, and were more responsive to histamine than control tissues. Despite this enhanced secretory response, approximately 35% of the worm burden was still present on day 21 p-i (compared with expulsion of > 95% by day 14 p-i in normal rats). Mast cell activation and hyperplasia, increased goblet cell (implying increased mucus synthesis) and intraepithelial leukocyte numbers, and abnormalities in Isc responses after electrical stimulation of enteric nerves were identified following infection. These events in nude rats were attenuated or delayed in onset as compared with conventional immunocompetent rats. Our results support the postulate that thymus-dependent T cells regulate the timing and/or nature of the mucosal response to enteric parasitic infections. However, ion secretion was not altered in the absence of T cells and, therefore, is more likely to be a consequence of mast cell activation.

Susceptibility of the Indian soft-furred rat, Millardia meltada, to infection with the intestinal helminth, Nippostrongylus brasiliensis, was examined. After subcutaneous infection with 1500 infective larvae (L3), daily faecal egg output (EPG) of both male and female animals reached a peak at 1 week post-infection (p.i.) with the same magnitude (about 20,000 epg faeces) and then rapidly decreased below detection level at around 2 weeks p.i. In male animals, however, after a transient cessation at 2 weeks p.i., parasite eggs reappeared in faeces 3 weeks afterwards, though the counts were far lower than the first peak. This phenomenon was rarely seen in female animals. High susceptibility of M. meltada to N. brasiliensis was confirmed by worm burdens. About 70% of the initial dose of larvae became adult worms in the intestine of male and female hosts. As suggested by the decline in egg counts, the majority of adult worms were expelled by 2 weeks p.i. The residual worm burden at 2 and 4 weeks p.i. was significantly higher in male than female animals. When orchidectomized males were infected with N. brasiliensis, the magnitude of residual worm burden was significantly reduced. On the other hand, ovariectomy did not affect the number of residual worms in females.

Female ICR mice, 6-8 weeks old, were exposed to 100 metacercarial cysts/host of Echinostoma trivolvis to determine the effects of this cyst dosage on worm infectivity, distribution, growth and acetabular attachment in the host small intestine. Of 42 exposed mice, 22 were infected 4 to 17 days postinfection (PI) with a mean worm recovery of 11 to 41%. Mean body area of worms increased from about 0.4 mm2 on day 4 PI to about 2.0 mm2 by day 9 PI. No consistent pattern of worm growth was seen beyond day 9. Distribution data showed that worms were found mainly in the anterior part of the small intestines on day 4 PI and then more posteriorly up to day 8 PI. Worm distribution patterns were quite variable beyond day 11 PI. Scanning electron microscopy showed that the acetabulum left a distinct 'fingerprint' or acetabular plug on the intestinal mucosa of the host. The 'fingerprint' was temporary and disappeared within 1 min after worms were removed from the intestines.

The infectivity and distribution of Echinostoma trivolvis were studied in male, conventional and congenitally athymic nude mice, each infected with 30 metacercarial cysts. In conventional mice, worm recoveries at 6 and 8 days post-exposure were 58.3 and 54.0%, respectively. Worm recovery declined to 44.0% by day 10, to 4.3% by day 13, and 0% by day 17. In athymic mice, worm recoveries at 6 and 8 days post-exposure were 61.7 and 36.3%, respectively. Worm recovery declined to 27.7% by day 10, to 0.7% by day 13, and 0% by day 17. The distribution of worms demonstrated a posteriad migration over time in both groups. Kinetic changes in the number of goblet and mucosal mast cells in the upper ileum of mice infected with E. trivolvis were examined. In conventional mice, the number of goblet cells increased rapidly to reach a peak at day 13 and then declined gradually. The number of goblet cells in athymic mice also increased to reach a peak at day 13, and then declined rapidly. However, the number of goblet cells in athymic mice was always less than that in conventional mice. The mast cell number in infected conventional mice increased rapidly to reach a peak at day 17 and then declined. There was no increase in the mast cell number of infected athymic mice throughout the experiment. Whereas common pathological changes occurred in the intestines of both mice groups infected with echinostomes some ultrastructural differences were observed in the gut epithelial cells of conventional versus athymic mice.

The influence of population size of Trichostrongylus colubriformis on the structures of the small intestine, especially with regard to the development and origin of an intestinal adaptive response, was examined in experimentally infected rabbits. The effects of low (500 L3) and high (50,000 L3) infection on histological (villous length, mucosa to serosa ratio, crypt surface) and biochemical (protein content, alkaline phosphatase and leucine aminopeptidase activities) aspects of the mucosa were assessed along the whole small intestine. The presence of a small number of worms induced only minor mucosal changes, indicating a regenerative response of the intestinal epithelium. The role of a local small population of T. colubriformis in the development of a previously described adaptive response appeared thus to be limited. On the other hand, the 50,000 L3 inoculum was associated with severe lesions of villi, marked crypt hyperplasia and with a major reduction of enzyme activities. The changes were found along the whole length of the small intestine. These results suggest that the generally recognized dose-dependent pathogenicity of the intestinal nematode infections could be ascribed to two different processes: firstly, a greater severity of the lesions; secondly, more extensive damage leading to the disappearance of any adaptive intestinal region.

The endogenous stages of Sarcocystis cameli (Mason, 1910) in the small intestine of dogs are described. These stages are mainly in the posterior third of the small intestine. They were observed only in the lamina propria of the distal third of the villi. There was no schizogonic process. Micro and macrogamonts were differentiated 18 h p.i. The first zygote was observed 24 h later. Unsporulated oocysts were found 30, 36, 42, 48 h and 4 days p.i. The oocysts started sporulation on the 5th day p.i. Completely sporulated oocysts were formed 8 days p.i.

The host-parasite interaction at the site of attachment of the adult hookworm, Ancylostoma ceylanicum, to the small bowel mucosa of the dog has been examined by transmission electron microscopy. The lamina propria around the heads of the worms showed intense infiltration with neutrophilic and eosinophilic leucocytes, and plasma cells were also prominent. Erythrocytes were extravasated within the lamina propria while the portions of mucosa engulfed into the buccal cavities of the worms were necrotic and included aggregates of collagen fibres. Within the lumina of the worms were erythrocytes in varying stages of lysis together with other necrotic debris. The mucous membrane adjacent to the heads of the worms was ulcerated while more distant enterocytes were small, distorted and displayed various degrees of microvillar loss. Many mucosal blood vessels had platelet aggregates within their lumina but no fibrin deposition was observed. Vessels were often seen in the bases of the ulcers and were prone to rupture. Erythrocytes and leucocytes were seen in the dog intestinal lumen in close proximity to the bodies of the worms.

After infection with Eimeria necatrix, chick intestinal cells undergo a profound increase in size. Herein, we describe methods for isolating and purifying infected cells containing second-genration schizonts at various times post-infection. Our purification procedures depends upon three fundamental properties of infected cells: namely (1) large size, (2) resistance to shearing and (3) decreased susceptibility to osmotic shock in hypotonic solutions. The availability of simple techniques for isolating infected whole cells should prove valuable in elucidating various intracellular aspects of infection during schizogony.

Our field study did not support anecdotal claims alleging pathogenicity on the part of P. cylindraceus in starlings. Within-clutch analysis of nestling starling weights (n = 25) over time showed that P. cylindraceus had no effect on position in clutch relative to siblings. Parasitized nestlings tended to weigh more than control siblings. Within-sex analysis of wild adult starling weight (n = 103) showed no difference between animals with acanthocephalans and uninfected animals and weight was not related to intensity of infection. Host response to the proboscis was limited to immediately-surrounding tissue (90 microns). Other observations made in this study included the following: (1) no evidence for deleterious intraspecific interaction among adult P. cylindraceus in starlings; (2) no apparent interspecific interactions between P. cylindraceus and (unidentified) cestode species in starlings; and (3) copulatory caps on male P. cylindraceus may be a response to environmental deterioration in dead hosts.