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Little data are available regarding the association of ancylostomiasis with overt gastrointestinal bleeding. This 6-year retrospective study describes the clinical and biological profiles of unexpectedly identified ancylostomiasis in a 4-month-old baby and four adults; they presented with melena and were referred for urgent diagnostic gastrointestinal endoscopy, which confirmed numerous small intestine injuries with surrounding blood pools caused by Ancylostoma duodenale worms. Gastric erosions were also encountered in one patient. Uniquely, worm biological activities were recorded live in vivo, including mucosal invasion through a vigorous, rapid piercing process, repeated bloodsucking habits, and gut appearance during the stages of feeding, digestion, and excretion in male and female worms. In conclusion, ancylostomiasis-induced melena may occur in all ages from infants to the elderly. Worm bloodfeeding occurs after quick mucosal piercing, with blood loss being aggravated by a repeated feeding behavior. After treatment is started, bleeding stops rapidly in response to anthelmintic therapy.

Ascaris lumbricoides is one of the most common human helminthic diseases worldwide. On ultrasound, it is seen as linear non-shadowing echogenic structures with target appearance in cross section, and the live worm may show writhing movements in real time. On barium meal follow through, it appears as radiolucent tubular filling defects within the bowel lumen. Though not sensitive, direct real-time visualization of Ascaris on ultrasound is quick, non-invasive, and definitive.

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.

The inhabitants of a rural community in southwestern Germany were examined for alveolar echinococcosis (AE). The study was prompted by the recent increase of the prevalence of the parasite in foxes and the increase of fox populations: in the study area, 75% of the foxes carried Echinococcus multilocularis. The human population was screened using hepatic ultrasound and serology. All participants were interviewed for demographic and potential risk factors. Of 2,560 participants, one was identified with active AE, while 3 others had suspicious liver lesions. Another 9 participants were seropositive for specific antibodies without detectable lesions. Demographic and behavioral factors were not correlated with active or suspected cases nor with seropositivity. If the prevalence of 40/100,000 (95% confidence interval = 15-295/100,000) for active cases would be representative for the rural population in high endemicity areas, the current number of AE cases in southwestern Germany is considerably higher than previously suspected.

Two hypotheses were tested to identify the mechanism(s) by which chronic Strongyloides stercoralis infections are maintained in experimental dogs as a model to explain delayed onset recrudescence in humans. Investigations tested the hypotheses that chronic infections result from 1) periodic reactivation of third-stage larvae from a reservoir of dormant parasites outside the gastrointestinal tract or 2) the periodic rejuvenation of postreproductive female worms remaining from a previous infection, lodged in the mucosal crypts. Populations of parenteral larvae survived in mature experimentally infected female dogs for 66 days; individual worms survived for 88 days, but there was no evidence that these larvae re-established patent, adult worm infections. Late in these infections, female worms were present in greater than predicted numbers with no evidence that autoinfection had occurred, suggesting that some postreproductive worms were long-lived. In separate trials, long-lived spent females were once again capable of producing viable larvae when the host was treated with corticosteroids.

Gamma camera scintigraphy of dogs infected with radiolabeled third-stage larvae of Strongyloides stercoralis was successful for visualizing larval migration in a live host. Ten-day-old pups were infected subcutaneously in a lateral inguinal site with 100,000 75Se-selenomethionine-labeled third-stage S. stercoralis and imaged serially using a clinical gamma camera during the prepatent period. Radioactivity corresponding to the larval inoculum was visualized at the infection site immediately after injection. Radioactivity spread diffusely, corresponding to radial dispersal of larvae from the infection site. The majority of the radioactivity concentrated over or through the abdomen from 48 to 144 hr after infection. Larvae arrived in the small intestine in numbers adequate for visualization beginning at 114 hr after infection. At no time was there concentration of radioactivity associated with the lungs of an infected pup. A control pup injected only with 75Se-selenomethionine showed uniform activity diffusely throughout the entire body at all times. We concluded that the majority of larvae moved to the gut by means other than the pulmonary route.

The activities of four disaccharidases were examined in resistant (C57Bl/6) and susceptible (C3H/HeN) mice during the primary infection with Giardia muris and after challenge with either trophozoite extract or cysts. Significant decreases in lactase, sucrase, trehalase, and maltase activities in C57Bl/6 mice and lactase and sucrase activities in C3H/HeN mice in the anterior 25% of the small intestine were observed on day 10 after infection. The activities of maltase, sucrase, trehalase, and lactase in the jejunum of C3H/HeN mice were significantly reduced after challenge with trophozoite extract, when compared with the uninfected or infected, but not challenged animals. Decreases in enzyme activities of C3H/HeN mice were evident as early as 12 hours after challenge with the extract. The resistant C57Bl/6 mice showed little change in disaccharidase activity after challenge with trophozoite extract. On the other hand, challenge with cysts resulted in a few decreases in disaccharidase activities in both strains of mice: C57Bl/6 mice showed decreases in the duodenum, while disaccharidases of C3H/HeN mice had lower activity more posteriorly. Thus, challenge with parasite antigen results in a more severe disaccharidase deficiency in susceptible hosts when compared with resistant ones.

Giardia lamblia cysts were isolated from patients in Riyadh, Saudi Arabia. Cysts and trophozoites (from axenically excysted cysts) were given orally by gavage to mice to establish the pathogenicity of the Riyadh isolate. There was no effect of varying the dose of administered parasite on parasite excretion or morbidity. A typical pathologic pattern of giardiasis was demonstrated by histologic methods and electron microscopy. Antigenic components of the Riyadh isolate were compared with the Portland strain and with Entamoeba histolytica by gel diffusion immunoprecipitation and immunoblotting. There were few antigens in common between Riyadh isolate and the Portland strain, and little cross-reactivity of the Riyadh isolate with Entamoeba histolytica was observed.

Thirty-nine falciparum malaria autopsy cases from the Hospital for Tropical Diseases, Mahidol University, Bangkok, Thailand were divided into two groups that had had either cerebral malaria (CM) or non-cerebral malaria (NCM). We then studied significant pathological differences between these groups in order to investigate the correlation between parasitized erythrocyte (PRBC) sequestration in small blood vessels in the brain, heart, lungs and small intestines. We found that the percentage of PRBC sequestration in the organs which we studied was higher in the CM patients than in the NCM patients. The difference of PRBC sequestration among the organs of two groups was significant (P less than 0.05). In the CM group, the average percentage of PRBC sequestration in the brain was significantly higher than in the heart, lungs and small intestines (P less than 0.05). No statistically significant difference was found between PRBC sequestration in the brains, hearts, lungs and small intestines in the NCM group (P greater than 0.05). Our study indicates that severity of malaria in the CM patients depends on PRBC sequestration, especially in the brain. A combination of functional disturbances of the other organs, in addition to the cerebral pathology, may augment the severity of the disease.

Six Schistosoma mansoni strains from Belo Horizonte (three from patients with the toxemic form of schistosomiasis and three from patients with the chronic intestinal form) have been experimentally compared. The following characteristics of infection were analyzed in the laboratory in mice: length of prepatent period, infectivity, total and differential white blood cell count, recovery of eggs in tissues, distribution of eggs in the viscera, and response to specific treatment. While significant differences existed among these six strains, those from patients with the toxemic form did not present a characteristic behavior that could clearly differentiate them from strains from non-toxemic patients. These results strongly suggest that the development of the toxemic form in man is not due to specific characteristics of the S. mansoni strain.

Groups of 6 to 8 grivet monkeys (Ceropithecus aethiops aethiops), each of which had been exposed to 600 cercariae of Schistosoma mansoni, were killed 3, 6, and 31 months after exposure. Other groups of monkeys were repeatedly challenged with cercariae beginning 4 or 23 months after the initial infection, and were killed 31 months after the first exposure. Peripheral blood leukocytes, eosinophiles, and schistosome eggs passed in the feces were determined during the course of the infection. At autopsy, gross and histopathologic observations were made, worms were recovered by perfusion, and the number of eggs in the tissues was determined by digestion. Monkeys became acutely ill about 8 weeks after the initial exposure, and death was attributed to acute'toxemic' schistosomiasis in 4 of 46 infected animals. The symptoms and signs of the acute phase did not recur with reinfection. Most subsequent natural deaths were caused by Klebsiella infection which occurred in both infected and control monkeys and did not appear to be related to the schistosome infection. Relatively stable infections were found after a single exposure to cercariae, with only a slight decrease in worm numbers and moderate decrease in egg passage after 31 months. With repeated reinfection, only 19% of challenge cercariae developed into adult worms. Oviposition by these worms was delayed and the rate of oviposition was substantially less than in monkeys infected only once. Eggs deposited in the tissues were rapidly destroyed. The calculated rate of oviposition varied from 658 eggs/day per female 3 months after a single infection to 299 eggs/ day per female 31 months after repeated infections. Although very heavy infections were present in repeatedly infected monkeys, only slight hepatic fibrosis was seen and no portal hypertension or portal-systemic collateral circulation developed. Severe intestinal disease was present in only two monkeys. The remaining animals had little diarrhea after the acute phase, and there was only slight loss of plasma protein into the feces 31 months after exposure.

A 56-year-old woman with acquired, common variable immunodeficiency was found to have persistent gastrointestinal as well as pulmonary infection with Strongyloides stercoralis. Repeated courses of treatment with thiabendazole led to marked reduction or loss of Strongyloides stercoralis larvae, but cessation of treatment always led to recurrence of Strongyloides infection. Several small bowel biopsies showed normal villous architecture and little inflammatory response to presence of larvae. Interestingly, no definite symptomatology could be attributed to the Strongyloides infection. It was postulated that the lack of signs and symptoms of strongyloidiasis, as well as poor response to treatment, was related to the immunodeficiency state. With low-dose, long-term interrupted courses of thiabendazole treatment, the Strongyloides infection finally seemed to be cured.

Specimens of resected small intestine from six patients aged 3 to 70 years with acute enteritis contained sexual forms of sarcosporidia. Histopathologically, the diagnoses were either segmental eosinophilic enteritis or segmental necrotizing enteritis. The presence of sarcosporidia in market beef (Bos indicus), and the patients' habit of eating the beef uncooked in the form of chili-hot dishes, suggest that the species is an ox-man parasite similar to Sarcocystis hominis (Railliet and Lucet, 1891) Dubey, 1976. Presence of numerous Gram-positive bacilli in segmental necrotizing enteritis suggests an interplay between two etiological agents in producing the hosts' inflammatory responses. Five patients recovered after resection, but one died due to extensive necrosis of the intestinal wall and leakage at the site of anastomosis. Only conventional antibiotics were given after the operations. None of the five surviving patients has had recurrent enteritis for at least 1 year.

Trematode eggs compatible in characteristics with those of Heterobilharzia americana, a probable cause of human schistosomal dermatitis in the Gulf States of the U.S., were found in the cirrhotic liver and other viscera of a wild-caught armadillo in Louisiana. Although adult worms were not found, the current observation suggests a need to extend the known host range of this common schistosome parasite of carnivores and other wild animals in the South, and may have additional implications in the context of the public health importance of the armadillo.

Rabbits were infected with Schistosoma japonicum of Japanese origin between 1973 and 1979. The distribution of lesions and eggs in the small intestine and colon changed significantly twice during that period, and the number of eggs per worm pair passed in the feces changed at least once. The shift in egg distribution and that in egg passage occurred at different times and appeared not to be causally related. The number of eggs per worm pair retained in the tissues of chronically infected rabbits was consistently greater in rabbits with colonic bilharziomas. We postulate that differences in the schistosome population were responsible for the alterations in worm behavior. These differences may have been caused by the introduction of new isolates from the field, or by selection during laboratory passage.

Cortisone (5 mg daily subcutaneously) suppressed both primary and secondary immune explusion of Strongyloides ratti, and reduced the intestinal mast cell response, but did not induce hyperinfection in rats. Cortisone-treated animals expelled primary worm burdens without complication about 2 wk after steroid treatment. A model for gastrointestinal hypersensitivity syndromes in discussed.

A method is described for purification of large quantities of Giardia muris trophozoites from the small intestine of the mouse by using density layer centrifugation and nylon fiber columns. Centrifugation of trophozoites obtained from the small intestine on Metrizamide, specific gravity 1.10, followed by incubation on a nylon fiber column at 37 degrees C for 120 min, yielded up to 15 X 10(6) viable purified trophozoites per infected mouse.

Eight of 10 young chimpanzees were infected with the Japanese strain of Schistosoma japonicum. In 6 of these, and in 1 normal chimpanzee, a surgical end-to-side portacaval shunt was constructed during the 8th week of infection. One additional infected chimpanzee was treated successfully with the nitrovinylfuran, SQ 18,506. In the four animals surviving both infection and shunting hepatic portal fibrosis was either absent or mild. In the 7-month survivors and in the drug-treated control animals there was evidence of healed portal endophlebitis and arterialization, but no active schistosomal liver lesion was found. Nevertheless, three of these animals showed variable degrees of active schistosomal glomerulopathy, similar to that seen in the unshunted infected control and to that described in earlier studies. There was a shift of the egg burden from the liver to the lungs, as well as evidence that the number of surviving adult worms had decreased following portacaval shunting. These observations sugggest that schistosomal nephropathy in chimpanzees is more closely related to infection intensity per se than to the degree of liver damage caused by infection.

The elimination of adult parasites from the intestines of rats after a first and second infection of Strongyloides ratti was studied. Expulsion after a second infection was anamnestic, indication that the response is immunologic. Intestinal mast cell responses accompanied damage and expulsion of worms, the secondary mast cell response being more rapid but less intense that the first. Antithymocyte serum suppressed expulsion as well as both the intestinal mast cell and circulating eosinophil responses to primary infection.

Twelve young adult captivity-born tamarin monkeys (Saguinus fuscicollis) were each exposed to 150 cercariae of Schistosoma mansoni (KEB strain): 6 by the percutaneous (pc) and 6 by the subcutaneous (sc) route. The prepatent period, as determined by eggs in the feces, was 34-39 days for both groups. Weekly quantitative fecal examinations revealed that although both groups actively passed eggs for as long as the duration of the experiment (18 months), the sc group excreted a significantly higher number of eggs/gram/day in the feces than did the pc group. Eggs recovered from the feces of both groups were viable: they hatched and the miracidia invaded snails which subsequently yielded infective cercariae. A significantly greater number of worms was recovered from tamarins infected by the sc route as compared to those with pc infections, and large numbers of eggs were found in affected organs of the sc group. Chronically infected tamarins with high tissue egg loads developed focal granulomatous nodules along the serosal walls of the small intestines, which in some cases, apparently had budded off to lie free in the abdominal cavity. Hepatic granulomas from animals with acute infections were significantly larger than those from chronically infected monkeys. Our results strongly suggest the presence of a skin barrier to infection in the tamarin monkey, and that if this barrier is bypassed, the tamarin can serve as a permissive host for S. mansoni. The small body size of this monkey (less than 400 g) is an obvious reason for the establishment of the tamarin monkey as a laboratory nonhuman primate model for human schistosomiasis mansoni.

Gerbils were maintained on a low-fiber (5%) or a high-fiber (20%) diet in which the major fiber source was cellulose. Animals in the low-fiber diet group were significantly more likely to become infected when inoculated with 100 Giardia lamblia cysts than were animals in the high-fiber group. No differences were detected in gastrointestinal transit, gastric, and small intestinal luminal pH, or in duodenal mucus blanket acidic glycoprotein between animals in the high- and the low-fiber diet groups at the time of cyst inoculation. The fiber content of the diet after cyst inoculation determined the infection rate. These data suggest that the dietary fiber effect occurred during trophozoite colonization of the small intestine. When infected animals on the low-fiber diet were placed on the high-fiber diet for 24 hr, trophozoite clearing occurred in the lower small intestine. In the jejunum, the number of trophozoites attached to the mucosal surface decreased, while the number associated with luminal mucus increased. We conclude that the fiber-induced mucus secretion and the bulk movement of the insoluble fiber reduced the attachment of trophozoites to the intestinal mucosa, which decreased the probability of trophozoites establishing and sustaining colonization of the mucosa.