[Agents against intestinal parasites].
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Four of six cockatiels died within a week after being purchased from a commercial breeder. A fifth bird was euthanatized and necropsied during this time, and tissues were collected for microscopic examination. The small intestine had moderate numbers of Cryptosporidium sp. parasites present. A few large, basophilic intranuclear inclusions were present in renal ductular epithelium. Cryptosporidium sp. oocysts were found in the feces of the surviving bird. Thirty oocysts were 7.2 by 5.5 microns. The shape index was 1.31. Morphological examinations of the fecal oocysts indicated that the Cryptosporidium species infecting the cockatiels was similar to C. baileyi, a parasite that is not usually associated with small-intestinal infections.
During infection in mice Echinostoma caproni is attached to the mucosa of the small intestine with the ventral sucker (acetabulum). The morphology, histology and dynamics of attachment sites from primary infections were examined. The sites were highly characteristic microscopically, and consisted of a plug of grasped mucosa occupying the cavity of the ventral suckers. The mucosa in the area of the small intestine where the parasite resided showed marked villous atrophy and crypt hyperplasia. The cellular composition of the attachment sites did not appear significantly different from what was seen in other parts of the mucosa in the residential area, and the study did not reveal any specific cellular host response at the attachment site. After mechanical removal of the parasites from unfixed tissue in saline, the attachment sites gradually reduced in size and disappeared. It is suggested that the attachment sites are only temporary structures, formed by the mechanical grasp of the ventral sucker as the parasites move about in the residential area of the intestine.
Hookworms are known to cause marked changes to the intestinal mucosa, especially in relation to erosion of the villi. However, since the development of enteropathy has not been examined thoroughly through quantitative experiments on infected animals, the results of experiments conducted in hamsters infected with Ancylostoma ceylanicum are reported. Changes to intestinal architecture were first apparent between 12 and 14 days after infection, and then increased in intensity for 3-4 weeks, persisting for as long as worms were present (>63 days). Following infection, the height of villi declined from a mean of 1002 micro m in naïve controls to less than 200 micro m and as low as 18 micro m in one case. The depth of the crypts of Lieberkuhn increased from a baseline value of 166 micro m in naïve controls to in excess of 600 micro m within 6 weeks of infection. Mitotic figures had a baseline value of 5.5 per villus-crypt unit, and this rose to in excess of 25 in some experiments. Changes were dependent on the intensity of the parasite burden on day 20, but by 30 days after infection changes in all three values were maximal and density-dependent relationships were no longer clearly apparent. Villus height and crypt depth returned to near normal values within a week of the removal of worms, although group means for both remained different from naïve controls for at least 3 weeks after treatment. Cellular division, as reflected in numbers of mitotic figures, stayed elevated for over 5 weeks after removal of worms. The results suggest that enteropathy in hookworm infections stems from a combination of intestinal immune responses and from the grazing activities of the adult worms on the mucosal surface, but is not sufficient per se for expulsion of this parasite.
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The spiral intestines of 7 Tawny nurse sharks (Nebrius ferrugineus; Rhincodontidae) from Australia and French Polynesia were examined for tapeworms. These sharks hosted 5 new species of Pedibothrium. The 5 species were prepared for light and scanning electron microscopy. Whereas 3 of the species exhibit the bipronged hooks typical of members of Pedibothrium, 1 species was found to possess tiny unipronged hooks or to lack some, or all, hooks, and all individuals of the fifth species appeared to lack bothridial hooks entirely. Nonetheless, the otherwise remarkable similarities between these species and the species of Pedibothrium bearing bipronged hooks were considered to be sufficient to justify the placement of these 2 species in this genus. All 5 species possess proglottid features typical of Pedibothrium, including a uterus that extends anteriorly only to the level of the cirrus sac and a cirrus sac that is bent anteriorly and is crossed by the vagina. All 5 species also exhibit uniloculated bothridia. Of particular note was the fact that all 5 species exhibit bladelike spinitrichs with elongated distal tips, a form of microthrix currently known only from species of Pedibothrium. As a consequence, these species were treated as possessing modified hooks or as having lost hooks. The diagnoses of Pedibothrium and Onchobothriidae were emended to include these species. Each of the 5 new species bears a strong resemblance to 1 or more species of Pedibothrium hosted by a species of rhincodontid shark other than N. ferrugineus. Much of Southwell's type and voucher material of Pedibothrium was located and used to verify the identity of Pedibothrium kerkhami and many of the hosts from which Southwell's material of Pedibothrium was collected. This material suggests that P. kerkhami parasitizes Stegostoma fasciatum and not N. ferrugineus.
Treatment of 13 urban Ethiopian children with mild ascariasis did not produce any evidence of improved intestinal morphology and absorption or nutritional status. Ascariasis treatment had no impact on anthropometric measures in an additional study group of 84 children. A review of the literature reveals that the nutritional consequences of ascariasis are uncertain.
The localization of 125I-UdR-labelled mesenteric lymph node cells in the small intestine and the fraction of the cardiac output delivered to this organ in mice has been examined. Concurrent measurements of these two phenomena in normal animals showed that there was a significant correlation between the localization of lymphoblasts and the distribution of regional blood flow along the small intestine. In mice undergoing enteric infection with Trichinella spiralis, however, the nature of the connection between lymphoblast localization and blood flow distribution in the small intestine was altered. More lymphoblast label accumulated in the small intestine of infected mice than in uninfected animals even at stages of the infection when no alteration in the proportion of the cardiac output received by the small intestine had occurred. Enhanced lymphoblast accumulation occurred in different segments of the infected small intestine as the infection proceeded and these changes paralleled the way in which the parasite burden was distributed in the intestine. The kinetics of lymphoblast accumulation in infected and uninfected small intestine was examined under circumstances where the delivery of blood-borne labelled cells was the same. This showed that both increased entry of lymphoblasts and enhanced retention of lymphoblasts occurred in the parasitized small intestine.
We examined 215 Florida manatees (Trichechus manatus latirostris) at necropsy to determine the helminth fauna. Six species were identified: Heterocheilus tunicatus (Nematoda: Ascaridoidea); Anoplocephala sp. (Cestoda: Cyclophyllidea); and 4 species of trematodes, Cochleotrema cochleotrema (Digenea: Opisthotrematidae), Chiorchis fabaceus (Digenea: Paramphistomatidae), Nudacotyle undicola (Digenea: Nudacotylidae), and Moniligerum blairi (Digenea: Opisthotrematidae). Seventy-three percent of the manatees examined were infected with at least 1 species of helminth. The mean number of species of helminths per infected manatee was 1.9 with a range of 1-4. Fifty-nine manatees were helminth-free; 30 of these were calves. No associations were found between the intensity of helminth infections and host sex, age class, season, and geographic location of recovery, or cause of death. Differences in parasite prevalence between age classes were highly significant for Chiorchis, Cochleotrema, and Heterocheilus, due to a low number of infected calves. A higher prevalence of Cochleotrema was found in manatees recovered from eastern Florida, and Heterocheilus was evident in significantly more manatees from western and souther Florida. Comparisons in the parasite fauna are made among Florida manatees and other sirenian populations, and a brief review of sirenian parasites is included.
Intestinal trichomoniasis was observed in 156 of 202 Tupaia belangeri (77.2%). The parasites were located principally in the cecum (75%) and were far less common in the proximal portion of the colon (19%) or terminal portion of the ileum (6%). Advanced trichomoniasis was associated with liquid cecal contents but not diarrhea. The trichomonads had a tendency to penetrate the mucosal epithelial layer, causing desquamation of entire crypts. They never penetrated the epithelial basement membrane and never triggered inflammatory responses. The trichomonads were characterized by three anterior flagella and one trailing flagellum that extended over the entire parasite body, connected to it by an undulating membrane. The capitulum of the straight axostyle formed a small but well defined pelta, and the stout costa had distinct banding. The parasites thereby matched the description of Tritrichomonas mobilensis.
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The presence of globule leukocytes in the lumen (LuGLs) of the small intestine was studied in Romney sheep reared parasite free and then experimentally infected or immunized with Trichostrongylus colubriformis infective larvae, or naturally infected when gazed on pasture. It was discovered that high numbers of LuGLs were associated with both parasitic infection and the sheep protective immune response. A high positive correlation was observed between LuGLs and tissue globule leukocytes. The highest correlation (r = 0.92) observed was between larval migration inhibition (LMI) and numbers of LuGLs. This was the only correlation between LMI and other parameters studied. Significant positive correlations were also observed between LuGLs and IgG1 and eosinophils. There was a negative correlation between LuGLs and the number of parasites in the intestine and parasite egg production. Progeny of genetically resistant and susceptible sires had significantly different abilities to produce LuGLs.
Histopathological studies of Neoechinorhynchus hutchinsoni infection in Nemacheilus kashmirensis show partial or complete damage of the host intestinal wall, depending upon the degree of penetration. Increased number of goblet cells are seen at the site of unperforated wounds but where the intestinal wall is completely perforated the goblet cells were undifferentiated. The parasite destroys the mucosa, lamina propria, muscle layer and serosa leading to perforation. This report of perforation by Neoechinorhynchus hutchinsoni is the first in the genus Neoechinorhynchus.
Adult female worms recovered from the jejunum of rats infected per os with 1000 larvae of Trichinella spiralis were significantly more fecund (peak jejunal fecundity = 35.7 +/- 3.1 newborn larvae per female) than females recovered from the terminal ileum (9.3 +/- 4.1 larvae per female) in the same infections. The majority of the adult worms were established in those sections of the small intestines that produced the most fecund females (r = 0.92; P less than 0.05). Worm fecundity is believed to be location-specific because adult females that were surgically implanted into the jejunum were significantly more fecund that were implanted into only the ileum. It is concluded that the physico-chemical conditions of the anterior small intestines are optimal for the parasites' reproductive fitness and this exerts a strong selective pressure on habitat selection behavior.
The mucosal biopsies from duodenum and jejunum of 31 patients showing Giardia lamblia in their feces were studied histologically. Although the trophozoites were found in all the biopsy specimens in the luman, the tissue invasion by the parasites in different stages, from their entry through the epithelium to the lamina propria could be demonstrated in 12 of them, all of the latter having diarrhea and steaterrhea. Varying histological changes in jejunal mucosa were also observed in 9 cases, of which 7 showed mucosal invasion by giardia trophozoites. In 17 of the series neither tissue invasion by the parasite nor mucosal change could be found.