Biosynthesis and catabolism of mannitol is developmentally regulated in the protozoan parasite Eimeria tenella

The mannitol cycle is a metabolic branch of the glycolytic pathway found in Eimeria tenella. In this paper, we describe the biosynthesis and consumption of mannitol during parasite development. Low micromolar levels of mannitol were detected in all of the asexual stages and mannitol production increased sharply during the sexual phase of the life cycle. Unsporulated oocysts had high mannitol content (300 mM or 25% of the oocyst mass). Mannitol-1-phosphate dehydrogenase (M1PDH), the first committed step of the mannitol cycle, was also elevated in sexual stages and this coincides with mannitol levels. Approximately 90% of the mannitol present in unsporulated oocysts was consumed in the first 15 hr of sporulation, and levels continued to drop until the sporulation process was complete at approximately 35 hr. Thus, mannitol appears to be the "fuel" for sporulation during the vegetative stage of the parasite life cycle. Evaluation of oocyst extracts from 6 additional Eimeria species for mannitol content and the presence of M1PDH indicated that the mannitol cycle was broadly present in this genus. This finding combined with the lack of mannitol metabolism in higher eukaryotes makes this pathway an attractive chemotherapeutic target.     

Isozyme patterns of Schistosoma japonicum and S. mansoni

Isozyme patterns of six enzymes, glucose-6-phosphate dehydrogenase, glucosephosphate isomerase, hexokinase, malate dehydrogenase, 6-phosphate dehydrogenase and phosphoglucomutase were examined in electrophoresed homogenates of adult male worms of Schistosoma japonicum and S. mansoni. In general, enzyme patterns obtained from the parasite homogenates differed from that of host (mouse) blood and muscle, indicating that electrophoretic patterns from parasite extracts are most probably of parasite origin. Adult male and female S. mansoni worms yielded identical patterns. However, all six enzyme patterns showed distinct differences between S. japonicum and S. mansoni. These results suggest that S. japonicum is clearly distinguishable from S. mansoni at the molecular level.     

Eimeria refractile body proteins contain two potentially functional characteristics: Transhydrogenase and carbohydrate transport

Abstract cDNA encoding an immunogenic protein from partially sporulated oocysts of Eimeria acervulina was cloned and used to search for the homologous counterpart in Eimeria tenella . Monospecific antibodies were raised against the recombinant expression product. Using these antibodies, the parasite proteins were found to be localised in the refractile bodies. The derived amino-acid sequences were compared by computer using the SWISSPROT protein database. In addition to high homology between the Eimeria species, extensive similarity was found with pyridine nucleotide transhydrogenase from Escherichia coli . Comparison with the sugar signature database also resulted in a possible sugar binding domain present only in the Eimeria proteins. It is possible that the corresponding parasite proteins play a role in the recently discovered mannitol cycle of Eimeria .     

Description and phylogeny of a new species of Eimeria from double-crested cormorants (Phalacrocorax auritus) near Fort Gaines, Georgia

The renal parasite Eimeria auritusi has caused several mortality events in double-crested cormorants (DCC; Phalacrocorax auritus) in the Midwest and southeastern United States. This parasite has only been detected during large-scale outbreaks, and its presence and prevalence in healthy populations of cormorants is unknown. In this study, 80 DCC were collected from the Chattahoochee River near Fort Gaines, Georgia, and examined for kidney and intestinal coccidia. Eighteen (22.5%) and 56 (70%) of the DCC were positive for E. auritusi and a new species of intestinal Eimeria, respectively. Oocysts of the new intestinal Eimeria species had a thin colorless wall, were ovoid with rare bumps on the outer surface, and measured 17.1 microm +/- 1.5 x 14.7 microm +/- 1.0 (16-18.5 x 13-17), with an average length:width ratio of 1.17 microm (1.03-1.29). A prominent micropyle (4-4.5 microm) was present, and a large oval-to-round polar body (2.5 microm) was located beneath the micropyle. Sporocysts were ovoid and measured 9.6 microm +/- 0.6 x 5.9 microm +/- 0.5 (8.5-10.5 x 5-6.5), with an average length:width ratio of 1.63 (1.3-1.82) with small stieda body present. Amplification and sequencing of a fragment of the 18S rRNA gene indicated that the 2 DCC Eimeria species and 2 Eimeria species from cranes were in a separate group from other Eimeriidae. These data indicate that E. auritusi and this new species of intestinal Eimeria are prevalent in this apparently healthy DCC population. The cause of renal coccidiosis outbreaks in other populations of cormorants is unknown but could be due to crowding or stress during the winter months or some other associated pathogen or immunosuppressor that might predispose individuals to clinical disease.     

Life cycle and cytochemical study of the endogenous developmental stages of Eimeria akeriana (coccidiida, Eimeriidae) from the Asia Minor gerbil

Three generations of schisonts in the life cycle of Eimeria akeriana, the intestinal parasite of Meriones blackleri, were determined. Gametogony begins in 94 hours, the first oocysts discharge in 5.5--6 days and lasts 14.5 to 15 days after the oocyst administration. A cytochemical study of the distribution of the nucleic acids, proteins and amylopectin at the stages of endogenous development of E. akeriana has revealed a considerable similarity among the parasites of Eimeria though each type is characterized by some cytochemical peculiarities.     

Infection with Eimeria tenella: modulation of lymphocyte blastogenesis by specific antigen, and evidence for immunodepression

The blastogenic effects of specific parasite antigen and of mitogens on the lymphocytes of chickens infected with Eimeria tenella were examined. Lymphocytes from infected chickens were stimulated to divide when cultured with parasite antigen, but their responses to the T-cell mitogen, phytohemagglutinin (PHA), were depressed throughout the period of infection. Responses to the B-cell mitogen, lipopolysaccharide (LPS), were depressed during the first week of infection but enhanced in the second week. The inclusion of plasma samples from infected chickens in the culture medium depressed the responses of normal spleen lymphocytes to PHA, suggesting that soluble suppressor factors are generated during infection.     

Characteristics of the development of Eimeria species from gerbils in secondary hosts

Peculiarities of endogenous and exogenous developmental stages of the life cycle of Eimeria salasuzica Musajev et Vejsov, 1960, a parasite of Persian jird, and E. akeriana Ismailov et Gaibova, 1983, a parasite of Meriones blackleri, in two first recognized secondary hosts (Meriones vinogradovi and M. lybicus) were studied. The paper gives comparative data on the duration of infection, endogenous stages of development and variability of oocysts of the studied species of Eimeria obtained from the main and secondary hosts.     

Enzyme variation of Eimeria arizonensis from Peromyscus truei and P. boylii

Cricetid rodents, Peromyscus truei and P. boylii, were inoculated with sporulated oocysts of Eimeria arizonensis collected from wild P. truei maintained in the lab. In P. truei the prepatent period was 4-5 days, the patent period was 9-11 days, and sporulated oocysts were 21.5 x 25.0 (20-23 x 24-26) microns with sporocysts 7.7 x 12.0 (6-8 x 10-13) microns. In P. boylii the prepatent period was 6-7 days, the patent period was 8-9 days, and sporulated oocysts were 20.1 x 23.2 (18-22 x 21-24) microns with sporocysts 6.8 x 10.0 (5-8 x 9-12) microns. Sporulated oocysts from both host species were used in direct side-by-side comparison of isozyme banding patterns using protein electrophoresis. The parasite has polytypic loci for leucine aminopeptidase (LAP), lactate dehydrogenase (LDH), and 6-phosphogluconate dehydrogenase (6-PGD). In oocysts from P. truei, LAP showed one band with fast migration and LDH and 6-PGD each showed two bands, one with fast and one with slow migration. In oocysts from P. boylii, LAP and LDH each had one band with slow migration and 6-PGD had one band with moderate migration. Oocysts of E. arizonensis collected from P. boylii were used to inoculate P. truei. The prepatent and patent periods, structural measurements, and isozyme banding patterns of the resultant oocysts were the same as those from P. truei when inoculated with oocysts from P. truei.     

Coccidian assemblages in the Wyoming ground squirrel, Spermophilus elegans elegans.

One thousand nineteen Wyoming ground squirrels (Spermophilus elegans elegans) from 4 populations in southern Wyoming were examined for intestinal parasites. The most prevalent parasites were 6 species of coccidia: Eimeria beecheyi, Eimeria bilamellata, Eimeria callospermophili, Eimeria larimerensis, Eimeria morainensis, and Eimeria spermophili. Most ground squirrels harbored 2 or more species. This eimerian assemblage was present across populations and over years. Differences in the prevalence of infection were not found among host age classes or between sexes. The presence or absence of helminths was independent of the presence and absence of Eimeria. A log-linear model to test the independence of the distribution of Eimeria spp. among hosts revealed 3 significant positive associations, for E. bilamellata and E. beecheyi, E. morainesis and E. callospermophili, and E. larimerensis and E. bilamellata.     

Interaction of Eimeria tenella with intestinal mucin in vitro

The mucus gel layer overlying the gastrointestinal epithelium plays an important role in host-pathogen interactions. The initial interaction between the coccidian parasite Eimeria tenella and host cells of the intestinal epithelium must occur across this mucus interface. In this study, we examined the relationship between E. tenella and avian mucin, in particular the effect of purified intestinal regional mucin on parasite adherence and invasion in vitro. Secreted mucin from the chicken duodenum and cecum was purified by density gradient centrifugation and gel chromatography. Parasite invasion studies were performed in the Madin-Darby bovine kidney cell model. Eimeria tenella adherence to chicken duodenal mucin was detected, whereas adherence to cecal or bovine mucin was not shown. Parasite invasion into epithelial cells was not influenced by bovine mucin, whereas chicken mucin purified from the duodenum and cecum significantly inhibited invasion. Inhibition of E. tenella invasion into cells by mucin from the duodenum was marginally greater than that of the cecum, but this was not significant. This study demonstrated E. tenella interaction with native chicken intestinal mucin, which in turn inhibited parasite invasion into epithelial cells in vitro.     

Factors influencing the fecal egg and oocyst counts of parasites of wild European rabbits Oryctolagus cuniculus (L.) in Southern Western Australia

Abundance of intestinal parasites was monitored by fecal egg and oocyst counts for samples of wild rabbits Oryctolagus cuniculus with different levels of imposed female sterility from 12 populations in southwestern Australia. Differences in egg counts of Trichostrongylus retortaeformis between seasons and age groups were dependent on the sex of the host. Pregnancy may have been responsible for these differences because egg counts were consistently higher in intact females than in females surgically sterilized by tubal ligation. Egg counts for Passalurus ambiguus were influenced by season and host age but there were no differences between sexes or between intact and sterilized female rabbits. No differences were detected in the oocyst counts of the 8 species of Eimeria between male and female rabbits or between intact and sterilized females. Seasonal differences were detected in oocyst counts of Eimeria flavescens and Eimeria stiedai. The overwhelming determinant of coccidian oocyst counts was host age, with 6 species being much more abundant in rabbits up to 4 mo of age. There was a suggestion that egg counts of T. retortaeformis and oocyst counts of several species of Eimeria were reduced in populations where rabbit numbers had been depressed for at least 2 yr, but there was no evidence that short-term variations in rabbit numbers had a measurable effect on parasite abundance.     

Infection with Eimeria tenella: Modulation of Lymphocyte Blastogenesis by Specific Antigen,and Evidence for Immunodepression1

ABSTRACT. The blastogenic effects of specific parasite antigen and of mitogens on the lymphocytes of chickens infected with Eimeria tenella were examined. Lymphocytes from infected chickens were stimulated to divide when cultured with parasite antigen, but their responses to the T-cell mitogen, phytohemagglutinin (PHA), were depressed throughout the period of infection. Responses to the B-cell mitogen, lipopolysaccharide (LPS), were depressed during the first week of infection but enhanced in the second week. The inclusion of plasma samples from infected chickens in the culture medium depressed the responses of normal spleen lymphocytes to PHA, suggesting that soluble suppressor factors are generated during infection.     

Evidence for host allozymes present on electrophoretic gels of trematode parasites (Digenea: Plagiorchiiformes)

An allozyme analysis of trematode species Glypthelmins californiensis, Glypthelmins quieta, Glypthelmins pennsylvaniensis, Glypthelmins hyloreus, and Haplometrana intestinalis from hosts Rana aurora, Rana clamitans, Hyla crucifer, Pseudacris triseriata, and Rana pretiosa, using starch gel electrophoresis, revealed allozymes for glucose-phosphate isomerase, lactate dehydrogenase, malate dehydrogenase, and isocitrate dehydrogenase that were similar in electrophoretic mobility to host tissue controls. Host allozymes were present on gels for only a fraction of the individual parasite samples examined and could be differentiated from parasite allozymes using host tissue controls. Based on these findings, it is suggested that host samples be included on each electrophoretic gel in genetic studies of parasites to reduce the likelihood of errors due to host enzyme contamination of parasite samples.     

Cell: sporozoite interactions and invasion by apicomplexan parasites of the genus Eimeria

The site specificity that avian Eimeria sporozoites and, to a more limited degree, other apicomplexan parasites exhibit for invasion in vivo suggests that specific interactions between the sporozoites and the target host cells may mediate the invasion process. Although sporozoite motility and structural and secreted antigens appear to provide the mechanisms for propelling the sporozoite into the host cell,there is a growing body of evidence that the host cell provides characteristics by which the sporozoites recognise and interact with the host cell as a prelude to invasion. Molecules on the surface of cells in the intestinal epithelium, that act as receptor or recognition sites for sporozoite invasion, may be included among these characteristics. The existence of receptor molecules for invasion by apicomplexan parasites was suggested by in vitro studies in which parasite invasion was inhibited in cultured cells that were treated with a variety of substances designed to selectively alter the host cell membrane. These substance included cationic compounds or molecules, enzymes that cleave specific linkages, protease inhibitors, monoclonal antibodies, etc. More specific evidence for the presence of receptors was provided by the binding of parasite antigens to specific host cell surface molecules.Analyses of host cells have implicated 22, 31, and 37 kDa antigens, surface membrane glycoconjugates,conserved epitopes of host cells and sporozoites, etc., but no treatment that perturbs these putative receptors has completely inhibited invasion of the cells by parasites. Regardless of the mechanism,sporozoites of the avian Eimeria also invade the same specific sites in foreign host birds that they invade in the natural host. Thus, site specificity for invasion may be a response to characteristics of the intestine that are shared by a number of hosts rather than to a unique trait of the natural host. Protective immunity elicited against avian Eimeria species is not manifested in a total blockade of parasite invasion. In fact, the effect of immunity on invasion differs according to the eliciting species and depends upon the area of the intestine that is invaded. Immunity produced against caecal species of avian Eimeria, for example Eimeria tenella and Eimeria adenoeides, inhibits subsequent invasion by homologous or heterologous challenge species, regardless of the area of the intestine that the challenge species invade. Conversely, in birds immunised with upper intestinal species, Eimeria acervulina and Eimeria meleagrimitis, invasion by challenge species is not decreased and often is significantly increased.     

Coccidia of whooping cranes

Coccidial oocysts were observed in 6 of 19 fecal samples from free-ranging whooping cranes (Grus americana) and 4 of 16 samples from captive whooping cranes. Eimeria gruis occurred in four free-ranging whooping cranes and E. reichenowi in two free-ranging and two captive whooping cranes. Fecal samples from two captive cranes contained oocysts of Isospora lacazei which was considered a spurious parasite. Oocysts of both species of Eimeria were prevalent in fecal samples collected from three free-ranging Canadian sandhill cranes (G. canadensis rowani) from whooping crane wintering grounds in Texas. These coccidia were prevalent also in fecal samples from 14 sandhill cranes (of 4 subspecies) maintained in captivity at the Patuxent Wildlife Research Center in Maryland.     

Changes in parasite transmission stage excretion after pheasant release

The production of parasite transmission stages was investigated in the faeces of 77 farm-bred ring-necked pheasants (Phasianus colchicus). Coccidian oocysts (Eimeria sp.), and nematode eggs (Heterakis sp., and Capillaria-like eggs) were recovered before and after release but all birds were treated prior to release. Treatment with fenbendazole significantly reduced the abundance of transmission-stage excretion for all parasites, and reduced the prevalence in the case of Eimeria sp. and Heterakis sp. Nonetheless, a significant increase in the excretion abundance for all parasites and in the prevalence of Eimeria sp. and Heterakis sp. was found after release. Eggs of Ascaridia sp. were found only after releasing, suggesting infection ocurred in the wild. A negative relationship was found between the pheasant body condition and Heterakis excretion abundance and a higher abundance of Capillaria sp. eggs in female birds. No significant relationship was found between parasite excretion abundance and pheasant survival. Despite this, results suggest that an increase in the excretion of parasite transmission stages follows the release of captive pheasants into the wild. This can in part explain restocking failures, but also means that autochtonous free-living birds may become exposed to new and potentially harmful pathogens. To avoid these risks it is proposed that improved prophylactic measures should be taken.     

Seasonal and demographic factors influencing gastrointestinal parasitism in ungulates of Etosha National Park

Host-parasite dynamics can be strongly affected by seasonality and age-related host immune responses. We investigated how observed variation in the prevalence and intensity of parasite egg or oocyst shedding in four co-occurring ungulate species may reflect underlying seasonal variation in transmission and host immunity. This study was conducted July 2005-October 2006 in Etosha National Park, Namibia, using indices of parasitism recorded from 1,022 fecal samples collected from plains zebra (Equus quagga), springbok (Antidorcas marsupialis), blue wildebeest (Connochaetes taurinus), and gemsbok (Oryx gazella). The presence and intensity of strongyle nematodes, Strongyloides spp. and Eimeria spp. parasites, were strongly seasonal for most host-parasite combinations, with more hosts infected in the wet season than the dry season. Strongyle intensity in zebra was significantly lower in juveniles than adults, and in springbok hosts, Eimeria spp. intensity was significantly greater in juveniles than adults. These results provide evidence that acquired immunity is less protective against strongyle nematodes than Eimeria spp. infections. The seasonal patterns in parasitism further indicate that the long dry season may limit development and survival of parasite stages in the environment and, as a result, host contact and parasite transmission.