Trichinella spiralis is a parasitic nematode that infects many mammals, including humans. Hosts may experience significant physiological changes or may die because of acute inflammatory immune responses toward the parasite. In this study, oldfield mice (Peromyscus polionotus) were used as a new experimental host for T. spiralis. Males of P. polionotus were infected with increasing doses of T. spiralis to determine the effect infection had on survival, mass change, total mass, and relative organ masses. Total juvenile worm burden increased in an asymptotic fashion with infective dose. Large doses (≥600 juveniles) significantly reduced survival. There were significant negative correlations between infection intensity (log₁₀[juveniles]/g) and both mass gain and final total mass. Infection had no effect on liver or spleen size. But there were significant negative correlations between T. spiralis intensity and both testis and seminal vesicle masses. These effects on male size and reproductive organs may help explain behavioral changes, such as the elimination of male dominance, seen in previous studies on mice infected with T. spiralis.

To determine if filarial infection causes any effect on the cardiovascular system of the host animal, stroke-prone spontaneously hypertensive rats were infected with Brugia pahangi under the assumption that these rats would reveal pathological changes more clearly and in a shorter period than would ordinary rats. The infection resulted in loss of body weight, increase in heart weight, enlargement of left ventricle, and higher mortality rate.

Microsporidia are obligate intracellular parasites of the phylum Microspora. To date, more than 1,200 species within 144 genera have been described, with 14 infecting humans. Currently, no effective treatment exists for human microsporidiosis. In this study, the biochemical properties of the aminopeptidases were investigated within several species of microsporidia. Aminopeptidase activity was detected in 3 species of microsporidia, Encephalitozoon cuniculi, E. hellem, and Vittaforma corneae, using a fluorometric substrate assay. Each species exhibited distinct aminopeptidase properties. The cytosolic neutral aminopeptidase activities of the Encephalitozoon spp. were characterized as preferentially cleaving leucine, whereas those of V. corneae cleaved arginine. Native polyacrylamide gel electrophoresis estimated the molecular mass of E. cuniculi, E. hellem, and V. corneae as 74, 72, and 79 kDa, respectively. Enzymatic activity was inhibited by bestatin and it's analogue, nitrobestatin, indicating that the enzyme was an aminopeptidase for all species. Inhibition with the chelating agents ethylenediaminetetraacetic acid and 1,10-phenanthroline characterized the enzymes as metalloaminopeptidases. Subcellular fractionation of the 3 microsporidial species suggested that the enzyme activity was localized in the cytosolic fraction. Optimal enzyme activity was observed at pH 7.2 for all species. This is the first report of enzyme characterization from these 3 species of microsporidia.

Schistosoma mansoni induces, in the vertebrate host, cutaneous production of interleukin-7 (IL-7), which is beneficial for parasite establishment and development. Infection of mice deficient in IL-7 expression leads to parasite dwarfism. Because similar findings were previously described in hypothyroid mice, this study aimed to elucidate the potential link between IL-7 and thyroid hormones (THs), using several models including hypo- and hyperthyroid mice, modified either transiently or constitutively. Mice treated with thyroxine led to increased worm numbers and development of giant worms, whereas an iodine-deficient diet reduced parasite maturation, egg laying, and liver pathology. Conversely, mice genetically deficient for either of the nuclear TH receptors displayed normal worm development despite modifications in hormone levels, suggesting that thyroxine action is mediated through host receptors. In addition, no modification of antibody titers has been evidenced in thyroxine-treated mice, whereas antibody levels were altered in transgenic animals. These observations suggest that the immune system is not likely to be involved in the modifications of parasite development reported in this study. Interestingly, concomitant treatment with IL-7 and thyroxine had a synergistic effect, leading to recovery of very large worms, thus raising questions about the complexity of interactions between IL-7 and metabolic hormones.

Four families of trematodes were observed in histological sections during a 1992–1997 investigation of the parasites of zebra mussels Dreissena polymorpha. These included Aspidogastridae, i.e., Aspidogaster, Echinostomatidae, Bucephalidae, i.e., Bucephalus polymorphus, and Gorgoderidae, i.e., Phyllodistomum folium. This article describes the precise location of these trematodes in the tissues of D. polymorpha, provides graphic evidence of their effect on the organs they inhabit, and highlights the distinguishing morphological characteristics. Evidence of defense reaction of host to trematode infection, i.e., encapsulation of Aspidogaster and nacrezation of B. polymorphus, is also presented and is the first such report for zebra mussels. The histological photomicrographs included represent the first comprehensive series published on trematode infection of zebra mussels. These images, in conjunction with the morphological descriptions presented, should assist researchers in identifying the 4 major trematode taxa that they are likely to encounter in the tissue sections of zebra mussels.

Development of Haemoproteus balmorali, H. dolniki, and H. tartakovskyi was followed in experimentally infected biting midges Culicoides impunctatus on the Curonian Spit in the Baltic Sea. Wild-caught flies were allowed to take blood meals on naturally infected spotted flycatchers Muscicapa striata, chaffinches Fringilla coelebs, or crossbills Loxia curvirostra harboring mature gametocytes of these parasites. The engorged biting midges were collected, held at 14–18 C, and dissected daily. Mature ookinetes of H. balmorali, H. dolniki, and H. tartakovskyi were numerous in the midgut content 36 hr postinfection (PI). Oocysts were first seen in the midgut wall 3 days PI. They were numerous in the midgut on the fourth day PI. Sporozoites were seen in salivary glands 5 days PI. The percentage of experimentally infected biting midges with sporozoites of H. balmorali was 36.1%: 8.8% with H. dolniki and 31.2% with H. tartakovskyi. Culicoides impunctatus is likely to be an important vector of Haemoproteus spp. in Europe. All investigated species of parasites can be distinguished on the basis of morphology or size (or both) of their vector stages. Morphological features of the ookinetes, oocysts, and sporozoites should be given more prominence in the description of new species of hemoproteids.

An enzyme-linked immunoabsorbent assay was developed to quantify the number of Giardia sp. trophozoites attached to a substratum. Trophozoites were allowed to attach for 5 or 10 min to untreated or modified substratum, or allowed to attach in the presence of cytoskeletal inhibitors. Microtubule inhibitors, cochicine and nocodazole, were ineffective in blocking attachment, although the actin-disrupting agent cytochalasin B produced significant inhibition of attachment. Three different mucins were associated with significant inhibition of Giardia trophozoite attachment, which was reversed by treating the mucin-coated wells with 0.1% poly-l-arginine. Examination of mucin-treated substrata by high-resolution field emission scanning electron microscopy showed the presence of thin linear fibrils, whereas treatment of mucin-coated wells with poly-l-arginine revealed similar fibrils but of thicker dimensions. These data support the concept that mucin may inhibit Giardia sp. trophozoite attachment in vitro by electrostatic repulsion and that this can be eliminated by treatment of mucin-coated surfaces with polycationic agents, such as poly-l-arginine or poly-l-lysine.

We examine the evolution of host specificity for species of Telorchis, using the methods developed by researchers studying phytophagous insect–plant systems. Optimization of “generalist” compared with “specialist” onto the phylogeny for Telorchis revealed ambiguous patterns, depending on how the 2 terms were defined. Regardless of that definition, most of the evolutionary diversification of this group has been carried out within eucryptodiran turtles, the ancestral host group. From that plesiomorphic background, there appears to have been 2 episodes of specialization by way of a host switch into caudates (ancestor of T. stunkardi T. sirenis) and snakes (T. auridistomi), and 1 episode of exuberant expansion producing a true generalist (T. corti). These results, which indicate that most species of Telorchis are tracking widespread plesiomorphic resources, mirror those reported for phytophagous insects and their plants. We believe that establishing a dialogue between the two research groups will be mutually beneficial to both and will strengthen our understanding of the complex factors underlying the evolution of coevolutionary associations.

The susceptibility of Bulinus tropicus, B. globosus, Biomphalaria pfeifferi, Lymnaea natalensis, and Melanoides tuberculata to Calicophoron microbothrium was examined. Bulinus tropicus had the highest prevalence (65.0%), followed by B. pfeifferi (37.5%), B. globosus (6.8%), and M. tuberculata (5.9%). Lymnaea natalensis was refractory to infection. Bulinus tropicus snails infected with C. microbothrium alone or coinfected with either Schistosoma haematobium or S. mattheei 0, 7, 14, and 21 days after exposure to C. microbothrium produced C. microbothrium cercariae only.

This study addresses the infrapopulation sizes of 2 larval trematode species Himasthla quissetensis and Zoogonus rubellus as they co-occur within their estuarine snail host Ilyanassa obsoleta. Rediae of H. quissetensis and sporocysts of Z. rubellus were counted in snails singly infected with each parasite and in snails infected with both. Comparisons of the counts indicate that infrapopulations of H. quissetensis were unaffected by co-occurrence with Z. rubellus. However, Z. rubellus infrapopulations were reduced when co-occurring with H. quissetensis. It is proposed that this situation does not result from an interspecific interaction between parasite species. Although this double infection is relatively frequent in certain snail populations, it is contended that these trematode species do not co-occur often enough to evolve responses to one another. However, the host environment must be encountered in each life cycle, and both trematode species must be adapted to use it. On this basis, whatever happens when these 2 species occupy the same host is based on adaptations of the parasites to the host. It is proposed that these parasites are adapted to self-limit their infrapopulations in the snail host. They can, thus, preserve and use the host for many years and thereby enhance total cercarial transmission (fitness). Infrapopulation sizes would be determined by host resource levels, which, among other factors, would be influenced by the presence of multiple parasite species. In single infections, by far the most common situation, host resource levels would be set by the nutritional status or age (size) of the host (or both). The reduced infrapopulation sizes of Z. rubellus on co-occurrence suggest that this trematode is more sensitive to host resource levels than is H. quissetensis.

We report the expression of 3 well-characterized adult Schistosoma mansoni glycan antigens among molluscan stages of the parasite. These antigens are LacdiNAc (LDN; GalNAcβ1-4GlcNAc-R), fucosylated LacdiNAc (LDNF; GalNAc[Fucα1-3]β1-4GlcNAc-R), and Lewis x (Le^x; Gal[Fucα1-3]β1-4GlcNAc-R). The presence of the glycans was determined by both immunoblot and immunohistological methods using monoclonal antibodies that specifically recognize each glycan epitope. Immunoblot analyses reveal that LDN and LDNF epitopes are expressed on many different glycoproteins, including eggs, mother sporocysts, daughter sporocysts, and cercariae, although LDN expression among daughter sporocysts is greatly reduced. LDN and LDNF epitopes are localized on the tegument and in the intrasporocyst cell masses of both in vitro–derived and in vivo–derived mother sporocysts and in the daughter sporocysts derived on day 16 after infection. Unexpectedly, high levels of LDN and LDNF glycans were detected in the infected, but not in the uninfected, snail hemolymph, suggesting that the infecting larvae secrete LDN and LDNF glycoconjugates into the snail hosts. In contrast, the expression of Le^x antigen among the molluscan stages is highly restricted. Le^x is present on a few high–molecular weight glycoproteins in eggs and cercariae but is undetectable in mother and daughter sporocysts. Taken together with our earlier studies on vertebrate stages of S. mansoni, these results show that LDN and LDNF glycans are conserved during schistosome development. The study further extends the evidence that Le^x is a developmentally regulated antigen in schistosomes.

The morphogenesis and the chronology of the life cycle of Nematodiroides zembrae (Bernard, 1965), a parasite of Oryctolagus cuniculus from Spain, were studied in detail in its natural host. For each experiment a morphological description of the different stages of the life cycle is provided. The free-living larvae developed in eggs until infective stage. First hatching began at 10 days. Twenty-one, worm-free rabbits were each infected per os with N. zembrae larvae and killed 3 days after infection (DAI) and every day from 4 to 22 DAI. By 3 DAI all recovered larvae were exsheathed and present in the small intestine. The third moult occurred between 6 and 7 DAI. The last moult occurred between 11 and 19 DAI. The prepatent period lasted for 21–22 days. The distribution of N. zembrae along the small intestine of the rabbit is described. Significantly different distributions of the parasite along the small intestine indicated that migrations occurred during the development of N. zembrae in the rabbit. The life cycle of N. zembrae is compared with the 5 known life cycles of Nematodirus spp. in ruminants. The biological data are very similar in both groups except for the prepatent period.

To facilitate ecotourism and research, free-ranging mountain gorillas of Uganda have been habituated to humans. Testing of fecal samples of gorillas (n = 100), people sharing gorilla habitats (n = 62), and local pre- and postweaned cattle (n = 50) having access to these habitats with fluorescein isothiocyanate–conjugated monoclonal antibodies revealed Giardia duodenalis cysts at prevalences of 2, 5, and 10%, respectively. The identification of G. duodenalis was confirmed by fluorescent in situ hybridization with 2 species-specific 18-bp oligonucleotide probes conjugated to hexachlorinated 6-carboxyfluorescein. The mean pathogen concentration was 2.5, 2.8, and 0.2 × 10⁴ cysts/g of the gorilla, people, and cattle feces, respectively. All cyst isolates aligned with genotype (assemblage) A, as confirmed by polymerase chain reaction amplification and sequencing of a 130-bp region near the 5′ end of the small subunit–ribosomal RNA gene. A single genotype (assemblage) A recovered from 3 genetically distant but geographically united host groups indicates anthropozoonotic transmission of G. duodenalis. A large percentage of the local community does not follow park regulations regarding the disposal of their fecal waste, as self-reported in a questionnaire. This genotype may have been introduced into gorilla populations through habituation activities and may have then been sustained in their habitats by anthropozoonotic transmission.

Life history trade-offs affect trematode parasites reproducing inside their 1st intermediate hosts. Within the constraint of the effect on host survival, parasite production of cercariae is subject to a size–numbers trade-off. Within each cercaria, resources must be partitioned between host-seeking and subsequent developmental functions. Three species of microphallid trematodes with the same 1st intermediate host (the gastropod Littorina saxatilis) were investigated. Maritrema arenaria periodically released many small cercariae. Microphallus similis released fewer, 15% larger, cercariae without periodicity. Microphallus similis cercariae were strong swimmers, moving toward the dark and downward in turbulent water, whereas Ma. arenaria cercariae remained suspended. Maritrema arenaria cercariae, although smaller in body and tail size, were produced at an average daily volume nearly twice that of M. similis. These differences are interpreted as transmission adaptations related to mobility and predictability of the 2nd intermediate host. Microphallus similis, with a mobile and less predictable crab host, adopted a ‘bet-hedging’ prolonged production of fewer cercariae by less intensive host exploitation, each cercaria having a high allocation to host-seeking behavior. Maritrema arenaria, with predictable sessile barnacle hosts, produced less mobile but potentially longer-lived cercariae in larger numbers. Microphallus piriformes metacercariae remain in the gastropod host. The number of M. piriformes metacercariae increased in larger hosts. The 3 species differed in the number of sporocysts and (meta)cercariae per sporocyst within the gastropod but not in the within-host volume of parasites. Variation in host exploitation and life history appeared adaptive for transmission to the next host.

Chagasic cardiomyopathy is a major life-threatening complication of Trypanosoma cruzi infection in human beings. This study focuses on the hypertrophic and hyperplastic mechanisms underlying the structural changes of the heart during experimental infection. Proliferating cell nuclear antigen (PCNA) expression, transversal diameter, nuclear area, and number of nuclei per unit volume were determined in the ventricular myocytes of T. cruzi–infected Wistar rats. PCNA expression was enhanced throughout the inflamed myocardium and in the spared areas of the left ventricular wall and the septum. Myocyte width increased from 26 to 75% at the inflammation-free myocardium (P < 0.0001), whereas it decreased 25% at the inflamed left ventricular wall areas (P < 0.001). Nuclear size increased in the inflammation-free myocardium of the left ventricle and the septum (>10–36%, P < 0.01 and >0.2–32%, P < 0.03, respectively) and decreased at the inflamed areas of the left ventricular wall (10–22%, P < 0.02) with respect to the controls. The number of nuclei per unit volume decreased at the inflamed myocardium regardless of topographical location (36–65%) with respect to the controls (P < 0.0001) and in the inflammation-free myocardium of the right ventricle and the septum (<21–37%, P < 0.002 and <8–39%, P < 0.002, respectively). These results show that the heart responds to T. cruzi infection with DNA repair and cell multiplication in the inflamed sites and with hypertrophy of the unaffected myocardium.

Africana telfordi n. sp. (Nematoda: Heterakidae) from the large intestine of the lizard Enyalioides heterolepsis collected in Panama is described and illustrated. Africana telfordi n. sp. represents the seventh species assigned to the genus and the second from the Neotropical Realm. It is distinguished from the other neotropical species, A. chabaudi, by the size and shape of the spicules. The spicules of A. telfordi are robust, analate, and 366–458 μm in length; those of A. chabaudi are narrow, alate, and 644–869 μm in length.

Parapharyngodon ocalaensis n. sp. (Nematoda: Pharyngodonidae) from the large intestine of a sand skink Neoseps reynoldsi collected in Florida is described and illustrated. Parapharyngodon ocalaensis n. sp. represents the 31st species assigned to the genus and the third from the Nearctic Realm. It is distinguished from the other 2 North American species by the presence in the male of 3 pairs of caudal papillae and smooth cloacal lips.

Cephalobium odontolateralis n. sp. (Nematoda, Cephalobiidae) is described and illustrated from the nymphs of Anurogryllus muticus (De Geer) (Orthoptera, Gryllidae) from Buenos Aires province, Argentina. It is characterized by a lateral large tooth in the stoma and by the arrangement and number of the genital papillae in the male; there are 6 pairs of postanal papillae, but none is preanal.

Rhabdochona (Rhabdochona) acuminata is redescribed from specimens parasitizing Diplomystes mesembrinus (Siluriformes: Diplomystidae) and Percichthys trucha (Perciformes: Percichthyidae) from the Chubut River, Patagonia, Argentina. The present report is the first record of this nematode in D. mesembrinus; it also confirms P. trucha as host and Patagonia as a region of distribution for R. (R.) acuminata. Morphological features of the species were described using light and scanning electron microscopy. When compared with previous descriptions from Brazil, very similar morphology is observed. But large morphometric variability is found, mainly in body size, spicule ratio, and number and arrangement of pre- and postcloacal papillae.

Two new species of Strelkovimermis are described from chironomid imagoes eclosing from northern Minnesota glacial lakes. The 2 species are distinguished from the other 12 species in the genus by terminal mouths, rounded or nippled posterior ends, short buccal funnels, short terminal limbs of the S-shaped vagina, and presence of a bursal sleeve. Strelkovimermis rubtsovi n. sp. is distinguished from S. ozawindibi n. sp. by the presence of a dorsal protractor. Procladius (Psilotanypus) bellus (Loew) is the host of S. rubtsovi. The chironomid host of S. ozawindibi has not been determined. An artificial key is provided to distinguish the 14 species of the genus.

In the course of a revision of Haemonchus Cobb, 1898 (Nematoda), commonly referred to as large stomach worms, significant new morphological information was discovered that allows the recognition of 2 species believed for more than 50 yr to be synonymous. Both species, Haemonchus mitchelli Le Roux, 1929, from the eland Taurotragus oryx and other African ruminants and H. okapiae van den Berghe, 1937, from the okapi Okapia johnstoni, have a synlophe of 42 ridges, but the synlophe of H. mitchelli is longer than that of H. okapiae. The distal tip of the left spicule of H. mitchelli bears a barb that is about twice as long as the short barb and half as long as the long barb on the right spicule. In contrast, the barb on the left spicule of H. okapiae is similar in size to the short barb and about 25% as long as the long barb of the right spicule. The dorsal ray of H. mitchelli is bifurcated distally for 25–39% (32%) of its length and its stem is expanded proximally, but the dorsal ray of H. okapiae is bifurcated 37–50% (42%) and its stem is of uniform thickness.

A new genus and species of philometrid nematode Dentiphilometra monopteri n. gen., n. sp., are described on the basis of the specimens found in the abdominal cavity of the ricefield eel (swamp-eel) Monopterus albus (Zouiev) from Liangzi Lake (the Yangtze River drainage system), Hubei Province, in central China. Dentiphilometra, assigned to the Philometrinae, differs from other genera of this subfamily mainly in the presence of a sclerotized oral ring armed on its inner surface by numerous small peribuccal teeth in the gravid female. The new species is characterized by minute cephalic papillae, a greatly developed anterior esophageal bulb separated from the cylindrical part of the esophagus, anterior extention of the esophageal gland anterior to the nerve ring, and by large caudal projections in females and equal spicules 0.051–0.096 mm long in males. This is the second philometrid species recorded from fishes of the Synbranchiformes.

A new species of Litomosoides was collected from the abdominal cavity of Oligoryzomys nigripes (Rodentia: Muridae) in a semideciduous secondary rainforest of Misiones, Argentina. Litomosoides odilae n. sp. belongs to the carinii group and is characterized by the amphids displaced dorsally; buccal capsule with an anterior segment transparent and an annular asymmetrical thickening; esophagus divided, with the posterior glandular portion slightly wider than the muscular; male cloacal aperture strongly protruded; and microfilaria sheathed with an attenuated tail. The morphology of the new species, which is similar to that of L. petteri, a parasite of marsupials in Brazil, suggests that host-switching events may have occurred in the diversification of this genus.

A phylogeny of haemosporidian parasites (phylum Apicomplexa, family Plasmodiidae) was recovered using mitochondrial cytochrome b gene sequences from 52 species in 4 genera (Plasmodium, Hepatocystis, Haemoproteus, and Leucocytozoon), including parasite species infecting mammals, birds, and reptiles from over a wide geographic range. Leucocytozoon species emerged as an appropriate out-group for the other malarial parasites. Both parsimony and maximum-likelihood analyses produced similar phylogenetic trees. Life-history traits and parasite morphology, traditionally used as taxonomic characters, are largely phylogenetically uninformative. The Plasmodium and Hepatocystis species of mammalian hosts form 1 well-supported clade, and the Plasmodium and Haemoproteus species of birds and lizards form a second. Within this second clade, the relationships between taxa are more complex. Although jackknife support is weak, the Plasmodium of birds may form 1 clade and the Haemoproteus of birds another clade, but the parasites of lizards fall into several clusters, suggesting a more ancient and complex evolutionary history. The parasites currently placed within the genus Haemoproteus may not be monophyletic. Plasmodium falciparum of humans was not derived from an avian malarial ancestor and, except for its close sister species, P. reichenowi, is only distantly related to haemospordian parasites of all other mammals. Plasmodium is paraphyletic with respect to 2 other genera of malarial parasites, Haemoproteus and Hepatocystis. Explicit hypothesis testing supported these conclusions.

Two hundred and forty-four specimens of Parapharyngodon riojensis n. sp. were found in the large intestines of 2 adult lizards Phymaturus punae collected from Quebrada del Leoncito, Province of La Rioja, Argentina. Parapharyngodon riojensis n. sp. represents the ninth species of the genus from the Neotropical Realm and the first species to be described from Argentina. It can be distinguished from all species of Parapharyngodon on the basis of the morphology of the anterior cloacal lip, the location of the ovary, and geographical distribution. Parapharyngodon riojensis n. sp. is most similar to P. senisfaciecaudus in that the ovary does coil around the esophagus and the number and location of caudal papillae in the males are the same. These 2 species differ in that the eggs of P. senisfaciecaudus are slightly asymmetrical, with a smooth, thin shell, whereas the eggs of P. riojensis are oval, with a punctate thick shell. In addition, the cloacal lip of males of P. senisfaciecaudus is smooth, whereas the cloacal lip of males of P. riojensis is echinate. A key to the species of Parapharyngodon in the Neotropical Realm is provided.

Rodentolepis asymmetrica (Janicki, 1904), is a common hymenolepidid cestode recorded in several vole species (rodents) in the Palearctic. Here, we report a detailed analysis of this species, which includes metrical features and multilocus enzyme electrophoresis. Worms isolated from 4 species of arvicolid hosts in 3 localities in Spain and France from 1994 to 1997 were studied. All the worms used in the morphological study ranged between 1 and 5 individuals per host. Furthermore, all individuals were analyzed electrophoretically. Statistical analysis of metrical features in scolex, sexual segments, and eggs was carried out, and significant differences were detected only in sexual structures of mature segments. These differences were found in worms from each host species in different localities and in the same host species in 2 localities. Multivariate statistical analysis shows correct classification of worms in all cases. Surprisingly, we observed a lack of genetic variability at the 11 enzymatic loci analyzed, which could be explained by 2 nonexclusive hypotheses: (1) a preferential selfing mode of reproduction for these parasites, and (2) a weak effective size of parasite populations.

This investigation applied polymerase chain reaction (PCR) using 3 sets of Trypanosoma cruzi–specific primers to amplify DNA from 31 archived formalin-fixed and fresh-frozen raccoon hearts. PCR successfully amplified T. cruzi–specific sequences, with at least 1 primer set, from multiple sites within the myocardium of formalin-fixed and fresh-frozen raccoon hearts that had previously tested positive using enzyme-linked immunosorbent assay and indirect immunofluorescent antibody titer in the absence of positive hemoculture results. Trypanosoma cruzi DNA was most frequently amplified from the interventricular septum, right ventricle, and left atrium. In addition, T. cruzi DNA was amplified with all 3 primers in at least 1 raccoon that was hemoculture positive and 2 animals that were borderline negative for the T. cruzi antibody and hemoculture negative. The amplification of T. cruzi–specific DNA sequences in the presence of an elevated antibody titer and negative culture results suggests good sensitivity of this method for detecting the presence of the parasite in archival tissues.

The effect of oryzalin on excystation and metacystic development of Entamoeba invadens strain IP-1 was examined by transfer of cysts to a growth medium containing the drug. Excystation, which was assessed by counting the number of metacystic amoebae after induction of excystation, was inhibited by oryzalin in a concentration-dependent manner. Metacystic development, which was determined by the number of nuclei in metacystic amoebae, was also inhibited by oryzalin because the percentage of 4-nucleate amoebae at day 1 remained unchanged at day 3. The addition of oryzalin after the induction of excystation decreased the number of metacystic amoebae, compared with control cultures. When cysts were incubated for 1 day in growth medium plus oryzalin, little increase in the number of metacystic amoebae was observed after removal of the drug. Excystation and metacystic development were further inhibited when the cysts were incubated for 30 min in encystation medium containing oryzalin before transfer to growth medium with the drug. When cysts were incubated for 30 min in encystation medium before transfer to growth medium without the drug, metacystic amoebae decreased in number. Pretreatment of cysts with oryzalin for 30 min in phosphate-buffered saline markedly reduced viability and prevented excystation in growth medium with or without the drug. The results indicate that oryzalin inhibits excystation and metacystic development of E. invadens, suggesting that it may be an inhibitor of Entamoeba infection.

A gene encoding cysteine proteinase from Clonorchis sinensis has been cloned and expressed in Escherichia coli. The cysteine proteinase cDNA fragment was amplified by reverse transcription–polymerase chain reaction using degenerate oligonucleotide primers derived from conserved active site of cysteine proteinases. The 5′ and 3′ regions of the gene were amplified using rapid amplification of cDNA ends. The cloned gene has an open reading frame of 696 bp and deduced amino acid sequence of 232. Sequence analysis and alignment showed significant homologies with the eukaryotic cysteine proteinases and conservation of the Cys, His, and Asp residues that form the catalytic triad. Analysis of the expressed protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the molecular weight of the protein was approximately 28.5 kDa. Proteolytic activity of the expressed protein was inhibited by cysteine proteinase inhibitors such as l-trans-epoxysuccinyl-leucylamide-(4-guanidino)-butane, iodoacetic acid, and leupeptin. The expressed protein showed biochemical properties similar to those of cysteine proteinases of other parasites. The expressed protein strongly reacted with the sera from patients with clonorchiasis but not with the sera from patients with paragonimiasis, fascioliasis, cysticercosis, and sparganosis, or with sera from normal human controls. These results suggest that the expressed protein may be valuable as a specific diagnostic material for the immunodiagnosis of clonorchiasis.

Given the constraints of classical diagnostic methods, i.e., morphological and isoenzymatic studies of proglottids, a polymerase chain reaction test complemented with restriction enzyme analysis has been modified by redesigning one of the primers to reduce nonspecific amplifications experienced when using field samples. The use of these new, highly cestode-specific primers and the restriction enzyme DdeI led to the development of a diagnostic assay that clearly distinguishes between Taenia saginata and T. solium proglottids in field samples. This assay confirms the presence of T. saginata in Ecuador. DNA amplification of some of these taeniids showed different patterns, suggesting the possibility that strain differences exist. These results demonstrate the need for development of useful molecular assays as reliable tools for epidemiological studies on cestodes.

The investigation reported herein was undertaken to determine which medium is more practical for the axenic laboratory culture of trichomonads. The growth of Tritrichomonas mobilensis was monitored in 2 different types of commercially available growth media. Although Roswell Park Memorial Institute (RPMI) 1640 medium is typically used as a mammalian cell culture medium, it was found to support the growth of trichomonads as well as the American Type Culture Collection (ATCC) medium 745 under similar conditions. Environmental variables, such as temperature and pH, known to affect the success of trichomonad cultures were controlled. The mean generation times (MGTs) of T. mobilensis in the log phase of growth were 5.1 and 4.9 hr for RPMI 1640 and ATCC medium 745, respectively. A stationary phase of zero growth was reached more quickly in the ATCC medium 745 cultures, and in both media a phase of rapid attrition followed this period of static growth. In assessing the practicality of the media, total cell amplification, as well as factors such as cost, ease of preparation, and storage capacity, were considered.

To determine the role of cytokines and a chemokine receptor in the susceptibility to, and outcome of, infection, 4 different knockout mice (IL-4, IL-10, IL-12, and CCR5) were infected with Cryptosporidium parvum and monitored for infection intensity by collection of fecal pellets from individual mice. Because adult immunocompetent mice are refractory to infection, wild-type mice on the same background as the knockout mice (C57BL/6) were used as a negative control. No infection was detected over a 4-wk time period in IL-4, IL-10, and CCR5 knockout mice inoculated with 10⁶ oocysts. IL-12 knockout mice inoculated with as little as 100 oocysts shed up to 10,000 oocysts/100 μl of feces on the peak infection day (day 8) and were able to fully recover by 2 wk after infection. IL-12 is an important inducer of IFN-γ, which probably accounted for susceptibility to infection. Previous studies using IFN-γ knockout mice have shown strain-related differences in infection intensity and outcome, with increased parasite loads and decreased survival among IFN-γ knockout mice on a C57BL/6 background compared with those on a BALB/c background. Similar results were observed in IL-12 knockout mice on a BALB/c background, which exhibited little or no infection, despite higher levels of inoculation (10⁶ oocysts/mouse).

This study investigated the influence of TLR (toll-like receptor)4, TLR2, and MyD88 in Toxoplasma gondii–infected wild-type (WT) mice and TLR4-, TLR2-, and MyD88-deficient mice. Ninety-five percent of MyD88-deficient mice died 10–16 days after intraperitoneal infection with 100 cysts of T. gondii Fukaya strain, whereas 95–100% of TLR4- and TLR2-deficient mice and WT C57BL/6 (B6) mice survived for more than 7 wk after T. gondii infection. The distribution of T. gondii in various organs of TLR4-, TLR2-, and MyD88-deficient mice and WT B6 mice was assessed 2 wk after T. gondii intraperitoneal infection using quantitative competitive polymerase chain reaction. In MyD88-deficient mice, high levels of T. gondii load were observed in the brain, tongue, heart, lungs, spleen, liver, mesenteric lymph node, and kidneys after infection. The T. gondii load was significantly increased in the lungs in both TLR4- and TLR2-deficient mice compared with WT B6 mice. High levels of anti–mouse heat shock protein (mHSP)70 autoantibody and anti-T. gondii HSP70 antibody production were detected in the sera from MyD88-deficient mice.

The oldest and most common parasite for which we have direct evidence, in the New World, is Enterobius vermicularis. Numerous archaeological sites, especially in the arid American southwest, have yielded fecal samples positive for pinworm ova, some of these dating back 10,000 yr. Reports of pinworm from the Old World are scarce. This article reports the first evidence of pinworm infection from Roman-occupied (30 BC–AD 395) Egypt.

To elucidate aspects of pathogenesis of congenital infections with Schistosoma japonicum, 5 Danish crossbred sows were infected during late pregnancy with a Chinese isolate of S. japonicum, and 17 of their offspring (fetuses and piglets) were examined 7, 20, 34, 54, and 69 days postinfection (PI). Organ samples were collected for histopathological examination with emphasis on liver and lung. Samples of the corresponding placenta were also collected from fetuses at postmortem examinations. Perfusions were performed on some of the fetuses to recover schistosomes, and in addition, amniotic fluid was examined for schistosomes. A schistosomulum was found in a 99-day-old fetus 3 wk PI. Eggs were found in meconium from 109-day-old fetuses 34 days after infection of the dam, showing that the prepatent time was the same as in postnatal infections. Piglets examined 54 and 69 days PI had inflammatory reactions in their livers, and progression toward healing and repair of the inflammatory reaction occurred from 54 to 69 days PI. This pilot study is one of the bases for the model of congenital schistosomiasis used currently at the Danish Centre for Experimental Parasitology.

Parastrongylus (=Angiostrongylus) cantonensis, a lung worm of rats, was first reported in the United States in 1987, with a probable introduction by infected rats from ships docking in New Orleans, Louisiana, during the mid-1980s. Since then, it has been reported in nonhuman primates and a boy from New Orleans, and in a horse from Picayune, Mississippi, a distance of 87 km from New Orleans. Parastrongylus cantonensis infection is herein reported in a lemur (Varencia variegata rubra) from New Iberia, Louisiana, a distance of 222 km from New Orleans, and in a wood rat (Neotoma floridanus) and in 4 opossums (Didelphis virginiana) from Baton Rouge, Louisiana, a distance of 124 km from New Orleans. The potential of a great variety of gastropods serving as intermediate hosts in Louisiana may pose a threat to wildlife as well as to domesticated animals in the areas where infected Norway rats (Rattus norvegicus) are present.

Equine protozoal myeloencephalitis is the most important protozoan disease of horses in North America and is usually caused by Sarcocystis neurona. Natural cases of encephalitis caused by S. neurona have been reported in skunks (Mephitis mephitis) and raccoons (Procyon lotor). Opossums (Didelphis spp.) are the only known definitive host. Sera from 24 striped skunks, 12 raccoons, and 7 opossums (D. virginiana) from Connecticut were examined for agglutinating antibodies to S. neurona using the S. neurona agglutination test (SAT) employing formalin-fixed merozoites as antigen. The SAT was validated for skunk sera using pre- and postinfection serum samples from 2 experimentally infected skunks. Of the 24 (46%) skunks 11 were positive, and all 12 raccoons were positive for S. neurona antibodies. None of the 7 opossums was positive for antibodies to S. neurona. These results suggest that exposure to sporocysts of S. neurona by intermediate hosts is high in Connecticut. The absence of antibodies in opossums collected from the same areas is most likely because of the absence of systemic infection in the definitive host.

Fatal disseminated toxoplasmosis was diagnosed in a Risso's dolphin (Grampus griseus) dam and its fetus on the basis of pathologic findings, immunohistochemistry, and structure of the parasite. The dolphin was stranded alive on the Spanish Mediterranean coast and died a few hours later. At necropsy the dam was in good condition. From the standpoint of pathology, however, it had generalized lymphadenomegaly and splenomegaly, enlargement of and multifocal hemorrhage in the adrenal glands, diffuse mucosal hemorrhage of the glandular and pyloric stomach, ulcerative glossitis and stomatitis, focal erosions and reddening of the laryngeal appendix, and severe paraotic sinusitis with intralesional nematodes Crassicauda grampicola. The dolphin was pregnant, most probably in the first gestational trimester. The most prominent microscopic lesions were multifocal granulomatous encephalomyelitis, diffuse subacute interstitial pneumonia, mild multifocal necrotizing hepatitis and nonsuppurative cholangiohepatitis, gastritis and adrenalitis, mild lymphoid depletion, medullary sinus and follicular histyocitosis, and systemic hemosiderosis. The fetus had foci of coagulative and lytic necrosis in the kidneys, the lung, and the heart. Most lesions were associated with tachyzoites and tissue cysts of Toxoplasma gondii. The diagnosis was confirmed immunohistochemically. This is the first report on toxoplasmosis in a Risso's dolphin (G. griseus) and on transplacental transmission to an early-stage fetus in any cetaceans.

This paper represents the first report of the nematode Anisakis simplex in the American shad (Alosa sapidissima) in its introduced range in the American Pacific Northwest. All the adult shad sampled from spawning populations in the Willamette (n = 9) and Umpqua (n = 12) rivers were infected with A. simplex with intensities ranging from 6 to 89 worms per fish. This preliminary investigation contrasts sharply with previous studies in the native range of American shad and confirms that this fish may be an important intermediate host for A. simplex in the Pacific Northwest. It is suggested that this new parasite–host relationship has led to an ecological expansion into rivers and Anisakis may present an emerging health risk for wildlife and some human consumers.

Metacercariae of parthenogenetic Fasciola sp. triploid were inoculated into the rat-like hamster Tscherskia triton. Flukes at various stages of growth were found in the bile ducts of all 8 (50%) animals that survived from 42 to 90 days. The body length to width ratio ranged from 1.8 to 2.9, and flukes with the highest ratio were passed 68 days after inoculation. Our results indicate that T. triton is a suitable host for experimental infection when induced by a small number of metacercariae (less than 5) of Fasciola sp.

Seven species of rotifers representing 6 genera, Epiphanes, Plationus, Asplanchna, Philodina species A, Philodina species B, Platyias, and Brachionus, were exposed to Giardia cysts isolated from the feces of experimentally infected holstein calves. Giardia cysts were prestained with a fluorescein isothiocyanate–conjugated monoclonal antibody and mixed with viable rotifers on 3-well Teflon-coated microscope slides. Organisms were observed with phase-contrast, differential interference contrast, and fluorescence microscopy. Five rotifer species, Epiphanes brachionus, Plationus patulus, Philodina (both A and B), and Platyias quadricornis, ingested varying numbers of cysts, which were retained within the rotifers' bodies throughout the observation period. Rotifer ingestion of Giardia cysts may represent a means of reducing water contamination.

Toxoplasma gondii was found in endemic Hawaiian birds, including 2 nene geese (Nesochen sandvicensis), 1 red-footed booby (Sula sula), and an introduced bird, the Erckels francolin (Francolinus erckelii). All 4 birds died of disseminated toxoplasmosis; the parasite was found in sections of many organs, and the diagnosis was confirmed by immunohistochemical staining with anti–T. gondii–specific polyclonal antibodies. This is the first report of toxoplasmosis in these species of birds.

For over 4 decades the antimalarial program in India has been prescribing a 5-day primaquine regimen as an antirelapse therapy to treat Plasmodium vivax malaria. In view of conflicting reports on the effectiveness of this regimen in the Indian subcontinent, and the varying prevalence of P. vivax in various ecosystems in India, the antirelapse efficacy of this regimen was evaluated in Orissa, a malaria endemic state in eastern India where P. falciparum predominates. In 723 cases of P. vivax infection treated with chloroquine alone and followed up weekly for 1 yr, the prevalence of recurrence of parasitaemia with fever was 8.6%. Among another 759 P. vivax cases treated with chloroquine and a 5-day regimen of primaquine at 15 mg/day (adult dose), the recurrence of infection was 6.5%. The difference in recurrence was not significant (P = 0.53). It is important to note that in a great majority of cases of P. vivax in this area, infection did not recur even without treatment with primaquine. This finding, that the use of the 5-day primaquine regimen with chloroquine had no significant advantage over the use of chloroquine alone, undermines the rationale of using primaquine as an antirelapse drug in forested areas with a high prevalence of P. falciparum.