When oncomiracidia of Neobenedenia girellae (Monogenea, Capsalidae) were incubated in wells with lyophilized extracts of fish skin epithelia on the bottom, some attached to the well bottom with the haptor unfolded and shed the ciliated epidermal cells. Based on these morphological changes in oncomiracidia, we developed a new assay method to examine the attachment-inducing capacities of various fish extracts for oncomiracidia. Attachment-inducing capacities were found only in extracts of fish skin epithelium and not in other fish extracts. No significant difference in capacities was observed among extracts of skin epithelia of 4 fish species. Wheat germ lectin and concanavalin A suppressed capacities in extracts of skin epithelia of Japanese flounder and yellowtail, respectively. Suppressed capacities were recovered by adding sugars that bound specifically to these lectins. These results indicate that some sugar-related chemical substances that exist specifically in fish epithelium induce the attachment of N. girellae oncomiracidia.

Acanthamoeba species can cause granulomatous encephalitis and keratitis in man. The mechanisms that underlie tissue damage and invasion by the amoebae are poorly understood, but involvement of as yet uncharacterized proteinases has been suggested. Here, we employed gelatin-containing gels and azocasein assays to examine proteinase activities in cell lysates and in medium conditioned by Acanthamoeba polyphaga trophozoites. Azocasein hydrolysis by cell lysates was optimally detected at pH 4.0–5.0 and was predominantly associated with the activity of cysteine proteinases. Compatible with enzyme activation during secretion, culture supernatants additionally contained a prominent azocasein hydrolyzing activity attributable to serine proteinases; these enzymes were better detected at pH 6.0 and above, and resolved at 47, 60, 75, 100, and >110 kDa in overlay gelatin gels. Although a similar banding profile was observed in gels of trophozoite lysates, intracellular serine proteinases were shown to be activated during electrophoresis and to split the substrate during migration in sodium dodecyl sulfate gels. Blockage of serine proteinases with phenylmethylsulfonylfluoride prior to electrophoresis permitted the detection of 43-, 59-, 70-, and 100–130-kDa acidic cysteine proteinases in cell lysates, and of 3 (43, 70, and 130 kDa) apparently equivalent enzymes in culture supernatants. Under the conditions employed, no band associated with a metalloproteinase activity could be depicted in substrate gels, although the discrete inhibition of supernatants' azocaseinolytic activity by 1,10-phenanthroline suggested secretion of some metalloproteinase.

Whereas terminological recommendations require authors to use mean intensity or mean abundance to quantify parasites in a sample of hosts, awkward statistical limitations also force them to use either the median or the geometric mean of these measures when making comparisons across different samples. Here, we propose to reconsider this inconsistent practice by giving priority to biological realism in the interpretation of different statistical descriptors and choosing the statistical tools appropriate to our decisions. Prevalence, mean intensity, and indices of parasite distribution (such as median intensity) are suitable descriptors to quantify parasites in a sample of hosts. These measures have different biological interpretations and need different statistical methods to be compared between samples.

The aggregated nature of helminth parasite populations has led to the suggestion that selectively treating heavily infected hosts can efficiently reduce parasite abundance and morbidity within a host population. Moreover, it has been postulated that a selective treatment protocol might have long-term effects on parasite transmission by disrupting the stability attributed to aggregated parasite population distributions by theoretical models. Long-term investigation has demonstrated year-to-year consistency in the population dynamics of Halipegus occidualis in green frogs from Charlie's Pond, North Carolina. In 1996, removal of all but 1 worm from each frog with ≥15 worms reduced the estimated component worm population by 45%, thereby decreasing mean intensity and aggregation (variance-to-mean ratio) of H. occidualis in the frogs by 85% and 63%, respectively. The following year, mean intensity, aggregation, and host colonization trends returned to pretreatment levels, indicating no effect of worm removal and demonstrating the stability of this host–parasite system. Although this result might be attributable to inefficient treatment or the presence of infection reservoirs, it is suggested that parasite population stability in this system might be governed by prevalence rather than intensity of adult worms. Therefore, repeated selective treatment might effectively modify intensity-dependent morbidity in similar host–parasite systems but should not affect further parasite transmission.

Margolisius abditus n. gen., n. sp. (Copepoda: Lernaeopodidae) is described from female specimens collected from gill lamellae of a remora, Remora remora (L.), captured in the Gulf of California near Punta Arena, Baja California. Comparison of this species with 13 lernaeopodid genera with which it shares (a) absence of posterior trunk processes; (b) presence of a relatively long cylindrical cephalothorax, usually reflected along the dorsal surface of the trunk; and (c) a marine habitat showed that it cannot be placed in any of them, thus necessitating establishment of a new genus. Margolisius abditus n. sp. is the smallest known lernaeopodid species, its ovigerous females measuring about 0.5 mm in total length.

Postoncomiracidia of Dionchus sp. are described from specimens collected from the skin of 2 blacktip sharks Carcharhinus limbatus, captured in the northern Gulf of Mexico. The parasites resemble nonciliated oncomiracidia hatched from eggs laid by Dionchus sp. on gills of a cobia Rachycentron canadum and adults of Dionchus remorae that were collected from gills of a common sharksucker Echeneis naucrates, captured in association with a third blacktip shark. The hamuli of the postoncomiracidia were morphologically similar to those of adult D. remorae. This is the first report of dionchids from an elasmobranch and from a location other than the gills. These findings support the idea that some dionchid oncomiracidia colonize the skin of sharks or other aquatic vertebrates that sponsor remoras, prior to transferring to other remoras and maturing.

Mist-netted birds were examined for ticks on Jekyll Island, Glynn Co., Georgia (32 bird species) in 1996–1998, and at Fort Morgan, Baldwin Co., Alabama (36 species) in 1998 during fall migration. Sixty-two (14.7%) of 423 birds from Jekyll Island and 22 (13.3%) of 165 birds from Fort Morgan were infested with ticks. The mean number of ticks per infested bird was 2.0 on Jekyll Island and 6.3 at Fort Morgan. Ten species of birds were infested with ticks on Jekyll Island where 87% of all ticks were recovered from 3 species: the common yellowthroat (Geothlypis trichas), gray catbird (Dumetella carolinensis), and northern waterthrush (Seiurus noveboracensis). Eight species of birds were infested with ticks at Fort Morgan where 83% of all ticks were recovered from 3 species: the brown thrasher (Toxostoma rufum), swamp sparrow (Melospiza georgiana), and common yellowthroat. Six species of ticks (Amblyomma americanum, Amblyomma maculatum, Haemaphysalis leporispalustris, Ixodes brunneus, Ixodes minor, and Ixodes scapularis) were recovered from the Georgia birds, whereas 3 species (A. maculatum, H. leporispalustris, and Ixodes dentatus) were recovered from the Alabama birds. Attempts to isolate Borrelia burgdorferi sensu stricto, the etiologic agent of Lyme borreliosis, from Ixodes spp. ticks recovered from birds were unsuccessful.

Argentophilic structures of Philophthalmus lucipetus miracidia and cercariae from Israel are described. Eighty-four of 87 miracidia examined displayed an epidermal plate arrangement of 6:8:4:2 = 20, similar to other Philophthalmus species. Twenty papilla-like structures are arranged on the terebratorium in 3 groups, along 1 axis. Sixteen body papillae are located at the bases of epidermal plates of row 1. Eyespots are mediodorsal, between rows 1 and 2. Excretory pores are lateral, between rows 2 and 3. Features common to Israeli and Bulgarian isolates, differentiating them from other species, include the presence of 16 body papillae as opposed to 10 in other species, and a maximum of 20 papillae on the terebratorium as opposed to 19 in the others. About 3% of the miracidia displayed different plate arrangements. Among the argentophilic structures of P. lucipetus cercariae, the Israeli and Bulgarian P. lucipetus show a common pattern of 2–4 excretory pores in the tail, but arrangement of cephalic C_I3 and C_I5 papillae in the 2 isolates is insufficiently unequivocal for species determination. The data presented show that miracidial characteristics, rather than those of cercariae, aid in determining the species of philophthalmids. They also support former evidence attesting to the identity of the Bulgarian and Israeli species.

Parasitism can affect size in gastropods by altering the host's growth rate, but other morphological effects of parasitism have rarely been examined. In this study, the relationship between variation in host morphology and parasitism was examined in a population of the freshwater snail Elimia livescens. Differences were found in the morphology of snails infected with the digenean Proterometra macrostoma and uninfected snails. In order to differentiate between 2 hypotheses to explain these differences in morphology, snails were experimentally infected in the laboratory and several morphological traits were measured after 180 days. One hypothesis suggests that parasite-induced changes in shell development explain differences in morphology between infected and uninfected snails. The other hypothesis suggests that selective mortality of infected hosts explains the difference. In the experiment, differences were found between infected snails and uninfected snails in overall size but not in any measurements of shape. The short duration of the experiment relative to the duration of most infections may account for why field-infected snails differed in shape but experimentally infected snails did not. Parasite-induced changes in growth rate are the most likely explanation for the larger size of infected snails relative to uninfected snails.

The sqt-1 gene is 1 of the several loci in Caenorhabditis elegans that primarily affects organismal morphology. Certain mutations in the sqt-1 gene can produce left roller animals, i.e., they rotate around their long axis and move in circular paths. We describe the morphological alterations seen in the cuticle of the left roller sqt-1(sc13). Deep-etched replica analyses showed that the fibrous layer is composed of a unique strand of parallel fibers, instead of the 2 meeting at an angle of 60° as observed in the wild-type strain. In addition, honeycomb elements, fibers organized in a pentagonal fashion above the fibrous layer, completely fill the intermediate layer that is empty spaces in the wild type. These morphological alterations are likely to be involved in generating the helical twist of the sqt-1(sc13) left roller mutant.

We examined the occurrence of 2 virus-like double-stranded (ds)RNAs in human and calf isolates of Cryptosporidium parvum senso latu and other microorganisms, including 7 other members of the genus. A total of 32 isolates of C. parvum, 16 from humans (5 from acquired immune deficiency syndrome patients) and 16 from calves, were analyzed. Ethidium bromide staining, or Northern blot analysis, or reverse transcription/polymerase chain reaction, or all 3 methods, revealed that both genotype 1 and genotype 2 isolates of C. parvum possessed these dsRNAs. No other Cryptosporidium spp. or other organisms examined possessed these dsRNAs. Comparison analysis of partial cDNA sequences of dsRNAs from human and calf isolates revealed a high degree of similarity (>92% and >93% identical nucleotides for large and small dsRNAs, respectively). Slight, consistent differences in nucleotide sequences could be seen at select sites and were associated with an isolate being either genotype 1 or 2. Because of the widespread distribution of the dsRNAs, the similarity of these molecules between isolates, and high host specificity, these nucleic acids may prove to represent species-specific molecular markers for C. parvum. Evidence also suggests that the dsRNA can be utilized for molecular genotyping of C. parvum.

Schistosome blood flukes parasitize birds, mammals, and crocodilians and are responsible for causing one of the great neglected diseases of humanity, schistosomiasis. A phylogenetic study of 10 schistosome genera using approximately 1,100 bases of the large subunit of the nuclear ribosomal gene complex revealed 2 major clades. One clade is entirely mammalian and includes the genera Schistosoma and Orientobilharzia. A close examination of relationships in this group suggests that the medically important Schistosoma arose in Asia and not in Africa as generally presumed and is paraphyletic. The second clade is primarily avian, consisting of 6 genera of exclusively avian parasites and 2 genera of North American mammal flukes. These results indicate a secondary host capture of mammals on the North American continent. This study provides little evidence concerning the ancestral molluscan or vertebrate schistosome host but does demonstrate that host switching has been an important feature of schistosome evolution. Evidence also indicates that the reduced sexual dimorphism characteristic of some avian schistosomes is derived evolutionarily.

Hepatozoon canis is a tick-borne apicomplexan parasite of dogs that infects neutrophils and parenchymal tissues. To study the antigenic characteristics of this parasite, a technique was devised for the purification of gamonts from peripheral blood neutrophils. White blood cells were separated on Ficoll–Hypaque density gradients and the gamonts were released from the host neutrophils by nitrogen cavitation. The blood used for purification originated from dogs with natural or experimental infections of H. canis with a parasitemia of 1.4–33%. The number of parasites collected ranged from 1.5 × 10⁶ to 4.2 × 10⁷. Portions of purified gamonts were separated and examined under phase and scanning electron microscopy, and the remaining purified parasites were then used as a source of antigens to characterize the humoral immune response by western blot analysis. Serum antibodies from infected dogs recognized more than 15 gamont antigens, and the antigenic patterns observed with sera from naturally and experimentally infected dogs were nearly similar. Four immunodominant protein bands of relative molecular weights of 107, 88, 63, and 28 kDa were recognized by all of the sera examined. The technique applied here for the isolation of host cell-free gamonts will facilitate studies on antigenic composition and immune responses against H. canis and on antigenic relationships between Hepatozoon from different host species and geographic regions.

The purpose of this study was to evaluate the effects of a crude Trypanosoma cruzi antigen (TCA) and its partially purified subfractions TCF1, TCF2 on peripheral blood mononuclear cells (PBMC) of normal donors and chagasic patients. TCF1 and TCF2 stimulated cells from normal donors and chagasic patients in association with a significant production of interleukin (IL)-10. Only PBMC from chagasic patients multiplied after incubation with TCA and released mainly interferon-γ but also IL-10. Neither the production of IL-2 and IL-4 nor CD4/CD8 ratios were changed after culture with antigens. These data suggest that some antigens active during the acute phase of T. cruzi infection would stimulate the production of cytokines that promote progression of infection, and the immune system can produce a desired cytokine(s) once the appropriate antigenic stimulus is used.

Differences in the immune response between 2 strains of interferon-γ knockout mice (BALB/c-GKO and C57BL/6-GKO) infected with Cryptosporidium parvum were examined because the course of infection among these 2 strains is markedly different. Infection of the BALB/c-GKO with C. parvum (2 × 10⁶ oocysts/mouse) resulted in slight weight loss, oocyst shedding, and recovery from infection by 2 wk postinfection (PI). Infection with 100 oocysts in the C57BL/6-GKO mice resulted in significant weight loss, oocyst shedding, and death by day 10 PI. Splenocytes from infected mice were able to proliferate in a dose-dependent manner to soluble C. parvum-sporozoite antigen (SAg). In vitro stimulation with SAg resulted in an increase in interleukin (IL)-2, IL-4, IL-5, and tumor necrosis factor-α mRNA cytokine expression from splenocytes of infected BALB/c-GKO mice. In contrast, only IL-5 mRNA expression was increased in the splenocytes from C. parvum-infected C57BL/6-GKO mice. Phenotypic analysis indicated no significant differences in the splenic cell populations. Previous studies indicated that susceptibility to C. parvum is dependent on CD4 T cells and interferon-γ production. The present study indicates that although both of these strains of knockout mice become infected with C. parvum, resolution of infection may be in part dependent on the expression of Th2 cytokines.

To measure the longevity of sporocysts of Schistosoma mansoni in nonsusceptible snails (13-16-R1 and Salvador strains of Biomphalaria glabrata, and Biomphalaria obstructa), the head-foot (HF) of miracidia-exposed snails was transplanted into the hemocoel of a susceptible NIH albino recipient at 1–36 days postexposure (DPE). Recipient snails which were not exposed to miracidia then were monitored for infection transferred by the implant, and infection prevalences in recipients of HF transplants from nonsusceptible donors were compared to those in snails implanted with an HF from NIH albino donors. Transplants from NIH albino snails between 1 to 15 DPE infected 98% of recipients. Similarly, at 1 DPE, 69–85% of transplants from nonsusceptible snails contained viable sporocysts, as shown by resulting patent infections in the recipients. Recipient infection prevalence, and presumably numbers of transplants containing viable sporocysts, declined as a function of DPE, and by 5–9 DPE this decrease was significant for all 3 types of nonsusceptible donors. However, viable sporocysts still occurred in B. obstructa and 13-16-R1 B. glabrata as late as 19 and 20 DPE, respectively, and in Salvador B. glabrata as late as 33 DPE. Thus, sporocysts persist in nonsusceptible snails considerably longer than suggested by results of previous histological studies.

Specimens of the freshwater snail Bulinus tropicus (Krauss, 1848) collected in the Free State, South Africa shed cercariae with an oral collar bearing 27 spines. Tadpoles of the African clawed toad Xenopus laevis laevis Daudin, 1802 collected from the same waters harbored metacercariae with a similar collar of spines. Adults were obtained after feeding infected tadpoles to laboratory-reared reed cormorants, Phalacrocorax africanus (Gmelin, 1789). The parasite was identified as Petasiger variospinosus (Odhner, 1910), the life cycle was experimentally completed, and stages described by the use of light and scanning electron microscopy.

Infective stages of helminths of 5 species that occur as adults in marine mammals were found in burbot, Lota lota (L.) (Gadidae), from the lower Kuskokwim River (southwestern Alaska): Diphyllobothrium alascense Rausch et Williamson, 1958; Pyramicocephalus phocarum (Fabricius, 1780); Corynosoma strumosum (Rudolphi, 1801); Corynosoma semerme (Forsell, 1904); and Pseudoterranova decipiens (Krabbe, 1878). Some larval stages were obtained also from smelt, Osmerus mordax dentex Steindachner, an anadromous fish important as prey of burbot. Burbot, which are freshwater fish, could become paratenic hosts of those helminths by means of at least 3 interactions: by consuming marine fishes in brackish waters at river mouths, by feeding on marine fishes that enter lower reaches of rivers, or by preying on anadromous fishes as they migrate up rivers. Consumption of burbot by people may result in infection by helminths of marine origin; of those recorded, only P. decipiens may be significantly pathogenic. Attempts to rear P. phocarum in dogs were unsuccessful. Plerocercoids of D. alascense, of very small size and found only in the gastric lumen of burbot, readily infected dogs. For study of their development, strobilae were obtained at intervals of 48 hr to 32 days postinfection. In heavy infections, some strobilae developed slowly, while others underwent rapid development.

Bovine trichomoniasis is a sexually transmitted disease associated with reproductive failure. Systemic immunization results in protective IgG antibodies in uterine and vaginal secretions. Because bovine IgG2 is a better opsonin than IgG1, it is potentially important in defense. Yet, Tritrichomonas foetus extracellular cysteine proteinase (TFECP) cleaves bovine IgG2, evading protective IgG2 responses. Variations in resistance of the 2 IgG2 allotypes to digestion may explain inherited differences in protection. To address this hypothesis, TFECP was incubated with both IgG2 allotypes at different concentrations and times. The digestion products were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, stained, and quantitated by image analysis. IgG2^a was digested faster by TFECP than IgG2^b. Differences in the sizes and numbers of digestion products were observed, but the presence of bands the size of Fc and Fd fragments indicated that both allotypes were cleaved at the hinge. Cysteine in the digestion mixture reduced the antibody molecules and increased the rate of digestion, but IgG2^a was still more susceptible to cleavage than IgG2^b in the absence of cysteine. Thus, not only reduced H chains can be cleaved by cysteine proteinase secreted by T. foetus but also intact functional antibody molecules. Because parasites may evade protective antibody responses by cleaving IgG2, animals with the more resistant IgG2^b allotype may be better protected by immunization than animals with the more readily digested IgG2^a allotype.

A gene encoding a cysteine proteinase from Paragonimus westermani has been cloned and expressed in Escherichia coli. The cysteine proteinase cDNA fragment was amplified by reverse transcription–polymerase chain reaction (RT-PCR) using degenerate oligonucleotide primers derived from the conserved active site of the cysteine proteinase. The 5′ and 3′ regions of the gene were amplified using a PCR technique for the rapid amplification of cDNA ends. The cloned gene has an open reading frame of 687 bp and deduced amino acid sequence of 229. Sequence analysis and alignment showed significant homologies with the eukaryotic cysteine proteinases and conservation of the Cys, His, and Asp residues that form a 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. The expressed protein reacted with the sera of patients with paragonimiasis but not with the sera of fascioliasis and clonorchiasis. These results suggest that the expressed protein may be valuable as a specific diagnostic material for the immunodiagnosis of paragonimiasis.

Fresh fecal samples from 5 caecilians (Dermophis mexicanus) were collected and examined for coccidia in the summer of 1998. The caecilians were collected in the Department of San Marcos, Guatemala. Two of the 5 (40%) specimens of caecilians contained an Eimeria species that is described here as new. This represents the first coccidia described from a gymnophionian host. Sporulated oocysts are spheroidal to subspheroidal, 19.5 × 17.7 (16–23 × 15–21) µm, micropyle and oocyst residuum are absent, and 3 (or more) polar granules are always present. Sporocysts are ovoidal, 11.0 × 7.2 (10–12 × 6–9); a Stieda body and sporocyst residuum are present.

Falcaustra kutcheri n. sp. (Nematoda: Kathlaniidae) from feces of the turtle Geoemyda yuwonoi is described and illustrated. Falcaustra kutcheri n. sp. represents the 68th species to be assigned to this genus and is distinguished from other oriental species by the distribution pattern of caudal papillae of the male: 10 pairs of sessile caudal papillae, 4 pairs precloacal, 1 pair adcloacal, 5 pairs postcloacal.

The genus Mesocestoides Vaillant, 1863 includes tapeworms of uncertain phylogenetic affinities and with poorly defined life histories. We previously documented 11 cases of peritoneal cestodiasis in dogs (Canis familiaris L.) in western North America caused by metacestodes of Mesocestoides spp. In the current study, DNA sequences were obtained from metacestodes collected from these dogs (n = 10), as well as proglottids from dogs (n = 3) and coyotes (Canis latrans Say, 1823 [n = 2]), and tetrathyridia representing laboratory isolates of M. corti (n = 3), and these data were analyzed phylogenetically. Two nuclear genetic markers, 18S ribosomal DNA and the second internal-transcribed spacer (ITS 2), were sequenced. Phylogenetic analysis of the 18S rDNA data recovered a monophyletic group composed of all samples of Mesocestoides spp., distinct from closely related outgroup taxa (Amurotaenia Akhmerov, 1941 and Tetrabothrius Rudolphi, 1819). Initial analysis of the ITS 2 data resolved 3 clades within Mesocestoides. Two proglottids from dogs formed a basal clade, a second clade was represented by tetrathyridial isolates, and a third clade included all other samples. Interpretation of these data from an apomorphy-based perspective identified 6 evolutionary lineages. We also assessed whether metacestodes from dogs (n = 4) are capable of asexual proliferation in laboratory mice. One tetrathyridial and 2 acephalic isolates from dogs proliferated asexually. Further investigation is warranted to determine which of the lineages represent distinct species and to determine the life history strategies of Mesocestoides spp.

Two hairworms from Argentina, Gordionus porosus n. sp. and Gordionus ondulatus (Nematomorpha, Gordioidea), are described and illustrated. The cuticle of both species shows only 1 areolar type. Areoles of G. porosus are polygonal and surrounded by minute bristles and the interareolar groove is wide and with large pores. Gordionus ondulatus is characterized by rectangular or irregular areoles from which margins cuticular elongations project as finger-like structures, giving an undulated appearance. Comparing these species to the remaining American species of Gordionus, G. porosus is close to Gordionus violaceus by virtue of the large number of small bristles surrounding the areoles and can be distinguished by the shape of these bristles and by the arrangement and shape of the areoles. Gordionus ondulatus differs from the other species of the genus by its undulating margins. Giordinus lineatus and Giordinus violaceus have been reported in North America, Giordinus platycephalus in North and Central America, Giordinus capitosulcatus in Central America, and Giordinus prismaticus, G. ondulatus, and G. porosus only in South America.

To evaluate higher-level affinities of Hepatozoon species within Apicomplexa, we sequenced the 18S rRNA gene from 2 parasites (Hepatozoon americanum and Hepatozoon canis) of dogs and 1 (Hepatozoon catesbianae) of bullfrogs. Sequences from other apicomplexans among the Sarcocystiidae, Eimeriidae, Theileriidae, Plasmodiidae, Cryptosporiidae, and Babesiidae, a Perkinsus species and 2 dinoflagellates were obtained from GenBank. Phylogenetic analysis indicated that Plasmodium, Cryptosporidium, and Hepatozoon form a monophyletic group distinct from representatives of other apicomplexan families. Although equivocal, our analysis indicated that Plasmodium and Cryptosporidium are sister taxa and that Hepatozoon is basal to them. To evaluate phylogenetic affinities among H. americanum, H. canis, and other species of Hepatozoon, we examined 18 morphologic and life-cycle features of 13 species currently assigned to Hepatozoon. This analysis indicates paraphyly of Hepatozoon (as currently arranged) because Hepatozoon lygosomarum was found most closely related to Hemolivia mauritanicum. These results, combined with results of previous studies, support elevating Hepatozoon to familial level (Hepatozoidae) as originally suggested by Wenyon in 1926. Both DNA sequence data and morphologic and life-cycle characters support a sister-group relationship between H. americanum and H. canis.

Coprological examination of 83 East African chameleon specimens revealed 32.5% prevalence of coccidian parasites. Six species are described as new: Eimeria tilburyi n. sp. from Chamaeleo jacksonii has cylindrical oocysts, 28.9 (26–33) × 16.0 (14–18) µm and occasionally a small polar granule. Sporocysts are oval to ellipsoidal, 10.6 (9–12) × 7.2 (6–8) µm, without Stieda and substieda bodies; endogenous stages were found in the gall bladder. Oocysts of Eimeria largeni n. sp. from Chamaeleo gracilis are broadly cylindrical, 31.2 (29.5–34) × 19.3 (18.5–20) µm, with 1–3 polar granules. Sporocysts are oval, 10.2 (10–11) × 7.6 (7–8.5) µm, without Stieda and substieda bodies. Eimeria bohemii n. sp. from Chamaeleo melleri has cylindrical oocysts, 25.0 (24–26) × 14.0 (13–15) µm, without a polar granule. Sporocysts are broadly oval, 9.4 (9–10) × 6.5 (6–7) µm, without Stieda and substieda bodies. Isospora wildi n. sp. from Chamaeleo dilepis has subspherical to broadly oval oocysts, 25 (22–28) × 21.4 (18–24) µm, with a smooth wall 1 µm thick. Sporocysts are broadly oval to ellipsoidal, 12.3 (12–13) × 9.7 (9–10) µm, with Stieda and substieda bodies. Oocysts of Isospora necasi n. sp. from C. melleri are subspherical to broadly oval, 26.6 (21–30) × 24.3 (20–27) µm, with a velvetlike wall 2 µm thick. Sporocysts are broadly ellipsoidal, 12.8 (12–14) × 9.8 (9–10) µm, with slightly pointed end and with Stieda and substieda bodies. Oocysts of Isospora muriyu n. sp. from C. jacksonii are spherical to subspherical, 23.6 (21.5–25) × 21.9 (21–23) µm, with a finely granulated wall 1.5 µm thick. Sporocysts are broadly ellipsoidal, 12.4 (12–13) × 8.7 (8–10) µm, with Stieda and substieda bodies.

Ascaridoid nematodes parasitize the gastrointestinal tract of vertebrate definitive hosts and are represented by more than 50 described genera. We used 582 nucleotides (83% of the coding sequence) of the mitochondrial gene cytochrome oxidase subunit 2, in combination with published small- and large-subunit nuclear rDNA sequences (2,557 characters) and morphological data (20 characters), to produce a phylogenetic hypothesis for representatives of this superfamily. This combined evidence phylogeny strongly supported clades that, with 1 exception, were consistent with Fagerholm's 1991 classification. Parsimony mapping of character states on the combined evidence tree was used to develop hypotheses for the evolution of morphological, life history, and amino acid characters. This analysis of character evolution revealed that certain key features that have been used by previous workers for developing taxonomic and evolutionary hypotheses represent plesiomorphic states. Cytochrome oxidase subunit 2 nucleotides show a strong compositional bias to A T and a substitution bias to thymine. These biases are most apparent at third positions of codons and 4-fold degenerate sites, which is consistent with the nonrandom substitution pattern of A T pressure. Despite nucleotide bias, cytochrome oxidase amino acid sequences show conservation and retention of critical functional residues, as inferred from comparisons to other organisms.

The Australian skink Egernia stokesii is parasitized uncommonly by Plasmodium circularis n. sp. and by Plasmodium mackerrasae. Plasmodium circularis is distinguished from all other plasmodiids by immature schizonts that encircle host cell nuclei, forming an unbroken ring from apparent fusion of the attenuated ends. Mature schizonts contract into halteridial or dumbbell-shaped forms 15.6 × 4.3 µm, LW 66.2 µm², with 19–52 nuclei. Rounded or oval gametocytes are 9.0 × 7.3 µm, LW 66.9 µm², and L/W 1.24. Gametocyte LW is 2.63× host erythrocyte nucleus size and 1.79× uninfected erythrocyte nuclei. Plasmodium mackerrasae occurs in high prevalence and often massive parasitemia in E. stokesii. Schizonts, often oblong, elongate, or oval, are 5.1 × 3.7 µm, LW 19.8 µm², with 7.2 merozoites. Immature gametocytes, elongate with terminal nucleus, may produce multiple infections of 6 or more parasites. Mature gametocytes, usually rounded, are 5.8 × 4.6 µm, LW 26.7 µm², and L/W 1.29. Gametocyte size is 0.98× host erythrocyte nucleus size and 1.03× uninfected erythrocyte nuclei. Phanerozoites, in endothelium or connective tissue of most organs, may appear in large numbers in circulating blood as seemingly intact bodies of regular form, similar to or larger than phanerozoites seen in sections. Previously unreported phenomena for hemosporidian parasites include extremely large, highly irregular exoerythrocytic schizonts, in circulating blood, perhaps torn from endothelial lining of blood vessels and sinuses, and a visible flooding of free merozoites into the blood stream.

Here,we report an inhibitory effect of a sesquiterpene lactone dehydroleucodine (DhL) on the growth of Trypanosoma cruzi in culture. At concentrations of the drug between 5 and 10 µg/ml in the medium,the parasites remained alive for at least 4 days. Higher concentrations of DhL were lethal for the parasites within a few hours. The effect of DhL is irreversible. Morphological changes induced by DhL were also observed in the parasites. The effect of DhL was blocked by the presence of reducing substrates such as glutathione or dithiothreitol, but these agents were not able to reverse the effect of DhL if added 2 days after the start of drug exposure.

Fecal smears of 90 snakes, 29 lizards, and 8 turtles and tortoises were tested for Cryptosporidium spp. oocysts and microsporidian spores. Microsporidian spores measured x̄ = 3.7 µm in length and x̄ = 2.3 µm in width and were present in feces of 19 snakes and 1 lizard (16%); 13 of these snakes also shed Cryptosporidium serpentis oocysts. The oocysts were numerous in all positive samples, whereas microsporidian spores were always sparse, irrespective if whether fecal samples contained the oocysts. Retrospective examination of reptile clinical records revealed that all animals shedding microsporidian spores died naturally due to diseases, pathologic conditions, and clinical problems or were killed due to severe cryptosporidiosis. The present study indicates that microsporidian infections in reptiles have the features of an opportunistic infection.

This study examined survival and distribution of Echinostoma caproni in the small intestine of ICR mice at various times up to 36 hr following the death of the host. Adult worms were obtained at 2-wk postinfection of 21 ICR mice each infected with 50 metacercarial cysts. Mice were killed with light ether anesthetization and cervical dislocation and maintained at room temperature (22 ± 1 C) until examination at 0 (controls), 2, 4, 6, 12, 24, and 36 hr postmortem. Survival was based on worm activity and distribution was assessed on the basis of worm location in 1 of 5 equal intestinal segments numbered from the pylorus to the ileocecal valve. Worms were alive up to 36 hr postmortem and were distributed mainly in segments 3 and 4 at all times postmortem. Histochemical Oil Red O studies on whole control and experimental worms showed neutral lipids localized in the protonephridial tubules and the excretory bladder. Eggs from experimental worms at all times produced miracidia that infected Biomphlaria glabrata snails.

Eggs of the trematode Aphalloides coelomicola were observed free in the abdominal cavity of Pomatoschistus microps from March 1993 to October 1995 (Pisces, Gobiidae) in the Vaccarès lagoon (delta du Rhône, France). The eggs were contained in a fine membrane of parasitic origin as no immunological reaction of the fish was noted. The alternatively high prevalence of adults and low prevalence of free eggs, and vice versa, suggest that P. microps is both the second intermediate and final hosts of the trematode Aphalloides coelomicola and that the mechanism of transfer to the first intermediate host is through death of the definitive host.

In order to verify the role of migrating birds as natural definitive hosts for Gymnophalloides seoi (Gymnophallidae), Palearctic oystercatchers, Haematopus ostralegus, were caught from several western coastal areas in the Republic of Korea and examined for intestinal flukes. Five (71.4%) of 7 oystercatchers were infected with 302–1,660 (mean 892) adult G. seoi. In intestinal sections of the host, worms were found in the intervillous space of the mucosal layer. We conclude that the oystercatcher is a natural definitive host for G. seoi.