Eight groups of rats were used to study the involvement of the enteric (ENS) and central (CNS) nervous systems in the development of Hymenolepis diminuta using surgical intestinal transection, or CNS denervation, or both procedures. The transection procedure was used to isolate the ENS of the small intestine from either orad and/or caudal portions of the alimentary system, while the CNS denervation was used to eliminate direct visceral efferent inputs from the CNS. Nine days after the surgical procedures, all rats were infected with 35 cysticercoids of H. diminuta. On 20 days postinfection, the infection intensity, tapeworm dry weight, tapeworm morphology, intestine length, and intestinal wet weight were recorded. Only the combination of the duodenal and ileal transections with a CNS denervation reduced infection intensity and prevented the increased intestinal length normally observed in infected rats. In contrast, none of the various intestinal transection procedures alone or CNS denervation alone had any effect on the survival, ability to produce oncospheres or morphology of the tapeworms. In conclusion, tapeworm survival is decreased when both CNS and ENS inputs into the small intestine are altered or absent.

The ability to withstand desiccation by entering anhydrobiosis is important for the survival of many nematode species. We are interested in the metabolic changes that occur during dehydration in the semiarid strain IS-6 of the insect parasitic nematode Steinernema feltiae. These changes may enable IS6 to be more tolerant to desiccation than temperate strains. We identified genes of IS-6 that exhibit changes in transcript levels during dehydration. These included glycogen synthase (Sf-gsy-1), which is the rate-limiting enzyme in the synthesis of glycogen, which is likely to play a role in desiccation survival. We established the changes in the steady state level of Sf-gsy-1 transcripts upon dehydration and determined the biochemical changes in the level of its product, glycogen, during the dehydration and rehydration of nematodes. Our results suggest a shift from glycogen to trehalose synthesis during dehydration, which is regulated at least in part by suppression of glycogen synthase transcription.

Developmental arrest in Ancylostoma caninum is associated with preparasitic, free-living third-stage (L3) larvae, as well as anthelmintic-resilient hypobiotic L3 larvae within the tissues of an infected dog. With the tissue-arrested larvae, pregnancy and, more specifically, the hormonal effects of estrogen and prolactin mediate reactivation resulting in transmammary transmission of infection to nursing puppies. Estrogen and prolactin have been shown to be critically involved in upregulation of transforming growth factor (TGF)-β2 during pregnancy, and studies on the soil nematode Caenorhabditis elegans further implicate TGF-β and insulin-like signaling pathways with larval arrest and reactivation. In this report, an in vitro assay was used to show that neither estrogen, prolactin, nor insulin had a direct effect on the feeding/reactivation response of tissue-arrested larvae; however, TGF-β isoforms 1 and 2 both had significant stimulatory effects that were comparable to the effects of dog serum. The stimulatory effects of serum could be blocked by preincubation with anti-TGF-β antibodies. Taken together, the results support the hypothesis that during pregnancy, host-derived TGF-β can signal a parasite-encoded receptor to trigger the reactivation of tissue-arrested larvae. TGF-β had no effect on preparasitic larvae, suggesting that different signals may be involved in reactivation of the 2 different arrested forms of A. caninum L3 larvae.

Hookworm is highly endemic to Hainan Province, an island located in the South China Sea. To investigate the prevalence and intensity of infection in the area, the village of Xiulongkan was surveyed between April and July 1998. A cross-sectional study was conducted in which fecal samples of 80% of the village residents (631 individuals) were tested for the presence of helminth eggs. Hookworm was the predominant intestinal helminth in Xiulongkan, where it was determined that 60% of those tested were infected. Necator americanus was the predominant species of hookworm in this population. The prevalence of hookworm increased with age, and then leveled to a plateau for ages 41 yr and up. This observation was in contrast to infections with Ascaris lumbricoides, where the highest prevalences occurred among school-aged children. Women had a significantly higher prevalence of hookworm than men and this difference emerged in early adulthood. The intensity of hookworm infection also significantly increased with age, with the highest intensity infections occurring among middle-aged and elderly residents. Females were more likely to have moderate or heavy infections, whereas males were more likely to have light infections. The rates of hookworm transmission are particularly high among the middle-aged and elderly residents of Xiulongkan.

Annual, seasonal, and interlake variation in prevalence and intensity of Ornithodiplostomum ptychocheilus (Faust) metacercariae was assessed in populations of fathead minnows (Pimephales promelas) collected from 4 lakes in north-central Alberta. Mean metacercariae intensity in young-of-the-year minnows varied extensively (5–123 metacercariae/host) among year, month, and lakes. In 2 of the lakes, prevalence always reached 100%, and mean intensity always peaked in September or October. The high spatial and annual variation in metacercarial recruitment was partly attributable to variation in host size, but variation in water depth, temperature, snail densities, and bird visitation likely also played a role. A laboratory experiment demonstrated that host and metacercariae survival was intensity-independent during a period of simulated winter. Thus, metacercariae recruited in the fall survive until the following spring.

Haliotrema abaddon n. sp. (Dactylogyridae) is described from the gills of West Australian dhufish Glaucosoma hebraicum (Teleostei: Glaucosomatidae), from the Indian Ocean near Fremantle, Western Australia. The parasite is recorded from cultured dhufish and from a major portion of the known geographic distribution of its host. In cultured dhufish, H. abaddon causes branchitis and hyperplasia and metaplasia of the lamellar epithelial cells and may be a limiting factor in the development of an economically feasible mariculture industry. Comparable prevalences and densities of the parasite on wild and cultured dhufish were observed. In heavily infested captive fish, clusters of eggs (egg strands) appear to restrict blood flow to localized regions of the gills as a result of entanglement of egg filaments with secondary gill lamellae. Hatching of oncomiracidia occurs in 7–10 days at 20–25 C.

Birds and their attendant ticks were surveyed for infection with the Lyme disease spirochete Borrelia burgdorferi, in chaparral and woodland-grass habitats in northwestern California from March to July, 1998 to 1999. In total, 234 birds were captured and recaptured (15%); nearly 2.5 times more birds were captured in chaparral than in woodland-grass. Overall, 34 species representing 15 families were collected during this study; of these, 24 species were caught in chaparral, 19 in woodland-grass, and 9 in both vegetational types. The most frequently captured birds were sage sparrows (Amphispiza belli) in chaparral, and American robins (Turdus migratorius) and oak titmice (Baelophus inornatus) in woodland-grass. Birds hosted 35 Ixodes pacificus (15 larvae, 20 nymphs) and 9 Haemaphysalis leporispalustris (3 larvae, 5 nymphs, 1 adult) ticks, of which 32 were removed from chaparral birds and 12 from woodland birds. The prevalence of tick infestation was 13% (21/167) in chaparral and 5% (3/67) in woodland-grass, but the relative and mean tick intensities of 0.19 and 1.5 for chaparral birds, and 0.18 and 4.0 for woodland birds, respectively, did not differ significantly by habitat. Spirochetes were not detected in either bird-blood or tick-tissue samples when tested by culture, immunofluorescence, or Giemsa-staining. In contrast, over 90% (86/94) of western fence lizards (Sceloporus occidentalis) collected in June or July were infested with an average of 6.9 and 8.9 immature I. pacificus in chaparral and woodland-grass, respectively. We conclude that birds contribute little to the enzootiology of B. burgdorferi in chaparral and woodland-grass habitats in northwestern California because of their limited parasitism by tick vectors and lack of detectable spirochetemias.

To characterize the extent of genetic diversity of Schistosoma haematobium within and among its definitive host (intra- and interhost parasite diversity), 133 individual isolates from 25 infected schoolchildren were compared using randomly amplified polymorphic DNA markers. With 4 primers, 53 unambiguous loci were identified, and of these, 22 were polymorphic. Mean heterozygosity in the population was 0.116 ± 0.043. Analysis of molecular variance showed the majority of variance occurred within, rather than between, hosts. Frequencies of certain alleles segregated the parasite population into 13 distinct clusters of associated genotypes, with 4 of these first appearing 10 mo after the initial survey. Considering the level of diversity within this limited geographical area and the possibility of rapid turnover of genotypes, parasite variance may impact acquired immunity and clinical outcome of the infection.

Immunoaffinity-purified TF1.17 adhesin antigen was compared biochemically and antigenically to Tritrichomonas foetus (TF) lipophosphoglycan (LPG) and a soluble glycosylated antigen (SGA) released from T. foetus and implicated in pathogenesis and immunity. The monoclonal antibodies (Mabs TF1.15 and TF1.17) specific for a glycosylated TF1.17 antigen were previously shown to prevent adhesion of the T. foetus parasites to bovine vaginal epithelial cells and to mediate killing by bovine complement. SGA was isolated from T. foetus–conditioned buffer and purified by octyl-Sepharose hydrophobic column chromatography. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis of SGA showed a major SGA1 component (approximately 190 kDa) and a minor SGA2 component (50–70 kDa), which migrated close to TF-LPG and TF1.17. The carbohydrate and lipid compositional analyses of affinity-purified TF1.17 and SGA2 by high-performance liquid chromatography (HPLC) and gas–liquid chromatography revealed the presence of monosaccharides and fatty acids as found in TF-LPG. All antigens contained terminal fucose as determined by α-fucosidase digestion followed by HPLC. ELISA and western blots were used to further characterize these glycosylated antigens and to analyze their relationships. The Mabs TF1.15 and TF1.17 reacted very strongly to TF-LPG and SGA2, as well as TF1.17 antigen, indicating that these molecules share common epitopes. These Mabs did not react with the SGA1 component either in ELISA and western blot analyses. Also, the monosaccharide composition of SGA1 was very different from the other three antigen, suggesting SGA1 was different from LPG, SGA2 and TF1.17. Although LPG reacted with Mabs to native TF1.17 antigen, LPG did not induce an immune response in cattle with the same route and adjuvant used to produce strong antibody responses to the native antigen. The latter response suggests that the tightly bound peptide present in the immunoaffinity-purified antigen is necessary for induction of a response to (an) epitope(s) in TF-LPG and TF1.17. Furthermore, vaginal fluid from T. foetus–infected heifers and serum from a cow with a T. foetus–associated pyometra recognized both TF1.17 and TF-LPG in western blots. These results suggest that T. foetus LPG and SGA2 are related to TF1.17 antigen, which was previously shown to play an important role in the pathogenesis and host response in bovine trichomoniasis.

In strains of the snail Biomphalaria glabrata (Gastropoda) that are resistant to the parasite Schistosoma mansoni (Trematoda), hemocytes in the hemolymph are responsible for elimination of S. mansoni sporocysts. The defensive role of reactive nitrogen species was investigated in in vitro interactions between hemocytes derived from the resistant 13-16-R1 strain of B. glabrata and the parasite. The nitric oxide synthase (NOS) inhibitor N_ω-nitro-l-arginine methylester (l-NAME) and the nitric oxide (NO^·) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide reduced cell-mediated killing of S. mansoni sporocysts. To determine if peroxynitrite (ONOO⁻) is involved in killing, assays were run in the presence of the ONOO⁻ scavengers uric acid and deferoxamine. These did not influence the rate of parasite killing, indicating that NO^· is directly responsible for mediating cytotoxicity, but ONOO⁻ is not. The combination of the NOS inhibitor l-NAME and catalase, an enzyme that detoxifies hydrogen peroxide (H₂O₂), reduced average sporocyst mortality to a greater extent than l-NAME alone. Killing of the sporocysts was, however, not totally inhibited. It is suggested that NO^· and H₂O₂ are both involved in hemocyte-mediated toxicity of 13-16-R1 B. glabrata against S. mansoni sporocysts.

Flow cytometric analysis of circulating blood cells (hemocytes) of Biomphalaria glabrata, molluscan intermediate host of Schistosoma mansoni, revealed the presence of 2 overlapping hemocyte subpopulations, designated R1 and R2. R1 hemocytes are characterized by their smaller size, reduced granularity, and the presence of the BGH₁ surface epitope, whereas R2 cells are larger, more granulated, and generally lack the BGH₁ cell marker. Both hemocyte subpopulations bound fluorescent dye (Oregon Green)-conjugated excretory–secretory glycoproteins (fESPs), although the specific fESP binding signal (geometric mean value), after correction for cellular autofluorescence, was greater in the R1 hemocyte subpopulation compared to that of the R2 subset. Partial inhibition of fESP binding to hemocytes consistently was achieved using various glycoconjugates (mucin, asialo-mucin, asialo-fetuin, heparin) and polysaccharides (fucoidan, dextran sulfate 8000), suggesting the involvement of hemocyte carbohydrate-binding receptors (CBRs) in reactions with ESP-associated glycans. Although sulfation of carbohydrate ligands contributed significantly to ESP blocking activity of some inhibitory polysaccharides and heparin, other sulfated proteoglycans (chondroitins A and B, heparan sulfate) were noninhibitory, indicating that charge alone was not solely responsible for the observed inhibition of hemocyte binding by fESPs. A similar blocking effect by desialylated glycoproteins (asialo-mucin, asialo-fetuin) further supports the contention that ESP–hemocyte interactions are mediated primarily through CBRs. The glycoconjugate inhibitors of ESP binding were only partially effective over a range of concentrations and their glycan moieties (oligosaccharides or long-chain polymers) comprised a diversity of major sugar groups, suggesting that hemocyte CBRs and S. mansoni larval ESPs likely represent a multiple receptor-ligand system. Previously reported findings of differential effects of ESPs on a variety of in vitro hemocyte functions are consistent with such a hypothesis.

Acanthoparyphium tyosenense Yamaguti, 1939 (Digenea: Echinostomatidae), was originally reported as an avian intestinal parasite; here, its presence is reported in 10 humans in the Republic of Korea. The patients were 9 adults aged 35–66 yr (males and females) and a young girl aged 7 yr residing in 2 coastal villages in Puan-gun, Chollabuk-do. The worms were recovered after treatment with praziquantel and purgation with magnesium salts. A total of 158 specimens (1–107 specimens/individual) was collected, together with varying numbers of other intestinal flukes. The patients had eaten various kinds of brackish water mollusks caught in an estuary near their villages. Five bivalves and a gastropod species suspected as sources of human infection were collected and examined. Two bivalves (Mactra veneriformis and Solen grandis) and the gastropod (Neverita bicolor) were found to be infected with the metacercariae of A. tyosenense; adult flukes were confirmed after the experimental infection of chicks. The results show that A. tyosenense infects humans and that brackish water mollusks are the source of human infection.

Mj-col-5, isolated from the plant parasitic nematode Meloidogyne javanica, has a longer carboxy-terminus than other members of the Caenorhabditis elegans COL-6 subfamily of cuticle collagen, including an extra tyrosine residue, and may form altered nonreducible cross-linkages. By semiquantitative determination at different life stages, Mj-col-5 transcript was shown to be more abundant in eggs than in juveniles/young females and adult females. To characterize further this gene's contribution to the changing cuticle of the nematode, we expressed a fusion protein containing a nonconserved 58-amino-acid sequence from the putative Mj-col-5 gene product and raised rabbit antiserum against the fusion protein. The antiserum detected a strongly reacting band (36 kDa, designated MJE36) on western blots of M. javanica eggs extracted with β-mercaptoethanol. MJE36 was sensitive to collagenase and was not detected on western blots of extracts from M. javanica second-stage juveniles or adult females. A band of the same molecular size was detected in Meloidogyne incognita egg extracts but not in those of Heterodera avenae. Immunoblot indicated that MJE36 is not present in egg shells of M. javanica.

The laboratory trials rank the virulence of entomopathogenic nematode strains (3 heterorhabditids and 6 steinernematids) to engorged female Boophilus annulatus ticks according to 3 parameters of the infection process: the effect of exposure time on tick mortality, the quantity of nematodes that penetrate ticks, and the rate of tick mortality after the injection of 1, 2, or 3 nematodes. Exposure of the ticks to heterorhabditid strains for 6 hr resulted in >80% mortality, but only 20 or 65% mortality after exposure to most steinernematids. The quantity of nematodes recovered per tick exposed to nematodes for 6 days averaged from 16 to 141. For steinernematids, a negative correlation was obtained between tick mortality and the average quantity of nematodes recovered. Injecting 1 infective juvenile from 1 of 2 heterorhabditid strains into each tick resulted in close to 100% mortality. Increasing the quantity of nematodes injected into each tick had little or no additive effect on tick mortality.

The aim of the present study was to assess the effect of a congenital Schistosoma japonicum infection on the establishment, fecundity, and pathogenicity of a postnatal challenge infection. Five prenatally S. japonicum–infected piglets received a challenge infection (prenatal challenge group), 5 prenatally infected piglets were followed without challenge (prenatal group), and 10 piglets, born by unexposed sows, served as challenge controls (challenge control group). Challenge infections were given 8 wk after the piglets were born (14 wk after the primary infection of the sows), and the study lasted another 11 wk. Variables included worm burden, tissue egg count, and liver pathology. Worm establishment and tissue egg count were comparable in the prenatal challenge group and in the challenge control group, both exceeding at a statistically significant level those in the prenatal group. No difference in worm fecundity (eggs/female worms/g tissue) was seen between the 3 groups. Liver pathology (i.e., portal and septal fibrosis) was more severe in the challenge control group compared to the other groups. A congenital S. japonicum infection in piglets thus affected neither establishment nor fecundity of a postnatal challenge infection. In spite of this, the challenge infection gave rise to much less liver pathology than the similarly sized challenge control infection.

Two species of protozoans were isolated from a harbor seal with fatal meninogoencephalitis. Serologic reactivity was detected to both Sarcocystis neurona and Toxoplasma gondii. Parasites associated with brain inflammation and necrosis reacted only with immunohistochemical stains utilizing polyclonal antisera raised against Sarcocystis neurona. However, 2 distinct parasites were observed in cell cultures derived from the seal's brain tissue. These parasites were separated by mouse passage and limiting dilution. Purified zoites from 1 isolate (HS1) reacted strongly with polyclonal antiserum to S. neurona and with the harbor seal's own serum (1:2,560 for each) on indirect immunofluorescent antibody tests (IFAT), but weakly to antisera to T. gondii and Neospora caninum (1:40). Zoites from the second isolate (HS2) reacted positively with T. gondii polyclonal antiserum (1:81,920) and with the harbor seal's own serum (1:640), but weakly to S. neurona and N. caninum antisera (1:80 or less). Amplification and sequence analysis of protozoal DNA encoding portions of the 18s ribosomal RNA (18s rDNA) and the adjacent first internal transcribed spacer (ITS1) were performed for both isolates, and resulting sequences were compared to those from similar protozoans. Based on molecular characterization, parasite morphology, serologic reactivity, histology, and immunohistochemistry, HS1 was indistinguishable from S. neurona, and HS2 was indistinguishable from T. gondii.

An unidentified Sarcocystis falcatula-like infection was diagnosed in a captive bee-eater (Merops nubicus) in a zoo in Florida. The bird died suddenly, probably due to protozoa-associated pneumonia. Protozoal schizonts were found in lungs and heart, and immature sarcocysts were seen in skeletal muscles. Ultrastructurally, schizonts were located in capillary endothelium and merozoites lacked rhoptries, consistent with the structure of Sarcocystis species. Sarcocysts were immature, microscopic, and contained only metrocytes. The sarcocyst wall had finger-like villar protrusions that were up to 0.7 µm long and up to 0.2 µm wide. The villar protrusions lacked microtubules, characteristically seen in sarcocysts of S. falcatula. Antigenically, parasites in lungs and muscles of the bee-eater reacted with a varying intensity with polyclonal rabbit antisera to S. falcatula and Sarcocystis neurona. Results indicated that sarcocysts in the bee-eater were morphologically different from the reported structure for sarcocysts of other S. falcatula infections.

Examination of type and new material of Platybothrium musteli Yamaguti, 1952, resulted in the erection of a new genus, Erudituncus, the new combination Erudituncus musteli (Yamaguti, 1952), and the redescription of the newly combined species. This species exhibits novel hook morphology. Each bothridium bears 2 pairs of hooks, the axial pair comprising 1 medial and 1 lateral bipronged hook and the abaxial pair comprising a lateral unipronged hook and a medial, simple hook element. Based on the position of the hook talons, we suggest that the inner prong of the axial hooks of Erudituncus is homologous to the single prong of the axial hooks of Calliobothrium and the axial prongs of Dicranobothrium, Platybothrium, Phoreiobothrium, and Onchobothrium; the outer prong of the axial hooks of Erudituncus is homologous to the abaxial prongs of Dicranobothrium, Platybothrium, Phoreiobothrium, and Onchobothrium; and the abaxial hooks of Erudituncus and Calliobothrium are homologous. Erudituncus musteli was lacking from 31 individuals of the type host of record, the triakid shark Mustelus manazo Bleeker, 1854, examined for this study, but was obtained from 2 individuals of the triakid shark Hemitriakis japanica (Müller and Henle, 1839). Therefore, H. japanica is proposed as the probable type host of E. musteli.

The spirurid nematode, Paraspirura bettinae n. sp., described from Mabuya spilogaster (Scincidae) in South Africa (Molopo Reserve), can be distinguished from the single known species of the genus, Paraspirura mabuyae Sandground, 1936 (also reviewed) by the larger size of the eggs, the shape of the tail of the female, and the smaller body size in both sexes. The cephalic anatomy of Paraspirura spp. does not fit the original description but appears similar to that of spirurid parasites of mammals, Spirura spp. and Protospirura spp. Previous descriptions did not mention the rim and bulges in members of Protospirura. Paraspirura appears close to Protospirura, particularly to Protospirura muricola from the Ethiopian region, but it is distinct because of the persistence of the larval caudal tubercles in the adult stage, the simple right spicule without alae, and the more developed rim and bulges. The species parasitic in saurians may have arisen from Protospirura spp. by capture, or the spirurids of mammals may have been derived from species of Paraspirura and quickly split into a Protospirura line and a more specialized Spirura assemblage.

A total of 53 spiral intestines from 3 species of rays collected in the Gulf of California, Baja, Mexico, was examined for cestodes of the order Lecanicephalidea. Four new genera and 5 new species were discovered as a result of this study. These are Aberrapex senticosus n. gen., n. sp., from Myliobatis californica, Paraberrapex manifestus n. gen., n. sp., from Squatina californica and Healyum harenamica n. gen., n. sp., Healyum pulvis n. sp. and Quadcuspibothrium francisi n. gen., n. sp., from Mobula japanica. Aberrapex n. gen. and Paraberrapex n. gen. can be distinguished from all other lecanicephalidean genera based on the lack of an apical structure (pars apicalis) on their scolex. Aberrapex n. gen. can be distinguished from Paraberrapex n. gen. based on the presence of an external seminal vesicle, a vagina positioned lateral rather than medial in the proglottid, and an ovary that is tetralobed rather than bilobed in cross section. Healyum n. gen. and Quadcuspibothrium n. gen. are unique among lecanicephalidean genera, including Aberrapex n. gen. and Paraberrapex n. gen., in their possession of a trilobed ovary in cross section. Quadcuspibothrium n. gen. can be distinguished from Healyum n. gen. based on its unique shape of the acetabula, which are diamond-shaped. The 2 species of Healyum n. gen. can be distinguished from one another based on the dimensions and the shape of the scolex, the diameter of the suckerlike acetabula, as well as the shape of the spiniform microtriches on the acetabular rims. Discobothrium arrhynchum is transferred to the genus Aberrapex n. gen. and the original description of this species is emended to include details of the vas deferens and the uterine duct and uterus. The microtrich patterns of the 5 new species and Aberrapex arrhynchum n. comb. are described. These are the first records of tapeworms of the Lecanicephalidea from the Gulf of California. Squatina californica and Mobula japanica represent new host records for lecanicephalidean tapeworms. The ordinal diagnosis of the Lecanicephalidea by Euzet (1994) is emended to include these 4 new genera.

The higher level phylogenetic relationships within the avian feather lice (Insecta: Phthiraptera: Ischnocera) are extremely problematic. Here we investigate the relationships of 1 family (Goniodidae), sometimes recognized as distinct within Ischnocera, using parsimony and likelihood analyses of nuclear and mitochondrial DNA sequences. These data support monophyly for a restricted definition of traditional Goniodidae, but recognition of this family would result in paraphyly of the large heterogeneous family Philopteridae. We show that the New World Chelopistes is not related to other members of Goniodidae, despite similarities in morphology, but rather is the sister taxon to Oxylipeurus. Within Goniodidae, genera are divided into those occurring on Galliformes (the Goniodes complex) and those occurring on Columbiformes (the Coloceras complex). Within the well-sampled Coloceras complex, or Physconelloidinae, several groups are identified. However, traditionally recognized genera such as Coloceras and Physconelloides appear to be paraphyletic. Whereas the phylogeny of Goniodidae reflects some aspects of host relationships, biogeography also influences coevolutionary history.

Hemogregarines, apicomplexan intracellular blood parasites, are cosmopolitan in distribution and infect a broad range of vertebrate and invertebrate hosts. Molecular phylogenetic studies have been hampered by lack of hemogregarine-specific polymerase chain reaction primers that would allow amplification of parasite, but not host, DNA. A novel method for separating parasite and host 18S rRNA genes has been developed, and new primers that are specific for hemogregarine rRNA genes have been designed. These primers were used to obtain sequences from 4 isolates of hemogregarines of lizards from California, the Caribbean island of Grenada, eastern Australia, and Israel. Combining these results with already published sequences, a preliminary phylogeny of hemogregarines and several other apicomplexan taxa has been created. The hemogregarines form a monophyletic group and appear to be more closely related to coccidia than to Plasmodium species. The difficulty of using 18S genes that have multiple copies in some apicomplexan parasites was explored for systematic studies.

Entomopathogenic nematodes in Steinernema, together with their symbiont bacteria Xenorhabdus, are obligate and lethal parasites of insects that can provide effective biological control of some important lepidopteran, dipteran, and coleopteran pests of commercial crops. Phylogenetic relationships among 21 Steinernema species were estimated using 28S ribosomal DNA (rDNA) sequences and morphological characters. Sequences of the rDNA internal transcribed spacers were obtained to provide additional molecular characters to resolve relationships among Steinernema carpocapsae, Steinernema scapterisci, Steinernema siamkayai, and Steinernema monticolum. Four equally parsimonious trees resulted from combined analysis of 28S sequences and 22 morphological characters. Clades inferred from analyses of molecular sequences and combined datasets were primarily reliably supported as assessed by bootstrap resampling, whereas those inferred from morphological data alone were not. Although partially consistent with some traditional expectations and previous phylogenetic studies, the hypotheses inferred from molecular evidence, and those from combined analysis of morphological and molecular data, provide a new and comprehensive framework for evaluating character evolution of steinernematids. Interpretation of morphological character evolution on 6 trees inferred from sequence data and combined evidence suggests that many structural features of these nematodes are highly homoplastic, and that some structures previously used to hypothesize relationships represent ancestral character states.

Five species of snakes in Florida, from Palm Beach County in the south and Alachua County 450 km to the north, occur in similar habitat but have distinctive Hepatozoon species characteristic of each host species. In Palm Beach County, Diadophis punctatus is host to Hepatozoon punctatus n. sp., Thamnophis sauritus sackenii to Hepatozoon sauritus n. sp., and Nerodia fasciata pictiventris to Hepatozoon pictiventris n. sp. In Alachua County, N. fasciata pictiventris is parasitized by Hepatozoon fasciatae n. sp., Seminatrix p. pygaea by Hepatozoon seminatrici n. sp., and Thamnophis s. sirtalis by Hepatozoon sirtalis n. sp. Each Hepatozoon sp. has distinctive gamonts and sporogonic characters and, in the 4 species where known, meronts. Nerodia floridana is host to Haemogregarina floridana n. sp. in both localities, with generic identification tentative, based upon presence of erythrocytic meronts. The presence of sporocysts in the proboscis of 31% of Aedes aegypti infected by H. pictiventris is the first report of infective stages of a reptilian Hepatozoon species within the mouthparts of a dipteran vector. This study suggests that in Florida, at least, the diversity of the Hepatozoon community not only equals but probably exceeds the diversity of the snake communities present, and that host specificity in nature may be much greater than that postulated from previous studies.

Prevalence of anti-Neospora caninum antibodies was determined in sera of 320 dogs from Argentina using the indirect fluorescent antibody test (IFAT). Antibodies to N. caninum were found in 121 of 320 (37.8%) sera with titers of 1:50 (21 dogs), 1:100 (23 dogs), 1:200 (23 dogs), 1:400 (17 dogs), 1:800 (23 dogs), and ≥1:1,600 (14 dogs). The seropositivity (IFAT, ≥ 1:50) was higher in dogs from dairy (48% of 125) and beef (54.2% of 35) farms than in dogs from urban areas (26.2% of 160). Prevalence of anti-N. caninum antibodies was higher in dogs more than 12 mo of age (47.7%, 105 of 222) versus in 12-mo-old or younger dogs (12.7% of 86), suggesting postnatal exposure of N. caninum infection in dogs.

We examined 2 cichlid fish species native to México, Cichlasoma callolepis and C. fenestratum, and 2 introduced African cichlids, Oreochromis aureus and O. niloticus, from 3 localities in southeastern México for monogeneans. Six monogenean species infected the African cichlids: Cichlidogyrus haplochromii, C. dossoui, C. longicornis longicornis, C. sclerosus, C. tilapiae, and Enterogyrus malmbergi. We found all these parasite species, except C. haplochromii and C. dossoui, on the native C. fenestratum and C. callolepis. Prevalences of Cichlidogyrus spp. were 3–10% and abundances ranged from 0.03 ± 0.2 to 0.1 ± 0.3 for native cichlids. We only recovered a single E. malmbergi from 1 C. callolepis. We found Sciadicleithrum bravohollisae, a monogenean of native Cichlasoma spp., on the gills of the introduced O. aureus from Lake Catemaco (prevalence 3%, abundance 0.03 ± 0.2). Although prevalence and abundance in atypical hosts were fairly low, the present findings provide evidence of monogenean transfer from African to American cichlids and vice versa. This is the first record of exotic monogeneans in the genus Cichlidogyrus and Enterogyrus infecting native American cichlid fish. It is also the first record from southeastern México of a native American monogenean infecting introduced African cichlids.

Neospora caninum is an apicomplexan parasite that causes neonatal neuromuscular disease in dogs and abortions in cattle. Bovine neosporosis is a major production problem worldwide. The parasite is transmitted to cattle via oocysts excreted by dogs or by transplacental transmission. Dogs are the only proven definitive host for N. caninum. One of 3 dogs fed mouse brains containing tissue cysts of a wild-type N. caninum strain CK0160SC3B (CKO) excreted oocysts in its feces. Two of 3 dogs fed mouse brains containing tissue cysts from a cloned line of the CKO strain excreted N. caninum oocysts in their feces. The results indicate that a single N. caninum tachyzoite contains all the genetic information needed to produce the asexual and sexual cycles in the canine intestine.

Following an investigation suggesting a protective role for Ascaris against cerebral malaria, possibly through immunomodulation, we examined whether Ascaris had any impact on mixed Plasmodium falciparum and Plasmodium vivax infections. We studied a cross section of 928 patient files between 1991 and 1999. Forty patients had contemporaneous mixed infections and 40 patients had P. falciparum infections, followed by P. vivax infections. There was a significant association between Ascaris infection and risk of having both contemporaneous or successive mixed P. falciparum and P. vivax infections (adjusted odds ratios respectively 6 [2–18] P = 0.001 and 3.6 [1.2–11.1] P = 0.02). There was a positive linear trend between the burden of Ascaris and the risk of mixed infections P < 0.0001. These results suggested the possibility that pre-existing Ascaris infection may increase tolerance of the host to different Plasmodium spp., thus facilitating their coexistence.

Adenosine and AMP in the salivary glands of the sand fly Phlebotomus argentipes were characterized by reversed-phase high-pressure liquid chromatography with diode-array detection and mass spectrometry. AMP and adenosine were measured in individual salivary gland pairs, yielding 76.8 ± 8.6 and 380 ± 25 pmoles per pair of salivary glands, respectively (mean ± SE, n = 12). These values decrease to 45 ± 7 and 181 ± 21 pmoles following a blood meal, indicating that AMP and adenosine were secreted. Because adenosine and AMP have anti-platelet, vasodilatory, and immunomodulatory properties, it is proposed that these salivary nucleotides help the fly to blood feed and may affect Leishmania transmission.

The electrophysiological responses of adult females of the insect-parasitic nematode Leidynema appendiculata, to 100 mM, 10 mM, and 1 mM acetylcholine were concentration dependent, with stimulation by 100 mM acetylcholine giving the largest increase in spike activity. By contrast, the delay in response was not concentration dependent. No increase in activity was obtained on stimulation with either 0.1 mM acetylcholine or phosphate-buffered saline. The lack of response to 0.1 mM acetylcholine was confirmed by sequential exposure of L. appendiculata to 0.1 mM acetylcholine and subsequently to 10 mM acetylcholine.

The mechanism of Entamoeba histolytica cyst cell wall synthesis is not well understood. Previous research has shown that cystlike structures formed in the presence of chitin synthase cofactors (Mg² , Mn² , and Co² ) resist 1% sodium dodecyl sulfate lysis (RCLS), whereas those formed in the absence of cofactors (CLS) do not, and trophozoites are immediately destroyed. This suggests that E. histolytica is able to synthesize chitin, initiating a differentiation process under axenic conditions. To test this hypothesis, polysaccharide hydrolysates from E. histolytica trophozoites, CLS, or RCLS were analyzed with high-performance liquid chromatography. The major components found in all 3 preparations were N-acetylglucosamine (NAG) and glucose (GLC), with RCLS possessing 129 and 180 times more NAG and 2.4 and 2.0 more GLC than trophozoites and CLS, respectively. After 36 hr of incubation with chitinase (16 U/ml) in a hypotonic medium (50 mOsm/kg), 68% of RCLS was lysed, and 100% lost affinity for calcofluor white M2R. The RCLS polysaccharides bound wheat germ agglutinin and appeared as long and thin or short and thick fibers. Accordingly, Mg² , Mn² , and Co² stimulated E. histolytica to synthesize a chitin-like material.

Enhanced atrial natriuretic factor (ANF) production by the heart is related to hemodynamic overload, cardiac growth, and hypertrophy. The heart is one of the most affected organs during Trypanosoma cruzi infection. We tested the hypothesis that myocarditis produced by parasite infection alters the natriuretic peptide system by investigating the behavior of plasma ANF during the acute and chronic stages of T. cruzi infection in rats. Sprague-Dawley rats were infected with T. cruzi clone Sylvio-X10/7. Cardiac morphology showed damage to myocardial cells and lymphocyte infiltration in the acute phase; and fibrosis and cell atrophy in the chronic period. Plasma ANF levels (radioimmunoassay) were significantly higher in acute (348 ± 40 vs. 195 ± 36 pg/ml, P < 0.05, n = 17) and chronic T. cruzi myocarditis (545 ± 81 vs. 229 ± 38 pg/ml, P < 0.001, n = 11) than in their respective controls (n = 10 and 14). Rats in the chronic phase also showed higher levels than rats in the acute phase (P < 0.01). The damage of myocardial cells produced by the parasite and the subsequent inflammatory response could be responsible for the elevation of plasma ANF during the acute period of T. cruzi infection. The highest plasma ANF levels found in chronically infected rats could be derived from the progressive failure of cardiac function.

Cysticercoides menidiae Chandler, 1935, described as a metacestode of an unknown dilepidid cestode from the intestinal wall and mesenteries of the silversides Menidia menidia (Pisces: Atherinidae), from Galveston Bay, Texas, was found to be conspecific with Ascodilepis transfuga (Krabbe, 1869), a tapeworm described from the spoonbill, Platalea ajaja Linnaeus (syn. Ajaja ajaja), from Brazil. Consequently, C. menidiae becomes a junior synonym of A. transfuga.

We developed a method for the in vitro production of mature Plasmodium vivax ookinetes. Gametocytemic blood was collected from 98 P. vivax-infected patients reporting to malaria clinics in Maesod and Maekasa Districts, Tak Province, Thailand. Briefly, gametogenesis was induced using xanthurenic acid and parasites were separated by density gradient centrifugation and then cultured in RPMI-1640, pH 7.8–8.2. At the same time that blood was collected, 200 Anopheles dirus mosquitoes were allowed to feed on each patient. Mosquito midguts were removed 2–36 hr postfeeding, and gut contents were smeared onto glass slides, as were cultured samples from varying time points. Slides were stained with Giemsa, and the in vitro and mosquito development of ookinetes compared. Mature ookinetes were produced in 48.0% (47/98) of in vitro cultures, with a total yield ranging from 10 to 248,500 (x̄ = 15,523, median = 600) ookinetes produced per 5 ml blood. The temporal development and the morphology of the P. vivax ookinetes produced in vitro was similar to that observed in the A. dirus mosquitoes. The method that we describe is simple, can be used at remote sites without sophisticated equipment, and yields high numbers of clean ookinetes. This method of producing mature P. vivax ookinetes will be a useful tool for studies on ookinetes in P. vivax endemic regions.

One-hundred and eighty yellow wagtails Motacilla flava belonging to 3 subspecies (Motacilla flava feldegg, Motacilla flava flava, Motacilla flava thunbergi) were caught during the spring migration in south Kazakhstan and investigated by microscopic examination of stained blood smears. Haemoproteus anthi, Haemoproteus motacillae, Leucocytozoon fringillinarum, Leucocytozoon majoris, Plasmodium relictum, Plasmodium polare, Atoxoplasma sp., Trypanosoma sp., and microfilariae were identified. The overall prevalence of infection was 47.8%. Prevalences of Haemoproteus spp. (27.2%), Plasmodium spp. (25.0%), Leucocytozoon spp. (8.9%), Atoxoplasma spp. (4.4%), Trypanosoma spp. (1.1%), and microfilariae (0.6%) were recorded. No differences were discernible in parasite fauna or intensities of infection between males and females or between different subspecies. However, prevalence of infection of Haemoproteus, Leucocytozoon, and Plasmodium spp. was different in different host subspecies. These differences can be explained by differences in geographical location of breeding areas of these birds.

DNA templates were extracted from isolates of Sarcocystis hominis-like cysts collected from cattle and water buffalo, as well as from Sarcocystis fusiformis cysts and Sarcocystis suihominis cysts. The 18S rRNA genes were amplified using DNA from a single cyst as the templates. Approximately 1,367–1,440 bp sequences were obtained. The sequence difference in isolates of Sarcocystis hominis-like cysts from water buffaloes, and isolates of S. hominis cysts from cattle were very low, only about 0.1%, much lower than the lowest value (1.7%) among different species. Combined with their morphological structure, these sequence data indicate that the 4 isolates from cattle and water buffalo might be the same species, i.e., S. hominis, suggesting that both cattle and water buffalo may serve as the intermediate hosts for this parasite. Apparently, this is the first report using a single cyst to do such work and is a useful way to distinguish the Sarcocystis cyst in an intermediate host that may be simultaneously infected by several different Sarcocystis species.

Sarcocystis miescheriana sarcocysts were identified in skeletal muscles of 9 (27%) of 33 swine slaughtered for human consumption. Sarcocysts were 144–180 μm × 20–38 μm in size. Ultrastructurally, the cyst wall resembled the type 10 sarcocyst wall. The villar protrusions (VP) were 3–4.5 μm long and 0.6–1.2 μm wide and had prominent longitudinally arranged microtubules extending from the VP tips to the granular layer (=ground substance). The parasitophorous vacuolar membrane with its underlying electron-dense layer (EDL) measured 25 nm in thickness. The base of the VP exhibited minute (0.42–0.87 μm) bulblike inpocketings. Each VP had 80–90 microtubules situated underneath the EDL. The granular layer was 0.5–1.2 μm thick, and contained hairlike microtubules continuous with those of the VP core. This is the first report of S. miescheriana in Philippine domestic pigs Sus scrofa.