Showing papers in "Journal of Parasitology in 2001"

Analysis of the systematic relationships among ticks of the genera rhipicephalus and boophilus (acari: ixodidae) based on mitochondrial 12s ribosomal dna gene sequences and morphological characters

Abstract: A portion of mitochondrial 12S rDNA sequences (337–355 base pairs) and 63 morphological characters of 36 hard-tick species belonging to 7 genera were analyzed to determine the phylogenetic relationships among groups and species of Rhipicephalus and between the genera Rhipicephalus and Boophilus. Molecular and morphological data sets were first examined separately. The molecular data were analyzed by maximum parsimony (MP), maximum likelihood, and neighbor-joining distance methods; the morphological data were analyzed by MP. After their level of congruence was evaluated by a partition homogeneity test, all characters were combined and analyzed by MP. The branches of the tree obtained by combining the data sets were better resolved than those of the trees inferred from the separate analyses. Boophilus is monophyletic and arose within Rhipicephalus. Boophilus species clustered with species of the Rhipicephalus evertsi group. Most of the clustering within Rhipicephalus was, however, consistent with previous c...

Interrelationships of the Platyhelminthes

Abstract: EARLY ORIGINS OF BASAL TAXA The Early Worm - Origins and Relationships of the Lower Flatworms Seth Tyler Contributions to the Phylogeny and Systematics of the Acoelomorpha Olga I. Raikova, Maria Reuter and Jean-Lou Justine The Nemertodermatida Kennet Lundin and Wolfgang Sterrer Phylogenetic Systematics of the Macrostomorpha Reinhard M. Rieger FREE-LIVING GROUPS The Proseriata Marco Curini-Galletti Molecular Taxonomy and Phylogeny of Tricladida Jaume Baguna, Salvador Carranza, Jordi Paps, Inaki Ruiz-Trillo and Marta Riutort Towards a Phylogenetic Classification and Characterisation of Dugesiid Genera (Platyhelminthes, Tricladida, Dugesiidae) - a morphological perspective Ronald Sluys SYMBIONTS AND PARASITES The Prolecithophora Ulf Jondelius, Michael Noren and Jan Hendleberg The Temnocephalida Lester R.G. Cannon and Boris I. Joffe Phylogenetic Relationships of the Monogenoidea Walter A.Boeger and Delane C. Kritsky The Gyrocotylidea, Amphilinidea and the Early Evolution of Cestoda Willi E.R. Xylander Phylogeny Among the Orders of the Eucestoda (Cercomeromorphae): Integrating Morphology, Molecules and Total Evidence Eric P. Hoberg, Jean Mariaux and Dan R. Brooks Cestode Systematics in the Molecular Era Jean Mariaux and Peter D. Olsen Interrelationships Among Tetraphyllidean and Lecanicephalidean Cestodes Janine N. Caira, Kirsten Jensen and Claire J. Healy The Aspidogastrea, an Archaic Group of Platyhelminthes Klaus Rohde The Digenea Thomas H. Cribb, Rodney A.Bray, D. Timothy J. Littlewood, Sylvie P. Pichelin, Elizabeth A. Herniou Molecular Phylogeny of the Suborder Plagiorchiata and its Position in the System of Digenea Vasyl V. Tkach, Jan Pawlowski, Jean Mariaux and Zdzislaw Swiderski The Schistosomatidae: Advances in Phylogenetics and Genomics Scott D. Snyder, Eric S. Loker, David A. Johnston and David Rollinson CHARACTERS AND TECHNIQUES Protonephridia as Phylogenetic Characters Klaus Rohde 20. Insights from Comparative Spermatology in the "Turbellarian" Rhabdocoela Nikki A. Watson Spermatozoa as Phylogenetic Characters for the Platyhelminthes Jean Lou-Justine Comparative Neurobiology of the Platyhelminthes Maria Reuter and David W. Halton The Use of Life Cycle Characters in Studies of the Evolution of Cestodes Ian Beveridge Embryology and Developmental Genes as Clues to Flatworm Relationships Maximilian J. Telford Small Subunit rDNA and the Platyhelminthes: Signal, Noise, Conflict and Compromise D. Timothy J. Littlewood and Peter D.Olson Flatworm Phylogeneticist: Between Molecular Hammer and Morphological Anvil Boris I. Joffe and Elena E. Kornakova Towards a Phylogenetic Supertree of the Platyhelminthes Mark Wilkinson, Joseph L. Thorley, D. Timothy J. Littlewood and Rodney A. Bray

Critical evaluation of five methods for quantifying chewing lice (Insecta: Phthiraptera).

Abstract: Five methods for estimating the abundance of chewing lice (Insecta: Phthiraptera) were tested. To evaluate the methods, feral pigeons (Columba livia) and 2 species of ischnoceran lice were used. The fraction of lice removed by each method was compared, and least squares linear regression was used to determine how well each method predicted total abundance. Total abundance was assessed in most cases using KOH dissolution. The 2 methods involving dead birds (body washing and post- mortem-ruffling) provided better results than 3 methods involving live birds (dust-ruffling, fumigation chambers, and visual examination). Body washing removed the largest fraction of lice ( .82%) and was an extremely accurate predictor of total abundance (r 2 5 0.99). Post-mortem-ruffling was also an accurate predictor of total abundance ( r2 $ 0.88), even though it removed a smaller proportion of lice (,70%) than body washing. Dust-ruffling and fumigation chambers removed even fewer lice, but were still reasonably accurate predictors of total abundance, except in the case of data sets restricted to birds with relatively few lice. Visual examination, the only method not requiring that lice be removed from the host, was an accurate predictor of louse abundance, except in the case of wing lice on lightly parasitized birds.

Cryptosporidium canis n. sp. from domestic dogs

Abstract: Oocysts of Cryptosporidium, from the feces of a naturally infected dog and from an HIV-infected human, were identified as the previously reported canine genotype of Cryptosporidium parvum, hereafter referred to as Cryptosporidium canis n. sp. Also among the oocysts from the dog, a trace amount of C. parvum bovine genotype was detected. Cryptosporidium canis oocysts from both the dog and human were infectious for calves. Oocysts excreted by calf 1 (dog source) were approximately 90% C. canis and 10% C. parvum, whereas those excreted by calf 3 (human source) were 100% C. canis. Oocysts from calf 1 infected calf 2 resulting in excretion by calf 2 of oocysts ∼90% C. parvum and 10% C. canis. Oocysts of C. canis were not infectious for BALB/c neonatal mice or immunosuppressed C57 juvenile mice, although all control mice became infected with the C. parvum Beltsville isolate. Oocysts of C. canis from calf 1 and the human were structurally indistinguishable from oocysts of the C. parvum Beltsville isolate (bovine)...

Cultural and physiological observations on Trypanosoma rhodesiense and Trypanosoma gambiense.

Abstract: The cultivation of the trypanosomes of the brucei group is generally conceded to be much more difficult than that of the members of the lewisi group. While the latter have been cultivated in a variety of media and have been studied to some extent from the standpoint of their nutritional requirements and metabolic activities (Lwoff, 1940; von Brand, Johnson, and Rees, 1946; Chang, 1948), the cultivation of the former has been less successful, and therefore very little physiological information is available concerning them. Reichenow (1937b) stated that the addition of sugar did not improve his medium for the cultivation of the pathogenic trypanosomes. von Brand and Johnson (1947) found that the respiration of the proventricular form of T. gambiense was sensitive to cyanide. This is in contrast to that of its bloodstream form. Three types of media have given some measure of success in the cultivation of the pathogenic African trypanosomes. On blood agar media they grow either in the water of condensation (Novy and McNeal, 1904; Thomson and Sinton, 1912), or form colonies on the surface of the agar (Weinman, 1946). In liquid media (von Razgha, 1929; Reichenow, 1932, 1934; Brutsaert and Henrard, 1938) they aggregate commonly on the surface of the settled red cells. Slightly more viscous media were developed by Ponselle (1924) and Weinman (1944). They did not indicate where growth occurs in this type of medium. Most investigators use human blood as the blood of choice in the preparation of their media. Those who have used animal blood (Thomson and Sinton, 1912; Reichenow, 1932; Ponselle, 1924; Prates, 1928) did not present data which indicate whether such blood will sustain subcultivation for an indefinite period. In the first section of this paper we describe a diphasic blood agar medium which incorporates a number of features from the above media. It is less difficult to prepare than Weinman’s (1946) medium which it resembles in several respects. The remarkable intensity of sugar consumption by the bloodstream form of the pathogenic African trypanosomes (Yorke, Adams, and Murgatroyd, 1929; von Brand, 1933; Chen and Geiling, 1945; von Brand and Tobie, 1948) suggested the desirability of quantitative studies on sugar utilization by culturestages of these species. The data concerning this point, as well as data on the ammonia production, are summarized in the second section of this paper. 1. CULTURAL OBSERVATIONS Media employed

First Isolation of Neospora caninum From the Feces of a Naturally Infected Dog

Abstract: Neospora caninum is a major cause of abortion in cattle worldwide. Cattle become infected with N. caninum by ingesting oocysts from the environment or transplacentally from dam to fetus. Experimentally, dogs can act as definitive hosts, but dogs excrete few oocysts after ingesting tissue cysts. A natural definitive host was unknown until now. In the present study, N. caninum was isolated from the feces of a dog. Gerbils (Meriones unguiculatus) fed feces from the dog developed antibodies to N. caninum in the Neospora caninum agglutination test, and tissue cysts were found in their brains. Neospora caninum was isolated in cell culture and in gamma-interferon gene knockout mice inoculated with brain homogenates of infected gerbils. The DNA obtained from fecal oocysts of the dog, from the brains of gerbils fed dog feces, and from organisms isolated in cell cultures inoculated with gerbil brains was confirmed as N. caninum. The identification of N. caninum oocyst by bioassay and polymerase chain reaction demonstrates that the dog is a natural definitive host for N. caninum.

Phylogeny of Steinernema travassos, 1927 (Cephalobina: Steinernematidae) inferred from ribosomal DNA sequences and morphological characters

Abstract: 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. Nematodes in Steinernema Travassos, 1927 (Steinernemati-

Oocyst Shedding by Cats Fed Isolated Bradyzoites and Comparison of Infectivity of Bradyzoites of the VEG Strain Toxoplasma gondii to Cats and Mice

Abstract: Infectivity of bradyzoites of the VEG strain of Toxoplasma gondii was compared in cats and mice. For this, tissue cysts were separated from brains of infected mice using a Percoll gradient, and bradyzoites were released by incubation in acidic pepsin solution. After filtration through a 3-µm filter, bradyzoites were counted and diluted 10-fold in RPMI tissue culture medium. Dilutions estimated to have 1, 10, 100, and 1,000 bradyzoites were fed to cats and inoculated into mice, orally or subcutaneously (s.c.). Three experiments were performed. In experiment 1, 2 of 2 cats fed 1,000 bradyzoites, 1 of 2 cats fed 100 bradyzoites, 1 of 4 cats fed 10 bradyzoites, and 1 of 4 cats fed 1 bradyzoite shed millions of oocysts; 1,000 bradyzoites were infective to all 4 inoculated mice s.c. but not to 4 mice inoculated orally, and 100 bradyzoites were infective to 2 of 4 mice injected s.c. but not to 4 mice inoculated orally. All 16 mice (8 oral, 8 s.c.) injected with 1 or 10 bradyzoites were negative for T. gondii. In...

Testosterone depresses innate and acquired resistance to ticks in natural rodent hosts: a force for aggregated distributions of parasites

Abstract: The effects of testosterone on acquired resistance to ticks, Ixodes ricinus, in their natural rodent hosts (voles, Clethrionomys glareolus, and wood-mice, Apodemus sylvaticus) were investigated by manipulating testosterone levels and exposing the hosts to repeated tick infestations. Testosterone reduced both innate and acquired resistance to tick feeding. During primary infestations, attachment rates were higher on rodents with high testosterone levels than on oil-implanted controls. Successive infestations on voles were accompanied by a decrease in tick feeding success and survival, but this decrease was significantly greater in ticks fed on control voles than in those fed on voles implanted with testosterone. When reduced feeding success had been induced, either by vaccination with tick salivary gland extract or by 4 successive infestations, implantation with testosterone partially reversed the acquired resistance. These effects of testosterone will generate heterogeneities within the rodent population with respect to tick distribution and microparasite transmission. The lowest innate and acquired resistance to tick feeding occurs in that fraction of the host population, i.e., sexually active males, most actively involved in the transmission of both Babesia microti and Borrelia burgdorferi s.l.

Killing of schistosoma mansoni sporocysts by hemocytes from resistant biomphalaria glabrata: role of reactive oxygen species

Abstract: The fate of Schistosoma mansoni (Trematoda) sporocysts in its molluscan host Biomphalaria glabrata (Gastropoda) is determined by circulating phagocytes (hemocytes). When the parasite invades a resistant snail, it is attacked and destroyed by hemocytes, whereas in a susceptible host it remains unaffected. We used 3 inbred strains of B. glabrata: 13-16-R1 and 10-R2, which are resistant to the PR-1 strain of S. mansoni, and M-line Oregon (MO), which is susceptible to PR-1. In an in vitro killing assay using plasma-free hemocytes from these strains, the rate of parasite killing corresponded closely to the rate by which S. mansoni sporocysts are killed in vivo. Hemocytes from resistant snails killed more than 80% of S. mansoni sporocysts within 48 hr, whereas sporocyst mortality in the presence of hemocytes from susceptible snails was <10%. Using this in vitro assay, we assessed the involvement of reactive oxygen species (ROS) produced by resistant hemocytes, during killing of S. mansoni sporocysts. Inhibition...

Transmission of Hepatozoon canis to Dogs by Naturally-Fed or Percutaneously-Injected Rhipicephalus sanguineus Ticks

Abstract: Hepatozoon canis is an apicomplexan protozoan parasite of dogs, prevalent in Asia, Africa, and southern Europe. Experimental transmission of H. canis to dogs was performed with laboratory-reared Rhipicephalus sanguineus nymphs that fed on a naturally infected dog or were percutaneously injected with canine blood containing H. canis gamonts. Dogs were inoculated by oral ingestion of adult ticks containing H. canis oocysts. Transstadial transmission of H. canis was recorded, whereas transovarial transmission could not be demonstrated. Oocysts were detected in 85% of the adult ticks that had engorged as nymphs on an infected dog and in 61% of the adult ticks resulting from nymphs injected percutaneously with blood from the same dog. Nine of 12 dogs (75%) inoculated with naturally fed or percutaneously injected ticks became parasitologically positive, and all showed seroconversion. Meronts were initially detected in the bone marrow 13 days postinoculation and gamonts 28 days after infection. The variation in ...

Penetration of Erythrocytes by Merozoites of Mammalian and Avian Malarial Parasites

Abstract: Entry of merozoites of Plasmodium berghei yoeli and of P. gallinaceum into erythrocytes has been elucidated by electron microscopy. Merozoites approach host cells with the conoid leading the way. At the point of contact between the anterior pole of the parasite and the host cell a focal depression of the red cell membrane forms, which deepens as the merozoite advances. The continuity of the host cell membrane is not disrupted. With deeper invagination of the red cell membrane the resulting cavity conforms to the shape of the merozoite. The site of initial parasite contact forms a relatively constricted orifice through which the posterior portion of the parasite passes. Later the edges of this orifice fuse and the parasite now lies in a vacuole inside the host cell. At this stage the merozoite undergoes a transformation and dedifferentiation. The pellicle loses the characteristic thick inner membrane. The parasite becomes rounded and the conoid and paired organelles are no longer discernible. Trophozoite d...

Isolation and Characterization of Two Parasitic Protozoa from a Pacific Harbor Seal (Phoca Vitulina Richardsi) With Meningoencephalomyelitis

Abstract: 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 sequ...

Phylogenetic and biogeographical relationships among some holarctic frog lung flukes (digenea: haematoloechidae)

Abstract: A phylogenetic study of 8 North American and European species of frog lung flukes belonging to Haematoloechus was conducted using approximately 850 to 1,000 bases of the internal transcribed spacer region (ITS 1 + 5.8S + ITS 2) and 1,250 bases of the large subunit (LSU) of the nuclear ribosomal DNA. Adequate phylogenetic resolution could not be obtained from 5.8S or ITS 2 data. Analysis of ITS 1 data produced 2 equally parsimonious trees that differed only in the position of Haematoloechus breviplexus relative to H. medioplexus and H. varioplexus. Single, identical trees were produced by analysis of both LSU sequence data and a data set comprised of all ITS and LSU data. All trees demonstrated 3 distinct evolutionary lineages within the Holarctic Haematoloechus examined. The results confirmed the taxonomic validity of H. abbreviatus and demonstrated that the presence or absence of extracecal uterine loops is not a character meaningful to the recognition of evolutionary lineages or differentiation of gener...

The flagellates : unity, diversity and evolution

Abstract: 1. The Flagellates: Historical Perspectives 2. The Flagellate Condition 3. Mechanisms of Flagellar Propulsion 4. The Flagellate Cytoskeleton: Introduction of a General Terminology for Microtubular Flagellar Roots in Protists 5. Molecular Aspects of the Centrin Based Cytoskeleton in Flagellates 6. The Cell Surface of Flagellates 7. Sensory Mechanisms: Phototaxes and Light Perceptions in Algae 8. Trophic Strategies 9. Amitochondriate Flagellates 10. Adaptations to Parasitism among Flagellates 11. Flagellates and the Microbial Loop 12. Functional Diversity of Heterotrophic Flagellates in Aquatic Ecosystems 13. Geographic Distribution and Diversity of Free Living Heterotrophic Flagellates 14. Cosmopolitan Haptophytes Flagellates and their Genetic Links 15. Occurrence and Loss of Organelles 16. Flagellate Phylogeny: an Ultrastructural Approach 17. Flagellate Megaevolution: the Basis for Eukaryote Diversification, Plymouth marine Lab, UK, Sharon McReady, John Raven, University of Dundee, UK, Michael Holwill, King's College London, UK, Helen Taylor, Ojvind Moestrup, University of Copenhagen, Denmark, Peter Hart, Jeff Salisbury, Mayo Clinic Foundation, USA, Burkhard Becker, Botanisched Institut, Germany, Hiroshi Kawai, Kobe University, Japan, Michael Sleigh, University of Southampton, UK, Hartmut Arndt, University of Cologne, Germany, Johanna Laybourn-Parry, Jackie Parry, University of Lancaster, UK, David Patterson, University of Sydney, Australia, Won Je Lee, Linda Medlin, Alfred Wegener Institute, Germany, Gut Brugerolle, Universite Blaise Pascal de Clemont-Ferrand, France, Keith Vickerman, University of Glasgow, UK, Mark Farmer, University of Georgia, USA, Marshall Darley, Serguei Karpov, University of St. Petersburg, Russia, Tom Cavalier-Smith, University of Oxford, UK,

Involvement of Nitric Oxide in Killing of Schistosoma Mansoni Sporocysts by Hemocytes From Resistant Biomphalaria Glabrata

Abstract: 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 Nω-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...

Phylogeny of Nuclear Small Subunit rRNA genes of Hemogregarines Amplified With Specific Primers

Abstract: 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.

Pathogenicity of entomopathogenic fungi to different developmental stages of rhipicephalus sanguineus (acari: ixodidae)

Abstract: The pathogenicity of 4 species of entomopathogenic fungi (Hyphomycetes species: Beauveria bassiana, Metarhizium anisopliae, Metarhizium flavoviride, and Paecilomyces fumosoroseus) to various developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae) ticks was compared under laboratory conditions. The most virulent isolate, M. anisopliae-108, caused 92–96% mortality to unfed larvae and nymphs on day 7 postinfection (PI) and 100% mortality to unfed adults and engorged females on day 21 PI. The pathogenicity of M. anisopliae-108 to engorged larvae and nymphs was lower—82.6 and 60%, respectively. All tested B. bassiana, M. flavoviride, and P. fumosoroseus isolates were significantly less virulent (P < 0.05) or avirulent toward most life stages of R. sanguineus. The M. anisopliae and M. flavoviride isolates also prevented or reduced the ability of the ticks to lay eggs several days before their deaths. Female ticks infected by the fungi achieved only 11.3–60.8% of their egg-laying capacity compared wit...

Prevalence of Neospora caninum infection in dogs from beef-cattle farms, dairy farms, and from urban areas of Argentina.

Abstract: Prevalence of anti-Neospora caninum antibodies was de- termined in sera of 320 dogs from Argentina using the indirect fluores- cent 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 expo- sure of N. caninum infection in dogs. Neospora caninumis an important cause of mortality in dogs and cattle in many countries including Argentina (Dubey and Lindsay, 1996; Dubey, 1999; Venturini et al., 1999; Lindsay and Dubey, 2000). Until recently, vertical transmission from prevalence of antibodies (IFAT, $ 1:50) was higher in dogs from beef (54.2% of 35) and dairy (48% of 125) farms than from dogs from urban areas (26.2% of 160); the differences were statistically significant (P , 0.001). Of the 153 urban dogs, the seroprevalence in males (28.1% of 71) was not sta- tistically different ( P 5 0.86) from that in females (25.6% of 82). Of the 153 dogs with breed data, seroprevalence was 23.9% of 117 in purebred dogs versus 36.1% of 36 crossbred dogs (not significant P 5 0.21). The antibody titers in dogs with clinical signs were not different from those in dogs without reported clinical signs. Prevalence of antibodies increased with age of the dog with seroprevalence of: 13% of 46, #12-mo- old; 12.9% of 31, 13-24-mo-old; 34.3% of 32, 25-48-mo-old dogs; and 45.4% of 44, 49-mo or older dogs (significant P 5 0.001). Prevalence of N. caninum antibodies was significantly higher (P , 0.001) in dogs .12 mo of age (60.9% of 87) versus #12- mo-old dogs (9.6% of 31) from dairy farms. Although the num- ber of dogs from beef farms was low, similar trends were ap- parent; antibodies to N. caninum were found in 2 of 9 (22%), 12-mo-old or younger dogs versus 17 of 28 (60.7%) dogs older than 12 mo from the beef farms. Overall, prevalence in 12-mo- old or younger dogs (12.7% of all dogs of known age) was significantly lower (P 5 0.001) than in dogs older than 12 mo (47.7% of 222).

Monogeneans in introduced and native cichlids in México: evidence for transfer.

Abstract: We examined 2 cichlid fish species native to Mexico, Cichlasoma callolepis and C. fenestratum, and 2 introduced African cichlids, Oreochromis aureus and O. niloticus, from 3 localities in southeastern Mexico 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 Af...

Sylvatic and domestic Trichinella spp. in wild boars; infectivity, muscle larvae distribution, and antibody response.

Abstract: Thirty-six wild boars were inoculated with Trichinella spiralis, Trichinella nativa, Trichinella britovi, Trichinella pseudospiralis (USSR), T. pseudospiralis (USA), T. pseudospiralis (AUST), Trichinella murrelli, Trichinella T6, and Trichinella nelsoni. The wild boars were killed at 5 and 10 wk postinoculation (PI), and the number of muscle larvae per g (lpg) of tissue was determined for 18 muscles or muscle groups. Five weeks PI, all Trichinella genotypes had established as muscle larvae, but their infectivity varied widely: T. spiralis established in high numbers (mean = 296 lpg), T. britovi, T. nelsoni, and 1 of the T. pseudospiralis genotypes (AUST) in moderate numbers (mean = 53–74 lpg), whereas the remaining genotypes were poorly infective (mean = 2–16 lpg). Because of considerable weight gain of the wild boars, an estimated total larval burden (live weight × lpg) was calculated for each animal. The total larval burden did not change significantly over time for T. spiralis, T. murrelli, T. britovi,...

Effect of sex, size, and age of commensal rat hosts on the infestation parameters of their ectoparasites in a rural area of Egypt.

Abstract: The present study was carried out in the Bilbeis area, Sharqiya Governorate, Egypt. A total of 127 male and 115 female black rats Rattus rattus and 124 male and 153 female Norway rats R. norvegicus was collected during the study period. A total of 20,643 and 40,997 ectoparasites was recovered from R. rattus and R. norvegicus, respectively. Three common mite species were recovered from both rat hosts: Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts: Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only louse species that infested both rat hosts. Rats that lived more than 12 mo formed about 24 and 14% of the populations of the black and Norway rats, respectively. The prevalences and general indices of many ectoparasites were significantly higher on males than on females of both rat hosts. Seasonal differences in prevalences and general indices of many ectoparasites were recorded between the 2 sexes of both rat species. Prevalences and general indices of most ectoparasites on both rat species showed a tendency to increase with increasing size and age of rat hosts. The type and degree of correlation between prevalences and general indices on the one hand and each of body size and age on the other hand differed among the species of ectoparasites.

Infection behavior of the rhabditid nematode phasmarhabditis hermaphrodita to the grey garden slug deroceras reticulatum

Abstract: Infection behavior of the rhabditid nematode Phasmarhabditis hermaphrodita to the grey garden slug Deroceras reticulatum was studied. The dauer (enduring or nonaging) juveniles of P. hermaphrodita invade D. reticulatum within 8–16 hr following external exposure, with the posterior mantle region containing the shell cavity serving as the main portal of entry. The dauer juveniles can recover, multiply, and produce new dauer juveniles in the slug and slug feces homogenates, but not in the soil extract. These results demonstrate that P. hermaphrodita is a facultative parasite of the slug and can complete its life cycle under nonparasitic conditions associated with the host. Although the juvenile and adult nematodes can kill the slug if injected into the shell cavity of the host, only the dauer juvenile can serve as an infective stage in the natural environment.

Persistent infection of myxobolus cerebralis, the causative agent of salmonid whirling disease, in tubifex tubifex

Abstract: The objective of this study was to quantify and determine the periodicity in the release of the triactinomyxon (TAM) stage of Myxobolus cerebralis, the causative agent of salmonid whirling disease, by its aquatic oligochaete host Tubifex tubifex. For this, 24 individual T. tubifex (infected as a group at 15 C) were examined daily for the release of M. cerebralis TAMs, and the number of waterborne TAMs released by each worm was quantified. The duration of the infection in these worms was also monitored using a polymerase chain reaction (PCR) diagnostic test. TAMs were first released 74 days postexposure (PE) and continued to be released until 132 days PE. During this period, each worm released on average, 1.5 3 10 3 waterborne TAMs 12 times; however, no pattern or periodicity was noted. The results of the PCR diagnostic tests conducted at 5, 7, 9, and 15 mo PE were positive, and the persistent infection was confirmed at 606 days PE (approximately 20 mo) when the remaining worms began releasing TAMs again. Similar results were observed in naturally infected T. tubifex, indicating that these worms remain infected for the duration of their natural lifespan and are capable of shedding viable TAMs, in temporally separate periods. These findings open the possibility of a seasonal periodicity in TAM release by T. tubifex. Whirling disease has been implicated in the recent decline of wild trout populations in several western states (Nickum, 1999). For example, in December 1994 it was reported that whirling disease was responsible for the death of over 90% of the wild rainbow trout in the Madison River in Montana (Rognlie and Knapp, 1998). The causative agent of whirling disease is the myxosporean parasite Myxobolus cerebralis.This parasite caus- es varying clinical signs in fish ranging from a whirling behav- ior, for which the disease is named, to blackened caudal regions and severe skeletal deformities. Heavy infections in young fish often result in death. The parasite can infect numerous species of salmonid fishes; however, rainbow trout are the most sus- ceptible to disease, followed in order of decreasing susceptibil- ity by sockeye salmon, golden trout, cutthroat trout, brook trout, steelhead, chinook salmon, atlantic salmon, and brown trout (O'Grodnick, 1979; Hoffman, 1990).

Sarcocystis neurona infections in sea otter (Enhydra lutris): Evidence for natural infections with sarcocysts and transmission of infection to opossums (Didelphis virginiana)

Abstract: Although Sarcocystis neurona has been identified in an array of terrestrial vertebrates, recent recognition of its capacity to infect marine mammals was unexpected. Here, sarcocysts from 2 naturally infected sea otters (Enhydra lutris) were characterized biologically, ultrastructurally, and genetically. DNA was extracted from frozen muscle of the first of these sea otters and was characterized as S. neurona by polymerase chain reation (PCR) amplification followed by restriction fragment length polymorphism analysis and sequencing. Sarcocysts from sea otter no. 1 were up to 350 μm long, and the villar protrusions on the sarcocyst wall were up to 1.3 μm long and up to 0.25 μm wide. The villar protrusions were tapered towards the villar tip. Ultrastructurally, sarcocysts were similar to S. neurona sarcocysts from the muscles of cats experimentally infected with S. neurona sporocysts. Skeletal muscles from a second sea otter failed to support PCR amplification of markers considered diagnostic for S. neurona b...

Helminth communities of green frogs Rana clamitans Latreille, from southwestern Michigan.

Abstract: A total of 239 green frogs Rana clamitans, collected between June 3 and August 27, 1998 from 6 locations in southwestern Michigan, was examined for helminths. Of the 26 helminth taxa found, the larval cestode Mesocestoides sp. had the highest mean intensity, followed by the larval trematode Fibricola sp. Of the helminths that mature in frogs, Haematoloechus varioplexus had the highest prevalence and Gorgodera amplicava had the highest mean intensity. Frogs from 118th Pond had the highest species richness (20), mean helminth species richness (5.2), and mean helminth abundance (153.7). Frogs from Constantine East had the highest mean helminth species diversity (0.8778) and evenness (0.6033), followed by frogs from 118th Pond. In all comparisons of mean helminth community species richness, abundance, diversity, and evenness, adult frogs had significantly higher or higher values than did juveniles at each location. Jaccard's coefficients of similarity for the helminth communities for location pairs ranged from 0.545 to 0.823. Nine and 2 core helminth taxa occurred at the local and regional levels, respectively. The differences in several helminth community measures in green frogs among locations stress the importance of local ecological conditions on helminth community structure.

Babesia leo n. sp. from lions in the Kruger National Park, South Africa, and its relation to other small piroplasms.

Abstract: Babesia leo, a small piroplasm isolated from lions in South Africa is described as a distinct species based on a phylogenetic analysis of the 18S rRNA gene. Intraerythrocytic trophozoite and merozoite stages of B. leo are morphologically indistinguishable from other small piroplasms of felids. Previous studies showed that B. leo was biologically and antigenically distinct from B. felis, which is known to infect wild and domestic felids in South Africa. Molecular characterization showed strong support for the phylogenetic seperation of B. leo as a distinct species from B. felis and other felid piroplasms. Phylogenetic analysis also showed that Babesia microti and all of the felid piroplasms from Africa with known 18S rRNA gene sequences available, including B. leo, formed a single, separate clade, sister to the other babesial and theilerial piroplasm parasites.

Characterization of the oregon isolate of neospora hughesi from a horse

Abstract: Neospora hughesi was isolated in cell cultures inoculated with homogenate of spinal cord from a horse in Oregon. Tachyzoites of this Oregon isolate of N. hughesi were maintained continuously by cell culture passage and tachyzoites were infective to immunosuppressed mice. Gamma interferon gene knockout (KO) mice injected with tachyzoites developed fatal myocarditis and numerous tachyzoites were seen in lesions. Gerbils (Meriones unguiculatus) inoculated with tachyzoites developed antibodies (≥1:500) as indicated by the Neospora caninum agglutination test but did not develop clinical signs, and Neospora organisms were not demonstrable in their tissues. Tissue cysts were not found in gerbils, nude mice, KO mice, immunosuppressed outbred Swiss Webster mice, or BALB/c mice injected with the Oregon isolate of N. hughesi. Ultrastructurally, tachyzoites of the Oregon isolate from the myocardium of infected KO mice and from cell culture were similar to N. caninum tachyzoites. Western blot analysis using NcSAG1 and...

Naturally-Occurring Neospora caninum Infection in an Adult Sheep and Her Twin Fetuses

Abstract: Neospora caninum tissue cysts were found in the brains of surgically delivered twin fetuses at 119 days of gestation. In the brains of both fetuses, there was an inflammatory reaction involving perivascular cuffings of mononuclear cells, glial nodules. The dam of these fetuses died because of metritis. Histopathological examination of the ewe revealed N. caninum tissue cysts and focal gliosis with mononuclear cell cuffings. A N. caninum-specific DNA fragment was detected in a brain homogenate of the ewe by the polymerase chain reaction method. This is the first report of N. caninum infection in twin ovine fetuses and in an adult sheep.

Importance of gender and sex hormones in regulation of susceptibility of the small intestine to peroral infection with Toxoplasma gondii tissue cysts.

Abstract: This study was performed to investigate whether the gender and sex hormones play a role in susceptibility of the small intestine of mice to peroral infection with Toxoplasma gondii tissue cysts. Female animals died significantly earlier than males, and early mortality of females was associated with greater numbers of tachyzoites and severe necrosis in their small intestines. Treatment of female mice with testosterone resulted in markedly reduced intestinal parasite numbers and pathology. Thus, the gender and sex hormones are important factors for determining susceptibility of the small intestine to T. gondii infection.