Showing papers in "Journal of Parasitology in 1998"
TL;DR: Oocysts remained infective up to 54 mo at 4 C and there was no loss of infectivity in oocysts stored for 106 days at -5 C and at -10 C and for 13 mo at 0 C and the survival of sporulated Toxoplasma gondii oocyst in water for various periods was investigated.
Abstract: The survival of sporulated Toxoplasma gondii oocysts in water at -10 C to 70 C for various periods was investigated. Infectivity of T. gondii was tested by bioassay in mice. There was no marked loss of infectivity of oocysts stored at 10 C, 15 C, 20 C, and 25 C for 200 days, whereas there was a 100-fold loss of infectivity of oocysts stored at 30 C for 107 days. Oocysts stored at 35 C were infective for 32 days but not 62 days, at 40 C oocysts were infective for 9 days but not 28 days, at 45 C, oocysts were infective for 1 day but not 2 days, at 50 C oocysts were infective for 1 hr but not 2 hr. At 55 C and 60 C oocysts were rendered noninfective in 2 and 1 min, respectively. Oocysts remained infective up to 54 mo at 4 C and there was no loss of infectivity in oocysts stored for 106 days at -5 C and at -10 C and for 13 mo at 0 C.
250 citations
TL;DR: Findings provide a guide for estimating the potential duration of oocyst infectivity within a wide range of environmental temperatures and demonstrate the relationship between amylopectin concentration and infectivity.
Abstract: Oocysts of Cryptosporidium parvum obtained from calves were cleaned of fecal debris by density gradient centrifugation and suspended in deionized water in microcentrifuge tubes. The tubes were placed in circulating water baths at temperatures of - 10, -5, 0. 5. 10. 15, 20. 25. 30, of 35 C. and 2 tubes were removed from each water bath 1, 2, 4, 8, 12, 16, 20, and 24 wk later. Oocysts from I tube were administered at the rate of 1.5 × 10 5 oocysts per mouse to 2 litters of neonatal BALB/c mice and were considered infective when developmental stages were found in histologic sections of mouse gut and/or a positive polymerase chain reaction (PCR) was obtained for C. parvum DNA in mouse ileum. The second tube was held at -70 C until tubes from all time periods were available, then oocysts within the tubes were assayed for amylopectin concentration. Oocysts held at - 10 C were infectious up to I wk of storage, and those held at -5 C were infectious up to 8 wk of storage, as determined by PCR but not histology. Oocysts held at 0, 5. 10, 15, and 20 C were still infectious after 24 wk of storage. By microscopic examination of mouse tissue, oocysts held at 20 C infected only I of 10 mice after 24 wk of storage, and the number of developmental stages began declining after 4 wk of storage; those held at 25 and 30 C each produced infections up to 12 wk after storage in 1 of 10 mice with reduced numbers of developmental stages beginning 4 wk after storage. Those held at 35 C produced light infections in 2 of 10 mice only up to I wk of storage, Amylopectin concentration decreased with increasing length of storage time or temperature. These findings provide a guide for estimating the potential duration of oocyst infectivity within a wide range of environmental temperatures and demonstrate the relationship between amylopectin concentration and infectivity.
199 citations
TL;DR: The basal position of the Caryophyllidea (and Spathebothriidea) is confirmed, and hence the plesiomorphic condition of monozoism, and the monophyly of the "higher tetrafossates" provided the nippotaeniids and tetrabothriids are included.
Abstract: Evolutionary relationships among the orders of the Eucestoda were examined based on data derived from partial sequences of genes encoding 18S rRNA. Considered in this study were 47 species-level taxa, including 1 from Monogenea, 1 from Amphilinidea, both of which were used as outgroups, and 45 from 10 orders of Eucestoda. Parsimony analysis of 1.1 kbp of aligned fragments yielded 480 shortest trees (length 704; consistency index 0.41) the strict consensus of which shows the following relationships: (Monogenea, (Amphilinidea, (Caryophyllidea, (Spathebothriidea, (Trypanorhyncha, (Pseudophyllidea, (Tetraphyllidea, ((Diphyllidea, Proteocephalidea), ((Cyclophyllidea, Tetrabothriidea), Nippotaeniidea))))))))). The Tetraphyllidea, Pseudophyllidea (because of the Diphyllobothriidae), and Cyclophyllidea (because of the Mesocestoididae) were found to be paraphyletic. This tree is almost completely congruent with the most recent hypotheses based on characters derived from comparative morphology, ontogeny, and ultrastructural studies. The only discrepancies between these separate analyses were in the position of the Trypanorhyncha and Diphyllidea. Among the main conclusions corroborated here are the following: (1) the basal position of the Caryophyllidea (and Spathebothriidea), and hence the plesiomorphic condition of monozoism; (2) the monophyly of the "higher tetrafossates" provided the nippotaeniids and tetrabothriids are included; (3) the close relationship between the Tetrabothriidea and Cyclophyllidea; and (4) the paraphyly of the Tetraphyllidea. At lower taxonomic levels, structure could not be defined within Proteocephalidea; within the Cyclophyllidea, all families represented by several taxa (Hymenolepididae, Davaineidae, and Dilepididae) were found to be monophyletic, and Taeniidae may be the most basal family. Furthermore, the validity of the Gryporhynchidae is confirmed. and it is suggested that the Mesocestoididae should be excluded from the Cyclophyllidea.
181 citations
TL;DR: The ultrastructural, antigenic, and molecular data support distinction of N. hughesi as a new species, separate from N. caninum, the only recognized species in this genus.
Abstract: Neospora hughesi n. sp. was isolated from the central nervous system tissue of an adult equine (Equus caballus) from California. The tachyzoites are crescent-shaped, approximately 2 x 5 microm (1.8-3.0 x 4.0-7.0 microm), with characteristic apical complex structures consisting of an anterior polar ring, conoid, numerous rhoptries filled with a uniform electron-dense material, and 22 microtubules extending posteriorly from the polar ring. Comparison of N. hughesi to canine and bovine Neospora caninum isolates showed phenotypic differences in immunoreactive proteins. Molecular analysis of the small subunit ribosomal RNA gene revealed no differences in the nucleotide sequence between N. hughesi and N. caninum isolates examined. However, the internal transcribed spacer I region revealed 7 nucleotide base differences between N. hughesi and N. caninum isolates (CN1 and BPA1) analyzed in this study. The existence of nucleotide base differences in the internal transcribed spacer regions suggests that this region may be a genetic marker for discriminating species within the genus Neospora. The ultrastructural, antigenic, and molecular data support distinction of N. hughesi as a new species, separate from N. caninum, the only recognized species in this genus.
176 citations
TL;DR: Spermatozoon ultrastructure and spermiogenesis in the Eucestoda is compared to that of other parasitic Platyhelminthes, with emphasis on structures of phylogenetic interest.
Abstract: Spermatozoon ultrastructure and spermiogenesis are significant characters for phylogenetic inference. Sperm ultrastructure is reviewed from the literature in 56 species of Eucestoda. Data are available for 11 of the 12 orders of Eucestoda (Lecaniccphalidea excepted), but in some orders data are scarce and often limited to a single species. Spermiogenesis and sperm ultrastructure in the Eucestoda is compared to that of other parasitic Platyhelminthes, with emphasis on structures of phylogenetic interest. Not only the descriptions of sperm structure, but those of the process of spermiogenesis, are necessary to define characters. Synapomorphies based on sperm ultrastructure for the Eucestoda include the absence of a mitochondrion in mature sperm and the presence of a crested body. A proposed synapomorphy for the Cyclophyllidea + Tetrabothriidea is the twisting of the peripheral microtubules; the absence of intercentriolar body and the absence of striated roots in the spermatid may constitute additional synapomorphies for this assemblage. Absence of flagellar rotation during spermiogenesis is synapomorphic for the Cyclophyllidea, and absence of proximodistal fusion could be synapomorphic for a part of the Cyclophyllidea. Several other characters could be useful for understanding phylogeny within the Eucestoda. The polarity of these characters could in several cases be determined, but diagnoses for taxa or relationships based on synapomorphies cannot be specified unequivocally due to putative convergence. Such characters and their putative polarity include: (1) the number of axonemes in mature spermatozoon (plesiomorphic = 2: apomorphic = 1); (2) size and number of crested bodies (p = 1; a = several); and (3) angle of twisted microtubules; shape of nucleus (p = compact cord; a = crescent and annulus). Additional apomorphic attributes include (I) presence of a periaxonemal sheath (a putative synapomorphy for the Cyclophyllidea + Tetrabothriidea if reversals are postulated in certain cyclophyllideans): (2) presence of proteinaceous transverse walls; (3) presence of dense granules; and (4) shape of apical cones and posterior structures. Studies of sperm structure in the poorly known orders and additional comparative studies in the Cyclophyllidea are expected to provide new information for elucidation of phylogenetic relationships.
172 citations
TL;DR: 3 nonparametric estimators of species richness were tested and it was found that the bootstrap estimator provides a better, but conservative, estimate of true richness than observed richness and should be used to correct for inadequate host sampling.
Abstract: Comparisons of species richness between parasite component communities are often confounded by uneven sampling effort and the possibility that rare species have been missed from some component communities. The use of nonparametric estimators of species richness could potentially alleviate this problem by allowing the number of missing species to be extrapolated from the observed data. The performance of 3 estimators and their sensitivity to true species richness and the frequency of rare species, i.e., species with low prevalence, were tested using computer-simulated parasite communities. When the number of hosts examined in a sample is large, the observed species richness is an accurate estimate of true richness; no extrapolation is necessary even when rare species make up a large part of the community. At small sample sizes, observed species richness is a poor underestimate of true richness. The jackknife estimator and Chao's estimator both improve the estimate of species richness, but they are imprecise and can seriously overshoot the true richness value when the community includes many rare species. The bootstrap estimator. on the other hand, gives a better estimate than observed richness. Bootstrap estimates are also less variable and less likely to overestimate true richness, independently of how frequent rare species are in the community. This estimator provides a better, but conservative, estimate of true richness than observed richness and should be used to correct for inadequate host sampling. Data from natural communities suggest that the use of richness estimators is often justified, and that many parasite species may regularly escape detection.
169 citations
TL;DR: The sequential activation of Th1-type and Th2-type responses in murine cysticercosis would appear to favor progressively parasite reproduction, explaining the long time residence and the massive parasite intensity reached in chronic infections.
Abstract: In early stages of experimental murine cysticercosis caused by Taenia crassiceps, there is a clear but transient Th1-type immune response (characterized by high levels of interleukin [IL]-2, interferon-gamma, concanavalin A, and antigen specific response, delayed-type hypersensitivity, and immunoglobulin [Ig]G2a antibodies) that associates with a low rate of parasite reproduction. As time of infection progresses an energic and more permanent Th2-type response follows (characterized by high levels of IL-4, IL-6, IL-10, IgG2b, and IgG1 antibodies) that in turn associates with an increment in the rate of parasite reproduction. The sequential activation of Th1-type and Th2-type responses in murine cysticercosis would appear to favor progressively parasite reproduction, explaining the long time residence and the massive parasite intensity reached in chronic infections.
167 citations
TL;DR: It is demonstrated that host immunoglobulins and the transstadial molt by themselves are not necessary for eliminating B. burgdorferi from infected nymphal ticks.
Abstract: In some populations of the western black-legged tick, Ixodes pacificus, the prevalence of infection with Lyme disease spirochetes (Borrelia burgdorferi) in nymphal ticks exceeds those in adult ticks by 3-4-fold. Experiments were conducted to determine if the reduced spirochetal prevalence in adult ticks is due to the presence of anti-borrelial antibodies or to another borreliacidal factor in the blood of the western fence lizard, Sceloporus occidentalis, a primary host of subadult I. pacificus, or to loss of spirochetes as nymphal ticks molt to the adult stage. Ten lizards were each exposed to the feeding activities of 10 nymphs having a 78% prevalence of B. burgdorferi infection. Five of the lizards had been hyperimmunized first with 10(8) heat-killed spirochetes and 5 were seronegative to B. burgdorferi. After repletion and the transstadial molt, none of 62 resultant adult ticks from both groups of lizards was found to contain spirochetes. In contrast, 11 of 20 (55%) infected nymphs that had fed on 4 preimmune rabbits passed spirochetes to adult ticks. Taken together, these findings demonstrate that host immunoglobulins and the transstadial molt by themselves are not necessary for eliminating B. burgdorferi from infected nymphal ticks. A novel in vitro assay revealed that nearly all spirochetes placed in plasma or sera from lizards died in less than 1 hr, whereas many spirochetes injected into mouse plasma or sera survived for 72 hr. When spirochetes were put in lizard sera that had been preheated (100 C for 10 min) and allowed to cool, survival was extended to 72 hr. We conclude that the blood of S. occidentalis contains a thermolabile, borreliacidal factor, probably a protein, that destroys spirochetes in the midgut diverticula of feeding I. pacificus nymphs.
162 citations
TL;DR: It is demonstrated that parasite load is a fundamental measurement for evaluating disease induced by N. caninum and that a type 1 cytokine response may be necessary for regulation of this parameter.
Abstract: Neospora caninum, an apicomplexan parasite closely related to Toxoplasma gondii, causes abortion, stillbirths, and congenital neurologic disease in multiple animal species. The present study focuses on the development of encephalitis and intracerebral parasite load that occurs 6 wk postinfection (PI). Utilizing BALB/c, C57BL/6, and B10.D2 mice, an initial investigation was undertaken to determine the relative resistance of inbred strains to N. caninum-induced encephalitis. Relative resistance was defined in terms of central nervous system lesion development and parasite load. Based on other protozoal infections in mice, it was hypothesized that BALB/c and C57BL/6 should be contrasting in their relative resistance to N. caninum, with BALB/c and congenic B10.D2 mice less susceptible than C57BL/6 mice. Contrary to expectation, BALB/c and C57BL/6 were both highly susceptible to the development of N. caninum-induced encephalitis, whereas B10.D2 mice were resistant. Both BALB/c mice and C57BL/6 mice had significantly higher numbers of brain lesions and intracerebral tachyzoites than B10.D2 mice. Resistance in B10.D2 was associated with a high interferon (IFN)-gamma: interleukin (IL)-4 ratio from antigen-stimulated splenocytes, whereas susceptibility in C57BL/6 and BALB/c mice corresponded with a low splenocyte IFN-gamma: IL-4 ratio. In vivo measurement of Neospora-specific isotype antibodies demonstrated predominately IgG2a in serum from B10.D2 mice and IgG1 in serum from BALB/c and C57BL/6 mice. In conclusion, susceptibility of mice to N. caninum is unique compared to other protozoal diseases. The present study also demonstrates that parasite load is a fundamental measurement for evaluating disease induced by N. caninum and that a type 1 cytokine response may be necessary for regulation of this parameter.
120 citations
119 citations
TL;DR: Microbiology and Microbial Infections, Micro Biology and Micro microbial Infections , مرکز فناوری اطلاعات و اصاع رسانی, کسورزی
Abstract: Microbiology and Microbial Infections , Microbiology and Microbial Infections , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
TL;DR: To determine the prevalence of the 3 primary clonal lineages of Toxoplasma gondii in a potential food source of infection for humans, isolates from pigs that had been collected from pigs at an abattoir in Iowa were analyzed.
Abstract: To determine the prevalence of the 3 primary clonal lineages of Toxoplasma gondii (strain types I, II, and III) in a potential food source of infection for humans, we analyzed 43 isolates of T. gondii that had been collected from pigs at an abattoir in Iowa. Parasites were harvested as in vitro-grown tachyzoites, and their genotypes were determined at the SAG1 and SAG2 loci. On the basis of the allele identified at the SAG2 locus, isolates were grouped into 1 of the 3 primary lineages. Type II strains were by far the most prevalent, accounting for 83.7% of the isolates. The type III genotype was identified in only 16.3% of the isolates. These prevalences differ significantly from a previous sampling of isolates from animals but are similar to the frequencies with which they occur in human disease cases. Similar to the previously characterized strain P89, strains P62 and P105 appeared to have recombinant genotypes. The type I genotype was not identified in the isolates from pigs although these strains have previously been shown to account for approximately 10-25% of toxoplasmosis cases in humans.
TL;DR: This study supports the initial hypothesis at the time of the outbreak that not only domestic cats, but also cougars, pose a risk to Victoria's water supply.
Abstract: One of 12 necropsied cougars (Felis concolor vancouverensis) from Vancouver Island, British Columbia, Canada, shed Toxoplasma gondii oocysts confirmed by mouse bioassay. Eleven of the 12 cougars (92%) had antibodies to T. gondii by the modified agglutination test with titers of <1:25 (1 cougar), 1:50 (8 cougars), and 1:500 (3 cougars). One additional cougar fecal sample collected from the Victoria watershed environment also contained T. gondii oocysts. In 1995, the largest reported outbreak of human toxoplasmosis was linked to municipal drinking water in Victoria, British Columbia. This study supports the initial hypothesis at the time of the outbreak that not only domestic cats, but also cougars, pose a risk to Victoria's water supply.
TL;DR: The definition of association allows this rather diverse, but related group, to be considered cohesively without dwelling on the sometimes sterile, and always complex, problem of defining parasitism, predation, and other relationships.
Abstract: Isopods associated with fishes are biologically and economically important. Unfortunately, little more than basic taxonomic studies have been conducted, with both isopod specialists and fish parasitologists largely ignoring their biology. This lack of knowledge has resulted in incomplete and erroneous portrayals of the group. To allay confusion concerning this important group, we first provide an overview and synoptic information and, second, directly address some of the published misconceptions. Essentially any isopod collected with a fish is suspected of having been associated with that fish. We refer to isopods on fishes as an "association" rather than "parasitism" because the exact relationship between host and isopod has not been established in all cases. A gradation from casually associated micropredation to parasitism occurs between flabelliferan isopod families, i.e., cirolanids to corallanids to aegids to cymothoids (Tables I, II). Sometimes this gradient can even occur within isopod genera. We define association as being in, or attached on, the host fish longer than is necessary to simply feed and drop off, as does a micropredator. Our definition allows this rather diverse, but related group, to be considered cohesively without dwelling on the sometimes sterile, and always complex, problem of defining parasitism, predation, and other relationships. We are not belittling the importance of establishing the exact relationships between isopods and fishes, just ignoring it for the sake of expediency. Isopods associate with fishes from Himalayan Mountain streams to abyssal depths of the sea, although most species are marine, shallow-water, and coastal. Some 500 species are known in 5 families (Tables I, II). Cymothoids and aegids are among the largest parasites of fishes, but other taxa, for example most gnathiids, are difficult to see without the aid of a dissecting microscope (Table II). Isopods attach to all external, branchial, and buccal surfaces of fishes, especially the gills, mouth, and anterior body. Some cymothoids also form pouches in the lateral musculature of a few freshwater and marine fishes. One cirolanid even burrows into the flesh of sharks (Bird, 1981). Most cymothoids are highly host and site specific. A few corallanids seem to have some host specificity, but other isopods apparently have none. Some prefer fishes from particular habitats or with certain behaviors. Species vary in biogeographic range from a short section of coast or single freshwater lake to those occurring worldwide. Gnathiids have been relatively successful in the greater depths. A few cymothoids occur in the inland fresh waters of South America, Asia, and Africa; a freshwater aegid occurs in Asia and Australia, freshwater corallanids in Asia, Java, Sulawesi, and Sumatra, and some marine or brackish water cymothoids invade coastal freshwaters. Many species occur in the tropics, but more numbers of individuals
TL;DR: Elevating the temperature of the cricket Acheta domesticus from room temperature to 33 C did not reduce the survival of parasitoid flies or reduce the number of gregarine gut protozoans, and crickets infested with these parasites showed no increase in their temperature preference.
Abstract: When infected, some insects can raise their body temperature by moving to warmer areas. This behavioral fever response can help the host overcome infection. However, not all parasites and pathogens are equally susceptible to increases in host temperature. Elevating the temperature of the cricket Acheta domesticus from room temperature (22 C) to 33 C did not reduce the survival of parasitoid flies or reduce the number of gregarine gut protozoans, and crickets infested with these parasites showed no increase in their temperature preference. Warmer temperatures (33 C) did not increase the survival of crickets infected with the bacterium Serratia marcescens, and infected crickets did not prefer warmer temperatures. However crickets infected with the intracellular parasite Rickettsiella grylli were more likely to survive when the host was exposed to warmer temperatures. Crickets infected with R. grylli increased their preferred temperature from 26 C to 32 C. In A. domesticus, behavioral fever may be a specific response induced by relatively few pathogens and parasites. Behavioral fever in insects may differ in this respect from fever in mammals that can be elicited by a wide variety of parasites and pathogens.
TL;DR: Cumulative evidence now establishes both superoxide anion (O2-*) and its dismutation product H2O2 in the cellular encapsulation response of D. melanogaster.
Abstract: Upon infection with the wasp parasitoid Leptopilina boulardi, the blood cells or hemocytes of Drosophila melano- gaster larvae become activated and manifest a type of communal phagocytosis wherein eggs of the parasitoid are enveloped by multicellular, melanotic capsules. Hemocytes engaged in this collaborative response generate reactive oxygen intermediates (ROI). These molecules, together with melanogenic intermediates, are believed to destroy intrahemocoelic parasites. Cellular uptake of 2',7'-dichlorofluorescin diacetate (DCF-DA) and the oxidation of its deacetylated form (DCF) to yield the fluorescent product dichlorofluorescein (DC) was used as an intracellular probe for oxidant generation. The selective uptake of the fluorescent probe only by activated plasmatocytes from immune-reactive larvae identified these hemocytes as the source of ROI. Inhibition of DCF oxidation by catalase established hydrogen peroxide (H202) as 1 of the principal oxidants generated during melanotic encapsu- lation. A sensitive spectrometric assay for assessing iron oxidation and complex formation with xylenol orange (FOX assay) also was used to document in vitro-enhanced H202-mediated oxidations by hemolymph from immune-competent larvae. Cumulative evidence now establishes both superoxide anion (O2l) and its dismutation product H202 in the cellular encapsulation response of D. melanogaster.
TL;DR: Current research into the biology and control ofTrypanosomiasis and leishmaniasis, Geoff Hide et al Landmarks of trypanosome research, Keith Vickerman, and current public health status of the trypano-leishmania and leishingmaniasis are reviewed.
Abstract: Current research into the biology and control of trypanosomiasis and leishmaniasis, Geoff Hide et al Landmarks of trypanosome research, Keith Vickerman Current public health status of the trypanosomiasis and leishmaniasis, David H. Molyneux Sequencing and mapping the African trypanosome genome, Najib M.A. El-Sayed, John E. Donelson The structure and biosynthesis of trypanosomatid glycosylphosphatidylinositols, Michael A.J. Ferguson A genetic analysis of the biosynthetic pathway of the leishmania virulence factor LPG, Salvatore J. Turco, Stephen M. Beverley The biology of antigenic variation in African trypanosomes, J. David Barry The expression sites for variant surface glycoprotein of trypanosome brucei, Piet Borst et al Glycolysis of kinetoplastida, Paul A.M. Michels et al Polyamine metabolism in trypanosomes, Alan H. Fairlamb, Sarah A. Le Quesne Sterol metabolism of leishmania and trypanosomes: potential for chemotherapeutic exploitation, Michael L. Chance, L. John Goad Proteinases of trypanosomes and leishmania, Graham H. Cooms, Jeremy C. Mottram Cell signalling in trypanosomatids, Etienne Pays et al Protein phosphorylation and protein kinases in trypanosomatids, Michael Boshart, Jeremy C. Mottram Chemotherapy of human leishmaniasis and trypanosomiasis, Simon L. Croft et al Drug resistance in trypanosomatids, Carole A. Ross, Diana V. Sutherland The population dynamics and control of zoonotic visceral leishmaniasis, Christopher Dye et al Molecular epidemiology of trypanosomatids, Geoff Hide Evolutionary genetics of trypanosome, leishmania and other microorganisms: epidemiological,taxonomical and medical implications, Michel Tibayrenc Current trends in parasite vector interactions, Susan C. Welburn, Ian Maudin The socio-economic impact of African trypanosomiasis, Andrew James Effects of trypanosomiasis on reproduction in domestic ruminants, Ian A. Jeffcoate, Peter H. Holmes Control strategies for African trypanosomiasis: their sustainability and effectiveness, John Barrett.
TL;DR: In this article, seven Pacific harbor seals with meningoencephalitis associated with Sarcocystis neurona-like protozoa were found stranded over an 80-km stretch of central California coastline.
Abstract: Seven Pacific harbor seals with meningoencephalitis associated with Sarcocystis neurona-like protozoa are described. Six of the 7 seals were free-ranging and were found stranded over an 80-km stretch of central California coastline; the other was captive. All had marked to severe nonsuppurative meningoencephalitis, most severe in the cerebellar cortex. Immunohistochemistry for S. neurona antigens was positive on brain tissue in all cases, revealing numerous merozoites as well as developing and mature schizonts, including rosette forms. Electron microscopy performed on 3 animals revealed merozoites and schizonts consistent with Sarcocystis sp., with the absence of rhoptries in merozoites, lack of a parasitophorous vacuole around schizonts, and division by endopolygeny. Serology using western blotting revealed the presence of anti-S. neurona immunoglobulins in the sera of 4 of 5 seals tested. Four animals also had a concurrent mild to moderate nonsuppurative myocarditis; in 1 seal, rare sarcocysts of undetermined species were present within cardiomyocytes.
TL;DR: The results suggest that zoo-born large mammals do serve as intermediate hosts for Sarcocystis species known from indigenous herbivores, and that there might be another species found in cattle that is morphologically very similar to S. hominis.
Abstract: Two Sarcocystis hirsuta isolates from 2 cattle (Bos taurus), 2 Sarcocystis hominis-like isolates from 2 cattle, 1 each Sarcocystis hominis-like isolate from a zoo-born dwarf zebu (B. taurus) and from a zoo-born bison (Bison bison), and 1 each Sarcocystis cruzi isolate from the dwarf zebu and the bison have been characterized by comparing the directly sequenced polymerase chain reaction products of their 18S rRNA genes. Sequences of 2 different isolates from the same species always showed a very high, nearly complete identity to each other both within all or only the conserved overlapping nucleotides. Thus, the 18S rDNA sequences of both S. hirsuta isolates proved to belong to a single species. The same is true for all 3 S. cruzi sequences. The 4 S. hominis-like isolates could not be placed within a single species using these criteria. They formed 2 separate groups (1 cattle isolate and the bison isolate, and the other cattle isolate and the dwarf zebu isolate). The results suggest that zoo-born large mammals do serve as intermediate hosts for Sarcocystis species known from indigenous herbivores, and that there might be another species found in cattle that is morphologically very similar to S. hominis.
TL;DR: A total of 23 records of the lone star tick, Amblyomma americanum (L., 1758), in 11 counties from hosts with no history of travel outside the state demonstrates that this tick is now a resident of Maine.
Abstract: The first records of 3 ixodid tick species collected in the state of Maine are reported. A total of 23 records of the lone star tick, Amblyomma americanum (L., 1758), in 11 counties from hosts with no history of travel outside the state demonstrates that this tick is now a resident of Maine. Ixodes dentatus Marx, 1899 is recorded from Waldo and Lincoln counties, and Ixodes uriae White, 1852 is recorded from Matinicus Rock in Knox County. This is the first report of I. uriae from the eastern United States. Disease agents such as those causing human monocytic ehrlichiosis, Lyme disease, Rocky Mountain spotted fever, and several arboviruses have been recorded from 1 or more of these tick species.
TL;DR: This work documents infection with both E. chaffeensis and the HGE agent in a single deer population, thereby supporting the importance of white-tailed deer in the natural history of the human ehrlichioses agents.
Abstract: The ticks Amblyomma americanum and Ixodes scapularis, strongly implicated vectors of Ehrlichia chaffeensis and the human granulocytic ehrlichiosis (HGE) agent, respectively, commonly are found on white-tailed deer (Odocoileus virginianus). As deer can be infected with E. chaffeensis, the HGE agent, and another Ehrlichia-like organism, a deer population parasitized by both tick species in coastal Georgia was tested for evidence of Ehrlichia spp. infection using serologic, molecular, and culture techniques. Antibodies to both E. chaffeensis (geometric mean titer = 111) and Ehrlichia equi, surrogate antigen for the HGE agent, (geometric mean titer = 1,024) were detected by indirect fluorescent antibody testing. Nested polymerase chain reaction employing species-specific primers demonstrated sequence-confirmed 16S rDNA fragments of 3 distinct Ehrlichia spp. in this population: E. chaffeensis (1/5), the HGE agent (3/5), and an Ehrlichia-like organism previously described from white-tailed deer (5/5). Ehrlichia chaffeensis was isolated in culture from the inguinal lymph node of a single deer. An Ehrlichia-type morula was identified in a neutrophil of 1 deer on examination of blood smears. This work provides the first evidence of the HGE agent in a nonhuman host in the southeastern United States and documents infection with both E. chaffeensis and the HGE agent in a single deer population, thereby supporting the importance of white-tailed deer in the natural history of the human ehrlichioses agents.
TL;DR: It is shown that the effects of host age and size on parasite recruitment do contribute to parasite aggregation and a combination of parasites with size- and age-dependent infrapopulations results in a size-dependent increase in infracommunity size.
Abstract: The independent effects of host age and size on parasite abundance are examined in yellow perch from Garner Lake in east-central Alberta. Older, larger perch tend to have more species of parasites combined with larger parasite infrapopulations. Sexual size dimorphism in perch generates 2 different size classes within each age class >2+ yr, thus allowing the opportunity to separate the effects of age and size on the recruitment of parasites by perch. The abundances of Diplostomum adamsi and Bothriocephalus sp. both increase with host age, whereas the increased abundances of Crepidostomum isostomum and Raphidascaris acus in larger fish are, in part, suggestive of size-specific feeding behaviors of the host. A combination of parasites with size- and age-dependent infrapopulations results in a size-dependent increase in infracommunity size. A comparison of variance-to-mean ratios within age classes to overall variance-to-mean ratios shows that the effects of host age and size on parasite recruitment do contribute to parasite aggregation.
TL;DR: The degree of intraspecific variation detected raises questions regarding the utility of the internal-transcribed spacer regions of the ribosomal DNA repeat for taxonomic diagnosis and in phylogenetic studies for poorly differentiated groups, such as the 37-collar-spined congeners.
Abstract: The recent finding of the 37-collar-spined Echinostoma revolutum in North America prompted rDNA nucleotide sequence comparisons between this worm and the sympatric Echinostoma trivolvis. Three isolates of E. revolutum from distinct sites and 2 isolates of E. trivolvis collected from a single site were used in this analysis. Sequence data were compared to those from previously sequenced members of the 37-collar-spine group. The 3 North American isolates of E. revolutum were found to be identical, but they differed from Eurasian isolates of E. revolutum at 9 of the 1,006 sites sequenced. Further, 1 of the E. trivolvis isolates studied herein was identical to the published sequence for this species, but 6 nucleotide changes were observed in the second E. trivolvis isolate. Restriction fragment length polymorphisms at this locus support the nucleotide differences found between the E. trivolvis isolates. The degree of intraspecific variation detected raises questions regarding the utility of the internal-transcribed spacer regions of the ribosomal DNA repeat for taxonomic diagnosis and in phylogenetic studies for poorly differentiated groups, such as the 37-collar-spined congeners.
TL;DR: The results suggest that exposure and infection are ubiquitous in this child population, and that A. lumbricoides intensity is influenced by gender-related behavioral and environmental factors that contribute to exposure.
Abstract: Ascaris lumbricoides worm counts were examined as the outcome products of exposure proxy variables. A survey of 663 children, 4-10 yr old, living in southeastern Madagascar revealed prevalences of 93% for A. lumbricoides, 55% for Trichuris trichiura, and 27% for hookworm. Worm expulsions were conducted on 428 of these children; the data revealed an overdispersed distribution of A. lumbricoides, with an arithmetic mean of 19.2 worms per child. A concurrent socioeconomic household survey was conducted by visitation and interview. Exposure to infection was assessed by environmental, demographic, behavioral, and socioeconomic indicators. Ascaris lumbricoides aggregations were associated with gender, housing style, ethnicity, and agricultural factors. The results suggest that exposure and infection are ubiquitous in this child population, and that A. lumbricoides intensity is influenced by gender-related behavioral and environmental factors that contribute to exposure.
TL;DR: The differential expression of the 2 N. caninum surface proteins Nc-p43 and N c-p36 and the dense granule protein Nc -p33 (NCDG1) within tachyzoites and bradyzoites of N.Caninum has been investigated.
Abstract: Morphologically, the tachyzoites and the tissue cysts of Neospora caninum are difficult to distinguish from those of other cyst-forming apicomplexan parasites such as Toxoplasma gondii. Several stage-specific antigens have been identified in T. gondii tachyzoites and bradyzoites, and respective antibodies are useful tools for discriminating between the 2 stages during tachyzoite-bradyzoite interconversion in T. gondii infections. Whereas several cell surface- and dense granule-associated proteins have been identified and characterized in N. caninum tachyzoites, not much is known about antigenic components expressed in N. caninum bradyzoites. In this study, the differential expression of the 2 N. caninum surface proteins Nc-p43 and Nc-p36 and the dense granule protein Nc-p33 (NCDG1) within tachyzoites and bradyzoites of N. caninum has been investigated.
TL;DR: Sporozoites, tachyzoites, and bradyzoites had similar numbers of rhoptries but differed in the numbers and sizes of micronemes, dense granule, amylopectin granules, and lipid bodies.
Abstract: Transmission and scanning electron microscopy were used to study the ultrastructure of the oocysts, sporocysts, and sporozoites of the VEG strain of Toxoplasma gondii and to compare the ultrastructure of sporozoites with tachyzoites (from the peritoneum of mice) and bradyzoites (from brain tissue cysts in mice). Oocysts were surrounded by a thin veil of finely reticulate material. The oocyst wall consisted of 3 layers and contained a previously unknown disc-shaped micropyle that appeared as a depression in the oocyst wall. The sporocyst contained 4 sporozoites and a residuum of lipid and amylopectin granules. The sporocyst wall was 3-layered with the innermost layer consisting of 4 curved plates held together at sutures by an interposed strip. Exposure to excysting fluid caused the interposed strip to separate from the curved plates, which curled inward releasing the sporozoites. Sporozoites had a posteriorly located nucleus and all the organelles typical for coccidian zoites. Sporozoites, tachyzoites, and bradyzoites had similar numbers of rhoptries but differed in the numbers and sizes of micronemes, dense granules, amylopectin granules, and lipid bodies.
TL;DR: In this article, the authors examined the species-specificity and sensitivity of a polymerase chain reaction (PCR)-based assay for Perkinsus marinus and compared its overall performance with the fluid thioglycollate medium (FTM) assay on oyster hemolymph, mantle, and rectum samples.
Abstract: We examined the species-specificity and sensitivity of a polymerase chain reaction (PCR)-based assay for Perkinsus marinus and compared its overall performance with the fluid thioglycollate medium (FTM) assay on oyster (Crassostrea virginica) hemolymph, mantle, and rectum samples. Our results indicated that the PCR-based methodology is species-specific because Perkinsus olseni, Perkinsus atlanticus, and Perkinsus spp. DNAs were not amplified with the PCR primers developed for P. marinus diagnosis. The sensitivity of the PCR method, as assessed through spike/recovery experiments, was established by the detection of as few as 1 cell of P. marinus in 30 mg of oyster tissue. Tissue samples from naturally infected oysters analyzed both by the FTM and PCR assay suggested that the latter was more sensitive for the diagnosis of P. marinus. Positive results for P. marinus infection ranged from 70% to 83% by FTM and from 92% to 100% by PCR, depending on the tissue examined. Therefore, species-specificity and sensitivity of the NTS-based PCR assay validate its use as a tool for assessment of P. marinus in mollusks.
TL;DR: The results suggest that both voles and muskrats are parasitized by the same species of Giardia, that this species is different from theGiardia that parasitizes humans, and that voles or muskrat do not contribute to the zoonotic character of human giardiasis.
Abstract: The small subunit ribosomal RNA (eukaryotic 16S rRNA) gene from Giardia trophozoites, isolated from 8 different prairie voles and 8 different muskrats, was amplified by the polymerase chain reaction. The 16S rDNA was sequenced in its entirety for 2 prairie vole and 2 muskrat Giardia. In addition, the 5' 500 nucleotides of the 16S rDNA from Giardia isolates from each of 6 voles and 6 muskrats were amplified and sequenced. The results show that Giardia from voles and muskrats are very similar to each other but differ substantially from Giardia isolated from humans. We believe that the Giardia isolate from voles and muskrats constitutes a distinct species, which will be referred to as Giardia microti. These results suggest that both voles and muskrats are parasitized by the same species of Giardia, that this species is different from the Giardia that parasitizes humans, and that voles and muskrats do not contribute to the zoonotic character of human giardiasis.
TL;DR: ITS 2 appears useful for phylogenetic inference in the Rhipicephalinae because in genetic distance, maximum likelihood, and maximum parsimony analyses, most branches leading to species had >95% bootstrap support.
Abstract: Most populations and some species of ticks of the genera Boophilus (5 spp.) and Rhipicephalus (ca. 75 spp.) cannot be distinguished phenotypically. Moreover, there is doubt about the validity of species in these genera. I studied the entire second internal transcribed spacer (ITS 2) rRNA of 16 populations of rhipicephaline ticks to address these problems: Boophilus microplus from Australia, Kenya, South Africa and Brazil (4 populations); Boophilus decoloratus from Kenya; Rhipicephalus appendiculatus from Kenya, Zimbabwe and Zambia (7 populations); Rhipicephalus zambesiensis from Zimbabwe (3 populations); and Rhipicephalus evertsi from Kenya. Each of the 16 populations had a unique ITS 2, but most of the nucleotide variation occurred among species and genera. ITS 2 rRNA can be used to distinguish the populations and species of Boophilus and Rhipicephalus studied here. Little support was found for the hypothesis that B. microplus from Australia and South Africa are different species. ITS 2 appears useful for phylogenetic inference in the Rhipicephalinae because in genetic distance, maximum likelihood, and maximum parsimony analyses, most branches leading to species had >95% bootstrap support. Rhipicephalus appendiculatus and R. zambeziensis are closely related, yet their ITS 2 sequences could be distinguished unambiguously. This lends weight to a previous proposal that Rhipicephcalus sanguineus and Rhipicephalus turanicus, and Rhipicephalus pumilio and Rhipicephalus camicasi, respectively, are conspecific, because each of these pairs of species had identical sequences for ca. 250 bp of ITS 2 rRNA.