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Showing papers in "Journal of Parasitology in 1994"



Journal ArticleDOI
TL;DR: Several new cell lines derived from embryonated eggs of northern (IDE lines) and southern (ISE lines) populations of the tick Ixodes scapularis were developed to facilitate investigations of the vector phase of tick-borne disease agents in vitro.
Abstract: Interest in tick-borne pathogens has been enhanced by the emergence of Lyme disease and, more recently, human and animal ehrlichioses. In order to facilitate investigations of the vector phase of tick-borne disease agents in vitro, several new cell lines derived from embryonated eggs of northern (IDE lines) and southern (ISE lines) populations of the tick Ixodes scapularis were developed. The establishment and characteristics of 4 IDE (IDE1, 2, 8, and 12) and 2 ISE (ISE5 and 18) lines were described. Primary cultures were initiated in L-15B medium at 31 C from a single egg mass each and established lines developed a morphologically distinct phenotype. Myoblasts were present during the first year after isolation in several lines as isolated clusters or sheets covering the whole flask. Cell line extracts resolved by isoelectric focusing were characterized for 3 isozymes (lactate dehydrogenase, malate dehydrogenase, and malic enzyme). The combined banding patterns allowed discrimination between Ixodes cell lines and a Rhipicephalus appendiculatus cell line. Two lines, i.e., ISE5 and ISE18, had unique isozyme bands. Chromosome numbers and morphology conformed to those described from tissue squashes of I. scapularis.

233 citations


Journal ArticleDOI
TL;DR: A new coccidian parasite has been found in stool specimens of humans with and without diarrhea and it is proposed the name Cyclospora cayetanensis n.
Abstract: A new coccidian parasite has been found in stool specimens of humans with and without diarrhea. The oocyst of this parasite measures 8.6 microns in diameter (7.7-9.9 microns), with ovoid sporocysts 4.0 x 6.3 (3.3-4.4 x 5.5-7.1) microns. Each oocyst has 2 sporocysts and each sporocyst contains 2 sporozoites. Based on these characteristics and the structures observed by electron microscopy, this parasite has been classified in the genus Cyclospora. We propose the name Cyclospora cayetanensis n. sp. for this new human parasite.

181 citations


Journal ArticleDOI
TL;DR: Characteristics of surface cuticular ridges (synlophe) are described, which for the first time provide morphological criteria for identifying individual adult specimens of either sex.
Abstract: ABSTRACr: The large stomach worms Haemonchus contortus, Haemonchus placei, and Haemonchus similis are important pathogens ofcattle and sheep. This paper describes characteristics of surface cuticular ridges (synlophe), which for the first time provide morphological criteria for identifying individual adult specimens of either sex. The diagnostic patterns of the synlophe on the anterior half of specimens can be observed at 400 x in temporary mounts on glass slides. The synlophe can be studied in cleared preserved specimens or in living or freshly thawed frozen specimens mounted in water. The synlophe of H. contortus has 30 ridges in the region of the posterior half of the esophagus, 4 fewer than H. placei and H. similis. The 4 extra ridges of H. placei and H. similis are consistently located bilaterally to the 3 ventralmost and the 3 dorsalmost ridges. The 4 extra ridges of H. similis extend to the end of the synlophe posterior to midbody, but in H. placei they extend posteriorly only to the end of the anterior quarter of the nematode. A key is included to the 3 species of Haemonchus parasitic in domestic sheep and cattle using characteristics of spicules, female reproductive system, female tail, and the synlophe. Three species of the genus Haemonchus Cobb, 1898, are known to occur in domestic and wild ruminants of North America. They are common parasites of domesticated ruminants and have achieved a worldwide distribution in part due to the movement of their economically important hosts. These 3 species of large stomach worms are among the most pathogenic nematodes of sheep, cattle, and goats worldwide, causing significant production losses due to morbidity, mortality, costs of treatment, and suboptimal use of contaminated pastures (Gibbs and Herd, 1986). Haemonchus contortus (Rudolphi, 1803) Cobb, 1898, primarily a parasite of domestic sheep, Ovis aries, also infects numerous other domestic and wild ruminants.

115 citations


Journal ArticleDOI
TL;DR: A group of 25 strains of Toxoplasma gondii were tested by immunoblot with 4 monoclonal antibodies against surface antigen P22 and the allele of the P22 gene correlated with reactivity of the 4 MAbs to lysates of each strain, but the allele did not correlate with the virulence of each strains for mice.
Abstract: A group of 25 strains of Toxoplasma gondii (4 mouse-virulent strains and 21 mouse-avirulent strains) were tested by immunoblot with 4 monoclonal antibodies (MAb) against surface antigen P22. Parasite lysates from only 12 strains were recognized by all 4 MAbs, while lysates from the remaining 13 strains (all avirulent) were not recognized by any of the 4 MAbs. Strains not recognized by the 4 MAbs were found to express an altered form of the P22 antigen. Sequencing of the P22 genes from 10 strains revealed only 2 alleles. One allele is identical to the gene from the virulent RH strain. The second allele carries 5 single nucleotide substitutions and an insertion of a GGT triplet when compared to the allele from the RH strain. Four of the 5 nucleotide changes result in amino acid substitutions and the triplet insertion results in an extra glycine residue. Four of the single base changes also result in restriction fragment length polymorphisms (RFLP). RFLP analysis of the P22 gene revealed only 2 patterns among the 25 strains. The allele of the P22 gene correlated with reactivity of the 4 MAbs to lysates of each strain. However, the allele of the P22 gene did not correlate with the virulence of each strain for mice.

112 citations


Journal ArticleDOI
TL;DR: Parasitological data should be incorporated into management plans for the conservation of native Hawaiian stream fishes as these parasites have been previously demonstrated to cause disease.
Abstract: The Hawaiian Islands harbor a depauperate native freshwater fish fauna comprised of 4 endemic gobies (Gobiidae) and 1 endemic sleeper (Eleotridae). We hypothesized that the natural helminth parasite community of these stream fishes would be depauperate because of colonizing constraints. In the absence of exotic fishes, native fishes in streams of Hanakapi'ai and Nu'alolo valleys harbored no adult helminth parasites. In Hakalau Stream on Hawai'i and Wainiha River on Kaua'i, we found introduced swordtails and guppies (Poeciliidae); here, the native gobioid fishes shared species of helminths with poeciliids. They were the nematode Camallanus cotti, the Asian tapeworm Bothriocephalus acheilognathi, and the leech Myzobdella lugubris. Such parasitological data should be incorporated into management plans for the conservation of native Hawaiian stream fishes as these parasites have been previously demonstrated to cause disease.

99 citations


Journal ArticleDOI
TL;DR: This review focuses on parasite-mediated interference with the structural and functional integrity of host hemocytes and argues that this is a common strategy of immune evasion.
Abstract: Many parasites develop in invertebrate hosts that possess internal defense systems (IDS) that vigorously defined self-integrity Invertebrates apparently do not produce a large diversity of finely tuned immunorecognition molecules but rather rely on recognition of patterns As a consequence, requirements for immune evasion are likely to be fundamentally different in such hosts Although parasites of invertebrates certainly employ diverse tactics to evade host IDS, this review focuses on parasite-mediated interference with the structural and functional integrity of host hemocytes and argues that this is a common strategy of immune evasion Parasites mediating such effects on host hemocytes are termed suppressors In some cases, interference is mediated by mutualistic symbionts carried by the suppressors Hemocytes from infected hosts exhibit diminished adherence to substrates, impaired spreading ability, and reduced ability to participate in phagocytosis or encapsulation reactions As a result of the action of suppressors, the host's vulnerability to opportunistic parasites is increased, a phenomenon termed acquired susceptibility A strategy of interference is therefore risky, particularly for suppressors with relatively long development times As a result, suppressors may provoke either a partial generalized interference or a selective interference with host IDS function, actively contribute to protection of the host to discourage growth of opportunists (termed parasite-mediated internal defense), or induce compensatory host responses that protect the host but that do not jeopardize their own development Some parasites consistently colonize previously infected hosts and seem to be specialized opportunists

91 citations


Journal ArticleDOI
TL;DR: Parasite-mediated sexual selection is reviewed with special emphasis on the bird literature, and comparative studies using pairwise comparisons of closely related taxa reveal that sexually dichromatic bird species have larger spleens, larger bursa of Fabricius, and higher concentrations of leukocytes than monochromatic species.
Abstract: Parasite-mediated sexual selection is reviewed with special emphasis on the bird literature. Choosy females may benefit from choosing parasite-free mates if such males provide better parental care, do not transmit contagious parasites, or provide resistance genes to offspring. There is evidence in support of each of these mechanisms. The immunocompetence handicap hypothesis posits that secondary sexual characters reliably reveal the ability of males to resist parasites due to the immunosuppressive effects of testosterone and other biochemicals. Several aspects of these negative feedback mechanisms are supported by laboratory studies, but evidence from free-living animals is almost completely absent. Corticosterone rather than testosterone may potentially mediate the immunocompetence handicap mechanism. A simple version of the immunocompetence handicap is developed suggesting that body condition of male hosts is a sufficient mediator of the handicap mechanism of reliable sexual signaling. Sexual selection appears to be more intense in sexually dichromatic bird species, and comparative studies using pairwise comparisons of closely related taxa reveal that sexually dichromatic bird species have larger spleens, larger bursa of Fabricius, and higher concentrations of leukocytes than monochromatic species. Parasite-mediated sexual selection is proposed to affect parasite biology by increasing (1) the variance-to-mean ratio in parasite abundance, (2) variance in the intensity of natural selection affecting hosts, and (3) speciation rates among parasites exploiting hosts subject to intense sexual selection as compared to those subject to less intense selection.

85 citations


Journal ArticleDOI
TL;DR: The possibility of a periparturient rise (PPR) in the excretion of Cryptosporidium parvum oocysts and Giardia duodenalis-type cysts and its implications in the epidemiology of these 2 pathogens were investigated.
Abstract: The possibility of a periparturient rise (PPR) in the excretion of Cryptosporidium parvum oocysts and Giardia duodenalis-type cysts and its implications in the epidemiology of these 2 pathogens were investigated. Fecal samples were taken from 32 lambing ewes every 2 wk from 4 wk before lambing until 8 wk after the start of lambing. Samples from both ewes and lambs were examined with a quantitative immunofluorescence assay. Excretion of Giardia sp. cysts by ewes increased at 2 wk prepartum, peaked at zero and 4 wk postpartum, and returned to low levels at 6 and 8 wk postpartum. Some ewes also excreted C. parvum oocysts at the start of lambing. Excretion rates and intensities of Giardia sp. cysts by lambs were high, whereas those of C. parvum oocyst excretion were light. The PPR in excretion of Giardia sp. cysts by ewes was considered to be the major source of giardiasis for lambs. Excretion of C. parvum oocysts by ewes at parturition also played a role in initiating cryptosporidiosis in lambs.

79 citations


Journal ArticleDOI
TL;DR: Histological examination of tick attachment sites showed that inflammatory cells consisting of neutrophils, eosinophils, and mononuclear cells (lymphocytes and monocytes) infiltrated the skin more intensively during reinfestations.
Abstract: BALB/c mice underwent 3 successive infestations with 15 Ixodes ricinus nymphs. No resistance was acquired as assessed by evaluating tick attachment, duration of blood meal, weights of engorged nymphs, and molting success. However, the hosts developed cutaneous immediate- and delayed-type hypersensitivity reactions when reinfested. Histological examination of tick attachment sites showed that inflammatory cells consisting of neutrophils, eosinophils, and mononuclear cells (lymphocytes and monocytes) infiltrated the skin more intensively during reinfestations. The number of intact mast cells did not vary between successive infestations, whereas the number of degranulated mast cells increased in the early stages of reinfestations. Basophils, which represent 12% of total infiltrating cells, were only observed and quantified in the skin of reinfested mice using transmission electron microscopy (TEM). Degranulating eosinophils were also observed by use of TEM.

73 citations


Journal ArticleDOI
TL;DR: Genetic crosses of the highly susceptible Rockefeller strain (ROCK) and the 2 selected sublines of the MOYO strain provide evidence for a complex mode of inheritance of Plasmodium susceptibility in Ae.
Abstract: Several studies have demonstrated a genetic basis for variation in susceptibility of Aedes aegypti to Plasmodium gallinaceum. Although 25 yr ago it was reported that P. gallinaceum susceptibility in Ae. aegypti is determined primarily by a single autosomal dominant gene, evidence for additional genetic factors has emerged. Two sublines, 1 refractory and 1 of intermediate susceptibility to P. gallinaceum, have been selected from the Moyo-In-Dry strain (MOALO) of Ae. aegypti. Prior to selection, the MOALO population was 20.3% refractory. Genetic crosses of the highly susceptible Rockefeller strain (ROCK) and the 2 selected sublines of the MOALO strain provide evidence for a complex mode of inheritance of Plasmodium susceptibility in Ae. aegypti

Journal ArticleDOI
TL;DR: Hormonal reconstitution experiments showed that 17-beta-estradiol increases parasite numbers whereas 5-alpha-dihydrotestosterone was ineffective, and a possible immunoendocrinological interaction involving estrogen as a depressor of cellular immunity is envisaged in the control of cysticercosis.
Abstract: In experimental murine cysticercosis caused by Taenia crassiceps, parasite reproduction is favored by thymectomy or by orchidectomy, and restricted by ovariectomy. Hormonal reconstitution experiments showed that 17-beta-estradiol increases parasite numbers whereas 5-alpha-dihydrotestosterone was ineffective. Parasite numbers decreased with increments in cellular immunity but were insensitive to antibody levels. A possible immunoendocrinological interaction involving estrogen as a depressor of cellular immunity is envisaged in the control of cysticercosis.

Journal ArticleDOI
TL;DR: P. laevis may serve as a very sensitive bioindicator for the presence of biologically available lead in aquatic ecosystems.
Abstract: Adults of Pomphorhynchus laevis were collected from the intestines of 10 chubs (Leuciscus cephalus) from the river Ruhr near Bochum, Germany. The acanthocephalans and various tissues of the fish (muscle, liver, and intestine) were analyzed for lead with electrothermal atomic absorption spectrometry. The mean lead level in the parasite was 54 micrograms/g wet weight, which was 284 times more than in the host intestine, 771 times more than in host liver, and 2,700 times more than in host muscle. Thus, P. laevis may serve as a very sensitive bioindicator for the presence of biologically available lead in aquatic ecosystems.

Journal ArticleDOI
TL;DR: Parasite populations were not normally distributed in any mosquito species but were adequately described by a negative binomial type of distribution.
Abstract: Sporogonic development of Plasmodium yoelii yoelii 17XNL was examined in 5 species of Anopheles mosquitoes; A. albimanus, A. dirus, A. freeborni, A. gambiae, and A. stephensi. The kinetics of ookinete formation differed among species. In A. freeborni, A. gambiae, and A. stephensi, mature ookinetes formed synchronously at 8 hr, then quickly subsided. In A. albimanus and A. dirus, ookinete formation was more protracted, and ookinete densities peaked from 12 to 24 hr. Losses in parasite abundance during the conversion of ookinetes to oocysts were similar between A. dirus and A. gambiae (55- and 41-fold losses, respectively) but were an order of magnitude less in A. stephensi (1.3-fold loss). Ookinete conversion to oocysts in A. albimanus was nil. Melanotic encapsulation of oocysts occurred in 25-30% of infected A. gambiae and A. dirus. Melanized parasites in A. gambiae at days 7-10 were small (10 microns diameter) and retort-shaped, whereas melanized parasites in A. dirus were generally as large as normal oocysts (60 microns) and many were incompletely melanized. Melanotic encapsulation did not occur in A. stephensi, A. freeborni, or A. albimanus. On day 16, sporozoites were present in the salivary glands of A. freeborni, A. gambiae, and A. stephensi, but only half of mosquitoes were mature oocysts also had gland infections. When present in the glands, sporozoites were successfully transmitted to mice via mosquito bite. Parasite populations were not normally distributed in any mosquito species but were adequately described by a negative binomial type of distribution.

Journal ArticleDOI
TL;DR: Assessment of host associations suggests extensive colonization but also a high degree of coevolution with Bovidae and Cervidae for Ostertagiinae+Haemonchinae; and biogeography for this assemblage is complex, but this analysis is compatible with a Palearctic or Eurasian origin.
Abstract: Phylogenetic analysis of the subfamilies of the Trichostrongylidae based on 22 morphological trans- formation series produced a single cladogram with a consistency index (CI) = 74.2%. Monophyly for the family was supported by the structure of the female tail and copulatory bursa. Two major clades are recognized: the Cooperiinae clade with the basal Cooperiinae and Libyostrongylinae Trichostrongylinae, and the Graphidiinae clade with the basal Graphidiinae and Ostertagiinae + Haemonchinae. Dendrograms presented by Durette- Desset (1985) (CI = 56.1%) and Lichtenfels (1987), based on the key to the Trichostrongylidae by Gibbons and Khalil (1982) (CI = 59.0%), were found to be relatively inefficient in describing character evolution and in supporting putative relationships among the subfamilies. Based on the current analysis, the intestine appears to have constituted the ancestral habitat for the trichostrongylids the stomach/abomasum having been in- dependently colonized in each clade. Assessment of host associations suggests extensive colonization but also a high degree of coevolution with Bovidae and Cervidae for Ostertagiinae + Haemonchinae. Biogeography for this assemblage is complex, but this analysis is compatible with a Palearctic or Eurasian origin for Cooperiinae, Haemonchinae, and Ostertagiinae.

Journal ArticleDOI
TL;DR: This book addresses major issues and new developments concerning Giardia and giardiasis that are attracting considerable interest worldwide.
Abstract: Summary Giardiais a parasitic protozoan which is attracting considerable interest worldwide. It can cause severe gastrointestinal problems in humans and has also been reported in a number of domestic and wild mammals. This book addresses major issues and new developments concerningGiardiaand giardiasis.

Journal ArticleDOI
TL;DR: Results suggest that H. polygyrus adults feed on tissue in the living host and not on host ingesta or blood.
Abstract: The aim of this study was to identify the food resources of Heligmosomoides polygyrus, a gastrointestinal nematode of mice. Gastrointestinal nematodes obtain food from 1 of 3 compartments: host ingesta, blood, or intestinal tissue. A method was developed to label these compartments differentially in the living host using 2 fluorescent marker dyes and to record in situ feeding activity of the parasite. Fluoresbrite is a yellow-green fluorescent dye bound to small-diameter beads that are membrane impermeable. Thus, it is restricted to the bloodstream when introduced there, or it remains in the ingesta when fed to the host. Rhodamine B, a red fluorescent dye, is membrane permeable and stains tissue cytoplasm. These dyes were fed to or injected into the bloodstream of the host. Following treatment, the worms were removed, and the contents of the worm intestines were examined by fluorescent microscopy. Worm intestinal contents only fluoresced with rhodamine B dye. These results suggest that H. polygyrus adults feed on tissue in the living host and not on host ingesta or blood.

Journal ArticleDOI
TL;DR: The presence of an hsp60-related protein in G. lamblia raises interesting questions concerning its origin and the distribution of this protein is evaluated by immunofluorescence microscopy.
Abstract: Giardia lamblia trophozoites contain a 60-kDa protein recognized in immunoblots by antibody to mammalian hsp60, a protein localized in mitochondria in eukaryotic cells. The cellular distribution of this protein is evaluated by immunofluorescence microscopy using monoclonal antibody to human hsp60, polyclonal antibody to rodent hsp60, and 2 monoclonal antibodies to mycobacterial 65-kDa antigen, a prokaryotic hsp60 homolog. All of these antibodies, except 1, which is specific for prokaryotic hsp60, give a punctate labeling pattern throughout the cytoplasm, indicating that the 60-kDa protein is concentrated at discrete sites in the cytoplasm. The polyclonal hsp60 antiserum reveals additional punctate labeling colocalized on axonemes of the anterior flagella. Postembedment immunogold labeling and electron microscopy confirm that the antigen is clustered at foci in the cytoplasm but show no evidence of association with a membranous organelle. The hsp60 reactivity is also observed on anterior axonemes within the cytoplasm and on the adhesive disc. Hoechst 33258 DNA staining as well as electron microscopy give no evidence of endosymbionts, so a false positive due to a prokaryotic hsp60 homolog is unlikely. The presence of an hsp60-related protein in G. lamblia raises interesting questions concerning its origin.

Journal ArticleDOI
TL;DR: This study showed that PLC hydrolysis products, inositol (1,4,5)triphosphate and diacylglycerol, are correlated with the initial events of flagellar development and are implicated in synchronizing this crucial transformation for the parasite and hence the continued transmission of the parasite, which leads to this debilitating disease.
Abstract: Cellular responses to growth factors, hormones, and other agonists have been shown in many animal cell systems to be mediated by the signal transduction cascade controlled by phospholipase C. One such response, calcium mobilization, is regulated by the concerted effect of several specific inositol (poly)phosphates. Another response, protein phosphorylation, is regulated by other phospholipase C (PLC) hydrolysis products. Mature gametocytes are specialized cells primed for transformation into gametes immediately upon removal from the vertebrate bloodstream, thereby initiating the sexual cycle in a vector mosquito. This study showed that PLC hydrolysis products, inositol (1,4,5)triphosphate and diacylglycerol, are correlated with the initial events of flagellar development; they are implicated in synchronizing this crucial transformation for the parasite and hence the continued transmission of the parasite, which leads to this debilitating disease.

Journal ArticleDOI
TL;DR: To study the effect of gamma-irradiation on the viability of Toxoplasma gondii tissue cysts, brains of mice inoculated with 95 newly isolated strains of T. Gondii from pigs and 10 other laboratory isolates were pooled, flattened, packed in vacuum, and irradiated to absorbed doses of 0.25 kGy.
Abstract: To study the effect of gamma-irradiation on the viability of Toxoplasma gondii tissue cysts, brains of mice inoculated with 95 newly isolated strains of T. gondii from pigs and 10 other laboratory isolates were pooled, flattened, packed in vacuum, and irradiated to absorbed doses of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.9 kGy at 5 C (+/- 0.5 C) with a 137Cs gamma-radiation source. Treated samples were bioassayed for viable T. gondii in mice, cats, or both. Tissue cysts of all strains were rendered nonviable at 0.4 kGy. To study the effect of temperature on inactivation by irradiation, tissue cysts were irradiated at -4, 0, 4, 8, 12, and 16 C (+/- 0.5 C) at 0.25 kGy. Temperature during irradiation had no marked effect on the viability of tissue cysts.

Journal ArticleDOI
TL;DR: Membranes from both ivermectin-sensitive and -resistant Haemonchus contortus L3 larvae were examined for the presence of high affinity [3H]ivermectins binding sites suggesting that target site modification was not involved in the development of drug resistance in this particular strain of H.contortus.
Abstract: Membranes from both ivermectin-sensitive and -resistant Haemonchus contortus L3 larvae were examined for the presence of high affinity [3H]ivermectin binding sites. Both tissue preparations displayed high affinity drug binding sites (Kd = 0.13 nM). Receptor density (Bmax = 0.4 pmol/mg) was the same in both the sensitive and resistant nematodes suggesting that target site modification was not involved in the development of drug resistance in this particular strain of H. contortus. The H. contortus ivermectin binding site appeared to be similar to the well characterized Caenorhabditis elegans ivermectin binding site with respect to affinity for ivermectin and receptor density.

Journal ArticleDOI
TL;DR: In vitro forms of the parasite resembled in vivo forms andCryopreservation and subsequent recovery of B. equi were easily achieved.
Abstract: Babesia equi was continuously cultured through 90 passages in an enriched chemically defined basal medium (HL-1) supplemented with 20% fetal bovine serum and serum replacement factors, including lipid-rich bovine serum albumin, bovine insulin, and human transferrin. Cryopreservation and subsequent recovery of B. equi were easily achieved. Inoculation of a splenectomized and an intact horse with cultured infected erythrocytes resulted in parasitemias and B. equi in vitro reisolation from both animals. In vitro forms of the parasite resembled in vivo forms. After establishment, parasitemias of 10-15% were commonly observed.

Journal ArticleDOI
TL;DR: The data indicate that a subset of murine lymphocytes consistent with the Th1 helper cell phenotype proliferates following in vitro stimulation with C. parvum antigen, characteristic of the previously described Th1 helpers cell subset.
Abstract: Spleen cells from mice immunized with Cryptosporidium parvum were enriched for T cells by passage over an affinity chromatography column. The proliferative response of these cells was > 2-fold higher than the response of unenriched cells. T-enriched cells were enriched further for either CD4+ cells or CD8+ cells. The proliferative response of CD4-enriched cells was > 4-fold higher than the response by unenriched cells. CD8+ cells were essentially nonresponsive to C. parvum antigen. Culture supernatant fractions from these variously enriched splenocyte populations were assayed for cytokine production. Cultures containing CD4+ cells produced gamma interferon and interleukin-2 following incubation with C. parvum antigen. None of the cultures produced interleukin-4. Production of gamma interferon and interleukin-2, but not interleukin-4, is characteristic of the previously described Th1 helper cell subset. Our data indicate that a subset of murine lymphocytes consistent with the Th1 helper cell phenotype proliferates following in vitro stimulation with C. parvum antigen.

Journal ArticleDOI
TL;DR: Excess positive associations between helminth species in bats are due to joint presences and absences in hosts rather than to interspecific facilitation, suggesting interspecific facilitation would be supported by observed positive correlations between the intensities of individuals of the species pairs.
Abstract: The null hypothesis that the number of positive pairwise covariances should equal the number of negative pairwise covariances in samples from communities of randomly associated helminth species was re- evaluated. The proportion of positive covariances in a sample from a community of independent species depends upon the proportion of rare species (prevalence less than 10%), the proportion of common species (prevalence greater than 90%), and the size of the sample of hosts. If rare species dominate, then there will be an excess of negative associations; if common species dominate there will be an excess of positive associations. Many helminth communities have more rare than common species, therefore samples from communities that show an equal number of positive and negative covariances have a greater number of positive associations than is expected for randomly associated species. Increased sample size will reduce the sampling bias, but at least 100 hosts are necessary and often 500-7,500 hosts are required. The excess of positive covariances between helminth species in 10 populations of bats disappeared after restricting the analyses to hosts in which both members of a species pair were present. This result suggests that excess positive associations between helminth species in bats are due to joint presences and absences in hosts rather than to interspecific facilitation. Interspecific facilitation would be supported by observed positive correlations between the intensities of individuals of the species pairs. The community matrix (Levins, 1968) has been used to describe the relationships among species in a community and it provides a mechanism by which community structure can be analyzed. The entries in a community matrix were originally intended to be measures of the effect of a par- ticular species on another, e.g., competition co- efficients; however, in practice they are more of- ten measures of niche overlap or association (Levins, 1968; Cody, 1974; Seifert and Seifert, 1976). Host-parasite systems are ideally suited for estimating community matrices because a population of hosts provides clearly demarcated, replicated habitats. Each host individual con-

Journal ArticleDOI
TL;DR: There was a decrease in antibody titration units that was significantly correlated with the number of outdoor exposure years experienced by the birds, despite the season-comparable epizootiologic conditions in their summer open-air habitat, concluding that the decrease of anti-malarial antibodies could be explained by an antibody-mediated equilibrium of immunity in naturally immunized birds harboring endothelial-stage parasites.
Abstract: An enzyme-linked immunosorbent assay (ELISA) utilizing 3 Plasmodium falciparum antigens, R32tet32, P.F.R27, and crude red blood cell extract, was developed for the detection of circulating anti-Plasmodium relictum or anti-Plasmodium elongatum antibodies in sera from naturally infected adult African black-footed penguins (Spheniscus demersus) at The Baltimore Zoo, Maryland. A concentration of 2.0 micrograms/ml of each antigen was optimal in terms of specificity, sensitivity, and test speed. It was possible to detect anti-Plasmodium spp. antibodies at a dilution of 10(-4.11). Low absorbance values (less than 0.050) of nonspecific background were observed. The binding efficacy of anti-penguin IgG coupled to alkaline phosphatase to antibodies in the penguin sera was significantly higher than the binding efficacy of anti-chicken IgG. All penguins, bled in the winter time, in controlled mosquito-free conditions had anti-Plasmodium spp. antibodies reactive with P. falciparum antigens. The penguins showed age-dependent variation in antibody levels. There was a decrease in antibody titration units that was significantly correlated with the number of outdoor exposure years experienced by the birds, despite the season-comparable epizootiologic conditions in their summer open-air habitat. We concluded that the decrease of anti-malarial antibodies could be explained by an antibody-mediated equilibrium of immunity in naturally immunized birds harboring endothelial-stage parasites. The ELISA described is sensitive, and it requires a minimal amount of equipment to collect the blood samples. The assay can be used for detecting and monitoring levels of anti-Plasmodium spp. antibodies in selected groups of penguins.

Journal ArticleDOI
TL;DR: Development of an avian ascaridoid in the intestine of a mammal increases the potential of this widespread species to infect other mammals, including humans.
Abstract: Juveniles of Contracaecum multipapillatum infected the Mayan cichlid (Cichlasoma urophthalmus) and adults infected the olivaceous cormorant (Phalacrocorax olivaceus) and the great egret (Casmerodius albus) in the coastal lagoon at Celestun, State of Yucatan, Mexico. All are new host records, and, even though the geographic locality record of Mexico for the species has not been published, unidentified but presumably conspecific specimens have been reported from there. When juveniles of C. multipapillatum were fed to a kitten, but not rats, ducks, or chickens, they developed into adults. Measurements and morphological data are provided on the specimens from the kitten. Development of an avian ascaridoid in the intestine of a mammal increases the potential of this widespread species to infect other mammals, including humans.

Journal ArticleDOI
TL;DR: Four species of helminths were identified from black bears collected in New Brunswick, including Trichinella spiralis, including Dirofilaria ursi, Baylisascaris transfuga, and Taenia krabbei, which represents the first documentation of T. spiralis in Maritime Canada and extends eastward the range of the species.
Abstract: Between May 1989 and October 1991, 544 black bears Ursus americanus were collected in New Brunswick and examined for Trichinella spiralis larvae. In addition, 110 of these bears were examined for filarial nematodes, and the entire intestinal tracts of 12 bears were examined for intestinal helminths. Four species of helminths were identified from these bears, including Trichinella spiralis, Dirofilaria ursi, Baylisascaris transfuga, and Taenia krabbei. This represents the first documentation of T. spiralis in Maritime Canada and extends eastward the range of T. krabbei.

Journal ArticleDOI
TL;DR: No correlations were found between changes in the values of blood parameters with season or age of penguins, and differences between these groups in total white blood cell (WBC) counts and relative lymphocytosis (LYMPHS) were not significant.
Abstract: Twenty-nine juvenile, captive-reared African black-footed penguins (Spheniscus demersus) were hematologically monitored every 2 wk over the period of 24 wk during their first outdoor exposure. Blood samples taken from the penguins were screened for 12 blood evaluation parameters. Parasitemic penguins were medically treated. Eighteen birds (62.1%) experienced naturally acquired malaria and 11 birds (37.9%) remained nonparasitemic. A total of 32 avian malaria episodes were noted; 25 (78.1%) were identified as Plasmodium elongatum, 5 (15.6%) as Plasmodium relictum, and 2 (6.3%) as Plasmodium spp. One P. elongatum (3.4%) and 3 P. relictum (10.3%) infections were fatal. All deaths occurred during the first episode of parasitemia. Gross lesions of the birds that died included hepatomegaly and splenomegaly. Interstitial pneumonia with schizonts was observed on histological examinations. The range, mean, and SD of 12 hematological parameters were determined for nonparasitemic and parasitemic penguins. Differences between these groups in total white blood cell (WBC) counts and relative lymphocytosis (LYMPHS) were not significant. The combined classes of total WBC counts (>20.0 x 103/tl) and LYMPHS (>60.0%) are not indicative of avian malaria infection in African penguins. No correlations were found between changes in the values of blood parameters with season or age of penguins. Treatment of parasitemic birds significantly reduced expected mortality from 50.0% to 13.8%.

Journal ArticleDOI
TL;DR: Fresh, sterile urine is an inexpensive substitute for serum in the culture of 2 strains of L. braziliensis, 1 infected with Leishmania RNA virus 1, and 1 uninfected, and both the infected and the unin infected strains grew to the same final cell density as the same strains grown in the presence of serum.
Abstract: Leishmania braziliensis cells are difficult to culture in vitro and usually require media supplemented with serum for sustained cell division. Fresh, sterile urine is an inexpensive substitute for serum in the culture of 2 strains of L. braziliensis, 1 infected with Leishmania RNA virus 1, and 1 uninfected. In the presence of urine, both the infected and the uninfected strains grew to the same final cell density as the same strains grown in the presence of serum. One strain of Leishmania major was also successfully cultured in urine-supplemented media.

Journal ArticleDOI
TL;DR: A high level of protection was obtained when antigen fractions of 56, 66, and 74 kDa were used together, and antigens with similar molecular weights were also detected in early steps of differentiation in T. solium cysticercosis.
Abstract: Cross immunity between Taenia solium and Taenia crassiceps parasites points to T. crassiceps cysticercosis as a convenient model to test promising antigens aimed at the development of a vaccine against T. solium cysticercosis. Since total antigens from T. crassiceps metacestodes induce significant levels of protection in pigs against T. solium cysticercosis, we initiated this work to identify the most interesting antigens involved in protection. Twelve different antigen fractions isolated from T. crassiceps cysticerci were evaluated with respect to their capacity to induce resistance against a challenge with 10 T. crassiceps cysticerci in male BALB/cAnN mice. Mice were intraperitoneally immunized with 2 doses of each antigen, 5 or 15 ig per mouse. The 12 antigen fractions were classified as protecting (200, 123, 74, 66, 56, 40-50, 27, and 8-14 kDa), facilitating (220-205 kDa), or irrelevant (150-160, 93, 108 kDa), according to their effect on the parasite load. The 3 most promising antigen fractions were reevaluated via subcutaneous immunization with Freund's complete adjuvant. A high level of protection was obtained when antigen fractions of 56, 66, and 74 kDa were used together. Interestingly, antigens with similar molecular weights were also detected in early steps of differentiation in T. solium cysti- cercosis. These observations may be helpful in the development of a synthetic or a recombinant vaccine against cysticercosis.