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PubMed2002

Mouse antibody response to a microsporidian parasite following inoculation with a gene coding for parasite ribosomal RNA.

This study found that a plasmid construct encoding the small-subunit ribosomal RNA (SSUrRNA) of the microsporidian Microgemma caulleryi generates a humoral response upon intramuscular inoculation in mice. The plasmid used was pCMV, following preliminary trials indicating efficient beta-galactosidase gene expression in mouse muscle cells transfected with pCMV/beta-Gal. The antibodies produced after inoculation with pCMV/SSUDNA recognized parasite spore antigens and reached maximum levels at 30 days postinoculation, subsequently remaining stable for at least 120 days. Due to the highly conserved sequence of the SSUrDNA in different microsporidian species, these results open up interesting prospects for broad-spectrum vaccination.

Animals↗
PubMed2000

An albumin-like protein in the serum of non-parasitic brook lamprey (Lampetra appendix) is restricted to preadult phases of the life cycle in contrast to the parasitic species Petromyzon marinus.

Previous work showed that the parasitic sea lamprey, Petromyzon marinus, has two different albumin-like serum proteins during the course of its life cycle. One of these, AS, is the predominant protein in the serum of larval and metamorphosing intervals but is absent in the upstream migration phase of the life cycle; the other, SDS-1, is found at its highest level in the upstream migration phase and is the predominant serum protein in this phase. The present investigation examines the nonparasitic brook lamprey Lampetra appendix for the presence of albumins. Using electrophoresis and antisera monospecific for serum proteins, it was found that L. appendix has a serum protein that is antigenically similar to the AS protein of P. marinus. This protein (LAS) makes up about 70% of the total serum protein of the Lampetra larva, is present in metamorphic stages 1,2,3,4 and 5 but is virtually absent from the remaining metamorphic stages and the adult. Furthermore, the adult of L. appendix has no serum protein that is antigenically similar to SDS-1 of the adult P. marinus; our study shows that, unlike P. marinus, there is no single protein that represents a major portion of the total serum protein content in the L. appendix adult.

Albumins↗
PubMed2004

Gametocyte sex ratio of a malaria parasite: response to experimental manipulation of parasite clonal diversity.

Sex ratio theory posits that the adaptive proportion of male to female gametocytes of a malaria parasite within the vertebrate host depends on the degree of inbreeding within the vector. Gametocyte sex ratio could be phenotypically flexible, being altered based on the infection's clonal diversity, and thus likely inbreeding. This idea was tested by manipulating the clonal diversity of infections of Plasmodium mexicanum in its lizard host, Sceloporus occidentalis. Naive lizards were inoculated with infected blood from a single donor or 3 pooled donors. Donors varied in their gametocyte sex ratios (17-46%, male), and sex ratio theory allowed estimation of the clonal diversity within donor and recipient infections. Phenotypic plasticity would produce a correlation between donor and recipient infections for infections initiated from a single donor, and a less female-biased gametocyte sex ratio in recipients that received a mixed blood inoculum (with predicted higher clonal diversity) than recipients receiving blood from a single donor. Neither pattern was observed. Gametocyte sex ratio of most infections ranged from 35 to 42% male, expected if clonal diversity was high for all infections. Alternative explanations are suggested for the observed variation of gametocyte sex ratio among P. mexicanum infections.

Animals↗
PubMed1998

Primary cause of mortality in the armyworm larvae simultaneously parasitized by parasitic wasp and infected with bacteria.

Parasitoid wasps never kill their hosts before the wasp larvae emerge from the host. However, almost 100% of the host armyworm larvae Pseudaletia separata die within 2-3 days by parasitization with the wasp Cotesia kariyai or by injection of polydnavirus, the wasp symbiont virus, when they are simultaneously infected by the pathogenic bacterium Serratia marcescens. The present study was conducted to elucidate the crucial factor causing this larval mortality. An insecticidal protein has been shown to exist in the hemolymph of dying host larvae; it has been purified by procedures consisting of reverse-phase column extraction, gel filtration and ion-exchange column chromatography. The purified protein showed a strong insecticidal effect with a median lethal dosage (LD50) of 13 pmol/larva and was estimated to have a molecular mass of 57 kDa. The amino acid sequence of the insecticidal protein was partially characterized and used for isolation and sequencing of the genomic DNA. The deduced amino acid sequence for this protein revealed striking similarity with the metalloprotease of S. marcescens enterobacter.

Amino Acid Sequence↗
PubMed1986

[A new onchocercal parasite, Onchocerca alcis n. sp., parasite of the moose Alces alces in Sweden].

Among the onchocercids of cervids, Onchocerca alcis n. sp., a parasite of the moose, Alces alces, belongs to that small palearctic group of evolved onchocercids consisting of O. jakutensis, O. garmsi and O. tarsicola. It is distinguished from its most closely related species, O. jakutensis, primarily on the characters of the lateral chord and cuticle, its greater spicule ratio, and the characteristic shapes of the anterior and posterior extremities of female worms.

Animals↗
PubMed1990

Genetic aspects of malaria parasite infection and the host immune response in relation to parasite evasion.

In relation to problems found up to now for the development of vaccines against malaria, recent studies have pointed out the different strategies evolved by the parasites to evade the host immune response. They include antigenic variation, antigenic polymorphism, antigenic mimicry and direct interference with the generation of the host immune response. These different mechanisms are rapidly reviewed and discussed with the aim of focusing the actual orientation of basic and applied research which has been developed to overcome these difficulties.

Animals↗
PubMed2000

Reversal of type 2 diabetes in mice by products of malaria parasites: I. Effect of inactivated parasites.

C57BL/KsJ-db/db and C57BL/KsJ-ob/ob mice are good models for studies on human obesity and type 2 diabetes. We have previously shown that infection with blood-stage malaria or injection of extracts from malaria-parasitized red blood cells induces hypoglycemia in normal mice and normalizes hyperglycemia in mice made moderately diabetic by streptozotocin. In the present study, we show that a single intravenous (IV) injection of Formalin-fixed Plasmodium yoelii YM (FFYM) preparation decreases blood glucose in db/db mice from an initial value of 19 mmol/L to a normal value of 7 mmol/L (P < .0001) for at least 24 hours and reduces food intake. Plasma insulin concentrations in db/db mice were not altered. FFYM was also active in normal and ob/ob mice, an effect associated with an increase in plasma insulin. Although the rate of weight gain in lean ob/+ and lean db/+ was not altered by this treatment, there was a significant reduction in weight gain in db/db and ob/ob mice (P < .001). We suggest that malaria-derived molecules, when fully characterized, may provide structural information for the development of new agents for the management of type 2 diabetes.

Animals↗
PubMed1983

Studies on the parasitic helminths of slaughtered animals in Iraq. I. Parasitic helminths of the liver of herbivores.

The livers and lungs of 580 sheep, 160 goats, 418 cattle, 50 camels and 48 buffaloes slaughtered in Baghdad in April-July, 1981 were examined for helminth parasites; 14.3% of the sheep, 0.6% of the goats, 18.2% of the cattle, 72.0% of the camels and 8.3% of the buffaloes were infected with trematodes and cestodes. Dicrocoelium dendriticum is reported from the livers of sheep in Iraq for the first time.

Animals↗
PubMed1978

Erythrocyte entry by malarial parasites. A moving junction between erythrocyte and parasite.

Invasion of erythrocytes by merozoites of the monkey malaria, Plasmodium knowlesi, was investigated by electron microscopy. The apical end of the merozoite makes initial contact with the erythrocyte, creating a small depression in the erythrocyte membrane. The area of the erythrocyte membrane to which the merozoite is attached becomes thickened and forms a junction with the plasma membrane of the merozoite. As the merozoite enters the invagination in the erythrocyte surface, the junction, which is in the form of a circumferential zone of attachment between the erythrocyte and merozoite, moves along the confronted membranes to maintain its position at the orifice of the invagination. When entry is completed, the orifice closes behind the parasite in the fashion of an iris diaphragm, and the junction becomes a part of the parasitophorous vacuole. The movement of the junction during invasion is an important component of the mechanism by which the merozoite enters the erythrocyte. The extracellular merozoite is covered with a prominent surface coat. During invasion, this coat appears to be absent from the portion of the merozoite within the erythrocyte invagination, but the density of the surface coat outside the invagination (beyond the junction) is unaltered.

Animals↗
PubMed1997

The novel oxygenated chalcone, 2,4-dimethoxy-4'-butoxychalcone, exhibits potent activity against human malaria parasite Plasmodium falciparum in vitro and rodent parasites Plasmodium berghei and Plasmodium yoelii in vivo.

Previous studies have shown that licochalcone A, an oxygenated chalcone, exhibits antileishmanial and antimalarial activities. The present study was designed to examine the antimalarial activity of an analog of licochalcone A, 2,4-dimethoxy-4'-butoxychalcone (2,4mbc). 2,4mbc inhibited the in vitro growth of both a chloroquine-susceptible (3D7) and a chloroquine-resistant (Dd2) strain of Plasmodium falciparum in a [3H]hypoxanthine uptake assay. The in vivo activity of 2,4mbc was tested in mice infected with Plasmodium berghei or Plasmodium yoelii and in rats infected with P. berghei. 2,4mbc administered either orally, intraperitoneally, or subcutaneously for 5 days protected the mice from otherwise lethal infections of these parasites. 2,4mbc administered orally for 5 days reduced parasitemia in the rats infected with P. berghei. These results demonstrate that 2,4mbc exhibits potent antimalarial activity and might be developed into a new antimalarial drug.

Animals↗
PubMed2006

Parasites as causative agents of human affective disorders? The impact of anti-psychotic, mood-stabilizer and anti-parasite medication on Toxoplasma gondii's ability to alter host behaviour.

With increasing pressure to understand transmissible agents, renewed recognition of infectious causation of both acute and chronic diseases is occurring. Epidemiological and neuropathological studies indicate that some cases of schizophrenia may be associated with environmental factors, such as exposure to the ubiquitous protozoan Toxoplasma gondii. Reasons for this include T. gondii's ability to establish persistent infection within the central nervous system, its ability to manipulate intermediate host behaviour, the occurrence of neurological and psychiatric symptoms in some infected individuals, and an association between infection with increased incidence of schizophrenia. Moreover, several of the medications used to treat schizophrenia and other psychiatric disease have recently been demonstrated in vitro to possess anti-parasitic, and in particular anti-T. gondii, properties. Our aim here was thus to test the hypothesis that the anti-psychotic and mood stabilizing activity of some medications may be achieved, or at least augmented, through their in vivo inhibition of T. gondii replication and invasion in infected individuals. In particular we predicted, using the epidemiologically and clinically applicable rat-T. gondii model system, and following a previously described and neurologically characterized 'feline attraction' protocol that haloperidol (an anti-psychotic used in the treatment of mental illnesses including schizophrenia) and/or valproic acid (a mood stabilizer used in the treatment of mental illnesses including schizophrenia), would be, at least, as effective in preventing the development of T. gondii-associated behavioural and cognitive alterations as the standard anti-T. gondii chemotherapeutics pyrimethamine with Dapsone. We demonstrate that, while T. gondii appears to alter the rats' perception of predation risk turning their innate aversion into a 'suicidal' feline attraction, anti-psychotic drugs prove as efficient as anti-T. gondii drugs in preventing such behavioural alterations. Our results have important implications regarding the aetiology and treatment of such disorders.

Animals↗
PubMed2004

Liver invasion by malarial parasites--how do malarial parasites break through the host barrier?

Malarial transmission to the human host is established by sporozoite infection of the liver. Sporozoites are released from the mosquito salivary glands and carried by the blood flow to the liver sinusoid. In the sinusoid, sporozoites leave the blood circulation by crossing the sinusoidal cell layer to infect hepatocytes, the site for their development into the erythrocyte-invasive forms. Traversal of the sinusoidal cell layer and subsequent hepatocyte infection are the most important events in sporozoite liver invasion, but the molecular basis of both events remains to be elucidated. The present review of sporozoite liver invasion focuses on recent advances in this topic obtained by application of reverse genetics. Sporozoites traverse host cells, rupturing the host cell membrane in the process. Three microneme proteins have important roles in this motility. Disruption of one of these genes abolishes or severely impairs cell traversal without affecting other types of invasive motility. Studies using these disruptant parasites indicate that cell-traversal ability is required for crossing the sinusoidal cell layer and accessing the hepatocytes for infection. This process is homologous to midgut epithelium penetration by the malarial ookinete, because identical or paralogous genes are critically involved in both processes. After arrival at the hepatocyte, the invasion mode of the sporozoites switches from cell traversal to hepatocyte infection.

Animals↗
PubMed1999

Comparison of a parasite lactate dehydrogenase-based immunochromatographic antigen detection assay (OptiMAL) with microscopy for the detection of malaria parasites in human blood samples.

Microscopic examination of blood smears remains the gold standard for malaria diagnosis, but is labor-intensive and requires skilled operators. Rapid dipstick technology provides a potential alternative. A study was conducted in The Gambia to compare the performance of OptiMAL, an immunochromatographic antigen detection assay for the diagnosis of malaria using parasite lactate dehydrogenase, against standard microscopy in patients with suspected malaria. For initial diagnosis of Plasmodium falciparum, irrespective of stage, this assay had a sensitivity of 91.3%, a specificity of 92%, a positive predictive value of 87.2%, and a negative predictive value of 94.7%. The sensitivity of the test decreased markedly at parasitemias < 0.01%. This assay can be used for the diagnosis of malaria in areas where microscopy is not available and for urgent malaria diagnosis at night and at weekends, when routine laboratories are closed and when relatively inexperienced microscopists may be on duty.

Animals↗
PubMed1999

Parasites of domestic and wild animals in South Africa. XXXVI. Arthropod parasites of yellow mongooses, Cynictis penicillata (G. Cuvier, 1829).

Eighty yellow mongooses, Cynictis penicillata, from five localities in South Africa were examined for arthropod parasites. Ten ixodid tick species, of which Haemaphysalis zumpti was the most abundant, prevalent and widely distributed, were collected. The mongooses were also infested with two mite species. Echidnophaga gallinacea was the most abundant of the eight flea species collected. It and Ctenocephalides connatus were present at every locality. A single biting louse species, Felicola cynictis, was recovered and it was the most prevalent ectoparasite on the mongooses.

Animals↗
PubMed2000

Observations on a lesser-known monogenean, Udonella myliobati, from a copepod parasite, Lepeophtheirus natalensis, parasitizing the spotted ragged-tooth shark, Carcharias taurus, from South African waters.

The phylogeny of the genus Udonella has been disputed for quite some time, but recent phylogenetic analysis of molecular data confirms that the genus is a monopisthocotylean monogenean. Specimens of Udonella myliobati parasitizing the copepod Lepeophtheirus natalensis, an ectoparasite of the spotted ragged-tooth shark, (Carcharias taurus), were collected and studied. A total of 771 monogenean specimens were recovered from 54 infected copepods examined, with a mean intensity of 14,3 worms per copepod. Most of the monogeneans were found attached to the dorsal surface of the lateral and frontal marginal membranes of the copepod carapace. Eggs, with filaments and adhesive discs, were found ventrally on the host, mainly attached to the maxillae and maxillipeds, in clusters of 12-14. Observations on the morphology, distribution and behaviour of this monogenean are presented with the aid of light and scanning electron microscopy.

Animals↗
PubMed2001

Parasites of domestic and wild animals in South Africa. XXXIX. Helminth and arthropod parasites of Angora goats in the southern Karoo.

Parasites were collected from 160 Angora goats and kids on the Jansenville Experimental Farm, Eastern Cape Province. Six nematodes were identified to species level and three to generic level. Nematodirus spathiger was the most numerous of the economically important nematodes recovered. It was always present, and fourth stage larvae were collected from untreated goats from August to March, while animals used as tracers also picked up most infection from August to March. Kids born on the farm during October acquired their first nematode infections between 2 and 3 months of age and the intensity of infection increased erratically thereafter to reach a plateau once the kids were 14 months of age. Eight of the nine kids between 3 and 5 months of age and examined between January and March were infected with Moniezia expansa. Five ixodid tick species were collected from the goats of which Rhipicephalus glabroscutatum was the most numerous and prevalent. Its immature stages were present mainly from March to September and adults from July to January. The goats also harboured the biting louse Damalinia limbata and the sucking louse Linognathus africanus. The greatest intensity of infestation with L. africanus occurred on the kids during the first few months of their lives. The larvae of the nasal bot fly, Oestrus ovis were present in kids at 1 month of age, and infestation took place mainly from spring to late summer.

Age Factors↗
PubMedDate not supplied

[Hypothesis of parasitic stress in parasitized insects caused by microsporidia].

Pathological alterations being similar to those that can be seen while hormonal dysbalance, particularly the increase of juvenile hormone (JH) titre, is one of the consequences of microsporidian infections. Though the increase of JH in insects infected with microsporidia has not been shown directly, there are many indirect proofs of this. It has been believed that JH is produced by microsporidia. But this has not been shown for microsporidia or for other endoparasites. In this article we want to propose another hypothesis. We suppose that during microsporidiosis the following events develop: exhaustion of host nutrition stores and other destructive consequences of microsporidian dwelling in host cells lead to the decrease of host biosynthetical and reparation activity in the infected cells and then to destructive alterations that can be seen by electro-microscopic methods. The infected cells are stressed and then the typical answer for many physiological stresses follows. Secretion of prothoracicotropic hormone by brain neurosecretory cells is inhibited and as a result the production and release of ecdysone is also inhibited and ecdysteroid titre decreases. The activity of JH-esterases is decreased and as a result the JH titre is increased. If microsporidian infection causes the stress in the host cells, the endocrine system will undoubtedly answer to this stress and this answer will definitely be the same as for all other stresses. Thus, in any case JH titre will be increased in infected insects independently of whether microsporidia produce JH or not. So, hormonal alterations in infected insects should be the consequence not of the microsporidian JH production but of the host response reaction to infection. We suppose that microsporidia do not differ from other parasites of insects and that they can not produce JH.

Animals↗
PubMed1991

Parasites of domestic and wild animals in South Africa. XXVIII. Helminth and arthropod parasites of Angora goats and kids in Valley Bushveld.

Two adult Angora goats were slaughtered each month for 24 consecutive months on a farm in Valley Bushveld in the eastern Cape Province. On the same farm 2 Angora goat kids were slaughtered each month for 2 consecutive years from the time they were 1 week old until they reached 12 months of age. All these goats were processed for the recovery of helminth and arthropod parasites. Fourteen nematode species, 2 nematode genera and 1 cestode species were recovered. Worm burdens were generally low in the adult goats. Nematode burdens increased erratically in the kids reaching the greatest numbers when they were 1 year old. The tapeworm, Moniezia expansa, was present in kids at 3 or 4 months of age and had usually disappeared by the time they reached 7 months of age.

Animals↗