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PubMed2005

Veterinary public health activities at FAO: cysticercosis and echinococcosis.

In many developing and transition countries, parasitic zoonoses such as cysticercosis and echinococcosis cause serious human suffering and considerable losses in agricultural and human productivity, thus posing a significant hindrance to their development. Although, effective and reliable tools for the diagnosis, prevention and control of parasitic zoonoses are now available, their implementation has not always been successful in many countries. This is primarily due to the lack of awareness on the presence or impact of the causing parasites (Taenia saginata, Taenia solium and Echinococcus spp.). In addition, often the needed intersectorial cooperation, resource management and political commitment for their control are (also) absent. FAO's regular programme has established a global network of professionals directly involved in zoonotic and food-borne diseases. The network provides a basic framework for the spread of information related to the diagnosis, prevention and control of major zoonotic diseases including cysticercosis and echinococcosis.

Animals↗
PubMed1994

A review on vaccination against protozoa and arthropods of veterinary importance.

The recent advances in immunology and biotechnology have stimulated much research on the control of parasitic diseases through vaccination. This is a review of the state of the art regarding important protozoan and arthropod veterinary parasites. A live oocyst vaccine for avian coccidiosis is still in use but much work has been done on the identification, cloning, and assay of protective antigens. The sporozoites of Eimeria tenella have been the preferred subject and at least four recombinant antigens have already been tested with partial success. Premunization against babesiosis is still widely used in Latin America as is a live vaccine with attenuated parasites in Australia. At least three Babesia bovis and three Babesia bigemina antigens that generate partial protection have been produced as recombinant proteins. A vaccine against canine babesiosis is being commercialized in France. Infection-treatment is still used to vaccinate against Theileria parva and a schizont vaccine against Theileria annulata. Recombinant sporozoite antigens have been assayed with partial success against both species but the identification and administration of protective schizont antigens, regarded as the most important, still requires considerable work. The immunological control of African trypanosomoses is still impaired by the antigenic variation that the parasites experience during the infection. Although some possibilities exist, most specialists are pessimistic about the promise of developing a vaccine in the near future. Control of Boophilus ticks with an occult tick intestine recombinant antigen seems to have potential in inhibiting reproduction of the tick but salivary antigens appear to be more effective at inhibiting feeding and pathogen transmission. Vaccination with a Hypoderma protein, recently cloned, has induced 90% protection against subsequent infestations. It is very likely that effective vaccines against veterinary parasites will become available in the near future.

Animals↗
PubMed1999

Veterinary parasitology: looking to the next millennium.

'Veterinary parasitology' has traditionally been concerned with the control of parasites of livestock and companion animals, with emphasis on chemotherapy and immunoprophylaxis. This will continue, but there must be less reliance on chemical control; the development of alternative strategies will be a major goal over the next ten years. Here, Andrew Thompson takes an optimistic look at the challenges, strengths and opportunities for veterinary parasitology as we enter the next millennium. In the space available here, he can only 'scratch the surface' about what the future holds for veterinary parasitology, and will attempt to identify the major trends that are emerging, some of which will be the subject of future in-depth articles in Parasitology Today.

Animals↗
PubMed2006

Leishmania-derived murine monocyte chemoattractant protein 1 enhances the recruitment of a restrictive population of CC chemokine receptor 2-positive macrophages.

Transgenic Leishmania parasites that encode the murine chemokine monocyte chemoattractant protein 1 (MCP-1) were generated. These parasites transcribed MCP-1 mRNA and secreted MCP-1 protein. Infection of BALB/c, C57BL/6, or MCP-1 knockout (KO) mice with these parasites resulted in minimal lesion development with fewer parasites in the infected foot, lymph node, and spleen compared to wild-type-infected mice. In contrast, transgenic parasites caused substantial lesions with relatively high numbers of parasites in CC chemokine receptor 2 (CCR2) KO mice, indicating that the parasites are viable and healthy and that the lack of lesion development is CCR2 dependent. Prior infection of mice with transgenic parasites offered no protection to subsequent wild-type L. major challenge, suggesting that the transgenic parasites are controlled by an early innate immune response. Consistent with innate immunity, flow cytometry of cells from the ears of mice infected with transgenic parasites revealed an increase in the number of CCR2-positive macrophages by day 7 postinfection. The enumeration of transgenic parasites in ear lesions demonstrated a significant reduction in parasite numbers, which coincided with the increased CCR2-positive macrophage migration. CCR2-positive macrophages isolated from ears of mice infected with transgenic parasites contained virtually no parasites. In vitro studies revealed that optimal parasite killing required the recruitment of CCR2-positive macrophages, followed by stimulation with a combination of both MCP-1 and gamma interferon (IFN-gamma). This work suggests that the parasite-derived MCP-1 can recruit a restrictive population of CCR2-positive macrophages into lesions that can be optimally stimulated by MCP-1 and IFN-gamma to efficiently kill Leishmania parasites.

Animals↗
PubMed1975

Attempts to transfer immunity to Trichobilharzia ocellata (Trematoda: Schistosomatidae) passively via lymphoid cells and/or serum.

White Pekin ducklings were injected with serum, lymphoid cells, or both, derived from donor birds which were immune to reinfection by the schistosome trematode, Trichobilharzia ocellata. Ducklings receiving serum and/or cells from susceptible birds, and untreated ducklings, served as controls. One set of experimental and control ducklings was kept alive and all of these birds passed viable T. ocellata eggs by day 20 indicating that protective immunity had not been transferred. Another set was killed 3-5 days after exposure. The schistosomula which were recovered from these were measured and in most cases no difference between experimentals and controls could be seen. However, birds which had received the maximum dose of serum (8 ml.) did produce worms of different length, the immune serum recipients having shorter parasites than controls. A second experiment was performed in which up to 60 ml. of immune serum was injected, controls being recipients of normal serum or saline. Recipients of immune serum either failed to pass worm eggs entirely, or passed low numbers after delayed onset. Controls were variable but exhibited earlier patency and heavier infections. Schistosomula recovered from birds killed 4 days after exposure were measured. In 3 of 4 groups, experimentals were significantly shorter than controls, but no significant differences were detected between normal serum and saline controls.

Animals↗
PubMed1989

BCG: a modifier of immune responses to parasites.

The use of BCG (Bacille Calmette-Guerin) as an adjuvant is well-established for vaccination against leprosy and tuberculosis. Dominique Frommel and Phillippe Lagrange discuss the effects of BCG in the control of parasite infections, particularly leishmaniasis, and the possibility of the development of anti-parasite recombinant BCG vaccines.

Journal Article↗
PubMed1994

Relationships between the parasites of some wild and cultured fishes in two lakes and a fish farm in central Finland.

A total of 526 Atlantic salmon and 500 brown trout from a fish farm were studied for parasites, as were 272 roach, 251 perch and 150 whitefish from the lake which formed the water source, and 196 roach and 136 perch from the effluent recipient lake. The cultured fish harboured 14 parasite species, of which most were protozoan generalist parasites. Nine species were found on salmon and 12 on brown trout. Epizootically the most important species were Ichthyobodo necator, Chilodonella cyprini and Ichthyophthirius multifiliis. The mean number of species per studied fish was 0.71 for salmon and 0.61 for brown trout. The seasonal occurrences of the ectoparasites were found to be irregular due to preventative bathing of the fish. The wild whitefish harboured 19 parasite species, roach 41 and perch 33. The proportions of the parasite species common to both wild and cultured fishes were 17% of the species from roach, 36% of those from perch and 47% of the species from whitefish. Jaccard's similarity index, indicating similarities between wild and farmed fish, was highest between whitefish and brown trout. It was concluded that the source of parasites in the fish farm is the water supplying lake, but the farm itself was unlikely to effect the fish parasite fauna of the water recipient lake, although some ectoparasites, which had high prevalences in this lake, could originate from the farm. The high standard of maintenance and hygiene in this farm kept problems caused by parasites under control.

Animals↗
PubMed1993

Natural resistance to infection with intracellular parasites: isolation of a candidate for Bcg.

Natural resistance to infection with intracellular parasites is controlled by a dominant gene on mouse chromosome 1, called Bcg, Lsh, or Ity. Bcg affects the capacity of macrophages to destroy ingested intracellular parasites early during infection. We have assembled a 400 kb bacteriophage and cosmid contig within the genomic interval containing Bcg. A search for transcription units by exon amplification identified six novel genes in this contig. RNA expression studies showed that one of them, designated Nramp, was expressed exclusively in macrophage populations from reticuloendothelial organs and in the macrophage line J774A. Nramp encodes an integral membrane protein that has structural homology with known prokaryotic and eukaryotic transport systems, suggesting a macrophage-specific membrane transport function. Susceptibility to infection (Bcgs) in 13 Bcgr and Bcgs strains tested is associated with a nonconservative Gly-105 to Asp-105 substitution within predicted transmembrane domain 2 of Nramp.

Amino Acid Sequence↗
PubMed2001

Biological control of field infections of nematode parasites of young sheep with Duddingtonia flagrans and effects of spore intake on efficacy.

A field study was undertaken to determine the effects of feeding Duddingtonia flagrans to young Merino sheep on pasture. A total of 60 mixed sex lambs 4-5 months old were divided into six even groups on the basis of liveweight. On Monday to Friday, each week for 6 months, three groups were offered barley grains on which D. flagrans had been cultured while the other three groups remained untreated. Every 4 weeks liveweights were recorded and faecal samples collected for nematode egg count estimation. Feeding D. flagrans reduced faecal egg counts and tended to improve liveweight gains, but considerable differences were observed between groups within treatment. These differences are thought to result from variations between the groups in consumption of the treated barley with the "best" consumers showing the greater effects of treatment.

Animals↗
PubMed1995

Clearance of Theileria sergenti-infected bovine red blood cells in severe combined immune deficiency mice.

Clearance of Theileria sergenti-infected bovine red blood cells (Bo-RBCs) from the blood circulation of severe combined immune deficiency (SCID) mice was studied to help understand the mechanisms of anemia developing in cattle infected with T. sergenti. For the clearance test, Bo-RBC samples having 2%, 58%, and 76% parasitemia and, as a control, parasite-free Bo-RBCs were prepared in the Bo-RBC-SCID mouse model. The T. sergenti-infected Bo-RBCs and the uninfected control Bo-RBCs were separately labeled with two, green and red, fluorescent dyes, mixed together, and injected intravenously into SCID mice. The blood samples collected at various time points were observed under a fluorescent microscope, and the numbers of green and red fluorescing RBCs were counted differentially to determine the clearance rates of T. sergenti-infected and uninfected Bo-RBCs. This test clearly demonstrated that the Bo-RBC samples having higher parasitemias were cleared faster from the blood circulation of SCID mice. The results suggest that the intravascular clearance system in SCID mice may have a mechanism by which T. sergenti-parasitized and non-parasitized Bo-RBCs are recognized and cleared differentially.

Animals↗
PubMed2005

Arginase and polyamine synthesis are key factors in the regulation of experimental leishmaniasis in vivo.

Arginase 1, an enzyme induced by Th2 cytokines, is a hallmark of alternatively activated macrophages and is responsible for the hydrolysis of L-arginine into ornithine, the building block for the production of polyamines. Upregulation of arginase 1 has been observed in a variety of diseases, but the mechanisms by which arginase contributes to pathology are not well understood. We reveal here a unique role for arginase 1 in the pathogenesis of nonhealing leishmaniasis, a prototype Th2 disease, and demonstrate that the activity of this enzyme promotes pathology and uncontrolled growth of Leishmania parasites in vivo. Inhibition of arginase activity during the course of infection has a clear therapeutic effect, as evidenced by markedly reduced pathology and efficient control of parasite replication. Despite the clear amelioration of the disease, this treatment does not alter the Th2 response. To address the underlying mechanisms, the arginase-induced L-arginine catabolism was investigated and the results demonstrate that arginase regulates parasite growth directly by affecting the polyamine synthesis in macrophages.

Animals↗
PubMed2002

[The phagocytic activity of blood platelets in different parasitic diseases].

Blood platelets take part in immune reactions of the organism, especially in anti-parasitic immunity. We conducted the phagocytic activity of blood platelets. This experiments were done on 40 patients infected with Giardia intestinalis (26), Ascaris lumbricoides (8), Entamoeba histolytica/Entamoeba dispar (6). Blood for analysis was collected thrice, before treatment (P1), after two weeks (P2), and after two months treatment with anti-parasitic drugs (P3). Control group consisted of 32 healthy people. The evaluation of platelet phagocytic activity revealed that the mean percentage of phagocytizing platelets in patients was 2.87 (P1), 2.94 (P2), 2.86 (P3), being significantly lower in controls (mean 2.15), the difference was statistically significant (p < 0.05). No statistically significant difference was found in the mean phagocytic index between patients (P1, P2, P3) and controls. Our general conclusion is--parasites are able to stimulate phagocytic activity of blood platelets.

Adult↗
PubMed1994

Update on llama medicine. Parasites.

Lamoids in North America harbor a wide variety of parasites. Treatment and control methods based on previous experience with parasites of cattle and sheep have been successful, but problems do exist. First, the pharmacokinetics for most anthelmintics have not been evaluated in llamas. Second, even though llamas, sheep, and cattle share many parasites, the two most common nematodes found in llamas (C. mentulatus and T. tenuis) are not part of the parasitic fauna of livestock. This presents difficulties in basing treatment and control methods on those recommended for cattle and sheep. Variability in host response to the same parasite also hinders the use of cattle and sheep as models for the llama. This is best demonstrated by F. magna and F. hepatica; the reaction induced by the first more closely resembles those seen in cattle than sheep, but the reaction induced by the second more closely resembles those seen in sheep than cattle. Finally, parasites known to be pathogenic in livestock (e.g., N. battus) have unknown effects in llamas. These examples illustrate that we must use caution when extrapolating existing knowledge regarding the parasites of sheep and cattle to llamas. Further research on the epidemiology of parasites peculiar to the llama is needed to enhance control efforts. Improved methods of diagnosis and treatment of parasites also are areas in which further efforts are needed.

Animals↗
PubMed2000

Larval cyathostomiasis.

Over the past few years, cyathostomiasis has become increasingly recognized as a clinical problem of horses in the United States. Clinical cyathostomiasis has been reported frequently in Europe for a considerable time. This clinical syndrome is usually related to the sudden release of large numbers of the larval stages of small strongyles from the mucosa of the large intestine. Typical clinical signs include diarrhea, ventral abdominal edema, pyrexia, colic, weight loss, and poor body condition. Hypoalbuminemia and the presence of large numbers of small strongyles being passed in the feces are also characteristic features of the disease. The disease may occur seasonally in late winter and early spring or after drug treatment to remove the luminal stages of small strongyles. Two commercially available drugs, moxidectin and fenbendazole, have been shown to be effective against the encysted larval stages of the parasites. Drug resistance of small strongyles to all classes of currently available antiparasitic compounds except the macrocyclic lactones (ivermectin and moxidectin) is a limiting factor in controlling these parasites and may result in an increased prevalence of clinical cyathostomiasis over time.

Animals↗
PubMed1996

The isolation and characterization of genomic and cDNA clones coding for a cdc2-related kinase (ThCRK2) from the bovine protozoan parasite Theileria.

The tick-transmitted protozoan parasites Theileria annulata and Theileria parva are important intracellular pathogens of domestic cattle in tropical and subtropical regions. Proliferative phases take place within both lymphocytes and erythrocytes. The lymphocyte is stimulated to enter the cell cycle by the parasite and the multinucleate parasite can establish a state in which karyokinesis and cytokinesis occur in phase with the host cell. The link between parasite nuclear division and cytokinesis is altered during the formation of merozoites (a non-dividing, invasive, extracellular stage). These features imply a high degree of control over parasite nuclear division and cytokinesis. Two different approaches have been used to identify clones from both species which are extremely highly conserved homologues. These encode a cdc2-related kinase which is > 60% identical to eukaryotic cyclin-dependent kinases of the p34cdc2/p32CDK2 subfamily. There is typical conservation of kinase domains, implying an in vivo protein kinase activity for the polypeptide. The PSTAIRE region, implicated in cyclin binding, is well conserved suggesting that ThCRK2 will bind cyclin molecules closely related to the eukaryotic A/B-type cyclins. However, there is divergence in certain key motifs potentially associated with binding of molecules that regulate the activity of the kinase. Expression patterns of RNA and protein indicate that ThCRK2 is likely to function in all dividing stages of the parasite and, taken together, the results point to a central role in the regulation of nuclear division.

Amino Acid Sequence↗