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PubMed2006

Bovine trypanotolerance: A natural ability to prevent severe anaemia and haemophagocytic syndrome?

Trypanotolerance is the capacity of certain West-African, taurine breeds of cattle to remain productive and gain weight after trypanosome infection. Laboratory studies, comparing Trypanosoma congolense infections in trypanotolerant N'Dama cattle (Bos taurus) and in more susceptible Boran cattle (Bos indicus), confirmed the field observations. Experiments using haemopoietic chimeric twins, composed of a tolerant and a susceptible co-twin, and T cell depletion studies suggested that trypanotolerance is composed of two independent traits. The first is a better capacity to control parasitaemia and is not mediated by haemopoietic cells, T lymphocytes or antibodies. The second is a better capacity to limit anaemia development and is mediated by haemopoietic cells, but not by T lymphocytes or antibodies. Weight gain was linked to the latter mechanism, implying that anaemia control is more important for survival and productivity than parasite control. Anemia is a marker for a more complex pathology which resembles human haemophagocytic syndrome: hepatosplenomegaly, pancytopenia and a large number of hyperactivated phagocytosing macrophages in bone marrow, liver and other tissues. Thus, mortality and morbidity in trypanosome-infected cattle are primarily due to self-inflicted damage by disproportionate immune and/or innate responses. These features of bovine trypanotolerance differ greatly from those in murine models. In mice, resistance is a matter of trypanosome control dependent on acquired immunity. However, a model of anaemia development can be established using C57BL/6J mice. As in cattle, the induction of anaemia was independent of T cells but its development differed with different trypanosome strains. Identification of the molecular pathways that lead to anaemia and haemophagocytosis should allow us to design new strategies to control disease.

Anemia↗
PubMed2005

Historical aspects for the control of soil-transmitted helminthiases.

Japan has been one of the very few countries that operated the nationwide control programme against soil-transmitted helminths (STH) infections and gained a great success. On the basis of researches and operational studies, periodical mass-examination using cellophane thick smear (Kato technique) and selective mass-treatment targeted at school children were employed as the most useful control measure. In later years, Japan's experience and the strategy for STH control programme were transferred to Asian countries through Asian Parasite Control Organization (APCO) and also to countries of Asia, Africa and Latin-America through seminar at a modified form of the integration programme (IP) of STH control with family planning and nutritional improvement. The parasitologists group conducted studies in all aspects to seek effective STH control measures for respective countries and obtained many successful results.

Adolescent↗
PubMedDate not supplied

Malaria therapy reinoculation data suggest individual variation of an innate immune response and independent acquisition of antiparasitic and antitoxic immunities.

Malaria therapy reinoculation data were examined for the possible detection of effects attributable to stable individual host-specific factors, through correlation between descriptive variables of first and second infections. Such an effect was demonstrated with respect to the first local maximum of the asexual parasite density, i.e., the density at which a host controls parasite growth. The effect was seen between an individual host's first and second Plasmodium falciparum infection, as well as between an individual host's first malaria infection with P. ovale and second malaria infection with P. falciparum. We give reasons to believe that the main underlying mechanism is individual variation of an innate immune response. The data were also examined for systematic changes from first to second P. falciparum infection, as indicators of acquired immunity. In addition to the well-known reduction in parasite density, the data show the early development of apparent parasite tolerance. We give reasons to interpret the latter as antitoxic immunity.

Animals↗
PubMed1999

Cell-mediated immunity to Toxoplasma gondii: initiation, regulation and effector function.

Cell-mediated immune responses are essential for host control of intracellular infections. Toxoplasma gondii is a protozoan parasite that infects multiple vertebrate species and invades multiple cell types. Upon initial encounter with the immune system, the parasite rapidly induces production of the type-1 promoting cytokine IL-12 most likely from a subpopulation of dendritic cells. NK and T cells are then activated and triggered to synthesize IFN-gamma, the major mediator of host resistance during the acute and chronic phases of infection. During the acute phase, a concomitant IL-10 response dampens the systemic type-1 cytokine production and prevents lethal immunopathology. Cytokine (IFN-gamma und TNF-alpha) rather than cytotoxicity-based effector functions are more critical for protective immunity both during the acute and chronic phases of T. gondii infection. Both hemopoietic and non-hemopoietic cellular elements act as IFN-gamma and TNF-dependent effectors of host resistance. Type II iNOS-derived nitric oxide (NO) is required mainly for hemopoietic cell-derived effector cell activity in the central nervous system (CNS) during the chronic phase of infection. Nevertheless, in both the acute and chronic stages, IFN-gamma-dependent but iNOS-independent mechanism(s) play a major function in parasite control and their identification remains an important challenge for this field.

Acute Disease↗
PubMed2004

Imaging movement of malaria parasites during transmission by Anopheles mosquitoes.

Malaria is contracted when Plasmodium sporozoites are inoculated into the vertebrate host during the blood meal of a mosquito. In infected mosquitoes, sporozoites are present in large numbers in the secretory cavities of the salivary glands at the most distal site of the salivary system. However, how sporozoites move through the salivary system of the mosquito, both in resting and feeding mosquitoes, is unknown. Here, we observed fluorescent Plasmodium berghei sporozoites within live Anopheles stephensi mosquitoes and their salivary glands and ducts. We show that sporozoites move in the mosquito by gliding, a type of motility associated with their capacity to invade host cells. Unlike in vitro, sporozoite gliding inside salivary cavities and ducts is modulated in speed and motion pattern. Imaging of sporozoite discharge through the proboscis of salivating mosquitoes indicates that sporozoites need to locomote from cavities into ducts to be ejected and that their progression inside ducts favours their early ejection. These observations suggest that sporozoite gliding allows not only for cell invasion but also for parasite locomotion in host tissues, and that it may control parasite transmission.

Animals↗
PubMed1999

Green fluorescent protein as a marker in Plasmodium berghei transformation.

We present a new marker that confers both resistance to pyrimethamine and green fluorescent protein-based fluorescence on the malarial parasite Plasmodium berghei. A single copy of the cassette integrated into the genome is sufficient to direct fluorescence in parasites throughout the life cycle, in both its mosquito and vertebrate hosts. Erythrocyte stages of the parasite that express the marker can be sorted from control parasites by flow cytometry. Pyrimethamine pressure is not necessary for maintaining the cassette in transformed parasites during their sporogonic cycle in mosquitoes, including when it is borne by a plasmid. This tool should thus prove useful in molecular studies of P. berghei, both for generating parasite variants and monitoring their behavior.

Animals↗
PubMed2001

Relationship of intestinal parasites to the environment and to behavioral factors in children in the Bolikhamxay Province of Lao PDR.

From March to July 1998 the infection rates of 732 children aged below 15 years were assessed. The investigation was conducted in selected villages of the Bolikhamxai Province in Lao PDR. Socio-economic conditions and behavioral pattern were studied. The three soil-transmitted helminths, Ascaris lumbricoides, Trichuris trichiura and hookworm were found with prevalence rates of 67.14, 17.49 and 12.83%, respectively. Infection rates with other intestinal parasites were negligible. Of the children investigated, 56.7% harbored one and 20.45% more than one parasite. Except for hookworms, no statistically significant differences were found between genders. The probability of being infected with A. lumbricoides is associated with living in mountainous areas. For hookworms, infection is associated with staying in the plains. A river in the vicinity of the village is linked with the probability of being infested with Trichuris trichiura. Not to belong to a family with the ability to own expensive items increases the probability by almost two times of getting infested with A. lumbricoides. Unhygienic behavioral factors were important in increasing the probability of suffering from A. lumbricoides and T trichiura infection. Behavioral factors did not seem to be related to hookworm infections. It was concluded that after mass treatment, besides promoting the construction of toilets, it is also important to improve personal hygiene so that a lasting impact on the infection rate of the most prevalent parasites in Lao PDR could be achieved. Measures to control parasitic infections do not have to be postponed until a marked improvement of the economic situation has occurred.

Adolescent↗
PubMed1981

Programming for preventive disease and improved production in sheep.

Sheep losses each year are high in all types of rearing systems throughout the United Kingdom. Losses could well be reduced by a closer relationship between the sheep owner and the veterinarian. A closer relationship should involve the development of a simple disease preventive programme requiring a number of regular farm visits each year. Any such programme could attempt to control disease mainly by preventive methods, establish a complete parasite control programme and incorporate a high degree of instruction. There is probably a need for many veterinarians to attend specialist sheep courses, and suggestions are offered whereby the situation could be improved.

Animals↗
PubMed1983

Research needs and priorities for ruminant internal parasites in the United States.

The management-chemotherapy approach is currently the most applicable means of effectively and practically controlling parasites of ruminants. Knowledge of regional patterns for major ruminant parasites, especially seasonal transmission dynamics, promises to lead to major improvements in management-chemotherapy systems. This knowledge also provides the fundamental context for design of new integrated control strategies that include other approaches such as immunization, chemical and biological control, and the interaction of environmental, physiologic, and nutritional factors. Greatly needed is a change in the protracted government regulatory process that obviates the availability of new, more effective drugs until years after they are available in other developed nations and that creates a dearth of "minor species, minor use" antiparasitic compounds. It is necessary to recognize both the need for product safety and the realities of investment limitations in the pharmaceutical industry. Also needed are new formulations and better methods of mass treatment for inaccessible herds of ruminants that will allow flexibility in strategic treatment programs based on seasonal transmission and other factors. More reliable cost-benefit assessments, more sensitive diagnostic indicators, and better knowledge of pathophysiologic mechanisms of damage by parasites will assist greatly in identifying the economically important effects against which economical control programs can be targeted. The opportunities for development and evaluation of novel prophylactic, diagnostic, and management approaches for animal parasitism are close at hand if the spectacular advances in molecular biology, immunology, computer science, and ecologic methodologies are assimilated in present research efforts. Although the emphasis of this report is on applied research and identification of approaches for the immediate future, the importance of more basic research on animal parasites and discoveries in other areas of modern biology and medicine are recognized as the essential pacesetters of the future. There is increasing concern by agricultural research workers that renewal of this base of fundamental knowledge is greatly needed. In this context, studies on the physiology, behavior, antigenicity, and genetic makeup of parasites, protective host responses, and mechanisms of tissue destruction and invasion by veterinary parasites are essential. Veterinary parasitologists must study host-parasite interactions directly with minimal reliance on rodent model systems; although this has disadvantages it offers special opportunities for research that is concurrently applied and fundamental. While the livestock industry can expect continuous progress on current problems, a long-term investment in basic research must be made for the future.

Animals↗
PubMed2003

Prevalence of intestinal parasite infections on a national scale among primary schoolchildren in Laos.

In order to investigate the epidemiological situation of intestinal parasite infections in Laos, parasitological surveys were carried out on a national scale including 17 provinces and the Vientiane Municipality. A total of 29,846 stool specimens were collected from primary schoolchildren from May 2000 to June 2002 and examined once with the cellophane thick smear technique. The cumulative egg positive rate for intestinal helminths was 61.9%. By species, the rate for Ascaris lumbricoides was 34.9%, hookworm 19.1%, Trichuris trichiura 25.8%, Opisthorchis viverrini 10.9%, Taenia spp. 0.6% and Hymenolepis spp. 0.2%. The northern mountainous regions such as Phongsaly, Huaphan or Saysomboune Province showed a higher prevalence (over 70%) of soil- transmitted helminths. The regions along the Mekong River such as Khammuane, Saravane or Savannakhet Province showed a higher prevalence (over 20%) of fish-borne parasites. On the other hand, Schistosoma mansoni eggs were detected in 1.7% of schoolchildren only in Champassak Province, a previously endemic area. The highest prevalence was noted in Phongsaly Province (96.0%) and the lowest in Bolikhamxay Province (27.5%). An additional small-scale survey by cellophane anal swab detected Enterobius vermicularis eggs in 35.7% of 451 schoolchildren aged 6-8 years in Khammuane, Vientiane, Champassak Province and the Vientiane Municipality. Meanwhile, the mean blood haemoglobin level of hookworm-infected children was not lower than that of children not infected with hookworm, suggesting that nutritional factors are more important than parasite infection per se. Nevertheless, the above results indicate that a nationwide parasite control project is necessary to reduce possible morbidity due to parasitic diseases in the country.

Child↗
PubMed2004

Technological advances and genomics in metazoan parasites.

Molecular biology has provided the means to identify parasite proteins, to define their function, patterns of expression and the means to produce them in quantity for subsequent functional analyses. Whole genome and expressed sequence tag programmes, and the parallel development of powerful bioinformatics tools, allow the execution of genome-wide between stage or species comparisons and meaningful gene-expression profiling. The latter can be undertaken with several new technologies such as DNA microarray and serial analysis of gene expression. Proteome analysis has come to the fore in recent years providing a crucial link between the gene and its protein product. RNA interference and ballistic gene transfer are exciting developments which can provide the means to precisely define the function of individual genes and, of importance in devising novel parasite control strategies, the effect that gene knockdown will have on parasite survival.

Animals↗
PubMed2001

Current status of human parasitic infections in Taiwan.

The eradication of the 2 mosquito-borne parasitic diseases, malaria and lymphatic filariasis, is one of the greatest achievements of the parasite control campaigns in Taiwan. Most of the soil-transmitted nematode infections, with the exception of pinworm infection, are currently well controlled and limited to some aboriginal areas. Food-borne parasitic zoonosis such as infections with Angiostrongylus cantonensis, Clonorchis sinensis, and Taenia saginata asiatica are not rare, but the former is seasonal and the latter 2 are ethnically and geographically associated. Intestinal protozoal infections with Giardia lamblia and Cryptosporidium parvum are at low levels but may be widely distributed. Opportunistic protozoal infections among patients with acquired immunodeficiency syndrome, which included amebic colitis, Pneumocystis carinii pneumonia, and cerebral toxoplasmosis, are becoming increasingly important. The rapid increase in international travel and the introduction of large numbers of foreign workers from other countries in Southeast Asia may change the epidemiological patterns of parasitic infections in Taiwan.

AIDS-Related Opportunistic Infections↗
PubMed2006

[Value of identification of gastrointestinal nematode third-stage larvae recovered from faeces and herbage].

Strategic parasite control programmes of ruminant gastrointestinal nematodes requires the knowledge of parasite population dynamics. In natural conditions, ruminants, in particular sheep and goats, are infected by different species of gastrointestinal nematodes. The life cycle of these parasites is influenced by a number of factors which include climatic variations. Therefore, it is important to utilise appropriate methods to identify the parasite population both in the host and from the pasture. In this paper faecal larval cultures and pasture larval counts used for herd health monitoring of nematode infections are discussed.

Animal Feed↗
PubMed1977

[Present trends in the development of pest control methods with reference to environmental protection].

Problems are discussed which result from the present change in principles of parasite control. The main task is maximum limiting the damage caused by certain parasite species. But ecological stability should be disturbed at minimum level. Likewise the introduction of physiologically active alien substances in the ecosystem should be minimal. The solution of this task for practice is joined with research on natural regulation systems in populations and biocenoses, for such system determine the degree and number of species. Three main steps for this solution were shown: Ist: Evaluation of the scope of control; IInd: Evaluation of the strategy of control; IIIrd: Evaluation of a measures program to realize the chosen strategy.

Ecology↗
PubMed2000

An upstream element of the TamS1 gene is a site of DNA-protein interactions during differentiation to the merozoite in Theileria annulata.

Apicomplexan parasites are major pathogens of humans and domesticated animals. A fundamental aspect of apicomplexan biology, which may provide novel molecular targets for parasite control, is the regulation of stage differentiation. Studies carried out on Theileria annulata, a bovine apicomplexan parasite, have provided evidence that a stochastic process controls differentiation from the macroschizont to the merozoite stage. It was postulated that this process involves the presence of regulators of merozoite gene expression in the preceding stage of the life cycle, and that during differentiation a quantitative increase of these factors occurs. This study was carried out to test these postulations. Nuclear run-on analysis showed that TamS1 expression is controlled, at least in part, at the transcriptional level. The transcription start site showed homology with the consensus eukaryotic initiator motif, and study of the 5' upstream region by the electrophoretic mobility-shift assay demonstrated that a 23 bp motif specifically bound factors from parasite-enriched nuclear extracts. Three complexes were shown to bind to a 9 bp core binding site (5'-TTTGTAGGG-3'). Two of these complexes were present in macroschizont extracts but were found at elevated levels during differentiation. Both complexes contain a polypeptide of the same molecular mass and may be related via the formation of homodimer or heterodimer complexes. The third complex appears to be distinct and was detected at time points associated with the transition to high level merozoite gene expression.

Adult↗
PubMed1984

Glycogen content in Gastrothylax crumenifer and Cotylophoron orientale after the isolation of parasites, their starvation and refeeding with various carbohydrates.

The average reserve glycogen content in unstarved (control) parasites, 4.7 +/- 0.14 g/100 g F.T. (fresh weight of tissue) in Gastrothylax crumenifer and 3.15 +/- 0.14 g/100 g F.T. in Cotylophoron orientale has been estimated biochemically. The consumption of endogenous glycogen was found to be 18.47%, 44.37%, 66.66% and 78.13% of F. T. in G. crumenifer and 14.92%, 40.95%, 66.34% and 71.42% of F.T. in C. orientale during 12, 24, 36 and 48 hours of starvation. Both the parasites were able to resynthesize 71.71% and 75.42% of lost glycogen (maximum up to 16 hours) on refeeding in nutrient medium containing glucose. The maximum resynthesis of lost glycogen in both the parasites was observed in nutrient medium containing glucose rather than the other carbohydrates such as fructose, lactose, sucrose and trehalose.

Animals↗
PubMed1996

Control of gastrointestinal parasitism in calves with albendazole delivered via an intraruminal controlled-release device.

The efficacy of albendazole in an intraruminal controlled-release device against gastrointestinal nematodes in calves was evaluated under field conditions. Calf productivity was monitored during the first and second grazing seasons. Two groups of parasite-naive Holstein Friesian heifer calves were grazed from May to October on adjacent, similarly contaminated paddocks. One group was given a Captec bolus at turnout, the group was left untreated. Pasture larval counts peaked on the paddock grazed by the untreated calves at 23,000 1 kg-1 dry matter in October. This precipitated clinical parasitic gastro-enteritis in the untreated calves with a mean peak faecal egg count of 335 epg, high blood pepsinogen and gastrin concentrations and a mean worm burden of 79,614 at 100 days post-turnout. Pasture larval counts on the paddock grazed by the treated calves remained less than 3000 1 kg-1 DM and the mean faecal egg count was zero until mid-August, peaking at 146 eggs per gram of faeces (epg) in October. The treated calves had body liveweight advantage of 19 kg at the end of September. During the second grazing season the first season untreated calves were refractory to infection. The first season treated calves showed signs of parasitic gastro-enteritis, although not to the extent exhibited by a group of first season parasite-naive tracer calves which were grazed on the same paddock.

Albendazole↗
PubMed2000

The prevalence of internal and external parasites in pigs of different ages and sexes in Southeast District, Botswana.

Botswana imports most pig-based products from neighbouring countries. Pig farming is limited by, among other things, the negative effect of parasites and diseases on production. The object of this study was to determine the prevalence of ecto- and endoparasites in pigs of different ages and sexes in the Southeast District of Botswana. Thirty-nine pigs were sampled for endoparasites and 19 for ectoparasites during a period of 2 1/2 months. Of all the pigs sampled, 54,55% were infected with Ascaris suum, 20,45% with Trichostrongylus spp. and 6,82% with Trichuris suis. Ascaris suum was found to be the most common endoparasite infesting both mature, i.e. 12 months and older, and young, i.e. less than 12 months old, pigs. Although not significantly different (P > 0,05), the prevalence of this parasite species was slightly higher (68,42% with an average of 1,023 +/- 545 eggs per gram (EPG) of faeces per pig) in mature than in young pigs (55% with an of average 1,500 +/- 846 EPG of faeces per pig). The prevalence of Trichostrongylus spp. was lower in mature (5,26% with 20 +/- 14 EPG of faeces per pig) than in young pigs (25% with 22 +/- 9 EPG of faeces per pig). The prevalence of T. suis was also lower in mature (0% infection) than in young pigs (15% with 9 +/- 4 EPG of faeces per pig). The prevalence of the three endoparasite species was not significantly different between the sexes A. suum (1,020 +/- 883 v. 1,503 +/- 522 EPG of faeces per pig), Trichostrongylus spp. (24 +/- 14 v. 18 +/- 8 EPG of faeces per pig) and T. suis (11 +/- 6 v. 2 +/- 4 EPG of faeces per pig) for male and female pigs respectively. Sarcoptes scabiei was the only ectoparasite identified on the pigs sampled for external parasites. It infested 40% of all pigs but the infestation on young pigs (70%) was higher than on the mature ones (33,33%). Since the infection of internal and external parasites was similar in young and old pigs of both sexes, controlling parasites is of great importance since these generally lead to reduced production and are also of public health concern. It is recommended that a further study be carried out to investigate the effect of internal and external parasites on productivity.

Age Factors↗