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PubMed2006

A preliminary survey of gastrointestinal and haemoparasites of beef cattle in the tropical livestock farming system in Nan Province, northern Thailand.

Parasitism is a primary cause of production losses in most cattle-producing countries of the world, including Thailand. A cross-sectional study was designed to determine baseline data on the prevalence of gastrointestinal and haemoparasites of beef cattle in Nan Province, northern Thailand and to investigate the factors associated with the prevalence of parasitic infections. A total of 207 faecal and 162 blood samples were collected during the summer of 2005. The basic data of management were recorded, including the number of animals on the farm or in the village, major animal health problems, deworming programme and veterinary service. The overall prevalence of gastrointestinal parasitic infections was 61% (126/207). The most common helminth infections in this study were rumen flukes 28% (58), followed by strongyles 27% (55), and the rest were due to Strongyloides 1% (2) and Trichuris 1% (2). The common protozoan infections were Buxtonella cysts 2% (5) and coccidia oocysts 2% (4). Of the 162 blood samples examined, 50% (81) contained Theileria sp., 2% (4) trypanosome, and 1% (1) microfilariae. The high rate of parasitic infections in these areas might be related to the poor management by the farmers, such as sharing the same grazing pasture.

Animals↗
PubMed1986

Immunity in intestinal helminth infections: present concepts, future directions.

Although intestinal helminth and protozoan infections are prevalent throughout the world, their impact is poorly known. Nevertheless, the morbidity and mortality that occur have stimulated research into host resistance and pathogenesis. Unfortunately, despite an increasing knowledge base, the actual effector molecules which lead to parasite loss are unknown. IgA antibody, intraepithelial leukocytes and mucosal mast cells are thought to be involved. The role of these and other responses in making the intestinal microenvironment hostile to the parasite through effects of neurotransmission, epithelial cell differentiation and function, smooth muscle activities, and local inflammatory responses must be studied. Future research will include: further definition of the cellular and molecular immunologic repertoire of the intestine, identification of local effector molecules and investigation of interactions between antigen-specific immune responses and intestinal physiology. Studies of human infections will be more restricted but must include: assessment of parasite-specific local immunologic responses, inflammatory events in the intestine, and development of relatively non-invasive techniques to study gastrointestinal physiology during parasitic infection. Perhaps most importantly, research facilities must be established in developing countries to investigate intestinal immunological, inflammatory and physiological responses during infection. Through such investigations, risk factors for susceptibility and disease severity may be identified and therapeutic or prophylactic strategies developed.

Animals↗
PubMed1998

Inactivation of viruses, bacteria, protozoa, and leukocytes in platelet concentrates.

Despite the increased safety of blood achieved through continued improvements in donor testing, concern remains about the safety of blood components. Transfusion of cellular components has been implicated in transmission of viral, bacterial, and protozoan diseases. While it is commonly recognized that hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV), and the retroviruses, such as human immunodeficiency virus (HIV) and the human lymphotrophic viruses (HTLV) can be transmitted through cellular components, other pathogens are emerging as potentially significant transfusion-associated infectious agents. For example, transmission of protozoan infections due to trypanosomes and babesia have been reported. In addition to viral and protozoal infectious agents, bacterial contamination of platelet concentrates continues to be reported; and may be an under reported transfusion complication. More importantly, new infectious agents may periodically enter the donor population before they can be definitively identified and tested for to maintain consistent safety of the blood supply. The paradigm for this possibility is the HIV pandemic which erupted in 1979. During the past decade a number of methods to inactivate infectious pathogens in blood components, including platelets, have been developed. This technology is now entering the clinical trial phase.

Animals↗
PubMed2000

New technologies for the inactivation of infectious pathogens in cellular blood components and the development of platelet substitutes.

Despite the increased safety of blood components, achieved through improved donor selection and testing, transfusion recipients remain at risk of transfusion-associated diseases. Transfusion of cellular blood components has been implicated in transmission of viral, bacterial and protozoan diseases. While it is commonly recognized that hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV), and retroviruses, such as human immunodeficiency virus (HIV) and the human lymphotrophic viruses (HTLV), can be transmitted through cellular components, other pathogens are emerging as potentially significant transfusion-associated infectious agents. For example, transmission of protozoan infections due to trypanosomes and Babesia have been reported. In addition to viral and protozoan infectious agents, cases of bacterial contamination of platelet and red cell concentrates continue to be reported and may be an under-reported transfusion complication. More importantly, new infectious agents continue to enter the donor population, and there is an inherent time delay before the new pathogens are definitively identified and new tests implemented in order to maintain consistent safety of the blood supply. The paradigm for this problem is the HIV pandemic. During the past decade a number of methods for inactivating infectious pathogens in platelet concentrates have been investigated as a strategy to improve the safety of platelet transfusion therapy. One method of treating platelet concentrates to inactive pathogens has now reached the advanced clinical trial phase in the United States and Europe. Similar efforts with a new class of compounds are underway for red cell concentrates, and two of these are in early phase trials. In addition to studies with allogeneic platelets and red cells, a number of laboratories have described methods for developing platelet substitutes or modified platelets to avoid the use of traditional platelet concentrates as a means to improve safety.

Anti-Infective Agents↗
PubMed1998

Prevalence of intestinal parasites in rural Southern Indians.

OBJECTIVE: To determine the prevalence of intestinal protozoal and helminthic infection in a rural population. METHOD: Seventy-eight members of 15 families from a village were studied. Stool samples from all subjects were examined on alternate days for one month. RESULTS: The overall prevalence rate of various parasitic infections was 97.4%, with only 2 of 78 subjects not excreting parasites in any of their 15 samples. Eighteen (23.1%) persons had only one type of parasite, while 58 (74.3%) excreted multiple parasites. Giardia and Cryptosporidium were the commonest protozoan infections, affecting 42/78 (53.8%) and 31/78 (39.7%), respectively. Hookworm infestations were the commonest helminthic infections, seen in 48/78 (61.5%). Based on excretion patterns, the asymptomatic individuals could be divided into 2 groups of infrequent and frequent excretors, indicating that the host response may determine the level of parasite replication in the gut.

Adolescent↗
PubMed1995

Disseminated acanthamoeba infection in patients with AIDS: case reports and review.

Acanthamoeba infection has been described as an opportunistic infection in persons with AIDS. We report two cases of patients with AIDS and acanthamoeba infection and review the manifestations of this protozoan infection in patients infected with human immunodeficiency virus. The diagnosis of this infection requires a high index of suspicion because the clinical and histologic manifestations may be confused with those of disseminated fungal or algal disease. Clinicians and laboratory personnel should be aware of this potentially fatal condition so that appropriate diagnostic studies can be performed and treatment can be urgently administered. Early initiation of therapy may alter the clinical outcome of the disease.

AIDS-Related Opportunistic Infections↗
PubMed2004

Protection against progressive leishmaniasis by IFN-beta.

Type I IFNs (IFN-alphabeta) exert potent antiviral and immunoregulatory activities during viral infections, but their role in bacterial or protozoan infections is poorly understood. In this study, we demonstrate that the application of low, but not of high doses of IFN-beta protects 60 or 100% of BALB/c mice from progressive cutaneous and fatal visceral disease after infection with a high (10(6)) or low (10(4)) number of Leishmania major parasites, respectively. IFN-beta treatment of BALB/c mice restored the NK cell cytotoxic activity, increased the lymphocyte proliferation, and augmented the production of IFN-gamma and IL-12 in the draining lymph node. Low, but not high doses of IFN-beta caused enhanced tyrosine phosphorylation of STAT1 and STAT4, suppressed the levels of suppressor of cytokine signaling-1, and up-regulated the expression of inducible NO synthase in vivo. The IFN-beta-induced increase of IFN-gamma production was dependent on STAT4. Protection by IFN-beta strictly required the presence of inducible NO synthase. In the absence of STAT4 or IL-12, IFN-beta led to an amelioration of the cutaneous and visceral disease, but was unable to prevent its progression. These results identify IFN-beta as a novel cytokine with a strong, dose-dependent protective effect against progressive cutaneous leishmaniasis that results from IL-12- and STAT4-dependent as well as -independent events.

Animals↗
PubMed1995

How many stool examinations are necessary to detect pathogenic intestinal protozoa?

Recent reports have suggested that examination of one stool specimen is sufficient to detect protozoa in symptomatic patients. To verify this hypothesis, we examined specimens submitted to the regional laboratory of a large, prepaid health plan that provides primary care to a membership representative of the general population in northern California. We examined the number and results of stool specimen examinations in the two-month period before detection of Entamoeba histolytica in 125 infected persons, of Giardia lamblia in 154 infected persons, and of Dientamoeba fragilis in 60 persons infected with this parasite. About 13% of the entire group had a single stool specimen examined, 19% had two examined, 65% had three examined, and 6% had more than three examined. Most infections were detected in the first specimen or specimens submitted, but many were not detected until later examination. Thirteen patients with E. histolytica (10.4%) required 4-9 examinations. The sensitivity of one examination was compared with that of three examinations; with the additional examinations, the yield increased 22.7% (95% confidence interval [CI] = 11.8-33.5%) for E. histolytica, 11.3% (95% CI = 6.9-81.8%) for G. lamblia, and 31.1% (95% CI = 17.7-54.4%) for D. fragilis. Our results suggest that a single stool specimen examination will miss many pathogenic protozoan infections in symptomatic persons.

Animals↗
PubMed1992

Seasonal prevalence of protozoan parasites in Nsukka, Nigeria.

Five hundred fresh stool specimens of patients with clinical symptoms of protozoan infections were examined for parasites. During June 1988-May 1991, the total number of positive cases was 261 (52.2 per cent). When the infectivity frequencies were segregated among the samples of different localities, it was observed that 6 (1.2 per cent) persons from the University of Nigeria community, 89 (17.8 per cent) urban dwellers and 166 (33.2 per cent) rural populace were infected. The highest incidence of Giardia lamblia (83, 47.8 per cent), Entamoeba histolytica (49, 28.3 per cent) and Chilomastix mesnili (34, 19.7 per cent) was found among the rural community. The infection started in April of each year (onset of rainy season), peaked between July and August, and was the lowest between November and March (dry season). Statistical interpretation of the results indicated that the parasitic infections depended on times of the year x2 0.01 > 4 calculated x2 0.01, 0.05 > 4 tabulated. The vehicle of transmission of the infection was green vegetable (Amaranthus viridans) which gets polluted by sewage oxidation pond at the locality.

Adult↗
PubMed2001

Adaptive physiological processes in the host during gastrointestinal parasitism.

Parasite infection of the gastrointestinal tract with helminths or protozoa induces detrimental effects on host tissues and host physiology, which have been extensively studied and reviewed. However, parasitism of the digestive system is also associated with adaptive, compensatory phenomena based on changes in host physiology or structures and which tend to counterbalance the negative consequences. The objective of this review is to describe these adaptive processes and their possible underlying mechanisms. Different processes which tend to attenuate the effect of either the loss of appetite, the intestinal malabsorption or the increased tissue losses have been assessed. These processes have been reported both for helminth and protozoan infections, where they present similar characteristics. The mechanisms involved in the adaptation to parasitism remain largely unidentified. The role of feedback mechanisms based on host regulation, possibly through gastrointestinal hormones, has been raised. On the other hand, some data support the proposal that parasites themselves may initiate some of the adaptive processes and consequently favour their own survival. These adaptive phenomena appear to be an essential component in the dynamic balance between host and parasites. Also, parasite infections represent unique models to study the adaptation of the gastrointestinal tract to aggressors.

Adaptation, Physiological↗
PubMedDate not supplied

Prevalence and pathogenicity of Entamoeba histolytica in three different regions of Pernambuco, northeast Brazil.

Parasitological examinations were carried out on 663 individuals of three different cities of Pernambuco State, Northeastern Brazil: Recife, Palmares and Bodocó. The population from a drought area of Pernambuco State, Bodocó, was investigated for amoebiasis and compared with Recife, metropolitan city (about 1.3 million of inhabitants) and another inland community, Palmares, located inside of the sugar-cane plantation region of the State. No evidence of invasive strains of E. histolytica were found in these inhabitants, provided that the isolated zymodemes I, III, IV, VIII, IX, X, XVII and XVIII are recognized as nonpathogenic strains of E. histolytica. Furthermore, the prevalence of intestinal helminths and other protozoan infections showed that these individuals are infected by other agents responsible for diarrhoeal diseases.

Adolescent↗
PubMed2002

History of human parasitology.

Humans are hosts to nearly 300 species of parasitic worms and over 70 species of protozoa, some derived from our primate ancestors and some acquired from the animals we have domesticated or come in contact with during our relatively short history on Earth. Our knowledge of parasitic infections extends into antiquity, and descriptions of parasites and parasitic infections are found in the earliest writings and have been confirmed by the finding of parasites in archaeological material. The systematic study of parasites began with the rejection of the theory of spontaneous generation and the promulgation of the germ theory. Thereafter, the history of human parasitology proceeded along two lines, the discovery of a parasite and its subsequent association with disease and the recognition of a disease and the subsequent discovery that it was caused by a parasite. This review is concerned with the major helminth and protozoan infections of humans: ascariasis, trichinosis, strongyloidiasis, dracunculiasis, lymphatic filariasis, loasis, onchocerciasis, schistosomiasis, cestodiasis, paragonimiasis, clonorchiasis, opisthorchiasis, amoebiasis, giardiasis, African trypanosomiasis, South American trypanosomiasis, leishmaniasis, malaria, toxoplasmosis, cryptosporidiosis, cyclosporiasis, and microsporidiosis.

Animals↗