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Parasitology Today is officially the Number One ranked journal in parasitology (impact factor 4.940). Since its launch in 1985, Parasitology Today has been part of the Trends Journal series - the most highly cited group of monthly review journals in the world, that includes Trends in Biochemical Sciences, Trends in Microbiology, Trends in Genetics, Immunology Today and Trends in Cell Biology.
Statistical analysis of parasitological data provides a powerful method for understanding the biological processes underlying parasite infection. However, robust and reliable analysis of parasitological data from natural and experimental infections is often difficult where: (1) the distribution of parasites between hosts is aggregated; (2) multiple measurements are made on the same individual host in longitudinal studies; or (3) data are from 'noisy' natural systems. Mixed models, which allow multiple error terms, provide an excellent opportunity to overcome these problems, and their application to the analysis of various types of parasitological data are reviewed here.
Serologically positive individuals without parasitological confirmation constitute an important problem for trypanosomiasis control programmes because of epidemiological and therapeutical consequences. In July 1997, in the focus of Quiçama (Angola), 4753 individuals were screened using CATT/T.b.gambiense on whole blood. In CATT-positive but parasite-negative individuals, CATT titration on serum was performed. Sixteen individuals showing an end-titre lower than 1/4 were considered noninfected according to the results of a previous study of serological status of parasitologically confirmed cases; 86 individuals with end titres >/= 1/4 were considered suspected of trypanosomiasis and were followed-up from July 1997 to July 1998 with controls every three months. After one year, 32 individuals whose antibody titres dropped < 1/4 were considered noninfected, 22 were confirmed by demonstration of parasites, 17 were further followed-up because antibody titres remained >/= 1/8 but parasites could not be found. Fifteen individuals did not show up for testing. Following the usual criterion, only parasitologically confirmed cases were treated. However, if it had been decided to treat parasite-negative individuals with a CATT end-titre > 1/8, 22 initially unconfirmed but infected individuals would have been treated earlier, whereas 5 noninfected individuals would have been treated unnecessarily. CATT titration on diluted serum or plasma is useful for making therapeutical decisions.
Six naturally infected dogs [two with no signs of leishmaniasis ('asymptomatic'), two with a few signs ('oligosymptomatic') and two with many signs ('polysymptomatic')] were studied before and after chemotherapy. Another two, non-infected dogs were kept as controls. The dogs were studied clinically, haematologically and parasitologically five times over 11 months and their infectivity to sandflies was evaluated before and after the treatment. The 'asymptomatic' dogs were as infective to sandflies as the 'symptomatic' before treatment but all dogs were un-infective for at least a few months following chemotherapy. Treatment led to a temporary improvement in the clinical and biochemical condition of most of the dogs, the symptomatic dogs becoming asymptomatic, but parasitological cure was uncommon after 10 months' follow-up. There was often no correlation between clinical condition, parasitological condition and infectivity to sandflies. Some dogs from both the 'asymptomatic' and 'symptomatic' groups became infective to sandflies several months post-treatment.
The diagnostic potential of circulating IgM and IgA antibodies against Schistosoma mansoni gut-associated antigens detected by the immunofluorescence test (IFT) on adult worm paraffin sections was evaluated comparatively to the fecal parasitological method, for epidemiological purposes in low endemic areas for schistosomiasis. Blood samples were collected on filter paper from two groups of schoolchildren living in two different localities of the municipality of Itariri (São Paulo, Brazil) with different histories and prevalences of schistosomiasis. The parasitological and serological data were compared to those obtained for another group of schoolchildren from a non-endemic area for schistosomiasis. The results showed poor sensitivity of the parasitological method in detecting individuals with low worm burden and indicate the potential of the serological method as an important tool to be incorporated into schistosomiasis control and vigilance programs for determining the real situation of schistosomiasis in low endemic areas.
Paleo-parasitology may be developed as a new tool to parasite evolution studies. DNA sequences dated thousand years ago, recovered from archaeological material, means the possibility to study parasite-host relationship coevolution through time. Together with tracing parasite-host dispersion throughout the continents, paleo-parasitology points to the interesting field of evolution at the molecular level. In this paper a brief history of paleo-parasitology is traced, pointing to the new perspectives opened by the recent techniques introduced.
The parasitological typology of lakes is proposed (with example of the Karelia-Kola limnological region). The characteristics of the main types of lakes with allowance of the parasitological data are given. The parasitological typology of lakes is based on studies of the parasite fauna diversity and differs from the trophical classification for lakes proposed by S. V. Gerd (1949).
We previously investigated malaria in the southern health district of the city of Dakar, which includes the oldest neighborhoods. In this study, we investigated malaria in the central health district, corresponding to the central area of the conurbation. The study was carried out at 12 sites, from March 1996 to February 1997. The sites were selected such that the entire district was covered and included 2 sites in the shanty town and three in an old village that has been absorbed into the city. We carried out prospective monthly entomological analyses with a view to identifying the vectors and the mode of transmission of malaria. We also carried out clinical and parasitological follow up to determine the incidence of parasitemia and of bouts of malaria. Insects were collected overnight from humans and the insects remaining the next morning in 10 bedrooms in the health district were collected. For clinical and parasitological follow up, families were visited at home once per week and their clinical state was assessed. Blood smears were taken to facilitate the detection of bouts of malaria. Body temperature was measured and we checked for the presence of organisms in the blood systematically during the last weekly visit of each month. For a total of 308 collections at night from human volunteers and 1,395 bedroom collections of residual fauna, we obtained 12,879 Culicidae females, 199 (1.5%) of which were anopheles mosquitoes, with Culex quinquefasciatus accounting for 98% of the remaining mosquitoes. As in the southern district, A. arabiensis was the only species of the A. gambiae complex collected. Anopheles mosquitoes accounted for only 0.3 bites per man per night and 0.07 females per room. They were therefore poorly represented in this district and were not detected at all at five sites. They were found in large numbers only during the rainy season, especially in September, when they accounted for 2.25 bites per man per night and 0.3 females per room at 3 sites in an undeveloped zone in which 81.4% of all the anopheles mosquitoes were collected. The parturition frequency of the biting females was 32.6% and that of the females collected in houses was 50.0%. None of the A. arabiensis females dissected (98.5% of those collected) carried Plasmodium sporozoites. The clinical and parasitological follow up concerned 2,583 individuals, aged from 1 month to 80 years, from 285 families resident in Dakar who volunteered for the study; 41.9% of these individuals were less than 15 years old and 92.2% had been living in Dakar for more than 2 years. Thick and thin blood smears taken monthly showed the frequency of the parasite to be 1.0% and that of gametocytes to be 0.1%. P. falciparum was the only parasite detected in the subjects. Plasmodium infections were observed in all age groups, with a frequency of 0.4% (adults over the age of 20 years) to 1.6% (children under two years of age). Parasitized subjects were detected in every month of the study, with a frequency of 0.4% (in January) to 1.9% (in December). The largest number of cases detected in a three-month period (38.8% of all cases) was that for October to December, the three-month period immediately after the rainy season (July to September). Parasite frequency, which was no higher than 1. 2% at 10 sites, was clearly higher at two sites in the shanty town (3.8 and 6.8%), mostly inhabited by immigrants from rural areas. At the end of the study year, satisfactory weekly follow up was considered to have been achieved for 1,067 of the participants. The annual incidence of parasitemia in this cohort was 5.1% and that of malaria was 2.4%. Incidence did not vary significantly with age and was between 1.8% and 7.6% for parasitemia and between 0.8% and 3.5% for malaria. However, significant differences in incidence were observed between areas. Incidence was higher at the two sites in the shanty town, with rates of 12.1% and 36.5% for parasitemia and 6.1% and 15.9% for malaria. (ABSTRACT TR
Parasites have natural habitats in the same way as a species: they are found in focal areas where the spatial distribution of the parasite, host, vector and required environmental conditions coincide. The spatial distribution of parasites is, therefore, a function of the interaction between abiotic and biotic environmental factors. The boundaries of distributions are not strictly fixed in space and time and may fluctuate with climate and other components of the environment or anthropical factors. Geographic Information Systems (GIS) and remote sensing (RS) technologies are being used increasingly to study the spatial and temporal patterns of disease. GIS can be used to complement conventional ecological monitoring and modelling techniques, and provide means to portray complex relationships in the ecology of disease. In addition, the use of GIS and RS to identify environmental features allows determination of risk factors and delimitation of areas at risk, permitting more rational allocation of resources for cost-effective control. Since 1996, GIS have been used in our territorial cross-sectional and longitudinal parasitological surveys in order to experiment new applications to plan sampling protocols and to display quickly, clearly, and analytically the spatial and/or temporal distribution of parasitological data. The use of GIS allowed us to draw the following types of descriptive parasitological maps: distribution maps, distribution maps with proportioned peaks, choroplethic maps with proportioned peaks, point distribution maps and point distribution maps with proportioned peaks. In a recent study, GIS and RS technologies have been used also to identify environmental features that influence the distribution of paramphistomosis in sheep from the southern Italian Apennines and to develop a preliminary risk assessment model. A GIS was constructed using RS and landscape feature data together with paramphistome positive survey records from 197 georeferenced ovine farms with animals pasturing in an area of the southern Italian Apennines. The GIS for the study area was constructed utilizing the following environmental variables: Normalized Difference Vegetation Index (NDVI), land cover, elevation, slope, aspect, and total length of rivers. In addition, data regarding the presence of watercourses smaller than rivers, namely, streams, springs and brooks were recorded in the field. All these variables were then calculated for "buffer zones" consisting of the areas included in a circle of 3 Km diameter centred on 197 farms. The environmental data obtained were analyzed by univariate and multivariate statistical analyses using the paramphistome farm coprological status (positive/negative) as the dependent variable. A multivariate stepwise discriminant analysis model was developed that included moors and heathland, sclerophyllus and coniferous forest vegetation, autumn-winter NDVI and presence of streams, springs and brooks on pasture. The variables entered in the model are consistent with the environmental requirements of paramphistomes and their snail intermediate host. In particular, the land cover types entered in the model in this area are indicators of marginal uncultivable and sloping zones where typically there is the presence of water (permanently or temporarily). In addition, since NDVI can be used as an indicator of regional thermal-moisture regime, the distribution of farms positive for paramphistomosis corresponding to relatively high values of winter NDVI indicated the presence of adequate moisture and temperatures favourable to the rumen fluke and the snails. In conclusion, GIS and RS are useful to define the habitats of parasites, especially for those with strong environmental determinants, and to produce forecasting maps requested for the planning and the monitoring of control strategies on small and large scale.
Feces of 798 male and female patients who attended the Parasitology Laboratory of the "Facultad de Ciencias Bioquímicas y Farmacéuticas de la Universidad Nacional de Rosario (República Argentina)" were examined. Out of the total number of samples, 281 were collected after a purgative, and 517 by serial collection. The samples were examined applying the routine parasitological analysis. Those which presented Blastocysts hominis were processed for their quantification and classification in different categories according to the number of cells per microscopic field with a magnification of 400 x. B. hominis appeared in 25.2% of the patients. Practically the same percentage was detected with either collection method. B. hominis was associated with other parasites, appearing as the only parasite in only 29.4% of the cases. Both its statistical association with the patient's age and its independence from sex were determined. The most frequent symptomatology in patients with B. hominis only was: abdominal pains, pruritus, flatulence, malaise, anorexia and diarrhea. Only 14.9% did not present any symptoms at all. The search for this protozoa should be a parasitological routine analysis since it is the cause of frequent intestinal disorders.
A parasitological (direct test and culture) and serological (IIF and ELISA) survey was carried out in 94 soldiers infested by a cutaneous South American leishmaniasis during a training in the guyanese forest. 52 p.c of the parasitological tests were positive, direct test being much more sensitive than cultures. By this technique, Leishmania Viannia guyanensis was detected 8 times, and Leishmania Viannia braziliensis twice. I.I.F. was negative in all cases because the utilization of a non-homologous antigen in the promastigote form and of the condition of its preparation. ELISA test utilizing the same antigen in a soluble form was specific and its sensitivity was 52 p.c. This technique was positive in 52 p.c of the cases, corroborating some diagnosis for which parasitological test was negative. 66 p.c of the total cases were confirmed.
Parasitological investigations carried out on 324 subjects of symptomatic and asymptomatic amoebiasis showed that formol-ether concentration was a superior technique than examination of 3 consecutive stool specimens by direct microscopy in cases of colitis, hepatitis and cyst passers. Culture of pus yielded better results than the other techniques for examination of stool in cases of liver abscess. Indirect haemagglutination test carried out with 238 sera from cases confirmed to be either positive or negative for Entamoeba histolytica revealed good correlation of its results with parasitological investigations in cases of dysentery and hepatitis. This test proved to be much superior to parasitological investigations in diagnosis of liver abscess. A close correlation between the results of gel-diffusion and I.H.A. was observed in dysentery and liver abscess groups, although I.H.A. was more sensitive. Precipitin band appeared in gel-diffusion test only when the I.H.A. titre was 1: 486 and the number of bands increased with rise in the titre.
The PCR is now widely introduced as a diagnostic and epidemiological tool in veterinary and human parasitology. Certain parasitic infections are detected using PCR with much higher sensitivity compared to conventional methods, and novel molecular approaches are considered for the analysis of infectiological questions. A broad spectrum of parasites relevant for veterinary and human parasitology already can be diagnosed by PCR. In the present review article, PCR-based methods developped or applied at the Institute of Parasitology in Berne for the detection of protozoan infections (Tritrichomonosis, Neosporosis, Toxoplasmosis) and helminthic infections (Echinococcosis, Taeniosis) are summarized.
Malaria remains one of the major health problems in many tropical countries. Plasmodium falciparum is the most common malaria parasite in Africa, and it causes much more severe and progressive illness than any of the other types of malaria parasite. Children living in sub-Saharan Africa are bearing the major burden of the disease and the mortality. Whatever parameter is used to measure the mortality or the morbidity from malaria, the true problem is likely to be underestimated. The pattern of morbidity and mortality depends on the transmission intensity; the more intensity of malaria transmission is increased, the earlier and more confined the age range of symptomatic malaria. The asymptomatic carrier status is common, and 60-80% of the children in highly endemic areas have P. falciparum parasitaemia at any given time. Consequently a case definition based on the mere presence of parasites in the blood is non-informative in terms of measuring morbidity. Recognizing that there are no specific diagnostic clinical parameters for malaria, but that fever is very common, and that morbidity is to some extent dependent on the parasite density, we described using a logistic regression model the probability of being sick from malaria in relation to body temperature and parasite density. Acquired clinical and parasitological immunity develop progressively over several years after repeated exposure to infection. Protection is acquired first against death or severe clinical disease, then against milder clinical attacks, but protection against infection is never complete. Clinical and parasitological immunity develop concomitantly, as demonstrated by relating the parasite densities to measured body temperature. However, the ability to control the disease and parasite density develops earlier than the ability to prevent the parasite infection. The individual immune mechanisms that are responsible for the acquired immunity remain uncertain, but classical transfer experiments with polyvalent gamma globulin from immune donors to non-immune individuals showed that antibodies play an important role. Potential targets for malarial vaccines include antigens on the surface of the sporozoites and the merozoites. Several protein antigens from P. falciparum have been characterized at the molecular level, and most of the characterized antigens have the common characteristic that they are recognized by immune sera from individuals living in malaria endemic areas. Working on the approach that potentially useful targets for protective vaccine development can be identified by correlating the naturally acquired immune responses with defined P. falciparum antigens, we examined antigens from both the sporozoite stage (CS-protein) and the blood stages (Pf155/RESA, GLURP, and MSP1), as well as P. falciparum induced neoantigens on the red blood cell (band-3 neoantigens). The relationship between the immune response to these defined P. falciparum antigens and clinical and parasitological protection was analysed in the individual age groups. The contribution of the antigen-specific immune response was evaluated, and a positive correlation of parasite density or probability of an episode of clinical malaria with antibody response to the individual antigens was identified in defined age groups. This correlation, however, did not span all age groups, and thus overall responses to defined antigens are not considered to be reliable indicators of protection. The findings may contribute to the understanding of immunological and clinical host responses to parasitaemia and to defined P. falciparum antigens. The studies on the impact of asexual stage infection and the human immune response led to studies on specific and non-specific responses to P. falciparum blood-stage parasites and observations on gametocytaemia. We demonstrated that pyrimethamine/sulfadoxine and chloroquine did not induce gametocytogenesis as suggested previously, but preformed gametocytes persisted after
Dehumidifiers (DH) are potentially effective appliances as coadjuvant therapy in the treatment of bronchial asthma caused by sensitization to house dust mites. The aims of this study were to analyze DH tolerance in asthmatic patients, to assess the parasitological effects and to analyze the environmental effects produced by the use of these appliances in the bedrooms of asthmatic patients sensitized to house dust mites. 10 stable asthmatic patients sensitized to house dust mites were studied. DH appliances (CD-300) were installed in their bedrooms. Each patient was given symptom scoring tables and a portable peak expiratory flow (P.E.F.) during a period of 5 months, 1 month before installing the DH and 4 months afterwards. To study the parasitological efficacy of the DHs, we analyzed dust samples from the bedrooms and determined the Der p I, Der f I and Der II allergens by means of a modified ELISA based on monoclonal antibodies. Dust samples were collected before installing the DHs and after they had been working for 2 and 4 months. Dry temperature and relative humidity measurements at three time intervals (7-9, 15-17 and 22-24 h) were carried out. The 1st measurement was done prior to installation of the DHs in the patients' bedrooms and the 2nd and 3rd were achieved 2 and 4 months respectively after the installation. Statistical analysis was done by comparison of paired means. No significant differences were detected in the patients' symptoms nor in the P.E.F. measurements in the course of the study. Decreases in the house dust mite allergens were observed in 4 bedrooms. A significant decrease in relative humidity in the bedrooms of mite asthma patients after use of dehumidifier appliances was observed (p < 0.01). Significant differences between the measurements of the bedrooms with and without DH were detected (p < 0.01). In summary, DHs were well tolerated by stable asthmatic patients, produced a significant decrease in the relative humidity level and showed some parasitological efficacy.
The sensitivity and specificity of parasite demonstration methods (smear, culture and histology) and serological assays (enzyme-linked immunosorbent assay [ELISA], direct agglutination test and immunoblot) were compared in the diagnosis of leishmaniasis in Ethiopia. Culture was found to be the most sensitive diagnostic method, followed by ELISA, for the diagnosis of cutaneous leishmaniasis (CL). When the clinical type of CL was taken into consideration, serological and parasitological methods were equally good for the diagnosis of diffuse cutaneous leishmaniasis. Overall, the serological assays were not sensitive enough to diagnose all the parasitologically confirmed cases of localized cutaneous leishmaniasis. Both groups of diagnostic methods performed equally well in the diagnosis of visceral leishmaniasis patients. In cases of CL where clinical diagnosis was a problem and histology could not give a definitive diagnosis due to the absence of demonstrable parasites, one of the serological assays, preferably ELISA, was very useful in establishing the final diagnosis.
In order to understand how the teaching of parasitology in veterinary schools and faculties in the world is carried out, a questionnaire was sent to all centres listed in the W.H.O. World Directory. A total of 91 replies were received. Additional information was obtained from the report of a symposium held in Hannover, Germany in 1978 and from the Education Committee of the American Association of Veterinary Parasitologists in 1981. The academic level, the place of parasitology in the veterinary curriculum, textbooks and practical instruction, evaluation techniques, teaching staff, institute organization and publications are discussed.
This review was part of a presentation made at the opening plenary session of the 12th Conference of the World Association for the Advancement of Veterinary Parasitology, held in Montreal, Quebec, Canada, 12-15 August 1987. That presentation and this review provide a bird's eye view of the country, its peoples, physiography, climate, natural resources, agriculture and animal population, highlights the activities of pioneers in parasitology, and provides some information about current research.