Workshop summary: equine parasitology.
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Medicinal plants are an important health resource in many regions of the Americas and are of particular importance to many Indian communities. Based on a recent ethnobotanical study in Mexico, we investigated the activity of 29 plant extracts against Entamoeba histolytica, three bacteria (Bacillus subtilis, Escherichia coli, and Micrococcus luteus) and two fungi (Cladosporium cucumerinum and Penicillium oxalicum). After separation of these extracts between CH2Cl2 and H2O the resulting phases were also evaluated.
Aiming to study the influence of long-term administration of lipid lowering agents (atorvastatin; AV), and to study the action of combined treatment with injectable contraceptive (medroxyprogesterone acetate; MPA) on tegumental ultrastrucutre and survival of Schistosoma worms, this study was established. AV (0.9 mg kg-1) was administered orally for 49 successive days to Schistosoma heamatobium-infected hamster starting from day 35 post-infection (pi). Another group of infected hamster was administrated MPA intramuscularly (0.1 ml kg-1) at days 7 and 35 pi followed by AV treatment regimen. Both treatment regimens significantly affected the surface ultrastructure of the male worms more pronouncedly than the female ones. Combined treatment was more severe in action compared to single one. The combined treatment was characterized by losing of spines and damaging of tubercles throughout the tegument, severe erosion and peeling and appearance of deep crakes in different parts of the tegument. Moreover, mild to sever destruction to the oral suckers of both female and male worms was noticed. On the other hand, both treatment regimens significantly reduced numbers of recovered S. haematobium worms and tissue egg load. Oogram pattern was affected only in case of combined treatment with high percentage of dead eggs. In conclusion, AV, if given continuously for long time, has a pronounced antischistosomal action especially when accompanied with contraceptive intake. These promising results may encourage further investigation with the intention of their possible application on treatment of schistosomiasis as a complement strategy to praziquantel chemotherapy.
A total of 964 adult fish farmers in five eastern districts in Nghe An province, Vietnam were investigated in late 2004 for food-borne trematodes and other helminth infections using duplicate Kato-Katz thick smears prepared from single stool samples. Eggs of fish-borne trematodes and of Fasciolopsis buski were found in 0.6 and 0.7% of farmers, respectively. Infection prevalences with soil-transmitted helminths (STHs), namely Ascaris lumbricoides, Trichuris trichiura and hookworm, were 34.8, 50.7 and 51.3%, respectively, and 81.8% were infected with at least one of the three STHs. While A. lumbricoides and T. trichiura were more prevalent in the eastern districts compared to the more western districts, the opposite was true for hookworm infections. The widespread prevalence of STH infections in fish farmers suggests that control of these infections in school-age children only may be inadequate. Identification of the human behavioural factors and environmental features responsible for the distribution and frequency of STHs among adults is needed as well as a sensitive diagnostic test of fish-borne trematodes at species level.
BACKGROUND: Maternal-fetal transmission of Trypanosoma cruzi generally occurs in 2-12% of pregnant infected mothers. This transmission form has been poorly studied in Mexico where only one case of congenital infection published in 1998 has been reported. METHODS: We screened 145 mothers and their delivered babies in two hospitals of endemic regions in Mexico (states of Chiapas and Veracruz) searching for anti-T. cruzi antibodies and circulating parasites by hemoculture and PCR. RESULTS: In Poza Rica, Veracruz, 3/85 (3.5%) mothers were seropositive for T. cruzi infection and in Palenque, Chiapas, 3/60 (5%) cases. In total 6/145 (4.1%) were seropositive subjects. Although cord blood samples of delivered babies from seropositive mothers have IgG anti-T. cruzi antibodies, none presented PCR and positive hemoculture. CONCLUSIONS: Although a high relative seroprevalence of T. cruzi infection in pregnant women was detected, no case of vertical transmission was recognized. Undoubtedly, further studies of large samples are necessary to evaluate maternal transmission risk in Mexico.
BACKGROUND: Multiple in-house polymerase chain reaction (PCR) assays for the diagnosis of parasitic and fungal diseases have been reported. Encouraging results have been published to anticipate or improve the diagnosis. However, the absence of standardized methods has led to discrepant results. As a consequence, these tests are not recognized as consensual diagnostic criteria. METHODS: The major breakthrough for improving the results of these methods is the emergence of real-time technologies. This markedly improves the reliability of the PCR results by dramatically decreasing the risk of false positive results due to PCR products carryover. Moreover, the quantitative results provided by these techniques allow to compare rapidly the efficiency of primers, probes, and DNA extraction. Therefore, one can expect a more consensual method to implement comparisons between laboratories. Automated DNA extraction should also be useful to achieve this goal. Whatever sophisticated technology is used, the meaning of detecting nucleic acids in a given clinical sample still needs to be defined. This requires well-designed studies with clinical consensual criteria and PCR techniques that are as similar as possible. CONCLUSIONS: The development of real-time technology should improve our knowledge in order to give the clinicians informative clues for decision-making.
To understand the interaction of Trypanosoma cruzi with caviomorph rodents, which supposedly have an ancient co-evolutionary history with this parasite, experimental infection of laboratory reared Trichomys apereoides with several isolates of both genotypes of the parasite was studied. Parasitemia, pattern of hematic cells, specific humoral immune response, histopathological features and parasite clearance were appraised. T. apereoides maintained stable infections independent of the T. cruzi genotype as demonstrated by positive PCR results in analyses of several tissues after a 5 months follow-up. The acute phase was characterized by abundant and disseminated presence of amastigotes, vacuolization and/or myocytolysis. Lymphocytosis was a common feature. The chronic phase was characterized mainly by lymphomacroeosinophilic infiltrates independent of the inoculated T. cruzi isolate. T. cruzi of different genotypes did not show any tissular preference in T. apereoides.
While examining some histological sections of a clinically suspected neoplastic nodule in a woman's breast, sections of Dirofilaria repens were noted in the same nodule along with sections of a different nematode. The latter appeared to be a specimen possibly belonging to the genus Anatrichosoma (family Trichosomoididae), a parasitic group of helminths rarely reported in humans. In view of the diagnostic interest in an exceptional event, such as a double parasitic infection in the same nodule, we report the details of the case and the morphological findings.
Genome sequencing efforts have provided a wealth of new biological information that promises to have a major impact on our understanding of parasites. Microarrays provide one of the major high-throughput platforms by which this information can be exploited in the laboratory. Many excellent reviews and technique articles have recently been published on applying microarrays to organisms for which fully annotated genomes are at hand. However, many parasitologists work on organisms whose genomes have been only partially sequenced and where little, if any, annotation is available. The focus of this review is on how to use and apply microarrays to these situations.
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In vivo infection routes of parasites have remained something of a "black box", in which only snapshot views of fixed tissues are available. Clearly, there exists a strong need for imaging approaches to visualise living parasites within intact organs and animals. In vivo imaging of fluorescent Plasmodium parasites now provides us with exciting insights into the infection process, from the bite of the infected mosquito to the invasion of liver cells, and alternative approaches using luciferase-expressing parasites have been used to monitor their dissemination in mice. This rapidly developing field will go a long way towards deepening our understanding of host-parasite interactions at different levels.
This study was conducted during 2002-2004 at Mae Sot District, on the Thai-Myanmar border, an area of multidrug-resistant Plasmodium falciparum malaria. Sixty-two patients with P. vivax malaria were included in the study. All were randomized into two groups to receive a 3-day regimen of chloroquine or a 3-day regimen of quinine. Primaquine was given to patients in both groups for the elimination of hepatic stages. Results from the present study suggest that the standard regimen of chloroquine and a 3-day course of quinine at the dose regimens under investigation were very effective and well tolerated for the treatment of P. vivax malaria in this area. All patients responded well to both drug regimens; the cure rates with chloroquine or quinine, when given concurrently with the tissue schizontocidal drug primaquine, were virtually 100% within 28 days of follow-up. No significant correlations between parasite clearance time (PCT) or fever clearance time (FCT) and inhibitory concentration 50 (IC50) were found. Patients who had PCT < or = 24 h and those with PCT >24 h had comparable IC50 to chloroquine (alone and plus primaquine) and quinine, as well as similar concentrations of chloroquine/desethylchloroquine (in blood) or quinine (in plasma) at the investigated time points.
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The future implementation of improved and sustainable control strategies for the major equine parasites will be dependent on a greater insight into their basic biology, pathogenicity and epidemiology together with an enhanced ability for accurate diagnosis. This paper will provide a review of the current molecular methods under development for the detection of equine parasites and their application to current scientific questions. In particular, the strongyles are recognised as important pathogens of horses and recent advances made in the study of this parasitic group at the single species level will be addressed. The ribosomal (r)DNA region of the parasite genome has been employed to distinguish between closely related species. Molecular probes designed to this target region were used in combination with PCR technology to allow the identification of individual species within mixed infections. They have been applied to all parasite stages to look at the role of individual species in natural infection, disease and drug resistance. Similar techniques have been developed to detect other equine parasites and these will also be discussed. Further opportunities for employing existing techniques and the need for new diagnostic tools will be highlighted.
Aiming to evaluate the efficacy of the treatment of canine visceral leishmaniasis, to verify the occurrence of a possible disease relapse, and to search for the presence of the parasites after the end of the treatment, seven dogs naturally infected by Leishmania (Leishmania) chagasi were used. The dogs were subjected to a treatment with 75 mg/kg meglumine antimoniate subcutaneously every 12 h for 21 days, and followed-up for a period of 6 months. During the whole experimental period the animals wore deltamethrin collars and were kept in a screened kennel to avoid reinfection. Lymph node and bone marrow aspiration biopsy was carried out to search for the parasite at seven moments: before the treatment, 30, 60, 90, 120, 150 and 180 days after the start of the treatment. After the end of the experiment all dogs were humanely euthanized. Then, spleen and liver "imprints" and in vitro cultures were carried out to search for amastigote forms of the parasite. During the treatment all animals presented remission of symptoms. However, two dogs were observed to present new symptoms in the course of the experiment. At the end of the experiment, the presence of amastigote forms of the parasite was evidenced in five of the seven dogs. This enabled us to conclude that the treatment promoted clinical cure but did not eliminate the parasites completely.
The relationship between prevalence of trypanosomal infections (Trypanosoma congolense) and average packed cell volume (PCV) in herds of communally managed adult Angoni breed cattle was investigated in four districts of eastern Zambia. In all areas, regression analyses showed that the herd average PCV decreased with increasing prevalence of trypanosomal infections. The slope of the equation between average PCV and trypanosome prevalence decreased with increasing prevalence of trypanosomal infections. For the same increase in prevalence of trypanosomal infection, the decrease in herd PCV was higher in the areas with low to medium prevalence. Season of sampling also determined the slope of the regression equation. For the same increase in prevalence of trypanosomal infection, the decrease in herd PCV was higher during the dry compared to the rainy season suggesting that trypanosomosis is less well tolerated during the dry season. Results from the study suggest that the relationship between the prevalence of trypanosomal infections and herd average PCV could be a useful tool in the management of trypanosomosis and planning of its control. Reasons for the spatial and temporal variations in the relationship are discussed.
A total of 51 women with urinary schistosomiasis haematobium were examined in order to identify diagnostic indicators for female genital schistosomiasis (FGS). Patients were selected at random from the outpatient department of the Mangochi District Hospital, Malawi. The medical histories were recorded according to a pre-designed questionnaire and the women were subjected to a thorough gynaecological examination including colposcopy and photographic documentation of lesions. Microscopy of genital biopsies revealed that 33 of the 51 women had S. haematobium ova in cervix, vagina and/or vulva in addition to the presence of ova in urine. The most sensitive diagnostic procedure was beside microscopic examination of a wet cervix biopsy crushed between two glass slides, which revealed 25 of the 33 genital infections. There was a significant correlation between the size of genital lesions and the number of ova counted per mm2 of crushed tissue. Women with FGS had significantly more tumours in the vulva than women with schistosomiasis limited to the urinary tract. Most of the observed genital pathology could easily be identified by the naked eye, but colposcopic examination yielded valuable additional information like the demonstration of neovascularisation around cervical sandy patches. Few of the symptoms previously regarded as indicators for FGS could be linked to the presence of schistosome ova in genital tissue. Husbands of infertile women with FGS had children with other women significantly more often than husbands of women who only had urinary schistosomiasis. This, together with the finding that the majority of the divorced women had FGS, indicates that the manifestation of this disease may have implications for the marital and sexual life of the affected women.
The buffy coat/dark ground techniques (BCT) and an antigen enzyme immunoassay (Ag-ELISA) were compared for the diagnosis of trypanosome infection in N'Dama, Gobra zebu and N'Dama x Gobra (F1) crossbred cattle following two sequential experimental Trypanosoma congolense infections. Both first and second challenge were performed by intradermal needle inoculation of trypanosome bloodstream forms. During the course of the first challenge, the overall trypanosome percentage of positive cases detected by BCT in blood samples was higher (P < 0.001) in comparison with that obtained by Ag-ELISA in tested serum samples of the three cattle breeds. Conversely, in the second infection the overall number of infections detected by BCT was lower in N'Dama (P < 0.005) and F1 (P < 0.001) than that obtained using Ag-ELISA; nearly identical positive rates were detected by the two diagnostic techniques in Gobra zebus. Both in the first and second T. congolense challenge, positive rate obtained using BCT significantly decreased as the infection progressed. On the other hand, the positive rate given by Ag-ELISA and its sensitivity manifested a significant opposite trend during the course of the first infection. No relationship between progression of infection and Ag-ELISA positive rate as well as Ag-ELISA sensitivity was found in the second T. congolense challenge. The Ag-ELISA was less than 50% sensitive in detecting circulating antigens during the first 2 months of the primary infection. However, it showed a high and stable sensitivity throughout the second trypanosome infection. It was concluded that the Ag-ELISA was suitable for use in detecting chronic or repeated infections but needs to be combined with BCT to provide reliable results.