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Biomedical subjects

D W MacPherson

Publications and source records attributed to D W MacPherson.

At least 19 recordsLinked to original sources
PubMed2007

The sero-prevalence of antibodies to trypanosoma cruzi in Latin American refugees and immigrants to Canada.

BACKGROUND: Chagas' disease is caused by infection with the protozoan agent Trypanosoma cruzi. An estimated sixteen to eighteen million people are infected in Latin America. Outside of endemic regions, Chagas' disease may be transmitted through the transfusion of infected blood components, congenital infection and organ transplantation. We sought to determine the sero-prevalence of antibodies to T. cruzi in a community sample of Latin American refugees and immigrants to Canada. METHODS: This was a sero-prevalence study in Latin American refugees and immigrants living in Canada. Eligible subjects were born in South America, Central America or in Mexico. Participants were recruited from a variety of community settings, as well as from medical clinics. Serum was tested by enzyme-linked immunoassay for antibodies to T. cruzi. RESULTS: A total of 102 participants were enrolled. One sample tested positive for antibodies for T. cruzi. The seroprevalence in our sample was 1.0% (95% CI: 0.2%- 5.3%). INTERPRETATION: We found a low sero-prevalence of Chagas' disease in a community sample of Latin American immigrants and refugees. Physicians who treat Latin American immigrants should consider the risk profile and clinical status of the individual in their decision to screen for Chagas' disease.

Adolescent↗
PubMed2006

Balancing prevention and screening among international migrants with tuberculosis: population mobility as the major epidemiological influence in low-incidence nations.

BACKGROUND: Tuberculosis infection and disease remain a significant cause of global morbidity and mortality. The burden of tuberculosis disease is greatest in the developing nations of the world, although the effect of imported disease is observed in low-incidence tuberculosis regions, represented predominantly by high-income countries. In these regions, national tuberculosis control and elimination programmes are increasingly challenged to address disease in foreign-born residents. Immigration policies and shifting migration patterns over the past 5 decades have brought larger numbers of permanent and temporary residency migrants from high-prevalence regions of the world into low tuberculosis incidence environments. As a consequence, both national immigration policies and global health strategies for the control of tuberculosis share common interest in mobile populations moving from high-to-low prevalence regions. Existing immigration medical screening practices in major immigrant-receiving nations were often designed to prevent and manage the importation of contagious, active pulmonary tuberculosis disease. Such programmes may be limited in addressing the long-term consequences of latent tuberculosis infection in foreign-born residents. In nations with a low incidence of tuberculosis, a direct link can be found between the globalization of health factors related to international population movements, as observed with tuberculosis and immigration policies and practices. Continued migration from high-endemic tuberculosis regions will increasingly influence the disease burden in low-endemic areas, and challenge local tuberculosis control and elimination programmes. Evidence-based approaches to meeting those challenges will allow for the effective use of resources and support ongoing programme evaluation.

Drug Resistance, Multiple, Bacterial↗
PubMed2006

Immigration medical screening and HIV infection in Canada.

HIV infection, particularly associated with AIDS, is often used by migrant screening nations to exclude entry into the country. The unique feature of the Canadian immigration HIV screening programme is that it was not primarily for determining inadmissibility of HIV-positive applicants, but for health promotion and disease prevention purposes. All applicants over 15 years of age for permanent residency or temporary residency from designated countries are HIV antibody tested. This includes persons seeking asylum from within Canada. The highest rates of HIV infection were found in migrant applicants from high prevalence areas of the world and reflected the demographic profile of the source region (predominately women). The majorities of HIV-positive persons are exempt from exclusion from Canada due to class of application (refugee, family) or are already in Canada (refugee claimant). Significant issues in notification, reporting and programme management have been identified as a consequence of this programme.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Meningoencephalitis associated with an unidentified apicomplexan protozoan in a Pacific harbor seal.

A Pacific harbor seal (Phoca vitulina richardsii) was found on the central California coast with neurologic signs and labored breathing, which were unresponsive to treatment. Necropsy revealed a nonsuppurative necrotizing meningoencephalitis, a multilocular thymic cyst, and nonsuppurative cystitis and renal pyelitis. Microscopic examination revealed protozoans in the brain, thymic cyst, and bladder mucosa. Ultrastructurally, the protozoal tachyzoites were different from those of Neospora caninum, Toxoplasma gondii, and Sarcocystis neurona; the rhoptries were small and had electron-dense contents, and the organism divided by endodyogeny. Specific antibodies were not detected in serum using agglutination (N. caninum, T. gondii) and immunoblot assays (S. neurona). Immunohistochemistry for these organisms was negative. Polymerase chain reaction on brain tissue using specific primers did not amplify T. gondii deoxyribonucleic acid. The meningoencephalitis in this seal thus appears to have been caused by a novel protozoan.

Agglutination Tests↗
PubMed2001

Malaria deaths in visitors to Canada and in Canadian travellers: a case series.

Over the last decade there has been a marked increase in case of drug-resistant and severe malaria in Canadian travellers. We report 7 deaths due to falciparum malaria that occurred in Canada or in Canadian travellers. Risks for malaria infection include inappropriate recommendations for malaria prevention by health care providers and lack of knowledge about or adherence to appropriate recommendations by the travelling public. Risks for death include delays in seeking medical attention, delays in diagnosis and inadequate care by Canadian physicians and hospitals, and lack of access to parenteral therapy for severe malaria. Malaria infections and deaths are preventable. Better education of health care providers and travellers about the risks of malaria and appropriate prevention and treatment measures may decrease this unnecessary burden on the Canadian health care system.

Adult↗
PubMed2001

Randomised, blinded, placebo controlled trial of doxycycline for chronic seronegative arthritis.

OBJECTIVE: To determine whether long term doxycycline improves symptoms in patients with chronic seronegative or reactive arthritis. METHODS: A randomised, triple blind, controlled clinical trial of three months' treatment with doxycycline or placebo of patients with chronic reactive or seronegative arthritis was conducted. The primary study end points were three month pain and functional status measured by a self administered Arthritis Impact Measurement Scales version 2 (AIMS2) quality of life questionnaire. Secondary end points were pain and functional status at 6-12 months, three month rheumatologist assessed joint count, pain, and arthritis activity, and treatment efficacy in those with previous exposure to chlamydia. RESULTS: Of 60 patients randomly allocated to receive doxycycline or placebo, results from 37 were evaluable at three months. Groups were well balanced for major prognostic variables. Doxycycline had no detectable effect at three months on pain change scores (mean difference 1.5, 95% CI -1.2 to 4.2, p=0.25) or composite functional change scores (mean difference 0.8, 95% CI -5.6 to 7.1, p=0.81). Furthermore, there were no differences in secondary study end points, and no apparent treatment effect in patients with previous chlamydia infection. CONCLUSION: Three months' treatment with doxycycline did not improve pain or functional status in patients with chronic reactive or seronegative arthritis.

Adolescent↗
PubMed2001

Human mobility and population health. New approaches in a globalizing world.

The globalization of economies in the last 25 years has greatly increased both the number of people on the move and the rapidity of their movement, and has brought attention to global disparities in health determinants and to the health of migrant populations themselves. Differences in epidemiological disease risk (prevalence gaps) may have negative, neutral, or positive health consequences for the migrant or receiving population. Population mobility represents a growing challenge to the development of public health programs and legislative policies to prevent the importation of disease, and to promote and protect the health of migrants and the local, receiving population. The inability to detect and contain imported disease threats at national borders requires a shift in immigration, quarantine, and public health approaches to health and mobile populations. A new paradigm is needed to facilitate the development of policies and programs to address the health consequences of population mobility.

Community Health Planning↗
PubMed2000

Population mobility and infectious diseases: the diminishing impact of classical infectious diseases and new approaches for the 21st century.

In an increasingly globalized world, rapid population mobility and migration is reducing the differences in infectious disease epidemiology between regions of the world. The movement and relocation of populations between locations where the prevalence and incidence of infections are markedly different poses current and future challenges to those involved in clinical infectious diseases and public health program management. Historically, international attention has focused on the screening and treatment of acute infections of epidemic potential, but, as immigration significantly changes the demography of many nations, chronic infections will require increased attention. In countries with large mobile populations, the population-based burden of infections with long latency periods or significant noninfectious sequelae will make up an increasing amount of the infectious disease caseload and will require more-modern approaches than the traditional screening of arrivals. The globalization of chronic infectious disease epidemiology will require corresponding development of integrated programs to anticipate and manage these diseases in response to an increasingly mobile patient population.

Communicable Disease Control↗
PubMed2000

Health issues associated with the smuggling and trafficking of migrants.

Approximately 4 million persons annually may be smuggled illegally across international borders. In 1997 it was estimated that 700,000 women or children were smuggled across international borders, of whom 175,000 were estimated to come from the former Soviet bloc; approximately 45,000-50,000 smuggled women and children arrived in the United States in that year. This article develops a framework to consider the impact of human trafficking on health within the context of migrant health and the destination population's health. Health risks are assumed by the individual being smuggled during the pre-journey, migratory, and arrival phases. In addition, the recipient country's population may also incur additional health burdens related to illegal arrivals from higher disease prevalence areas of the world. Some of this disease risk potential may be from transmissible agents, but there is increasing concern, and some evidence, that noncontagious diseases may be a significant problem associated with human trafficking. The global consideration of human smuggling and the individual and social impact on health are the focus of this paper.

Journal Article↗
PubMed1999

Entamoeba histolytica and Entamoeba dispar: epidemiology and comparison of diagnostic methods in a setting of nonendemicity.

Recent studies suggest that stool antigen assays are more sensitive and specific than microscopy for the diagnosis of Entamoeba histolytica infection. One hundred twelve patients presenting at 3 centers with symptoms or risk factors of E. histolytica infection were prospectively enrolled in this study to evaluate new diagnostic tests for infections with E. histolytica and Entamoeba dispar. Four ELISA-based stool antigen kits for detecting E. histolytica or E. dispar were blindly compared with stool microscopy. Amebic serology was assessed by indirect hemagglutination. When antigen assays were used as the reference standard, microscopy performed at referral centers was more specific (68.4% vs. 9.5%) but less sensitive (70.4% vs. 92.1%) than microscopy performed in community laboratories. Diagnosis with the E. histolytica test and Merlin Optimun S ELISA indicated that only 3 (4.2%) of 72 coproantigen-positive stools were positive for E. histolytica. Indirect hemagglutination was a good predictor of E. histolytica infection when titers of antibody to ameba were >/=1:512.

Animals↗
PubMed1999

Intestinal parasites in returned travelers.

Parasites in the returned traveler can present in any organ system and at time periods quite distant from the activity or geographic exposure that created the risk for infection. All clinicians need to be aware that the most efficient approach to these unusual diseases starts with taking a travel history. The exciting challenge to the diagnostician and the laboratorian is to be able to respond to these clinical demands.

Disease Outbreaks↗
PubMed1996

Cyclosporiasis: a new cause of diarrhea.

Cyclospora cayetanensis, a coccidian parasite, is a new cause of prolonged diarrhea. It has been most recently associated with ingestion of contaminated fruit. Although infection with C. cayetanensis is considered rare, the exact prevalence in Canada is unknown. Transmission is thought to occur through contaminated food and water. The incubation period varies from days to weeks. Patients present with nausea, vomiting, anorexia, bloating, abdominal cramping, increased gas and watery diarrhea. The illness may last up to 6 weeks and may respond to treatment with trimethoprim-sulfamethoxazole. C. cayetanensis is differentiated from other coccidians by its sporulation characteristics and its autofluorescence. To obtain a positive result of a laboratory test for the organism, a modified Ziehl-Neelsen acid-fast stain is recommended. Proper laboratory handling of specimens is facilitated by inclusion of clinical information on requisition forms.

Animals↗
PubMed1996

Modified technique to recover microsporidian spores in sodium acetate-acetic acid-formalin-fixed fecal samples by light microscopy and correlation with transmission electron microscopy.

Microsporidia are an emerging cause of significant disease, particularly in the immunocompromised host. Until recently, the diagnosis of enteric infections has required invasive sampling, the use of expensive technology, and considerable technological expertise. The purpose of the present study was to examine three modifications to the processing of fecal specimens for light microscopy (LM) examination for microsporidian spores: the use of pretreatment with potassium hydroxide, modified centrifugation conditions, and a modified staining technique. A sodium acetate-acetic acid-formalin-fixed fecal sample containing numerous microsporidian spores confirmed to be positive by transmission electron microscopy (TEM) was used in all studies performed. A simulation of a heavy to lightly infected individual was used. The results of LM were correlated with those of TEM. Duplicate smears were stained with Weber's modified trichrome and Giemsa (GS) stains. The stained slides were randomized and examined blindly by LM at x 625 and x 1,250 magnifications. A portion of the dilutions after centrifugation were fixed for TEM. The Weber modified trichrome stain performance rating was higher than the Giemsa stain rating because of ease of interpretation, and material stained with Weber modified trichrome stain required less examination time at a lower magnification. The number of positive smears and the quantity of spores detected were significantly higher following pretreatment of the sample with KOH. TEM was positive only when numerous spores were present, but the quality of the photomicrographs was superior after pretreatment with KOH. Pretreatment of sodium acetate-acetic acid-formalin-fixed fecal samples with 10% KOH and then a 5-min centrifugation time and staining with Weber modified trichrome stain provide for the excellent recovery of microsporidia in the routine diagnostic parasitology laboratory.

AIDS-Related Opportunistic Infections↗
PubMed1995

Evidence-based medicine.

Clinical practice guidelines are an important product of the National Committee to Advise on Tropical Medicine and Travel (CATMAT). Recent guidelines have been published on the guiding principles for clinical practice guidelines. The ninth principle states: "Clinical practice guidelines should: (a) cite the specific evidence bearing upon the conclusion, (b) indicate the strength of the evidence [and] (c) specify the date of the most recent evidence considered." The following is CATMAT's statement on evidence-based medicine and the scales used to grade its recommendations.

Canada↗
PubMed1995

Prevention of transfusion-associated Chagas' disease: efficacy of white cell-reduction filters in removing Trypanosoma cruzi from infected blood.

BACKGROUND: Transfusion-associated Chagas' disease (TA-CD) is a worldwide problem. Measures adopted to prevent TA-CD include the clinical and serologic screening of blood donors and/or the inactivation of Trypanosoma cruzi present in collected blood, using gentian violet as the trypanocidal agent. This study investigated the efficacy of white cell-reduction filters in removing T. cruzi from infected blood. STUDY DESIGN AND METHODS: Human blood was contaminated with 2 or 150 T. cruzi parasites per mL and then left unfiltered or filtered with white cell-reduction filters that provided either 2, 3, or 6 log10 white cell removal. The efficacy of the parasite removal of these filters was evaluated by microscopic enumeration of active forms of T. cruzi both in vivo and in vitro. The in vivo experiments were done in Swiss mice that had been intraperitoneally inoculated with T. cruzi-infected human blood. The in vitro experiments were performed with fresh human blood that had been deliberately contaminated with T. cruzi. RESULTS: The number of parasites seen in mice inoculated with unfiltered blood containing 2 or 150 parasites per mL was significantly higher than the number of parasites seen in mice inoculated with blood from the same sample, but filtered with white cell-reduction filters providing 3 or 6 log10 white cell removal. Fifty to 70 percent of the mice given T. cruzi-infected (2 parasites/mL) filtered blood did not develop T. cruzi infection. In vitro, the use of white cell-reduction filters, providing 2, 3, or 6 log10 white cell removal, significantly reduced the number of parasites seen in culture. CONCLUSION: The present experimental data provide evidence that white cell-reduction filters are effective in reducing the number of parasites in T. cruzi-infected blood and that this efficacy depends, in part, on the concentration of parasites in the artificially infected blood. Properly designed clinical studies of known carriers of T. cruzi must be conducted to determine whether the use of white cell-reduction filters may be an alternative method of reducing the incidence of TA-CD.

Animals↗
PubMed1995

Enteric parasitology. Interpreting laboratory reports.

Intestinal parasites are common in the stools of human beings. With care and due attention to the techniques of testing, they are relatively easy to find. Unfortunately, deciding on the clinical importance of stool findings is often difficult. This article is an introduction and guide to interpreting enteric parasitology laboratory reports.

Animals↗