Biomedical subjects

Calum N L Macpherson

Publications and source records attributed to Calum N L Macpherson.

4 recordsLinked to original sources

PubMed2006

Seroprevalence of Toxoplasma gondii in pregnant women and cats in Grenada, West Indies.

Prevalence of antibodies against Toxoplasma gondii was studied in 534 pregnant women and 40 domestic cats in Grenada, West Indies. Antibodies (IgG) for T. gondii were sought in human sera by an enzyme-linked immunosorbent assay and in cat sera by using the modified agglutination test (MAT). Antibodies were found in 57 % of pregnant women. Seroprevalence increased with age; 51% of 15- to 19-yr-old women (100 total) had antibodies versus 60% of 20- to 24-yr-old women (127 total). Antibodies to T. gondii (MAT, 1:25 serum dilution) were found in 35% of cats; titers were 1:25 in 7 cats, 1:50 in 4 cats, and 1:500 in 3 cats. Epidemiological data suggested that the ingestion of food or water contaminated with oocysts was an important mode of transmission of T. gondii to women.

Adolescent↗

PubMed2005

Human behaviour and the epidemiology of parasitic zoonoses.

The behaviour of Homo sapiens has a pivotal role to play in the macro and microepidemiology of emerging or re-emerging parasitic zoonoses. Changing demographics and the concomitant alterations to the environment, climate, technology, land use and changes in human behavior, converge to favour the emergence and spread of parasitic zoonoses. The recent unprecedented movements of people, their animals and their parasites around the world, introduce and mix genes, cultural preferences, customs, and behavioral patterns. The increasing proclivity for eating meat, fish, crabs, shrimp, molluscs raw, undercooked, smoked, pickled or dried facilitates a number of protozoan (Toxoplasma), trematode (Fasciola sp., Paragonimus spp., Clonorchis sp., Opisthorchis spp., Heterophyes sp., Metagonimus sp., Echinostoma spp., Nanophyetus sp.) cestode (Taenia spp, Diphyllobothrum sp.) and nematode (Trichinella spp., Capillaria spp., Gnathostoma spp., Anisakis sp., Parastrongylus spp.) caused zoonoses. The increasing world population and the inability to keep pace with the provision of adequate sanitation and clean, safe drinking water, has led to an increased importance of waterborne zoonoses, such as those caused by Giardia, Cryptosporidium and Toxoplasma. Our close relationship with and the numerous uses to which we put companion animals and their ubiquitous distribution has resulted in dogs and cats unwitting participation in sharing over 60 parasite species including: Giardia, Cryptosporidium, Toxoplasma, most foodborne trematode species, Diphyllobothrum, Echinococcus spp., Ancylostoma and Toxocara. Changing human behaviour through education, to encourage the proper cooking of food, which may have cultural and social significance, will remain as challenging as controlling stray and feral pet populations, improving hygiene levels and the provision of safe drinking water and the proper use of sanctuary facilities. Long pre-patent periods and the normally insidious sub-clinical nature of most zoonoses makes advice requiring behavioural change for their control a difficult task. Our clearer understanding of the heterogeneity of susceptibility to infection, the complex genetic variations of people and parasite species and the development of molecular epidemiological tools is shedding more light on transmission routes and the spectrum of disease that is observed. Improved and new serological, molecular and imaging diagnostic tests and the development of broad spectrum chemotherapeutic agents has led to the attenuation of morbidity and mortality due to parasitic zoonoses in economically advantaged regions. Such advancements, in partnership with supportive behavioural change, has the potential for a sustainable global reduction in the burden of ill health due to parasitic zoonoses. Whether this will materialise is a challenge for us all.

Animals↗

PubMed2005

Dengue in Grenada.

OBJECTIVES: Dengue fever is endemic in the country of Grenada and is grossly underreported as a source of morbidity. The goal of this study was to assess the status of dengue fever in a representative community in Grenada. METHODS: Surveys were conducted in the Mont Tout/Grand Anse Valley area in the parish of St. George's from March to June 1996. The objectives of the survey were to: (1) to assess the knowledge, attitudes, and practices (KAP) of residents; (2) to determine the presence of larval and adult Aedes aegypti and their potential breeding sites; and (3) to identify the seroprevalence of specific immunoglobulin G (IgG) dengue antibodies in the local population. RESULTS: Out of the 102 respondents to the KAP survey, 100 of them (98%) reported never having had dengue fever. Of the 75 persons who agreed to have blood samples taken, 70 of them (93%) (95% confidence interval = 85.1%-97.8%) tested positive with the IgG enzyme-linked immunosorbent assay, indicating past exposure. In terms of water storage, 98 of 102 respondents (96%) stored fresh water in containers. The vector survey found 57 of the 102 households (56%) had Ae. aegypti larvae in water containers on their property, and 94 of 102 dwellings (92%) had adult Ae. aegypti mosquitoes indoors. CONCLUSIONS: Although many people were familiar with dengue fever and mosquitoes, the 1996 survey found that their knowledge of the important relationships among mosquitoes, human behavior, and disease transmission was incomplete. Since 1996, continued education efforts have been made in the public school system and with national public health campaigns, yet little effort has been specifically targeted towards our study community. These data suggest Grenada has a need for continued community education that addresses dengue fever transmission and Ae. aegypti reduction.

Dengue↗

PubMed2003

Performance characteristics and quality control of community based ultrasound surveys for cystic and alveolar echinococcosis.

The probability of disease given the results of a test, is called the predictive value of the test. The predictive value of a test is not a property of the test itself but will vary according to the prevalence of the disease in the studied population. The positive predictive value (PPV) is the probability that the subject tested has the disease given that a positive result is obtained. The negative predictive value (NPV) is the probability that the subject tested is normal given that a negative result is obtained. As the prevalence of a disease in a population approaches zero so does the PPV and most of the positive cases will be 'false positives'. Conversely the NPV will be very high at low prevalences and there will be few 'false negative' results. The sensitivity and specificity of a test are properties of the test and do not vary with prevalence. The higher the sensitivity and specificity of a particular test the greater the predictive values will be at any given prevalence of the disease. Ultrasound (US) is increasingly used for detecting lesions due to cystic and alveolar echinococcosis (CE and AE) and portable US scanners facilitate community based mass screening surveys in remote rural communities. Screening is justified with AE and CE in endemic areas as diagnosis at an early stage can lead to a better prognosis following treatment. The sensitivity and specificity of US has been reported to be between 88-98% and 95-100% respectively for CE and the sensitivity is a little higher for AE. Both species have pathognomonic signs on US and the technique is considered to be the 'gold standard' although it is still an imperfect test. Clinical, laboratory and epidemiological data also play an important role in the diagnosis of CE and AE. US results where possible, should be evaluated in relation to these findings. Suspected CE and AE images, may benefit from the use of other imaging techniques such as magnetic resonance imaging, computerised tomography and in the case of AE angiography or cholangiography. Immunological tests or molecular biological techniques also provide a useful back up, especially for AE. As sensitivity and specificity are properties of the US diagnostic test they should not vary if the case mix reported in different studies remains the same. The use of the WHO standardised US classifications for CE and AE should be used so that the properties of the test are standardised. Quality control of field based studies will depend on geographical variations in the case mix and the relative proportions of cyst types without pathognomonic signs. The latter will have the most bearing on variations in specificity, as would the use of different classifications. Inter- and intra-observer variability and differences in prevalence will affect the performance of US in different endemic settings. Community based surveys must adhere to the highest ethical standards and the outcome of surveys should result in appropriate treatment and follow-up strategies for all infected individuals and suspected cases found during the surveys.

Animals↗