Computer-generated dot maps as an epidemiologic tool: investigating an outbreak of toxoplasmosis

Seropositivity of Anti-Toxoplasma gondii Antibodies in Owners and Their Dogs Living on Island and Mainland Seashore Areas of Southern Brazil

Although toxoplasmosis has been considered among the most neglected zoonoses worldwide, no study has focused on the frequency and associated risk factors of owners and their dogs living on an island and mainland seashore areas. Accordingly, anti-Toxoplasma gondii IgG antibodies were screened by indirect fluorescent antibody test (IFAT) in owners and dogs from three oceanic islands and two nearby mainland harbor areas, with associated risk factors for toxoplasmosis assessed by univariable and multivariable logistic regression models. Overall, anti-T. gondii seropositivity was observed in 59/328 (18.0%) owners and 66/283 (23.3%) dogs, with no statistical difference between owners (p = 0.360) and dogs (p = 0.655) from islands and mainland areas. Consumption of local water springs (p = 0.016; OR = 2.11) was an associated risk factor for T. gondii seropositivity, and owners with the habit of spring water intake were twice more likely seropositive (p = 0.014; OR = 2.14). Presence of anti-T. gondii antibodies in dogs was associated with seropositive owners (p = 0.008; OR = 2.81), household consumption of beef meat (p = 0.042; OR = 1.7) and chicken (p = 0.026; OR = 2.9). Despite being lower than the worldwide prevalence, toxoplasmosis seropositivity in owners and their dogs in southern Brazil was influenced by the positive owner, water source, and meat consumption, and not by inhabiting islands or seashore mainland areas, presence of dogs, cats, or both. In addition, drinking water quality should always be considered a critical risk factor for toxoplasmosis on islands.

Communicating infectious disease prevalence through graphics: Results from an international survey

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The impact of graphics to inform the general public on health knowledge is unknown.

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Heat maps were evaluated as superior to dot maps or picto-trendlines.

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Heat maps are a viable option to widely disseminate information about infectious diseases.

Background

Graphics are increasingly used to represent the spread of infectious diseases (e.g., influenza, Zika, Ebola); however, the impact of using graphics to adequately inform the general population is unknown.

Objective

To examine whether three ways of visually presenting data (heat map, dot map, or picto-trendline)—all depicting the same information regarding the spread of a hypothetical outbreak of influenza—influence intent to vaccinate, risk perception, and knowledge.

Design

Survey with participants randomized to receive a simulated news article accompanied by one of the three graphics that communicated prevalence of influenza and number of influenza-related deaths.

Setting

International online survey.

Participants

16,510 adults living in 11 countries selected using stratified random sampling based on age and gender.

Measurements

After reading the article and viewing the presented graphic, participants completed a survey that measured interest in vaccination, perceived risk of contracting disease, knowledge gained, interest in additional information about the disease, and perception of the graphic.

Results

Heat maps and picto-trendlines were evaluated more positively than dot maps. Heat maps were more effective than picto-trendlines and no different from dot maps at increasing interest in vaccination, perceived risk of contracting disease, and interest in additional information about the disease. Heat maps and picto-trendlines were more successful at conveying knowledge than dot maps. Overall, heat maps were the only graphic to be superior in every outcome.

Limitations

Results are based on a hypothetical scenario.

Conclusion

Heat maps are a viable option to promote interest in and concern about infectious diseases.

Why does geoprivacy matter? The scientific publication of confidential data presented on maps

We examined published maps containing sensitive data, and the protection methods, if any, that were used. We investigated whether the many published warnings about disclosure risk have been effective in reducing privacy risk. During an 8-year period (2005-2012), 19 journals related to GIScience, geography, spatial crime analysis, and health geography were examined. We identified 41 articles that display actual confidential information and 16 articles where confidential information is protected by the use of a geographical mask. During the investigated time frame, the numbers of articles with unmasked confidential data increased, and in total more than 68,000 home addresses were disclosed. One of the more significant findings of this study is that efforts to instill sensitivity to location privacy and disclosure risk have been relatively unsuccessful.

A protozoal-associated epizootic impacting marine wildlife: mass-mortality of southern sea otters (Enhydra lutris nereis) due to Sarcocystis neurona infection

During April 2004, 40 sick and dead southern sea otters (Enhydra lutris nereis) were recovered over 18km of coastline near Morro Bay, California. This event represented the single largest monthly spike in mortality ever recorded during 30 years of southern sea otter stranding data collection. Because of the point-source nature of the event and clinical signs consistent with severe, acute neurological disease, exposure to a chemical or marine toxin was initially considered. However, detailed postmortem examinations revealed lesions consistent with an infectious etiology, and further investigation confirmed the protozoan parasite Sarcocystis neurona as the underlying cause. Tissues from 94% of examined otters were PCR-positive for S. neurona, based on DNA amplification and sequencing at the ITS-1 locus, and 100% of tested animals (n=14) had elevated IgM and IgG titers to S. neurona. Evidence to support the point-source character of this event include the striking spatial and temporal clustering of cases and detection of high concentrations of anti-S. neurona IgM in serum of stranded animals. Concurrent exposure to the marine biotoxin domoic acid may have enhanced susceptibility of affected otters to S. neurona and exacerbated the neurological signs exhibited by stranded animals. Other factors that may have contributed to the severity of this epizootic include a large rainstorm that preceded the event and an abundance of razor clams near local beaches, attracting numerous otters close to shore within the affected area. This is the first report of a localized epizootic in marine wildlife caused by apicomplexan protozoa.

Sexual recombination punctuated by outbreaks and clonal expansions predicts Toxoplasma gondii population genetics

The cosmopolitan parasitic pathogen Toxoplasma gondii is capable of infecting essentially any warm-blooded vertebrate worldwide, including most birds and mammals, and establishes chronic infections in one-third of the globe's human population. The success of this highly prevalent zoonosis is largely the result of its ability to propagate both sexually and clonally. Frequent genetic exchanges via sexual recombination among extant parasite lineages that mix in the definitive felid host produces new lines that emerge to expand the parasite's host range and cause outbreaks. Highly successful lines spread clonally via carnivorism and in some cases sweep to pandemic levels. The extent to which sexual reproduction versus clonal expansion shapes Toxoplasma's current, global population genetic structure is the central question this review will attempt to answer.

Waterborne toxoplasmosis--recent developments

Humans become infected with Toxoplasma gondii mainly by ingesting uncooked meat containing viable tissue cysts or by ingesting food or water contaminated with oocysts from the feces of infected cats. Circumstantial evidence suggests that oocyst-induced infections in humans are clinically more severe than tissue cyst-acquired infections. Until recently, waterborne transmission of T. gondii was considered uncommon, but a large human outbreak linked to contamination of a municipal water reservoir in Canada by wild felids and the widespread infection of marine mammals in the USA provided reasons to question this view. The present paper examines the possible importance of T. gondii transmission by water.

Emerging and Re-emerging Infectious Diseases

Emerging diseases include outbreaks of previously unknown diseases or known diseases whose incidence in humans has significantly increased in the past two decades. Re-emerging diseases are known diseases that have reappeared after a significant decline in incidence (http://www3.niaid.nih.gov/research/topics/emerging).

Congenital toxoplasmosis: priorities for further health promotion action

Toxoplasmosis is a disease of considerable public health impact. As the transmission, occurrence and phenotype of this disease are influenced in a complex way by host genetics, immunity, behaviour and by the agent characteristics, prevention will not be simple. This article aimed to review studies defining seroprevalence of and characteristic sociodemographic, biological and lifestyle risk factors for Toxoplasma gondii infection in pregnant women, to evaluate screening and educational programmes, and to assemble recommendations for combating toxoplasmosis in populations at risk. Electronic databases were searched, using a specific search strategy, from 1975 to 2007. There is a high prevalence of T. gondii antibodies in pregnant women worldwide, with some geographic discrepancies attributed to climatic conditions, local food customs, hygiene, lifestyle and cultural differences. The main risk factors for toxoplasmosis in pregnant women are unsanitary feeding habits, poor immune system, contact with cats, contact with soil, pregnancy, number of births, older age, race, travelling outside the country, drinking beverages prepared with unboiled water, consumption of municipal or uncontrolled (well/spring) water and T. gondii strain virulence. Knowledge of these risk factors helps to identify priorities for further epidemiological work and defines effective preventive measures along five main themes of action: information and health education; screening of pregnant women and infants; limiting harm from risk behaviour; treatment of cases found to be at risk; and vaccination.

Spatial confidentiality and GIS: re-engineering mortality locations from published maps about Hurricane Katrina

Background

Geographic Information Systems (GIS) can provide valuable insight into patterns of human activity. Online spatial display applications, such as Google Earth, can democratise this information by disseminating it to the general public. Although this is a generally positive advance for society, there is a legitimate concern involving the disclosure of confidential information through spatial display. Although guidelines exist for aggregated data, little has been written concerning the display of point level information. The concern is that a map containing points representing cases of cancer or an infectious disease, could be re-engineered back to identify an actual residence. This risk is investigated using point mortality locations from Hurricane Katrina re-engineered from a map published in the Baton Rouge Advocate newspaper, and a field team validating these residences using search and rescue building markings.

Results

We show that the residence of an individual, visualized as a generalized point covering approximately one and half city blocks on a map, can be re-engineered back to identify the actual house location, or at least a close neighbour, even if the map contains little spatial reference information. The degree of re-engineering success is also shown to depend on the urban characteristic of the neighborhood.

Conclusion

The results in this paper suggest a need to re-evaluate current guidelines for the display of point (address level) data. Examples of other point maps displaying health data extracted from the academic literature are presented where a similar re-engineering approach might cause concern with respect to violating confidentiality. More research is also needed into the role urban structure plays in the accuracy of re-engineering. We suggest that health and spatial scientists should be proactive and suggest a series of point level spatial confidentiality guidelines before governmental decisions are made which may be reactionary toward the threat of revealing confidential information, thereby imposing draconian limits on research using a GIS.

A probable outbreak of toxoplasmosis among boarding school students in Turkey

In total, 171 students from a boarding school in Izmir, Turkey, with mild and non-specific symptoms of toxoplasmosis, were screened during September-October 2002. All 171 students were seropositive for Toxoplasma gondii IgG and IgM. Of 43 students tested, 40 (93%) had low IgG avidity. None showed evidence of ophthalmic involvement. The data suggest that T. gondii may spread rapidly in close living conditions, possibly following exposure to cat litter. This is the largest recent outbreak of toxoplamosis described in the medical literature.

Toxoplasma gondii spreading in an urban area evaluated by seroprevalence in free-living cats and dogs

Infection by the protozoan parasite, Toxoplasma gondii is widely prevalent in humans and animals throughout the world. Transmission takes place mainly by ingestion of raw or undercooked meat that contains parasite cysts or by ingestion of oocysts excreted in cat faeces, which can contaminate water and raw vegetables. The incidence of toxoplasmosis in urban areas can thus be also related to environmental contamination with oocysts. A direct measure of this environmental contamination by oocyst counting is unfeasible for technical reasons. An interesting alternative for measuring T. gondii urban spreading is the seroprevalence in free-living urban animals, used as sentinels, once they are exposed to similar risks of Toxoplasma infection-like humans. With this aim, we tested serum samples from stray cats and dogs for antibodies to T. gondii by indirect haemagglutination assay (IHA) and enzyme-linked immunosorbent assay (ELISA). Antibodies to T. gondii were found in 40% (40 of 100) of the cats, less than the 50.5% (101 of 200) found in dogs by ELISA (P < 0.05). Haemagglutination showed low resolution and concordance, precluding their use for diagnosis of T. gondii infection compared with ELISA. The prevalence of T. gondii was lower among stray cats probably due to their selective alimentary habits and lower water and food intake. Toxoplasma gondii seroprevalence in stray dogs and cats could be an indirect indicator of the parasite spreading in urban areas.

Rapid immunochromatographic test using recombinant SAG2 for detection of antibodies against Toxoplasma gondii in cats

An immunochromatographic test using recombinant truncated surface antigen 2 for detection of antibodies against Toxoplasma gondii was developed. Evaluation of detection of the antibody in mice and cats suggests that this test is rapid, simple, accurate, relatively inexpensive, and suitable for use under field conditions.

Molecular evidence for multiple Toxoplasma gondii infections in individual patients in England and Wales: public health implications

We sought to determine the SAG2 genotypes of Toxoplasma gondii associated with cases of acute human toxoplasmosis in England and Wales. The samples examined were collected from a wide range of cases including congenital infections, AIDS and immunosuppressed patients and were derived from a number of different tissues. Parasite DNA was detected by PCR amplification without the need for prior template purification, and SAG2 genotype was determined by both restriction enzyme analysis and direct DNA sequencing of the PCR amplification products. Parasites of both SAG2 type I and type II genotypes were seen with approximately equal frequency amongst the samples examined. Neither of these genotypes was found to be more frequently associated with a particular clinical presentation or sample tissue. Unexpectedly, we found clear evidence of mixed (SAG2 type I+type II) infections in approximately the same number of samples as were seen to be associated with either type I or II alone. Our use of direct DNA sequencing rather than simple restriction analysis was essential for the detection of mixed infections since incomplete restriction digestion of samples containing a single parasite type was occasionally observed. It is possible that the presence of more than one type of parasite in single samples might be related to our recent demonstration that mixtures of SAG2 type I and type II parasites are present in a significant proportion of commercial meat preparations. Moreover, the presence of mixed infections in single patients might offer a direct molecular method of assessing risk factors for infection.

Isolation of purified oocyst walls and sporocysts from Toxoplasma gondii

Toxoplasma gondii oocysts are environmentally resistant and can infect virtually all warm-blooded hosts, including humans and livestock. Little is known about the biochemical basis for this resistance of oocysts, and mechanism for excystation of T. gondii sporozoites. The objective of the present study was to evaluate different methods (mechanical fragmentation, gradients, flow cytometry) to separate and purify T. gondii oocyst walls and sporocysts. Oocyst walls were successfully separated and purified using iodixanol gradients. Sporocysts were successfully separated and purified using iodixanol and Percoll gradients. Purification was also achieved by flow cytometry. Flow cytometry with fluorescence-activated cell sorting (FACS) yielded analytical quantities of oocyst walls and intact sporocysts. Flow cytometry with FACS also proved useful for quantitation of purity obtained following iodixanol gradient fractionation. Methods reported in this paper will be useful for analytical purposes, such as proteomic analysis of components unique to this life cycle stage, development of detection methods, or excystation studies.

GIS-based analysis of drinking-water supply structures: a module for microbial risk assessment

Water-related infections constitute an important health impact world-wide. A set of tools serving for Microbial Risk Assessment (MRA) of waterborne diseases should comprise the entire drinking-water management system and take into account the Hazard Analysis and Critical Control Point (HACCP) concept which provides specific Critical Control Points (CCPs) reflecting each step of drinking-water provision. A Geographical Information System (GIS) study concerning water-supply structure (WSS) was conducted in the Rhein-Berg District (North Rhine-Westphalia, Germany). As a result, suitability of the existing water databases HYGRIS (hydrological basis geo-information system) and TEIS (drinking-water recording and information system) for the development of a WSS-GIS module could be demonstrated. Spatial patterns within the integrated raw and drinking-water data can easily be uncovered by GIS-specific options. The application of WSS-GIS allows a rapid visualization and analysis of drinking-water supply structure and offers huge advantages concerning microbial monitoring of raw and drinking water as well as recognition and investigation of incidents and outbreaks. Increasing requests regarding health protection and health reporting, demands for a better outbreak management and water-related health impacts of global climate change are major challenges of future water management to be tackled with methods including spatial analysis. GIS is assumed to be a very useful tool to meet these requirements.

Toxoplasma gondii: from animals to humans

Toxoplasmosis is one of the more common parasitic zoonoses world-wide. Its causative agent, Toxoplasma gondii, is a facultatively heteroxenous, polyxenous protozoon that has developed several potential routes of transmission within and between different host species. If first contracted during pregnancy, T. gondii may be transmitted vertically by tachyzoites that are passed to the foetus via the placenta. Horizontal transmission of T. gondii may involve three life-cycle stages, i.e. ingesting infectious oocysts from the environment or ingesting tissue cysts or tachyzoites which are contained in meat or primary offal (viscera) of many different animals. Transmission may also occur via tachyzoites contained in blood products, tissue transplants, or unpasteurised milk. However, it is not known which of these routes is more important epidemiologically. In the past, the consumption of raw or undercooked meat, in particular of pigs and sheep, has been regarded as a major route of transmission to humans. However, recent studies showed that the prevalence of T. gondii in meat-producing animals decreased considerably over the past 20 years in areas with intensive farm management. For example, in several countries of the European Union prevalences of T. gondii in fattening pigs are now <1%. Considering these data it is unlikely that pork is still a major source of infection for humans in these countries. However, it is likely that the major routes of transmission are different in human populations with differences in culture and eating habits. In the Americas, recent outbreaks of acute toxoplasmosis in humans have been associated with oocyst contamination of the environment. Therefore, future epidemiological studies on T. gondii infections should consider the role of oocysts as potential sources of infection for humans, and methods to monitor these are currently being developed. This review presents recent epidemiological data on T. gondii, hypotheses on the major routes of transmission to humans in different populations, and preventive measures that may reduce the risk of contracting a primary infection during pregnancy.