Walking distance for vulnerable populations to public health emergency response points of dispensing in New York City

During certain public health emergencies, points of dispensing (PODs) may be used to rapidly distribute medical countermeasures such as antibiotics to the general public to prevent disease. Jurisdictions across the country have identified sites for PODs in preparation for such an emergency; in New York City (NYC), the sites are identified based largely on population density. Vulnerable populations, defined for this analysis as persons with income below the federal poverty level, persons with less than a high school diploma, foreign-born persons, persons of color, persons aged ≥65 years, physically disabled persons, and unemployed persons, often experience a wide range of health inequities. In NYC, these populations are often concentrated in certain geographic areas and rely heavily on public transportation. Because public transportation will almost certainly be affected during large-scale public health emergencies that would require the rapid mass dispensing of medical countermeasures, we evaluated walking distances to PODs. We used an ordinary least squares (OLS) model and a geographically weighted regression (GWR) model to determine if certain characteristics that increase health inequities in the population are associated with longer distances to the nearest POD relative to the general NYC population. Our OLS model identified shorter walking distances to PODs in neighborhoods with a higher percentage of persons with income below the federal poverty level, higher percentage of foreign-born persons, or higher percentage of persons of color, and identified longer walking distances to PODs in neighborhoods with a higher percentage of persons with less than a high school diploma. Our GWR model confirmed the findings from the OLS model and further illustrated these patterns by certain neighborhoods. Our analysis shows that currently identified locations for PODs in NYC are generally serving vulnerable populations equitably-particularly those defined by race or income status-at least in terms of walking distance.

Hospital-level factors associated with death during pneumonia-associated hospitalization among adults-New York City, 2010-2014

Background

In New York City (NYC), pneumonia is a leading cause of death and most pneumonia deaths occur in hospitals. Whether the pneumonia death rate in NYC reflects reporting artifact or is associated with factors during pneumonia-associated hospitalization (PAH) is unknown. We aimed to identify hospital-level factors associated with higher than expected in-hospital pneumonia death rates among adults in NYC.

Methods

Data from January 1, 2010–December 31, 2014 were obtained from the New York Statewide Planning and Research Cooperative System and the American Hospital Association Database. In-hospital pneumonia standardized mortality ratio (SMR) was calculated for each hospital as observed PAH death rate divided by expected PAH death rate. To determine hospital-level factors associated with higher in-hospital pneumonia SMR, we fit a hospital-level multivariable negative binomial regression model.

Results

Of 148,172 PAH among adult NYC residents in 39 hospitals during 2010–2014, 20,820 (14.06%) resulted in in-hospital death. In-hospital pneumonia SMRs varied across NYC hospitals (0.77–1.23) after controlling for patient-level factors. An increase in average daily occupancy and membership in the Council of Teaching Hospitals were associated with increased in-hospital pneumonia SMR.

Conclusions

Differences in in-hospital pneumonia SMRs between hospitals might reflect differences in disease severity, quality of care, or coding practices. More research is needed to understand the association between average daily occupancy and in-hospital pneumonia SMR. Additional pneumonia-specific training at teaching hospitals can be considered to address higher in-hospital pneumonia SMR in teaching hospitals.

Community-setting pneumonia-associated hospitalizations by level of urbanization-New York City versus other areas of New York State, 2010-2014

Background

New York City (NYC) reported a higher pneumonia and influenza death rate than the rest of New York State during 2010–2014. Most NYC pneumonia and influenza deaths are attributed to pneumonia caused by infection acquired in the community, and these deaths typically occur in hospitals.

Methods

We identified hospitalizations of New York State residents aged ≥20 years discharged from New York State hospitals during 2010–2014 with a principal diagnosis of community-setting pneumonia or a secondary diagnosis of community-setting pneumonia if the principal diagnosis was respiratory failure or sepsis. We examined mean annual age-adjusted community-setting pneumonia-associated hospitalization (CSPAH) rates and proportion of CSPAH with in-hospital death, overall and by sociodemographic group, and produced a multivariable negative binomial model to assess hospitalization rate ratios.

Results

Compared with non-NYC urban, suburban, and rural areas of New York State, NYC had the highest mean annual age-adjusted CSPAH rate at 475.3 per 100,000 population and the highest percentage of CSPAH with in-hospital death at 13.7%. NYC also had the highest proportion of CSPAH patients residing in higher-poverty-level areas. Adjusting for age, sex, and area-based poverty, NYC residents experienced 1.3 (95% confidence interval [CI], 1.2–1.4), non-NYC urban residents 1.4 (95% CI, 1.3–1.6), and suburban residents 1.2 (95% CI, 1.1–1.3) times the rate of CSPAH than rural residents.

Conclusions

In New York State, NYC as well as other urban areas and suburban areas had higher rates of CSPAH than rural areas. Further research is needed into drivers of CSPAH deaths, which may be associated with poverty.

Infectious Disease Hospitalizations, New York City, 2001-2014

OBJECTIVE

Hospital discharge data are a means of monitoring infectious diseases in a population. We investigated rates of infectious disease hospitalizations in New York City.

METHODS

We analyzed data for residents discharged from New York State hospitals with a principal diagnosis of an infectious disease during 2001-2014 by using the Statewide Planning and Research Cooperative System. We calculated annual age-adjusted hospitalization rates and the percentage of hospitalizations in which in-hospital death occurred. We examined diagnoses by site of infection or sepsis and by pathogen type.

RESULTS

During 2001-2014, the mean annual age-adjusted rate of infectious disease hospitalizations in New York City was 1661.6 (95% CI, 1659.2-1663.9) per 100 000 population; the mean annual age-adjusted hospitalization rate decreased from 2001-2003 to 2012-2014 (rate ratio = 0.9; 95% CI, 0.9-0.9). The percentage of in-hospital death during 2001-2014 was 5.9%. The diagnoses with the highest mean annual age-adjusted hospitalization rates among all sites of infection and sepsis diagnoses were the lower respiratory tract, followed by sepsis. From 2001-2003 to 2012-2014, the mean annual age-adjusted hospitalization rate per 100 000 population for HIV decreased from 123.1 (95% CI, 121.7-124.5) to 40.0 (95% CI, 39.2-40.7) and for tuberculosis decreased from 10.2 (95% CI, 9.8-10.6) to 4.6 (95% CI, 4.4-4.9).

CONCLUSIONS

Although hospital discharge data are subject to limitations, particularly for tracking sepsis, lower respiratory tract infections and sepsis are important causes of infectious disease hospitalizations in New York City. Hospitalizations for HIV infection and tuberculosis appear to be declining.

Infectious Disease Hospitalizations: United States, 2001 to 2014

BACKGROUND

Infectious disease epidemiology has changed over time, reflecting improved clinical interventions and emergence of threats such as antimicrobial resistance. This study investigated infectious disease hospitalizations in the United States from 2001 to 2014.

METHODS

Estimated rates of infectious disease hospitalizations were calculated by using the National (Nationwide) Inpatient Sample. Infectious disease hospitalizations were defined as hospitalizations with a principal discharge diagnosis of an infectious disease. Diagnoses according to site of infection and sepsis were examined, as was occurrence of in-hospital death. The leading nonsepsis infectious disease secondary diagnoses for hospitalizations with a principal diagnosis of sepsis were identified.

RESULTS

The mean annual age-adjusted infectious disease hospitalization rate was 1,468.2 (95% CI, 1,459.9-1,476.4) per 100,000 population; in-hospital death occurred in 4.22% (95% CI, 4.18-4.25) of infectious disease hospitalizations. The mean annual age-adjusted infectious disease hospitalization rate increased from 2001-2003 to 2012-2014 (rate ratio, 1.05; 95% CI, 1.01-1.09), as did the percentage of in-hospital death (4.21% [95% CI, 4.13-4.29] to 4.30% [95% CI, 4.26-4.35]; P = .049). The diagnoses with the highest hospitalization rates among all sites of infection and sepsis diagnoses were the lower respiratory tract followed by sepsis. The most common nonsepsis infectious disease secondary diagnoses among sepsis hospitalizations were "urinary tract infection," "pneumonia, organism unspecified," and "intestinal infection due to Clostridium [Clostridioides] difficile."

CONCLUSIONS

Although hospital discharge data are subject to limitations, particularly for tracking sepsis, lower respiratory tract infections and sepsis seem to be important contributors to infectious disease hospitalizations. Prevention of infections that lead to sepsis and improvements in sepsis management would decrease the burden of infectious disease hospitalizations and improve outcomes, respectively.

Pneumonia-Associated Hospitalizations, New York City, 2001-2014

OBJECTIVES

Death certificate data indicate that the age-adjusted death rate for pneumonia and influenza is higher in New York City than in the United States. Most pneumonia and influenza deaths are attributed to pneumonia rather than influenza. Because most pneumonia deaths occur in hospitals, we analyzed hospital discharge data to provide insight into the burden of pneumonia in New York City.

METHODS

We analyzed data for New York City residents discharged from New York State hospitals with a principal diagnosis of pneumonia, or a secondary diagnosis of pneumonia if the principal diagnosis was respiratory failure or sepsis, during 2001-2014. We calculated mean annual age-adjusted pneumonia-associated hospitalization rates per 100 000 population and 95% confidence intervals (CIs). We examined data on pneumonia-associated hospitalizations by sociodemographic characteristics and colisted conditions.

RESULTS

During 2001-2014, a total of 495 225 patients residing in New York City were hospitalized for pneumonia, corresponding to a mean annual age-adjusted pneumonia-associated hospitalization rate of 433.8 per 100 000 population (95% CI, 429.3-438.3). The proportion of pneumonia-associated hospitalizations with in-hospital death was 12.0%. The mean annual age-adjusted pneumonia-associated hospitalization rate per 100 000 population increased as area-based poverty level increased, whereas the percentage of pneumonia-associated hospitalizations with in-hospital deaths decreased with increasing area-based poverty level. The proportion of pneumonia-associated hospitalizations that colisted an immunocompromising condition increased from 18.7% in 2001 to 33.1% in 2014.

CONCLUSION

Sociodemographic factors and immune status appear to play a role in the epidemiology of pneumonia-associated hospitalizations in New York City. Further study of pneumonia-associated hospitalizations in at-risk populations may lead to targeted interventions.

Sensitivity and Positive Predictive Value of Death Certificate Data Among Deaths Caused by Legionnaires' Disease in New York City, 2008-2013

OBJECTIVES

Death certificates are an important source of information for understanding life expectancy and mortality trends; however, misclassification and incompleteness are common. Although deaths caused by Legionnaires' disease might be identified through routine surveillance, it is unclear whether Legionnaires' disease is accurately recorded on death certificates. We evaluated the sensitivity and positive predictive value of death certificates for identifying deaths from confirmed or suspected Legionnaires' disease among adults in New York City.

METHODS

We deterministically matched death certificate data from January 1, 2008, through December 31, 2013, on New York City residents aged ≥18 years to surveillance data on confirmed and suspected cases of Legionnaires' disease from January 1, 2008, through October 31, 2013. We estimated sensitivity and positive predictive value by using surveillance data as the reference standard.

RESULTS

Of 294 755 deaths, 27 (<0.01%) had an underlying cause of death of Legionnaires' disease and 33 (0.01%) had any mention of Legionnaires' disease on the death certificate. Of 1211 confirmed or suspected cases of Legionnaires' disease, 267 (22.0%) matched to a record in the death certificate data set. The sensitivity of death certificates that listed Legionnaires' disease as the underlying cause of death was 17.3% and of death certificates with any mention of Legionnaires' disease was 20.9%. The positive predictive value of death certificates that listed Legionnaires' disease as the underlying cause of death was 70.4% and of death certificates with any mention of Legionnaires' disease was 69.7%.

CONCLUSIONS

Death certificates had limited ability to identify confirmed or suspected deaths with Legionnaires' disease. Provider trainings on the diagnosis of Legionnaires' disease, particularly hospital settings, and proper completion of death certificates might improve the sensitivity of death certificates for people who die of Legionnaires' disease.

Reporting of False Data During Ebola Virus Disease Active Monitoring-New York City, January 1, 2015-December 29, 2015

The New York City Department of Health and Mental Hygiene (DOHMH) began to actively monitor people potentially exposed to Ebola virus on October 25, 2014. Active monitoring was critical to the Ebola virus disease (EVD) response and mitigated risk without restricting individual liberties. Noncompliance with active monitoring procedures has been reported. We conducted a survey of 4,075 eligible persons to evaluate (1) the frequency of reporting of false data during active monitoring, and (2) factors associated with reporting of false temperature data. A total of 393 persons (9.6%) responded to the survey. Fifty-five (14.0%) provided false temperature data, 5 (1.3%) did not report EVD-like symptoms that they had experienced, and 2 (0.5%) did not report a hospital or emergency room visit. Having visited Liberia (OR: 3.4, 95% CI: 1.4-7.9), Sierra Leone (OR: 3.4, 95% CI: 1.6-7.5), or multiple EVD-affected countries (OR: 12.9, 95% CI: 3.5-47.7); being aged <50 years (OR: 7.5, 95% CI: 1.7-33.1); and rating the importance of active monitoring as low (OR: 1.4, 95% CI: 1.1-1.8) were associated with increased odds of reporting false temperature data. Over 10% of respondents reported providing false data during EVD active monitoring. However, it remains unclear whether reporting of false data during active monitoring impedes the ability to rapidly identify EVD cases in settings with a low burden of EVD.

Burden of Adult Community-acquired, Health-care-Associated, Hospital-Acquired, and Ventilator-Associated Pneumonia: New York City, 2010 to 2014

BACKGROUND

Although pneumonia is a leading cause of death in New York City (NYC), limited data exist about the settings in which pneumonia is acquired across NYC. Cases of pneumonia acquired in community settings are more likely to be preventable with vaccines and treatable with first-line antibiotics than those acquired in noncommunity settings. The objective of this study was to estimate the burden of hospitalizations associated with community-acquired (CAP), health-care-associated (HCAP), hospital-acquired (HAP), and ventilator-associated (VAP) pneumonia from 2010 to 2014.

METHODS

This retrospective analysis was performed by using an all-payer reporting system of hospital discharges that included NYC residents aged ≥ 18 years. Pneumonia-associated hospitalizations were defined as any hospitalization that included a diagnostic code for pneumonia among any of the discharge diagnoses. Using published clinical guidelines, we classified hospitalizations into mutually exclusive categories of CAP, HCAP, HAP, and VAP and defined pneumonia acquired in the community setting as the combination of CAP and HCAP.

RESULTS

Of 4,614,108 hospitalizations during the reporting period, 283,927 (6.2%) involved pneumonia. Among pneumonia-associated hospitalizations, 154,158 (54.3%) were CAP, 85,656 (30.2%) were HCAP, 39,712 (14.0%) were HAP, and 4,401 (1.6%) were VAP. Death during hospitalization occurred in 7.9% of CAP-associated hospitalizations, compared with 15.6% of HCAP-associated hospitalizations, 20.7% of HAP-associated hospitalizations, and 21.6% of VAP-associated hospitalizations.

CONCLUSIONS

Most pneumonia-associated hospitalizations in NYC involve pneumonias acquired in the community setting. Although 15.6% of pneumonia-associated hospitalizations were categorized as HAP or VAP, these pneumonias accounted for > 25% of deaths from pneumonia-associated hospitalizations. Public health pneumonia prevention efforts need to target both community and hospital settings.

A Large Community Outbreak of Legionnaires' Disease Associated With a Cooling Tower in New York City, 2015

OBJECTIVES

Infections caused by Legionella are the leading cause of waterborne disease outbreaks in the United States. We investigated a large outbreak of Legionnaires' disease in New York City in summer 2015 to characterize patients, risk factors for mortality, and environmental exposures.

METHODS

We defined cases as patients with pneumonia and laboratory evidence of Legionella infection from July 2 through August 3, 2015, and with a history of residing in or visiting 1 of several South Bronx neighborhoods of New York City. We describe the epidemiologic, environmental, and laboratory investigation that identified the source of the outbreak.

RESULTS

We identified 138 patients with outbreak-related Legionnaires' disease, 16 of whom died. The median age of patients was 55. A total of 107 patients had a chronic health condition, including 43 with diabetes, 40 with alcoholism, and 24 with HIV infection. We tested 55 cooling towers for Legionella, and 2 had a strain indistinguishable by pulsed-field gel electrophoresis from 26 patient isolates. Whole-genome sequencing and epidemiologic evidence implicated 1 cooling tower as the source of the outbreak.

CONCLUSIONS

A large outbreak of Legionnaires' disease caused by a cooling tower occurred in a medically vulnerable community. The outbreak prompted enactment of a new city law on the operation and maintenance of cooling towers. Ongoing surveillance and evaluation of cooling tower process controls will determine if the new law reduces the incidence of Legionnaires' disease in New York City.

Spatiotemporal Co-occurrence of Flanders and West Nile Viruses Within Culex Populations in Shelby County, Tennessee

West Nile virus (WNV) and Flanders virus (FLAV) can cocirculate in Culex mosquitoes in parts of North America. A large dataset of mosquito pools tested for WNV and FLAV was queried to understand the spatiotemporal relationship between these two viruses in Shelby County, TN. We found strong evidence of global clustering (i.e., spatial autocorrelation) and overlapping of local clustering (i.e., Hot Spots based on Getis Ord Gi*) of maximum likelihood estimates (MLE) of infection rates (IR) during 2008-2013. Temporally, FLAV emerges and peaks on average 10.2 wk prior to WNV based on IR. Higher levels of WNV IR were detected within 3,000 m of FLAV-positive pool buffers than outside these buffers.

Migration and Gene Flow Among Domestic Populations of the Chagas Insect Vector Triatoma dimidiata (Hemiptera: Reduviidae) Detected by Microsatellite Loci

Triatoma dimidiata (Latreille, 1811) is the most abundant and significant insect vector of the parasite Trypanosoma cruzi in Central America, and particularly in Guatemala. Tr. cruzi is the causative agent of Chagas disease, and successful disease control requires understanding the geographic distribution and degree of migration of vectors such as T. dimidiata that frequently re-infest houses within months following insecticide application. The population genetic structure of T. dimidiata collected from six villages in southern Guatemala was studied to gain insight into the migration patterns of the insects in this region where populations are largely domestic. This study provided insight into the likelihood of eliminating T. dimidiata by pesticide application as has been observed in some areas for other domestic triatomines such as Triatoma infestans. Genotypes of microsatellite loci for 178 insects from six villages were found to represent five genetic clusters using a Bayesian Markov Chain Monte Carlo method. Individual clusters were found in multiple villages, with multiple clusters in the same house. Although migration occurred, there was statistically significant genetic differentiation among villages (FR T = 0.05) and high genetic differentiation among houses within villages (FSR = 0.11). Relatedness of insects within houses varied from 0 to 0.25, i.e., from unrelated to half-sibs. The results suggest that T. dimidiata in southern Guatemala moves between houses and villages often enough that recolonization is likely, implying the use of insecticides alone is not sufficient for effective control of Chagas disease in this region and more sustainable solutions are required.

Sources of blood meals of sylvatic Triatoma guasayana near Zurima, Bolivia, assayed with qPCR and 12S cloning

Background

In this study we compared the utility of two molecular biology techniques, cloning of the mitochondrial 12S ribosomal RNA gene and hydrolysis probe-based qPCR, to identify blood meal sources of sylvatic Chagas disease insect vectors collected with live-bait mouse traps (also known as Noireau traps). Fourteen T. guasayana were collected from six georeferenced trap locations in the Andean highlands of the department of Chuquisaca, Bolivia.

Methodology/Principal Findings

We detected four blood meals sources with the cloning assay: seven samples were positive for human (Homo sapiens), five for chicken (Gallus gallus) and unicolored blackbird (Agelasticus cyanopus), and one for opossum (Monodelphis domestica). Using the qPCR assay we detected chicken (13 vectors), and human (14 vectors) blood meals as well as an additional blood meal source, Canis sp. (4 vectors).

Conclusions/Significance

We show that cloning of 12S PCR products, which avoids bias associated with developing primers based on a priori knowledge, detected blood meal sources not previously considered and that species-specific qPCR is more sensitive. All samples identified as positive for a specific blood meal source by the cloning assay were also positive by qPCR. However, not all samples positive by qPCR were positive by cloning. We show the power of combining the cloning assay with the highly sensitive hydrolysis probe-based qPCR assay provides a more complete picture of blood meal sources for insect disease vectors.

The World Health Organization (WHO) estimates that 7 to 8 million people are currently infected with Trypanosoma cruzi, the parasite that causes Chagas disease. The WHO recommends insect vector control as the primary prevention method; and insecticide spraying is the most commonly used intervention technique. Sylvatic insect vectors are a special concern because they are a source of reinfestation after insecticides have been applied to living quarters (domestic) and immediate surroundings (peridomestic). To better understand sylvatic insect vector movement, we used two molecular biology techniques to detect the blood meal sources of sylvatic insect vectors. The first technique, cloning of 12S PCR products, allows us to cast a wide net and detect blood meal sources with no previous knowledge of vertebrates or mammals in the study site. After acquiring knowledge of vertebrates in the study site (either through the aforementioned cloning technique, literature review or survey of the area), the second technique, the species-specific hydrolysis probe-based qPCR provides a highly sensitive assay for particular taxa.

Household model of Chagas disease vectors (Hemiptera: Reduviidae) considering domestic, peridomestic, and sylvatic vector populations

ABSTRACT Disease transmission is difficult to model because most vectors and hosts have different generation times. Chagas disease is such a situation, where insect vectors have 1-2 generations annually and mammalian hosts, including humans, can live for decades. The hemataphagous triatominae vectors (Hemiptera: Reduviidae) of the causative parasite Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) usually feed on sleeping hosts, making vector infestation of houses, peridomestic areas, and wild animal burrows a central factor in transmission. Because of difficulties with different generation times, we developed a model considering the dwelling as the unit of infection, changing the dynamics from an indirect to a direct transmission model. In some regions, vectors only infest houses; in others, they infest corrals; and in some regions, they also infest wild animal burrows. We examined the effect of sylvatic and peridomestic vector populations on household infestation rates. Both sylvatic and peridomestic vectors increase house infestation rates, sylvatic much more than peridomestic, as measured by the reproductive number R0. The efficacy of manipulating parameters in the model to control vector populations was examined. When R0 > 1, the number of infested houses increases. The presence of sylvatic vectors increases R0 by at least an order of magnitude. When there are no sylvatic vectors, spraying rate is the most influential parameter. Spraying rate is relatively unimportant when there are sylvatic vectors; in this case, community size, especially the ratio of houses to sylvatic burrows, is most important. The application of this modeling approach to other parasites and enhancements of the model are discussed.

Ecohealth interventions limit triatomine reinfestation following insecticide spraying in La Brea, Guatemala

In this study, we evaluate the effect of participatory Ecohealth interventions on domestic reinfestation of the Chagas disease vector Triatoma dimidiata after village-wide suppression of the vector population using a residual insecticide. The study was conducted in the rural community of La Brea, Guatemala between 2002 and 2009 where vector infestation was analyzed within a spatial data framework based on entomological and socio-economic surveys of homesteads within the village. Participatory interventions focused on community awareness and low-cost home improvements using local materials to limit areas of refuge and alternative blood meals for the vector within the home, and potential shelter for the vector outside the home. As a result, domestic infestation was maintained at ≤ 3% and peridomestic infestation at ≤ 2% for 5 years beyond the last insecticide spraying, in sharp contrast to the rapid reinfestation experienced in earlier insecticide only interventions.

Vector blood meals and Chagas disease transmission potential, United States

A high proportion of triatomine insects, vectors for Trypanosoma cruzi trypanosomes, collected in Arizona and California and examined using a novel assay had fed on humans. Other triatomine insects were positive for T. cruzi parasite infection, which indicates that the potential exists for vector transmission of Chagas disease in the United States.

PCR reveals significantly higher rates of Trypanosoma cruzi infection than microscopy in the Chagas vector, Triatoma infestans: high rates found in Chuquisaca, Bolivia

Background

The Andean valleys of Bolivia are the only reported location of sylvatic Triatoma infestans, the main vector of Chagas disease in this country, and the high human prevalence of Trypanosoma cruzi infection in this region is hypothesized to result from the ability of vectors to persist in domestic, peri-domestic, and sylvatic environments. Determination of the rate of Trypanosoma infection in its triatomine vectors is an important element in programs directed at reducing human infections. Traditionally, T. cruzi has been detected in insect vectors by direct microscopic examination of extruded feces, or dissection and analysis of the entire bug. Although this technique has proven to be useful, several drawbacks related to its sensitivity especially in the case of small instars and applicability to large numbers of insects and dead specimens have motivated researchers to look for a molecular assay based on the polymerase chain reaction (PCR) as an alternative for parasitic detection of T. cruzi infection in vectors. In the work presented here, we have compared a PCR assay and direct microscopic observation for diagnosis of T. cruzi infection in T. infestans collected in the field from five localities and four habitats in Chuquisaca, Bolivia. The efficacy of the methods was compared across nymphal stages, localities and habitats.

Methods

We examined 152 nymph and adult T. infestans collected from rural areas in the department of Chuquisaca, Bolivia. For microscopic observation, a few drops of rectal content obtained by abdominal extrusion were diluted with saline solution and compressed between a slide and a cover slip. The presence of motile parasites in 50 microscopic fields was registered using 400× magnification. For the molecular analysis, dissection of the posterior part of the abdomen of each insect followed by DNA extraction and PCR amplification was performed using the TCZ1 (5' – CGA GCT CTT GCC CAC ACG GGT GCT – 3') and TCZ2 (5' – CCT CCA AGC AGC GGA TAG TTC AGG – 3') primers. Amplicons were chromatographed on a 2% agarose gel with a 100 bp size standard, stained with ethidium bromide and viewed with UV fluorescence.

For both the microscopy and PCR assays, we calculated sensitivity (number of positives by a method divided by the number of positives by either method) and discrepancy (one method was negative and the other was positive) at the locality, life stage and habitat level. The degree of agreement between PCR and microscopy was determined by calculating Kappa (k) values with 95% confidence intervals.

Results

We observed a high prevalence of T. cruzi infection in T. infestans (81.16% by PCR and 56.52% by microscopy) and discovered that PCR is significantly more sensitive than microscopic observation. The overall degree of agreement between the two methods was moderate (Kappa = 0.43 ± 0.07). The level of infection is significantly different among communities; however, prevalence was similar among habitats and life stages.

Conclusion

PCR was significantly more sensitive than microscopy in all habitats, developmental stages and localities in Chuquisaca, Bolivia. Overall we observed a high prevalence of T. cruzi infection in T. infestans in this area of Bolivia; however, microscopy underestimated infection at all levels examined.