Valor pronóstico de los parámetros hematológicos y los parámetros metabólicos de la PET/TC con [18F]FDG en el cáncer de cabeza y cuello / Prognostic value of haematological parameters and [18F]FDG PET/CT metabolic parameters in head and neck cancer

Objetivo Determinar la utilidad de los cocientes neutrófilos/linfocitos (N/L) y plaquetas/linfocitos (P/L), así como de parámetros cuantitativos de la PET/TC con [18F]FDG, como factores pronósticos para la supervivencia global (SG), la supervivencia cáncer específica (SCE) y la supervivencia libre de progresión (SLP) en pacientes con carcinoma escamoso de cabeza y cuello (CyC) Material y métodos Se valoraron retrospectivamente 66 pacientes (56 hombres) diagnosticados de CyC durante un intervalo de 8años. Se determinaron los parámetros SUV máximo (SUVmax), volumen metabólico tumoral (MTV) y glucólisis tumoral total (TLG) del estudio PET/TC al diagnóstico. Tras tratamiento con quimiorradioterapia, se valoró la supervivencia de los pacientes. El modelo de regresión de Cox y el método de Kaplan-Meier se utilizaron para analizar factores pronósticos y curvas de supervivencia. Resultados El seguimiento medio fue de 50,4meses, produciéndose 39 recurrencias-progresiones y 39 fallecimientos. En el análisis univariante los parámetros metabólicos, excepto el SUVmax, fueron factores predictivos para las tres supervivencias, y los dos parámetros sanguíneos lo fueron para la SG y la SCE. La TLG fue el único factor predictivo en el análisis multivariante. Las tres curvas de supervivencias fueron significativamente diferentes para los parámetros metabólicos y la curva de SG para el cociente N/L. Se apreciaron correlaciones entre el cociente N/L, el MTV y la TLG. No se demostraron correlaciones entre el cociente P/L y los parámetros metabólicos. Conclusión El uso de marcadores hematológicos y metabólicos permitiría identificar pacientes con un alto riesgo de recurrencias y pobre supervivencia e individualizar el tratamiento aplicando terapias más agresivas (AU)

Aim To determine the usefulness of neutrophil/lymphocyte (N/L) and platelet/lymphocyte (P/L) ratios as well as quantitative [18F]FDG PET/CT parameters as prognostic factors for overall survival (OS), cancer-specific survival (CSS) and progression-free survival (PFS) in patients with head and neck squamous cell carcinoma (HyN). Material and methods Sixty-six patients (56 men) diagnosed with HyN carcinoma were retrospectively assessed over an 8-year interval. Maximum SUV (SUVmax), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) parameters were determined from the PET/CT study at diagnosis. After treatment with chemoradiotherapy, patient survival was assessed. The Cox regression model and the Kaplan-Meier method were used to analyse prognostic factors and survival curves. Results Median follow-up was 50.4months, with 39 recurrences-progressions and 39 deaths. In the univariate analysis, metabolic parameters, except SUVmax, were predictive factors for all three survivals and the two blood parameters were predictive for OS and EFS. TLG was the only predictive factor in the multivariate analysis. The three survival curves were significantly different for the metabolic parameters and the OS curve for the N/L ratio. Correlations were seen between N/L ratio, MTV and TLG. No correlations were demonstrated between P/L ratio and metabolic parameters. Conclusion The use of haematological and metabolic markers would allow to identify patients with a high risk of recurrences and poor survival and to individualise treatment by applying more aggressive therapies (AU)

Cumplimentación del consentimiento informado en cirugía radioguiada por los servicios de Cirugía General y Medicina Nuclear de una unidad de cirugía radioguiada / Completion of the informed consent in radioguided surgery by the General Surgery and Nuclear Medicine services of a radioguided surgery unit

Objetivo Identificar la frecuencia de errores en los documentos de consentimiento informado en cirugía radioguiada en un hospital de tercer nivel y detectar posibles causas o factores asociados a un mayor riesgo de error. Material y método Se analizaron los consentimientos informados de un total de 369 intervenciones de cirugía radioguiada, cumplimentados por los servicios de Medicina Nuclear y Cirugía General, y se analizó el grado de cumplimentación de los mismos y su correlación con facultativos responsables, tipo de enfermedad e intervención, tiempo de espera y cumplimentación del consentimiento de la otra especialidad. Resultados Se identificaron errores en 22 consentimientos de Medicina Nuclear y 71 consentimientos de Cirugía General. El error más común fue la ausencia de identificación del facultativo responsable (17 en Medicina Nuclear, 51 en Cirugía General), y el segundo más común la ausencia de documento (2 en Medicina Nuclear, 20 en Cirugía General). Existieron diferencias significativas en los errores cometidos en función del médico responsable, sin encontrarse correlación significativa con el resto de las variables. Conclusiones Los médicos responsables fueron el principal factor asociado a un mayor riesgo de error en la cumplimentación de consentimientos informados. Serían recomendables nuevos estudios para analizar factores casuales y posibles intervenciones para minimizar errores (AU)

Objective To identify the frequency of errors in the informed consent documents in radioguided surgery in a third level hospital and to detect possible causes or factors associated with a greater risk of error. Material and method The informed consents of a total of 369 radioguided surgery interventions, completed by the Nuclear Medicine and General Surgery services, were analyzed, as well as their degree of completion and its correlation with responsible physicians, type of pathology and intervention, waiting time and completion of the consent of the other specialty. Results Errors were identified in 22 consent forms for Nuclear Medicine and 71 consent forms for General Surgery. The most common error was the absence of identification of the responsible physician (17 in Nuclear Medicine, 51 in General Surgery), and the second most common was the absence of a document (2 in Nuclear Medicine, 20 in General Surgery). There were significant differences in the errors made depending on the doctor in charge, without finding a significant correlation with the other variables. Conclusions The responsible physicians were the main factor associated with a greater risk of error in the completion of informed consent. New studies would be recommended to analyze causal factors and possible interventions to minimize errors (AU)

Criterios PERCIST, Hopkins y parámetros metabólicos de la PET/TC como factores pronósticos en el cáncer escamoso de cabeza y cuello / PERCIST and Hopkins criteria and PET/CT metabolic parameters as prognostic factors in squamous head and neck cancer

Objetivo Valorar la utilidad clínica de los criterios PERCIST, Hopkins y de los cambios en los parámetros cuantitativos de la PET/TC con [18F]FDG como factores pronósticos para la supervivencia libre de progresión (SLP) y la supervivencia cáncer específica (SCE) en pacientes con cáncer escamoso de cabeza y cuello tratados mediante quimiorradioterapia. Material y métodos Se valoraron retrospectivamente 40 pacientes (34 hombres) diagnosticados de cáncer escamoso de cabeza y cuello durante un intervalo de 8 años. Se utilizaron los criterios PERCIST y Hopkins para determinar la respuesta al tratamiento. Así mismo, se cuantificaron las variaciones de los parámetros metabólicos SUV máximo (ΔSUVmax), volumen metabólico tumoral (ΔMTV) y glicólisis tumoral total (ΔTLG) entre los estudios PET/TC pre- y postratamiento. El modelo de regresión de Cox, las curvas ROC y el método de Kaplan-Meier se aplicaron para el análisis de factores pronósticos y curvas de supervivencia. Resultado El seguimiento medio fue de 39,4 meses produciéndose 24 recidivas-progresiones y 22 muertes. Tanto los criterios PERCIST y Hopkins como los tres parámetros metabólicos fueron factores predictivos en análisis univariante y solo el ΔSUVmax en el multivariante. El análisis de supervivencia mostró curvas de SLP y SCE significativamente diferentes para los cinco parámetros considerados. Conclusión La aplicación de los criterios PERCIST y Hopkins, así como los ΔSUVmax, ΔMTV y ΔTLG de los estudios PET/TC demostraron ser factores pronósticos para la supervivencia en pacientes de nuestro entorno tratados por cáncer de cabeza y cuello. Los resultados podrían ayudar a personalizar el tratamiento (AU)

Aim To assess the clinical utility of PERCIST and Hopkins criteria and changes in [18F]FDG PET/CT quantitative parameters as prognostic factors for progression-free survival (PFS) and cancer-specific survival (CSS) in patients with head and neck squamous cell carcinoma treated by chemoradiotherapy. Material and methods Forty patients (34 men) diagnosed with head and neck squamous cell carcinoma were retrospectively assessed over an interval of 8 years. PERCIST and Hopkins criteria were used to assess response to treatment. Variations in the metabolic parameters maximum SUV (ΔSUVmax), metabolic tumor volume (ΔMTV) and total lesion glycolysis (ΔTLG) between pre- and post-treatment PET/CT studies were also determined. Cox regression model, ROC curves and Kaplan-Meier method were used for the analysis of prognostic factors and survival curves. Results The average follow-up was 39.4 months, with 24 progressions and 22 deaths. Both PERCIST and Hopkins criteria and the three metabolic parameters were predictive factors in the univariate analysis and only ΔSUVmax in the multivariate analysis. Survival analysis showed statistically significant differences in PFS and CSS curves for the five parameters considered. Conclusion Application of PERCIST and Hopkins criteria as well as ΔSUVmax, ΔMTV and ΔTLG from PET/CT studies proved to be prognostic factors for survival in patients in our setting treated for head and neck cancer. The results could help to personalize treatment (AU)

Completion of the informed consent in radioguided surgery by the General Surgery and Nuclear Medicine services of a radioguided surgery unit.

OBJECTIVE: To identify the frequency of errors in informed consent documents in radioguided surgery in a third level hospital and to detect possible causes or factors associated with a greater risk of error. MATERIAL AND METHODS: Informed consent forms of a total of 369 radioguided surgery interventions, completed by the Nuclear Medicine and General Surgery services, were analyzed, and the degree of completion of the forms and its correlation with the physicians responsible, type of pathology, intervention, and waiting time were compared with the completion of consent by another specialty. RESULTS: Errors were identified in 22 consent forms from Nuclear Medicine and 71 from General Surgery. The most common error was the absence of identification of the physician responsible (17 in Nuclear Medicine, 51 in General Surgery), and the second most common was the absence of a document (2 in Nuclear Medicine, 20 in General Surgery). There were significant differences in the errors made depending on the doctor in charge, with no significant correlation with the other variables. CONCLUSIONS: The physicians responsible were the main factor associated with a greater risk of error in the completion of informed consent forms. Further studies are needed to analyze the causal factors and possible interventions to minimize errors.

PERCIST and Hopkins criteria and PET/CT metabolic parameters as prognostic factors in squamous head and neck cancer.

AIM: To assess the clinical utility of PERCIST and Hopkins criteria and changes in [18F]FDG PET/CT quantitative parameters as prognostic factors for progression-free survival (PFS) and cancer-specific survival (CSS) in patients with head and neck squamous cell carcinoma treated by chemoradiotherapy. MATERIAL AND METHODS: Forty patients (34 men) diagnosed with head and neck squamous cell carcinoma were retrospectively assessed over an interval of 8 years. PERCIST and Hopkins criteria were used to assess response to treatment. Variations in the metabolic parameters maximum SUV (ΔSUVmax), metabolic tumor volume (ΔMTV) and total lesion glycolysis (ΔTLG) between pre- and post-treatment PET/CT studies were also determined. The Cox regression model, ROC curves and the Kaplan-Meier method were used for the analysis of prognostic factors and survival curves. RESULTS: The mean follow-up was 39.4 months, with 24 progressions and 22 deaths. Both PERCIST and Hopkins criteria and the three metabolic parameters were predictive factors in the univariate analysis and only ΔSUVmax was in the multivariate analysis. Survival analysis showed statistically significant differences in PFS and CSS curves for the five parameters considered. CONCLUSION: Application of PERCIST and Hopkins criteria as well as ΔSUVmax, ΔMTV and ΔTLG from PET/CT studies proved to be prognostic factors for survival in patients in our setting for treating head and neck cancer. The results may help to personalize treatment.

Terapia con péptidos radiomarcados con [177Lu]Lu-DOTA-TATE / Peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE

Esta formación pretende presentar, de forma clara y de fácil comprensión, la biología de los tumores neuroendocrinos (TNE), las características de los receptores de somatostatina, cómo debe realizarse la selección de pacientes candidatos a terapia con péptidos radiomarcados (PRRT), si el paciente cumple los criterios para beneficiarse del tratamiento con los mínimos efectos adversos posibles, el protocolo de administración, seguimiento y evaluación de respuesta. También, se desarrollan los estudios de imagen funcional necesarios para explorar la biología del tumor e individualizar el tratamiento, que constituyen la piedra angular para el desarrollo de la teragnosis.Se están desarrollando ensayos clínicos para definir mejor la posición de PRRT dentro del amplio panorama terapéutico y, entre las perspectivas de futuro, hay varias líneas de investigación para mejorar la tasa de respuesta objetiva y la supervivencia con PRRT, centradas en el desarrollo de nuevos agonistas y antagonistas del receptor de somatostatina, nuevos radionúclidos y terapias combinadas radiosensibilizantes.En conclusión, la PRRT es un tratamiento bien tolerado, seguro y con efectos secundarios agudos, generalmente leves y autolimitados, que constituye una gran herramienta terapéutica que debe secuenciarse en el mejor momento de la evolución de la enfermedad de los pacientes con TNE. Los pacientes candidatos a la PRRT deben ser valorados siempre por un comité clínico multidisciplinar (AU)

This continuing education aims to present in a clear and easy-to-understand way, the biology of neuroendocrine tumors (NETs), the characteristics of somatostatin receptors, the selection of patients for radiolabelled peptide therapy (PRRT), the inclusion criteria to benefit from treatment with the minimum possible adverse effects, the administration protocol, follow-up and response evaluation. The functional imaging studies necessary to explore the biology of the tumor and to individualize the treatment are also carried out, and constitute the cornerstone for the development of teragnosis.Clinical trials are being developed to better define the position of PRRT within the broad therapeutic options, and among the future perspectives, there are several lines of research to improve the objective response rate and survival with PRRT, focused on the development of new agonists and somatostatin receptor antagonists, new radionuclides and radiosensitizing combination therapies.In conclusion, PRRT is a great therapeutic, well-tolerated and safe tool with generally mild and self-limited acute side effects, that must be sequenced at the best moment of the evolution of the disease of patients with NET. Candidate patients for PRRT should always be evaluated by an multidisciplinary clinical committee (AU)

Peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE.

This continuing education aims to present in a clear and easy-to-understand way, the biology of neuroendocrine tumors (NETs), the characteristics of somatostatin receptors, the selection of patients for radiolabelled peptide therapy (PRRT), the inclusion criteria to benefit from treatment with the minimum possible adverse effects, the administration protocol, follow-up and response evaluation. The functional imaging studies necessary to explore the biology of the tumor and to individualize the treatment are also carried out, and constitute the cornerstone for the development of teragnosis. Clinical trials are being developed to better define the position of PRRT within the broad therapeutic options, and among the future perspectives, there are several lines of research to improve the objective response rate and survival with PRRT, focused on the development of new agonists and somatostatin receptor antagonists, new radionuclides and radiosensitizing combination therapies. In conclusion, PRRT is a great therapeutic, well-tolerated and safe tool with generally mild and self-limited acute side effects, that must be sequenced at the best moment of the evolution of the disease of patients with NET. Candidate patients for PRRT should always be evaluated by a multidisciplinary clinical committee.

Multi-channel receptors based on thiopyrylium functionalised with macrocyclic receptors for the recognition of transition metal cations and anions.

We report herein the synthesis and characterization of a family of ligands containing different cation binding sites covalently connected to a thiopyrylium signalling reporter. The receptors L1-L6 are able to signal the presence of certain metal cations via three different channels; i.e. electrochemically, fluorogenically and chromogenically. An acetonitrile solution of L1-L6 shows a bright blue colour due to a charge-transfer band in the 575-585 nm region. The colour variation in acetonitrile of L1-L6 in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Ni2+, Pb2+ and Zn2+ has been studied. A selective hypsochromic shift of the blue band was found for the systems L4-Pb2+ and L5-Hg2+. Additionally, L1-L6 are poorly fluorescent but coordination with certain metal cations induces an enhancement of the fluorescence at ca 500 nm. For instance, the presence of Cu2+ and Fe3+ induced a remarkable 42-fold and 45-fold enhancement in the emission intensity of L1 centred at 500 nm, respectively. Also remarkable was the 18-fold enhancement observed for L4 and L5 in the presence of Fe3+ and Cu2+, respectively. The electrochemical behaviour of receptors L1-L6 was studied in acetonitrile using platinum as a working electrode and [Bu4N][BF4] as a supporting electrolyte. This family of receptors showed a one-electron reversible redox process at ca. -0.46 V versus sce attributed to the reduction of the thiopyrylium group. A moderate anodic shift in the presence of certain metal cations was observed. The effect in the UV-visible spectra of acetonitrile solutions of receptor L1-L6 in the presence of anions was also studied. A remarkable bleaching was found in the presence of cyanide.

Analysis of survival of young and old Aedes aegypti (Diptera: Culicidac) from Puerto Rico and Thailand.

It generally is assumed that the daily probability of survival of wild adult mosquitoes is independent of age. To test this assumption we conducted mark-release-recapture studies in Puerto Rico and Thailand to determine if estimated daily survival rates between two different age cohorts of the dengue vector Aedes aegypti (L.) were the same. Survivorship was estimated with nonlinear regression analysis using bootstrapping to obtain estimates of errors. Initial recapture success of the younger cohort was greater than the older cohort at both locations. Our analysis revealed a significantly greater survival rate for the younger cohort of females in Puerto Rico, and no significant differences between age cohorts in Thailand. For comparison, a traditional approach for analyzing these type of data, linear regression of log-transformed captures over time (exponential model), was used to calculate the probability of daily survival based on slopes of linear regression lines for recaptured mosquitoes. With this method, the estimated daily survival rate of older females (13-23 d old) was significantly greater than survival of younger ones (3-13 d old) in Puerto Rico and Thailand. In addition, short-range movement of mosquitoes was observed in Puerto Rico; maximum dispersal distance detected was 79 m. Survival rates of adult Ae. aegypti may be age-dependent and nonlinear regression analysis is a sensitive approach for comparing patterns of mosquito survival based on mark, single release, multiple recapture data.

Spatial distribution of factors that determine sporogonic development of malaria parasites in mosquitoes.

Mosquitoes transmit malaria, but only a few species permit the complete development and transmission of the parasite. Also, only a fraction of the ingested parasites develop in the vector. The attrition occurs in different compartments during the parasite's complex developmental scheme in the insect. A number of factors, both physical and biochemical, that affect the development have been proposed or demonstrated. Each of these factors is located within a specific space in the insect. We have divided this space into six compartments, which are distinct in their biochemical and biophysical nature: Endoperitrophic space, Peritrophic matrix, Ectopretrophic space, Midgut epithelium, Haemocoel and Salivary gland. Because factors that influence a particular stage of parasite development share the same microenvironment within these compartments, they must be considered collectively to exploit them for designing effective transmission blocking strategies. In this article we discuss these factors according to their spatial location in the mosquito.

Increased fecundity of Aedes aegypti fed human blood before release in a mark-recapture study in Puerto Rico.

Laboratory experiments suggest that utilization of blood rather than natural sugar sources for energetic needs affords female Aedes aegypti a reproductive advantage over conspecifics that use sugar. To test this hypothesis under field conditions, we carried out a mark-release-recapture study in Florida, PR. Adult females (F1) reared from field-collected eggs were provided with a diet of human blood alone or human blood plus a 20% honey solution before their release. Backpack aspirators were used to collect mosquitoes from release houses for 5 consecutive days beginning the 2nd day after release. Survival was estimated from the slope of the regression line of the log-transformed daily number of recaptures for each treatment group. To compare fecundity of the treatment groups, each recaptured female was dissected, ovaries were removed, oocytes counted, and Christophers' stages of oocyte development scored. Recapture rates were 30% for the blood-only group and 23% for blood plus honey group. The daily survival rate of the blood-only group (55%) was not statistically different from that of the blood plus honey group (69%) (t = 0.32, P > 0.05). By analysis of variance, fecundity (average number of stage III-V oocytes) was significantly higher in the females fed human blood alone (n = 103, 109 oocytes/female) than in the group fed on blood and honey (n = 50, 95 oocytes/female) (P = 0.0007). The observed gonotrophic cycle length of the recaptured females ranged from 3 to 7 days. Results from our field study are consistent with laboratory life-table experiments that suggest feeding exclusively on human blood provides a reproductive advantage for female A. aegypti.

Survival of starved Aedes aegypti (Diptera: Culicidae) in Puerto Rico and Thailand.

Survival of adult Aedes aegypti (L.) was studied in Thailand (1995) and Puerto Rico (1996) during periods of high and low dengue virus transmission. Resting males and females were collected inside houses by aspiration. Females were separated into different cages by their degree of engorgement and ovarian development. Teneral adults were obtained from pupae collected from natural breeding sites. All mosquitoes were given access to water, held at ambient temperature in the shade, and their survival monitored daily. We calculated median survival for each stage to estimate when mosquitoes had to feed again or die. No differences in survival between seasons were observed in Thailand. In Puerto Rico, except for wild males, survival was longer in the cool/dry season than in the hot/rainy season, indicating that mosquitoes may need to feed more frequently during the high than low dengue transmission season. During both study periods and at both sites, blood-engorged females survived as long or longer than mosquitoes in other gonotrophic or developmental stages. Except in Puerto Rico during the cool season, when females had a relatively high probability of surviving 3-4 d without feeding, females needed to feed approximately every other day to avoid death caused by starvation. Our results indicate that in some regions, there are seasonal differences in the length of time female Ae. aegypti can survive without feeding, females with a blood meal can survive for a longer time than those without blood, and teneral males can live longer without food than teneral females.

An experimental study on the detection of fructose in Aedes aegypti.

Male and female Aedes aegypti fed a 10% sucrose solution and/or blood were tested to determine the duration of fructose detection in their bodies and the volume of sugar solution they ingested. The limit of detection of fructose by the cold anthrone test was investigated in a series of experiments. Results were applied to the interpretation of sugar feeding by Ae. aegypti collected inside houses in Puerto Rico during times of low (cool season) and high (hot season) dengue transmission in 1996. We conclude that, under our experimental conditions, the cold anthrone test can detect a 10% sucrose solution in male and female Ae. aegypti up to approximately 4 days after ingestion, even the smallest volumes of 10% sucrose solution ingested by experimental mosquitoes are detectable, the test is sensitive enough to detect 0.6 microgram of fructose, and the cutoff point for defining positive fructose values in field-collected females should be based on blood-engorged specimens. We confirmed that female Ae. aegypti collected from natural resting sites inside houses in Puerto Rico seldom, compared to males, contain detectable amounts of fructose.

Life table study of Aedes aegypti (Diptera: Culicidae) in Puerto Rico fed only human blood versus blood plus sugar.

Life table studies were performed in 1996 with Aedes aegypti (L.) during the low (cool/dry) and high (hot/rainy) dengue virus transmission seasons in Puerto Rico. Mated adult females from field-collected pupae were placed individually in cages and divided into 2 treatment groups: one was fed only human blood and the other human blood plus a 10% sucrose solution. Survival and number of eggs laid were recorded daily for each female. During both seasons, age specific survivorship was higher for the blood plus sugar group, groups fed only human blood had higher reproductive outputs (mx), and net replacement rates (Ro) for blood only groups were higher than for those fed blood plus sugar. Intrinsic rates of growth (r) were the same for both treatments during the low (cool/dry) transmission season, but higher for the blood-only treatment during the high (hot/rainy) transmission season. Our results indicate that feeding on only human blood provides an evolutionary advantage to Ae. aegypti females in Puerto Rico. These results are similar to those from an earlier study carried out with Ae. aegypti in Thailand; the advantage of feeding on human blood does not seem to be restricted to a particular geographic region. We also found that the benefits associated with human feeding persist through epidemiologically different times of the year. We conclude that feeding on human blood is reproductively beneficial for Ae. aegypti, which may increase their contact with human hosts, and therefore may influence their vectorial capacity for dengue viruses through frequent feeding on blood.

Aedes aegypti (Diptera: Culicidae) movement influenced by availability of oviposition sites.

Marked Aedes aegypti (L.) (5-6 d old) were released inside 2 groups of 5 houses (100 females per house) in a residential community in Florida, PR, to compare behavior of gravid females at sites where oviposition containers were absent to sites where containers were abundant (i.e., 2 tires and 10 ovipots were added to each yard). Two sequential releases were made so that both groups of houses were evaluated with oviposition containers removed and added. Mosquitoes resting inside the 10 release houses plus 20 additional neighboring houses were collected with backpack aspirators for 4 consecutive days, beginning 2 d after release. Because 172 of the 185 recaptured females (93%) were collected in the same houses in which they had been released, dispersal patterns were not directly comparable. However, the recapture rate in houses with containers added (13%) was significantly higher (P < 0.0001) than in houses with containers removed (6%). No difference was observed in the mean number of potential oviposition containers among the nonrelease houses at the 2 sites (3.9 versus 3.8 aquatic containers per house in the prerelease survey). Our results are consistent with the hypothesis that availability of oviposition sites is inversely correlated with the potential for female Ae. aegypti to disperse. These results have important implications because campaigns to reduce Ae. aegypti larval sites during dengue epidemics could have the undesirable effect of inducing the dispersal of infected adult female mosquitoes.

Experimental transmission of Powassan virus (Flaviviridae) by Ixodes scapularis ticks (Acari:Ixodidae).

Transmission experiments were performed with Ixodes scapularis ticks from an uninfected laboratory colony. Immature and adult ticks were exposed to Powassan (POW) viremic hamsters and rabbits, respectively. Oral infection rates for engorged larvae, nymphs and females fed on POW-infected hosts were 10%, 40%, and 57%, respectively. Transstadial transmission rates for nymphs exposed to POW virus as larvae, adults exposed as larvae, and adults exposed as nymphs, were 9.5%, 10%, and 54%, respectively. Evidence of transovarial transmission occurred when two uninfected hamsters, exposed to F2 larvae and nymphs originally exposed to POW virus in the F1 nymphal stage, seroconverted to POW virus with hemagglutination inhibition titers of 80 and 5,120, respectively; the transovarial transmission rate was 16.6%. All developmental stages were able to transmit virus orally to uninfected hosts regardless of when the ticks were originally exposed to the virus. These results suggest that I. scapularis is a competent vector of POW virus under experimental conditions.

Lyme disease. A Canadian perspective.

Lyme disease is an expanding community health issue in the United States. This has led to greater public awareness in Canada, although the disease remains rare here. We review the biology of ticks and show how feeding patterns are relevant to disease transmission. Diagnosing Lyme disease is sometimes problematic, but treatment can be effective, particularly in the early stages. Preventive measures are aimed at avoiding tick contact and early tick removal.