Circulating tumour cells for early detection of clinically relevant cancer

Given that cancer mortality is usually a result of late diagnosis, efforts in the field of early detection are paramount to reducing cancer-related deaths and improving patient outcomes. Increasing evidence indicates that metastasis is an early event in patients with aggressive cancers, often occurring even before primary lesions are clinically detectable. Metastases are usually formed from cancer cells that spread to distant non-malignant tissues via the blood circulation, termed circulating tumour cells (CTCs). CTCs have been detected in patients with early stage cancers and, owing to their association with metastasis, might indicate the presence of aggressive disease, thus providing a possible means to expedite diagnosis and treatment initiation for such patients while avoiding overdiagnosis and overtreatment of those with slow-growing, indolent tumours. The utility of CTCs as an early diagnostic tool has been investigated, although further improvements in the efficiency of CTC detection are required. In this Perspective, we discuss the clinical significance of early haematogenous dissemination of cancer cells, the potential of CTCs to facilitate early detection of clinically relevant cancers, and the technological advances that might improve CTC capture and, thus, diagnostic performance in this setting.

The potential of using circulating tumour cells and their gene expression to predict docetaxel response in metastatic prostate cancer

Background

Docetaxel improves overall survival (OS) in castration-resistant prostate cancer (PCa) (CRPC) and metastatic hormone-sensitive PCa (mHSPC). However, not all patients respond due to inherent and/or acquired resistance. There remains an unmet clinical need for a robust predictive test to stratify patients for treatment. Liquid biopsy of circulating tumour cell (CTCs) is minimally invasive, can provide real-time information of the heterogeneous tumour and therefore may be a potentially ideal docetaxel response prediction biomarker.

Objective

In this study we investigate the potential of using CTCs and their gene expression to predict post-docetaxel tumour response, OS and progression free survival (PFS).

Methods

Peripheral blood was sampled from 18 mCRPC and 43 mHSPC patients, pre-docetaxel treatment, for CTC investigation. CTCs were isolated using the epitope independent Parsortix^® system and gene expression was determined by multiplex RT-qPCR. We evaluated CTC measurements for post-docetaxel outcome prediction using receiver operating characteristics and Kaplan Meier analysis.

Results

Detection of CTCs pre-docetaxel was associated with poor patient outcome post-docetaxel treatment. Combining total-CTC number with PSA and ALP predicted lack of partial response (PR) with an AUC of 0.90, p= 0.037 in mCRPC. A significantly shorter median OS was seen in mCRPC patients with positive CTC-score (12.80 vs. 37.33 months, HR= 5.08, p= 0.0005), ≥3 total-CTCs/7.5mL (12.80 vs. 37.33 months, HR= 3.84, p= 0.0053), ≥1 epithelial-CTCs/7.5mL (14.30 vs. 37.33 months, HR= 3.89, p= 0.0041) or epithelial to mesenchymal transitioning (EMTing)-CTCs/7.5mL (11.32 vs. 32.37 months, HR= 6.73, p= 0.0001). Significantly shorter PFS was observed in patients with ≥2 epithelial-CTCs/7.5mL (7.52 vs. 18.83 months, HR= 3.93, p= 0.0058). mHSPC patients with ≥5 CTCs/7.5mL had significantly shorter median OS (24.57 vs undefined months, HR= 4.14, p= 0.0097). In mHSPC patients, expression of KLK2, KLK4, ADAMTS1, ZEB1 and SNAI1 was significantly associated with shorter OS and/or PFS. Importantly, combining CTC measurements with clinical biomarkers increased sensitivity and specificity for prediction of patient outcome.

Conclusion

While it is clear that CTC numbers and gene expression were prognostic for PCa post-docetaxel treatment, and CTC subtype analysis may have additional value, their potential predictive value for docetaxel chemotherapy response needs to be further investigated in large patient cohorts.

The Identification of Plasma Exosomal miR-423-3p as a Potential Predictive Biomarker for Prostate Cancer Castration-Resistance Development by Plasma Exosomal miRNA Sequencing

Castration-resistant prostate cancer (CRPC) is the major cause of death from prostate cancer. Biomarkers to improve early detection and prediction of CRPC especially using non-invasive liquid biopsies could improve outcomes. Therefore, we investigated the plasma exosomal miRNAs associated with CRPC and their potential for development into non-invasive early detection biomarkers for resistance to treatment. RNA-sequencing, which generated approximately five million reads per patient, was performed to identify differentially expressed plasma exosomal miRNAs in 24 treatment-naive prostate cancer and 24 CRPC patients. RT-qPCR was used to confirm the differential expressions of six exosomal miRNAs, miR-423-3p, miR-320a, miR-99a-5p, miR-320d, miR-320b, and miR-150-5p (p = 7.3 × 10^-8, 0.0020, 0.018, 0.0028, 0.0013, and 0.0058, respectively) firstly in a validation cohort of 108 treatment-naive prostate cancer and 42 CRPC patients. The most significant differentially expressed miRNA, miR-423-3p, was shown to be associated with CRPC with area under the ROC curve (AUC) = 0.784. Combining miR-423-3p with prostate-specific antigen (PSA) enhanced the prediction of CRPC (AUC = 0.908). A separate research center validation with 30 treatment-naive and 30 CRPC patients also confirmed the differential expression of miR-423-3p (p = 0.016). Finally, plasma exosomal miR-423-3p expression in CRPC patients was compared to 36 non-CRPC patients under androgen depletion therapy, which showed significantly higher expression in CRPC than treated non-CRPC patients (p < 0.0001) with AUC = 0.879 to predict CRPC with no difference between treatment-naive and treated non-CRPC patients. Therefore, our findings demonstrate that a number of plasma exosomal miRNAs are associated with CRPC and miR-423-3p may serve as a biomarker for early detection/prediction of castration-resistance.

0343 Associations of Endogenous Hormones and Phthalate Exposure with Subjective and Objective Sleep Measures in Midlife Women

Introduction

Impaired sleep during the menopausal transition reduces quality of life and increases risk of multiple diseases. The changing hormonal milieu during midlife is associated with impaired sleep. Endocrine disrupting chemicals, such as phthalates, may also contribute to the increased prevalence of sleep disturbances in midlife women. Phthalates are known to impact the endogenous hormones associated with sleep. However, the link between phthalate exposure and sleep quality remains unexplored.

Methods

We recruited 26 midlife women (median age 50 years) through the Carle Regional Sleep Disorders Center in Urbana, Illinois. Subjective sleep was assessed through the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, and self-reported frequency of sleep disturbances, insomnia, and restless sleep. Objective sleep was measured using actigraphy and manual sleep logs (7-day average). Serum levels of follicle-stimulating hormone, estradiol, progesterone, testosterone, free estradiol, and free testosterone were quantified using ELISAs from a single sample from each participant. Phthalate metabolites were quantified from urine using high performance liquid chromatography-mass spectrometry (HPLC-MS). Covariates, including depression, hot flashes, quality of life, demographics, and lifestyle factors, were measured via surveys.

Results

Preliminary unadjusted logistic regression was used to determine the association between hormone values and subjective sleep quality binomial variables, including daytime sleepiness, sleep efficiency, sleep onset latency, sleep duration, number of sleep disturbances, and frequency of sleep disturbances. Each of these subjective sleep measures is significantly associated with one or more hormones.

Conclusion

Our results are consistent with literature identifying associations between hormones and subjective sleep in midlife women. Additional analyses will determine associations between hormones and objective sleep, and phthalates with both subjective and objective sleep measures. Excitingly, our study will be among the first to investigate the association between endocrine disruption and sleep quality in this population.

Support

Carle Illinois Seed Grant Program

Abstract 2580: Investigation of plasma exosomal miRNA as a biomarker and its potential function in prostate cancer castration resistant development

Prostate cancer (PCa) ranks as the second most frequent cancer and the fifth leading cause of cancer death in men worldwide. Androgen-deprivation therapy is the principal treatment for locally advanced and metastatic disease. Although a majority of patients initially respond well to ADT, most will progress to castration-resistant prostate cancer (CRPC), which contributes to the majority of PCa deaths. Exosomes are small vesicles that contain numerous molecular constituents, including lipids, proteins, RNAs and DNAs, and can mediate cell-cell communications. The aim of this study is to identify plasma exosomal miRNAs correlated with CRPC development, which may serve as a biomarker to monitor disease status and may reveal new role of exosome in CRPC development. Next-generation sequencing (NGS) of plasma exosomal miRNAs was performed in 24 treatment-naive PCa patients and 24 CPRC patients. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to validate candidate miRNAs in 108 treatment-naive PCa patients and 42 CRPC patients and a group of 38 non-CRPC patients under hormone therapy (treated non-CRPC). To study the miRNA function, hormone-dependent PCa cell line LNCaP was cultured in hormone-depleted media. MiRNA was overexpressed by transient transfection of miRNA mimic. Post transfection, transwell assays and cell viability assays were performed to determine the effect of miRNA on cell migration and proliferation. RNA NGS generated an average of approximately 5-million reads per sample and identified differentially expressed miRNAs. QRT-PCR validation showed six miRNAs were significantly differentially expressed between treatment-naïve PCa and CRPC (p-value&lt;0.05). It also showed that five of these miRNAs were differently expressed in CRPC compared treated non-CRPC patients (p-value&lt;0.001). When receiver operating characteristic curve was applied, one of the exosomal miRNAs, miR-423-3p, achieved area under the curve (AUC) = 0.784 when predicting CRPC from treatment-naïve PCa and AUC = 0.883 when predicting CRPC from treated non-CRPC. Overexpression of miR-423-3p had no effect on LNCaP proliferation, but significantly increased cell migration. This study demonstrated that plasma exosomal miRNAs play important roles in CRPC development and may serve as a biomarker for CRPC occurrence prediction.

Citation Format: Tianyu Guo, Yang Wang, Xueying Mao, Lei Xu, Jacek Marzec, Edwina Burke, Glenda Scandura, Elzbieta Stankiewicz, Caitlin R. Davies, John Hines, Greg Shaw, Jonathan Shamash, Daniel Berney, Prabhakar Rajan, Karen Tipples, Alistair Grey, Yong-jie Lu. Investigation of plasma exosomal miRNA as a biomarker and its potential function in prostate cancer castration resistant development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2580.

Multi-scale analysis of the associations among egg, larval and pupal surveys and the presence and abundance of adult female Aedes aegypti (Stegomyia aegypti) in the city of Merida, Mexico

Despite decades of research, there is still no agreement on which indices of Aedes aegypti (Stegomyia aegypti) (Diptera: Culicidae) presence and abundance better quantify entomological risk for dengue. This study reports the results of a multi-scale, cross-sectional entomological survey carried out in 1160 households in the city of Merida, Mexico to establish: (a) the correlation between levels of Ae. aegypti presence and abundance detected with aspirators and ovitraps; (b) which immature and egg indices correlate with the presence and abundance of Ae. aegypti females, and (c) the correlations amongst traditional Aedes indices and their modifications for pupae at the household level and within medium-sized geographic areas used for vector surveillance. Our analyses show that ovitrap positivity was significantly associated with indoor adult Ae. aegypti presence [odds ratio (OR) = 1.50; P = 0.03], that the presence of pupae is associated with adult presence at the household level (OR = 2.27; P = 0.001), that classic Aedes indices are informative only when they account for pupae, and that window screens provide a significant level of protection against peridomestic Ae. aegypti (OR = 0.59; P = 0.02). Results reinforce the potential of using both positive collections in outdoor ovitraps and the presence of pupae as sensitive indicators of indoor adult female presence.

Spatial variation in the effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus

The effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus populations were compared between coral reefs open or closed (no-take marine reserves) to fishing and among four geographic regions of the Great Barrier Reef (GBR), Australia. The specific reproductive metrics investigated were the sex ratio, the proportion of vitellogenic females and the spawning fraction of local populations. Sex ratios became increasingly male biased with length and age, as expected for a protogyne, but were more male biased in southern regions of the GBR (Mackay and Storm Cay) than in northern regions (Lizard Island and Townsville) across all lengths and ages. The proportion of vitellogenic females also increased with length and age. Female P. leopardus were capable of daily spawning during the spawning season, but on average spawned every 4·3 days. Mature females spawned most frequently on Townsville reserve reefs (every 2·3 days) and Lizard Island fished reefs (every 3·2 days). Females on Mackay reefs open to fishing showed no evidence of spawning over 4 years of sampling, while females on reserve reefs spawned only once every 2-3 months. No effect of length on spawning frequency was detected. Spawning frequency increased with age on Lizard Island fished reefs, declined with age on Storm Cay fished reefs, and declined with age on reserve reefs in all regions. It is hypothesized that the variation in P. leopardus sex ratios and spawning frequency among GBR regions is primarily driven by water temperature, while no-take management zones influence spawning frequency depending on the region in which the reserve is located. Male bias and lack of spawning activity on southern GBR, where densities of adult P. leopardus are highest, suggest that recruits may be supplied from central or northern GBR. Significant regional variation in reproductive traits suggests that a regional approach to management of P. leopardus is appropriate and highlights the need for considering spatial variation in reproduction where reserves are used as fishery or conservation management tools.

Age estimation and validation for South Pacific albacore Thunnus alalunga

Validated estimates of age are presented for albacore Thunnus alalunga, sampled from a large part of the south-western Pacific Ocean, based on counts of annual opaque growth zones from transverse sections of otoliths. Counts of daily increments were used to estimate the location of the first opaque growth zone, which was completed before the first assumed birthday. The periodicity of opaque zones was estimated by marginal increment analysis and an oxytetracycline mark-recapture experiment. Both validation methods indicated that opaque zones formed over the austral summer and were completed by autumn to winter (April to August). The direct comparison of age estimates obtained from otoliths and dorsal-fin spines of the same fish indicated bias, which was assumed to be due to poor increment clarity and resorption of early growth zones in spines, resulting in imprecise age estimates. As such, age estimates from otoliths are considered to be more accurate than those from spines for T. alalunga. This is consistent with results for a growing number of tropical and temperate tuna Thunnini species. It is recommend that validated counts of annual growth zones from sectioned otoliths is used as the preferred method for estimating age-based parameters for assessment and management advice for these important stocks.

Comparative biology of tropical Lethrinus species (Lethrinidae): challenges for multi-species management

Life-history characteristics of six tropical Lethrinus species sampled from the Great Barrier Reef World Heritage Area were compared. Two species groups were identified based on fork length (LF ): large species with maximum LF > 640 mm (longface emperor Lethrinus olivaceus, yellowlip emperor Lethrinus xanthochilus and spangled emperor Lethrinus nebulosus) and small species with maximum LF < 480 mm (Pacific yellowtail emperor Lethrinus atkinsoni, pink ear emperor Lethrinus lentjan and ornate emperor Lethrinus ornatus). Lifespan was not correlated with LF . Early growth for all species was rapid and similar during the first few years of life, but coefficients of the von Bertalanffy growth function varied considerably among species. Growth also differed between sexes for L. atkinsoni. Reproductive characteristics varied among species, with peak periods of spawning occurring in November to December for L. atkinsoni, July to August for L. nebulous, September to October for L. olivaceus and a protracted season for L. lentjan, although fewer samples were available for the last two species. Sex-specific LF and age distributions and gonad histology of L. lentjan were suggestive of a functional protogynous reproductive pattern, as observed in other lethrinids. Gonad histology indicated non-functional protogynous hermaphroditism for L. atkinsoni and L. nebulosus. The diversity of life histories among these closely related species emphasizes the difficulty in devising single management strategies appropriate for multi-species fisheries and illustrates the importance of understanding species-specific life histories to infer responses to exploitation.

Practical approach for typing strains of Leishmania infantum by enzyme polymorphism: a cross sectional study in Northwest of Iran

In present study, All samples collected from Kalybar and Ahar districts in Northwest of Iran from 12 patients (bone marrow aspirates), 26 dogs (spleenic and hepatic aspirates) and more than 100 sand flies between years 2004-2006. All patients were clinically diagnosed to have visceral leishmaniasis. Serological profiles of all sera samples from both human and dogs were in accordance with leishmaniasis (DAT). Isoenzyme profiles of these isolates were compared with those of reference using 12 enzyme systems. L. infuntum MON-1 is the only zymodeme present in all samples of dogs, sand flies and human. The enzymatic polymorphism is compared to that of neighboring countries (Azarbaijan, Iraq and Turkey etc.) and we concluded that the Visceral Leishmaniasis (VL) focus in northwest of Iran is evidently Mediterranean focus of zoonotic VL, which extends from Portugal and Morocco to Pakistan and the central Asian republics. Domestic doges act as the reservoir host, where Phlebotomus kandellakii and Perfiliewi ariasi are vectors.

House-level risk factors for triatomine infestation in Colombia

BACKGROUND

Chagas disease, transmitted domestically by triatomine bugs, is the most important vector-borne disease in Latin America. The association between triatomine infestation and housing characteristics was investigated based on a standardized survey in 41 971 houses in 15 Departments in Colombia.

METHODS

Multivariate logistic regression was used to test for associations of two highly correlated infestation measures of infestation (householders reporting having seen triatomines inside the house, and sending triatomines to the survey team), with 15 household-level risk factors. Risks were measured relative to a reference category of houses with up to three inhabitants, area up to 50 m(2), unplastered adobe walls, thatch roof and no outbuildings or domestic animals.

RESULTS

The probability of seeing triatomines was highest for households with over seven inhabitants (OR = 1.24, 95% CI 1.11-1.39), overhead storage space (OR = 1.16, 95% CI 1.03-1.32), grain shed (OR = 1.25, 95% CI 1.02-1.52), cats (OR = 1.27, 95% CI 1.14-1.42) and pigs (OR = 1.16, 95% CI 1.03-1.30). Lowest risks were in houses with wooden walls (OR = 0.46, 95% CI 0.34-0.61), fully plastered walls (OR = 0.78, 95% CI 0.68-0.88), roofs made of tiles (OR = 0.51, 95% CI 0.33-0.78) and flagstone floors (OR = 0.57, 95% CI 0.42-0.76). Results for householders returning triatomines support this set of risk factors, but with wider confidence intervals.

CONCLUSIONS

Surveillance of a few easily assessed household characteristics provides an accurate, rapid assessment of house-level variation in risk. Measured effect sizes for specific structural characteristics could be used to maximize the cost-effectiveness of programmes to reduce vector infestation and interrupt Chagas disease transmission by improving house quality.

Deltamethrin-impregnated bednets reduce human landing rates of sandfly vector Lutzomyia longipalpis in Amazon households

The entomological efficacy of using 25% deltamethrin EC insecticide-treated bednets (ITNs) was evaluated against the sandfly Lutzomyia longipalpis Lutz and Neiva (Diptera: Psychodidae), the principal vector of zoonotic visceral leishmaniasis (ZVL) in Latin America. A crossover field study in Amazon Brazil (Marajó Island, Pará State) demonstrated that, compared with untreated nets, the insecticide increased the barrier effect of nets by 39% (95% confidence interval [CI] 34-44%), reduced human landing rates by 80% (95% CI 62-90%) and increased the 24-h mortality rate from 0% to 98% (95% CI 93-99%) inside ITNs. The presence of an ITN also reduced the human landing rate on unprotected persons outside the net in the same room by 56% (95% CI 52-59%), and increased 24-h mortality to 68% (95% CI 62-73%) compared to 0.4% (0.1-2.0%) in untreated houses. The reduction in human landing rates in ITN rooms was associated with a doubling in the proportion of sandflies alighting on walls compared with that in untreated rooms, which was attributed to insecticide-induced excito-repellency. There was no evidence that sandflies were diverted onto unprotected hosts. Human landing catches inside houses peaked between 19.00 hours and 23.00 hours and declined steadily to zero at 02.00 hours and thereafter. House-to-house questionnaires established that only 34% of households owned at least one net (median two, range 1-8), only 20% of the population slept under a net (33% of 0-5-year-old children), and the majority (73%) of the population slept in hammocks. Combined data pertaining to sleeping times for children and sandfly activity period indicate that > 50% of sandfly bites inside houses, and substantially more outside houses, were taken before a third of children were potentially protected by a net. This study demonstrates the clear entomological efficacy of ITNs against Lu. longipalpis in this endemic region. The effectiveness of ITNs at preventing ZVL infection and disease has still to be evaluated.

Are mosquitoes diverted from repellent-using individuals to non-users? Results of a field study in Bolivia

Outside sub-Saharan Africa, Anopheline mosquito exophagic and/or crepuscular behaviour patterns imply that insecticide-treated nets may provide incomplete protection from malaria-infective mosquito bites. Supplementary repellent treatment has been recommended in such circumstances, especially where vectors are exophilic and so are not susceptible to residual insecticide spraying. As maintaining complete usage of repellents in a community is unrealistic, the potential negative impact on non-users of repellent usage by 'neighbours' in the same community needs to be addressed in the context of health policy promoting equity. This study quantifies diversion of host-seeking mosquitoes, from repellent wearing to unprotected individuals, 1 m apart under field conditions in Bolivia. Each of the six volunteer-pairs sat >20 m apart from other pairs. Volunteers were allocated di-ethyl toluamide (DEET) or mineral oil in ethanol control. Treatments were rotated, so that during the trial, both pair-members wore repellent on 72 occasions; both pair-members wore control on 72 occasions; and on 36 occasions, one pair-member wore repellent and the other control. Unprotected (control) pair-members received 36.4% [95% confidence interval (CI): 8.1-72.0%] more Anopheles darlingi landings (P = 0.0096) and 20.4% (95% CI: 0.6-44.0%) more mosquito landings (P = 0.044), when their 'partner' wore repellent than when their partner also wore control. A second, smaller Latin-square trial using 30% lemongrass (Cymbopogon citratus) repellent, with control, obtained 26.0% (95% CI: 5.2-51.0%) more mosquito landings when controls sat with repellent-wearers rather than other controls (P = 0.0159). With incomplete community repellent usage, non-users could be put at an increased risk of malaria. The results also have implications for repellent-efficacy assay design, as protection will appear magnified when mosquitoes are given a choice between repellent-users and non-users.

Efficacy of Thermotherapy to Treat Cutaneous Leishmaniasis Caused byLeishmania tropicain Kabul, Afghanistan: A Randomized, Controlled Trial

BACKGROUND

Pentavalent antimony is the agent recommended for treatment of cutaneous leishmaniasis (CL). Its use is problematic, because it is expensive and because of the potential for drug-associated adverse effects during a lengthy and painful treatment course.

METHODS

We tested the efficacy of thermotherapy for the treatment of CL due to Leishmania tropica in a randomized, controlled trial in Kabul, Afghanistan. We enrolled 401 patients with a single CL lesion and administered thermotherapy using radio-frequency waves (1 treatment of >or=1 consecutive application at 50 degrees C for 30 s) or sodium stibogluconate (SSG), administered either intralesionally (a total of 5 injections of 2-5 mL every 5-7 days, depending on lesion size) or intramuscularly (20 mg/kg daily for 21 days).

RESULTS

Cure, defined as complete reepithelialization at 100 days after treatment initiation, was observed in 75 (69.4%) of 108 patients who received thermotherapy, 70 (75.3%) of 93 patients who received intralesional SSG, and 26 (44.8%) of 58 patients who received intramuscular SSG. The OR for cure with thermotherapy was 2.80 (95% confidence interval [CI], 1.45-5.41), compared with intramuscular SSG treatment (P=.002). No statistically significant difference was observed in the odds of cure in comparison of intralesional SSG and thermotherapy treatments. The OR for cure with intralesional SSG treatment was 3.75 (95% CI, 1.86-7.54), compared with intramuscular SSG treatment (P<.001). The time to cure was significantly shorter in the thermotherapy group (median, 53 days) than in the intralesional SSG or intramuscularly SSG group (median, 75 days and >100 days, respectively; P=.003).

CONCLUSIONS

Thermotherapy is an effective, comparatively well-tolerated, and rapid treatment for CL, and it should be considered as an alternative to antimony treatment.

Effect of insecticide-impregnated dog collars on incidence of zoonotic visceral leishmaniasis in Iranian children: a matched-cluster randomised trial

BACKGROUND

Deltamethrin-impregnated dog collars reduce sandfly bite rates on dogs, and are effective in killing sandflies that attempt to feed. Because domestic dogs are the principal reservoir hosts of zoonotic visceral leishmaniasis, we tested whether community-wide application of dog collars could protect children against infection with Leishmania infantum, the parasite that causes the disease.

METHODS

18 villages were paired, matched by preintervention child prevalence of L infantum infection. Within pairs, villages were randomly assigned to either control or intervention. All domestic dogs in intervention villages were provided with collars for the transmission season. The main outcome measure was incidence of L infantum infection after 1 year measured by seroconversion. Secondary outcomes were leishmanin skin test (LST) conversion and seroconversion in dogs.

FINDINGS

The seroconversion rate in children was 1.49% (17/1141) in the intervention villages and 2.41% (26/1078) in control villages (odds ratio 0.57, 95% CI 0.36-0.90, p=0.017). LST conversion was also lowered, but not significantly (odds ratio 0.66, 0.41-1.08, p=0.096). The seroconversion rate in dogs in intervention villages was also significantly reduced (0.46, 0.30-0.70, p=0.0003).

INTERPRETATION

Community-wide application of deltamethrin-impregnated dog collars not only protects domestic dogs from L infantum infections, but might also reduce the risk of L infantum infection in children. These dog collars could have a role in control of visceral leishmaniasis and replace controversial dog culling programmes in some countries. However, the effectiveness of dog collars will depend on the importance of wild versus domestic canids as reservoir hosts of L infantum.

American cutaneous leishmaniasis in domestic dogs: an example of the use of the polymerase chain reaction for mass screening in epidemiological studies

Domestic dogs (Canis familiaris) are firmly incriminated as reservoir hosts of zoonotic visceral leishmaniasis. As an increasing number of studies have reported high infection rates with American cutaneous leishmaniasis (ACL) in dogs, it is suggested that they should also be incriminated as reservoir hosts of ACL. The evidence to incriminate dogs as ACL reservoir hosts is reviewed, and we conclude that there is, as yet, only circumstantial evidence to support that claim, one of the reasons being that diagnostic tests (mainly serology) used in the studies underestimate the true rate of infection. We report results from the first large-scale study to measure ACL infection rates using the polymerase chain reaction (PCR). A high prevalence of ACL was detected in blood and bone marrow of dogs surveyed in an area of Peru endemic for Leishmania braziliensis and L. peruviana, providing further evidence for their suspected role as ACL reservoir hosts. However, the relatively low ACL prevalence detected in symptomatic dogs (i.e., dogs with ACL lesions or scars) demonstrated that PCR alone cannot be the diagnostic 'gold standard' for mass screening of samples in epidemiological studies.

Distribution of putative male sex pheromones among Lutzomyia sandflies (Diptera: Psychodidae)

Male Lutzomyia longipalpis produce terpene sex pheromones in glandular tissue underlying the cuticle. The pheromones are transmitted to the surface via cuticle-lined ducts (measuring 0.25 microm in diameter), each of which reaches the surface in the centre of a papule (measuring 3-3.5 microm in diameter). Similar papules, in a range of shapes but all characterized by the presence of a central pore and absence of macroserae, occur in some other species of sandfly. The aim of the present study was to determine the distribution of sex pheromones in sandflies of the genus Lutzomyia that do and do not have the papules. The results indicate that sex pheromones are not widely distributed amongst male Lutzomyia spp. Male members of the genus can be subdivided into three groups: those that produce terpenes and have cuticular papules; those that do not produce terpenes but still have the associated papules; and those that have neither terpenes nor papules. The papules seen in the species that do not synthesise sex pheromones are presumably vestigial, non-functional structures. Such species may have stopped producing pheromone as the result of changes in the way in which the females found and selected mates or changing feeding preferences. A similar event has occurred in the Lepidoptera, where vestigial pheromone-secreting structures remain in some species which no longer produce pheromone. Lutzomyia lenti collected in southern Brazil produced a novel diterpene whereas male L. lenti from north-eastern Brazil did not, supporting suggestions by others that L. lenti is, like L. longipalpis, a species complex.

Assessment of Leishmaniasis notification system in Santiago del Estero, Argentina, 1990-1993

Using a capture-recapture method, this study evaluates the completeness of the cutaneous leishmaniasis (CL) surveillance system in four districts of Santiago del Estero province, Argentina, for the period 1990-1993. Four reporting sources were evaluated: medical records kept by health facilities, interviews conducted during a case-control study, and the national and provincial levels of the leishmaniasis surveillance system (LSS). Using the capture-recapture method it was estimated that 210 cases (95% confidence interval [CI]: 202-218) of CL occurred in the four districts during the study period. Completeness of reporting to the leishmaniasis surveillance system at the national level was estimated to be 44.8% (95% CI: 43.2-46.4). The study results indicate that there is substantial underreporting within the LSS, although it did show the appropriate secular trends. The reasons for under-reporting and methods for addressing this problem are discussed.

Phlebotomine sandfly responses to carbon dioxide and human odour in the field

Responses of Lutzomyia sandflies (Diptera: Psychodidae: Phlebotominae) to carbon dioxide (CO2) and human odour were investigated by field experiments in Parana State, southern Brazil. Catches of two predominant species: Lu. intermedia (Antunes & Coutinho) and Lu. whitmani Lutz & Neiva, were compared between traps baited with a human adult or with CO2 emitted at the human-equivalent rate. When the baits were only 40 cm apart, no difference of attractiveness was detected. When baits were separated by 20 m, however, significantly fewer sandflies (44% Lu. intermedia, 46% Lu. whitmani) were trapped with CO2 compared with human bait. This is the first field evidence that anthropophilic sandflies are attracted by human kairomones in addition to CO2. For both species [Lutzomyia intermedia and Lu. whitmani] [corrected], the proportion of human attractiveness attributable to CO2 was significantly more [corrected] for males than females; for Lu. intermedia males human bait was no more attractive than CO2 alone. Gender differences in sandfly olfactory sensitivity are likely to be associated with behavioural differences on the host, where females feed on blood and males find mates. With traps 20 m apart, both Lutzomyia spp. showed roughly linear increased responses (log-log scale) to 0.08-0.55% CO2 equivalent to 0.5-4 humans. This would explain why host size is generally proportional to attractiveness, as observed for other species of phlebotomine sandflies.

Topical insecticide treatments to protect dogs from sand fly vectors of leishmaniasis

We compared the susceptibility of sand fly vectors to four topical insecticide treatments applied to domestic dogs, a reservoir of human leishmaniasis. Dogs were exposed to sand flies pretreatment and at 1 week, 1 month, and 2 months posttreatment. Sand fly bloodfeeding and survival rate of both fed and unfed flies were significantly reduced by the permethrin, deltamethrin, and fenthion treatments, but diazinon had no effect. The survival rate of bloodfed sand flies was reduced by up to 86% with deltamethrin collars. The antifeeding effect suggests that deltamethrin collars may be recommended to dog owners to protect their pets from sandfly- borne diseases. The combined effects on sand fly feeding and survival indicate that epidemiologic, community-based trials are warranted to test whether deltamethrin collars could reduce the incidence of canine and, hence, human leishmaniasis.

Temperature and perfusion responses of muscle and lung tissue during chronic heating in vivo

For the first time, both temperature and perfusion responses have been obtained from in vivo studies of chronically heated lung and muscle tissue of calves. In each tissue, the spatial temperature distribution was measured by thermistors placed in needles at several distances from an implanted heated disc. A perfusion parameter was defined for a bioheat transfer model that describes temperature dynamics with distance from the heated disc. Estimates of perfusion were obtained by a least-squares fit of the model output to a step change in heat flux. Except for short transient experiments several times a week, a constant heat flux of 0.04, 0.06 or 0.08 Wcm(-2) was maintained at the disc surface for up to seven weeks. At the higher heat fluxes, the steady-state tissue temperature decreased with heating duration. Also, the characteristic time constants of the tissues decreased with heating duration. Muscle perfusion showed a statistically significant increase during chronic heating. Tissue adapts to chronic heating above 42 degrees C by allowing more capillary blood flow that increases heat loss to reduce tissue temperature.

Spraying houses in the Peruvian Andes with lambda-cyhalothrin protects residents against cutaneous leishmaniasis

A household vector control trial was carried out in the Peruvian Andes to measure the effect of spraying inside walls and ceilings with lambda-cyhalothrin on the risk for residents of cutaneous leishmaniasis caused by Leishmania peruviana. The mortality rates of Lutzomyia verrucarum measured with WHO contact bioassay cones set on adobe walls characteristic of the endemic region indicated an LD95 for lambda-cyhalothrin of about 20 mg/m2, and no reduction in effectiveness for at least 6 months on indoor adobe walls sprayed with 25 mg/m2. A random selection of 112 houses were sprayed (starting in 1992/93) at 6-monthly intervals with a mean dose of 34 mg/m2, leaving 154 control houses (with closely matched pre-intervention measurements of incidence and sandfly abundance). Comparisons of pre- and post-intervention sandfly indoor abundance, measured at regular intervals for up to 2 years using CDC light traps, in 22 sprayed and 21 control houses demonstrated that spraying significantly reduced the indoor abundance of Lu. verrucarum by an average of 78% and of Lu. (Helcocyrtomyia) peruensis by 83%. Spraying was also associated with a significant reduction of 77% in the proportion of bloodfed sandflies collected in light traps. The proportion of susceptible householders acquiring leishmaniasis during the trial was significantly reduced by 54% as a result of spraying. The observed impact of spraying was greatest, 81% (95% confidence intervals 20-95%), when the cases detected during the first 6 months after the intervention were excluded from the analysis, suggesting a significant pre-patent period.

The epidemiology and control of leishmaniasis in Andean countries

This paper reviews the current knowledge of leishmaniasis epidemiology in Venezuela, Colombia, Ecuador, Peru, and Bolivia. In all 5 countries leishmaniasis is endemic in both the Andean highlands and the Amazon basin. The sandfly vectors belong to subgenera Helcocyrtomyia, Nyssomiya, Lutzomyia, and Psychodopygus, and the Verrucarum group. Most human infections are caused by Leishmania in the Viannia subgenus. Human Leishmania infections cause cutaneous lesions, with a minority of L. (Viannia) infections leading to mucocutaneous leishmaniasis. Visceral leishmaniasis and diffuse cutaneous leishmaniasis are both rare. In each country a significant proportion of Leishmania transmission is in or around houses, often close to coffee or cacao plantations. Reservoir hosts for domestic transmission cycles are uncertain. The paper first addresses the burden of disease caused by leishmaniasis, focusing on both incidence rates and on the variability in symptoms. Such information should provide a rational basis for prioritizing control resources, and for selecting therapy regimes. Secondly, we describe the variation in transmission ecology, outlining those variables which might affect the prevention strategies. Finally, we look at the current control strategies and review the recent studies on control.

Further evidence that deltamethrin-impregnated collars protect domestic dogs from sandfly bites

In many foci of zoonotic visceral leishmaniasis (ZVL), domestic dogs are important reservoir hosts of the causative Leishmania parasites transmitted by phlebotomine sandflies (Diptera: Psychodidae). We tested the protective value of impregnated dog collars (20 g plastic containing deltamethrin 800 mg ai) against Phlebotomus papatasi (Scopoli) sandflies in Iran. For each assay, the dog was sedated and caged in a net with 70-100 wild-caught sandflies overnight (23.30-06.30 hours). Dogs wearing the collars were bitten by approximately 80% fewer sandflies than before collars were fitted, i.e. 51% vs. 11% of hungry female flies exposed. Sandfly mortality rates following 20 h exposure to dogs with collars (18%) or without collars (17%) were not significantly different. Effects of collars were tested when dogs had been wearing them for 8 days. A previous trial against the sandfly P. perniciosus Newstead in France, using smaller dogs, showed that effects of such collars were not fully realized until they had been worn for 2 weeks or more; they remained effective for at least 8 months and killed significant proportions of the sandflies exposed. Present results with P. papatasi, confirming that this simple device provides effective protection against sandflies, are considered sufficiently encouraging to justify a community-wide field trial of deltamethrin-impregnated dog collars against ZVL vector sandflies in Iran.

Use of PCR to detect Leishmania (Viannia) spp. in dog blood and bone marrow

A PCR-based protocol for the detection of Leishmania (Viannia) parasites in canine blood, buffy coat, and bone marrow was developed and was then tested with field samples taken from a random sample of 545 dogs from villages in Peru where Leishmania (Viannia) braziliensis and Leishmania (Viannia) peruviana are endemic. Comparative tests with cultured parasites mixed with dog blood showed that the PCR assay's sensitivity was significantly dependent on the DNA extraction protocol and the PCR primers used. Mass screening of field samples by the preferred PCR protocol detected American cutaneous leishmaniasis (ACL) in 44 of 545 (8.1%) dogs; 31 of 402 (7.7%), 20 of 223 (9.0%), and 8 of 46 (17.4%) were PCR positive when whole blood, buffy coat, and bone marrow aspirates, respectively, were tested. The high prevalence of Leishmania in both asymptomatic (7.6%) and symptomatic (18.0%) dogs provides further circumstantial evidence for their suspected role as reservoir hosts of ACL and indicates that hematogenous dissemination of parasites may be a more common pathological phenomenon than has previously been acknowledged. However, unlike for zoonotic visceral leishmaniasis, the comparatively low prevalence of Leishmania (Viannia) in the blood of symptomatic dogs indicates that PCR with blood cannot be the "gold standard" for the (mass) screening of samples in epidemiological studies.

Domesticity of Lutzomyia whitmani (Diptera: psychodidae) populations: field experiments indicate behavioural differences

The sandfly Lutzomyia whitmani (Antunes & Coutinho) is an important vector for cutaneous leishmaniasis throughout much of Brazil, and has recently been shown to consist of more than one mitochondrial lineage. It has frequently been asserted that the degree of adaptation of L. whitmani to human environments varies across its range. As a standardized test of indoor feeding for three geographically distant populations of L. whitmani, catches inside experimental chicken sheds of varying degrees of wall closure (0%, 33%, 67% and 98%) were compared. Each increment in shed closure reduced catches of females (relative to the most open shed) by a similar degree for each population: geometric mean catches dropped by 11-40% with 33% closure, by 41-62% with 67% closure, and by 69-100% with 98% closure. Geometric mean catches of males from the two more northerly populations also decreased with increasing shed closure, by 18% and 22% for 33% closure, 58% and 69% for 67% closure, 91% and 93% for 98% closure. Males from the most southerly population showed significantly different behaviour, with 33% closure causing a 54% increase in geometric mean catch, 67% closure causing a 6% increase, and 98% closure causing a 32% reduction. For this southerly population, sex ratios became more male biased with increasing density in more closed sheds, suggesting aggregation driven by intra-specific communication. Lutzomyia intermedia (Lutz & Neiva) was relatively more likely than L. whitmani to approach baits in the three more closed sheds, rather than the most open shed, offering a behavioural explanation for observed differences in indoor biting rates between the species.

Is the domestic dog (Canis familiaris) a reservoir host of American cutaneous leishmaniasis? A critical review of the current evidence

Originally associated with forested areas, the transmission cycle of American cutaneous leishmaniasis (ACL) has now adapted to the domestic environment in at least 9 Latin American countries. Several studies have suggested that the domestic dog (Canis familiaris), which is already incriminated as the primary reservoir host of zoonotic visceral leishmaniasis (ZVL), may have a reservoir role in the domestic transmission of human ACL caused by Leishmania braziliensis, L. panamensis, and L. peruviana. This article reviews more than 90 studies reporting ACL infections in dogs, and concludes that as yet there is only circumstantial evidence to support that claim. Almost no data are available on the infectiousness of dogs to sandfly vectors of ACL, and there are few indications that either dog ownership or dog abundance are risk factors for ACL. Nevertheless, it has been proposed that incidence of ACL in humans could be reduced by targeting infected dogs. While this control strategy has been used for many decades against ZVL in Latin America, Europe, and Asia, there is little evidence to demonstrate its effectiveness either in theory or in practice. Particular concerns over the sensitivity and specificity of diagnostic tools, low compliance rates among dog owners, and cost-effectiveness are likely to apply equally to ACL control.

Epidemiological surveys confirm an increasing burden of cutaneous leishmaniasis in north-east Brazil

Health service records for north-east Brazil suggest a consistent rise in numbers of cases of cutaneous leishmaniasis due to Leishmania (Viannia) braziliensis over the past decade. In a study site in Pernambuco, prospective, cross-sectional and retrospective epidemiological surveys of infection (a positive Montenegro skin test response) and/or clinical symptoms confirmed a high current force of infection (0.092/year), and an approximately 10-fold increase in transmission during the last 10 years. Cross-sectional analysis indicated that the incidence rate among children (aged < or = 15 years) was lower than that among adult immigrants exposed for similar time periods, but there was no apparent difference in transmission rate according to gender. Coupled with the known behaviour of the local sandfly vector, Lutzomyia whitmani, this suggests that most people are infected outside their houses, rather than either indoors or while visiting remnant rainforest. The estimated proportion of infections which lead to cutaneous lesions (0.81-0.87) is relatively high for L. braziliensis areas. However, an unusually low proportion of clinical infections (0.0042) apparently leads to metastasis.

Age, acquired immunity and the risk of visceral leishmaniasis: a prospective study in Iran

In order to investigate the phenomenon of age-related immunity to visceral leishmaniasis, a 1 year prospective survey was carried out on 5671 people in a Leishmania infantum focus in north-west Iran. The average incidence rate of infection since 1985 was 2.8%/year with all ages equally at risk. One in 13 infections in children led to visceral leishmaniasis (VL), and this ratio decreased significantly with age. Seroprevalence also dropped rapidly with age, suggesting that the same process may affect both clinical outcome and the humoral immune responses. Cell-mediated immunity was associated with a reduction in the seroconversion rate and an increase in the serorecovery rate. Even amongst people with no detectable cell-mediated immunity to Leishmania, the seroconversion rate decreased and the serorecovery rate increased with age. All current VL patients had a negative leishmanin skin test response. Hence, adults may develop protection against L. infantum through 2 processes, 1 dependent and 1 independent of acquired cell-mediated immunity.

Experimental comparison of anthropophily between geographically dispersed populations of Lutzomyia whitmani (Diptera: Psychodidae)

Lutzomyia whitmani, a major vector of cutaneous leishmaniasis in Brazil, occupies diverse habitats from the Amazon forest canopy to suburban animal pens. Three mitochondrial lineages of Lu. whitmani ('Amazonian', 'North-South' and 'North-east') have parapatric distributions coinciding with different ecological zones. We assessed the host preferences of populations representing the three lineages in standardized field experiments, and found that Lu. whitmani in all sites were significantly more attracted to humans than to dogs or chickens. Females from a southerly population of the North-South lineage showed the greatest degree of anthropophily. Lu. whitmani from Amazonia were also strongly attracted to human baits, contradicting previously published accounts. Intraspecific comparisons in non-Amazonian sites suggest that Lu. whitmani is less anthropophilic than Lu. intermedia but more so than Lu. longipalpis. No significant difference was detected in anthropophily between Lu. whitmani in the Amazon and either Lu. dendrophyla or Lu. gomezi. Anthropophilic behaviour was demonstrated in the same site for Lu. complexa, Lu. flaviscutellata and Lu. brachyphalla, but not for Lu. infraspinosa.

A mitochondrial DNA phylogeny indicates close relationships between populations of Lutzomyia whitmani (Diptera: Psychodidae, Phlebotominae) from the rain-forest regions of Amazônia and northeast Brazil

Phylogenetic analysis of all 31 described mitochondrial (cytochrome b) haplotypes of Lutzomyia whitmani demonstrated that new material from the State of Rondônia, in southwest Amazônia, forms a clade within a lineage found only in the rain-forest regions of Brazil. This rain-forest lineage also contains two other clades of haplotypes, one from eastern Amazônia and one from the Atlantic forest zone of northeast Brazil (including the type locality of the species in Ilhéus, State of Bahia). These findings do not favour recognizing two allopatric cryptic species of L. whitmani, one associated with the silvatic transmission of Leishmania shawi in southeast Amazônia and the other with the peridomestic transmission of Le. braziliensis in northeast Brazil. Instead, they suggest that there is (or has been in the recent past) a continuum of inter-breeding populations of L. whitmani in the rain-forest regions of Brazil.

Natural infections of Leishmania peruviana in animals in the Peruvian Andes

Evidence that domestic dogs may act as reservoir hosts for cutaneous leishmaniasis in the Peruvian Andes is provided by the isolation, for the first time, from naturally infected dogs of parasites identified (by isoenzymes) as Leishmania peruviana. Leishmania parasites were isolated from nasal aspirates or biopsies from 5 (1.8%) of 279 asymptomatic dogs samples in endemic villages of the Peruvian Andes. In addition, Leishmania (Viannia) infections were identified in 15 (5.4%) of 276 nasal samples by the polymerase chain reaction (PCR) using subgenus-specific primers. Further circumstantial evidence for a reservoir role for dogs comes from the finding of a relatively high dog blood index among the sandfly vectors collected inside houses (29% for Lutzomyia peruensis and 17% for Lu. verrucarum). Possible wild mammal reservoir hosts for Andean cutaneous leishmaniasis were also detected in endemic villages. At least 8 species were identified among the 1266 small mammals trapped. Leishmania parasites were isolated from blood or skin biopsies taken from 2 (2.6%) of 78 Didelphis albiventris and 6 (1.2%) of 511 Phyllotis andinum. Three isolates were identified by isoenzymes as L. peruviana, and the other 5 were identified by PCR as Leishmania (Viannia) species. Leishmania (Viannia) infections were also identified by PCR directly on skin biopsies taken from 2 (2.8%) of 72 D. albiventris, 1 (0.2%) of 499 P. andinum, and 4 (2.6%) of 153 Akodon sp.

Characterization of tissue morphology, angiogenesis, and temperature in the adaptive response of muscle tissue to chronic heating

Previous investigations on the in vivo effects of chronic heat on tissue suggest a response whereby heated tissue temperatures decrease over time. This response occurred in conjunction with localized angiogenesis, which possibly contributed to the temperature decreases by increasing local perfusion and enhancing tissue heat transfer. Our own studies were the first to use a chronic heat source to heat tissue at initial interfacial temperatures between 40 degrees C and 46 degrees C. Initial temperatures above 45.3+/-2.2 degrees C caused necrosis of adjacent tissue. Through an adaptive response, the necrosis was removed by 7 weeks and replaced by a highly vascularized tissue capsule at 41.8+/-0.5 degrees C. The present study sought to characterize the spatial distribution, number of capillaries, and temperatures associated with this adaptive response. Heated and control muscle tissue sections were removed after 2, 4, and 7 weeks of heating at 0.08 W/cm2. Tissue layer thicknesses and capillary densities were measured and correlated with corresponding tissue temperatures. Necrosis was present adjacent to the heat source at 2 and 4 weeks; however by 7 weeks, a highly vascularized fibrous tissue capsule had replaced nearly all necrosis. Capillary densities, particularly near the heat source, were significantly greater at 7 weeks than at either 2 or 4 weeks. Capillary densities in heated tissue capillary fronts tripled from 2 to 7 weeks (106.4+/-14.3 caps/mm2 versus 39.1+/-18.5 caps/mm2). Furthermore, a mean temperature of 41.7+/-0.9 degrees C was measured in heated tissue capillary fronts at all durations, suggesting that this may be a threshold temperature for heat-induced angiogenesis or endothelial cell survival. These findings more completely characterize the perfusion component of the current mathematical model for heat transfer in tissue and will help to establish guidelines for the functional heat loss that an implantable, heat-producing device may allow.

Evaluation of the fungus Beauveria bassiana as a potential biological control agent against phlebotomine sand flies in Colombian coffee plantations

In Colombia, the entomopathogenic fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes) is widely used to control the coffee berry borer Hypothenemus hampei (Coleoptera: Scolytidae) in coffee plantations. Recent studies suggested that this fungus is also pathogenic to several important vectors of disease, including Phlebotomus papatasi and Lutzomyia longipalpis (Diptera: Psychodidae). The present study evaluated the use of B. bassiana as a potential biological control agent against phlebotomine sand flies in Colombian coffee plantations. Histopathologic examination indicates that B. bassiana is unable to infect sand flies under natural conditions, although dead sand flies were shown to be readily infected. In addition, laboratory bioassays where flies were exposed to the fungus applied onto coffee plants (though not filter paper) showed lower mean survival times than the control.

Heat from an implanted power source is mainly dissipated by blood perfusion

Heat dissipation and its effects on tissue and blood interfaces are common problems associated with the development and increased use of artificial hearts, because all of the implantable actuators for artificial hearts generate waste heat due to inefficiencies of energy conversion. To determine the mechanisms of heat dissipation from artificial hearts, heated disks producing constant heat fluxes of 0.08 watts/cm2 were implanted adjacent to the left lung and the latissimus dorsi muscle in calves for 2 weeks, 4 weeks, and 7 weeks. At the end of each experiment, a series of acute studies was performed in which blood perfusion to the heated tissue was decreased or stopped to observe the contribution of blood perfusion to heat dissipation. The cooling effect of ventilation was also examined to determine its relative contribution to heat dissipation in lung tissue by decreasing the minute ventilation volume. The importance of blood perfusion for heat dissipation was demonstrated by the temperature rise after cessation of blood perfusion to the heated tissue. The contribution of ventilation to heat dissipation in the heated lung tissue was minimal. Contribution of total blood perfusion to heat dissipation was increased with time in the muscle tissue, which has relatively low resting blood perfusion, but not in the lung tissue, which has relatively high blood perfusion. In the heated muscle tissue, the in vivo adaptive response to chronic heat was functionally shown by the increased perfusion. In conclusion, blood perfusion was the main mechanism of heat dissipation from tissues that were adjacent to an implanted power source.

Cutaneous leishmaniasis in the Peruvian Andes: factors associated with variability in clinical symptoms, response to treatment, and parasite isolation rate

The severity of cutaneous leishmaniasis may be determined by host immunity, parasite virulence, and host or vector behavior. We performed a multivariate analysis to identify the main causes of the variability in clinical symptoms, response to treatment, and parasite isolation rate among Peruvian patients. The effect of host immunity was demonstrated first by the finding that secondary infections induced smaller lesions associated with a lower parasite isolation rate than did primary infections and, second, by the finding of fewer lesions in older patients. Phenotypic differences between parasite populations were suggested by the observation that the mean scar size and number varied between villages: patients had more scars in villages where the transmission rates were higher. Human behavior probably determined the site of lesions on the body, since most lesions in the cooler South were on the head, whereas in the North, lesions were equally frequent on the extremities. In addition, older patients, who were more likely infected through occupational exposure, had fewer head lesions. Geographic variation in the pattern of exposure to sandflies indicates that uta control strategies should be region specific.

Sensitivity analysis of one-dimensional heat transfer in tissue with temperature-dependent perfusion

Design criteria for implantable heat-generating devices such as the total artificial heart require the determination of safe thresholds for chronic heating. This involves in-vivo experiments in which tissue temperature distributions are obtained in response to known heat sources. Prior to experimental studies, simulation using a mathematical model can help optimize the design of experiments. In this paper, a theoretical analysis of heat transfer is presented that describes the dynamic, one-dimensional distribution of temperature from a heated surface. Loss of heat by perfusion is represented by temperature-independent and temperature-dependent terms that can reflect changes in local control of blood flow. Model simulations using physiologically appropriate parameter values indicate that the temperature elevation profile caused by a heated surface adjacent to tissue may extend several centimeters into the tissue. Furthermore, sensitivity analysis indicates the conditions under which temperature profiles are sensitive to changes in thermal diffusivity and perfusion parameters. This information provides the basis for estimation of model parameters in different tissues and for prediction of the thermal responses of these tissues.

Cutaneous leishmaniasis in the Peruvian Andes: risk factors identified from a village cohort study

Risk factors for cutaneous leishmaniasis were identified from a comparative study of transmission rates in 27 villages in the Departments of Lima, Ancash, and Piura in Peru. To evaluate regression analysis as a tool for the incrimination of sand fly vectors in the absence of other biologic evidence, univariate and multivariate logistic regression analyses were used to identify which of 14 variables (the abundance of nine sand fly species, four social factors, and region) predicted transmission rates in villages (incidence, active prevalence, or cumulative prevalence). In general, suspected or proven vectors (e.g., Lutzomyia peruensis) had the strongest associations with transmission rate, indicating that regression is a useful supplementary method of incriminating vectors. Regression was then used to quantify the importance of suspected risk factors. Transmission rate increased with the abundance of Lu. peruensis, Lu. ayacuchensis, Lu. noguchii, and, to a lesser extent, Lu. verrucarum and transmission was higher among villagers who slept more frequently in temporary shelters in crop areas. There were also weak effects of the number of dogs/ person (negative) and the number of persons/household (positive). Linear regressions failed to detect a threshold sand fly density below which transmission ceases. The minimal adequate multiple regression model explained 82% of the variance in village incidence rates. This model was used to predict the effect on incidence of reducing each of the four suspected vectors in northern and southern Peru. The results indicate that vector control programs in the south should aim at Lu. peruensis, Lu. verrucarum, and Lu. noguchii, but focus on Lu. ayacuchensis in the north.

Description of Warileya lumbrerasi n. sp. (Diptera:Psychodidae) from Peru

Warileya lumbrerasi n. sp. is described from the northern Peruvian Andes. This species was collected inside houses, and is the seventh species described within the genus Warileya Hertig, 1948.

Human genetic susceptibility and infection with Leishmania peruviana

Racial differences, familial clustering, and murine studies are suggestive of host genetic control of Leishmania infections. Complex segregation analysis has been carried out by use of the programs POINTER and COMDS and data from a total population survey, comprising 636 nuclear families, from an L. peruviana endemic area. The data support genetic components controlling susceptibility to clinical leishmaniasis, influencing severity of disease and resistance to disease among healthy individuals. A multifactorial model is favored over a sporadic model. Two-locus models provided the best fit to the data, the optimal model being a recessive gene (frequency .57) plus a modifier locus. Individuals infected at an early age and with recurrent lesions are genetically more susceptible than those infected with a single episode of disease at a later age. Among people with no lesions, those with a positive skin-test response are genetically less susceptible than those with a negative response. The possibility of the involvement of more than one gene together with environmental effects has implications for the design of future linkage studies.

The relationship between CDC light-trap and human-bait catches of endophagic sandflies (Diptera: Psychodidae) in the Peruvian Andes

A study was carried out in the Peruvian Andes to test the suitability of CDC light traps for monitoring changes in the human-landing rate of endophagic phlebotomine sandflies, following house-spraying with pyrethroid insecticide. On four pairs of consecutive nights, sandflies were caught inside eight sprayed and eight unsprayed houses, either by human bait or by CDC light traps. The sandflies collected were Lutzomyia verrucarum (97%) and Lu.peruensis (3%), both probable vectors of Leishmania peruviana, and the species composition was unaffected by house-spraying. A non-linear relationship was detected between light-trap and human-bait catches, but the relationship did not diverge significantly from linearity within the range of sandfly abundance found in most houses in the endemic area (i.e. between 3 and 200 sandflies/house-night), and did not differ significantly between sprayed and unsprayed houses. However, light trap catches had a significantly lower proportion of blood-fed females in sprayed than in unsprayed houses, probably due to an insecticidal effect on post-blood-feeding behaviour. The proportion of Lu. verrucarum was significantly higher in light trap than in human bait catches, indicating that Lu.peruensis is either more anthropophilic or less phototropic than Lu.verrucarum.

Extensive polymorphism at the Gp63 locus in field isolates of Leishmania peruviana

Genetic diversity within and between tandemly arrayed copies of the Gp63 gene occurs in laboratory isolates of Leishmania spp., but the extent to which this represents natural genetic diversity has not been assessed. Here, the Gp63 locus is examined in 58 fresh isolates of L. peruviana, and clones derived from them, collected throughout the Peruvian Andes. Extensive polymorphism is observed, both in size of Gp63 containing chromosomes, and for restriction-fragment-length polymorphisms (RFLPs) at the Gp63 locus. All clones within an isolate are identical, including those with two distinct Gp63-hybridising chromosomal-sized pulsed-field gel electrophoresis (PFGE) bands, consistent with diploidy but with size differences in homologous chromosomes. For RFLP analysis, three enzymes were selected to cut within the coding region (PstI), in the intergenic region (SalI) and outside (EcoRI) the Gp63 gene cluster. PstI gave identical banding patterns across all isolates/clones. For EcoRI and SalI, all clones within an isolate were identical, but isolates were polymorphic for fragments at 13 (2-30 kb) and 8 (2.6-8.8 kb) different molecular mass locations generating 19 and 16 distinct RFLP patterns or genotypes for each enzyme, respectively. EcoRI restriction patterns, analysed by PFGE, were consistent with the presence of two clusters of Gp63 genes on each homologous chromosome, one contained within EcoRI fragments large enough to carry from 3 to 10 copies of the Gp63 gene, the second on fragments which could carry 1 or 2 copies of the gene. SalI patterns indicated variable restriction sites within clusters, but not within every intergenic region. A hierarchical analysis of variance of allele frequencies, expressed in terms of Wright's F-statistic, indicated significant barriers to gene flow at all levels, valleys within regions (north/south), villages within valleys, and individuals within villages. This extreme polymorphism at the Gp63 locus of L. peruviana demonstrates the great potential for generation of genetic diversity in parasite populations.

Cutaneous leishmaniasis in the Peruvian Andes: an epidemiological study of infection and immunity

A prospective longitudinal survey of cutaneous leishmaniasis (Leishmania peruviana) was carried out in Peru on a study population of 4716 persons living in 38 villages (Departments of Lima, Ancash and Piura). Demographic and clinical data were collected from all individuals, and a Montenegro skin test (MST) was carried out on 72% (3418) of the study population. Each household was revisited at 3-monthly intervals for up to 2 years to detect new leishmaniasis cases; 497 people received a second MST at the end of the study. Analysis of the epidemiological data indicated that (i) 17% (16/94) of all infections were subclinical, (ii) this percentage increased significantly with age, (iii) clinical infections led to 73.9% protective immunity (95% C.I. 53.0-85.5%) and relatively permanent MST responsiveness (recovery rate = 0.0098/year; 95% C.I. 0.000-0.020/year), (iv) sub-clinical infections led to protective immunity, which was positively correlated with their MST induration size (increasing by 17.9% per mm; P < 0.0001), and a mean MST recovery rate of 0.114/year (4/421 man-months), and (v) recurrent leishmaniasis was dominated by reactivations, not by reinfections.

An association between phlebotomine sandflies and aphids in the Peruvian Andes

As the composition of natural sugars in the diet of adult sandflies (Diptera: Psychodidae: Phlebotominae) may affect the development of Leishmania (Kinetoplastida: Trypanosomatidae) in sandfly guts, and so play an important role in the epidemiology of leishmaniasis, there is increasing interest in the sources of sugars for wild sandflies. Advanced chromatography techniques have provided indirect evidence that wild sandflies feed on honeydew, a substance released by aphids (Hemiptera: Aphididae) when feeding. Our objective was to determine whether sandfly density can be influenced directly by the local density of aphids. Aphid density was determined by counting absolute numbers of aphids on alfalfa stems in Purisima Valley, Peru, where sandflies transmit Leishmania peruviana causing Andean cutaneous leishmaniasis (uta). Sandfly relative abundance was measured using sticky trap sampling repeatedly in alfalfa fields. Lutzomyia verrucarum accounted for 92% of the total sandflies collected. As there was a female bias in sandflies collected close to houses, only the numbers of male sandflies were used in analysis. Most of the adult aphids found feeding on alfalfa were either Therioaphis trifolii forma maculata (97%) or Acyrthosiphon pisum (3%). By regression analysis, a significant relationship was found between the density of Lu.verrucarum males and the density of adults of both aphid species. This is the first ecological study to support the hypothesis that aphid honeydew may be a source of sugar for sandflies.

Electronic Integration of Glottic Closure and Cricopharyngeal Relaxation for the Control of Aspiration: A Canine Study

Aspiration can result from muscular weakness or paralysis of laryngopharyngeal muscles after lower motor neuron disorders (e.g., stroke) or unchecked gastroesophageal reflux. We submit that rehabilitation of the finely tuned swallowing mechanism should provide at least restoration of the normal dynamic relationships between glottic closure and cricopharyngeal relaxation. In three dogs under general endotracheal anesthesia, the recurrent laryngeal nerves and the pharyngeal musculature were exposed through a midline cervical incision. A tracheotomy was performed to allow unhindered laryngoscopic exposure of the vocal cords. A no. 9 endotracheal tube passed through the upper esophageal sphincter was used as a pressure transducer by saline inflation of its cuff and linked to an oscilloscope. The cricopharyngeus was placed under baseline tension with pulse trains administered by an intramuscular needle electrode with a circuit previously used for agonist/antagonist coupling of reinnervated facial musculature. A second output channel was linked to the contralateral recurrent laryngeal nerve by a bipolar electrode. As the pulse width of the current to the recurrent laryngeal nerve increased, that to the cricopharyngeus was reciprocally decreased, producing snug glottic closure and synchronous cricopharyngeal relaxation. Results were documented on videotape. These findings were highly reproducible. We believe that the novel approach proposed in the current model offers an attractive solution to long-term aspiration problems resulting from an imbalance between vocal cord and cricopharyngeal activities.