The risk of Aedes aegypti breeding and premises condition in South Mexico.

A recent innovation instrumented for the Dengue Prevention and Control program in Mexico is the use of the premises condition index (PCI) as an indicator of risk for the vector Aedes aegypti infestation in dengue-endemic localities of Mexico. This paper addresses whether further improvements for the dengue control program could be made if the prevalence and productivity of Ae. aegypti populations could be reliably predicted using PCI at the household level, as well as medium-sized neighborhoods. We evaluated the use of PCI to predict the infestation with Aedes aegypti (breeding sites and immature productivity) in Merida, Mexico. The study consisted of a cross-sectional survey based on a cluster-randomized sampling design. We analyzed the statistical association between Aedes infestation and PCI, the extent to which the 3 components of PCI (house maintenance, and tidiness and shading of the patio) contributed to the association between PCI and infestation and whether infestation in a given premises was also affected by the PCI of the surrounding ones. Premises with the lowest PCI had significantly lower Aedes infestation and productivity; and as PCI scores increased infestation levels also tended to increase. Household PCI was significantly associated with Ae. aegypti breeding, largely due to the effect of patio untidiness and patio shade. The mean PCI within the surroundings premises also had a significant and independent explanatory power to predict the risk for infestation, in addition to individual PCI. This is the 1st study in Mexico showing evidence that premises condition as measured by the PCI is related to Ae. aegypti breeding sites and immature productivity. Results suggest that PCI could be used to streamline surveys to inform control efforts at least where Ae. aegypti breeds outdoors, as in Merida. The effect of individual premises, neighborhood condition, and the risk of Aedes infestation imply that the risk for dengue vector infestation can only be minimized by the mass effect at the community level.

Triatoma dimidiata infestation in Chagas disease endemic regions of Guatemala: comparison of random and targeted cross-sectional surveys.

BACKGROUND: Guatemala is presently engaged in the Central America Initiative to interrupt Chagas disease transmission by reducing intradomiciliary prevalence of Triatoma dimidiata, using targeted cross-sectional surveys to direct control measures to villages exceeding the 5% control threshold. The use of targeted surveys to guide disease control programs has not been evaluated. Here, we compare the findings from the targeted surveys to concurrent random cross-sectional surveys in two primary foci of Chagas disease transmission in central and southeastern Guatemala. METHODOLOGY/PRINCIPAL FINDINGS: Survey prevalences of T. dimidiata intradomiciliary infestation by village and region were compared. Univariate logistic regression was used to assess the use of risk factors to target surveys and to evaluate indicators associated with village level intradomiciliary prevalences >5% by survey and region. Multivariate logistic regression models were developed to assess the ability of random and targeted surveys to target villages with intradomiciliary prevalence exceeding the control threshold within each region. Regional prevalences did not vary by survey; however, village prevalences were significantly greater in random surveys in central (13.0% versus 8.7%) and southeastern (22.7% versus 6.9%) Guatemala. The number of significant risk factors detected did not vary by survey in central Guatemala but differed considerably in the southeast with a greater number of significant risk factors in the random survey (e.g. land surface temperature, relative humidity, cropland, grassland, tile flooring, and stick and mud and palm and straw walls). Differences in the direction of risk factor associations were observed between regions in both survey types. The overall discriminative capacity was significantly greater in the random surveys in central and southeastern Guatemala, with an area under the receiver-operator curve (AUC) of 0.84 in the random surveys and approximately 0.64 in the targeted surveys in both regions. Sensitivity did not differ between surveys, but the positive predictive value was significantly greater in the random surveys. CONCLUSIONS/SIGNIFICANCE: Surprisingly, targeted surveys were not more effective at determining T. dimidiata prevalence or at directing control to high risk villages in comparison to random surveys. We recommend that random surveys should be selected over targeted surveys whenever possible, particularly when the focus is on directing disease control and elimination and when risk factor association has not been evaluated for all regions under investigation.

Effect of untreated bed nets on blood-fed Phlebotomus argentipes in kala-azar endemic foci in Nepal and India

Observational studies in the Indian subcontinent have shown that untreated nets may be protective against visceral leishmaniasis (VL). In this study, we evaluated the effect of untreated nets on the blood feeding rates of Phlebotomus argentipes as well as the human blood index (HBI) in VL endemic villages in India and Nepal. The study had a "before and after intervention" design in 58 households in six clusters. The use of untreated nets reduced the blood feeding rate by 85 percent (95 percent CI 76.5-91.1 percent) and the HBI by 42.2 percent (95 percent CI 11.1-62.5 percent). These results provide circumstantial evidence that untreated nets may provide some degree of personal protection against sand fly bites.

Effect of untreated bed nets on blood-fed Phlebotomus argentipes in kala-azar endemic foci in Nepal and India.

Observational studies in the Indian subcontinent have shown that untreated nets may be protective against visceral leishmaniasis (VL). In this study, we evaluated the effect of untreated nets on the blood feeding rates of Phlebotomus argentipes as well as the human blood index (HBI) in VL endemic villages in India and Nepal. The study had a 'before and after intervention' design in 58 households in six clusters. The use of untreated nets reduced the blood feeding rate by 85% (95% CI 76.5-91.1%) and the HBI by 42.2% (95% CI 11.1-62.5%). These results provide circumstantial evidence that untreated nets may provide some degree of personal protection against sand fly bites.

The costs of preventing and treating chagas disease in Colombia.

BACKGROUND: The objective of this study is to report the costs of Chagas disease in Colombia, in terms of vector disease control programmes and the costs of providing care to chronic Chagas disease patients with cardiomyopathy. METHODS: Data were collected from Colombia in 2004. A retrospective review of costs for vector control programmes carried out in rural areas included 3,084 houses surveyed for infestation with triatomine bugs and 3,305 houses sprayed with insecticide. A total of 63 patient records from 3 different hospitals were selected for a retrospective review of resource use. Consensus methodology with local experts was used to estimate care seeking behaviour and to complement observed data on utilisation. FINDINGS: The mean cost per house per entomological survey was $4.4 (in US$ of 2004), whereas the mean cost of spraying a house with insecticide was $27. The main cost driver of spraying was the price of the insecticide, which varied greatly. Treatment of a chronic Chagas disease patient costs between $46.4 and $7,981 per year in Colombia, depending on severity and the level of care used. Combining cost and utilisation estimates the expected cost of treatment per patient-year is $1,028, whereas lifetime costs averaged $11,619 per patient. Chronic Chagas disease patients have limited access to healthcare, with an estimated 22% of patients never seeking care. CONCLUSION: Chagas disease is a preventable condition that affects mostly poor populations living in rural areas. The mean costs of surveying houses for infestation and spraying infested houses were low in comparison to other studies and in line with treatment costs. Care seeking behaviour and the type of insurance affiliation seem to play a role in the facilities and type of care that patients use, thus raising concerns about equitable access to care. Preventing Chagas disease in Colombia would be cost-effective and could contribute to prevent inequalities in health and healthcare.

Pupal surveys for Aedes aegypti surveillance and potential targeted control in residential areas of Mérida, México.

A mosquito larval-pupal survey was conducted in 1,160 households of the Mexican city of Mérida during the rainy season of 2003 to determine their differential productivity for Aedes aegypti. Larvae and pupae were detected in 15 broad categories of container types. All breeding sites were found in the patios (backyards) and were potentially rain filled. Ae. aegypti pupae were produced from all categories of breeding site, and no single container type was predominately responsible for pupal production. The most productive buckets comprised 42% of the pupae-positive containers and provided 34% of the total pupae collected. Pupal production in buckets, together with plastic rubbish, pet dishes and basins, utensils for cooking and washing, tires, and flowerpots, accounted for almost 87% of pupal production. However, the most important pupal producers had low infestation indices for immature forms, illustrating that the use of positive-container indices can underestimate the importance of certain breeding sites. Overall, 40% of containers that were observed harboring Ae. aegypti pupae were classified as disposable. The remaining containers were considered useful, although some were seldom used. The discussion focuses on the potential utility of the pupal survey for targeting control, and its resulting pupae-per-person entomological indicator, both for comparison with a theoretical threshold for dengue transmission and for targeting vector control in this Mexican city.

Morphometric evidence for a possible role of Rhodnius prolixus from palm trees in house re-infestation in the State of Barinas (Venezuela).

The main vector of Chagas disease in Venezuela is Rhodnius prolixus. Specimens of Rhodnius sp., identified elsewhere as R. prolixus by molecular tools, were collected in Barinas State (Venezuela) before insecticide application, and compared by morphometric techniques with post-spraying, re-infesting insects after control. Geometric morphometry was applied, allowing separate analyses of shape and size. The idea of a single species sharing silvatic and domestic/peri-domestic ecotopes was supported, suggesting new evolutionary scenarios for the controversial R. prolixus origins. The same data allowed to understand the possible mechanisms of villages re-infestation after a control campaign, either recolonization by local recovery of survivors or re-infestation by external migrants. Both mechanisms were apparent. Although shape properties could distinguish very close subpopulations such as insects from houses and insects from peri-domestic shelters, they were unable to identify the insects from palm trees as a distinct subpopulation. This strongly suggested that human environment could receive immigrants from palm trees. The pattern of size variation supported the hypothesis of a one-way exchange from silvatic to human environments, but did not support the reverse movement. Thus, morphometric data indicated that a silvatic population of the local vector is probably responsible for re-infesting villages after insecticide application, and they also pointed to the existence of re-infestation by local recovery of survivors. According to this interpretation, new epidemiological scenarios must be considered to improve Chagas disease control in Venezuela.

Effect of knowledge and economic status on sandfly control activities by householders at risk of cutaneous leishmaniasis in the subandean region of Huila department, Colombia / Efecto del conocimiento y nivel socioeconómico sobre las actividades de control realizadas por la población en riesgo de adquirir leishmaniasis cutánea en la región subandina del departamento del Huila, Colombia

Introducción. Las medidas de control vectorial en el ámbito familiar pueden ser estimuladas por campañas de promoción en salud que tengan en cuenta los conocimientos y actitudes de la población con énfasis en vacíos claves en el conocimiento. Objetivos. Describir las prácticas de control para flebótomos realizadas por las familias en un área endémica de leishmaniasis cutánea en el departamento del Huila, Colombia, y determinar cómo estas prácticas son influenciadas por las actitudes, conocimientos y el estatus socioeconómico. Materiales y métodos. Se aplicó un cuestionario a nivel familiar para recolectar información sobre: demografía, estatus socioeconómico, conocimientos sobre leishmaniasis cutánea y sobre los flebótomos y su papel en la transmisión, y la práctica de actividades de control. La abundancia intradomiciliar de flebótomos fue estimada con trampas de luz. Resultados. De 249 entrevistados, 86 por ciento conocían la leishmaniasis cutánea y 98 por ciento los flebótomos. 35 por ciento de los entrevistados que conocían la leishmaniasis cutánea practicaron medidas para su control. Estas prácticas fueron mayores, 32 por ciento, en las familias que conocían que los flebótomos transmiten la LC. Sin embargo, 82 por ciento de los entrevistados practicaron medidas de control para los flebótomos, y estas prácticas estuvieron significativamente asociadas con altas abundancias de flebótomos. Las medidas de control practicadas incluyeron humazo, toldillos, fumigación intradomiciliar con insecticidas o con sustancias no insecticidas. Las familias que usaron medidas de costo alto (toldillos e insecticidas) tenían el estatus económico más alto. Conclusiones. Los programas de educación en salud deben considerar que la molestia sanitaria causada por los flebótomos puede iniciar la práctica de medidas de control y que el conocimiento del papel de los flebótomos en la Transmisión puede aumentar estas actividades. Los resultados con relación al estatus socioeconómico in...

Introduction. Householder vector control measures can be encouraged by health promotion campaigns which take into account peoples’ attitudes and focus on key gaps in knowledge. Objectives. To describe household sandfly control practices in an endemic area of cutaneous leishmaniasis in the department of Huila, Colombia, and determine how these are influenced by attitudes, knowledge and socioeconomic status. Materials and methods. A household questionnaire was applied to collect information on: demography, socioeconomic status, knowledge of cutaneous leishmaniasis and of sandflies and their role in transmission, and the control activities practiced. Indoor sandfly abundance was estimated by light trap collections. Results. Amongst 249 interviewees, 86% knew about cutaneous leishmaniasis and 98% sand flies. 35% of interviewees who knew about cutaneous leishmaniasis practiced measures with the purpose of its control. This practice was higher amongst the 32% who knew that sand flies transmit cutaneous leishmaniasis. However, 82% of interviewees practiced sand fly control measures, and these were significantly associated with high sand fly abundance. Measures included smoke, bednets, and house spraying with insecticide or non-insecticidal substances. Householders using the high cost measures (bednets and insecticide) had the highest economic status. Conclusions. Health education programmes should note that sand fly nuisance can initiate control measures, but that knowledge of the role of sand flies in transmission could enhance activities. The socioeconomic findings indicate that targeted bednet subsidies could reduce inequities in health status amongst cutaneous leishmaniasis endemic communities.

Leishmania panamensis transmission in the domestic environment: the results of a prospective epidemiological survey in Santander, Colombia / Transmisión de Leishmania panamensis en ambientes domésticos: resultados de un estudio epidemiológico prospectivo en Santander, Colombia

Introducción. La transmisión doméstica de Leishmania panamensis parece ser la fuente de infección mas frecuente en regiones deforestadas, caracterizadas por el reemplazo del bosque primario por plantaciones permanentes como cacao y café. Este papel presenta los resultados de los patrones de enfermedad en una población representativa del foco del Opón, en Santander, Colombia. Objetivo. Los objetivos principales fueron: 1) cuantificar la tasa de incidencia en una población representativa de la población del foco del Opón; 2) identificar los factores de riesgo demográficos para la infección; 3) estimar la proporción de infecciones que causan enfermedad; 4) estimar la protección contra la enfermedad según la inmunidad adquirida; 5) estimar la frecuencia de reactivaciones, y 6) estimar el riesgo de leishmaniasis mucosa. Materiales y métodos: Se llevó a cabo un estudio prospectivo de leishmaniasis causada por Leishmania panamensis durante 19 meses, entre 1.380 personas habitantes de una región cacaotera del departamento de Santander, Colombia. La población fue diagnosticada por clínica y por la prueba de Montenegro (en dos tiempos). Resultados: La tasa de incidencia fue de 0,19 infecciones/persona-año, 31 por ciento de los cuales tuvieron una infección aparentemente subclínica. El riesgo de adquirir leishmaniasis cutánea decrece con la edad aún en ausencia de infecciones previas aparentes. Una inmunidad protectiva subsiguió a las infecciones clínicas y subclínicas, persistiendo por lo menos durante 10 años posterior a una infección primaria. La leishmaniasis mucocutánea se detectó en 12 por ciento de la población con lesiones cutáneas, de las cuales 77 por ciento tuvieron síntomas no severos, y 23 por ciento perforación del tabique nasal. El riesgo de leishmaniasis mucosa fue más grande para hombres y para personas cuyas lesiones primarias se localizaron en la cabeza. Conclusión. El promedio de edad de infección en el Opón, 7,7 años (1/l), y la ausencia de factores...

Introduction. Domestic transmission now appears to be the principal route of Leishmania panamensis infection in deforested regions characterized by the replacement of primary forest by permanent plantations, i,e coffee or cacao crops. This paper presents the results of the disease patterns in a representative population of the Opón focus, in Santander, Colombia. Objective. The principal aims were: 1) to measure the incidence rate in a representative population of the Opón focus; 2) to identify demographic risk factors for infection; 3) to estimate the proportion of infections which cause disease; 4) to estimate the protection against disease from acquired immunity; 5) to estimate the frequency of reactivations, and 6) to estimate the risk of mucosal leishmaniasis. Material and methods. A 19 month prospective survey of leishmaniasis caused by Leishmania panamensis was carried out amongst 1380 people in a cacao growing region of Santander Department, Colombia. The population was diagnosed clinically and by the Montenegro skin test (at two time points). Results: The incidence rate was 0.19 infections/person-year, with 31% of infections apparently subclinical. The risk of acquiring cutaneous leishmaniasis decreased with age even in the absence of apparent previous infections. Protective immunity followed both clinical and subclinical infections, persisting for at least 10 years after a primary lesion. Mucocutaneous leishmaniasis was detected in 12% of the population with cutaneous lesions, of which 77% had mild symptoms, and 23% perforated nasal septa. The risk of mucosal leishmaniasis was greatest for males, and for people whose primary cutaneous lesion was on the head. Conclusion. The average age of infection in Opón, 7.7 years (1/l), and the absence of gender as a risk factor is highly indicative of intradomiciliary or peridomiciliary transmission.

Could the Chagas disease elimination programme in Venezuela be compromised by reinvasion of houses by sylvatic Rhodnius prolixus bug populations?

The Andean Pact Initiative (1997) committed Andean countries to eliminate vectorial transmission of Chagas disease by 2010 via widespread residual insecticide spraying. In Venezuela, this aim could be compromised by reinvasion of houses by palm tree populations of the major vector Rhodnius prolixus. To test this hypothesis, a multivariate logistic regression was undertaken of risk factors for triatomine infestation and colonization in 552 houses and 1068 peri-domestic outbuildings in Barinas State. After adjusting for other risk factors, including palm roofs, R. prolixus infestation and colonization of outbuildings (and, to some extent, houses) was significantly associated with proximity to high densities of Attalea butyracea palm trees. House infestation and/or colonization was also positively associated with bug density in peri-domestic outbuildings, the presence of pigsties and nests. Hence, R. prolixus populations in ineffectively sprayed outbuildings could also provide an important source of house re-infestations. The secondary vector Triatoma maculata was mainly found associated with the presence of hens nesting both indoors and outdoors.

Extinction of experimental Triatoma infestans populations following continuous exposure to dogs wearing deltamethrin-treated collars.

Dogs are domestic reservoir hosts of Trypanosoma cruzi, the etiological agent of Chagas disease. We evaluated the effect of deltamethrin-treated dog collars (DTDCs) over time on the population dynamics of Triatoma infestans, a main T. cruzi vector. Forty founder bugs of mixed life stages were allowed to colonize mud-thatched experimental huts and exposed continuously to either uncollared control dogs (N = 3) or dogs wearing DTDCs (N = 7) for a period of up to 196 days. When compared with bugs exposed to control dogs, bugs exposed to collared dogs were shown to have reduced feeding success (odds ratio [OR] = 0.40; 95% confidence interval [CI], 0.26-0.63; P < 0.001) and lower survival (OR = 0.15; 95% CI, 0.08-0.29; P < 0.001); in fact, all of the bug populations exposed to collared dogs became extinct 77-196 days after study initiation. Bugs exposed to DTDC-wearing dogs were also shown to have a lower fecundity (i.e., number of eggs produced per live female bug: OR = 0.64; 95% CI, 0.51-0.81; P < 0.001) and molting rate to first-instar nymphs (OR = 0.32; 95% CI, 0.13-0.75; P < 0.01) than those bugs exposed to control dogs. DTDCs could represent a novel tool to prevent and control canine and (hence) human Chagas disease.

Leishmania panamensis transmission in the domestic environment: the results of a prospective epidemiological survey in Santander, Colombia.

INTRODUCTION: Domestic transmission now appears to be the principal route of Leishmania panamensis infection in deforested regions characterized by the replacement of primary forest by permanent plantations, i,e coffee or cacao crops. This paper presents the results of the disease patterns in a representative population of the Opón focus, in Santander, Colombia. OBJECTIVE: The principal aims were: 1) to measure the incidence rate in a representative population of the Opón focus; 2) to identify demographic risk factors for infection; 3) to estimate the proportion of infections which cause disease; 4) to estimate the protection against disease from acquired immunity; 5) to estimate the frequency of reactivations, and 6) to estimate the risk of mucosal leishmaniasis. MATERIAL AND METHODS: A 19 month prospective survey of leishmaniasis caused by Leishmania panamensis was carried out amongst 1380 people in a cacao growing region of Santander Department, Colombia. The population was diagnosed clinically and by the Montenegro skin test (at two time points). RESULTS: The incidence rate was 0.19 infections/person-year, with 31% of infections apparently subclinical. The risk of acquiring cutaneous leishmaniasis decreased with age even in the absence of apparent previous infections. Protective immunity followed both clinical and subclinical infections, persisting for at least 10 years after a primary lesion. Mucocutaneous leishmaniasis was detected in 12% of the population with cutaneous lesions, of which 77% had mild symptoms, and 23% perforated nasal septa. The risk of mucosal leishmaniasis was greatest for males, and for people whose primary cutaneous lesion was on the head. CONCLUSION: The average age of infection in Opón, 7.7 years (1/lambda), and the absence of gender as a risk factor is highly indicative of intradomiciliary or peridomiciliary transmission.

Effect of knowledge and economic status on sandfly control activities by householders at risk of cutaneous leishmaniasis in the subandean region of Huila department, Colombia.

INTRODUCTION: Householder vector control measures can be encouraged by health promotion campaigns which take into account peoples' attitudes and focus on key gaps in knowledge. OBJECTIVES: To describe household sandfly control practices in an endemic area of cutaneous leishmaniasis in the department of Huila, Colombia, and determine how these are influenced by attitudes, knowledge and socioeconomic status. MATERIALS AND METHODS: A household questionnaire was applied to collect information on: demography, socioeconomic status, knowledge of cutaneous leishmaniasis and of sandflies and their role in transmission, and the control activities practiced. Indoor sandfly abundance was estimated by light trap collections. RESULTS: Amongst 249 interviewees, 86% knew about cutaneous leishmaniasis and 98% sand flies. 35% of interviewees who knew about cutaneous leishmaniasis practiced measures with the purpose of its control. This practice was higher amongst the 32% who knew that sand flies transmit cutaneous leishmaniasis. However, 82% of interviewees practiced sand fly control measures, and these were significantly associated with high sand fly abundance. Measures included smoke, bednets, and house spraying with insecticide or non-insecticidal substances. Householders using the high cost measures (bednets and insecticide) had the highest economic status. CONCLUSIONS: Health education programmes should note that sand fly nuisance can initiate control measures, but that knowledge of the role of sand flies in transmission could enhance activities. The socioeconomic findings indicate that targeted bednet subsidies could reduce inequities in health status amongst cutaneous leishmaniasis endemic communities.

Lessons from a national survey of Chagas disease transmission risk in Colombia.

In recent years, there has been a revitalization of large-scale programmes to control parasitic disease in developing countries. In 1997, the Governments of Colombia, Venezuela, Ecuador and Peru committed themselves to replicate the cost-effective elimination of Trypanosoma cruzi transmission achieved in the Southern Cone by using insecticides against the domestic triatomine vectors (in combination with blood-bank screening). Central American Governments launched a complementary initiative. All plan to interrupt vectorial transmission throughout the region by 2010 but specific targets are decided nationally. In this article, we highlight the novel approach taken by the Colombian Government for determining the geographic distribution of Chagas disease risk to select where to intervene first.

Predicting geographic variation in cutaneous leishmaniasis, Colombia.

Approximately 6,000 cases of cutaneous leishmaniasis are reported annually in Colombia, a greater than twofold increase since the 1980s. Such reports certainly underestimate true incidence, and their geographic distribution is likely biased by local health service effectiveness. We investigated how well freely available environmental data explain the distribution of cases among 1,079 municipalities. For each municipality, a unique predictive logistic regression model was derived from the association among remaining municipalities between elevation, land cover (preclassified maps derived from satellite images), or both, and the odds of at least one case being reported. Land cover had greater predictive power than elevation; using both datasets improved accuracy. Fitting separate models to different ecologic zones, reflecting transmission cycle diversity, enhanced the accuracy of predictions. We derived measures that can be directly related to disease control decisions and show how results can vary, depending on the threshold selected for predicting a disease-positive municipality. The results identify areas where disease is most likely to be underreported.

Are insecticide-impregnated dog collars a feasible alternative to dog culling as a strategy for controlling canine visceral leishmaniasis in Brazil?

In a zoonotic visceral leishmaniasis (ZVL)-endemic area in Brazil, deltamethrin-impregnated collars (DMC) were fitted to 136 dogs for 5 months and significantly reduced the odds of increasing their anti-Leishmania antibody titer during this period by 50% (95% confidence interval 29-87%, P=0.01), as compared with a population of 97 uncollared dogs with pre-intervention prevalence within the same town. Mathematical modeling suggests that under typical Brazilian ZVL-endemic conditions, the epidemiological impact of community-wide DMC application should be greater than the currently practiced dog culling strategy, but that its impact will be dependent on collar coverage and loss rate. Both interventions should have a higher proportional impact in regions of lower endemicity, but the relative advantage of DMC over culling increases with transmission rate. Sensitivity analyses indicate that the impact of either intervention is not significantly affected by variation in the biology of the sandfly vector, but is greatly influenced by variation in dog mortality and serorecovery rates.

The transmission dynamics of canine American cutaneous leishmaniasis in Huánuco, Peru.

The epidemiology of canine American cutaneous leishmaniasis (ACL) due to Leishmania (Viannia) spp. was investigated in Huánuco, Peru to 1) describe the natural course of canine L. (Viannia) infections and 2) assess the role of domestic dogs as ACL reservoir hosts. Over a three-year period 1,022 dogs were surveyed, with cumulative village L. (Viannia) prevalence being 26% (range = 0-100%). The incidence of L. (Viannia) was estimated to be 0.285 dogs/year (95% confidence interval [CI] = 0.160-0.410) using cross-sectional data and 0.291 dogs/year (95% CI = 0.195-0.387) using data from 108 dogs that were surveyed prospectively. The recovery rate was estimated to be 0.456 dogs/year (95% CI = 0.050-0.862) and 0.520 dogs/year (95% CI = 0.302-0.738), respectively. Using those findings, the basic reproduction number was estimated to be R0 approximately to 1.9; if dogs were the principal ACL reservoirs, the mean yearly effort (i.e., coverage or elimination) of a dog control intervention (e.g., collaring, culling, or vaccination) to ensure the elimination of L. (Viannia) spp. transmission would be as low as 47%.

Domestic dog ownership: a risk factor for human infection with Leishmania (Viannia) species.

An epidemiological study has shown that cumulative, village prevalence of Leishmania (Viannia) infection in dogs ranges from 8% to 45% in Huánuco, Peru. Using data from a prospective survey of human American cutaneous leishmaniasis (ACL) collected during 1994-98, it was shown that the village-level risk of human ACL did not significantly increase with dog abundance, neither in absolute terms (P = 0.659) nor in relation to dog:human ratios (P = 0.213). A significant positive association was observed between risk of human ACL and village dog ACL prevalence (P = 0.022). When controlled for village dog ACL prevalence, there also was an association between the average number of dogs per household and risk of human ACL (P = 0.033). The results suggest that dogs play a role in the (peri)domestic transmission of Le. (Viannia) to humans in Huánuco and indicate that a control intervention targeting dogs to control human ACL is warranted.

Indoor and peridomestic transmission of American cutaneous leishmaniasis in northwestern Argentina: a retrospective case-control study.

A case-control study was carried out during 1990-1994 to identify risk factors associated with American cutaneous leishmaniasis (ACL) in Santiago del Estero, Argentina. The study subjects consisted of 171 cases and 308 controls matched by age, sex, and place of residence. The analysis was performed by conditional logistic regression. Risk factors found to be significantly associated with ACL were related to indoor transmission (few rooms in the house, dirt floor, and a permanent opening in lieu of a window); peridomestic transmission (presence of a pond or woodland within 150 m of the house and an agricultural area within 200 m of the house); and human behavior (sleeping in the backyard, collecting water, bathing, and performing agricultural activities). Most transmission appears to have occurred indoors and in the peridomicile. These environments should be included in further research and control policies.