Rapid Detection of Leishmania infantum Infection in Dogs: Comparative Study Using an Immunochromatographic Dipstick Test, Enzyme-Linked Immunosorbent Assay, and PCR

Current zoonotic visceral leishmaniasis (ZVL) control programs in Brazil include the culling of Leishmania infantum-infected reservoir dogs, a strategy that has failed to prevent a rise of canine and human ZVL cases over the past decade. One of the main reasons this strategy has failed is because of a long delay between sample collection, sample analysis, and control implementation. A rapid, sensitive, and specific diagnostic tool would be highly desirable, because it would allow control interventions to be implemented in situ. We compared an immunochromatographic dipstick test to enzyme-linked immunosorbent assay (ELISA) and PCR for detecting L. infantum infections in dogs from an area of ZVL endemicity in Brazil. The dipstick test was shown to have 61 to 75% specificity and 72 to 77% sensitivity, compared to 100% specificity for both ELISA and PCR and 71 to 88% and 51 to 64% sensitivity for ELISA and PCR, respectively. Of the field samples tested, 92 of 175 (53%), 65 of 175 (37%), and 47 of 175 (27%) were positive by dipstick, ELISA, and PCR, respectively. The positive and negative predictive values for the tested dipstick were 58 to 77% and 75%, respectively. Efforts should be made to develop a more specific dipstick test for diagnosis of leishmaniasis, because they may ultimately prove more cost-effective than currently used diagnostic tests when used in mass-screening surveys

Leishmaniasis: new approaches to disease control.

The leishmaniases afflict the world's poorest populations. Among the two million new cases each year in the 88 countries where the disease is endemic (fig 1), it is estimated that 80% earn less than $2 a day. Human infections with Leishmania protozoan parasites, transmitted via the bite of a sandfly, cause visceral, cutaneous, or mucocutaneous leishmaniasis. The global burden of leishmaniasis has remained stable for some years, causing 2.4 million disability adjusted life years (DALYs) lost and 59 000 deaths in 2001. Neglected by researchers and funding agencies, leishmaniasis control strategies have varied little for decades, but in recent years there have been exciting advances in diagnosis, treatment, and prevention. These include an immunochromatographic dipstick for diagnosing visceral leishmaniasis; the licensing of miltefosine, the first oral drug for visceral leishmaniasis; and evidence that the incidence of zoonotic visceral leishmaniasis in children can be reduced by providing dogs with deltamethrin collars. There is also hope that the first leishmaniasis vaccine will become available within a decade. Here we review these developments and identify priorities for research

Evaluation of PCR as a diagnostic mass-screening tool to detect Leishmania (Viannia) spp. in domestic dogs (Canis familiaris).

Several studies have suggested that the PCR could be used in epidemiological mass-screening surveys to detect Leishmania (Viannia) spp. infection in human and animal hosts. Dogs from an area of Leishmania braziliensis and Leishmania peruviana endemicity were screened for American cutaneous leishmaniasis (ACL) infection by established PCR-based and enzyme-linked immunosorbent antibody test (ELISA) protocols. PCR detected Leishmania (Viannia) infection in a total of 90 of 1,066 (8.4%) dogs: 32 of 368 (8.7%), 65 of 769 (8.5%), and 7 of 42 (16.7%) dogs were PCR positive by testing of whole blood, buffy coat, and bone marrow aspirates, respectively. ELISA detected infection in 221 of 1,059 (20.9%) tested dogs. The high prevalence of Leishmania (Viannia) detected by PCR and ELISA in both asymptomatic (7.5 and 19.2%, respectively) and symptomatic (32 and 62.5%, respectively) dogs is further circumstantial evidence for their suspected role as reservoir hosts of ACL. However, the low sensitivity of PCR (31%) compared to ELISA (81%) indicates that PCR cannot be used for mass screening of samples in ACL epidemiological studies. Unless more-sensitive PCR protocols were to be developed, its use should be restricted to the diagnosis of active (canine and human) cases and to the parasitological monitoring of patients after chemotherapy

Domestic dog ownership in Iran is a risk factor for human infection with Leishmania infantum.

One explanation proposed for the widespread failure to control zoonotic visceral leishmaniasis by culling infected domestic dogs is that wild canids or humans play significant roles in transmission. The aim of this study was to determine the importance of domestic dogs as the reservoir hosts of visceral leishmaniasis in northwest Iran. A random sample of 3,872 children and 199 dogs in 38 villages was surveyed by the direct agglutination test. Dog ownership details among these households were collected by questionnaire. Parasites isolated from 16 patients and 12 dogs were characterized as Leishmania infantum MON-1. Average seroprevalence in dogs (21.6%) was much higher than in children (7%). Child seropositivity increased significantly with village dog density in absolute terms (P < 0.001) and in relation to dog/human ratios (P = 0.028). Dog ownership within villages also was a significant risk factor for child seropositivity (P = 0.003)

Leishmania (Viannia) spp. dissemination and tissue tropism in naturally infected dogs (Canis familiaris).

First evidence is presented for Leishmania (Viannia) spp. dissemination and tissue tropism in the domestic dog. Using PCR and histology, parasites were detected in the conjunctiva, lung, lymph nodes and ovaries of 2 naturally infected Peruvian dogs. The detection of parasites in the blood indicates that parasite dissemination to those organs may have been haematogenous

Transmisión de Leishmania panamensis en ambientes domésticos: resultados de un estudio epidemiológico prospectivo en Santander, Colombia

Introduction. Domestic transmission now appears to be the principal route of Leishmaniapanamensis infection in deforested regions characterized by the replacement of primary forestby permanent plantations, i,e coffee or cacao crops. This paper presents the results of thedisease 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 representativepopulation of the Opón focus; 2) to identify demographic risk factors for infection; 3) to estimatethe proportion of infections which cause disease; 4) to estimate the protection against diseasefrom acquired immunity; 5) to estimate the frequency of reactivations, and 6) to estimate the riskof mucosal leishmaniasis.Material and methods. A 19 month prospective survey of leishmaniasis caused by Leishmaniapanamensis was carried out amongst 1380 people in a cacao growing region of SantanderDepartment, Colombia. The population was diagnosed clinically and by the Montenegro skintest (at two time points).Results: The incidence rate was 0.19 infections/person-year, with 31% of infections apparentlysubclinical. The risk of acquiring cutaneous leishmaniasis decreased with age even in theabsence of apparent previous infections. Protective immunity followed both clinical andsubclinical infections, persisting for at least 10 years after a primary lesion. Mucocutaneousleishmaniasis was detected in 12% of the population with cutaneous lesions, of which 77% hadmild symptoms, and 23% perforated nasal septa. The risk of mucosal leishmaniasis was greatestfor 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 genderas a risk factor is highly indicative of intradomiciliary or peridomiciliary transmissionIntroducción. 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% 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% de la población con lesiones cutáneas, de las cuales 77% tuvieron síntomas no severos, y 23% 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 de riesgo relacionados con el género indican que la transmisión es intra o peri domiciliaria.

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