RESUMO
To develop long-lasting, topical pour-on insecticides for dogs to control zoonotic visceral leishmaniasis, two deltamethrin-based formulations (emulsifiable concentrate [EC] and suspension concentrate [SC]) were tested for their efficacy against the phlebotomine sandfly Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae), vector of Leishmania infantum Nicolle (Kinetoplastida: Trypanosomatidae). The entomological outcomes tested were anti-feeding effect (proportion of female sandflies unfed), lethal effect (24-h female sandfly mortality) and these two effects combined, and the insecticide persistence time at 50% (residual activity, RA50) and 80% (RA80) efficacy. On initial application, the proportions of female flies that demonstrated anti-feeding activity or were killed were similar for both formulations, at 0.93 (95% confidence interval [CI] 0.856-0.977) vs. 0.81 (95% CI 0.763-0.858) (anti-feeding) and 0.86 (95% CI 0.787-0.920) vs. 0.76 (95% CI 0.698-0.817) (24-h mortality) for EC and SC, respectively. The RA(50) rates for anti-feeding and mortality caused by the EC formulation were 4.7 months (95% CI 4.18-5.84) and 2.5 months (95% CI 2.25-2.90), respectively, compared with 1.1 months (95% CI 0.96-1.15) and 0.6 months (95% CI 0.50-0.61), respectively, for the SC formulation. The RA(50) for the combined anti-feeding and mortality effects of EC was 5.2 months (95% CI 4.73-5.96), compared with only 0.9 months (95% CI 0.85-1.00) for the SC formulation. The four- to six-fold superior residual activity of the EC formulation was attributed to the addition of a solvent-soluble resin in the formulation which improved fur adhesion and acted as a reservoir for the slow release of the active ingredient. These results identify the potential of such a low-cost formulation to reduce the inter-intervention interval to 5-6 months, similar to that recommended for deltamethrin-impregnated dog collars or for re-impregnation of conventional bednets, both of which are currently used to combat Leishmania transmission. Finally, a novel bioassay was developed in which sandflies were exposed to fur from treated dogs, revealing no detectable tolerance (24-h mortality) in wild-caught sandflies to the insecticide formulations up to 8 months after the initiation of communitywide application of the insecticides to dogs.
Assuntos
Doenças do Cão/parasitologia , Inseticidas/uso terapêutico , Leishmaniose Visceral/prevenção & controle , Nitrilas/uso terapêutico , Piretrinas/uso terapêutico , Administração Tópica , Animais , Brasil/epidemiologia , Doenças do Cão/prevenção & controle , Cães , Feminino , Cabelo/parasitologia , Abrigo para Animais , Humanos , Consentimento Livre e Esclarecido , Inseticidas/administração & dosagem , Leishmaniose Visceral/epidemiologia , Leishmaniose Visceral/veterinária , Masculino , Nitrilas/administração & dosagem , Psychodidae , Piretrinas/administração & dosagem , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
The epidemiological role of the crab-eating fox Cerdocyon thous in the transmission of Leishmania infantum is assessed in a longitudinal study in Amazon Brazil. A total of 37 wild-caught foxes were immunologically and clinically monitored, and 26 foxes exposed to laboratory colonies of the sandfly vector Lutzomyia longipalpis, over a 15-month period. In total 78% (29/37) of foxes were seropositive for anti-Leishmania IgG on at least 1 occasion, and 38% (8/37) had infections confirmed by PCR and/or by culture. Point prevalences were 74% (serology), 15% (PCR), and 26% (culture). No signs of progressive disease were observed. None of the foxes were infectious to the 1469 sandflies dissected from 44 feeds. A conservative estimate of the possible contribution of foxes to transmission was 9% compared to 91% by sympatric domestic dogs. These results show that crab-eating fox populations do not maintain a transmission cycle independently of domestic dogs. The implication is that they are unlikely to introduce the parasite into Leishmania-free dog populations.
Assuntos
Reservatórios de Doenças , Raposas/parasitologia , Leishmania infantum/isolamento & purificação , Leishmaniose Visceral/transmissão , Leishmaniose Visceral/veterinária , Envelhecimento , Animais , Anticorpos Antiprotozoários/imunologia , Antígenos de Protozoários/imunologia , Brasil/epidemiologia , Doenças do Cão/parasitologia , Doenças do Cão/transmissão , Cães , Feminino , Raposas/imunologia , Imunoglobulina G/imunologia , Incidência , Leishmania infantum/genética , Leishmania infantum/imunologia , Leishmaniose Visceral/epidemiologia , Leishmaniose Visceral/imunologia , Masculino , Reação em Cadeia da Polimerase , PrevalênciaRESUMO
The sensitivity and specificity of PCR, serology (ELISA) and lymphoproliferative response to Leishmania antigen for the detection of Leishmania infantum infection were evaluated in a cohort of 126 dogs exposed to natural infection in Brazil. For PCR, Leishmania DNA from bone-marrow was amplified with both minicircle and ribosomal primers. The infection status and time of infection of each dog were estimated from longitudinal data. The sensitivity of PCR in parasite-positive samples was 98%. However, the overall sensitivity of PCR in post-infection samples, from dogs with confirmed infection, was only 68%. The sensitivity of PCR varied during the course of infection, being highest (78-88%) 0-135 days post-infection and declining to around 50% after 300 days. The sensitivity of PCR also varied between dogs, and was highest in sick dogs. The sensitivity of serology was similar in parasite-positive (84%), PCR-positive (86%) and post-infection (88%) samples. The sensitivity of serology varied during the course of infection, being lowest at the time of infection and high (93-100%) thereafter. Problems in determining the specificity of serology are discussed. The sensitivity and specificity of cellular responsiveness were low. These data suggest that PCR is most useful in detecting active or symptomatic infection, and that serology can be a more sensitive technique for the detection of all infected dogs.
Assuntos
Doenças do Cão/diagnóstico , Imunidade Celular , Leishmania infantum/isolamento & purificação , Leishmaniose Visceral/veterinária , Reação em Cadeia da Polimerase/veterinária , Animais , Anticorpos Antiprotozoários/imunologia , Antígenos de Protozoários/imunologia , Brasil , Estudos de Coortes , Estudos Transversais , DNA de Protozoário/química , Doenças do Cão/parasitologia , Cães , Ensaio de Imunoadsorção Enzimática/veterinária , Leishmania infantum/genética , Leishmaniose Visceral/diagnóstico , Estudos Longitudinais , Sensibilidade e EspecificidadeRESUMO
The failure of control programs for visceral leishmaniasis (VL) that depend on elimination of infected dogs suggests that other reservoir hosts may participate in the transmission cycle. To determine whether persons infected with Leishmania chagasi can infect the vector sand fly, laboratory-reared Lutzomyia longipalpis were allowed to feed on Brazilian subjects with active, cured, and asymptomatic VL and on asymptomatic residents of houses of persons with active VL. Of 3747 insects that had fed, 26 acquired infection from 11 of the 44 persons with active VL, but none acquired infection from the 137 asymptomatic persons. Among persons <4 years old with active VL, a history of diarrhea and higher peripheral blood neutrophil counts were independent predictors of infectivity. Further experiments using larger numbers of insects are necessary to evaluate the reservoir competence of persons with asymptomatic infections, who represent a large segment of the population of several Brazilian cities.
Assuntos
Leishmania , Leishmaniose Visceral/transmissão , Adolescente , Animais , Brasil , Criança , Pré-Escolar , Reservatórios de Doenças , Cães , Ensaio de Imunoadsorção Enzimática , Humanos , Lactente , Reação em Cadeia da Polimerase , PsychodidaeRESUMO
The direct agglutination test (DAT) was used to evaluate the serological response of 150 serum samples taken from 15 captive-bred capuchin monkeys Cebus apella. These animals had been experimentally infected with either L. (Leishmania) amazonensis, L. (Viannia) lainsoni or L. (V.) braziliensis. Monkeys infected with L. (L.) amazonensis or L. (V.) lainsoni were challenged with the homologous parasite one month after their spontaneous cure. DAT antigens were prepared from L. (L.) donovani, L. (L.) amazonensis and L. (V.) braziliensis. Antigens were difficult to standardise and it was impossible to produce an L. (V.) lainsoni antigen as parasites remained aggregated even after trypsinization. The DAT detected significant humoral responses in all the infected monkeys. Titres were higher when homologous antigens were used, especially in secondary responses. This suggests that homologous antigen should be used to detect antibodies in human cutaneous leishmaniasis.
Assuntos
Anticorpos Antiprotozoários/sangue , Leishmania braziliensis/imunologia , Leishmania mexicana/imunologia , Leishmaniose Cutânea/imunologia , Testes de Aglutinação , Animais , CebusRESUMO
We estimate the incidence rate, serological conversion rate and basic case reproduction number (R0) of Leishmania infantum from a cohort study of 126 domestic dogs exposed to natural infection rates over 2 years on Marajó Island, Pará State, Brazil. The analysis includes new methods for (1) determining the number of seropositives in cross-sectional serological data, (2) identifying seroconversions in longitudinal studies, based on both the number of antibody units and their rate of change through time, (3) estimating incidence and serological pre-patent periods and (4) calculating R0 for a potentially fatal, vector-borne disease under seasonal transmission. Longitudinal and cross-sectional serological (ELISA) analyses gave similar estimates of the proportion of dogs positive. However, longitudinal analysis allowed the calculation of pre-patent periods, and hence the more accurate estimation of incidence: an infection-conversion model fitted by maximum likelihood to serological data yielded seasonally varying per capita incidence rates with a mean of 8.66 x 10(-3)/day (mean time to infection 115 days, 95% C.L. 107-126 days), and a median pre-patent period of 94 (95% C.L. 82-111) days. These results were used in conjunction with theory and dog demographic data to estimate the basic reproduction number, R0, as 5.9 (95% C.L. 4.4-7.4). R0 is a determinant of the scale of the leishmaniasis control problem, and we comment on the options for control.
Assuntos
Anticorpos Antiprotozoários/sangue , Doenças do Cão/epidemiologia , Doenças do Cão/transmissão , Leishmania infantum , Leishmaniose Visceral/veterinária , Animais , Medula Óssea/parasitologia , Brasil/epidemiologia , Estudos de Coortes , Estudos Transversais , Doenças do Cão/parasitologia , Cães , Ensaio de Imunoadsorção Enzimática , Imunofluorescência , Incidência , Leishmania infantum/imunologia , Leishmania infantum/isolamento & purificação , Leishmania infantum/fisiologia , Leishmaniose Visceral/imunologia , Leishmaniose Visceral/parasitologia , Estudos Longitudinais , Parasitemia/veterináriaRESUMO
The direct agglutination test (DAT) was evaluated for serodiagnosis of visceral leishmaniasis (VL) in human and canids (dogs and foxes Cerdocyon thous). The results were compared with those of the immunofluorescent antibody assay (IFAT) and enzyme-linked immunosorbent assay (ELISA). The sera used were from: humans (303): confirmed VL (16), suspected VL (65), other conditions (102), negative controls (15) and individuals from an endemic area (105); dogs (82): from an endemic area (68), Salvaterra/Marajó/Pará (21 of which were parasitologically positive), and negative controls (14), from Belém; foxes (9): caught on Marajó Island. Antigens for DAT were prepared from promastigots of L. (L.) donovani, L. (L.) chagasi. Antigens used in ELISA and IFAT were prepared from promastigotes (soluble antigen) and amastigotes respectively of L. (L.) chagasi. In humans, the specificity and sensitivity of DAT using L. (L.) donovani were high (98.4% and 100% respectively) and comparable to that of IFAT (97.5% and 100%). ELISA was less specific (84.8%) although similarly sensitive (100%). In dogs, DAT was more specific using L. (L.) donovani as antigen than using L. (L.) chagasi. However, both DAT and ELISA were less sensitive (both 71.4%) than IFAT (100%). This difference was reflected in the results from endemic dogs, 87% of which were positive by IFAT but only 54% by ELISA and 49% by DAT. Similarly, all 9 fox sera were positive by IFAT, 7 of 9 (78%) by ELISA but none by DAT. In conclusion, DAT using L. (L.) donovani antigen can provide a useful test for human VL; utilization on a large scale would be possible with a suitable reference laboratory to monitor antigen quality. However, DAT appears less useful for canine studies, as it was less sensitive than ELISA and especially IFAT in detecting canine infection.
Assuntos
Testes de Aglutinação , Leishmaniose Visceral/diagnóstico , Animais , Antígenos de Protozoários/imunologia , Brasil , Doenças do Cão/diagnóstico , Doenças do Cão/imunologia , Cães , Ensaio de Imunoadsorção Enzimática , Técnica Indireta de Fluorescência para Anticorpo , Raposas , Humanos , Leishmania/crescimento & desenvolvimento , Leishmania/imunologia , Leishmaniose Visceral/imunologia , Leishmaniose Visceral/veterináriaRESUMO
As a means of assessing the usefulness of the monkey Cebus apella as an experimental model for the study of cutaneous leishmaniasis, 5 of these animals were inoculated intradermally at 8 sites along the tail with 3 X 10(6) promastigotes of L. (V.) braziliensis, while a further 5 monkeys received similar inoculations with 3 X 10(6) promastigotes of L. (L.) amazonensis. Following the inoculations, weekly examinations and monthly biopsies showed evolution of resulting skin lesions to be as follows: a) L. (V.) braziliensis: lesions were first visible 15-20 days post-inoculation (p.i), and at 30 days they were clearly of an erythematous-papular nature, which assumed a nodular form at 60 days; after 3 months a spontaneous ulceration of these lesions was noted and, at 4 months, the initiation of healing. In one animal total healing was apparent 5 months p.i; in two others at 6 months, in another monkey after 7 months, and in the last animal at 10 months p.i. Amastigotes were demonstrated in smears from the lesions of all monkeys up to 90 days p.i; up to 120 days in two animals, and at 180 days p.i. in the monkey which showed resolution of the lesions after 10 months. b) L. (L.) amazonensis lesions were first apparent after 20 days p.i; at 30 days they were of an erythematous-papular nature, developing into nodules at 60 days. From the third month of infection onwards, however, the lesions diminished rapidly and, at 90 days p.i. amastigotes were no longer detectable in the skin.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Leishmaniose/complicações , Animais , Cebus , Feminino , MasculinoRESUMO
The susceptibility of the monkey Cebus apella (Cebidae) to experimental infection by Leishmania (Viannia) lainsoni has been investigated. For this purpose, five young monkeys, 2 males and 3 females, were intradermally, inoculated, in eight different places along the dorsal surface of the tail with 3 x 10(6) promastigotes of the parasite (MHOM/BR/81/M6426, Benevides, Pará), from stationary phase culture in Difco B45 medium. After inoculations, infection in the monkeys was indicated by the presence of amastigotes in the skin lesions produced in these animals at the points of inoculation, confirming the susceptibility of the monkey Cebus apella to experimental infection by Leishmania lainsoni, with an infection period of four months. This represents a suitable period for testing antileishmanial drugs or studying the pathogenesis of the disease caused by this parasite.