Amazonian visceral leishmaniasis--distribution of the vector Lutzomyia longipalpis (Lutz & Neiva) in relation to the fox Cerdocyon thous (linn.) and the efficiency of this reservoir host as a source of infection

Arthropod-Borne Pathogens in Wild Canids

Wild canids, as well as other wild animal species, are largely exposed to bites by ticks and other hematophagous vectors where the features favoring their presence and spread are found in wooded and semi-wooded areas. Much of the information about arthropod-borne infections concerns domestic and companion animals, whereas data about these infections in wild canids are not exhaustive. The present study is a narrative review of the literature concerning vector-borne infections in wild canids, highlighting their role in the epidemiology of arthropod-borne bacteria and protozoa.

Leishmania infantum infecting the carnivore Nasua nasua from urban forest fragments in an endemic area of visceral leishmaniasis in Brazilian Midwest

Introduction

The aim of the present study was to investigate the occurrence of Leishmania infantum in South American coatis inhabiting two forest fragments in Campo Grande, Mato Grosso do Sul, Midwest region of Brazil, an endemic area of human and canine visceral leishmaniasis (VL).

Material and methods

A total of 110 South American coatis were sampled in the conservation unit "Parque Estadual do Prosa" (PEP) and in the residential area "Vila da Base Aérea" (VBA) from March 2018 to April 2019. As a longitudinal study that include up to six recaptures of the same individual, a total of 190 capture events were obtained. Blood, bone marrow and skin samples were obtained for parasitological (axenic culture), serological (Enzyme Linked Immunosorbent Assay - ELISA and Dual-path Platform immunoassay - DPP^® CVL) and molecular diagnostic assays (targeting kDNA for Leishmania spp. and L. infantum; and HSP70 followed by sequence analysis).

Results

Seropositivity for L. infantum was found in 33 individuals, six in PEP and 27 in VBA. Furthermore, L. infantum was detected by molecular analysis in 16 individuals, seven from PEP and nine from VBA. We also isolated L. infantum from bone marrow of one individual and detected a single positive skin sample in molecular assay from other individual, both from VBA.

Discussion

An overall infection rate of 36.4% (40/110) was observed, significantly higher in the VBA (49.1%) than in the PEP (21.6%), probably because VBA presents: (i) a large number of resident dogs and chickens that would be attracting sandflies; (ii) a denser population of this wild mammal species; and (iii) physical barriers and a lack of functional connectivity in the surroundings, preventing these animals to disperse out. We conclude that South American coati populations living in urban forest fragments of Campo Grande are affected by the epidemiological scenario of VL, known to involve dogs, vectors and humans. We highlight the importance of investigate the parasitism by L. infantum in this and other potential L. infantum reservoirs that inhabit urbanized regions endemic to VL.

Divergent impacts of warming weather on wildlife disease risk across climates

Disease outbreaks among wildlife have surged in recent decades alongside climate change, although it remains unclear how climate change alters disease dynamics across different geographic regions. We amassed a global, spatiotemporal dataset describing parasite prevalence across 7346 wildlife populations and 2021 host-parasite combinations, compiling local weather and climate records at each location. We found that hosts from cool and warm climates experienced increased disease risk at abnormally warm and cool temperatures, respectively, as predicted by the thermal mismatch hypothesis. This effect was greatest in ectothermic hosts and similar in terrestrial and freshwater systems. Projections based on climate change models indicate that ectothermic wildlife hosts from temperate and tropical zones may experience sharp increases and moderate reductions in disease risk, respectively, though the magnitude of these changes depends on parasite identity.

Occurrence of Lutzomyia longipalpis Lutz & Neiva 1912 and Cerdocyon thous Linnaeus 1977, in a visceral leishmaniasis endemic area in Brazil

Cerdocyon thous presents a wide geographic distribution in Brazil and its role as a possible Leishmania infantum reservoir in a visceral leishmaniasis (VL) transmission cycle regardless of dogs (Canis familiaris) has been discussed. From this perspective, this work describes the occurrence and use of the habitat by Cerdocyon thous in a Lutzomyia longipalpis occurrence area Teresina (Piaui - Brazil), VL endemic region. Three specimens of C. thous were monitored with the use of radio telemetry and trails and footprints, seeking to find possible natural dens in order to collect the sanflies from the site. Luminous CDC and Damasceno traps were simultaneously installed at the visited sites, where two specimens of L. longipalpis and one L. termitophila were captured. The identification of the dens and trails, allows us to infer that the dens are not used only by the C. thous. Finding the VL vector in natural C. thous natural dens, reinforces the hypothesis of transmission of Le. infantum in the outskirts of the large urban centers, in a cycle that independs from dogs.

Bloodmeal Identification in Field-Collected Sand Flies From Casa Branca, Brazil, Using the Cytochrome b PCR Method

PCR-based identification of vertebrate host bloodmeals has been performed on several vectors species with success. In the present study, we used a previously published PCR protocol followed by DNA sequencing based on primers designed from multiple alignments of the mitochondrial cytochrome b gene used to identify avian and mammalian hosts of various hematophagous vectors. The amplification of a fragment encoding a 359 bp sequence of the Cyt b gene yielded recognized amplification products in 192 female sand flies (53%), from a total of 362 females analyzed. In the study area of Casa Branca, Brazil, blood-engorged female sand flies such as Lutzomyia longipalpis (Lutz & Neiva, 1912), Migonemyia migonei (França, 1924), and Nyssomyia whitmani (Antunes & Coutinho, 1939) were analyzed for bloodmeal sources. The PCR-based method identified human, dog, chicken, and domestic rat blood sources.

LEISHMANIA SPP. IN DIDELPHIS SPP. FROM NORTHEASTERN BRAZIL

The synanthropic behavior of marsupials of the genus Didelphis in endemic areas of leishmaniasis suggests that these animals may play an important role in the epidemiology of this infection. The aim of the present study was to detect Leishmania spp. DNA in Didelphis albiventris (white-eared opossum) and Didelphis aurita (big-eared opossum) living in forested and peridomestic areas of northeastern Brazil. Blood samples were collected from 25 animals (23 D. albiventris and 2 D. aurita ) by cardiac puncture and then analyzed via PCR. Leishmania (Viannia) braziliensis DNA complex was detected in 4 (16%) of the 25 samples, whereas no samples scored positive for Leishmania (Leishmania) donovani complex. Our data suggest that D. albiventris participates in the wild enzootic cycle of the L. (V.) braziliensis complex. Therefore, humans living in this area are at risk of infection, because Didelphis species are in constant movement between wild and urban environments.

Detection of Leishmania Infantum in red foxes (Vulpes vulpes) in Central Greece

This is the first record of Leishmania detection in foxes in Greece. Spleen, lymph nodes, bone marrow and blood samples were collected from 47 red foxes (Vulpes vulpes) found dead or captured, narcotized and freed after bleeding, from November 2009 to 2011, in Fthiotida prefecture, central Greece. This is an endemic for canine leishmaniasis area with several human visceral leishmaniasis cases. The samples were tested for Leishmania infantum and Leishmania tropica by molecular methods (polymerase chain reaction (PCR) and restriction fragment length polymorphism) and serology (indirect immunofluorescent antibody test; when blood samples were available). Leishmania infantum DNA was detected in 28 animals (59·5%). PCR positivity was related to animal age, sex, weight, characteristics of the area trapped, presence of leishmaniasis symptoms and presence of endo- and ecto-parasites. The results were related to dog seropositivity obtained earlier in the area. The findings support the hypothesis that this wild canid may serve as a reservoir for Leishmania in areas where the sandfly vectors are found. In the prefectures of Larisa and Magnisia, adjacent to Fthiotida, Phlebotomus perfiliewi and Phlebotomus tobbi (known vectors of L. infantum) have been reported.

Epidemiologic, clinical, diagnostic and therapeutic aspects of visceral leishmaniasis in renal transplant recipients: experience from thirty cases

BACKGROUND

Visceral leishmaniasis is a disease caused by the protozoan Leishmania sp. and is transmitted by Lutzomyia longipalpis (sand fly). In renal transplant recipients, visceral leishmaniasis causes severe damage to the liver, spleen, and hematopoietic system, as well as poor outcomes for patients with transplanted kidneys. This study describes the largest series of cases of visceral leishmaniasis in renal transplant recipients, providing important information about the diagnostic routines and therapeutic strategies in this patient population.

METHODS

A retrospective, descriptive study was performed to analyze the distribution and evaluate the extent of the epidemiologic, clinical, diagnostic and therapeutic aspects of 30 renal transplant recipients from endemic regions who presented with visceral leishmaniasis in the post-transplantation period.

RESULTS

In this study, visceral leishmaniasis was more frequent in men (80%). The mean age of presentation was 40 ± 10.5 years. The majority of patients worked in urban areas (66.7%), cohabitated with domestic animals (90%), and were from low-income households. In 73.3% of cases, diagnosis was made by direct isolation of Leishmania forms. Patients were treated with liposomal amphotericin, resulting in a high degree of disease remission (80%).

CONCLUSIONS

This study describes the largest series of visceral leishmaniasis in renal transplant recipients and expands clinical-epidemiological knowledge for transplantation teams to perform adequate disease management for this specific patient population.

Wild and synanthropic reservoirs of Leishmania species in the Americas

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Leishmania parasites are maintained by multiple hosts included in seven mammal orders.

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Reservoir hosts are the assemblage of species responsible for Leishmania maintenance.

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Mammal host–Leishmania interaction determines host competence to infect vectors.

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Associate ecological and parasitological data are crucial to understand the wild cycle.

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Prevention of human cases is dependent on a thorough knowledge of the wild cycle.

The definition of a reservoir has changed significantly in the last century, making it necessary to study zoonosis from a broader perspective. One important example is that of Leishmania, zoonotic multi-host parasites maintained by several mammal species in nature. The magnitude of the health problem represented by leishmaniasis combined with the complexity of its epidemiology make it necessary to clarify all of the links in transmission net, including non-human mammalian hosts, to develop effective control strategies. Although some studies have described dozens of species infected with these parasites, only a minority have related their findings to the ecological scenario to indicate a possible role of that host in parasite maintenance and transmission. Currently, it is accepted that a reservoir may be one or a complex of species responsible for maintaining the parasite in nature. A reservoir system should be considered unique on a given spatiotemporal scale. In fact, the transmission of Leishmania species in the wild still represents an complex enzootic “puzzle”, as several links have not been identified. This review presents the mammalian species known to be infected with Leishmania spp. in the Americas, highlighting those that are able to maintain and act as a source of the parasite in nature (and are thus considered potential reservoirs). These host/reservoirs are presented separately in each of seven mammal orders – Marsupialia, Cingulata, Pilosa, Rodentia, Primata, Carnivora, and Chiroptera – responsible for maintaining Leishmania species in the wild.

Heterogeneities in Leishmania infantum infection: using skin parasite burdens to identify highly infectious dogs

Background

The relationships between heterogeneities in host infection and infectiousness (transmission to arthropod vectors) can provide important insights for disease management. Here, we quantify heterogeneities in Leishmania infantum parasite numbers in reservoir and non-reservoir host populations, and relate this to their infectiousness during natural infection. Tissue parasite number was evaluated as a potential surrogate marker of host transmission potential.

Methods

Parasite numbers were measured by qPCR in bone marrow and ear skin biopsies of 82 dogs and 34 crab-eating foxes collected during a longitudinal study in Amazon Brazil, for which previous data was available on infectiousness (by xenodiagnosis) and severity of infection.

Results

Parasite numbers were highly aggregated both between samples and between individuals. In dogs, total parasite abundance and relative numbers in ear skin compared to bone marrow increased with the duration and severity of infection. Infectiousness to the sandfly vector was associated with high parasite numbers; parasite number in skin was the best predictor of being infectious. Crab-eating foxes, which typically present asymptomatic infection and are non-infectious, had parasite numbers comparable to those of non-infectious dogs.

Conclusions

Skin parasite number provides an indirect marker of infectiousness, and could allow targeted control particularly of highly infectious dogs.

Zoonotic visceral leishmaniasis is a sandfly-borne disease of humans and dogs caused by the intracellular parasite Leishmania infantum. Dogs are the proven reservoir. The disease is usually fatal unless treated, and is of global health significance. Diagnosis of canine infections relies on serum antibody-based tests that measure infection. In some endemic regions, a test-and-slaughter policy of seropositive dogs forms part of the national control policy to reduce human infection. However, this strategy is not considered effective. Since not all infected dogs are infectious to sandfly vectors, one option is to target control at infectious dogs, as only these dogs maintain transmission. We quantify Leishmania numbers in individual host tissues from time of infection using molecular methods. Comparing these results with their infectiousness to sandflies, we also evaluate the performance of molecular and immunological assays to identify infectious animals. Parasite numbers varied substantially between individuals, increasing with duration and severity of disease. Infectiousness to the sandfly vector was associated with high parasite numbers, and parasite loads in the skin was the best predictor of being infectious. The results suggest that molecular quantitation is useful in identifying individuals and populations responsible for maintaining transmission, with potential application in operational control programmes.

Outbreak of autochthonous canine visceral leishmaniasis in Santa Catarina, Brazil

The present study reports the first outbreak of autochthonous canine visceral leishmaniasis in Florianópolis, Santa Catarina, southern Brazil. Following the report of two cases of CVL, the Control Center of Zoonotic Diseases conducted a serological survey by ELISA and IFAT assays in seven districts of the Santa Catarina Island. Eleven seropositive dogs of autochthonous transmission were used in the present study. Infection by Leishmania sp. was confirmed by parasitological examination of bone marrow, liver, spleen and lymph nodes, culture in Schneider's medium and PCR. Leishmania sp. isolates were characterized by PCR-RFLP and hybridization with specific probes, allowing for the identification of Leishmania infantum. Autochthonous transmission of this disease in an area with high tourist traffic presents a major public health concern and signifies the emergence of an important zoonosis in southern Brazil. Therefore, the implementation of surveillance and control measures is imperative to prevent the spread of the disease among the canine population as well as transmission to the human population.

Visceral leishmaniasis in a captive crab-eating fox Cerdocyon thous

Visceral leishmaniasis (VL) is a zoonotic disease with worldwide distribution. The crab-eating fox (Cerdocyon thous) is considered a wild reservoir of many zoonotical diseases, particularly VL. This study reported the presence of Leishmania infantum amastigotes in different organs of one captive C. thous found dead in a zoo. This animal was positive by the indirect fluorescence antibody test and had many clinical signs of VL. Intracellular amastigote forms of L. infantum were seen in neutrophils and macrophages in sample tissues from skin, lymph nodes (popliteal, submandibular, prescapular, and mesenteric), spleen, and liver. The numbers of positive cells and intracellular parasites were higher in macrophages than in neutrophils. In addition, polymerase chain reaction demonstrated extensive distribution of Leishmania DNA in C. thous tissues from multiple organs. The presence of intracellular amastigotes in neutrophils and macrophages as well as DNA of the parasite in tissues, specifically skin demonstrate that this crab-eating fox is an adequate host for L. infantum and reinforce the importance of VL for symptomatic wild canids kept in captivity in endemic areas.

Comparative microsatellite typing of new world leishmania infantum reveals low heterogeneity among populations and its recent old world origin

Leishmania infantum (syn. L. chagasi) is the causative agent of visceral leishmaniasis (VL) in the New World (NW) with endemic regions extending from southern USA to northern Argentina. The two hypotheses about the origin of VL in the NW suggest (1) recent importation of L. infantum from the Old World (OW), or (2) an indigenous origin and a distinct taxonomic rank for the NW parasite. Multilocus microsatellite typing was applied in a survey of 98 L. infantum isolates from different NW foci. The microsatellite profiles obtained were compared to those of 308 L. infantum and 20 L. donovani strains from OW countries previously assigned to well-defined populations. Two main populations were identified for both NW and OW L. infantum. Most of the NW strains belonged to population 1, which corresponded to the OW MON-1 population. However, the NW population was much more homogeneous. A second, more heterogeneous, population comprised most Caribbean strains and corresponded to the OW non-MON-1 population. All Brazilian L. infantum strains belonged to population 1, although they represented 61% of the sample and originated from 9 states. Population analysis including the OW L. infantum populations indicated that the NW strains were more similar to MON-1 and non-MON-1 sub-populations of L. infantum from southwest Europe, than to any other OW sub-population. Moreover, similarity between NW and Southwest European L. infantum was higher than between OW L. infantum from distinct parts of the Mediterranean region, Middle East and Central Asia. No correlation was found between NW L. infantum genotypes and clinical picture or host background. This study represents the first continent-wide analysis of NW L. infantum population structure. It confirmed that the agent of VL in the NW is L. infantum and that the parasite has been recently imported multiple times to the NW from southwest Europe.

Leishmaniasis is a vector borne disease with a broad spectrum of clinical forms caused by protozoan parasites of the genus Leishmania. Visceral leishmaniasis is the most severe, systemic form of the disease. It is caused by parasites belonging to the Leishmania donovani complex, which includes L. infantum and L. donovani in the Old World (OW) and L. infantum (syn. L. chagasi) in the New World (NW). The identity and origin of the causative agent of VL in the Americas have been the subjects of much debate for decades. Different scientific approaches led to different conclusions, either favouring the hypothesis of indigenous origin of this parasite and its status as distinct species, or a recent importation of L. infantum by European colonists and synonymy of L. infantum and L. chagasi. We performed the first broad population study of these parasites from the NW using highly variable microsatellite markers. The level of heterogeneity and population structure was very low in contrast to the OW. Using a combined data analysis of NW and OW strains we have provided conclusive evidence of recent multiple introductions of L. infantum from Southwest Europe into the New World and for synonymy of L. infantum and L. chagasi.

Canine visceral leishmaniasis due to Leishmania (L.) infantum chagasi in Amazonian Brazil: comparison of the parasite density from the skin, lymph node and visceral tissues between symptomatic and asymptomatic, seropositive dogs

Canine visceral leishmaniasis (CVL) is recognizable by characteristic signs of disease and is highly lethal. The infection, however, may be quite inapparent in some seropositive dogs, and this has raised the polemic question as to whether or not such animals can be a source of infection for Lutzomyia longipalpis, the vector of American visceral leishmaniasis (AVL). In this study we have examined 51 dogs with acute CVL from an AVL area in Pará State, northern Brazil, and compared the parasite density, amastigotes of Leishmania (L.) infantum chagasi, in the skin, lymph node and viscera of symptomatic with that of nine asymptomatic but seropositive dogs (IFAT-IgG). Post-mortem biopsy fragments of these tissues were processed by immunohistochemistry, using a polyclonal antibody against Leishmania sp. The X² and Mann Whitney tests were used to evaluate the means of infected macrophage density (p < 0.05). There was no difference (p > 0.05) in the skin (10.7/mm² x 15.5/mm²) and lymph node (6.3/mm² x 8.3/mm²), between asymptomatic and symptomatic dogs, respectively. It was higher (p < 0.05), however, in the viscera of symptomatic (5.3/mm²) than it was in asymptomatic (1.4/mm²) dogs. These results strongly suggest that asymptomatic or symptomatic L. (L.) i. chagasi-infected dogs can serve as a source of infection, principally considering the highest (p < 0.05) parasite density from skin (10.7/mm² x 15.5/mm²), the place where the vetor L. longipalpis takes its blood meal, compared with those from lymph node (6.3/mm² x 8.3/mm²) and viscera (1.4/mm²x 5.3/mm²).

American visceral leishmaniasis dissociated from Lutzomyia longipalpis (Diptera, Psychodidae) in the State of Espírito Santo, Brazil

The occurrence of American visceral leishmaniasis in the State of Espírito Santo, Brazil has always been associated with the presence of the Lutzomyia longipalpis vector. The geographic distribution of this vector in this state is related to the presence of specific geoclimatic characteristics, such as a dry climate, low elevations (< 450m), steep slopes and rocky outcrops. The occurrence of human autochthonous cases of American visceral leishmaniasis in municipalities without these geoclimatic characteristics justifies the present study and our main goal was to test the association between the occurrence of American visceral leishmaniasis and the presence of the Lu. longipalpis. Sand flies were captured monthly from July 2006 to August 2007 using Shannon and CDC traps in two municipalities with records of autochthonous American visceral leishmaniasis and one with no record. We captured 13,112 sand flies, but no Lu. longipalpis was found. The absence of Lu. longipalpis and the possible role of another American visceral leishmaniasis vector in these localities were discussed.

Control of visceral leishmaniasis in latin america-a systematic review

BACKGROUND

While three countries in South Asia decided to eliminate anthroponotic visceral leishmaniasis (VL) by 2015, its control in other regions seems fraught with difficulties. Is there a scope for more effective VL control in the Americas where transmission is zoonotic? We reviewed the evidence on VL control strategies in Latin America-diagnosis, treatment, veterinary interventions, vector control-with respect to entomological and clinical outcomes.

METHODOLOGY/PRINCIPAL FINDINGS

We searched the electronic databases of MEDLINE, LILACS, and the Cochrane Central Register of Controlled Trials, from 1960 to November 2008 and references of selected articles. Intervention trials as well as observational studies that evaluated control strategies of VL in the Americas were included. While the use of rapid diagnostic tests for VL diagnosis seems well established, there is a striking lack of evidence from clinical trials for drug therapy and few well designed intervention studies for control of vectors or canine reservoirs.

CONCLUSION

Elimination of zoonotic VL in the Americas does not seem a realistic goal at this point given the lack of political commitment, gaps in scientific knowledge, and the weakness of case management and surveillance systems. Research priorities and current strategies should be reviewed with the aim of achieving better VL control.

Transmission, reservoir hosts and control of zoonotic visceral leishmaniasis

Zoonotic visceral leishmaniasis (ZVL) caused by Leishmania infantum is an important disease of humans and dogs. Here we review aspects of the transmission and control of ZVL. Whilst there is clear evidence that ZVL is maintained by sandfly transmission, transmission may also occur by non-sandfly routes, such as congenital and sexual transmission. Dogs are the only confirmed primary reservoir of infection. Meta-analysis of dog studies confirms that infectiousness is higher in symptomatic infection; infectiousness is also higher in European than South American studies. A high prevalence of infection has been reported from an increasing number of domestic and wild mammals; updated host ranges are provided. The crab-eating fox Cerdocyon thous, opossums Didelphis spp., domestic cat Felis cattus, black rat Rattus rattus and humans can infect sandflies, but confirmation of these hosts as primary or secondary reservoirs requires further xenodiagnosis studies at the population level. Thus the putative sylvatic reservoir(s) of ZVL remains unknown. Review of intervention studies examining the effectiveness of current control methods highlights the lack of randomized controlled trials of both dog culling and residual insecticide spraying. Topical insecticides (deltamethrin-impregnated collars and pour-ons) have been shown to provide a high level of individual protection to treated dogs, but further community-level studies are needed.

A long-lasting topical deltamethrin treatment to protect dogs against visceral leishmaniasis

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.

Lutzomyia longipalpis (Diptera, Psychodidae, Phlebotominae) and urbanization of visceral leishmaniasis in Brazil

The article discusses habits related to the vectorial competence of Lutzomyia longipalpis, along with evidence confirming the importance of this sand fly species in the epidemiological chain of visceral leishmaniasis in Brazil. A new epidemiological profile for visceral leishmaniasis is also postulated, associated with domestic environments and the role of Lu. longipalpis in this process, its sylvatic origin, and its capacity to adapt to a wide range of habitats. Another sand fly species, Lu. cruzi, is mentioned as a vector of visceral leishmaniasis in some municipalities in Central Brazil, based on studies in endemic areas of the country.

Can fleas from dogs infected with canine visceral leishmaniasis transfer the infection to other mammals?

In order to investigate the possible role of dog fleas in the transmission of trypanosomatids, ectoparasites were removed from 59 dogs testing positive for canine zoonotic visceral leishmaniasis according to the indirect fluorescent antibody test (IFAT). Of the fleas collected, 4/207 (1.9%) showed the presence of promastigotes in smears stained by Giemsa, whilst 43/144 (29.9%) exhibited positive polymerase chain reaction (PCR) amplification assays for Leishmania DNA. Fleas (409) from 9 Leishmania chagasi-infected dogs, each hosting more than 20 fleas per animal, were macerated and administered by peritoneal injection or orally to 36 hamsters. After 6 months, the 30 surviving hamsters were sacrificed and liver and spleen fragments were removed for PCA assay and to produce imprint smears, whilst blood samples were subjected to IFAT assay. Sixteen hamsters tested positive for Leishmania infection, 14 on the basis of PCR amplification and four by IFAT assay (two animals testing positive in both assays). Of the infected hamsters, 11/16 (68.7%) had been infected peritoneally and 5/16 (31.2%) orally. The imprint smears for all animals were, however, negative. Since both PCR and IFAT could present cross-reactivity for Leishmania and Leptomonas, the possibility of oral transmission of L. chagasi by fleas cannot be proven unambiguously even though the hamsters developed infection.

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.

Antibodies against Lutzomyia longipalpis saliva in the fox Cerdocyon thous and the sylvatic cycle of Leishmania chagasi

Sera of 11 wild Cerdocyon thous foxes from an endemic area for American visceral leishmaniasis were tested for the presence of antibodies against salivary gland homogenates (SGH) of Lutzomyia longipalpis. All foxes had higher levels of anti-Lu. longipalpis SGH antibodies than foxes from non-endemic areas, suggesting contact between foxes and the vector of visceral leishmaniasis. Sera of humans and dogs living in the same area were also tested for reactivity against Lu. longipalpis SGHs and had a lower proportion of reactivity than foxes. Antibodies against Leishmania chagasi were not detected in any of the foxes, but three foxes showed the presence of parasites in the bone marrow by direct examination, PCR or by infecting the vector. Both humans and dogs had higher levels of anti-Le. chagasi IgG antibodies than C. thous. The finding of an antibody response against saliva of Lu. longipalpis among C. thous together with the broad distribution of the vector in resting areas of infected foxes suggests that the natural foci of transmission of Le. chagasi exists independently of the transmission among dogs and humans.

Lutzomyia longipalpis and the eco-epidemiology of American visceral leishmaniasis, with particular reference to Brazil: a review

An historical review is given of American visceral leishmaniasis (AVL), with particular reference to the eco-epidemiology of the disease in Brazil. Following the first records of AVL in this country, in 1934, the sandfly Lutzomyia longipalpis (Lutz and Neiva, 1912) was incriminated as the principal vector. It is now generally accepted, however, that there exist a number of cryptic species under the name of Lu. longipalpis s.l. and that variations in the quantity of the vasodilatory peptide maxadilan in the saliva of flies from different populations of Lu. longipalpis s.l., may account for the variable clinical manifestations of AVL seen in different geographic regions. Distribution of AVL has been shown to extend throughout most of South and Central America, with the domestic dog serving as the principal reservoir of infection for man. However, while one hypothesis suggests that the causative parasite is Leishmania infantum, imported from Europe with the Portuguese and Spanish colonists, the demonstration of a high rate of benign, inapparent infection in foxes in Amazonian Brazil raised an opposing suggestion that the parasite is indigenous to the Americas. Recent reports of similar infections in native marsupials, and possibly rodents, tend to support this view, particularly as Lu. longipalpis is primordially a silvatic sandfly. Although effective control measures in foci of the disease will diminish the number of canine and human infections, the presence of such an enzootic in a variety of native animals will render the total eradication of AVL unlikely.

Leishmaniose visceral no Brasil: quadro atual, desafios e perspectivas

No Brasil, a importância da leishmaniose visceral reside não somente na sua alta incidência e ampla distribuição, mas também na possibilidade de assumir formas graves e letais quando associada ao quadro de má nutrição e infecções concomitantes. A crescente urbanização da doença ocorrida nos últimos 20 anos coloca em pauta a discussão das estratégias de controle empregadas. Neste artigo foram analisados os principais aspectos biológicos, ambientais e sociais que influenciaram no processo de expansão e urbanização dos focos da doença. Os métodos disponíveis para o diagnóstico e tratamento não apresentam a eficácia e aplicabilidade desejadas, embora avanços promissores tenham sido alcançados com as pesquisas de novos testes diagnósticos e drogas terapêuticas. As medidas de controle da doença até agora implementadas foram incapazes de eliminar a transmissão e impedir a ocorrência de novas epidemias. É feita uma breve análise destas medidas e dos desafios a serem enfrentados. A prevenção da doença nos cães através da imunoprofilaxia aparece como uma alternativa para o controle. Uma nova vacina para cães, já testada em campo, está sendo industrializada e será comercializada no Brasil a partir de 2004. Apesar da existência de inúmeros estudos sobre a leishmaniose visceral humana e canina, muitas lacunas ainda precisam ser preenchidas.

American visceral leishmaniasis: wild animal hosts

In Colombia it has been suggested that the rodent Proechimys canicollis may be a reservoir-host of Leishmania (L.) chagasi, the cause of American visceral leishmaniasis, based on polymerase chain reaction/hybridization tests. We have detected no infection in laboratory-bred specimens of another species, P. guyannensis, after their inoculation with promastigotes or amastigotes of this parasite from Amazonian Brazil.

Susceptibility of spiny rats (Proechimys semispinosus) to Leishmania (Viannia) panamensis and Leishmania (Leishmania) chagasi

The role of Proechimys semispinosus as reservoir of Leishmania (Viannia) panamensis on the Colombian Pacific coast was experimentally evaluated. The susceptibility to L. chagasi also was assessed to determine the utility of this rodent as a model for studying reservoir characteristics in the laboratory. Wild-caught animals were screened for natural trypanosomatid infections, and negative individuals were inoculated intradermally (ID) in the snout or feet with 10(7) promastigotes of L. panamensis. L. chagasi was inoculated intracardially (10(7) promastigotes) or ID in the ear (10(8) promastigotes). PCR-hybridization showed that 15% of 33 spiny rats were naturally infected with L. Viannia sp. Animals experimentally infected with L. panamensis developed non-ulcerated lesions that disappeared by the 7th week post-infection (p.i.) and became more resistant upon reinfection. Infectivity to sand flies was low ((1/2)0-(1/4)8 infected/fed flies) and transient, and both culture and PCR-hybridization showed that L. panamensis was cleared by the 13th week p.i. Animals inoculated with L. chagasi became subclinically infected and were non-infective to sand flies. Transient infectivity to vectors of spiny rats infected with L. panamensis, combined with population characteristics, e.g., abundance, exploitation of degraded habitats and high reproductive rates, could make them epidemiologically suitable reservoirs.

Canine visceral leishmaniasis: dog infectivity to sand flies from non-endemic areas

Canine visceral leishmaniasis (VL), caused by Leishmania infantum (Leishmania chagasi in the New World), is a zoonotic, endemic disease in Western Europe and Latin America. The potential spreading to new regions was suggested by the appearance of canine VL among foxhounds in the US. Although the sand fly vectors in the major foci of transmission have been described, no information exists on other sand flies that could propagate the infection outside endemic areas. We evaluated the capacity of Lutzomyia shannoni (Dyar) and Lutomyia youngi (Feliciangeli & Murillo), which are widely distributed in the New World, to acquire L chagasi (Cunha and Chagas) infections. A high proportion of L youngi were infected after feeding on an oligosymptomatic dog (51 per cent) or a polysymptomatic individual (95 per cent), but the intensity of infection was low (< 200 promastigotes/fly). L shannoni became infected only by feeding on the polysymptomatic dog, and the infection rate was lower (9 per cent) than in Lutzomyia longipalpis (36 per cent), and Lutzomyia evansi (Nunez-Tovar) (Lutz and Neiva) (38 per cent), but the intensity of infection (200 to > 500 promastigotes/fly) was comparable (L longipalpis) or higher (L evansi) than in the New World vectors. It is hypothesised that the presence of infected dogs in areas where L shannoni or L youngi occur could initiate new endemic cycles of VL in both South and North America.

Gene flow between natural and domestic populations of Lutzomyia longipalpis (Diptera: Psychodidae) in a restricted focus of American visceral leishmaniasis in Venezuela

The epidemiology of the visceral leishmaniasis in the Americas is associated with both a natural and a domestic cycle. The existence of reproductively isolated populations of Lutzomyia longipalpis (Lutz & Neiva), and the scarcity of records of this species from natural habitats in areas where it has been associated with domestic habitats indicated that natural populations could be genetically distinct from domestic ones. Therefore, we compared the genetic structure and estimated the gene flow between L. longipalpis from domestic and peridomestic habitat and from an adjacent undisturbed natural environment along a 1.2-km transect. The analyses were performed on electrophoretic data from eight isozyme loci. The absence of fixed differences in the diagnostic loci Ak and Hk indicated that all specimens belonged to one of the two cryptic species identified in Venezuela. The average number of alleles per locus ranged from 2.0 to 2.9 and the average heterozygosity ranged from 7.8 to 13.4%. No differences were detected in the genetic structure of this species from domestic or peridomestic habitats and those trapped as far as 1.2 km from human dwellings. Nm, estimated from Wright's Fst, indicated that at least 208 individuals per generation migrated between the peridomestic habitat and a 1.2-km distant point to maintain the observed similarities in allelic frequencies. This high rate of gene flow indicated that this species has high migration rates between domestic and natural environments, and has the potential to transport for Leishmania from natural to domestic environments.

[Notes on fleas (Siphonaptera) of the fox Cerdocyon thous (Canidae) from an endemic area of visceral leishmaniasis in Jacobina, Bahia, Brazil]

From July to September of 1998, 152 fleas were collected from 18 specimens of the fox Cerdocyon thous captured in the visceral leishmaniasis endemic area of Jacobina, State of Bahia, Brazil. The fleas were identified as: 136 Rhopalopsyllus lutzi lutzi, 11 Pulex irritans, 2 Ctenocephalides canis, 1 Ctenocephalides felis felis and 2 Xenopsylla cheopis.

Dynamics of Leishmania chagasi infection in small mammals of the undisturbed and degraded tropical dry forests of northern Colombia

The infection rate with Leishmania chagasi and the population dynamics of small mammals were studied in an undisturbed forest reserve (Colosó) and an area of highly degraded forest (San Andrés de Sotavento [SAS]) in northern Colombia, both endemic for visceral leishmaniasis. Live trapping of mammals was done every month, and species, age, sex and reproductive status determined. L. chagasi was detected in samples of skin or spleen by the polymerase chain reaction, after extraction of deoxyribonucleic acid using specific primers (DB8/AJS3), and dot blood hybridization. Didelphis marsupialis was found to be infected in Colosó (3/21, 14.3%) and SAS (13/137, 9.5%); its relative abundance was higher in SAS (93/113, 82% of the captures). Although Proechimys canicollis was also found to be infected in Colosó (3/34, 8.8%) and SAS (2/4), its relative abundance was much lower (4%) in SAS than in Colosó (56% of 77 animals captured). Sciurus granatensis, Marmosa robinsoni, Heteromys anomalus, Zygodontomys brevicauda and Metachirus nudicaudatus were less common, and no L. chagasi infection was detected in them.

Ecological interactions of visceral leishmaniasis in the state of Bahia, Brazil

The laboratory and field observations summarized in this paper on visceral leishmaniasis ecology in the State of Bahia, Brazil are based on the author's observations over the past 35 years in a number of state's foci, public health records and literature citations. The disease is endemic with epidemic outbreaks occurring every ten years and its geographical distribution is expanding rapidly in the last years. Leishmania chagasi is the main ethiologic agent of the visceral leishmaniasis but Le. amazonensis s. lato was the only leishmania isolated by other authors from some visceral leishmaniasis human cases in the state. Lutzomyia longipalpis (with one or two spots on tergites III and IV and two sized different populations) was epidemiologically incriminated as the main vector. It was found naturally infected with promastigotes, and it was infected with four species of leishmanias in the laboratory. Although the experimental transmission of Le. amazonensis by the bite of Lu. longipalpis to hamsters was performed, the author was not successful in transmitting Le. chagasi in the same way. The dog is the most important domestic source for infection of the vector, however it is not a primary reservoir. The opossum Didelphis albiventris was found naturally infected with Le. chagasi but its role as reservoir is unknown. Foxes and rodents were not found infected with leishmanias in Bahia.

Visceral leishmaniasis in the hoary zorro Dusicyon vetulus: a case of mistaken identity

The historical identification of the Brazilian 'north-eastern' zorro as Dusicyon vetulus is questioned in relation to its incrimination as a reservoir of Leishmania chagasi, the agent of American visceral leishmaniasis. Comparative cranial and dental morphology showed that specimens of this north-eastern species more closely resemble the crab-eating zorro Cerdocyon thous, conforming with the documented geographical ranges of the respective species. We conclude that the single 'wild' canid host of L. chagasi in the neotropics in C. thous.

Epidemiology of canine leishmaniasis: a comparative serological study of dogs and foxes in Amazon Brazil

The paper describes a longitudinal field study of canine leishmaniasis in sympatric domestic dog and crab-eating fox (Cerdocyon thous) populations. Dogs were studied in house-to-house surveys, and foxes were studied by live-trapping and radio-telemetry. Because serological tests (IFAT in this case) for leishmaniasis are often of uncertain sensitivity and specificity, we draw conclusions comparatively. Both cross-sectional (age-prevalence) and longitudinal analyses indicate that incidence in dogs was highest in the dry season. Seasonal changes in the age-prevalence relationship for dogs suggest that serological conversion and recovery rates decline with prior exposure to infection, where 'recovery' may be due to loss of a positive antibody titre or death from leishmaniasis. The mean incidence in dogs was higher in the rural than in the urban population and higher in hunting dogs than pet dogs. Cross-sectional and longitudinal analyses of fox serological data suggest that foxes remain positive for longer than dogs on average, either because detectable antibody is more persistent or because they experience a lower mortality rate due to leishmaniasis.

Response of adult sandflies, Lutzomyia longipalpis (Diptera: Psychodidae), to sticky traps baited with host odour and tested in the laboratory

The responses of adult Lutzomyia longipalpis Lutz and Neiva to sticky traps baited with entrained volatiles from a hamster were assessed in the laboratory. In a two-choice test, significantly more females and males were caught on odour-baited sticky traps than on control traps, and only a few adults remained alive and untrapped at the end of the experiments. In contrast, significantly fewer flies of both sexes were caught in a series of tests where both traps were unbaited. Twice as many males as females were caught in the control traps in the tests with odour, an observation in accordance with known male lekking behaviour around hosts. The results show that sandflies of both sexes are attracted to traps by host odour alone, in the absence of any other host cues or pheromones from the male flies.

Tegumentary and visceral leishmaniases in Brazil: emerging anthropozoonosis and possibilities for their control

The existence of a number of different species of Leishmania, the persistent increase in the infection rate of diseases caused by this parasite (tegumentary and visceral forms), the different epidemiological situations found in regions of both recent and older colonization, and the trend towards urbanization have led to the adoption of different strategies to control leishmaniases in Brazil. The control measures involve studies related to the parasite, vectors, sources of infection (animal and human), clinical aspects, geographical distribution, historical and socioeconomic factors, integration of health services, and adequate technologies for diagnosis, treatment, and immunoprophylaxis. Finally, successful control requires work with human communities, involving education, provision of information, health promotion, and participation of these communities in the planning, development, and maintenance of control programs.

Serological diagnosis of leishmaniasis: on detecting infection as well as disease

Serological tests are very frequently used in epidemiological surveys of leishmaniasis and other parasitoses. Their sensitivity and specificity are generally defined with respect to parasitism and disease, rather than infection. The reason is that known positives are those individuals most likely to yield parasites, or who have distinctive clinical signs, and concomitantly high antibody titres. This paper investigates the performance of one serological method, the indirect fluorescent antibody test (IFAT), in detecting Leishmania infantum infection during an intensive 2-year cohort study of dogs in southern France. The results show that sensitivity and specificity with respect to infection can be simultaneously high, but maximum sensitivity is probably < 80%, and lasts for a relatively short period of 2-3 months after a lengthy incubation period. The IFAT gave the incidence of infection as 18-65% in the first year, whereas the best estimate of incidence based on parasite isolation and clinical observation was 72%. But data from the second year suggest that the 72% was itself an underestimate. We argue that, during epidemiological surveys, the IFAT in particular, and serological tests for leishmania in general, will underestimate prevalence, incidence and hence the scale of the control problem. However, there is evidence that tests for canine leishmaniasis employing high threshold titres will identify the most infectious animals, allowing selective treatment or culling of those which contribute disproportionately to transmission.

Avaliação de três esquemas terapêuticos com o antimoniato de N-metil-glucamina no tratamento da leishmaniose visceral no estado do Pará, Brasil

Avaliaram-se, de forma retrospectiva, três esquemas terapêuticos à base do antimoniato de N-metil-glucamina (Glucantime) usados no tratamento de 43 casos autóctones de leishmaniose visceral (Estado do Pará), observados em crianças de 1 a 12 anos de idade, no período de 1985 a 1990. Dos 43 casos, 28 (grupo A) foram tratados com 40 mg/SbV/kg administrados IV a intervalos de 48 hs, em séries de 15 doses (esquema I); 8 (grupo B) receberam 40mg/SbV/kg administrados IV diariamente, durante 15 dias (esquema II), e 7 (grupo C) receberam 20 mg/SbV/kg administrados IV diariamente, durante 15 dias (esquema III). Considerando que o controle de cura da doença foi essencialmente clínico, admitiu-se que o esquema III representaria a melhor opção terapêutica, em razão de: a) ter promovido taxa de cura equivalente aos esquemas que usaram o dobro dessa dose, b) a relação custo-benefício desse esquema torna-o menos dispendioso, c) pode ser usado durante período mais prolongado, com menor risco de produzir efeitos de toxicidade, e d) não existem, a nível local (Pará), relatos de casos de resistência da doença associados ao uso desse esquema.

Mathematical modelling and theory for estimating the basic reproduction number of canine leishmaniasis

The paper describes a mathematical model for canine leishmaniasis and presents formulae which can be used to estimate the basic reproduction number, R0. The primary concern has been to devise methods of estimation which make best use of those data most easily obtained by fieldwork, e.g. surveys of prevalence in dog (by age) and sandfly populations. A range of formulae are offered which are more or less demanding of data, and which consequently give more or less precise estimates of R0. They include methods for assessing the influence on R0 of heterogeneous biting rates of sandflies on dogs, in which the essence of heterogeneous transmission can be captured merely by measuring relative rather than absolute contact rates.