Odour of domestic dogs infected with Leishmania infantum is attractive to female but not male sand flies: Evidence for parasite manipulation.

Globally visceral leishmaniasis (VL) causes thousands of human deaths every year. In South America, the etiologic agent, Leishmania infantum, is transmitted from an infected canine reservoir to human hosts by the bite of the sand fly vector; predominantly Lutzomyia longipalpis. Previous evidence from model rodent systems have suggested that the odour of infected hosts is altered by the parasite making them more attractive to the vector leading to an increased biting rate and improved transmission prospects for the pathogen. However, there has been no assessment of the effect of Le infantum infection on the attractiveness of dogs, which are the natural reservoirs for human infection. Hair collected from infected and uninfected dogs residing in a VL endemic city in Brazil was entrained to collect the volatile chemical odours present in the headspace. Female and male Lu. longipalpis sand flies were offered a choice of odour entrained from infected and uninfected dogs in a series of behavioural experiments. Odour of uninfected dogs was equally attractive to male or female Lu. longipalpis when compared to a solvent control. Female Lu. longipalpis were significantly more attracted to infected dog odour than uninfected dog odour in all 15 experimental replicates (average 45.7±0.87 females attracted to infected odour; 23.9±0.82 to uninfected odour; paired T-test, P = 0.000). Male Lu. longipalpis did not significantly prefer either infected or uninfected odour (average 36.1±0.4 males to infected odour; 35.7±0.6 to uninfected odour; paired T-test, P = 0.722). A significantly greater proportion of females chose the infected dog odour compared to the males (paired T-test, P = 0.000). The results showed that the odour of dogs infected with Le. infantum was significantly more attractive to blood-seeking female sand flies than it was to male sand flies. This is strong evidence for parasite manipulation of the host odour in a natural transmission system and indicates that infected dogs may have a disproportionate significance in maintaining infection in the canine and human population.

Ocular manifestations of leishmaniasis in a cat: first case report from Brazil / Manifestações oculares da leishmaniose em um gato: primeiro relato de caso do Brasil

An 8-year-old domestic short hair female cat initially presented with bilateral uveitis with pseudotumoral appearance. The patient tested negative for feline immunodeficiency virus (FIV), feline leukemia virus (FeLV) and Toxoplasma gondii. Histopathology of a granulomatous lesion on the upper left conjunctiva revealed amastigotes compatible with Leishmania spp. Aqueous humor was aspired and the diagnosis was confirmed after isolation of promastigotes cultivated in biphasic NNN medium and by positive polymerase chain reaction (PCR) for Leishmania infantum. Treatment with allopurinol (10mg/kg/ BID/PO) was commenced and a natural insect repellent was prescribed. Six months of treatment with allopurinol associated with the initial topical medications helped to improve ocular signs. Leishmaniasis should be considered as a differential diagnosis in cats presenting uveitis with pseudotumoral appearance. To our knowledge, this is the first report of feline leishmaniasis with ocular manifestation in Brazil, in which diagnosis was confirmed by aqueous humor analysis.(AU)

Uma gata, sem raça definida, de oito anos de idade, foi atendida inicialmente com uveíte bilateral, com aparência pseudotumoral em íris. Foi realizado teste para o vírus da imunodeficiência felina (FIV), da leucemia felina (FeLV) e de Toxoplasma gondii, obtendo-se resultados negativos. O exame histopatológico da conjuntiva superior do olho esquerdo revelou amastigotas compatíveis com Leishmania spp. Foi realizada paracentese, e promastigotas foram isoladas no humor aquoso, cultivadas em meio NNN bifásica. Reação em cadeia da polimerase (PCR) confirmou diagnóstico positivo para Leishmania infantum. Tratamento com alopurinol (10mg/kg/BID/PO) foi iniciado, e um repelente natural de insetos foi prescrito. Seis meses de tratamento com alopurinol associado aos medicamentos tópicos iniciais ajudaram a melhorar os sinais oculares. Leishmaniose deve ser considerada como um diagnóstico diferencial nos gatos que apresentam uveíte com aparência pseudotumoral de íris. Até o presente momento, este é o primeiro relato de leishmaniose felina com manifestação exclusivamente ocular da doença no Brasil cujo diagnóstico foi confirmado por meio de análise de humor aquoso.(AU)

Análisis cuantitativo del crecimiento y cambio morfométrico en poblaciones de Leishmania chagasi y Trypanosoma cruzi mantenidos en cultivos axénicos puros y mixtos / Quantitative approach to the analysis of the growth and morphometric change in populations of Leishmania chagasi and Trypanosoma cruzi maintained in pure and mixed axenic cultures

Las relaciones que se establecen entre géneros de la familia trypanosomatidae en condiciones de coexistencia en el mismo medioambiente pueden estar vinculadas a respuestas compensatorias inter-poblacionales que incluyen cambios morfológicos (diferentes estadios) y morfométricos (diferencias mensurables). El análisis cuantitativo de tales respuestas en cultivos axénicos puros de Leishmania chagasi y trypanosoma cruzi, así como en isomezclas axénicas de L. chagasi-T. cruzi mantenidas in vitro, no ha sido abordado, desconociéndose por lo tanto, particularidades biológicas. Muestras interdiarias de cultivo se fijaron, colorearon, observaron, digitalizaron y procesaron cuantitativamente. Además de cuantificar las densidades poblacionales, se registraron las magnitudes numéricas de variables morfométricas que, posteriormente, se analizaron con herramientas estadísticas. Los resultados indicaron cambios específicos en las variables investigadas, así como heterogeneidad morfométrica entre los mismos morfotipos de los mismos géneros al ser mantenidos en cultivos puros o mixtos. Los modelos de cambio morfométrico de L. chagasi y T. cruzi en cultivos puros difieren de los modelos de cambio morfométrico en los cultivos mixtos (L. chagasi-T. cruzi). Las metodologías biométricas discriminan, en términos morfométricos, poblaciones del mismo estadio (morfotipo) en ambientes diferentes.

The relations established among genera of the Trypanosomatidae family in coexisting conditions in the same environment may be linked to inter-population compensatory answers that include morphological (differences among stages) and morphometrical (measurable difference) changes. The quantitative analysis of these answers in Leishmania chagasi and Trypanosoma cruzi pure axenic cultures, as well as in L. chagasi - T. cruzi axenic iso-mixtures in vitro maintained has not been approached, and consequently, potentially useful biological particularities in the control of these important human parasites are unknown. Every other day culture samples were fixed, stained, observed, digitalized and quantitatively processed. In addition to quantify, the population densities and the appearance-disappearance stage (morphotypes) dynamics, the numeric magnitudes of the morphometric variables were recorded and later analyzed with multivariate statistical techniques. The results indicate specific changes in the investigated variables, as well as morphometric heterogeneity between the same morphotypes of the same genera when maintained in pure or mixed cultivation. The morphometric change models for L. chagasi and T. cruzi in pure culture differ from the models of morphometric change in mixed cultivation (L. chagasi-T. cruzi). The biometric methodologies discriminate in morphometric terms populations of the same stage (morfotype) in different environments.

Leishmania (Leishmania) chagasi interactions with Serratia marcescens: ultrastructural studies, lysis and carbohydrate effects.

Studies on the lysis of L. chagasi caused by the bacteria Serratia marcescens were carried out. In vitro experiments demonstrated that S. marcescens variant SM 365, a prodigiosin pigment producer, lysed this species of Leishmania but variant DB11, a nonpigmented bacteria, was unable to lyse the parasite. High concentrations of d-mannose were found to protect L. chagasi markedly diminishing the lysis by S. marcescens SM 365. Promastigotes of L. chagasi bound the lectin Concanavalin A conjugated with FITC, the fluorescence was intensely found at the base of the flagellum (flagellar pocket). Scanning electron microscopy revealed that the bacteria adherence occurred mainly in the flagellar pocket. S. marcescens SM 365 formed filamentous structures, identified as biofilms, which connect the protozoan to the developing bacterial clusters, in low concentrations of bacteria after 30 min incubation time. We suggest that bacterial mannose-sensitive (MS) fimbriae are relevant to S. marcescens SM 365 in the lysis of L. chagasi.