Leishmania parasites expose phosphatidylserine (PS) on their surface, a process that has been associated with regulation of host's immune responses. In this study we demonstrate that PS exposure by metacyclic promastigotes of Leishmania amazonensis favours blood coagulation. L. amazonensis accelerates in vitro coagulation of human plasma. In addition, L. amazonensis supports the assembly of the prothrombinase complex, thus promoting thrombin formation. This process was reversed by annexin V which blocks PS binding sites. During blood meal, Lutzomyia longipalpis sandfly inject saliva in the bite site, which has a series of pharmacologically active compounds that inhibit blood coagulation. Since saliva and parasites are co-injected in the host during natural transmission, we evaluated the anticoagulant properties of sandfly saliva in counteracting the procoagulant activity of L. amazonensis . Lu. longipalpis saliva reverses plasma clotting promoted by promastigotes. It also inhibits thrombin formation by the prothrombinase complex assembled either in phosphatidylcholine (PC)/PS vesicles or in L. amazonensis . Sandfly saliva inhibits factor X activation by the intrinsic tenase complex assembled on PC/PS vesicles and blocks factor Xa catalytic activity. Altogether our results show that metacyclic promastigotes of L. amazonensis are procoagulant due to PS exposure. Notably, this effect is efficiently counteracted by sandfly saliva.

The number of visceral leishmaniasis (VL) cases has increased over the past 10 years in Brazil, especially in the North and Northeast regions of the country. The aim of this study was to evaluate the urbanisation of VL vectors in Barcarena, Pará, an area in northern Brazil where VL is endemic. Sandflies were captured using Centers for Disease Control (CDC) light traps along an urban-rural gradient. The CDC traps were installed inside hen houses at a height of 150 cm. A total of 5,089 sandflies were collected and 11 species were identified. The predominant species was Lutzomyia longipalpis (rate of 95.15%), which suggests its participation in the transmission of VL. A total of 1,451 Lu. longipalpis females were dissected and no Leishmania infections were detected. Most of the sandflies were captured at the border of a forest (88.25%) and no flies were captured in the urban area, which suggests that transmission is still restricted to rural sites. However, the fact that a specimen was collected in an intermediate area indicates that urbanisation is a real possibility and that vector monitoring is important.

A actinomicose oronasal é uma infecção raramente descrita na literatura, especialmente na forma de coinfecção com tuberculose pulmonar. Descrevemos o caso de um paciente de 48 anos de idade, admitido em enfermaria de isolamento por tuberculose pulmonar bacilífera, com história de diabetes e alcoolismo. Durante a internação, o paciente referiu queixas de disfagia e regurgitação alimentar por via nasal. O exame da cavidade oral revelou uma fístula oronasal. O agente infeccioso foi identificado, e o tratamento foi realizado com sucesso. Apresentamos também uma breve revisão da literatura e uma descrição e discussão completa do processo de investigação deste raro caso clínico.

Oronasal actinomycosis is an infection seldom described in the literature, especially in the form of a co-infection with pulmonary tuberculosis. We report the case of a 48-year-old male admitted to the isolation ward due to active pulmonary tuberculosis, with a history of diabetes and alcohol abuse. While hospitalized, the patient complained of dysphagia and nasal regurgitation of food. The examination of the oral cavity revealed an oronasal fistula. The infecting agent was identified, and the treatment was successful. We also present a brief review of the literature, as well as a full description and discussion of the process of investigating this rare clinical case.