DDI - Teses de doutoramento
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- Borrelia lusitaniae and Lyme borreliosis in Portugal: a contribution to the study of an emerging bacterial zoonosis with an impact on public healthPublication . Lopes de Carvalho, Isabel; Núncio, Maria Sofia; Carolino, M. ManuelaLyme borreliosis, is a tick-borne disease caused by Borrelia burgdorferi sensu lato, that is considered an emerging disease in some regions of the world, namely in Portugal. The B. burgdorferi s. l. complex includes 16 different species that are transmitted to the vertebrate host by the tick vector. The principal vector in Europe is Ixodes ricinus. LB is a multisystem disease involving many organs such as the skin, the nervous system, the joints, and the heart. The main goal of this project is to examine specific biological and molecular aspects of B. lusitaniae. The aims of this dissertation are divided into two main topics: Human infection and the eco-epidemiological study of B. burgdorferi s.l. in Portugal. Although LB is a mandatorily notifiable disease in Portugal, the evaluation of CEVDI/INSA data concerning human cases and the number of notified cases shows that this disease is clearly underreported in Portugal. In the period of 1999-2004, the estimated incidence was 0.4 per 100 000 inhabitants, which is relatively low when compared with some endemic countries. In this work it was reported an isolation of B. lusitaniae from a human patient presenting with a vasculitis-like syndrome that confirm the patogenicity of this genospecies. This clinical report supports also the hypothesis that the clinical manifestations associated with infection by B. lusitaniae include some clinical symptoms until this moment considered unspecific for LB. In a prospective study, twelve patients with clinical diagnostic of LB were analysed and enabled the first detection of B. afzelii DNA in a patient with neurological symptoms. A survey of ixodid ticks collected in Madeira Island and southern region revealed that both are hotspot regions for the presence of B. lusitaniae, however other Borrelia genospecies were detected in Madeira Island. Moreover, Ixodes ricinus species was confirmed as the principal vector of this zoonosis in Portugal. Other species such as Dermacentor marginatus were found to contain Borrelia DNA, but the ability of this tick to transmit B. burgdorferi is unknown. The sequences analysis of the isolates obtained from ticks from the southern region reveal that some recombinants strains are present which could indicate that an intersection in the allelic profiles of the B. lusitaniae populations exists. In this dissertation is also described the first report of dual infections of Rickettsia helvetica, R. monacensis and R. slovaca, each of which infected with B. lusitaniae, highlighting the increased likelihood of infection by multiple agents to humans. Concerning the study on migratory shorebirds the detection of B. garinii DNA was observed in three different genera (black-tailed godwits Limosa l. limosa, Icelandic black-tailed godwit Limosa l. islandica and little stints Calidris minuta) and also Francisella tularensis subsp. holarctica DNA in a little stint. The studies conducted in animal species prove the involvement of the small mammals, Apodemus sylvaticus, as a potential reservoir of B. lusitaniae with the first isolate from this animal species. Seropositive samples were obtained from M. spretus and R. rattus species. Phylogenetic analyses grouped this new isolate near other B. lusitaniae strains isolated within this dissertation and most closely aligned to the North African clade. Furthermore the importance of lizards (Teira dugessi) in the maintenance of B. burgdorferi s.l. was confirmed. Potential B. valaisiana isolation from lizard tissues and detection on parasitizing ticks was reported for the first time, but this observation needs conformation. B. lusitaniae DNA was also detected in lizard tissues and in ticks that are collected from them. However, the sequence data from lizards’ isolation suggest the co-existence of B. lusitaniae. This data indicates that there may exist a sylvatic cycle specific to the B. lusitaniae, maintained by a variety of hosts and reservoirs. Many aspects introduced and explored in this work will require more detailed investigations. However, this dissertation contributes to clarify some important epidemiological aspects of the clinical and laboratorial diagnosis of LB, a disease with impact in public health in Portugal.