How do bats maintain infections? Mathematical modelling to disentangle mechanisms driving the temporal cycles of infection in Australian bats

Zoonotic pathogens, (pathogens that can be transmitted from animals to humans), repre-sent an increasing public health concern. Cross-species transmission can only occur when particular conditions of reservoir host ecology, infection dynamics and species distribu-tions align, making spillovers (the transmission of a pathogen from a vertebrate animal to a human) at the same time a global public health concern and a complex and poorly under-stood phenomenon. Pathogen circulation in reservoir host populations is one of the fac-tors contributing to spillover risk, therefore, understanding the mechanisms driving infec-tion dynamics can help us in preventing spillovers to occur. In Australia, the recent changes in land use caused a rapid modification in bat behaviour that coincided with the emergence of Hendra virus (HeV). HeV is maintained in wildlife by bats of the Pteropus genus (flying foxes) and can be transmitted from bats to horses and from horses to humans. Bats do not show marked signs of infection, but in humans and horses the symptomatology is very severe, with a high fatality rate (57% and 80% re-spectively), pointing out the need to avoid HeV spillovers. HeV spillovers usually occur in winter and often coincide with an increase in viral shedding in urines from bats, sug-gesting a temporal trend in pathogen circulation in reservoir host populations. Several fac-tors can contribute to drive the observed temporal dynamics, and different maintenance routes have been theoretically hypothesized to explain the cyclicity of infection. To disentangle the mechanisms driving the pathogen dynamics in reservoir host, we ap-plied a set of mathematical models to an historical dataset collected in Boonah (Queens-land, Australia) between July 2013 and June 2014. We used a system of four differential equations (SEIR model type) to simulate infection dynamics in the host population, and we included time dependent parameters to simulate the seasonality of infection and perio-dicity of births. We showed that the sole population dynamic of bats, with the introduction in the system of susceptible new-borns, can not explain the annual cycles of HeV shedding, and either a waning of the immunity in adult bats or the development of a chronic infection with cyclic viral reactivation must be hypothesized to explain the observed infection dynamics. Our results support the hypothesis that cyclicity in HeV shedding can be driven by envi-ronmental stressors, like winter food shortages, that can affect bat immune response to pathogens. These findings evidence the need to reduce anthropogenic stressors that might exacerbate HeV shedding from bats. Furthermore, given the adaptability of the modelling framework, the method proposed can be applied to other infections/bat species

Lost and found : Helminths infecting invasive raccoons introduced to Italy

North American raccoons (Procyon lotor) have been introduced to several European countries, where they may represent a sanitary threat as hosts of several pathogens such as the zoonotic ascarid Baylisascaris procyonis. We carried out parasitological analysis on raccoons introduced to Italy to verify whether the species had carried along B. procyonis or any other gastro-intestinal helminths that may threaten humans, livestock or native wildlife. We examined 64 raccoons culled in Northern Italy during control activities and 3 roadkills opportunistically sampled from a separate population located in central Italy. Helminths were collected from the gastro-intestinal tract through standard parasitological techniques and identified based on a combination of morphology and molecular methods. Overall, examined raccoons showed a poor parasitic fauna, with almost 30% of individuals free of any helminth infection. The most prevalent species were the nematodes Strongyloides procyonis (26.9%), Aonchotheca putorii (25.4%) and Porrocaecum sp. (19.4%). Plagiorchis sp. trematodes were also common (13.4%), whereas cestodes were scarcely represented. With the exception of S. procyonis introduced from North America, all the other identified taxa have either a Eurasian or a wide Holarctic distribution. Despite not finding any B. procyonis in the examined raccoons, passive surveillance for this parasite should be implemented, especially in Tuscany, since the limited host sample examined in the present survey does not allow to exclude its presence

Healthy invaders do it better: loss of parasites in mammals introduced to Italy

With Lusophone African studies gaining significant prominence in academe, this volume is a welcome addition to the field. It contributes a debate on short story writing in Mozambique within the framework of the country’s internal tensions, social and political. The book is divided into three sections. Part I, “O conto: espaços e linguagens”, opens with a brief account of the emergence and evolution of the short story in Europe and South America, and then concentrates on an assessment of the p..

Valutazione dell’efficacia delle strategie di intervento per il controllo delle malattie infettive attraverso la simulazione matematica della dinamica di infezione

Introduzione Le strategie di gestione sanitaria delle infezioni sono disparate, variano tra loro per efficacia, costo e realizzabilit\ue0, ma in molti casi manca un\u2019analisi comparativa e sistematica della loro efficacia e questa mancanza rende controversa la scelta della migliore strategia per la gestione sanitaria di un\u2019infezione. L\u2019utilizzo di modelli matematici, permettendo la simulazione a priori della dinamica delle infezioni in diversi scenari, consente un\u2019analisi sistematica degli effetti degli interventi sulle popolazioni di interesse, e rappresenta uno strumento efficace per le scelte di gestione sanitaria. Un esempio di infezione la cui gestione sanitaria \ue8 ancora dibattuta \ue8 Baylisascaris procyonis, un elminta il cui ospite definitivo \ue8 il procione (Procyon lotor). L\u2019ingestione delle forme infettanti di B. procyonis da parte dell\u2019uomo pu\uf2 essere causa di sindrome da larva migrans, ad esito anche fatale, ma ad oggi non esiste una strategia d\u2019intervento d\u2019elezione per questa infezione. Le strategie attualmente prese in considerazione spaziano dalla rimozione dei procioni infetti, alla rimozione delle feci dall\u2019ambiente, al trattamento antiparassitario degli animali. Obiettivi Per effettuare una corretta valutazione a priori dell'efficacia delle suddette strategie, \ue8 stato sviluppato un modello matematico per lo studio della dinamica di B. procyonis, simulando l'effetto dei diversi interventi. Metodi \uc8 stato innanzitutto elaborato un modello deterministico di tre equazioni differenziali, adattato all\u2019interazione tra le popolazioni ospite (procione) e parassita (adulti e fase infettante di B. procyonis). Sono stati poi simulati i tre tipi di intervento gestionale (depopolamento, somministrazione di antielmintici e rimozione di feci dall\u2019ambiente), dei quali \ue8 stato valutato l\u2019effetto sull'infestazione ambientale delle forme infettanti. Le simulazioni sono state adattate a due diversi scenari, il caso di una popolazione parassitaria stabilizzata, e quello di una popolazione parassitaria in espansione. Risultati Le simulazioni hanno evidenziato come il metodo pi\uf9 rapido per l'eliminazione delle forme infettanti dall\u2019ambiente sia la rimozione delle feci, ma come questo metodo necessiti di un grande sforzo di intervento per ottenere il risultato desiderato. La somministrazione di antielmintici e la rimozione dei procioni dall\u2019area di intervento risultano invece pi\uf9 lenti nell\u2019eliminare le forme infettanti, ma quest'ultima strategia permette il conseguimento del risultato con un minor sforzo, risultando quindi l'intervento pi\uf9 idoneo. Conclusioni I risultati ottenuti evidenziano come l\u2019utilizzo di un modello matematico rappresenti un valido strumento per la valutazione a priori dell'efficacia e dell'applicabilit\ue0 delle strategie di gestione sanitaria delle infezioni, permettendo l'individuazione della tipologia di intervento pi\uf9 adatta in base alle risorse disponibili e alle tempistiche desiderate

How to choose the best control strategy? Mathematical models as a tool for pre-intervention evaluation on a macroparasitic disease

During the last century, emerging diseases have increased in number, posing a severe threat for human health. Zoonoses, in particular, represent the 60% of emerging diseases, and are a big challenge for public health due to the complexity of their dynamics. Mathematical models, by allowing an a priori analysis of dynamic systems and the simulation of different scenarios at once, may represent an efficient tool for the determination of factors and phenomena involved in zoonotic infection cycles, but are often underexploited in public health. In this context, we developed a deterministic mathematical model to compare the efficacy of different intervention strategies aimed at reducing environmental contamination by macroparasites, using raccoons (Procyon lotor) and their zoonotic parasite Bayilsascaris procyonis as a model system. The three intervention strategies simulated are raccoon depopulation, anthelmintic treatment of raccoons and faeces removal. Our results show that all these strategies are able to eliminate the parasite egg population from the environment, but they are effective only above specific threshold coverages. Host removal and anthelmintic treatment showed the fastest results in eliminating the egg population, but anthelmintic treatment requires a higher effort to reach an effective result compared to host removal. Our simulations show that mathematical models can help to shed light on the dynamics of communicable infectious diseases, and give specific guidelines to contain B. procyonis environmental contamination in native, as well as in new, areas of parasite emergence. In particular, the present study highlights that identifying in advance the appropriate treatment coverage is fundamental to achieve the desired results, allowing for the implementation of cost- and time-effective intervention strategies