Search

Leishmaniases are a spectrum of diseases caused by protozoans from the genus Leishmania(Kinetoplastida: Trypanosomatidae) and are divided into 2 main clinical forms: tegumentary leishmaniasis (TL) and visceral leishmaniasis (VL). Transmission occurs after the bite of sandfly vectors (Diptera: Phlebotominae) when females take a blood meal from the vertebrate host [1]. In the New World, several species of Leishmania (~20) cause disease to man, the symptoms and epidemiology of which vary depending on species. However, there are species that are nonpathogenic to humans, such as L. enriettii. In 1946, Medina observed ear lesions in 2 farm-reared guinea pigs (Cavia porcellus [Rodentia: Cavida]) from the neighboring state of Sao Paulo. After lesion analysis, Leishmania was confirmed as the pathogen. The complete L. enriettii description was published by Muniz and Medina in 1948 at the Federal University of Parana, Brazil [2]. Although this species has been used as a model for cutaneous leishmaniasis (CL), many aspects of its biology remain unknown. In the past 6 years, an increased interest has emerged after the finding of a similar isolate in the red kangaroo (Macrofus rufus) in Australia [3]. This article aims to summarize some of the most important publications on this unique pathogen. It demonstrates a high phenotypic plasticity, being able to infect different vertebrate hosts and vectors. It also discusses recent human and veterinary infections due to other L. enriettii complex members.

Host-range shifts in influenza virus are a major risk factor for pandemics. A key question in the study of emerging zoonoses is how the evolution of transmission efficiency interacts with heterogeneity in contact patterns in the new host species, as this interplay influences disease dynamics and prospects for control. Here we use a synergistic mixture of models and data to tease apart the evolutionary and demographic processes controlling a host-range shift in equine H3N8-derived canine influenza virus (CIV). CIV has experienced 15 years of continuous transfer among dogs in the United States, but maintains a patchy distribution, characterized by sporadic short-lived outbreaks coupled with endemic hotspots in large animal shelters. We show that CIV has a high reproductive potential in these facilities (mean R0 = 3.9) and that these hotspots act as refugia from the sparsely connected majority of the dog population. Intriguingly, CIV has evolved a transmission efficiency that closely matches the minimum required to persist in these refugia, leaving it poised on the extinction/invasion threshold of the host contact network. Corresponding phylogenetic analyses show strong geographic clustering in three US regions, and that the effective reproductive number of the virus (Re) in the general dog population is close to 1.0. Our results highlight the critical role of host contact structure in CIV dynamics, and show how host contact networks could shape the evolution of pathogen transmission efficiency. Importantly, efficient control measures could eradicate the virus, in turn minimizing the risk of future sustained transmission among companion dogs that could represent a potential new axis to the human-animal interface for influenza., Author Summary Influenza virus infects a range of vertebrate hosts, including domesticated animals as well as humans. Some of the most serious influenza pandemics in humans have involved host range shifts, when an influenza virus jumps from one host species to another. Importantly, however, host range shifts do not always cause pandemics. Rather, epidemiological patterns tend to be unpredictable in new host species, causing disease patterns that change over space and time. In this paper, we analyze epidemiological and evolutionary dynamics of canine influenza virus (CIV), which jumped to dogs in the late 1990s from an equine strain (EIV) prevalent in horses. We show that the epidemiology and evolution of CIV is strongly influenced by heterogeneous patterns of infectious contact among dogs in the US. A few large populations in metropolitan animal shelters serve as reservoirs for CIV, but the virus cannot be maintained for long in smaller facilities or in the companion dog population without input from the larger shelters, which represent disease hotspots. These hotspot dynamics give a clear picture of what can happen in the time between the beginning of a host range shift and the onset of a possible pandemic, allowing more targeted strategies for control and eradication.