Vector-borne parasitic zoonoses: Emerging scenarios and new perspectives
Introduction
Humans are currently experiencing a time of unprecedented change in their lives and those of the animals on which they depend and interact with. The change is not merely the much discussed alterations in climate (Tabachnick, 2010) but there are dramatic changes in human demographics, behaviour, land use practices as well as changes in the environment at both large and small scales (Sutherst, 2004). These changes, alone and in concert, alter the interactions between humans and infectious disease agents leading to clear emergence of infectious and zoonotic diseases (Jones et al., 2008, Otranto and Eberhard, 2011). These changes also influence the vectors (e.g., ticks, fleas, black flies, mosquitoes and sand flies) of zoonotic parasites and change their relationships with humans. Under the above circumstances, arthropod vectors may enhance their potential to spread bacteria, viruses, protozoa and helminths. Thus, there is a great deal of discussion among scientists regarding the magnitude and extent of changes in vector-borne parasitic zoonosis (VBPZ) distribution, not only because of their impact on human and animal health (WHO, 2004) but also because they may represent a major threat to the economy, causing millions of dollars in losses to the livestock industry annually (Bram et al., 2001). These infections affect public health mainly in developing countries (e.g., Africa, South and Central America and Far East) where control and prevention strategies are oftentimes impaired by economic constraints (Irwin and Jefferies, 2004, Rosenthal, 2009, Otranto et al., 2009b). Whether VBPZ-causing pathogens will spread from the tropics and lower latitudes, where the greatest animal biodiversity is concentrated, toward northern hemisphere, is a crucial issue to be addressed.
There is increasing interest in the role of climate changes in the epidemiology and distribution of VBPZs (Rosenthal, 2009, Randolph, 2010). However, a complete approach to predict the upsurge of VBPZs should not only assess the effect of climatic factors, but also examine the linkage between socio-economic and political issues and the emergence of these diseases. Thus this article discusses the changing epidemiological scenarios of VBPZs, which are of emerging or re-emerging concern. In addition, it discusses the extant socio-economic and political events (e.g., liberalization of economy, wars, and population movements) that might affect the spreading and the control of vector-borne zoonotic parasites.
Section snippets
Changing vector-borne parasitic zoonoses in a changing world
In the past, research aimed at predicting the spread of vectors and pathogens in non-endemic areas mostly focussed on the effects of climate change, particularly global warming (Lindgren and Gustafson, 2001, Rosenthal, 2009), and have only marginally considered the complexity of changes in the environment as well as changes in human behaviour. A suite of factors affects the degree of contact between hosts and parasite vectors in a manner well described by the theory of island biogeography (
Ancient diseases, contemporary scenarios
VBPZs have long been a cause of morbidity and mortality in humans. Historically, diseases like leishmaniasis and malaria have had a great impact on humans and they are still causing a huge burden on public health worldwide (Hotez et al., 2006). However, as the world is changing, new diseases are being discovered and even the epidemiology of ancient diseases like malaria and Chagas disease is changing. This scenario is a result of complex interactions between changes related to vectors,
Potentially emerging human vector-borne parasites
In addition to many vector-borne parasites-causing parasites for which the zoonotic potential has been known for long time, a number of agents have spurred the interest of the scientific community as new human pathogens. Indeed, some filarids from domestic mammals (e.g., Dirofilaria spp.), and wild mammals (e.g., Onchocerca, Dipetalonema and Loaina) have a zoonotic potential (Botero et al., 1984, Beaver, 1989, Orihel and Eberhard, 1998). Onchocerca volvulus affects about 17.7 million people
Conclusion
VBPZs are part of the constantly changing world and, because of this, they are constantly adapting to their new circumstance. They are changing their vectors, their hosts, their distribution and also their virulence. Medical and veterinary personnel need to be constantly attuned to these changes and need to keep up-to-date about new emerging pathogens and about potential secondary ways of transmission of pathogens that are primarily transmitted by arthropods. Awareness is the first step toward
Conflict of interest statement
The authors declare that there is no conflict of interest.
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