<br><br />Acknowledgments<br />Authors are grateful to Simon Hugh Wheeler for proofreading. Work supported by grants from the Instituto Federal Catarinense (IFC), 455/2014 PROEX/IFC and from the National Council for Scientific and Technological Development (CNPq), No. 468602/2014-3.<br /><br><br />Introduction<br />The dog is considered an important reservoir of zoonotic visceral leishmaniasis (VL), which is caused by Leishmania infantum in Brazil, and represents an important worldwide public health issue (Mauricio et al., 2000; Quinnell and Courtenay, 2009). The disease affects mainly children and immunocompromised adults, occurring endemically in the Americas (Campos-Ponce et al., 2005; Lainson and Rangel, 2005), Europe and Mediterranean (Ballart et al., 2012) and in Asia (Stauch et al., 2011). In the Americas, the sand fly Lutzomyia longipalpis (Lutz and Neiva, 1912) is considered to be the primary vector for L. infantum infection (Lainson and Rangel, 2005).<br />In the last decades, expansion of VL has been following a strong urbanization tendency. The increasing incidence of human and canine cases in endemic areas (Lopes et al., 2010) has evidenced the ineffectiveness of current control measures and the need for broadening scientific knowledge (Romero and Boelaert, 2010). In Brazil, the control of VL has been focused on vector control by using environmental chemical pesticides, early diagnosis and treatment of human cases, health education and elimination of seropositive dogs (Brasil, 2014).<br />The control of VL in Brazil is mainly based upon the elimination of seropositive (above the cut-off value) dogs for anti-Leishmania antibody in ELISA tests. The dog culling program has been rejected by society and criticized by scholars in the field, whether for the ethical and social aspects involved or the low efficiency (Courtenay et al., 2002; Costa-Nery, 2011; Costa et al., 2013). It has been shown that once the seropositive dogs are removed, they <a href='http://www.cyclo-rgdfk.com/viewtopic.php?f=2&t=7651
'>cannabinoid receptors</a> are immediately replaced by puppies that are susceptible to developing high parasitic loads due to their immunological immaturity (Andrade et al., 2007; Nunes et al., 2008). VL has a complex pathophysiology that involves the immunological competence of the dog (Pinelli et al., 1994; Amorim et al., <img src="http://farm5.static.flickr.com/4390/37053294362_4b5d1c8b07.jpg
" align="left" width="255" style="padding:10px;"/> 2011), and culminates with the development of extremely variable and individual clinical manifestations (Solano-Gallego et al., 2011). Studies on dog infectiousness have shown that the mere positive result in serological tests is not enough to indicate that a given dog is actually capable to transmit the pathogen to the vector. The lack of a sensitive method to distinguish the dogs that actually transmit the parasite from all seropositive dogs is an important aspect associated with the low efficiency of control measures for VL (Courtenay et al., 2002). A well standardized and sensitive method would rather allow greater focus on the control actions of infectious dogs and, consequently, a better control program effectiveness, also considering the high heterogeneity that exists in the infections by L. infantum, which implies in different levels of infectiousness of the dogs (Courtenay et al., 2013).<br />Xenodiagnosis is the only technique that evaluates whether a particular host that is infected with a pathogen is able to transfer <a href='https://en.wikipedia.org/wiki/Aneuploidy
'>Aneuploid</a> by natural means to its potential vector (Guarga et al., 2000a). It is relatively sensitive, despite its high specificity, and may vary according to animal-related factors, such as its parasite load, or to variations in procedure implementation (Travi et al., 2001).<br />The objective of this study was to evaluate the infectivity of dogs, classified by different methods, with different clinical presentations of the infection by L. infantum to the vector L. longipalpis, evaluating the infectiousness of dogs under different procedures of xenodiagnosis and ways to classify the animals clinically. Moreover, due to the indication of culling seropositive dogs in Brazil, seropositivity in ELISA tests was a criterion to select dogs for xenodiagnostic evaluation.