More than the eyes can see: The worrying scenario of canine leishmaniasis in the Brazilian side of the triple border

Abstract

A cross-sectional epidemiological study in the extreme-west of the state of Paraná was carried out to access the prevalence, distribution, and risk variables of canine Visceral Leishmaniases (cVL). This study was conducted in three areas, two cities of far west of Parana state: Foz do Iguaçu (FI) and Santa Terezinha de Itaipu (STI), and along two transects between these two municipalities. To sample the entire urban area, the cities (FI and STI) were divided into a grid of squares of 400 m2 (patch). Among the 526 patches, 123 in FI, 40 in the transects and 33 in STI were selected according to the ‘worst scenario’ criterion. In the transect areas, in each 0.86 km five dogs from houses were surveyed to leishmaniasis. In each patch, blood of five dogs from houses (and from neighborhood when necessary) in the areas that seemed to be the most appropriate for the proliferation of vector were surveyed. The infection of the dogs by cVL were assessed using two serological tests were used (cELISA and TR-DPP®), and, for those seropositive for both methods, the PCR method were used. Moreover, dogs presenting clinical signs or cutaneous lesions were sampled to PCR. The identification of Leishmania species was confirmed using PCR-RFLP followed by DNA sequencing. Micro, meso and macro scale environmental variables were also surveyed and statistically analyzed. The prevalence rate Leishmania infantum was 23.8% in FI, 4.7% in STI and 9.1% in the transects areas. Among the extrinsic variables analysed, the number of vectors and the presence of infected dogs in neighbouring were positively correlated with the occurrence of infected dogs. Dog size was positively correlated with cVL infection, while the quality of the dog’s nutrition affected cVL negatively. As for cutaneous leishmaniasis (CL), the first registry of dogs infected with L. braziliensis in the region shows that there is potential for transmission in peri-urban areas, since environmental conditions allow the proliferation of vectors capable of transmitting this species of parasite. cVL is widely spread in FI, with high prevalence. This supports the hypothesis that the parasite has been present in the region for longer than previously believed, despite the fact that the presence of leishmaniais in the region has only been recognized recently. It is important to control the population of dogs infected with L. infantum (parasite and non-antibodies) to prevent the spread of the disease to other dogs and also to people in the region.

Twice upon a time: The progression of canine visceral leishmaniasis in an Argentinean city

“…longipalpis was found in PI since 2010 [12], but not in PL or the other sampled sites up to 2014. Further, as it was observed also in the Brazilian side, the border cities of Brazil and Argentina, Foz do Iguaçu and Puerto Iguazú respectively, seem to be a 'gateway for CVL’ spread to the western portion of the state of Paraná-Brazil [8] and northern region of Misiones-Argentina, providing allochthonous CVL cases. Therefore, in order to forecast the spatial spread of urban CVL and so HVL, cities prevalence, road network, transit and migration fluxes should be addressed [35,36].…”

“…Nevertheless, an effect of the environmental conditions given by the different sampling moments is not discarded, but a longitudinal study is necessary to evaluate this. On the other hand, to sample clusters of five dogs around a site prone to have vectors (to increase vector trapping sensitivity) could bias the dog prevalence to higher values than those obtained by an eventual random sampling [13], but the CVL prevalence obtained for PI is of the same order as those obtained in emergent cities of Brazil as the closest one to PI, Foz do Iguaçu [8,39].…”

“…The occurrence of HVL cases tends to cluster close to areas with a higher incidence of CVL [5,6]. Multiple factors such as dog size, age and presence of ectoparasites have been found to be associated with CVL seroprevalence [7,8], highlighting the necessity to address CVL epidemiology.…”

Hidden danger: Unexpected scenario in the vector-parasite dynamics of leishmaniases in the Brazil side of triple border (Argentina, Brazil and Paraguay)

“…The presence of large numbers of Lu . longipalpis throughout the city combined with the large numbers of infected dogs reveals a scenario of potential autochthonous humans and dog VL according to Thomaz-Soccol et al [ 13 ]. There is a huge risk evidenced by the Path Analysis and maximum entropy analysis that the presence and the number of dogs influence positively the prevalence of Lu .…”

“…Subsequently, canine visceral leishmaniasis (cVL) and human (HVL) cases were firstly reported in 2013 and 2016 respectively, and the number of VL cases has been increased in the following years [ 10 – 12 ]. For instance, Thomaz-Soccol et al [ 13 ] showed that about 23.8% dogs in FI presents cVL. In this way, delineating the sand fly fauna´s distribution is essential to understand adequately VL´s status in the region, and to reduce the risk of future epizootics.…”