Ecology and Epidemiology
Infections caused by L. loboi in humans are restricted to Mexico, Central America, and some countries in South America (Bermudez et al. 2009; Francesconi et al. 2014; Paniz-Mondolfi et al.
2012; Paniz-Mondolfi and Sander-Hoffmann 2009; Talhari and Talhari 2012; Vilela and Mendoza 2015). In these areas, the disease is more prevalent in dense forests with large rivers, geographical areas usually having elevated annual rainfall, high humidity, and hot temperatures. Most cases are diagnosed around the Brazilian Amazon basin, but several cases are also reported in the rainforest areas of Colombia and Venezuela and less frequently in Bolivia, Ecuador, Guyana, Peru, Surinam, Central America (Costa Rica and Panama), and Mexico. In addition, imported cases outside these areas such as North America (Canada and the USA), Europe (France, Germany, Greece, the Netherlands), and South Africa have been reported (Arju et al. 2014; Burns et al. 2000; Elsayed et al. 2004; Fischer et al. 2002; Papadavid et al. 2012; Saint-Blancard et al. 2000; Symmers 1983; Vilela and Mendoza 2015). These cases were mainly diagnosed in individuals that had visited endemic areas in South America or were exposed, through direct contact with infected dolphins.In contrast, the majority of reports in dolphins occurred in the coastal areas of Florida, USA (Bossart et al. 2015; Murdoch et al. 2010; Reifet al. 2006, 2009). The disease has been also diagnosed in other geographical areas such as Brazil (Daura- Jorge and Simoes-Lopes 2011; Sacristan et al. 2016), Costa Rica (Bessesen et al. 2014), France (Symmers 1983), Spain (Esperon et al. 2012), Japan (Minakawa et al. 2016; Tajima et al. 2015; Ueda et al. 2013), Madagascar (T. aduncus, Kiszka et al. 2009), South Africa, Surinam (de Moura et al. 2014), and Venezuela (Bermudez et al. 2009).
Because human infections by L. loboi and the culturable P.
brasiliensis are restricted to Central and South America, the finding of P. brasiliensis var. ceti affecting dolphins in Spain (Esperon et al. 2012), Japan (Minakawa et al. 2016; Tajima et al. 2015; Ueda et al. 2013), and the USA (Rotstein et al. 2009; Vilela et al. 2016) is significant. The phylogenetic data suggest that earlier in the life history of the pathogen, some dolphins swimming along South America coastal areas could have been infected around the river estuaries of the above endemic countries, with propagules from an ancestor of P. brasiliensis. Newly infected dolphins probably stayed around South America coastal areas, and others could have migrated to North America and other oceans. The fact that P. brasiliensis var. ceti cannot be cultured suggests that the pathogen muted from its original form or that this was indeed a unique strain derived from culturable P. brasiliensis ancestor. Two hypotheses are possible: (1) infected animals could transmit the pathogen by direct contact with non-infected dolphins or (2) dolphins are constantly in contact with propagules of the pathogen located around South America river estuaries. One clue supporting the first hypothesis is that the majority of bottlenose dolphins around the US coastal regions stay in those areas for long periods before developing skin granulomas (Bossart et al. 2015; Murdoch et al. 2010; Reif et al. 2006, 2009). More importantly, phylogenetic analysis showed that P. brasiliensis var. ceti affecting dolphins probably originated from an ancestral strain located in South America.Since L. loboi and P. brasiliensis var. ceti resist culture, the epidemiology of the infection caused by these two pathogens remains an enigma. In humans, however, it is believed that L. loboi is acquired after contact with environmental propagules. A support for this theory came after a tribe of Caiabi Indians in Brazil was relocated from the Tapajos River (a hyperendemic area of lacaziosis) to the Xingu National Park. Before relocation, numerous cases of the disease were annually diagnosed, whereas new cases have not been reported after relocation (Baruzzi et al. 1973;
Talhari and Talhari 2012; Lacaz et al. 1986). Since phylogenetic analysis placed L. loboi with the dimorphic Onygenales, it is quite possible that conidia (yet to be found) of this unique pathogen may be present in the environment. In humans, the disease is considered occupational or related to recreational activities. Paracoccidioides brasiliensis var. ceti affecting dolphins can be considered a zoonotic pathogen because transmission between dolphins and humans has been documented (Symmers 1983). However, the infection rate may be low (Norton 2006; Reif et al. 2013). Accidental laboratory transmission (Rosa et al. 2009) and successful experimental infections in animals (Belone et al. 2001; Madeira et al. 2000; Sampaio and Dias 1970) and humans (Borelli 1962; Lacaz et al. 1986) have been reported.
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