Treatment
14.8.1 Treatment with Antimicrobial Compounds
The most important class of antifungal drugs used to treat chytridiomycosis in amphibians is that of the imidazole, triazole and thiazole or “azole” group.
The most widely used azole antifungal in treating chytridiomycosis is itraconazole. In general, most itraconazole treatment protocols are based on a study performed by Nichols et al. (2000) describing successful treatment of chytridiomycosis by bathing Bd-infected amphibians in a 0.01% solution (100 mg/L) of itraconazole diluted in 0.6% saline, daily for 5 min during 11 days (Nichols et al. 2000; Forzan et al. 2008; Une et al. 2008; Pessier and Mendelson 2010; Georoff et al. 2013). Studies describing successful treatment of chytridiomycosis with minor adaptations to this protocol (other concentration, other diluting agent and longer exposure time or treatment period) also exist (Garner et al. 2009; Tamukai et al. 2011; Jones et al. 2012; Georoff et al. 2013). However, treatment failure and adverse side effects due to itraconazole toxicity at this concentration (and even lower concentrations) have also been reported for some amphibian species (Brannelly et al. 2012; Woodhams et al. 2012a, b). Variable outcome of itraconazole treatment in clearing Bd infections might be explained not only by the used concentration but also by the frequency of exposure to itraconazole (Woodward et al. 2014). Other antifungals belonging to the azole group used to treat chytridiomycosis are miconazole and voriconazole. Nichols et al. (2000) demonstrated that treatment by using miconazole baths at a concentration of 100 pg/ml, once daily for 5 min during 8 days was effective in clearing Bd infections. Voriconazole has been shown to have potent Bd inhibitory effects both in vitro and in vivo (Woodward et al. 2014, Martel et al. 2011), with successful clearance of Bd in experimentally and naturally infected amphibians using a treatment protocol composed of topically spraying voriconazole once daily during 7 days at a concentration of 1.25 pg/ml (Martel et al. 2011).Topical treatment of Bsal-infected animals with a combination of polymyxin E (2000IU/ml) and voriconazole (12.5 pg/ml) at an ambient temperature of 20 °C results in clearance of Bsal infections (Blooi et al. 2015a, b). For all treatments, posttreatment assessment for clearance of infection is necessary, and treatments may need to be repeated.
14.8.2 Physical Therapy
Short exposure to relatively high ambient temperatures (37 °C less than 16 h (Woodhams et al. 2003) and 30 °C, 10-day exposure (Chatfield and Richards- Zawacki 2011) and longer exposure to lower ambient temperatures (27 °C, clearance after 98 days; Berger et al. 2004) have been able to clear Bd infections from adult amphibians. Exposure to 26 °C during 5 days was able to clear Bd infections in midwife toad (Alytes obstetricans) larvae (Geiger et al. 2011). Ten-day exposure at 25 °C is able to clear salamanders from Bsal infections (Blooi et al. 2015a, b). The main disadvantages linked to temperature treatment of chytrid infections is that elevated temperature might not be endured by all amphibian species and that thermal shock might occur (especially when taking into account that the treatment is applied on sick individuals). Furthermore, strain dependent thermal preferences of Bd or Bsal may compromise thermal treatment protocols.
14.9