- Author
- Zhimin Li
- Promoter
- An Martel (UGent) and Frank Pasmans (UGent)
- Organization
- Abstract
- Amphibian species are declining at unprecedented rates. Declines are caused by a myriad of factors, including habitat loss, chemical pollution, invasive alien species and infectious diseases such as chytridiomycosis. Emergence of the two sister species, Batrachochytrium dendrobatidis (Bd) and Bsal (Bsal) has resulted in the decline of at least 501 species (6.5% of all amphibian species) alongside the presumed extinction of 90 species worldwide. Two third of European amphibian species are endemic, and potentially threatened by recent invasion of both chytrid fungi. Therefore, it is urgent to assess the risks of chytrid dispersal in Europe on local amphibians and to search for efficient mitigation measures. In chapter 1, we predicted the risk of invasion of populations of threatened Mediterranean salamanders of the genus Lyciasalamandra by the pathogenic chytrid fungus Bsal by combining field sampling and lab trials. We investigated the prevalence of Bsal in 494 samples across all seven Lyciasalamandra species. The results showed that there was no Bsal present. By comparing the infection dynamics of Bsal between Lyciasalamandra helverseni and the reference urodele species for susceptibility: the fire salamander (Salamandra salamandra), we found that L. helverseni develop chytridiomycosis and die post infection of Bsal. Meanwhile, the overlap between thermal behavior of the host species and the thermal niche of the pathogen limited the salamanders' defense opportunities. Despite the high probability of local salamander population declines upon invasion by Bsal, the unfavorable landscape that shaped intraspecific host genetic diversity, lack of known alternative hosts and rapid host mortality after infection present barriers to further, natural pathogen dispersal between populations and thus species extinction. In chapter 2, we studied the interaction between the troglobiont urodele salamander, Proteus anguinus and Bsal. Unlike Bsal susceptible species (S. salamandra and Lyciasalamandra), P. anguinus showed high tolerance to Bsal infection. Although P. anguinus did not develop any obvious clinical signs of infection after inoculation, long term proliferation of the fungus within the olm keratinized limb tissue was observed. The olm’s skin is likely to temper Bsal infection and dampen the pathogen’s virulence. P. anguinus is one of few western Palearctic urodeles that is tolerant to Bsal infection and may act as a subterranean disease reservoir, yet costs of subclinical infection are not understood and may compromise olm fitness on the long term. In chapter 3, we assessed the efficacy of mitigation measures in an attempt to contain a Bsal outbreak near one of Europe’s most threatened, small range urodeles, the Montseny Brook newt (Calotriton arnoldi). The latter was susceptible to Bsal chytridiomycosis in a lab trial. In a combined effort involving policy, science, and management, the following disease control measures were implemented: biosecurity, habitat management and disinfection, host removal and disease surveillance throughout the park. These efforts were demonstrated to contain the disease at least during the duration of the measures applied. With the emergence and spread of Bd and Bsal, co-infections are likely to occur. The outcomes of co-infection by two pathogen species/isolates are largely unknown. In chapter 4, we predicted that BdGPL co-existence with amphibian communities is mediated by low virulence of the present BdGPL isolates and explore the extent to which low-virulence isolates confer protection against hypervirulent Bd or Bsal. We found that prior infection with low-virulence Bd isolates protect some species against the subsequent invasion by hypervirulent Bd or Bsal. However, for Bsal, this protective effect appears to be host species-dependent, and was not observed in fire salamanders (S. salamandra). We provided evidence that the protection conferred is associated with expression of several potential virulence factors that correlate with Bd colonization ability and invasiveness, such as Crinkler genes and metalloproteases. In conclusion, we demonstrated that Bsal poses a variable risk on European herpetofauna. Endemic infections with Bd may protect at least a proportion of the European urodeles against the disease. While this opens novel perspectives for disease mitigation, imposing fast and drastic measures currently seems the only realistic option to contain and potentially eradicate the disease in Europe.
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Citation
Please use this url to cite or link to this publication: http://hdl.handle.net/1854/LU-8742246
- MLA
- Li, Zhimin. Host Susceptibility of Amphibians to Chytridiomycosis : Lessons for Mitigation. Ghent University. Faculty of Veterinary Medicine, 2022.
- APA
- Li, Z. (2022). Host susceptibility of amphibians to chytridiomycosis : lessons for mitigation. Ghent University. Faculty of Veterinary Medicine, Merelbeke, Belgium.
- Chicago author-date
- Li, Zhimin. 2022. “Host Susceptibility of Amphibians to Chytridiomycosis : Lessons for Mitigation.” Merelbeke, Belgium: Ghent University. Faculty of Veterinary Medicine.
- Chicago author-date (all authors)
- Li, Zhimin. 2022. “Host Susceptibility of Amphibians to Chytridiomycosis : Lessons for Mitigation.” Merelbeke, Belgium: Ghent University. Faculty of Veterinary Medicine.
- Vancouver
- 1.Li Z. Host susceptibility of amphibians to chytridiomycosis : lessons for mitigation. [Merelbeke, Belgium]: Ghent University. Faculty of Veterinary Medicine; 2022.
- IEEE
- [1]Z. Li, “Host susceptibility of amphibians to chytridiomycosis : lessons for mitigation,” Ghent University. Faculty of Veterinary Medicine, Merelbeke, Belgium, 2022.
@phdthesis{8742246, abstract = {{Amphibian species are declining at unprecedented rates. Declines are caused by a myriad of factors, including habitat loss, chemical pollution, invasive alien species and infectious diseases such as chytridiomycosis. Emergence of the two sister species, Batrachochytrium dendrobatidis (Bd) and Bsal (Bsal) has resulted in the decline of at least 501 species (6.5% of all amphibian species) alongside the presumed extinction of 90 species worldwide. Two third of European amphibian species are endemic, and potentially threatened by recent invasion of both chytrid fungi. Therefore, it is urgent to assess the risks of chytrid dispersal in Europe on local amphibians and to search for efficient mitigation measures. In chapter 1, we predicted the risk of invasion of populations of threatened Mediterranean salamanders of the genus Lyciasalamandra by the pathogenic chytrid fungus Bsal by combining field sampling and lab trials. We investigated the prevalence of Bsal in 494 samples across all seven Lyciasalamandra species. The results showed that there was no Bsal present. By comparing the infection dynamics of Bsal between Lyciasalamandra helverseni and the reference urodele species for susceptibility: the fire salamander (Salamandra salamandra), we found that L. helverseni develop chytridiomycosis and die post infection of Bsal. Meanwhile, the overlap between thermal behavior of the host species and the thermal niche of the pathogen limited the salamanders' defense opportunities. Despite the high probability of local salamander population declines upon invasion by Bsal, the unfavorable landscape that shaped intraspecific host genetic diversity, lack of known alternative hosts and rapid host mortality after infection present barriers to further, natural pathogen dispersal between populations and thus species extinction. In chapter 2, we studied the interaction between the troglobiont urodele salamander, Proteus anguinus and Bsal. Unlike Bsal susceptible species (S. salamandra and Lyciasalamandra), P. anguinus showed high tolerance to Bsal infection. Although P. anguinus did not develop any obvious clinical signs of infection after inoculation, long term proliferation of the fungus within the olm keratinized limb tissue was observed. The olm’s skin is likely to temper Bsal infection and dampen the pathogen’s virulence. P. anguinus is one of few western Palearctic urodeles that is tolerant to Bsal infection and may act as a subterranean disease reservoir, yet costs of subclinical infection are not understood and may compromise olm fitness on the long term. In chapter 3, we assessed the efficacy of mitigation measures in an attempt to contain a Bsal outbreak near one of Europe’s most threatened, small range urodeles, the Montseny Brook newt (Calotriton arnoldi). The latter was susceptible to Bsal chytridiomycosis in a lab trial. In a combined effort involving policy, science, and management, the following disease control measures were implemented: biosecurity, habitat management and disinfection, host removal and disease surveillance throughout the park. These efforts were demonstrated to contain the disease at least during the duration of the measures applied. With the emergence and spread of Bd and Bsal, co-infections are likely to occur. The outcomes of co-infection by two pathogen species/isolates are largely unknown. In chapter 4, we predicted that BdGPL co-existence with amphibian communities is mediated by low virulence of the present BdGPL isolates and explore the extent to which low-virulence isolates confer protection against hypervirulent Bd or Bsal. We found that prior infection with low-virulence Bd isolates protect some species against the subsequent invasion by hypervirulent Bd or Bsal. However, for Bsal, this protective effect appears to be host species-dependent, and was not observed in fire salamanders (S. salamandra). We provided evidence that the protection conferred is associated with expression of several potential virulence factors that correlate with Bd colonization ability and invasiveness, such as Crinkler genes and metalloproteases. In conclusion, we demonstrated that Bsal poses a variable risk on European herpetofauna. Endemic infections with Bd may protect at least a proportion of the European urodeles against the disease. While this opens novel perspectives for disease mitigation, imposing fast and drastic measures currently seems the only realistic option to contain and potentially eradicate the disease in Europe.}}, author = {{Li, Zhimin}}, language = {{eng}}, pages = {{VIII, 185}}, publisher = {{Ghent University. Faculty of Veterinary Medicine}}, school = {{Ghent University}}, title = {{Host susceptibility of amphibians to chytridiomycosis : lessons for mitigation}}, year = {{2022}}, }