Novel, panzootic and hybrid genotypes of amphibian chytridiomycosis associated with the bullfrog trade.

Global amphibian declines are linked with the presence of specific, highly virulent genotypes of the emerging fungal disease chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) known as the global panzootic lineage (Bd-GPL). The global trade in amphibians for human consumption is suspected to have facilitated emergence of the disease, but evidence to support this is largely lacking. Here, we investigated the role the Lithobates catesbeianus (North American bullfrog) trade in spreading Bd genotypes by comparing strains associated with L. catesbeianus to a global panel using 36 sequenced loci from multiple chromosomal regions. Most bullfrogs were infected with Bd-GPL genotypes, but we also detected novel, highly divergent Bd genotypes (Bd-Brazil) from a live bullfrog in a US market and from native Brazilian anurans in the Atlantic Forest where bullfrogs are widely farmed. Sexual reproduction was also detected for the first time in Bd in the form of a hybrid genotype between the Bd-GPL and Bd-Brazil lineages in the Atlantic Forest. Despite the demonstration that ribosomal RNA types in Bd fail to undergo concerted evolution (over 20 sequence types may be found in a single strain), the Bd-GPL and Bd-Brazil lineages form largely separate clusters of related internal transcribed spacer (ITS) RNA sequences. Using ITS sequences, we then demonstrate the presence of Bd-Brazil in Japan, primarily on invasive L. catesbeianus. The finding that Bd is capable of sexual reproduction between panzootic and endemic genotypes emphasizes the risk of international wildlife trade as a source of additional Bd epizootics owing to hybridization.

Potential environmental and host gender influences on prevalence of Haemogregarina platessae (Adeleorina:Haemogregarinidae) and suspected Haemohormidium terraenovae (incertae sedis) in Brazilian flounder from the Patos Lagoon Estuary, southern Brazil.

Flounder, Paralichthys orbignyanus (Valenciennes), were captured in polluted and non-polluted sites within the Patos Lagoon Estuary, southern Brazil, over four seasons. Blood films showed a high prevalence of infection with a haemogregarine, or mixed parasitaemias of this and an organism resembling Haemohormidium terraenovae So, 1972. Haemogregarine gamont stages conformed to existing descriptions of Desseria platessae (Lebailly, 1904) Siddall, 1995 from flatfishes, but intraerythrocytic division of meronts was observed, leading to the recommendation for nomenclatural correction, placing the haemogregarine in the genus Haemogregarina (sensu lato) Danilewsky, 1885. Statistical analyses suggested that although sample sizes were small, infections with meront stages, immature and mature gamonts were all influenced by site, and possibly therefore, by pollution. Season also appeared to determine likelihood of infection with meronts and immature gamonts, but not mature gamonts, while adult fish gender apparently affected infection with immature and mature gamonts, but not meronts. The H. terraenovae-like organism exhibited unusual extracellular forms and did not match closely with the type description of H. terraenovae; precise identification was therefore difficult. Data analyses suggested that parasitism by this organism was influenced by site and fish gender, since females and males from non-polluted water were infected, but only females from the polluted site. Season was also important and significantly more adult fish of both sexes were infected with this parasite in the Brazilian summer and autumn, compared with winter and spring. Finally, these appeared to be the first observations of Haemogregarina platessae, and possibly H. terraenovae, from the southern hemisphere.