Ranavirus and helminth parasite co-infection in invasive American bullfrogs in the Atlantic forest, Brazil

• Published in: International journal for parasitology. Parasites and wildlife 2024-04, Vol.23, p.100924-100924, Article 100924
• Main Authors: Ash, Lauren V., Campião, Karla Magalhães, Teixeira, Cauê Pinheiro, Gotelli, Nicholas J.
• Format: Article
• Language: English
• Subjects: adults; Aquarana catesbeiana; Brazil; bullfrogs; Co-infection; confidence interval; ecosystems; forests; Helminth; helminths; Invasive species; Lithobates catesbeianus; liver; mixed infection; Nematoda; parasite load; parasitology; pathogens; quantitative polymerase chain reaction; Ranavirus; species; viral load; wildlife
• ISSN: 2213-2244; 2213-2244
• DOI: 10.1016/j.ijppaw.2024.100924

Emerging infectious diseases threaten amphibian species across the globe. In Brazil, the American bullfrog (Aquarana catesbeiana) is a highly invasive species that can potentially transmit parasites and pathogens to native amphibians. This is the first assessment of co-infection of Ranavirus and helminth macroparasites in invasive populations of bullfrogs in South America. We collected, measured, and euthanized 65 specimens of A. catesbeiana sampled from 9 sites across three states of Brazil in the Atlantic Forest biome. We collected and identified helminth macroparasites and sampled host liver tissue to test for the presence and load of Ranavirus with quantitative PCR. We documented patterns of prevalence, parasite load, and co-infection with generalized linear mixed models, generalized logistic regressions, and randomization tests. Most individual bullfrogs did not exhibit clinical signs of infection, but the overall Ranavirus prevalence was 27% (95% confidence interval, [CI 17–38]). Bullfrogs were infected with helminth macroparasites from 5 taxa. Co-infection of helminth macroparasites and Ranavirus was also common (21% CI [12–31]). Bullfrog size was positively correlated with total macroparasite abundance and richness, and the best-fitting model included a significant interaction between bullfrog size and Ranavirus infection status. We observed a negative correlation between Ranavirus viral load and nematode abundance (slope = −0.22, P = 0.03). Invasive bullfrogs (A. catesbeiana) in Brazil were frequently infected with both Ranavirus and helminth macroparasites, so adult bullfrogs could serve as reservoir hosts for both pathogens and parasites. However, many macroparasites collected were encysted and not developing. Coinfection patterns suggest a potential interaction between Ranavirus and macroparasites because helminth abundance increased with bullfrog size but was lower in Ranavirus infected individuals. Future studies of bullfrogs in the Atlantic Forest should investigate their potential role in pathogen and parasite transmission to native anurans. [Display omitted] •First documented evidence of widespread Ranavirus infection in invasive adult bullfrogs (Aquarana catesbeiana) in Brazil.•Invasive adult bullfrogs may act as reservoirs of both viral and macroparasitic infections, potentially impacting native anuran communities.•Patterns of co-infection indicate a potential interaction between Ranavirus and helminth macroparasites.