Epizootiology of Spirorchiid Infection in Green Turtles (Chelonia Mydas) in Hawaii

Abstract

We describe the epizootiology of spirorchiid trematode infections in Hawaiian green turtles (Chelonia mydas) by quantifying tissue egg burdens in turtles submitted for necropsy and by assessing antibody response to crude adult worm and egg antigens among a variety of age groups. Hapalotrema sp. and Laeredius sp. predominated in turtles infected with spirorchiids. Tissue egg burdens decreased with increasing size and increased with deteriorating body condition of turtles. No relationship was found between tissue egg burdens and sex or fibropapillomatosis status. Tissue egg burdens increased in turtles from southeast to northwest in the main Hawaiian Islands (Hawaii to Kauai). Hatchling and captive-reared turtles had significantly lower levels of antibodies against crude worm and egg antigens. Based on tissue egg burdens and antibody status, we hypothesize that immature turtles become infected with spirorchiids shortly after recruiting into coastal foraging pastures from the pelagic environment, that infection levels decrease with age, and that spirorchiids detrimentally affect the body condition of sea turtles independent of tumor burden. The low intensity of infection in turtles with the endemic trematode Carettacola hawaiiensis suggests either that turtles are less susceptible to infection with this parasite or that the parasite is outcompeted by species of Hapalotrema and Laeredius. Given that the 2 latter species are found in the Pacific and other oceans, they are not likely endemic and were probably introduced into Hawaii through an undetermined route.

The Foragining Ecology of the Green Turtle in the Baja California Peninsula: Health Issues

“…Gordon et al (1998) found that Cadmium concentrations in green turtles from Australia were up to three times higher than the levels reported in commercial seafood products. The presence of epibionts, parasites (internal and external) might occasionally cause the death of some marine turtles and being predecessors of fibropapiloms (Aguirre y Lutz, 2004;Work, 2000, Work et al, 2005. The presence of fibropapiloms in Hawaiian waters was related with the presence of hirudineans (Díaz, et al, 1992).…”

Diversity, impacts and diagnosis of pathogenic parasites in sea turtles from Queensland, Australia

“…Genetic analyses suggested that a range of unique Neospirorchis genotypes were present, with various site and host affinities evident (Stacy, 2008). While Neospirorchis was the most prevalent spirorchiid genus in this Florida survey, studies from Hawaiian turtles did not detect this genus at all (Work et al, 2005). It is difficult to compare these studies due to differences in sampling method, i.e.…”

“…However, significant spirorchiid associated pathology was observed even in robust turtles, indicating that flukes may potentially act as primary pathogens rather than just secondary opportunists (Stacy et al, 2010a). In Hawaii, spirorchiid infections appear to increase with emaciation of the host (Work et al, 2005;Work et al, 2015).…”

“…It is difficult to compare these studies due to differences in sampling method, i.e. splenic egg counts (Work et al, 2005) as opposed to inspection of all tissues (Stacy et al, 2010a). In Moreton Bay, Gordon et al (1998) observed numerous spirorchiid ova within the spleen on histological examination, but did not attempt to identify the egg types found.…”

“…Further, the ability of the test to detect an infection relies on the host developing a sufficient immune response to the pathogen, which does not occur in all cases (Ndao, 2009). Graczyk et al (1995), Herbst et al (1998) and Work et al (2005) used ELISA tests to detect exposure to spirorchiids in green turtles. While these tests show potential for some applications, these are limited by various factors including age-related antigen heterogeneity, the persistence of antibodies in the blood post-treatment, and potential for cross reactivity with other fluke families.…”