Sea turtles are exposed to a range of anthropogenic stressors, including habitat degradation and pollution. Along the Brazilian coast, the discharge of untreated sewage into marine environments introduces fecal pathogens and contributes to habitat contamination. Owing to their longevity, migratory behavior, and ecological sensitivity, sea turtles are recognized as effective sentinels of environmental change. Rather than focusing on isolated records, this review advances a conceptual framework that interprets detections of Strongyloides sp., Hymenolepis sp., and Ascaris sp. in Cheloniidae as indicators of cross ecosystem disturbance. We critically examine possible exposure pathways, including sewage-driven contamination, sediment persistence, and altered trophic interactions, and discuss how these helminths may function as sentinels of fecal pollution and ecosystem health. Finally, we highlight knowledge gaps and research priorities necessary to validate these taxa as bioindicators.

• Cheloniidae

• Environmental Parasitology

• Sea Turtles Health

• Bioindicators

• Sewage Pollution

Barata RA, Kirchpfennig FZ (2025) Human-Associated Helminths in Sea Turtles (Testudines: Cheloniidae) from Brazil: Ecological Implica tions and the Bioindicator Potential for Environmental Health. J Vet Med Res 12(3): 1287.

Sea turtles are key components of marine ecosystems, contributing to nutrient cycling, habitat maintenance, and food web dynamics [1-3].However, their survival is threatened by a range of anthropogenic pressures, including coastal development, marine debris, incidental capture in fisheries, and, notably, pollution from untreated sewage and industrial waste [4,5].

On the Brazilian coastline, rapid urban expansion and deficient sanitation infrastructure have led to the discharge of significant volumes of untreated domestic effluents into marine environments [6-8]. This contamination introduces a wide array of pathogenic microorganisms and organic pollutants into aquatic systems, many of which can persist in sediments or bioaccumulate in marine organisms [9-11]. Sea turtles, due to their long lifespans, broad migratory ranges, and ecological plasticity, are particularly vulnerable to such disturbances and have been proposed as effective sentinels for marine environmental health [12,13].

Environmental parasitology has increasingly recognized the utility of parasites as bioindicators of ecological integrity and pollution. Parasites can reflect changes in host health, trophic interactions, and contaminant exposure, offering a sensitive and integrative means to assess anthropogenic impacts on ecosystems [14-16]. Among such indicators, helminths with life cycles dependent on environmental conditions and intermediate hosts may be particularly informative.

While previous studies have documented the occurrence of terrestrial-origin helminths in sea turtles, their broader ecological implications remain largely unexplored. This article does not present new field data but instead develops an interpretive synthesis that reframes such findings as signals of terrestrial-marine connectivity.

Reports from the Brazilian coast described Strongyloides sp. eggs in Eretmochelys imbricata, Hymenolepis sp. eggs in both E. imbricata and Chelonia mydas, and Ascaris sp. eggs in C. mydas [17]. These helminths are classically associated with terrestrial hosts and sanitation failures [18,19]. which makes their detection in marine turtles particularly striking. Rather than treating these occurrences as anomalies or artifacts, we interpret them as potential ecological indicators of fecal pollution and ecosystem disturbance [14-16].

The occurrence of terrestrial-origin helminths in sea turtles, as reported by [17], can be explained by multiple non-exclusive mechanisms. One possible route is the direct input of untreated sewage, which introduces eggs and larvae into marine environments, consistent with studies highlighting sewage as a source of aquatic contamination [9-19].

Another pathway involves the persistence of resistant eggs in sediments and their trophic transfer, reflecting the high environmental resilience of these parasites [20]. Furthermore, chemical contaminants are known to compromise immune responses in reptiles and marine mammals, which may facilitate atypical infections that would otherwise remain transient [21,22]. Together, these mechanisms underscore the complex interface between deficiencies in human sanitation, coastal ecosystem integrity, and marine wildlife health.

From an environmental parasitology perspective, the detection of terrestrial-origin helminths in sea turtles [17], should be interpreted as a signal of sewage-driven contamination. The use of parasites as bioindicators is well established in aquatic ecosystems [13-23]. Helminths such as Ascaris spp., due to the remarkable resistance of their eggs, and Strongyloides spp., directly associated with fecal pollution [18-24]. reinforce the applicability of this approach. Moreover, studies have shown that pollutants can interfere with parasite development and transmission, altering host–parasite interactions and further strengthening their role as indicators [25,26].

To consolidate the use of human-associated helminths as bioindicators in sea turtles, several research priorities must be addressed. First, studies should quantify prevalence and infection intensity across different regions and turtle species, generating robust epidemiological baselines [2,3]. Second, efforts are required to differentiate true infections from mere contamination, through histopathology and molecular diagnostics, which have proven effective in distinguishing parasite–host interactions in wildlife studies [24]. Third, parasitological data must be correlated with environmental parameters such as water quality, sewage discharges, and land-use patterns, strengthening causal inferences between contamination and parasite occurrence [6-8].

Another essential priority is to evaluate the health impacts of these parasites on turtles themselves, especially regarding immune function under contaminant exposure, since pollutants are known to impair immunity in marine vertebrates [21,22]. Finally, parasitological surveillance should be integrated into long-term conservation programs, allowing these organisms to contribute effectively to interdisciplinary assessments of marine ecosystem health [12-16]. Addressing these gaps will provide the empirical foundation necessary to validate the bioindicator potential of Strongyloides, Hymenolepis, and Ascaris in sea turtles.

The occurrence of Strongyloides, Hymenolepis, and Ascaris in sea turtles should not be dismissed as accidental. Instead, these findings provide a unique window into the eco-epidemiological effects of sewage on marine ecosystems. By reframing terrestrial-origin helminths as potential bioindicators, we highlight their value for conservation monitoring and propose their integration into interdisciplinary assessments of marine ecosystem health.

To Petróleo Brasileiro S.A. by Aquatic Biota Monitoring Information System.

Ricardo Andrade Barata: Conceptualization, Formal analysis, Writing - original draft.

Fábio Souza Kirchpfennig: Formal analysis, Writing - original draft.

1. Wilson EG, Miller KL, Allison D, Magliocca M. Why healthy oceans need sea turtles: the importance of sea turtles to marine ecosystems. In: Oceana, Protecting the World’s Oceans. 2005.
2. Hamann M, Godfrey MH, Seminoff JA, Arthur K, Barata PCR, Bjorndal KA, et al. Global research priorities for sea turtles: informing management and conservation in the 21st century. Endanger. Species Res. 2010; 11: 245-269.
3. Patel E, Kotera M, Phillott AD. Parasites of marine turtles: A review of known species from the Indian Ocean region. Indian Ocean Turtle News. 2022; 36: 23-31.
4. Witherington BE, Martin, RE. Understanding, assessing, and resolving light-pollution problems on sea turtle nesting beaches. Florida Mar Res Inst Tech Rep. 2000.
5. Cáceres-Farias L, Reséndiz E, Espinoza J, Fernández-Sanz H, Alfaro- Núñez A. Threats and vulnerabilities for the globally distributed olive ridley (Lepidochelys olivacea) sea turtle: a historical and current status evaluation. Animals (Basel) . 2022; 12: 1837.
6. Bertrand G, Hirata R, Pauwels H, Cary L, Petelet-Giraud E, Chatton E, et al. Groundwater contamination in coastal urban areas: anthropogenic pressure and natural attenuation processes. Example of Recife (PE State, NE Brazil). J. Contam. Hydrol. 2016; 192: 165-180.
7. Silva JHC, Silva-Filho E, Leite A, Molisani MM. Effects of a recent urbanization event on coastal groundwater in the southeastern coast of Brazil: a case study of the Macaé municipality. Rev Bras Cienc Ambient. 2022; 57: 114-124.
8. Martinez AS, Underwood T, Christofoletti RA, Pardal A, Fortuna MA, Marcelo-Silva J, et al. Reviewing the effects of contamination on the biota of Brazilian coastal ecosystems: Scientific challenges for a developing country in a changing world. Sci Total Environ. 2022; 803: 150097.
9. Pougnet R, Pougnet L, Allio I, Lucas D, Dewitte JD, Loddé B. Maritime environment health risks related to pathogenic microorganisms in seawater. Int Marit Health. 2018; 69: 35-45.
10. Menghi CI, Gatta CLE, Santoni G, Nicola F, Smayevsky J, Krivokapich SJ. Infección humana con Pseudoterranova cattani por ingesta de ceviche en Buenos Aires, Argentina. Rev. Argentina Microbiol. 2020; 52: 61-70.
11. Rz?d I, Wi?caszek B, Linowska, A, Korzelecka-Orkisz A, Dzika E. Diphyllobothrium sp. and other parasites of migrating and rare fish species in the southern Baltic sea and coastal waters, Poland. Animals. 2024; 14: 1029.
12. Sures B. Environmental parasitology: relevancy of parasites in monitoring environmental pollution. Trends Parasitol. 2004; 20: 170-177.
13. Nachev M, Sures B. Environmental parasitology: Parasites as accumulation bioindicators in the marine environment. J Sea Res. 2016; 113: 45-50.
14. MacKenzie K, Williams HH, Williams B, McVicar AH, Siddall R.Parasites as indicators of water quality and the potential use of helminth transmission in marine pollution studies. Adv Parasitol. 1995; 35: 85-144.
15. Marcogliese DJ. Parasites of the superorganism: Are they indicators of ecosystem health? Int J. Parasitol. 2005; 35: 705-716.
16. Vidal-Martínez VM, Wunderlich AC. Parasites as bioindicators of environmental degradation in Latin America: A meta-analysis. J Helminthol. 2017; 91: 165-173.
17. Barata RA, Bodevan EC, Kirchpfennig FS. Survey of parasites in sea turtles rescued off the coast of Santa Catarina and Paraná, Brazil (2020–2022) and their relationship with marine pollution. Mar Pollut Bull. 2024; 201: 116190.
18. Berk SL, Verghese A, Alvarez S, Hall K, Smith B. Clinical and epidemiologic features of strongyloidiasis. A prospective study in rural Tennessee. Arch Intern Med. 1987; 147: 1257-1261.
19. Sharma RS, Rana A, Panthari D. Wastewater pollution induced detrimental impacts on aquatic biodiversity: A review. In: Advances in Environmental Pollution Management: Wastewater Impacts and Treatment Technologies. Agricul. Environ. Media, Haridwar (Uttarakhand). 2020; 113-127.
20. Khan RA, Thulin J. Influence of pollution on parasites of aquaticanimals. Adv Parasitol. 1991; 30: 201-238.
21. Keller JM, McClellan-Green PD, Kucklick JR, Keil DE, Peden-AdamsMM. Effects of organochlorine contaminants on loggerhead sea turtle immunity: comparison of a correlative field study and in vitro exposure experiments. Environ Health Perspect. 2006; 114: 70-76.
22. Desforges JP, Sonne C, Levin M, Siebert U, De Guise S, Dietz R. Immunotoxic effects of environmental pollutants in marine mammals. Environ Int. 2016; 86: 126-39.
23. Vidal-Martínez VM. Helminths and protozoans of aquatic organisms as bioindicators of chemical pollution. Parassitologia. 2007; 49: 177-184.
24. Graham EA, Los Kamp EW, Thompson NM, Tillis SB, Childress AL, Wellehan JFX, Walden HDS, Ossiboff RJ. Proliferative strongyloidiasis in a colony of colubrid snakes. Vet Pathol. 2024; 61: 109-118.
25. Sures B. Environmental parasitology. Interactions between parasites and pollutants in the aquatic environment. Parasite. 2008; 15: 434- 438.
26. Grabner D, Rothe LE, Sures B. Parasites and Pollutants: Effects of Multiple Stressors on Aquatic Organisms. Environ Toxicol Chem. 2023; 42: 1946-1959.