A deadly parasite turns jaguar conservation into a human health priority

In Brazil‘s Pantanal, the world’s largest tropical wetland, Paul Raad crouched in the undergrowth, scanning the ground for signs of jaguar activity. He wasn’t looking for the big cats themselves; instead, the veterinarian from São Paulo State University (UNESP) was searching for fresh jaguar feces. Spotting a recent sample, Raad carefully collected it, stored it in a sterile container, and sent it to a lab to be analyzed. It was one sample of dozens that he’s collected since 2022.

The team of technicians at the wildlife postgraduate program at UNESP made a surprising discovery in the jaguar scat: the presence of the tapeworm genus Spirometra. While Spirometra have been widely documented in scat from wildlife in Asia and Europe, this marked their first detection in jaguar droppings in the Pantanal.

“We found it in many fecal samples. [This tapeworm] wasn’t even the main target of the study, but it stood out so much — screaming, ‘Look, I’m here’ — that we ended up prioritizing it,” Felipe Fornazari, a UNESP professor and supervisor of Raad’s master’s research, told Mongabay.

It was an important discovery. Although parasites evoke negative connotations, researchers see them playing a key role in jaguar conservation. Jaguar populations are at risk from retaliatory killings by farmers, who see them as pests endangering livestock, especially in the Brazilian Pantanal, where about 90% of the land is privately owned by cattle ranchers.

Yet jaguars are vital for sustaining healthy ecosystems — and surprisingly this tapeworm parasite may help highlight this importance. Adult Spirometra live harmlessly in jaguars and pose no danger to humans. However, in their larval stage — found in feral hogs (both prey for jaguars and a food source for people living in the Pantanal), other animals and water sources — they can cause sparganosis, a severe infection in humans that can invade the eyes, brain or other body parts, sometimes proving fatal. By preying on hogs, jaguars help curb the spread of this dangerous parasite. They also offer researchers a window into the region’s environmental health and parasitic risks.

“If you wouldn’t have jaguars, who would eat the feral hogs and other larvae carriers?” Raad, whose research was completed in December 2024 but hasn’t been published yet, told Mongabay. “Jaguars are saving lives. They are being a bioindicator, telling humans that this parasite is here and can affect them too.”

Conservationists are using this evidence to reframe jaguars as essential allies in ecological balance and public health. Since October, Raad, in partnership with local ranch syndicates and wildlife conservation NGOs WWF and Ampara Silvestre, has organized five workshops across the Pantanal to promote coexistence with jaguars. At the Pousada Piuval eco-lodge and cattle ranching property, a key spot for his research, he’s given lectures highlighting the benefits of jaguar conservation and practical strategies to protect cattle from predation. These sessions also educate locals on safe water practices from natural resources, a common source for the local drink known as terere, and proper preparation of bushmeat, such as feral hogs, to mitigate the risk of sparganosis.

In addition to supporting jaguar conservation and community well-being, the research helps build trust with local populations by demonstrating that scientists are there to help them, rather than simply visiting these biomes for academic or career pursuits, Raad said.

“I want this product of research to be useful not only for me and the university but also for the community,” he said. “Jaguars are saving lives, and through this work, we’re saving jaguars too.”

Studying parasites

Parasites play an important role in conservation, providing key insights into their hosts (such as jaguars) and ecosystems (such as the Pantanal). For example, analyzing parasitic infections can help scientists gauge the size and health of animal populations, assess habitat quality, and determine the level of connectivity between animal groups in a particular region.

“Overexploitation, habitat loss and fragmentation, invasive species, and climate change are major threats to animal conservation, and all of these can be informed by parasites,” a 2021 study published in the journal Conservation Biology reads. “Research on parasites can also augment knowledge of the primary host and thereby potentially inform conservation.”

For his tapeworm study, Raad worked with teams from the zoonoses and genetics departments at UNESP, led by Felipe Fornazari and Ligia Silveira da Mota, respectively, and the pathology department at the Federal University of Mato Grosso, led by Richard Pacheco. They analyzed dozens of jaguar fecal samples from Poconé municipality in the north of the Pantanal, including the Pousada Piuval ranch, by extracting the DNA of the tapeworm from the feces. Most tested positive for the parasite. While the exact number of jaguars represented by these samples remains uncertain, Fornazari estimated it to be around eight — a compelling finding that underscores the need for further research, as well as highlighting jaguars’ crucial role in the ecosystem and the importance of adopting better health practices for communities in the wetlands.

“It is a study that is being carried out with an important species — the jaguar — in a very important region where the environment and livestock intersect,” Fornazari said. “This parasite hasn’t been studied much in Brazil. We know it can cause diseases in domestic animals, wild animals and people, and this could be happening in Brazil but we’re not detecting it.”

Spirometra tapeworms have a complex life cycle, closely tied to aquatic environments like the Pantanal’s floodplains. Its larval stages infect crustaceans, amphibians, reptiles and mammals, eventually maturing in definitive hosts such as jaguars. Cases of sparganosis, caused by consuming undercooked infected meat or contaminated water, are mostly found in East and Southeast Asia. A 2011 study identified three cases in Brazil, including one case where the patient had Spirometra larvae in her eye.

The low number of sparganosis reports in Brazil may indicate underreporting rather than a lack of infections, Fornazari suggested. “In remote areas with limited health services, many cases of disease go unreported,” he said.

The relationship between the environment, the parasite, the jaguar and the local community can be explained by the One Health paradigm, a concept developed by the World Health Organization, according to Raad. One Health recognizes that the health of people, animals and the environment are all closely connected, and when one of these areas has problems, it can affect others.

“We cannot discuss human health without considering animal health, and we cannot address animal and human health without acknowledging the health of the environment,” Raad said.

Minimizing jaguar – human conflict

Educating the local community about jaguars as bioindicators is part of broader efforts to protect these big cats and mitigate human-jaguar conflicts. At Pousada Piuval, Raad has worked with jaguar expert Rafael Hoogesteijn and the Ampara Institute on an electric fencing project to prevent jaguars from preying on calves. The 7,000-hectare (17,300-acre) ranch, home to 2,200 head of cattle with an annual birth rate of 1,000 calves, has demonstrated significant reductions in calf predation through these interventions.

Ranchers identify pregnant cows nearing calving and move them to designated maternity areas where electric corrals provide overnight protection from 5 p.m. to 6 a.m., the jaguars’ peak hunting hours. In 2022, there were 20 attacks. This declined to four in 2024, with no attacks at all within the electric fencing area. That means the project has so far been 100% effective in preventing jaguar attacks on calves and cattle within the fenced areas, and 80% successful overall in reducing attacks.

The project has reduced calf losses from 30 in 2022 to just one in 2024. Camera traps have also captured footage of a young jaguar receiving a mild shock from the fence and learning to avoid it on subsequent visits.

“Jaguars learn quickly,” Raad said. “When they encounter fencing, they associate cows with a negative experience and avoid them in the future. We cannot confirm that they will never hunt again, but we can say that we have reduced the chances of them attacking the cattle.

“Piuval has become a school for ranchers and a school for jaguars on how to hunt without going after cattle,” he added.

The project has provided additional benefits to farmers by facilitating essential herd management, according to Eduardo Eubank, owner of the Pousada Piuval ranch. “This has improved herd care,” he told Mongabay. “In addition to enclosing the calves, the cowboys register births and ensure all health protocols are met.”

Junior Lozano, a veterinarian overseeing livestock at Pousada Piuval, said electric fencing is essential for sustainable cattle farming in the Pantanal. “I think this is the future for us here,” he told Mongabay. “People need to trust in this project — it’s the only viable way forward.”

The next step, he said, is to build larger electric enclosures to continue protecting young calves once they leave the maternity pen after two weeks post-birth to graze in the pastures.

The initiatives to save jaguars illustrate the far-reaching benefits that the conservation of a single species can bring, Raad said. “This electric fencing project and the parasite discovery have shown that protecting jaguars leads to healthier ecosystems and communities,” he said. “Now, we need to replicate these successes on a larger scale.”

Citations:

Gagne, R. B., Crooks, K. R., Craft, M. E., Chiu, E. S., Fountain-Jones, N. M., Malmberg, J. L., … VandeWoude, S. (2021). Parasites as conservation tools. Conservation Biology, 36(1). doi:10.1111/cobi.13719

Anantaphruti, M. T., Nawa, Y., & Vanvanitchai, Y. (2011). Human sparganosis in Thailand: An overview. Acta Tropica, 118(3), 171-176. doi:10.1016/j.actatropica.2011.03.011

Mentz, M. B., Procianoy, F. Maestri, M. K., & Rott, M. B. (2010). Human ocular sparganosis in southern Brazil. Revista do Instituto de Medicina Tropical de São Paulo, 53(1). doi:10.1590/S0036-46652011000100009

This article by Sarah Brown was first published by Mongabay.com on 30 December 2024. Lead Image: tudying faecal samples and putting up electric fences are part of a large conservation project to protect the Pantanal’s jaguars as well as help the local community. Image © Paul Raad.

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