New parasite discovered amid decline of California's unique Channel Island fox

 

California's Channel Islands are home to the Channel Island fox (Urocyon littoralis), one of the smallest and most cherished species of island fox in the United States. Although no longer on the Endangered Species List, they remain a species of special concern due to their ecological importance.

In the 1990s, the San Miguel Island fox nearly went extinct, dropping to just 15 individuals. A recovery program restored their numbers by 2010. However, from 2014 to 2018, the population fell to 30% of its peak right after a new acanthocephalan parasite, commonly known as thorny-headed worms, was identified on the island. This also occurred while a multi-year draught heated San Miguel Island, making it harder to identify the impact of the new parasite on San Miguel foxes.

To identify this parasite and determine the pathologic consequences of its infection on the health of foxes, a highly collaborative scientific effort, including a Florida Atlantic University researcher, used morphological and molecular methods to identify acanthocephalan parasites. They also used an extensive record of island fox necropsies and associated parasite collections to investigate the impact of the acanthocephalan parasite on the health of foxes at an individual and population level.

Results of the study, published in the International Journal for Parasitology, identify the parasite as Pachysentis canicola, a common acanthocephalan in multiple carnivore species in mainland North America. The parasite was detected in 69% of the necropsied foxes from San Miguel Island and was not found in any of the other five Channel Island fox subspecies.

Health issues linked to the acanthocephalan parasite, such as severe intestinal damage and inflammation, were seen in 47% of infected foxes. Other parasites did not significantly impact the health or survival rates of San Miguel Island foxes until the acanthocephalan arrived. After 2018, improved rainfall may have helped body condition recover, but it remained 27% lower than before the acanthocephalan outbreak, indicating that both environmental factors and parasites affect fox populations.

"We suspect that this parasite likely arrived on the island through infected arthropods such as insects inadvertently transported by humans," said Ale Aleuy, DVM, MPVM, Ph.D., senior author and an assistant professor in the FAU Department of Biological Sciences within the Charles E. Schmidt College of Science. "This discovery raises concerns about the impact of human activity on isolated ecosystems and underscores the importance of monitoring parasitic infections in vulnerable wildlife populations."

Researchers used detailed fox capture-recapture data from 4,269 captures of 846 foxes to investigate population health and demographic trends of foxes before and after the parasite was detected. They analyzed and monitored changes in body condition and weight from 2006 to 2022. Before the acanthocephalan arrived, the foxes had good health and low mortality despite other parasites.

"This parasite attaches to the intestinal wall of its host, which is particularly problematic for heavily infected foxes that exhibited more significant health issues such as emaciation, enteritis, and in some cases, death," said Aleuy. "After the parasite's arrival, foxes showed poorer body condition and lower weight, which worsened during drought conditions. This highlights the importance of understanding this parasite's life cycle and its impact on fox health, as well as preventing its spread to other Channel Islands."

Environmental stress may influence disease dynamics, and while foxes can survive with P. canicola in good conditions, they may need extra support during droughts.

"The acanthocephalan parasite did pose serious health challenges for the foxes, leading to issues like weight loss and intestinal complications. However, after the drought, we've seen a positive shift. While their condition is still not back to pre-parasite levels, the overall health of the foxes is stabilizing, and they are showing signs of improvement," said Aleuy. "This resilience gives us hope for their continued recovery."

The researchers suggest that it's also possible that P. canicola was present before 2012 but went undetected, potentially due to changes in fox diets increasing their exposure to intermediate hosts.

"Implementing appropriate management strategies is crucial to ensuring the health and longevity of this important species of fox," said Aleuy. "Controlling the invertebrates that spread the parasites might help, especially if they aren't native to the island."

The main goal is to prevent the parasite from spreading to other Channel Islands. Findings of this study highlight the importance of biosecurity in the Channel Islands National Park and more research on P. canicola and its impact on fox populations.

Journal Reference:

1. O. Alejandro Aleuy, Leslie W. Woods, Benjamin J. Padilla, Dennis Richardson, Juliann T. Schamel, Stacy Baker, Martín García-Varela, Charlotte Hammond, Sarah P. Lawson, Jasmine N. Childress, Jason Rohr, Kevin D. Lafferty. The invasive acanthocephalan parasite Pachysentis canicola is associated with a declining endemic island fox population on San Miguel Island. International Journal for Parasitology, 2024; DOI: 10.1016/j.ijpara.2024.09.003 

Courtesy:

Florida Atlantic University. "New parasite discovered amid decline of California's unique Channel Island fox." ScienceDaily. ScienceDaily, 23 October 2024. <www.sciencedaily.com/releases/2024/10/241023131048.htm>.

 

 

 

 

H5N1 virus isolated from infected dairy worker is 100% lethal in ferrets, but does not appear to be circulating in nature anymore

 

A strain of H5N1 avian influenza virus found in a Texas dairy worker who was infected this spring was able to spread among ferrets through the air, although inefficiently, and killed 100% of infected animals in studies University of Wisconsin-Madison researchers performed with the strain earlier this year.

The good news: the dairy worker experienced mild symptoms and fully recovered, and the H5N1 strain that infected the worker does not appear to have continued spreading in the wild.

Still, the findings highlight the risks posed by a virus that continues to spread among dairy cattle and occasionally to farm workers, and the study's lead scientist says he was surprised by the ease with which this particular strain was able to kill ferrets.

"This is one of the most pathogenic viruses I've ever seen in ferrets," says Yoshihiro Kawaoka, a UW-Madison professor of pathobiological sciences who spearheaded the work, described Oct. 28, 2024, in the journal Nature.

Ferrets are a common model for studying how influenza viruses that primarily affect birds are able to adapt to mammals, a topic that Kawaoka and his colleagues at UW-Madison's Influenza Research Institute investigate since such a jump could trigger an influenza pandemic.

Like other influenza viruses, H5N1 viruses mutate at a relatively rapid clip as they infect new hosts. Sometimes these mutations allow the viruses to more easily infect and spread among new species. That's how the current viruses, which have been infecting birds around the world in recent years, began to spread among mammals, most notably North American dairy cattle in 2024.

Kawaoka and his collaborators found that the H5N1 virus that infected the Texas dairy worker included a mutation that the team first identified in 2001 as important for causing severe disease. Luckily, Kawaoka says, the strain with that mutation seems to have died out.

"This isolate is unique among the H5N1 viruses circulating in cows," he says.

Kawaoka hypothesizes that H5N1 viruses took two paths when they made the jump from birds to cows, both facilitated by mutations that made the virus better adapted to mammals.

Kawaoka and his colleagues suggest that one path resulted in the more concerning mutation found in the Texas dairy worker, while the other led to a less dangerous mutation in the same protein.

"Both mutations give the virus the ability to adapt to mammals, but the good thing is the one containing this more pathogenic mutation has not been detected again," Kawaoka says. "So there are no extremely pathogenic H5N1 viruses currently circulating in cows. However, if a currently circulating cow H5N1 virus acquires that mutation, then that would be an issue."

Whether a virus with such a mutation would be dangerous for humans remains to be seen.

"The puzzling thing is why the human who got this virus did not have a severe infection," says Kawaoka, noting a few possibilities.

Perhaps exposure to seasonal influenza viruses provides some level of protection via antibodies, or maybe the route of infection is important; the Texas dairy worker's main symptom was conjunctivitis, suggesting the virus entered through the eye rather than the more typical respiratory route.

Alternatively, more robust surveillance of influenza cases among American dairy workers since the virus began spreading on farms might mean more cases -- including mild ones -- are being identified. Another possibility is this particular strain might simply be less severe in humans than mammals like ferrets.

"Those are all possibilities, but we don't know," says Kawaoka. "So, we're now trying to understand why this virus is so pathogenic in ferrets and what that could mean for human infections."

Journal Reference:

1. Chunyang Gu, Tadashi Maemura, Lizheng Guan, Amie J. Eisfeld, Asim Biswas, Maki Kiso, Ryuta Uraki, Mutsumi Ito, Sanja Trifkovic, Tong Wang, Lavanya Babujee, Robert Presler, Randall Dahn, Yasuo Suzuki, Peter J. Halfmann, Seiya Yamayoshi, Gabriele Neumann, Yoshihiro Kawaoka. A human isolate of bovine H5N1 is transmissible and lethal in animal models. Nature, 2024; DOI: 10.1038/s41586-024-08254-7 

Courtesy:

University of Wisconsin-Madison. "H5N1 virus isolated from infected dairy worker is 100% lethal in ferrets, but does not appear to be circulating in nature anymore." ScienceDaily. ScienceDaily, 28 October 2024. <www.sciencedaily.com/releases/2024/10/241028131451.htm>.