Friday, April 03, 2020

Mites, Microbes, and Cancer in Santa Catalina Island Foxes by Alexandra DeCandia

(Thank you to our guest blogger Alexandra DeCandia a doctoral candidate at Princeton University)

Over the last few decades, we've realized that organisms are far more complicated than they initially appear. What may look like an individual fox is actually an ecosystem containing trillions of microorganisms on every square inch. [Figure 1]

Despite their tiny size, microbes influence important host functions, such as development, digestion, stress tolerance, behavior, and even immunity. Therefore learning more about these hidden actors can inform wildlife conservation of at-risk species in the modern molecular era.

Looking into the ear canal of an island fox.
Microbes may be particularly important to species that lack genetic diversity, such as Channel Island foxes, especially where disease threatens long-term persistence. On Santa Catalina Island, scientists discovered extremely high rates of ear canal tumors, where roughly half of adult foxes have growths in their ears. Although the exact cause is unknown, researchers linked ear mite infection to tumor growth and development. The most prominent hypothesis states that infection with ear mites leads to inflammation and rampant cell growth in the ear canal, which in turn leads to tumors. Thankfully, treating foxes with the acaricide Ivermectin has already decreased mite burdens and tumor rates in these foxes.

However, there's more to this story. We still don't fully understand how mite infection leads to tumor growth. In particular, my collaborators and I wondered whether microbes play a role in this system. For example, do mites disrupt healthy microbes and cause secondary bacterial infections? And do those infections then contribute to the chronic inflammation that precedes tumor growth?

Figure 2: Island fox is swabbed during health check
To address these questions, my collaborators at the Catalina Island Conservancy collected microbe samples by swabbing ear canals (and a few other body sites) of healthy and mite-infected foxes. [Figure 2] (This process is similar to cleaning your ears with a cotton swab, except you don't throw away the swab afterwards.) Once a bunch of foxes were swabbed, all samples were sent to New Jersey, where I extracted DNA, collected genetic sequences, and analyzed the data.

 The results came back loud and clear: microbes differed between mite-infected and uninfected ear canals. Rather than a rich community of diverse microbes (as seen in healthy ears), mite-infected ear canals had fewer microbial species present. We further found that the balance of microbes (know as "relative abundance") differed between infection groups.  [Figure 3]

Figure 3: Classes of bacteria found in swab samples
As it turned out, this pattern was almost entirely driven by an overabundance of one bacterial species: Staphylococcus pseudintermedius (Class: Bacilli, shown in brown in Figure 3).

Even though this microbe is commonly found on canid species (such as domestic dogs and foxes), it can become an opportunistic pathogen when healthy communities are disrupted. Once it proliferates, it can be incredibly difficult for the immune system or even antibiotics to eradicate, leading to chronic inflammation.

We now hypothesize that mite infection and secondary bacterial infection with Staphylococcus pseudintermedius contribute to chronic inflammation and tumor growth in Santa Catalina Island foxes. 

Photo courtesy of Glenn Jensen
Although further tests are needed to definitively establish causation, these insights into the microbial dynamics of mite infection can help us monitor the population for antibiotic resistant forms of Staphylococcus pseudintermedius that could cause a disease outbreak. They can further help us explore other open questions, such as why Santa Catalina Island foxes are the only subspecies with ear canal tumors, despite ear mites on other islands. As always in science, answers lead to more questions. But at least one thing is clear: there's more to this story (and indeed, to all organisms) than what initially meets the eye.  

Alexandra DeCandia, Department of Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey.

Read the full paper: Ear mite infection is associated with altered microbial communities in genetically depauperate Santa Catalina Island foxes (Urocyon littoralis catalinae)

More Research Regarding Island Foxes:
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Friday, March 27, 2020

Fox Foto Friday - Meeting Up Island Fox Style


Island fox or human, it can be tricky to get to know someone new right now. A wildlife trap camera on Santa Rose Island captured these images of two island foxes meeting on a pathway.

A quick sniff can tell an island fox a lot about another fox. The female on the left is figuring out if she knows this male. Has she detected his scent before or is he a newcomer to her area? She can evaluate his health and what he's been eating in a sniff.

The two island foxes also communicate to each other through their physical stance. Tail and ears up - she is being friendly. Head down and tail at a medium height, he is letting her take the lead.


Both of these island foxes look healthy and well fed. Notice the female is also wearing a radio-tracking collar. Biological technicians on the islands are monitoring this female island fox. During summer counting, we may learn whether or not this meeting led to pups. 

Island foxes know all about epidemic disease. COVID-19 does not impact dogs or island foxes, but other viruses are a serious threat to them. Find out more about the current threat from canine distemper.

Island foxes on Catalina Island survived a catastrophic epidemic from 1998–2000.   

Monday, February 17, 2020

Distemper Virus on the Rise in California Winter 2020

Wildlife veterinarian Dr. Deana Clifford, a longtime island fox advocate and member of the Island Fox Conservation Working Group, was on the radio for the US Fish & Wildlife (USFWS) warning about the rise of canine distemper virus in California this winter.

2019 was a good year for wildlife, including island foxes. On the mainland, raccoon, striped skunk, and gray fox populations have all increased. (The gray fox is the ancestor of the island fox.) State wildlife agencies are also seeing an increase of canine distemper virus (CDV) among these species. Distemper is the dog equivalent of measles–it impacts the neurological and respiratory system, is highly contagious, and can be deadly to pet dogs and wild animals.

The collapse of the Santa Catalina Island fox population in 1998 was caused by a wild raccoon carrying CDV that was transported to the island. The introduction of distemper from this one raccoon nearly wiped out the Catalina Island fox.

island fox being vaccinated
Ideally, between 100 and 300 island foxes are vaccinated against CDV and rabies on each island. This ensures that if an introduction of distemper occurs at least a minimal number of island foxes might survive. Distemper is highly fatal among island foxes. On Santa Cruz Island, it means 100 would survive, but approximately 2,000 island foxes would perish. 

island fox with a radio-tracking collar
Introduced disease is the primary threat to island fox survival. This is why monitoring is so important and why FIF helps fund radio collars and health checks.

The USFWS and Friends of the Island Fox urge you to 
protect your pets, wildlife, and the island fox

Vaccinate your pets against the canine distemper virus (CDV).

Wednesday, February 05, 2020

Won't You Be F257's Valentine?


It's February – time to help the unique island foxes that live on California's Channel Islands!

Why does Friends of the Island Fox ask for your donations? 

Funding is essential for island fox conservation.


You can help this pup.
Won't you be her Valentine?


Island fox F257 is a female 10-month-old island fox. Last summer she was captured on Santa Rosa Island during annual health checks. A sample of her blood was taken, she was micro-chipped, and a whisker was collected for diet analysis.

In December of 2019, she was fitted with a radio-tracking collar funded by FIF and had another whisker removed for analysis.  
All of this work–the examination and work by the technician; blood sample testing, the microchip, radio-tracking collar, and diagnostic research on the whiskers–requires funding.

That is where you can make a difference. We ask you to donate, so FIF can help fund important island fox conservation work across the Channel Islands in conjunction with the various island land managers.

Pup F257 has so much to tell us.

Throughout her life, when captured, her microchip reveals her identity. Her data, gathered during annual check-ups, will form her profile history. Data collected on individual foxes is valuable for researchers and understanding how to keep island fox populations healthy and stable. Her radio collar will monitor her movements and safety.

The analysis of her two whiskers will tell us how her diet has changed from a very young pup to her life at 10 months old. If the winter rains don't return and F257 faces her first year in drought conditions, will she change her diet? FIF's Research Grant recipients are investigating important science on island fox health. Are foxes finding adequate nutritional food in their island ecosystem? Can we expect F257 to live a lifespan of 8–12 years?

This young pup is starting her life on Santa Rosa Island. You can be part of her success. Your donation will help make sure she is watched over and healthy.


Please be a Valentine for F257 and all the other island foxes
Donate today – Thank You!

Friday, January 24, 2020

Island Foxes and Island Spotted Skunks


On two of the Channel Islands, island foxes share their ecosystem with island spotted skunks.

The island spotted skunk is smaller than the island fox, and even more elusive. Because the skunk is primarily nocturnal, few people encounter them and, until recently, little was known about them.

When the island fox faced near-extinction on Santa Rosa and Santa Cruz Islands in 2000, people took note of the island spotted skunk for the first time. The first counting of island spotted skunks occurred when they were captured during island fox counting.

When the island fox population was low, the population of island spotted skunks soared. This gathering of spotted-skunk and island-fox cake pops, illustrates the overwhelming number of spotted skunks to island foxes. 


By 2014, however, the foxes were overtaking the skunks in reproduction and survival; island fox numbers almost equaled the estimated number of spotted skunks. As island foxes continued to increase across Santa Rosa and Santa Cruz Islands, the island spotted skunk population continued to decline dramatically. (Or at least, the number of island spotted skunks captured during island fox counting has declined.)

The gathering of cake pops–compiled by researchers Juliann Schamel and Angela Guglielmino–demonstrates how drastic the population shift has become.


What we don't know is: Why? Why have island spotted skunk numbers declined so much? What is the normal population relationship between these two species? Are island foxes out-competing island spotted skunks or is something else at play?

In the past few years, researchers have begun looking into the life and behavior of the island spotted skunk. FIF contributed support to researcher Ellie Boas to supply batteries for the first trap cameras that were put out to capture images of island spotted skunks. Researchers continue to try to capture images of island foxes and spotted skunks interacting, but it has been a challenge.

2020 opened with an important meeting of biologists, wildlife veterinarians, researchers, and invested organizations and institutions to pursue inquiry into the island spotted skunk. Following the example of the Island Fox Conservation Working Group and the successful conservation efforts for the island fox, the group will work to solve questions and develop action plans.

Friends of the Island Fox sends a resounding "Yip, Yip" to the newly formed Island Spotted Skunk Conservation Working Group. 

May we all work together to understand the important relationship between these two unique island species.

Thursday, January 09, 2020

How Structures in Teeth Could Provide Accurate Age Information for Island Foxes?


In October 2019, Friends of the Island Fox funded a research study, via a donation from Safari West, to investigate the use of cementum analysis as a method to determine island fox age at death. The current standard method for estimating age in island foxes is based on the wear of the upper first molar. This method is imprecise as tooth wear is heavily influenced by diet and varies significantly between islands and even among habitats on the same island.

Knowing the age at death is very valuable as it allows the National Park and other island managers to track the island fox lifespan. This is important as a fox who dies at age 9 or 10, after reproducing for many years, has contributed to the survival of the species. A fox that dies at 3 or 4 may not have had a chance to replace itself in the population or pass on its genes.

Image 1 - see sources below
Cementum is a thin mineralized tissue covering the root surface of teeth and functions as a tooth supporting device which anchors the tooth in the socket. Unlike bone, cementum is produced throughout one's life and forms annual layers (annuli)–a fact that makes it useful in aging techniques.

Cementum Analysis
To determine the age of an island fox after it has died, the lower canine tooth is removed and sent to the lab for aging.

Photo provided by S. Baker 2019
Once the tooth is received at the lab it is cleaned to remove any dirt and soft tissue, then undergoes processing to decalcify the tooth in preparation for analysis.

This makes the tooth very soft and pliable. The tooth is then preserved by fixing it in formaldehyde, also known as formalin, to preserve proteins and vital structures within the tooth. Next, it is embedded in a paraffin wax block which provides a support medium to make it easier to cut thin slices for examination.

The paraffin embedded tooth is cut into sections, approximately 15 microns thick (about the size of a droplet of mist or fog) on a device called a microtome, which is very similar to a deli slicer. The thin sections are mounted on glass microscope slides as the final step prior to analysis.

Paraffin embedded sample on a microtome being sectioned, courtesy M. Watling 2019
 The sections are stained with a special histological dye that is taken up by annuli at varying degrees (light blue or darker blue) depending on the amount of cementum laid down in a given year. This provides both a highlight and contrast for the purposes of counting the number of growth rings (aging) under a microscope.

The picture of cementum annuli in the photo below indicates the growth rings with the black arrows.
Image 4 - see sources below
Significance
If it is possible to accurately determine a fox's age at time of death, it can be used to monitor average longevity and to investigate many questions across all six of the Channel Island. Questions such as:
  • What age group of foxes are most likely to be hit by cars?
  • How old were foxes collected during annual mortality monitoring?
  • Do males or females have a greater lifespan?
Friends of the Island Fox is committed to research that will expand understanding of island fox biology and behavior. The more we know about island foxes, the more we can protect their future.
- Mike Watling, FIF Advisory Committee 

Image sources
  • Image 1 - The chemical and microbial degradation of bones and teeth. Advance in human palaeopathology. John Wiley & Sons - Scientific Figure on ResearchGate. Available from https://www.researchgate.net/figure/Simplified-cross-section-of-a-tooth-incisor-and-jaw_fig4_292711354 (accessed 17 Dec., 2019)
  • Image 4 - Tochigi, Kahoko & Aoki, Yukino & Maruyama, Tetsuya & Yamazaki, Koji & Kozakai, Chinatsu & Naganuma, Tomoko & Inagaki, Akino & Masaki, Takashi & Koike, Sinsuke. (2019). Does hard mast production affect patterns of cementum annuli formation in premolar teeth of Asian black bears (Ursus thebetanus)? PLOS ONE. 14.e0211561. 101371/journal.pone.0211561