. The very word invokes revulsion in many people. For veterinary professionals, the term conjures sights, smells, and, yes, sounds. The munching of maggots crawling inside a patient echoes in our memories.

When a maggot case arrives in a hospital, some professionals move toward the patient, and others find reasons to walk in the opposite direction. Myiasis, or fly-strike, is common in debilitated animals with infected or necrotic tissue.

Beyond manual removal, it is common to ensure the eradication of these distasteful dipterans from our patients with medications such as nitenpyram. An alternative is any of the isoxazoline drugs. The onsets of action for nitenpyram and isoxazolines are similar, with the obvious benefit of extended duration with isoxazolines of a month or more.

If you are wondering which to use based on label use, both choices have extralabel benefits with on-label dosing. If you have not heard of this, don’t be hard on your pharmaceutical representatives for not telling you—they can’t. The FDA has strict rules against extralabel promotion.

Pharmaceutical technical team members can only answer direct extralabel questions. Thus, unless you specifically ask, “Can I use your product to kill maggots?” company representatives cannot tell you. The 24-hour emergency hospital where this author was medical director regularly dealt with myiasis cases, and unless funds or patient logistics were an issue, the health care team regularly utilized isoxazolines.

Any pet on monthly isoxazolines will not be affected by myiasis. In some situations of debilitation, this could become a disadvantage.

Photo: Judy Gallagher/iNaturalist.org.png

Is there ever an advantage to being riddled with maggots? Yes, but this is not a reason to stop prescribing year-round isoxazolines for your indoor and outdoor patients. In current cases with myiasis, those baby dipterans are often helping the animal.

, the common green bottle fly. Parasitologists, forensic entomologists, and some doctors are fascinated by these insects. 

often recognizes an individual’s death before anyone else. Within minutes of a person’s or animal’s demise, these flies will lay eggs upon the corpse.

This egg-laying timing allows scientists to use maggots to help determine the time of death in some forensic investigations. The maggots’ larval instar, or stage, can help scientists know how long ago the fly eggs were laid.

Although far less common today, doctors have used 

as a surgical maggot since the early 1800s. This myiasis leads to improved tissue regeneration and lower bacterial levels within patients. Wounds of injured Civil War soldiers who were left in the field were occasionally noted to be unusually bright and clean, and the effect was given the term 

. With the discovery of penicillin not occurring until the next century, these neglected soldiers in the field often had better survival rates than those with bandaged wounds in the medical tent who developed gangrene.

Civil War Angel’s Glow did not arise from maggots, per se. The greenish-blue bioluminescence arose from a nematode-associated bacterium that infected the wound. The maggots managed the cleanliness. Patient survival was a team effort: the maggots' removal of necrotic tissue and the bacterium’s antimicrobial exotoxin helped save lives. Until a 2001 high school science project elucidated the bacterial role, the flies took the credit.

Secondary myiasis typically is not painful because these maggots stop eating at the edges of healthy tissue. This is common for the calliphorid flies endemic to the United States. Calliphorids bear the common name of blow flies.

Although medical professionals and some injured soldiers of the Civil War had positive experiences with the flies, most sheep producers detest them because of their proclivity for laying eggs in damp wool. Any skin disease, such as infection, can quickly lead to unwanted myiasis.

only provides secondary myiasis, meaning that tissue must be damaged or necrotic for maggots to feed. Primary myiasis caused by the New World screwworm (NWS), 

, was eradicated in the US as of 1966, except for a brief invasion in 2016. It is currently endemic in Cuba, Haiti, the Dominican Republic, and countries in South America.

NWS has recently spread to Costa Rica, Nicaragua, Honduras, Guatemala, and now Mexico for the first time in 3 decades. The US Department of Agriculture is expecting reinvasion of NWS in the US. A family member of 

, NWS generates primary myiasis—its larvae eat healthy tissue of any warm-blooded animal. Their victims include cattle, sheep, pigs, dogs, cats, and humans.

Since primary myiasis eats living tissue, there is no pain-free Angel’s Glow here. These maggots induce excruciating tissue destruction with potentially fatal sequelae for their victims. If this foreign animal disease arrives here, we will witness an onslaught of myiasis cases like we haven’t seen before. Take a nap on the backyard hammock next to your dog, and you may both awaken with 

eggs laid upon you. Within 24 hours, the maggots emerge from their eggs and begin to devour healthy flesh.

In late 2024, the US canceled all Mexican cattle imports, due to NWS being identified in Chiapas, Mexico.

 Despite this measure, concerns remain that the northern movement of NWS will not be stoppable.

The USDA best describes the etymology of the name 

“The name screwworm refers to the maggots’ feeding behavior as they burrow (screw) into the wound, feeding as they go like a screw being driven into wood. Maggots cause extensive damage by tearing at the hosts’ tissue with sharp mouth hooks. The wound can become larger and deepen as more maggots hatch and feed on living tissue. As a result, NWS can cause serious, often deadly damage to the animal.”

Although there is no certainty NWS will arrive in the US, the risk is realistic and high. If this eventuality occurs, we will have myiasis cases where the maggots do not benefit the animal. The flies neither need nor search for debilitated or recently dead animals. Screwworms prefer their meat grade A.

sampled from a canine myiasis case, 2024.

What can we do now? First, continue to prescribe year-round isoxazolines for your indoor and outdoor patients. Secondly, be vigilant. Beyond the patient’s travel history and clinical presentation, several key features help define the maggot. Start at the posterior end of the maggot where breathing occurs. (

boast Calliphorid-type spiracles (the external breathing apparatus), which look like 3 lines pointed toward a button (

). To differentiate these 2 species, look for 

’s pigmented tracheal trunks, visible on the dorsal aspect of the maggots.

NWS has prominent hooks on its anterior end— imagine a vampire maggot. Many maggots will have these hooks, but they are large on NWS (

Finally, if you suspect NWS, report it. Take samples and contact your local health department and state veterinarian.

, demonstrating the diminutive hooks, in contrast to 

is a preventive medicine specialist who practices in emergency medicine. He also is an item writer for the North American Veterinary Licensing Examination.

Cutolo AA, Perier N, Menz I, Thyssen P, Silva FO, Beugnet F. Efficacy of afoxolaner (NexGard) on the treatment of myiasis caused by the New World screwworm fly 

(Diptera: Calliphoridae) in naturally infested dogs. 

. 2021;24:100569. doi:10.1016/j. vprsr.2021.100569

Correia TR, Scott FB, Verocai GG, et al. Larvicidal efficacy of nitenpyram on the treatment of myiasis caused by 

. 2010;173(1-2):169-172. doi:10.1016/j.vetpar.2010.06.019

Ricciuti E. How blow flies compete (or not) for decomposition duties. 

. October 27, 2020. Accessed February 24, 2025. https://entomologytoday.org/2020/10/27/ how-blow-flies-compete-decomposition-duties/

Miller GL. Historical natural history: insects and the Civil War. Montana State University. Accessed February 24, 2025. https:// www.montana.edu/historybug/civilwar2/flies.html

Horobin AJ, Shakesheff KM, Woodrow S, Robinson C, Pritchard DI. Maggots and wound healing: an investigation of the effects of secretions from 

larvae upon interactions between human dermal fibroblasts and extracellular matrix components. 

. 2003;148(5):923–933. doi:10.1046/j.1365-2133.2003.05314.x

Lyons J. “Glowing” Wounds: why Civil War soldiers had injuries that shone. War History Online. October 19, 2018. Accessed February 24, 2025. https://www.warhistoryonline.com/ instant-articles/glowing-wounds-civil-war.html

New World screwworm. US Department of Agriculture. February 6, 2025. Accessed February 13, 2025. https:// www.aphis.usda.gov/livestock-poultry-disease/cattle/ticks/ screwworm

Staff Report. US suspends Mexican cattle imports after flesh-eating worm detected in Chiapas. 

. November 28, 2024. Accessed February 24, 2025. https://mexiconewsdaily.com/news/mexico-cattle-screwworm/

Companion Animal Parasite Council. Cochliomyia hominivorax. May 9, 2017. Accessed February 24, 2025. https://capcvet.org/ guidelines/cochliomyia-hominivorax/

Articles

Understanding this parasitic fly larva and the risk it may pose is the first step for preventing infestation

Screwworms: when the larvae don't care about boundaries

Domenico Santoro, DVM, MS, DrSc, PhD, DACVD, DECVD, DACVM discusses preventive measures to reduce the risk of dermatophyte infection

Talking to clients about fungal infection prevention

In this interview, Domenico Santoro, DVM, MS, DrSc, PhD, DACVD, DECVD, DACVM, associate professor at the University of Florida College of Veterinary Medicine in Gainesville, and service chief of dermatology in the Department of Small Animal Clinical Sciences, talks about preventive measures against fungal infections that dog and cat owners should be aware of to minimize the risk of infection.

Below is the interview transcript, which has been lightly edited for clarity:

Domenico Santoro, DVM, MS, DrSc, PhD, DACVD, DECVD, DACVM: 

My name is Domenico Santoro. I'm an associate professor in dermatology at the University of Florida. I have a PhD in immunology, and I'm service chief of the dermatology service here.

], there is not really much to do in the sense that this is a commensal, so every dog, every cat, has it. So we just need to be aware of the underlying problem, like allergies, for example, [that] develop as a primary issue for these patients.

For dermatophytes, the most important prevention measure will be essentially [being] careful with new cats or new dogs coming in the household, or [coming into] contact [with other animals], specifically in doggy parks where there is contact with other animals that may be infected. Or even [being careful with] dogs who like to go outside and dig or chase wildlife animals because that is, for some of those dermatophytes, the soil and/or rodents can be the reservoir for the infection. So having dogs that dig outside—really, you can’t really prevent that type of behavior, but it is important to note it in the history, so that the veterinarian will know which type of fungus to consider, and they [can put] that organism in a differential diagnosis.

Happy Friday dvm360 readers! Did you know that we are less than 2 months away from our next Fetch conference of the year, Fetch Nashville? Join the dvm360 team, our amazing attendees, and key industry leaders for 2 days of education, networking, and fun! You can 

 today to secure your spot, and we will see you in Nashville!

After you finish registering for Fetch Nashville, here is what was popular this week on dvm360.com:

 a case of antifreeze poisoning in community cats in a mobile home community after 3 cats are believed to have been killed by the act of violence after officials found 3 bowls of tuna mixed with antifreeze and bleach.

 that its 2 oldest residents, Mommy and Abrazzo, who are both critically endangered Western Santa Cruz Galapagos Tortoises, welcomed 4 hatchlings. These births are the first in the zoo’s 150+ years for this species and Mommy is the oldest first-time mother of the species.

 of The Vet Blast Podcast presented by dvm360, Madonna Livingstone, BVMS, MRCVS, and host Adam Christman, DVM, MBA, discuss handling exotic pets and how the human-animal bond is not species-specific.

 this week that an unapproved antiparasitic and antimicrobial drug is now legally available for use with ornamental finfish to treat 

 which is also known as “Ich” or “white spot disease.

 with dvm360, Aaron Shaw, OTR/L, CHT, CSCS, host of the podcast 

, provided dvm360 with some strategies veterinary professionals can utilize when coping with the stress that the profession can bring.

Recently, Clemson University’s Harvey S. Peeler Jr. College of Veterinary Medicine reached a 

 in its construction with a traditional beam signing ceremony on the site of the future first veterinary school in South Carolina.

Wrap up: Four critically endangered Western Santa Cruz Galapagos Tortoises hatched at the Philadelphia Zoo, and other news

Animal Neurology Center (ANC) officially opened its doors in its state-of-the-art facility in Creve Coeur County in St Louis, Missouri on February 14, 2025. The facility was a $3.5 million investment and is a 7,200-square-foot center providing animal care as well as educational facilities for the veterinary industry, while aiming to foster strategic partnerships with biotechnology leaders. Along with the investment back to the community through opening the center, the opening also brought 20 jobs to its local community and has the capability to host 600 veterinarians and veterinary students visiting annually.

In this interview conducted by Adam Christman, DVM, MBA, chief veterinary officer for dvm360, talks to Fred Wininger, VMD, MS, DACVIM (Neurology) about the opening of the Animal Neurology Center and what opening it was like for Wininger.  

On site interview with Adam Christman, DVM, MBA, and Fred Wininger, VMD, MS, DACVIM (Neurology)

ANC was founded by Fred Wininger, VMD, MS, DACVIM (Neurology), a member of the dvm360 Editorial Advisory Board and a Fetch speaker, after he returned to St. Louis in order to establish the center According to a release from the Missouri Department of Economic Development, Wininger’s vision to create this center was ‘driven by a passion to deliver world-class care and advance the field through innovation. Wininger and the ANC team celebrated the grand opening in January 2025, the ribbon cutting ceremony on April 4, 2025, but began treating patients in December 2024.

“Our hospital is dedicated exclusively to diseases of the brain and spine, which allows us to focus intensely on our area of specialized expertise. But we are more than just a hospital. While providing compassionate care and offering clear communication and support for our clients are at the heart of what we do, our mission is also driven by a commitment to teaching the next generation of veterinary professionals,” expressed Wininger.

“We have allied ourselves with companies that traditionally focus on human medical care. Companies like Siemens Healthineers, Karl Storz Endoscopy, and Zoetis recognize the expectation that pet parents want medical capabilities commensurate with what they would receive themselves. They have recognized the ANC as a center of excellence and an opportunity to advance human and veterinary medicine together,” he continued. 

Fred Wininger, VMD, MS, DACVIM (Neurology), Natalie L. Marks, DVM, CVJ, CCFP, Elite FFCP-V, and Adam Christman, DVM, MBA, all attending the ribbon cutting ceremony at Animal Neurology Center (Image courtesy of Adam Christman, DVM, MBA) 

Built on 3 pillars of compassionate care, education, and industry collaboration, ANC is committed to provide empathetic care to those who seek care for their pets at the facility. Along with its clinical services, the facility is opening its doors to veterinary students by offering clinical rotations, running a residency program through the University of Missouri, and hosting seminars for practitioners. ANC will also work with industry leaders to make sure the use of cutting-edge technology and drive innovation in the veterinary industry.1

“We’re pleased to see an innovative employer like The Animal Neurology Center establishing and creating jobs in the St. Louis area,” said Governor Mike Kehoe. “This company’s success is a testament to our state’s ability to support entrepreneurs and innovators. We congratulate The Animal Neurology Center on its opening as it joins a long list of world-class, Missouri-made employers.”

Jobs are being added as part of the Animal Neurology Center’s new location and will pay ‘an average wage well above the county average.’

 ANC will also benefit from the Missouri Works program which is a tool to help companies retain workers and expand by giving access to capital through tax credits or withholdings for the creation of jobs

dvm360’s chief veterinary officer Adam Christman, DVM, MBA, recently attended the ribbon cutting ceremony and interviewed Wininger on site! You can check out that interview on dvm360’s Instagram account.

The Animal Neurology Center establishes in Creve Coeur, investing $3.5 million and creating 20 new jobs. News release. Missouri Department of Economic Development. February 14, 2025. Accessed April 10, 2025. 

https://ded.mo.gov/press-room/animal-neurology-center-establishes-creve-coeur-investing-35-million-and-creating-20-new

Animal Neurology Center in St Louis, Missouri brought 20 jobs to the area after investing $3.5 million in the center 

Veterinary specialty center brings millions back to community 

Sandra Koch, DVM, MS, DACVD, talks about the importance of patience, dedication, and collaboration 

Practicing compassion and spectrum of care with clients and itchy patients

Resources on feline atopic skin syndrome:

Clinical presentations of feline atopic skin syndrome

The challenges of diagnosing feline atopic skin syndrome

Treatment options for cats with feline atopic skin syndrome

Creative solutions for feline atopic dermatitis

In this video from an earlier interview on feline atopic skin syndrome at the 2025 WVC Conference in Las Vegas, Nevada, Sandra Koch, DVM, MS, DACVD, reminds veterinary professionals to be compassionate with clients as they navigate their cat’s skin condition. She also highlights the importance of spectrum of care and collaboration among the veterinary team to achieve an improved quality of life for their patients.

Below is the interview transcript, lightly edited for clarity:

I do hope that we have more research for cats in order to help better understand the disease to provide better treatment options, because we do need better options to help our superior species.

And because managing allergies in cats can be so difficult, can be so challenging for pet parents and veterinarians, it's very important that we practice compassion with our owners because they're going to be frustrated, they're going to be angry, they're going to be upset, right?

Financially, it can be a big burden, so practicing spectrum of care and trying to work with them with something that works for them, not just their cats, and understanding that despite the limitations that we have, if we are persistent and we work together with our clients, we should be able to [help them] get them better. I mean, of course, there are those cases that are nightmare cases, right, that we're all like pulling our hairs out to figure out.

But I think with patience and dedication and working as a team—as a care team with our clients, and in pairing with our nurses and technicians—I think we're able to improve their quality of life, and that's the main goal, right?

And by improving their quality of life, we're also improving the quality of life for their families, because everybody suffers when they’re itchy.

Videos

With chronic hepatitis potentially being more common in cats than believed, according to a feline virologist at the City University of Hong Kong, a group of researchers and specialists are coming together to study the first hepatitis B-related virus found in carnivores. Specifically, their research will center on how the virus affects cats, including its link to liver disease and cancer in these felines.

For the study, Texas A&M Gastrointestinal Laboratory (GI Lab) is partnering with Julia A. Beatty, BVetMed, PhD, FRCVS (Feline Medicine), FANZCVS, GAICD, chair professor of veterinary medicine and infectious disease at the City University of Hong Kong. Beatty will work with Jörg M. Steiner, DrMedVet, PhD, DACVIM (SAIM), DECVIM-CA, AGAF, GI Lab director and regents professor in the Department of Small Animal Clinical Sciences at the College of Veterinary Medicine and Biomedical Sciences (VMBS), and his team.

Hepatitis B is known to be a global health concern in the human world, and animal variants of the virus have been studied for with human health in mind.

However, “the health of domestic cats is the primary driver for our work,” shared Beatty in a Texas A&M report. According to Texas A&M, the recently discovered feline “cousin” of the hepatitis B virus—discovered by Beatty and her team—is the first virus related to hepatitis B that has been found in a carnivore and companion animal

Beatty explained that the team’s goal is to investigate whether the feline cousin of the hepatitis B virus leads to disease in cats like in the same way it does in humans.

In humans, hepatitis A, B, and C can all affect the liver, although the severity varies for each type.

 Hepatitis A is generally food-borne. Although this illness has high transmissibility, the damage it does to the liver is mild.

On the other hand, hepatitis B spreads via contact with infected bodily fluids. Mothers can also transmit the disease to their babies.

 This form of hepatitis, along with hepatitis C, can cause chronic disease and lead to long-term liver damage, cancer, and cirrhosis—a condition in which the liver’s healthy tissue is replaced with scar tissue, permanently damaging the liver.

In humans and cats, hepatocellular carcinoma (HCC) is the most common type of primary liver cancer. In humans, this type of cancer is most often caused by chronic liver diseases like cirrhosis.

“The goal of our study is to determine whether the feline hepatitis B-like virus causes disease in cats like it does in humans,” Beatty said.1 “We have already identified an association between the virus and both chronic hepatitis and...HCC, the most common type of liver cancer in cats.”

“In fact, about a quarter of feline HCC cases are positive for the virus. But more work must be done to fully understand how the virus affects cat health,” she continued.

 “These diseases are not incredibly common in cats, but it’s possible that chronic hepatitis is more common than we think.”

According to Texas A&M, the same hepatitis B-like virus has been identified in a limited number of dogs. Yet, no evidence exists that shows dogs can get liver disease due to the virus.

Beatty stated there is also no evidence that the virus can infect humans. This hepatitis B-like virus, however, has been found in large-cat species, such as the endangered Iberian lynx.

Currently, there is no feline vaccine for the hepatitis B virus, and the hepatitis B vaccine for humans is highly toxic to cats, explained Beatty. However, “there are already some new virus treatments that can point researchers in the right direction,” she said in the report.

 “There’s already a lot of knowledge in this area.”

Price C. Texas A&M Gastrointestinal Laboratory collaborates with virologist to prevent liver disease in cats. Texas A&M University. April 9, 2025. Accessed April 10, 2025. 

https://stories.tamu.edu/news/2025/04/09/texas-am-gastrointestinal-laboratory-collaborates-with-virologist-to-prevent-liver-disease-in-cats/?utm_source=newsletter&utm_medium=email&utm_content=Texas%20A%26amp%3BM%20Gastrointestinal%20Laboratory%20Collaborates%20With%20Virologist%20To%20Prevent%20Liver%20Disease%20In%20Cats&utm_campaign=today_04-09-2025

Hepatitis. Penn Medicine. Accessed April 10, 2025. 

https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/hepatitis

Cirrhosis. National Institute of Diabetes and Digestive and Kidney Diseases. Accessed April 10, 2025. 

https://www.niddk.nih.gov/health-information/liver-disease/cirrhosis#:~:text=Print%20All%20Sections-,Definition%20%26%20Facts,your%20liver%20begins%20to%20fail

Hepatocellular carcinoma. Mayo Clinic. Accessed April 10, 2025. 

https://www.mayoclinic.org/diseases-conditions/hepatocellular-carcinoma/cdc-20354552#:~:text=Hepatocellular%20carcinoma%20(HCC)%20is%20the%20most%20common,by%20hepatitis%20B%20or%20hepatitis%20C%20infection

The recently discovered feline “cousin” of the hepatitis B virus is associated with liver cancer in felines