Medical research conducted by veterinarians in a humanitarian, painless way is a two-way street. Not only does it benefit mankind, but it also produces effective treatments for sick animals.
The latest such study, which saves cats with painful eye infections, has been conducted by veterinarians at the Hebrew University of Jerusalem’s Koret School of Veterinary Medicine, which is located in Rehovot, in collaboration with the School of Veterinary Medicine at the University of California, Davis. They found that cold sore cream commonly used on people is safe and effective for feline use.
The study was led by Dr. Oren Pe’er, together with Dr. Lionel Sebbag and Prof. Ron Ofri from Koret’s ophthalmology department, together with Prof. Sara Thomasy and her team in California. It showed that a topical cream approved by the US Food and Drug Administration and commonly used in human dermatology can be repurposed safely for treating feline herpesvirus (FHV-1) eye infections, which are the leading cause of eye disease in cats. The three Israelis are the only ophthalmological animal experts in the country.
Their research has just been published in the journal Research in Veterinary Science under the title “Ocular tolerance and tear film pharmacokinetics of 1% penciclovir cream in cats.” The cost of the cream in Israel, which is off-label and prescribed only for humans, is about NIS 40. The condition is very infectious in cats, but humans do not contract it.
Treating feline herpies
Pe’er said cat owners must not treat their own pets; it should be performed by a vet, who has to diagnose the condition first. “We are teaching vet general practitioners how to do it,” Pe’er said. “We have presented our findings at international conferences, where we were enthusiastically received.”
Pe’er told The Jerusalem Post in an interview that he and his colleagues have been working on the problem for four or five years. “This kind of herpes occurs only in cats; there’s a different kind that is much less common in dogs.”
Although the three specialists treat the eyes of all kinds of animals in Israel – mammals from dogs and cats to horses and rhinoceroses; reptiles, including snakes; amphibians; and birds but, of course, not insects – they have not been called to zoos to treat the disease in lions, tigers, or leopards. This is fortunate, because the cream has to be applied to the diseased eye twice a day for two or three weeks.
There are some 500,000 licensed dogs living at home and 300,000 domestic cats in Israel. Estimates for the number of street cats here vary, with the Agriculture Ministry providing an estimate of about one million, while other sources, including a recent Knesset report, suggest the number could be between 500,000 and 1.5 million, but others estimate several million.
The virus attacks the lining of the nose, tonsils, conjunctiva (lining of the eye), and cornea. As the virus continues to make copies of itself, it may spread through secretions or close direct contact, resulting in signs like squinting, redness, and discharge. The infections can lead to more severe issues over time, including corneal ulcers, scarring, and, in some cases, blindness. If not treated early, the virus can even enter the bones in the nose and mouth, causing long-term physical damage.
VETERINARY GENERAL practitioners don’t feel comfortable treating FHV-1, said Pe’er, who graduated from the veterinary school in Kosice, Slovakia. After working at a private veterinary clinic in Ramat Gan, in 2017, he began a four-year ophthalmology residency program at Koret, under Ofri’s supervision.
Many cats recover from herpes viral conjunctivitis and then become lifelong carriers of the virus. Flare-ups can be triggered in cats by stress. Reported exposure rates in some cat populations around the world are estimated at up to 97%. Thus, the Koret School’s discovery will be a boon everywhere.
Koret’s veterinary students treat mostly cats brought in by their owners but also some street cats, and municipalities and voluntary organizations try to find them a home.
“Every day, there is something different,” Pe’er continued. “The basic structure and tissues in the eyes of all animals are similar, but there are differences.”
Treatment of FHV-1 ocular disease is challenging; until now, it has been treated less successfully with a pill, but it had to be forced on cats, and they didn’t like it.
Standard antiviral medications such as oral famciclovir can be difficult for owners to administer and have limited absorption in cats. They can also be expensive and require good owner and patient compliance. Selecting the appropriate therapeutic approach requires good clinical judgement, with an assessment of factors such as severity and stage of clinical disease, patient and owner compliance, and financial considerations.
The retrospective survey was distributed to over 100 owners of cats identified in Koret’s medical records as having presumed FHV-1 keratoconjunctivitis and treated with the drug. When applied to cats’ eyes, the 1% penciclovir cream (commercially known as Fenlips) was safe, well-tolerated, and maintained antiviral levels for over eight hours.
The team’s discovery highlights an “innovative, practical treatment approach that could simplify therapy for cat owners and improve outcomes in one of the most common feline eye diseases,” the researchers said. “Our findings suggest that a simple over-the-counter cream could offer an easier, effective option for cat owners struggling to manage recurrent eye infections,” said Pe’er.
In a retrospective survey, most cat owners reported excellent tolerance and visible improvement when using Fenlips, with 85% noting no side effects and 80% rating the treatment as effective or highly effective. The remaining 15% noted mild, transient signs, such as ocular redness and discharge. To confirm safety and effectiveness, the researchers conducted additional studies in healthy cats over a month-long period. No adverse reactions were observed, and tear tests showed that penciclovir levels stayed above the concentration needed to inhibit the herpes virus for over eight hours after application.
“This means twice-daily application could be enough to keep the virus in check,” he continued. “It’s a major step toward improving both animal welfare and treatment compliance.”
The researchers stressed that while the results were encouraging, further studies in larger numbers of felines are needed before the treatment can be formally approved for ophthalmic use in cats.
“The results of this study contribute to a growing body of evidence supporting the use of human-labeled antiviral drugs for veterinary applications,” the authors concluded.