MIDDLEBURY — Sitting on her porch one day this summer, Cindy Hill suddenly noticed that she could not see out of the inside corner of her right eye. Thinking that she must have scratched it, she decided to wait and see if it improved.
“I’ll sleep on it and then in the morning if it’s not cleared up, I’ll call the eye doctor,” the Middlebury resident said to herself.
When she woke up the next morning Hill’s whole right eye was blurry. Her eye doctor told her that she should go to Fletcher Allen Health Care immediately, but she had to wait to be seen until the following Monday. Over the weekend she became sick, with swollen lymph nodes and aches and pains. By the time she went to Fletcher Allen on July 3, vision out of her right eye was black. She discovered that her optic nerve was blown out.
The culprit of Hill’s vision loss is “Bartonella,” a disease more widely known as cat scratch fever or cat scratch disease.
Cat scratch disease is aptly named due to the disease’s form of transmission, which is most commonly through a cat scratch, bite or lick on an open wound. The manifestation of the disease in humans is caused by the bacterium Bartonella henselae that, according to the CDC, is carried by 40 percent of cats at some time in their lives. Another study said that as much as 50 percent of feral cats carry the disease.
The bacteria are transmitted from cat to cat through fleas. Kittens, the most likely to scratch and bite while playing, are more likely to transmit the disease to humans than older cats.
Most cats carrying the bacterium show no signs of illness, unlike humans, who commonly first present a small reddish-brown bump near the inoculation site. Other symptoms in humans include swollen lymph nodes near the site of infection, fatigue, fever, headache and loss of appetite. Hill only experienced these symptoms after losing vision in her eye, a somewhat unusual result of cat scratch disease. A more serious outcome like vision loss is uncommon in someone of her age and good health — children and people with compromised immune systems are more likely to experience the extreme effects of Bartonella.
Cat scratch disease is not widely seen as a great danger to human health, but those familiar with the disease say that more widespread knowledge of Bartonella would be helpful. Children and those with immune system problems might especially take note.
Dr. William Raszka, a pediatric infectious disease specialist with Fletcher Allen Health Care and the University of Vermont College of Medicine, is familiar with the effects of cat scratch disease. He acts as a consult for cases that are more difficult to diagnose, or those in which a child’s symptoms are not improving. Given the number of cases he sees, Raszka is confident that pediatricians are at least aware of the disease.
“In clinical practice every single practitioner who cares for children is going to see this multiple times in a year,” he said.
Raszka estimates that he is a consult for about 12 cases of the disease a year. A child’s primary care physician is usually able to take care of the patient without needing consultation; Raszka sees the more difficult cases. As a result he has treated the more extreme complications cat scratch disease can cause. Among the complications he has seen are swollen lymph nodes that persist for long periods of time, fever of unknown origin, bone infection, micro-abscesses of the liver and spleen, and encephalopathy, causing altered mental status and seizures.
In extreme cases, complications can also include heart valve infection, which can cause death, and neuroretinitis, or inflammation of the optic nerve.
HILL’S DIAGNOSIS
Neuroretinitis was the first symptom Hill attributed to cat scratch disease, followed by flu-like symptoms and what she describes as a feeling of fire running through her veins. Since her diagnosis she has been on antibiotics and has regained some of the vision in her right eye, although the eye is never expected to regain the sight it had before. Despite Hill’s symptoms, doctors are still unable to make a diagnosis based on tests of her blood; blood tests commonly aren’t a good diagnostic for cat scratch disease.
Raszka also finds difficulty in making a diagnosis using tests.
“None of the diagnostic tests are perfect,” he said, “which leaves doctors to rely on the clinical signs and symptoms” in order to make a diagnosis.
Bartonella stealthily enters the body, hiding in red blood cells and endothelial cells and making treatment and diagnosis tricky. The disease will generally go away by itself, but many doctors choose to treat with antibiotics in hopes that they will speed recovery. Raszka only uses antibiotics with immunocompromised patients, or patients who present severe symptoms, due to the lack of evidence that they truly aid in recovery. According to Raszka, only one randomized control trial on treating cat scratch disease with antibiotics has been conducted, and the only benefit the antibiotics gave patients, in comparison to those who didn’t take antibiotics, was reduced swelling in lymph nodes.
This lack of knowledge about Bartonella not only applies to treatment and diagnosis, but to knowledge of how infection takes place. Bartonella is already known to be transmitted through cat scratches, but there has lately been debate over the possibility of transmission by ticks and fleas. Raszka is open to this possibility.
“What we’re saying is that the flea could transmit the disease and the tick could transmit the disease, it’s just that we’re having trouble right now saying that the flea will transmit the disease and the tick will transmit the disease,” he said.
According to the Columbia University Medical Center’s Lyme and Tick-Borne Diseases Research Center, evidence for ticks as vectors of Bartonella organisms is circumstantial but strong. Differences between the tick-transmitted and cat-transmitted manifestations of the disease are unknown and complicated by the possibility of co-infection with other tick-transmitted diseases. Despite the lack of clear evidence implicating ticks in the transmission of Bartonella, Dr. Raszka has seen patients infected by the bacteria with no prior contact with cats.
“In Lyme disease we know the tick,” he said. “We know a lot about the tick, but we really don’t know anything about ticks and cat scratch.”
OWNING A CAT
Despite owning three cats herself, Hill believes that she contracted the disease from a tick she discovered on her right eyebrow before she lost sight in the eye, although there is no way of being sure of the cause. The cats could still very well be the source — even if the tick was responsible, it could have come from her cats. Still, Hill has no plans to get rid of the cats. This leaves a complicated question of how to balance the danger of having cats as pets with the love pet owners feel for their animals.
“My cats are looking at me with guilt and fear in their eyes,” said Hill.
Many pet owners are unaware of cat scratch disease, and it is not common practice to warn families of the possibility of infection, according to Dr. Thomas Munschauer, a veterinarian at Middlebury Animal Hospital.
“Well, the disease is so uncommon that, of the things that we warn people about when they’re getting a new pet, that one is sort of way down on the list,” he said.
The CDC does not keep track of the number of cases of cat scratch disease. As reported by Iowa State University’s College of Veterinary Medicine, one 1993 study estimated that 22,000-24,000 cases of Bartonella may occur yearly in the United States, most of these cases involving children. However, affected individuals might not even be aware that they have the disease, attributing their symptoms to other illnesses. This, combined with the difficulty in detecting and testing for the disease, makes an estimate of the number of cases per year uncertain.
Hill is past the diagnostic stage and is now worried about her future health.
“I was on an intense course of antibiotics,” she remembered. “Will it (the disease) be gone? Will I ever have ongoing or recurrent issues with the illness?”
Hill teaches at Champlain College and Community College of Vermont, does writing and editing in law and policy and practices part-time as a lawyer, but has been having trouble going back to work. She still has difficulty driving and looking at bright lights and computer screens, not to mention the time she spends going to doctors’ appointments. For her, the experience has been life-changing, encouraging her to inform the public.
Despite the low mortality rate, Raszka also believes that pet owners should be more aware of the disease.
“I don’t think there needs to be a national campaign about cat scratch disease,” he said. “I just say that whenever you take care of pets there are consequences and that parents have to balance that.”
Hill has a different solution to the danger kittens pose to children.
“Get them a puppy or pony instead,” she said. “I’d go for the pony, definitely.”