Rat lungworm, Legionnaires’ and now cat scratch disease.

A rare disease involving cats is affecting Hawaii children 3-1/2 times more than those on the mainland.

The prevalence of cat scratch disease, caused by the bacteria Bartonella henselae, is higher among island keiki because of the higher population of feral cats and year-round humid weather. That was the conclusion of University of Hawaii doctors after examining cases over the past eight years at Kapiolani Medical Center for Women &Children. The bacterial infection is spread between cats by fleas and to people through scratches and bites.

“We know that it is greater in the feral cat population because their flea burden is going to be greater. It’s much more year-round here in Hawaii … and children are outdoors more. All those things are playing a role and making the risk higher,” said Jessica Kosut, assistant professor of pediatrics at the University of Hawaii John A. Burns School of Medicine and a pediatric hospitalist at Kapiolani.

The doctors studied about 20 cases at Kapiolani but said the disease is largely underestimated because providers typically don’t test for it and the most common test is unreliable. In most of the cases, children were hospitalized for a prolonged period of time for cat scratch involving the liver, spleen, bone and inflammation of the brain and eyes.

Symptoms, which typically present weeks to months later after exposure, include swollen lymph nodes, prolonged fever and tiredness. While generally benign, in rare cases so-called cat scratch fever can lead to serious conditions that include bone infections, encephalitis (inflammation of the brain), seizures, coma or even blindness.

“A lot of times the children have a prolonged fever, and parents and doctors are naturally very nervous,” said Scarlett Johnson, lead researcher and a Hawaii island native, in a news release. “If we can get good diagnostic testing and we can start treatment earlier maybe we can avoid some of the expense and emotional stress for families.”

Controlling the flea population is one way to prevent the spread of the disease, as well as avoiding contact with wild cats and regularly treating domestic felines with flea medication.

Kosut estimates several hundred children on Oahu contract the disease annually but either don’t get tested or are treated for symptoms with antibiotics anywhere from four weeks to four months.

“That’s the risk. A child could play with a cat and then end up being in the hospital for a few weeks and end up on antibiotics for months,” she said.