(CNN) Two newborn babies experienced illnesses rare for their age group after they were bitten by ticks, according to a case study published Wednesday in the medical journal Pediatrics.
The infants, one girl and a boy, were taken to hospitals in New York because they were experiencing common signs of infection: rashes, fever and irritability.
What wasn't common to the doctors who treated the babies were the more unusual symptoms: anemia, an elevated heart rate and a low blood platelet count.
The doctors, from Stony Brook Children's Hospital and Hampton Community Healthcare in New York, said that the infants were suffering from tick-borne infections that are rare in newborns because of limited exposure.
Lyme disease and other tick-borne diseases are a growing threat to the health of people in the United States, according to the US Centers for Disease Control and Prevention. The number of reported cases of these diseases grew from more than 48,000 in 2016 to nearly 60,000 in 2017. New tick-borne germs have been discovered, too.
"These two cases really underscore just the extent to which these ticks are spreading and bringing the tick-borne infections along with them," said Dr. Andrew Handel, who helped treat the babies and practices in the Pediatric Infectious Diseases division at Stony Brook Children's Hospital. "As we see those ticks being spread throughout the community, we also see a growing population of individuals who can become infected with them."
Changes in land use patterns may contribute to the spread of ticks, as suburban development in forest areas means ticks and animal hosts are in close contact.
A 6-week-old previously healthy infant boy was brought to a hospital in June after experiencing symptoms including irritability, poor feeding, vomiting and high fever.
Lab results showed the boy was also anemic, with a low blood platelet count.
He was treated with antibiotics and was transferred to Stony Brook Children's Hospital, where more testing revealed worsening anemia and blood platelet counts, as well as elevated levels of liver enzymes, which hint at an injured liver and a risk for liver disease.
His mother remembered seeing a bloody "flea" on her son's arm 20 days before his symptoms began. The family lives in a tick-endemic area, their home surrounded by tall grasses. Tick-borne diseases occur most frequently in the Northeast, mid-Atlantic and Upper Midwest.
Another round of antibiotics was started, but the boy's hemoglobin level severely dropped, requiring a packed red blood cell transfusion.
A test confirmed the boy to have babesiosis -- a rare, sometimes severe disease caused by the bite of a tick infected with Babesia microti, a microscopic parasite that infects red blood cells.
In August, a 5-week-old previously healthy infant girl was brought to the hospital emergency department because of a fever and an unusual rash.
Her parents reported removing an engorged black bug from her ear six days before her symptoms started. Their baby was rarely outdoors, although the family's dogs walked outside.
"Pets are well-known to carry ticks into the home. So take avoidance maneuvers," said Dr. Paul Auwaerter, clinical director of infectious diseases at John Hopkins University School of Medicine. "Shampoo or collars can be helpful." Auwaerter was not involved in either of the case studies.
The baby girl's heart was beating at a higher than normal rate. She was diagnosed with early disseminated Lyme disease, meaning the bacteria causing the disease had spread throughout her body.
Both babies' illnesses were remedied by rounds of antibiotics, but because no data exists to guide Lyme disease management in newborns, doctors referred to the American Academy of Pediatrics Red Book, which offers care solutions for infectious diseases.
There are also no clinically validated or FDA-approved tests for tick-borne infection for newborns.
Many questions remain, but the doctors thought that reporting their "ideas and conclusions that we came up with while treating these two infants might be helpful for future providers who come across similar cases," Handel said.
For older groups, there is testing to find tick-borne illnesses earlier and treatments that resolve symptoms. Both help to prevent long-term complications.
Children have a higher risk of getting Lyme and other tick-borne diseases because they tend to be more exposed to them.
"Kids, especially when they get beyond a certain age, bathe themselves, and they're not really looking for ticks," Auwaerter said. "Children tend to be outdoors more in play."
Having pets leaves your family more at risk, too. They can carry ticks in from outside, and sometimes the ticks are hard to find because of a pet's fur. Pet owners can talk with their veterinarians about medications for preventing tick bites.
There are ways you can protect yourself, your kids and your pets getting tick-borne diseases -- most importantly, "doing your nightly tick checks," Handel said.
The CDC recommends also avoiding high grasses, using insect repellent, bathing or showering as soon as you get inside, conducting full body tick checks and putting clothes in the dryer on high heat to kill ticks.
Although tick-borne illnesses are rare for newborns, doctors should consider them if they meet an infant who has a fever, an unusual rash or other signs of infection and lives in a tick-endemic area, Handel said.
"We don't want parents to hear about these cases and have an excess of anxiety that this could happen to their child," Handel said. "Of course, that did happen and it can happen. But this is very unusual."