Tick-borne disease rises in central Oregon, with the city seeing numbers that are unusually higher than previous records. In the last 10 years, the Oregon Health Authority has tallied less than one case of Colorado tick fever every year on the average. In the early summer of 2018, four cases surfaced.

The Centers for Disease Control and Prevention and Oregon health officials performed an investigation to identify the clinical manifestations, exposures, and the geographical dispersion of patients with confirmed disease, as well as the number of additional cases. The groups obtained their data via phone interviews and study of existing medical records.

Investigation About The New Cases

Out of the four cases discovered in 2018, three were men, and one was a woman. Their counties of residence, though different, were close by geographical location. All of them sought care from one county with the same health care system.

All the patients started having symptoms, such as fever, low white blood cell count, and low platelet count, in May 2018.

Three of the patients experienced having fever, and initial signs and symptoms reappear after a few days.

Only three of the patients were admitted in the hospital for about one to three days. All of them recovered from the disease.

The diagnosis of CTF was verified via CDC's reverse transcription-polymerase chain reaction assay. The diagnostic examination for tick-borne pathogens differed, but all the patients underwent RT-PCR as this method is more responsive than blood serum tests during the initial phase of the disease. Before the confirmation of CTF was made, the patients started receiving doxycycline as empirical treatment.

All patients said that they spent about five hours outdoors, including being in bushy and wooded places. They all reported having a tick bite two weeks before they first had signs and symptoms.They all wore long-sleeved shirts and pants, but none of them applied insect repellent. Three of them reported identified exposures in two of the locations with elevations of about 3,200 to 4,500 feet above sea level. No geographic groupings were determined because the separation of the land area between the three locations covered about 540 square miles.

More Cases Discovered

During review of electronic medical records, the researchers found three suspected cases of CTF. They used the 10th edition of the International Classification of Diseases for fever and leukopenia to determine possible CTF cases. A suspected case is defined by having fever and leukopenia from April 15, 2018 to July 31, 2018, without any other possible cause. Out of the three suspected cases, two were children and one was a man in his 60s. The man had a tick bite a few days prior to the onset of his clinical manifestations, while hunting in the same county where the two confirmed cases were recorded.

"More CTF cases were identified in Oregon in 2018 than in previous years, possibly because of increased tick activity or heightened provider awareness and testing," CDC reported. There was no common location identified, signalling that the virus was lurking in a number of areas in central Oregon in the spring of 2018.

What Is CTF?

CTF is a virus caused by the transmission of infected Rocky Mountain wood ticks. Symptoms include fever, and nonspecific clinical signs. Management is mainly supportive as there is no definitive treatment for the disease. Deaths from CTF is rare and about 30 percent require hospital admission. Six territories, including Oregon, require reporting of such cases.

As per the CDC, health departments should push through with promoting tick control strategies, such as use of EPA-registered insect repellents, and target communication to people going outdoors in locations where there are high risks of tick exposure.

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