A 65-year-old avid gardener worked hard every summer maintaining his wooded property in rural New Jersey.

He would spend hours outdoors, trimming trees and bushes, mulching and landscaping, and invariably would be bitten by insects.

He considered that a small price to pay for the great pleasure of communing with nature. He also had grown accustomed to aches and pains after a strenuous day in the yard.

This year, however, he felt more uncomfortable than usual. After several weeks of treating himself with a buffet of over-the-counter pain remedies, he became concerned when he developed night sweats and increasing fatigue.

His wife persuaded him to see his primary physician. The evaluation was a bit surprising at first.

His symptoms and the results of the initial lab work, which indicated he was profoundly anemic, suggested he could have lymphoma, infective endocarditis, a number of autoimmune disorders, or some sort of protozoan infection, such as malaria.

Malaria, which was eradicated in North America during the 1950s, seemed unlikely.

The patient had not traveled outside the Philadelphia metro area in quite some time and had never visited India, Southeast Asia, or Africa, where the disease is endemic.

But the man's blood tests showed he had a low platelet count - 95,000. Normal is above 150,000.

Solution:

The blood-count clue, along with the gardener's constellation of symptoms and green thumb, led his doctors to consider another possibility. A pathogen very similar to its tropical counterpart - Babesia.

Like malaria, Babesia lives and reproduces in human red blood cells. Both diseases cause destruction of those cells - a process known as hemolysis, which leads to anemia. Both diseases also cause flulike symptoms and night sweats.

Though malaria is transmitted by the mosquito, however, Babesia is spread by the deer tick, the same little creature that carries Lyme disease. The pathogen is in their saliva and they transmit it when they bite.

Babesia commonly afflicts cattle and rodents, but two subspecies of the parasite - Babesia microti in the United States and Babesia divergens in Europe - infect humans.

Many people infected with Babesia microti do not feel any ill effects. But it can be life-threatening in the elderly, people without a spleen, and those whose immune systems are weakened by medications or disease.

The only way to confirm the diagnosis was to identify the pathogen under the microscope.

The Babesia organism forms bluish rings similar to various malaria species, but notably smaller.

The protozoa also appear inside and outside infected red blood cells in a distinctive X-like pattern called the "Maltese Cross."

The hematology technician looked at slides of the patient's blood smear.

There, visible through lenses that magnified the protozoa 1,000 times, was the conclusive evidence.

Doctors treated the gardener with the antibiotic Azithromycin and the antimalarial drug Atovaquone.

On the third day of his hospital stay, the gardener began to feel much better. His lab work showed his red blood cells were no longer hemolyzing and were beginning to regenerate. His flulike symptoms dissipated, and he was discharged to enjoy the remainder of his summer, with the strong recommendation that he treat himself to some bug repellent.

Bradley Johnson is a second-year resident in the department of medicine at Pennsylvania Hospital.