UENOS AIRES - When there is an extraordinary new
outbreak of a well-known disease, it can provide new insights into
how the disease is spread.
A case in point is Chagas' disease, which exists only in the
Americas, where it has infected an estimated 16 million people and
causes about 50,000 deaths each year.
This parasitic infection usually is transmitted through the bite
of the kissing bug (also known as the reduviid bug and the
triatomine bug). The insect lives in cracks and holes in poor
housing, where it bites people, often on the face, while they sleep.
Occasionally, Chagas' is transmitted through blood transfusions,
organ transplants and from mother to child at birth.
Recently, Brazilian health officials have reported a widespread
outbreak in which Chagas' apparently was transmitted orally through
contaminated sugar cane juice. Brazil has banned the sales of the
juice, which was used to make a popular drink, guarapa, which is
usually consumed fresh. The product is not believed to have been
exported.
Although the outbreak is small (25 laboratory-confirmed cases as
of April 4), three people have died of the disease, making the
outbreak unusually virulent. The ages range from 3 to 73.
The outbreak has led Brazil to ask Argentina and other
neighboring countries to warn the hundreds of thousands of people
who flocked to the beaches in the state of Santa Catarina and
elsewhere in southern Brazil since Feb. 1 in the steamy South
American summer to get medical checkups if they drank sugar cane
juice and became ill. (One case was reported from Italy.)
In their investigation scientists hope to determine how the
contamination of the juice occurred and how much effect food-borne
transmission can play in spreading Chagas'. The investigation so far
has traced the source to a single site in Navegantes, Brazil, a
coastal city.
The disease is named after Carlos Chagas, a Brazilian physician
who first described it, in 1909. Chagas' usually spreads when
someone is bitten by an insect, engorging itself with blood and
passing the parasite in its feces onto the skin.
The parasite then enters the body when an affected person
scratches the skin or touches an open cut or the eyes or mouth.
The initial symptoms of Chagas' are usually mild or nonexistent.
It generally takes decades for the Chagas parasite to cause death by
slowly damaging heart muscle, the esophagus and the colon. By that
time, drugs are ineffective in reversing the damage.
But in this outbreak, the symptoms and medical problems have
developed within days after ingestion of the parasite, and they have
been severe in a large proportion of victims. The most common were
fever, headache, muscle aches, vomiting and a rash.
Many also experience swollen lymph glands and spleen; abdominal
pain; intestinal bleeding; jaundice from liver damage; and
encephalitis, said Dr. Luis G. Castellanos of the Pan American
Health Organization, a branch of the World Health Organization, in
Brasília. Also, Dr. Castellanos said, a buildup of fluid in the
lungs has resulted from an acute infection of the heart.
Brazil has advised doctors who examine patients with symptoms
suggestive of Chagas' disease to test their patients' blood for
evidence of infection from the parasite, Trypanosoma cruzi.
Patients may benefit from either of two drugs: Benzonidazol, made
by Roche, and Nifurtimox, made by Bayer. The drugs can be effective
in treating the earliest stages of Chagas' infection, said Dr.
Ricardo Gurtler, an expert in the biology and epidemiology of
Chagas' disease at the University of Buenos Aires.
Dr. Kennedy L. Schisler, a specialist in allergies and immunology
who practices in Iguaçu Falls, Brazil, said, "News of the outbreak
has shocked and flabbergasted us," in part because of the severity
of the initial symptoms. In recent years, as health workers have
stopped or reduced the transmission of Chagas' by the kissing bugs
in Santa Catarina and in a number of other areas, doctors have
deduced in a few instances that the disease was spread through
contaminated food. But documentation was limited.
Doctors have reported a couple celebrating their 50th wedding
anniversary died of Chagas' after acquiring the parasite at the
party. In other outbreaks, entire families have become infected by
eating contaminated food in their homes.
The Santa Catarina outbreak is believed to be the largest known
food-borne outbreak of Chagas' and the first that has led to an
international warning, said Jennifer Marcone, a spokeswoman for the
Centers for Disease Control and Prevention in Atlanta. She also said
that the C.D.C. was not participating in the investigation because
Brazil has many experts on Chagas' disease.
Why the symptoms appear to be more severe in this outbreak than
in earlier ones is under investigation. One theory is that many more
parasites entered the body from the contaminated juice than would
have found their way into the blood from a bug bite. Another theory
is that the victims may have been infected with an unusually
virulent strain of the Chagas' parasite.
Epidemiologists theorize that animals like the gamba, carrying
the reduviid bugs, could have deposited the parasite in the sugar
cane and left before the cane was crushed. Another theory is that
the bugs were in the sugar cane when it was crushed.
The investigations are also aimed at determining how long the
parasite can survive in feces outside the reduviid bug and in fluids
after the bug is crushed. The information is important because it
can help health workers devise strategies to prevent oral
transmission.
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