Chikungunya in Cuba

The opening of Cuba will put Keys at risk of mosquito-borne illnesses

Wednesday, June 17, 2009
The opening of Cuba will put Keys at risk of mosquito-borne illnesses
By EDSEL M. FUSSELL Guest Columnist

There is little doubt that travel to and from Cuba is on the horizon.
Whether this will be good or bad remains to be seen. There is plenty to
be said about the benefits of opening the gates and how it will give a
much-needed boost to the local economy. However, this being paradise and
not Eden, you might expect a few problems to arise from all the back and
forth travel.

Outside Cuba, information regarding the presence of mosquito-borne
diseases in that island country is essentially nonexistent. We can
speculate that dengue and West Nile virus are present, and know from
history there were devastating yellow fever epidemics in Cuba prior to
1900. That is when Maj. Walter Reed, a U.S. Army physician, and his team
confirmed that yellow fever is transmitted by mosquitoes. Between 1867
and 1888, Key West suffered nine yellow fever epidemics without knowing
mosquitoes were the cause. Despite the development of an effective
yellow fever vaccine, and its commercial use beginning in the 1950s,
non-vaccinated populations in Central and South America continue to be
at risk.

The only thing preventing a recurrence of epidemics of mosquito-borne
diseases in this country is mosquito control. All the mosquito species
that were responsible for the great epidemics of the past still are with
us today. We also have a very susceptible human population. The
causative agents commonly are transported through the Keys via infected
birds and humans. Infected travelers arrive almost daily at the Miami
airport. Some are showing signs of illness while they are clearing
through Customs and are detected. While others are in the early stages
of the infection and show no symptoms of illness. They get through
Customs without being detected and proceed to their destinations, where
they may be bitten by a mosquito that then can spread the disease to
unsuspecting individuals in the community.

This is where mosquito control comes into play. The causative agent,
susceptible humans and the mosquito all are present in the same area,
which constitute conditions that are required for an outbreak of a
disease. In this case, the mosquito usually is the easiest to remove
from the equation, thereby interrupting and, hopefully, preventing the
occurrence of an outbreak.

Many of the very serious mosquito-borne diseases seem to originate in
Africa. This is the case of an exotic mosquito-borne viral disease known
as chikungunya, which was first isolated from the blood of a febrile
patient in Tanzania in 1953. Chikungunya is a serious disease similar
to, but more debilitating than, dengue. In the language of the Makonde
people of Tanzania, chikungunya is derived from the word meaning “that
which bends up.”

According to the U.S. Centers for Disease Control and Prevention,
chikungunya virus has since been cited as the cause of numerous human
epidemics in many areas of Africa and Asia, and most recently in Europe.
The epidemics in Europe occurred in two neighboring villages in the
province of Ravenna, Italy. The two villages were separated by a
slow-moving stagnant river and lock system that produces large numbers
of mosquitoes, including the Asian tiger mosquito that was the vector
species in this case.

An excellent example of how such diseases are spread can be illustrated
by the way chikungunya was transported from India to Italy. A male
resident of one of the villages in Ravenna traveled to the
chikungunya-active Kerala state in India during June of 2007. He had two
episodes of fever in late June 2007. While ill, and back in his home
village, he visited his cousin, who became ill on July 4. By Sept. 21,
2007, 292 chikungunya cases were identified within the transmission
zone. However, by the end of August, cases were reported with no known
exposure in the two villages. This indicated that local transmission in
adjacent areas was probably fueled by the dispersal of infective mosquitoes.

Are the Keys at risk? Absolutely. According to the Centers for Disease
Control, there have been at least 38 confirmed cases of chikungunya in
travelers to the U.S. during the past three years. One of these cases
occurred in Volusia County, Fla.

In addition to being a seasoned medical entomologist, I also have a
master’s degree in epidemiology from Yale University School of Medicine.
As such, I follow the spread of mosquito-borne diseases and I feel that
our greatest potential vulnerability in the Keys will come when travel
is resumed between Key West and Cuba. The risk could be lessened if
strict procedures are followed at ports of embarkation in Cuba and entry
ports in the Keys. These measures could prevent the entry of
disease-carrying mosquitoes and travelers that are infected with a
disease organism such as chikungunya virus or any other mosquito-borne
disease causative agent.

Edsel M. Fussell is director of the Florida Keys Mosquito Control District.

The opening of Cuba will put Keys at risk of mosquito-borne illnesses | (17 June 2009)

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