Development & Aid, Headlines, Health, Latin America & the Caribbean

HEALTH-CARIBBEAN: Region on Alert for Disease-Carrying Mosquito

Terry Ally

BRIDGETOWN, Nov 13 1997 (IPS) - At this time of year when Caribbean countries are doing battle against the Aedes aegypti mosquito which spreads dengue fever, health experts say there could be another more potentially dangerous insect to worry about.

It is the Aedes albopictus, which, looks remarkably like the Aedes aegypti and which can also spread dengue fever but at the same time, at least under laboratory conditions, can carry 22 or more different viruses including yellow fever and encephalitis.

Dengue fever is a seasonal illness that occurs during the annual June to November rainy season throughout the Caribbean and is spread by the mosquito. The symptoms include fever, vomiting and pains in the muscles and joints.

After becoming infected by a mosquito carrying the virus, there is an incubation period of between five to seven days before the onset of illness.

During the incubation period, the virus can spread from person to person through the mosquito.

There are four strains of the virus: Dengue one, two, three and four and any of which can cause dengue fever but the severe symptoms associated with the deadly dengue haemorrahagic fever (DHF) and dengue shock syndrome (DSS) come from strains two and three according to the World Health Organisation.

Since the start of this year two persons in the southern Caribbean country of Trinidad and Tobago have died from DHF. A serious outbreak of the disease in the region could have adverse economic as well as human consequences, the experts say.

In 1994 an outbreak in Puerto Rico saw 21,000 persons contracting the disease, a large number of hospitalisations and six deaths. The cost of medical care and of loss of work was estimated at between 150 and 200 million dollars.

In 1981 the DHF/DSS epidemic in Cuba was estimated to have cost 103 million dollars; 41 million dollars worth of medical care, five million for salaries paid to adult patients on sick leave, 14 million dollars in lost production and 43 million dollars in direct initial cost of the Aedes aegypti control programme.

The risk of contracting DHF increases when a person becomes infected with more than one strain of the virus and that is why the Aedes albopictus is of serious concern to health officials because of its ability to spread all the strains of dengue fever.

“But the jury is out on whether it will do this in nature,” says Dr. Michael Nathan, entomologist with the Pan American Health Organisation.

“In countries where you have tourism, it could become a serious nuisance, it is aggressive and will descend on you in large numbers and bite you, especially in the daytime.”

Tourism is the main foreign exchange earner in many of the region’s countries bringing in some 10 billion dollars each year. On average, these islands receive 10 to 11 million visitors each year.

So aggressive is the insect which is also referred to as the “Tiger Asian Mosquito”, that in some urban areas it has actually beaten the Aedes aegypti into submission.

It can live around the home where it breeds in containers in the yard, just like the Aedes aegypti, but it prefers to live in the wild, near forest borders, in tree holes or rock holes filled with water.

Ten years ago it arrived in the United States from Asia in a shipment of car tyres. Since then it has rapidly spread and has infested 537 counties in 25 states or territories mostly in the southern United States.

It has also spread southward through Central America into Guatemala and Honduras in 1995, and El Salvador in 1996. It was discovered in Bolivia in 1995 but the authorities say they have been successful in eliminating it.

In the Caribbean one larva was intercepted in a shipment of Japanese tyres at the Bridgetown Port in Barbados in 1987.

Since then the mosquito arrived in other car tyre shipments in the Dominican Republic in 1993, Cuba in 1995 and in September 1997 in the Cayman Islands which ironically is one of the few Caribbean countries where the Aedes aegypti is not found.

Dr. Sam Rollins of the Caribbean Epidemiology Centre raised the possibility that the Aedes albopictus could very well be in some other Caribbean states, but has remained undetected.

“I cannot say that they are but there is a possibility that it could be present in some islands because no one is searching for it,” he told IPS.

Rollins says even though international regulations stipulate that there should be surveillance at ports of entry for the mosquito larvae and eggs, the reality is that surveillance is not as stringent as it should be in some Caribbean states.

Added to that, the eggs are very similar to those of the Aedes aegypti and require the keen eye of a technician to detect. “When it gets into the island and you don’t detect it early enough, it becomes an intractable problem. Experience has shown that once it gets into a country, the authorities have been unsuccessful in eradicating it,” says Nathan.

 
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