Dawn Marie Roper, Freelance Writer

Chen

Very little is said about the role of climate change in the outbreak and spread of mosquito-borne diseases in the Caribbean. People usually blame poverty and poor vector control for mosquito-borne diseases such as malaria, yellow fever and dengue. These diseases have killed thousands of people in the Caribbean since colonial times.

With climate change now a serious concern worldwide, climatologists in the region are now making it clear that the phenomenon is deadlier to Caribbean peoples than previously thought. At a recent forum on biodiversity held in Kingston, Professor Anthony Chen of the Climate Studies Department at the University of the West Indies, Mona, spoke about the impact of climate change on the Aedes aegypti mosquito, the vector responsible for dengue fever.

"The incubation period of the Aedes aegypti mosquito shortens at high temperatures," Professor Chen said. "The higher the temperature, the quicker the mosquito breeds. The parasite will become more active in a shorter time. That means the transmission of the disease will become greater."

Not to be taken lightly

This is not a warning to be taken lightly by any Caribbean territory, particularly Jamaica, which is again trying to eliminate malaria, once thought to be eradicated in Jamaica, but has re-emerged.

The Caribbean never had the luxury of being totally free from dengue fever. It is a seasonal disease, but it is always here. According to Professor Chen, incidences of dengue fever in the Caribbean have historically coincided with times of high temperatures and high rainfall. This is alarming for two main reasons. First, the tropical climate of the Caribbean now features continually increasing temperatures and, second, most Caribbean countries are developing nations.

The latest climate change report published by the Intergovernmental Panel on Climate Change (IPCC) in 2007, says that by the year 2080, temperatures in the Caribbean will rise by about two degrees Celsius. Professor Chen, who sits on the IPCC, pointed out that the Aedes aegypti mosquito's feeding and metabolic rate increase in high temperatures.

"Based on studies, temperature increase of two degrees is expected to give a three-fold increase in the transmission of dengue," he noted.

If our climate scientists are right, then in addition to poverty and poor mosquito control practises, the Aedes aegypti mosquito has a new ally: climate change.

But with climate change and the Aedes aegypti mosquito not going away, climatologists like Chen are proposing, "an early warning system called the moving average temperature (MAT) Index. The MAT index is used to show when there is a great potential for dengue fever to occur," Chen told the forum.

MAT index

To come up with the MAT index researchers collected climate data from past dengue outbreaks in the region. The researchers examined the temperature changes from month to month and mapped their correlations to the disease's prevalence. In doing this, they came up with a formula for the temperature threshold which will indicate the likelihood of a dengue outbreak.

"This MAT index is very easy to measure," said Professor Chen. This is because the temperature data can be easily obtained from the daily, weekly and monthly readings done by the meteorological stations in the Caribbean. So, the basic infrastructure for utilising the MAT index is already in place.

But how are Caribbean policymakers likely to receive the MAT Index as a dengue-management strategy? Attempts to get a response from the Vector Control Division of the Jamaican Ministry of Health proved futile. Currently, the management of dengue includes epidemiological surveillance, training and deployment of health inspectors - typically expensive undertakings. Furthermore, dengue is classified as a Class Two disease and is not as high a priority as HIV/AIDS. Cash-strapped governments would be hard-pressed to put more funding into dengue.

But utilising the MAT index could help Caribbean governments save money. According to Professor Chen, by using the MAT index as the first strategy in dengue management, expensive epidemiological surveys would only be necessary if the index says there is the likelihood of a dengue outbreak.

Too early to comment

Jeffery Spooner, from the climate branch of the Meteorological Office in Kingston, said that the climate change focal point in the Met Office endorses the work done by Professor Chen and his colleagues. He said it was too early to comment on the usefulness of the MAT Index he promised that it would be looked into.

"We have to be guided by policies," Spooner said. "It needs buy-in from government policymakers, the communities and other stakeholders."

He added, however, that the output from Professor Chen's work on the MAT Index would be reported in the second national communication to the United Nations Framework Convention on Climate Change in 2008. One hundred and ninety countries are bound by international agreement to report to this world body on their activities regarding climate change.

The article above is part of Panoscope, a series produced by Panos Caribbean. Email: jamaica@panoscaribbean.org