Malaria is a disease caused by one of four species of Plasmodium – a human blood-borne protozoan parasite:– P vivax, P falciparum, P malariae & P ovale. They all have in common that they are transmitted by the bite of an Anopheles mosquito, of which there are several species in habiting the CMSs, which have varying levels of efficiency as vectors of the disease. Falciparum malaria (endemic in the island of Hispaniola and CMSs mainland countries of Guyana, Suriname and Belize) is the most serious form of the disease, and must be treated promptly, since complications of this disease may prove lethal especially in endemic countries. WHO indicates that there may be as much as 1-2 million deaths due to malaria – especially in children – each year.
The Anopheles vector becomes infected by taking an infectious blood meal from a malaria-positive patient, with parasites in peripheral blood. The organisms undergo sexual reproduction and multiplication within the mosquito, which after the incubation period of 12-30 days (depending on the species), the vector becomes infectious, and on biting a susceptible human host, may transmit the disease.
There are no vaccines for malaria at this time, so persons travelling to a malaria–endemic country need to be wary of the symptoms of high fever alternating with chills at specific intervals – 36-48hr or 72hr intervals. Chemoprophylaxis starting before the entry into a malarious country is important, bearing in mind that P falciparum in most countries is now resistant to once useful drug such as chloroquine.
On returning from a visit to a malarious country, any sign of alternating fever and chills symptoms should be investigated for the disease and treatment be done promptly. We need to beware the re-introduction of the transmission of malaria in the CMS countries as occurred in Jamaica, 10-12 years ago, and took a long period and lots of resources to eliminate the disease once more.
There is no evidence of current malaria transmission in any of the CMS island countries other than Hispaniola, but in most of them there is the occurrence of the vector, Anopheles spp. It is thus possible that if there were an imported case of malaria and if conditions were appropriate, then transmission of the disease could resume back to what occurred before 1962 - before malaria elimination was successfully achieved.
In Hispaniola (by An albimanus) and mainland countries of Guyana and Suriname there is transmission – mainly by Anopheles darlingi – and in Belize probably transmitted by An albimanus. There are occasional reports of limited transmission of malaria in selected other CMSs after the importation of malaria, presumably by an infected malaria patient and transmitted by the local Anopheles mosquitoes – resulting in autochthonous malaria. Fortunately, any occurrences such as these were promptly addressed, and transmission eliminated. Such efforts in terms of patient treatment, and tracing as well as appropriate vector management to eliminate the small focus of infection, has proved to be quite expensive. It underlines the need for active programmes of surveillance and vector management, which will become part of our IVM programme region wide.