Eulalee Thompson

About now, the infected female mosquito of the species, Anopheles, is public enemy number one. She could be carrying dangerous strains of the Plasmodium - a parasitic, single-cell organism - linked to the parasitic, protozoan infection known as malaria.

The female Anopheles, if she is infected, should be avoided at all cost. She will pounce on unsuspecting victims, biting them as she feeds for her blood meal and, in the process, inject the malaria-causing parasite into the victim's blood stream.

Dr. Dwight Robinson, entomologist, Life Sciences Department, University of the West Indies, said that the Anopheles mosquito is always present here but what has changed in the disease cycle equation is that the parasite (that causes malaria) is also now present.

Different species of mosquitoes operate in different ways. The Culex species (the ones that loves to come out between dusk and dawn) Dr. Robinson said, for instance, has a long breathing tube and this is perhaps why its preferred breeding ground is stagnant, dirty water. On the other hand, the Anopheles doesn't have that long breathing appendage and prefers clearer water.

Deadly form

Entomologists have identified two stages in the life cycle of the parasite — one in the mosquito host and the other in the human host.

According to The World Health Organisation, the infective form of the parasite travels to the liver where it divides many times before being released back into the bloodstream. It infects red cells, replicate again, bursting the red cell and releasing more parasites into the bloodstream to infect yet more red cells. After a number of such cycles, male and female forms of organism are created (called gametocytes). It is the gametocytes which are ingested by a feeding Anopheles mosquito; they go through another life cycle in the mosquito.

Laboratory tests of the first four cases of malaria recently identified in Kingston and St. Andrew confirmed that they had acquired the most serious and life-threatening form of the malaria-causing parasite — the Plasmodium falciparum.

There are four species of the malaria-causing parasites that can infect people through a bite from the female Anopheles mosquito:

1. Plasmodium falciparum

2. Plasmodium vivax

3. Plasmodium ovale

4. Plasmodium malariae

According to a Health Ministry advisory issued, the other three species were not identified. The Health Ministry is also indicating that the malaria cases appear to be locally acquired.

Jamaica-Haiti connection

There have been speculations that the unexplained re-emergence of new cases of malaria, after a 50- year hiatus in Jamaica, may be linked to travelling between Jamaica and Haiti, where malaria is endemic in underground, contraband activities.

"It is extremely strange that it would re-emerge. From my standpoint, what is happening is that it has to be coming from somewhere and we have to look at the relationship between Jamaica and Haiti where it (malaria) is endemic," said public health specialist Dr. Winston Davidson.

He said that the locus of the outbreak — sections of Kingston and St. Catherine — is where the epidemiologists will find their answers. He also indicated that it is important from a public health standpoint to find the 'index case', that is the first case. The index case would have to be bitten by a female Anopheles mosquito, which then moves to someone else for a blood meal, to spread the condition.

He stressed that for the condition to come in undetected, "We may have to look at the underground, contraband activity." Dr. Davidson said that from a public health standpoint, it seems "most plausible."

"You are able to trace quickly from the ports of entry and you have to be coming from an endemic country ... otherwise for the case to have come in undetected, we have to look at the contraband trade," he said.

Dr. Davidson is, however, quite certain that the disease spread will be brought under control.

"We have done it before and we can do it again, " he said.

Symptoms

Malaria is a class 1 notifiable disease which was eradicated here in the early 1960s. The most frequent symptoms include:

Fever, intermittent fever, flu-like illness including chills, headache, muscles aches, tiredness. Loss of appetite, nausea, vomiting and diarrhoea may also occur.

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