Malaria is a mosquito-borne illness often encountered by divers, especially in tropical regions. Divers should inquire about malaria protection and start on chloroquine once a week starting two weeks before departure. Divers should also protect themselves from mosquito bites.
When planning a diving holiday, preparations relating to equipment and travel are so much in mind that medical problems are usually not considered. Your diving checklist, however, should include a reminder to ask your family physician about diseases specific to the area you will be visiting. Tropical regions are often the source of common mosquito borne illnesses, one of which is malaria.
Malaria, a serious and potentially fatal disease, is still a major problem in many tropical areas of the world. It remains the most common of all tropical diseases, with an estimated 150 million new cases every year. It once occurred in the southern USA but was eventually eradicated by mosquito control measures. Two cases recently reported in New Jersey were owing to mosquito borne transmission from infected migrant workers on local farms.
Malaria has been known since antiquity. It is transmitted by a specific type of mosquito called the Anopheles. Anopheles has a unique resting posture; the proboscis, head and thorax are held in a straight line, while the entire body is at an angle to the resting surface.
If a malaria infected mosquito bites a human, malaria organisms carried by the insect are injected directly into the bloodstream. A serious chain of events is then started. The malaria organisms pass into the liver and grow silently there during a latent period, without any signs or symptoms of the disease. This period can last from 6 to 11 days, depending on the type of malaria parasite involved.
The malaria infection occurs in three stages, closely related to events occurring in the bloodstream. When the organism has matured in the liver, it invades the red blood cells, grows and breaks out of the cells. This process causes a rapid rise in temperature associated with a feeling of intense cold and is accompanied by 15 to 60 minutes of shivering severe enough to make the teeth chatter. The increase in temperature can be severe. Fevers of 39 to 40 [degrees] C (102 to 105 oF), vomiting and headaches are common. During the high temperature, the malaria parasites just released from the red cells invade more red blood cells. The third phase is sweating, which can be severe enough to cause a large fluid loss. This occurs several hours later. The temperature falls rapidly, accompanied by severe sweating and the victim may drop into a deep sleep. The victim will usually awake feeling well again. However, the cycle repeats again and again at 48 or 72 hour intervals until the disease becomes chronic. The number of days between fevers is unique to the species of malaria parasite that has caused the infection.
This is a serious illness that is best avoided. When going to the tropics, you should inquire about malaria protection and whether your destination is in a high risk area or not. Prevention is achieved with chloroquine (500 milligrams) taken once a week starting two weeks before departure and continuing throughout the period of exposure and for four to six weeks afterward. Sometimes the illness will occur after a several week delay. If any unexpected illness occurs even weeks after a visit to a malaria infested area, let your doctor know you visited a country or region that has a malaria. There are special blood tests to detect the malaria parasite and these should be done if there is a suspicion of this diagnosis.
In some areas malaria parasites are resistant to chloroquine and other medications should be used. All malaria medications should be prescribed by your physician. The entire IndoPacific area, most of Africa and some areas of Central America, including the Western Caribbean, should be regarded as malaria infested. The U.S. Centers for Disease Control, in Atlanta, give updated information on areas of the world where malaria is a problem.
General measures to protect against mosquito bites are the first line of defense and are definitely worthwhile. The following are recommended: long sleeved shirts, trousers or slacks and mosquito repellent for any exposed skin surfaces. The effect of some repellents may not last long enough to give protection at dawn if applied the night before and reapplication is a must. Mosquitoes are most active at dawn and dusk. Unless you are sleeping in a mosquito proof building, mosquito nets should be used at night; insecticide sprays are also useful. Incidentally, filariasis and encephalitis can also be transmitted by the Anopheles mosquito. These are more reasons for avoiding contact with these insects.
The malaria infection lasts variable periods of time, depending on the type of parasite involved. One type of infection may last for many years. Others will disappear in two to three years without treatment. Treatment of malaria is often prolonged and difficult; prevention is much easier.
Efforts at eradicating malaria in high risk areas have been frustrated by the need to take medication continuously. Tests of vaccines, mosquito control measures and education about avoiding mosquito bites are all part of a worldwide effort to control malaria.
In the continuing efforts to limit the impact of this disease, scientists are constantly testing new methods of vector control and drug therapy. Despite these efforts, malaria remains a major lethal and debilitating disease in the tropics, killing two million children annually in Africa.
Malaria vaccine research has been underway for many years. A group of scientists working in Tanzania, an area of intense continuous malaria infection, gave a newly developed vaccine to children aged one to five years. The incidence of malaria infection was similar in this group and a control group but the incidence of clinical malaria was reduced from 35 to 25 percent by the vaccine. Similar results were found in studies of adults in southern Venezuela and Ecuador. The vaccine (called SPf66), although not fully protective, does reduce the incidence of active malaria infection. It is not yet available for general use and will probably be used first in areas where many people are infected with malaria. In the future, there will likely be a vaccine that will confer long term immunity to casual travelers and eliminate the need to take prophylactic medications.
As more areas of the world become available for tourism and diving, the risk of acquiring diseases increases. Vaccines will make travel safer. Their impact on the health of whole countries and the potential for eliminating malaria by eliminating the pool of infected people who spread the disease, is by far the greater benefit.