Travel Health – Malaria

Of all the possible diseases you can get while traveling overseas, none of them cause more concern or strike up fear like malaria, and for good reason.

It is estimated to be up to a half a billion cases of malaria annually with about 1 million deaths, particularly among young children.

It is considered the most important parasitic disease affecting humans. The disease has great socio-economic importance and helps in keeping poor countries poor in a vicious cycle.

According to the Centers for Disease Control and Prevention (CDC), about 1,300 cases of malaria are diagnosed in the United States each year. The vast majority of cases in the United States are in travelers and immigrants returning from malaria-risk areas, many from sub-Saharan Africa and South Asia.

The protozoan parasite belongs from the genus Plasmodium. There are many species of Plasmodium that infect vertebrates, but only 4 that are important to humans. The four species are:

o Plasmodium falciparum
o Plasmodium vivax
o Plasmodium malariae
o Plasmodium ovale

There have been some documented cases of people getting simian malaria (P. knowlesi).

Human malaria is considered a tropical disease, but some cases happen outside the tropics. Most cases are found in Southeast Asia, China, India, and Africa, parts of the Middle East, Mexico, Central and South America.

For malaria to occur you must have the following; a susceptible population, malaria carriers and the right mosquito vector (the female Anopheles mosquito).

The life cycle for all the malaria species is essentially the same. It’s very complicated (with part in the mosquito and part in the human) but in a nutshell, in humans it goes like this: During a blood meal, a malaria-infected female Anopheles mosquito inoculates the parasite into the human host.

The parasite almost immediately infects liver cells and goes through a maturation series and ruptures. Just a side, P. vivax and P. ovale can have a dormant stage in the liver and can cause relapses in the blood weeks to years later.

The parasite then moves on to infect red blood cells. Blood stage parasites are responsible for the clinical manifestations of the disease.

The parasite is later ingested by an Anopheles mosquito during a blood meal and the cycle in the mosquito happens. It really is a vicious cycle.

The disease may manifest itself after an incubation of days to months. Once the parasites build up in the blood, symptoms are non-specific; fever, chills, body aches, diarrhea and vomiting. At this point the only way to confirm is finding the parasites in blood. These early stages resemble many other febrile diseases.
Paroxysms (due to rupture and release of the parasite and metabolic products into the system), happen every 48-72 hours depending on the species.

There is a cold stage which leads to teeth chattering, shaking chills followed by a hot stage (fever) where temperatures may reach 106°F. Convulsions may develop particularly in children.

Untreated P. falciparum (the life-threatening species) can lead to severe malaria. Severe malaria is characterized by cerebral malaria, severe anemia, renal filure (black water fever), respiratory distress and bleeding disorders and shock.

Prompt treatment for falciparum malaria is essential cause death from cerebral complications may occur.

The other human malarias are not usually life-threatening. People who are partially immune or non-immune but taking prophylactic anti-malarials, may show atypical symptoms and a longer incubation period.

Active malaria is most frequently diagnosed by observing the parasite in blood smears. There are molecular and antibody detection techniques to complement microscopic examination.

Treatment of malaria depends on several factors; The type (species) of the infecting parasite, the area where the infection was acquired and its drug-resistance status, the clinical status of the patient, any accompanying illness or condition, pregnancy, drug allergies, or other medications taken by the patient.

Chloroquine, Fansidar, mefloquine, Malarone, quinine, doxycycline and artemisin derivatives (not licensed for use in the United States, but often found overseas) can be used to treat malaria.

As a traveler in a malaria endemic area, what preventive measures can you take?

There is no vaccine currently available for malaria. According to the CDC all travelers to malaria-endemic areas should be advised that taking an appropriate drug regimen and using antimosquito (insecticide treated bed nets, stay in well screened areas, DEET insect repellent) measures will help prevent malaria. Travelers should be informed that no method can protect completely against the risk for contracting malaria.

Climate and Health

Although global warming may bring some localized benefits, such as fewer winter deaths in temperate climates and increased food production in certain areas, the overall health effects of a changing climate are likely to be overwhelmingly negative. Climate change affects social and environmental determinants of health like clean air, safe drinking water, sufficient food and secure shelter. Moreover, extreme high air temperatures contribute directly to deaths from cardiovascular and respiratory disease, particularly among elderly people. In the heat wave of summer 2003 in Europe for example, more than 70 000 excess deaths were recorded (UNEP, 2004, March). Noticeably high temperatures also raise the levels of ozone and other pollutants in the air that exacerbate cardiovascular and respiratory disease.

Globally, the number of reported weather-related natural disasters has more than tripled since the 1960s. Every year, these disasters result in over 60 000 deaths, mainly in developing countries (WHO, 2017, July). Relating to the rising sea levels and increasingly extreme weather events particularly will destroy homes, medical facilities and other essential services. More than half of the world’s population lives within 60 km of the sea (Creel, 2003, September). And people may be forced to move, which in turn heightens the risk of a range of health effects, from mental disorders to communicable diseases. Increasingly variable rainfall patterns are likely to affect the supply of fresh water. A lack of safe water can compromise hygiene and increase the risk of diarrheal disease, which kills thousands children aged less than 5 years, every year. In extreme cases, water scarcity leads to drought and famine.

Floods are also increasing in frequency and intensity, and the frequency and intensity of extreme precipitation is expected to continue to increase throughout the current century. Floods contaminate freshwater supplies, heighten the risk of water-borne diseases, and create breeding grounds for disease-carrying insects such as mosquitoes. They also cause drownings and physical injuries, damage homes and disrupt the supply of medical and health services.

In addition, climatic conditions strongly affect water-borne diseases and diseases transmitted through insects, snails or other cold blooded animals. Changes in climate are likely to lengthen the transmission seasons of important vector-borne diseases and to alter their geographic range. For example, climate change is projected to widen significantly the area of China where the snail-borne disease schistosomiasis occurs (WHO, 2009). Malaria is strongly influenced by climate. Transmitted by Anopheles mosquitoes, malaria kills over 400 000 people every year – mainly African children under 5 years old (WHO, 2017, April).

To sum up, climate change normally affect all populations, but some are more vulnerable than others. People living in small island developing states and other coastal regions, megacities, and mountainous and polar regions are particularly vulnerable. Children, in particular, children living in poor countries that are among the most vulnerable to the resulting health risks and will be exposed longer to the health consequences.

Reference

Ottmar Edenhofer, R. P.-M. (2014). Summary SPM for Policymakers.

UNEP. (2004, March). Impacts of Summer 2003 heat wave in Europe. Environment Alert Bulletin.

Organization, W. H. (2017, July). Climate change and health. Media centre.

Creel, L. (2003, September). Ripple Effects: Population and Coastal Regions. Population Reference Bureau.

WHO. (2009). Climate change and health. WHO representative office China.

WHO. (2017, April). Malaria. Media Centre.