Malaria and Mosquito-Born Diseases: How Do They Catch on?

Under what circumstances and conditions does a mosquito-born disease initiate and latch on in an affected region? It has to be brought to the region from somewhere. This is often the case with infectious diseases, and they spread like wildfire in new areas where the local population does not have the immunity, drugs or infrastructure in place to cope with it.

Workers wait before spraying insecticide aimed at preventing the spread of Aedes aegypti mosquito. 

Zika, became a crisis in Brazil in early 2015. The first cases are thought to have come to country through traveling individuals. Genetic analysis of the strains from cases in Brazil were found to be similar to those from outbreaks in Pacific Island nations. One possibility is that an individual carrying it came from Chile, as exposure to the disease was found in a returning individual on vacation from Easter Island. Another possibility is that the virus was introduced in Rio de Janeiro following a canoe race, in which competitors from Pacific Islands were present. 

In Sub-Saharan Africa, for example, where malaria has long since taken hold, these factors describe the affected regions perfectly. They lay a solid foundation on which diseases can build a rampant and lasting presence. For regions of the world where malaria is endemic, the presence and alignment of the layers is glaringly obvious. This raises concern for parts of the world that may be extremely susceptible to the spread of current diseases or to the introduction of new diseases that could take over in a short span of time. Scientists are looking for trends in areas hit the hardest by mosquito-borne diseases in order to create solutions to existing problems and hopefully prevent crisis in the future.

The following excerpt is from an article detailing the multi-level array of factors that contribute to the ideal environment in which mosquito-borne diseases like malaria thrive. For the whole article by Dr. Vittor from the University of Florida School of Medicine, click here.

In the News: Mixed Strain Malaria Infections

Malaria is caused by 5 species of parasite that is carried by over 30 different species of mosquitoes. This makes for some major complications. "We found that when hosts are co-infected with drug-resistant and drug-sensitive strains, both strains are competitively suppressed," said Mary Bushman. "Anti-malarial therapy, by clearing drug-sensitive parasites from mixed infections, may result in competitive release of resistant strains." Read the article from Emory Health Sciences here.

Mosquitoes feed often, exposing them to a variety of strains of the malaria infection.

Inborn Immunity to Malaria: Sickle-Cell Anemia

Nature has devised a fascinating defense against malaria. It involves altering the very shape of the body's red blood cells (RBC). Sickle cell anemia is a disorder that changes the shape of RBC, as shown in the picture below, due to a mutation in the genetic code that is responsible for the formation of the beta-subunit portion of a hemoglobin molecule. As a result, the RBC will take a rigid sickled-shape. This leads to two important consequences: 1) malaria immunity and 2) organ damage and anemia symptoms.

Normal RBC compared with a sickle shaped one.

A mutation in the genetic code for hemoglobin causes sickle-cell anemia.
The mutation codes for a valine rather than a glutamic acid to be produced.

The Global Distribution of Anopheles Mosquito

The Anopheles mosquito is spread across the globe, and poses the threat of spreading the malaria vector worldwide. Collecting data about the mosquito type in a region provides key information about controlling populations and vector transmission.

From Kiszewksi et al., 2004. American Journal of Tropical Medicine and Hygiene 70(5):486–498

Check out the World Health Organization's world malaria report here.

Rise in Immunity Spurs International Concern

"Malaria is still a devastating disease, with nearly 250 million cases and more than one million deaths every year. Mosquitoes have developed resistance to existing insecticides and there is evidence of emerging resistance by the parasite to the drugs used to treat the disease.”-Professor Steve Ward, Deputy Director, of LSTM reports

Staying Safe While in Danger

Before traveling to Africa for the first time, my parents were very concerned about the risks of contracting malaria and wanted to ensure our family’s safety. We asked for advice about how to prevent and treat malaria, and now I'm extending my recommendations, after years of travel experience. 

1.  Prevent mosquito bites between dusk and dawn. This is when the mosquitoes that carry malaria bite. Stay inside, wear bug repellent (DEET), and sleep under a mosquito net.
2. Take prophylactics: Doxycycline has fewer side effects than Malarone. Make sure to take the full course of the medication, starting before you travel and continuing well after your return.
3. Take medicine with you. Depending on where you are traveling, it may be in short supply. Quinine and Coartem are pretty common and will be your best bets.

I've spent time in high-risk areas where malaria is extremely rampant. So much so, in fact, that I even contracted the disease myself, despite taking certain precautions. As I learned, hyper-attention to detail makes a huge difference. I got malaria when I was volunteering for a month at the Chitokiloki hospital in rural Zambia. This is arguably the best place to get sick, as there is readily available medicine as well as medical staff who treat the disease every day. The hospital is overflowing with malaria patients during the rainy season.

Amazingly, malaria is totally curable. You have to get to medication early, however, and this is one of the major challenges in rural areas, as it is modes of transportation are slow and unreliable.