Mosquito and cucumber salad anyone?

How it all begins – the malaria parasite life cycle

The transmission of the parasite plasmodium begins with the female mosquito, which needs blood to make eggs. When the mosquito bites an infected human it ingests parasite sperm and eggs. These then unite in the stomach of the mosquito to form what’s known as ookinetes - cells that become embedded in the stomach wall.

These ookinetes migrate through the mosquito’s stomach wall and produce thousands of infectious daughter cells known as sporozoites. After 10-20 days they move to the mosquito salivary glands and are ready to infect another human.

Once inside the human body, the sporozoites are carried by the blood to the victim's liver where they hide from the immune system. In the liver they invade the cells and multiply into thousands of cells. After 9-16 days they return to the blood and infiltrate red blood cells where again they stay invisible to immune surveillance. Within the red blood cells they multiply once more forming parasite sperm and egg cells. This process destroy’s the victim’s red blood cells which releases the parasitic cells into the bloodstream to be ingested by a mosquito - thus renewing the transmission cycle.

Patients with malaria exhibit extreme feverish attacks, flu-like symptoms, tiredness, diarrhea, nausea, vomiting and shivering while the malarial parasite damages the liver and blood cells. The severity of the symptoms depends on several factors, such as the species (type) of infecting parasite and the patient’s acquired immunity and genetic background.

Cucumbers that eat themselves alive - and malaria

The malaria parasite Plasmodium has been studied for decades, but because of its ability to evade the immune system a vaccine has been hard to develop.

Most drugs that are available are active against the parasites while they are in the human blood. However, there is an emergence of parasite strains that are resistant to many of the existing anti-malarial drugs thus making the discovery of new therapies essential.

Recently, an International team of researchers, led by Professor Bob Sinden from the Imperial College in London, has found that the sea cucumber makes a chemical that is toxic to the fatal malarial parasite.

The sea cucumber is a worm-like scavenger that feeds on plankton and debris in the ocean and is made of a tough gelatinous tissue. A slimy mass of muscular tissue, the cucumber has the unusual ability to violently expel its internal body organs during times of stress. These can later be regenerated. Another fascinating feature is their ability to slowly digest themselves to cope with periods of starvation.

Cucumbers that cure

Some varieties of sea cucumbers are said to have excellent healing properties so it may be no surprise that this creature has found medicinal use, both formally and in alternative therapies. Extracts have found their way into oils, creams and cosmetics. Sea cucumber extract has also been shown to heal wounds more quickly and reduce scarring. Other extracts from sea cucumbers inhibit blood vessel formation thus making it an excellent potential therapy for cancer.

Researchers have now found that this slug like creature also produces a protein which impairs development of the malaria parasite. Called lectin (CEL-III), this protein has been shown to damage human and rat red blood cells. Lectin is poisonous to the parasites when they are still in the early ookinete stage of development – before they migrate out of the mosquito’s stomach to produce the millions of sporozoites which end up in the insect’s saliva.

Inhibiting this ookinete development is a potential way to eliminate the transmission of sporozoites to the human host thus breaking the transmission cycle.