May 1, 2014
Cracking The Tsetse Fly DNA
Sleeping Sickness is an insidious and dangerous killer, attacking both animals and humans. In Sub-Saharan Africa millions of people are at risk either directly by becoming infected themselves or indirectly when livestock is affected. 36 countries and as many as 70 million people are under threat. Scientists have now cracked the DNA code of the tsetse fly that carries the disease, bringing hope that better control is in sight. It can’t come too soon.
Infection begins innocently enough. It might seem like just another fly landing on a bare arm or leg. If that bug is a disease carrying tsetse fly and it manages to bite, you are in big trouble. The bite will introduce protozoan parasites into the bloodstream where they attack the central nervous system. Fever is followed by signs that the parasites are affecting the brain; such as confusion, speech problems, personality changes, seizures, and difficulty walking, which completely debilitate the victim. The disease can be fatal if untreated. Even the treatments are very unpleasant in themselves, as they involve the use of toxic chemicals. The most common drug is an arsenic derivative and is lethal in 10 percent of patients. Its use only continues because the alternative is so horrendous.
To make matters worse the parasites are highly efficient and hard to eradicate. With incredible stealth, they are able to outwit the body’s immune system. They protect themselves with an armor-like coating of protein, which they can adapt and change before the immune system can find a way to break in. For this reason, no vaccine for Sleeping Sickness exists. As most cases are in remote and hard to reach areas with little in the way of health care provision, detection and monitoring of the disease is extremely challenging.
So the parasites that deliver Sleeping Sickness, or Trypanosomiasis, into the human body are a formidable enemy. No wonder then that 10 years ago the UN Food and Agriculture Organisation (FAO) and the International Atomic Energy Agency came together to begin the task of finding the genome of the tsetse fly. This was a multi-million pound effort, but one that has the potential to save far more if it is successful. The researchers have now announced that the DNA has been decoded. The hope is that this will lead to better methods of controlling and attacking the flies themselves and the race is on to do just that.
Until now, the main methods of control have been to trap the insects and kill them with pesticides, or sterilize the male flies by radiation. These attempts have not been without success, as the fly has been totally eradicated in Zanzibar. Major progress has also been made in countries like Senegal and Ethiopia. The World Health Organisation reports that its aim of reducing the number of new cases to under 2,000 a year is moving in the right direction. It received notification of fewer than 6,000 cases last year, compared to over 26,000 in 2001, and claims that the disease is entering a “phase of elimination.” While this might seem optimistic with so many areas and people still at risk, the decoding of tsetse DNA brings hope that eradication, or massive reduction in some cases, will come sooner rather than later.
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