Plague of locusts causes mass allergy attack
By Shaoni Bhattacharya, NewScientist.com
LONDON, Nov. 03, 2003 — A plague of locusts is being blamed for an epidemic of allergic attacks in central Sudan. At least 11 people have died and thousands are reported to have been hospitalised, suffering from what Sudanese officials are calling “lung eczema”.
The outbreak centres around Sudan’s second largest city of Medani, 180 kilometres south of the capital Khartoum. The annual locust swarm has been particularly ferocious in 2003 and experts believe it has triggered an allergic reaction in the local population, aggravating asthma.
The local authorities told Sudan’s national news agency that there had been an above average increase in asthma cases from 22 October: “We consider [it] an epidemic for patients suffering from asthma.” The mass allergic reaction is the first ever reported in Sudan.
Abdel Moneim Hassan Khalifa, an agricultural official in the Medani area, told Sudan’s al-Rai al-Amm newspaper the illness is linked to a pheromone released by locusts during their mating season. It has “a strong effect on people with asthma,” he said.
“I wouldn’t be surprised,” says entomologist Janet Hemingway, director of the Liverpool School of Tropical Medicine in the UK. “Insects release various chemicals, and the scales come off them as well. You can certainly get respiratory illness linked to working with insects, and not just locusts.”
Face mask
Insects are well known sources of allergens and there are strict rules to safeguard the health of UK scientists working with them in the lab. For example, scientists with respiratory problems are forbidden from this kind of work, and all researchers must wear a face mask.
Previous studies have shown that scientists working with locusts in the lab are much more likely than researchers not handling the tropical pests to develop work-related wheezing.
Outbreaks of desert locust are not unusual in Sudan, but the UN Food and Agriculture Organization in Rome issued an alert on 20 October warning that a particularly bad plague might threaten crops in Sudan, Niger and Mauritania.
“The number of locusts is increasing rapidly. They are beginning to concentrate themselves into groups characteristic of an outbreak,” warned FAO’s Locust Group in a statement.
Swarm behaviour
The group notes that: “Desert locusts are normally solitary, scattered insects but when climatic conditions are favourable, for example after good rains and a mild temperature, they can rapidly increase in number.” The pests tend to congregate as the rainy season ends and the vegetation dies off, leaving only isolated pockets.
After several years of drought, exceptional rains in Mauritania had allowed the desert locusts to breed and increase in number in 2003, says the FAO. “Vegetation had dried out much quicker than expected in the country, causing locusts to concentrate in three areas,” it adds.
Hemingway says that the actions, not just the presence, of the locusts could also be responsible for the allergy epidemic. A swarm of locusts devastating vegetation can leave lots of dust in the air, while chemicals, such as phenols, can be released from the breakdown of vegetation. “It could be a whole raft of things,” she says.