New data buoy hopes for promising malaria vaccine—but questions remain

There was a time when the Republic of Djibouti seemed to be on the verge of eliminating Malaria. There were only 27 cases in the Horn of Africa in 2012 Between February and May of last year, there were 1228 cases of the disease. Many people fell sick in the city. Malaria is not a big problem in Africa.

The Anopheles stephensi mosquito, which appeared to have arrived in Africa from Asia before the outbreak, is a new threat. The mosquito is to blame for more than 73,000 Malaria cases in the country last year. At the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH) in Seattle last week, a study was presented linking an unusual malaria outbreak in Ethiopia to the same culprit. Stephensi has been seen in Sudan, Nigeria, and other countries.

According to a medical entomologist at the World Health Organization, this is one of the biggest movements of a mosquito-borne disease in the last 50 years. Half a million people are killed by Malaria in Africa each year, most of them children under the age of 5. The World Health Organization launched a new initiative in September to better gauge the threat.

Anstephensi, a native of South Asia and the Arabian Peninsula, had made a short jump to Africa, according to a paper published in 2004. The paper raised the alarm about what this might portend: Unlike most of the African mosquitoes that transmit the Malaria parasites, An. stephensi is a city dweller.

It is well-known that An. stephensi is an efficient mosquito that can be used in cities. It is possible to transmit both parasites that cause Malaria. It thrives in artificial water sources such as cisterns and deep wells. African cousins, such as An. gambiae and An. funestus, prefer rural environments and lay their eggs in puddles during the rainy season in many countries.

Researchers are trying to figure out what the threat is. 126 million people could be at risk of Malaria if the mosquito is not stopped. Jan Kolaczinski is a medical entomologist at WHO. In some areas where An. stephensi has been found, there has not been an increase in the number of malaria cases.

In order to better understand the mosquito's role, Fitsum Tadesse of the Armauer Hansen Research Institute in Ethiopia and colleagues tracked the number of cases of Malaria in Dire Dawa, a city in the eastern part of the country. There were 205 cases in the city in the entire year. They compared household members of 80 Malaria patients with household members of 210 Malaria patients without the disease. People living with people with the disease were more likely to get it. The team reported at the meeting that 98% of the adult mosquitoes were An. Stephensi.

A geneticist who was not involved in the study says that the study provides the most direct evidence to date that the insect can cause an increase in malaria cases. He says that it is a big step in the right direction.

Data from the University of Khartoum showed that An. stephensi was found in 39 of 61 sites. A majority of households had the mosquito in their homes. Solomon Karoki of the Kenyan Ministry of Health said that the country hasn't picked up the species yet. Tadesse thinks the mosquito has spread to all corners of the world, possibly by hitching rides in shipping containers.

Sarah Zohdy is an entomologist at the U.S. Centers for Disease Control and Prevention. She says that they call it an urban mosquito.

The An. stephensi strains found in Africa are mostly resistant to the most widely used pesticides and prefer to rest in barns or sheds rather than human homes. Standard mosquito control measures may not be very effective.

One way to control mosquitoes is to keep the water covered so that they can't lay their eggs in it. Adding an insecticidal solution to the water is another way to kill mosquitoes. Both approaches help control mosquitoes that transmit diseases. According to a malaria expert at Ethiopia's Ministry of Health, the country has built its action plan in part on its strategies for mosquito-borne diseases.

The World Health Organization needs more research on An. stephensi in order to make recommendations for control. The balance is important according to him. We have to put time and effort into understanding its impact.