Amid rumours and panic over the Zika virus, the Brazilian government is preparing to launch a “mega-operation” to eliminate potential mosquito breeding sites and to educate the public about its role in combating the spread of disease.



Brazil’s public health experts have welcomed the initiative, but few believe that these actions alone will eradicate the Aedes aegypti – the mosquito species that carries the virus.



And without concrete information about the virus and its link to microcephaly, none of the anti-mosquito strategies proposed by the authorities are without their share of controversy.

In a nationally televised broadcast last week, President Dilma Rousseff announced the mobilisation of 220,000 soldiers to accompany the country’s 300,000 health workers on house-to-house visits.

“As science has not yet developed a vaccine against the Zika virus, the only effective remedy we have to prevent this disease is a vigorous fight against the mosquito,” she said.



According to the ministry of health, health workers or members of the armed forces have visited 20.7m Brazilian homes, equivalent to about 30% of all the country’s private residences. The ministry estimates that 80% of the breeding grounds of the Aedes aegypti mosquito are based on private properties.



As well as Zika, which has been linked to a surge in cases of microcephaly, Aedes aegypti also transmit chikungunya and dengue fever, which killed 843 Brazilians in 2015.

It takes seven to 10 days for a hatched egg to develop to adulthood; as such, health workers recommend Brazilians check their properties at least once a week. Gutters should be cleared; bottles upturned; rubbish bins firmly closed and water tanks sealed.



It is clearly a mammoth task, with little chance of total success. “The Aedes aegypti cannot be eradicated,” Christoph Hatz, a professor of epidemiology at the Swiss Tropical and Public Health Institute, told the BBC.



But Brazil did succeed in eliminating the insect once before. In 1958, the Pan-American Health Organization (PAHO) declared Brazil free of the Aedes aegypti mosquito.

Eleven years earlier, an outbreak of yellow fever prompted the PAHO to launch a Continental Campaign for the Eradication of the Aedes aegypti in 1947.

In part, this continent-wide programme built on much of the progress made by Brazilian researchers in the first part of the 20th century.



Vaccination programmes, improved public sanitation and the widespread use of insecticide succeeded in dramatically reducing the incidence of mosquito-borne disease and eventually led to the eradication of the Aedes aegypti in 11 countries in the Americas.



But the success came at a cost. A compulsory vaccination programme implemented in Rio de Janeiro in 1904, carried out by the “Brigadas Mata Mosquitos” [Mosquito-Killing Brigades] resulted in some of the worst rioting in the city’s history. The success of the pesticide campaign meant that DDT continued to be used as a form of vector control in Brazil until 1997.



Aedes aegypti reappeared in the Amazonian city of Belém in 1967, and then began to spread across Brazil in the late 1970s and early 1980s.

For the historian Rodrigo Cesar da Silva Magalhães, who wrote his doctoral thesis on the eradication programme, the responsibility for the current epidemic rests just as much with the government as with the public.

In an interview with O Estado de São Paulo in the midst of last year’s dengue epidemic, he argued, “while there is no political will on the part of the state and investment in research, sanitation, urbanization and permanent anti-mosquito activities, it [the mosquito] will continue to kill”.

Alongside the current campaign, researchers are also experimenting with other methods of controlling the mosquito population, including the deployment of genetically modified mosquitos and

the introduction of Wolbachia, a naturally occurring bacterium which prevents disease transmission, into the local mosquito population.



But given how much remains unknown about the Zika virus and its potential link with microcephaly, health workers and researchers in Brazil have to contend with a deeply sceptical public.



On social media sites rumours abound about the disease and its causes. The Brazilian health ministry has taken the unusual step of reassuring the public that the cases of microcephaly are not linked to a course of vaccines for pregnant women; nor are they a by-product of the bacterial anti-mosquito campaign.



It has also denied a rumour that there has been a surge in cases of serious neurological disorders among young children and the elderly.



Still, many Brazilians are reluctant to let government agents into their homes and there have been reports of thieves masquerading as health visitors.



As Dr Magalhães observed, there remains a tension between the basic tenets of a democratic society and the goal of eradicating the mosquito.



“How do you make people open their homes to health agents without recourse to authoritarian laws or attitudes?”

