Zika could be transmitted by mosquito found in New Zealand
A mosquito found in New Zealand may be able to transmit the Zika virus.
Scientists in Brazil have been able to infect the Culex quinquefasciatus species of mosquito, which has been in this country since at least 1848, with the virus.
The findings showed it was misguided and potentially dangerous to assume New Zealand did not have mosquito vectors capable of transmitting the virus, Dr Jose Derraik, senior research fellow at the Liggins Institute, University of Auckland, said.
"Culex quinquefasciatus was the first foreign mosquito to become established in this country ... It is present in much of the North Island and in northern areas of the South Island.
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"It is considered to be a species of 'domestic' habits, with a tendency to live in association with humans," he said.
"It breeds in a variety of man-made habitats, including polluted waters in drains and septic tanks. Culex quinquefasciatus is considered a pest in some urban areas, and it will often come indoors to bite humans in the night time.
"As a result, even though the risk of mosquitoes transmitting viruses to humans in New Zealand is lower than in other countries, this possibility cannot be simply disregarded," he said.
"Those arriving from overseas infected with an exotic virus (such as Zika) should avoid being bitten by mosquitoes in New Zealand, to minimise the chances of local transmission."
Scientists in Brazil announced they had been able to infect Culex quinquefasciatus with the virus in a laboratory. That raised concerns Zika could be carried by a species more prevalent than Aedes aegypti, which had been identified as the main transmitter of Zika infections.
The scientists emphasised much more research was needed to learn whether Culex mosquitoes could actually transmit Zika infections.
Acting Director of Public Health Dr Stewart Jessamine said the risk of local transmission of the Zika virus remained "very low".
From talking to international mosquito experts, the Ministry of Health understood that for the Culex mosquito to become a carrier of the Zika virus, it needed both the presence of an efficient vector - such as Aedes aegypti - and reasonably high levels of disease in the community, he said.
Derraik said the Brazilian scientists had been able to detect Zika virus in the salivary glands of the infected Culex quinquefasciatus mosquitoes.
"It seems that both the viral load in salivary glands and the rate of infection among mosquitoes were high, providing evidence that Culex quinquefasciatus may also be a vector of Zika virus," Derraik said.
"The results are preliminary, and researchers are now collecting specimens from areas where Zika virus is circulating, to identify whether the mosquitoes in the 'wild' are indeed carrying the virus.
"These developments indicate that the widespread claim that Zika is transmitted only by Aedes mosquitoes is probably erroneous, as it has been based on assumptions rather than on thorough investigation of the ecology of the virus.
"Importantly, these findings highlight an issue that has been misunderstood by many commenting on the risk posed by Zika virus to New Zealand. It is true that the mosquitoes said to have been transmitting the virus overseas (ie. mainly Aedes aegypti and Aedes albopictus) do not occur in this country. However, there are 15 mosquito species present in New Zealand, Derraik said.
"So, while it is correct to say that the known mosquito vectors of Zika virus are not present in New Zealand, it is misguided (and potentially dangerous) to assume that we do not have mosquito vectors capable of transmitting the virus. Zika virus in particular, has been very poorly studied until the outbreak in Brazil, which means that we simply do not know whether the species of mosquitoes in New Zealand are able to transmit the virus to humans."
Zika has been around for decades and most people infected with it don't get sick, and those that do usually develop mild symptoms – fever, rash, joint pain, and red eyes – which usually last no more than a week.
But current outbreaks raised major worries as scientists found mounting evidence linking Zika infection in pregnant women to a rare birth defect called microcephaly, in which a newborn's head is smaller than normal and the brain may not have developed properly.
A rare nerve condition called Guillain-Barre that can cause paralysis has also been linked with Zika outbreaks, but the relationship is not yet proven.