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Mosquito studies show rapid Zika spread, rule out some US species
Filed Under:
Zika
Lisa Schnirring | News Editor | CIDRAP News
| Jul 19, 2016 In a pair of new studies on Zika virus in mosquito populations, researchers found the virus in Aedes mosquitoes near the homes of infected patients in southern Mexico, with hints that it was introduced from Guatemala, and another team found that two species found in large parts of the United States aren't likely to transmit the disease.
The first report adds evidence for the northward spread of Zika virus in the Americas, while the second one provides a bit of reassurance, though more studies to gauge the risk in different mosquito populations are needed.
Mexican mosquito investigation
The findings in Mexican mosquitoes resulted from a study launched in the wake of a Zika outbreak at the end of 2015 in Chiapas state, near the border with Guatemala. Researchers from Mexico and the University of Texas Medical Branch at Galveston reported their findings today in the Journal of Infectious Diseases.
The area had experienced a wave of chikungunya illnesses the year before, and the infections in late 2015 were originally thought to be from dengue virus. Of 119 suspected Zika illnesses, 25 were confirmed by reverse-transcriptase polymerase chain reaction testing.
Mosquitoes were tested in and around patients' homes, and, of 796 collected, Zika was detected in Aedes aegypti from 15 of 55 pools. No virus, however, was detected in Culex quinquefasciatus mosquitoes, and only two Aedes albopictus mosquitoes had Zika virus.
Analysis of Zika gene sequences from both patients and mosquitoes suggested a point-source introduction from Guatemala. The team also noted that other recent Zika virus strains from elsewhere in Chiapas state hinted at importation from Martinique.
The researchers said the findings show a rapid northward spread of Zika virus and show for the first time that Ae aegypti is a principal vector in North America.
Susceptibility tests in other US vectors
In the second study, researchers from the University of Wisconsin Madison used experimentally infected mice to see of two other common vectors?aside from the two Aedes species known to transmit Zika virus?are susceptible.
One was Culex pipiens, found in the northern half of the country and known to carry West Nile virus, and the other was Aedes triseriatus, found from Florida to eastern Canada and a natural vector and overwintering hose of La Crosse virus.
The team reported its findings yesterday in a letter to Emerging Infectious Diseases. As positive controls, they also included Ae aegypti and Ae albopictus. They used the Asian Zika virus strain responsible for fueling the outbreak in the Americas in their tests.
All C pipiens samples were negative for Zika virus. They saw positives in Ae triseriatus only when the mosquitoes were exposed to mice with the highest viral levels, but the infected mosquitoes disseminated virus, and none had the capacity to transmit Zika.
For now, the findings suggest that only Ae aegypti and Ae albopictus would drive Zika circulation, if it occurs, in the United States, the group said. However, they added that it's possible that other species could be competent vectors, showing the need to test other Zika-mosquito combinations.
See also:
Jul 19 J Infect Dis abstract
Jul 18 Emerg Infect Dis letter
Mosquito studies show rapid Zika spread, rule out some US species
Filed Under:
Zika
Lisa Schnirring | News Editor | CIDRAP News
| Jul 19, 2016 In a pair of new studies on Zika virus in mosquito populations, researchers found the virus in Aedes mosquitoes near the homes of infected patients in southern Mexico, with hints that it was introduced from Guatemala, and another team found that two species found in large parts of the United States aren't likely to transmit the disease.
The first report adds evidence for the northward spread of Zika virus in the Americas, while the second one provides a bit of reassurance, though more studies to gauge the risk in different mosquito populations are needed.
Mexican mosquito investigation
The findings in Mexican mosquitoes resulted from a study launched in the wake of a Zika outbreak at the end of 2015 in Chiapas state, near the border with Guatemala. Researchers from Mexico and the University of Texas Medical Branch at Galveston reported their findings today in the Journal of Infectious Diseases.
The area had experienced a wave of chikungunya illnesses the year before, and the infections in late 2015 were originally thought to be from dengue virus. Of 119 suspected Zika illnesses, 25 were confirmed by reverse-transcriptase polymerase chain reaction testing.
Mosquitoes were tested in and around patients' homes, and, of 796 collected, Zika was detected in Aedes aegypti from 15 of 55 pools. No virus, however, was detected in Culex quinquefasciatus mosquitoes, and only two Aedes albopictus mosquitoes had Zika virus.
Analysis of Zika gene sequences from both patients and mosquitoes suggested a point-source introduction from Guatemala. The team also noted that other recent Zika virus strains from elsewhere in Chiapas state hinted at importation from Martinique.
The researchers said the findings show a rapid northward spread of Zika virus and show for the first time that Ae aegypti is a principal vector in North America.
Susceptibility tests in other US vectors
In the second study, researchers from the University of Wisconsin Madison used experimentally infected mice to see of two other common vectors?aside from the two Aedes species known to transmit Zika virus?are susceptible.
One was Culex pipiens, found in the northern half of the country and known to carry West Nile virus, and the other was Aedes triseriatus, found from Florida to eastern Canada and a natural vector and overwintering hose of La Crosse virus.
The team reported its findings yesterday in a letter to Emerging Infectious Diseases. As positive controls, they also included Ae aegypti and Ae albopictus. They used the Asian Zika virus strain responsible for fueling the outbreak in the Americas in their tests.
All C pipiens samples were negative for Zika virus. They saw positives in Ae triseriatus only when the mosquitoes were exposed to mice with the highest viral levels, but the infected mosquitoes disseminated virus, and none had the capacity to transmit Zika.
For now, the findings suggest that only Ae aegypti and Ae albopictus would drive Zika circulation, if it occurs, in the United States, the group said. However, they added that it's possible that other species could be competent vectors, showing the need to test other Zika-mosquito combinations.
See also:
Jul 19 J Infect Dis abstract
Jul 18 Emerg Infect Dis letter