Local transmission of Zika virus (ZIKV) in the Americas was fi rst confi rmed in February, 2014, on Easter Island. In May, 2015, 16 patients from the Brazilian states of Bahia and Rio Grande do Norte were found to be ZIKV-positive. 22 countries and territories have subsequently identifi ed autochthonous transmission within the region (fi gure). Until recently, ZIKV infection was only associated with mild symptoms (headache, rash, joint pain, conjunctivitis) but a possible link between ZIKV infection during pregnancy and subsequent birth defects (most notably microcephaly) was identifi ed in November, 2015. Approaching 4000 cases of suspected ZIKV-related microcephaly have arisen in Brazil alone where initial fi gures suggest between 440 000 and 1·3 million people have been infected so far. Concern in the region is escalating, with public health authorities in Colombia, Ecuador, El Salvador, and Jamaica all issuing an unprecedented health notice warning their residents to avoid pregnancy until 2018. ZIKV is a fl avivirus related to dengue virus (DENV) and historically has been transmitted by the same mosquito species, Aedes aegypti (fi gure). There is no available treatment or vaccine so disease control is limited to the management of mosquitoes which currently relies on either insecticides or the destruction of larval breeding sites. In Brazil, ultra-low-volume space spraying is recommended only during dengue outbreaks. However, widespread insecticide resistance (including high pyreth roid resistance rates) and the impracticality of identifying and eliminating standing pools of water on a city-wide scale provide little hope for the containment of this disease. Vaccine development is anticipated to take several years; in the more immediate term, what options are left for the control of ZIKV? Two novel approaches that have shown considerable promise in recent years are the genetic control of A aegypti mosquitoes and the development of mosquitoes that are resistant to arbovirus infection. The fi rst fi eld-trialled genetic control strategy is known as RIDL (the Release of Insects carrying Dominant Lethal genes) and involves the mass rearing of A aegypti that have been genetically modifi ed to express a repressible lethal gene. During their rearing in insectaries, the mosquitoes are provided with a dietary supplement not present in nature (eg, tetracycline), and this supplement represses the lethal gene activation. Only male mosquitoes are released and these compete with wild males to mate with wild females. Off spring do not survive to the adult stage because they do not receive the dietary additive in the wild. Lines of RIDL males have been shown to have minimal fi tness costs (ie, they are competitive with wild males) and the recent fi eld release in Bahia, Brazil, reportedly achieved a 95% reduction in local mosquito populations. An alternative approach is the use of endosymbiotic bacteria to prevent arboviruses replicating within the mosquito. The Eliminate Dengue project has been able to demonstrate that Wolbachia bacteria from Drosophila fruit fl ies can prevent DENV transmission in A aegypti mosquitoes without signifi cant fi tness costs.
Zika virus outbreak in the Americas: the need for novel mosquito control methods.
Published 2016 in Lancet Global Health
ABSTRACT
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- Publication year
2016
- Venue
Lancet Global Health
- Publication date
2016-03-01
- Fields of study
Biology, Medicine, Environmental Science
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
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