As international travel and global connectivity increase, European countries must ensure they are prepared with efficient and cost-effective strategies to deal with mosquito-borne diseases, researchers in Italy wrote in a new paper.
The study examined outbreaks of Chikungunya virus (CHIKV) in Italy in 2007 and 2017 in order to identify cost-effective control strategies. Chikungunya mostly occurs in Asia, Africa and the Indian subcontinent, but has been identified in more than 60 countries across Asia, Africa, Europe and the Americas, according to the World Health Organisation (WHO). Invasive tiger mosquitoes, which carry the Chikungunya virus as well as Zika and dengue, are present in nearly all Italian provinces, making Italy more at risk of Chikungunya than any country in Europe.
When transmitted from mosquitoes to humans, the Chikungunya virus causes fever and severe joint pain, which can be debilitating in some cases. Since there is no cure for the disease, treatment focuses on relieving the symptoms.
The study, led by Bocconi University in Milan, was published in the journal Scientific Reports. The results showed that the specific control strategies required are highly dependent on what time of year the first cases are identified.
“If Chikungunya cases are notified in late spring or during summer, the combination of larvicides, adulticides and breeding sites removal represents the optimal response strategy,” explained co-author Alessia Melegaro, from Bocconi’s Dondena Centre. “On the other hand, larvicides are proven to be more cost effective in early summer and in the warmer seasons, while adulticides should be preferred in the fall and colder seasons.”
Because no treatment or vaccine is available yet for many emerging mosquito-borne diseases, including Chikungunya and Zika virus, “the containment of potential future outbreaks mainly relies on the interruption of the transmission chain by means of well-designed preventive and reactive strategies to reduce the mosquitoes’ density,” according to the study.
Researchers said that their findings could help public health authorities make urgent decisions in response to emerging vector-borne epidemics. The team wrote in the study that they hope their work will “inform the design of future policy recommendations to face new potential CHIKV outbreaks in Europe.”
However, the team noted that other mosquito-borne diseases would likely require different control strategies from those that are cost-effective for CHIKV.
The threat of mosquito-borne diseases is increasing in Europe as more travellers visit areas where these viruses are prevalent.
“There is a real risk of creating a local cycle of transmission,” France’s public health authority warned in a statement in April. The authority added that southern France recorded 18 cases of locally transmitted dengue fever in 2014 and 2015, with 17 cases of Chikungunya reported on the French Riviera last year.
Growing populations of tiger mosquitoes have added to the problem – in the past two years, both the number of tiger mosquitoes and the area they affect have doubled. Out of France’s 96 départements, the tiger mosquitoes have spread to 42.
Other experts have also raised concerns about the spread of tropical diseases in Europe. Last month, London School of Hygiene and Tropical Medicine Professor Ron Behrens warned that Europe must be prepared to confront outbreaks of viruses like Zika, Ebola and others, which spread from endemic regions.
“The Zika virus could well spread to Southern Europe, which is why public health and surveillance bodies have got to catch these outbreaks early,” he said.
Behrens added that investment in effective control strategies and public health would be crucial to containing the viruses. “Outbreaks are inevitable,” he said. “The reaction depends on the quality of resources made available for public health.”