Hot summers, like those we have experienced in recent years, are leading to changes in the distribution of mosquitoes and ticks. These pests are becoming more prolific and invading new areas. Their presence is not only bothersome, even in Ticino. It also poses health risks because these small organisms can carry viruses and other pathogens that may be transmitted to humans when they feed on our blood.
Diseases transmitted by infected mosquitoes are well known in tropical regions of the Americas, Asia, and Africa. One of the most notable among these is dengue fever, which is estimated to cause over 100 million infections worldwide each year. Last year, Brazil and neighbouring countries experienced the most significant dengue fever epidemic on record, resulting in thousands of deaths. Another concern is the Zika virus, particularly when pregnant individuals are infected, as the virus can cross the placenta and cause serious harm to fetal development. We all remember the images of babies born with microcephaly-a condition characterised by a significantly smaller-than-average brain size-during the Zika epidemic in South America in 2015-16. Other mosquito-borne viruses, such as West Nile and Japanese Encephalitis, affect the brain. When these viruses reach the brain, hospitalisation becomes necessary. Even if a patient recovers, the disease can still lead to permanent neurological damage. These viruses can transmit serious, and sometimes fatal, diseases, particularly affecting the most vulnerable populations, such as senior citizens or individuals with weakened immune systems due to treatments for autoimmune diseases or cancer.
In the past, these diseases were rare in our region and were primarily brought in by travellers returning from exotic destinations. However, recent years have seen a significant increase in cases, even among individuals who have not travelled outside Europe. For instance, northern Italy has experienced major outbreaks of West Nile Encephalitis over the last three years, resulting in thousands of infections during the summer months. Additionally, epidemics of Dengue fever and Chikungunya, another mosquito-borne disease, have also occurred in Italy, Spain, and France.
But why are these diseases also coming to us?
"There are many types of mosquitoes, but only some can transmit the pathogens that cause disease," says Francesco Origgi , director of the Institute of Microbiology at SUPSI. "In Ticino and other regions of Europe, favourable climatic conditions and rising temperatures are leading to an increase in the prevalence of mosquitoes capable of transmitting infectious agents." This area is of great scientific interest at SUPSI, where activities are carried out in collaboration with leading European universities and coordinated by the Vector Ecology and Biosafety departments, headed by researchers Eleonora Flacio and Valeria Guidi , assisted by Eva Veronesi. "Our tasks involve collecting and cataloguing information to determine which species are present and whether any have the potential to transmit pathogens that can be dangerous to humans. The unique ability of RNA viruses, such as West Nile and Dengue, to mutate poses a significant challenge for public health. In some cases, these mutations can enable certain species of mosquitoes to transmit the viruses more effectively."During the summer months, mosquitoes are captured using traps in various areas of the canton, as part of an important surveillance activity. The laboratories are equipped with high-pathogen containment biological safety areas, known as "Biosafety Level 3," which allow for the testing of mosquitoes for harmful viruses. "In 2022, we detected the presence of the West Nile virus in mosquitoes collected in Ticino for the first time, and this was confirmed again in 2023. Unfortunately, this finding is not surprising, given the recent outbreaks just a few hundred kilometres away, such as those in northern Italy."
The Institute of Microbiology has been coordinating activities for years to reduce the population of tiger mosquitoes, which are known to potentially transmit Dengue and Chikungunya. "We are experimenting with using specialised mosquitoes, such as sterile male tiger mosquitoes. By introducing these sterile males, we aim to reduce the overall tiger mosquito population over time. An experiment in this regard has been conducted in the municipality of Morcote." This marks the first implementation of this innovative method in Switzerland, and the results from the pilot study are very promising. Plans for further research are underway, with the intention of making this technique available to municipalities and private individuals.
New challenges in the field of transfusion
The rising presence of these viruses in our area has caught the attention of the Transfusion Service of the Red Cross of Southern Switzerland , led by Stefano Fontana. "Some of these viruses, including the West Nile and Dengue, can also be transmitted through blood transfusions. Our service has been collaborating with transfusion services across the Alps and with cantonal authorities to study the epidemiology of infectious diseases that can be transmitted through blood transfusions. As the organisation responsible for supplying blood products to hospitals in Ticino, we must ensure the safety of our products and prevent the transmission of infections through blood transfusions. The blood samples collected from our donors across Ticino provide a valuable opportunity to identify the presence of various diseases within our population. It is becoming increasingly important to understand the risk that these mosquito-borne infections, which are new to our region, pose now and in the future for blood transfusions and the general public."Thanks to these converging interests, a pilot study - supported by the Fidinam Foundation - will be carried out in this field next summer, marking a new collaboration between the SRC Blood Transfusion Service of Southern Switzerland, the SUPSI Institute of Microbiology and the Institute for Research in Biomedicine, all’of which will benefit our region.
What type of medication is available to treat these diseases?
Vaccines are now available for Dengue fever and Chikungunya, with the Dengue vaccine recently receiving approval in Switzerland to help prevent or reduce the severity of the disease. However, no vaccines currently exist for other infections like West Nile encephalitis. This is one of the reasons we have been working at the IRB for the past two years on a study, in collaboration with researchers in Serbia, the Czech Republic, and the United States, to understand why the immune systems of certain individuals respond more effectively than others after infection with the West Nile virus. This information will be valuable for developing vaccines and other countermeasures against West Nile encephalitis, preventing the dreaded brain infection.A better understanding of tick-borne diseases
Just like mosquitoes, ticks are also expanding into new areas. In Switzerland, viral diseases such as tick-borne meningoencephalitis were once limited to certain regions around the canton of Zurich and in the Bernese Oberland. However, in recent years, this disease has been considered endemic throughout the entire country. This expansion is believed to be linked to climate change. In addition to tick-borne encephalitis, these small organisms can transmit other pathogens that cause serious illnesses, including Borreliosis, or Lyme disease. To better understand this development, it is worth noting the important "citizen science" initiative (i.e. a research project involving ordinary citizens) involving the Swiss Reference Centre for Tick-borne Diseases, directed by Gilbert Greub and based at the University Hospital of Lausanne (Chuv).Greub explains: "If we find a tick attached to our skin after an outing, we should remove it carefully and secure it to a piece of paper using adhesive tape. We can then place the paper with the tick in an envelope and send it to our centre in Lausanne. A series of tests will be conducted to check whether the tick contains traces of Borreliosis, the meningoencephalitis virus, or other pathogens."
In addition to sending the tick, citizen scientists will pinpoint its exact location using a map feature in the dedicated Zecca app on their mobile phones. The pilot study, which began in 2018, has already recorded the submission of over 2,000 ticks for analysis, and there is hope that this number will grow significantly in the future. This initiative will aid in better mapping the spread of tick-borne pathogens across the country. The app is expected to be enhanced with telemedicine capabilities in a later phase. If a tick test returns positive, citizens will be contacted by phone, informed of the associated risks, and prescribed an approved (if available) or experimental medication.
This is therefore an excellent opportunity to determine the effectiveness of new drugs, which is also why the IRB is working closely with colleagues in Lausanne on the clinical development of a monoclonal antibody against tick-borne encephalitis. In fact, despite the existence of an effective vaccine against this disease, its uptake is not very high, with an estimated 10,000 cases of meningoencephalitis worldwide each year. A medication taken shortly after being bitten by an infected tick could prevent the infection from reaching the brain.
Content written and published in collaboration with laRegione .
Zeta come... zanzare e zecche che portano malattie (laRegione in collaborazione con Davide Robbiani)