Context: Aedes-borne Viral Diseases (ABVD) that include Dengue, Zika, and Chikungunya hurt India’s productivity. Aedes aegypti mosquitoes bite during the day time. Mosquito control methods like outdoor fumigation are not that effective, which necessitates revised strategies against Aedes Mosquitoes.
Relevance of the Topic: Prelims: Key facts about Aedes-borne Viral Diseases; Wolbachia Method.
Aedes-borne Viral Diseases
1. Dengue:
- Viral illness caused by the dengue virus, an RNA virus.
- Transmission:
- Bites of infected Aedes aegypti mosquitoes.
- There is no evidence that dengue can be transmitted directly from person to person through casual contact, coughing/sneezing, or sexual contact.
- Rare cases of vertical transmission (from mother to child during pregnancy or childbirth) have been reported, but this is not a common mode of spread.
- Symptoms: Flu-like symptoms, including high fever, severe headache, joint and muscle pain, and rash. In severe cases, it can lead to life-threatening dengue haemorrhagic fever.
2. Zika:
- Caused by Zika virus, an RNA virus.
- Transmission: Bites of infected Aedes aegypti mosquitoes. Can be transmitted from mother to foetus during pregnancy; through sexual contact, blood transfusion; organ transplantation.
- Zika infection during pregnancy causes microcephaly (underdeveloped brain) and other congenital malformations.
3. Chikungunya:
- Caused by the chikungunya virus (CHIKV), an RNA virus.
- Transmission: Bites of infected Aedes aegypti mosquitoes. An infected person cannot spread the infection directly to other persons (i.e. it is not a contagious disease).
- Symptoms: Fever, chills, headache, nausea, vomiting, joint pain, and rash. Severe joint pain (arthritis) which is the most common feature of the disease.
- Chikungunya is diagnosed by blood test (ELISA).
Wolbachia Method for Mosquito Control
- Wolbachia is a form of biological control method to reduce mosquito population.
- In this method, naturally occurring Wolbachia bacteria is introduced into male population by infecting insects in a laboratory, and then releasing them into the wild.
- These Wolbachia-infected male mosquitoes mate with female mosquitoes (not infected with the same strain of Wolbachia).
- These bacteria are passed on to their offspring through the normal reproductive process, and their offspring are less likely to survive or reproduce.
- The method does not suppress mosquito populations or involve genetic modification, so it is safe for humans, animals and the environment.
Challenges in controlling Mosquito population:
- Limitations of conventional methods: Aedes mosquito feeds indoors during the day, and at night under artificial light. Methods like outdoor fumigation, vaporisers, and bed nets are thus ineffective against it. Additionally, the mosquitoes have evolved to gain tolerance to these chemicals.
- Lack of Vaccines: Dengue vaccine trials are underway, but these offer no protection against Zika or chikungunya.
- Expensive: High costs and weak institutional support limit the adoption of advanced mosquito control methods like Wolbachia.
- Increased plastic pollution: Plastic pollution is directly linked to the risk of ABVD transmission. Discarded plastics can collect water and act as mosquito breeding sites).
Way Forward
- Application of safe non-insecticides (topical repellents) on the skin. By releasing volatile compounds, these repellants impair the mosquito’s sense of smell, thus making human hosts essentially invisible to them.
- E.g., Para-menthane-diol (PMD), derived from the essential oil of the lemon eucalyptus plant; Picaridin (derived from pepper plant)
- Using materials coated with delayed-release transfluthrin. These spatial emanators, like jute sheets, provide 15-days of continued protection in living spaces.
- Local community actions to remove larval breeding sites of Aedes mosquitoes. Regular trash collection/flood management protects against ABVD.
Public Health Campaign in Delhi: 10 Weeks, 10 AM, 10 Minutes
- Called the rule of 10, “10 Weeks, 10 AM, 10 Minutes,” it reinforces larval source reduction as the primary strategy.
- It encourages every residential welfare association to mobilise each household to set aside 10 minutes at 10 AM every Sunday for 10 weeks from September to November.
- The goal is to find and eliminate sources of stagnant water during this high-risk season.
Also Read: Malaria Elimination: Efforts & Challenges