Aedes spread to remote rural areas

In July, a survey of Aedes mosquito larvae was conducted in Boladia Union of Nesarabad Upazila in Pirojpur. Aedes larvae were discovered in 7 out of 10 houses in the area.

The accepted method for measuring the density of Aedes mosquito larvae is the ‘Breeding Index (BI)’. A larval density exceeding 20 per cent according to this criterion indicates a high prevalence of dengue disease. The BI in Boladia village stands at 80 per cent.

Pirojpur’s Civil Surgeon, Hasnat Yusuf Zaki, informed Prothom Alo, “We found many Aedes mosquitoes this time; last time, it was only a quarter of this amount.”

The ‘Elimination of Malaria and Aedes-borne Disease Control Programme,’ under the Disease Control Wing of the Directorate General of Health Services, conducted larval surveys in 15 districts across the country.

It has been observed that Aedes mosquitoes have spread to remote rural areas, with the density of mosquito larvae in rural areas sometimes surpassing that in cities. Aedes aegypti, a major dengue transmitter, now appears to be more prevalent in rural areas than before.

Aedes outside Dhaka: From 2019 to 2023

Jashore Pourashava is among the places where the survey was conducted after the outbreak of dengue. This year, the BI (Breeding Index) for this pourashava is 80. The highest number of dengue infections in Bangladesh was recorded in 2019. According to a survey conducted by the DGHS at that time, the average BI in the pourashava was 22.

The average BI in Chattogram City Corporation area was 16 in 2019 and remained at 16 last year. However, this time it has surged to 46.

The density of BI or larvae has been observed to be exceptionally high this year in both rural areas and cities outside Dhaka. Angaria Union of Dumki Upazila in Patuakhali witnessed a BI of 100 this year.

The former chief entomologist of the Disease Control Wing of the DGHS, Khalilur Rahman, said, “The density of Aedes larvae in the remote areas of the country that we observed this time is completely unprecedented. It has increased at an alarming rate.”

Kabirul Bashar, an entomologist and professor of zoology at Jahangirnagar University, believes that the situation may become dire in the future due to the increase in the density of Aedes mosquitoes in rural areas. He stated, “The way Aedes has spread in the rural areas this time, it does not seem that this mosquito can be eliminated from this country this year.”

Aegypti is growing

Aedes aegypti and albopictus are among the 26 species of mosquitoes that transmit dengue. Aegypti predominates in the cities, while albopictus is more common in rural areas.

Previously, Aegypti was more prevalent in the capital city Dhaka, Chattogram, and several districts, with Albopictus found in other areas. However, in recent times, the prevalence of Aegypti has increased in rural areas.

In 2017, researcher and entomologist Hasan Mohammad Al-Amin from the University of Queensland in Australia conducted a survey of mosquitoes in different parts of the country. He stated, “In 2017, I found no more than 10 per cent Aegypti in Rajshahi. This year’s DGHS survey showed that it had increased to 20 per cent. In 2017, I recorded a 50 per cent presence in the hill tract areas, and this time in Rangamati, it has risen to 65 per cent.”

Professor Kabirul Bashar has discovered Aegypti mosquitoes in several villages, including Islamnagar in Savar, Gopalnagar, and Dohar, this year. He remarked, “I have never seen Aegypti in these areas before.”

Since 30 July until yesterday, Sunday, more dengue patients have been admitted to hospitals outside Dhaka than in Dhaka. However, despite the lower number of infections in Dhaka, the death rate is high. Former director of the Disease Control Wing of the DGHS, Be-Nazir Ahmed, suggests that the increased risk of death in Dhaka may be due to many patients being infected for the second time.

Mushtuq Hussain, an advisor at the government’s Institute of Epidemiology, Disease Control, and Research, stated, “Entire Bangladesh is now a dengue risk area.”

Public health experts emphasize that while there are some preventive measures in major cities like Dhaka to control Aedes, there is little in rural areas. Aegypti breeds in rural areas, but dengue is said to be transmitted through albopictus. Entomologist Khalilur Rahman believes it is important to identify this. Public health specialist Be-Nazir Ahmed also argues that dengue has now spread across the country, necessitating an expanded plan that includes the entire Bangladesh territory.

Another 16 people died

Another 16 people have died due to dengue in the country. Earlier on Saturday, DGHS reported the death of a maximum of 21 patients due to dengue. With this, 634 people died of dengue in the country this year.