Malaysia: 80pc decrease in dengue cases in hotspots

VEENA BABULAL and TEOH PEI YING New Straits Times 4 Mar 19;

KUALA LUMPUR: THE government’s bid to battle dengue using Wolbachia-infected Aedes aegypti mosquitoes appears to be on the right track, with seven dengue hotspots recording an 80 per cent decrease in dengue cases.

This was the outcome of a pilot study undertaken since March 2017 in neighbourhoods in Keramat here and in Shah Alam, Selangor, where three million Wolbachia-infected Aedes aegypti mosquitoes were released.

The project aims to assess the effectiveness of using Wolbachia-infected mosquitoes to block the ability of the mosquito population to transmit dengue to human beings.

Speaking to the New Straits Times, Institute for Medical Research (IMR) director Datuk Dr Fadzilah Kamaludin said once the “invasion” of the Wolbachia-infected mosquitoes reached its peak, more than 90 per cent of dengue transmission would be interrupted.

This, she said, was observed in AU2 Keramat and Mentari Court in Shah Alam, which recorded a 77 per cent and 80 per cent reduction in dengue cases, respectively.

The results, she said, were seen in the same year the mosquitoes were first released.

Dr Fadzilah, however, said the success rate was dependent on several factors, such as the type of housing in the area they were released in and natural boundaries that impede the mosquitoes’ coverage area.

These boundaries include highways, river, vegetation, open space and industrial sites.

Dr Fadzilah said the density of Aedes mosquitoes would have an impact on the invasion of Wolbachia-infected mosquitoes on the wild population.

Asked if the Health Ministry was taking a gamble with the project as it was earlier reported that the infection could not take hold outside the 26 °C-to-37 °C bracket, Dr Fadzilah said the wAlbB (Wolbachia) strain used could withstand heat.

“A study conducted by Ross et. al. (2017) on the heat tolerance of three strains of Wolbachia — wMel, wAlbB and wMel-Pop-CLA — found that only the wAlbB strain is heat tolerant, has a high density of Wolbachia in Aedes aegypti and can transmit from mother to offspring with high reliability at 26 °C to 37 °C.”

“Studies by our collaborators indicated that this strain is tolerant to tropical temperatures. As long as the mosquito has Wolbachia, the dengue virus cannot multiply, hence transmission will be interrupted.”

She said the five-year research was funded by the United Kingdom-based Wellcome Trust Fund, with a grant of RM3.8 million.

Dr Fadzilah said the control method using the pathogen was effective, safe, sustainable and did not have undesirable impact on the environment.

Asked why the ministry did not go with the Toxorhynchites (a predatory jungle mosquito) instead to biologically control the menace, she said there was no evidence that the release of such mosquitoes was effective.

“Toxorhynchites is not an urban mosquito and is unlikely to survive in urban environments. Aedes aegypti, however, is highly urbanised,” she said.

On reports that the 20 to 30 per cent of the mosquito population needed to be infected
to ensure the project’s success, as well as the high mortality
rates involving infected young mosquitoes, Dr Fadzilah said the bacterial strain originated from “Aedes albopictus and has a low fitness cost on the mosquito”.

“This means it will not have any untoward effect on Aedes aegypti. The Wolbachia strain used in Malaysia could easily infect the wild population, achieving Wolbachia infection frequency of upwards of 95 per cent.”

She, however, cautioned that Wolbachia was not a silver bullet to combat the menace and would be integrated with the Health Ministry’s other control programmes.

The government’s unorthodox approach to tackling dengue comes at a time when the disease outbreak appears to be at its peak.


Kelantan dengue cases soar by 330pct in first two months of 2019
Bernama New Straits Times 4 Mar 19;

KOTA BARU: Kelantan recorded 107 cases of dengue fever in the first nine weeks of 2019, bringing the state’s total to 805 cases with two deaths.

State health director Dr Zaini Hussin said the number had increased by 618 cases (330.5 per cent) over the same period last year.

Kelantan also recorded two new chikungunya cases during the ninth week, one each at Lorong Masjid Lundang, Kubang Krian and Jalan Embi in Kota Baru.

This makes 20 cases of the disease recorded in the first two months of the year, compared to 33 cases in the same period last year.

"Throughout week nine until March 2, 59 local dengue outbreaks were reported, compared to seven in the same period last year, with 22 of them still active," he told Bernama here, today.

Dr Zaini said his department has inspected 76,021 premises, of which 2,988 were found to be breeding grounds for mosquito larvae.

"The department has issued 465 compounds with a proposed value of RM232,500 under the Destruction of Disease-Bearing Insects Act 1975; and a total of 182 Section 8 notices were issued for cleaning up and destroying places that are potential Aedes mosquito breeding grounds," he added.--Bernama

The Health Ministry on Wednesday said dengue cases had seen a 163 per cent jump this year, compared with the same period last year.