After the floods come the mosquitoes – but the disease risk is more difficult to predict


Cameron Webb, University of Sydney

We’re often warned to avoid mosquito bites after major flooding events. With more water around, there are likely to be more mosquitoes.

As flood waters recede around Townsville and clean-up efforts continue, the local population will be faced with this prospect over the coming weeks.

But whether a greater number of mosquitoes is likely to lead to an outbreak of mosquito-borne disease is tricky to predict. It depends on a number of factors, including the fate of other wildlife following a disaster of this kind.

Mozzies need water

Mosquitoes lay their eggs in and around water bodies. In the initial stages, baby mosquitoes (or “wrigglers”) need the water to complete their development. During the warmer months, it doesn’t take much longer than a week before they are grown and fly off looking for blood.

So the more water, the more mosquito eggs are laid, and the more mosquitoes end up buzzing about.

But outbreaks of disease carried by mosquitoes are dependent on more than just their presence. Mosquitoes rarely emerge from wetlands infected with pathogens. They typically need to pick them up from biting local wildlife, such as birds or mammals, before they can spread disease to people.




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Mosquitoes and extreme weather events

Historically, major inland flooding events have triggered significant outbreaks of mosquito-borne disease in Australia. These outbreaks have included epidemics of the potentially fatal Murray Valley encephalitis virus. In recent decades, Ross River virus has more commonly been the culprit.

A focal point of the current floods is the Ross River, which runs through Townsville. The Ross River virus was first identified from mosquitoes collected along this waterway. The disease it causes, known as Ross River fever, is diagnosed in around 5,000 Australians every year. The disease isn’t fatal but it can be seriously debilitating.

Following substantial rainfall, mosquito populations can dramatically increase. Carbon dioxide baited light traps are used by local authorities to monitor changes in mosquito populations.
Cameron Webb (NSW Health Pathology)

In recent years, major outbreaks of Ross River virus have occurred throughout the country. Above average rainfall is likely a driving factor as it boosts both the abundance and diversity of local mosquitoes.

Flooding across Victoria over the 2016-2017 summer produced exceptional increases in mosquitoes and resulted in the state’s largest outbreak of Ross River virus. There were almost 1,700 cases of Ross River virus disease reported there in 2017 compared to an average of around 300 cases annually over the previous 20 years.




Read more:
Explainer: what is Ross River virus?


Despite plagues of mosquitoes taking advantage of flood waters, outbreaks of disease don’t always follow.

Flooding resulting from hurricanes in North America has been associated with increased mosquito populations. After Hurricane Katrina hit Louisiana and Mississippi in 2005, there was no evidence of increased mosquito-borne disease. The impact of wind and rain is likely to have adversely impacted local mosquitoes and wildlife, subsequently reducing disease outbreak risk.

Applying insect repellent is worthwhile even if the risk of mosquito-borne disease isn’t known.
From shutterstock.com

Australian studies suggest there’s not always an association between flooding and Ross River virus outbreaks. Outbreaks can be triggered by flooding, but this is not always the case. Where and when the flooding occurs probably plays a major role in determining the likelihood of an outbreak.

The difficulty in predicting outbreaks of Ross River virus disease is that there can be complex biological, environmental and climatic drivers at work. Conditions may be conducive for large mosquito populations, but if the extreme weather events have displaced (or decimated) local wildlife populations, there may be a decreased chance of outbreak.

This may be why historically significant outbreaks of mosquito-borne disease have occurred in inland regions. Water can persist in these regions for longer than coastal areas. This provides opportunities not only for multiple mosquito generations, but also for increasing populations of water birds. These birds can be important carriers of pathogens such as the Murray Valley encephalitis virus.




Read more:
Giant mosquitoes flourish in floodwaters that hurricanes leave behind


In coastal regions like Townsville, where the main concern would be Ross River virus, flood waters may displace the wildlife that carry the virus, such as kangaroos and wallabies. For that reason, the flood waters may actually reduce the initial risk of outbreak.

Protect yourself

There is still much to learn about the ecology of wildlife and their role in driving outbreaks of disease. And with a fear of more frequent and severe extreme weather events in the future, it’s an important area of research.

Although it remains difficult to predict the likelihood of a disease outbreak, there are steps that can be taken to avoid mosquito bites. This will be useful even if just to reduce the nuisance of sustaining bites.

Cover up with long-sleeved shirts and long pants for a physical barrier against mosquito bites and use topical insect repellents containing DEET, picaridin, or oil of lemon eucalyptus. Be sure to apply an even coat on all exposed areas of skin for the longest lasting protection.The Conversation

Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Muslim Groups Demand Closure of Large, Legal Church in Indonesia


Hundreds of demonstrators from outside area try to create image of local opposition.

JAKARTA, Indonesia, February 25 (CDN) — Hundreds of Muslims from outside the area where a 600-member church meets in West Java staged a protest there to call for its closure this month in an attempt to portray local opposition.

Demonstrators from 16 Islamic organizations, including the hard-line Islamic Defenders Front (FPI), gathered on Feb. 15 to demand a stop to all activities by the Galilea Protestant Church (GPIB) in the Galaxy area of Bekasi City.

The Rev. M. Tetelepta, pastor of the church, told Compass that the church has had the required consent of local residents and official permission to worship since its inception in 1992.

“From the beginning we had permission to worship from both the government and the nearby residents,” Tetelepta said. “We worked on the building permit and had received principle clearance from the mayor of Bekasi. We had also received permission from the Bekasi Interfaith Harmony Forum.”

At the Galaxy area demonstration, FPI Bekasi branch head Murhali Baeda tried to impugn the legal status of the Galilea church by telling ANTARA, the official news agency of the Indonesian government, that he was “certain” that “a number of the church buildings” in the area “do not have complete permission.”

“This is proved by the large number of posters and banners that are displayed in the alleys and public gathering places rejecting the presence of these [church] buildings,” Murhali told ANTARA.

A Joint Ministerial Decree promulgated in 1969 and revised in 2006 requires the permission of more than 60 neighbors and a permit from local authorities to establish a place of worship in Indonesia.

Representatives of Islamic organizations at the demonstration shouted, “Churches are not allowed in Galaxy” and carried posters and banners declaring, “We Faithful Muslims Reject the Presence of Churches,” as well as “Beware of Christianization of Galaxy.”

Local organizations represented at the demonstration included the Bekasi Dakwah Council, the Bina An Nisa Dakwah Council of Bekasi and the Galaxy Mosque and Mushola Forum, but Tetelepta said he was sure that 95 percent of the protestors were not local people.

Also present at the demonstration were representatives of the Islamic Youth and Student Forum, Islamic Unity, the Committee to Enact Syariah (Law), Muhammadiyah, the Islamic Youth Movement, the Syariah Concern Society, the Islamic Youth Federation, the Bungin Dakwah Council, the Gembong River Society, Irene Centre and the Indonesian Mujahadin Council.

Baeda of the FPI accused the church of “Christianizing” local residents by distributing food “and the nine essentials at a reduced price.”

“The church is distributing these things as incentive to confess Jesus as their Lord,” Baeda told Compass. “We have received several reports of this from people who have accepted these distributions.”

This type of activity disturbs society, he added. “I consider this wrong-doing.”

The local FPI leader told ANTARA that there are at least six churches and a number of homes that function as churches.

“At night praises to their God in the form of songs disturbs the people’s sleep,” he reportedly said.

Tetelepta denied that the church had tried to “Christianize” people.

“We have never distributed food or the nine essentials,” he said. “The only thing we have done is to spray for mosquitoes near the church.”

Before coming to Galaxy the congregation had worshipped in various places in Bekasi. At the suggestion of the government, Tetelepta said, the church purchased the property in Galaxy in 2006 in order to construct a worship place.

He added that there has been an effort to discredit the church in the Bekasi area.

“Our worship services will continue as usual in spite of the demonstrations,” he said. “We are coordinating things with the police.”

Report from Compass Direct News