This report investigates the conditions that result in mosquito bourne illnesses being a threat to Far North Queensland and the steps taken to control and reduce the risks of contracting dengue fever.
Dengue fever is a disease that is very infectious and its spreading is caused by the female mosquito also known as Aedes aegypti. It’s said to usually take 3-14 days after getting bitten by a dengue infected mosquito and contracting sickness. When a person recovers from dengue fever, they develop immunity to that mosquito bourne type disease. Different dengue fever viruses that are also transmitted by mosquitos are the Dengue Shock Syndrome and the Dengue Haemorrhagic. These fevers are passed around from one person to another by the mosquitos biting an already infected person then moving along and transferring the virus by biting and uninfected person.
Symptoms and signs of dengue fever are nausea, high fever, fatigue, severe muscle and joint pains, headaches, pain behind the eyes and red rash. Other common symptoms are easy bruising, sore throat, rapid breathing or bleeding gums. If any of these symptoms or signs are being shown or present to the body you should seek medical advice and/or help. If diagnosed by a doctor or medical professional, you may be prescribed with pain relief such as the common Panadol. When recovering from this disease, symptoms such as fatigue or in worse cases prolonged depression can come along. Healing can vary in each person though, in much worse cases it can take a person many months to fully recover from the disease.
Dengue fever is primarily found in the tropics. The tropics is found between the latitude lines of the Tropic of Cancer and the Tropic of Capricorn. The tropics include the Equator and parts of North America, South America, Africa, Asia, and Australia in a band that surrounds the equator from 23º north latitude to 23º south latitude.
Mosquitos have a life-cycle with dramatic changes in shape, function, and habitat. The female mosquitoes lay their eggs on the inner, wet walls of containers with water. The larvae then hatch when water inundates the eggs as a result of rain or the result of water by people. Following on, the larvae will then feed on microorganisms and particulate organic matter, shedding their skins three times to be able to grow from first to fourth instars. When the larva has gained enough energy and size and is in the fourth instar, metamorphosis is triggered, changing the larva into a pupa Pupae. Now, the newly formed mosquito emerges from the water after breaking the pupal skin. The life cycle lasts about 8-10 days at room temperature, depending on the level of feeding. Aedes aegypti live in tropical and subtropical regions all over the world, mainly between the latitudes of 35°N and 35°S where the winter temperature is no colder than 10°C. Because Aedes aegypti require a warm climate, they typically do not live at altitudes above 1000 m, where the temperature is colder. These mosquitoes are associated with the living spaces of humans.
In Far North Queensland, Dengue viruses are carried and spread by female mosquitoes, which are sensitive to environmental conditions. Temperature, precipitation, and humidity are critical to survival, reproduction, and development of a/the mosquitos. The high temperatures reduce the time required for the virus to replicate and disseminate in the mosquito. The process “extrinsic incubation period” must occur before the virus can reach the mosquitoes salivary glands and then soon to be transmitted to humans. If the mosquito becomes infected faster because temperatures are higher/warmer, it has a greater chance of infecting a human before it dies.
Globally, the disease of dengue has been increasing. Although climate may contribute to changing dengue incidence and distribution, it is one of the many factors included. Other important factors potentially contributing to worldwide changes in dengue include population growth, urbanization, lack of sanitation, increased long-distance travel, ineffective mosquito control, and increased reporting capacity.
To reduce the spread of dengue fever across Australia, the Queensland Department of Health has created and introduced a management plan for dengue. The objective is to reduce the spread of the dengue fever disease across QLD and to support the detection and reporting of the future dengue incidences. The general public, are encouraged to help prevent the spread of the disease. The use of repellents suitable for mosquitos and wearing long sleeved shirts and long pants, also removing any mosquito breeding grounds such as small containers, pots, discarded car tyres and bird baths that are around and full of water can reduce the threat.
Dengue control aims to break the cycle of transmission by detecting and reducing populations. In North Queensland towns with established Aedes Aegypti populations, work is done to educate and support the act to remove domestic container habitats. Mosquito surveillance is required to monitor the presence and numbers of mosquitos in risk areas, ports and airports. These activities require a joint effort from local government, quarantine officers from the Australian Government Department of Agriculture, health authorities and the public. Mosquito killing traps (e.g. lethal ovitraps) and sprays may be added in high risk spots and schools. Most outbreaks occur during the summer wet season.
In dengue receptive areas, an outbreak prompts urgent and intensive mosquito control activities around the addresses where the cases may have been viraemic. Water filled containers are treated with insect growth regulators (e.g. methoprene), Bti or pesticide sprays. Tipping out or removal of containers is most effective.
Overall, in summary the dengue fever virus is known to be uncontrollably infectious. The research that I conducted, I found that the female mosquito is the only carrier that is able to make the disease spreadable and that it contains four types of viruses. It was also found that there were more cases involving dengue in QLD last year then any other time.