Mosquitoes - Dengue and Chikungunya
Vector control remains the most generally effective measure to prevent transmission of dengue, Chikungunya and malaria infections.
THE frequency and magnitude of dengue epidemics worldwide has increased markedly in the last three decades. This has come about because the main mosquito vector, Aedes aegypti, and the dengue viruses have expanded their geographical distribution, due to a number of factors, which include population growth, urbanisation, modern transportation and the lack of effective mosquito control programmes in tropical urban areas.
There has been a marked increase in the number of dengue cases in the previous few months In Malaysia. The Health Ministry recorded 3,211 cases for the period January 4 to 17, 2009, compared to 1,514 cases for the same period in 2008. (http:www.moh.gov.my/MohPortal/newsFull.jsp?action=load&id=391 Accessed 28 January 2009).
There were eight deaths in 2009 compared to five for the same period in 2008. There were also 364 cases of Chikungunya infections recorded for the same period compared to 4,271 for the whole of 2008.
An advisory from the World Health Organization attributed the increase in the dengue cases to:
·Public apathy regarding the environment and cleanliness resulting in an increase of mosquito breeding places.
·The rainy season which resulted in an increased collection of clear water in breeding places in and around the house and surroundings.
There were no Chikungunya infections in Malaysia until the past couple of years. Its advent has been attributed to modern transportation.
It is not feasible to eliminate dengue and Chikungunya infections as our tropical climate is very conducive to mosquito breeding. However, there are effective control and prevention methods.
Although this article is focused on dengue and Chikungunya infections, it must be remembered that mosquitoes are also transmitters (vectors) of malaria and any action to reduce the mosquito population will also be of help in malaria control. Vector control remains the most generally effective measure to prevent transmission of dengue, Chikungunya and malaria infections.
The current situation is of concern not only to those who provide care for the infected persons but also to everyone in the population. This article is written to provide information for anyone who cares for their family members to take the necessary action to prevent and control these infections.
Infections
Dengue (DF) is a mosquito borne acute viral infection with varied clinical features. It may present as:
·A fever with a rash (often seen in children);
·A fever with flu-like symptoms; or
·The classical condition with two or more of the following: fever, headache, bone, joint and/or muscle pain, pain behind the eyes, rash and bleeding tendencies.
Recovery in adults may be associated with prolonged fatigue. Bleeding complications may appear during epidemics eg bleeding from the gums and nose, and skin bruises.
There is no specific treatment for DF apart from symptomatic treatment, rest, and rehydration. It is vital to distinguish DF with haemorrhagic features from dengue haemorrhagic fever (DHF) so that appropriate treatment can be initiated for DHF. Very few people die from DF, but the death rate from DHF can be high.
Dengue haemorrhagic fever (DHF) is characterised by:
·Fever or recent history of fever;
·Bleeding phenomena (presence of skin bruises or bleeding from mucosa, gastrointestinal tract, injection sites, or others);
·Low blood platelet count (thrombocytopenia);
·Plasma leakage, due to increased capillary permeability, and associated concentration of the blood.
DHF usually lasts between seven to 10 days. Appropriate intensive supportive therapy reduces mortality to less than 1%. The patient’s condition may suddenly deteriorate in severe cases after a few days of fever with the temperature dropping, followed by circulatory failure and rapidly development of shock with death in 12 to 24 hours or is followed by rapid recovery with appropriate volume replacement.
Chikungunya is a mosquito borne viral infection with an abrupt febrile onset that is often accompanied by joint pain. The other common features include muscle pain, headache, nausea, fatigue and rash. The joint pain is often incapacitating, but there is recovery usually within a few days or weeks.
Most patients recover fully, but the joint pain may persist, in some patients, for months or even years.
The symptoms in infected individuals are often mild and it may be unrecognised, or is misdiagnosed as dengue. Serious complications are rare but it has been associated with death in senior citizens.
Same culprits
Dengue and Chikungunya are transmitted from an infected person to another person by the bites of infected mosquitoes. The mosquitoes commonly involved are Aedes aegypti and Aedes albopictus, both of which also transmit other mosquito-borne viruses.
The mosquitoes bite throughout the daylight hours, although they may be more active in the early morning and late afternoon. Both species are found outdoors, but Aedes aegypti is also found indoors.
The Aedes mosquitoes breed in natural and artificial water filled container habitats. Small collections of clear water are sufficient for it to breed. This means that the prevention and control of both infections relies markedly on the reduction of these habitats.
Mosquito control
There are several methods available to control the mosquitoes.
The proximity of the mosquito breeding sites to homes and offices means that both natural and artificial water filled container habitats have to be reduced considerably.
This can be done by physically managing artificial water containers, for example, mosquito-proof covers for water storage containers and recycling of solid waste like discarded tyres, bottles, cans, tins and styrofoam food packages.
There are biological methods that kill or reduce the mosquito larval populations in water containers, for example, fish that feed on the larvae. Chemical methods, for example temephos sand granules, can be used against the larvae in water containers. Chemical methods, for example insecticide sprays, can also be used against adult mosquitoes.
Personal protection methods, which include the use of repellents, vaporisers, mosquito coils, and insecticide-treated screens, curtains, and bed-nets, reduce indoor biting. Repellents can be applied to exposed skin or clothing in accordance with the product label instructions. These methods are useful for those who sleep during the day especially children, the ill and senior citizens.
Insecticide spraying (fogging) has to be done repeatedly, is expensive, is of limited effectiveness and only controls the adult mosquitoes. The Aedes aegypti likes to rest inside houses, so insecticide spraying cannot reach mosquitoes resting in hidden places. Home owners may also refuse entry to spraying teams, or close windows and doors to prevent outdoor insecticidal fogs from entering their house, thereby reducing its effectiveness.
Because of all these factors, the adult mosquitoes return rapidly after spraying. As such, the community needs to be involved in the control of larval habitats.
Stop the blame game
There has been no shortage of finger pointing in the print and electronic media for months. The issues raised include the number of cases and who is responsible for control and prevention, with responsibility being passed around. Inconsequential issues are also raised, for example, what is endemic and epidemic.
Many have been blamed. Healthcare professionals have also not been spared. It appears that some have forgotten that the doctors are at the end of the chain of events and are attending to what has not been done in the first place.
If the time and energy spent on the rhetoric and blaming is utilised more productively by mobilising and supporting individual and community action, the infections can be brought under control sooner than later, with considerable reduction in suffering and loss of lives.
Individual action
One needs to inspect and destroy potential mosquito breeding places within and without the house at least once a week. These are any articles that can contain water. They include bottles, cans, tins, tyres, flower pots with trays, decorative garden items and blocked rain water gutters outside the house.
Items within the home include decorative items with water trays, pails and uncovered water containers.
Water that is stored for use must be in containers that are adequately covered to prevent mosquito breeding. These include overhead water storage tanks, toilet flushing cisterns, pails and other containers.
Whenever the water is replaced, the side walls of the containers must be washed to remove any mosquito eggs stuck to it. The addition of insecticide to any water collections that are not used for human consumption will kill the larvae. The whole process of inspection and destruction of potential breeding places will not take much time, perhaps about 10 minutes in a week!
The chances of being bitten by mosquitoes can be reduced by avoiding being outdoors at dawn and dusk. If one needs to be outdoors during these times, repellents should be used. The use of personal protection items listed above within the house is also helpful.
The early seeking of medical attention when there is fever with other symptoms described above, will facilitate early treatment and notification to the health authorities. The latter would lead to early prevention and control activities in the locality.
Community action
The following extract from a World Health Organization speaks volumes and sums up what needs to be done in all areas, especially the “hotspots”.
“In Johore state, Malaysia, an integrated social mobilisation and communication campaign motivated householders in Johor Bahru district to seek prompt diagnosis for any fevers, to destroy any larval breeding sites found around their premises, and to organise voluntary teams to inspect and control larval breeding sites in public spaces such as community halls, parks, and vacant lots.
“Dengue volunteer inspection teams (DeVIT) were formed in 48 localities. Some 615 volunteers came forward to join DeVIT teams. During the three-month campaign period, DeVIT teams gave advice to 100,956 people, distributed 101,534 flyers, and inspected 1,440 vacant lots.
“The campaign resulted in a dramatic drop in the occurrence of dengue in the district; three months after the campaign, tracking surveys revealed that 70% householders were still checking their household premises. Today, 95% of DeVIT volunteers continue their work and many of them have even requested more responsibilities.
The Government of the state of Johore has decreed that the campaign be implemented throughout the State.” – Source: World Health Organization. Planning social mobilization and communication for dengue fever prevention and control (2004): 13
Recent Health Ministry data indicate that its Communication for Behavioural Impact (COMBI) programme has resulted in an 84% decrease in the incidence of dengue.
There are 11,892 volunteers in the COMBI programme in 598 locations throughout the country as at January 19, 2009. (http://www.moh.gov.my/MohPortal/newsFull.jsp?action=load&id=391Accessed 28 January 2009). Community organisations can take the initiative to activate the COMBI programme in their locality by approaching the nearest district health office.
Conclusion
While we cannot change what nature has bestowed upon us, we, as individuals and communities, can do much to control the breeding of mosquitoes, which is the primary effective measure for controlling and preventing mosquito borne infections.
Individual actions, when added together, can be substantial. It is well documented that community action, particularly in affected localities, will contribute significantly to the reduction of the breeding places.
This is not a time for words. It is a time for action i.e. taking the initiative to activate the COMBI programme in respective localities.
It is well to remember the advice of William Osler, the father of modern medicine. “By far the most dangerous foe we have to fight is apathy – indifference from whatever cause, not from a lack of knowledge, but from carelessness, from absorption in other pursuits, from contempt bred of self satisfaction.”
- THE STAR
THE frequency and magnitude of dengue epidemics worldwide has increased markedly in the last three decades. This has come about because the main mosquito vector, Aedes aegypti, and the dengue viruses have expanded their geographical distribution, due to a number of factors, which include population growth, urbanisation, modern transportation and the lack of effective mosquito control programmes in tropical urban areas.
There has been a marked increase in the number of dengue cases in the previous few months In Malaysia. The Health Ministry recorded 3,211 cases for the period January 4 to 17, 2009, compared to 1,514 cases for the same period in 2008. (http:www.moh.gov.my/MohPortal/newsFull.jsp?action=load&id=391 Accessed 28 January 2009).
There were eight deaths in 2009 compared to five for the same period in 2008. There were also 364 cases of Chikungunya infections recorded for the same period compared to 4,271 for the whole of 2008.
An advisory from the World Health Organization attributed the increase in the dengue cases to:
·Public apathy regarding the environment and cleanliness resulting in an increase of mosquito breeding places.
·The rainy season which resulted in an increased collection of clear water in breeding places in and around the house and surroundings.
There were no Chikungunya infections in Malaysia until the past couple of years. Its advent has been attributed to modern transportation.
It is not feasible to eliminate dengue and Chikungunya infections as our tropical climate is very conducive to mosquito breeding. However, there are effective control and prevention methods.
Although this article is focused on dengue and Chikungunya infections, it must be remembered that mosquitoes are also transmitters (vectors) of malaria and any action to reduce the mosquito population will also be of help in malaria control. Vector control remains the most generally effective measure to prevent transmission of dengue, Chikungunya and malaria infections.
The current situation is of concern not only to those who provide care for the infected persons but also to everyone in the population. This article is written to provide information for anyone who cares for their family members to take the necessary action to prevent and control these infections.
Infections
Dengue (DF) is a mosquito borne acute viral infection with varied clinical features. It may present as:
·A fever with a rash (often seen in children);
·A fever with flu-like symptoms; or
·The classical condition with two or more of the following: fever, headache, bone, joint and/or muscle pain, pain behind the eyes, rash and bleeding tendencies.
Recovery in adults may be associated with prolonged fatigue. Bleeding complications may appear during epidemics eg bleeding from the gums and nose, and skin bruises.
There is no specific treatment for DF apart from symptomatic treatment, rest, and rehydration. It is vital to distinguish DF with haemorrhagic features from dengue haemorrhagic fever (DHF) so that appropriate treatment can be initiated for DHF. Very few people die from DF, but the death rate from DHF can be high.
Dengue haemorrhagic fever (DHF) is characterised by:
·Fever or recent history of fever;
·Bleeding phenomena (presence of skin bruises or bleeding from mucosa, gastrointestinal tract, injection sites, or others);
·Low blood platelet count (thrombocytopenia);
·Plasma leakage, due to increased capillary permeability, and associated concentration of the blood.
DHF usually lasts between seven to 10 days. Appropriate intensive supportive therapy reduces mortality to less than 1%. The patient’s condition may suddenly deteriorate in severe cases after a few days of fever with the temperature dropping, followed by circulatory failure and rapidly development of shock with death in 12 to 24 hours or is followed by rapid recovery with appropriate volume replacement.
Chikungunya is a mosquito borne viral infection with an abrupt febrile onset that is often accompanied by joint pain. The other common features include muscle pain, headache, nausea, fatigue and rash. The joint pain is often incapacitating, but there is recovery usually within a few days or weeks.
Most patients recover fully, but the joint pain may persist, in some patients, for months or even years.
The symptoms in infected individuals are often mild and it may be unrecognised, or is misdiagnosed as dengue. Serious complications are rare but it has been associated with death in senior citizens.
Same culprits
Dengue and Chikungunya are transmitted from an infected person to another person by the bites of infected mosquitoes. The mosquitoes commonly involved are Aedes aegypti and Aedes albopictus, both of which also transmit other mosquito-borne viruses.
The mosquitoes bite throughout the daylight hours, although they may be more active in the early morning and late afternoon. Both species are found outdoors, but Aedes aegypti is also found indoors.
The Aedes mosquitoes breed in natural and artificial water filled container habitats. Small collections of clear water are sufficient for it to breed. This means that the prevention and control of both infections relies markedly on the reduction of these habitats.
Mosquito control
There are several methods available to control the mosquitoes.
The proximity of the mosquito breeding sites to homes and offices means that both natural and artificial water filled container habitats have to be reduced considerably.
This can be done by physically managing artificial water containers, for example, mosquito-proof covers for water storage containers and recycling of solid waste like discarded tyres, bottles, cans, tins and styrofoam food packages.
There are biological methods that kill or reduce the mosquito larval populations in water containers, for example, fish that feed on the larvae. Chemical methods, for example temephos sand granules, can be used against the larvae in water containers. Chemical methods, for example insecticide sprays, can also be used against adult mosquitoes.
Personal protection methods, which include the use of repellents, vaporisers, mosquito coils, and insecticide-treated screens, curtains, and bed-nets, reduce indoor biting. Repellents can be applied to exposed skin or clothing in accordance with the product label instructions. These methods are useful for those who sleep during the day especially children, the ill and senior citizens.
Insecticide spraying (fogging) has to be done repeatedly, is expensive, is of limited effectiveness and only controls the adult mosquitoes. The Aedes aegypti likes to rest inside houses, so insecticide spraying cannot reach mosquitoes resting in hidden places. Home owners may also refuse entry to spraying teams, or close windows and doors to prevent outdoor insecticidal fogs from entering their house, thereby reducing its effectiveness.
Because of all these factors, the adult mosquitoes return rapidly after spraying. As such, the community needs to be involved in the control of larval habitats.
Stop the blame game
There has been no shortage of finger pointing in the print and electronic media for months. The issues raised include the number of cases and who is responsible for control and prevention, with responsibility being passed around. Inconsequential issues are also raised, for example, what is endemic and epidemic.
Many have been blamed. Healthcare professionals have also not been spared. It appears that some have forgotten that the doctors are at the end of the chain of events and are attending to what has not been done in the first place.
If the time and energy spent on the rhetoric and blaming is utilised more productively by mobilising and supporting individual and community action, the infections can be brought under control sooner than later, with considerable reduction in suffering and loss of lives.
Individual action
One needs to inspect and destroy potential mosquito breeding places within and without the house at least once a week. These are any articles that can contain water. They include bottles, cans, tins, tyres, flower pots with trays, decorative garden items and blocked rain water gutters outside the house.
Items within the home include decorative items with water trays, pails and uncovered water containers.
Water that is stored for use must be in containers that are adequately covered to prevent mosquito breeding. These include overhead water storage tanks, toilet flushing cisterns, pails and other containers.
Whenever the water is replaced, the side walls of the containers must be washed to remove any mosquito eggs stuck to it. The addition of insecticide to any water collections that are not used for human consumption will kill the larvae. The whole process of inspection and destruction of potential breeding places will not take much time, perhaps about 10 minutes in a week!
The chances of being bitten by mosquitoes can be reduced by avoiding being outdoors at dawn and dusk. If one needs to be outdoors during these times, repellents should be used. The use of personal protection items listed above within the house is also helpful.
The early seeking of medical attention when there is fever with other symptoms described above, will facilitate early treatment and notification to the health authorities. The latter would lead to early prevention and control activities in the locality.
Community action
The following extract from a World Health Organization speaks volumes and sums up what needs to be done in all areas, especially the “hotspots”.
“In Johore state, Malaysia, an integrated social mobilisation and communication campaign motivated householders in Johor Bahru district to seek prompt diagnosis for any fevers, to destroy any larval breeding sites found around their premises, and to organise voluntary teams to inspect and control larval breeding sites in public spaces such as community halls, parks, and vacant lots.
“Dengue volunteer inspection teams (DeVIT) were formed in 48 localities. Some 615 volunteers came forward to join DeVIT teams. During the three-month campaign period, DeVIT teams gave advice to 100,956 people, distributed 101,534 flyers, and inspected 1,440 vacant lots.
“The campaign resulted in a dramatic drop in the occurrence of dengue in the district; three months after the campaign, tracking surveys revealed that 70% householders were still checking their household premises. Today, 95% of DeVIT volunteers continue their work and many of them have even requested more responsibilities.
The Government of the state of Johore has decreed that the campaign be implemented throughout the State.” – Source: World Health Organization. Planning social mobilization and communication for dengue fever prevention and control (2004): 13
Recent Health Ministry data indicate that its Communication for Behavioural Impact (COMBI) programme has resulted in an 84% decrease in the incidence of dengue.
There are 11,892 volunteers in the COMBI programme in 598 locations throughout the country as at January 19, 2009. (http://www.moh.gov.my/MohPortal/newsFull.jsp?action=load&id=391Accessed 28 January 2009). Community organisations can take the initiative to activate the COMBI programme in their locality by approaching the nearest district health office.
Conclusion
While we cannot change what nature has bestowed upon us, we, as individuals and communities, can do much to control the breeding of mosquitoes, which is the primary effective measure for controlling and preventing mosquito borne infections.
Individual actions, when added together, can be substantial. It is well documented that community action, particularly in affected localities, will contribute significantly to the reduction of the breeding places.
This is not a time for words. It is a time for action i.e. taking the initiative to activate the COMBI programme in respective localities.
It is well to remember the advice of William Osler, the father of modern medicine. “By far the most dangerous foe we have to fight is apathy – indifference from whatever cause, not from a lack of knowledge, but from carelessness, from absorption in other pursuits, from contempt bred of self satisfaction.”
- THE STAR
MOHD ADHA MOHD ZAIN (ADHA ZAIN)
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