(September 02, Hong Kong, Sri Lanka Guardian)It was reported that around 192 people have died from dengue fever in the first seven and a half months of this year. The total number of infected people came to more than 26,824 and there can be no doubt that the entire population of Sri Lanka is in critical danger. But there still does not appear to be any visible, practical or successful plan to deal with the spread of this killer disease. The government of Sri Lanka have not implemented or adopted any effective measures to face this challenge. Dengue has spread to almost all districts in the country. In particular the disease is threatening the entire population of Jaffna North to Matara South and Batticaloa East to Colombo West and Kandy Central. The afflicted victims are those from the rich and the poor as the disease shows no distinction.
Dengue is one of the problems that the Sri Lankan health sector has faced during the last century, similar to many other tropical countries. Indeed, the World Health Organization (WHO) recognizes this disease as one of the endemics in the world scenario.
Dengue is a vector born disease. Dengue fever (DF) and dengue hemorrhagic fever (DHF) are the two major phases of the disease. According to the present medical information there is a third phase known as Dengue Shock Syndrome (DSS) which is much more fatal. Dengue is transmitted to humans by the Aedes (Stegomyia) aegypti mosquito or more rarely the Aedes albopictus mosquito both of which feed exclusively during daylight hours. Dengue can be seen in many tropical areas like northern Argentina, northern Australia, Bangladesh, Barbados, Bolivia, Belize, Brazil, Cambodia, Colombia, Costa Rica, Cuba, Dominican Republic, French Polynesia, Guadeloupe, El Salvador, Guatemala, Guyana, Haiti, Honduras, India, Indonesia, Jamaica, Laos, Malaysia, Melanesia, Mexico, Micronesia, Nicaragua, Pakistan, Panama, Paraguay, Philippines, Puerto Rico, Samoa, Western Saudi Arabia, Singapore, Sri Lanka, Suriname, Taiwan, Thailand, Trinidad, Venezuela and Vietnam, and increasingly in southern China. The most seriously affected areas are in Southeast Asia and the Western Pacific.
WHO says some 2.5 billion people, two fifths of the world's population, are now at risk from dengue and estimates that there may be 50 million cases of dengue infection worldwide every year. The disease is now endemic in more than 100 countriesi.
The history of dengue in Sri Lanka
Dengue was known to be endemic from early this century but it has only been serologically confirmed since 1962. In the year 1965 there was a dengue outbreak throughout the country and 51 cases were found resulting in 15 deaths. Then continuously it was found in many parts of the country. The disease was mainly spread in the western costal belt and later it was found in other suburbs as well. Later a few outbreaks were reported in 1966, 1967, 1968, 1972, 1973, and 1976. Again the dengue outbreak came to a peak in 1988.
Up to 1988 the reported cases of dengue were considered as type 1 and 2 as classified by the Sri Lankan Medical Authority. But by 1989, different serological types other than the type 1, and 2 were also detected. The new cases reported were serious in nature (i.e. patients with more dengue haemorrhagic fever were reported) and the number of deaths were significantly higher. In 1988, 20 deaths were figured and 203 patients were also diagnosed. In 1990 the death toll was 363 and the number of reported cases was 1350. In the year 2009 the total number of cases reported in dengue fever was 35, 007 and the total number of deaths reported was 346.
In the years 2009 and 2010 an outbreak of dengue in Sri Lanka was encountered but it was much worse than on any other occasion reported. The same endangering situation prevails throughout the country. Until now even in the year 2010, the same pathetic situation of dengue is evident all over the country but in more alarming numbers.
First, the reported cases from dengue fever were normal in their makeup but in latter stages it was shown that a much more dangerous version existed. This, it was discovered, was due to genetic mutation.
Significant outbreaks of dengue fever tend to occur every five or six months according to the records. The cyclical rise and fall in numbers of dengue cases is thought to be the result of seasonal cycles interacting with a short-lived cross-immunity for all the four strains in people who have had dengue. When the cross-immunity wears off the population is more susceptible to transmission whenever the next seasonal peak occurs. Thus, over time, there remain large numbers of susceptible people in affected populations despite of previous outbreaks due to the four different serotypes of dengue virus and the presence of unexposed individuals from childbirth or immigrationii.
Around 10 years ago children were the most affected or vulnerable group in Sri Lanka. But in recent years, a number of adult victims have been encountered causing significant morbidity and mortality.
The most alarming figures came in the recent past
WHO considers when a figure of dengue deaths in country goes beyond 1 percent it becomes an alarming situation. Sri Lanka faced such a situation in 1989 and 1992. In the second half of the year 2009 Sri Lanka experienced the most alarming situation ever before by having 349 deaths, while having around 22 000 infected patients. When Sri Lanka is compared with the regional situation it is now similar to the situation of Indonesia, Bhutan and India.
In the year 1989 the total number of suspected cases of DF/DHF was 203 and the serologically confirmed cases was 87. Out of that the number of deaths was 20 and the case fatality rate was 9.9%. That constituted a vulnerable situation but in the later years a decline was seen. In 1990 the rate was 4% and the 1991 was 3%. In 1992 2.3% and in 1993 it was 0.9%.
But from 1994 onwards the deaths increased again. In that particular year the percentage was 1.2% and in 1995 it was 2.5. In the year 1996 it was 4.2 and in 1997 1.7.
Distribution of suspected DF/DHF by week, Sri Lanka 2004 -2010(up to 20/08/2010) iii
The dangerous seasons of Sri Lanka and other vector born diseases
Dengue mosquitoes lay eggs in stagnant water. Only 5 to 10 ml of water is enough and it is said the eggs are quite robust. Sri Lanka receives rain according to the seasons but from the beginning of May to the end of September annually Sri Lanka sees its devastated rainy period. The annual monsoon happens and the mosquito density is increased accordingly as is the potentiality of the spread of dengue.
Dengue mosquitoes breed in stored, exposed water collection systems. The favoured breeding places are: barrels, drums, jars, pots, buckets, flower vases, plant-pots, tanks, discarded bottles, tins, tyres, water coolers and any other place where rain water is collected or stored.
Dengue is not the only decease that is spread because of mosquitoes, Malaria, Filara, Japanese Encephalitis are some other disease spread by mosquitoes. Due to malaria Sri Lanka suffered early in this century in a worst manner compared to other deceases. It is said that the Sri Lankan civilization was moved from the north to the south due to the spread of malaria.
Malaria was a major problem for the government around 1931 as the country was renovated to provide irrigation and cultivation in the dry zone areas. Nearly 40% of the population was subject to malaria annually and malaria deaths accounting for 6% of total deaths from all causes. In 1945, the estimated malaria cases and deaths were around 2.5 million and 8,500 respectivelyiv. Successful spraying methods finally experienced a high success rate. The 'Suriyamal Movement' was the most effective and successful campaign that was to combat the epidemic.
Hong Kong out of danger of dengue
Hong Kong’s climate is more or less similar to Sri Lanka. It exhibits a monsoonal climate in which the south-west monsoon occurs from May to September similar to Sri Lankan situations. Then it is a hot and wet summer. The north-west monsoon occurs from November to March bringing Hong Kong to a colder climate. Hong Kong’s temperature ranges between 25 to 28 centigrade and in winter it is between 15 to 21 centigrade.
Even in Hong Kong Ae. Albopictus and Ae. Aegypti mosquito species are found. There were 13 different species under these two. On the other hand as Hong Kong port was one of the world largest and most efficient ports and Hong Kong airport is one of the most efficient international airports which see millions of travelers from around the world, there were many avenues to get these mosquitoes into the country.
At one time Hong Kong also faced the endemic situation of dengue. It also had to deal with dengue infected patients from 1994 to 2007. Mostly the reason for this was many travelers from different regions of the world especially from the South Eastern Asian countries coming to the territory for commerce and tourism. But finally Hong Kong authorities went with a determined strategy and achieved success in their task. It is worth to study how they got these results in this difficult task.
How Hong Kong overcame dengue?
Under the programme of Dengue vector survelliance, a special instrument called oviposition trap (ovitrap) was used widely in early 2000 as a very successful way for the surveillance programme. State agencies toughly scrutinized the vector by this method. It is a device that can monitor, control and detect aedes mosquito populations thus acting as an early warning signal to pre-empt any impending dengue outbreaks. The technique was developed by Jakob and Bevier in 1969. The device is black in colour and it attracts female mosquitoes and in turn they lay eggs. However, when the eggs hatch and develop into adults they cannot fly away because, as the name suggested: it is a trap! It can be used effectively to control the Aedes population within any area, region or country.
The device is analysed weekly and it was able to identify hot spots of breeding sites. Three ovitrap models had been developed to analyse the ovitrap breeding data collected. The analysis results are used to plan vector surveillance and control operations. It has been used in countries like Singapore and United States also since the 1970s.
These ovitraps were used in human concentrated selected areas like housing estates, schools and hospitals. All the selected areas were surveyed every month to closely monitor the situation of each location and to obtain a territory-wide picture of the vectoral situation. Then the ovitraps were collected back to the laboratory. Then the state agencies collected data and made fact sheets finally providing a 'Ovitrap Index'. After examining the result of the ovitrap index the decision making bodies were able to go for a quick reference for taking prompt follow-up mosquito control actions, each of the ovitraps collected was examined immediately for the presence of mosquito larvae. The larvae found were identified under compound microscopes to species level and the Provisional Ovitrap Index (POI) was worked out. Finally the made Area Ovitrap Index (AOI) and Monthly Ovitrap Index (MOI) were made available to the public.
State agencies were able to get strong public support for this whole process. One of the most important findings indicates that the situation of Hong Kong getting better and better. At the same time they found some urban areas also had faced the same situations. Sea ports and air port areas were significantly positive and it was suspected that increased air travel, which can transport dengue-carrying mosquitoes is also a possibility. Further it was speculated that travelers and sailors from infected areas are coming to Honk Kong adding much trouble to the excising condition of the country.
Mosquitoes control methods are very much similar in all the countries in the world. But in some countries they have developed new methods. The success in Hong Kong was a combination of these two. First they used very much similar methods like basic mosquito control methods. The breeding places of the vector include a variety of small water bodies such as discarded buckets, empty lunch boxes, sand pits, and surface drainage channels, keyholes of manhole covers, bamboo stumps, and saucers underneath plant pots. It was well recognized that the key issue of success was the fullest participation of the public. An annual territory-wide anti mosquito campaign was organized to promote community participation and forge close partnership of government departments and nongovernmental organizations in controlling the mosquitoes. The dengue vector surveillance programme served as a tool not only to monitor the local dengue vector distribution but also to provide objective information for taking appropriate actions by the community against dengue vectors.
Government agencies were able to release effectively to the public a Geographical Information System which is accessible by registered users through the government intranet. They are able to target mosquito control action at venues.
Other methods
Control measures mainly relied on source reduction, e.g. proper disposal of disused articles, lunch boxes, containers, etc. Potential breeding sites such as saucers underneath plant pots, surface drainage channels, roadside gully traps or keyholes of manhole covers were inspected weekly and accumulation of water was removed promptly. Larvicides were applied whenever immediate elimination of breeding sources was not feasible. When the Ovitrap Index reached Level Four, space spaying of insecticides was carried out at the resting places of the adult mosquito to contain the mosquito problem. On health education, health talks were organized for schoolchildren, estate management, construction sites as well as local organizations such as area committees to disseminate the message of mosquito prevention and control. Training was also organized for pest control personnel in the government. Operatives of pest control contractors providing mosquito control services funded by the government were also required to receive proper training on general pest control, including mosquito control and dengue fever.
Successful results in Hong Kong
Finally in 2007 no further trace of Ae. Aegypti or Ae. Alboppictus were found and was in general it was all under control.
The key points in this success were active and efficient participation of the government, local organizations and the public. Timely target-specific control efforts were achieved through the coordination of district-based anti-mosquito task force led by the government.
Necessity of implementation of Successful National Policy on Prevention of Vector-Borne Disease in Sri Lanka
Dengue has been endemic in Sri Lanka for many decades. Its impact on the country in terms of the society and economy is serious and can only become worse. The impact of dengue in Thailand has been calculated as US$ 61 per family and that sum generally exceeds the average monthly income. In Sri Lanka the economic impact has yet been not calculated but it may be safely assumed that the effect would be of the same magnitude.
The responsibility of the state to protect its citizen from dengue
Prevailing climatic condition, environmental pollution, rapid urbanization, overcrowding of cities and careless human practices are providing for rapid breeding of the mosquitoes and spreading of the disease. Recently there has been much written in the press about the garbage situation in Colombo itself and apart from complaints written to the relevant local government bodies no effective action has been taken. If this is the situation in Colombo itself what can be expected from the remainder of the country?
When it comes to the state responsibility the central government, the provincial councils and the local government bodies all are responsible for this crisis in that they have allowed it to continue unabated. However, the final blame must rest squarely and solely with the ruling regime for not taking adequate action to eradicate this menace.
It is not ethically possible for the ruling regime to place the blame on previous government. The problem exists now as does the ruling regime and the responsibility for finally controlling dengue is not transferable to the next government. The government prides itself on defeating the LTTE, any government in that the world that can do that should have little trouble with dengue. As in Hong Kong and other areas that have virtually eradicated dengue a great deal of assistance and support must be sought from the citizens but it is not their responsibility to start this process. They do not have the financial and technical resources necessary.
The government of Sri Lanka must adopt adequate legislation for the regulation, enforcement and life cycle approach in management of the pesticides as well as for effective vector control operations. It is urgent for Sri Lanka to go for a strong and effective management of public health pesticides under decentralized governance and health systems for the use of less hazardous and cost-effective pesticides. The current use of substandard, illegal and counterfeit pesticides available on the market must be banned.
These basic facts have been clearly mentioned even in the Resolution passed by the 126th Executive Board meeting of WHO held in January 2010. It further stressed to its member states to go for the establishment and strengthening of capacity for the regulations and sound management of pesticide throughout their life-cycle.
As Hong Kong can be an example for Sri Lanka in the control of corruption so also it can be an example for the virtual eradication of dengue. The Sri Lankan government can only learn a positive lesson from these effective methods to save the country from tragedy.
References
i Dengue epidemic threatens India's capital
ii http://en.wikipedia.org/wiki/Dengue_fever
iii http://www.epid.gov.lk/pdf/dhf-2010/week32-2010-25-08-2010.pdf
iv A http://www.epid.gov.lk/Dengue_updates.htm
v M.W. Lee, M.Y. Fok, Dengue vector surveillance in Hong Kong – 2007-world health organization website- http://www.searo.who.int/LinkFiles/Dengue_Bulletins_004_vol32.pdf
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