First vaccine against dengue, which FDA approved two years ago, is yet to be put under trial by Indian Council of Medical Research.
Illustration: Saai
Chennai:
Despite an outbreak of dengue each year, the management of dengue depends solely on preventive measures. After various studies and researches to defeat dengue, vaccines and biological methods to control dengue have been introduced in many other countries. However, such practices are yet to be implemented in Tamil Nadu due to lag in research projects.
Though various area-specific studies focusing on social-economic factors have been conducted, the prevention of aedes aegypti mosquito breeding and dengue outbreaks are yet to be explored. However, entomologists said that breeding of the mosquitoes cannot be prevented. Only control measures can be taken.
Tamil Nadu recorded 23,294 cases of dengue and 65 deaths due to the same in 2017. In 2018, 4,486 people were affected and around 25 deaths were recorded. This year, at least 1,800 cases of dengue have been registered till now as per the state health department.
The World Mosquito Programme had signed an MoU with the Indian Council of Medical Research (ICMR) to investigate the use of self-sustaining wolbachia bacteria to combat dengue and other mosquito-borne diseases in India in 2016. After more than three years, the research is nowhere near completion.
The World Mosquito Programme is working in Brazil to protect local communities on similar lines and first released wolbachia-infected bacteria in September 2014 in Rio de Janeiro, after receiving government approval and support from the local community. The trials and research took about two years and have been in practice for the past five years now.
Researcher Dr Luciano Moreira, who is associated with the programme in Brazil, said that mosquitoes infected with wolbachia showed reduced virus in saliva, indicating that wolbachia can block Zika transmission.
The tropical weather is suitable for mosquito breeding. Every year, the outbreak of fever and dengue cases occur after the rains. “Aedes mosquito is the carrier for four viruses – Dengue, Chikungunya, Yellow Fever and Zika. Tamil Nadu gets light to moderate rainfall during these months and it is not enough to wash away the larvae of aedes mosquitoes. It can breed even in a small puddle of rainwater. Thus it can breed wherever it rains and water is being collected,” said Dr S Senthilnathan, entomologist.
However, comprehensive research on biological determinants that lead to dengue outbreak almost every year has not been explored yet. Surveillance of vectors, population and virus has to be done to analyse its occurrence throughout the country. It takes a high-level programme to eliminate dengue,” added Dr Senthilnathan. An ICMR bulletin by Dr SK Bhattacharya states that although dengue has been a recurring outbreak for many years now, due to lack of region-specific and in-depth knowledge on its aetiology, epidemiology and pathogenesis, an effective surveillance strategy has not yet been developed.
Entomologist at Stanley Medical College and Government Hospital, Dr P Srinivasan, said that the pattern of dengue cases has remained the same. Vector tests are being done on the mosquitoes and their eggs to find its genetics. As all aedes mosquitoes do not carry viruses, the eggs of the mosquitoes with the virus are being tested, said Dr Srinivasan. After the dengue outbreak in 2017, the Central government sent public health specialists to help the State government study the situation and look for ways to deal with the situation. However, these steps are being undertaken only after an outbreak.
Even the first vaccine against dengue, Dengvaxia, which was approved two years ago by the Food and Drug Administration (FDA), is yet to be put under trial by ICMR. It had stated that a study on the epidemiology of dengue virus would be conducted in various zones in the country in 2017. Though dengue vaccines are in use in other countries after receiving approval, the vaccine in India is still in the review phase.
Former Director-General of ICMR Saumya Swaminathan said that the vaccine is only on restricted usage in other countries and in India, the clinical trial needs various clearances. The vaccine can be approved only after that. However, the trial is not yet in the picture. Officials with the State health department said that prevention of breeding cannot be done but limiting the factors that develop a favourable environment for the mosquitoes to breed can be reduced. Regulatory clearances and approval from the Centre to do studies which would influence the mosquito population are the major hurdles, officials said.
For a study by the National Institute of Health on favouring and limiting factors relating to a community-based intervention to control the dengue vector, management approach such as water container covers, clean-up campaigns and dissemination of dengue information through school children were done. The result of the study showed that there was a substantial increase in dengue understanding in the intervention group with only minor knowledge management. The study concluded that a community-based approach with other stakeholders that promoted interventions to prevent dengue vector breeding led to a substantial reduction in dengue vector density. Thus, officials said that a community-based approach to control the virus can be taken.
Though vaccines are in use in other countries, the vaccine in India is still in review phase.
Despite an outbreak of dengue each year, the management of dengue depends solely on preventive measures. After various studies and researches to defeat dengue, vaccines and biological methods to control dengue have been introduced in many other countries. However, such practices are yet to be implemented in Tamil Nadu due to lag in research projects.
Though various area-specific studies focusing on social-economic factors have been conducted, the prevention of aedes aegypti mosquito breeding and dengue outbreaks are yet to be explored. However, entomologists said that breeding of the mosquitoes cannot be prevented. Only control measures can be taken.
Tamil Nadu recorded 23,294 cases of dengue and 65 deaths due to the same in 2017. In 2018, 4,486 people were affected and around 25 deaths were recorded. This year, at least 1,800 cases of dengue have been registered till now as per the state health department.
The World Mosquito Programme had signed an MoU with the Indian Council of Medical Research (ICMR) to investigate the use of self-sustaining wolbachia bacteria to combat dengue and other mosquito-borne diseases in India in 2016. After more than three years, the research is nowhere near completion.
The World Mosquito Programme is working in Brazil to protect local communities on similar lines and first released wolbachia-infected bacteria in September 2014 in Rio de Janeiro, after receiving government approval and support from the local community. The trials and research took about two years and have been in practice for the past five years now.
Researcher Dr Luciano Moreira, who is associated with the programme in Brazil, said that mosquitoes infected with wolbachia showed reduced virus in saliva, indicating that wolbachia can block Zika transmission.
The tropical weather is suitable for mosquito breeding. Every year, the outbreak of fever and dengue cases occur after the rains. “Aedes mosquito is the carrier for four viruses – Dengue, Chikungunya, Yellow Fever and Zika. Tamil Nadu gets light to moderate rainfall during these months and it is not enough to wash away the larvae of aedes mosquitoes. It can breed even in a small puddle of rainwater. Thus it can breed wherever it rains and water is being collected,” said Dr S Senthilnathan, entomologist.
However, comprehensive research on biological determinants that lead to dengue outbreak almost every year has not been explored yet. Surveillance of vectors, population and virus has to be done to analyse its occurrence throughout the country. It takes a high-level programme to eliminate dengue,” added Dr Senthilnathan. An ICMR bulletin by Dr SK Bhattacharya states that although dengue has been a recurring outbreak for many years now, due to lack of region-specific and in-depth knowledge on its aetiology, epidemiology and pathogenesis, an effective surveillance strategy has not yet been developed.
Entomologist at Stanley Medical College and Government Hospital, Dr P Srinivasan, said that the pattern of dengue cases has remained the same. Vector tests are being done on the mosquitoes and their eggs to find its genetics. As all aedes mosquitoes do not carry viruses, the eggs of the mosquitoes with the virus are being tested, said Dr Srinivasan. After the dengue outbreak in 2017, the Central government sent public health specialists to help the State government study the situation and look for ways to deal with the situation. However, these steps are being undertaken only after an outbreak.
Even the first vaccine against dengue, Dengvaxia, which was approved two years ago by the Food and Drug Administration (FDA), is yet to be put under trial by ICMR. It had stated that a study on the epidemiology of dengue virus would be conducted in various zones in the country in 2017. Though dengue vaccines are in use in other countries after receiving approval, the vaccine in India is still in the review phase.
Former Director-General of ICMR Saumya Swaminathan said that the vaccine is only on restricted usage in other countries and in India, the clinical trial needs various clearances. The vaccine can be approved only after that. However, the trial is not yet in the picture. Officials with the State health department said that prevention of breeding cannot be done but limiting the factors that develop a favourable environment for the mosquitoes to breed can be reduced. Regulatory clearances and approval from the Centre to do studies which would influence the mosquito population are the major hurdles, officials said.
For a study by the National Institute of Health on favouring and limiting factors relating to a community-based intervention to control the dengue vector, management approach such as water container covers, clean-up campaigns and dissemination of dengue information through school children were done. The result of the study showed that there was a substantial increase in dengue understanding in the intervention group with only minor knowledge management. The study concluded that a community-based approach with other stakeholders that promoted interventions to prevent dengue vector breeding led to a substantial reduction in dengue vector density. Thus, officials said that a community-based approach to control the virus can be taken.
Effectiveness of Dengvaxia vaccine yet to be established
Dengue vaccine, Dengvaxia, contains weakened viruses that are treated as foreign bodies by the immune system once given to a person. The immune system makes antibodies against the viruses and if the same person comes in contact with the dengue virus, antibodies will act against them. Antibodies, with other components of the immune system, help protect the person against the disease. However, international scientists are divided on the same as many virology experts state that there is no vaccine effective against dengue. Various studies state that Dengvaxia is effective at reducing the risk of dengue in people who have had dengue infection in the past. However, people who have not had dengue infection in the past may have a higher risk of the disease if infected with the virus after vaccination with Dengvaxia. Therefore, the effectiveness of the vaccine is debatable and its effectiveness has not been established.