You should know: 5 deadliest mosquito-borne diseases in India
In requesting the Centre to put aside political squabbling for two months to fight dengue, Delhi chief minister Arvind Kejriwal has wised up to the fact that mosquitoes are among India’s deadliest foes, evading public health efforts to control disease with enviable ease.
While the dengue outbreak in Delhi has hit the national headlines, little attention has been given to equally worrying data from states such as Karnataka, Kerala and Tamil Nadu, which between them account for almost half of India’s 22,079 dengue cases till September 13, the last day till when country-wide data is available.
A man sleeps with a mosquito net covering his rickshaw. As Delhi battles its worst dengue outbreak in five years, authorities are grappling with complaints of medical negligience and insufficient infrastructure. (Arun Sharma/ HT Photo)
Dengue deaths are the highest in Kerala, which accounts for 19 of the 45 recorded deaths this year. In 2014, dengue hit Maharashtra the hardest, with 8,573 cases and 54 deaths.
Infection is higher in all states this year compared to the corresponding period last year. In 2014, India had 10,097 cases and 37 deaths to date.
The crowded dengue ward of GTB Hospital in New Delhi. (Arun Sharma/ HT Photo)
The top five mosquito-borne diseases in India are:
Dengue is caused by one of four closely related but antigenically distinct viruses (DEN-1, DEN-2, DEN-3 and DEN-4) that, between them, can infect the same person several times in their life. Symptoms begin with high fever, severe frontal headache, pain behind the eyes, muscle and joint pains, with or without measles-like rash and nausea and vomiting, which can to dengue haemorrhagic shock and multi-organ failure.
The good news is that since more people are getting tested and treated, the case fatality ratio -- number of deaths per 100 cases – this year is 0.2%, compared to almost 3% in 1996, when Delhi reported its first outbreak.
A rickshaw-puller sleeps while covering himself under a mosquito net amid dengue outbreak in the national Capital. (Arun Sharma/ HT Photo)
Malaria infection caused by four different species of the genus Plasmodium (P) -- P. falciparum, P. malariae, P. vivax, and P. ovale. Of these, P falciparum infection is the deadliest as it affects the brain and is most likely to cause death.
A decade ago, P. falciparum infections accounted for 30 per cent malaria cases in India, mostly in the north-eastern states, Orissa, West Bengal and Jharkhand. Now the brain strain of the disease is reported from across India and accounts for 60 per cent of malaria infections.
Resistance to the anti-malarial drugs chloroquine is spreading fast in India — increasing from 30 per cent before 1996 to 91 per cent in 2000-2001. Since using a single drug is ineffective, a cocktail of drugs is given to control infection.
A view of Hindu Rao Hospital's Dengue ward. There are reportedly 1,714 confirmed cases of dengue in New Delhi. (Saumya Khandelwal/ HT Photo)
The Japanese encephalitis (JE) virus has a complex life cycle involving domestic pigs and the Culex tritaeniorhynchus mosquito, which breeds in flooded rice fields, marshes, and standing water around planted fields. After infection, the virus invades the central nervous system, including the brain and spinal cord.
Most infected persons develop mild symptoms or no symptoms at all. In people who develop severe disease, JE usually starts with flu-like fever, chills, tiredness, headache, nausea, vomiting, confusion and agitation. Next, the illness progresses to infection of the brain (encephalitis), killing 30 per cent of those infected and causing serious brain damage, including paralysis, in 30 per cent who survive.
JE is endemic in 15 states and Union Territories, with the biggest outbreak occurring in eastern Uttar Pradesh in 2005. There’s a vaccine against JE, which is given free under India’s immunization programme to children under 15 years living in endemic areas.
Students wear full sleeves as a precaution against dengue at a school in New Delhi. (Arun Sharma/ HT Photo)
Chikungunya spreads through the bite of the Aedes aegypti mosquito, which also causes dengue. Symptoms -- headache, fever, fatigue, nausea, vomiting, muscle pain and severe joint pain – are mild in most cases, but acute infection can last a couple of weeks. Originally from Africa, chikungunya recurred in India after 32 years in 2006 with cases reported in Gujarat, Andhra Pradesh, Maharashtra, Madhya Pradesh, Tamil Nadu, Karnataka and Kerala.
There is no vaccine and symptomatic treatment is used to treat aches and fever. Chikungunya doesn’t kill but causes severe and painful limb deformity that may last several months.
Congress workers staged a protest outside Delhi chief minister Arvind Kejriwal's residence to draw his attention to the rising cases of dengue in the national Capital. (Arun Sharma/ HT Photo)
Lymphatic filariasis, commonly known as elephantiasis, is a disabling infection that damages the lymphatic system and causes painful, swollen limbs (lymphoedema or elephantiasis). The lymphatic damage leads to frequent attacks of infection.
LF is caused by three thread-like parasitic filarial worms, Wuchereria bancrofti, Brugia malayi, and Brugia timori, all transmitted transmitted by mosquitoes. In India, 99.4 per cent cases are caused by Wuchereria bancrofti, with infection being transmitted by the Culex quinquefasciatus mosquito. The National Health Policy aims at Elimination of Lymphatic filariasis by 2015-end with the use of mass administration of the drug diethylcarbamazine and mosquito control measures.