World Health Day 2014 - vector-borne diseases : AVOID SMALL INSECTS BITE - “Small bite, big threat”

World Health Day 2014: vector-borne diseases
AVOID SMALL INSECTS BITE
“Small bite, big threat”
Pro. Dr.M.A.Aleem M.D.D.M(Neuro) ,
Vice principal, HOD & Professor of Neurology, KAPV Government Medical College & MGM Government Hospital, Trichy – 620017.Tamilnadu India. Cell: 94431-59940
More than half the world’s population is at risk from diseases such as malaria, dengue, leishmaniasis, Lyme disease, schistosomiasis, and yellow fever year, carried by mosquitoes, flies, ticks, water snails and other vectors. Every year, more than one billion people are infected and more than one million die from vector-borne diseases.
This World Health Day – 7 April – World Health Organization is highlighting the serious and increasing threat of vector-borne diseases, with the slogan “Small bite, big threat”.
The organization also emphasizes that these diseases are entirely preventable. Newly published “A global brief on vector-borne diseases” outlines steps that government, community groups and families can all take to protect people from infection.
“A global health agenda that gives higher priority to vector control could save many lives and avert much suffering. Simple, cost - effective interventions like insecticide – treated bed nets and indoor spraying have already saved millions of lives,” say Dr Margaret Chan, WHO Director – General. “No one in the 21st century should die from the bite of a mosquito, a sandfly, a blackfly or a tick.” Vector – borne diseases affect the poorest populations, particularly where there is a lack of access to adequate housing, safe drinking water and sanitation. Malnourished people and those with weakened immunity are especially susceptible.
Schistosomiasis, transmitted by water snails, is the most widespread of all vectors – borne diseases, affecting almost 240 million people worldwide. Children living and playing near infested water are particularly vulnerable to this disease which causes anaemia and a reduced ability to learn. Schistosomiasis can be controlled through regular mass treatment of at – risk groups with a safe, effective medicine, as well as improving access to safe drinking water and sanitation.
Within the past two decades, many important vectors – borne diseases have also re – emerged or spread to new parts of the world. Environmental changes, a massive increase in international travel and trade, changes in agricultural practices and rapid unplanned urbanization are causing an increase in the number and spread of many vectors worldwide and making new groups of people, notably tourists and business travelers, vulnerable.
Mosquito – borne dengue, for example, is now found in 100 countries, putting more than 2.5 billion people – over 40% of the world’s population – at risk.
Dengue has recently been reported in China, Portugal and the state of Florida, in the United States of America.
Reports from Greece say that malaria has returned there for the first time in 40 years. This highlights the continual threat of reintroduction and the need for continued vigilance to ensure that any malaria resurgence can be rapidly contained.
“Vector control remains the most important tool in preventing outbreaks of vector – borne diseases,” say Dr Lorenzo Savioli, Director of WHO’s Department of Control of Neglected Tropical Diseases. “Increased funds and political commitment are needed to sustain existing vector – control tools, as well as medicines and diagnostic tools – and to conduct urgently needed research.” On World Health Day 2014, WHO is calling for a renewed focus on vector control and better provision of safe water, sanitation and hygiene – key strategies outlined in WHO’ s 2011 Roadmap for the control, elimination and eradication of neglected tropical diseases, diseases, which sets targets for the period 2012-2020.
Key Facts on vector borne disease.
Vector – borne diseases account for more than 17% of all infectious diseases, causing more than 1 million deaths annually.
More than 2.5 billion people in over 100 countries are at risk of contracting dengue alone.
Malaria causes more than 600 000 deaths every year globally, most of them children under 5 years of age.
Other diseases such as Chagas disease, leishmaniasis and schistosomiasis affect hundreds of millions of people worldwide.
Many of these diseases are preventable through informed protective measures.
Main vectors and diseases they transmit
Vectors are living organisms that can transmit infectious diseases between humans or from animals to humans. Many of these vectors are bloodsucking insects, which ingest disease – producing microorganisms during a blood meal from an infected host (human or animal) and later inject it into a new host during their subsequent blood meal.
Mosquitoes are the best known disease vector. Others include ticks, flies sandflies, fleas, triatomine dugs and some freshwater aquatic snails
Mosquitoes
Aedes
Dengue fever
Rift Valley fever
Yellow fever
Chikunguya

Anopheles
Malaria
Culex
Japanese encephalitis
Lymphatic filariasis
West Nile fever
Sandflies
Leishmaniasis
Sandfly fever
Ticks
Crimean – Congo. haemorrhagic fever
Lyme disease
Relapsing fever
Rickettsial diseases (spotted fever and Q fever )
Tick – borne encephalitis
Tularaemia
Triatomine bugs
Chagas disease
Tsetse flies
Sleeping sickness (African trypanosomiasis )
Fleas
Plague (transmitted by fleas from rate to humans )
Rickettsiosis

Black flies
Onchocerciasis (river blindness )
Aquatic snails
Schistosomiasis (bilharziasis)
Vector borne diseases are diseases caused by pathogens that are transmitted to humans through insects and ticks carrying the pathogen. They are difficult to prevent because of several challenges facing the control of vector and transmissibility of the pathogen. Here are top 10 vector borne diseases that contribute to increased morbidity and mortalily
Malaria: According to the World Health Organisation (WHO), malaria is the deadliest of all vectors – borne diseases, which accounts for nearly 1.2 million deaths all over the world every year and is prevalent in about 100 countries. The disease is caused by the protozoan parasite Plasmodium. The most common species of Plasmodium responsible for most malaria cases are Plasmodm flaciparum and Plasmodium vivax. The parasite is transmitted to humans via the vector female Anopheles mosquito. The mosquito bearing the protozoa transmits the disease to humans by biting at night. The parasite then attacks the red blood cells and reaches the liver causing symptoms like fever, chills and anemia.
Kala Azar: Leishmaniasis or Kala Azar ranks second (malaria being the first on the list) on the list of fatal diseases caused by parasites. It is mainly prevalent in India, Bangladesh, Ethiopia, Brazil and Sudan. It is caused by protozoan parasite of the genus Leishmania. In India, Leishmania donovani is the only parasite causing the disease. The parasite is transmitted to humans by female sand flies. Upon entry, the parasite attacks the immune system and causes ulcers or sores at the site of entry.
Dengue: Dengue is common in tropical and sub – tropical regions of the world. In the recent years transmission of dengue has significantly increased in urban areas and has become a major public health concern. According to the current estimates of WHO, dengue infections have reached 50 – 100 million worldwide, annually. Dengue is caused by a virus that is transmitted to humans by the vector Aedes Aegypti mosquito.
Plague: Plague had an explosive epidemic and was a major health concern at the beginning of the 20th century. It is a deadly disease caused by the bacteria Yersina pestis. It is primarily transmitted by rodents. But it is also spread through insects that acquire the infection from rate harboring the bacteria. Common insect that acquires the bacteria from rodents is flea. The bacteria enter the blood stream after a flea bite and attack the cells of the immune system. They secrete toxins which causes clots and tissue death.
Filariasis : Lymphatic filariasis is commonly called elephantiasis. Although the disease is quite widespread, it is neglected diseases because it is more disfiguring and disabling than fatal. Currently, more than 120 million people are infected and nearly 40 million people suffer from the fully developed disease. Filariasis is caused by thread like filarial worms or nematodes. Wuchereria bancrofti is the most common filarial worm, causing the disease in 90 percent of the cases. The worm is carried by and transmitted to humans by mosquitoes – mainly Culex mosquito. The worm invades the lymphatic system causing profuse selling mainly in the legs.
Chickungunya: Chickungunya has been identifien in 40 different countries including India. It is caused by a virus classified under the family Togaviridae, genus Alphavirus. It is transmitted to humans by Aedes mosquito (mainly Aedes aegypti) in the daytime. Common symptoms of the disease are similar to dengue.
Lyme disease: Lyme disease is caused by the spirochete bacterium Borrelia burgdorferi. It is transmitted to humans by black – legged ticks that are infected with the bacteria. Upon entry, the bacterium attacks the central nervous system and causes neurological problems.
Yellow fever: Mainly found tropical South America and sub – Saharan Africa region, yellow fever is a mosquito – borne viral disease. The disease is caused by the yellow fever virus and spread by female mosquito of Aedes aegypti species. The virus affects the cells of the immune system and causes symptoms like fever, chills, nausea and muscle pain.
Chagas’ disease: Chagas ’ Disease is widely found in communities of Latin America. It is caused by the protozoan parasite Trypanosoma cruzi and transmitted by a large insect called ‘kissing bug’ (Reduviidae Tratominae). The Parasite damage several organs and mainly affects heart function.
Japanese encephalitis: It is a viral disease that is spread through infected Culex mosquito. The virus mainly affects the central nervous system and causes headache, fever, meningitis, coma, tremors, paralysis and loss of coordination. Several cases of the disease have been found in India. The most affected states include Tamil Nadu, Karnataka and Kerala.
Vector – borne diseases are illnesses caused by pathogens and parasites in human populations. Every year there are more than 1 billion cases and over 1 million deaths from vector – borne diseases such as malaria dengue schistosomiasis human African trypanosomiasis leishmaniasis Chages disease, yellow fever, Japanese encephalitis and onchocerciasis, globally.
Vector – borne diseases account for over 17% of all infectious diseases.
Distribution of these diseases is determined by a complex dynamic of environmental and social factors.
Globalization of travel and trade, unplanned urbanization and environmental challenges such as climate change are having a significant impact on disease transmission in recent years. Some diseases, such as dengue, chikungunya and west Nile virus, are emerging in countries where they were previously unknown.
Changes in agricultural practices due to variation in temperature and sinfall can affect affect the transmission of vector – borne diseases. Climate information can be used to monitor and predict distribution and longer – term trends in malaria and other climate – sensitive diseases.