Dengue is viral disease caused by the arbovirus called, Dengue virus has four serotypes DENV 1 - 4. Dengue is the most rapidly
spreading mosquito-borne viral disease in the world.
It is transmitted by the bite of the infective female mosquitoes, Aedes aegypti and Aedes albopictus; commonly called the "Tiger mosquitoes"
because of its characteristic white stripes on a black body. These mosquitoes usually bite during the day both indoors and outdoors.
Aedes mosquitoes usually breed in artificial collections of fresh water during the monsoon season. Common places of breeding include drums,
jars, pots, buckets, flower vases, plant saucers, tanks, bottles, tins, tyres, drip tray of fridge, coconut shells etc..
People of all age groups are affected. Both sexes are equally affected. Infection with any one serotype confers lifelong immunity to that virus serotype. Although all four serotypes are antigenically similar, they are different enough to elicit cross protection for only a few months after infection by any one them.
The Spectrum of Dengue infection can range from being a simple undifferentiated fever to much more severe forms like Dengue haemorrhagic
fever and Dengue Shock Syndrome. Common symptoms include Fever with Chills and Rigor, Nausea/vomiting, rashes commonly over the
neck and chest, Joint pain, Generalised muscle fatigue. Some of the warning symptoms of Dengue include abdominal pain, persistent vomiting,
edema, distension of abdomen, and difficulty in breathing, mucosal bleeding, lethargy or restlessness.
Dengue is usually a self-limiting viral disease, but when severe can lead to death. There is no specific treatment for Dengue. It is only
symptomatic. Control strategies include source reduction by identification and elimination of its breeding places, and personal protection.
Chikungunya is a viral disease caused by an arbovirus. The disease is trasmitted by the same mosquitoes involved in the transmission of
dengue, Aedes aegypti and Aedes albopictus. The proximity of mosquito breeding sites to human habitation is a significant risk factor for chikungunya.
After the bite of an infected mosquito, onset of illness occurs usually between 3 and 7 days but can range from 2 to 12 days. It also shares some
clinical signs with dengue, and can be misdiagnosed as dengue. Chikungunya is characterized by an abrupt onset of fever frequently accompanied by
joint pain, other symptoms during chronic phase can include fatigue and depression. In addition, it includes muscle pain, headache, nausea, and rash.
Most patients recover fully, but in some cases the joint pain may be chronic.
Children and pregnant women are more prone for serious complications. There are no specific drugs to cure the disease. Treatment is directed
primarily at relieving the symptoms, including the joint pain. There is no commercial Chikungunya vaccine.
Rabies is a zoonotic disease (a disease that is transmitted to humans from animals). It is an acute viral disease caused by "rabies" virus belonging
to the Rhabdoviridae family. Rabies has a 100% fatality rate.
The virus is found in wild and some domestic animals, and is transmitted to other animals and to humans through their saliva (i.e. following bites,
scratches, licks on broken skin and mucous membrane). In India, dogs are responsible for about 97% of human rabies, followed by cats (2%), jackals,
mongoose and others (1%). The disease is mainly transmitted by the bite of a rabid dog.
The incubation period can range from 2 weeks to 12 weeks, though incubation periods as short as four days also have been observed. Symptoms include
partial paralysis, anxiety, insomnia, confusion, agitation, abnormal behaviour, paranoia, terror, and hallucinations, progressing to delirium.
Rabies is perhaps the most painful and horrible of all communicable diseases in which the sick person is tormented at the same time with thirst
and fear of water (hydrophobia). Once the initial symptoms appear, the patient deteriorates rapidly and death ensues in 2-10 days.
Rabies is a vaccine-preventable viral disease. Cleaning the wound immediately and immunization within a few hours after contact with a
suspected rabid animal can prevent the onset of rabies and death. Control strategies include vaccination of animals to eliminate rabies in them. It also includes pre-exposure prophylaxis to those at higher risk either due to their occupation or other activities.
Chagas disease or American trypanosomiasis, is caused by the protozoan Trypanosoma cruzi. It is transmitted by
infected faeces of triatomine bug, also known as ‘kissing bug’. It is estimated that 6-7 million people are
infected worldwide, and more than 25 million people risk acquiring the disease. Chagas disease mostly affects Latin America.
In the acute phase of infection, symptoms may be mild or absent. Skin lesions or purplish swellings of eyelids maybe seen
in 50% patients, along with fever, headache and enlarged lymph nodes. Of those infected, 10-30% patients develop chronic
infection and suffer damage to the heart, digestive system and nervous system. The disease can be confirmed by blood smear
examination and serological tests.
Chagas disease can be treated with benznidazole and also nifurtimox. . Vector control remains the most useful method to
prevent infection and blood screening is vital to avoid infection through transfusion and organ transplantation. Screening
and diagnosis in pregnant women and their children are essential control measures.
Human African trypanosomiasis
Human African trypanosomiasis or sleeping sickness is caused by parasites of the species Trypanosoma brucei. It is
transmitted by the bite of the tsetse fly (Glossina species). Sleeping sickness threatens millions of people in 36 countries
in sub-Saharan Africa. In 2012, there were 7216 cases recorded. The disease, which can be fatal if untreated, mostly affects
rural areas of Africa. Travellers to these regions are also at risk of becoming infected.
In the first stage of infection, the parasites are found in the peripheral circulation and this manifests as fever, headache
and joint pains. In the second stage, they enter the central nervous system, leading to seizures, coma and death.
The infection can be diagnosed by confirming the presence of the parasite in any body fluid, usually blood or the lymph system.
Serological tests are also available. The drugs for treatment of the disease are pentamidine, suramin, melarsoprol and
eflornithine. Preventive measures are aimed at minimizing contact with tsetse flies.
The Leishmaniaseis are diseases transmitted by the bite of female phlebotomine sandflies, infected by parasites of Leishmania
species. There are three main forms of the disease: cutaneous, visceral and mucocutaneous.
Cutaneous Leishmaniasis, the most common form of the disease, manifests as papules, plaques or ulcers, or may persist as nodules.
Healing results in scar formation and therefore disfigurement and disability. An estimated 0.7 million to 1.3 million new cases of
cutaneous leishmaniasis occur worldwide annually. Visceral Leishmaniasis or kala-azar, involves internal organs (particularly, spleen,
liver, and bone marrow). It is the most severe form of the disease and is fatal if left untreated. The disease is characterized by
irregular bouts of fever, weight loss, anaemia, and enlargement of the spleen and liver. Mucocutaneous Leishmaniasis, results from
dissemination of parasites to naso-oropharyngeal mucosa, and leads to mutilation of the mucous membranes.
Leishmaniasis is diagnosed by detecting Leishmania parasites (or DNA) in tissue specimens. Serological tests are also available.
Drugs available include sodium stibogluconate and amphotericin B. Surveillance is an essential component of control or elimination
programmes for Leishmaniasis.
Buruli ulcer is one of the 17 neglected tropical diseases. It is caused by infection with Mycobacterium ulcerans, an organism which belongs to the family of bacteria that causes tuberculosis and leprosy.
Infection leads to destruction of skin and soft tissue with large ulcers usually on the legs or arms. Patients who are not treated early suffer long-term functional disability. Early diagnosis and treatment are the only ways to minimize morbidity and prevent disability.
Buruli ulcer has been reported in 33 countries in Africa, the Americas, Asia and the Western Pacific. Most cases occur in tropical and subtropical regions except in Australia, China and Japan.The exact mode of transmission of Buruli ulcerans is still unknown.Buruli ulcer often starts as a painless swelling (nodule). It can also initially present as a large painless area of induration (plaque) or a diffuse painless swelling of the legs, arms or face (oedema).
The treatment of Buruli ulcer can be straightforward if the patient is detected early and costly if found in the advanced stage. This consists of combination antibiotics and complementary treatments.
Leprosy is a chronic infectious disease caused by Mycobacterium leprae. It is a slow growing bacillus since one Leprosy bacillus takes 12–14 days to divide in to two.
Although not highly infectious, it is transmitted via droplets, from the nose and mouth, during close and frequent contact with untreated cases. The disease is characterized by a long incubation period of generally 5-7 years.
It has a wide range of clinical manifestations, but most commonly the skin and peripheral nerves are affected. The cardinal skin manifestation is hypo-pigmented patches with sensory deficit. Involvement of the peripheral nerves, is demonstrated by thickening of the nerves with a loss of sensation with or without weakness of the corresponding muscles of the hands, feet or eyes. Depending upon the skin smear and extent of skin and nerve lesions, leprosy is grouped as Pauci bacillary and Multi bacillary. “Chaulmoogra” oil was used for leprosy treatment until “Dapsone” was discovered with antileprosy effects in 1940s. It was in 1970s when multi drug therapy (MDT) consisting of Rifampicin, Clofazimine and Dapsone were identified as cure for leprosy which came into wide use from 1982 following the recommendations of WHO. The duration of the treatment ranges from 6 to 12 months.
Since then the services for leprosy patients gradually changed from institutional to outpatient care through health centres and field clinics. Gradually the infected and cured leprosy patients began to be accepted by the community as a result of intensive health education and also due to successful results of MDT
Trachoma is an ocular infection caused by the bacterium, Chlamydia trachomatis. Trachoma is the leading infectious cause of blindness. Globally, 53 countries are endemic for blinding trachoma.
It is spread by direct contact with eye and nose discharges from infected individuals or by contact with fomites (inanimate objects that carry infectious agents) such as towels etc.. Eye-seeking flies can also be a route of mechanical transmission.
Infection often begins during infancy or childhood and can become chronic. If left untreated, the infection eventually causes the eyelid to turn inwards, which in turn causes the eyelashes to rub on the eyeball, resulting in intense pain and scarring of the eye. This ultimately leads to irreversible blindness, typically between 30 and 40 years of age.
Control strategy known as SAFE strategy is implemented in most of the endemic districts in the world. It includes Surgery, Antibiotic treatment, Facial cleanliness and Environmental improvement for preventing and curing active trachoma.
Yaws, also known as framboesia or pian is the most common of the endemic treponematoses. Endemic treponematoses are a group of chronic bacterial infections caused by treponemes. The other infections are endemic syphilis and Pinta.
Yaws is caused by Treponema pallidum subspecies pertenu. Children are commonly affected with the peak incidence being between 6-10 years. Males and females are equally affected. Low socio-economic status and overcrowding are considered as risk factors.
Yaws is transmitted by direct skin contact with the fluid from the lesion of an infected person. Incubation period is about 2-4 weeks. After which a single skin lesion develops at the point of entry of the bacterium. If left untreated, multiple lesions appear all over the body. It can lead to chronic disfigurement and disability. Overcrowding, poor personal hygiene and poor sanitation facilitate the spread of the disease. Yaws can be treated by antibiotics, the drug of choice being Azithromycin.
Cysticercosis is a parasitic tissue infection caused by larval cysts of the tapeworm Taenia solium. These larval cysts infect brain, muscle, or other tissue, and are a major cause of adult onset seizures in most low-income countries.
People do not get cysticercosis by eating undercooked pork. Eating undercooked pork can result in intestinal tapeworm only if the pork contains larval cysts. Pigs become infected by eating tapeworm eggs in the feces of a human infected with a tapeworm. The highest rates of infection are found in areas of Latin America, Asia, and Africa that have poor sanitation and free-roving pigs that have access to human feces.
Both the tapeworm infection, also known as taeniasis, and cysticercosis occur globally.The location that most often prompt a medical consultation is the central nervous system, followed by the eye and its surrounding tissues. Symptoms are for example epileptiform attacks, headaches, learning difficulties and convulsions.
Prevention is based on strict meat inspection, health education, cooking pork and beef well, hygiene, and widespread sanitary installations. Treatment of cysticercosis is very difficult with varying success: praziquantel + corticosteroids + albendazole. Treatment of taeniasis is easy using praziquantel.
Guinea-worm disease is caused by the parasitic worm Dracunculus medinensis or "Guinea-worm". This worm is the largest of the tissue parasite affecting humans. The adult female, which carries about 3 million embryos. It is caused by drinking water containing water fleas (Cyclops species) that have ingested Dracunculus larvae.
In the human body, the larvae are released and migrate through the intestinal wall into body tissues, where they develop into adult worms. The female worms move through the person’s subcutaneous tissue, causing intense pain, and eventually emerge through the skin, usually at the feet, producing oedema, a blister and eventually an ulcer, accompanied by fever, nausea, and vomiting. If they come into contact with water as they are emerging, the female worms discharge their larvae, setting in motion a new life cycle.
There are no drugs available for the treatment of this disease. However, it can be prevented by protecting water sources and filtering potentially contaminated water. Guinea-worm disease is rarely fatal. However, the patient remains sick for several months. India was declared free of this disease by WHO on 15th Feb 2001.
Human echinococcosis is a zoonotic disease (a disease that is transmitted to humans from animals) that is caused by parasites, namely tapeworms of the genus Echinococcus. Echinococcosis occurs in 4 forms.The two most important forms, which are of medical and public health relevance in humans, are cystic echinococcosis and alveolar echinococcosis. In endemic regions, human incidence rates for cystic echinococcosis can reach greater than 50 per 100,000 person/year, and prevalence levels as high as 5-10% may occur in parts of Argentina, Peru, east Africa, central Asia, and China.
A number of herbivorous and omnivorous animals act as intermediate hosts of Echinococcus. This means they get infected by ingesting the parasite eggs in the contaminated ground and develop parasitic larval stages in their viscera.
Humans are accidental hosts and are not able to transmit the disease.Human infection with E. granulosus leads to the development of one or more hydatids located mainly in the liver and lungs, and less frequently in the bones, kidneys, spleen, muscles, central nervous system, and eyes.
Both cystic echinococcosis and alveolar echinococcosis are often expensive and complicated to treat, sometimes requiring extensive surgery and/or prolonged drug therapy.
Food borne trematodes
Foodborne trematodiases are estimated to affect more than 56 million people throughout the world.They are caused by trematode worms ("flukes"), of which the most common species affecting humans are Clonorchis, Opisthorchis, Fasciola and Paragonimus. Cases of foodborne trematodiases have been reported from over 70 countries worldwide; however East Asia and South America are the most affected areas. In these regions, infections with foodborne trematodes represent a significant public health problem.
People become infected through the consumption of raw or poorly cooked food: fish, crustaceans and vegetables that harbour the minute larval stages of the parasites Foodborne trematodiases are zoonoses, i.e. they are naturally transmissible from vertebrate animals to people and vice versa. Direct transmission is however not possible, as the relevant causative parasites become infective only after having completed complex life-cycles that usually involve stages in intermediate, non-human hosts.
People become infected when they ingest the second intermediate host that is infected with larval forms of the parasite. In the case of fascioliasis, people become infected when the larvae are ingested together with the aquatic vegetables to which they are attached.
Early and light infections often pass unnoticed, as they are asymptomatic or only scarcely symptomatic. Conversely, if the worm load is high, general malaise is common and severe pain can occur, especially in the abdominal region, and this occurs most frequently in the case of fascioliasis.
Chronic infections are invariably associated with severe morbidity. Symptoms are mainly organ-specific and reflect the final location of the adult worms in the body.
Treatment can be offered through preventive chemotherapy or individual case-management.
Lymphatic filariasis, commonly known as elephantiasis, is a painful and profoundly disfiguring disease. While the infection is usually acquired in childhood, its visible manifestations occur later in life, causing temporary or permanent disability. An estimated 120 million people in tropical and subtropical areas of the world are infected with lymphatic filariasis; of these, almost 25 million men have genital disease (most commonly hydrocele) and almost 15 million, mostly women, have lymphoedema or elephantiasis of the leg. In endemic countries, lymphatic filariasis has a major social and economic impact.
The disease is caused by three species of thread-like nematode worms, known as filariae - Wuchereria bancrofti, Brugia malayi and Brugia timori. Male worms are about 3-4 centimetres in length, and female worms 8-10 centimetres. The male and female worms together form "nests" in the human lymphatic system, the network of nodes and vessels that maintain the delicate fluid balance between blood and body tissues. The lymphatic system is an essential component of the body’s immune system.
Filarial infection can cause a variety of clinical manifestations, including lymphoedema of the limbs, genital disease (hydrocele, chylocele, and swelling of the scrotum and penis) and recurrent acute attacks, which are extremely painful and are accompanied by fever. The vast majority of infected people are asymptomatic, but virtually all of them have subclinical lymphatic damage and as many as 40% have kidney damage, with proteinuria and haematuria.
Prevention of lymphatic filariasis is possible by stopping the spread of the infection. Large-scale treatment involves a single dose of 2 medicines given annually to an entire at-risk population in the following way: albendazole (400 mg) together with ivermectin (150-200 mcg/kg) or with diethylcarbamazine citrate (DEC) (6 mg/kg).
Onchocerciasis or 'river blindness’ is transmitted by bites of infected black flies (of the genus Simulium) and the causative agent is filarial worm Onchocerca volvulus. Onchocerciasis affects eyes and skin.
The death of microfilariae causes debilitating itching in the skin and in the eyes, this may lead to visual loss and irreversible blindness. Vector control is the prevention strategy i.e. killing the larvae of the black fly vectors with environmentally safe insecticides.
Schistosomiasis is a disease that leads to chronic ill-health. Disease is acquired on contact with water, contaminated with larval forms (cercariae), of parasitic blood flukes (schistosomes), which are released by freshwaer snails. The microscopic adult worms lay eggs which are trapped in the tissues and the body’s reaction to them can cause damage.
Urogenital schistosomiasis is caused by Schistosoma haematobium and intestinal schistosomiasis by any of the organisms S. guineensis, S. intercalatum, S. mansoni, S. japonicum, and S. mekongi. Stool or urine samples can be examined microscopically for parasite eggs. Control of schistosomiasis is based on drug treatment, snail control, improved sanitation and health education.
Soil transmitted helminths
Soil-transmitted helminth infections are infections with intestinal worms transmitted through contaminated soil. They affect the poorest and most deprived communities where sanitation is poor. The main species that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and the hookworms (Necator americanus and Ancylostoma duodenale.
These helminths live in the intestine and their eggs are passed in the feces of infected persons. They usually present with intestinal manifestations (diarrhoea, abdominal pain), general malaise and weakness. The disease is more severe if the worm burden is more. Hookworms cause chronic intestinal blood loss that result in anaemia. Periodic administration of antihelminths, health education and improvement in sanitation are strategies to control the disease.
3 more diseases/conditions
3 more diseases/conditions ( Mycetoma,Snake bite and Scabies) are included in the NTD list (Communication from Dr.Revankar, New Jersey).