1 .Definition

            Chikungunya fever is a viral disease transmitted to humans by the bite of infected mosquitoes. It is a preventable and self limiting disease. The term 'chikungunya' in Swahili  language stands for 'that which bends up.'  (1) Chikungunya should be suspected when an epidemic  occurs with characteristic triad of fever, rash and rheumatic manifestations

Suspected Case

An acute illness characterized by sudden onset of fever with several of following symptoms: joint pain, headache, backache, photophobia, arthralgia, and rash.

 Probable Case

As above and positive serology (when single serum sample is tested)

Confirmed Case

  A probable case with any of the following:

            Four fold HI antibody difference in paired serum samples.

            Detection of IgM antibodies.

            Virus isolation from serum.

            Detection of Chikungunya virus nucleic acid in sera by RT-PCR. (2)

2. Epidemiology

Virus (CHIK)

            Group IV (+) (RNA)

            Family Togaviridae

            Genus Alphavirus

            Species  Chikungunya


CHIKV was first isolated from the blood of a febrile patient in Tanzania in 1953, and has since been identified repeatedly in west, central and southern Africa and many areas of Asia, and has been cited as the cause of numerous human epidemics in those areas since that time.


CHIKV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on a person infected with CHIKV. Monkeys, and possibly other wild animals, may also serve as reservoirs of the virus. Infected mosquitoes can then spread the virus to other humans when they bite.

Aedes aegypti, a household container  breeder and aggressive daytime biter , is the primary vector of CHIKV to humans. Aedes albopictus (the Asian tiger mosquito) may also play a role in human transmission in Asia, and various forest-dwelling mosquito species in Africa have been found to be infected with the virus. Aedes aegypti, which bites during daylight hours, breeds in several types of domestic and peri-domestic containers. This mosquito is mainly found in urban areas but during past two decades, due to developmental activities, it has spread to many rural areas.(2).

According to CDC, Chikungunya fever can be  transmitted to humans by the bite of infected  Culex mosquitoes  also



Outbreaks typically involve several hundreds or thousands of cases but deaths are rarely encountered.


Present Epidemic

Since the beginning of the epidemic in March 2005, 2, 66 000 cases of chikungunya fever are estimated to have occurred on the island of Reunion, a French overseas territory. Weekly estimates of suspected cases are based on the number of patients with suspected chikungunya seen by sentinel physicians on the island of Reunion and extrapolation of these figures to the entire island population. Numbers of newly estimated cases peaked at 45 000 in week 5 (first week of February 2006), and have since decreased. By June 2006, the estimated weekly number of cases was around 400. The islands of the southwest Indian Ocean (including Comoros, Madagascar, Mauritius, Mayotte, and Seychelles), and several states of India have been affected by chikungunya epidemics in 2005-2006.

Since December 2005, an outbreak of chikungunya virus (CHIKV) infection has been ongoing in various states of India (Karnataka, Maharashtra, Andhra Pradesh, Tamil Nadu, Madhya Pradesh, Gujarat, Orissa and Kerala) with potential spread to neighbouring states [1,2]. Cases were first recognised and reported in December 2005. In July 2006, India's National Vector Borne Disease Control Programme (NVBDCP) reported a reduction in the number of cases in the affected districts while other districts are now becoming affected for the first time. The spread is of unprecedented magnitude and over 896 500 suspected chikungunya cases have been reported since December 2005 from the five worst affected states (Andhra Pradesh, Karnataka, Maharashtra, Tamil Nadu and Madhya Pradesh) [3]. No chikungunya cases have been reported from the northern states.

Recent large-scale outbreaks of fever caused by CHIKV infection in India have confirmed the re-emergence of chikungunya in this part of Indian subcontinent. Since the end of 2004, chikungunya has emerged in the islands of the southwestern Indian Ocean (Comoros, Mauritius, Seychelles and Reunion), where several hundred thousand cases have been reported. Chikungunya was later also reported in Madagascar and in India [4,5]. Chikungunya is not new to the Indian subcontinent. Since it was first detected in Calcutta in 1963 [6], there have been reports of CHIKV infection in different parts of India [7,8,9]. Previously, the most recent Indian chikungunya outbreak was reported in 1973 in western India, in Barsi, Sholapur district, Maharashtra state [10]. Subsequently, there has been no active or passive surveillance carried out in India and it was believed that chikungunya had disappeared from the Indian subcontinent [11,12].

 However, recent reports of large scale outbreaks of fever caused by chikungunya virus infection in several parts of Southern India have confirmed the re-emergence of this disease. It has been estimated that over 1,80,000 cases have occurred in India since December 2005. Andhra Pradesh (AP) was the first state to report this disease in Deccmber 2005, and one of the worst affected (over 80,000 suspected cases). Several districts of Karnataka state such as Gulbarga, Tumkur, Bidar, Raichur, Bellary, Chitradurga, Davanagere, Kolar and Bijapur districts have also recorded large number of chikungunya virus related fever cases. Over, 2000 cases of chikungunya fever have also been reported from Malegaon town in Nasik district, Maharashtra state, India between February-March 2006. During the same period, 4904 cases of fever associated with myalgia and headache have been reported from Orissa state as well. According to the National Institute of Virology, Pune, out of 362 samples collected from different places in AP such as Kadapa, Secunderabad, Chittoor, Anantapur, Nalgonda and Prakasam, Kurnool and Guntur districts, 139 were found positive for chikungunya , antibodies, six for dengue fever and 15 related to both the fevers. Apart from India, several small countries in the southern Indian Ocean such as the French Reunion Islands, Mauritius, Seychelles and other countries have also been reporting large scale outbreaks of chikungunya virus infection this year. (3)

Imported cases of chikungunya have been reported from several European countries. The vector, responsible for the transmission in the French territories of the Indian Ocean is known to be Aedes albopictus. This mosquito has been detected on the French Mediterranean coast, between the cities of Menton and Nice, and recently in the Bastia area of Corsica, a French Mediterranean island. (euro 2006). From April 2005 to June 2006 inclusive, 766 imported cases of chikungunya were identified in metropolitan France. The mean age was 48 years (range: 5 months-83 years), and the male:female sex ratio was 0.9:1.

CDC alerts that since April 2006, a chikungunya fever outbreak has been on-going in three states in India (Karnataka, Maharastra, and Andhra Pradesh) with possible spread to neighborning states. A chikungunya outbreak on the Indian Ocean islands of Mayotte, Mauritius, Réunion (territory of France), and the Seychelles that began in March 2005 is waning. However, travellers can still occur and travellers to all tropical and subtropical areas of the world are reminded to take precautions to avoid mosquito bites.

According to European Centre for Disease Prevention and Control, Stockholm, Sweden, since March 2005, 255 000 cases of chikungunya fever are estimated to have occurred on the island of Réunion, a French overseas territory in the Indian Ocean [1]. A huge increase in estimated cases occurred at the end of December 2005, culminating in an estimated peak incidence of more than 40 000 cases in week 5 of 2006 [2]. Since then, the estimated weekly incidence trend is downwards, although there have been an estimated 3000 new cases per week since week 13 of 2006. In total, 213 deaths have been linked to the disease. In Mayotte, the nearby French territorial collectivity, 5834 cases have been notified . Chikungunya cases have also been reported on other islands in the Indian Ocean, and imported cases have been confirmed in several European countries (Table).



 Number of chikungunya cases reported by various countries, February 2005 to April 2006*.


The data in this table is not meant to be exhaustive, and is based on information supplied by Eurosurveillance editorial advisors and the Institut de Veille Sanitaire in April and May 2006.More than 100 000 chikungunya cases have been reported in India since December 2005.

The precise reasons for the re-emergence of chikungunya in the Indian subcontinent as well as the other small countries in the southern Indian Ocean are an enigma. Although, it is well recognized that re-emergence of viral infections are due to a variety of social, environmental, behavioural and biological changes, which of these contributed to the re-emergence of chikungunya virus would be interesting to unravel. Genetic analysis of chikungunya viruses have revealed that two distinct lineages were delineated, one containing all isolates from western Africa and the second comprising all southern and East African strains, as well as isolates from Asia. Phylogenetic trees corroborated historical evidence that the virus originated in Africa and subsequently was introduced into Asia. Such studies need to be conducted on virus isolates obtained during the current outbreak in order to understand if any mutation has occurred in the virus that has facilitated the large scale spread of this virus in the region. Alternatively, one could take the simplistic view that the lack of herd immunity within the country probably lead to its rapid spread across several states. A sero survey conducted at Calcutta a decade ago did reveal that only 4.37% of the sera tested were positive for chikungunya antibodies with the highest seropositivity rates observed in the age group of 51-55 years and no chikungunya antibodies detected in the young and young adults. These findings probably suggest that there is indeed lack of herd immunity to chikungunya virus. Yet another challenge faced during this large outbreak in the country has been the lack of rapid diagnostic facilities. Although, the National Institute of Virology at Pune, has been of great help in determining the etiology of the outbreak relying on one institute in the country to render diagnostic help for case management would be foolhardy. It would be therefore desirable to ensure that several virology laboratories in the country are enrolled and networked to deliver rapid diagnosis in large outbreaks. ( 3)

            NICD also reviews the current scenario of re-emergence of chikungunya infection. According to them, the global outbreak of Chikungunya was discovered in Port Klng in Malaysia in 1999 affecting 27 people.  From 27th February 2005- 28 March 2006, 3115 cases of Chikungunya have been notified by 31 physicians from a sentinel network on La Reunion.  Estimations from a mathematical model evaluate that about 2,04,000 people may have been infected by Chikungunya virus since March, 2005 on La Reunion.  The presenting clinical symptoms were consistent with Chikungunya infection, since the beginning of January 2006, other countries in the South West Indian Ocean have reported Chikungunya cases: Mayotee(9 January  10 March,2833 suspected cases), Mauritius (1 January  5 March, 6000 suspected cases including 1200 confirmed cases) Several European countries have reported imported cases in people returning from these islands: France (160 imported cases), Germany, Italy, Norway and Switzerland. In India after quiescence of about two and half decades an outbreak of Chikungunya with sporadic cases of dengue is being reported from different parts of India  (2).


Chikungunya infection in pregnancy:


Evidence for intrauterine infection in pregnant women and vertical transmission has been obtained. Survey of the Reunion Island outbreak shows that three of nine miscarriages before 22 weeks of gestation could be attributed to the virus. 3 829 births took place during this time. Among the 151 infected women, 118 were viremia negative at delivery, and none of the newborns showed any damage. Among the 33 with positive viremia at delivery, 16 newborns (48.5%) presented neonatal Chikungunya. Though fetal contamination risks appear to be rare before 22 weeks of gestation, they are potentially dangerous. After 22 weeks gestation, newborns infection occurs if the mother is viremia positive at delivery. Transplacental transmission is suspected, but the pathogenic mechanism remains unknown.(4)


3. Clinical features


Incubation period is 2-3 days (range 1-12days)


–Acute phase lasts 2  3 days

–Abrupt rise in temperature

–Often reaching upto 39 to 40 degree Centigrade

–Intermittent shaking chills

–May remit for 1-2 days & then return (“saddle back” fever curve).


–Polyarticular, migratory

–Predominantly affect small joints of hands, wrists, ankles and feet, with lesser involvement of larger joints

–Swelling may occur but fluid accumulation is uncommon

–Generalized myalgias, back & shoulder pain  common


Pain on movement

–Worse in the morning

–Improved by mild exercise

–Exacerbated by strenuous exercise


Milder articular manifestations  usually symptom free within a few weeks, More severe cases takes months to resolve entirely


Cutaneous manifestations

–Flush over face & Trunk is typically present

–Usually followed by Rash, generally described as maculopapular. Trunks & Limbs commonly involved. Face, palms & soles very rarely  involved 


Other associated manifestations in acut

  –Most patients have headache;  not usually severe

–Photophobia, retro orbital pain may also occur

–Conjunctival congestion  in some cases

–Some patients have sore throat and Pharyngitis on examination


  Meningo-encephalitis, especially in New-borns and in  those with pre-existing medical conditions

  Severe cases are observed in  elderly, in very young (newborns) & in immunocompromised patients

Outbreaks typically result in several hundreds or thousands of cases but deaths are rarely encountered.



Differential Diagnosis


–Dengue & Dengue Haemorrhagic fever

–Onyong-nyong virus infection

–Sindbis virus infection (2)


This disease is almost always self-limited and rarely fatal. (1)

Chikungunya is a self-limiting febrile illness but the current outbreak seems to be more severe than previous outbreaks, because many patients developed complications and deaths have also been reported. Some cases at Réunion had mild haemorrhagic signs. A small retrospective study in Bangalore, India showed serum samples that were clinically referred as dengue haemorrhagic fever were negative for dengue, but when further tested, several samples were positive for chikungunya. The laboratory investigations and clinical presentations in some of these cases showed thrombocytopenia and petechial haemorrhage. Severe haemorrhagic symptoms have not been reported in chikungunya cases in Africa; however, they have been reported in some cases during earlier epidemics that in south Asia and southeast Asia .

The current outbreak can be attributed partly to the absence of herd immunity in the affected population, although in India there was an indication of chikungunya virus activity at a low level. During the present outbreak, Schuffenecker and colleagues investigated changes in the virus genome leading to its virulence and change in the behaviour and morbidity associated with the disease. They surmised that the outbreak began with a strain related to east African strains of the virus. All the recent Indian Ocean viral genetic sequences examined shared certain areas, which are different from the previously determined sequences (flutrackers.com).During the recent epidemic in the Indian Ocean islands, 12 cases of meningoencephalitis have been confirmed, which could suggest that the present strain is more virulent than those causing previous epidemics; six cases were diagnosed in neonates whose mothers had contracted the virus 48 h before giving birth and six in elderly people. 77 death certificates issued in the region between Jan 1, 2006, and March 2, 2006, state Chikungunya as the cause of death, but, for most of them, there was underlying comorbidity and the median age was 78 years (5).(The Lancet 2006; 368:186-187 July 15, 2006)

According to CDC, no deaths, neuroinvasive cases, or hemorrhagic cases related to CHIKV infection have been conclusively documented in the scientific literature. CHIKV infection (whether clinical or silent) is thought to confer life-long immunity.(1)Most patients with acute CHIKV infection presented with high fever(38.5- 40 degree centigrade),muscle pain,headache and swelling and severe pain in the joints with polyarthritis followed by an itching maculopapular rash five days after onset. Symptoms where generally self limiting and lasted 1- 10 days. Almost 10% of cases reported prolonged joint pain for more than threee weeks. However joint pain may persists for several months or weeks. Females were more affectd  than males, a feature probably associated with the day time bite and indoor feeding habits of the mosquito vector in India, Aedes aegyptii. All age  groups are evenly represented (6)



4. Diagnosis and lab investigations


Laboratories currently  working on Chikungunya in India

National Institute of virology, Pune

National Institute of Communicable diseases, Delhi

Rajiv Gandhi Centre for Bio Technology Trivandrum



Serological diagnosis  Virus specific IgM antibodies are readily detected by Capture ELISA in patients recovering from Chikungunya infection and they persist in excess of 6 months. No commercial tests are yet available.

Haemagglutination Inhibition (HI) antibodies appear with the cessation of viremia. All patients will be positive by day 5 to 7 of illness.

Collection, Storage and transportation of sample.


For serology, Acute sample collected upto 5 days after the onset of illness. Convalescent or paired sample should be collected 10-14 days after the first sample.


For isolation of the virus and RT-PCR, Blood should be collected within 5 days of illness. Transport  specimens to the laboratory at 2-8degree C as soon as possible. Do not freeze whole blood, as haemolysis may interfere with serology test results.If more than 24 hrs delay is expected before specimen can be submitted to the laboratory, the serum should be separated from the red blood cells and stored frozen.(NICD)


Diagnosis is usually made by IgM-capture ELISA. However, PCR is useful for diagnosis with acute samples. (The Lancet 2006; 368:186-187 July 15, 2006) Chikungunya serological testing in France is carried out by two national reference centres for arboviral diseases and two private laboratories. (euro 24 august, 2006)


5. Management

The illness is usually self  limiting & will resolve with time

During acute joint symptoms, the patients can manage with supportive care and rest. Stiffness & morning arthralgia may show improvement with movement & mild exercise. Heavy exercise may exacerbate rheumatic symptoms.



Antipyretics & analgesics

Non-aspirin and Non Steroidal anti inflammatory drugs are recommended (NICD)

In unresolved arthritis refractory to nonsteroidal anti-inflammatory drugs, chloroquine phosphate (250 mg/day) has shown promising results.


No vaccine or specific antiviral treatment for chikungunya fever is available. Treatment is symptomatic with rest and  fluids. Ibuprofen, naproxen, acetaminophen, or paracetamol may relieve symptoms of fever and aching. Aspirin should be avoided. Infected persons should be protected from further mosquito exposure (staying indoors and/or under a mosquito net during the first few days of illness) so that they can't contribute to the transmission cycle. (CDC)


No specific drug treatment against chikungunya virus is available; thus, treatment of chikungunya fever is supportive: bed rest, fluids, and mild pain medications such as ibuprofen, naproxen, acetaminophen, or paracetamol may relieve symptoms of fever and aching, provided that the person has no contra-indications to these medications. Because aspirin can increase the risk of bleeding and possibly Reye syndrome, it should be avoided during the acute stages of the illness. Few cases are severe enough to warrant hospitalization. All persons with chikungunya fever should be protected against additional mosquito bites to reduce the risk of further transmission of the virus. (lancet)



6. Prevention and control


There is no vaccine or specific medication available against Chikungunya infection.  Vector Control is thus very important in controlling of preventing Chikungunya.  The elimination of breeding sides, or source reduction is an effective method of control.  Aedes aegypti is typically a container habitat species and breeds preliminary in artificial container and receptacles. 


Control of Mosquito breeding:

 Ø        All water tanks, cistems, barrels, trash containers, etc. need to be covered tightly with a lid. 

 Ø        Remove or empty water in old tyres, tin cans, buckets, drums, bottles or from other places where mosquitoes breed. 

Ø         Clogged gutters and flat roofs that may have poor drainage need to be checked regularly.

Ø         Water in bird baths and plant pots or dip trays should be changed at lease twice each week.

Ø         Pets water bowls need to be emptied daily.

Ø         In ornamental water tanks/garden, larvivorous fish (e.g.gambusia, guppy) need to be introduced.  They eat mosquito larvae.

Ø         Weeds and tall grass should be cut short; adult mosquitoes look for these shady places to rest during the hot daylight hours.

Ø         In case water containers cannot be emptied on daily/weekly basis, Temephos (1 ppm) should be used.


Protection from mosquito bites:


Ø         Insecticide treated mosquito curtains/nets should be used.  Especially children should sleep under nets during daytime.

Ø         Insecticide spray should be done to kill mosquitoes.  For knockdown effect, well planned fogging operations is strongly recommended with 2% pyrethrum space spray in high risk villages/wards where clustering of cases has been reported.


Epidemiological and entomological surveillance needs to be intensified. Reporting of fever cases is to be monitored closely.

Active surveillance by health workers using the case definitions for 'cases presenting with acute fever associated with arthralgia/arthritis (Painful and stiff joints) is recommended to detect new cases early for treatment.  This will help in identifying affected areas so the control measures may be initiated.

Vector surveillance (both adult and aquatic stages of mosquitoes) should be intensified.   This will help in identifying high risk areas for initiating control measures and assessing impact.

Medical and health institutes, professional association, private practitioners, NGOs should be involved for fever reporting and proper case management.

IEC  Activities

IEC activities are crucial for community sensitization and participation People need to be educated about the disease, mode of its transmission, availability of treatment and adoption of control measures.  The activities have to be identified particularly to effect changes in practice of storage of water and personal protection.  They should also be reassured that this a preventable disease.  People should be encouraged to use personal protective measures in the form of full sleeve clothes, use of mosquito repellant and insecticide treated mosquito net (even while sleeping during daytime)/curtains etc.   They should be advised to cooperate in fogging and take measures for eliminating breeding places.  Community ownership has to be encouraged in the long term for sustaining low larval and adult densities of mosquitoes and use of personal protection measures. 

Special campaigns may be carried out with the involvement of mass media including local vernacular newspapers/magazines, radio and TV as well as outdoor publicity like hoardings, miking, drum beating, rallies etc.  Health education materials should be developed and widely disseminated in the form of posters, pamphlets, handbills.  Interpersonal communication through group meetings, traditional/folk media particularly must be optimally utilized Involvement of NGOs, Faith based Organizations, Community Based Organizations, Women's Self-Help Groups, professional associations like Indian Medical Association, Nehru Yuva Kendras, NSS/NCC units in schools and colleges in control activities should be promoted actively.

The best way to avoid CHIKV infection is to prevent mosquito bites. There is no vaccine or preventive drug. (CDC)

        ·   Use insect repellent containing an DEET or another  active ingredient  on exposed skin. Always follow the directions on the package.

·           Wear long sleeves and pants (ideally treat clothes with permethrin or another repellent).

·           Have secure screens on windows and doors to keep mosquitoes out.

·           Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Keep children's wading pools empty and on their sides when they aren't being used.

·           Additionally, a person with chikungunya fever or dengue should limit their exposure to mosquito bites in order to avoid further spreading the infection. The person should stay indoors or under a mosquito net.

Although the disease is self limiting , intense control measures( such as regular fogging with pesticides, awareness of the disease and the vector, detection and elimination of vector breeding sources, proper facilities for health care, and community  awareness about the prophylactic measures ) are required to control the further spread(6)

The main preventive measure is to stop the proliferation of mosquitoes by reducing their breeding grounds. These  include anti-vectoral activities and the destruction of domestic breeding sites, coupled with an extensive public health education campaign, using mass media and community associations to sensitize the population about protective measures. Epidemiological surveillance and vectoral surveillance is also being reinforced. (7)

Mosquito control is the main outbreak control activity. Close to habitation, these two mosquito species ( A. aegypti and A. albopictus) multiply in collections of stagnant water, mostly in artificial containers. To control the mosquitoes, their breeding sites must be removed, destroyed, protected, frequently emptied and cleaned, or treated with insecticides. During epidemics,  insecticides are also often applied as space sprays to kill the adult mosquitoes.

WHO recommends no special restrictions on travel or trade to or from these areas. However , it is recommended that individuals take precaution to protect themselves  from mosquito bite, eg by wearing clothes that minimizes skin exposure and applying insect repellents to exposed skin or  clothing in accordance. (10)

There are no preventive medications or FDA-approved vaccines for chikungunya fever (CDC). There are steps, travelers can take to reduce their risk of being bitten by infected mosquitoes.

·           Use insect repellent on exposed skin surfaces when outdoors, particularly             during the day.

o          Repellents containing 30% to 50% DEET (N,N-diethyl-m-toluamide) are recommended. Lower concentrations of DEET offer shorter-term protection requiring more frequent reapplication.

o          Repellents containing picaridin are available in the U.S. only in low-concentration (7%) formulations, which require frequent reapplication. Repellents with higher concentration formulations of picaridin may be available in some regions outside the U.S.

·           Wear long-sleeved shirts and long pants when outdoors.

o          Clothing may also be sprayed with repellent containing permethrin or another EPA-registered repellent for greater protection.

·           Stay in hotels or resorts that are well screened or air-conditioned and that take measures to reduce the mosquito population, where possible.

·           Reduce Aedes breeding sites by emptying standing water that may have collected in containers (e.g., uncovered barrels, flower vases, or cisterns) by overturning the vessels or by  covering the opening.

·           If illness develops, stay under a mosquito net or indoors to limit mosquito bites and to avoid further spread of infection.

During Chikungunya on La Réunion pregnant women, families with young children, people older than 70 years, and those with significant comorbidity were prevented from travelling to the Indian Ocean islands. The message on protective measures against mosquito bites was reinforced. This document emphasises the importance of disease-surveillance communication networks, which allow the constant modification of preventive and therapeutic measures.( The Lancet 2006; 368:186-187 July 15, 2006)


Vector control

Although good patient management can be effective for individual cases, currently no alternative to vector control is available for the prevention of dengue. Most endemic countries have a vector control component in their programs; however, the application of vector control measures is frequently insufficient, ineffective, or both and is currently failing to reduce the public health burden to an acceptable level.

Most Aedes control programs rely on the application of larvicides and adulticidal insecticide space sprays (Zaim and Jambulingham 2004). Because Ae. aegypti characteristically breeds in water that does not contain high levels of organic pollutants, control measures typically must be applied to water stored for household purposes, including drinking water. WHO currently approves five insecticides for application to potable water (FAO 1999; WHO 1991). Since the early 1970s, the organophosphate temephos has been the most widely used, but increasing levels of resistance to this insecticide are reducing the duration of effectiveness of treatments in some countries ( Brengues and others 2003; Lima and others 2003; Rodriguez and others 2001). An additional challenge is the growing objection among householders, particularly in Latin America, to the application of chemicals to drinking water.

Biological control agents, including larvivorous fish and copepods, have had a demonstrable role in integrated control of Ae. aegypti, but operational difficultiesparticularly a lack of facilities and of expertise in mass rearing and the need for repeated introduction of these agents into some container habitatshave largely precluded their widespread use. One encouraging exception is Vietnam, where indigenous species of predatory copepods are increasingly used to control semipermanent larval habitats of Ae. aegypti ( Kay and others 2002; Nam and others 2000). However, some communities have strong cultural objections to the introduction of live animals into household water storage containersfor example, in Thailand, where bathing with water that contains small fish or other creatures is widely regarded as unacceptable.

Environmental management is generally considered the core component of dengue prevention and control, including clean- up campaigns, regular emptying and cleaning of containers, installation of water supply systems, solid waste management, and urban planning. However, huge investments in infrastructure are needed to increase access to safe and reliable water supplies, to provide solid waste management services, and to dispose of liquid waste. In addition to overall health gains, such provision would have a major effect on vector ecology, although the relationship is not invariably an inverse one. Cost-recovery mechanisms, such as the introduction of metered water, may encourage household collection and storage of roof catchment rainwater that can be harvested at no cost. Although unproven, the installation of community water services in rural townships and villages may be contributing to the rural spread of dengue in Southeast Asia and elsewhere.

At the household and community levels, where most vector control efforts are centered, increasing attention is given to such activities as covering or frequently cleaning water storage vessels, removing discarded food and beverage containers, and storing or disposing of used tires in such a way that they do not collect rainwater. Such tasks would seem to be simple and well suited to engagement by communities, but with a few exceptions, achievements to date have been unspectacular. Nevertheless, such community-based interventions are widely seen as the most promising way of achieving sustainable control through behavior change (Parks and Lloyd 2004 Disease Control Priorities Project)


Text Box: Mosquito lifecycle


life span

Female ---- Average 3 weeks

Male --- 8  10 days

Flight - up to 11km in wind direction  (Usually  1 to 1.5km)

Day biter-  Aedes

Night biter  Culex, Anopheles, Mansoni

After a bloody meal, 100  200 eggs are laid  in 2 to 3 days

  they lay eggs 8 to 10  times in their life. That means ,In 3 weeks  1500 to 2000 eggs are laid

Breeding Places

Aedes - All water tanks, cisterns, barrels, trash containers, empty water in old tires, tins, cans, buckets, drums, bottles, flower vases, air coolers, sun shade of buildings etc

If water gets dried before egg hatches, still it can remain alive up to 1 year

Culex - They thrive in dirty water and also in paddy fields & water logged grass fields

Anopheles -It is seen in clear water of wells, ponds, tanks etc


Main types of Mosquitoes and  the disease that they produce

1)         Culex ………… Filaria & Japanese encephalitis

2)         Anopheles …… Malaria

3)         Aedes aegypti ........ Dengue & Chikungunya

4)         Mansonia …….  Filaria

5)         Armigerous ….. bites between 6 to 7.30pm (non disease spreading)


Its very difficult to control the adult Mosquitoes and therefore control of larva is most important.


Measures to control larva

Environment control 

public involvement is very essential in this method. Identify breeding places & remove them by filling, leveling & drainage. Observing dry day every week is vey important in controlling the Mosquitoes. Adding  salt in stagnant water can reduce Mosquitoes to large extend .Dispose home waste by burial or burning.

 Chemical control

Oil pouring -  diesel, kerosine, crude oil or kitchen waste oil

Pesticides - Spray abate, phenthion (resident's association/Panchayath)

 Biological control

put larva eating fish gappy & gambusia in wells, ponds & fish tank

Other Measures

 Cover vent pipes with mosquito net, cement spaces in between slabs of septic tanks.

Measures to control adult mosquitoes

Residual  spraying (DDT, DHC, Malathion etc)

Space spray (fogging) Malathion, pyretrum etc

Genetic control

Bush clearance

Self protection  - mosquito net, home screening, mosquito repellents etc



1.Centre for Disease control (CDC), Atlanta, USA

2.CD Alert, the Monthly News Letter of National Institute of Communicable Disease, Directorate General of Health Services, Govt. of India,  February 2006, Vol. No.10:No.2.

3.Indian Jornal of Medical Microbiology(IJMM) Conference case

41: J Gynecol Obstet Biol Reprod (Paris). 2006 Oct;35(6):578-583.

5.The Lancet 2006; 368: July 15, 2006

6.Department of Microbiology, Nizam's Institute of Medical Sciences , Hyderabad, India

7.Chikungunya in Mauritius, Seychelles, Mayotte (France) and La Reunion island (France) WHO,March -1-2006

8.Emerging viral diseases of Southeast Asia and the Western Pacific.  Conference     presentations- 2001

9.Chikungunya in La Reunion island (France), WHO, February 17- 2006

10.Chikungunya in La Reunion island (France), Mayotte, Maurice, Seychelles and India WHO March -17 -06

11.Trivandrum Tunes, Monthly News letter of IMA Trivandrum, September 2006










Need for control of mosquitoes

1.     Mosquitoes bite all human beings, from infants to adults, irrespective of the time of the day and render sleepless nights.

2.     It spreads deadly diseases such as Malaria, Dengue fever, Japanese encephalitis, Filaria, Chikungunia and other viral diseases.  Of these malaria, dengue fever and Japanese encephalitis have already caused deaths of millions of people all over the world.  Although death is uncommon with filariasis it causes extreme morbidity. Chikungunia also results in severe morbidity, but deaths are rare.

Life cycle of mosquitoes

 There are over 2500 different species of mosquitoes throughout the world, but four types of mosquitoes spreading diseases are mainly seen in Kerala. They are Culex, Anopheles, Aedes and Mansonia.  A fifth variety known as Armigerus subalbatus which bites but doesn’t spread any disease is also found in our State.

All mosquitoes have one common requirement - they need stagnant/ standing water to complete their life cycle.  This water can range in quality from melted snow water to sewage effluent and it can be in any container imaginable.  The type of water in which the mosquito larvae are found can be an aid to the identification of the species to which it belongs.

There are four stages in the life cycle of a mosquito: egg, larva, pupa and adult.

The female mosquito needs the blood meal to develop her eggs.  Male mosquitoes do not bite - they feed solely on plant nectar. Female mosquitoes can develop several hundred eggs after each blood meal and lay them in or around water. The eggs are attached to one another to form a raft or the individual eggs float on the water.These eggs hatch within 24-48 hours releasing larvae that are commonly called "wrigglers" because you can usually see them wriggling up and down from the surface of the water.  Wrigglers occur in all kinds of standing water, such as; ditches, woodland pools and anything that holds water for more than a week.In about 7-10 days the mosquito life cycle is completed, eggs releasing larvae, larvae changing to pupae and then becoming adult mosquitoes.  The newly emerging mosquito has to stand on still water for a few minutes to dry its wings before it can fly away. That is one reason that mosquitoes don't breed in rapidly moving water such as running brooks and streams or even a pond that has a fountain.

            The feeding habits of mosquitoes are quite unique in that it is only the adult females that bite human beings and other animals. The male mosquitoes feed only on plant juices. Some female mosquitoes prefer to feed on only one type of animal or they may feed on a variety of animals. Female mosquitoes feed on human beings, domesticated animals, such as cattle, horse, goat etc; all types of birds including chicken; all types of wild animals including deer and rabbit. They also feed on snakes, lizards, frogs, and toads.

            Most female mosquitoes have to feed on an animal and get sufficient blood meal before she can develop eggs. If they do not get this blood meal, then they will die without laying viable eggs. However, some species of mosquitoes have developed the means to lay viable eggs without getting a blood meal.

            The flight habits of mosquitoes depend again on the species. Most domestic species remain fairly close to their point of origin while some species are known for their migratory habits. The flight range for females is usually longer than that of males. Many times wind is a factor in the dispersal or migration of mosquitoes. Most mosquitoes stay within one to three kilometers of their source. However, some have been recorded to migrate as far as 12 km from their breeding source.

            The length of life of the adult mosquito usually depends on several factors: temperature, humidity, sex of the mosquito and time of the year. Most males live a very short period, about 8 to10 days; and females live about a month depending on the above factors.

Aedes (A. aegypti) mosquitoes are persistent biters causing pain and attack during daylight hours (not at night). They do not enter dwellings and prefer to bite mammals like humans. Aedes mosquitoes are strong fliers and are known to fly many kilometers from their breeding sources.

Aedes mosquitoes are responsible for the spread of Chikungunia & Dengue Fever

Culex (Cx.Quinquefasciatus, Cx.Pipiens & Cx.Sitiens) is the commonest species found in Kerala. Their bites are painful and they also are persistent biters, but prefer to attack at dusk and after dark and readily enter dwellings for blood meals. Domestic and wild birds are preferred over human beings, cows, and horses. Culex are generally weak fliers and do not move far from source, although they have been known to fly up to three kilometers. Culex usually lives only a few weeks during the warm summer months.

They cause Filaria & Japanese encephalitis

Anopheles (A. Stephensis & A..Fluviatiles) Anopheles mosquitoes enter the house between 5 p.m. and 9.30 p.m. and again in early hours of the morning. They start biting by late evening and the peak of biting activity is at midnight and early hours of morning. They can fly up to several kilometers and they can reach far off places by taking shelter in motor vehicles, ships and aircraft. The average life span of a mosquito is 2-3 weeks. It can be longer in ideal living conditions.

They cause Malaria

Mansonia (M.uniformis) Adults appear to be active only during the summer and autumn months; they can disperse a few kilometers from habitats and readily attack humans and other animals including birds; biting mostly at night but also during the day in or near shelters.

They cause Lymphatic Filariasis

Armigerus subalbatus: They are big black mosquitoes that bite at dusk only but do not cause any diseases

After a bloody meal mosquitoes lay eggs in 2 to 3 days. They lay about 100 to 300 eggs at a time and hence about 1500 to 2500 eggs in its life span. That means one mosquito multiplies to about 2000 in 3 to 4 weeks time. Imagine their explosive multiplication in short   time.


































CULEX: 80% of the mosquito population in Kerala belongs to this group.  They lay eggs in dirty drains, foul smelling and decayed-matter-filled water clogging, drainage spills, septic tanks, dirty wells, ponds and spills from cattle shed.

The species of culex that spread Japanese encephalitis lay eggs in paddy fields and large grass filled pools of water. 


ANOPHELES:   Anopheles mosquitoes breed in clean water collections. Therefore, breeding increases dramatically in the rainy season because many artificial water collections occur. During the rains, water collects in bottles, tins, tender coconut shells, buckets, tyres etc., that are thrown out in the open and these provide ample breeding ground. Also wells, ponds, water tanks, paddy fields etc., act as breeding grounds. Construction sites provide ample breeding places for the mosquito - water on the concrete slabs (used for curing), water collected in tanks, water collected in and around the construction sites owing to blockage of water drains - all these help breeding. It is very important to drain these artificial water collections or to keep them properly covered to prevent breeding.


AEDES:  Flower-pot plates, flower vases, earthen jars for landscape or decorative purposes, and pails left lying around. Some plants are also natural containers for water whenever there is rain. In addition, potted plants with hardened soil can also collect water on the surface of the soil and the Aedes can breed in it. All water containers, gully traps and toilet bowls and anything that can contain water that is left or discarded in the open like coconut shells, tires, egg shell, etc.

If the water dries out in these containers before eggs hatch, they will remain alive up to an year and will hatch when they come in contact with water.


MANSONIA:   They lay eggs on the under surface of the leaves of weeds seen in lagoons and lakes.


Once the adult mosquitoes are hatched and fly into atmosphere it is almost impossible to go after them and destroy.  The best way of mosquito control is to destroy it when it is in the larval state in water.  For this the first step is to do the mapping of the larval sources which have been described earlier. 

Vector control can be achieved mainly by four ways. 

1.                              Environmental control (Mechanical)

2.                              Chemical

3.                              Biological

4.                              Genetic


Environmental Control (Mechanical)

1.                  Identify the water clogging areas and do filling, leveling or making way for draining the water which ever is appropriate.

2.                  Put salt if the water collections are small.

3.                  Dry day observation – the premises of households and institutions have to be checked once a week and any collection of water should be searched for and removed.

4.                  Burn household wastes in pits or dispose appropriately.

5.                  Search for any space in between septic tank slabs and it should be sealed with cement.

6.                  Mosquito netting of the vent of the pipe from septic tanks.

7.                  Bush clearance in the premises of houses and institutions.


I. Using oils:

Apply diesel / crude oil / kerosene / kitchen waste oil into stagnant water collections around houses and institutions. The larvae will die because it cannot breathe due to oil blocking the respiratory passage.

II. Impregnates:

Clothing and bed nets can be impregnated; clothing with benzyl benzoate and bed nets with pyrethroids which will kill mosquitoes.

III. Repellents: 

Repellents like lemon grass oil, eucalypts oil, odomos, etc. can be applied on the exposed parts of the body that will keep the mosquitoes away. 

Mosquito coils, mats and vaporizers can also be used.

IV. Insecticides:

a.                  Residual treatments: Chlorinated hydrocarbons like D.D.T. (Dichloro Diphenyl Trichloro ethane), B.H.C. (Benzene Hexa Chloride) and Organo phosphates like Malathion solutions can be sprayed on the walls of houses and other places where the mosquitoes commonly sit.  This should be done once a month and mosquitoes sitting on it will be killed.

b.                  Interior space treatment:  Applied in the form of small droplets or powder inside rooms of houses.  Chemicals used are lime sulfur, Synthetic D.D.T. and B.H.C and plan products like pyrethrum, ocimum (Thulasi) and neem (Vepu).  This is sprayed using hand pump.  The disadvantage of this is that the action is short lived and it has to be done daily.  But lime sulfur DDT and BHC are toxic and can not be used daily.  But the plant products can be used daily.  This is very useful during outbreaks of epidemic. 

c.                   Larvicidal spray:  Larvicides like Malathion, Fenthion, Temethos, etc. can be sprayed in water cloggings which will kill the larvae.  This should be done once a week and it is very effective in controlling mosquitoes. 


V.  Fumigants:

1.   Fumigation with camphor in the evenings can be done in the houses. 

2.   Fumigation with pyerthroids (Cyflotherin 10% alpha pyro methane 5% concentration) pyerthroids (Cyflotherin 10% alpha pyro methane 5% concentration) Hydrogen Cyanide and Sulphur dioxide can be done in institutions.

5.   Application of space spray (Fogging) using malathion should be done in public places.     Malathion 5 parts added to 95 parts diesel has to be fogged at 5 to 8 km/hr. speed and 150 liters per hour has to be used.

4.   Space spray through helicopter on selected areas.


Biological:  - Using a living organism for the destruction of another living organism.


1.                  Introduce larva eating fish like Gambusia, Gappi, Topminnows, and Poe Celia into fish tanks, wells and ponds. These fish eat larvae while ornamental fish do not.  Poe Celia can breed in polluted water – Viviparous and they are good for culex control.

2.                  Introduce bacteria like thurigensis and bacillus spharicus in water collections which will kill the larvae.

3.                  Using tiny water creatures called mesocyclops which will eat early stages of mosquito. 


I.    Chemosterilants:

Mosquitoes can be effectively controlled by using some chemosterilants (chemicals are sprayed on places were mosquitoes sit and cause male sterility) especially alkalating agents like tepa 0.1% and metapa 0.06% and alpholate 0.6%.

II.   Irradiating males:

Another method is the radio sterilization of males with gamma irradiation causing a distortion of chromosomes and there by making them sterile.  Large number of such sterile males is introduced into high density mosquito population areas thereby producing unfertile eggs. 

III. Cytoplasmic incompatibility:

Normal offspring was prevented in crosses between alien strains (of different geographical origin) owing to the incompatible factors in the egg cytoplasm.

The sperms from the males enter the egg cell and even induce embryo formation but the sperm nucleus is prevented from uniting with the egg nucleolus by plasma genes in the cytoplasm.



            Poisonous insecticides are diluted with hold or liquid carriers.

a)                                                      Dust mixed with talc or phyrophyllite 50%

b)                                                     Solution – dissolved in mineral oils like kerosene.

c)                                                      Emulsifiers – dissolving in organic solvents like xylene, and suitable emulsifiers are added like soft soap.

d)                                                     Suspension.  Very commonly used.  Concentrated insecticides are mixed with inert dusts and to the mixture are added small quantities of detergents or emulsifiers like soft soap.

Strength – 25%, 50%, 75%

Concentration available      75        = 15

Concentration required       5

i.e.  1:15

Criteria for choosing the technique


1.                              Effectiveness in the context

2.                              Time consumption

3.                              Cost effectiveness

4.                              Easiness of execution.


Criteria weights




Public Places





Time consumption




Cost effectiveness




Easiness of execution





who should use what?


Italics and underlined are for local bodies to do

1.                  Dry day observation

2.                  Salting

3.                  Filling/ levelling/ drainage

4.                  Sealing septic tanks & netting vents

5.                  Bush clearance

6.                  Burn house wastes

7.                  Interior residual treatment (DDT, BHC, Malathion) Once a month

8.                  Interior space treatment (pyrethrum) during epidemics

9.                  Spray larvicides (Malathion, Fenthion, Abate temephos) Weekly once

10.              Apply diesel/crude oil/kerosene/kitchen waste oil on water clogging

11.              Application of repellents (Lemon grass oil, Eucalyptus oil, Odomos) mosquito coils & mats, vapourizers

12.              Application of impregnates (Mosquito nets with Pyrethroids)

13.              Larvivorous fish (gappy, gambusia, topminnows, poe celia) in fish tanks & wells

14.              Fumigation at households (camphor)


Italics and underlined are for local bodies to do

1.                  Dry day observation

2.                  Salting

3.                  Filling/ levelling/ drainage

4.                  Sealing septic tanks & netting vents

5.                  Bush clearance

6.                  Interior residual treatment (DDT, BHC, Malathion) Once a month

7.                  Interior space treatment (pyrethrum) during epidemics

8.                  Spray larvicides (Malathion, Fenthion, Abate temephos) Weekly once

9.                  Apply diesel/crude oil/kerosene/kitchen waste oil on  water clogging

10.              Application of repellents (Lemon grass oil, Eucalyptus oil, Odomos) mosquito coils & mats, vapourizers

11.              larvivorous fish (gappy, gambusia, topminnows) in fish tanks & wells

12.              Fumigation with pyerthroids, hydrogen cyanide, sulphur dioxide, methyl bromide


Public places

Local bodies to act

1.                  Filling/ levelling/ drainage

2.                  Bush clearance

3.                  Proper waste disposal

4.                  Spray larvicides (Malathion, Fenthion, Abate temephos)

5.                  Introduce larvivorous fish (Gambusia, Gappi, Topminnows) into wells and ponds

6.                  Mesocyclops eat mosquitoe’s early stages

7.                  Using bacteria called thurigensiss which is larvicidal

8.                  Application of chemosterilants (Tepa 0.1%, Metapa 0.6%

9.                  Gamma irradiation of male mosquitoes

10.              Application of space spray, called fogging (Malathion)

Priority of Action

1.                  Elimination of breeding places

2.                  Larvicidal spraying once a week

3.                  Residual spraying once a month

4.                  Fogging

5.                  Bush clearance

During epidemics fogging needs highest priority.

 Society Role

Resident’s Associations/NGO’s/NSS/Other organizations

l                  Form volunteer squads & make house to house visits and destroy all breeding places

l                  Leave no house unchecked

l                  Role of councilors, Panchayath members & Residents Assn. are valuable

Government role



l                  Health and Local Administration together should

1.                  Give technical guidance

2.                  Oversee operations

l                  Source reduction activities

l                  Spraying insecticides & larvicides

l                  Fogging

l                  Vector survey

3.                  Regular surveillance


l                  Emergency Control

l                                          Corporation/Panchayath should step into fill the gaps in effectiveness

l                                          Emergency fogging with Malathion (1 part of technically pure Malathion in 19 parts of Diesel at a speed of 5-8 km/hr and 0.5 lr. Per hector)

l                                          Space spraying with pyrethrum (least harmful to man) 3%concentrate 15cc per 1000 cubic feet and pyerthroids (Cyflotherin 10% alpha pyro methane 5% concentration) on hospitals, schools, colleges, theatres, offices, etc.

l                                          Residual spraying of insecticides

l                                          Source reduction

l                                          Application of insecticides at breeding places

l                  Long term Control

l                                          Stakeholders handle their own assigned duties

l                                          Follow up of source reduction measures

l                                          Periodical spraying with insecticides

l                                          Periodical fogging at lease once in a fortnight

l                                          Application of suitable insecticides through helicopter




What is Chikungunya?

Chikungunya fever is a viral disease transmitted to humans by the bite of infected mosquitoes. It is a preventable and self limiting disease.

The classical symptoms are fever, rash and joint pain.

What is the current status of the disease?

The virus is called Alphavirus (Species – Chikungunya).

It was first isolated from the blood of a febrile patient in Tanzania in 1953, and has since been identified repeatedly in west, central and southern Africa and many areas of Asia, and has been cited as the cause of numerous human epidemics in those areas since that time.

CHIKV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on a person infected with CHIKV. Infected mosquitoes can then spread the virus to other humans when they bite.
Aedes aegypti, a household container breeder and aggressive daytime biter which is attracted to humans, is the primary vector of CHIKV to humans.

Outbreaks typically involve several hundreds or thousands of cases but deaths are rarely encountered.

Present epidemic
Since the beginning of the epidemic in March 2005, 2, 66 000 cases of chikungunya fever are estimated to have occurred on the island of Reunion, a French overseas territory. The islands of the southwest Indian Ocean (including Comoros, Madagascar, Mauritius, Mayotte, and Seychelles), and several states of India have been affected by chikungunya epidemics in 2005-2006.

Chikungunya virus is no stranger to the Indian sub-continent. Since its first isolation in Calcutta, in 1963, there have been several reports of chikungunya virus infection in different parts of India. The last outbreak of chikungunya virus infection occurred in India in 1971. Recent reports of large scale outbreaks of fever caused by chikungunya virus infection in several parts of Southern India have estimated that over 1,80,000 cases have occurred in India since December 2005.

Chikungunya infection in pregnancy: Virus can spread to the baby in the uterus from an infected mother. What are the symptoms of the disease?

The disease starts 2-3 days (range 1-12days) after bite of an infected mosquito who injects the virus to the blood of man. The symptoms are Fever which lasts for 2 – 3 days usually. The temperature can be very high with occasional chills. There would be pain in the joints, usually affecting hands, wrists, ankles and feet, with lesser involvement of larger joints. Muscle ache may also occur. Mild joint symptoms will last only a few weeks. More severe cases takes months to get well. Patients can also have rashes on the skin. Headache and redness of eyes also can occur. The disease could be rarely dangerous in those who are ill otherwise or have low resistance power (very old/ newborn).

Outbreaks typically result in several hundreds or thousands of cases but deaths are rarely encountered.


Some blood tests are available for confirming diagnosis. However these need not be done for treatment purpose and is required only for research and planning purposes.


The disease is usually selflimiting & will resolve with time. Rest and proper nutrition is important. Drugs are given for fever, pain and fluids if there is dehydration. Patients should be protected from further mosquito exposure (staying indoors and/or under a mosquito net during the first few days of illness) so that they don’t cause further spread of disease.


 The best way to avoid CHIKV infection is to prevent mosquito bites. There is no vaccine or preventive drug.

·                     Use insect repellents.

·                     Wear long sleeves and pants.

·                      Have secure screens on windows and doors to keep mosquitoes out.

·                     Get rid of mosquito breeding sites by emptying standing water from flowerpots, buckets and barrels. Avoid water collection sources in the vicinity of hoses like tyres, coconut shells, plastic cups etc. Keep the premises absolutely dry on at least one day in a week.

·                     A person with chikungunya fever should limit their exposure to mosquito bites in order to avoid further spreading the infection. The person should stay indoors or under a mosquito net.