Chikungunya an update

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CHIKUNGUNYA an update

• Dr.T.V.Rao MD

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What is Chikungunya

• Manifest with Crippling Arthritic disease of
  sudden onset.
• Name is derived from Swahili Chikungunya
  meaning that which bends up
• Virus isolated in 1953 from serum and Aedes
  mosquitoes and Culex spp

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What is Chikungunya?

• Chikungunya is a virus that is transmitted from
  human to human mainly by infected Aedes
  albopictus and Aedes aegypti mosquitoes (later
  referred to as Aedes mosquitoes) acting as the
  disease-carrying vector
• Chikungunya causes sudden onset of high fever,
  severe joint pain, muscle pain and headache
• As no vaccine or medication is currently
  available to prevent or cure the infection,
  control of Chikungunya involves vector control
  measures and encouraging people to avoid mosquito
  bites

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Emerging disease

• Change in vector distribution due to global
  warming/ changing weather patterns
• Endemicity to epidemic

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History

• Isolated in Aedes aegypti mosquitoes and man in
  1952 in Tanzania
• Appeared in India in 1963
• Major epidemic outbreaks in Calcutta, madras and
  other areas
• Manifested with Major epidemics till 1973

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Current distribution of Chikungunya
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Chikungunya risk zones

• Outbreaks of Chikungunya virus are usually found
  in
• Africa
• Southeast Asia
• Indian subcontinent and islands in the Indian
  Ocean

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What is important in Chikungunya?

• Togaviridae alphavirus
• RNA virus able to evolve rapidly and expand
  vector
• Endemic in Africa and Asia, especially India
• Vectored by Aedes species (albopictus, aegypti)

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Chikungunya Virus

• Family Togaviridae
• Genus - Alpha virus
• Chikungunya viral infection manifests with
  febrile illness

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Chikungunya Virus

• Enveloped virions spherical, 60 to 70 nm in
  diameter positive-sense, single-stranded RNA
  genome, ca. 11.7 kilobases long.

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Chikungunya Virus

• Two changes to the structure of E1 Makes the
  virus more likely to enter mosquito cells and
  replicate after the insect has fed on the blood
  of an infected person.

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EPIDEMIOLOGICAL TRIAD
AGENT
VECTOR
HOST
ENVIRONMENT
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Epidemics of Chikungunya

• Large epidemics were recognized in Transvaal of
  South Africa, Zambia, India and South east Asia,
  Philippines.

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Out Breaks of Chikungunya

• Out breaks occur during rainy season with
  increasing densities of Aedes aegypti mosquito
• Mosquitos bites infect the Humans
• Laboratory acquired infection can also occur

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Recent History

• 2005-2007 epidemic in India 1.4 million infected
  in 2006, 56K infected 2007 Cases continuing to be
  reported every month
• Outbreak in Italy in 2007

OMG!
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Natural cycle

• Aedes mosquitoes
• Feed in daytime
• Breed in stagnant water
• Small puddle
• Reservoir
• Primates
• Transient viremia 3-7 days

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Cycle of Infection
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Other vectors

• Both Ae. aegypti and Ae. albopictus have been
  implicated in large outbreaks of Chikungunya.
  Whereas Ae. aegypti is confined within the
  tropics and sub-tropics, Ae. albopictus also
  occurs in temperate and even cold temperate
  regions. In recent decades Ae. albopictus has
  spread from Asia to become established in areas
  of Africa, Europe and the Americas.
• In Africa several other mosquito vectors have
  been implicated in disease transmission,
  including species of the A. furcifer-taylori
  group and A. luteocephalus. There is evidence
  that some animals, including non-primates, may
  act as reservoirs

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Clinical features

• Incubation 3 12 days
• Fever may rise to 1030c to 1040c with rigors
• Viremia lead to fever.
• Fever leads to release of large amount of
  Interferons

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Clinical events in Chikungunya
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Clinical manifestations

• Fever,
• Crippling Joint pains
• Lymphadenopathy
• Conjunctivitis
• A Maculopapular rash
• May lead to hemorrhagic manifestations,
• Fever is biphasic with remission after 1 - 6 days
  of fever.

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Clinical disease

• Significant morbidity, minimal mortality
• Fever, rash, nausea, fatigue, arthralgia lasting
  days to weeks
• Arthritis may be long-term sequellae

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How some Indian patients presented

• In India but not in Africa, patients presented
  with Inguinal lymphadenopathy and red swollen
  ears, and are observed as part of clinical
  picture.

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Diagnosis of Chikungunya ( WHO )

• Several methods can be used for diagnosis.
  Serological tests, such as enzyme-linked
  immunosorbent assays (ELISA), may confirm the
  presence of IgM and IgG anti-Chikungunya
  antibodies. IgM antibody levels are highest three
  to five weeks after the onset of illness and
  persist for about two months. The virus may be
  isolated from the blood during the first few days
  of infection. Various reverse transcriptasepolyme
  rase chain reaction (RTPCR) methods are
  available but are of variable sensitivity. Some
  are suited to clinical diagnosis. RTPCR products
  from clinical samples may also be used for
  genotyping of the virus, allowing comparisons
  with virus samples from various geographical
  sources.

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Diagnosis

• The primary differential diagnosis of
  Chikungunya, should be made from Dengue, and
  ONyong nyong fevers
• Chikungunya manifest with Myalgia rather than
  Arthritis.

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Laboratory criteria

• Laboratory criteria at least one of the
  following tests in the acute phase
• Virus isolation
• Presence of viral RNA by RT-PCR
• Presence of virus specific IgM/IgG antibodies in
  single serum sample collected
• Seroconversion to virus-specific antibodies in
  samples collected at least one to three weeks
  apart

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Microbiological Diagnosis

• Isolation of Virus
• Amplification of Nucleic acid
• Routine Diagnosis with serology
• Detection of IgM antibody provides a
  specific and reliable means for early diagnosis
• ELISA and Dot blotting methods are used

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Treatment

• Chikungunya fever is not a life threatening
  infection. Symptomatic treatment for mitigating
  pain and fever using anti-inflammatory drugs
  along with rest usually suffices. While recovery
  from Chikungunya is the expected outcome,
  convalescence can be prolonged (up to a year or
  more), and persistent joint pain may require
  analgesic (pain medication) and long-term
  anti-inflammatory therapy

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CDC guidelines for Management of Chikungunya

• There is no vaccine or specific antiviral
  treatment currently available for Chikungunya
  fever. Treatment is symptomatic and can include
  rest, fluids, and medicines to relieve symptoms
  of fever and aching such as ibuprofen, naproxen,
  acetaminophen, or paracetamol. Aspirin should be
  avoided. Infected persons should be protected
  from further mosquito exposure (staying indoors
  in areas with screens and/or under a mosquito
  net) during the first few days of the illness so
  they can not contribute to the transmission cycle.

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Vaccines for Chikungunya

• An experimental live attenuated vaccine ( TSI
  GSD 218 ) enveloped by passage of an isolate
  from Thailand in MRC 5 cell.
• At present used in some laboratory workers who
  can be protected,
  Vaccine produces neutralizing
  antibodies

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Preventive measures Seeking protection from
Chikungunya

• When staying in affected areas
• Wear long-sleeved shirts and long trousers
• Use mosquito repellents, coils or other devices
  that will help fend off mosquitoes
• If possible, sleep under bed nets pre-treated
  with insecticides
• If possible, set the air-conditioning to a low
  temperature at night mosquitoes do not like
  cold temperatures
• Pregnant women, children under 12 years old, and
  people with immune disorders or severe chronic
  illnesses should be given personalised advice

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How Chikungunya can be Prevented

• There is neither Chikungunya virus vaccine nor
  drugs are available to cure the infection. 
  Prevention, therefore, centres on avoiding
  mosquito bites.  Eliminating mosquito breeding
  sites is another key prevention measure.   To
  prevent mosquito bites, do the following
• Use mosquito repellents on skin and clothing
• When indoors, stay in well-screened areas.   Use
  bed nets if sleeping in areas that are not
  screened or air-conditioned.
• When working outdoors during day times, wear
  long-sleeved shirts and long pants to avoid
  mosquito bite.
•  

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Breeding places of Aedes mosquitostry to
eliminate .
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Reducing the spread of the vector

• The vector lives in a number of different
  habitats
• The presence of water is of great importance for
  mosquitoes breeding as their eggs require water
  in order to develop into adult mosquitoes

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Use of larvicides

• (i)  Where the water cannot be removed but used
  for cattle or other purposes, Temephos can be
  used once a week at a dose of 1 ppm (parts per
  million).
• (ii) Pyrethrum extract (0.1 ready-to-use
  emulsion) can be sprayed in rooms (not outside)
  to kill the adult mosquitoes hiding in the house.

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Severity of Indian Epidemic

• Till 10 October 2006, 151 districts of eight
  states/provinces of India have been affected by
  Chikungunya fever. The affected states are Andhra
  Pradesh, Andaman Nicobar Islands, Tamil Nadu,
  Karnataka, Maharashtra, Gujarat, Madhya Pradesh,
  Kerala and Delhi.
• More than 1.25 million cases have been reported
  from the country with 752,245 cases from
  Karnataka and 258,998 from Maharashtra provinces.
  In some areas attack rates have reached up to
  45.

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Current Research on Chikungunya

• Researchers at the Institute Pasteur have managed
  to retrace the origin and evolution of the
  Chikungunya virus in the Indian Ocean through
  complete sequencing of the genome of six viral
  strains isolated from patients from Reunion
  Island and the Seychelles, as well as through
  partial sequencing of the viral protein E1 from
  127 patients from the Indian Ocean islands
  (Reunion, Madagascar, Seychelles, Mauritius,
  Mayotte). Their study, published in PLoS
  Medicine, opens up new research paths that should
  help to explain the magnitude of the epidemic and
  the occurrence of severe forms of the disease.

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