Chikungunya virus (Alphavirus, Togaviridae) (Arbovirus: Arthropod Borne Virus): Type specific antibodies specific by neutralization; Molecular diagnosis (RT-PCR and sequencing).

Information 30-12-2014.

Microbiological-clinical information

The producer of Chikungunya fever virus is an arbovirus. This epidemiological term corresponds to the initials of Arthropod Borne Virus, ie arthropod - borne viruses. There are many arthropod - borne viruses, families and genera belonging to very different viruses.

Family Flaviviridae - Genus Flavivirus.
Togaviridae family - Genus Alphavirus.
Bunyaviridae family - Genres Phlebovirus and Bunyavirus.
Family Reoviridae - Gender Orbivirus.
Family Rhabdoviridae -

Alphavirus (family Togaviridae)

These viruses are a large group, all arthropod borne, whose characteristics being covered with RNA viruses ss (ssRNA).

Many of them produce asymptomatic infections, and others lead to a disease whose clinical characteristics are variable and can lead to a fever or not accompanied by rash or a serious condition that can be life threatening as is encephalitis or fever hemorrhagic.

Alphavirus leading producers of human diseases, their arthropod vectors and their preferred places of endemicity are:

Equine Encephalitis virus (EEE: Equine Encephalitis Eastern): mosquitoes, North America. Its natural hosts are birds and rodents and their main transmitters in the US ornithophilic are mosquitoes, which keep the reservoir transmitting between birds and rodents such as Culiseta melanua transmitting in Eastern US; Culex spp. in Mexico, Central and South America to Argentina. Less restrictive as mosquitoes Aedes spp. and Coquilletidia spp. transmitted to humans and horses. There is little overlap with WEE EEE in its US distribution However, EEE and WEE are enzootic in Central and South America

equine encephalitis virus West (WEE: Western Equine Encephalitis): mosquitoes, North America.

Virus O'Nyong-Nyong: mosquitoes, Africa.

Sindbis Virus: mosquitoes, universal.

Semliki forest virus.

virus Venezuelan equine encephalitis (VEE: Equine Encephalitis Venezuelan): mosquitoes, Central and South America. It is a complex group of antigenic subtypes virus 6 (I-VI). Subtypes I and III differ in IAB to IF and IIIA to IIIC. There are some variations such as Everglades virus, found in Florida, classified as subtype IC IAB or VEE, and virus Bijou (Bijou virus Bridge) bridge in Colorado (USA), classified as IIIB VEE subtype.

Chikungunya Virus:

The virus, first detected in 1953 in the town of Newala Swahili in Tanzania (Africa) district, Chikungunya fever causes a self - limiting febrile viral disease that has caused outbreaks in Africa and Southeast Asia. He recently caused outbreaks in Western countries in temperate zones around the world, including Europe and the US It is transmitted by mosquitoes Aedes aegypti and Aedes albopictus. Its clinical manifestations include high fever, joint pain, rash, headache and myalgia. Joint pain can last for months or years and may progress to chronic joint pain. Since 2004, this virus has caused outbreaks in Asia and Africa, affecting more than 2 million people. In Spain there Aedes albopictus in all provinces of the east, from Girona to Murcia, and cases have been detected in the Balearic Islands, Castilla La Mancha, Catalonia, Madrid, Extremadura and Galicia.

Chikungunya virus epidemiology

This virus is transmitted by the bite of Aedes mosquitoes diurnal (A. aegypti and A. albopictus). The virus is maintained in nature between people, animals and mosquitoes. People are the main reservoirs during epidemics. In interepidemic periods, the virus remains in a wild forest cycle between primates, monkeys, and mosquitoes such as Aedes furcifer sylvan, A. taylori luteocephalus A., A. A. africanus or neoafricanus. The sylvatic cycle has not been found outside Africa. In Asia, the virus remains in an urban cycle that includes humans and Aedes aegypti, remains unknown how interepidemic periods. Unlike what happens with Dengue and Aedes aegypti to chikungunya it has not been shown transovarial transmission in mosquitoes. The ability to infect the mosquito species Aedes albopictus, has been linked to a mutation in the E1 glycoprotein, which changes an alanine to valine at position 226, causing him to lose the requirement of cholesterol for replication, so it acquires ability to replicate in other mosquito species lacking cholesterol as Aedes albopictus. This has opened the possibility that the virus out of the tropics and can be transmitted by mosquitoes found in temperate zones.

Imported cases have been reported in the US, Caribbean Islands, United Kingdom, France, Germany, Sweden, Portugal, Spain, etc. In U.S.A. imported cases have been found since 2006 (1.938 cases until December 2014 in 47 US states and two US territories, Puerto Rico and the Virgin Islands). In addition , a first case of indigenous transmission described in a person who had not traveled outside the US in July 2014, and until December 2014 have been reported 11 indigenous cases, all in Florida. In addition , 3,402 indigenous cases were reported in 86 cases Puerto Rico and the Virgin Islands.

Clinical manifestations of Chikungunya virus infection

Chikungunya virus infection has some clinical manifestations that overlaps with other viral infections (fever, rash and polyarthritis), as with dengue fever. Both infections are transmitted by the same mosquito.

Chikungunya fever is a self - limiting disease, but there are some cases complications in patients with cardiovascular diseases, respiratory or neurological base. In infants, the elderly and immunocompromised, some with fatal end. Complications found cases of hepatitis, meningoencephalitis, pneumonias and bullous dermatitis. Unlike other alphavirus species it is not neurovirulence, but there have been reports of neurological involvement in epidemics India, encephalitis, myelitis, neuropathies, seizures, abnormal cerebrospinal fluid, flaccid paralysis, peripheral neuropathy and syndrome Guillain-Barré .

Unlike what happens with Dengue virus infection, hemorrhagic manifestations are rare, and when there are slight (epistaxis, gingival bleeding, subconjunctival hemorrhage, petechiae and purpuric rash).

Typically , patients have high fever, pharyngitis, conjunctivitis and photophobia. In some rare cases there are cervical or generalized lymphadenopathy. The usually polyarticular arthralgias and migratory and affects small joints of hands, wrists and ankles and less frequently larger joints such as the knee and shoulder. Patients may present with skin manifestations characterized by facial redness and chest, followed by an erythematous maculopapular rash diffuse in the trunk and extremities, which sometimes affects palms and soles of the feet. In some outbreaks they have been found neurological manifestations characterized by mental disturbance, headache, seizures, motor dysfunction and sensory abnormalities. Other rare presentations include cases of rheumatoid arthritis, neuroretinitis, uveitis, deafness, myocarditis and cardiomyopathy.

There is no antiviral treatment for Chikungunya fever. Mitigation measures to consider are: hydration, control the hemodynamic status, and antipyretics. In case of severe arthralgia may be administered non-steroidal anti - inflammatory (when you exclude Dengue). No steroids, nor any of the available antivirals are recommended.
As preventive measures
it is recommended that travelers to endemic areas use mosquito repellent, wear long sleeves and long pants, and reside in homes with mosquito netting. Patients with suspected infection should be avoided during the first week of infection contact with mosquitoes, to prevent local transmission of the disease.

Microbiological tests recommended for diagnosis of Chikungunya virus infection

Diagnosis can be made by the following tests:

• IgM antibodies by ELISA. IgM antibodies may appear when viremia ceases, at 5 to 7 days of clinical manifestations have been initiated, and remain positive for 3 to 6 months.
• IgG antibodies by ELISA. IgG antibodies appear within 7 to 10 days and may remain several months. To confirm a case by IgG antibodies requires demonstrate seroconversion.
• Virus isolation in culture. It can be isolated during the first 3 days of clinical manifestations, when there
is viremia, blood from the patient.
• Molecular tests. The RT-PCR test to detect viral RNA during the first 7 or 8 days of the disease, from whole blood, plasma or serum.

Tests in IVAMI

Molecular tests: RT-PCR to detect viral genome with two RT-PCR for E2 and NS4 genomic regions, recommended in the first 7 to 8 days of onset of disease.
• I DENTIFICATION: identification confirmation by sequencing of amplicons obtained positive RT-PCR test.

Molecular tests (RT-PCR)

• whole blood collected with EDTA (5 mL), extracted in the first 7 or 8 days of the disease.
• Plasma or serum (1 mL), extracted in the first 7 or 8 days of the disease.
• LCR- Cerebrospinal fluid (the possible; recommended at least 1 mL) when there neurological manifestations.
• Biopsy central nervous system in case of encephalitis.

Delivery of results

• RT-PCR: 48 hours.
• Identification sequencing: 72 hours.

Preservation and sample shipping

• Refrigerated (preferred) for less than 2 days.
• Frozen: over 2 days.