Crimean-Congo hemorrhagic fever (CCHF) - Molecular diagnosis (RT-PCR).
The Crimean-Congo hemorrhagic fever (CCHF: Crimean-Congo Hemorrhagic Fever) is caused by a virus with the same name (CCHFV). This virus is included in the Bunyaviridae, genus Nairovirus family, and is characterized by having a genome of single stranded RNA (ss RNA) of negative sign, divided into three segments: L, M and S. The (large, Large) L segment encodes RNA viral polymerase the; M (medium) segment encodes the surface glycoproteins G1 and G2; and segment S (small, Small) encodes the nucleocapsid protein (N). This virus has a genetic variability which has made consider the existence of six phylogenetic branches: I, including strains of West Africa (Senegal); II, with the strains of Democratic Republic of Congo (and Uganda); III, with strains of Southern Africa, West and East (South Africa, Nigeria, Sudan); IV, with Asian and Middle Eastern strains (China, Pakistan, Iran, Iraq, Oman, Uzbekistan and Tajikistan); V, with European strains (Russia, Turkey, Kosovo); and VI, with the Greek AP92 strain isolated from the tick Ripicephalus bursa.
The first clinical descriptions of this disease occurred in Crimea (1944) when 200 Soviet soldiers in this region were affected during World War II. The virus was identified in 1967, and was found to be similar to a virus previously described in Congo (1956), so virus Crimean-Congo hemorrhagic fever was called. The virus has a wide geographical distribution: Africa, Asia, Middle East, Eastern Europe and Southern Europe. Southern Europe, the Balkan region is considered an endemic region with the appearance of sporadic cases and outbreaks annually. In Spain we had a first case recently with a secondary case in a toilet.
Clinical manifestations: have differentiated four distinct phases in the course of the disease: incubation period (3 to 7 days); prehemorrágica phase (4-5 days); hemorrhagic phase (2 to 3 days); and convalescent (10 to 20 days). Prehemorrágica in the initial phase, patients develop a fever of sudden onset, high fever of 39 to 41 ° C, chills, severe headache, malaise, facial flushing, myalgia, arthralgia, dizziness, nausea, ..., and the the most striking of hemorrhagic disease stage, and what is called "hemorrhagic fever" are the cutaneous and mucosal bleeding manifestations (cutaneous petechiae, epistaxis, bruising, hematemesis, bloody diarrhea, ...). The presence of visceral hemorrhage is considered a sign of poor prognosis. They have also been reported mild cases in which there has been no type of hemorrhagic phenomenon. Mortality has indicated that it can reach 30% with wide margins (5 to 60%).
Transmission mechanisms: the virus has as a reservoir for various types of animals (sheep, goats, cattle, ...) and infected ticks. Ticks are the main transmission mechanism. It noted the tick Hyalomma spp, the main vector, but the virus has been found in up to 31 different species of ticks five different genres both group hard ticks (Ixodidae:.. Hyalomma spp, Rhipicephalus spp. , Dermacentor spp, Haemaphysalis spp), as the soft ticks (Argasididae:... Ornithodorus spp), with prevalence of infections in different studies between 0.2 and 33%.
During disease virus found in biological fluids of the patient (blood, saliva, respiratory secretions, urine, ...), so it is common human transmission. This form of inter - human transmission has been found frequently in health workers who treat patients but also family members who have been in contact with the patient at home.
Another method of transmission is through contact with infected animals or their tissues, so that contact with blood or tissues of viremic cattle should be avoided. In addition, there are occasional infections such as those due to the ingestion of raw meat products from infected animals (eg., Ingestion of raw liver in Sudan).
For the foregoing reasons, they are considered preferential risk groups pastoralists, farmers, veterinarians, health workers and soldiers.
Antiviral treatment: Ribavirin has been used, although the mechanism of action against the virus is unknown and there are no randomized clinical trials supporting its usefulness, but effects have been observed in observational studies. When used it should be given at the beginning of the disease.
Protective measures: to prevent inter - human transmission is recommended mask, goggles, double pair of gloves and waterproof coat.
Possible methods of diagnosis:
- Molecular diagnosis: currently the recommended method by RT-PCR tests simple, nested RT-PCR (nested) RT-PCR or real - time. The advantage of this method lies in its speed and the lowest degree of risk for technical staff, since the samples are inactivated to purify RNA. The most important to consider for molecular diagnosis problem is the high genetic variability of this virus, so primers (primers) are used capable of binding sequences existing strains in the region where it is suspected that has occurred the infection (see previous comments on the six phylogenetic branches described).
- Viral antigen by EIA: not currently used, by not available enzyme immunoassay diagnostic equipment where needed in addition to requiring the risk to staff when handling samples.
- Detection antibodies (serological diagnosis) detecting IgM antibodies to early disease is usually performed in many places are not available molecular methods. Detection of IgG antibodies is usually negative when the patient is in the prehemorrágica or hemorrhagic phase.
- Culture isolation of the virus: virus isolation is possible, but usually not recommended by the risks of exposure for technical staff.
Tests in IVAMI:
- Molecular diagnosis (RT-PCR) in sample obtained at the initial stage of the disease.
- Molecular diagnosis of infection in ticks by RT-PCR.
- Clinical diagnosis of diseased or contacts: whole blood or serum separated from the blood, collected in sealed tube and protected by placing within a second outer plastic tube.
- Detecting infection in ticks: ticks captured.
Preservation and shipment of sample:
- Refrigerated (preferred) for less than 2 days.
- Frozen: over 2 days.
Delivery time :
- Molecular diagnosis: less than 24 hours.
Cost of the test:
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