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CRIMEAN-CONGO
HAEMORRHAGIC FEVER (CCHF)
INTRODUCTION :
Haemorrhagic fever cover a wide
field in medicine (infectious and non infectious) that cause fever associated
with fever. The term viral haemorrhagic fever is restricted to some groups of RNA viruses in which the fever
is associated with significant bleeding tendency in addition to the other
features. These groups and diseases caused by them is shown in the table below.
Crimean-Congo
haemorrhagic fever:
Is the only type of viral haemorrhagic fever that was present in Iraq (the
early cases were reported in late seventies and subsequent cases were reported
in eighties and early nineties of last century, then disappeared till now), but
awareness of the presence of such a disease here and there in our country is still
important.
HISTORY:
During
the summers of 1944 and 1945 over 200 cases of a severe, acute, febrile illness
with marked hemorrhagic manifestations occurred in the USSR in the Western
Crimea. Many of the cases were among troops of the Soviet Union. Virus was
isolated from blood samples of patients with acute disease and from the tick
Hyalomma. It was later realized that a similar disease had been known for many
years in other areas of the USSR, particularly Central Asian republics, and the
same syndrome has since been described in areas bordering the Black and Caspian
Seas and Bulgaria and former Yugoslavia. In 1969, it was shown that the virus
causing CCHF was identical to the virus named Congo which had been isolated in
1956 from the blood of a febrile child in Zaire. This virus is widely spread in
East and West Africa. More recently, CCHF or antibody to it, has been shown to
have appeared in Dubai, Iraq, South Africa, Pakistan, Greece, Turkey, Albania,
Afghanistan, and India. Geographical variation in virulence has been observed,
for example, the disease in Africa, where haemorrhagic phenomena and deaths are
only rarely reported, does not seem to be as virulent as in Asia. Probably
because CCIHF is associated with severe haemorrhagic features, secondary cases
are relatively common. In an outbreak in Saudi Arabia, one case resuscitated in
an accident and emergency unit gave rise to seven secondary cases. In 1967,
five laboratory-acquired cases were recognized. Hospital-associated outbreaks
were described in Pakistan in 1976 and in Dubai in 1980. In November 1996, 15
cases of CCHF were confirmed in South Africa. All of the patients worked in the
slaughtering unit of the same ostrich farm. Ostriches, like other birds, are
thought to be fairly resistant to infection with CCHF, but they undoubtedly
suffer heavy burdens of Hyalomma spp., which could be vectors of the disease.
VIROLOGY
•
Name: CCHF VIRUS
•
Genus: Nairovirus
•
Family: Bunya virus (bunyaviridae)
•
Type: RNA virus
•
Vector: Tick
•
Zoonosis: Transmitted from animals to human
being.
CCHF
RESERVOIRS AND VECTORS
The
CCHF virus may infect a wide range of domestic and wild animals. Many
birds are resistant to infection, but ostriches are susceptible and may
show a high prevalence of infection in endemic areas. Animals become infected
with CCHF from the bite of infected ticks.
A
number of tick genera are capable of becoming infected with CCHF virus, but the
most efficient and common vectors for CCHF appear to be members of the Hyalomma
genus. Trans-ovarial (transmission of the virus from
infected female ticks to offspring via eggs) and venereal transmission have
been demonstrated amongst some vector species, indicating one mechanism which
may contribute to maintaining the circulation of the virus in nature.
Once
infected, the tick remains infected through its developmental stages,
and the mature tick may transmit the infection to large vertebrates, such as
livestock. Domestic ruminant animals, such as cattle, sheep and goats,
are viraemic (virus circulating in the bloodstream) for around one week after
becoming infected.
The
animals develop (little or no symptoms).
TRANSMISSION:
Humans who become infected with
CCHF acquire the virus from direct contact with blood or other infected
tissues from livestock during this time, or they may become infected from
a tick bite. The majority of cases have occurred in those involved with the
livestock industry, such as agricultural workers, slaughterhouse
workers, butchers and veterinarians.
CLINICAL
MANIFESTATION
1.
The incubation period
is about 2 - 7 days, and has not been recorded as longer than 12 days. The
disease is more common in adult and older children than the small children
(more exposure to the source in adult). The disease is fatal during pregnancy.
It occurs mainly during hot seasons starting in late spring, summer, and early
autum, and rare during cold seasons like winter. This is because the life cycle
of tick and the virus life cycle in tick are affected by temperature variation.
2.
Prodromal stage:
Illness begins abruptly with
•
High
fever,
•
Myalgia,
•
Headache,
•
Vomiting
•
Pain
in the epigastrium, lower back and thighs.
•
Loose
stools, dry cough, tachycardia, although relative bradycardia may be present.
3.
Haemorrhagic manifestation: Some patients recover quite suddenly after
seven or eight days, but up to 75% begin to show haemorrhagic features after 3
- 5 days.
•
Petechial
rashs often appears in the mucous members and skin
•
Ecchymosis
( blue and black patches) in skin
•
Haematemesis
and melaena
•
Epistaxis
•
Conjunctival
injection and haemorrhages
•
Haematuria.
Despite
high viraemia, there is often a marked neutrophilia.
4.
Other features and complications:
•
The
liver is enlarged and tender, liver and tissue transaminases are elevated and
•
disseminated intravascular coagulation (DIC)
may follow.
•
Death
may occur (30 -50% of cases) on the seventh to ninth day, following a period of
shock, oliguria and, sometimes, respiratory distress syndrome.
•
Leucopenia
and thrombocytopenia
5.
Convalescence: The patient may recover gradually, starting on day 10
onwards. The skin rashes (petechia and ecchymosis) fade, bleeding stops and
fever subsides. The recovery is usually complete, although some describe a type
of neuritis and asthenia which may remain for some time. The patient is usually
less infectious and even in late days of this stage is non infectious, and his
serum can be used for prophylaxis (passive immunity) for contacts in future.
The immunity is permanent for all strains of CCHF viruses. The patient remains
in hospital for an average of 20 days.
Causes
of bleeding in CCHF
- Generalized
capillary damage is the major cause.
- Rarely
DIC may occur in severe conditions, late in the disease; may play a role
as indicated by prolonged PT, PTT and increase in fibrin degradation
products (FDP).
- Thrombocytopenia
is usually mild and usually not plays an important role in bleeding.
Causes
of shock in CCHF
- Bleeding
is the major cause
- Dehydration
due to vomiting and diarrhea
- Occasionally
immunological causes (Ag-Ab complex) leading to release of mediators.
Causes
of death in CCHF
- Shock
is the most important cause
- Multiple
organ failure
- Renal
failure
- Secondary
bacterial infection
- Intra
cranial haemorrhage
- Respiratory
distress syndrome
CONFIRMING THE DIAGNOSIS:
Early
diagnosis is possible using
- Antigen
detection by
immunofluorescence techniques. Some laboratories use reverse transcriptase
PCR methods.
- Antibody
detection: by using immunofluorescence test and
ELIZA test
IgM
antibodies are often detectable after the first five to seven days of fever,
but their concentration diminishes significantly after about 10 days, and is
replaced by rising IgG levels.
3.The virus is readily cultured in commonly-available cell lines
such as monkey kidney cells.
MANAGEMENT
- SPECIFIC
TREATMENT
There
is evidence that CCHF responds to treatment with ribavirin amelioration
of fever and lessening or avoidance of haemorrhagic features. The use of
ribavirin is complicated in these patients by its tendency to cause significant
anaemia, mainly due to haemolysis. (also can be given to contacts)
- INTENSIVE
SUPPORTIVE MANAGEMENT
is
required at an early stage and sometimes for prolonged periods by cases of
CCHF. The intensive Supportive management includes:
- Correction
of dehydration, electrolytes, and blood transfusion.
- Monitoring
of the patient and follow up chart.
- Treatment
of DIC.
- Routine
steroid and antibiotics are not indicated.
- Management
of other complications if present.
3. OTHER MEASURES AND PROTECTING
AGAINST HOSPITAL – ACQUIRED CASES
- Isolation
of the patient in a single room in hospital
- Decrease
the number visitors and medical personnel to the patient
3. Provision
of adequate disposable equipment and protection
clothing.
4.
Notification of the disease to health authorities within 24 hours.
5.
Good staff training and supervision
6.
Regular observation of all contacts for any symptom; samples of
blood may be taken from them for
serology.
- Send
samples of blood for serological, CBC, blood group and Rh;
Labeling them as a “Highly
infectious samples” to avoid Lab.
Personnel’s contamination.
- Bone
marrow examination may be needed sometimes to exclude blood diseases
like leukaemia.
8. A vaccine is not available for CCHF at
time being.
DECONTAMINATION:
The virus is killed by common
disinfectants, solvents, and dry heat (56°C, 30 min.). The vectors (ticks of
the genus Hyalomma) also need to be controlled with acaricides and possible
animal reservoirs will need to be monitored.
DIFFERENTIAL
DIAGNOSIS :
1.
Other non infectious diseases or conditions that need to be eliminated like
leukaemia, and aplastic anaemia.
2.
Other infectious diseases that may be associated with haemorrhagic
manifestations like:
•
Leptospirosis
(spirochaetal disease)
Leptospirosis
(spirochaetal disease)
•
Listeriosis
Bacterial infections
•
Meningococcal
septicaemia
•
Q
fever
•
Other
viral hemorrhagic fevers: Usually these are not present in our country but may
be present in other countries. These are also caused by RNA viruses (look to
the table below) and include:
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