See: "What is Congo Crimean Haemorragic Fever?"
Hyalomma ticks are known to transmit the disease to animals and man. There is a brief but hightitre viraemic phase in mammals, at which stage their blood is highly infectious.
Note
Antibodies to CCHF have been detected in cattle, sheep and small mammals over a wide area in
Southern Africa without evidence of disease, and antibodies have been found in farm workers with no confirmation of Congo Fever disease.
Several human outbreaks and individual cases have been reported previously in South Africa.
In November, 1996, a number of cases of Congo Crimean Haemorrhagic Fever (CCHF) were identified in individuals working in an ostrich abbatoir in the town of Oudtshoorn, Western Cape
Province, South Africa.
It remained to be determined whether ostriches can be infected (and themselves serve as an infectious source), or whether they may merely carry infected ticks (they certainly do carry ticks) that can be passed to humans.
See: "Some Fascinating Facts about the 1996 CCHF Outbreak," by Bob Swanepoel
The following is an extract from an article in the SAMJ, Vol. 62, p576-580, October,1982 by James H. S. Gear et al.
Congo-Crimean haemorrhagic fever
Congo-Crimean haemorrhagic fever was first observed in the Crimea by Russian scientists in
1944 and 1945. At that time it was established by studies in human volunteers that the aetiological agent was filtrable and that the disease in man was associated with the bite of the tick Hyalomma marginatum . The agent was detected in the larvae and in adult ticks, as well as in the blood of patients during the fever. This agent, presumably a virus, was not maintained in the laboratory and was lost.
Congo virus was first isolated in Africa from the blood of a febrile patient in Zaire in 1956. In
1967 Simpson et al.
described 12 cases of a feverish illness of which 5 were laboratory infections; the virus was isolated by the inoculation of blood into newborn mice. Simpson showed that these viruses were similar to the one isolated in 1956. Casals then showed that the viruses isolated in cases of Crimean haemorrhagic fever and the Congo virus were serologically indistinguishable and demonstrated that other virus strains from Central Asia, the USSR and
Bulgaria were similar.

The virus has been classified as a Nairovirus in the genus Bunyavirus in the family Bunyaviridae.
It contains RNA and is inactivated by lipid solvents and detergents.
Laboratory studies have shown that Congo virus is related to Hazara virus isolated from ticks in
Pakistan, and to Nairobi sheep disease virus; together they form the Nairovirus group.
In Africa the virus has been isolated from a variety of animals, including cattle, sheep, goats, hares and hedgehogs, and from a number of ticks which parasitize them, including Hyalomma sp., Amblyomma variegatum , Boophilus decoloratus and Rhipicephalus sp.
The most important transmitters of the infection to man are species of the genus Hyalomma , the life history of which is shown in the figure below.
The larval and nymphal stages of some species parasitize birds, including migratory birds, some of which fly from south-eastern Europe to South Africa and thus may carry the infection over long distances. To verify whether this actually happens will require further study of the ticks and their hosts in South Africa and on their way from Europe.
Clinical picture
The infection is usually transmitted to man by the bite of a tick, but an increasing number of cases have occurred among the medical and nursing staff caring for patients in hospital and in laboratory personnel carrying out investigations of these patients. In these cases the infection has apparently been acquired by contagion, particularly by contact with the patient's blood or bloodcontaminated specimens. Exposure to the blood of infected animals, especially cattle and sheep, has led to severe and often fatal infections.
The incubation period is 2 - 7 days. The onset of the illness is sudden, with fever, chills, severe muscular pains, headache, vomiting and pain in the epigastric and lumbar regions. A haemorrhagic state develops from the 3rd to the 5th day and manifests as petechial haemorrhages or purpura in the skin, and bleeding from the mucous membranes manifests as epistaxis, haemoptysis, haematemesis, melaena and haematuria. At this stage the conjunctivae are injected,

the face is flushed and the tongue is dry, often coated with dry blood. The pulse is slow in the beginning, but with continuing loss of blood becomes fast and feeble; the blood pressure drops and the heart sounds become weak - clear signs of impending shock and vascular collapse. The liver is enlarged and tender and there is tenderness over the epigastrium and splenic region. In patients who recover, the temperature falls between the 10th and the 20th day and bleeding stops, but convalescence is prolonged up to 4 weeks or longer. In fatal cases, death from massive haemorrhage and cardiac arrest occurs, usually 7 - 9 days after the onset of the illness. Massive haemorrhage into the gastro-intestinal tract, with scattered haemorrhages into the viscera, is found at autopsy.
The diagnosis is suggested on clinical grounds when the patient has a history of a tick bite or of exposure to ticks in the environment, and after an incubation period of 2 - 7 days develops an illness of sudden onset of muscle pains, headache fever and a rapidly evolving severe illness with the development of a haemorrhagic state with bleeding from the mucous membranes and petechiae in the skin, associated with thrombocytopenia and leucopenia.
The diagnosis may be confirmed in the laboratory by intracerebral inoculation of baby mice with blood of a patient; the mice sicken about 1 week after inoculation. The virus is identified by using known specific Congo virus antiserum in an immunofluorescent test. The development of antibodies in patients' serum as the illness progresses may be demonstrated in immunofluorescent tests using chamber slides with tissue culture cells infected with Congo virus.
The authors are grateful to Professor 0. W. Prozesky, Director of the National Institute for Virology, and to Dr R. Swanepoel, Dr K. Struthers, Mrs E.
Rossouw and Miss G. McGillivray, staff members of the high-security laboratory, and to Dr P. Jupp of the Arbovirus Unit of the National Institute for
Virology for undertaking, as a matter of urgency, the investigations which led to the incrimination of the Congo virus as the cause of this patient's fatal illness. The authors are grateful to Mrs M. Anderson, who prepared the chart of its life cycle.
REFERENCES
1.
Gear JH S. Haemorrhagic fevers of Africa, an account of two recent outbreaks. J. S Afr Vet Assoc 1977;
48: 5-8.
2.
Pattyn SR, cd. Ebola Virus Haemorrhagic Fever. Amsterdam: Elsevier North Holland Bioniedical Press,
1978: 301.
3.
Simpson DIH, Knight EM, Courtois G et al. Congo virus: a hitherto undescribed virus occurring in Africa.
1. Human isolations - clinical notes. East A fr Med J 1967; 44: 86-92.
4.
Hoogstraal H. The epidemiology of tick-bome Crimean-Congo hemorrhagic fever in Asia, Europe and
Africa., J Med Entomol 1979; 15: 307-417.
5.
Burney MI, Ghafoor A, Saleen M, Webb PA, Casals J. Nosocomial outbreak of viral hemorrhagic fever caused by Crimean hemorrhagic fever - Congo virus in Pakistan, January 1976. Am J Trop Med 1980; 29:
941-947.
6.
.Tantawi HH, AI-Moslih MI, AI-Janabi NY et al. Crimean-Congo haemorrhagic fever virus in Iraq: isolation, identification and electron microscopy. Acta Virol (Praha) 1980; 24: 464-467.
7.
Suleiman MN, Muscat-Baron JM, Harries JR et al. Congo/Crimean haemorrhagic fever in Dubai: an outbreak at the Rashid Hospital. Lancet 1980;ii: 939-941.
Page prepared by Linda Stannard, Div of Medical Virology, UCT.
Updated December,1999.

from Bob Swanepoel
The 1996 outbreak of CCHF in Oudtshoorn created a new awareness of this rare disease. At that time, we were given answers to some of our questions, by
Prof. Bob Swanepoel of the National Institute for Virology in Johannesburg who kindly supplied a unique insight into the nature of the 1996 outbreak.
About the ticks that transmit CCHF:
"The world distribution of CCHF virus coincides pretty well with the distribution of Hyalomma ticks (Africa, eastern Europe and
Asia). Locally, Hyalomma species are called "bontpootluise".
"Bont" means multicoloured or variegated, and refers to the reddish-brown and white bands on the legs of ticks of the genus
Hyalomma.
Other ticks can transmit, but there seems to be a particular link with Hyalommas , and this has certain epidemiologic consequences, relating for instance to the host preferences of the immature and adult ticks (which differ from ticks of other genera) : larvae and nymphs feed on small mammals up to hare size and ground-frequenting birds , while adults prefer large animals , the larger the

better.
This means that humans are not bitten by the immatures ("seed" or "pepper" ticks) of
Hyalommas (humans are bitten by the immatures of other ticks) and even the adults are not that partial to humans, although they do bite if given good reason.
If this all were otherwise, and Hyalommas loved feeding on humans, we would be in a sorry mess for antibody surveys on livestock sera show that we live in a sea of CCHF virus within the distribution range of Hyalommas, and
the miracle is that there are so few human cases,
NOT that there are so many."
How do human infections originate?
"Humans gain infection from tick bite (yes, the occasional Hyalomma ), or from contact of infected fresh blood (or other tissues) with broken skin
- with the infected blood/tissues coming either from human patients (nosocomial infections - needle sticks etc), or other animals,' commonly sheep and cattle."
How does CCHF affect other animals?
"To our knowledge, only humans and newborn mice readily succumb to disease; other animals, including nonhuman primates, are either refractory or undergo mild infection, sometimes with transient viraemia - including sheep and cattle (our unpublished results).
Sheep and cattle are viraemic for up to about a week, and often exposure to ticks and virus infection occurs at an early age. Farmers may castrate, dehorn, stick in ear tags or immunize the young animals, and thus expose themselves through getting infected blood onto broken skin.
Sometimes animals meet tick infestation for the first time late in life and then succumb to tickborne diseases of livestock (such as babesiosis or anaplasmosis) at the same time that they happen to have first met CCHF virus, and are thus viraemic at a time when they are treated, autopsied, or even butchered by farmers, veterinarians or farm workers respectively. This constitutes another type of incident leading to common source outbreaks."
So when are humans at risk?
"Most often the disease affects stockmen and other farm dwellers , and townspeople only become infected when they visit the countryside and get tick bite, or hunt and slaughter animals etc.
It is also enough to squash infected ticks with bare fingers - one does not have to be bitten.
The only town dwellers who are regularly exposed to infection are slaughtermen at abbatoirs - since they encounter fresh blood and other tissues of livestock (commonly sheep and cattle) hundreds of times daily - sometimes more than a thousand head of sheep or cattle a day, they must come across animals in the short viraemic phase of infection fairly often, and we know they

get the disease more frequently than other people, and it seems, also a relatively mild/silent infection with seroconversion.
All the same, there would probably be many more abbatoir infections if the viraemia in livestock were more intense than it is - very low-titered in comparison with Rift Valley fever for instance.
Ticks which detach from hides and skins at slaughterhouses, after their engorgement has been so rudely interrupted, will sometimes attach to whatever is available, and this constitutes another hazard for abbatoir workers.
What then of risk for the urban consumer of meat?
" In 17 years of looking at about 2000 cases of suspected viral haemorrhagic fever, we have never found CCHF in a town dweller who did not have a history of recent tick bite, or animal blood contact in the countryside or at an abbatoir, nor were we able to isolate virus from meat from experimentally infected sheep killed in viraemia.
The virus is not very resistant to heat and pH extremes etc, and we assume the fall in pH associated with "maturation" of meat by hanging of carcases after slaughter, is sufficient to put paid to residual virus after "bleeding out" of the animal at slaughter.
Can ostriches be a source of infection?
"Incidentally, there was a worker at an ostrich slaughterhouse near Oudtshoorn who became infected in 1984 - he claimed that Hyalomma ticks on ostriches scratched his hands and arms as he pulled off the skins from the birds, and we thought that was one possible way of becoming infected.
Another would be ticks transferring to the slaughtermen after detachment from ostrich skins, and of course, another possibility is that ostriches can become viraemic - which we are setting out to investigate now.
We previously failed to obtain ostriches to experiment on, and tested guinea fowl and chickens - which were fairly resistant to the virus - but they may be quite different to ostriches which, I think, many have a slightly different thermoregulatory capacity from other birds, for one thing."
"Having said all that, we come to Oudtshoorn, the centre of an ostrich industry which sells
(locally and abroad), feathers, skins and meat. An ostrich farmers' co-operative runs several slaughterhouses, and these resumed slaughtering (after an off season) on 21 October, 1996; (two of the abbatoirs are in Oudtshoorn). By pure coincidence a survey was undertaken at the largest of the abbatoirs of the tick burden (mainly Hyalomma truncatum ) on birds coming in from various farms, and it was found that six consigmnets were heavily infested. This is the slaughterhouse where the outbreak occurred towards the end of October, 1996.
Antibody detection and PCR did a splendid job of rapid laboratory confirmation for us."

For a while, all of the abbatoirs were closed and by the end of the theoretical incubation period no further primary common source cases had been observed. There appear to have been no secondary (human-to-human cases).
What advice was given to ostrich farmers?
In November 1996, "I advised that farmers should have a section of their feedlots double fenced, the inner fence to be small animal proof, and that ostriches should be treated with a short half life pyrethroid acaricide (non residual) 14 days before being sent for slaughter and placed in the fenced off "quarantine" section for this period - they should then ( by analogy with sheep and cattle experiments) arrive at the slaughterhouse tick- and virus- and acaricide-free, but we still need to do ostrich experiments. Pyrethroids in any event have very rapid "knockdown" (lethal) effect on ticks, and very low mammalian toxicity."
Bob Swanepoel ,
November 1996 .
Subsequent investigations
"Meanwhile Dr Willem Burger of the ostrich producers research lab has sent us ten half grown chicks (tick free) to do experimental viraemia studies etc.
(they are big enough to look you in the eye, and they defaecate a bucketful)
Also, I shall be visiting the area and, with Dr Burger, will visit farms to collect ticks etc. From our sheep and cattle surveys we know that the virus is everywhere, and while we are not trying to incriminate anybody, it will be interesting to see if we can get virus isolates from ticks to match up by nucleotide sequencing with any isolates from patients.
(The fact that most infections have been relatively benign is interesting of itself)."
Results of follow-up experiments
SUMMARY
Following the occurrence of an outbreak of Crimean-Congo haemorrhagic fever (CCHF) among workers at an ostrich abattoir in South Africa in 1996, nine susceptible young ostriches were infected subcutaneously with the virus in order to study the nature of the infection which they undergo. The ostriches developed viraemia which was demonstrable on days 1-4 following infection, with a maximum intensity of 4.0 log10 mouse intracerebral LD50/ml being recorded on day 2 in one of the birds. Virus was detectable in visceral organs such as spleen, liver and kidney up to day 5 post-inoculation, one day after, it could no longer be found in blood. No infective virus was detected in samples of muscle, but viral nucleic acid was detected by reverse

transcription-polymerase chain reaction in muscle from a bird sacrificed on day 3 following infection.
It was concluded that the occurrence of infection from ostriches at abattoirs could be prevented by keeping the birds free of ticks for 14 days before slaughter.
Despite the apparent lack of evidence of disease in urban consumers of meat, it remains unacceptable that CCHF infected animals should reach abattoirs to pose a potential threat to workers and the public. Tick infested animals pose an additional threat to abattoir workers since partially engorged ticks tend to detach from their hosts after slaughter, or from the hides and skins of the hosts, and may then attach to any humans in the vicinity.
From the publication "Experimental infection of ostriches with Crimean-Congo haemorrhagic fever virus" by:
R. SWANEPOEL 1 , P.A. LEMAN 1 , F.J. BURT 1 , J. JARDINE 1 , D.J. VERWOERD 2 , I.CAPUA
3 ,
G.K. BRÜCKNER
4 and W.P. BURGER 5
1. National Institute for Virology and Department of Virology, University of the Witwatersrand, Private Bag X4, Sandringham 2131, South Africa
2 .Onderstepoort Veterinary Institute, Onderstepoort 0110, South Africa
3. Istituto Zooprofilattico Sperimentale, Teramo, Italy
4. Directorate of Veterinary Public Health, Pretoria 0001, South Africa
5. Klein Karoo Co-operative Ltd, Oudtshoorn 6620, South Africa
RETURN to Congo Fever Update
Medical Virology Homepage
CCHF diagnosis is done at the National Institute for Virology in Johannesburg.
Acknowledgement:
Drawings of ticks by Mrs M. Anderson, from a publication in SAMJ, Vol. 62, p576-580, October,1982
Page prepared by Linda Stannard, Div of Medical Virology, UCT.
Updated December,1999.

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