The expansion of this disease, initially limited to Africa and a few European countries (Turkey, Bulgaria and more recently Spain), is favored by climate change.
In France, a first detection of the Crimean-Congo hemorrhagic virus was confirmed in October 2023 on ticks collected from cattle farms. in the Eastern Pyrenees. It also circulates in Corsican farmsas the study explains published in the American journal Emerging Infectious Diseases. The Regional Health Agency (ARS) of Corsica specifies in a press release dated April 24, 2024, that “the presence of the Crimean-Congo hemorrhagic fever virus has been known in Corsica for several years in cattle”. And, “what is new is the detection of the disease in ticks, insect vectors and therefore making the disease potentially transmissible to humans.”
The Health Security Agency (ANSES) and the High Council of Public Health were used following these cases to develop recommendations. In the meantime, health authorities advise following recommendations to protect yourself from ticks.
However, rest assured, no cases have been detected in humans in France to date.
1. Crimean-Congo hemorrhagic fever, what is it? Definition
Crimean-Congo hemorrhagic fever is a serious viral infection. It is caused by a virus of the Nairoviridae family and the Orthonairovirus genus. Its natural host is ticks, especially ticks of the Hyalomma spp family. The virus can be transmitted by a tick bite, or by direct contact with contaminated blood from humans or wild animals. It is an endemic disease in Africa, Asia, the Middle East, southern Europe and the Balkans. In recent years, global warming and the international livestock trade have driven this virus to spread to Europe (particularly in Spain and Corsica in sheep, cattle and goats), specifies the Practitioner’s Review. Individuals at risk are therefore people who have frequent contact with wild animals and livestock, that is to say breeders, field veterinarians, slaughterhouse employees, etc., as well as people potentially in contact ticks, such as hunters, forest rangers, hikers. Crimean-Congo hemorrhagic fever causes sudden fever and hemorrhages, which can lead to death in 10 to 40% of cases, depending on the strain of virus encountered.
2. How is Crimean-Congo hemorrhagic fever transmitted?
Contamination with the Crimean-Congo hemorrhagic fever virus can occur in several ways. First of all, and this is the main mode of contamination for both humans and animals, by tick bites, of the family Ixodidae, mainly those of the genus Hyalomma. In the larval state, these ticks are mainly found in birds, hedgehogs and hares. Then, as nymphs, the ticks look for a new host, and most frequently choose a large mammal (sheep, cattle, wild animals, etc.). But they can also be hosted by cats, dogs, mice or rats. The virus is then transmitted to humans through the bites of ticks caught in contact with these animals. Less common are contaminations by direct contact with the blood or bodily fluids of individuals or animals carrying the virus. In all cases, barrier measures are necessary.
3. What are the symptoms of Crimean-Congo fever?
The symptoms of Crimean-Congo hemorrhagic fever vary in intensity depending on the individual. Not all infections cause symptoms, so infection with this virus may go completely unnoticed. In the event of mild symptoms initially, diagnostic wandering may occur, with the doctor mistakenly associating the symptoms with a flu-like illness. We traditionally distinguish four phases in this pathology:
- The incubation phase: its duration depends on how the person was contaminated. If the contamination is due to a tick bite, the incubation period is 3 to 6 days and a maximum of 9 days, specifies the WHO. In the event of contamination by contact with contaminated blood or infected tissues, this period is 5 to 6 days and a maximum of 13 days, again according to the same source.
- The prehemorrhagic phase: it lasts from 1 day to 1 week. The symptoms are those of a flu syndrome. The person has a sudden fever, body aches, dizziness, neck stiffness, headache, nausea and abdominal pain. As well as a rush of blood (hyperemia) to the face, neck and chest and mental confusion.
- The hemorrhagic phase: depending on the case, it occurs within 3 to 6 days after the first symptoms of the disease. Under the skin, small pinhead-shaped red dots (petechiae) appear, as well as bruises and hematomas. On palpation, we see that the liver has increased in volume, this is called hepatomegaly. The person is also subject to bleeding from the gums, nose, skin at the site of the bites, as well as tachycardia. Blood is observed in the urine and stools. In forms of Crimean-Congo hemorrhagic fever with serious complications, a sharp deterioration in kidney function, liver necrosis, cerebral hemorrhage or pulmonary failure is observed. In the latter cases, the vital prognosis is engaged. Death then generally occurs during the second week in 10 to 40% of cases.
- Convalescence: for patients who recover, convalescence is most often 15 days to 3 weeks after the first manifestations of the disease, but the patient’s total recovery can take up to a year. Among the cases observed throughout the world, no cases of relapse have been noted.
4. What is the diagnosis and treatment for Crimean-Congo hemorrhagic fever?
To make the diagnosis of Crimean-Congo hemorrhagic fever, the doctor bases himself on the clinical examination of the patient, but also on analyses. This includes a blood test. In conditions of extreme biological containment due to the high risks of contamination, this can also involve molecular biology or viral culture.
If the diagnosis confirms infection with Crimean-Congo hemorrhagic fever virus, it is necessary isolate the patient, to prevent it from contaminating other people as much as possible. To date, there is no specific treatment for Crimean-Congo hemorrhagic fever. Medical care will therefore mainly consist of relieving the patient’s symptoms. For this, doctors prescribe analgesics, antipyretics, antiemetics, corticosteroids and antidiarrheals. As well as blood products: fresh frozen plasma (FFP), platelets, erythrocytes (red blood cells). Furthermore, ribavirin-type antivirals, taken orally or intravenously, would give satisfactory results when prescribed for around ten days. Failing to cure this disease with drug treatment, it is therefore advisable to emphasize means of prevention.
5. Is there a vaccine against Crimean-Congo hemorrhagic fever?
At this stage of scientific advances, No vaccine exists to protect against Crimean-Congo hemorrhagic fever, neither for humans nor for animals. Some countries like the former USSR and Turkey have tested a vaccine since the 1970s, but it was not deemed effective enough to be scaled up. Research for the development of a vaccine is in progress, specifies the journal Médecine/Sciences, a vaccine centered on the tick itself and aimed at preventing it from feeding. If this vector were neutralized, then the spread of the virus would also be neutralized. The WHO also mentions progress on a vaccine obtained from mouse brains, and currently being tested on a small scale only.
6. How to protect yourself from Crimean-Congo hemorrhagic fever?
Prevention measures for Crimean-Congo hemorrhagic fever are essential to limit the risks of spreading the virus. They use various channels, recalls the World Health Organization:
- The fight against Crimean-Congo hemorrhagic fever disease in ticks and tick host animals: it involves the use of acaricides, products toxic to ticks, which prevent their larvae from developing. It also involves placing animals intended for the slaughterhouse systematically in quarantine two weeks before their slaughter, and giving them a treatment with a pesticide on this occasion.
- Prevention at the human level: this involves wearing clothing that covers (long pants, tops with sleeves) and is light in color (color on which ticks are more easily detected). But also to spray approved tick repellents on clothing and skin. If, despite these precautions, the person is bitten by a tick, it must be removed as quickly as possible and the bite disinfected. Finally, as far as possible, you should avoid going to places where ticks multiply, especially during the seasons when ticks are most active, that is to say in spring and fall.
- Prevention of contamination from animals to humans: in the event of contact with animals in an endemic region, it is strongly recommended to wear gloves and covering clothing. And wash your hands thoroughly after this contact.
- Prevention of human-to-human contamination: to avoid being contaminated by the Crimean-Congo fever virus, it is recommended to respect barrier measures. That is to say, you should not approach people affected by the virus, unless absolutely necessary if you are a caregiver. With regard to caregivers, and staff required to handle samples from patients, care must be provided while wearing gloves and protective clothing, and systematic hand washing must take place after each contact with the patient, or with samples of the latter’s blood or fluids.
Sources:
INRS, The Practitioner’s Review, Infectiology, Merck manual, Medicine/Science, World Health Organization