The Community of Madrid has just confirmed a case of Crimean-Congo haemorrhagic fever (CCHF) in a 74-year-old man admitted last Friday. This case is in addition to the one detected by the Junta de Castilla y León last April, when a patient was bitten by a tick in Salamanca. He finally passed away.
It is a viral disease transmitted by ticks and caused by the Crimean-Congo hemorrhagic fever virus, belonging to the genus OrthonairovirusIt was first described in 1944, during World War II, when An outbreak affected a group of Soviet soldiers in the Crimean peninsulaTwenty years later, in 1967, the virus was finally identified and named Crimean-Congo virus, based on the similarities found with the virus that affected a febrile patient in the former Belgian Congo in 1956.
Four out of ten affected people die
Crimean-Congo haemorrhagic fever is a potentially fatal disease, with fatality rates that can reach 40%. The virus is transmitted through the bite of several species of ticks of the genus Hyalomaespecially the species Hyalomma marginatumwhich acts as a vector of the disease, although other species of ticks, such as some of the genera Rhipicephalus y Amblyommamay play a role in transmission and the maintenance of the virus in endemic regions. Some species of our wildlife, such as deer, act as reservoirs. As a result, the Crimean-Congo haemorrhagic fever virus circulates in a silent tick-vertebrate-tick enzootic cycle.
In Spain, where the first identified cases of patients with Crimean-Congo haemorrhagic fever date back to just over a decade ago, the mortality rate has reached 30%. The genome of the Crimean-Congo haemorrhagic fever virus consists of three segments: small (S), medium (M) and large (L). The S segment has been widely used in phylogenetic studies, which have defined 6 of 7 lineages of the virus, each with a different geographic range. Unfortunately, it has been shown that 3 different genotypes (III, IV and V) of the Crimean-Congo virus circulate in wild animals in Spain, even in the same geographic area, so the human population is exposed to the pathogen.
Camels also have ticks
The Crimean-Congo haemorrhagic fever virus has been identified in Africa, Asia and Europe, in territories located south of the 50th parallel North, an area inhabited by its main competent vectors, the ticks Hyalomma marginatum y Hyalomma lusitanicusThe two species generally do not coexist, because Hyalomma marginatum prefers open habitats at low elevation, while Hyalomma lusitanicus It is found at higher elevations and in colder areas.
Hyalomma marginatum It is well adapted to dry and even desert climates, and is characterized by its active search for potential hosts. The immature stages of the tick usually parasitize micro-mammals and birds, while the adult stages are hosted by large mammals such as deer, horses, cows, sheep, wild boars or camels. Of course, humans can also be parasitized.
Too many infected ticks in Spain
The Crimean-Congo haemorrhagic fever is considered endemic in areas of southwestern Europe. The current situation is a cause for deep concern, because a recent multidisciplinary study Focusing on the analysis of 12,584 ticks, analysed as sentinels of the disease, it has determined that the virus responsible for the pathology is currently circulating in Spain and is distributed throughout a large part of the Iberian Peninsula, where it apparently arrived via migratory birds.
In Spain, the first detection of the virus was in 2010 in ticks in Cáceres. The first human cases were diagnosed in 2016 and sporadic cases have been reported since then. In addition, the identification of another case retrospectively, corresponding to 2013, has been described in the scientific literature, which would be the first human case identified to date in Spain.
Africa and Asia also have problems
The distribution of the disease is constantly expanding. Several studies show that climate change has contributed to the spread of a wide variety of tick species in Africa, Europe and Asia, increasing the potential risk of spreading Crimean-Congo haemorrhagic fever.
Agricultural practices, changes in land use and movements of livestock and game also increase the risk. The abandonment of rural areas and cultivated fields has led to the proliferation of hares, rabbits and small rodents, with a consequent increase in the tick population.
A priority emerging pathogen with epidemic potential
Crimean-Congo hemorrhagic fever virus (CCHFV) is considered a Biosecurity risk pathogen level 4 (the highest level) by the US Centers for Disease Control and Prevention (CDC) and a priority emerging pathogen with epidemic potential. Hence the importance of understanding how it spreads.
The most common form of transmission to humans is through bite from an infected tickHowever, it can also be transmitted between people in case of close contact with blood, secretions, organs or other bodily fluids of infected individuals. It is also possible to become infected by slaughtering and handling infected animals that currently have the virus in their blood.
Following a tick bite, the incubation phase is generally one to three days, with a maximum of nine days. The incubation period after contact with infected blood or tissue is usually five to six days, with a documented maximum of 13 days.
The spectrum of clinical manifestations of the disease varies from subclinical diseasesincluding fever, headache, malaise, myalgia, sore throat, dizziness, abdominal pain, nausea, vomiting, conjunctivitis and photophobia, up to acute infections with haemorrhage, multi-organ failure and death. During the haemorrhagic period, small bruises (petechiae) appear which can later become larger on the skin and mucous membranes. Bleeding from the nose and gums or urine, vomiting blood or black stools are also common.
There is no specific treatment, vaccine or medication to cure Crimean-Congo haemorrhagic fever. The antiviral drug ribavirin Favipiravir has been used in the treatment of this disease in humans in some countries, but trials have not yielded conclusive results. Favipiravir has shown significant protective effects in some infected animal models. During the acute phase, blood replacement and fluid balance management are essential to increase survival.
Precautions when hiking
Control strategies include avoiding tick bites and using appropriate protection when slaughtering or grooming animals. Therefore, when walking through natural spaces and areas with abundant vegetation, as well as when hiking off-trail, especially during the spring and summer months, it is advisable to take precautionary measures.
It is advisable to wear closed shoes, high socks, long-sleeved clothing, long pants and even apply topical repellents to uncovered areas of the skin. In addition, light-colored clothing makes it easier to locate ticks.
If we walk with our pets, it is advisable to use anti-parasitic collars and to carry out a thorough examination of the animal, as well as our own skin, after the excursion.
This article was originally published in The Conversation. You can read it here.
Source: www.eldiario.es
