They are infections transmitted mainly by ticks, also widespread in Italy. Knowing symptoms, modes of transmission and prevention helps reduce risks, especially in the warmer months and in natural environments
Rickettsioses are a group of infectious diseases caused by bacteria transmitted to humans mainly through the bite of some arthropods (small animals such as ticks, mites, fleas or lice). In Italy the best known form is Mediterranean button fever, mainly linked to the bite of the dog tick.
In most cases the disease has a benign course, especially if recognized and treated early with antibiotics. However, as with many vector-borne infections, it is important to know the symptoms, modes of transmission and prevention strategies, especially for those who live or spend time in natural environments.
What is rickettsiosis
Rickettsia is a very particular genus of bacteria. Unlike many other bacteria, in fact, it lives and multiplies inside the cells of the organism it infects. For this reason it is defined as an obligate intracellular parasite.
In most cases, humans are considered accidental hosts and the infections they can cause are grouped under the name rickettsioses. There are different forms, including:
- Mediterranean button fever;
- Rocky Mountain exanthematous fever (Rocky Mountain spotted fever), widespread throughout the United States and diagnosed mainly from April to September;
- African tick bite fever;
- Queensland tick typhus;
- North Asian tick fever.
These infections can cause various symptoms and disorders, but often have some common clinical features, such as fever and rashes.
When the infection affects people we talk about rickettsiosis in humans, a condition that can affect both adults and children and which in Italy is closely associated with tick bites.
Transmission and carriers
Rickettsioses are transmitted to humans through the bite of blood-sucking arthropods, i.e. animals that feed on blood. Among the main carriers we find:
- ticks;
- fleas;
- lice;
- mites.
In Italy the most important vector is the scientifically named dog tick Rhipicephalus sanguineus. Occasionally, this tick can also bite humans.
Many animals act as a “reservoir of infection”, that is, they host the bacterium without becoming seriously ill. Among these:
- dogs;
- rodents;
- cattle;
- sheep.
The transmission cycle is generally this: the tick becomes infected by biting an animal carrying the bacterium, then it can transmit the infection to humans with a subsequent bite.
An important aspect to remember is that rickettsiosis is not transmitted from person to person: contagion almost always occurs through the vector.
Epidemiology and geographical distribution
Rickettsioses are widespread in many parts of the world, but the different forms of the disease have different geographical distributions.
In Italy the most frequent form is the aforementioned Mediterranean button fever, which represents an endemic disease, i.e. permanently present in the territory. It is transmitted by various species of ticks and above all by Rhipicephalus sanguineus, a common parasite of dogs and other domestic and wild animals (rabbits, hares, sheep, goats and cattle). The pathogen of Mediterranean button fever is represented by Rickettsia conorii and by other rickettsiae.
The regions where the most cases are recorded are above all:
- Sicily;
- Sardinia;
- Calabria;
- Lazio;
- different areas of Southern Italy.
The disease also shows seasonality: cases increase in spring and summer, when ticks are more active.
The risk is greater for people who frequent natural environments, such as countryside,
woods, rural areas, areas with the presence of domestic or wild animals.
Symptoms of rickettsiosis
The symptoms of rickettsiosis can appear after an incubation period that varies depending on the form of the disease.
In Mediterranean button fever, symptoms generally appear 5–7 days after the tick bite, while in typhus they can appear after 10–14 days.
The first signs are often similar to those of a flu syndrome, with:
- fever;
- headache (headache);
- marked tiredness;
- muscle and joint pain;
- general sense of malaise;
- vomit.
In some cases the following may also appear:
- enlargement of the liver and spleen (hepatosplenomegaly);
- neurological disorders such as confusion or drowsiness;
- in the worst cases: instability of the cardiovascular circulation.
After a few days a maculopapular rash may appear, i.e. a skin rash made up of small raised spots. It usually appears between the third and sixth days of fever and can spread to much of the body, including the palms of the hands and soles of the feet. Rash, fever and headache represent a classic triad of presentation.
A very characteristic sign is the tache noirealso called eschar: it is a small dark skin lesion at the site of the tick bite.
Complications and severity
If diagnosis is timely and treatment is adequate, complications are rare. Although the vast majority of cases resolve without problems, it is good to know that, if left untreated, the infection can involve multiple organs. In the worst infections, complications can occur, the main ones being:
- cardiovascular complications, i.e. myocarditis, hypotension, shock;
- renal complications, i.e. acute renal failure and intestinal or urinary incontinence;
- neurological complications, among which we find meningoencephalitis, hearing loss, speech or swallowing disorders, cerebellar motor dysfunctions, learning difficulties and behavioral problems, partial paralysis of the lower limbs;
- respiratory complications, i.e. pneumonia or bronchopneumonia (so-called “rickettsial pneumonia”).
Coagulation disorders and reduction of platelets in the blood may also appear.
The mortality rate of button fever is generally less than 3% even in the absence of treatment. In other forms of rickettsiosis, such as epidemic typhus or some severe forms such as Rocky Mountain spotted fever, mortality can reach 20–30% in the absence of timely antibiotic treatment.
The risk of severe forms increases in the presence of:
- immunosuppression;
- diabetes;
- heart disease;
- advanced age.
Diagnosis of rickettsiosis
The diagnosis of rickettsiosis is based primarily on clinical suspicion. Anamnesis is therefore fundamental, i.e. the collection of the patient’s clinical history: for example a recent tick bite, contact with animals or a stay in rural areas. The doctor takes into consideration:
- patient symptoms;
- presence of rash or eschar;
- geographical area of origin;
- time of year.
Several tests can be used to confirm infection:
- serological tests, in particular the search for IgG and IgM;
- PCR (molecular test useful for early identification of the bacterium’s DNA);
- Skin biopsy of skin lesions.
The doctor must also distinguish rickettsiosis from other diseases that can cause fever and rash, such as measles, rubella, scarlet fever, and other infectious forms.
When rickettsiosis is suspected, laboratory tests help confirm the diagnosis. Some alterations may be highlighted such as reduction in platelets and sodium in the blood (thrombocytopenia and hyponatremia), increase in inflammation indices or alterations in liver enzymes.
Treatment of rickettsiosis
Treatment of rickettsiosis is mainly based on antibiotics. If clinical suspicion is strong, it is important to start treatment as soon as possible, even when the diagnosis is not yet confirmed. This reduces the risk of complications.
The drug of choice is doxycycline, which is effective against most Rickettsia species. For a long time, the use of doxycycline in children under 8 years of age was avoided, but today this antibiotic is considered safe and is recommended due to the high mortality associated with severe forms.
In some situations alternative medications may be used, such as:
- azithromycin, especially in younger children, pregnant women or in case of allergies;
- chloramphenicol.
Antibiotic therapy in rickettsiosis involves therapeutic schemes that vary based on the patient’s age and the severity of the disease.
In general, treatment with doxycycline lasts approximately 5-7 days and is continued at least until 72 hours after the fever has disappeared. In more severe cases, hospitalization and supportive therapy may be necessary.
Prevention and protection from ticks
Rickettsiosis prophylaxis is mainly based on the prevention of tick bites, as there are no vaccinations available.
When frequenting natural environments it is useful:
- wear long pants, socks and long-sleeved shirts;
- use insect repellents;
- walk preferably on paths avoiding tall grass and bushes.
Some repellents contain DEET, generally recommended for older children (over 12 years old), while permethrin can be used to treat clothes.
After outdoor activities it is important to check the skin carefully, especially in the skin folds, behind the knees, under the armpits and on the scalp.
Pets should be protected with anti-parasitic treatments against ticks.
In the event of a bite, the tick must be removed quickly and completely. This reduces the risk of transmission because the bacteria need a few hours (or more) to transmit the infection. For correct removal, tweezers are used: grasp the tick as close to the skin as possible and gently pull upwards, avoiding twisting or crushing the body. Then disinfect the affected area.
Methods such as petroleum jelly, alcohol, nail polish or heat are not effective.
Antibiotic prophylaxis after the sting is generally not recommended.
Other tick-borne diseases
Ticks can also transmit other infections in addition to rickettsiosis. Among these:
- Lyme disease, caused by Borrelia burgdorferiwhich often causes a characteristic erythema migrans and can affect the skin, nervous system and joints;
- anaplasmosis, caused by Anaplasma phagocytophilumtransmitted by ticks of rodents, deer and other ruminants, manifests itself with fever and non-specific symptoms in the spring and summer months.
These diseases have different clinical manifestations and diagnostic methods, but they share a common element: prevention of tick bites remains the most effective strategy to reduce the risk of infection.
In conclusion: alert, but without fear
We must not give up walks in the countryside or contact with nature for fear of rickettsioses. The key to everything lies in observation. When we return from an excursion, we transform “tick control” into a game or a daily hygiene habit to carry out together with our children, just like brushing their teeth.
Identifying a tick promptly or recognizing the first signs of the disease allows you to intervene with a simple and effective therapy.
