Rickettsial diseases are zoonoses transmitted to humans by infected arthropods such as ticks, lice or fleas. They result in a feverish state, fever, headache and a rash. They can, in some cases, have a fatal outcome. Treatment is based on antibiotics, without waiting for diagnostic test results, to avoid worsening symptoms, death or prolonged recovery.

Diseases occurring more frequently due to the increase in international travel, a febrile state occurring within fourteen days after returning from an endemic area should raise suspicion of rickettsiosis, even in the absence of rash and introduction antibiotic treatment should be considered.

Doxycycline is the treatment of choice. Chloramphenicol is an alternative in children and pregnant women. Prevention is based on measures to prevent all contact with the animals in question in endemic areas, the wearing of highly protective clothing, the careful and regular examination of the skin to remove a possible tick as quickly as possible.

Rickettsial diseases are zoonoses, that is, infections transmitted from animals to humans. In the case of rickettsioses, the pathogens are intracellular, Gram-negative bacteria called rickettsiae, the reservoir of which is animal and the transmission vector is an infected arthropod such as a tick, a louse or a flea.

There are many species of rickettsiae, but three of them cause most human rickettsioses:

• Rickettsia rickettsia ;
• Rickettsia prowazekii ;
• Rickettsia typhi.

Rickettsia can be classified into two groups:

• Rickettsia of the “spotty” group, including Rickettsia rickettsii, which are transmitted mainly by ticks or fleas;
• Rickettsia of the “typhus” group, including Rickettsia prowazekii and Rickettsia typhi, which are transmitted by fleas or lice.

In mainland France, it is mainly rickettsioses transmitted by ticks that are diagnosed, such as Mediterranean spotted fever. Endemic in the Mediterranean basin and in sub-Saharan Africa, this fever is transmitted by the brown dog tick Rhipicephalus sanguineus, mainly in summer when the ticks are active. 

Rickettsial infections actually include a variety of diseases, including:

• Rocky Mountain Spotted Fever: Caused by Rickettsia rickettsii which is transmitted to humans by ticks. Endemic in America, mainly in the countryside, it is one of the most severe rickettsioses. It is indeed associated with high mortality even in young and healthy people;
• Epidemic typhus: caused by Rickettsia prowazekii which is transmitted to humans by the human body louse, Pediculus humanus, which lives in clothing. Unlike other rickettsioses, in which humans are only an accidental host, epidemic typhus is an anthropozoonosis, that is, an infection that is transmitted naturally from animals to humans and vice versa. In this case, humans are the main reservoir for Rickettsia prowazekii. This infection, endemic in the highlands of South America, Africa and Asia, is encountered in situations that promote the proliferation of body lice such as poor hygiene conditions, poverty (homeless), cold weather, groupings and overcrowding (prisons, refugee camps);
• Murine typhus or endemic typhus: caused by Rickettsia typhi which is transmitted to humans by the rat flea, Xenopsylla cheopis. It is a zoonosis of which the rat is the main reservoir. Murine typhus is found worldwide but is particularly prevalent in hot countries such as countries in southern Europe, Africa and Asia. It can be imported into Europe by travelers exposed to pet fleas in countries where the disease is endemic.

Rickettsial infections are frequent causes of fever after returning from trips abroad. This is why, before traveling to an endemic area, it is recommended to plan the implementation of preventive measures against tick, flea or louse bites: 

• covering clothes;
• frequent applications of insect repellent;
• restriction of contact with animals.

Symptoms of rickettsial disease usually appear two to fourteen days after a bite from an infected arthropod and include:

• A fever of sudden onset;
• Severe headaches;
• A feeling of discomfort, prostration;
• And, in most cases, a characteristic rash.

Potentially fatal complications can occur.

Treatment is based on antibiotics. Indeed, when rickettsiosis is suspected, empiric treatment should be started before the diagnosis is confirmed in order to avoid worsening of symptoms, possibly death or prolonged convalescence.

Since rickettsiae are resistant to antibiotics of the β-lactam family, aminoglycosides and trimethoprim-sulfamethoxazole, the antibiotics indicated include:

• As first-line, doxycycline 200 mg orally once then 1 mg twice / day in adults for at least 100 days;
• As an alternative in children and pregnant women, chloramphenicol 500 mg orally or intravenously 4 times / day for 7 days.