Boutonneuse fever may be regarded as the prototype of the group. It is the most widely distributed geographically, occurring throughout the African continent, in those parts of Europe and the Middle East adjacent to the Mediterranean, Black and Caspian Seas, and in India. Boutonneuse fever is a mild to moderately severe febrile illness of a few days’ to two weeks’ duration. It is characterized by a primary lesion that develops at the site of the infected tick bite and a generalized maculopapular erythematous rash that appears about the fourth day. As in Rocky Mountain spotted fever, agglutinins against Proteus OX-19 (Weil-Felix reaction) usually appear during convalescence, as do specific complement-fixing antibodies against the rickettsial organisms.
History, Distribution, Etiology, and Epidemiology.
Boutonneuse fever was first recognized in 1910 in Tunisia by Conor and Bruch. During the next several decades the occurrence of similar diseases was noted in Africa, Europe, and the Middle East; these were given various local names. However, it was not until modern serologic methods employing specific rickettsial antigens were applied
Although the rickettsial nature of North Asian tick-borne rickettsiosis was demonstrated in 1938, only in recent years has its etiologic agent, R. siberica, been clearly differentiated from other members of the spotted fever group of organisms.
The etiologic agents of the three diseases of the Eastern Hemisphere are all members of the spotted-fever group of rickettsiae. Together with R. rickettsi and R. akari they possess common group antigens that are readily demonstrated by agglutination and complement-fixation procedures. In addition, type-specific antigens characterize each member of the spotted fever group; these are demonstrated by similar in vitro serologic procedures employing specially purified antigens. Rickettsia conori, R. australis, and R. siberica may be differentiated from one another and from R. rickettsi and R. akari by complement- fixation tests using antisera from mice, by crossvaccination tests performed in guinea pigs, or by cross-neutralization tests using the mouse lethal toxin obtained from each agent and homologous antisera. Experimental infection of animals with one member of the spotted fever group of rickett-siae induces appreciable resistance to infection with other members.
For the most part, the epidemiology of the three tick-borne rickettsioses of the Eastern Hemisphere resembles that of spotted fever in the Western Hemisphere. Thus, the rickettsial agents are maintained in nature by cycles involving ixodid ticks and small wild animals; man, if he intrudes into the cycles, serves as a dead end in the chain of transmission. Boutonneuse fever in the Mediterranean area has a more domesticated and urbanized pattern. Here, another cycle is also involved with the brown dog tick as the vector and the dog as the animal host.
In fatal cases, which are few and usually limited to the aged and debilitated, the findings are similar to those in Rocky Mountain spotted fever except for the presence of the tache noire, the black button-like necrotic primary lesion that is generally found on the surface areas of the body ordinarily covered by clothing. The basic pathologic changes are found in the small blood vessels (see article on Rocky Mountain Spotted Fever).
Symptoms, Laboratory Findings, and Diagnosis of Boutonneuse Fever.
The three tick-borne rickettsioses that occur in different parts of the Eastern Hemisphere re- 3£JXlble one another closeiy. FoUo-Ning an incubation period of about five to seven d&yg, tk€ dl§€SS€ begins with fever, headache, malaise, and con- j;unctival injection. The primary lesion, which is present in most cases at the onset of fever , consists of a small ulcer 2 to 5 mm. in diameter with a black center and a red areola; the regional lymph nodes are enlarged. The generalized erythema: ?us maculopapular rash appears about t”he fourth day and quickly involves most of the body, including the palms and soles and often the face. In severe cases the rash becomes hemorrhagic. Fever abates during the second week. The prognosis is good, except in the aged and debilitated. Complications and sequelae are unusual.
The laboratory findings are those derived from the Weil-Felix add. nckett- sial complement-fixation tests. Agghitanins against Proteus OX-19 develop during the second week and complement-fixing antibodies appear shortly thereafter.
Diagnosis is established by the- clinical picture including the tache noire, the geographic location and positive serologic reactions In the different: a.1 diagnosis the typhus fevers, meningococcal infections, and measles must be considered.
Adequate information is available to indicate that treatment with the broad- spectrum antimicrobial drugs is as effective in patients with African tick typhus as in those with other rickettsioses (see article on Rocky Mountain spotted fever for details of therapy). Presumably, these measures are also applicable to the other two tick-borne rickettsioses of the Eastern Hemisphere.
Prophylaxis of Boutonneuse Fever.
Prevention of human disease is based on avoiding the bites of infected ticks. In the article on Rocky Mountain spotted fever are set forth details regarding personal prophylaxis, including the use of chemical insect repellents, and for reduction of tick populaton by measures involved in terrain control. Experimental vaccines prepared from formalin-treated yolk sac tissue infected with each of the Eastern Hemisphere rickettsiae under discussion are effective in animals, but commercial vaccines for human use are not available