Biology of Borrelia species.

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Update on Meningococcal Disease with Emphasis on Pathogenesis and Clinical Management

In recent years, the frequency of serious cardiovascular infections such as endocarditis has increased, particularly in association with nosocomially acquired antibiotic-resistant pathogens. Growing evidence suggests a crucial role for the interaction of bacteria with human platelets in the pathogenesis of cardiovascular infections. Here, we review the nature of the interactions between platelets and bacteria, and the role of these interactions in the pathogenesis of endocarditis and other cardiovascular diseases.

The interaction of bacterial pathogens with platelets.

This review covers the history of meningococcal meningitis in Africa since epidemics of the infection were first described around 100 years ago. It is possible that an epidemic strain of the meningococcus was introduced into West Africa from the Sudan by pilgrims returning from the Haj around the turn of the century. Since 1905 major epidemics of meningococcal meningitis have occurred in countries of the Sahel and sub-Sahel every few years, culminating in a massive epidemic in which nearly 200,000 cases were reported in 1996. Attempts to control epidemic meningococcal meningitis in Africa by vaccination with meningococcal polysaccharide vaccines have met with only modest success because epidemics can progress with great rapidity and vaccination is often started too late. This situation should be improved as a result of a recent initiative, the International Coordinating Group (ICG), which is contributing to better surveillance in countries at risk and ensuring that vaccine is available when needed. However, in the medium term, the best prospect for the control of meningococcal meningitis in Africa lies in the recent development of polysaccharide-protein conjugate vaccines which, unlike polysaccharide vaccines, are immunogenic in the very young, induce immunological memory and are likely to give long-lasting protection.

Manson Lecture. Meningococcal meningitis in Africa.

The body louse, Pediculus humanus humanus, is a strict human parasite, living and multiplying in clothing. Louse infestation is associated with cold weather and a lack of hygiene. Three pathogenic bacteria are transmitted by the body louse. Borrelia recurrentis is a spirochete, the agent of relapsing fever, recently cultured on axenic medium. Historically, massive outbreaks have occurred in Eurasia and Africa, but currently the disease is found only in Ethiopia and neighboring countries. Bartonella quintana is now recognized as an agent of bacillary angiomatosis bacteremia, trench fever, endocarditis, and chronic lymphadenopathy among the homeless. Rickettsia prowazekii is the agent of epidemic typhus. The most recent outbreak (and the largest since World War II) was observed in Burundi. A small outbreak was also reported in Russia in 1997. Louse infestation appears to become more prevalent worldwide, associated with a decline in social and hygienic conditions provoked by civil unrest and economic instability.

The Body Louse as a Vector of Reemerging Human Diseases

: Sixty-two patients with louse-borne relapsing fever in Addis Ababa, Ethiopia, from 1966 to 1968 were studied. The clinical presentation varied. Fever, headache, skeletal and abdominal pain, and the usual symptoms of acute infection were common. Tachypnoea and upper abdominal tenderness with a palpable liver and spleen were found in two-thirds of the patients, jaundice in one- third, and purpura in one-sixth. Thrombocytopenia was the rule. Biochemical evidence of hepatocellular damage was found in most patients. Myocardial damage was suspected in one third of them. Pulmonary ventilation and cardiac output were increased and there was evidence of impaired gas exchange. Evidence of renal and cerebral damage was less striking. The literature on the immune response has been reviewed in order to understand the phenomenon of the crisis. Treatment was with intravenous tetracycline, and was followed by a Jarisch- Herxheimer raction. The clinical and physiological features of this reaction are described. Spirochaete death and phagocytosis, resulting in the release of endogenous pyrogen, may be responsible for all its features. Hyperpyrexia in the chill phase and hypotension and cardiac failure in the flush phase can be fatal. The mortality was 5 per cent. The epidemic and pathological processes which determine the prognosis of this disease are discussed.

Louse-Borne Relapsing Fever; A Clinical and Laboratory Study of 62 Cases in Ethiopia and a Reconsideration of the Literature

Louse-borne relapsing fever

Out of 717 patients with meningococcal disease 53 showed one or more of the three allergic complications: 47 (6·6%) developed arthritis, 12 (1·7%) developed cutaneous vasculitis, and 6 developed episcleritis. These complications, which were often multiple, occurred six to nine days after the beginning of the illness and three to six days after the start of successful antibiotic therapy. Those patients with severe systemic disease were prone to the complications. Histological and bacteriological study of the arthritis and vasculitis showed that these lesions were probably not due to persisting infection and suggested that they might be due to immune complex disease.

https://www.bmj.com/content/bmj/2/5869/733.full.pdf

Allergic complications of meningococcal disease. I. Clinical aspects.

In a controlled trial chloramphenicol proved as effective and much cheaper than penicillin for the treatment of group A meningococcal meningitis in Zaria, Nigeria. A short course of five days cured most patients. Adults and older children were soon able to take chloramphenicol by mouth, which reduced the cost and simplified treatment.It is suggested that chloramphenicol is a suitable alternative to sulphonamides for the treatment of meningococcal meningitis in those parts of Africa where the organism is sulphonamide-resistant.

https://www.bmj.com/content/bmj/3/5876/379.full.pdf

E.H.O. Parry

Papers

Louse-Borne Relapsing Fever; A Clinical and Laboratory Study of 62 Cases in Ethiopia and a Reconsideration of the Literature

Louse-borne relapsing fever

Allergic complications of meningococcal disease. I. Clinical aspects.

Trial of chloramphenicol for meningitis in northern savanna of Africa.

Meningococcal antigen in diagnosis and treatment of group A meningococcal infections.