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Rocky Mountain spotted fever (RMSF) and epidemic typhus are the major rickettsial diseases. Specific rickettsias commonly infect ticks and lice, which are the common vectors of RMSF and typhus; Rickettsia rickettsii and Rickettsia prowazekii belong to the family Rick-ettsiaceae. In RMSF and typhus, the Weil-Felix reaction is positive in many cases, and antibodies to each specific antigen appear and permit confirmation of the specific diagnosis. After rickettsias gain access to man via the skin or mucous membranes, the agents of RMSF and epidemic typhus distribute widely throughout the vascular system. In RMSF and epidemic typhus, small blood vessels characteristically show endothelial cell swelling, cellular proliferation, and degeneration with thrombus formation and partial or full occlusion of the vascular lumen. Louse-borne typhus fever ranks among the top epidemic diseases causing suffering and death. Epidemic typhus is just as severe as RMSF; murine typhus resembles mild epidemic typhus or epidemic typhus modified by prior immunization.

Serum samples from patients in Kenya with febrile illnesses were screened for antibodies against bacteria that cause spotted fever, typhus, and scrub typhus. Seroprevalence was 10% for spotted fever group

Excerpt The factors which may be responsible for the development of azotemia in severe infectious diseases have been recently reviewed.1The diagnosis of azotemia depends upon the biochemical analys...

Excerpt The therapeutic effect of para-aminobenzoic acid (PABA) in experimental murine typhus infection of white mice was reported in 1942.1Subsequently, evidence bearing on the action of PABA in e...

Experiments are described which demonstrate that human body lice (Pediculus humanus corporis), were infected experimentally with murine and epidemic louse-borne strains of typhus fever by feeding on suitably prepared rabbits. Details of the two methods of infection, the "bleb technique" and the "I.V. technique," are presented. It is concluded that the experimental infection of human lice with typhus can be accomplished very easily and rapidly with these methods. The possible applications of the method are discussed.

Brill-Zinsser disease is an exacerbation of epidemic louse-borne typhus fever caused by Rickettsia prowazekii . The organisms are not eradicated from the original infections and reappear, sometimes several years distant, as a mild form of the disease. The disease is passed by the body louse and in rare instances by lice and fleas from flying squirrels.

Typhus exanthematicus in Bosnia and Herzegovina held in endemic areas from which especially quickly began spread after 1945. That year, in 1945, one hundred epidemics of typhus fever appeared, with the highest incidence rate in Europe of 215.04 per 1,000. Directions of unique program in the world were to eradicate lice of the body, but also establish monitoring of the recidivism, Brill-Zinsser disease. Since 1971, typhus exanthematicus (classical typhus) hasn't appeared in Bosnia and Herzegovina, so epidemic typhus can considered as an eradicated communicable disease.

The work reported in this paper relates to the bacteria which can be cultivated from the blood and spleen of guinea pigs at different stages of infection with the virus of typhus fever. The studies show that during the period of incubation and before the onset of fever no ordinary bacteria appear in the cultures, while on the 1st day of the febrile reaction different bacteria were found in 6 of 26 guinea pigs cultured; on the 2nd day, in 10 of 16; on the 3rd day, in 3 of 4; and on the 4th day in cultures of all of the 4 guinea pigs observed. The findings indicate that the virus of typhus fever is distinct from ordinary cultivable bacteria, and, as the disease set up by the virus progresses, the infected guinea pigs become subject to invasion by secondary or concurrent bacteria which thus induce a mixed infection. The bacteria which under the influence of the virus of typhus fever thus invade the body of the guinea pig are of several kinds, and vary not only among themselves, but also with the day of the fever on which the examination is made. Thus, on the 1st day of the fever Plotz' bacilli were recovered twice and anaerobic streptococci, proteus bacilli, aerobic diphtheroids, Gärtner type bacilli, and Staphylococcus aureus each once. On the 2nd day Plotz' bacilli were found four times, anaerobic streptococci three times, Gärtner type bacilli, aerobic diphtheroids, Bacillus welchii, aerobic Gram-positive diplobacilli, and Staphylococcus aureus each once. On the 3rd day Plotz' bacilli were recovered once, as were anaerobic streptococci and Grtner type bacilli. On the 4th day Staphylococcus aureus was found twice and Plotz' bacilli and Bacillus proteus each once. This variation in the kind of bacteria as well as the lack of predominance of one kind over another during the different stages of the febrile reaction in guinea pigs leads us to infer that they occur concurrently with the typhus virus. And since the more unusual of these organisms, the Plotz bacillus, the anaerobic streptococcus, the aerobic diphtheroid, and the diplobacillus are non-pathogenic for guinea pigs, while the more common bacteria such as the Gärtner type bacillus, Welch's bacillus, the proteus bacillus, and the staphylococci induce distinctive effects, and since all the bacteria could be suppressed without their reappearance in guinea pig passages of the virus containing them, we believe that they are independent and unrelated to the true virus of typhus fever.

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Most of the published descriptions of R. prowazeki in lice have dealt with the minute round, oval, diplococcal or dumb-bell forms found by Ricketts and Wilder (1910), Sergent, Foley and Vialatte (1914), da Rocha-Lima (1916), and others.

In a communication dealing with the etiology of typhus fever, Plotz1 presented a review of the evidence which led him to believe that the virus is nonfiltrable. No effort was made at that time to give all the facts leading to this conclusion. It is the purpose of my paper to analyze the previous work, and to present new evidence bearing on the nonfiltrability of typhus virus. The basis for the assertion that the virus is filtrable is a single, very doubtful, experiment of Nicolle, Conor, and Conseil.2 As additional support, the single incomplete experiment of Wilder3 is usually quoted. Thus, Wolbach4 classified typhus among the filtrable viruses on such evidence; so did Lofifler5 and Lipschiitz.6 R. Kraus7 stated dogmatically that typhus-fever virus was filtrable, while Park and Williams8 asserted that there was "the possibility of the virus having a filtrable stage." Jordan9 quite recently stated that "inoculation with filtered blood does, however, render monkeys refractory to further infection, according to the testimony of several observers." In reviewing the original sources of the assumption that the virus is filtrable I shall analyze Nicolle's work first. All his work on this problem may be summarized in a resume of 5 series of experiments. The first series comprised 4 monkeys ? 1 injected with unfiltered, the other 3 with filtered typhus serum. All failed to react, except 'Bonnet 47,' which was injected with filtered serum; this animal showed an elevation of one-half degree (Centigrade) between the 16th and 18th days after inoculation. After a time all these monkeys were reinoculated with typhus virus and all except Bonnet 47 developed the

The Weil-Felix reaction has received general acceptance as an empiric laboratory test of considerable merit in establishing the diagnosis of typhus fever. The testimony of writers is uniform in affirming that the reaction is positive in over 90 per cent of cases of clinical typhus. It may appear as early as the fourth day of the disease, but usually does not develop until the second week and yields maximal titres about the time that the temperature returns to normal or shortly thereafter. Complete agglutination of the strain of B. proteus known as X19 in a dilution of the patient's serum greater than 1:50 is looked upon as of specific diagnostic significance. So far as can be determined the organism has no etiologic relationship to the disease and the mechanism of the reaction is not clearly understood. An excellent discussion of the immunological principles involved and the technique of the reaction has been published by Bengtson in the Public Health Reports, October 31, 1919.

The forms under consideration resemble Rickettsia prowazeki—the supposed cause of typhus fever—which occurs in lice that have fed on typhus fever patients.

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1. Rickettsia prowazeki can be cultivated for many generations in vitro, without diminution in numbers or virulence, in media similar to those described by Maitland, Rivers, and others for the cultivation of certain viruses. In all probability, such cultures can be maintained indefinitely. 2. It has been impossible, thus far, to cultivate the typhus rickettsia without employing living tissue.

Summary To determine the spatial distribution of murine typhus fever in San Antonio in 1944 and 1945 rats were collected throughout the city and tested for the presence of complement fixing antibodies for typhus. The human cases were investigated to determine the most probable source of infection. The city was divided into 6 arbitrary districts according to the characteristics of the inhabitants and amount of typhus. Rats positive for typhus fever have been found in all districts but the good residential areas have low percentages of positives. The fairly good residential areas and the business districts have about 40 per cent of rats positive. The very poor slum district has about 60 per cent of the rats positive. Human cases originated in all districts and showed a general but not detailed correlation with the percentages of positive rats. Apparently human infections depend upon a local concentration of positive rats rather than a uniform distribution of infected rats in an area.

I truly appreciate the honor conferred on me by the Society in inviting me to deliver the fifth Charles Franklin Craig Lecture. This honor is appreciated not only on account of the high regard I entertain for Doctor Craig but also because the Society has complimented me by assuming that I may approach the high standard set by the four previous lecturers, to whom I have had the pleasure of listening. In this paper no attempt will be made to present an adequate review of typhus fever since such a presentation would require many times the space and time permissible. Only those features of the disease will be mentioned which it is necessary to discuss in arriving at an understanding of the problems of control which face us today. With this in mind no effort has been made to make reference to all who have contributed to the voluminous literature dealing with typhus in recent years, mention being reserved for the work of those investigators whose contributions best illustrate the points under discussion at the moment.

Endemic (murine) typhus fever is undoubtedly the most widespread of all the rickettsial group of infections, among which, fortunately, it may be classified as the more benign. Although not of epidemic nature it co-exists geographically with the classical old world louse-borne typhus prevalent throughout the European countries, in North A:frica and the Middle East, and throughout Asia, especially in India, Russia, and China. Japan has known both the epidemic (louse-borne) and murine (flea-borne) diseases and each of these typhus infections has been contracted by the peoples of Central American countries including Mexico, Chile, and Nicaragua. When so associated with the virulent epidemic form of typhus the murine disease is always the more benign, always the more sporadic, with a greater seasonal incidence during the summer and fall in contradistinction to the winter tendencies of the louseborne type. The above-mentioned countries are not the limiting boundaries of endemic typhus. It is being observed constantly that combinations of rats, fleas and crowded populations in tropical and subtropical climates suggest the probable presence of murine typhus. In all of the Atlantic seaboard cities, and in