Brucellosis

Clinical and Laboratory Aspects

Edward J. Young, Michael J. Corbel

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000141900
• Edition: 1
• Topic: Médecine
• Subtopic: Médecine vétérinaire

Fourteen brucellosis experts from seven countries discuss the history, epidemiology, microbiology, immunology, diagnosis, treatment, and control of brucellosis in animals and man. Edited by members of the World Health Organization's Expert Committee on Brucellosis, this text is the first comprehensive treatment of the disease since The Nature of Brucellosis by Wesley W. Spink in 1956. Topics reviewed with current references include infection caused by newer species of Brucella, such as B. canis, newer diagnostic techniques, such as radioimmunoassay and ELISA, and newer treatments, such as rifampin and the quinolones. The pathogenesis and pathophysiology of brucellosis is reviewed in depth, correlating the disease in animals with the illness in humans. This volume is extremely useful for clinicians, researchers, and students in medicine, veterinary science, microbiology, immunology, epidemiology, public health, and international health.

Chapter 1

HISTORY OF BRUCELLA AS A HUMAN PATHOGEN

Wendell H. Hall

TABLE OF CONTENTS

I.	Introduction
II.	Brucella melitensis
III.	Brucella abortus
IV.	Brucella suis
V.	Brucella canis
VI.	Conclusions
References

I. Introduction

Brucellosis is an infectious disease caused by the bacterial species now called Brucella in honor of the physician David Bruce, who first discovered the organism in 1887 in spleens from British soldiers fatally infected while stationed on the island of Malta.¹ In the first patient, sections of spleen were stained by Gram’s method and also with methylene blue, revealing large numbers of “micrococci”. In another four cases, bits of spleen tissue were inoculated into tubes containing nutrient agar, and small round colonies appeared after incubation at 37°C for 68 h. Upon examination of stained smears under high power, numerous “micrococci” were again visualized. In a second paper, Bruce described the presence of similar bacteria in another fatal case, with organisms measuring 0.0008 to 0.001 mm in diameter, singly and in pairs, scattered throughout the organ. A monkey inoculated with the bacteria died, and organisms were found in its liver and spleen.² In two later reports, Bruce described the pathology of the disease in man, contrasting it with typhoid fever (no enteric lesions), and malaria (no parasites). He then described the microorganism as Gram-negative.^3,4

In 1897 Almroth Wright and his colleagues^5,6 described the serum agglutination test which, in modified form, has become the most widely used method for diagnosing brucellosis. In this test, diluted serum was mixed with either live or dead brucella in capillary tubes, and observed for visible clumping. Agglutinating antibodies were found in the sera of infected patients, even when cultures of their blood were sterile. Moreover, the test was said to be “specific” and could be used to distinguish patients with brucellosis from those with typhoid and other enteric fevers.

The same year (1897), M. Louis Hughes published a monograph describing his extensive experience (1890 to 1896) with the disease in Malta, stressing the “undulant” course of the fever in man.⁷ Hughes confirmed Bruce’s finding that specific microorganisms were present in the enlarged spleens of rare (2%) fatal infections in man, but he found no specific pathological lesions. He also failed to identify the source of the disease (infected goats); instead, he placed the blame on poor sanitary conditions.

II. Brucella Melitensis

In 1904, owing to the high prevalence of “Mediterranean Fever” among civilians and in members of the British Army and Navy in Malta, the Royal Society of London, together with the Governor of Malta, established a Commission with David Bruce as Chairman, to study the disease. The findings of the Mediterranean Fever Commission (see also Chapter 2), were described in a series of seven “Reports” published in London between 1905 and 1907.⁸ Only those reports relevant to our subject need be reviewed here, as they have been abstracted previously.^{9, 10, 11} In Part I,⁸ R. T. Gilmour described a method for cultivating in broth, the causal organism, Micrococcus melitensis, from small amounts of blood from Malta fever victims. E. A. Shaw also found small numbers of the microorganism in the circulation of patients from as early as the 7th day, to as late as the 98th day of the disease (Reference 8, Part I, page 95, Part III, page 5). W. H. Horrocks found that bacteremia persisted in some patients even after they were clinically well (Reference 8, Part III, page 56). Horrocks and J. C. Kennedy also cultured the bacteria from the urine of patients; the bacteria occurred either as sudden gushes of enormous numbers, or as a prolonged excretion of small numbers (Reference 8, Part I, page 21, Part III, page 56).

Wishing to carry out experimental studies in animals, Horrocks found that goats were the only animals readily available in Malta. He was assisted by a Maltese physician, Themistokles Zammit, who gathered together six goats from two different herds. Zammit performed serum agglutination tests for M. melitensis prior to inoculation, and to his surprise, found that five of six goats had strongly positive reactions (Reference 8, Part III, page 83). M. melitensis was later recovered from the blood of one of these goats prior to experimental challenge. At that time there were about 20,000 goats in Malta, in herds numbering 4 to 35 animals. The human population consisted of about 200,000 civilians and approximately 25,000 British military personnel. Fresh, unboiled milk, cheese and ice cream from local goats were important items in the diet of residents of the island, and M. melitensis was found in large numbers in these dairy products (Reference 8, Part IV, page 37). Studies revealed that several million brucella could be present in a gram of fresh goat’s milk cheese. Uninfected goats and monkeys fed the bacteria, or the milk of infected goats, developed brucellosis after 3 to 4 weeks, even though they often appeared healthy, with no obvious physical changes in their milk. Unfortunately, the Commission did not report on abortions among pregnant goats, nor did they analyze placental tissue or newborn kids for evidence of the disease.⁹ In 1906, as a result of the Commission’s findings, the British authorities prohibited the consumption of fresh goat’s milk and its products by military personnel in Malta. The incidence of brucellosis and deaths due to the disease among the military promptly fell, while the disease continued unabated among civilians who continued to consume fresh milk from infected goats.¹² Subsequently, Horrocks discovered that boiling (sterilization) or heating to 68°C for 10 min (pasteurization) destroyed M. melitensis in contaminated milk.¹³ The literature on the epidemiology and control of brucellosis in animals has been reviewed elsewhere¹¹ (see also Chapter 3).

The synonym “Mediterranean Fever” implied that brucellosis in animals and humans was not confined to Malta, for it was also prevalent in goats, sheep, cattle, and humans in Gibraltar, Spain, southern France, northern Africa, and Italy early in the 20th century.⁹ The disease was subsequently found to be endemic in the U.S. among persons drinking goat’s milk in southwest Texas as early as 1911.¹⁴

In 1943,1. Forrest Huddleson, a veterinary microbiologist at Michigan State University, reviewed the microbiological features of the organism causing brucellosis.¹⁵ He described Brucella melitensis as an aerobic, Gram-negative coccobacillus which did not require CO₂ for primary isolation. He also described in detail the growth characteristics of the organism, including metabolic activities, and the inhibition of growth by low concentrations of certain aniline dyes, which aided in identifying the various species of Brucella.

In Huddleson’s text, J. B. Polding briefly reviewed experiments carried out in Malta (1937 to 1939) which clearly showed that B. melitensis caused abortions in some, but not all, pregnant goats when they were challenged by subcutaneous injections of a smooth colony type. He also showed that pregnant goats were more susceptible to infection than nonpregnant animals. Bacteremia occurred following challenge and infection spread rapidly to disease-free animals upon contact with infected goats within herds. Brucella was cultured from both vaginal secretions and the milk of infected animals. Brucella was also readily recovered from the placenta and from tissues of aborted fetuses. Kid goats were relatively resistant to infection by direct contact, but were easily infected by subcutaneous inoculation. Unfortunately studies of the histopathology of organs from infected animals were not reported, nor were attempts made to reco...