Microbiology, 2021

CHAPTER 26
Nervous System Infections
Figure 26.1 This dog is exhibiting the restlessness and aggression associated with rabies, a neurological disease
that frequently affects mammals and can be transmitted to humans. (credit: modification of work by the Centers for
Disease Control and Prevention)
Chapter Outline
26.1 Anatomy of the Nervous System
26.2 Bacterial Diseases of the Nervous System
26.3 Acellular Diseases of the Nervous System
26.4 Fungal and Parasitic Diseases of the Nervous System
INTRODUCTION Few diseases inspire the kind of fear that rabies does. The name is derived from the Latin
word for “madness” or “fury,” most likely because animals infected with rabies may behave with
uncharacteristic rage and aggression. And while the thought of being attacked by a rabid animal is terrifying
enough, the disease itself is even more frightful. Once symptoms appear, the disease is almost always fatal,
even when treated.
Rabies is an example of a neurological disease caused by an acellular pathogen. The rabies virus enters
nervous tissue shortly after transmission and makes its way to the central nervous system, where its presence
leads to changes in behavior and motor function. Well-known symptoms associated with rabid animals
include foaming at the mouth, hydrophobia (fear of water), and unusually aggressive behavior. Rabies claims
tens of thousands of human lives worldwide, mainly in Africa and Asia. Most human cases result from dog
bites, although many mammal species can become infected and transmit the disease. Human infection rates
are low in the United States and many other countries as a result of control measures in animal populations.