Ch 22. Microbial Diseases of the Nervous System

Tetanus: Etiological agent

Clostridium tetani (endospore)

Tetanus: Taxonomic classification

Gram positive bacterium (bacilli)

Tetanus: Transmission

parenteral route introduces spores

- Spores of C. tetani enter the body through a puncture wound

- Spores encyst in a scab creating an anaerobic environment

- C. tetani proliferate, producing the neurotoxin tetanospasmin

- Accumulation of the toxin causes spasming of the muscles

Tetanus: Significant symptoms

Accumulation of the toxin causes spasming of the muscles

- Typically, first muscles to experience spasming are the jaws (lockjaw) and

face (rictus grin)

- Spasming (tetany) of the chest, neck, back, and buttocks can result in

opisthotonos (arching of the whole body), fractures and muscle tearing

Tetanus: Diagnosis, treatment, and prevention

Diagnosis: recognition of symptoms

Treatment: monoclonal antibody therapy, antibiotics (metronidazole, benzodiazepines to control muscle spasms, tracheotomy and ventilation

Prevention: DPR vaccine, prophylaxis boosters, wound care, avoiding

risky behaviors

Tetanus: Other

Prevalence: >209,000 cases worldwide annually

Mortality: ~10% (respiratory and muscular paralysis)

Botulism: Etiological agent

Clostridium botulinum (durable endospores)

Botulism: Taxonomic classification

Gram positive bacterium (bacilli)

Botulism: Transmission

Primarily through consumption of tainted food (Likely anaerobically sealed food packaged w/o O2 like a can or jar)

- C. botulinum grows in anaerobic environments, and produces one of many types of neurotoxins

- Consumption of food tainted with the neurotoxin begins intoxication

Botulism: Significant symptoms

- Initial symptoms are similar to other forms of food poisoning;

nausea, abdominal and lack of fever

- As accumulation of neurotoxin progresses, blurred vision, progressive flaccid paralysis, reduced muscle movement, and dyspnea (labored breathing)

- Untreated symptoms can lead to total paralysis

Botulism: Diagnosis, treatment, and prevention

Diagnosis: identification of symptoms, testing for spores and/or neurotoxin in stool

Treatment: antitoxin

Prevention: avoiding spoiled food

Botulism: Other

Mortality: 7.5% (respiratory and muscular paralysis)

Prevalence: >1,000 cases worldwide annually

Listeriosis: Etiological agent

Listeria monocytogenes

Listeriosis: Taxonomic classification

Gram positive bacterium (bacilli)

Listeriosis: Transmission

- consumption of tainted food (usually cold foods, high in sugar, high fat), vertical transmission from mother to fetus

- Consumption of tainted foods with L. monocytogenes allows the bacterium to enter the body

Listeriosis: Significant symptoms

- The bacterium produces beta hemolysin in the bloodstream, causing systemic symptoms such as fever, muscle aches, and diarrhea

- Accumulation of the bacterium in the nervous system causes meningitis (swelling of the meninges) and encephalitis (swelling of the brain)

- Prolonged infection can lead to sepsis

Listeriosis: Diagnosis, treatment, and prevention

Diagnosis: isolation of bacterium from blood or CSF

Treatment: antibiotics (ampicillin)

Prevention: hygiene and sanitation, avoiding soft cheese in "at-risk"

group

Listeriosis: Other

- Prevalence: >1,600 cases worldwide annually

Mortality: ~16% (sepsis, meningitis, encephalitits)

- Fetal mortality: ~ 22%

- Leading cause of foodborne death in the US

Lyme disease: Etiological agent

Borrelia sp.

Lyme Disease: Taxonomic classification

Gram negative bacterium (spirochetes)

Lyme Disease: Transmission

bite of an infected Ixodes sp. ticks (KNOW TICK)

- An infected tick or flea bites a patient, introducing the bacteria

- Spirochetes colonize the bloodstream and lymphatic system

Lyme Disease: Significant symptoms

- At the site of infection, waves of inflammation causes bull's eye rash

- Systemic symptoms include fatigue, headache, body aches, fever,

chills, muscle pain, joint pain

- Neurological symptoms include aseptic meningitis, photosensitivity, partial loss of vision, facial palsy, impaired motor or sensory functions, arthritis

Lyme Disease: Diagnosis, treatment, and prevention

Diagnosis: recognition of symptoms (Bullseye rash), serological testing

Treatment: antibiotics (doxycycline)

Prevention: insect repellent, avoiding risk areas, pet control, wearing long sleeves/legged clothes (Keeping ticks off body)

Lyme Disease: Other

Prevalence: 25,000 cases worldwide annually

Seasonal: (April - September)

Mortality:

Hansen's Disease (Leprosy): Etiological agent

Mycobacterium leprae

Hansen's Disease (Leprosy): Taxonomic classification

Acid-fast bacterium (bacilli)

Hansen's Disease (Leprosy): Transmission

direct contact with infected persons or animal vectors

- Mechanism for transmission for M. leprae is mostly unknown

- Once the bacterium is in the body, it disseminates through the nervous

system, causing systemic infection

Leprosy: Significant symptoms

Systemic symptoms include runny nose, and muscle weakness

- Neurological symptoms include loss of sensation in the extremities

- Skin symptoms include dry skin, discoloration of the skin, thickening of the facial skin

Leprosy: Diagnosis, treatment, and prevention

Diagnosis: recognition of symptoms, neurological testing (poke with needle and ask if it hurt), acid-fast staining

Treatment: multi-drug therapy

Prevention: avoiding contact with infected persons, avoiding armadillos

Leprosy: Other

Prevalence: >200,000 cases worldwide annually

Mortality: ~2% (organ failure) facial lesions

Cryptococcosis: Etiological agent

Cryptococcus sp.

Cryptococcosis: Taxonomic classification

Fungus (yeast)

Cryptococcosis: Transmission

inhalation of fungal spores

Inhalation of Cryptococcal spore will allow the spores to germinate in the lungs and become yeast like

- Initial germination causes reparatory symptoms

Cryptococcosis: Significant symptoms

Initial germination causes reparatory symptoms such as cough, shortness of breath, chest pain and fever

- As a yeast, they will disseminate into central nervous system, encapsulating on the brain and meninges

- At the yeast grows, waste produces will cause headache, fever, neck pain, nausea, vomiting, photosensitivity, confusion, and meningitis

Cryptococcosis: Diagnosis, treatment, and prevention

- Diagnosis: agglutination of antigens in serum or CSF

- Treatment: antifungals (amphotericin B)

- Prevention: avoiding bird droppings, regular screening in "at-risk" groups, prophylactic antifungals

Cryptococcosis: Other

- Prevalence: >900 cases worldwide annually

- Mortality: 60% (meningitis, complications in the brain)

Poliomyelitis: Etiological agent

Poliovirus

Poliomyelitis: Taxonomic classification

Group IV nonenveloped icosahedral virus

Poliomyelitis: Transmission

consumption of tainted water

- The host ingests water tainted with poliovirus

-Poliovirus enters the GI system by binding to CD155n receptor of the endothelium

-The virus replicates in the GI system, causing GI symptoms such as sore throat, low fever and abdominal discomfort

Poliomyelitis: Significant symptoms

- The virus replicates in the GI system, causing GI symptoms such as sore throat, low fever and abdominal discomfort

- If the virus disseminates to the central nervous system, the infection becomes more severe

- Neurological symptoms include headache, neck pain, back pain, abdominal pain, extremity pain, fever, vomiting, lethargy, aseptic meningitis, and paralysis

Poliomyelitis: Diagnosis, treatment, and prevention

Diagnosis: identification of flaccid paralysis, identification of virus in stool sample

Treatment: analgesics for pain, physical therapy, surgery, respirators

Prevention: hygiene and sanitation, polio vaccine

Poliomyelitis: Other

Prevalence: >600 cases worldwide annually

Mortality: 2 - 75% (respiratory and muscular paralysis, meningitis)

Rabies: Etiological agent

Rabies lyssavirus

Rabies: Taxonomic classification

Group V nonenveloped helical virus

Rabies: Transmission

being bitten by an afflicted animal

The host is bitten by an animal infect with rabies, and the virus is transmitted through the saliva

The virus will slowly divide in the host's nervous system for months

Rabies: Significant symptoms

- First symptoms are typical general and systemic, such as fever or headache

- As symptoms progress, the patient can display aggressive neurological symptoms, such as meningitis, paralysis, anxiety, insomnia, confusion, agitation, abnormal psychological behaviors, photosensitivity, paranoia, terror, hallucinations, delirium, and coma

- Some patients will develop "dumb" rabies, with less aggressive symptoms like lethargy,

depression, loss of coordination, and coma

Rabies: Diagnosis, treatment, and prevention

Diagnosis: identification bite through patient history

Treatment: rabies vaccine "after-bite"

Prevention: rabies vaccines, vaccinating animals, pet control, avoiding wild animals

Rabies: Other

Prevalence: Endemic

Mortality: Nearly ALWAYS Fatal (cardio-respiratory arrest, paralysis)

Trypanosomiasis: Etiological agent

Trypanosoma brucei

Trypanosomiasis: Taxonomic classification

Flagellated protozoan (Mastigophora)

Lifestyle: obligate parasite (human = intermediate host)

Trypanosomiasis: Transmission

being bitten a Tsetse fly

- The host is bitten by Tsetse fly, and the fly deposits the trophozoites in saliva

- The trophozoites travel through the blood vessels to the central nervous system

- Matured trophozoites cause systemic symptoms through production of waste products

Trypanosomiasis: Significant symptoms

- Matured trophozoites cause systemic symptoms through production of waste products such as fever, headache, joint pain, itching, weakness, fatigue, enlargement of the liver and spleen, swelling of the lymph nodes

- As the infection progresses, severe symptoms develop, such as sleep-wake inversion, tremors, hemiparesis, hallucinations, anxiety, delirium, mania, confusion, coma

Trypanosomiasis: Diagnosis, treatment, and prevention

Diagnosis: microscopy of ulcer fluid, blood or CSF for parasitemia

Treatment: antiprotozoals (fexinidazole)

Prevention: insect repellent, avoiding risk areas, wearing long sleeved/legged clothing, fly traps

Trypanosomiasis: Other

Prevalence: <600 cases worldwide annually

Mortality: FATAL if untreated (coma, organ failure)

Variant Creutzfeldt-Jakob Disease (Mad

Cow: Etiological agent

PrPSc

VCJD (Mad

Cow): Taxonomic classification

prion

Mad Cow Disease: Transmission

Consumption of tainted meats, or contact with tainted blood or semen

The prion is consumed in tainted meat

Through methods unknown, the prion converts healthy proteins in the brain into infectious prions

- As prions accumulate in the brain, the brain tissue will begin to congregate together in spongiform encephalopathy

-Neurological symptoms begin to manifest shortly after

Mad Cow Disease: Significant symptoms

Patients will display psychiatric problems, behavioral changes, extreme pain, loss of coordination, dementia, involuntary muscle movements

Mad Cow Disease: Other

Prevalence:

Kuru

(isolated case of prionic diseases) Kuru is caused by a prion from the same family as VCJD

- The prion is consumed in tainted meat

- Through methods unknown, the prion converts healthy proteins in the brain into infectious prions

- As prions accumulate in the brain, the brain tissue will begin to congregate together in spongiform encephalopathy

- Neurological symptoms begin to manifest shortly after

- Patients will display headache, joint pain, unsteady gait, decrease muscle control, dysarthria (inability to speak), tremors, uncontrollable sporadic laughter, dysphagia (inability to swallow)

Mortality: ALWAYS FATAL (destruction of the brain and spinal cord)

Mad Cow Disease nd kuru: Diagnosis, treatment, and prevention

- Diagnosis: examination of brain tissue

- Treatment: none.

- Prevention: avoiding tainted beef products, avoiding tainted blood/blood transfusions, condoms

- For Kuru, avoiding cannibalism