Microbiology: Chapter 19

African Sleeping Sickness

Trypanosoma brucei •Hemoflagellate: lives in the blood and tissues of the human host •Trypanosomiasis affects millions of individuals in 36 countries in Africa •Transmitted by the tsetse fly •T. brucei gambiense T. brucei rhodesiense

Rabies

Virus: rabies virus

Encephalitis

Viruses: Arboviruses Herpes Simplex 1 and 2 JC Virus

Both ____ and ____ can cross the placenta and infect the fetus.

West Nile and Toxoplasma gondii

The _____ _____ barrier restricts certain molecules and microbes from entering the CNS.

blood-brain

Coccidioides

"Valley Fever" Fungus with a distinctive morphology: •25°C: moist white to brown colony with abundant, branching, septate hyphae •37°C to 40°C: parasitic phase, small spherule True systemic fungal infection of high virulence Genetic susceptibility gives rise to more serious disease

The ________ virus may live in a dormant state in neurons.

herpes

Lessened immune response in the brain is known as "________ ________."

immunologically privileged

Meningitis

inflammation of the meninges of the brain and spinal cord often caused by bacteria such as Neissera meningitidis and Haemophilus influenzae

Subacute Encephalitis

Symptoms take longer to show up and are less striking Common causes: •Toxoplasma •Persistent measles infection •Prions

Neonatal and Infant Meningitis

-Streptococcus agalactiae, Escherichia coli, Listeria monocytogenes, and Cronobacter sakazakii •Usually the result of an infection transmitted by the mother in utero or during passage through the birth canal •As more premature babies survive, rates of neonatal meningitis increase •Morbidity has increased but mortality rates have significantly declined •Two most common causes are Streptococcus agalactiae and Escherichia coli •Listeria monocytogenes is also found frequently in neonates

Explain the difference between the oral polio vaccine and the inactivated polio vaccine and the advantages and disadvantages of each.

-The oral contains attenuated virus that can multiply in vaccinated people and spread to others. -IPV, using killed virus is the only vaccine used in the U.S

Identify the conditions for which vaccination is available.

-Meningitis (Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae) -Rabies -Poliomyelitis -Tetanus -Botulism

List the possible causative agents for meningitis and neonatal/infant meningitis.

-Neisseria meningitidis -Streptococcus pneumoniae -Haemophilus influenzae -Listeria monocytogenes -Cryptococcus neoformans -Coccidioides -Viruses Neonatal and Infant Meningitis -Streptococcus agalactiae -Escherichia coli, strain K1 -Listeria monocytogenes -Cronobacter sakazakii

Toxoplasma gondii Infection During Pregnancy

33% chance of the mother transmitting the infection to the fetus Congenital infection in the first or second trimester associated with: •Stillbirth •Liver and spleen enlargement •Liver failure •Hydrocephalus •Convulsions •Damage to retina, blindness

Deadliness of selected diseases affecting the nervous system

75%-100% ----------Rabies, HIV 50%-74%------------TB, Ebola, Plague 25%-49%------------Syphilis 0%-24%-------------Rhinovirus, Malaria, Polio, Mumps, C.diff, Cholera, Seasonal Flu, Dengue, Lyme Disease, Campylobacter, Norovirus, Chickenpox, Rubella, Smallpox, Pertusiss, Measles, Rotavirus, Hepatitis B

Protozoa

Acanthamoeba - Meningoencephalitis Naegleria fowleri - Meningoencephalitis Toxoplasma gondii - Subacute encephalitis Trypanosoma brucei subspecies gambiense and rhodesiense - African sleeping sickness

Poliomyelitis

Acute enteroviral infection of the spinal cord •Can cause neuromuscular paralysis Signs and symptoms: •Fever, headache, nausea, sore throat, myalgia •Neurotropic: infiltrates the anterior horn of the motor neurons of the spinal cord •Also attacks the spinal ganglia, cranial nerves, and motor nuclei Paralytic disease: •Various degrees of flaccid paralysis of the muscles of the legs, abdomen, back, intercostals, diaphragm, pectoral girdle, and bladder Bulbar poliomyelitis: •Brain stem, medulla, and cranial nerves are affected •Loss of control of cardiorespiratory regulatory centers Post-polio syndrome: •Progressive muscle deterioration in 25 to 50% of patients decades after the initial infection

Acute Encephalitis

Almost always caused by viral infection Signs and symptoms: •Behavior changes or confusion due to inflammation •Decreased consciousness and seizures Symptoms of meningitis Treatment is usually with acyclovir

Acute Encephalitis

Arboviruses (viruses causing West Nile, La Crosse, Jamestown Canyon, Powassan, and eastern equine encephalitis) Herpes simplex 1 or 2 JC virus Postinfection Encephalitis

RNA viruses

Arboviruses: Eastern equine encephalitis virus, LaCrosse virus, Jamestown Canyon virus, Powassan virus, West Nile virus - Encephalitis Measles virus - Subacute sclerosing panencephalitis Poliovirus - Poliomyelitis Rabies virus - Rabies

The CNS consist of ________ and ________. The PNS consist of _______ and _______.

CNS - brain and spinal cord PNS - nerves and ganglia

Blood-Brain Barrier

Cells that make up the walls of blood vessels around the brain allow very few molecules to pass through •Freer passage of ions, sugars, and other metabolites in other areas of the body Prohibits most microorganisms from passing into the CNS Drugs and antibiotics are difficult to introduce into the CNS when needed

gram-positive endospore-forming bacteria

Clostridium botulinum - Botulism Clostridium tetani - Tetanus

Tetanus

Clostridium tetani: •Common resident of soil and GI tracts of animals •Gram-positive, endospore-forming rod •Endospores are only produced under anaerobic conditions

Prions

Creutzfeldt-Jakob prion - Creutzfeldt-Jakob disease

gram-negative bacteria

Cronobacter sakazakii - Neonatal and infant meningitis Escherichia coli - Neonatal meningitis Haemophilus influenzae - Meningitis Neisseria meningitidisv- Meningococcal meningitis

Fungi

Cryptococcus neoformans - Meningitis Coccidioides species - Meningitis

The Nervous System and Its Defenses

Defenses of the nervous system are mainly structural: •Bony casings of the brain and spinal cord protect them from traumatic energy •CSF serves as a cushion against impact •Blood-brain barrier

The three layer of the meninges are

Dura mater Arachnoid mater Pia mater

Botulism

Intoxication: caused by an exotoxin Associated with eating poorly preserved foods 10 to 30 outbreaks per year in the United States Three major forms: •Food-borne botulism •Infant botulism Wound botulism

Meningoencephalitis

Encephalitis: inflammation of the brain •Because of the close association of the brain and spinal cord, infection of one structure may involve the other Amoebas cause meningoencephalitis: •Naegleria fowleri •Acanthamoeba

Toxoplasma gondii

Extensive worldwide distribution •Estimated that the majority of the world's population is affected at some time in their lives •Infection in the fetus and immunodeficient is often fatal •People with a history of Toxoplasma are more likely to display thrill-seeking behaviors Flagellated parasite •Can attack at least 200 species of birds and mammals •Primary reservoir is felines, both wild and domestic Signs and symptoms: •Usually asymptomatic •Sore throat, lymph node enlargement, low-grade fever •Chronic or subacute encephalitis in patients with immune suppression

Communicability of selected diseases affecting the nervous system

Extremely Comm----------Measles, Malaria, Mumps, Rotavirus, Pertussis Very Comm----------------Chickenpox Communicable------------TB, Polio, Rubella, Smallpox, Dengue, Rhinovirus Somewhat or Min-----------C. diff, Cholera, Seasonal Flu, Ebola, Hepatitis B, Lyme Disease, Norovirus, Plague, Rabies, Campylobacter, HIV, Syphilis

Signs and Symptoms of Meningitis

Meningitis has the following typical symptoms, regardless of the cause: •Photophobia •Headache •Painful or stiff neck •Fever •Increased WBC in CSF •Certain microorganisms may cause additional characteristic symptoms Can manifest as acute or chronic disease: •Some organisms are more likely to cause acute meningitis, others cause chronic meningitis In a healthy person, it is difficult for microorganisms to gain access to the nervous system •Successful organisms have specific virulence factors

Structure of the Peripheral Nervous System

Ganglia: swelling in the nerve where cell bodies of neurons congregate Nerves: bundles of neuronal axons that transmit nerve signals •Axons and dendrites of adjacent neurons communicate over a synapse •Neurotransmitters released from one cell act on the next cell in the synapse

Herpes Simplex Virus

Herpes simplex types I and II can cause encephalitis in newborns of HSV-positive mothers •Virus is disseminated and progress is poor Older children and adults over 50 are also susceptible •Caused most commonly by HSV-I •Represents a reactivation of dormant HSV from the trigemminal ganglion

DNA viruses

Herpes simplex virus 1 and 2 - Encephalitis JC virus - Progressive multifocal leukoencephalopathy

Polio Prevention

Humans are the only known reservoir Vaccination as early in life as possible with 4 doses, starting at 2 months of age •IPV: developed by Salk in 1954, used in the United States •OPV: developed by Sabin in the 1960s

Meningitis

Inflammation of the meninges Anatomical syndrome: •Different microbes cause meningitis, and produce a similar constellation of syndromes •Noninfectious causes of meningitis exist as well, but are less common Serious forms of acute meningitis are caused by bacteria Entrance into CNS is facilitated by coinfection or previous infection with respiratory viruses

Human Microbiome Project

Information from the HMP is revealing a potential link between the gut microbiome and the nervous system Gut microbiota may induce CNS autoimmunity •Appear to cause changes in the brain chemistry and behavior •Phenomenon is known as the gut-brain axis

Discuss the current state of knowledge regarding the normal biota of the nervous system.

It is still believed that the CNS and PNS lack normal biota of any kind.

N. meningitidis Pathogenesis and Virulence Factors

Meningococcemia: •Rare, high mortality rate Endotoxin acts as a potent WBC stimulator •Damage to blood vessels caused by cytokines released by WBC leads to vascular collapse, hemorrhage, and crops of red or purple lesions called petechiae on the trunk and appendages

Escherichia coli

K1 strain is second most common cause of neonatal meningitis Most common in premature babies Prognosis is poor: •20% mortality rate Brain damage among those who survive Usually transmitted by the mother's birth canal transmitted: verticle (during birth) prevention: N/A

La Crosse, Jamestown Canyon, and Powassan Viruses

La Crosse Virus •Reported in the eastern half of the United States and Texas •Maintained by infection of small mammals •Neuroinvasive form occurs primarily in children <16 years old Rarely fatal Jamestown Canyon Virus •Cycles between mosquitos and deer or moose 22 cases reported in 2013 Powassan Virus •Maintained in nature by ticks and groundhogs •15 cases reported in 2013 •Distributed in NE and Great lakes states

Brain and Spinal Cord

Made up of neurons surrounded by bone: •Brain inside the skull •Spinal cord inside the spinal column Brain surrounded by meninges: •Dura mater •Arachnoid mater •Pia mater Cerebrospinal fluid (CSF): •Fills the subarachnoid space •Clear, serum-like fluid •Provides nutrition to the CNS •Provides a liquid cushion for the brain and spinal cord

Discuss important features of meningoencephalitis, encephalitis, and subacute encephalitis.

Mostly directly involve the brain Meningoencephalitis -Inflammation of brain and spinal cord -N. Fowleri and Acanthamoeba - N. Fowleri found in water and Acanthamoeba from direct contact Encephalitis -Inflammation of the brain, subacute or acute - Acute caused by viral infections (Almost always caused by insects, west nile, herpes) -Subacute caused by T. Gondii, measles or prions -Subacute symptoms take longer to appear Subacute encephalitis - Inflammation of the meninges. -Toxoplasma gondii and Prions -The more serious forms are caused by bacteria, often facilitated by coinfection or previous infection with respiratory viruses. - Severe headache, painful or stiff neck, fever, and nausea and vomiting.

Identify which of the agents causing meningitis is the most common and which is the most deadly.

N. Meningitidis: -Gram-negative diplococcus; causes most serious form of acute meningitis. H. influenzae: Declined sharply because of vaccination. L. monocytogenes: -Most cases are associated with ingesting contaminated dairy products, poultry, and meat. C. neoformans:-Fungus; causes chronic form with more gradual onset of symptoms. Coccidioides species:-"Valley Fever"; begins in lungs but can spread quickly throughout body; highest incidence in SW U.S, Mexico, and parts of Central and S America. Viruses:-Very common, particularly in children; 90% are caused by enteroviruses.

Identify which encephalitis-causing viruses you should be aware of in your geographic area.

Naegleria fowleri Acute encephalitis - West Nile, Jamestown Canyon Virus, La Crosse virus

Tetanus Prevention

One of the world's most preventable diseases Vaccination with the tetanus toxoid, usually in combination with diphtheria and pertussis toxoids Vaccinations given to children under 7 years •Td booster should be given every 10 years thereafter Toxoid should also be given to injured persons who have never been immunized, have not completed the series, or whose last booster was received more than 10 years previously Vaccine can also be given with passive TIG

Subacute Encephalitis:Other Conditions to Consider

Other conditions may display subacute encephalitis symptoms: •Rickettsial diseases (Rocky Mountain spotted fever) (chapter 20) •Lyme disease (chapter 20) •Bartonella or Anaplasma disease (chapter 20) •Tapeworm disease—Taenia solium (chapter 22) Syphilis—Treponema pallidum (chapter 23)

Prions

Proteinaceous infectious particles: •Contain no genetic material •Cause transmissible spongiform encephalopathies: •Creutzfeldt-Jacob disease (CJD) •Gerstmann-Strussler-Scheinker disease •Kuru •Fatal familial insomnia •Scrapie in sheep and goats •Transmissible mink encephalopathy •Bovine spongiform encephalopathy (BSE) Normal protein in the brain (PRP^C) is transformed into a prion protein (PRP^SC) Altered protein spontaneously converts other PRPC proteins into PRP^SC proteins Accumulation of PRP^SC proteins cause plaques and spongiform damage (holes) in the brain Can cause disease when transferred to a new host •Contaminated instruments Infected meat

Subacute Encephalitis

Protozoa: Taxoplasma gondii Virus: Measles virus Prions: prions

List the possible causative agents for each of the following conditions: rabies, poliomyelitis, tetanus, botulism, and African sleeping sickness.

Rabies - Rabies virus (bite from wild or stray animal) Poliomyelitis - Poliovirus (fecal-oral, vehicle) Tetanus - Clostridium tetani (puncture wounds, burns, umbilical stumps, frostbite, crushed body parts, passed to baby from mother) Botulism - Clostridium botulinum (wound, puncture, food-borne) African sleeping sickness - Trypanosoma brucei (tsetse flies)

Rabies Transmission and Epidemiology

Reservoirs: wild mammals such as canines, skunks, raccoons, badgers, cats, and bats •Spread to domestic animals and humans through bites, scratches, and inhalation of droplets Estimated 35,000 to 50,000 human cases per year worldwide •United States: 6000 to 7000 animal cases per year •2004: transmission of rabies through donated organs and tissues Transmission through cornea implants

Important Functions of the Nervous System

Sensory: •Sensory receptors at the ends of peripheral nerves •Generate nerve impulses transmitted to the CNS Integrative: •Translates impulses into sensation or thought •Drives motor function Motor: Involves muscles and glands

Rabies

Slow, progressive zoonotic disease characterized by fatal encephalitis Furious rabies: •Agitation, disorientation, seizures, twitching Hydrophobia Dumb rabies: •Patient is paralyzed, disoriented, stuporous Both forms progress to a coma phase: Death results from cardiac or respiratory arrest

Naegleria fowleri

Small, flask-shaped amoeba that moves by means of a single pseudopod •Rounded, thick-walled uninucleate cyst that is resistant to temperature extremes and mild chlorination Infections reported in people who have been swimming in warm, natural bodies of freshwater Amoebas forced into nasal passages utilize the olfactory nerve to enter the brain Enters the subarachnoid space causing primary amoebic meningoencephalitis (PAM) Causes rapid, massive destruction of brain and spinal tissue Cases are rare, but the disease advances so rapidly that treatment is futile •3 in 133 cases in the United States have survived transmitted: vehicle (exposure while swimming) prevention: limit water entering nasal passages

gram-positive bacteria

Streptococcus agalactiae - Neonatal meningitis Streptococcus pneumoniae - Meningitis Listeria monocytogenes - Meningitis, neonatal meningitis

Subacute Encephalitis

Toxoplasma gondii Subacute sclerosing panencephalitis Prions

True/False: The general symptoms of meningitis are similar, regardless of the cause.

True

Nervous System Defenses and Normal Biota

bony structures, blood-brain barrier, microglial cells, and macrophages

Central Nervous System (CNS)

brain and spinal cord

Which of the following diseases can not be prevented with a vaccine? a.Polio b.Tetanus c.African sleeping sickness d.Meningitis caused by Haemophilus influenzae

c.African sleeping sickness

neurons

cells that make up tissues of the brain and spinal cord that receive and transmit signals to and from the PNS and CNS

2 parts of the nervous system

central nervous system (CNS) peripheral nervous system (PNS)

blood-brain barrier

decreased permeability of the walls of blood vessels in the brain, restricting access to that compartment

Tetanus causes _________ paralysis and botulism causes _________ paralysis.

spastic, flaccid

ganglia

swelling in the nerve where cell bodies of neurons congregate

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

Peripheral Nervous System (PNS)

the sensory and motor neurons that connect the CNS to the rest of the body

meninges

the tough tri-layer membrane covering the brain and spinal cord. consist of the dura mater, arachnoid mater, and pia mater.

True/False: The gut microbiota has an influence on the nervous system and brain chemistry.

true

True/False: There is no normal biota in the central nervous system.

true

Measles Virus: Subacute Sclerosing Panencephalitis

•"Slow virus infection" •Symptoms appear years after an initial measles episode •Caused by direct viral invasion of neural tissue •Unclear what factors lead to persistence of the virus in some people

Immune Privilege of the CNS

•A different or partial immune response when exposed to immunologic challenge •Functions of the CNS are vital for the life of an organism and temporary damage from a "normal" immune response could be detrimental •Cells in the CNS express lower levels of MHC antigens •Lower quantities of complement proteins

Streptococcus pneumoniae

•Also referred to as the pneumococcus •Causes the majority of bacterial pneumonias •Most frequent cause of community-acquired meningitis •Does not cause petechiae •Most likely to occur in patients with underlying susceptibility •Carriage rates exceed 30% in some populations

List the natural defenses present in the nervous system

•Bony casings of the brain and spinal cord protect them from traumatic energy •CSF serves as a cushion against impact •Blood-brain barrier

Describe the important anatomical features of the nervous system

•Central nervous system (CNS): brain and spinal cord •Peripheral nervous system (PNS): nerves emanating from the brain and spinal cord to sense organs and to the periphery of the body

West Nile Encephalitis

•Emerged in the United States in 1999 •CDC reported in 2008 that 1% of the U.S. population had evidence of past or present infection •All encephalitis cases are treated with acyclovir, in case they are caused by this virus

Eastern Equine Encephalitis

•Endemic to an area along the eastern coast of North America and Canada •Sporadic with occasional epidemics in humans and horses •Life cycle involves birds and mosquitoes •Cases first appear in horses and caged birds •Vaccine exists for horses and its use is strongly urged to eliminate the virus from its reservoir Human case fatality rate can reach 70%

Normal Biota of the Nervous System

•Finding microorganisms of any type in these tissues represents a deviation from a healthy state •Certain viruses live in a dormant state in the nervous system between episodes of acute disease •Example: herpes simplex viruses Not considered normal biota

Cronobacter sakazakii

•Found mainly in the environment and can survive very dry conditions •Implicated in outbreaks of neonatal and infant meningitis through contaminated powdered infant formula •Cases of Cronobacter meningitis are rare •Mortality rates can reach 40% transmitted: vehicle (baby formula) prevention: safe preparation and use of, or avoidence of powdered formula

Viral Meningitis

•Four of five meningitis cases are caused by one of a wide variety of viruses •Aseptic meningitis: viral meningitis is assumed when a patient shows symptoms of meningitis but no bacteria or fungi are found in CSF •Majority of cases in children •90% caused by enteroviruses •HSV-2 is sometimes known to cause meningitis •Other herpesviruses (HHV-6, HHV-7, and HHV-3), arboviruses, arenaviruses, adenoviruses, and HIV can manifest as meningitis as well Generally milder than bacterial or fungal meningitis •Usually resolved in 2 weeks Mortality rate is less than 1% transmitted: droplet contact prevention: N/A

Cryptococcus neoformans

•Fungus that causes chronic meningitis with a gradual onset of symptoms •In AIDS patients: fast onset and acute disease •Widespread in human habitats •Spherical to ovoid shape with a large capsule •Transmitted in bird droppings transmitted: vehicle (air, dust) prevention: N/A

Haemophilus influenzae

•Gram-negative coccobacillus •Causes one of the most severe forms of meningitis in humans •Often called "Hib" because serotype B is the most common cause of infection •Vaccination has reduced asymptomatic carriage rates and has virtually eliminated Hib in the United States transmitted: droplet contact prevention: Hib vaccine, ciprofloxacin, rifampin, or ceftriaxione

Neisseria meningitidis

•Gram-negative diplococci lined up side by side •Also known as the meningococcus •Associated with epidemic forms of meningitis •Causes the most serious form of acute meningitis •Responsible for 25% of all meningitis cases •Polysaccharide capsule protects against phagocytosis transmitted: droplet contact prevention: conjugated vaccine, ciprofloxacin, rifampin, or ceftriaxione used to protect contacts

Listeria monocytogenes

•Gram-positive, ranges in morphology from coccobacilli to long filaments in palisade formation •Does not produce capsules or endospores •Has 1 to 4 flagella •Not fastidious, resistant to cold, heat, salt, pH extremes, and bile •Grows inside host cells, moves directly from an infected cell to an adjacent healthy cell transmitted: vehicle (food) prevention: cooking food, avoiding unpasteurized dairy products

Rabies Prevention and Treatment

•Imperative that treatment begins after exposure and before symptoms develop •Passive and active postexposure immunization •Vaccination of domestic animals, veterinarians, animal handlers, laboratory personnel, and travelers •Vaccine incorporated into bait to treat wild animals

African Sleeping Sickness Signs and Symptoms

•Intermittent fever, enlarged spleen, swollen lymph nodes, joint pain •Personality and behavioral changes •Extreme fatigue and sleep disturbances •Uncontrollable sleepiness during the day, sleeplessness at night •Muscle tremors, shuffling gait, slurred speech, seizures, local paralysis •Death results from coma, secondary infections, and heart damage

Streptococcus agalactiae

•Lancefield group B streptococci •Colonizes 10 to 30% of female genital tracts •Most frequent cause of neonatal meningitis •Treated with IV Penicillin G sometimes supplemented with an aminoglycoside transmitted: verticle (during birth) prevention: culture and treatment of mother

Acanthamoeba

•Large, amoeboid trophozoite with spiny pseudopods and a double-walled cyst •Invades broken skin, conjunctiva, lungs, and urogenital epithelia •Causes granulomatous amoebic meningoencephalitis (GAM) •Course of infection is lengthier than PAM •2 to 3% survival rate transmitted: direct contact prevention: N/A

When Meningitis Is Suspected?

•Lumbar puncture to obtain CSF •Gram stain and/or culture of CSF •Begin treatment with broad-spectrum antibiotics with a shift in treatment after a diagnosis has been confirmed

Specialized Immune Cells in the CNS

•Microglial cells display phagocytic activity •Brain macrophages exist in the CNS •Activity of both types of cells is less than that of phagocytic cells elsewhere in the body

Listeriosis

•Mild in healthy adults •Causes meningitis and septicemia in the elderly, immunocompromised, fetuses, and neonates •Bacterium can cross the placenta and cause premature abortion and fetal death •Associated with contaminated dairy products, poultry, and meat

Tetanospasmin

•Neurotoxin •Binds to target sites on peripheral motor neurons on the spinal cord, brain, and sympathetic nervous system •Blocks inhibition of muscle contraction, causing muscles to contract uncontrollably, resulting in spastic paralysis •Death results from paralysis of respiratory muscles and respiratory arrest

Coccidioides Transmission and Epidemiology

•Occurs endemically in natural reservoirs •C. immitis causes disease in California; C. posadasii is found in northern Mexico, Central and South America, and the American Southwest, especially Arizona transmitted: vehicle (air, dust, soil) prevention: avoiding airborne endospores

S. pneumoniae

•Small, gram-positive flattened coccus that appears in end-to-end pairs •Distinctive appearance in a Gram stain of CSF •Has a polysaccharide capsule that protects against phagocytosis •Produces an alpha-hemolysin and hydrogen peroxide, both of which have been shown to induce damage in the CNS •Resistant to penicillin, cephalosporins, and macrolide antibiotics Three vaccines are available transmitted: droplet contact prevention: two vaccines, prevnar (children and adults) and Pneumovax (adults)

Botulinum Toxin

•Toxin travels from the bloodstream to the neuromuscular junctions of skeletal muscles •Prevents the release of acetylcholine, resulting in flaccid paralysis •Utilized by doctors to treat uncontrolled muscle spasms, migraine headaches, and other conditions Also used cosmetically

Arboviruses

•Viruses transmitted by arthropod vectors •Worldwide distribution •Clustered in the tropics and subtropics; periodic epidemics in temperate zones •Most vectors feed on the blood of hosts •Peak incidence usually from late spring through early fall •Warm blooded hosts maintain the infection during cold and dry seasons •Millions of infections per year, thousands die No satisfactory treatment for most arboviral infections