Chapter 34
Vectorborne and
Soilborne Microbial
Pathogens
Animal Transmitted Pathogens
Rabies: and Endozootic or Epizootic
Rabies – Viral Encephalopathy
Rabies virus: Ass (-) RNA enveloped virus..looks like a
bullet. Kills 55,000 people world wide/year.
Rabies Virus
TEM infected animal
75 x 180 nm
Brain Histology, Negri Bodies
~ 2 - 10 nm
Virus infects CNS after an animal bite (virus is in the Saliva)
Classic Painting
of Louis Pasteur
Holding desiccated
rabbit spinal
column after
infection with
rabies (saliva from
rabid dog) virus.
Viruses were not
known at this time,
Pasteur injected
health animals with
rabid saliva
disease.
Pasteur Observing
Vaccination
(Rabies) of Joseph
Meiser who was just
recently bitten by a
rabid dog.
IP injection
A
Le Bon
Louis Pasteur Poster
Clicker Question:
A
Virtually all domestic animals (dogs and cats) are
vaccinated against rabies at 3 months old. Boosters every
3 years.
Animal bites in USA, 20,000 get postexposure prophylaxis.
And only about 3 cases/year.
The rest of the world gets 14 million postexposure
prophylaxis.
Rabies Treatment
Human patients: passively immunized with purified
rabies immunglobin injected at the site of animal bite,
and IM,
and Injected with Rabies Vaccine.
Only disease with 100% effective treatment.
Disease Reservoir: wild animals. Oral subunit vaccines
consisting of vaccinia virus or canary pox virus with
genes that encode rabies coat proteins…placed on food
baits.
Rocky Mountain Spotted Fever
Rickettsia disease Typhus transmitted by the head or
body Louse.
Rickettsias are small Gram Negative bacteria that are
obligate intracellular parasites.
Rickettsia prowazekii – Typhus.
Rickettsia rickettsii – Rocky Mountain Spotted Fever
transmitted by ticks.
Tick hemocytes
In granular hemocyte of wood Tick
Whole body RMSF rash
Spotted Fever in the USA, ~2,000 cases/yr
Spotted Fever Rickettsiosis
R. rickettssii in the salivary gland and ovaries of the dog
and wood ticks.
R. rickettssii grows in the nucleus of infected cells (unlike
all other rickettsias which grow in the cytoplasm.
Incubation period 3-12 days. Symptoms: fever, severe
headache and then the whole body rash + intestinal upset
(both ends).
Tetracycline or chloramphenicol promotes rapid recovery.
Less than 1% mortality (30% mortality untreated).
Lyme Disease and Borrelia
Male
Female
nymph
larvae
Disease of Humans, White tailed deer, White footed Mouse.
Transmitted by Ixoides, the deer tick which can also transmit
Borrelia burgdorferi to other rodents.
Lyme Disease Epidemiology
Tick after blood meal
Characteristic erythema migrans.
Erythema migrans after several days
Bull’s Eye – after the Tick Bite
Erythema Migrans
Your text photo of Borrelia…hard to see
the spiral shape
Borreilia burgdorferi
A
Tick – before and after
A
Lyme Disease and the Tick Life Cycle
Ixoides tick Life
Cycle of Hosts
White Tailed Deer
White Footed Mouse
Symptoms Following Erythema Migrans
1. FIRST STAGE
Fever, headache, chills, stiff neck, dizziness
2. SECOND STAGE
Cardiac and CNS  Crippling arthritis
Clicker Question:
Malaria: Mosquitos and Plasmodium
Infects 350 to 500 million people  killing 1 million/yr
Plasmodium vivax, P. falciparum, P. ovale, P. malariae
Malaria zone = Distribution of Anopheles mosquito
Plasmodium Life Cycle
Merozoites in RBCs
A
A
Merozoite Replication
Merozoite  Schizont  Many Merozoites
Malaria Symptoms
Merozoites bring about the major symptoms by
consuming 25-75% hemoglobin in the RBC, and
then lysing the host RBC…releasing Hb
breakdown products.
Synchronized release of merozoites brings on
paroxysms of chills and fever…at intervals of 48
or 72 hours.
P. falciparum can cause RBC to agglutinate leading to
reduced blood flow and drop of oxygen
(ischemia).
As hemoglobin breakdown products accumulate 
blackwater fever.
Malaria Epidemiology in USA
Malaria Vaccine Trials – Phases
UPDATE: Live attenuated malaria vaccine designed to protect through hepatic CD8 +
T-cell immunity. Epstein, et al. SCIENCE Oct, 2011 334:475-480
Vaccine: radiation attenuated P. falciparum sporozoites; ID and Subcut – humans
and IV- non-human primates,rabbits and mice. IV produced resistance =
challenge + 2 rechallenges.
Humans (80 naive) injected by mosquito or needles – adverse affects in ~50%
(non serious). Developed low Ab response, low CD8 T cell response.
Gates Foundation
A
Bubonic Plague and Yersinia
Plague Transmission
Cycle of Hosts Expanded
Plague: Pathology, Treatment and Control
Plaque forms: Pneumonic..rarely survive 2 days,
Septicemic..rapid without buboes, and
Bubonic..buboes, multiple local
hemorrhages = blacking of skin as
it get to the septicemic stage.
Antibiotic Treatment works if rapidly diagnosed.
Untreated death rate: 90%
Treated death rate: <10%
Concern about the use of Yersina pestis as a
bioterrorism agent.
Control: surveillance and control of animal reservoirs.
Soilborne Pathogen:
Tetanus and Clostridium tetani
Wound infections. What is the
relationship to the metabolism
of Clostridium ?
Tetanospasmin = Tetanus Toxin
Wound Infection  Tetanus Toxin
Tetanospasmin blocks Inhibitory Nerves, muscles can only CONTRACT
Tetanus Spastic Paralysis
A
Tetanus Toxin Inhibits the
Inhibitory Neural Circuits
Clicker Question:
Other Endospore Pathogens in Soil
Clostridium botulinum – Botulism
C. difficile – colon infections following antibiotic
treatments.
C. Perfringens – Gas gangrene
Bacillus anthracis – Anthrax and veterinary
pathogen.