Chapter 34

Vectorborne and Soilborne Microbial

Pathogens

Animal Transmitted PathogensRabies: and Endozootic or Epizootic

Rabies – Viral Encephalopathy

ARabies virus: ss (-) RNA enveloped virus..looks like a bullet. Kills 55,000 people world wide/year.

Rabies Virus

TEM infected animal Brain Histology, Negri Bodies 75 x 180 nm ~ 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

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Le Bon Louis Pasteur Poster

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Clicker Question:

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

Disease of Humans, White tailed deer, White footed Mouse.

Transmitted by Ixoides, the deer tick which can also transmit Borrelia burgdorferi to other rodents.

Male Female nymph larvae

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

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Tick – before and after

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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 STAGEFever, headache, chills, stiff neck, dizziness

2. SECOND STAGECardiac 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

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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

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Bubonic Plague and Yersinia

Plague Transmission

Cycle of Hosts Expanded

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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

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Tetanus Spastic Paralysis

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.