Methods for Transmission of Zoonoses
Contact with the skin
A bite or scratch from an animal
Direct inhalation or ingestion
The bite of an arthropod vector
Vector
insect or any living carrier that transports an infectious agent from an infected individual or its wastes to a susceptible individual or its food or immediate surroundings
Examples of Vectors
Various species of rodents (rats and mice)
Arthropods (mosquitoes, ticks, sand flies, biting midges)
Vector-Borne Diseases
Malaria
Leishmaniasis
Plague (black death)
Lyme disease
Rocky Mountain spotted fever
Infectious Agents of Malaria
Plasmodium falciparum
Most deadly
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plague
The bacterium Yersinia pestis is the infectious agent for plague, a condition that infects both animals and humans.
Transmitted by the bite of a flea harbored by rodents.
Lyme Disease
A condition identified in 1977 when a cluster of arthritis cases occurred among children around the area of Lyme, Connecticut.
The causative agent for the disease is a bacterium known as Borrelia burgdorferi.
Transmission of Lyme disease to humans is associated with
infected black-legged ticks (Ixodes scapularis) that ingest blood by puncturing the skin
Rocky Mountain Spotted Fever
Causal agent is Rickettsia rickettsii, a rickettsial agent.
A febrile disease
Case fatality rate up to 25% among untreated patients
Transmitted by the bite of an infected tick
Arthropod-Borne Viral Diseases
Also known as arboviral diseases.
A group of viral diseases that can be acquired when blood-feeding arthropod vectors infect a human host.
Vectors that transmit arboviruses include
ticks, sand flies, biting midges, and mosquitoes
Emerging Zoonoses
Refers to zoonotic diseases that are caused by either apparently new agents or by known agents that occur in locales or species that previously did not appear to be affected by these known agents.
Factors Associated with the Rise of Emerging Zoonoses
Ecological changes that result from agricultural practices (e.g., deforestation, conversion of grasslands, and irrigation)
Other factors include changes in the human population and human behavior (e.g., wars, migration, and urbanization).
Examples of Emerging Zoonoses and Their Contributing Factors
Non-conventional agent:
Bovine spongiform encephalopathy
Changes in rendering process
Viral:
Hantaviruses
Ecological/environmental changes
Increasing rodent contacts
Bacterial:
Escherichia coli O157:H7 (hemolytic-uremic syndrome)
Mass food processing tech
Hantavirus Pulmonary Syndrome (HPS)
The causative agent is the hantavirus, part of the viral family known as Bunyaviridae.
May be transmitted when aerosolized (airborne) urine and droppings from infected rodents are inhaled.
primary vector of hantavirus pulmonary sundrome
four species of rodents: cotton rat, rice rat, white-footed mouse, and deer mouse
Dengue Fever
Caused by flaviviruses
The proportion of deaths can be as high as 40% to 50% when the disease is untreated.
Occurs primarily in tropical subtropical areas of the world, for example, Southeast Asia, tropical Africa, and South America
Primary vector of transmission of Dengue Fever
Aedes aegypti mosquito.
Control of Mosquito-Borne Diseases
Use sentinel chickens to monitor for presence of viruses.
Drain standing water.
Introduce mosquito-eating fish into ponds.
Wear repellents and protective clothing.
Repair window screens.
National Priorities List (NPL)
EPA's list of the most serious uncontrolled or abandoned hazardous waste sites in the United States identified for possible long-term remedial action under Superfund
Heavy Metals
A heavy metal has a high atomic weight with a specific gravity that exceeds the specific gravity of water by five or more times
Classification of Toxic Effects of Metals
Major toxic metals with multiple effects
Essential metals with potential for toxicity
Metals related to medical therapy
Minor toxic metals
Bioaccumulation
Toxic substances such as heavy metals become more concentrated and potentially more harmful as they move up the food chain
Modes of Exposure
Lungs (through inhalation of dusts, metal fumes, and vapors)
Skin (through contact with dusts)
Mouth (by ingestion)
Symptoms of Long-Term Exposure at Lower Levels
Difficult to differentiate from those of chronic medical conditions
Reduced cognitive functioning (e.g., learning impairment)
Fetuses, Infants, and Children and Exposure to Heavy Metals
For these groups, heavy metals are known to present serious hazards, which can include:
impairment of physical and mental development
damage to internal organs and the nervous system
some forms of cancer
mortality
Fetal Exposure Effects
Lead and mercury have the capacity to cross the placental barrier, causing potential fetal brain damage
Standards for Arsenic
10 �g of arsenic per liter of drinking water, , had been lowered from 50 mg
Effects of Cadmium Exposure
Osteoporosis in women
Height loss in men
Kidney damage
Elevated blood pressure
Cardiovascular diseases
"Itai-Itai" disease
Erin Brockovich
Advocated for residents of Hinkley, California, against a power company accused of polluting the town's water with chromium (VI)
Mercury Deposition in Lakes and Rivers
Even at low levels, mercury deposited in bodies of water represents a potential hazard to human health.
Methylation�microorganisms convert elemental mercury into methyl mercury.
The process of bioaccumulation causes mercury levels to become more concentra
Legacy of Mercury Contamination
Minamata disease- ataxia, numbness in the hands and feet, general muscle weakness,
Water contamination around the New Almaden mine in California
Lead
Sources of environmental lead include leaded gasoline, tap water from soldered pipes, and painted surfaces in older buildings.
Another common source of household lead exposure is imported pottery that is used in food service.
Aluminum
This silver-white metal is used widely in food and beverage containers, in pots and pans, and in construction sites.
An ingredient in various medicines and cosmetics, for example, buffered aspirin and antiperspirants
Concern about possible association wit
Advantages of Hazardous Chemicals
Essential to the functioning of modern society
15,000 chemicals made and used in high volume in the United States for manufacturing clothing, phones, computers, cars, building materials, rugs and other furnishings
Disadvantages of Hazardous Chemicals
implicated as human health hazards for example, in etiology of cancer and adverse birth outcomes
Aromatic compound
organic molecule that contains a benzene ring, for example, benzene and toluene
Hydrocarbon
an organic compound ( as acetylene, benzene, or butane) containing only carbon and hydrogen and often occuring in petroleum, natural gas, coal and bitumens
Organic Chemical
naturally occuring (animal or plant produced or synthetic ) substances containing CHON
ordinary table sugar
Persistent Organic Pollutants (POPs)
Toxic chemicals that adversely affect human health and the environment around the world.
Because they can be transported by wind and water, most POPs can and do affect people and wildlife far from where they are used and released.
An example is the pestic
Polycyclic Aromatic Hydrocarbons (PAHs)
a group of over 100 different chemcials that are formed during the incomplete burning of coal, oil and gas, garbage or other organic substances like tobacco or charbroiled meat
Volatile Organic Compounds (VOCs)
Organic compounds that evaporate readily into the air
examples of VOCs
benzene, toluene, methylene chloride, and methyl chloroform
Not Mutually Exclusive Categories
Benezene is:
-aromatic compound
-hydrocarbon
- volatile organic compound (VOC)
-organic solvent
Pesticide
any substance of mixture of substances in tended for preventing, destroying, repelling, or mitigating pests
pests can be insects, rodents, weeds and a host of other unwanted organisms
Insecticide
a pesticide compound specifically used to kill or prevent the growth of insects
herbicide
a chemcial pesticide designed to control or destroy plants, weeds, or grasses
Fungicide
a pesticide that is used to control deter or destroy fungi
Nematocide
A chemical agent that is destructive to nematodes
Rodenticide
A chemical or agent used to destroy rats or other rodent pests, or to prevent them from damaging food, crops, etc.
Pesticides are not
Always highly toxic to humans
All synthetic chemicals
Always the best weapon against insect pests
Four Major Classes of Pesticides and Insecticides Derived from Organic Chemicals
Organophosphates (OPs)
Organocarbamates (also called carbamates)
Organochlorides (also known as organochlorines)
Pyrethroids (from the class of pyrethrins)
Organophosphate Pesticides (Anticholinesterases)
Can be used to control a wide range of insects, thus eliminating the need for multiple applications of different pesticides
Have not been weakened by the resistance of insects
Tend not to persist in the environment
Frequent cause of fatal poisonings
Effects of Organophosphate Poisoning
Acute effects: Anticholinesterase activity happens soon after exposure and causes impairment of the neural impulse transfer mechanism.
Long-term effects: may include a condition known as organophosphate-induced delayed polyneuropathy, which is manifested
Examples of Organophosphate Pesticides
Diazinon, malathion, methyl parathion, and parathion
Appear in a wide variety of products: sprays, baits, indoor foggers and bombs, flea collars, pet shampoos, powders, animal dips, and granules
Malathion has been approved for direct application to food c
Carbamates
Close relatives of the organophosphate pesticides
Dissipate quickly from the environment as a result of breaking down into other substances
Some are approved for controlling garden pests (e.g., wasps, hornets, and snails).
An ingredient in some products a
Examples of Carbamates
Carbyl (Sevin)
Aldicarb
Fenoxycarb
Propoxur
Metam sodium
Methyl Isocyanate (MIC)
An intermediate chemical used for the manufacture of carbamate pesticides.
When acute exposure occurs, MIC is extremely toxic to life forms (e.g., human beings, aquatic organisms, and plants).
Organochlorines
Derived from chlorinated hydrocarbons, which are chemical compounds that contain chlorine, carbon, and hydrogen
Characteristically stable and fat-soluble; persist in the environment and bioaccumulate in the food chain
Associated with suppression of the im
Examples of Organochlorine Pesticides
DDT
Lindane
Chlordane
Mirex
Hexachlorobenzene
Methoxychlor
DDT (Dichlorodiphenyltrichloroethane)
Widespread use of DDT began during the early 1940s and reached a maximum during the 1960s.
Due to concerns about the possible adverse effects upon the health of humans and wildlife, application of DDT was prohibited in 1972 in the U.S.
Most developed nati
Facts about DDT
Not regarded as a highly toxic pesticide
Formerly employed worldwide to control insects and harmful mosquitoes that carry malaria
Was credited at one time with saving millions of people from death due to malaria
Concentrates in the adipose (fatty) tissues
Human health effects of DDT
Linked to:
Cancer (pancreatic, non-Hodgkin's lymphoma, and breast)
Reproductive effects
Impaired lactation
Falling sperm counts
Impaired neurologic function (irritability, dizziness, and numbness)
Pyrethrins
Derived from natural sources--certain varieties of chrysanthemum flowers
Have great ability to paralyze and kill flying insects
Interfere with transmission of neural impulses via action on sodium channels
Use of Pyrethrin Insecticides
Generally have low concentrations of the active ingredient
Used inside the home in aerosol cans, insecticide bombs, insecticidal pet shampoos, treatments for lice applied directly to humans, and mosquito repellents
May be inhaled as a result of spraying a
Herbicides/Defoliants
Examples of chemicals in the category of herbicides and defoliants are:
Atrazine
Paraquat
Agent Orange (2,4-D and 2,4,5-T)
Agent Orange
Used during the Vietnam War, during Operation Ranch Hand (1962 to 1971)
Approximately 19 million gallons of defoliants sprayed on 3.6 million acres in Vietnam and Laos
Contained small amount of dioxins
Health Effects of Agent Orange
The Institute of Medicine (U.S.) concluded that there was sufficient evidence that Agent Orange was associated with several forms of cancer:
Soft tissue sarcoma
Non-Hodgkin's lymphoma
Hodgkin's disease
Chronic lymphocytic leukemia
Dioxins
a family of chemical compounds that are unintentional byproducts of certain industrial, non-industrial and natural processes, usually involving combustion.
Biopesticides
Pesticides derived from natural materials such as animals, plants, bacteria, and certain minerals
Examples:
Microbial pesticides
Plant-Incorporated Protectants
Biochemical pesticides
Facts about Dioxins
A total of 419 compounds in the dioxin family are known to exist.
Scientists regard only about 30 of these as being the most poisonous.
Stable, persistent, and bioaccumulate within the food chain
What Natural Events Produce Dioxins?
Forest fires and volcanic eruptions emit dioxins into the environment.
Dioxins that originate from these sources are called "natural background" dioxins.
What Human Activities Produce Dioxins?
Incineration of industrial and municipal wastes
Burning of some fuels
Bleaching of wood pulp for paper manufacturing process
Manufacture and application of some herbicides
Tobacco combustion, which gives rise to minute amounts of dioxin in cigarette smoke
Health Effects of Exposure to Dioxin Depend on:
Duration of exposure
Frequency of exposure
When the exposure occurred
Child, adult
Concentration of the agent
Route of entry into the body
Health Effects of Exposure to Dioxin Include:
Chloracne
Skin rashes
Skin discoloration
Growth of excessive body hair
Liver damage
Possible cancer risks
Endocrine (glands) effects
Reproductive and developmental effects
Polychlorinated Biphenyls (PCBs)
Two common uses before their manufacture was terminated:
Insulating fluid in transformers and capacitors
Lubricant
PCBs present in the environment tend to bioaccumulate in fish and other animals used for food and, in turn, impact human health
PCB Contamination
PCBs are known to be present at as many as 500 sites denoted on the 1,598 sites that the EPA has provided on the National Priorities List.
Because of concerns about their environmental and health effects, the manufacture of PCBs was terminated in 1977.
Health Effects of PCBs
Cause cancer in animals and are designated as probable human carcinogens
May impact the immune system, reproductive system, and children's intellectual development
May limit the development of immune responses to the Epstein-Barr virus and other viral and
Organic Solvents
Refers to "a liquid substance capable of dissolving other substances;
'the solvent does not change in forming a solution.'
Solvents: Modes of Exposure
Breathing their vapors directly
Ingesting them in foods and water
Using foods and cosmetics packed in certain types of plastics
Smoking cigarettes
Working in a factory: chronic exposure
Inhaling vapors released by industrial facilities
Drinking solvent-co
Examples of Solvents
Tetrachloroethylene
Trichloroethane
Trichloroethylene (TCE)
Toluene
Acetone
Benzene
Chemicals Used in Plastics Manufacture: Styrene
Used for the manufacture of polystyrene resins, which are components of many types of plastics
Short-term inhalation of styrene can produce central nervous system effects such as muscle weakness, and problems concentrating on tasks; irritation of the resp
Chemicals Used in Plastics Manufacture: Vinyl Chloride
Used mainly for the manufacture of polyvinyl chloride, which is an ingredient in plastic products such as pipes, vinyl siding for houses, plastic coatings, and upholstery
Classified as a human carcinogen
Environmental Estrogens
Some organic chemicals (e.g., chlorinated hydrocarbon pesticides) may have estrogenic activity (EA).
(EA) can potentially cause adverse health effects, sometimes at low doses in fetal through juvenile stages with effects detected in adults.
Sometimes DDT
Effects of Environmental Estrogens
May have abnormal influences on the reproductive systems of exposed humans and animals
May act as cancer promoters by having an influence on the onset of female cancers that are thought to be caused by estrogenic activity
Radiation
energy traveling through space
some types of radiation associated with radioactivity are alpha and beta particles and gamma and X rays
radiation also includes nuetrons which are uncharged