EESA10 Final

Infectious disease

Is a host-centered concept. Human body is a habitat and host to many organisms. Associations that harm or bother us are infectious

Zoonosis

Is an infectious disease transmissible to humans from other animals

Types of Pathogens

1. Worms --> multicellular;parasitic

2. Protozoa--> unicellular;parasitic

3. Bacteria --> unicellular; most not parasitic (aerobic vs anaerobic;or tolerate either, and some form spores)

4. Viruses --> strand of DNA or RNA; parasitic

The Body's Defense Against Pathogens

1. Immune system distinguishes "self" from "foreign" (active immunity- on first exposure to antigen, body produces antibodies)

2. Vaccination (antigen preparation --> active immunity, Antibody preparation--> passive immunity)

3. Herd immunity --> practical protection (if enough members of a group are immune, hard to maintain chain of infection)

Evolution of Strategies for Managing Transmission of Disease

1. Segregation of sick or exposed persons

2. Isolation (the separation of persons who have an infectious illness)

3. Quarantine (the separation of persons who have been exposed to an infectious agent)

4. Sanitation (its beneficial)

5. Vaccination to prevent illness

6. Antibiotics to treat illness (populations of pathogens become resistant over time, high reproductive rate allow them to become genetically resistant quickly and overuse of antibiotics can cause methicillin-resistant staphylococcus aureus (MRSA). Also antibiotics used in food additives to boost livestock)

7. Pesticides to control vectors (organism such as mosquitoes, ticks, and flies)

Transmission of Infectious Diseases (1)

1. Transmission through closeness/contact (so like droplet transmission (coughing/sneezing). Example of infectious diseases transmitted through droplets are diphtheria, tuberculosis, pertussis, influenza, measles, mumps, rubella, covid-19. Another way is direct oral contact and some examples are strep, herpes, infectious mononuclesis. Lastly, transmission by formite (object or substance capable of carrying infectious organisms), like skin cells, hair , clothing, and bedding.

2. Airborne transmission in aerosols (tiny particles that stay suspended in air for a while)

Transmission of Infectious disease (2)

3. Fecal-oral transmission of diarreheal disease (one persons infectious diarrheal disease becomes next person's disease of fecal origin. So if sewage not well controlled, waterborne transmission dominates or via soil and by hand-to-mouth transmission. For example, cholera, typhoid fever, dysentery; giardiasis, cryptosporidium (zoonoses); hepatitis A, Norwalk virus and polio)

4. Non-fecal organisms also transmitted in water or soil (like guinea worm disease, tetanus)

5. Via food (fooborne transmission, like housefly as a mechanical vector)

Global patterns of infectious disease mortality

1. Fast global spreading (travelling)

2. Total about 12.3 million deaths (respiratory infections (29%), diarrheal disease (20%), and HIV/AIDS (14%) are leading infectious causes of death)

3. Worldwide, 22% of all deaths (highest in africa 53%), southwest asia (27%), and eastern mediterranean (25%))

Infectious disease as a cause of cancer

1. Infection can increase cancer risk (ex: chronic irritation --> proliferation)

2. Known infectious causes of cancer account for about 18% of cancers worldwide (liver [hepatitis B/C viruses, liver fluke], cervix [human papillomavirus], and stomach [helicobacter pylori bacterium]

3. Higher percentage in lower-income countries

Some important types of pathogens

1. Bacteria (tuberculosis, anthrax, plague)

2. Viruses (yellow fever, HIV, bird flu, west nile virus)

3. Protozoa (malaria)

Tuberculosis

Tuberculosis (TB) is one of the worlds deadliest diseases:

- one third of the worlds population is infected with TB

- annually nearly 9 million people around the world became sick TB disease

- annually nearly 1.4 million TB-related deaths worldwide

- TB is a leading killer of people who are HIV infected

- Differences in health care systems

- most commonly attacks the lungs

- Symptoms include chest pain, coughing up blood, and a productive, prolonged cough for more than three weeks, fever, chills, night sweats, appetite loss, weight loss, paleness, and often a tendency to fatigue very easily

- Transmissions by cough, sneeze, speaking, kissing, or spit of an ill person

Anthrax

- Bacillus anthracis (large, spore forming bacteria)

- produce toxin

- all forms may lead to septicemia and death

- bioterrorism related; no smell or taste, to small to be seen by naked eye

-cannot be transmitted from person to person

- three major clinical forms (cutaneous (on the skin), inhalation, gastrointestinal)

Cutaneous Anthrax

- The most common naturally occurring types (>95%)

- After skin contact with contaminated meat, wool or leather from infected animals

- The incubation period ranges from 1-12 days

- Begins as a small raising bump, progresses into vesicle and then a painless ulcer

- fever, headache, and lymph glands swell

- 20% of untreated cases results in death

Inhalation Anthrax

- The most lethal form

-Inhalation of spores of anthrax

- Incubation period 1-60 days

- Starts as viral respiratory illness: sore throat, mild fever, and muscle aches

- May progress to respiratory failure and shock with developing meningitis

- 75% of cases result in death even with all possible supportive care

Gastrointestinal Anthrax

- Consumption of raw or undercooked contaminated meat

- Incubation period 1-7 days

- Nausea, loss of appeitite, vomitting, and fever, followed by abdominal pain, vomitting blood and bloody diarrhea

- 25-60% of cases result in death

- Effect of early treatment is not defined

Bioterrorism Related Anthrax

- Mixed with powder to transport the bacteria

- Suspicious mails

- what should people do when they get a suspicious letter/parcel? (dont touch it)

- environmental testing

- diagnosis

- cure (antibiotics and vaccine)

Plague

- Caused by Yersinia pestis

- Can be used as a bioweapon

- Antibiotics, no vaccine

Bubonic plague

Bubonic plague is the most common form. When a person is bitten by a flea that has been infected by bitting an infected rodent. Also through a break in a person's skin. Swollen, tender lymph glands (called buboes), fever, headache, chills and weakness. Does NOT spread from person to person.

Pneumonia plague

- infection of lungs

- from person (or animal) to person through the air

- Complication of bubonic plague

Septicemic Plague

- When plague bacteria multiply in the blood

- Complications of Pneumonic or Bubonic Plague or it can occur by itself

- Some symptoms as Bubonic plague but not buboes

- Does NOT spread from person to person

Yellow Fever

- Caused by virus

Mosquitoes transmit yellow fever to humans

- Incubation period of 3-6 days

- First phase of symptoms: fever, muscle pain, backache, headache, and vomiting

- 85% if victims recover after the first phase

- Other unfortunate victims develop the "toxic" phase with jaundice, internal bleeding, kidney failure

- 50% of victim who develop the "toxic" phase recover

- Those victims who do not recover and left untreated die after 10-14 days

- Yellow fever is native to West Africa, from Cameroon to Mauritania

- Areas with tropical and subtropical climates are more vulnerable than temperate climates

- Spread to the Americas during European exploration:

- Epidemic in Philadelphia, USA, during the summer of 1793 killing 4,044 people

- Haiti 1801 epidemic killed 90% of Napoleon's force that were sent to

- Haiti to crush a revolt against the french colonial authorities (Failure to recognize the spread of the disease with mosquitoes, so efforts were concentrated on quarantining victim and sanitation, and Many large nineteenth-century homes in New Orleans had open verandas and porches, with many windows and doors, designed to encourage air circulation. Unfortunately, this also provided routes for mosquitoes to enter the homes)

Yellow fever- Today

- Yellow fever was eradicated from North America by the mid-1900s through a combination of vaccinations, drainage of swamplands, and insecticide control of mosquitoes

- Yellow fever is still present in nine South American countries, and some of Caribbean islands

- 33 African countries suffer from yellow fever epidemics

How is Human Immunodeficiency Virus (HIV) transmitted?

Infection with HIV occurs by transfer of blood, semen, vaginal fluid, or breast milk.

What happens to the immune system when a person is infected with HIV?

The immune system begins to fail, leading to life-threatening infections.

When was HIV first recognized?

HIV was first recognized on December 1st, 1981.

What is the current status of HIV infection in humans?

HIV infection in humans is now pandemic.

How is HIV considered in terms of pandemics?

It's one of the most destructive pandemics in recorded history.

How many people were living with HIV in 2018?

About 37.9 million people were living with HIV in 2018.

What was the number of deaths caused by HIV in 2018?

HIV resulted in 770,000 deaths in 2018.

Is there a cure for HIV infection?

There is no cure for HIV infection.

What is the average survival time after HIV infection without treatment?

The average survival time after infection is 11 years.

What percentage of people with HIV may remain healthy for many years without noticeable symptoms?

About one in ten remains healthy for many years, with no noticeable symptoms.

How does treatment with antiretroviral drugs affect life expectancy for people infected with HIV?

Treatment with antiretroviral drugs, where available, increases the life expectancy of people infected with HIV.

Bird Flu

- Physical contact with infected birds

- H5N1 may mutate into strain capable of efficient human-to-human transmission

- Major world threat to possibly millions of lives

How bird flu spreads to humans

1. Waterfowl can carry H5N1 with few effects

2. Chickens are much more susceptible

3. They can pass it to humans who are in close contact

What is the main route of human infection for West Nile Virus?

Through the bite of an infected mosquito

Which animals are primarily infected by West Nile Virus?

Mainly birds, but also humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, and domestic rabbits

What percentage of infected people will become seriously ill from West Nile Virus?

< 1%

Where did West Nile Virus originate?

In the area from Egypt to Iran

In which regions has West Nile Virus been described?

Africa, Europe, the Middle East, West and Central Asia, Oceania, and North America

When was West Nile Virus first detected in the United States?

In 1999

How is control of West Nile Virus achieved?

Through mosquito control

West Nile Virus Effects on Humans

1. Asymptomatic infection - similar as flu

2. West nile fever - fever, headaches, chills, weakness, excessive sweating, rash, can take up to two months to resolve

3. West nile meningitis or encephalitis - decreased level of consciousness, sometimes approaching near-coma, death

What causes malaria?

Malaria is caused by the four species of the Protozoa Plasmodium which lives as a parasite in the gut of a female mosquito.

How is malaria spread?

Malaria is spread by several species of mosquitoes.

Where does Plasmodium reproduce in the human body?

Plasmodium reproduces in the human's liver and bloodstream.

What happens when an infected person is bitten by another mosquito?

The mature plasmodium can be passed on, creating a transmission cycle.

How many people does malaria kill annually?

Malaria kills between 1 to 3 million people annually.

What are some factors contributing to foodborne illnesses?

Food production practices, including the use of chemicals like fertilizers and pesticides.

What are some examples of transmissible diseases that can cause foodborne illnesses?

Bacteria such as Escherichia coli, Clostridium botulinum, Salmonella, and Listeria.

What types of diseases are considered non-transmissible in relation to foodborne illnesses?

Shellfish-associated toxins, color additives, obesity, and diabetes.

What is a characteristic of organic food in the context of foodborne illnesses?

Organic food is often associated with genetically modified food.

Use of chemical fertilizers

- Extensive use of nitrate fertilizers (nitrites in groundwater)

- Direct human health effect (nitrites in water change hemoglobin to form that cannot carry oxygen. Causes methemoglobinemia (blue baby syndrome) in young infants)

Use of Chemical Pesticides

- Pesticide = chemical used to kill pests (Active ingredient = the one intended to kill pest)

Types of pesticides (theres 9)

1. Insecticides (ex: Natural (pyrethrum: from chrysanthemum plant, and Inorganic compounds)

2. Organochlorine insecticides (ex: DDT, chlordane, aldrin, dieldrin, heptachlor. They are Neurotoxin; low acute human toxicity and Persistent and bioaccumulative. Many banned in more developed countries; stockholm convention)

3. Organophosphate insecticides (they are Neurotoxins; not persistent in environment, Acute toxicity to people varies widely)

4. Carbamate insecticides (Chemical action similar to organophosphates and Low acute toxicity to people)

5. Pyrethroid (pyrethrum-like) insecticides (Low acute toxicity to people and Used in some consumer products)

6. Herbicides (Selective herbicides some kill broad-leaved plants; do not kill plants in grass family (ex: grain crops, turfgrass) and In military context, used to kill large plants that provide cover to enemy combatants)

7. Non Selective herbicides (kill all plants (ex: monsanto's roundup, roundup ready - genetically engineered soybeans))

8. Fungicides (used in agriculture to prevent, kill, or control fungal diseases in plants)

9. Rodenticides (often anticoagulant (prevent blood from clotting and causing internal bleeding instead) bait)

Limitations of pesticides

1. Resistance (Some pests resistant (genetic makeup) and Resistant individuals survive and breed)

2. Human health effects of pesticides (Difficult to study chronic effects because Difficult to assess exposure accurately, Changing mix of chemicals, Workers lack information, Variation in practices, protective gear, Hard to separate acute and chronic effects)

4. Neurologic and reproductive effects; cancer

5. Disparities in exposures and impacts (Pesticide production workers, Farmers and their families, Hired farmworkers [In US, mostly men, about half Hispanic, half foreign-born and Often inadequate protections, facilities, warnings])

6. In lower-income countries; more hazardous pesticides may still be in use

Transmissible Foodborne Illness

- Careless food handling (like food standing too long at room temperature, improper cooking, contaminated cutting boards and kitchen tools)

- Types of foods: Meat, milk, dairy products, unpasteurised fruit and vegetable juices, raw or undercooked eggs, chicken, tuna, potato and macaroni salads, cream filled pastries, fresh produce, species, chocolate, and seafood

Symptoms of Foodborne Illness

- Diarrhea, abdominal cramping, fever, vomiting headache, sometimes blood in the stool

- Usually last only a day or two sometimes 7-10 days

- For most people not life threatening

- Severe for young children, the very old and people with certain diseases and conditions such as liver disease, iron disorder, diabetes, and cancer

Prevention of Foodborne Illnesses

1. Starts in supermarket

2. Safe storage

3. Safe food preparation

4. Keep everything clean

5. Wash your hands

6. Cook properly

7. Keep hot food hot and cold food cold

8. Proper storage of leftovers

Bacteria: Esherichia Coli

- Food poisoning usually associated with eating unwashed vegetables and meat contaminated post-slaughter

- Grounded beef

- Diarrhea, abdominal cramps

- Complications Hemolytic Uremic Syndrome in which the red blood cells are destroyed and kidneys fail (2-7% of cases)

Bacteria: Clostridium Botulinum (Botulism)

- Rare but serious illness (fatal)

- Nerve toxin of bacterium clostridium

- Caused by toxin, not by the bacterium itself

- Commercially canned foods should undergo "botulinum cook" in a pressure cooker at 121 degree celsius (250 F) for 3 minutes

- Home-canned foods

(some unusual sources are garlic or herbs stored covered in oil, improperly handled baked potatoes wrapped in aluminium foil, home-canned or fermented fish)

Main Kinds of Botulism

1. Foodborne botulism

2. Wound botulism

3. Infant botulism

Symptoms of Foodborne Botulism

- Occur between 12-36 hours after consuming the botulinum toxin

- Double and/or blurred vision

- Difficulty swallowing, severe constipation

- Muscle weakness, lead to body paralysis

- Respiratory failure

Bacteria: Salmonella

-Salmonella bacteria are found naturally in the intestines of animals especially poultry, swine, birds, reptiles, some pets and some humans

- The bacteria can also be found in the environment

-People who eat food contaminated by Salmonella can become ill with salmonellosis

- They symptoms of salmonellosis can feel like the flu

- Usually no need for treatment

- Infants, the elderly and people who are immunocompromised may require hospitalization

- Long-term complications may include severe arthritis

Examples of Food Recalls in Canada

- January 25,2018, Ontario. Certain sesame seeds recalled due to salmonella

- January 29, 2018, Prince Edward Island, Quebec. Coconut Tree brand shredded young coconut recalled due to Salmonella

-January 29, 2018 , Ontario. Bhugga sold at Rajdhani sweets and restaurant recalled due to salmonella

- December 28, 2017, National. Various brands of sandwich products recalled due to Listeria monocytogenes

- January 31, 2018 Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Prince Edward Island, Saskatchewan. Sawler brand Turnip sticks recalled due to Listeria monocytogenes

Listeria Monocytogens (Listeriosis)

- Found in soil, vegetation, water, sewage, silage, and in the feces of humans and animals

- Animals and humans can carry the bacterium without knowing it

- Listeria can survive and sometimes grow on foods being stored in the refrigerator

- Foods that are contaminated with this bacterium look, smell and taste normal

- Listeria can be killed by proper cooking procedures

- Serious disease called listeriosis, especially among pregnant women the elderly or individuals with a weakened immune system

- In serious cases in can lead to brain infection (meningitis or encephalitis) and even death

Maple Leaf Listeria Outbreak

- August 2008 - maple leaf foods announced a massive recall of 243 types of ready-to-eat meat products supplied to stores, restaurants and cafeterias

- Test results indicate a Maple Leaf Foods plant in Toronto is the source of a listeria outbreak that has killed 4 people

Parasites and Foodborne Illnesses

- Live and reproduce within the tissues and organs of the infected human and animal host

- May be transmitted from: animals to humans, Humans to humans, Humans to animals)

- Some are very small, some are visible with naked eye (worms)

- Often excreted in feces

How do parasites and foodborne spread?

- If food comes in contact with excrements

- Raw or undercooked wild game (bear, boar, deer, fish)

Non Transmissible Foodborne Illnesses

1. Shellfish-associated toxins

2. Colour additives

3. Obesity

4. Diabetes

5. Genetically Modified crops

Shellfish-Associated Toxins

- Caused by group of toxins from planktonic algae upon which the shellfish feed

- Toxins are accumulated and sometimes metabolized by the shellfish

- Symptoms depends on: type of the toxin, concentration in the shellfish, amount of the shellfish consumed

- Shellfish harvested along the Florida coast and the Gulf of Mexico (mussels, clams, scallops, oysters)

- Not very frequent disease

Symptoms of Shellfish-associated toxins illnesses

- Neurological symptoms: numbness, drowsiness, incoherent speech, respiratory paralyzes, memory loss, coma

- Gastrointestinal symptoms: nausea, vomiting, diarrhea

Colour Additives

- Colourful history

- They are everywhere

- Only certified colours should be used

- Marketing of any colour addictive that has been found to cause cancer is prohibited regardless of amount

Obesity

- The main causes for the rapid acceleration of obesity in Western society are:

- Excessive nutrient intake

- Sedentary lifestyle - sitting or remaining inactive for most of the day

- Genetics

- Physical and mental illnesses

- Hormones and other chemicals

- Microbiological aspects

- Social determinants (ex: Income differentials, level of education, Friends, siblings or spouse)

Possible life threatening risks of Obesity

Osteoarthritis, Heart disease, Type 2 diabetes, Non-alcoholic liver disease, Sleep apnea, High blood pressure, High blood cholesterol, Cancer

Diabetes

High blood sugar resulting from either Low levels of the hormones insulin (type 1 diabetes mellitus) or Insulin resistance or reduced insulin sensitivity, combined with reduced insulin secretion (Type 2 Diabetes Mellitus)

Prevention of Diabetes

-Food is not a direct cause

- Genetics

- Changes in diet and increasing physical activity

- At least 2 ½ hours of exercise per week

- Having a modest fat intake

- Eating a good amount of fiber and whole grains

- Moderate alcohol intake may reduce the risk??

- Eating foods of low glycemic index (the ones that produce only small fluctuations in our blood glucose and insulin levels) (ex:Most fruit and vegetables (except potatoes, watermelon and sweet corn), whole grain pasta, beans, and lentils)

What plants and Animals feed the world?

- 14 plants and 8 terrestrial animals supply 90% of global intake of calories

- Wheat, rice and corn- ½ of calories

- ⅔ of the world survives on traditional grains; can not afford meat

- Income rise → more meat consumed

- Fish and shellfish in coastal areas

Organic food: a growing trend

- $35 billion/year worth industry

- Social movement-green lifestyle

- Organic certification

- >3670 certified farms in canada

Genetically Modified Crops

- What are GMC (genetically modified crops)?

- Favr Savr Tomato by calgene corporation in 1994 (the first government approved genetically engineered food)

The risks

The benefits of Genetically Modified Crops

- Rationale: increase of global food supply (crops that resist disease, repel pests, ripen faster)

- Process (isolate gene for desired characteristic, using loop of bacterial DNA, transfer this gene (transgene or biotech gene) into DNA of another species)

The risks of Genetically Modified Crops

1. Allergic reactions to GM foods (Allergens are proteins; chemical structure determined by DNA of species, proteins of donor species in transgenic plant (thus, for example, allergenic protein from another plant species could occur in GM soybeans), and Cant distinguish GM foods; cant prevent spread of GM plants in environment)

2. Spread of antibiotic resistance (ex: in silos, in the gut of humans or other animals, and in the field - recent evidence from canola plants)

Transport

movements of contaminants within or between environmental media

Fate

physical, chemical or biological transformations of contaminants in the environments

Physical- chemical Properties

-Fate and transport of chemicals is affected by their physical-chemical properties

- How harmful a substance is, depends on physical-chemical properties of the substance

Examples of chemical properties

- Volatility

- Polarity

- Solubility (ex: Water soluble toxins and Fat soluble toxins (lipophilic tendency))

- Oxidation state

- Molecular weight

Consequences of lipophilic tendency

1. Bioaccumulation - building up over time, in individual organisms

2. Biomagnification - building up over time, across the levels in a food chain

Generally, higher-molecular weight chemical are..

- More lipophilic and more persistent

- Less volatile and less water-soluble

- Persistence in environment (so like, Quantified as a half-like in air, water, or soil. and Affected by environmental conditions)

Toxicology

- the science of the effects of toxic substances and of their fate and transport in the body

-"Study of poisons"

- "The science which studies toxic substances or poisons, that are substances which cause alteration or perturbation in the function of an organisms leading to harmful effects"

What four concepts does toxicology focus on?

1. Receptor

2. Exposure

3. Dose

4. Response

Receptor

- Organism (human?) receiving exposure or dose

- The human envelope - boundary that separates the interior of the body from the exterior environment

- Age

- General health

- Genetic Makeup

Exposure

- Contact with the human envelope

- Routes of exposure (ex: Ingested (often greatest source of chemical exposure, 85%). Inhaled (air pollution, particles and volatiles, 10%). Absorbed through the skin (industrial, 5%))

- Frequency of exposure

Exposure Assessment

- Goal is to quantify exposure (or to find out Dose)

- Methods draw on understanding of both:

-Environmental science (fate and transport of toxicants in environment)

- Toxicology (fate and toxicants in the body)

Completing the conceptual model of exposure

-Conceptual model of exposure begins with source of exposure

- And concepts with toxicokinetics and effects in the body

Toxicokinetics

the disposition of toxicants in the body

Quantifying Exposure

- Translating event of exposure into a dose estimate

- Tools for area monitoring and personal monitoring

- Units of absorbed dose: mg/ (kg*day) (Mass of toxicant, Normalized to body weight, Averaged over time)

- Other sources of exposure info: Questionnaires, diaries, Surrogate measures (measure of effect of a specific treatment that may correlate with a real), Geographic information systems (GIS)

What is the definition of dose?

A quantification of exposure (the amount of substance a person has ingested, inhaled, or absorbed).

What is an acute dose?

A single dose, usually high.

What is a chronic dose?

Repeated or continuous low dose over time.

What does long-term dose refer to?

Low dose over a lifetime.