Exam 2 Environmental Health

Zoonotic diseases used to contribute greatly to?

the world’s burdens of morbidity and mortality

During the late 19th and 20th century what advances in medicine have made progress in infectious disease control?

vaccines, antibiotics, PUBLIC HEALTH ACHIEVEMENTS, improved environmental sanitation, disinfection of drinking water, and methods of food storage

What are the pathogens for Zoonotic and Vector Born disease?

Bacteria, Virus, Parasite, Rickettsia, Prions

Zoonotic Disease (Zoonosis)

An infection or infectious disease transmissible under natural conditions from vertebrate animals (reservoir/host) to humans

What are the methods of transmission for zoonotic pathogens?

Direct contact with skin: bite/scratch and Direct inhalation or ingestion of the pathogens

Vector

an insect or any living organism that transports an infectious agent (virus, bacteria, parasite) from one host to another

Vector Borne Disease

infectious disease transmitted to humans (or animals) through the bite of arthropod vectors that carry the infectious agent

Arthropods

blood-feeding arthropods: mosquitoes, ticks, sand flies, and biting midges

Malaria pathogen

Plasmodium parasites

Malaria vector

Anopheles Mosquito

Malaria Transmission

Mosquito with parasite sporozoites bites human → travel to liver cells and infect them → mature parasites bust out of liver cells into the blood → invades RBCs → random female Anopheles mosquito bites and ingests the parasite

Where is malaria endemic to (highly occurring)?

warmer geographic areas like Central and South America, Africa, Middle East, India, Southeast Asia, and Oceania

Malaria Global cost

$12 billion USD: treatment (hospitalization and meds), disease prevention (pesticide use), tourism impact, and lost earnings

When do symptoms of Malaria occur?

9-14 days after the bite

When did the US stop being endemic for Malaria?

1940s

What was a major activity of the Antimalaria campaign of 1947?

Spraying homes with DDT, but eventually ruled as harmful to wildlife and birds

When was Malaria declared under control?

1949

Leishmaniasis pathogen

Leishmania parasites (protozoa)

Cutaneous Leishmaniasis

sore on the skin that forms after an incubation period of weeks to months

Where is Leishmaniasis endemic to?

countries surrounding the Mediterranean (82), especially Middle East and South America

Leishmaniasis vector

sand fly (phlebotomus fly)

Cutaneous Leishmaniasis reservoir/host

wild rodents, humans, and carnivores (domestic dogs and cats)

Leishmaniasis transmission

sandfly bites human and injects parasite promastigotes → macrophages eat the parasite → parasite infects macrophage → macrophage bursts → sandfly bites and gains parasite

Environmental factors for increase in Leishmaniasis

• Human population movement into endemic areas

• Deployment of US military into regions like Afghanistan and Iraq

• Extension of agricultural projects into endemic areas

• Increasing urbanization

• Climate change due to global warming

Leishmaniasis control

• Periodic application of long-acting insecticides

• Using screens to block sand flies from entering homes

• Eliminating rodent burrows and domestic dogs control

Plague pathogen

Bacterium: Yersinia Pestis infects humans and animals

Plague (Black Death) vector

fleas

Plague symptoms

Fever, Chills, Headache → Lymphadenitis at bite site

Plague treatment

antibiotics (effective if treated promptly)

Plague is a vector borne disease, but in some regions considered a zoonotic disease? T or F

True

Plague reservoir/host

wild rodents, humans, (In western US, it’s ground squirrels)

Pets can bring plague containing fleas into the house. Can they also transmit the bacteria through a bite or scratch?

Yes! Very rare

How is pneumonic plague spread?

Respiratory droplets (aerosol)

Infected patients of Plague and clothing should be sterilized and isolated. People in contact should quarantine. T or F

T

How is environmental control of the plague accomplished?

• Avoid enzootic areas (animals have this in specific areas)

• Avoid direct contact with rodents (don’t feed)

• prevent rats from entering buildings and remove potential food sources

• Shipping areas patrolled for rodents

Lyme pathogen

spirochetal bacteria Borrelia burgdorferi

Where did Lyme come from

1977, arthritis cases in children, Lyme Connecticut

Where did most cases occur in 2014?

northeastern, mid-Atlantic, and upper midwestern regions of US

Lyme vector

Black-Legged ticks

Lyme host

wild rodents and humans

Who is at risk of developing lyme?

people who work or come into contact with tick-infested areas

Prevent Lyme?

reduce exposure to ticks

Lyme treatment

antibiotics

Rocky Mountain spotted fever (RMSF) pathogen

Rickettsia Rickettsii (a rickettsial agent (bacteria that cannot grow outside of a host cell))

RMSF symptoms

sudden onset fever with a rash up to 3 weeks

RMSF treatment

antibiotics

RMSF vector

Rocky Mountain wood tick or American dog tick

RMSF transmission

tick bite

Arthropod-Borne Viral (Arboviral) Diseases

A group of viral diseases that cannot grow outside be acquired through the bite of blood-feeding arthropod vectors (ticks, sandflies, biting midges, and mosquitoes)

Arboviral transmission

involves a nonhuman vertebrate host and an arthropod vector

Four main clinical symptoms of Arboviral

• Acute CNS illness

• Acute self-limited fevers

• Hemorrhagic fevers

• Polyarthritis and rash

Arboviral Encephalitis cause

virus that produces an acute inflammation of sections of the brain, spinal cord, and meninges (Japanese Encephalitis)

Arboviral Encephalitis symptoms

mainly asymptomatic, but can have a severe illness with a high fever, disorientation, coma, paralysis, and death

Arboviral Encephalitis host and vector

Host: birds

Vector: mosqitoes

West Nile Fever cause

West Nile Virus: a mosquito borne viral fever

What is Neuroinvasive disease

the most severe form of West Nile

West Nile host and vector

Host: Birds

Vector: Mosquitoes

Who is most at risk for contracting West Nile?

those who spend a lot of time outdoors

Zika Fever: Emerging cause

mosquito borne and caused by zika virus and associated with birth outcomes like microcephaly

Zika virus first discovered

in a monkey, 1947 in Uganda

US cases of Zika virus

from travel

Rift Valley Fever (RVF) (reemerging)

first discovered in Kenya 1931 in a sheep

RVF cause

virus Phlebovirus

RVF symptoms

fever, liver abnormalities

RVF can produce an epizootic disease through mosquitoes to livestock and then infected mosquitoes can infect humans

True

Mosquito disease control

sentinel chickens

Viral Hemorrhagic Fever (VHF)

a severe, multi-system syndrome characterized by damage of overall vascular system and impairment of body’s ability to regulate itself.

VHF examples

Ebola, Hantavirus pulmonary, Dengue Hemorrhagic

Most VHFs need animal host. Very few are arthropod

True

Viruses are limited to the place where the host resides. humans become infected through animal contact

true

Ebola: Zoonotic VHF

highly fatal and acute disease of ebola virus

ebola symptoms

fever, diarrhea, vomiting, internal and external bleeding

Ebola transmission

direct contact of bodily fluids from infected person. could also come from animal like a bat or primate

first ebola case

1976 Sudan and Congo

Hantavirus Pulmonary (HPS): Emerging Zoonotic VHF

severe and sometimes fatal respiratory condition

HPS cause

hantavirus

HPS host and vector

Host: north america deer

vector: mouse

HPS transmission

inhalation of aerosolized urine and droppings of rodents

Famous HPS outbreak

four corners in 1993

Dengue Fever: Reemerging Zoonotic VHF

caused by flaviviruses. life threatening with abdominal pain and bleeding.

DSS

Dengue Hemorrhagic Fever with shock. Fatal

Dengue transmission

bite of Aedes aegypti mosquito

Us cases of dengue are mainly from travelers and immigrants

true

Monkeypox

a virus spread through close contact with infected persons, rodents, or primates. Endemic in congo, similar to smallpox with lymph nodes swelling

Anthrax

spore forming bacterium Bacillus Anthracis and occurs among cattle and sheep. inhaled anthrax is severe and fatal. 2001 powder anthrax letters

Rabies (hydrophobia)

acute and highly fatal disease of the CNS caused by a virus transmitted through saliva from the bites if infected animals (dog, raccoon, skunk, fox, bat, etc.)z Always fatal.

Tularemia (rabbit fever)

bacterial disease from infected animals to humans OR transmitted by arthropod bite. Swollen lymph glands

Psittacosis (parrot fever)

bacterial agents from dry bird droppings

Influenza A: Spanish Flu 1918-20, Asian flu 1957, Hong Kong flu 1976, Chicken Flu 1997

Birds are main reservoir. Transmission from close contact of livestock or people. Urbanization

Toxic Metals origin

man made and natural sources

Heavy metals

high atomic weight and specific gravity that exceeds water by 5 or more

Exposure of toxic metals

low levels from natural sources like volcano and soil. additional exposure from man made sources like hazardous waste and automobiles

Acute exposure of toxic metals at high levels

ingestion: gastrointestinal effects - vomiting and stomach pain

inhalation: neurological effects

Chronic exposure to toxic metals at low levels

reduced cognitive functioning - learning impairment and lethargy

NPL (National Priorities List)

lists hazardous waste sites for long term remedial action under Superfund

SPL (Substances Priority List)

rank ordered list of hazardous substances that are most common at NPL sites. revised every 2 years. determined based on known or expected toxicity and likelihood of human exposure

Important top 20 metals on the 2026 SPL list RANKED

Lead, Arsenic, Cadmium, Nickel, Beryllium, Manganese

Routes of exposure to metals

ingestion: gi tract

inhalation: respiratory tract

dermal: skin

contact with high concentrations of toxic metals is most likely to occur in occupational settings

true