Hello everybody my name is Zohir Chowdhury, today's topic is about disease pathogens host
and environment as it applies to vector borne diseases and zoonotic diseases a pathogen is
any biological agent that can cause disease or illness in its host these pathogens can
be bacterial viruses protozoa parasites helmets prions the table below displays
the different types of pathogens viruses can only reproduce inside a living cell examples are human
immunodeficiency virus HIV hepatitis V virus and hepatitis C virus as well as influenza virus and
those that cause a common cold virus is carried by arthropods such as mosquitoes and ticks are
known collectively as arboviruses bacteria are single-celled organisms present everywhere some
of which can cause disease important bacteria causing human diseases include ecoli which are
responsible for urinary tract infection diarrhea streptococci responsible for only infection sepsis
as well as death death when conditions are not conducive to bacterial growth and reproduction
bacteria form bacterial spores or endospores which has thick wall cells to preserve the
cell's genetic material this allows them to remain in a dormant state until conditions
for multiplying return and the spores can survive for extreme length of time most types of bacteria
cannot change to the endospore form examples of bacteria capable of forming endospores
include bacillus and Clostridium protozoa are single-celled microorganisms that are larger
than bacteria examples of disease-causing protozoa include amoebas and Giardia which cause diarrhea
Helmut's include round worms tapeworms and flukes they infect humans primarily through ingestion of
eggs or or when the larvae penetrate the skin or mucous membranes helmets can cause direct damage
to internal organs physically and chemically I can modulate the hosts immune response and can result
in anemia and malnutrition prions on the other hand our form of infectious protein believed to
be the cause of several neurodegenerative diseases such as Chris Feld Jakob disease a severe brain
disease like viruses prions are not considered living they multiply by inducing the host proteins
to refold into an abnormal shape accumulate in and destroy neurons a host is a living organism on or
in which a parasite lives there are different types of hosts primary host is one in which a
parasite reaches maturity and impossible producers reproduces sexually secondary or intermediate host
harbors a parasite only for a short transition period during which some development stage may
be completed parrot anak host is a potential or substitute an immediate host that serves until
the appropriate definitely definitely the host is reached and in which no development of the
parasite occurs it may or may not be necessary to the completion of the parasites life cycle
accidental host is one that accidentally harbours an organism that is not ordinarily parasitic in
that particular species reservoir hosts can Harbor a pathogen indefinitely with no ill effects and
dagger on the side shows a specific disease that gives you the relationship between the
definitely host the intermediate hosts that parrot anak host as well as accidental hosts humans
natural reservoirs of an infectious agent is the habitat in which the agent normally leaves grows
and multiplies a natural reservoir is a host that does not experience disease when infected by the
pathogen in some books and websites you may find a different definition of reservoir the terminology
reservoir is sometimes used interchangeably host as defined earlier there are three main types of
natural reservoirs humans animal or insects and environmental so human reservoirs asymptomatic or
passive or healthy human carriers are those who never experience symptoms despite being
infected human reservoirs or carriers commonly transmitted disease because they do not realize
they're infected and consequently take no special precautions to prevent transmissions
a symptomatic or passive or healthy carriers are those who never experience symptoms despite being
infected animals on the other hand can also be reservoirs humans are subject to diseases that
have animal reservoirs many of these diseases are transmitted from animal to animal with humans as
incidental hosts examples are deer ticks which may carry Lyme disease bacteria raccoons which
may carry the rabies virus or fish which may carry parasites that humans ingest the
environment can also be a reservoirs plants soil water air and inanimate objects also known as for
mites in the environment are also reservoirs for some infectious agents many fungal agents
such as those that cause histoplasmosis live and multiply in the soil outbreaks of Legionnaires
disease are often traced to water supplies in cooling towers and evaporative condensers
these are environmental reservoirs for the causative organism Legionella pneumophila
examples of inanimate objects include tissue doorknobs telephones bed linens toilet seats
and clothing environmental reservoirs can be water from fish tanks or flower vases which can
which may contain pathogens and are especially dangerous for compromised patients air filters
that have not been properly maintained sinks soiled linens and gloves needles or sharps or
in a inadequately sterilized instruments these are all environmental reservoirs
the disease triangle represents a super simple concept in order for a parasite
to cause pathology that is for that for the disease to occur the parasite must be
present a susceptible host must be present and environmental conditions must be sufficient to
result in pathology if you chop off one side of the triangle there will be no disease in
the diagram to the right you can see this interaction among pathogen or disease agent
host an environment vector is shown in the center of this triangle to show that diseases can also
be transmitted with the help of vectors which will be explained in the next slide so what
is a vector a disease vector is a living agent that transfers a pathogen from one organism to
another the vector can transport the pathogen from an infected individual or it's waste to
a susceptible individuals food or immediate surroundings diseases carried by vectors are
known as vector borne diseases vectors act like vehicles that transport pathogens from one host
to another as shown in this figure insect vectors are shown in the middle connecting the animals
with animals or animals with humans in this slide you can see examples of vectors for example you
have mosquitoes ticks fleas roaches and lice as well as sand flies kissing bugs snails and mites
sunos zoonosis or zoonotic diseases the term zoonosis refers to an infectious disease that
is transmissible under natural conditions from vertebrate animals to humans contact with skin
bite or scratch of an animal direct inhalation or ingestion for example eating contaminated
meat can lead to zoonotic diseases long recognized monadic diseases include plague from rodent like
from rodents and trucks from sheep tularemia from Reb this and and rabies from bats and
raccoons sorry to remya from rabbits I'm sorry and rabies from bats and raccoons dogs and other
mammals many newly recognized infectious diseases in humans include hiv/aids Ebola
infection and SARS all of these are thought to have emerged from animal house zoonosis as
compared to on top on OSes infectious agents vary greatly in how the transmitted disease diseases
transmissible from humans - humans are known as entrepreneurs example rubella smallpox diphtheria
these pathogens have adapted by evolution to the human species as their primary usually exclusive
hosts in contrast zoonosis are diseases erections visible from animals to animals or from animals
to humans but animals are the natural reservoir for those infectious agents example rabies there
are directly transmitted entrepreneurs such as TB HIV AIDS and measles and zoonosis example rabies
they are also indirectly transmitted vector bran entrepreneurs such as malaria dengue fever yellow
fever as well as zoonosis such as bubonic plague and Lyme disease the term zoonosis ending in es
is plural which means multiple diseases whereas the term zoonosis ending in is is which means
one single infection zoonotic diseases can also spill over to humans in this figure the darker
green shaded area waving up and down in here represents cycles of currents of the pathogen
in wild animals in wild animals reservoirs you can see transmission of the infected agents and
amplification in people in bright red shaded area occurs after the pathogen from wild animal moves
into livestock to cause an outbreak in light green that amplifies the capacity for pathogen
transmission to people bill over arrows in pink shows cross-species transmission wild animal to
domestic animals wild animals or domestic animals to humans all zoonosis have non-human reservoir
hosts and that dynamics of the pathogen in this host often determines the risk of outbreaks in
people early detection and control efforts during appropriate time can reduce disease
incidence in people and animals understanding of the relation between the between environment
wildlife population dynamics and the dynamics of the microbes can be used to forecast risk of human
infection this risk can vary with geography season seasons or through multi year cycles
and can depend on factors such as changes in land use weather climate or environment investigations
into the dynamics of zoonotic pathogens in their wildlife reservoir can act as an early warning
system to better inform the risk of an outbreak in livestock or people and reduce the number of
cases of human cases so let's do some quick concept check which of the following is not a
pathogen d mosquito mosquito is a vector is not a pathogen which of the following answer choice
is not a vector e birds birds is not a vector birds a reservoir the term zoonosis refers to
any living agents that transfer pathogen from one organism to another true or false false
zoonosis must have animal in in here in this case is just saying living agents that transfer
positive from on one organs of Jennifers is not specific to Geonosis thank you that's all