Principle of Infectious Diseases

By: Xavia Hutchinson & Bri Smith

Objective:

Students will learn the infectious disease causing agents.

Students will know how to treat infectious diseases.

Students will learn Koch’s postulates.

Starter Question

What type of infectious diseases do you know that animals can

get?

Vocab:

Anthrax: a bacterial infection within the skin, intestines, and respiratory system.Vector: organism that transmits disease.Prokaryotic: cells without membrane bound organelles.Anemia: low in red blood cells.Systemic: affecting entire body.

Vocab cont.

Lyme Disease: bacterial infection that is in humans and animals that can cause symptoms such as fatigue and joint pains.

Antimicrobial: agent that hinders the growth or kills microorganism.

Bacteriostatic: agent that slows the rate of growth in bacteria.

Antiseptic: germicides that can be used on the skin of animals.

Disinfectants: germicides that are too harsh to be used on skin but can be used on inanimate objects or surfaces.

Background info of Koch’s postulates:

Why was Koch’s postulates made? Anthrax outbreak in 2001 caused

German physician Robert Koch to investigate why certain diseases were occurring.

What did Koch study? Anthrax in cattle.

Foundation of Koch’s Postulate:

The infectious agent should be detectable in sick animals but not healthy animals.

It should be possible to isolate and culture the organism.

Organisms taken from the culture and introduced into a healthy animal should cause the same disease.

The same organism should be isolated from the second animal.

What did Koch’s postulate do…

Helped establish germ theory

Understanding infectious diseases

Causes of Infectious Diseases:

Microorganisms (An organism of microscopic or submicroscopic size)

May be a single cell or multicellular organism

Microorganisms are very diverseMicroorganism live in all types of

environments, all around the world

Disease Agents:

Traditionally, infectious diseases are divided into four classes of agents:Bacteria

Viruses

Fungi

Parasites

Bacteria:

One celled prokaryotic organisms They are affected by the

environment There is good bacteria and bad

bacteria (pathogens)Pathogens (signs of disease)

when a deadly bacteria invades a host it multiplies, during this incubation stage pathogen numbers increase rapidly.

Bacteria cont. :

Endo/Exo toxins (These toxins help in the result of the signs of diseases.) Exotoxins are proteins produced and released by secretion.

Endotoxins is the cell wall of the bacteria that is only released after the bacteria dies.

Prodomal phase stage in disease when first signs of illness occurs, in this

short period of time symptoms are physically present, then quickly progress into a more severe stage.

Classifying bacteria is an ongoing process gram-positive & gram-negative etc.

Bacterial Infections: Strangles

Commonly found in Horses Bacteria (streptococcus equi) Symptoms (anorexia, fever, nasal discharge)

Wooden tongue Commonly found in Cow and Sheep Bacteria (actinobacillus lignieresi) Symptoms (inflammation of tongue or lymph nodes)

Kennel Cough Commonly found in Canines Bacteria (bordetella bronchiseptica) Symptoms ( dry cough & anorexia)

VirusesA virus is an infective agent that

typically consists of a nucleic acid molecule in a protein coat, and is able to multiply only within the living cells of a host.

Process of infection Virus locates host cell and attaches itself to

it Viruses can be specific in the host/host cells

it infects Virus penetrates Virus uses either DNA or RNA to multiply

inside the host.

Viruses cont. :

Virus then releases lysosomes that will destroy the host cells

The assembled viruses are then released out the host and wait for their next host.

Some viruses require a vector (an organism, such as a mosquito or tick, that carries disease-causing microorganisms) to transmit themselves from one host to another

Viral Infections: Equine Influenza

Commonly found in Horses

Virus (Equine influenza virus)

Symptoms (fever, cough, nasal discharge)

Shipping fever Commonly found in Cows

Virus (IBR*)

Symptoms (high fever, ocular discharge, severe pneumonia)

Feline Leukemia Commonly found in Cats

Virus (retrovirus)

Symptoms (weight loss, anemia, tumors)

Fungi:

Fungi are eukaryotic cells with cell walls

Fungi gain nutrients by absorbing nutrients from their surroundings

Fungi are spore producers (spores provide the ability to spread the organism to other areas)

Fungi can affect animals in several ways

Fungi cont. :

Infects outer layer of the body (skin, hair/fur, nails/claws)

Infects the internal organs then spreads to other regions of the body (systemic)

Infects food sources (indirectly infecting animals)

Fungal Infections: Valley Fever

Commonly found in Cats & Dogs

Fungus (coccidiodes immitis)

Symptoms (lumps & abscesses)

Ringworm

Affects all species

Fungus (microsporum sp.)

Symptoms (hair loss, crusting, flaking)

Histoplasmosis

Commonly found in Cats & Dogs

Fungus (histoplasma capsulatum)

Symptoms (respiratory infection, weight loss, diarrhea)

Parasites:

Single celled organisms or Large arthropods

Parasites can be internal or external Parasites use their host as a source

of nutrients and protectionParasites have complex life cycles

allowing them to survive and infect others

Parasites cont. :

Full life cycles require more than one host

Animal that carries the adult parasite is called the “definitive host”

Animal that carries immature stage of parasite, such as larvae, is called the “intermediate host”

External parasites are called “arthropods” mites

ticks

fleas

Parasitic Infections:

Hookworms Commonly in Cats & Dogs Parasite (anclyostoma sp.) Symptoms (diarrhea, anemia, anorexia)

Strongylosis Commonly found in Horses Parasite (strongylus sp.) Symptoms (colic, diarrhea, weight loss)

Heart worm Commonly found in Dogs Parasite (dirofilaria immitis) Symptoms (coughing, fluid in abdomen, cardiac

failure)

Treatments Many chemicals exist to hinder growth

or kill these infectious disease agentsAntimicrobial = AntibioticAntibiotics are capable of killing

bacteria NOT virusesAntimicrobials

Bacteriostatic (an antibiotic that only slows the rate of growth of bacteria)

Antiseptics (used on animals skin)Disinfectants (used only on

inanimate objects)

Clinical Practice

Culturing is a technique used to isolate and identify microorganismProper sampling and handling Sample added to medium for growth Incubation in proper temperaturesSpecific time period Antibiotic sensitivity tests performedAnalysis of results

Treatments

Anthelmintic is a process used to identify the animals who need to be treated for parasitic infections

Anthelmintic process Animals are evaluated by the color of its

mucous membrane

Color chart compares mucous membrane with the color conjunctiva of the eyes

Animals with the palest mucous membranes are then treated

Treatments & Clinical Practice

Supportive Treatment (supplementing vital nutrients and care to lame animals)Fluids given to animals lacking in

water

Tubes connected to the stomach to pump food into the body