Midterm Exam Review

History and Principle of Disease, Disease of Cattle

Trichomoniasis

A venereal disease caused by a protozoan, Trichomona fetus; Infects the genital tract of the bull and is transmitted to the cow during breeding

• Clean bulls can also be infected by breeding

“dirty” cows

• Can also be transmitted through infected

semen, even when artificial insemination is

used.

Trichomoniasis Symptoms

Abortion in early gestation

• Low fertility

• Irregular heat periods

• Uterine infection

• Cows may have discharge from their genital tract

• Bulls may not show any symptoms but still be capable of

transmitting the disease during breeding

• Identified by microscopic examination of material from an

aborted fetus, the prepuital cavity of the bull or vaginal discharge

from the cow

Trichomoniasis Prevention

When purchasing bulls, purchase virgin bulls if possible

• Semen testing

• Cull and sell positive bulls for slaughter only!

• Keep the neighbor’s bull out of your cow pasture

• Testing cows before breeding

• Pregnancy check cows in a timely manner after the breeding season to

identify any infected cow early

• Using only clean bulls on clean cows

• Selling all open cows

• Vaccination can control and prevent the disease in cows, but does not

protect bulls

Trichomoniasis Treatment

Currently, there is no approved treatment for cattle infected with Trichomoniasis. Control is by culling infected bulls and rigorous biosecurity

Bovine Virus Diarrhea (BVD)

a member of the pestivirus genus

• Common throughout the United States

• May appear in mild, acute & chronic forms

• Spreads by contact

Mild BVD Symptoms

Often no symptoms

• If they are present:

• Fever

• Coughing

• Discharge from the nose

• Slow gains

• Rapid breathing

• Mild diarrhea

• Animals that have had the mild form of the disease are

immune to further infection.

Acute BVD Symptoms

Fever

• Difficult breathing

• Discharges from the

nose and mouth

• Possible lameness

• Dehydration

• Weight loss

• Diarrhea after 3-7 days

Chronic BVD Symptoms

All the same symptoms as the acute plus

–Slow gains

–Rough hair coat

–Lameness

BVD Prevention

Modified live virus vaccine

• Vaccinate calves between 1 day of age and 3 weeks before

weaning

• May be vaccinated upon arrival in the feedlot

• They should not be vaccinated if they were vaccinated as

calves

• Pregnant cattle should not be vaccinated

• Adult cattle should only be vaccinated

• After calving

• At least 3 weeks before breeding

• Replacement heifers should be vaccinated between 9 & 12

months of age but not during the last 3 weeks before breeding

• No cure

Mastitis

an inflammation of the

udder caused by a wide variety of

bacteria OR occasionally other

types of infectious organisms that

enter the udder from the outside

environment

Acute Mastitis Symptoms

Inflamed udder

• Swollen, hot, hard, tender quarter

• Drop in milk production

• Abnormal milk

• Lumpy, stringy, straw-colored,

contains blood, yellow clots

• Cow goes off feed, shows

depression, dull eyes, rough hair,

chills

• Death may result

Chronic Mastitis Symptoms

Abnormal milk-clots, flakes, watery

• Slight swelling and hardness of udder that

comes and goes

• Sudden decrease in milk production

• May not show any symptoms

• Often not treated

• Sometimes does not respond to treatment

• More of an economic problem than the acute

form

• Both acute and chronic mastitis may cause

permanent udder damage

Mastitis Somatic Cell Count

Mastitis increases the presence of white

blood cells (leukocytes) that fight infection

• Somatic cells are leukocytes and other

blood cells

• All normal milk contains some somatic cells

• Goal of the dairy herd should be an average

of no more than 150,000-200,000 cells per

milliliter

• 90% of the herd should be below 200,000

cells per milliliter

Somatic cell count can vary greatly from

month to month in cows that have mastitis

infection

• Somatic cells counts over 500,000 usually

indicated a bacteria infection, a cow in late

lactation, udder injury or an old cow

• Problem cows should be culled

Mastitis Economic Loss

Causes losses by;

• Lowering milk production from infected

cows

• Increasing the cull rate in the herd

• The cost of treatment

• Loss of infected milk that must be thrown

away

• Increased labor cost to treat infected cows

• Possible loss of permit to sell milk if

infection becomes serious enough

Mastitis Prevention

Maintain milking equipment in proper operating

condition

• Practice proper milking procedures

• Identify the bacteria causing the infection and

determine the extent of the infection in the herd

• Promptly treat identified cases of mastitis

• Treat all quarters of cows when at drying off time

• Cull cows with chronic mastitis problems that do

not respond treatment

Mastitis Treatment

When clinical mastitis is detected, the

cow is milked out and then given an

intramammary infusion of antibiotic (i.e.

infused directly into the infected gland).

• Clear identification of the treated cow is

critical to be sure the cow's milk is not

inadvertently put into the milk tank.

Shipping milk contaminated with antibiotics

can lead the producer to lose their permit to

ship Grade A milk.

• Use of leg-bands or some other physical

marker on the cow, as well as clear records

of antibiotic administration are essential for

this process.

• It is quite common for a cow to be treated

multiple milkings with the antibiotic

Milk Fever (hypocalcemia)

Also called parturient

paresis, occurs most commonly in

dairy cattle around the time of

calving.

• These cows undergo a sudden loss

of calcium when milk production

begins, which interferes with

normal nerve and muscle function.

Milk Fever Symptoms

Affected cows first go through

a period of restlessness and muscle tremors

before becoming unable to stand and death,

if left untreated.

Milk Fever Treatment

Intravenous injection of calcium.

Milk Fever Prevention

Feed a balanced ration to dry

cows with the correct calcium-phosphorus

ratio.

Displaced Abomasum

The abomasum is the true stomach of

ruminants.

•Due to its relatively loose attachments to

other abdominal organs, it may become

displaced following excess gas

accumulation or other processes that

affect its function or motility.

•Type of ration being fed appears to be

involved.

Too rapid an increase in grain feeding just

before calving increases the chance of

DA.

•Poor quality, moldy roughage or too much

silage in the ration also increase DA.

Displaced Abomasum Symptoms

Can range from decreased food

intake and mild abdominal pain, to severe

cases in which animals rapidly become

weak, poor appetite, depressed, bloated,

diarrhea, drop in milk production, and

dehydration.

Displaced Abomasum Treatment

Treatment - replacing the abomasum in its

normal position. Preferably, the veterinarian

also prevents recurrence by tacking the

abomasum to the body wall. Often the

abomasum can be returned to its usual

place by casting and rolling the animal onto

its back. Surgery is rare.

Displaced Abomasum Prevention

Do not over feed silage and

concentrates to dry cows. Increase the

amount of concentrate slowly at calving

time.

Retained Placenta

A condition in which the placenta is not discharged within 12-24 hours after calving

Retained Placenta Causes

Caused by infection in the reproductive tract

during pregnancy.

•Deficiencies of vitamin A or E, iodine, and selenium

•Calcium to phosphorus ratio in diet out of balance.

•Breeding a cow too soon after calving

•Normal for 10-12% of dairy cows.

•A higher rate indicates a problem that needs

attention.

Retained Placenta Treatment

Manual removal of the retained membranes is

no longer recommended and is potentially

harmful.

• Trimming of excess tissue that is objectionable

to animal handlers and contributes to gross

contamination of the genital tract is

permissible.

• Untreated cows expel the membranes in 2-11

days, with 40% of cases requiring no treatment.

• Early use of antibiotics may also slow down the

release of the membrane.

Retained Placenta Prevention

• Good management is the best practice

to prevent retained placenta.

• Specifically, observe the cow closely

for signs of illness and treat any

symptoms that occur.

• Regular weekly progesterone sampling

can help determine if there has been

any effect of the RP on the cow’s

return to normal reproductive activity

Symbiosis

colonization of one organism by another

Mutualism

when the symbiotic relationship benefits both organisms (E.g. healthy microflora in human gut)

Commensalism

a symbiotic relationship in which one organism benefits and the other is not harmed

Parasitism

occurs when the infecting organism benefits and the host is harmed. If the host sustains injury or pathological changes in response to the parasite, the process is an infectious disease! (E.g Liver fluke in animals)

Host

an organism that shelters and supports the growth of pathogenic organisms

Pathogen

a disease-causing organism

Infection

the invasion or colonization of the body by pathogenic organism

Disease

an abnormal state in which all or part(s) of the body is not functioning properly. It is any biological abnormality which results in impaired fertility, hatchability, livability, productivity or product quality

Ethiology

the manner of causation of a disease or condition

Idiopathic

describes a disease of unknown cause; etiology is unknown

Pathology

the scientific study of disease through laboratory analysis of tissue, blood, urine, or other body fluids

Disease Transmission

the passing of a disease-causing organism from an infected host to another host

Symptoms

physical or mental problems that a person experiences, and which may indicate a disease or condition

Incubation Period

Period between contraction and the display of symptoms

Syndrome

a collection/set of symptoms or conditions that occur together, and suggest the presence of a certain disease or an increased chance of developing the disease

Acute Disease

a disease that develops rapidly, can be severe, but lasts a relatively short time

Chronic Disease

disease or condition that persists or progresses over a long period of time; They are difficult to prevent by vaccines or cured by medication

Epidemiologic Triad (Triangle)

Factors that impact outcome severity (Host, agent, and environment); disease is produced through the exposure of a susceptible host to a noxious agent in the presence of facilitating or hindering environmental factors

Herd Immunity

occurs when a large portion of a population becomes immune to a disease (through vaccination or prior infection), which makes it harder for the disease to spread from person to person

Koch’s Postulates

4 criteria established by Robert Koch for the

identification of the causative agent of a disease. These

include;

1. The organism must be present in all cases of the disease

2. The organism must be isolated from the diseased host and

grown in pure culture

3. The disease must be reproduced when a pure culture of the

organism is introduced into a healthy, susceptible host

4. The same organism must be re-isolated from the

experimentally infected host

Limitations of Koch’s

1. Some bacteria and viruses cannot be grown on artificial

media

2. Some diseases are caused by a variety of microbes (E.g.

Pneumonia)

3. Some pathogens cause different diseases (E.g.

Streptococcus pyogenes --- causes pharyngitis, scarlet

fever, cellulitis)

4. Some pathogens only cause disease in humans (E.g. HIV)

Diseases are classified by…

Frequency, severity, and infectivity

Sporadic

a disease that occurs as an isolated incident in few animals (E.g. scrapie disease)

Enzootic

diseases that occur at a steady or predictable rate in animals of a specific geographic area, or at a particular season (E.g. Bovine leukosis in cattle)

Epizootic

disease that occurs among a population of animals at a frequency higher than that expected in a given time period. The disease spreads rapidly over a large geographic area, such as an entire state, and affects a large number of animals of same kind at the same time, in a short period of time (E.g. Anthrax)

Panzootic

disease that occurs in a widespread outbreak among a large number of animals, usually affecting more than one species. (E.g. Highly Pathogenic Avian Influenza)

Acute

develops rapidly; reactions to the disease can be severe, but lasts a short time (E.g. Influenza)

Chronic

develops more slowly, reactions to the disease are less severe, and are likely to be continual or recurrent for long periods (E.g. Tuberculosis, Hepatitis B)

Subacute

intermediate between acute and chronic (E.g. Sclerosing panencephalitis)

Latent

the causative agent remains inactive for a time but then becomes active to produce symptoms (E.g. Shingles – reactivation of chickenpox virus in the body)

Noninfectious Diseases

diseases that are not caused by biological agents and cannot be shared (transmitted) from one person to another

Infectious diseases

diseases caused by biological agents that include Metazoa and Microbes (Protozoa, Fungi, Bacteria, Rickettsia, Viruses, and Prions)

Causes of Noninfectious Diseases are…

Dietary problems, metabolic disorder, trauma, poisonous plants & toxic substances, congenital, age, littering, cancer, and autoimmune diseases

Dietary Problems

nutritional deficiency or inadequate feed consumption

Metabolic Disorder

usually result from intensive animal production

Trauma

caused by wound or injury

Congenital

birth defects can be hereditary, or caused by mutation of genes in the fetus.

Autoimmune Diseases

occur when the animal’s own immune system attacks cells in its body.

World Organization for Animal Health (OIE)

aim at improving animal health and welfare of terrestrial animals, as well as veterinary public health. The implementation of these standards also ensures international safe trade in animals and animal products.

World Animal Health Information System (WAHIS)

global online platform run by WOAH (World Organisation for Animal Health, formerly OIE) that collects, verifies, and shares information about animal diseases worldwide

Parasites

organisms that have to live on or in other organisms (such as animals) in order to survive (cause infectious disease)

External Parasites

Flies, lice, fleas, ticks and mites can cause skin irritation and damage

Internal parasites

round worms, flukes and tapeworms can live in the stomach, intestines, lungs, and liver of animals (cause reduced weight gain & other forms of production loss)

Protozoa

single-cell organisms (unicellular eukaryotes) with a well-defined nucleus (microbe causing infectious disease)

Fungi

group of eukaryotic organisms that include unicellular microorganisms such as yeasts and molds, as well as multicellular fungi that produce familiar fruiting forms known as mushrooms (microbe causing infectious disease)

Bacteria

autonomously replicating unicellular organisms that lack both an organized nucleus (which defines the class of cells called prokaryotes) and organized intracellular organelles. They have only a single circular chromosome of double-stranded DNA (dsDNA), some extrachromosomal DNA, and most have a cell wall containing the polymer peptidoglycan. They can live in animals and cause disease (microbe causing infectious disease)

Viruses

smallest of all microbes; Are obligate intracellular parasites. They must live inside cells in order to survive and multiply; They cause about 60% of disease outbreaks in animals and humans (microbe causing infectious disease)

Prions

infectious agents that do not have any genes; They consist of a protein with an aberrant structure (perhaps misfolded); Prions replicate in animal or human tissue and cause severe damage to the brain. (microbe causing infectious disease)

Stages of Disease Development

1) incubation period 2) prodromal period 3) illness 4) period of decline 5) period of convalescence

Direct Transmission

immediate transfer of an infectious agent from an infected animal to a susceptible animal (vertical or horizontal)

Direct Transmission (Vertical)

infection that is transmitted from a parent to its offspring via infected semen or ovum, through the placenta, in the birth canal, via milk

Direct Transmission (Horizontal)

any form of infection transmission from one animal to the other

Indirect Transmission can occur through…

Aerosol (airborne), fomite, vectorborne, or zoonotic

Aerosol (Airborne)

Pathogenic agents contained in aerosol droplets are passed from one animal to another

Fomite

A contaminated inanimate object transmits a disease agent from one susceptible animal to another. E.g. animal contact with contaminated shovels, clothing

Vector-borne

An insect acquires a pathogen from one animal and transmits it to another either mechanically or biologically

Zoonotic

are diseases that can be passed from animals to humans

Anthrax

highly infectious disease caused by Bacillus anthracis (Bacteria) (traditional)

Traditional Animal Diseases

Usual, known, familiar diseases

Emerging Animal Diseases

New, latest, understudied diseases

Foot-and-Mouth Disease (FMD)

highly contagious viral disease of cattle and swine (traditional) Controlled with vaccine, BUT may reappear because i) some farms do not routinely vaccinate, and ii) intensive rearing of animals

Brucellosis

caused by various species of Brucella bacteria (traditional) disease may re-emerge because, brucellosis has been discovered in bison herds

Classical Swine Fever (CSF)

a highly contagious and economically significant viral disease of pigs (traditional)

Equine Encephalomyelitis

a disease caused by a group of viruses spread by mosquito vectors, and cause 3 significant diseases in Eastern, Western, and Venezuelan areas (traditional)

Postweaning Multisystemic Wasting Syndrome (PMWS)

viral disease in swine (emerging)

Poult Enteritis Mortality Syndrome (PEMS)

caused by a range of viruses in turkey poults at the age of 1–4 weeks (emerging) Characterized by high mortality and 100% morbidity

Exotic Newcastle Disease

a serious viral disease of birds (emerging)

Transmissible Spongiform Encelopathies

caused by proteinaceous particles called prions; Any fatal, incurable degenerative disease of the brain transmitted by prions; They have recently emerged in almost every sector of animal agriculture – though no large losses; Are also zoonotic (Creutzfeldt-Jakob disease in Humans) 1. Scrapie in sheep

2. Bovine spongiform encelopathies (BSE) in cattle

3. Chronic wasting disease (CWD) recently emerged in deer

Avian Influenza (Bird Flu)

caused by virus; primarily infect birds (zoonotic) The strains can mutate to become highly pathogenic and infect humans

Gastroenteritis-causing bacteria

bacteria residing in the gastrointestinal tract of food animals; frequently asymptomatic and harmless in the animals, but are disease-causing in humans

Control

prompt disposal of infected carcasses to avoid spore exposure