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Bovine Diseases and Disorders

VT-226 Large Animal Theory II September 2016

BRUCELLOSIS

Definition

• Zoonotic bacterial infection causing abortions after the 5th month of gestation in cattle

Cause: Brucella abortus

Transmission: by ingestion

Signs

• Abortion after the 5th month

• Orchitis, epididymitis, mastitis, lameness

• Affected animals become carriers for life

Prevalence/Geographical Distribution

• Almost eradicated in USA and Canada

• Some natural wildlife reservoirs still present

Diagnosis

• Bacterial culture, PCR and serology

• Surveillance of B. abortus in dairy cattle by milk ring test

• Assesses the presence of agglutinating antibody in milk

Treatment

• Treatments are not effective

• Oxytetracycline and streptomycin have been used to reduce shedding

• Affected cattle rarely treated

• Usually sent to slaughter to eradicate the disease

Recovery

• Cattle who abort their 1st pregnancy are capable of carrying subsequent pregnancies to term

• But remain chronic carriers…



Zoonotic potential

• Humans can become infected by ingesting unpasteurized milk products or by handling

contaminated body fluids or tissues

• “Undulant fever”

Prevention

• Vaccination (RB51) to young heifers before pregnancy

• Surveillance methods

JOHNE’S DISEASE

Definition

• An insidious chronic disease affecting ruminants and other animals, causing weight loss and

diarrhea

Cause:

• Mycobacterium avium subspecies paratuberculosis

• Different strains are recognized (e.g., cattle strain, sheep strain, etc.)

Transmission:

• Fecal-oral route is the most important mode of transmission

• Typically infected during the perinatal period when suckling from teats stained with manure

• Organism ingested, spreads to lymph nodes

• Can also be transmitted in utero and through colostrum/milk

Signs:

• Most animals are asymptomatic

• Affected animals show gradual weight loss, despite normal appetite, and decreased milk

production

• As disease progresses, profuse diarrhea develops

• At this stage, animal appears cachectic with intermandibular and ventral edema due to

hypoalbuminemia



Onset:

• Chronic and insidious with long incubation period (longer than 2 years)

• For every mature cow showing advanced signs, it is estimated 15-25 others from the herd are

also infected (the “iceberg effect”)

Prevalence/Geographic Distribution:

• Common disease

• Worldwide

Diagnosis:

• Fecal culture is the gold standard

• Downside is long incubation period of 16-20 weeks

• ELISA test commonly used

• Other: AGID, PCR

Treatment:

• No effective treatment is available

Recovery:

• There is no recovery.

• Animals with advanced clinical signs die due to cachexia and dehydration.

• Usually animals are sent to slaughter before they develop advanced clinical signs.

Zoonotic Potential:

• There is an association between M. avium subspecies paratuberculosis and Crohn’s disease in

humans

• Possibility of a causative relationship unclear

Prevention:

• Biosecurity measures aimed at reducing exposure of young animals

• Killed vaccine available in some states, but requires USDA accredited veterinarian AND approval

of state veterinarian

• Does not eliminate infection but delays onset of clinical signs



BOVINE RESPIRATORY SYNCYTIAL VIRUS

Cause:

• BRSV

• Paramyxovirus

• A primary BRD pathogen

• Frequent and common

• LRT pathogen

• Predisposes to secondary bacterial infection

Signs:

• Fever, depression, anorexia, increased RR, cough, eye/nasal discharge

• Dyspnea later in disease

• Secondary bacterial pneumonia common

Diagnosis:

• Requires laboratory confirmation

• Difficult to detect

• PCR the best option

• Followed by IFA

Treatment:

• Focuses on antimicrobial therapy to control secondary bacterial pneumonia

• Support

• Most animals recover without treatment

Prognosis:

• In outbreaks, morbidity is high, and case fatality rate can be up to 20% if secondary pneumonias

occur

• In the absence of bacterial pneumonia development, the prognosis is good

• Primary exposures always cause severe respiratory disease



• Secondary exposures are mild or subclinical

Prevention:

• Vaccines exist

• Efficacy is uncertain

BOVINE VIRAL DIARRHEA

Definition:

• Viral disease causing a number of clinical syndromes

• Cause of devastating economic losses because of decreased milk production, reproductive

failure, secondary infectious diseases, etc...

Cause:

• BVD virus

• Flavivirus, multiple biotypes

• Cytopathic (CP)

• Non-cytopathic (NCP) Type 1 and Type 2

Transmission:

• Direct contact with body fluids from persistently infected (PI) cattle most common

• Indirect: insects, contaminated needles

• Vertical and horizontal transmission

• PI animals are the main source of transmission in a herd – shed lots of virus

Signs:

• Numerous, depending on:

• Age

• Reproductive and vaccine status

• Concurrent stressful conditions

• Prevalence of PI animals in the herd

• Viral factors (strain, biotype, etc.)



Persistent Infection (PI):

• Infection with noncytopathic-BVDV before 125 days of gestation

• Usually asymptomatic

• Although some may be weak at birth and grow poorly

• A few may die shortly after birth

Acute BVDV infection:

• Non PI animals 2-24 months of age

• Fever, lethargy, anorexia, diarrhea, oral erosions and ulcers, and decreased milk production

• Infection causes immunosuppression, predisposing to secondary infection, particularly

respiratory (e.g., pneumonia) and GI (e.g., salmonella, E. coli, etc.)

Hemorrhagic Syndrome:

• Noncytopathic BVDV Type 2 infection

• Virus-mediated thrombocytopenia bloody diarrhea, epistaxis, hyphema, hemorrhage from

mucosal surfaces, bleeding from injection sites, etc.

Reproductive Implications:

• Virus can cause:

• Infertility

• Early embryonic death

• Abortions any time during gestation

• Fresh or frozen semen can serve as source of infection

Congenital Disease:

• Infection of the fetus in the 2nd trimester can cause congenital abnormalities:

• Hydrocephalus, cerebellar hypoplasia, microphthalmos, cataracts, retinal atrophy,

hypotrichosis, brachygnathia, skeletal anomalies, pulmonary hypoplasia

Mucosal Disease:

• Occurs when PI cattle are infected with a CP-BVDV strain



• Biphasic fever, tachycardia, tachypnea, profuse diarrhea, erosive lesions in mucosa (oral

cavity, vulva) in addition to interdigital spaces and teats

• Affected cattle develop bacterial infection and die within a few days

Onset:

• Acute or chronic

Prevalence/Geographical Distribution:

• Seroprevalence ranges from 20-90% in many countries

Diagnosis:

• Serology, virus isolation, PCR, fluorescent antibody, immunohistochemistry, and antigen-capture

ELISA are used for diagnosis of specific forms of the disease

Treatment:

• No specific treatment is available

Recovery:

• Variable, depending on the form or clinical manifestation of the disease

Zoonotic Potential:

• None

Genetic Prevalence:

• Not known

Prevention:

• Vaccination used after infection to restrict the disease (limits viral replication)

• Identifying PI animals is an important tool to reduce source and rate of infection in a herd

PARAINFLUENZA

Cause:

• Parainfluenza-3 virus (PI-3)

• Paramyxovirus

• High morbidity, but mild to subclinical infections



• Most important role is it to serve as initiator that predisposes to lower respiratory infections

Signs:

• Pyrexia, cough, nasal/ocular discharge, increased RR

• Signs worsen with onset of bacterial pneumonia

• Fatalities from PI-3 alone are rare

Diagnosis:

• Similar to BRSV

Treatment and Prevention:

• Treatment focuses on antimicrobial therapy against bacterial pneumonia

• NSAIDS are also a consideration

• PI-3 vaccines available (combined with IBR)

INFECTIOUS BOVINE RHINOTRACHEITIS (IBR)

Definition:

• Viral infection of the URT characterized by high fevers, nasal discharge, and white plaque

formation in the nasal and tracheal mucosa

• Other forms of the disease include:

• Infectious pustular vulvovaginitis (IPV)

• Infectious balanoposthitis

• Conjunctivitis, abortions, neonatal encephalitis

Cause:

• Bovine Herpes virus type I (BHV1)

Transmission:

• Direct contact or aerosol

• Can establish latent infection in neural tissue

• Stress or steroids can reactivate



Signs:

• Respiratory form

• Fever, tracheitis, rhinitis

• Pustules in nasal mucosa diphtheritic white plaques

• Immunosuppressive 2° bacterial pneumonia

• Conjunctivitis with corneal opacity and ocular discharge may be the only signs

(conjunctival form)

Onset:

• Chronic and latent infection with recrudescence


• Widely distributed

Diagnosis:

• Clinical signs in addition to paired serology, IFA, and virus isolation

Treatment:

• Supportive

• Prophylactic antibiotics to prevent secondary bacterial pneumonias

Recovery:

• Good, unless secondary pneumonia develops

• High morbidity, low mortality

Zoonotic potential:

• None

Prevention:

• Avoid management practices that induce stress

• Vaccination; parenteral and intranasal available



BLACKLEG

Definition:

• An acute, rapidly fatal, histotoxic clostridial infection causing extensive emphysematous,

hemorrhagic, and necrotic lesions in muscle tissue

Cause:

• Clostridium chauvoei, an anaerobic spore-forming bacterium

Transmission:

• Contaminated pasture is the source

• Organism can survive in soil for years

• When ingested, gains access to circulation, reaching muscle tissue

• Spores remain dormant in muscle until injury creates anaerobic conditions

Signs:

• Young animals, in good body condition, are more commonly affected

• Outbreaks occur, and not unusual to find animals dead with no previous signs

• Initial fever lethargy, lameness swelling of muscle death within 24-48 hours (toxemia)

Onset:

• Sudden onset


• Worldwide

Diagnosis:

• Typical clinical signs in young animals

• Aspirate of swelling dark, brown-colored fluid and gas

• Gram-stain aspirate large G(+) rods

• Post-mortem: dark red to black muscle, visible gas bubbles, sweet odor (gas gangrene)

Treatment:

• Unrewarding once clinical signs present



• If caught early: Penicillin, IV fluids, NSAIDS, and support

• Surgical fenestration allowing exposure to air

Recovery:

• High mortality rates

Zoonotic Potential:

• Organism has potential to cause “gas gangrene” in humans

Prevention:

• Vaccination is very effective in prevention

• Many toxoids available

• Young cattle should be vaccinated in endemic areas

BOVINE RESPIRATORY DISEASE COMPLEX

Definition:

• The most common and costly problem encountered in feedlot calves

• AKA “Shipping Fever”

• Major economic losses due to reduced average daily gain, feed efficiency, and overall

performance

Definition:

• BRD is a respiratory complex that occurs most often within 14 days after calves have been

weaned

• Weaning is stressful and stress is immunosuppressive.

• At that time, calves are castrated, extensively handled, commingled, and shipped

• And simultaneously exposed to many infectious agents

Definition:

• Other factors include movement through sale yards, poor body condition, and transport over

long distances

• On arrival, calves are often dehydrated, exhausted, and vulnerable to infection

• Many calves develop bronchopneumonia and even die from “shipping fever”



Infectious Agents:

• Viruses: BVD, IBR, BRSV, PI-3

• These open opportunities for bacteria

• Bacteria: Mannheimia haemolytica, Pasteurella multocida, Haemophilus somnus

Signs:

• Seen within 14 days of weaning

• Variable presentation (multifactorial)

• Early signs: depression, anorexia, dull eyes

• These calves should be pulled immediately and checked for fever

• Temperatures >104°F indicate early BRD

Signs:

• Later signs: rapid/labored breathing, droopy ears, coughing, diarrhea, sudden death, staggering,

nasal discharge

• Onset of BRD should be expected, so every calf should be looked at twice daily after the

weaning process

• Left untreated, calves with severe BRD will die from asphyxiation

Treatment:

• Most involve antibiotics to treat pneumonia

• NSAIDs +/- vitamins

• Response to therapy usually seen within 24 hours

• Early recognition of BRD = successful outcome

Diagnosis:

• Usually by clinical signs and response to treatment

• Necropsy recommended on all dead calves to confirm BRD and identify all viruses and bacteria

involved

Prevention Strategies:

• Good nutrition prior to weaning



• Reducing stresses of S/H

• Vaccinating pre-weaning

• Acclimate to eating from a bunker prior to shipping

• Any calves that appear sick/febrile should be treated with antibiotics during processing

ANAPLASMOSIS

Definition:

• Intraerythrocytic infection with Anaplasma marginale (rickettsia) causing progressive anemia.

Cause:

• Anaplasma marginale

• Anaplasma marginale subspecies centrale causes mild disease

Systems Affected:

• Erythropoietic system

• Erythrocytes become infected, which can be detected with a blood smear

Transmission:

• Persistently infected animals are an important reservoir for transmission

• Transmitted by ticks and biting insects

• Iatrogenic infection by use of contaminated needles, dehorning, castration, and ear-tagging

instruments

Signs:

• Depends on virulence of the strain and host susceptibility

• Calves and youngstock more resistant than adults

• Prepatent period: 15-30 days

• Peracute: may die within an hour

• Acute: fever, anorexia, lethargy, decreased milk production, MM pale and icteric, weight

loss

• Recovered animals become persistently infected for life, are asymptomatic, and serve as

reservoirs



Prevalence/Geographic Distribution:

• Most prevalent tick-borne infection in cattle around the world

Diagnosis:

• Made by identification of A. marginale in rbcs with a substantially decreased PCV

• Persistently infected animals are diagnosed by serology (ELISA)

• Absence of hemoglobinuria helps to rule out other hemolytic diseases such as babesiosis

Treatment:

• Oxytetracycline is treatment of choice in the acute stage, but clearance of the organism is not

acheived

Recovery:

• Variable

• Immune system can suppress the infection but cannot completely clear it

Prevention:

• Modified live vaccine licensed for use only in California

• Tick and biting fly control

ANTHRAX

Definition:

• A soil-borne bacterial zoonotic disease causing acute septicemia and high mortality rates

Cause:

• Bacillus anthracis, a large rectangular-shaped gram-positive rod.

• In unfavorable conditions, bacteria forms spores that are very resistant and persist infectious in

the environment for decades

Transmission:

• Ingestion of spores from the soil when grazing

• Spores vegetate in the host and escape phagocytosis

• Rapid multiplication septicemia, multiorgan dysfunction, toxic shock, death



Signs:

• Usually not seen due to rapidity of disease

• Cattle are commonly found dead

• Animals that die often have bloody exudate from body orifices and rapid decomposition of

carcasses

Onset:

• Peracute, with rapid progression and death

Diagnosis:

• Suspect animals dying from anthrax should not be opened in the field, or moved from where

they are found, to prevent bacterial sporulation

• Recommended that suspicious cases be called into veterinary regulatory officials

• A reportable disease in USA and Canada

Treatment:

• Usually no time

Zoonotic Potential:

• Anthrax is a zoonotic disease.

• In humans can present in 3 forms

• Cutaneous (most common)

• Gastrointestinal

• Inhalational

Prevention:

• Handling carcasses is a key factor in preventing spread of the disease

• Carcasses should not be opened or moved

• Must be buried deeply and covered with quicklime or burned (preferable)



ACUTE HYPOCALCEMIA

Definition:

• Milk fever

• An acute decrease in serum calcium levels seen in cattle 24 hours before through 72 hours after

parturition

Cause:

• Decreased calcium due to increased demands from fetal maturation, colostrum production, and

early lactation

Transmission:

• Not a transmissible disease, but a metabolic disease

Signs:

• Initial excitation and restlessness

• Progresses to weakness, diminished rumen contractions, and bloat

• Cow becomes recumbent, and unable to rise

• Untreated, die within 12 hours of onset

Diagnosis:

• Clinical signs

• If needed, serum calcium concentration can be measured

Treatment:

• Parenteral calcium borogluconate

Recovery:

• Good with appropriate treatment in a timely manner

Prevention:

• Nutritional management of dairy cows in the dry period is important to prevent the disease



DISPLACED ABOMASUM (DA)

Defined:

• The abomasum (or true stomach) normally lies on the floor of the abdomen, but can become

filled with gas and rise to the top of the abdomen, when it is said to be ‘displaced’.

• The abomasum is more likely to be displaced to the left (LDA) than the right (RDA)

Cause:

• Calving - The majority of cases occur soon after calving.

• During pregnancy the uterus displaces the abomasum, so that after calving the abomasum has

to move back to its normal position, increasing the risk of displacement

Cause:

• Atony of the abomasum -- If the abomasum stops contracting and turning over its contents,

accumulation of gas will occur and the abomasum will tend to move up the abdomen.

• This tends to be a cause of inadequate nutrition

Signs:

• Loss of appetite

• Drop in milk yield

• Reduced rumination

• Mild diarrhea

Diagnosis:

• History

• Clinical signs

• “Ping” sound

Treatment:

• Treatment requires replacing the abomasum in its normal position.

• Preferably, the veterinarian also prevents recurrence by tacking the abomasum to the body wall.

• Surgery can be performed, however isn't always necessary.



Treatment:

• Often the abomasum can be returned to its usual place by casting and rolling the animal onto its

back, permitting the abomasum to "float" back into its normal position.

• Rolling can be used in conjunction with a blind suture

• This significantly reduces the relapse rate.

Prevention:

• Prevention should be aimed at ensuring dry matter intake is maintained in early lactation

• It is likely that a farm with numerous DA problems is feeding the late dry and/or early lactation

cows wrongly

MASTITIS

Definition:

• Clinical or subclinical infection of the mammary gland

Cause:

• Contagious organisms through milking machines

• Environmental organisms

Transmission:

• Contamination of teats, udder, and milking machines is the principal mode of transmission of

environmental pathogens

Signs:

• Most cases are subclinical

• Mild cases have alterations in milk

• Moderate cases have visibly inflamed mammary glands and milk alterations

• Severe cases have the above and show signs of systemic illness (lethargy, weakness, etc.)

Prevalence:

• A prevalent disease in dairy cattle causing substantial economic losses

• >2 billion dollars per annum



Diagnosis:

• Subclinical screening tests

• California Mastitis Test (CMT)

• Somatic Cell Count (SCC)

• Electrical conductivity of milk

• Clinical mastitis is done by clinical signs

Treatment:

• Antibiotic therapy

• Frequent milk-out is recommended to remove secretions from the mammary gland

Recovery:

• Good to poor, depending on organism involved and severity of disease

Zoonotic Potential:

• Many pathogens in raw milk can be transmitted to people

• Pasteurization is used to reduce the risk of milk-related foodborne illness

Prevention:

• Use of individual cloth to prepare teats

• Use of gloves by milkers

• Antibiotic therapy of dry cows

• Frequently removing manure from lots

• Avoiding overcrowding

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