Infectious Disease

Johne’s Disease (Paratuberculosis)

• Causative agent: Mycobacterium paratuberculosis• Extremely slow onset, chronic, progressive,

incurable, fatal– minimum 18 months to clinical status– incubation period up to 10 years

• Prevalent in 20% of US herds• 5-20% of ALL dairy cattle infected

– 25-30% of all herds– increasing in both dairy and beef– sheep, goats and deer also susceptible

International Prevalence

•Denmark:

•almost half of all herds test positive

•Holland:

•50 –80% of herds infected?

•New Zealand:

•16 – 50% of herds infected

History

“Johne’s disease is not at all widespread.

It does occur, however, and as the years go

by it will become more and more common

and will places a great tax on the cattle

industry”

Beach and Hastings 1922

Johne’s Disease (Paratuberculosis)

• Following calfhood exposure there is no evidence of infection for six months to several years– Rate of progression dependent on age, genetic

background, nutritional status, management, etc

Johne’s symptoms

• Clinical status after “high stress” period– Progressive and fatal– Non-treatable

• Primarily affects intestine and associated lymph tissues

• Causes proliferation of intestinal tissue– Malabsorption diarrhea– Animal loses condition– Displays diarrhea and constipation– Decreased milk, same feed intake (until late stages)

Fig 35-1. Cows with Johne's disease typically lose tremendous amounts of body weight, although feed consumption may be normal (Courtesy of Mark Kirkpatrick)

Johne’s Disease (Paratuberculosis)

• Apparently healthy animals can spread the disease– Test at regular intervals of 3-6 months

– Diagnostic testing is often inaccurate

– Fecal culture is most accurate method in live animals• False negatives are still a problem

• No treatment – Prevention through keeping infected animals isolated

Johne’s Transmission

• Fecal-oral– Organism remains viable in feces for 6-11 months

• Transplacental transfer• Organism present in milk, colostrum• Severity of infection depends on level of infective

dose• Age of exposure is critical• <5% of infected animals develop clinical

symptoms

Age Effects

• Newborn calf most susceptible– susceptibility decreases with age– not clinical - no shedding until > 9 mos.

• Cows least susceptible– infection unlikely after 1 year of age– shedding rate highest in mature, clinically

infected cows

Costs

• Lost milk costs• Lost cow value and slaughter value• Lost marketing ability of herd• Longer calving intervals• Increased mastitis• Increased vet costs• $250/cow (all cows, not just infected)• Infected 100 cow herd with average infection rate

loses $25,000/year

Antibody Tests

Fig 35-2. Enzyme-linked immunosorbent assays (ELISA's) are a useful diagnostic tool for estimating the prevalence of Johne's disease in infected herds (Courtesy of Mark Kirkpatrick)

Testing

• ELISA’s and other antibody tests have high incidence of “false positives”– If ELISA or antibody test is positive, fecal culture

should be used to confirm status

• Fecal cultures take 16 weeks, very expensive– Negative result does not necessarily indicate uninfected

cow, just non-shedding cow

– Positive result is fairly accurate

Fig 35-3. To confirm infection with Johne's disease, tissues can be stained for the immunohistological detection of M. paratuberculosis (Courtesy of Mark Kirkpatrick)

Johne’s Disease (Paratuberculosis)

• Control measures for infected herd– Reduce contamination by good sanitation– Do not spread manure on pasture land– Raise young stock in uncontaminated

environment, separate from mature animals

Control Program

• Prevent transmission– sanitary maternity barn– clean perineal area and udder– Remove calf from dam prior to nursing, wash

udder well prior to milking– feed colostrum from test-negative cows– raise “shedders” separate from “susceptibles”– spread manure on crop ground, not pasture

Control Program• Reduce incidence in herd

– test mature animals every 6 months– remove test-positive animals immediately– cull any apparent clinicals

• regardless of test results

– purchase only from tested clean herds– vaccinate infected herds

• not cost-effective in clean herds• does not prevent disease, only reduces severity• interferes with antibody tests

Is Johnes a Food Safety Issue?

Crohn’s disease is a bowel disease in humans

Overall incidence 5.6 cases per 100,000

Severe and very unpleasant condition

Cause unknown, maybe infectious agent like Mycoplasma

Johnes organism found in Crohn’s patients

No firm link established, the evidence is still inconclusive - but the issue is a source of concern to the dairy industry

Bovine Virus Diarrhea (BVD)

• Incubation period of 7-9 days• Characterized by

– High temperature (105-107 F)– Nasal discharge– Rapid breathing– Loss of appetite– Diarrhea

• Causes abortions in pregnant cows (3-6 weeks after infection)

• Decrease in milk production in lactating cows

Bovine Virus Diarrhea (BVD)

• Prevention– Avoid contact with infected animals– Keep away from contaminated feed and water– Isolate all incoming animals for 30 days

• Treatment– Electrolytes – Antibiotics combat the secondary bacterial

invaders

Bovine Virus Diarrhea (BVD)

• If BVD is a constant problem, vaccinate animals– Intramuscular administration of modified live or

inactivated vaccines• One vaccination should last a lifetime

• DO NOT vaccinate pregnant cows– Causes abortions

• DO NOT vaccinate calves under 6 months of age– Ineffective due to interference from maternal antibodies from

colostrum

• Replacement heifers should be vaccinated at 9-12 months of age

BVD control

• Multiple strains exist (identify!)

• Fecal-oral– Sanitation crucial

• Vaccines highly effective– not 100%

• BVD-PI (persistently infected) are exceptional situation

BVD-PI animals• 1 in every 200 calves is PI• Infected in utero between 80 and 120 days• Infection from 120-150 days

– congenital defects– weak calf syndrome

• Infection after 150 days – immune response– abortion, mummification

BVD-PI calves

• No immune response– recognizes virus as “self” permanently

• Virus replication unchecked– incredibly high shedding rates– potential threat to entire operation

• Difficult to identify– Ab titers ineffective method– must directly test for presence of virus

Fig 35-4. Obtaining an ear notch tissue sample for immunohistochemical diagnosis of BVD infection (Courtesy of Mark Kirkpatrick)

Fig 35-5. Immunohistochemical techniques help veterinarians visualize the BVD virus in ear tissue (Courtesy of Mark Kirkpatrick)

Salmonella• Invasive coliform

– fecal-oral transmission

– penetrates gut lining

– systemic infection common

• Present on up to 75% of dairies – clinical expression after stress (shipping)

• Highly rate of transmission– “herd epidemics” common

– high shedding rate

– high mortality rate

Salmonella• Pathogen associated with stress and immunocompromised

animals– Calves and transition cows most susceptible

• maternity barn sanitation• isolation of sick or recently purchased animals

• Characterized by rapid onset and severe watery diarrhea – Weak and rapidly dehydrated– Often becomes systemic infection

• Pathogen transmitted in feces– High sanitation standards are critical

• Infected cattle should be isolated– Animals are responsive to antibiotics

Challenges

• Some strains infect people

• Carriers include pets and pests

• Different strains present in different herds– S. typhimirium DT 104 is problem pathogen

• multiple antibiotic resistance (cassette resistance)

• resistant to ampicillin, florfenicol, streptomycin, sulphonamides, and tetracyclines

• use of one antibiotic selects for the rest

Treatment

• Identify early• Isolate infected animals• Extreme sanitary measures

– cows AND people

• Use appropriate antibiotic treatment– test for susceptibility

• Supplemental fluids crucial • Use herd-specific vaccine if necessary

Drenching Fluids

Bovine Respiratory Disease Complex (BRDC)

• Acute respiratory disease– Most common in calves

– Commonly associated with transportation stress

• First sign of disease is a tired appearance and reduced appetite – Depression, nasal discharge, high temperature, cough,

rapid breathing

– Loss of appetite, then loss of body weight and milk production

Bovine Respiratory Disease Complex (BRDC)

• Caused from multiple infection due to interaction of viruses and bacteria– Accentuated by environmental conditions and

stress

• Three main causative viruses– Infectious bovine rhinotracheitis– Bovine virus diarrhea– Parainfluenza

Fig 35-6. Adequate ventilation is one of the most important considerations for the prevention of bovine respiratory disease complex in dairy cattle (Courtesy of USDA)

Bovine Respiratory Disease Complex (BRDC)

• Immunity against the three main viruses can be achieved– Modified live or inactive vaccines, in single or

combination forms

• Treatments, if given early in the course of disease, are effective– Antibiotics and sulfa drugs

Fig 35-7. For this ELISA test for BRSV virus, the intensity of the blue color is proportionate to the titer of specific antibody in the sample (Courtesy of Mark Kirkpatrick)

Pneumonia

• Inflammation of lungs in which the air sacs fill with discharge– Often a disease secondary to other conditions

• If left untreated, 50-75% of animals die

• Characterized by elevated temperature– Quick shallow breaths, nasal discharge, cough,

no appetite

Fig 35-8. Fever, dullness, inappetance, coughing, and nasal discharge are the most common symptoms of pneumonia in calves (Courtesy of University of Illinois)

Pneumonia

• Causes are numerous– Many microorganisms and many different viruses

– Changeable weather and poorly ventilated damp barns are conducive to pneumonia

• Prevention– Providing good hygienic surroundings with adequate

ventilation

• Segregate sick animals• Treat sick calves with broad spectrum antibiotics

Pinkeye (Keratitis)

• Several causes - two most common types, one caused by virus, one by bacteria

• Characterized by liberal flow of tears and inability to keep eye open– Redness and swelling of the membrane lining

of eye

• If untreated can cause blindness

Pinkeye (Keratitis)

• In viral pinkeye, causative organism is infectious bovine rhinotracheitis– Eyeball is only slightly affected

– Mainly affects eyelids and tissues surrounding the eye

– Occurs most frequently in winter

– Highly contagious by direct or indirect contact

– Prevention• Proper vaccination prior to disease onset

– Treatment is seldom of value

Pinkeye (Keratitis)

• Bacterial pinkeye caused by Moraxella bovis– Produces a toxin that irritates and erodes the

coverings of the eye– Occurs mainly in warm weather– Transmission mainly by flies and direct contact

between animals– Prevention

• Controlling face flies, isolate infected animals

Pinkeye (Keratitis)

• Bacterial pinkeye treatment:– Application of antibiotics or sulfa drugs to the

affected eye– Cortisone injected into eye can reduce swelling– Eye patch– Isolate animal

Ringworm

• Contagious disease of the outer layers of skin• Caused by microscopic molds or fungi• Characteristics

– Incubation period of one week

– Round scaly patches of skin, devoid of hair

• Organisms spread between animals– Must disinfect surfaces as well as treat animals

– Isolate infected animals

Coccidiosis

• Parasitic disease caused by microscopic organisms called coccidia– Cattle infected by 21 species of coccidia

• Only Eimeria bovis and Eimeria zuerni cause the most serious infections

– Infected animals pass organism through feces• Gains entry into an animal by being swallowed• In the host’s intestine the outer membrane of oocyte

ruptures, releasing the sporozoites which destroy epithelial cells

Coccidiosis

• Severe infection produces diarrhea and bloody feces– Hemorrhage of blood vessels into intestinal

lumen– Segregate infected animals immediately

• Try to keep feed/water from being contaminated

Foot and Mouth Disease (FMD)

• Highly contagious disease of cloven-footed animals– Humans are mildly susceptible

• Characterized by appearance of watery blisters in mouth and on skin between claws of the hoof– Moderate fever, excessive salivation

Fig 35-9. Foot and mouth disease (FMD) is characterized by blister-like vesicles on the tongue and lips, mouth, on the teats, and between the hooves (Courtesy of USDA)

Fig 35-10. The blisters in the mouth and on the tongue caused by foot and mouth disease result in excessive slobbering (Courtesy of USDA)

Foot and Mouth Disease (FMD)

• Infective agent is a small virus– Six different strains– Virus is present in blisters, blood, milk, meat,

saliva, and urine of infected animals• Can be spread through infected biological products

and by cattle fever ticks

Anaplasmosis

• Caused by parasite, Anaplasma marginale– Invades red blood cells

– Transmitted by biting insects

• Once infected, the animal permanently retains parasite in blood– No signs of ill health may be evident

– Clinical symptoms generally do not appear until 18 months of age

• Calves usually only have mild symptoms

Anaplasmosis

• In mature animals – Symptoms of anemia and jaundice skin– Rapid heart rate, labored breathing, fever, loss

of appetite– Recovery is usually slow, yet the animal still

retains the parasite

HBS - One Syndrome with Several Names

• HBS: Hemorrhagic bowel syndrome

• JHS: Jejunal hemorrage syndrome

• BBS: Bloody bowel syndrome

Hemorrhagic Bowel Syndrome

• Sporadic in morbidity

• A typical case incidence rate is 2-3%, with some farms experiencing an outbreak form

• Mortality may approach 85-100% of cases due to peracute nature

Clinical Signs of “HBS”

• Short incubation period – hours rather than days

• Severe sweats

• Bruxism (teeth grinding)

• Sternal recumbancy

• Lethargy (extreme depression)

• Enopthalmia (sunken eyes)

Clinical Signs of “HBS”

• Slight bloating may be evident

• Pale mucous membranes

• Fluid slosh in lower right abdomen

• Distended gut loops per rectal palpation

• SUDDEN DEATH

Post-Mortem Findings

• Severe segmental small intestinal inflammation

• Segmental hemorrhaging and clotting forming a functional plug.Necrosis +/-Impaction

Diagnostics

• Appearance of characteristic lesions and clinical signs

• Isolation of Clostridium perfringens type A from the lesion site in high numbers. Overgrowth occurs fast.

• Fecal cultures not diagnostic

Treatment Efforts

• Prognosis is extremely poor

• Surgical interventionSome areas of segmental clots may be

massaged out to resolve the caseIntestinal resection & anastamosis is usually

required to remove affected tissue

– Success Rate ~ 5-10%

Are Clostridial species involved?

– C. perfringens type A has to be present in the diet to cause disease

– Readily fermentable carbohydrate is needed to support growth & sporulate

– Partial slowdown or stoppage of ingesta flow allowing proliferation of C. perfringens.

– Generation time = 8.8 min.

Field Observations

• Model of Infection

Lamb Lamb Enterotoxemia:Enterotoxemia:

Carbohydrate engorgement or

presence in small intestine in high

amounts.

Gut Physiology?Gut Physiology?Rumen emptying rates,

local hypomotility?Serum Ca levels?

Food Poisoning:Food Poisoning:Is there a source of C. perfringens type A (human model)?

Herd Breaks

• Fermentable Carbohydrate– NFC levels in excess of 40%?– Which high moisture feeds are being used in

the ration and at what levels?– How soluble are the starches?

Wet vs. DryFermented

Fineness of Grind

Vaccination?Vaccination?

Commercial Vaccines:Commercial Vaccines:Vaccination with a 7-way Clostridial 7-way Clostridial bacterin/toxoidbacterin/toxoid has shown little effect.C. perfringens C&D toxoidC. perfringens C&D toxoid may have some effects if the infection was mixed.

SummarySummary

Feed Feed ContaminationContaminationPoor fermentation

Contamination

Carbohydrate Carbohydrate availability availability

Acidosis?Acidosis?Rumen Emptying Rate?Rumen Emptying Rate?

Intestinal Intestinal MotilityMotility

Ca Levels, DMI Ca Levels, DMI or Acidosisor Acidosis

Reproductive Diseases and Disorders

Brucellosis (Bang’s Disease)

• Causative bacteria: Brucella melitensis– Contagious abortion disease in cattle, Brucella

abortus• Hidden, lesions frequently are not evident

– In other species , can cause similar problems

• National testing program– Control and eradication has helped lower

infection rates

Brucellosis (Bang’s Disease)

• Symptoms are indefinite– Abortions in cattle, but not all animals infected will

abort– Infected animal may have a normal birth, but calf may

be weak, milk production reduced– Joint pain, abcesses

• Humans are susceptible to all three species of brucellosis– Swine organism causes most severe disease

• Undulant fever caught by handling affected animals, raw meat or milk

Brucellosis (Bang’s Disease)

• Brucella organism is resistant to drying– Killed by disinfectants and pasteurization– Found in tissues, membranes, and fluids, of the

aborted young– Harbored indefinitely in the udder

• Brucellosis is contagious– Licking infected animals – Through contaminated feed/water

Brucellosis (Bang’s Disease)

• Control programs– Testing– Removal of infected animals– Strict sanitation

• Brucellosis eradication program (1934)– Finding infected animals and eliminating them– Vaccinating where there is a disease problem– Certifying brucellosis-free herds and areas– Providing indemnity to farmers whose animals are

condemned under the program

Leptospirosis

• Humans can contract disease through skin abrasions when handling infected animals, raw meat or milk

• Usually a mild disease– Fever, poor appetite, abortion, ropy milk

• Caused by several species of corkscrew shaped organisms

Fig 36-1. Leptospirosis can cause abortions during the last half of gestation (Courtesy of USDA)

Leptospirosis

• Preventative measures– Test animals prior to purchase, isolate for 30

days, then retest– Keep premises clean– Control rodents and other vectors (canines)– Vaccinate susceptible animals annually if

disease is present in the area

Leptospirosis

• Carrier animals spread the infection by shedding organism in their urine– Recovered animals remain carriers for 2-3

months

Vibriosis

• Infectious venereal disease– Causes infertility and abortion

– Must be diagnosed through laboratory

• Caused by Campylobacter fetus• Prevention

– Avoid contact with diseased animals and contaminated feed, water, and materials

– Vaccinate annually

– Artificial insemination

Bovine Trichomoniasis

• Protozoan venereal disease– Causes early abortions and temporary sterility

• Caused by Trichomonias foetus– Found in aborted fetuses, fetal membranes and fluids,

vaginal secretions

– Infected bull is source of infection• Disease is self limiting in cows

• Signs not shown in bulls, but cows indicate infection

• Prevention: use clean bulls or AI

Fig 36-2. This bull, infected with trichomoniasis, appears normal and will breed normally, but can infect an entire herd through natural service (Courtesy of University of Illinois)

Metritis

• Inflammation of uterus caused by various bacteria– Usually develops after giving birth

• Symptoms– Foul smelling discharge from vulva, brown color

– High temperature, rapid breathing, loss of appetite, lowered milk production

• Affected animals may die in 1-2 days or acute infection may cause sterility

Metritis

• Most commonly caused by Escherichia coli

• Preventative measures– Alleviate predisposing factors

• Bruises and tears while giving birth

• Exposure to wet and cold

• Introduction of bacteria during or after birth

Bovine Protozoal Abortion

• Not all infected cows will abort– Calves born from infected cows will experience

nervous system disease

• Caused by Neospora– Transmitted through congenital infection and

fecal-oral transmission

Foothill Abortion

• Reported in western US and Europe• Cows abort when 3-6 months pregnant

– Some calves are stillborn while others are weak at birth• Caused by a virus

– A soft bodied tick is the vector• Prevention

– Move cattle out of tick-infested areas during 3-6 month gestation period

– Animals that have aborted are usually immune and can be returned to herd