Bovine Diseases - Pathogenesis, Etiologies, Infectious Agents, etc

displaced abomasum

anatomical movement of the abomasum

1. left; dorsally on the right

2. volvulus; right

displaced abomasum…

• (1) most commonly ____ displacement, but may also displace…

• (2) may also see abomasum ________ with displacement - more common on the _____

1. nutritional - hypocalcemia, hypokalemia, high conc. diets

2. metabolic - abomasal hypomotility

3. anomaly

4. infectious - endotoxemia

5. traumatic - 80% are 1 month post-partum

what are the 5 etiologies of displaced abomasum?

• the abomasum is naturally pushed more to midline during pregnancy

• abomasum hypomotility results in gas build-up & distention

• allows abomasum to shift to the left side of the body

• decreases digestive flow due to partial obstructions of the inflow & outflow of the abomasum

describe the pathogenesis of left displaced abomasum

• female calf born twin to a male

• in the womb, there is an anastomosis between their vasculature resulting in male genotype / hormones circulating in the female

• this causes sterility & some masculine traits during development

describe the pathogenesis of freemartinism

XX / XY

freemartins are __/__ chimeras

false

true or false: there is not debate on decreased fertility in the male calfs born twin to females (freemartins)

• cow ingests metallic foreign object that penetrates the reticulum, causing infection / abscess to form

• if object is long enough & in the right location, can also penetrate the diaphragm & pericardial sac, causing pericarditis

• may occur more with pregnancy due to displacement of organs & growing fetus

describe the pathophysiology of hardware disease

55-75%

__-__% of cattle slaughtered in the eastern US have hardware in the reticulum

infection with mycobacterium bovis

etiology of bovine tuberculosis

• transmitted via resp. secretions, saliva, milk, urine, semen, and feces

• most often, infection occurs through inhalation

• bacteria go through the mucous membranes or in to the alveoli

• phagocytosis occurs by macrophages & they are carried into the bloodstream / lymphatics

• ability to destroy phagocytes & then repopulate in new areas

• circulate to lymph nodes, lungs, and other organs & form granulomas

describe the pathophysiology of bovine tuberculosis

bacillus anthracis

what is the bacterial infectious agent of anthrax?

• spores infecte macrophages

• proliferate at site of infection

• release lethal toxins that cause local necrosis & edema

• may progress to bacteremia

describe the pathogenesis of anthrax

infection with mycobacterium avium subsp paratuberculosis (MAP)

etiology of Johne’s diseasecauses chronic inflammation in the intestines, leading to malabsorption and severe diarrhea.

• ingestion of bacteria via contaminated feed / water / milk

• bacterium invades Peyer’s patches in the ileum to infect macrophages

• months to years later, will disseminate to local lymph nodes & then to the rest of the animal

• cows won’t show symptoms until widespread disease is present & often subclinical infections are undetectable with diagnostic testing

describe the pathogenesis of Johne’s disease

1. subclinical / non-detectable infection = infection present, but undetectable ante-mortem

2. subclinical shedder = measurable bacterial load into feces, but clinically normal

3. clinical disease = weight loss with intermittent diarrhea often brought on by stress

4. endstage disease = emaciation & liquid diarrhea; will lead to death

what are the 4 stages of Johne’s disease?

• inflammation of the mammary gland, resulting from infectious bacteria that commonly contaminate the environment or are contagious between herd mates

• infection ascends up the teat to invade the udder & mammary chains

describe the pathogenesis of bovine infectious mastitis

• staph aureus

• strep agalactiae

• E. coli

• klebsiella

what are the 4 common agents of bovine infectious mastitis

true - may become chronic

true or false: bovine infectious mastitis may be subclinical

etiology = vector-born virus of family rhabdoviridae

vectors = biting flies, midges, and sand flies

etiology & vectors of vesicular stomatitis

may occur from lesions contaminating shared water sources or direct contact

transmission of vesicular stomatitis

• pathogenesis poorly understood

• no apparent viremia

• virus stops at local lymph nodes from where infection occurred

• possible due to upregulation of interferon

describe the pathogenesis of vesicular stomatitis

2-8 days

incubation period of vesicular stomatitis

1. aphthovirus

2. seven (7)

3. 1929

foot & mouth disease -

• (1) _________ of cloven-hoofed animals

• (2) __ strains fond around the world

• (3) eradicated from the US in _____

spread via secretions such as saliva, urine, feces, milk, semen, etc

transmission of foot & mouth disease

around 4 days

incubation period of foot & mouth disease

false - can survive as virion on fomite for months

true or false: the infective agent of foot & mouth disease CANNOT survive outside the host for long periods of time

vesicular stomatitis & bluetongue

the clinical signs of foot & mouth disease are consistent with other vesicular diseases that are not foreign animal diseases, such as…

true

true or false: foreign animal diseases have the potential to cause massive economic devastation to the agriculture sector

6 million; 5 billion

a 2001 outbreak of foot & mouth disease in the UK resulted in __ million animals culled & __ billion dollars in losses

grass tetany (aka hypomagnesemia)

disease resulting from Mg deficiency

• works with calcium to regulate muscle function

• functions in conduction of signals between neurons

functions of Mg

1. spring

2. young, cool; cereal grains

3. lactation

grass tetany -

• (1) occurs most often in the _______

• (2) more often seen in animals on _______, _____-season grass or _______ ______ that is low in Mg

• (3) more common during _________

hypocalcemia or parturient paresis

milk fever, aka…

1. lactation

2. 24-48

milk fever -

• (1) most often occurs in dairy cows at start of ________ demands

• (2) __-__ hours post-calving most often

• hyper-excitability

• decreased muscle strength

• paresis

describe the pathophysiology of milk fever

infectious bovine keratoconjunctivitis

pinkeye, aka…

infectious agent = morazella bovis

vector = face fly (musca autumalis)

infectious agent & vector of pinkeye

true

true or false: pinkeye may be spread via fomites

false

true or false: pinkeye is less common with higher UV exposure

bovine resp. disease complex

shipping fever, aka…

stress (often during shipping) weakens the immune system & allows multifactorial infection

describe the pathogenesis of shipping fever

• bovine viral diarrhea virus

• infectious bovine rhinotracheitis virus

• bovine resp. synctial virus

• para-influenza type 3

• manneheimia hemolytica

• pasteurella multocida

• mycoplasma bovis

what are the 7 pathogens associated with shipping fever?

pestivirus

infectious agent of bovine viral diarrhea

3-5 days

incubation period of bovine viral diarrhea

• most often direct contact

• fomites

• vertical

how may bovine viral diarrhea be transmitted?

3-7 days

how long do symptoms of BVD last for non-PIs

fetus infected in utero that survives may be persistently infected (PI)

describe vertical transmission of BVD & what it results in

• classical - ingestion of contaminated tissues

• atypical - naturally occurring (no known transmission)

how may BSE be transmitted?

2-10 years

incubation period of BSE

1986

when was BSE discovered?

• scrapie in sheep / goats

• chronic wasting disease in deer / elk / moose

• Creutzfeldt-Jakob disease in humans

what other diseases processes is BSE related to?

prion (misfolded protein)

infectious agent of BSE

maggots burrow deep into wounds, destroying live tissue & causing deeper wounds that can be fatal

describe the pathogenesis of new world screwworm

eradicated in 1966 via sterilized flies

when & how was the new world screwworm formerly eradicated in the US?

• infectious agent = orbivirus spp. (non-enveloped RNA virus)

• vector = culicoides spp.

infectious agent & vector of bluetongue

virus replicates in phagocytes, endothelial cells, and lymphocytes; causes injury to capillaries, resulting in hemorrhage, ulceration, and necrosis

describe the pathogenesis of bluetongue

• bovine tuberculosis

• anthrax

• vesicular stomatitis

zoonotic bovine diseases

• bovine tuberculosis

• anthrax

• vesicular stomatitis

• foot & mouth disease

• bovine spongiform encephalopathy

• new world screwworm

• bluetongue

reportable bovine diseases

• foot & mouth disease

• new world screwworm

foreign animal bovine diseases