13. fresh cow infectious diseases

immune status during transition period

• inflammatory-like state

• increased plasma concentrations of positive acute phase proteins, haptoglobin, cerulopasmin, and serum amyloid A

• when energy substrates are low, proliferation, differentiation, and viability of macrophages and PMNs decrease

• NEFAs increase apoptosis & necrosis in macrophages and PMNs + increase production of pro-inflammatory cytokines

• higher lactate levels in ketotic cows can also impair immune function

• increased levels of circulating cortisol

what portion of gram negative bacteria causes endotoxemia?

lipopolysaccharide (LPS), specifically lipid A

• variable oligosaccharide region

• highly conserved core polysaccharide and lipid A region

clinical signs of endotoxemia

generally nonspecific

• fever

• increased heart & respiratory rate

• cold extremities

• rumen stasis

• GI hypomotility

biochemical changes seen with endotoxemia

• hyperglycemia

• hyperlactatemia

• increased plasma cortisol

• hypocalcemia

hematologic changes seen with endotoxemia

• leukopenia, neutropenia, degenerative left shift

• thrombocytopenia

clinical signs of metritis

• fever

• dullness

• inappetence

• decreased milk production

• red-brown, watery, foul-smelling vaginal discharge

• rectal exam: flaccid uterus with fluid distention

what gram negative organisms may be responsible for infection in cases of metritis?

• e. coli

• fusobacterium necrophorum

• prevotella spp.

• bacterioides spp.

what is physometra? when should it be considered a differential?

• gas-fluid filled uterine horn

• can be confused with other viscera such as distended cecum

• should be on differential list for caudal-dorsal ping in periparturient cow

what is the first line treatment for metritis?

systemic antibiotics

• 3rd generation cephalosporins (ceftiofur)

• labelled for treatment of acute postpartum metritis

• 0 milk withdrawal

how are oxytetracycline & ampicillin used in metritis treatment?

would provide effective coverage against offending organisms, but would constitute extra-label drug use & these antibiotics have milk withdrawal times

(refractory cases)

what route is banamine given for metritis treatment? what are potential side effects?

• IV once daily or divided into 2 doses q12h for up to 3 days

• potential side effects: abomasal ulcers and nephrotoxicity

fluid / calcium metritis treatment

• oral ± IV calcium

• oral ± IV fluids

  • 7.2% (hypertonic) saline ideal for treatment of cattle displaying signs of septic shock

  • MUST follow with oral fluids — hypertonic fluids restore circ. volume but are not hydrating

causative agents of coliform (environmental) mastitis

gram (-) bacteria

• e. coli

• klebsiella spp. — causes most dramatic & persistent signs of endotoxemia

when is risk for coliform mastitis the greatest?

immediate post-partum period

• udder edema

• incomplete milk out → leaking milk

• metabolic disease → increased lying time

clinical signs & diagnosis of coliform mastitis - udder

• acute inflammation of one or more quarters accompanied by systemic signs of illness

• warm, swollen, painful quarter

• watery or serum-like milk secretions

• definitive diagnosis: milk culture

systemic clinical signs of coliform mastitis

• inappetence

• depression

• rumen stasis

• fever

• may become recumbent due to combination of electrolyte disturbances & endotoxemia

coliform mastitis treatment

treatment is controversial

• bacteremia is repeatable finding

  • no antibiotics labelled for systemic treatment

• intra-mammary infections likely to resolve spontaneously

  • clinical signs are from endotoxins & other inflammatory mediators

which systemic antibiotics may be used to treat coliform mastitis?

** all constitute extra-label drug use

• oxytetracycline

• amipcillin trihydrate

• 3rd generation cephalosporins (ceftiofur)

supportive treatment for coliform mastitis

• frequent milk out (every 4-6 hrs) for 1-2 days

  • oxytocin may be administered to facilitate let-down

• NSAIDs

• calcium — 1 500mL bottle 23% calcium gluconate for recumbent cattle; oral appropriate for ambulatory cattle

• hypertonic saline followed by oral fluids

• corticosteroids — controversial

  • dexamethasone intramammary once

common causative agent of fresh cow enterocolitis

salmonella enterica spp.

• facultative intracellular; protected from normal defense mechanisms

salmonella enterica pathology & transmission

• organism attaches to & destroys enterocytes in small intestine + colon → submucosa → lymphatics → bacteremia

• fecal-oral transmission

clinical signs & diagnosis of salmonella sp. enterocolitis

• watery diarrhea ± frank blood

• dehydration

• fever

• inappetence

• definitive diagnosis: fecal culture or PCR

enteric salmonellosis treatment

• fluid therapy

  • oral most practical on farm

  • hypertonic saline for severe cases

• antibiotics — controversial

  • make decisions on case-by-case basis

• NSAIDs — anti-endotoxic effects

• anti-diarrhea medications — kaopectate, endosorb boluses

  • no scientific evidence supporting use; may help, won’t hurt

• isolate animal if possible; at minimum, keep separated from other immunocompromised cattle (young & sick)

educate farm workers about zoonotic potential