Systemic Complications Associated with Mastitis in a Holstein Cow
Christina Butler
Clinical Advisor: Dr. Emil Olsen
Basic Science Advisor: Dr. Rodrigo Bicalho
Senior Seminar Paper
Cornell University College of Veterinary Medicine
February 5th, 2014
Keywords: mastitis, cow, endotoxemia, endocarditis
Summary:
An eight-year-old Holstein cow presented to Cornell’s Equine and Farm Animal Hospital for
mastitis unresponsive to treatment. She was referred to Cornell from her primary veterinarian
following a six day history of mastitis, weakness, anorexia and drop in milk production. On
presentation she was febrile, tachycardic, moderately dehydrated and had bilateral hemorrhagic
sclerae. Her udder was warm, firm, hyperemic and asymmetrically swollen and her milk was
yellow and watery with white flakes. Initial blood work revealed several hematological and
biochemical abnormalities suggestive of systemic inflammation. Over the next few days the
patient developed a heart murmur of increasing intensity and serial echocardiography revealed
evidence of endocarditis and pericardial effusion. Milk, blood and pericardial fluid samples
cultured negative for growth of aerobic and anaerobic bacteria, however the cow continued to
have recurrent episodes of fever and lethargy. As such, no definitive etiology for the patient’s
clinical signs could be identified. This case study will discuss the possible etiologies and
treatment strategies of mastitis with secondary endotoxemia, bacteremia and sequelae such as
endocarditis and pericarditis in the bovine.
1
Signalment and Case History:
An eight year old Holstein dairy cow, 275 days in milk, presented to Cornell for mastitis which
was diagnosed while at a state show five days previously. The patient had an extensive show
history and was from a small herd with no history of problems with mastitis. Following
diagnosis, she was treated by the referring veterinarian with intramammary antimicrobials and
prednisone and was treated systemically with IV fluids, tribrissen, ceftiofur, and flunixin
meglumine. Two days following initial diagnosis she developed bilateral scleral hemorrhage and
went off-feed and was subsequently treated with intramammary gentamicin, intravenous calcium
gluconate and subcutaneous penicillin. Despite treatment her clinical signs continued to worsen,
and she was referred to Cornell the following day.
Presenting Complaint and Initial Clinical Findings:
Upon arrival at Cornell’s Farm Animal Hospital the patient’s presenting complaints were a five
day history of mastitis non-responsive to treatment, inappetence, depression, and a possible heart
murmur which was previously ausculted by the referring veterinarian. On initial physical exam,
the patient was dull and depressed, febrile and tachycardic with a temperature of 105.1°F and
heart rate of 96 beats per minute. Her mucous membranes were pale with a capillary refill time
of less than 2 seconds and she had bounding jugular pulses bilaterally, but no other evidence of
heart failure such as brisket edema or bottle-jaw. The heart murmur previously ausculted by the
referring veterinarian was not noted on initial physical exam, but was detected the following day.
Her eyes were sunken, she was approximately 8-10 percent dehydrated and her sclerae were
bilaterally hemorrhagic. Her udder was diffusely firm, warm and hyperemic and the left side was
enlarged to two times the size of the right udder. Milk sampled from the left front and hind
2
quarters was yellow and serum-like in appearance with many white flakes, and all four quarters
were 3+ positive on California Mastitis Test (CMT). In the middle third of her neck was a firm,
swollen, painful region overlying her jugular, which was presumed to be the site of previous
intravenous injections.
Significant findings on point of care blood work included mild hypokalemia (1.8 mg/dL) and
hypocalcemia (1.13 mg/dL). Abnormalities noted on CBC included an inflammatory leukogram
(segmented neutrophils 6.8 thou/uL, band neutrophils 4.2 thou/uL), as well as moderate
thrombocytopenia (91 thou/uL).
Problem List and Differential Diagnoses:
Based on history, physical exam findings and initial diagnostic test results, the patient’s problem
list included a painful, swollen udder with grossly abnormal milk in all four quarters, fever,
tachycardia, moderate dehydration, a heart murmur, bounding jugular pulses, bilateral
hemorrhagic sclerae, anorexia, hypocalcemia, hypokalemia, an inflammatory leukogram and
moderate thrombocytopenia. From this list, two major problems were identified: mastitis and
systemic inflammation or infection, with endotoxemia and septicemia being the most likely
causes for the patent’s systemic illness. The most common causes of endotoxemia in cattle are
toxic mastitis and metritis1; with other possible causes including pneumonia, pleuritis, peritonitis,
pericarditis, acute enteritis, ruminitis or abomasitis, endocarditis or vasculitis. The patient’s
clinical mastitis with no response to treatment was the most likely cause for her signs of systemic
illness; however, endocarditis could not be ruled out given her heart murmur, tachycardia and
jugular pulses. Initially, vasculitis was also a differential as given the painful area overlying the
patient’s left jugular vein, but this differential was ruled out following ultrasonographic
3
evaluation which indicated that the inflammation was limited to the soft tissues superficial to the
vein.
Initial Stabilization and Treatment:
To address the patient’s hypovolemia and tachycardia presumptively resulting from endotoxemia
she was initially stabilized with intravenous administration of 2 liters of hypertonic saline
followed by a 30 liter bolus of intravenous plasmalyte supplemented with 20 mEq/L of
potassium chloride to treat her electrolyte abnormalities. Additionally, 500 mL of calcium
gluconate was added to her fluids to treat her mild but persistent hypocalcemia. She was given
flunixin meglumine, an NSAID, as an anti-pyretic, anti-inflammatory, and analgesic. In cases of
toxic mastitis, frequent stripping of the affected quarters is essential to remove remaining
intramammmary organisms, endotoxin and phagocytes whose presence in the udder may cause
ongoing immune stimulation1. Given this fact, the patient was given intravenous oxytocin and
hand-milked every four hours. The patient was also administered intravenous oxytetracycline, a
broad spectrum tetracycline antibiotic, for control of bacteremia and prevention of systemic
infection.
Diagnostic Plan:
Following initial stabilization, a diagnostic plan was formulated to further characterize the cause
of the patient’s mastitis as well as her signs of systemic inflammation. Milk samples were taken
from each quarter and submitted for culture and sensitivity to determine the bacterial cause of
her mastitis. The presumptive cause of the patient’s systemic signs was toxic mastitis resulting in
endotoxemia, causing her persistent tachycardia, pyrexia and bounding jugular pulses. However,
the following morning, the heart murmur described by the referring veterinarian was clearly
4
ausculted on the patient’s left thorax. Persistent tachycardia, bounding jugular pulses and heart
murmur of growing intensity could have been resulting purely from endotoxemia, but further
work-up was required to rule out concurrent heart disease or sepsis. To assess the patient’s
cardiac status, the diagnostic plan included an echocardiogram and a cardiac troponin level to
assess the heart’s function and rule out heart failure. Additionally, blood was collected and
submitted for culture, complete blood count and chemistry panel to help determine the cause of
the patient’s systemic signs.
Diagnostic Test Results:
Blood Work:
The results of blood work submitted the following day were fairly consistent with point of care
blood work from initial presentation. The CBC showed an increasingly severe neutrophilia with
a left shift (segmented neutrophils 18 thou/uL, band neutrophils 5.8 thou/uL) and toxic change,
indicating persistent systemic inflammation, and a persistent but improving thrombocytopenia
(109 thou/uL). The chemistry panel abnormalities showed a persistent hypokalemia (2.7 mEq/L),
hypomagnesemia (1.2 mEq/L) and hypoalbuminemia (3.0 g/dL), and the cardiac troponin level
was zero, which indicated that there was no evidence of myocardial damage.
Echocardiography:
The first echocardiogram was performed the day following initial presentation. The tricuspid and
mitral valves showed evidence of mild thickening and increased turbulence and regurgitation of
blood flow. On the mitral valve were two foci of increased echogenicity. Additionally, there was
mild effusion and a few fibrin strands within the pericardial space. Over the next few days the
patient underwent two more echocardiograms which showed progressive thickening of the
5
mitral, tricuspid and aortic valves and enlargement of the lesions on the mitral valve. Fluid and
fibrin strands continued to accumulate within the pericardial space.
Culture Results:
Milk samples from all four quarters were submitted for culture and sensitivity, all of which
returned no growth. Similarly, blood cultures were negative as well as cultures of pericardial
fluid performed following demonstration of pericardial effusion on echocardiogram.
Interpretation:
The majority of the patient’s blood work abnormalities including hypocalcemia, hypokalemia
and hypomagnesemia, were consistent with toxic mastitis. Thrombocytopenia occasionally
occurs with endotoxemia, and often is observed in conjunction with disseminated intravascular
coagulopathy. DIC may have been occurring in the patient given her bilateral scleral
hemorrhage, but she exhibited no other signs of coagulopathy, and scleral hemorrhage can also
be a direct result of circulating toxins in cattle1. The presence of an inflammatory leukogram is
indicative of systemic inflammation; however, toxic mastitis commonly results in a mature
neutropenia rather than neutrophilia due to massive recruitment of neutrophils from general
circulation to affected udder tissues. The patient’s persistent neutrophilia in the face of severe
clinical mastitis was indicative of a concurrent ongoing inflammatory process.
Echocardiographic evidence of valvular thickening and rapidly growing lesions on the patient’s
mitral valve were diagnostic for endocarditis. The acute development of the vegetative lesions
and the rapidly increasing intensity of the patient’s heart murmur strongly suggested that
endocarditis had developed secondarily to a bacteremia which occurred in conjunction with
endotoxemia resulting from toxic mastitis. The additional diagnosis of acute bacterial
6
endocarditis was supported by the patient’s development of intermittent fevers, persistent
tachycardia and neutrophilia, all of which are common findings with bacterial endocarditis2.
Diagnoses:
The patient’s final diagnoses were mastitis, which was definitive based solely on gross
abnormality of her milk and inflammation of her udder, with toxic mastitis resulting in
endotoxemia being the presumptive cause of her systemic illness. Additionally, the diagnoses of
endocarditis and pericarditis were confirmed via echocardiogram.
Treatment:
Supportive therapy with intravenous fluids and flunixin meglumine was continued to counteract
the effects of the patient’s endotoxemia. Due to the fact that no causative organism was
identified on milk or blood culture, she was treated systemically with oxytetracycline and
penicillin to offer broad spectrum coverage of both gram-negative and gram-positive organisms.
She was treated with an intramammary infusion of amikacin for coverage of gram-negative
organisms, and dexamethasone, a corticosteroid to decrease inflammation in the udder. Because
the patient’s milk production continued to decline, she was treated with Spectramast, a broad
spectrum dry cow treatment, in all four quarters and subsequently dried off.
Prognosis:
Over the next few days, the patient continued to exhibit intermittent fevers and went on and off
feed. She remained persistently tachycardic and her heart murmur continued to increase in
intensity, progressing to a grade IV/VI continuous murmur which was auscultable on the left and
right thorax. Despite the evidence of clinical progression of endocarditis, she remained stable
7
and the owner elected to bring her home. The patient was discharged with a grave prognosis for
long term survival following eight days as an inpatient at Cornell’s Farm Animal Hospital.
Because of this poor prognosis, a recommendation was made to the owner to begin a
superovulation protocol to harvest her ova for in-vitro fertilization.
Outcome:
Following her discharge, the patient showed slow but steady improvement over the course of the
next three weeks. By three months later she had returned to normal weight, had an excellent
appetite and showed no clinical signs of disease and the owner expressed plans to breed her in
the coming year.
Discussion:
Toxic Mastitis
Many mastitis-causing organisms can also cause signs of systemic illness. Staphylococcus aureus
and other gram-positive cocci, Mycoplasma bovis, Pseudomonas aeruginosa, Bacillus cereus and
mycotic infections have been shown to cause clinical signs which, in the absence of positive
culture results, can be virtually indistinguishable from severe coliform mastitis3. However,
mastitis caused by severe infection with coliforms is by far the most common cause of systemic
illness in cattle1. Coliforms are gram-negative lactose fermenting rod-shaped bacteria such as E.
coli, Klebsiella and Enterobacter species. Lipopolysaccharides (LPS), also known as endotoxins,
are large molecules found in the outer membrane of these bacteria and when the bacteria are
destroyed, this cell membrane component can trigger a powerful systemic inflammatory
reaction4.
8
Upon entering the teat, coliforms multiply rapidly by 16 hours after entering the streak canal and
overcoming local resistance mechanisms1. Once in the mammary gland, the bacteria are
destroyed by phagocytosis and intracellular killing within local phagocytes. Lysis of the bacteria
releases endotoxin, causing recruitment of large numbers of neutrophils from systemic
circulation. This rapid recruitment results in highly efficient bacterial destruction, but also causes
release of even more endotoxin.
Damage to local mammary tissue as well as leaky blood vessels allows endotoxin to cross into
the blood stream, initiating a cascade of systemic inflammation. In addition to endotoxemia,
bacteremia may also occur when surviving bacteria are able to escape into general circulation
through these same mechanisms.
Systemic circulation of endotoxin causes activation of inflammatory mediators including
histamines, serotonin, prostaglandins, IL-1, IL-6 and TNFa, resulting in clinical signs such as the
fever, bounding jugular pulses, tachycardia and weakness which were observed in the patient.
While it is widely agreed that supportive therapy should be the mainstay of treatment for toxic
mastitis, use of systemic antimicrobials remains controversial due to the pathophysiology of
infection with gram-negative organisms1. Intramammary bacterial concentrations peak and
decline very rapidly following initial infection and resultant large-scale recruitment of
neutrophils. The subsequent release of endotoxin following bacterial destruction, not viable
bacteria, is the inciting cause for systemic illness associated with toxic mastitis. This has led to
debate as to whether systemic antimicrobial therapy is indicated in cases of toxic mastitis, and
several studies examining this question have produced mixed results3. However, bacteremia may
9
also occur in up to 48 percent of toxic mastitis cases, which is a strong argument for the use of
systemic antimicrobials in the treatment of severe coliform mastitis3.
Treatment of severe clinical mastitis is further confounded when culture results are negative,
which indeed is often the case. In fact, recent literature has shown that between 25 to 44 percent
of milk samples from quarters showing clinical infection return no growth on culture5.
Furthermore, molecular sequencing techniques have revealed that microbial populations present
within bovine mastitic milk may be more diverse than was previously believed, and that
conventional culturing techniques may not reveal the true inciting bacterial cause of mastitis6.
Endocarditis:
Diseases which cause bacteremia allow circulating bacteria to colonize the heart valves and
endocardium and remain relatively protected from the immune system. The most common
organisms which cause endocarditis in cattle are Trueparella pyogenes and Streptococcus
species, but Staphylococcus species and gram negative organisms such as coliforms may also
cause the disease2,7.
In cattle the most consistent clinical signs of bacterial endocarditis are intermittent fever,
tachycardia and a systolic heart murmur, and definitive diagnosis is via echocardiographic
demonstration of valvular thickening and vegetative lesions8.
Long-term antimicrobial treatment is required for treatment of bacterial endocarditis, and
successful blood cultures allow for selection of the appropriate antibiotic. However, up to 50% of
blood cultures will be negative despite definitive diagnosis of bacterial endocarditis1.
10
The prognosis for bacterial endocarditis is guarded for survival of longer than six months, with
early recognition and treatment offering the best outcome2.
Pericarditis:
Echocardiography revealed the presence of effusion and fibrin strands within the patient’s
pericardial space. This was a particularly confusing aspect of the case due to the fact that
endocarditis and pericarditis are two separate disease processes, which initially suggested that
the patient’s bacteremia may have also caused pericarditis or there was a completely different
cause for the pericardial effusion. Pericarditis in cattle is most commonly caused by traumatic
reticulopericarditis, secondary to pneumonia or pleuritis, neoplastic effusion secondary to
lymphoma or mesothelioma and idiopathic aseptic pericarditis2. A pericardiocentesis revealed
serosanguinous fluid which showed inflammatory cells and fibrin with no evidence of bacteria
on cytology and no bacterial growth on culture. Additionally, radiographs of the cranial abdomen
and caudal thorax showed no evidence of traumatic reticulopericarditis. Definitive diagnosis is
again via echocardiogram, with demonstration of fluid within the pericardial space. Treatment
and prognosis for pericarditis is dependent on its etiology and severity, with clinical evidence of
heart failure being a poor prognostic indicator1,2. A definitive cause for the patient’s pericardial
effusion could not be identified, and because the amount of fluid within the pericardial space did
not increase, specific treatments such as drainage of the fluid or pericardiostomy were not
indicated.
References
1. Divers, T.J.; Peek, S.F.; Rebhun, W.C.; Diseases of Dairy Cattle. St. Louis, Mo.:
Saunders/Elsevier; 2007.
11
2. Buczinski, S.; Rezakhani, A.; Boerboom, D.; Heart disease in cattle: Diagnosis, therapeutic
approaches and prognosis. The Veterinary Journal. 2010; 184(3):258-263.
3. Erskine, R.J.; Wagner, S.; DeGraves, F.J.; Mastitis therapy and pharmacology. Veterinary
Clinics of North America: Food Animal Practice. 2003; 19(1):109-138.
4. Smith, G.W.; Supportive therapy of the toxic cow. Veterinary Clinics of North America: Food
Animal Practice. 2005; 21(3):595-614.
5. Taponen, S.; Salmikivi, L.; Simojoki, H.; Koskinen, M. T.; Pyörälä, S.; Real-time polymerase
chain reaction-based identification of bacteria in milk samples from bovine clinical mastitis with
no growth in conventional culturing. Journal of Dairy Science. 2009; 92(6):2610-2617.
6. Oikonomou, G.; Machado, V. S.; Santisteban, C.; Schukken, Y.H.; Bicalho, R.C.; Microbial
diversity of bovine mastitic milk as described by pyrosequencing of metagenomic 16s rDNA.
PLoS ONE. 2012; 7(10).
7. Buczinski, S.; Francoz, D.; Fecteau, G.; Difruscia, R.; A study of heart diseases without
clinical signs of heart failure in 47 cattle. The Canadian veterinary journal. La revue vétérinaire
canadienne. 2010; 51(11):1239-46.
8. Buczinski, S.; Tsuka, T.; Tharwat, M.; The diagnostic criteria used in bovine bacterial
endocarditis: A meta-analysis of 460 published cases from 1973 to 2011. The Veterinary
Journal. 2012; 193(2):349-357.
12