A case of Theileria sergenti in a nine-year-old Holstein dairy cow
Adam M. Townsend
Clinical Advisor - Dr. Emil Olsen
Basic Science Advisor - Dr. Heather Priest
Pre-Clinical Advisor - Dr. Thomas Divers
Senior Seminar Paper
Cornell University College of Veterinary Medicine
February 5th, 2013
Key Words: Theileriosis, anemia, lymphocytosis, cattle, blood parasite
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Abstract
A nine-year-old Holstein dairy cow presented to Cornell University Equine and Farm Animal Hospital for
acute onset anemia. On presentation, she was quiet, but alert and responsive. Her physical
examination revealed pallor, tachycardia, and weakness. There was no evidence of acute blood loss on
physical examination or with point of care diagnostic testing. The patient was stabilized with a
transfusion of six liters of bovine whole blood and treated for a presumptive Anaplasma marginale
infection. Blood smear evaluation performed by the Clinical Pathology service revealed racquet to oval
shaped piroplasms consistent with either Theileria or Babesia species. A broad PCR amplified and
identified Theileria, a reportable blood parasite endemic to Africa, the Mediterranean, and Asia. The
patient failed to respond to supportive treatment, antimicrobial therapy with oxytetracycline and
imidocarb, and euthanasia and necropsy were elected.
Case History
A nine-year-old Holstein dairy cow was referred to Cornell University Equine and Farm Animal Hospital
for acute onset anemia. She was an award winning show cow for much of her life, with an extensive
travel history around the east coast of the United States, but had not been off of the farm in one year
leading up to presentation, when she traveled to Harrisburg, PA for a show and to an Ova collection
facility in Maryland. At presentation, she was six to seven months pregnant, and had been dried off two
week prior. She had not calved since 2011. The herd had recently purchased a handful of cattle from
local auctions.
She was first noted to have a decreased appetite and was lethargic ten days before presentation. Her
owner treated her empirically with a charcoal product and monitored her closely. Her condition
progressed to inappetance and anemia. The referring veterinarian treated her with Excenel (ceftiofur),
Banamine (flunixin meglumine), an iron injection, and intravenous dextrose and calcium before referring
her to Cornell University for evaluation of anemia.
Clinical Findings - Presentation
Upon presentation, the patient was quiet, but alert and responsive. Her temperature and respiration
rate were within normal limits, with an elevated heart rate of 120 beats per minute. Her mucous
membranes were white, and a capillary refill time could not be determined. She was mildly ataxic while
getting off of the trailer, but no other signs of neurologic disease made weakness a likely cause. She had
weak rumen contractions and minimal other gastrointestinal sounds.
Initial bloodwork (Table 1) revealed several abnormalities including a severe anemia, mild
hypoproteinemia, marked lymphocytosis, moderate thrombocytopenia, and a metabolic lactic acidosis
with respiratory compensation. Creatinine was normal upon presentation.
Ultrasound was within normal limits with the exception of a subjectively enlarged gall bladder
presumably secondary to inappetance.
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Measure
Value
Units
Normal Range
PCV
TP
Lymphocytes
Platelet Count
10
6.0
38.0
79
%
mg/dL
thou/uL
thou/uL
25-33
6.9-8.6
2.5-7.5
100-800
mmol/L
g/dL
mmHg
mg/dL
7.35-7.45
0.3-1.5
25-30
35-45
0.4-2.2
pH
7.335
Lactate
13.69
Bicarbonate
15.6
pCO2 (venous)
29.1
Creatinine
0.7
Table 1. Initial bloodwork upon presentation.
Differential Diagnosis
The differential diagnosis for anemia in cattle can be broken down into three broad categories,
increased erythrocyte loss, decreased erythrocyte production, and destruction of erythrocytes.
Common causes of increased blood loss in cattle include abomasal ulcer, lymphosarcoma,
endoparasites, and a primary thrombocytopenia. Abomasal ulceration was unlikely given the lack of
melena on physical examination. Lymphosarcoma can cause blood loss by two mechanisms, either by
infiltrating the abomasum and causing secondary ulceration, or less commonly by infiltrating the spleen
and causing acute splenic rupture. A normal spleen ultrasonographically ruled this down.
Endoparasites, while still an issue on today's dairy farms, are unlikely to cause such an acute
presentation of anemia. A primary thrombocytopenia can cause anemia when hemostasis cannot be
achieved. Common findings of anemia secondary to thrombocytopenia include petechiation and
ecchymosis of mucous membranes, epistaxis, and prolonged bleeding from minor lacerations or
abrasions. None of these clinical signs were noted in our patient, and the thrombocyte count was not
low enough to cause spontaneous bleeding, ruling this down as a cause of anemia in our patient.
Decreased production of erythrocytes can be due to primary bone marrow disease, Bracken Fern
toxicity, iron deficiency, or kidney disease. Primary bone marrow disease and iron deficiency could not
be ruled up or down without the aid of clinical pathology. Bracken Fern toxicity was unlikely given that
our patient was the only animal affected in an intensively managed herd. There was no evidence of
kidney disease on initial bloodwork, no evidence of pyelonephritis on rectal palpation, and the anemia
was too acute, ruling down decreased erythropoeitin production by the kidneys.
Destruction of red blood cells can be caused by infectious disease, toxins like onion and Brassica
species, immune mediated disease, and a paraneoplastic syndrome. Toxins are unlikely because she is
from an intensively managed herd and she is the only affected animal. Immune mediated disease and
neoplasia could not be ruled out without clinical pathology. Due to the acute onset of the anemia, and
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the increasing prevalence of infectious anemia in the Northeast, Anaplasma marginale was ruled up, and
therapy was initiated for this disease.
The major differentials for her lymphocytosis included a reactive lymphocytosis secondary to a viral
infection, Bovine Leukosis Virus (BLV) infection, or a non-viral neoplasia such as thymoma, lymphoma,
lymphosarcoma, and leukemia. A presumptive diagnosis of BLV infection was made due to the patient's
age and the high prevalence of this infection in commercial dairy herds.
Stabilization/Treatment
Our patient was initially stabilized with six liters of bovine whole blood from the hospital's donor cow.
She was monitored closely through the transfusion, and was noted to have a fever early in the
transfusion. She was given a dose of flunixin meglumine for suspected transfusion reaction. She was
started on 6.6 mg/kg of oxytetracycline every 12 hours diluted in one liter of isotonic saline for a
presumptive anaplasmosis infection.
Diagnostics
Free-catch urine was collected during the blood transfusion, and was strongly positive for bilirubin and
blood. The blood in the urine could have been due to intravascular hemolysis, however bilirubin in the
urine is conjugated, and would support cholestasis, however, this was not supported in the bloodwork.
The admission blood work was stored overnight and submitted to Cornell University's Clinical Pathology
Service for a chemistry panel, complete blood count, and blood smear evaluation. Serum was submitted
to the New York State Veterinary Diagnostic Lab for a BLV ELISA, which was positive
The chemistry panel (Table 2) showed hepatocyte damage characterized by elevated sorbitol
dehydrogenase (SDH) and glutamate dehydrogenase (GLDH). This was suspected to be due to hypoxia
secondary to the decreased oxygen carrying capacity caused by anemia. Aspartate aminotransferase
was elevated, and is indicative of either liver or muscle damage from recumbency. Creatinine kinase
was elevated secondary to recumbency and muscle fasciculations. Hyperbilirubinemia was
characterized by an elevation in indirect bilirubin, and iron was elevated, both indicative of hemolysis
and erythrocyte turnover. The total protein was confirmed to be low, and was characterized by a
hypoglobulinemia. The albumin was normal. This was unexpected and likely indicated some degree of
immunosuppression. The magnesium was mildly decreased, likely due to her inappetance.
Measure
SDH
GLDH
AST
Creatinine
Kinase
Total
Bilirubin
Indirect
Value
491
470
1197
1120
Units
u/L
u/L
u/L
u/L
Normal Range
12-50
11-83
61-162
76-376
2.3
mg/dL
0.1-0.2
2.2
mg/dL
0.0-0.1
4
Bilirubin
Iron
369
Total
5.9
Protein
Globulin
2.5
Magnesium 1.1
Table 2 - Results of chemistry panel at presentation
ug/dL
g/dL
83-205
6.9-8.6
g/dL
mEq/L
3.1-5.4
1.6-2.4
The complete blood count results (Table 3) confirmed the point-of-care diagnostic tests. The anemia
was characterized as a macrocytic, hypochromic, and regenerative, confirming the bone marrow was
responding to the anemia. The lymphocytosis and thrombocytopenia were confirmed.
Measure
Value Units
Hematocrit
10
%
MCV
89
fL
MCHC
28
g/dL
Nucleated RBC
30
/100 WBC
Lymphocytes
33.8
thou/uL
Platelet Count
160
thou/uL
Table 3 - Results of the complete blood count at presentation
Normal Range
25-33
38-51
34-38
0
1.7-7.5
252-724
The blood smear evaluation (Figures 1-3) confirmed the
regenerative anemia, with anisocytosis, polychromasia, and
basophilic stippling. The lymphocytosis was characterized
as persistent, and was attributed to the positive BLV status.
The red blood cells contained small, oval to racquet-shaped
piroplasms that were consistent with either Babesia or
Theileria species. Due to the fact that Theileria is reportable
in the United States, the Diagnostic Laboratory requested
serum for a broad Babesia and Theileria PCR, which
amplified and identified Theileria sergenti.
Treatment
Figure 1 - Marked regeneration of
anemia, note anisocytosis,
polychromasia (thin arrow),
basophilic stippling (thick arrow).
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Figure 2 - Note morphologically normal
lymphocytes, regeneration of anemia.
Figure 3 - Note parasites within red blood
cells (arrows).
The patient was continued on oxytetracycline twice daily, given B-vitamins IV once daily to stimulate her
appetite, and was treated with imidocarb, an antimicrobial used in areas with endemic Theileriosis to
clear the infection. She was maintained on free choice hay, water, and electrolytes, and fed a sweet
feed grain twice daily.
Progression of condition
The patient had sustained tachycardia between
90 and 120 beats per minute, and developed
an arrhythmia. All four heart sounds could be
auscultated, and cardiac troponin was
measured at 6.9 µg/L (normal = 0.0 µg/L),
which was indicative of myocardial damage.
Cardiology was consulted and performed an
ECG and echocardiogram, which revealed
increased contractility and ventricular
premature contractions (VPCs - Figure 4).
Cardiology recommended a second blood
transfusion to improve cardiac function by
Figure 4 - ECG from the patient, note the
improving oxygenation. The patient was
tachycardia (98 bpm) and VPC (starred).
transfused with six liters of bovine whole blood
from another donor cow. This failed to raise her PCV, and resulted in marked hemoglobinuria and
bilirubinuria, suggesting the patient hemolyzed the transfusion.
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The patient failed to respond to treatment over the course of a week, and euthanasia was elected.
Necropsy
The gross necropsy revealed icterus, lympadenomegaly, splenic modules, and multifocal hepatic
necrosis. Histopathology revealed a presumptive T-Cell lymphoma (typing not performed) infiltrating
the spleen, intestines, and lymph nodes, an inflammatory, fibrosing myocarditis, and hepatic necrosis.
Discussion
Theileria species are reportable in the United States. They are tick transmitted, obligate intracellular
protozoa that primarily affect cattle, but can infect small ruminants and horses as well. They are
transmitted by Ixodid ticks, and have complex life cycles in both vertebrate and invertebrate hosts. The
two most economically important species of Theileria are T. parva and T. annulata. Most species are
endemic to Asia and Africa, with the exception of T. buffeli, a typically non-pathogenic strain of Theileria,
which is distributed worldwide.
T. parva is endemic to southeastern Africa, and causes East Coast Fever, which is characterized by
lymphadenopathy, which is typically focal and turns generalized. The animals then have a rise in
temperature, which is followed by anorexia, excessive lacrimation, nasal discharge, diarrhea, dyspnea,
recumbency, and death. The ultimate cause of death in these animals is pulmonary edema. Mortality in
immunologically naive animals approaches 100%. T. parva is a dose dependent disease, which means
that the level of tick infestation is related to both severity and time course of the disease. Differential
diagnosis in endemic areas include heartwater, typanosomosis, babesiosis, anaplasmosis, and malignant
catarrhal fever. It is diagnosed by blood smear, impression smear of lymph nodes at necropsy, PCR, or
ELISA.
T. annulata causes tropical theileriosis, and is endemic to the Mediterranean. It causes a very similar
clinical syndrome as East Coast Fever, with the addition of anemia and icterus secondary to hemolytic
anemia. Most animals die within 2-3 weeks after infection.
Theileria sergenti, typically a benign hemotropic parasite of cattle, is endemic to Asia. There is limited
literature on this parasite, but it is considered non-pathogenic in adult animals. It causes a self-limiting
anemia in calves, which is associated with some economic loss. It is typically found in grazing cattle, and
has a very low incidence in confined animals. The incidence in Japan has been reported to be 0.7-1.0%
in cattle less than 12 months of age, and 0.2% in animals greater than 12 months of age. It can be
diagnosed by light microscopy, but one study from Japan stated that infected animals only had between
one and five parasites per 70,000 erythrocytes. PCR and ELISA are also available for diagnosis. The
reason for the clinical syndrome in our cow is unclear, but the immunosuppression caused by her BLV
infection and lymphoma is likely to blame.
Cattle succumbing to infection with Theileria species typically thought to be benign has been reported in
the literature. A case report from Michigan State University in 2001 described an cow very similar to our
patient. A single eight-year-old beef cow presented to their hospital with anemia and lymphocytosis.
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She was found to be BLV positive and was treated for presumptive Babesiosis. They amplified and
identified T. buffeli, which is considered non-pathogenic. The cow failed to respond to treatment and
was euthanized in this case report.
Treatment for Theileriosis is primarily supportive, but in endemic areas imidocarb is used to clear
infections. Imidocarb is a urea derivative used as an antiprotozoal for treatment of Babesiosis and
Theileriosis. The use of imidocarb in the United States is off-label, and FARAD (Food Animal Residue
Avoidance Database) must be contacted before use to ensure proper milk and meat withdrawals are
followed.
Reliable attenuated vaccines are available for T. parva and T. annulata.
Conclusion
This is the first reported case of Theileria sergenti in the United States. While it is unclear where this
cow acquired the infection, her extensive travel history and the recent addition of cattle to the herd can
lead to the hypothesis that she was infected at a show or by a tick from an infected animal purchased
into the herd. Theileria sergenti is a reportable disease, but is not considered an important foreign
animal disease due to its relatively low pathogenicity. While it has not been described in the United
States, it may have a higher prevalence than previously thought, and should be considered in older
cattle with a positive BLV ELISA, anemia, and erythrocyte parasites on a blood smear.
BLV infection is strongly associated with lymphoma occurrence in adult cows, but these are almost
always B-cell lymphoma. Our patient's lymphoma was described as a T-cell lymphoma morphologically,
but immunophenotyping was not performed, so it is unclear if it is a separate process or was a
misdiagnosed B-cell lymphoma. Either way, she was possibly immunosuppressed by her lymphoma,
which allowed this rare parasitic infection to cause such severe clinical disease.
References
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