CASE NOTES

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Chronic Weight Loss, Partial Blindness and Three Swollen Legs in a 2.5-Year-Old Angus Steer

Bruce Watt, Central Tablelands Local Land Services, Bathurst, George Corones, Corones and O'Hehir Veterinary Surgeons, Bathurst and Leah Johnson, Elizabeth Macarthur Agricultural Institute, Menangle

This paper was first published in the Australian Cattle Veterinarian, Vol 101, December 2021, pp 12-14

Posted Flock & Herd February 2022

Introduction

One of 15 2-2.5-year-old steers presented as alert but lethargic with weight loss over several months, partial blindness and three swollen legs. The differentials, lead poisoning, sporadic bovine encephalomyelitis, pestivirus and hepatic encephalopathy were ruled out (as was transmissible spongiform encephalopathy). The diagnosis, suspected at necropsy and confirmed by histology, was reasonably obvious with the benefit of hindsight.

History

One of 15 2019 drop steers, having lost weight for 6-8 weeks, presented as thin, lethargic and apparently blind with a swollen front leg. The steers had been weaned over 12 months previously and were recently drenched. The mob has been grazing a paddock dominated by blue heliotrope (Heliotropium amplexicaule) until a few weeks prior. There were no known sources of lead. Of interest, the owner commented that he had previously seen steers, presumably intoxicated by blue heliotrope, lose weight and become dull and aggressive before dying.

The steer, treated symptomatically by one of us (GC), responded initially but then continued to deteriorate and subsequently died.

Clinical findings

The 2.5-year-old Angus steer was examined on the 26 July 2021. It had grown slowly compared to its cohorts and was in fat score 2.0. When examined in the yard the steer appeared to be partially blind but was able to avoid objects. On examination the steer had weak tongue withdrawal but no oral lesions. There was no menace response in either eye, but the right pupil constricted with light while the left pupil only partially constricted with light. There was slight bilateral exophthalmos. The right front leg was swollen, particularly around the carpus, and both hocks were distended. The heart rate was slow at about 50 bpm and there was reduced rumen motility. The steer had a normal temperature and the prescapular and prefemoral lymph nodes were not enlarged.

Figure 1. Steer examined 26 July

INITIAL LABORATORY FINDINGS 26 July 2021

Biochemistry — Sample 11322
Test	Normals	Units	Results
GGT	0-35	U/L	109 H
GLDH	0-30	U/L	87 H
AST	0-120	U/L	160 H
BIL	0.0-24.0	µmol/L	33.5 H
CK	0-300	U/L	104
Urea	2.1-10.7	mmol/L	2.9
Creat	0-186	µmol/L	97
Phos	0.80-2.80	mmol/L	1.38
Ure/Crea	0.00-0.07		0.03
Protein	60.0-85.0	g/L	68.8
Albumin	25.0-38.0	g/L	25.3
Glob	30.0-45.0	g/L	43.5
Alb/Glob	0.7-1.1		0.6 L
BHB	0.00-0.80	mmol/L	0.14
Ca	2.00-2.75	mmol/L	2.14
Mg	0.74-1.44	mmol/L	0.59 L
Hapto	0.00-0.30	g/L	3.40 H
Serum HB	0.00-0.20	g/dL	0.17
Blood Lead	<0.20	µmol/L	<0.10

Necropsy findings

The steer died and was necropsied on 2 August 2021. Multiple petechial haemorrhages were seen on most serosal surfaces and fascial planes, with more extensive haemorrhages over the serosa of the omasum, abomasum and duodenum. The right apical lung lobe was consolidated and the liver was enlarged, brownish orange with rounded edges. There were extensive coalescing haemorrhages over both internal and external surfaces of the heart. The pharyngeal lymph nodes were enlarged and fleshy and there were areas of necrotic bone and cartilage in the frontal sinuses and behind the ethmoid plate.

Figure 2. Carcase of the affected steer with ribs and abdominal musculature removed

Figure 3. Heart and anterior lung lobes (pericardium opened)

Figure 4. Endocardial haemorrhages

Figure 5. Cranium split and brain removed, presumably neoplastic tissue frontal sinus and ethmoid region

Figure 6. Neoplastic pharyngeal lymph node in situ

Laboratory Findings

MICROBIOLOGY / SEROLOGY

Enzootic bovine leucosis ELISA was negative and Chlamydia complement fixation test was negative (<8). EDTA blood was PCR negative for Malignant Catarrhal Fever (tested because of vasculitis on histopathology) and tail hair samples were negative for pestivirus antigen (PACE). Samples tested negative for prion protein.

Histopathology

Histopathology revealed lymphoma affecting the liver, kidney, pharyngeal tissue/tonsil, lymph node, bone marrow, brain and heart. Within the tonsil and lymph node, sheets of neoplastic cells infiltrated and effaced normal architecture, while infiltrates were multifocal in the kidney and periportal within the liver. Within the heart and brain, small numbers of neoplastic cells were within and around blood vessels. Neoplastic cells were large, round, had distinct cell borders, scant cytoplasm and contained a large nucleus with stippled chromatin and a single nucleolus. Mitotic figures averaged approximately 1-3 per high power field. Neoplastic cells were present within vessels in multiple tissues. Within the section of lung examined, there was a marked, acute, widespread fibrinonecrotising pleuropneumonia with vasculitis, thrombi, oedema and abundant intralesional bacteria. Within and surrounding a suspected section of lymph node, in addition to sheets of neoplastic round cell infiltrates, there were marked, multifocal to extensive areas of fibrin and necrosis, multifocal haemorrhage and fibrinonecrotising vasculitis. Within the cerebellum, there was a focal, mild area of malacia and haemorrhage.

Figure 7: Neoplastic round cell infiltrates (lymphoma) within the liver

Discussion

In hindsight this was clearly a multifocal disease affecting the brain, optic nerves, liver, lymphatic system, lungs, heart and peripheral circulation. A widely disseminated lymphoma is the most likely cause.

As this case was serologically negative for enzootic bovine leucosis virus (EBL), it is classified as sporadic (or atypical) bovine leucosis (SBL). SBL typically has three forms; juvenile (usually in calves less than six months and characterised by generalised lymphadenopathy), thymic (most commonly in animals from 6 months to 2 years) and the cutaneous form (in cattle 1-3 years of age). However atypical cases affecting older cattle and different organs have been reported and cases can have characteristics of more than one category (Constable et al. 2017, Grünberg and Eisenberg 2013, Hendrick 2002).

References

1. Constable P, Hinchcliff KW, Done S and Gruenberg W (2016). Veterinary Medicine, 11th Edition, A textbook of the diseases of cattle, horses, sheep, pigs and goats - two-volume set, pp 834-6
2. Grünberg W, Eisenberg SW (2013). Atypical form of sporadic bovine leukosis (SBL) in the Netherlands. The Veterinary Record 173(16):398
3. Hendrick SH (2002). Atypical sporadic bovine leukosis in a beef feedlot heifer. Canadian Veterinary Journal 43(8):617-619