Meintjes_pp39-53.qxd


INTRODUCTION

Farmers in the Kuruman district of the Northern
Cape Province, Republic of South Africa have
recently experienced mortalities in their free-ranging
cattle herds. The mortalities, approximately 200
head of cattle, were ascribed to nephrotoxicity
induced by a previously unknown poisonous plant
(Du Plessis, Joubert, Prozesky, Naudé, Herman &
Van der Westhuizen 2004). Clinically, weakness,

malaise, and perineal and brisket oedema were
observed. Necropsy findings included severe ana-
sarca, ascites, perirenal oedema and nephrosis,
and mild hepatosis. Microscopical examination
revealed extensive degeneration and necrosis of
tubular epithelial cells in the renal cortex, accom-
panied by large numbers of protein and, some-
times, cellular casts in the tubular lumens. Dosing
trials conducted by the Division of Toxicology, On-
derstepoort Veterinary Institute confirmed Nolletia
gariepina (DC) Mattf. as the causative plant (Du
Plessis 2004).

The primary aim of the current trial was to elucidate
the pathophysiological changes in renal function in
sheep induced by N. gariepina. A secondary objec-
tive was to evaluate the toxic effects and patho-
logical findings following administration of this
nephrotoxic plant to sheep. 

39

Onderstepoort Journal of Veterinary Research, 72:39–53 (2005)

Toxicity, pathophysiology and pathology in sheep
following dosing of the nephrotoxic plant
Nolletia gariepina (DC) Mattf.

R.A. MEINTJES1, C.J. BOTHA2 and L. PROZESKY2

ABSTRACT

MEINTJES, R.A., BOTHA, C.J. & PROZESKY, L. 2005. Toxicity, pathophysiology and pathology in
sheep following dosing of the nephrotoxic plant Nolletia gariepina (DC) Mattf. Onderstepoort Journal
of Veterinary Research, 72:39–53

Ingestion of the plant Nolletia gariepina was confirmed as the cause of acute mortalities in cattle in
the Kuruman area of the Northern Cape Province of South Africa. The aim of this trial was to inves-
tigate the toxic effects of this plant with respect to clinical signs, pathophysiology and pathology
using the sheep as a model. At dosages of 1.5 g dried, milled plant material/kg body mass  there
were no detectable abnormal findings, while at dosages of 2.8–3.0 g/kg most of the animals died
acutely. In subacutely affected sheep, depression, inappetance, teeth grinding, tachycardia, weak
ruminal movements and recumbency were noticed. The most prominent pathophysiological changes
observed, included a sharp rise in non-protein nitrogen substances in the plasma, remarkable
decline in glomerular filtration rate, increase in sodium and potassium excretion, and a rise in urine
gamma glutamyltransferase activity. Macroscopically a severe nephrosis was present in all the ani-
mals. The most important findings detected histologically were necrosis of the proximal convoluted
tubular epithelium and large numbers of protein casts in the lumens.

Keywords: Kidney, nephrotoxicity, Nolletia gariepina, plant poisoning, sheep

1 Department of Anatomy and Physiology, Faculty of Veterinary
Science, University of Pretoria, Private Bag X04, Onderste-
poort, 0110 South Africa. E-mail: roy.meintjes@up.ac.za

2 Department of Paraclinical Sciences, Faculty of Veterinary
Science, University of Pretoria, Private Bag X04, Onderste-
poort, 0110 South Africa. E-mail: christo.botha@up.ac.za
and leon.prozesky@up.ac.za

Accepted for publication 27 July 2004—Editor



MATERIALS AND METHODS

Nolletia gariepina was collected on the farm Tom
Brown, situated in the quadrant 2226 Cb of the
Kuruman district, Northern Cape. The plant materi-
al was air dried, finely milled and frozen (at  –10 °C)
before being used.

Nine Mutton Merino wethers, 9–18 months of age,
were individually placed in steel metabolic crates in
an experimental animal housing facility. The room
temperature was set and maintained at 22 °C. Lu-
cerne hay and drinking water were available ad lib.
To facilitate the collection of unsoiled urine the sheep
were fitted with faecal collection bags. The total vol-
ume of urine voided per day was collected in refrig-
erated containers located under each crate.

The sheep were placed in the metabolic crates for
an adjustment period of 5 days prior to a 5-day con-
trol phase during which baseline values for the dif-
ferent parameters were established as each animal
served as its own control. Immediately following the
control period the sheep were deprived of feed for
24 h and then dosed with dried, milled plant materi-
al (1.5–3 g/kg body mass) by stomach tube as indi-
cated in Table 1. 

Daily clinical examinations (habitus, rectal tempera-
ture, pulse, respiration and rumen motility) were
conducted to evaluate the animals’ health. Feed
and water intake and urine volume were recorded
daily. 

An aliquot of urine was collected for conventional
urinalysis (Combur urinary dip stick [Merck]). Uri-
nary creatinine, sodium (Na) and potassium (K)
concentrations, gamma glutamyltransferase (GGT)
activity and osmolarity were also determined. The
GGT:creatinine ratios served as early detection of
renal tubular damage. 

Blood samples were collected for determination of
haematocrit, osmolarity and plasma protein, Na, K,
creatinine and urea concentrations. In addition,
GGT and aspartate aminotransferase (AST) activi-
ties were determined to establish if any hepatic
damage had occurred.

From the above variables the following were derived:

1. Glomerular filtration rate (GFR)

The plasma clearance of endogenous creatinine
was equated to GFR on the assumption that
creatinine is neither secreted nor absorbed by
the renal tubule in sheep (Nawaz & Shah 1984;
Bastl, Rudnick & Nairns 1985).

Thus, GFR = Uvol.U[creatinine] / Pl[creatinine] (l/d)

where

Uvol = Volume of urine passed per day
(l/d)

U[creatinine] = Creatinine concentration in urine
(mMolar)

Pl[creatinine] = Creatinine concentration in plas-
ma (mMolar)

2. Fractional excretion of sodium (FENa)
(Bastl et al. 1985)

This represents the amount of filtered sodium
excreted in the urine expressed as a percentage.

FENa = Uvol.U[Na].100 / GFR.Pl[Na] (%) 

where 

Pl[Na] = Sodium concentration in plasma
(mMolar)

U[Na] = Sodium concentration in urine
(mMolar)

The carcasses of sheep that died or were eutha-
nased (overdose of pentobarbitone sodium [Eutha-
naze, Centaur] administered intravenously) were
submitted for necropsy. Tissue specimens (approx-
imately 10 mm3) from several organs were collected
and fixed by immersion in 10 % neutral buffered for-
malin for at least 5–7 days. Specimens were routine-
ly processed for light microscopy and stained with
haematoxylin and eosin (HE). 

Renal tissue specimens were collected from two
cases (no. 13 and 42) within minutes of death, cut
into 1 mm2 blocks and fixed in labelled glass vials
containing 2.5 % gluteraldehyde in 4 % 0.1 M
Millonig’s buffer. Samples were routinely processed
for electron microscopy using a transmission elec-
tron microscope and photographed. 

RESULTS

Toxicity

The clinical signs observed and pathological find-
ings are summarized in Table 1. Four of seven ani-
mals that were dosed with 3 g/kg N. gariepina plant
material died acutely within 24 h. One sheep, which
was depressed, recumbent and exhibited respiratory
distress (hyperventilation, groaning, frothing at the
mouth) was euthanased 8 h after being dosed with
3 g/kg milled plant material. Only two animals,
which had received 3 g/kg plant material, survived

40

Toxicity, pathophysiology and pathology of the nephrotoxic plant Nolletia gariepina (DC) Mattf.



41

R.A. MEINTJES, C.J. BOTHA & L. PROZESKY
T

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42

Toxicity, pathophysiology and pathology of the nephrotoxic plant Nolletia gariepina (DC) Mattf.
T

A
B

L
E

 1
(c

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n
tin

u
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R.A. MEINTJES, C.J. BOTHA & L. PROZESKY

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FIG. 1 Serum urea concentration in four sub-acutely affected sheep following administration
of dried, milled Nolletia gariepina plant material

FIG. 2 Serum creatinine concentration in four sub-acutely affected sheep following adminis-
tration of dried, milled Nolletia gariepina plant material



for longer periods, but were depressed, anorexic
and had weak rumen movements and tachycardia. 

Administration of half the dose (1.5 g/kg) to two
wethers elicited no clinical effects. Following a
washout period of 7 days the same two sheep were
dosed with 2.25 g/kg N. gariepina plant material.
Only one animal was mildly affected clinically
(decreased appetite and weak ruminal movements),
but was judged fully recovered after 6 days. More
than 3 months later the same two wethers were
dosed again with 2.8 g/kg and at this dose, moder-
ate to severe clinical signs developed (Table 1).

Pathophysiology

Non-protein nitrogen (NPN) substances in serum

The most noticeable aberrations in blood chemistry
were the remarkable increases in serum urea and
creatinine concentrations in sheep that survived for
24 h or longer (Fig. 1 and 2). 

Serum AST and GGT activities

A moderate increase in AST activity (96–157 U/l)
above the reference range (5–60 U/l) occurred in
some sheep. There was no noticeable increase in
GGT activity. 

Daily urine volumes

Following dosage of the sheep with N. gariepina,
even at doses of 1.5 g/kg, urine production in gen-

eral increased. In some cases, however, e.g. sheep
A5 and sheep A9 dosed with 3 g/kg, the increase
was preceded by virtual anuria on the day immedi-
ately following dosage (Table 2).

Urinalysis

Semi-quantitative urinalysis (urinary dip stick)
revealed mild proteinuria and presence of haemo-
globin in the urine after dosing.

Glomerular filtration rate (GFR)

Dramatic decreases in GFR were calculated in
sheep, which survived at least one day post-dosing,
when the plant material was dosed in excess of
1.5 g/kg (Table 3).

Urinary sodium excretion 

During the control phase no sodium could be
detected in the urine, but within 24 h of dosing the
Nolletia plant material at doses of 2.8 g/kg and
above, urinary sodium concentrations rose. The
fractional excretion of sodium is given in Table 4.

Urinary potassium excretion

The fractional excretion of potassium increased,
even after receiving relatively low doses (1.5 g/kg)
of Nolletia plant material. As potassium is excreted
by the nephron tubule, values in excess of 100 %
are encountered, sometimes even under control
conditions.

44

Toxicity, pathophysiology and pathology of the nephrotoxic plant Nolletia gariepina (DC) Mattf.

TABLE 2 Urine volumes (l) of sheep-control values and values following dosing with Nolletia gariepina

Dose rate Sheep Control Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 
no. mean (SD) post post post post post post post 

dosing dosing dosing dosing dosing dosing dosing

1.5 g/kg 42 0.21 (0.06) 0.64 0.66 0.71
13 0.275 (0.069) 0.35 0.33 0.27

2.25 g/kg 42 0.21 (0.06) 0.64 1.42 3.047 1.7 2.129 2.042
13 0.275 (0.69) 0.71 0.37 0.445 0.44 0.52 0.56

2.8 g/kg 42 0.33 (0.11) Died
13 0.161 (0.044) 0.59 0.28 0.64 0.71 0.6 0.6 1

3.0 g/kg A9 0.874 (0.25) 0.099 1.37 1.46 1.068 1.305 1.46 2.67
A5 0.643 (0.165) 0 0.86 3.12 1.21 0.66 Euth*
A4 0.868 (0.207) Euth.*
S5 0.32 (0.15) Died
A14R 0.573 (0.14) Died
A13B 0.378 (0.15) Died
A13R 0.754 (0.1) Died

*  Euth. =  Euthanasia



45

R.A. MEINTJES, C.J. BOTHA & L. PROZESKY

TABLE 3 Glomerular filtration rates (l/day) of sheep—control values and values following dosing with Nolletia gariepina

Dose rate Sheep Control Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 
no. mean (SD) post post post post post post post 

dosing dosing dosing dosing dosing dosing dosing

1.5 g/kg 42 37.29 (4.06) 43.05 44.43
13 49.07 (8.25) 46.83 38.33

2.25g/kg 42 37.29 (4.06) 4.8 6.56 1.93 3.07
13 49.07 (8.25) 15.42 26.38 23.85 37.44

2.8 g/kg 42 37.73 (8.09) Died
13 33.11 (9.48) 16.53 28.06 10.71 1.62 2.18 4.01

3.0 g/kg A9 87.79 (11.95) 0.49 5.27 2.76 1.15 1.59 1.89 4.73
A5 62.03 (15.15) –a 8.74 15.99 4.65 1.95 Euth*
A4 41.89 (2.06) Euth.*
S5 75.32 (1.96) Died
A14R 68.14 (1.55) Died
A13B 33.22 (10.55) Died
A13R 103.41 (12.19) Died

*  Euth. =  Euthanasia
a =  No urine produced

TABLE 4 Fractional excretion of sodium (%) and potassium (%) in sheep—control values and values following dosing with Nolletia
gariepina

Dose rate Sheep no. Control Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 
mean post post post post post post post 
(SD) dosing dosing dosing dosing dosing dosing dosing

1.5 g/kg 42 Na 0 0 0
K 82 (4.2) 101 195

13 Na 0 0 0
K 101 (11) 101 150

2.25 g/kg 42 Na 0 0 0 0 0
K 82 (4.2) 444 695 2 533 1 989

13 Na 0 0 0 0 0
K 101 (11) 180 178 276 229

2.8 g/kg 42 Na 0 Died
K 51 (18)

13 Na 0 1 0.1 5.4 16 7.8 9.0
K 37 (14) 33 45 166 614 573 378

3.0 g/kg A9 Na 0 5.7 1.8 11.8 13.9 11.9 16.5
K 97 (53) 315 845 1 028 1 225 1 084 796

A5 Na 0 –a 0 5.9 10.1 5.25 Euth*
K 89 (15) –a 45 533 673 648

A4 Na 0 Euth.*
K 137 (39)

S5 Na 0 Died
K 89 (38)

A14R Na 0 Died
K 102 (20)

A13B Na 0 Died
K 124 (46)

A13R Na 0 Died
K 68 (8)

*  Euth. =  Euthanasia
a =  No urine produced



Urine osmolarity

In most of the animals, which did not die within 24 h
of dosing the plant material, urine osmolarity de-
creased markedly (Table 5).

Urinary GGT activity

Although no change in serum GGT activity was
noticed following dosing with Nolletia plant material,

urine GGT activity tended to rise and then fall with-
in a week (Table 6).

Pathology

Macroscopic pathology

A severe nephrosis was present in all the animals.
The kidneys exhibited various degrees of swelling,
bulged slightly on cut surface and ranged in colour

46

Toxicity, pathophysiology and pathology of the nephrotoxic plant Nolletia gariepina (DC) Mattf.

TABLE 5 Urine osmolarity (mOsm/l) of sheep—control values and values following dosing with Nolletia gariepina

Dose rate Sheep Control Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
no. mean (SD) post post post post post post post 

dosing dosing dosing dosing dosing dosing dosing

1.5 g/kg 42 2 516 (357) 1 267 1 721
13 2 647 (79) 2 312 2 900

2.25 g/kg 42 2 516 (357) 624 566 496 566 634
13 2 647 (79) 813 1 877 2 182 2 237 2 440

2.8 g/kg 42 1 452 (222) Died
13 2 355 (163) 1 311 990 658 567 659 635

3.0 g/kg A9 1 375 (364) 582 508 520 550 613 584 444
A5 1 470 (597) –a 493 255 539 567 Euth.*
A4 1 071 (145) Euth.*
S5 1 948 (456) Died
A14R 1 875 (406) Died
A13B 1 947 (366) Died
A13R 1 498 (243) Died

* Euth. =  Euthanasia
a =  No urine produced

TABLE 6 Urine gamma glutamyltransferase (GGT) concentrations (units/l) in sheep—control values and values following dosing
with Nolletia gariepina

Dose rate Sheep Control Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 
no. mean (SD) post post post post post post post 

dosing dosing dosing dosing dosing dosing dosing

1.5 g/kg 42 25 (13) 10 10
13 26 (8) 15 15

2.25 g/kg 42 25 (13) 36 75 30 18
13 26 (8) 9 36 24 9

2.8 g/kg 42 14 (7) Died
13 35 (23) 9 48 117 69 30 39 21

3.0 g/kg A9 10.5 (1) 66 165 90 42 36 21 10
A5 13 (3) –a 96 71 71 58 Euth.*
A4 18 (15) Euth.*
S5 16 (7) Died
A14R 19 (6) Died
A13B 12 (3) Died
A13R 16 (2) Died

*  Euth. =  Euthanasia
a =  No urine produced



47

R.A. MEINTJES, C.J. BOTHA & L. PROZESKY

from light brown to greyish-white (Fig. 3 and 4).
Widespread serosal haemorrhages; mild accumu-
lation of fluid in the body cavities; moderate hepato-
sis characterized by mild swelling of the liver with
rounded edges, slightly pale colour and a taut cap-
sule; and lung congestion and oedema were often
seen (Table 1).

Light microscopy

KIDNEY

A severe nephrosis was the most striking lesion
present. The epithelium of the proximal convoluted
tubules (PCT) in the cortex and straight tubules in
the cortico-medullary junction was the most severe-

FIG. 3 and 4 Severe nephrosis in a sheep dosed with Nolletia gariepina plant material

3

4



ly affected. Epithelial cells showed karyolysis, kary-
orrhexis or pyknosis of nuclei with clumping and
dissociation of the brightly eosinophilic cytoplasm
(necrosis), or increased eosinophilia and vacuolated
appearance (hydropic degeneration) of the cyto-
plasm. The tubules contained large numbers of pro-
tein casts in the lumens (Fig. 5 and 6). Single neu-

trophils were present in the interstitial tissue and a
mild neutrophilia was evident in the blood vessels.
In one animal (no. 13) a few tubules were dilated
and single tubules exhibited moderately basophilic
epithelial cells with large, vesicular nuclei indicative
of early regeneration. No specific lesions were visi-
ble in the glomeruli. 

48

Toxicity, pathophysiology and pathology of the nephrotoxic plant Nolletia gariepina (DC) Mattf.

FIG. 5 and 6 Widespread necrosis of renal tubular epithelium, particularly in the proximal con-
voluted tubules. The tubules contain large numbers of protein casts in the lumens

5

6



LIVER

Mild hepatocellular swelling with accumulation of
multiple small vacuoles in the cytoplasm of hepato-
cytes (indicating hydropic degeneration) was the
most striking lesion in most animals. Scattered hepa-

tocytes throughout the parenchyma were necrotic,
evidenced by increased eosinophilia of the cyto-
plasm and karyorrhexis, karyolysis or pyknosis of
the nuclei. No specific lesions were visible in the
portal tracts and bile ducts.

49

R.A. MEINTJES, C.J. BOTHA & L. PROZESKY

FIG. 7 Proximal convoluted tubule epithelial cell. Note the swollen mitochondria with loss of
internal structure ( ). Parallel orientation of mitochondria to the cell axis is lost 

FIG. 8 Proximal convoluted tubule epithelial cell. Note the increase in intracellular electron-
dense bodies interpreted as primary lysosomes ( )

7

8



Transmission electron microscopy

KIDNEY

The most striking changes occurred in the PCT of
both animals (Fig. 7–10). Individual cells lining the
tubules could not be identified because of loss of

the cell membranes. Affected tubules were demar-
cated by the intact basement membrane. The usu-
ally conspicuous brush border and apical canaliculi
of the epithelial cells had disappeared. The cyto-
plasmic organelles and nuclei were disorganized
and dispersed as a loose mass within the tubular
lumen.

50

Toxicity, pathophysiology and pathology of the nephrotoxic plant Nolletia gariepina (DC) Mattf.

FIG. 9 and 10 Proximal convoluted tubule epithelium. Note the loss of cell membranes ( ) with
chromatin margination (C). Cytoplasmic organelles are disorganized and dispersed
as a loose mass within the tubular lumen( ). The basal membrane is intact ( )

9

10

C

C



Nuclear changes ranged from chromatin margina-
tion and karyolysis to pyknosis. Chromatin margina-
tion, the most common change exhibited, was evi-
dent as condensation of the chromatin in irregular
clumps (karyorrhexis), or as a thin continuous rim
along the inner membrane of the nuclear envelope,
with disappearance of the chromatin from other
areas of the nucleus and loss of nucleolus. Some
affected nuclei were interpreted as being in an
intermediate stage between margination and lysis.
Pyknotic nuclei were recognized by the shrunken
nucleus with diffuse condensation of the chromatin.

The most conspicuous change in the proximal tubu-
lar epithelial cell cytoplasm was increased numbers
of electron-dense, single membrane-bound bodies
interpreted as primary lysosomes. Also present were
variably sized, single membrane-bound vacuolar
bodies which contained medium electron–dense,
finely granular material that could not be identified
because of the advanced stage of breakdown and
degradation and most probably represented auto-
lysosomes. Scattered between the necrotic cellular
organelles were residual bodies loaded with undi-
gested electron-dense residues of various kinds. 

The normal basal distribution of the mitochondria,
with parallel orientation to the cell axis, was lost.
Mitochondria had a rounded form and some were
severely swollen with a loss of internal structure,
whereas others were electron-dense and could not
be distinguished unequivocally, by morphological
features alone, from other vesicular structures in
the cell including primary lysosomes.

DISCUSSION

Following ingestion of N. gariepina there appears to
be a threshold before toxicity will be induced. When
3 g/kg of dried, milled plant material was dosed
orally, five of the seven sheep died acutely or were
euthanased for humane reasons. On the other hand,
administration of 1.5 g/kg elicited no clinical signs
and 2.25 g/kg only induced mild clinical signs. During
the reported field outbreaks, the cattle were deprived
of feed for 24–48 h and, following their release, they
presumably consumed large quantities of the plant
material (Du Plessis 2004; Du Plessis et al. 2004),
thus most probably exceeding the threshold level.

Although this plant is highly toxic it has, except for
the outbreak in cattle, never before been associat-
ed with poisoning of livestock (Du Plessis 2004).
The acute mortalities observed in this study could
be ascribed to other toxins, besides the nephrotox-

in(s), contained by the plant. Analysis of the plant
material for cyanogenic potential gave negative
results. The nephrotic syndrome corroborated by
the gross and histological findings was only repro-
duced in sheep that survived for longer than 24 h. 

The concentrations of non-protein nitrogen sub-
stances in the plasma generally increase when GFR
decreases by more than 75 % (more than 75 % kid-
ney damage has occurred). This is because of the
large “reserve capacity” of the kidneys (Rose &
Renkke 1994). In the animals, which did not die
acutely, kidney damage was so severe, enough to
induce marked increases in the plasma concentra-
tions of creatinine and urea as well as a low GFR.
As no specific damage to the glomerulus was de-
scribed on histopathology and there is no reason to
believe that the azotaemia was pre-renal (the ani-
mals were not dehydrated, neither was any cardiac
pathology detected), the drastic fall in GFR was due
to blockage of proximal tubules by cellular debris
and protein casts (as was obvious on the histopatho-
logical findings). The reverse pressure across the
filtration membrane due to such blockage would
effectively stop the filtration process.

The appearance of sodium in the urine and the rise
of potassium concentration in the urine, as well as
the increase in urine volume, despite the marked fall
in GFR, could be ascribed to two factors. The flow
of filtrate in non-damaged nephrons may have been
so rapid that there was little chance for the reab-
sorption of sodium, potassium and water. More like-
ly, however, in damaged nephrons (proximal tubular
epithelial damage with loss of brush border), which
still permitted filtrate flow, sodium, potassium and
water reabsorption would be compromised. Most of
the sodium, potassium and water reabsorption
occurs in the PCT and damage to the renal epithe-
lium in this region would account for losses of large
amounts of electrolytes and water (by osmotic di-
uresis) (Knepper & Burg 1983).

The reduction in urine osmolarity indicates, that, in
spite of the natriuresis and kaliuresis, more water
relative to electrolytes was lost. This may be a phe-
nomenon associated purely with proximal tubular
damage or possibly the distal part of the nephron
duct becomes refractory to the effects of antidiuretic
hormone (as in chronic nephritis). 

Gamma glutamyltransferase is present in the brush
border of the proximal convoluted tubule where it
facilitates transfer of glutamate into the tubular cells
(Welbourne & Mathews 1999). A rise in urine GGT
activities when there is proximal tubular damage, is

51

R.A. MEINTJES, C.J. BOTHA & L. PROZESKY



therefore in accordance with the pathological find-
ings in this section of the nephron tubule, as was
seen in this trial.

The pathological lesions in the experimental sheep
correspond to a large extent with the lesions
described in the experimentally produced cases in
cattle, but were much less pronounced compared to
the lesions in the field outbreak in cattle (Du Plessis
2004). In both species under experimental condi-
tions gross lesions included mild to moderate accu-
mulation of fluid in body cavities, severe nephrosis
and a moderate hepatosis. Contrary to the situation
in the experimentally produced cases in cattle,
perirenal oedema was not a striking feature in
sheep, whereas widespread serosal haemorrhages
were present in the latter.

Nephrosis was characterized by degeneration and
necrosis of particularly the PCT and affected tubules
contained large numbers of protein casts in the
lumens. The mild neutrophyllic infiltration in the
interstitial tissue was most likely in response to the
tubular necrosis. Scattered tubules were dilated
and in one animal early tubular epithelial regenera-
tion was displayed. Transmission electron micro-
scopy confirmed that the basement membrane of
affected tubules was still intact and a significant
increase of autolysosomes was displayed in the
affected lining epithelial cells of the PCT. No struc-
tural visible lesions were evident in the glomeruli.
Most animals revealed mild hepatocellular swelling,
with accumulation of multiple small vacuoles in the
cytoplasm of hepatocytes indicating hydropic
degeneration.

The PCT epithelium is the most susceptible to both
toxic and hypoxic injury because of its high meta-
bolic rate (Jamison, Myers & Neild 1997; Confer &
Panciera 2001). Degeneration and necrosis of the
tubular epithelium in the kidneys (nephrosis), espe-
cially the PCT, is a non-specific lesion. It can be
hypoxic or nephrotoxic in origin. The former follows
on a period of hypotension causing marked renal
ischaemia. Complete ischaemia of more than 2 h
duration causes irreversible tubular necrosis, espe-
cially of the PCT (Confer & Panciera 2001). 

Nephrotoxic acute tubular necrosis (ATN) can be
distinguished from ischaemic ATN by two histologi-
cal features viz. extensive necrosis of predominant-
ly PCT epithelium and intact tubular basement mem-
branes. The opposite is true for ischaemic ATN,
where necrosis is patchy and mostly affects the
PCT with disruption of the basement membrane
(Maxie 1993; Jamison et al. 1997; Confer & Panciera
2001). 

Toxic damage to tubular epithelium has a better
prognosis if the animal survives the initial toxic
insult, as the basement membranes that are neces-
sary for epithelial regeneration are intact (Maxie
1993), and some nephrotoxic drugs can cause
ischaemia rather than direct toxic damage to the
renal tubules (Jamison et al. 1997). 

In conclusion, dosing of N. gariepina plant material
to sheep in doses exceeding 2.8 g/kg resulted in
acute death of most animals and marked changes
in the clinical chemistry of the survivors character-
ized by a sudden, marked decrease in GFR, azo-
taemia, elevated fractional excretion of Na and K,
and increased urinary GGT activity.

Sheep, which died or were euthanased, exhibited
severe nephrosis that was histologically character-
ized by necrosis of predominantly lining epithelial
cells of the PCT and the presence of protein and
cellular casts.

ACKNOWLEDGEMENTS

We thank Ms H. Engelbrecht and Ms H. Rossouw,
Section of Physiology; Ms E. Myburgh, Section of
Clinical Pathology; Ms E. van Wilpe and Ms D.
Meyer, Electron Microscopy Unit, Faculty of Veter-
inary Science, University of Pretoria; and Ms L.
Labuschagne, Division of Toxicology, Onderste-
poort Veterinary Institute for their valuable assis-
tance. The authors also express their gratitude to
the National Research Foundation (NRF) of South
Africa and Mr W. du Plessis, the farmer, for funding
this trial. The research reported here emanates
from Project 36.5.520, approved by the Animal Use
and Care and Research Committees of the Faculty
of Veterinary Science, University of Pretoria. 

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