651468
VDIXXX10.1177/1040638716651468Vernonia poisoning of sheep in UruguayDutra et al.
research-article2016
Full Scientific Report
Journal of Veterinary Diagnostic Investigation
2016, Vol. 28(4) 392–398
© 2016 The Author(s)
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DOI: 10.1177/1040638716651468
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Poisoning of sheep by
Vernonia plantaginoides (Less.)
Hieron in Uruguay
Fernando Dutra,1 Agustin Romero, Carina Quinteros, Ruben Araújo,
Carmen García y Santos
Abstract. Vernonia plantaginoides (Less.) Hieron, previously known as Vernonia squarrosa, is a rhizomatous subshrub
with purple flowers that is prevalent in the natural grassland of Uruguay, Argentina, and southern Brazil. We report an
outbreak of V. plantaginoides (yuyo moro) intoxication in sheep in Treinta y Tres Department, northeastern Uruguay. A total
of 54 of 463 (12%) recently weaned lambs died 2–7 days after entering a natural pasture that had been invaded by sprouting V.
plantaginoides. The first cases were found dead. Affected lambs showed marked jaundice, edema of the face, ears, and eyelids,
and severe photodermatitis. At the autopsies of 3 lambs, the carcass was yellow, the liver was enlarged with a marked acinar
pattern (“nutmeg liver”), and hemorrhages were observed on serous membranes. Microscopic lesions were characterized by
diffuse periacinar hepatocellular necrosis and cholemic nephrosis. Three female lambs were experimentally dosed with the
aerial parts of V. plantaginoides collected immediately after the outbreak. The lamb that was dosed once with 40 g/kg body
weight died after 36 h with severe hepatic necrosis. The lamb dosed with 20 g/kg daily for 4 days showed clinical signs and
microscopic lesions in the liver with multiple apoptotic hepatocytes in the periacinar zone. The third lamb, dosed with 30, 17,
and 15 g/kg daily over 3 days, respectively, showed transient clinical signs and a rise in liver enzymes, but recovered, and no
lesions were found postmortem. These results demonstrate that V. plantaginoides was responsible for severe field outbreaks
of poisoning in sheep in Uruguay.
Key words: Hepatic necrosis; ovine; photosensitization; plant poisoning; Uruguay; Vernonia.
Introduction
Vernonia Schreb (family Asteraceae) is a large genus of
perennial forbs and shrubs with red or purple flowers, distributed mostly in the tropics and subtropics of Asia, Africa,
and America.22 Some species in North America are given the
name “ironweed” because of their stout stems that often persist throughout the winter. In South America, the genus is
represented by ~350–400 species that grow mostly in southeastern Brazil, northern Argentina, Uruguay, Paraguay, and
Bolivia.7 The Vernonia genus has been reported to possess a
plethora of bioactive compounds with medicinal properties,30 and some are edible and have nutritional value.12 A
few—all in South America—are recognized as being toxic to
livestock. Among these, Vernonia mollissima9 and especially
Vernonia rubricaulis4,27 are reported to cause outbreaks of
hepatotoxicity in cattle in central-western Brazil. Mortality
occurs annually during the late dry or early wet season when
the plants are sprouting and other green forage is scarce,
when the stocking rate is high, or after moving naive cattle
from other ranches.17 Poisoning by V. rubricaulis has been
induced experimentally in cattle and sheep,4,20 whereas V.
mollissima has been confirmed as hepatotoxic in cattle,
sheep, goats, and rabbits.13,25,29 However, cases of natural
poisoning by V. rubricaulis and V. mollissima have never
been reported in sheep (R Lemos, pers. comm., 2015),
despite this species being, as are cattle, highly susceptible to
both plants.4 Another species of Vernonia, V. nudiflora, in
Rio Grande do Sul, Brazil, has been experimentally proven
to cause gastrointestinal disorders in cattle and sheep, but
given its low palatability and toxicity, it is unlikely to cause
spontaneous poisoning in livestock.8
Vernonia plantaginoides (Less.) Hieron, previously known
as V. squarrosa (Less.) Lessing, is a perennial, rhizomatous
subshrub ~60–80 cm in height, with stout stems branched at
the top, ascending linear leaves of 5–12 cm long and 1–6 mm
wide, with revolute margins and white tomenta on the back,
and purple inflorescences (Fig. 1).5 Given its striking purple
flowers, in Uruguay it is commonly known as yuyo moro
(purple weed), or mio-mio moro (purple mio-mio), due to its
Veterinary Laboratory Division (DILAVE) Miguel C Rubino, Eastern
Regional Laboratory, Treinta y Tres, Uruguay (Dutra, Romero, Quinteros,
Araújo); and Department of Toxicology, Veterinary Faculty, University of
the Republic (UDELAR), Montevideo, Uruguay (García y Santos).
1
Corresponding Author: Fernando Dutra, DILAVE Miguel C Rubino,
Avelino Miranda 2045, CP 33000, Treinta y Tres, Uruguay.
fdutra@mgap.gub.uy
Vernonia poisoning of sheep in Uruguay
393
Uruguay. It affected a flock of 463 recently weaned crossbred
Merino lambs (5–6 months of age) that were introduced into
a large paddock of native pasture that had been invaded by
vegetative and early flowering V. plantaginoides. Clinical,
epidemiologic, and management data were collected during
visits to the farm. Thorough autopsies and complete histologic evaluation were performed on 3 affected sheep (sheep
1–3), the first a few hours postmortem and the other 2 following euthanasia with intravenous (IV) sodium pentobarbital
and exsanguination. Tissue samples, including from the central nervous system, were fixed in 4% buffered formaldehyde,
processed routinely, and 5-µm sections cut and stained with
Mayer hematoxylin and eosin (HE) for histology.
Figure 1. Flowering Vernonia plantaginoides (commonly
known as yuyo moro) in northeastern Uruguay, March 2012.
similarity with Baccharis coridifolia (mio-mio). The plant
grows in the hilly natural grassland of northeastern Uruguay
and adjacent provinces of Argentina and southern Brazil.5
The reserve compounds in the underground organs enable the
rapid development of new shoots when the aerial parts die or
are damaged by drought or frost, or are lost during the dormancy stage of the plant in winter,1 so it is one of the first
plants to green after rain in spring and autumn, or as soon as
the weather is hot and humid (i.e., practically anytime during
the year in the temperate climate of Uruguay).
Poisoning of sheep by V. plantaginoides has been known
for decades by local people, farmers, and veterinarians in
northeastern Uruguay. In some rural communities, folk stories commonly relate losses as high as 3,000–6,000 sheep in
the 1960s during the shearing season in spring (August–
November) or after weaning in summer or fall (January–
March). A similar or identical local problem in sheep was
investigated in the 1960s–1970s in the municipality of Uruguaiana, southern Brazil, close to the Uruguay frontier.28 The
outbreaks were attributed to alecrim or Vernonia squarrosa
(i.e., V. plantaginoides) because it was the main weed found
in the affected farms and because the plant was experimentally lethal to sheep and cattle in doses of 30–50 g/kg body
weight (bw); however, spontaneous cases were never seen,
and the importance of the plant under natural conditions
remained undetermined. We report an outbreak of spontaneous intoxication by V. plantaginoides (Less.) Hieron in sheep
in northeastern Uruguay. The clinical findings and pathology
from experimental administration of V. plantaginoides to
sheep are also described.
Materials and methods
Spontaneous cases
The outbreak occurred in March 2012 on a mixed sheep and
cattle farm situated on Las Pavas hill (latitude: 33°18′S; longitude: 54°94′W), Treinta y Tres Department, northeastern
Experimental poisoning
The experiment was carried out according to the recommendations of the Uruguayan Honorary Commission of Animal
Experimentation (CHEA). Fresh plants of V. plantaginoides
were collected from the paddock where lambs died during
the outbreak. In the laboratory, leaves and young stems were
separated, chopped, and refrigerated at 4°C until dosing.
Three female weaned lambs (4–6), 4–5 months of age, were
used for experimental reproduction of the disease. Animals
were kept grazing in a small paddock with water ad libitum
during the experimental period and were given 5–7 days to
acclimate to the test environment and to facilitate their subsequent clinical evaluation. Following 6–8 h of fasting (food
but not water), the animals were weighed and the aerial parts
of the plant were administered orally by hand. A single oral
dose of 40 g/kg bw was administered to lamb 4 (Corriedale,
18 kg bw), whereas lamb 5 (crossbreed Merino, 23 kg bw)
received 4 consecutive doses of 20 g/kg bw at 0, 24, 48, and
72 h (total dose of 80 g/kg bw), and lamb 6 (Corriedale, 24
kg bw) received 3 decreasing doses of 30, 17, and 15 g/kg at
0, 24, and 72 h (total dose of 62 g/kg bw). The lambs were
bled, urine-sampled, and clinically examined twice a day
prior to dosing to establish a baseline and every 4–6 h thereafter. Their behavior, heart rate (determined by auscultation),
respiratory rates (abdominal-costal movements), and rectal
temperature were recorded.
Serum activities of alkaline phosphatase (ALP), aspartate
aminotransferase (AST), and γ-glutamyl transferase (GGT)
were determined using routine laboratory techniques at the
Laboratory of Clinical Analysis, Veterinary Faculty, Montevideo, Uruguay. Urine samples were subjected to physical
examination and semiquantitative determinations of protein,
glucose, specific gravity, pH, bilirubin, urobilinogen,
ketones, and hemoglobin using a strip reagent.a Clinical and
biochemical data are presented as means ± standard deviation. A routine postmortem examination was performed on
all lambs immediately following death or after euthanasia
with an IV injection of sodium pentobarbital. Tissue samples
were fixed in formalin and processed as above for the spontaneous cases.
394
Dutra et al.
Figure 2. Marked edema and hyperemia of the face, ears, and
eyelids can be seen in spontaneously affected lamb 2.
lambs died at this stage, but survivors showed photosensitization, with cracking and sloughing of the skin of the muzzle, face, eyelids, and the tips of the ears. At autopsy, the
carcasses of cases 1–3 were icteric with yellow fluid under
the skin and in the abdominal, pleural, and pericardial cavities. There were ecchymoses and petechiae on the serous
membranes, mainly of the epicardium, tiny ulcers in the
abomasal mucosa, and dried and mucoid content in the colon
and rectum. The gallbladder was distended and edematous,
the kidney cortex was pale yellow, and the urine appeared
dark. The liver, which was consistently affected in all animals, was enlarged and had a diffuse mottled appearance
with red, depressed areas intercalated with a pale yellow network of parenchyma (“nutmeg liver”; Fig. 3).
Histologically, the changes in the liver were characterized
by periacinar to midzonal coagulative and hemorrhagic
necrosis, slight intrahepatic cholestasis, and swollen, vacuolated periportal hepatocytes. In cases 1 and 2, the hemorrhagic areas were confluent (bridging necrosis), whereas in
case 3, the necrosis was centrilobular only. Marked pulmonary hyperemia, epicardial hemorrhages, and moderate cholemic nephrosis were found in cases 1 and 2. Chitinous body
fragments or heads of the sawfly Perreyia flavipes (family
Pergidae) larvae were not found in the reticulum, rumen, or
omasum. Microscopic lesions were not found in any animals
in the splenic white pulp or mesenteric lymph nodes, central
nervous system, or other organs.
Experimental poisoning
Figure 3. The liver of lamb 2 is enlarged and has a marked
acinar pattern (“nutmeg liver”) and edematous gallbladder.
Identification of the plant
Samples of the whole plant were sent for botanical identification to Dr. Eduardo Alonso, Department of Botany, Faculty of
Chemistry, and to Dr. Ana C. González, Herbarium Bernardo
Rosengurtt, Faculty of Agronomy, Montevideo, Uruguay.
Results
Spontaneous cases
Sixty lambs were affected and 54 died 2–7 days after entering the pasture. The first cases were found dead. Later, clinically affected animals showed depression, recumbency, and
moderate to severe edema over the face, ears, and eyelids,
with concurrent jaundice and congestion of the skin, sclera,
and mucous membranes (Fig. 2). Cattle and horses in the
same pasture were not affected.
In severe cases, the swelling involved the submandibular
region and extended down to the throat and upper neck. Most
Clinical signs. In lamb 4 (single dose of 40 g/kg bw), the
heart rate (from 100 ± 17 predosing to 160 beats/min at the
end of dosing), respiratory rate (79 ± 11 to 180 breaths/min),
and rectal temperature (39.9°C ± 0.2°C to 40.9°C) increased
during the administration of the plant (Fig. 4). Clinical signs
were first seen 4–12 h after the end of dosing. The lamb
stopped eating and appeared listless and indifferent to the
environment. Respiratory rate dropped strikingly, and
remained shallow and significantly slower than the predosing level until death at 36 h after ingestion (42 vs. 79 breaths/
min, T = −9.4, p = 0.000, df = 9). By 12–16 h, the lamb
appeared weak but was walking around. At 21–25 h, it was
depressed and reluctant to move, with marked tachycardia
(148–166 beats/min), cyanotic mucous membranes, and mild
bloat. By 30–36 h, the lamb was in sternal recumbency with
the head forward and the chin on the ground, and the heart
rate and rectal temperature began to decline. It had opisthotonos, leg paddling, and muscle twitching, dying just before it
could be euthanized.
Lamb 5 (4 daily doses of 20 g/kg bw) became listless and
partially anorexic 6–8 h after the first dose. The following
morning, the lamb appeared bright and alert, with normal
appetite, but signs worsened and became more apparent after
the second dose. After the third dose, the lamb gradually
developed mild facial and ear edema, reddening of eyelids,
Vernonia poisoning of sheep in Uruguay
Figure 4. Changes in respiratory rate, heart rate, and rectal
temperature in lamb 4 experimentally challenged (time = 0) with
a single dose of 40 g/kg body weight of Vernonia plantaginoides.
Bar = administration period; arrow = sternal recumbency; cross =
death.
Figure 5. Changes in activity of the enzymes AST, ALP, and
GGT in serum from experimental lamb 4 (single dose of 40 g/kg
body weight of Vernonia plantaginoides). Bar = administration
period.
engorged episcleral vessels, and scant serous ocular and nasal
discharge. After the last dose, depression deepened, the heart
rate was elevated, respiration was rapid, there was rumen
atony, and slight abdominal distension was observed; the
lamb remained standing for long periods with the head lowered, or lying down with the head turned against its side,
although it stood when prompted. Rectal temperature was not
altered. The animal was euthanized 24 h after the last dose.
Lamb 6 (3 decreasing doses) had only mild clinical signs.
After the first and second doses, the lamb appeared somewhat
depressed and inappetent, had a respiratory rate of 40–45
breaths/min, moderate hyperthermia (40.4–40.6°C), and
tachycardia (144 beats/min). Appetite was regained by 72 h
395
Figure 6. The cut surface of the liver of lamb 4 has a nutmeg
appearance.
and thereafter appeared clinically normal. It was euthanized
24 h after the last dose.
Serum and urine biochemistry. Figure 5 depicts the changing serum enzyme activities of lamb 4. Predosing activities
of AST, GGT, and ALP were within published reference
intervals: 258 ± 10.2, 50 ± 2, and 290 ± 18 U/L, respectively.16 By 12 h post-dosing, there was a dramatic rise in the
serum activity of AST (1,710 U/L) and GGT (197 U/L),
reaching 9,160 and 345 U/L at 30 h, respectively, when the
lamb was recumbent. Changes in the activity of ALP were
similar to those for AST and GGT, but of lower magnitude,
reaching 7 times (2,840 U/L) the basal activity 6 h before
death. Mild elevation of GGT occurred in lamb 5 at 12–24 h
after each dosing (59–62 U/L), whereas AST (380 U/L)
increased in lamb 6 at 31 h after the first dose (6 h after the
second dose), returning to the pre-dosing activity (141 ± 21
U/L) by 44 h. The urine of lamb 4 was bilirubin positive at 16
h after dosing and strongly positive at 25 and 30 h. Proteinuria was first detected by 16 h (150–1,000 mg/L), whereas
pH dropped markedly from 8 to 5 just before death. In lambs
5 and 6, proteinuria was detected 24 h after initial dosing and
remained positive until death.
Pathology. Macro- and microscopic lesions of the 3 experimental cases were similar to those of the spontaneous cases.
The liver of lamb 4 (40 g/kg) was swollen with rounded edges
and had a marked “nutmeg” appearance; on cut surface, it had
irregular, depressed, bright-red areas that were regularly
intermingled with a network of yellow bulging parenchyma
(Fig. 6). The gallbladder was distended and edematous. There
was mild jaundice, multiple subendocardial and subepicardial
petechial hemorrhages, and a large amount of yellow fluid in
the pericardial sac and less in the pleural and abdominal cavities. Kidneys were pale and moist with a yellow pelvis, and
the lungs had severe congestion and edema, frothy fluid on
cut surface, and dense foam filling the tracheal and bronchial
396
Dutra et al.
Figure 7. Centrilobular hemorrhagic necrosis is observed
around a centrilobular vein (upper right corner) in the liver of lamb
4 (40 g/kg body weight). Hematoxylin and eosin. 100×.
lumens. In lamb 5, the liver was pale and had a slight, barely
visible, red mottled appearance on cut surface. There was
scarce pleural and pericardial serous effusion, and dry content
in the colon and rectum. The only recognized gross abnormality in lamb 6 was a slightly pale liver.
The liver of lamb 4 had severe centrilobular hemorrhagic
necrosis with marked vacuolation of midzonal and periportal
hepatocytes (Fig. 7). In the lung, there was alveolar hyperemia, interstitial and alveolar edema, and discrete air bubbles
in the alveolar lumens. The kidneys had marked hydropic
degeneration of tubular epithelial cells, mainly in the proximal
convoluted tubules, mild interstitial edema, and proteinaceous
fluid in the tubular lumen and Bowman space. Marked microscopic lesions were found in the central nervous system. There
were multiple perivascular hemorrhages in the cerebral cortex,
particularly at the junction of the gray and white matter, and
less frequently in the thalamus, midbrain, medulla oblongata,
and obex. Moderate swelling of astrocytes and dilation of the
pericapillary spaces were evident in the subcortical white matter. No microscopic lesions were found in other organs. In
lamb 5, there was dissociation of hepatic laminae, microhemorrhages around the hepatic venules, vacuolated hepatocytes,
and multiple apoptotic hepatocytes in the periacinar and midzonal zones. There was pulmonary hyperemia and moderate
hydropic degeneration of renal tubules. No significant histologic lesions were found in lamb 6.
Identification of the plant
All of the collected plants were identified as V. plantaginoides
(Less.) Hieron. Voucher specimens are kept in the herbarium
of the Faculty of Chemistry, identified as MVFQ 4381.
Discussion
Clinical signs, gross and histopathology of the liver, and the
presence of young defoliated plants of V. plantaginoides in
the affected paddock strongly suggested intoxication by this
plant. Feeding experiments showed that the plant was hepatotoxic and lethal to lambs, thus confirming that V. plantaginoides was the cause of the spontaneous disease. The
outbreak was short and severe, killing 54 lambs in only 5
days, which is in line with old local stories describing devastating mortalities associated with yuyo moro (V. plantaginoides) in northeastern Uruguay, and alecrim (V. squarrosa) in
southern Brazil.28 The reason why such a historic and severe
disease was not diagnosed and reported earlier is unknown;
possible explanations include the limited access of veterinarians and farmers to a diagnostic laboratory (the East Regional
Laboratory was founded in 1989), the short duration of the
outbreaks, poor monitoring of extensively managed flocks,
and the secondary role of sheep in the farming economy. The
marked decline in sheep numbers and value after the collapse
of the wool price in the 1990s may have also contributed to
the delay in diagnosis.
The present outbreak was epidemiologically and pathologically almost indistinguishable from the poisoning caused
by the South American sawfly P. flavipes. Both diseases
occur as a point epidemic with many animals found dead
within a few days, while clinical signs of jaundice and photosensitization appear late in the outbreak, and the main
autopsy finding is a “nutmeg liver” due to severe, diffuse,
centrilobular hepatocellular necrosis.10,26 Furthermore, the
present outbreak was diagnosed in a county with a highly
significant geographical clustering of sawfly poisoning in
Uruguay (Dutra F, et al. Descriptive statistics and spatiotemporal analysis of bovine hepatotoxic diseases diagnosed in
Uruguay. Proceedings of the 8th International Symposium
on Poisoning Plants, 2009 May 4–8, João Pessoa, Paraíba,
Brazil), which can be explained by the fact that V. plantaginoides and P. flavipes larvae coexist on the same hilly grassland ecosystem of northeastern Uruguay and southern
Brazil.22,23 Although the present outbreak occurred in late
summer to early autumn and sawfly poisoning occurs mostly
in winter (June–September),10 both diseases may overlap in
time because cases of P. flavipes poisoning can occur in early
autumn10 and V. plantaginoides (V. squarrosa) poisoning is
traditionally reported in August–November during shearing.28 Thus, differential diagnosis between these diseases
must rest on a careful postmortem examination, looking for
chitinous fragments and larval heads with typical sensory
hairs in the ruminal content24 and, harder to notice, lymphocytolysis in the spleen and other lymphoid organs, which is
widespread in sawfly poisoning10,26 and minimal or absent in
V. plantaginoides. Hepatogenous photosensitization in sheep
grazing plants containing lithogenic saponins produces
rather similar clinical signs (“yellow big head”) both in eastern Uruguay (Heliotropium ocellatum, unpublished data)
and southern Brazil (Brachiaria spp.),21 but this possibility
was ruled out by the microscopic absence of crystalloid
material in the liver and bile ducts. There were no Cestrum
parqui, Wedelia glauca, Xanthium spp., or other common
397
Vernonia poisoning of sheep in Uruguay
local hepatotoxic plants in the affected paddock; nor did the
lambs have access to clover pastures or any other type of
feed, ruling out chronic copper poisoning.
An important factor in the outbreak reported herein was
the access of hungry or stressed and recently weaned lambs
to an area of the paddock where large amounts of V. plantaginoides were sprouting. In those conditions, they ate large
quantities of young plants in a short period of time. It would
appear that V. plantaginoides is harmful at a certain stage of
growth and that certain climatic and management factors are
necessary for the disease to occur. It is apparently consumed
by sheep only when fleshy, basal leaves are developing, and
becomes rapidly unpalatable when it is growing or is fully
grown and fibrous leaves and stems predominate. This is
supported by the characteristic experience that the disease
stops spontaneously after a few days or weeks, and also suggests that it would be a good practice to avoid grazing for a
time (e.g., 15–30 days) or to move sheep to another pasture
as soon as the disease appears. In the present outbreak, only
sheep were affected despite cattle also grazing in the same
paddock when the disease occurred. This difference in susceptibility could be caused by different grazing behavior,
because cattle—in contrast to sheep—tend to avoid the steep
or hilly areas where V. plantaginoides predominates, or prefer different plants in the pasture or, more likely, because
cattle have a greater and more variable threshold level of toxicity than sheep.28 Thus, both species may be at risk, and
although the plant is quite bitter tasting and typically is not
eaten except under dire circumstances, sheep are most likely
to eat the sprouting plants and are at greatest risk.
The experimental toxic dose of V. plantaginoides in the
present study was relatively high, in line with a previous
report.28 A single dose of 40 g/kg was lethal in 36 h, whereas
35 g/kg or 20 g/kg bw were found to be poisonous after the
first administration, but not lethal even when administered
for 3 or 4 consecutive days, suggesting a noncumulative
effect of the plant. Thus, large quantities of plants sprouting
at once are necessary to attain toxic levels in the invaded
pasture in addition to hungry or naive animals and a high
stocking rate in order for the outbreak to occur. In contrast,
other closely related hepatotoxic plants, such as V. rubricaulis4 and V. mollissima,13 are lethal to cattle and sheep in single doses of only 2–10 g/kg and 10–20 g/kg bw, respectively.
The toxic compound of V. plantaginoides is unknown.
Phytochemical investigations of Vernonia spp., both in
America and Africa, have resulted in the isolation of numerous classes of cytotoxic sesquiterpene lactones with potent
biological activities.18,30 Glaucolides, hirsutinolide derivatives, and related sesquiterpene lactones have been isolated
from South American poisonous V. nudiflora and V. mollissima.3,6 However, despite the hundreds of terpenoids isolated
from the Vernonia genus, only a limited number have been
tested for toxicity, and it is not certain which phytochemical
is responsible for the hepatotoxic effects. There are reports of
hepatotoxicity in mice by alcohol extracts of V. amigdalina,14
and in rats by extracts of V. colorata.15 In contrast, the terpenoid fraction of the plants also seems to be hepatoprotective
and is able to reduce acetaminophen- and carbon tetrachloride–induced hepatotoxicity in rats.2,11 However, it has been
shown in rats that the hepatic enzymes significantly increase
in a time- and dose-dependent manner in both the low- and
high-dose groups when compared with the control group.19
This seems to indicate that when consumed in large quantities, the plants may indeed elicit hepatotoxicity, as occurred
in the present outbreak.
Acknowledgments
We thank students Juan Martín Da Fonseca, Alejandro Costa, and
Ignacio Paiva for assistance with experimental animals; Eduardo
Alonso and Ana C. González for confirmation of the Vernonia plantaginoides species; Dr. Franklin Riet-Correa for reviewing the manuscript; and Dr. Analia Rodriguez for the biochemical analysis of
serum samples.
Authors’ contributions
F Dutra contributed to design of the study; contributed to analysis and
interpretation of data; drafted the manuscript; and critically revised the
manuscript. A Romero and C Quinteros contributed to design of the
study; contributed to acquisition and analysis of data; and critically
revised the manuscript. R Araújo contributed to conception of the study,
and contributed to acquisition and analysis of data. C García y Santos
contributed to design of the study; contributed to analysis and interpretation of data; drafted the manuscript; and critically revised the manuscript. F Dutra, A Romero, C Quinteros, and C García y Santos agreed
to be accountable for all aspects of the work in ensuring that questions
relating to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All authors gave final approval.
Sources and manufacturers
a. Urine Strip 10, Wiener Laboratories, Rosario, Argentina.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
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