Received: 23/09/2024 Accepted: 04/11/2024 Published: 21/01/2025 1 of 11
https://doi.org/10.52973/rcfcv-e35522 Revista Cientíca, FCV-LUZ / Vol. XXXV
ABSTRACT
Tick paralysis is a rapidly progressing motor paralysis caused by a
neurotoxin in the saliva of certain tick species. Delayed diagnosis
can lead to increased mortality due to respiratory failure. Thus,
the aim of this study is to describe thoracic ultrasonography
lesions in dogs with tick paralysis and to identify potential
patterns that could aid in diagnosis and prognosis prediction.
The animal material consisted of 58 dogs in total, 10 of which
were healthy and 48 of which were suspected to be affected by
tick paralysis. Clinical, laboratory and thoracic ultrasonographic
examinations were performed. Expiratory dyspnea with sinus
tachycardia; ne crackles, polyphonic wheezing, and pleural rub
on lung auscultation were observed in the tick–paralyzed dogs.
The most common abnormal thoracic ultrasonography patterns
were, in order of prevalence: B–lines > 3, wet lung, pulmonary
nodule, confluent B–lines, loss of A–lines, consolidation, brosis,
and isolated B–lines. In addition, the pleural thickness of the
tick–paralyzed dogs was higher than that of the healthy ones.
Among these ndings, B–lines > 3 were interpreted as indicative of
possible pulmonary parenchymal damage, while the loss of A–lines
was attributed to decreased aeration. The presence of pulmonary
nodule and fibrosis might be due to bronchopneumonia and
aspiration pneumonia due to regurgitation. The wet lung pattern
was associated with a predisposition to lung congestion. It was
concluded that recognizing thoracic ultrasonography ndings may
assist in identifying the presence and grading the extent of lung
damage, as well as determining the necessity of lung decongestion
treatment in tick paralysis cases.
Key words: B–lines; dog; pleural thickness; wet lung; thoracic
ultrasonography
RESUMEN
La parálisis por garrapatas es una parálisis motora de rápida
progresión causada por una neurotoxina en la saliva de ciertas
especies de garrapatas. Un diagnóstico tardío puede llevar a un
aumento en la mortalidad debido a insuciencia respiratoria.
Por lo tanto, el objetivo de este estudio fue describir las lesiones
detectadas mediante ecografía torácica en perros con parálisis
por garrapatas e identicar patrones potenciales que puedan
ayudar en el diagnóstico y la predicción del pronóstico. El material
animal consistió en un total de 58 perros, 10 de los cuales estaban
sanos y 48 se sospechaba que estaban afectados por parálisis
por garrapatas. Se realizaron exámenes clínicos, de laboratorio
y ecográficos torácicos. Se observó disnea espiratoria con
taquicardia sinusal; estertores nos, sibilancias polifónicas y roce
pleural en la auscultación pulmonar de los perros paralizados por
garrapatas. Los patrones anormales más comunes en la ecografía
torácica fueron, en orden de prevalencia: líneas B > 3, pulmón
húmedo, nódulo pulmonar, líneas B confluyentes, pérdida de
líneas A, consolidación, brosis y líneas B aisladas. Además, el
grosor pleural de los perros con parálisis por garrapatas fue mayor
que el de los sanos. Entre estos hallazgos, las líneas B > 3 se
interpretaron como indicativas de posible daño parenquimatoso
pulmonar, mientras que la pérdida de líneas A se atribuyó a una
disminución de la aireación. La presencia de nódulo pulmonar
y brosis podría deberse a bronconeumonía y neumonía por
aspiración debido a regurgitación. El patrón de pulmón húmedo
se asoció con una predisposición a la congestión pulmonar. Se
concluyó que el reconocimiento de los hallazgos ecográcos
torácicos puede ayudar a identicar la presencia y a clasicar la
extensión del daño pulmonar, así como a determinar la necesidad
de tratamiento de descongestión pulmonar en casos de parálisis
por garrapatas.
Palabras clave: Líneas B; perro; grosor pleural; pulmón húmedo;
ecografía torácica
Ultrasonographic evaluation of the thorax in dogs with tick paralysis
Evaluación ecográfıca del tórax en perros con parálisis por garrapatas
Erdem Gülersoy* , Canberk Balıkçı , İsmail Günal , Adem Şahan , Esma Kısmet
Harran University, Veterinary Faculty, Department of Internal Medicine. Şanlıurfa, Türkiye.
*Corresponding author: egulersoy@harran.edu.tr
Thoracic ultrasonography of tick-paralyzed dogs / Gülersoy et al._____________________________________________________________________
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INTRODUCTION
Tick paralysis, a case of acute flaccid paralysis characterized by
vomiting, regurgitation and sudden onset of lower motor neuron
weakness and respiratory failure in severe cases, is a signicant
veterinary problem in certain parts of the world [1].
A wide variety
of domestic animals are affected, including horses, cattle, dogs,
cats, sheep, and poultry [2].
After attaching to the host, ticks
typically undergo a latent period of 3-6 days (d), during which they
engorge and their salivary glands enlarge, producing a neurotoxin.
Paralysis signs usually result from the engorgement of a single
tick, although multiple ticks may also contribute, and occasionally,
no tick is found [3]. Early clinical signs typically include hind limb
ataxia, which often progresses to quadriplegia [4].
In addition to
the non–specic clinical ndings observed in tick paralysis cases,
mortality rates can reach up to 100% in untreated cases due to
complications involving the cardiovascular, gastrointestinal, and
respiratory systems. The major clinical abnormality and cause of
mortality in tick paralysis cases is respiratory failure [5]. Current
hypotheses explaining the development of respiratory failure
in tick paralysis involve neuromuscular blockade of respiratory
muscles, potentially leading to hypoventilation. This effect may
be exacerbated by central respiratory depression. Additionally,
paralysis of the pharynx and larynx can result in upper airway
obstruction, while pulmonary parenchymal disease may also
contribute [6]. Pulmonary parenchymal disease in tick paralysis
is commonly linked to cardiogenic pulmonary edema resulting
from the tick’s salivary toxin. Aspiration pneumonia is a common
complication in patients with tick paralysis–related lung disease. It
is related to dysfunction of the esophagus, pharynx, and larynx, all of
which are frequently observed in patients with tick paralysis [2, 7].
During the last decade, thoracic ultrasonography has seen
increased use as both a diagnostic and monitoring tool. Previous
descriptions have detailed the identication of lung consolidations
on thoracic ultrasonography, characterized by either a tissue sign
involving the full width of the lung lobe or a shred sign affecting part
of the lung lobe’s width, along with an increased number of B–lines
and the presence of pleural effusion [8, 9]. In Veterinary Medicine,
point–of–care (POC) thoracic ultrasonography has been used to
identify pulmonary hemorrhage, congestive heart failure, and
alternative causes of alveolar–interstitial syndrome [10].
Thoracic
ultrasonography has shown promising diagnostic performance in
critically ill patients experiencing respiratory failure from various
causes. It was reported that it offers more valuable clinical insights
compared to physical examination and bedside radiography [11,
12]. Nevertheless, there is currently no study examining thoracic
ultrasonography ndings in dogs with acute flaccid paralysis due
to tick paralysis.
Discerning the primary pathological processes is essential for guiding
treatment and determining prognosis for patients. Managing clinical
cases related to pulmonary disease poses signicant challenges for
veterinarians and often carries a poor prognosis. Therefore, early
recognition of pulmonary edema and parenchymal disease is crucial
for improving survival rates. Considering that the leading cause of
mortality in tick paralysis cases are respiratory abnormalities such as
pulmonary edema, aspiration pneumonia and respiratory failure, the
purpose of this study is to describe thoracic ultrasonography lesions
in dogs with tick paralysis and to identify patterns that may aid in
diagnosis, treatment planning, and prognosis prediction.
MATERIALS AND METHODS
This study received approval from the Local Ethics Committee
for Animal Experiments at Harran University on 09/05/2022 with
session 2022/003 and decision number 01-06. All animal owners
gave their consent for participation in the study.
Animals
The Patient group for this study consisted of 48 dogs (Canis
lupus familiaris), each displaying symptoms indicative of acute
flaccid paralysis, including anorexia, regurgitation, ataxia, abnormal
vocalization, and weakness in standing, and all were found to have
ticks upon examination. The Healthy group comprised 10 clinically
healthy dogs admitted for vaccination and/or check–up purposes.
All animals were admitted to the animal hospital of Veterinary
Faculty, Harran University.
Inclusion/Exclusion Criteria and Forming Groups
The inclusion criteria for the tick–paralyzed dogs required that
dogs have no history of prior diseases other than tick paralysis—
including respiratory, cardiovascular, or gastrointestinal disorders
that could cause vomiting, diarrhea, anorexia, labored breathing,
or rapid fatigability—have not been treated with antiparasitic
medication within the past month, and exhibit signs of acute
flaccid paralysis. The accepted clinical ndings for acute flaccid
paralysis include sudden onset weakness that intensies within
a few days, characterized by weakness in respiratory muscles
and swallowing ability. Additionally, there is typically an absence
of spasticity, hyperreflexia, clonus, extensor plantar reflexes,
and muscle contraction due to impairment of motor pathways
extending from the cortex to muscle bers [13].
The primary differential diagnosis for the clinical manifestations
observed in the dogs included in the study and suspected
of tick paralysis involved considering common lower motor
neuron conditions in dogs, including botulism, acute idiopathic
polyneuropathy, and snake envenomation [14]. In summary,
botulism can occur in dogs following the consumption of rotten food
or carcasses; however, this was not the case for the dogs described
here, as they are solely fed commercial dry dog food. Clinically, it
is marked by difculties in grasping and swallowing food, along
with drooling. Acute idiopathic polyneuropathy has been observed
in dogs that have come into contact with raccoon saliva or have a
history of systemic illness. It is characterized by hyperesthesia and
neurogenic muscle atrophy enduring for over ve to seven days [3,
14]. Although acute idiopathic polyradiculoneuritis can involve the
cranial nerves and result in partial or complete respiratory paralysis
due to the involvement of intercostal or phrenic nerves, the majority
of clinical symptoms are usually limited to the limbs [15]. Typically,
the respiratory pattern in the neuromuscular paralysis conditions
mentioned is rapid and shallow. In contrast, the present cases
exhibited a slow respiratory pattern with a notable expiratory
effort, resembling what is seen in tick paralysis [3]. Myopathy
was also excluded, as it is manifests as proximal weakness or
fatigue, preserved sensitivity, and followed by a loss of reflexes,
typically following signicant atrophy [16]. While the neurological
manifestations discussed here share similarities with those of
other lower motor neuron diseases, they closely resemble the
ndings typically associated with tick paralysis [17], the cases
Thoracic ultrasonography of tick-paralyzed dogs / Gülersoy et al._____________________________________________________________________
_________________________________________________________________________________________________Revista Cientica, FCV-LUZ / Vol.XXXV
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were validated by the quick improvement (median: 26 hours (h),
min: 16 h, max: 35 h) observed after acaricidal treatment and
tick removal [14]. Hence, the neurological symptoms described
here were differentiated from other common causes of lower
motor neuron diseases that mimic tick paralysis. Dogs that did not
exhibit this clinical presentation were excluded from the study.
Also, dogs exhibiting signs of acute flaccid paralysis but with no
ticks detected, those with a different etiology determined based
on medical history, clinical evaluation, and laboratory tests, and
those affected by other neurological diseases in dogs (such as
spinal cord pressure, epidural abscesses, and exposure to toxic
plants or snakes) were also excluded from the study. Moreover, 8
dogs were excluded from the study because they did not improve
clinically despite acaricidal treatment and tick removal.
Consequently, dogs diagnosed with tick paralysis due to
Rhipicephalus sanguineus (each collected tick was stored in separate
vials and identied at the species level through morphological
analysis) were conrmed through the ex juvantibus method [2, 7,
14], were included in the Patient group (n: 40). Dogs that did not
have any history of disease and were deemed to be healthy as a
result of physical, laboratory, radiographic and ultrasonographic
examinations were included in the Healthy group (n: 10).
Physical Examinations
Heart and respiratory rates, body temperature, heart and lung
auscultation (using Littmann classic III stethoscope, 3M Health,
Minnesota, USA), palpable lymph nodes and gingival capillary
rell times (CRT) of all dogs were evaluated. Additionally, the
body weight (using a digital veterinary scale, Lider Terazi, İstanbul,
Türkiye) and body surface area (BSA) using the formula K × (body
weight in grams
2/3
) × 10
-4
, K = constant (10.1 for dogs) of each dog
were calculated. The presence of ticks was assessed by manually
counting them on various anatomical body parts including the head,
ears, chest–neck, thorax, abdomen, front and hind legs, interdigital
areas, axilla and tail, and the number of ticks was recorded.
Laboratory Examinations
Venous blood samples (5-10 mL) were drawn from all dogs
via cephalic vein puncture, ensuring minimal stress. Complete
blood count (CBC) was performed from blood samples which
were transferred to Ethylenediaminetetraacetic acid (EDTA) tubes
within 15 min (using and autoanalyzer, Sysmex pocH-100i, Japan).
Within the scope of CBC, leukocyte count, lymphocyte count,
granulocyte count, monocyte count, red blood cell count (RBC),
mean corpuscular volume (MCV), hematocrit, mean corpuscular
hemoglobin (MCH), mean corpuscular hemoglobin concentration
(MCHC), red cell distribution width (RDW) and hemoglobin were
evaluated. The leftover sample was used for microscopic blood
smear examinations, which included blood and buffy coat smears
for Anaplasma platys, Ehrlichia canis, Babesia spp., and Hepatozoon
canis. Each smear was examined using a light microscope (with
Diff–quik staining and oil immersion, 1000x magnication, Olympus
2-U050H2 light microscope, Tokyo, Japan).
Thoracic radiography
To investigate the presence of any concomitant disorders, such
as cardiomegaly, masses, pneumothorax, or effusions, thoracic
radiographs were performed as part of the inclusion/exclusion
criteria verification. Each thoracic radiographic examination
included three projections: right and left lateral images, as well
as both ventrodorsal (VD) and dorsoventral (DV) images, using
the Fujilm Veterinary CR X–ray System, Prima II, Tokyo, Japan.
Thoracic ultrasonography
Thoracic ultrasonographic examinations were conducted on all
dogs of the present study. The examinations were performed with
the dogs in a standing or sternal position, using a microconvex
probe (5-8 MHz, 6C2P transducer, Mindray Z60, Shenzhen, China).
Prior to the examination, an appropriate amount of alcohol and/
or gel was applied to the area without shaving it. All animals were
assessed with a single portable ultrasound machine (Mindray Z60,
Shenzhen, China), and the depth was adjusted to suit the clinician’s
preferences for each individual animal. To visualize the gator sign,
which includes the pleural line and two ribs, the transducer was
placed in a transverse position relative to the ribs. Four regions
were examined on each thoracic side (caudodorsal, perihilar,
middle, and cranial) with one scan for each region [18]. The
presence of A–lines accompanied by lung sliding was interpreted
as indicative of a normally aerated lung. B–lines were used to
recognize interstitial–alveolar edema. The occurrence of B–lines
was classied according to a 5-point scale. The shred sign indicates
partial lung consolidation, characterized by a deeper border of
consolidated lung tissue that appears shredded and irregular where
it connects with the aerated lung. The tissue–like sign manifests
when lung tissue resembles that of the liver, which is caused by
translobar consolidation. The pulmonary nodule sign indicates a
well–circumscribed area fully enveloped by aerated lung. B–lines
project from the distal border of each consolidation type downward
on the screen. According to earlier studies in human medicine,
additional ultrasound abnormalities were described, including the
shred sign, tissue–like sign, and nodule sign [19, 20].
Statistical analysis
Data analysis was conducted with SPSS 25.00 (SPSS for Windows®)
statistical software, employing the one–sample Kolmogorov–
Smirnov test to assess whether the data were parametric or
non–parametric. Non–parametric data were evaluated as median
(min, max) using Mann–Whitney U, Kruskal–Wallis test. Statistical
signicance was regarded as P<0.05.
RESULTS AND DISCUSSION
Animals
All dogs included in the study were owned and fed commercial
dry dog food. It was learned that the dogs of the Patient group
were outdoor (31; 77.5%) or were taken outside twice a day for
the toilet (9; 22.5%). 22 were male, 18 were female and the
majority were mixbreed. The Healthy group comprised 4 male
and 6 female mixed–breed dogs. Anamnestic data revealed that all
dogs included in the study had no previous history of disease. Some
had been vaccinated once (16; 40%), some twice (11; 27.5%), and
the remaining dogs had not been vaccinated at all (13; 32.5%).
Thoracic ultrasonography of tick-paralyzed dogs / Gülersoy et al._____________________________________________________________________
4 of 11 5 of 11
TABLE I
Physical examination ndings
Parameters
Patient group, n:40
median (min–max)
Healthy group, n:10
median (min–max)
P–value
Body weight (kg) 7.3 (6-17.1) 9.45 (4.2-16.7) 0.3510
BSA (m
2
) 0.37 (0.25-0.67) 0.45 (0.25-0.64) 0.4620
Heart rate (beats/min) 101.5 (68-144) 78 (65-96) 0.0001
Body temperature (°C) 39.1 (36.6-40) 38.1 (37.7-38.5) 0.0001
Respiratory rate
(breaths/min)
82 (44-99) 35 (24-46) 0.0001
CRT (sec) 3 (2-4) 3 (2-3) 0.0640
BSA: Body surface area, using the formula K × (body weight in grams
2/3
) × 10
-4
, K = constant
(10.1 for dogs). CRT: Capillary rell time
TABLE II
Complete Blood Count ndings
Parameters
Patient group, n:40
median (min–max)
Healthy group, n:10
median (min–max)
P–value
Leukocyte (×10
9
·L
-1
) 11.01 (5.58-18.5) 12.28 (6.12-15.17) 0.7040
Lymphocyte (×10
9
·L
-1
) 3.82 (1.37-7.09) 2.77 (1.8-7.4) 0.6470
Monocyte (×10
9
·L
-1
) 1.25 (0.1-3.16) 1.6 (0.29-3.3) 0.5110
Granulocyte (×10
9
·L
-1
) 5.78 (1.33-13.4) 4.32 (2.92-12.74) 0.7330
Erythrocyte (×10
9
·L
-1
) 6.84 (5.13-8.83) 7.25 (5.99-8.16) 0.1580
MCV (fL) 65.35 (56-71.2) 67.1 (54.5-79.3) 0.3460
Hematocrit (%) 44.45 (34-60) 47.5 (37-61) 0.3720
MCH (pg) 22.12 (17.7-25.11) 20.5 (17.5-24) 0.1770
MCHC (g·L
-1
) 31.35 (26.9-39.42) 29.5 (28.9-33.4) 0.1470
RDW (fL) 10.45 (8.26-14) 11 (9.7-14.8) 0.2720
Hemoglobin (g·dL
-1
) 14.9 (11.2-19.7) 14.9 (10.7-18.2) 0.8760
MCV: Mean corpuscular volume, MCH: Mean corpuscular hemoglobin, MCHC: Mean
corpuscular hemoglobin concentration, RDW: Erythrocyte distribution width
Lung slide Gator sign A lines Z lines
0
10
20
30
40
50
60
70
80
90
100
110
Dogs (%)
Thoracic ultrasonographic examination findings in Healthy dogs
5
5
5
8
12
15
15
15
20
Isolated B-line
Fibrosis
Consolidate
Loss of A-line
Confluent B-line
Thick pleura
Pulmonary nodule
Wet lung
B-lines >3
0 5 10 15 20
Abnormal findings in Patient group
(%)
FIGURE 1. Distribution of thoracic ultrasonographic ndings in the Healthy (A)
and Patient (B) groups
A
B
Physical Examinations
The symptom duration of the tick–paralyzed dogs was 6 (4-11)d.
The majority of the detected ticks {median: 39 (13-110)} were on
the head, ears, chest–neck and less commonly on the tail base,
respectively. The most common ndings reported by the owners
were difculty standing (20; 50%) and ataxia (13; 32.5%). No
abnormalities in terms of temperature, pain, or swelling were
detected in the palpable lymph nodes of dogs with tick paralysis.
Conjunctival mucosa was normal in color. Expiratory dyspnea was
evident in the dogs of the Patient group (30; 70%). Fine crackle (14,
35%), polyphonic wheezing (10; 26%) and pleural rub (16; 40%)
were determined as the most common abnormal sounds in lung
auscultation. Auscultation of the heart revealed no abnormalities
other than sinus tachycardia (26; 65%). Additionally, during the
clinical examination, more ticks were removed from the dogs,
and all were treated with a spot–on formulation containing 10%
Fipronil and 9% (S)–Methoprene (Frontline Combo, Merial S.A.S.,
France). Rectal body temperature and respiratory and heart rates
were higher in the Patient group dogs than in the Healthy group
dogs (P<0.0001). Physical examination ndings are presented in
Supplementary le (TABLE I).
Complete blood count
The CBC analysis revealed no statistical difference in the
comparison of the investigated parameters between the two groups.
CBC ndings are presented in Supplementary le (TABLE II).
Thoracic ultrasonography
As a result of the thoracic ultrasonographic examination of
healthy dogs, lung slide, the gator sign, and A–lines were observed
in all dogs (10, 100%). In addition to A lines in the Healthy group,
Z lines were also detected in 3 dogs (30%). The distribution
of thoracic ultrasonographic ndings for the Healthy group is
presented in FIG. 1A, and thoracic ultrasonographic images
are presented in FIGS. 2, 3, 4 and 5. Thoracic ultrasonographic
examination of the Patient group revealed that the most common
abnormal ndings were B–lines > 3 (8, 20%), wet lung (6, 15%),
pulmonary nodule (6; 15%), thick pleura (6; 15%), confluent B–
line (5; 12%), loss of A–line (3; 8%), consolidate (2; 5%), brosis
Thoracic ultrasonography of tick-paralyzed dogs / Gülersoy et al._____________________________________________________________________
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FIGURE 2. Gator sign. The rounded rib heads resemble eyes (blue arrows), and
the pulmonary–pleural interface looks like the bridge of a nose (yellow arrow),
as if a partially submerged alligator is peering at the sonographer
(2;5%) and isolated B–line (2; 5%). In addition, the pleural
thickness of the tick–paralyzed dogs (median: 0.18 cm, minimum:
0.10, maximum: 0.24) was higher than that of the healthy ones
(median: 0.10 cm, minimum: 0.08, maximum: 0.13) (P<0.0001).
Distribution of thoracic ultrasonographic ndings of dogs with tick
paralysis are presented in FIG. 1B and thoracic ultrasonographic
images are presented in FIGS. 6 to14.
Thoracic ultrasonography is a valuable and accessible diagnostic
tool for assessing lower respiratory tract pathologies. Utilizing this
technique is advisable in suspected cases of cardiogenic pulmonary
edema, consolidation, atelectasis, embolism, neoplasia, pneumonia,
pneumothorax, and interstitial lung diseases, particularly those with
brosis. It is also benecial for evaluating other lower respiratory
tract signs, including dyspnea, pleural pain, fluid accumulation, and
acute cough. This method is relatively inexpensive, non–ionizing,
portable, and widely available. Moreover, it does not necessitate
anesthesia or uncomfortable patient positioning, which is very
important in critical care settings [19]. While respiratory failure
was previously attributed solely to hypoventilation resulting from
neuromuscular paralysis, recent pathogenesis studies in dogs
affected by tick paralysis have highlighted the involvement of
parenchymal disease and pulmonary edema. These ndings suggest
that hypoxemia may independently contribute to respiratory
compromise in affected dogs. In cases of tick envenomation,
respiratory decline is unique in that it may occur through one of
two independent pathways: neuromuscular weakness (resulting
in hypoventilation) or pulmonary disease (leading to hypoxemia)
[5, 21]. As such, identifying the underlying pathophysiological
process contributing to respiratory compromise in patients with
tick paralysis can be crucial for determining tailored interventions
and supportive treatments for each individual [22]. Therefore, the
abnormal thoracic ultrasonography patterns detected in the present
study, such as B–lines > 3, loss of A–lines, wet lung, and pulmonary
nodule, may contribute to the development of individualized
treatment protocols for dogs suffering from tick paralysis.
Comprising skin, subcutaneous fat, and muscle layers, the chest
wall shows alternating patterns of hyper – and hypoechogenicity
in the near eld, immediately below the transducer. The parietal
pleura lining the thoracic wall may not be distinctly visible; however,
in a healthy dog, the visceral pleura and lung surface create
a continuous echogenic line. Differentiation of the two pleural
interfaces is possible through the gliding sign, with the hyperechoic
pleuropulmonary interface gliding smoothly against the parietal
pleura of the chest wall during breathing [23]. This sign is absent in
conditions where the two pleural layers are not in contact with each
other, such as in pneumothorax or pleural effusion. Correspondingly,
it is not detected when the pleura are closely adhered to each other,
as seen in pneumonia complicated by adhesions, pleurodesis, or
in situations of absent respiration [24, 25].
Previous reports indicate that in animals affected by tick
intoxication, the prevalence of fibrin, hemorrhage, and high–
protein edema fluid in fatal tick paralysis strongly suggests either
an inflammatory reaction or direct toxin effects on endothelial cells
or type I pneumocytes. Such effects could contribute to greater
vascular damage or enhanced permeability [22]. Lung slide was
observed in all dogs included in the present study, both those
affected by tick paralysis and those that were healthy. This nding
may be attributed to the non–infectious nature of tick paralysis, as
opposed to disorders where lung slide is absent due to their etiology
[26]. However, since acute lung injury may develop in dogs with tick
paralysis, it may be important to investigate physiological patterns
such as lung slide in evaluating the second phase of the inflammatory
reaction, taking into account the duration of symptoms. In addition,
alterations in the initial phase of the acute phase response that
result in either exuberant or diminished brin deposition may
give rise to early complications during convalescence, such as
bleeding, thrombosis, systemic inflammatory response syndrome,
or infection [27]. Therefore, the absence of normal ndings on
thoracic ultrasonography may convey critical clinical information
regarding prognosis.
Normal lung tissue beneath the visceral pleural interface is
obscured by shadowing and reverberation artifacts. Ribs appear
bilaterally adjacent to the pleura, displaying smooth curvilinear
echogenic interfaces with acoustic shadowing forming the gator
sign (FIG. 2). These ribs are visualized at regular intervals while
scanning the chest wall [28]. As reverberation artifacts, A–lines
show up as horizontal, parallel lines at equal distances from one
another. These lines are frequently observed in healthy individuals
and indicate the presence of air or gas beneath the pleura. This
air reflects ultrasound waves back to the probe, causing a back–
and–forth movement of waves between the transducer and the air
beneath the pleura (FIG. 3), thereby producing this artifact [25].
A–lines may be erased by B–lines or enhanced in the presence
of pneumothorax [29]. False B–lines, such as Z–lines, appear
perpendicular to the pleural line and can be confused with true
B–lines. These lines, which are vertical and bundle–like in shape,
originate from the pleural line. However, they are typically ill–
dened, do not erase A–lines, and are not perfectly synchronous
with respiratory movements [30]. Thoracic ultrasonography
ndings such as A–lines, Z–lines, and gator signs of the healthy
dogs of the present study (FIGS. 4 and 5) were consistent with
previously reported ultrasonographic ndings of normal lung and
were related to the air below the pleural line and the reflection of
this air to ultrasound waves [31]. Previous studies have reported
pulmonary parenchymal changes such as alveolar oedema,
Thoracic ultrasonography of tick-paralyzed dogs / Gülersoy et al._____________________________________________________________________
6 of 11 7 of 11
FIGURE 3. Lung slide. A back–and–forth movement of the visceral pleura in
contact with the parietal pleura (yellow asteriks) is described as a shimmering
or twinkling of the pleural line
FIGURE 6. Loss of A–lines. Loss of A–lines indicating decreased or absence of
aeration due to acute lung injury in the present case
FIGURE 5. Z–lines. Vertical, bundle–like shaped lines emerging from the pleural
line (blue arrows); however, these are not well dened, do not erase A–lines,
and are not fully synchronized with respiratory movements
FIGURE 4. A–lines. Reverberation artifacts (blue arrows) that appear as
horizontal, parallel lines equidistant from each other
interstitial and alveolar congestion, and alveolar brin exudation
in dogs with tick paralysis [22]. For this reason, the loss of A–lines
determined in the dogs with tick paralysis (FIG. 6) may be related to
the decrease in lung aeration resulting from parenchymal changes
[32]. In addition, while areas with poor ventilation can be used to
predict the development of atelectasis, it can also be interpreted
as serving as a buffer zone between areas where ventilation is
reduced and lung tissue collapses [33]. Thus, investigating the
loss of A–line pattern may have prognostic importance in dogs
with tick paralysis.
Unlike A–lines, B–lines are observed in interstitial–alveolar
edema. They result from the repeated oscillation of ultrasound
beams between air and fluid, producing a long, vertical hyperechoic
artifact that starts at the pleural line and extends downward on the
screen, moving in harmony with the pleural line during respiration
[34]. The occurrence of these lines is attributed to small fluid
accumulations in lung tissue, surrounded by air, creating a high
impedance gradient. Both the number and width of these lines
are related to the severity of the pathology. However, B–lines
alone are inadequate for making a denitive diagnosis, as they
indicate interstitial–alveolar fluid that can occur in both non–
cardiogenic and cardiogenic pulmonary edema, as well as in
conditions such as ARDS, pulmonary hemorrhage of various
origins, pneumonia, lung contusion, neoplastic lung metastasis, or
pulmonary brosis [35]. Assessing the number of B–lines is crucial,
as an increase in lines during follow–up examinations indicates
disease progression, while a decrease suggests that the treatment
is effective. A single B–line may be physiological, however more
indicate lung pathology [36]. In previous studies, a progressive
reduction in respiratory rate and increase in inspiratory effort,
hypoxaemia, marked hypercapnia, congestion and edema of the
lung parenchyma and aspiration pneumonia were determined in
dogs with tick paralysis [5, 14]. Findings such as confluent B–lines
(FIG. 7) and pulmonary nodule (FIG. 8), as well as the observation
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FIGURE 8. Pulmonary nodule. Yellow arrow(s) indicating a slightly hyperechoic
pulmonary nodule with a regular rounded shape and well–dened margins
(magnied thumbnail in the corner)
FIGURE 10. Consolidated lung area. A medium–sized area of consolidation,
accompanied by minimal pleural eusion (yellow arrow), is dened by hypoechoic
hepatized tissue (blue arrow). Within the consolidation, hyperechoic punctiform
areas are observed and interpreted as air bronchograms (white arrow)
FIGURE 7. Conuent B–lines. B–lines are fused with each other, occupying more
than 50% of the image, dened as conuent B–lines (yellow arrow), indicating
severe pulmonary edema.
FIGURE 9. B–lines. Scattered B–lines (blue arrows), characterized by laser–like,
vertical echogenic lines arising from the thickened irregular pleural line (yellow
arrow) and extending to the bottom of the image, indicating pneumonia
of B–lines > 3 (FIG.9), may result from aspiration pneumonia
and brin exudation [22], especially in tick–paralyzed dogs with
megaesophagus and/or prominent crackling sounds on lung
auscultation in the present study.
B–lines can be found not only in cardiogenic pulmonary edema
but also in other types of non–cardiogenic inflammatory pulmonary
edema, such as acute respiratory distress syndrome (ARDS). The
distribution pattern of B–lines is instrumental in differentiating
between cardiogenic pulmonary edema and ARDS: cardiogenic
edema commonly shows a base–apex gradient, while ARDS
tends to have an irregular and heterogeneous distribution [37].
In cases of chronic brosing interstitial diseases, key signs involve
the presence of B–lines displaying particular features: a non–
homogeneous distribution (dependent on the underlying pathology)
and an irregularly thickened pleural line, often disrupted by small
subpleural consolidations (FIG. 10), and B–lines that are thicker
and more irregular (FIG. 11) compared to those found in cardiogenic
pulmonary edema [38]. Thus, when evaluating the characteristics
of the B–lines in the present study, the abnormal thoracic patterns
can be considered to originate from the pulmonary parenchyma
and pleura [39]. Also, the presence of B–lines > 3 may conrm
that the development of pulmonary parenchymal disease is one
of the important complications of tick paralysis.
It was reported that tick neurotoxin has cardiotoxic effects [22].
Also, dogs with tick paralysis have been shown to have varying
degrees of heart failure [6]. Myocardial dysfunction and subsequent
left–sided congestive heart failure have been postulated as the
causes of the pulmonary edema identified in dogs with tick
paralysis [22]. Venous congestion, peribronchial fluid inltration,
and pulmonary edema due to heart failure result in a wet lung
appearance on thoracic ultrasonography [40]. Pulmonary edema
Thoracic ultrasonography of tick-paralyzed dogs / Gülersoy et al._____________________________________________________________________
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FIGURE 11. Isolated B–line. Visualization of two isolated B–lines (blue arrows)
with a regular pleura (yellow arrow) in a single scan, which may be considered
a normal nding horizontal
FIGURE 12. Wet lung. A wet lung appearance with a regular and thin pleura (blue
arrow), along with increased, slightly blurred B–line (yellow arrow), which may
be related to venous congestion in the present case
FIGURE 13. Thickened pleural line. A small focus of lung consolidation (blue
arrow) is probably related to the inammatory pneumonic process associated
with ongoing tick paralysis, with thickened pleura (yellow arrow, 0.27 cm) that
may indicate exudate
is a common nding in animals affected by tick paralysis. The
pathophysiology of this process remains unclear, but it is an
ongoing area of research interest. Previously, it was reported that
pulmonary edema and congestion were observed in 9 out of 25
dogs euthanized due to tick paralysis [41]. In the present study, the
detection of a wet lung on thoracic ultrasonography in dogs with
tick paralysis ( FIG. 12) may indicate impending acute heart failure
decompensation. Observing this pattern in dogs with tick paralysis
may prompt lung decongestion therapy. Nevertheless, the risk of
developing left–sided heart failure due to neuromuscular paralysis
in dogs with tick paralysis should always be considered [6].
Benign pleural thickening resulting from brosis ranks as the
second most common pleural abnormality following pleural
effusion. Such thickening typically arises as a consequence of
lung and pleural inflammation, with common causes encompassing
apical cap formation and pleural plaque development. Diffuse
pleural thickening commonly arises after an episode of pleuritis,
which leads to pleural brosis primarily involving the visceral pleura
and causing adhesions to the parietal pleura [42]. Additionally,
brotic lung diseases that affect the distal airways and pleura
may also result in areas of pleural thickening or irregularity [43].
A previous study reported proteinaceous edema, along with mild
to severe congestion, bronchopneumonia, and brin inltration, in
the lung histopathology of dogs with tick paralysis [5, 22]. In the
present study, the pleural thickness of the dogs with tick paralysis
(FIG. 13) was higher than that of the healthy dogs (P<0.0001).
This nding may be associated with the previously mentioned
presence of bronchopneumonia in dogs with tick paralysis, along
with the development of brin exudation and brosis, especially
considering the duration of symptoms [22, 43]. Although pulmonary
brosis (FIG. 14) can be induced by various factors, the release
of brosis–inducing factors such as IL-6, transforming growth
factor β (TGF–β), and plasminogen activator inhibitor-1 (PAI-1)
during the inflammatory phase of tick paralysis could contribute
to this condition [44].
The limitations of this study include the absence of radiographic
evaluation of the thorax, histopathological lung examinations,
assessment of arterial blood gases or other functional
measurements to evaluate lung ventilation and oxygenation of
the tick–paralyzed dogs. Also, the lack of thoracic ultrasonographic
examinations after recovery can also be considered a limitation.
Moreover, a limitation is that the correlations between the evaluated
laboratory parameters and abnormal thoracic ultrasonography
ndings were not investigated.
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FIGURE 14. Fibrosis. Mild brotic pulmonary involvement with multiple vertical
comet–tail artifacts (yellow arrow) with an irregular, slightly thickened pleural
line (blue arrow, 0.21 cm)
CONCLUSIONS
In this study, the most signicant ndings during the physical
examination of dogs with tick paralysis were identied through
lung auscultation. Fine crackle, polyphonic wheezing and pleural
rub were the most prominent abnormal sounds. CBC results were
within reference ranges. As a result of thoracic ultrasonography
examination performed in 4 regions on both sides of the thorax, B–
lines > 3, wet lung, pulmonary nodule, thickened pleura, confluent
B–lines, consolidate, brosis and isolated B–line were determined
as abnormal patterns in dogs with tick paralysis. Among these
findings, it was thought that B–lines > 3 are due to possible
pulmonary parenchymal damage; loss of A–lines, due to decreased
aeration resulting from possible acute lung injury; pulmonary
nodule and brosis formation might be due to bronchopneumonia
and aspiration pneumonia in cases of tick paralysis. Additionally,
wet lung was associated with a predisposition to develop lung
congestion due to possible left heart failure in dogs with tick
paralysis. In conclusion, recognition of thoracic ultrasonography
ndings in cases of tick paralysis may be helpful in identifying the
presence and grading the extent of lung damage and deciding on
the necessity of lung decongestion treatment. Evaluating these
abnormal thoracic ultrasonography ndings in conjunction with
the results of radiographic, tomographic, and histopathological
lung examinations, as well as arterial blood gas analyses and
other functional measurements, may enhance the diagnostic and
prognostic effectiveness of these patterns.
ACKNOWLEDGMENTS
No specic grant was received for this research from public,
commercial, or non–prot funding agencies. The authors express
their appreciation to their faculty and institute.
Conflict of interest
The authors declare there is no conflict of interest.
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