Prevalence of Bovine Tuberculosis (BTB) by
post-mortem inspection and bacteriological
culture in the municipal slaughterhouse of
Mejía canton (Pichincha-Ecuador)
Prevalencia de Tuberculosis Bovina (TBB) mediante
inspección post-mortem y cultivo bacteriológico en el matadero
municipal del cantón Mejía (Pichincha-Ecuador)
Diego Martín Cushicóndor-Collaguazo
1
Roberto Darwin Coello-Peralta
2
Estefania Ortega
3
Enrique Xavier Rodriguez Burnham
4
Abstract: This cross-sectional study was carried out at the Municipal
Slaughterhouse of Canton Mejía between May 27 - July 17, 2013 in
order to estimate the apparent prevalence of TBB tuberculosis in
slaughtered cattle based on macroscopic post-mortem inspection and
isolation of M. bovis. In total, 395 heads of cattle were examined
during the study period, of which 4 animals were diagnosed with
tuberculous lesions compatible with the disease at the lung level,
giving an apparent prevalence of 1.01% (IC95%: 0.28% - 2.57 %);
while, through bacteriological culture, isolates compatible with M.
bovis were identified in 6 animals, giving an apparent prevalence of
1.52% (IC95% = 0.56% – 3.28%). Risk factors such as age, biotype,
sex and origin of the animals were not significant in the apparent
prevalence of the disease. In conclusion, a significant prevalence of
macroscopic lesions and of M. bovis was obtained without obtaining
significant association of the factors that predispose to a greater
presentation of visible lesions and of the pathogen, therefore, control
strategies could not be redirected in the different populations that
could be at risk.
Keywords: Prevalence, Bovine tuberculosis, post-mortem, isolation,
M. bovis, risk factors.
Published
Edwards Deming Higher Technological
Institute. Quito - Ecuador
Periodicity
January-March
Vol. 2, Num. 1, 2023
http://centrosuragraria.com/index.php/revista
pp. 76-92
Dates of receipt
Received: May 21, 2022
Approved: October 31, 2022
Correspondence author
cdmcushicondor@outlook.com
Creative Commons License
Creative Commons License, Attribution-
NonCommercial-ShareAlike 4.0
International.https://creativecommons.org/lice
nses/by-nc-sa/4.0/deed.es
1 Magister en Producción y Sanidad Avícola,
Docente-Investigador de la FMVZ de la Universidad
de Guayaquil, Guayaquil, Ecuador,
cdmcushicondor@outlook.com,
https://orcid.org/0000-0002-5238-673X
2 Magister en Microbiología-mención Biomédica,
Docente-Investigador de la FMVZ de la Universidad
de Guayaquil, Guayaquil, Ecuador,
roberto.coellope@ug.edu.ec, https://orcid.org/0000-
0001-5152-2843
3 Master in Microbiology, Professor-Researcher of
the Faculty of Biological Sciences, Universidad
Central del Ecuador, Quito, Ecuador,
estefania1058@gmail.com, https://orcid.org/0000-
0003-3885-4186
4 Magister en Microbiología-mención Biomédica,
Docente-Investigador de la Universidad de
Guayaquil, Guayaquil, Ecuador,
xavier.rodriguezb@ug.edu.ec, https://orcid.org/0000-
0002-4275-3831
January - March vol. 2. Num. 1 - 2023
77
Resumen: Este estudio transversal se realizó en el Matadero
Municipal del Cantón Mejía entre el 27 de mayo y el 17 de julio de
2013 con el objetivo de estimar la prevalencia aparente de
tuberculosis TBB en bovinos sacrificados a partir de la inspección
macroscópica post-mortem y el aislamiento de M. bovis. En total, se
examinaron 395 cabezas de ganado bovino durante el periodo de
estudio, de las cuales 4 animales fueron diagnosticados con lesiones
tuberculosas compatibles con la enfermedad a nivel pulmonar, dando
una prevalencia aparente del 1,01% (IC95%: 0,28% - 2,57%);
mientras que, mediante cultivo bacteriológico, se identificaron
aislados compatibles con M. bovis en 6 animales, dando una
prevalencia aparente del 1,52% (IC95% = 0,56% - 3,28%). Factores
de riesgo como la edad, el biotipo, el sexo y el origen de los animales
no fueron significativos en la prevalencia aparente de la enfermedad.
En conclusión, se obtuvo una prevalencia significativa de lesiones
macroscópicas y de M. bovis sin obtener asociación significativa de
los factores que predisponen a una mayor presentación de lesiones
visibles y del patógeno, por lo que no se pudieron reorientar las
estrategias de control en las diferentes poblaciones que pudieran estar
en riesgo.
Palabras clave: Prevalencia, Tuberculosis bovina, post-mortem,
aislamiento, M. bovis, factores de riesgo.
Introduction
Bovine tuberculosis (BTB) is an infectious-contagious disease with a
wide distribution in cattle worldwide (Michel et al., 2010) and a
potential risk to human health (de Kantor et al., 2012). (de Kantor et al.,
2012).. The disease is caused by some mycobacteria of the
Mycobacterium tuberculosis complex that develop granulomatous
lesions in different organs, especially in the lungs, lymph nodes (Acha
& Szyfres 2001; OIE, 2021), liver and/or kidneys (Shitaye et al., 2006).
In cattle, Mycobacterium bovis has been shown to be the main pathogen
causing tuberculosis (Amanfu, 2006), which causes trade restrictions,
morbidity and mortality of animals that consequently generate
economic losses in livestock production (OIE, 2021).
In Ecuador, cattle production has intensified (Proaño-Pérez et al.,
2011), favoring the maintenance and spread of M. bovis infection due
to direct contact (Palmer et al., 2006). In developed countries, control
and eradication programs have reduced and/or eliminated the disease in
cattle populations; however, BTB is still prevalent in developing
countries (FAO, 2012), possibly due to a limited use of labaratory tests,
low efficiency in post-mortem inspection due to lack of veterinary
Prevalence of Bovine Tuberculosis (BTB) through post-mortem inspection and bacteriological
culture in the municipal slaughterhouse of canton Mejía (Pichincha-Ecuador).
78
inspectors and highly qualified personnel (de Kantor & Ritacco 2006);
Proaño-Pérez et al., 2011).
BTB has been reported in several Latin American countries (de Kantor
et al., 2012), where in the northern highlands of Ecuador, it is endemic
in cattle with different prevalences, using different diagnostic methods
(Echeverría et al., 2014); which may also be related to the geographical
area, breeds, ages and breeding methods (Regassa et al., 2010). In
Ecuador, a policy of skin testing and slaughter of positive animals is
being applied on a voluntary basis; likewise, complementary diagnostic
tests such as veterinary inspection and bacteriological culture can be
used as an option for disease surveillance.
The present study was carried out to determine the prevalence of TBB
by post-mortem inspection and bacteriological culture in cattle
slaughtered at the Municipal Slaughterhouse of Cantón Mejía in the
Province of Pichincha-Ecuador.
Materials and methods
This study was conducted between May 27 - July 17, 2013 at the
Municipal Slaughterhouse of Cantón Mejía, which is located in the
southeast of the Province of Pichincha, at the coordinates 11° 50' 222''
South; 39° 36' 444'' West longitude and at an altitude of 2000 meters
above sea level. The slaughtering center mainly receives cattle for
slaughter from the cattle ranches of Cantón Mejía, although there was
an important influx of zebu cattle from the extensive systems of the
Ecuadorian coast.
Study population: During the study period, 395 samples were obtained
from animals slaughtered in the slaughterhouse. Sample selection was
systematically randomized, with an average of 49 samples collected per
day. The animals that were inspected and sampled included 71 (18%)
mestizos, 103 (26%) zebus and 222 (56%) Europeans. Zebuino type
animals are under an extensive breeding system; purebreds and
mestizos are under an intensive breeding system because they are
primarily engaged in milk production. The main sources of cattle that
supplied the slaughterhouse in this study were from the cantons of
Mejía with 49% (194/395), Santo Domingo de los Tsáchilas with 34%
(133/395), Rumiñahui with 8% (31/395), Saquisilí with 5% (20/395)
and Quito with 4% (17/395). Slaughterhouse hygiene was similar to
January - March vol. 2. Num. 1 - 2023
79
others in Pichincha province, including poor drainage and poor lighting.
The average number of animals slaughtered in the slaughterhouse was
1200 cattle/month.
An observational, descriptive, cross-sectional, descriptive
epidemiological study was carried out, which involved macroscopic
inspection of the animals that arrived at the slaughterhouse and the
collection of 3 tissue samples from selected cattle for the isolation of
M. bovis. In addition, the age, biotype, sex and origin of each animal
were recorded in order to determine the association between the study
variables in relation to the presence or absence of macroscopic lesions
and M. bovis.
Age was categorized according to age group: under 2 years, young; 2
to 6 years, adult; and over 6 years, old as determined by dentition
characteristics (Pace & Wakeman, 2003). The European, zebu and
mestizo biotype was according to Pourrain (2007) and, the origin was
established according to the animal mobilization guides.
Post-mortem examination: Inspection was performed according to the
procedures used by Proaño-Pérez et al. (2011), consisting of visual
examination, palpation and incision (using knife disinfected with 10%
chlorine bleach) at approximately 2 mm and 2 cm intervals in the lymph
nodes (left tracheobronchial and caudal mediastinal) and lungs,
respectively, to detect the presence of lesions compatible with BTB.
Sample collection: Based on macroscopic inspection, 1185
lung/ganglionic tissue samples (two lymph node and one lung sample)
were obtained from the 395 animals. Precautionary measures were
taken during sample collection to avoid cross-contamination of samples
or possible biological risk. Each sample was collected individually in
sterile airtight bags, previously labeled, to be stored under isothermal
conditions in a cooler and transported, the same day, to the laboratories
of the Centro Internacional de Zoonosis, in Quito, where they were
stored frozen at -20oC until the time of processing in the mycobacteria
laboratory.
Isolation of mycobacteria: A standard procedure for bacterial isolation
(OIE, 2009) was used, using aseptic techniques in the level III
microbiology laboratory, in a type 2B biological safety cabinet (II
BSC), to avoid cross-contamination between samples and their possible
biological risk. A portion equal to that used for maceration was stored
at -80°C, in case a repeat test is necessary. Fat and connective tissue
Prevalence of Bovine Tuberculosis (BTB) through post-mortem inspection and bacteriological
culture in the municipal slaughterhouse of canton Mejía (Pichincha-Ecuador).
80
were removed from each sample and approximately 1 cm3 was taken.
The 3 samples, obtained from one individual, were pooled for
homogenization for 10 minutes and decontamination was with 4%
NaOH in a 1:1 or 1:2 volume (modified Petroff's method).
Subsequently, it was incubated at 37°C for 20 minutes with
intermediate shaking every 5 minutes. Then, it was centrifuged at 3000
rpm for 20 minutes, the supernatant was decanted in 5% phenol solution
and the sediment was re-suspended in 500 µl H2O to neutralize with
600 µl H2SO4 (0.1N), using phenol red as pH indicator. Four drops of
the obtained solution were inoculated in Löwenstein-Jensen (L-J)
culture media with pyruvate (0.4%) and in Stonebrink medium, in both
media in duplicate. The tubes were incubated at 37°C for a maximum
period of 8 weeks, with weekly observations. Any colony growth that
presented phenotypes suggestive of mycobacteria was observed by the
Ziehl-Neelsen technique, for confirmation of acid fast bacilli alcohol
resistant (BAAR).
Identification of M. bovis: A bacteriological culture positive for M.
bovis was taken into account for its growth time (Gathogo et al., 2012).
In Stonebrink medium the average growth time of 5 weeks was
observed (Corner et al., 2012) and in Löwenstein-Jensen a longer time
(8 weeks) was considered (OIE, 2009) and with little colony growth
(Toledo et al., 1999). Also taken into account were characteristics of
appearance, color and shape that are clues to suspect M. bovis (OIE,
2021); however, they are not always constant in all strains of a species
(Lévy-Frébault & Portaels, 1992).
In a Microsoft Excel spreadsheet version 2010, a database was created
containing information on age, biotype, sex, origin of each animal,
positivity for visible lesions (VL) and M. bovis. Apparent prevalence
was determined as a proportion of carcasses with visible lesions and/or
M. bovis isolates, out of the total carcasses examined and pool of
samples processed, respectively (Thrusfield, 2008).. Confidence
intervals for apparent prevalences were calculated with 95% confidence
using the PropCIs package of the statistical program "R" (version
3.0.2.). Additionally, the Rcomander package of R was used to perform
Chi-square tests, Fisher's exact test and a univariate and multivariate
binomial analysis using a generalized linear logistic regression model
(GLM) to identify whether possible risk factors such as age, biotype,
sex and origin are associated with the occurrence or positivity of visible
January - March vol. 2. Num. 1 - 2023
81
lesions or M. bovis. For all the analysis performed, a p-value of less
than <0.05 was taken as statistically significant.
3. Result
The apparent prevalence of lesions compatible with BTB by
macroscopic post-mortem inspection in cattle slaughtered at the
Municipal Slaughterhouse of Cantón Mejía during the study period was
1.01% (4/395) [CI95% = 0.28% - 2.57%] (Table 1). Of the 4 cases of
visible lesions at the lung level, M. bovis colonies were isolated in only
one sample. Macroscopically, small tubercles surrounded by a fibrous
capsule not easily detached from the lung tissue were observed. When
obtaining apparent prevalence of macroscopic lesions in slaughter
cattle, by individual variables (Table 1), the results show that only adult
animals (1.19%) tend to develop macroscopic lesions compared to
young and old animals. Similarly, mestizo cattle (1.45%) are more
affected than European (1.25%) and Zebu cattle. Also, only females
(1.35%) presented visible lesions. Finally, the presence of lesions was
only found in cattle from Cantón Mejía (2.06%).
Table 1.- Apparent prevalence of visible lesions total and with respect
to age, biotype, sex and canton*.
Factor
(POS)/T
BP % (95% CI)
Apparent prevalence
4/395
1.01% (0.28 - 2.57)
Age (years)
< 2
0/34
(0 - 10.28)
2 a 6
3/336
1.19(0.33 - 3.02)
> 6
0/25
(0 - 13.72)
Biotype
Cebuino
0/104
(0 - 3.48)
European
3/222
1.25(0.28 - 3.90)
Mongrel
1/69
1.45(0.04 - 7.81)
Sex
H
4/296
1.35(0.37 - 3.42)
M
0/99
(0 - 3.66)
Canton
Saquisili
0/20
(0 - 16.84)
Mejia
4/194
2.06(0.56 - 5.19)
Quito
0/17
(0 - 19.51)
Rumiñahui
0/31
(0 - 11.22)
Prevalence of Bovine Tuberculosis (BTB) through post-mortem inspection and bacteriological
culture in the municipal slaughterhouse of canton Mejía (Pichincha-Ecuador).
82
S. Domingo
0/133
(0 - 2.74)
* POS = positive for macroscopic lesions compatible with BTB; T =
total carcasses examined, PA = apparent prevalence, CI = confidence
interval.
The apparent prevalence of M. bovis by bacteriological culture, from
395 animals slaughtered at the Municipal Slaughterhouse of Cantón
Mejía, was 1.52% (6/395) [IC95% = 0.56 - 3.28]. Of the 6 positive
isolates, 5 were obtained from samples without visible lesions. Of the 6
isolates considered to be M. bovis, 3 were obtained on L-J culture media
with pyruvate and the other 3 on Stonebrink culture media. The colonies
were small, raised, friable, unpigmented after approximately 6 to 14
weeks, rounded, smooth and beige in color. When obtaining the
apparent prevalence of M. bovis in slaughter cattle by individual
variables (Table 2), the results show that old animals (4%) tend to have
a relatively higher frequency of M. bovis compared to adult (1.49%)
and young animals. Likewise, European cattle (2.25%) presented a
higher presence of the microorganism than mestizo (1.45%) and zebu
cattle. Also, the female sex (2.03%) was the only one that tested positive
for the pathogen. Finally, the highest prevalence of M. bovis was found
in animals from Canton Rumiñahui (6.45%) in relation to Canton Mejía
(2.06%) and the other cattle from the different origins did not present
isolations of the microorganism.
Table 2.- Apparent prevalence of M. bovis total and with respect to
age, biotype, sex and canton*.
Categories
(POS)/T
BP % (95% CI)
Apparent prevalence
6/395
1.52% (0.56 - 3.28)
Age (years)
< 2
0/34
(0 - 10.28)
2 a 6
5/336
1.49 (0.48 - 3.44)
> 6
1/25
4 (0.10 - 20.35)
Biotype
Cebuino
0/104
(0 - 3.48)
European
5/222
2.25 (0.74 - 5.18)
Mongrel
1/69
1.45 (0.04 - 7.81)
Sex
H
6/296
2.03 (0.75 - 4.36)
January - March vol. 2. Num. 1 - 2023
83
M
0/99
(0 - 3.66)
Canton
Saquisili
0/20
(0 - 16.84)
Mejia
4/194
2.06 (0.56 - 5.19)
Quito
0/17
(0 - 19.51)
Rumiñahui
11355
6.45 (0.79 - 21.42)
S. Domingo
0/133
(0 - 2.74)
* M. bovis = Mycobacterium bovis, POS = positive for M. bovis, T =
total tissue pool seeded, PA = apparent prevalence, CI = confidence
interval.
In this study, when analyzing the age, biotype, sex and origin of the
animals in relation to the positivity or presence of macroscopic lesions
compatible with the disease and M. bovis, no significant association
was found. Therefore, it could not be inferred that the factors analyzed
influenced the apparent prevalence of macroscopic lesions and M.
bovis, which also means that there is the same probability for any
category analyzed of presenting visible lesions or M. bovis in cattle
slaughtered in the Municipal Slaughterhouse of Cantón Mejía.
Different countries or regions can fit into one of three categories,
depending on the prevalence of the disease: less than 1%, low; between
0.1% and 1%, intermediate; greater than 1%, high (de Kantor &
Ritacco, 2006); according to the category, different control strategies
should be followed in order to reduce the prevalence of the disease, in
addition to making use of diagnostic tests with greater sensitivity ( de
Kantor & Ritacco, 2012 ). The apparent prevalence of lesions
compatible with BTB of 1.01% in the Municipal Slaughterhouse of
Cantón Mejía by post-mortem macroscopic inspection in the present
study represents a high prevalence, and among the factors that can
influence the prevalence of the disease are the production systems to
which the cattle are subjected (intensive dairy cattle breeding), the
geographic area and the size of the farm (small, medium or large)
(Proaño-Pérez et al., 2011); however, a high prevalence is possible in
housed cattle as infection through the respiratory tract is more likely to
subsequently produce lesions at the level of the lungs ( de Kantor &
Ritacco, 2012) .
The high apparent prevalence (greater than 1%) found in the current
study by post-mortem inspection is comparable with the results found
at the slaughterhouse level by Proaño-Pérez et al. (2011) [2.33%
Prevalence of Bovine Tuberculosis (BTB) through post-mortem inspection and bacteriological
culture in the municipal slaughterhouse of canton Mejía (Pichincha-Ecuador).
84
(16/687) and 2.42% (17/703) in 2007 and 2008, respectively] and
Espinoza (2011) [Pelileo 7.92% (55/307) and Ambato 4.30% (32/744],
in the same way similar findings have been reported by Torres (2009)
in Argentina [1.2% (140,840/12,018,251), Biffa et al. (2009) in
Ethiopia [10.2% (337/3,322)], Aliyu et al. (2009) in Nigeria [4.05%
(12,259/302,700)], Gathogo et al. (2012) in Kenya [18.95% (176/926)]
and Koro et al. (2013) in Cameroon [1.03% (168/16,316)]. On the other
hand, the prevalence found in this study presents a difference with the
average prevalence (0.1% - 1%), found in the Ecuadorian coast such as:
Guayas (0.47% 16/3.425), Santo Domingo de los Tsáchilas (0.21%
6/2.778) (Proaño-Pérez et al., 2011); and in other countries such as:
Argentina [0.9% (116,798/13,483,515) in 2009) (Torres, 2009),
California, Mexico (0.12 and 0.46% in 1995 and 1996, respectively)
(Hernández et al., 1997) and Minas-Gerais, Brazil [0.71%
(681/954,640)] (Baptista et al., 2004) and similarly shows a difference
with the low prevalence (less than 0.1%) in Ethiopia [0.050%
(699/1,336,266)] (Shitaye et al., 2006).
A higher prevalence of BTB compared to other regions of medium and
low prevalence could be related to the lack of an adequate testing and
slaughter policy, intensive management practices, where there is greater
contact between animals and the lack of preventive measures that make
the disease endemic; however, it should be considered that macroscopic
lesions could not be detected in 83% (5/6) of the animals infected with
M. bovis (confirmed by isolation) ( de Kantor & Ritacco, 2012 ). These
results may be due to the fact that not all organs and tissues present
visible lesions, because the animal is in an early stage of the disease,
and it may be the case that not all organs and tissues present visible
lesions, because the animal is in an early stage of the disease.The three
lesions from which it was not possible to isolate M. bovis may be due
to other granulomatous diseases that are not correctly examined (OIE,
2019); on the other hand, the three lesions from which it was not
possible to isolate M. bovis may be due to other granulomatous diseases
(Mellau et al., 2012). (Mellau et al., 2010) such as Actinomycosis,
Acninobacillosis and Leukosis, which have been diagnosed in the
Machachi animal farm (OIE, 2021), or other opportunistic pathogenic
microorganisms that cause this type of lesions (Oloya et al., 2010).
(Oloya et al., 2007)..
In addition, there is no adequate control of cattle movement in the
country, and there are deficiencies in post-mortem inspection protocols;
January - March vol. 2. Num. 1 - 2023
85
therefore, these procedures should be improved and adjusted to the
conditions of each area in Ecuador, or propose a protocol that can be
followed to obtain favorable results, which have been shown to increase
their level of efficiency fourfold, and thus can be used in the
surveillance of the disease. Finally, the microorganisms that can cause
lesions compatible with the disease and that generate confusion in the
macroscopic diagnosis should be studied (de Kantor & Ritacco, 2012).
There have been no previous data on apparent prevalence of M. bovis
by bacteriological culture from tissues of slaughtered cattle; therefore,
the present result is not comparable with other studies. The apparent
prevalence of M. bovis was 1.52% (6/395) in the Municipal
Slaughterhouse of Cantón Mejía by bacteriological culture. The
isolation of M. bovis was performed from 5 animals that did not present
visible lesions, results that are related to the reports of Echeverría et al.
(2014), who demonstrated by nested PCR (for M. bovis) a prevalence
of 4.33% (25/578), in two areas of the northern highlands of Ecuador.
In 75% (3/4) of the animals that presented encapsulated granulomatous
lesions, isolation of the microorganism was not possible because it has
been shown to be negatively correlated with the growth of M. bovis in
culture media; however, the highest isolation can be achieved from
caseous/purulent lesions (Gathogo et al., 2012). However, isolation of
the organism from tissues with or without lesions may be affected by a)
the effect of the decontaminant because mycobacteria are sensitive to
sodium hydroxide (Miller et al., 2002), b) choice of culture medium
used (Corner et al., 2012) and c) loss of viability during sampling
(Latini et al., 1997) or during the period of time between sample
collection and processing (Araújo et al., 2005), since concentrations
higher than 10 bacilli/ml are required to obtain a positive culture (Nava
& Prieto, 2001).
The colonies of acid fast bacilli that represented 40% (4/10) could be
atypical mycobacteria that have been isolated from Löwenstein-Jensen
medium or Stonebrink medium; among which the following have been
found: Mycobacterium terrae, Mycobacterium avium, Mycobacterium
chelonae, Mycobacterium gordona, Mycobacterium fortuitum,
Mycobacterium flavescens, Mycobacterium smegmatis,
Mycobacterium smegmatis, Mycobacterium flavescens and
Mycobacterium smegmatis (Cleaveland et al., 2007). (Cleaveland et al.,
2007), Mycobacterium smegmatis (Cleaveland et al.,
2007)Mycobacterium aviumintracellulare-scrofulaceum,
Mycobacterium gordonae and Mycobacterium szulgai (Proaño-Pérez et
Prevalence of Bovine Tuberculosis (BTB) through post-mortem inspection and bacteriological
culture in the municipal slaughterhouse of canton Mejía (Pichincha-Ecuador).
86
al., 2006).These mycobacteria are sometimes found causing infection
in cattle and possibly affect production performance (Biet et al., 2005).
(Biet et al., 2005). Similarly, it could be Mycobacterium caprae or
Mycobacterium tuberculosis that has been diagnosed in cattle (Ameni
et al., 2011).
The prevalence may be influenced by the season, since old or poor
condition animals are usually sold at certain times of the year (Boukary
et al., 2012), usually at Livestock Fairs and with respect to
bacteriological culture results, they indicate the presence of M. bovis in
the farms of origin (Milian-Suazo et al., 2000), could help to re-direct
surveillance strategies with better diagnostic tests.
The higher prevalence of visible lesions and M. bovis in older cattle
could be explained by the longer time spent in endemic environments,
long term productive activity (Acha & Szyfres, 2001), chronicity of the
disease and immunosuppression (Humblet et al., 2009). (Humblet et al.,
2009).. The greater presence of lesions found according to biotype
could be attributed to the fact that the few mestizo cattle remain together
with European cattle, which are more susceptible than zebu and
crossbred cattle (Humblet et al., 2009). (Omer et al., 2001; Cadmus et
al., 2010).
Despite an apparent resistance of TBB in zebu cattle (Inangolet et al.
(Inangolet et al., 2008)(Inangolet et al., 2008), the disease has been
diagnosed in this type of cattle, due to the increased contact between
high-producing animals and the overcrowding of dairy production
systems (Proaño-Pérez et al., 2011). (Proaño-Pérez et al., 2011).In this
study, the presence of lesions and M. bovis was only found in females,
but males used as steers could also present the disease (Kazwala et al.,
2011). (Kazwala et al., 2001).. Finally, the lesions found in animals
from Cantón Mejía could be due to the fact that the disease is endemic
in this area and adequate control measures have not been carried out,
especially in this area with a high density of dairy cattle ((Proaño-Pérez
et al., 2011).
M. bovis infection was higher in Cantón Rumiñahui because it is related
to an endemic area, a possible sporadic outbreak and/or inadequate
control of cattle movement. A null or decreased prevalence in other
areas is more likely to be related to the type of production (extensive
systems), since transmission through the respiratory route is minimal.
January - March vol. 2. Num. 1 - 2023
87
4. Conclusions
In conclusion, this study, which was carried out in an area with high
cattle movement, showed a high prevalence of lesions compatible with
bovine tuberculosis and M. bovis in cattle slaughtered in the Municipal
Slaughterhouse of Cantón Mejía. Tuberculosis control programs must
be carried out in the different cattle populations in order to have
adequate epidemiological data collection and, in the future, to have
access to export markets for cattle and livestock products. Due to the
scarcity of information on tuberculosis in cattle at the slaughterhouse
and laboratory levels, studies such as this one, but with significant
values, could help redirect control strategies in the different populations
predisposed to contracting BTB, so that the economic and public health
impacts of the disease can be reduced.
Acknowledgments
We are grateful for the scientific and financial support of the Centro
Internacional de Zoonosis; to Dr. Marco Coral for his help with part of
the statistics. I also thank Bioq. Paulina Fernández for her collaboration
in the laboratory and finally the staff of the Cantón Mejía
Slaughterhouse, Dr. Antonio Viteri, Dr. Pablo Tuyapanda and Dr.
Carlos Luna for their collaboration during the field work.
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