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Research Article
Interpretation Criteria for Comparative Intradermal
Tuberculin Test for Diagnosis of Bovine Tuberculosis in
Cattle in Maroua Area of Cameroon
J. Awah-Ndukum,1J. Temwa,1V. Ngu Ngwa,1M. M. Mouiche,1
D. Iyawa,2and P. A. Zoli1
1School of Veterinary Medicine and Sciences, University of Ngaound´
er´
e, BP 454, Ngaound´
er´
e, Cameroon
2Regional Delegation of Livestock, Fisheries, Animal Industries, Far North Region, Cameroon
Correspondence should be addressed to J. Awah-Ndukum; awahndukum@yahoo.co.uk
Received April ; Revised July ; Accepted July
Academic Editor: Francesca Mancianti
Copyright © J. Awah-Ndukum et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Intradermal tuberculin test (TST) is the choice method for diagnosis of bovine tuberculosis (Tb) in live animals. is work was
done to assess the performance of single intradermal comparative cervical tuberculin (SICCT) test in randomly selected cattle in
Maroua, Cameroon, against detection of Tb lesions and detection of Tb lesions plus acid fast bacilli in lesions. While .% of
slaughtered cattle presented Tb lesions at meat inspection, detection rates of anti-bovine-Tb antibody, Tb lesions, and Tb lesions
plus acid fast bacilli were .%, .%, and .%, respectively. SICCT-bovine-Tb positive cattle were .%, .%, .%,
.%, and .% at ≥ mm, ≥. mm, ≥ mm, ≥. mm, and ≥ mm cut-os, respectively. Higher sensit ivity and predict ive values
were obtained at severe interpretations. e best performance was at ≥mmand≥. mm cut-os. Against detection of Tb lesions,
≥mm and ≥. mm showed sensitivity of .% and specicity of .% and .%, respectively. For detection of Tb lesions
accompanied with acid fast bacilli in lesions, ≥mmand ≥. mm showed sensitivity of .% and specicity of .% and .%,
respectively. ese ndings revealed that interpretations of SICCT-bovine-Tb should be at ≥mmand/or≥. mm cut-os. Severe
interpretation of TST is essential for optimal diagnosis of bovine Tb in cattle in Maroua, Cameroon.
1. Introduction
Bovine tuberculosis (Tb) is a major chronic bacterial disease
of animals and humans caused by Mycobacterium bovi s.
ough zoonotic, bovine Tb is neglected and underinves-
tigated in Sub-Saharan Africa including Cameroon [, ].
In areas where bovine Tb is endemic and not controlled or
partially controlled, human Tb due to M. bovis may occur
resulting from ingesting contaminated fresh milk and meat
products and by inhaling cough spray from infected cattle
[–]. Widespread bovine Tb in cattle has been diagnosed
in some parts of Cameroon following comparative cervical
tuberculin test, detec tion of Tb lesions during abattoir slaugh-
ter meat inspection, acid fast staining of bacilli, and molecular
analysisofculturedisolates[,,].Also,M. bovis in human
hasbeenreportedintheWestandNorthwestRegionsof
Cameroon [, ].
Bovine Tb has signicant impact on international trade
of livestock and animal products []. Intradermal tuberculin
skin test (TST) is the international choice method for eld
diagnosisofbovineTbinliveanimalsandtheWorldOrgan-
isation for Animal Health (OIE) recommended dierence
between the increases in skin thickness for the test to be
positive should be at least mm aer hours []. However,
the performance of TST is aected by environmental and
host factors and the nature of the tuberculin used [–]. A
perfect cut-o point in a specic geographic area or country
may not be useful in another environment or another countr y
[, , ] and the ability of the test to accurately predict true
positive disease status depends on its sensitivity, specicity,
andprevalenceofthediseaseinthepopulationtested[].
e OIE recommended cut-o value was established mainly
in developed countries for Bos taurus cattle and dierent
Hindawi Publishing Corporation
Veterinary Medicine International
Volume 2016, Article ID 4834851, 8 pages
http://dx.doi.org/10.1155/2016/4834851
Veterinary Medicine International
cut-o values are applied according to a particular country’s
diseasestatusandobjectiveofitsdiseasecontrolprogramme
[]. Severe interpretations have been used in Chad, Ethiopia,
and Tanzania [, , –] and in regions or herds where M.
bovis infection had been conrmed based on the discretion
of the veterinarian [].
TST together with slaughter of positive reactors to exam-
ine for Tb lesions; culture of suspected Tb specimens; and
other modern diagnostic techniques (e.g., gamma-interferon,
ESAT- tests, and serologic and uorescence polarization
assays)havebeencomparedandarebeingvalidatedfor
maximum diagnosis of bovine Tb in cattle in various envi-
ronmental conditions [, –]. is study was therefore
carriedouttoestimatetheprevalenceofbovineTbandassess
the diagnostic performance of TST in the diagnosis of bovine
Tb zebu cattle in Maroua area of Cameroon.
2. Materials and Methods
2.1. Study Area and Population. Cattle from the livestock
markets in the environs of Maroua destined for slaughter at
theMakabayeabattoirweresampledforthestudy.About
twenty cattle are slaughtered daily in the Makabaye abattoir
which provides beef to inhabitants of Maroua city and
neighbouring areas (∘–∘Nand
∘–∘E). A
TST bovine Tb prevalence rate of .% (.%–.%)
recorded by Awah-Ndukum et al. [] in the highlands of
Cameroon using OIE recommended standards was used to
estimate the number of cattle required to detect at least one
positive reactor with % condence and a desired precision
of ≥% as previously described []. e selection of cattle
for the study was based on haphazard arrival of animals at
the abattoir and on random-number generation method of
cattle owners from the daily abattoir records whose animals
were judged as t to be slaughtered. However, cattle used for
the TST performance study were animals that were judged as
t to be slaughtered and were not slaughtered until at least
-hour stay at the abattoir.
2.2. Detection of Bovine Tuberculosis. During November
to March , blood was collected by venopuncture of the
jugular vein from randomly selected cattle intended for
slaughter to extract serum for lateral ow assay of anti-BTb
antibody (Anti-Bovine Ab). Single intradermal comparative
cervical tuberculin (SICCT) skin test was done on random
cattle of the selected animals [] that were slaughtered
at least hours later. Following slaughter of these
animals, intensive meat inspections were carried out by JT
assisted by veterinary sta of the abattoir based on the
government’s legislation regulating veterinary health inspec-
tion and notication of contagious animal diseases [].
Evidence of pathologies was also supported by postmortem
examination of carcasses as earlier described [–]. Briey,
the inspection procedure employed visual examination and
palpation of the lungs, liver, and kidneys, lymph nodes of the
thoracic and head regions, the mesenteric lymph nodes, and
other lymph nodes of the body and various other parts/organs
of the carcass.
e sera were extracted and stored at −∘Cuntilanalysis
was carried out. Similarly, tissues specimens, with suspi-
cious TB lesions ( thoracic and abdominal lymph nodes
andlivertissues)fromtheSICCTbovineTbcattleofthe
slaughtered zebu cattle in the study were collected into
sterile plastic containers and also stored at −∘Cforupto
two months before analysis. Individual animal information
such as age estimated by examining the incisors [], sex,
breed [, ], and body condition scores [] was recorded
during blood collection. Grinding of TB lesions [] and
direct smear microscopy with Ziehl-Neelsen (ZN) staining
for conrmation of acid fast tubercle bacilli and lateral-
ow-based rapid test for detection of antibodies in serum
were done following standard procedures [, –] and as
described by manufacturer (Anigen Bovine Tb Ab,BioNote
Inc., Korea). Briey, in the ready-to-use disposable lateral
ow kit, 𝜇L of test serum was poured into the sample well
and, aer minute, drops of developing buer (provided
aspartofthekit)wereplacedinthebuerwell.eresult
was interpreted aer minutes. e presence of two purple
coloured bands within the result window, the test area and
control line, indicated antibodies positive result whereas no
band in the test area in addition to a visible control purple line
was negative. An invalid test was one where no coloured band
was visible within the result window. e appearance of a
controlcolourband,forpositiveornegativeassays,indicated
that the test was working properly.
Risk assessments of the project were performed by the
researchers to avoid hazards to all persons and animals
involved in the project. Ethical clearances were obtainedfrom
the required authorities before carrying out the study. e
purpose of the study was explained to the targeted partic-
ipants usually with the assistance of resident veterinarians,
local leaders at the abattoir, and or trusted intermediaries.
An animal was tested aer an informed consent was given
by the owner. Apart from minor jugular vein puncture for
blood collection, intradermal injections of avian and bovine
tuberculin, and procedural restraining manipulations for
safety purposes, the animals were not subjected to suering.
Slaughtering and dressing of cattle carcasses were done as
described by the Cameroon veterinary services []. All
laboratory analyses including ZN staining were carried out
in a laboratory equipped with a category II Biosafety cabinet.
2.3. Data Analysis. e data were entered into Microso
Excel and then transferred to SPSS and R soware.
Frequency distributions of bovine Tb were generated for
the dierent diagnostic techniques. e Chi-square test was
used to evaluate the sensitivity of TST and assess various
associations. e ROC (Receiving Operating Characteristic)
analysis was also used to evaluate diagnostic performance of
TST at dierent cut-o points [].
3. Results
3.1. Prevalence of Bovine Tuberculosis. Over .% () of
cattle slaughtered at Makabaye-Maroua during the study
period presented macroscopic Tb lesions at meat inspection.
e cattle with Tb lesions were distributed as follows: of
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(.%) male animals, of (.%) female animals,
of (.%) animals aged to years, of (.%)
animalsagedoveryears,of(.%)PeulhofSahel
zebu, of (.%) Bororo/Fulani zebu, and of
(.%) Toupouri-Massa zebu.
However, .% (% CI: .–.) of randomly
selected cattle were positive for anti-bovine Tb antibodies
with lateral ow assay. Single intradermal comparative cer-
vical tuberculin (SICCT) skin test done on of these
cattle showed (.%, % CI: .–.), (.%,
% CI: .–.), (.%, % CI: .–.), (.%,
% CI: .–.), and (.%, % CI: .–.) positive
reactors at ≥ mm, ≥. mm, ≥ mm, ≥. mm, and ≥mm
cut-o points, respectively. Of the animals, Tb lesions and
Tblesionsplusacidfastbacilliweredetectedinanimals
(.%, % CI: .–.) and animals (.%, %
CI: .–.), respectively. Over .% () of the SICCT
animals were positive for anti-bovine Tb antibodies corre-
sponding to apparent rates of .%, .%, .%, .%,
.%, and .% animals positive for SICCT bovine Tb
and anti-bovine Tb antibody at < mm, ≥ mm, ≥. mm,
≥ mm, ≥. mm, and ≥mmcut-opoints,respectively.
3.2. Diagnostic Performance of Tuberculin Skin Test to Detect
Bovine Tuberculosis in Cattle. e performances of SICCT
technique at various cut-o points to diagnose bovine Tb in
cattle in Maroua, Cameroon, using detection of Tb lesions
and detection of Tb lesions accompanied with acid fast bacilli
in the lesions as references for dening the status disease
are shown in Table . Based on computed sensitivity and
specicity values of SICCT compared to detection of Tb
lesionsandTblesionsplusacidfastbacilli,severeinterpre-
tations of SICCT tests detected more diseases cases. ough
highest detection of disease cases by SICCT tests was detected
at ≥. mm cut-o point, the overall performances were
superior at ≥mmand≥. mm cut-o values. e sensitivity
of SICCT at ≥mmand≥. mm cut-o points compared to
the sensitivity at ≥ mm cut-o was not signicantly higher
[𝑃 > 0.05] against detection of Tb lesions but signicantly
higher [𝑃 < 0.05] against detection of Tb lesions plus acid
fast bacilli to dene disease status.
It is worth mentioning that overall the predictive values
were usually superior at SICCT ≥mmand≥. mm cut-o
points compared to the OIE recommended (≥ mm) cut-o
point. Indeed, the performance of SICCT against detection of
Tb lesions revealed positive predictive values of . (.–
.); . (.–.); . (.–.); . (.–.);
. (.–.) and negative predictive values of . (.–
.); . (.–.); . (.–.); . (.–.); .
(.–.) at reactors at ≥ mm, ≥. mm, ≥ mm, ≥. mm,
and ≥ mm cut-o points, respectively. Accordingly, the
performance of SICCT against detection of Tb lesions plus
acid fast bacilli revealed positive predictive values of .
(.–.); (.–.); . (.–.); (.–
.); . (.–.) and negative predictive values of
; . (.–); . (–); . (–); . (.–
.).
Furthermore, the ROC (Receiving Operating Character-
istic) analysis showed that the area under the curve was
signicantly higher at cut-o points < mm, particularly at
≥. mm cut-o point according to detection of Tb lesions
[. (.–.)] and detection of Tb lesions plus acid fast
bacilli in the lesions [. (.–)] [Figure ]. e area under
the ROC curves according to detection of Tb lesions for all
SICCT cut-o points was between . and . suggesting
that these cut-o values are only fairly informative for the
detection of bovine Tb. However, SICCT at ≥. mm cut-o
point showed signicantly higher (𝑃 < 0.001) discriminatory
power compared to SICCT at ≥ mm cut-o point. For the
ROC curves according to detection of detection of Tb lesions
plus acid fast bacilli in the lesions, all SICCT cut-o points
< mm were between . and , particularly for ≥mm and
≥. mm cut-o points, indicating that these cut-o values
are very informative for the detection of bovine Tb. erefore,
the ROC ndings also conrmed severe interpretations of
SICCT bovine Tb detection [particularly at ≥mm and
≥. mm cut-o points] as for sensitivity and specicity
evaluations.
4. Discussion
e detection rates of macroscopic Tb lesions [.–.%]
in cattle in this study are much higher than values, ranging
from <to.%,reportedinthelittoralandwestern
highland regions of Cameroon [, ], while the prevalence
of anti-bovine Tb antibodies [.% and .%] was higher
than % recorded in the Bamenda area [] and .%
recorded in the highland regions []. Also, signicantly
higherSICCTbovineTbprevalenceestimatesbasedon
tuberculin skin tests at cut-o points ≥ mm, ≥ mm, and
≥ mm were obtained compared to .%–.%, .%–
.%, and .%–.% recorded by Awah-Ndukum et al.
[] in the highland regions. However, the rates of SICCT
bovine Tb/anti-bovine Tb antibodies animal responses in
this study agree with that of Awah-Ndukum et al. []
who reported that the proportion of SICCT bovine Tb/anti-
bovine Tb antibody reactors was signicantly higher at the
≥mm followed by the ≥mm and ≥mm cut-o point
groups. ese ndings suggest that bovine Tb is highly
endemic in cattle in the Maroua area compared to other parts
of Cameroon and require severe interpretations of SICCT
bovine Tb results.
Postmortem examination of Tb lesions and demonstra-
tion of acid fast bacilli by direct microscopy were used in
this study to dene disease status of bovine Tb in cattle, to
evaluate the performance of tuberculin skin test as opposed
to bacteriological culture that was used elsewhere as reference
diagnostic test []. However, detection of Tb lesions showed
lower sensitivity values compared to detection of Tb lesions
accompanied with demonstration of acid fast bacilli in the
lesions. Macroscopic examination of Tb lesions and demon-
stration of acid fast bacilli have also been used by Ameni et al.
[] in Ethiopia and Ngandolo et al. [] in Chad to evaluate
the diagnostic performances of tuberculin skin tests. In this
study optimal detection of bovine Tb in cattle in Maroua,
Cameroon, was obtained at severe interpretations of SICCT
and particularly at ≥mm and ≥. mm. ese ndings are
similartothoseofAmenietal.[]whoreportedthat
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T : Performances of single intradermal comparative cervical tuberculin (SICCT) skin test at various cut-o points to diagnose bovine tuberculosis in zebu cattle in Maroua, Cameroon,
using detection of tuberculosis lesions and detection of tuberculosis lesions accompanied with acid fast bacilli in lesions to dene disease status.
SICCT cut-o point
Detection of tuberculosis lesions to dene disease status Detection of tuberculosis lesions and acid fast bacilli in lesions to dene
disease status
Sensitivity Specicity Sensitivity Specicity
Value, %
(% CI) 𝑃value [𝜒2]Valu e , %
(% CI) 𝑃value [𝜒2]Valu e , %
(% CI) 𝑃value [𝜒2]Valu e , %
(% CI) 𝑃value [𝜒2]
≥mm .
(.–.) .∗[.] .
(.–.) .∗[.] .∗[.] .
(.–.) .∗[.]
≥. mm .
(.–.) .∗[.] .
(.–.) . [.] .
(.–.) .∗[.] .
(.–.) . [.]
≥3.0 mm 67.8
(57.8–77.7) 0.118 [2.44] 94.7
(89.9–99.4) 0.534 [0.38] 89.4
(82.8–95.9) 0.004∗[8.28] 92.4
(86.76–98.03) 0.674 [0.17]
≥3.5 mm 67.8
(57.8–77.7) 0.118 [2.44] 96.5
(92.6–100) 1[0] 89.4
(82.8–95.9) 0.004∗[8.28] 93.9
(88.81–98.98) 1[0]
≥mm .
(.–.) /.
(.–) /.
(.–.) /.
(.–.) /
∗Signicantly dierent [𝑃 < 0.05]whencomparedto≥mm cut-o point.
Veterinary Medicine International
SICCT ≥ 2 mm
SICCT ≥ 2.5 mm
SICCT ≥ 3 mm
SICCT ≥ 3.5 mm
SICCT ≥ 4 mm
SICCT ≥ 2 mm
SICCT ≥ 2.5 mm
SICCT ≥ 3 mm
SICCT ≥ 3.5 mm
SICCT ≥ 4 mm
0.811 (0.720−0.926)
0.813 (0.704−0.922)
0.813 (0.701−0.925)
0.822 (0.711−0.932)
0.768 (0.647−0.890)
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.90 (0.86−0.97)
0.90 (0.85−0.99)
0.91 (0.82−1)
0.92 (0.83−1)
0.84 (0.71−0.96)
Skin cut-o
points
Area under curve
(CI: 95%)
Asymptomatic
signicant
Skin cut-o
points
Area under curve
(CI: 95%)
Asymptomatic
signicant
ROC curve A
0.0 0.2 0.4 0.6 0.8 1.0
0.0
0.2
0.4
0.6
0.8
1.0
Sensitivity
1−specicity
ROC curve B
0.0
0.0
0.2
0.4
0.6
0.8
1.0
0.2 0.4 0.6 0.8 1.0
Sensitivity
1−specicity
SICCT 2 mm
SICCT 2.5 mm
SICCT 3 mm
SICCT 3.5 mm
SICCT
Reference line
4mm
SICCT 2 mm
SICCT 2.5 mm
SICCT 3 mm
SICCT 3.5 mm
SICCT
Reference line
4mm
F : ROC (Receiving Operating Characteristic) analysis of the performances of SICCT to detect bovine Tb. Classication of the single
intradermal comparative cervical tuberculin (SICCT) skin test cut-o point performance with detection of tuberculous lesions as reference
test (curve A). Classication of the single intradermal comparative cervical tuberculin (SICCT) skin test cut-o point performance with
detection of tuberculous lesions and acid fast bacilli as reference test (curve B).
improved diagnostic performances of tuberculin skin test in
zebu cattle in Ethiopia were obtained at severe interpretations
of > mm cut-o point. In Chad, Ngandolo et al. [] also
stated that optimum diagnostic performance of tuberculin
skin test in Arab zebus and Bororo zebus was >mmcut-o
point. e present results agree with those of Awah-Ndukum
et al. [] who observed that improved diagnosis of bovine Tb
by tuberculin skin test was obtained at ≥mmcut-o when
compared to anti-bovine Tb antibody detection in Goudali,
Red Bororo, and White Fulani zebus and their crosses in the
highlands [Adamawa and Northwest] of Cameroon.
e tuberculin skin tests are currently the best available
and aordable techniques for international eld diagnosis of
bovine TB in live animals [, ]. Also, the tests are based
on delayed hypersensitivity reactions []. e intradermal
comparative cervical tuberculin (ICCT) skin test involving
the intradermal injection of bovine tuberculin (BT) and avian
tuberculin (AT) at separate sites in the skin of the neck gives
more specic results than the simple intradermal tuberculin
(SIT) skin test which uses only BT [, ]. e World
Organisation for Animal Health (OIE) recommended dier-
ence between the increases in skin thickness for the test to
be positive should be > mm aer hours []. However,
the OIE recommended cut-o value was established mainly
in developed countries for Bos taurus cattle [], in an
epidemiologic context of very low prevalence of bovine Tb
[≤.%] and the implementation of a strict test and slaughter
eradication policy []. Indeed, dierent cut-o values have
been applied worldwide according to a particular country’s
disease status and objective of its disease control programme
[]. In Africa, for example, the > mm, ≥ mm, > mm, and
≥mmcut-opointshavebeenusedinChad,Ethiopia,and
Tanzania[,,,,].
e ROC analysis and sensitivity evaluations support
severe interpretation of tuberculin skin tests in this study,
particularly at ≥mm and ≥. mm cut-o points and []
had proposed severe interpretations of tuberculin skin tests
forthediagnosisofbovineTbinBos indicus cattle in
Cameroon, where the prevalence of bovine Tb is high and
widespread. e performance of tuberculin skin tests has also
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been aected by environmental factors, host factors (status
of immunity, genetics, etc.), prevalence of the disease in the
population tested, and the nature of the tuberculin used [–
]. A perfect cut-o point in a specic geographic area may
not be so useful at another environment [, ] and the
ability of the test to accurately predict the true positive disease
status depends on its sensitivity, specicity, and prevalence
of the disease in the population tested []. Excessively high
sensitivity of tuberculin skin tests will generate false positive
reactions during interpretations of test results. However,
severe interpretations for improved diagnosis have been done
in regions or herds where M. bovis infection had been
conrmed based on the discretion of the veterinarian [].
In this study, the best individual sensitivity [.% (.–
.) at ≥. mm cut-o point] of tuberculin skin test, with
detection of Tb lesions as the reference test, recorded is
lower than the median individual sensitivity [% (.–)]
stated by OIE [] at the recommended >mmcut-opoint
[]. e best individual sensitivity [.% (.–.) at
≥. mm cut-o point] of tuberculin skin test, with detection
ofTblesionsplusacidfastbacilliinlesionsasthereference
test, recorded is higher than the median individual sensitivity
stated by OIE at the recommended cut-o point. e OIE
proposed value is a median from a very wide dispersion
(.–%) compared to very narrower dispersions for best
overall values in the present study (.–.% and .–
.%). For SICCT bovine Tb detection, the study showed
higher (nonsignicant for detection of Tb lesions and sig-
nicant for detection of Tb lesions accompanied with AFB
inlesionsasgoldstandards)sensitivitiesatsevere(<mm
cut-o) interpretation compared to interpretation at the OIE
recommended (≥ mm) cut-o value. Severe interpretation
of SICCT results diagnosed more bovine Tb cases and is very
essential in managing high zoonotic potential [] as well as
high socioeconomic and cultural implication [] of bovine
Tb in Cameroon. e sensitivities obtained in this study
are similar to the values of Ameni et al. [] who reported
.% at >mm cut-o point in Ethiopia and Delafosse
etal.[]whoreported%at≥mm in Chad. Various
factors can inuence the sensitivity of tuberculin skin test
and the hypersensitivity reactions can uctuate considerably
depending on the animal. Delayed hypersensitivity reactions
provoked by tuberculin injection can become established
to weeks aer exposure of the host to bacilli agents
while recently infected animals may not react suciently to
tuberculin injection []. e reaction is reduced in young
animals [calves] and pregnant females [cow] near term [].
Anergy has been reported to cause false negative reac-
tions during tuberculin skin test but the reasons are still
poorly understood []. However, recently infected cattle,
cattle under stress due to malnutrition, gastrointestinal par-
asitoses, other concurrent infections, and cattle with gener-
alized Tb would be anergic and fail to react to tuberculin
skin test [, ]. erefore, cattle presenting dierential
SICCT skin thickness of ≤mmshouldnot beexcludedthat
they are not aected by bovine Tb, especially animals in
highly endemic areas and animals sensitized to environmen-
tal mycobacteria such as in Cameroon []. ese animals
couldactuallybeinfectedbutlowreactingornotreacting
at all because their immune systems may not be suciently
stimulated for a positive response to occur at the ≥mmOIE
recommended cut-o point [, ]. Also, conditions such
as stress may compromise their immune function [] and
animals may be sensitized to environmental mycobacteria
[]. Furthermore, in late stages or towards the end of the
course of the disease, the capacities of the infected hosts may
become saturated and the expected hypersensitivity reactions
may not be observed []. Also, –% of some animals may
be totally anergic during their entire lifespan [, ]. ese
phenomena are responsible for the uctuating sensitivities of
tuberculin skin tests according to environments and amongst
animal populations.
is study revealed that severe interpretation of tuber-
culinskintests,atcut-ovalueslessthantheOIErec-
ommended cut-o value of > mm, is essential for optimal
diagnosis of bovine Tb in Bos indicus cattle in Maroua,
Cameroon. e interpretations should be done at either
≥mm or≥. mm cut-o points given the epidemiological
and environmental context of the region.
Competing Interests
e authors declare that they have no competing interests.
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