Prevalence of bovine tuberculosis in slaughtered cattle identified by nested-PCR in abattoirs from two dairy areas of Ecuador

Abstract

Bovine tuberculosis (bTB) is a chronic granulomatous disease that primarily affects lung tissue and lymph nodes (LN) in cattle, with economic impact on their productivity. Furthermore, it is potential zoonoses that may cause public health hazard. In this study, we evaluated the presence of bTB in two abattoirs: Cayambe and Pelileo countries located in the Ecuadorian provinces of Pichincha and Tungurahua, respectively. In total, 578 cattle were sampled (Cayambe 271 and Pelileo 307): 1,156 LN and 578 lung tissue samples were collected to apply in vitro culture and nested-PCR, respectively. The results determined a total apparent prevalence of 4.33%, with 4.06% at Cayambe's abattoir and 4.56% at Pelileo's abattoir. Additionally, the Bayesian analysis showed a total true prevalence of 2.51%, with 89.7% of sensitivity and 97.6% of specificity. The risk factors were evaluated by the use of simple logistic regressions with and without the random effect of places of origin. Associations of the origin of cattle in the selected slaughterhouses were found. The results showed an efficient method for the detection of bTB, which could identify a large number of infected animals, and the usefulness of lung tissue samples for early diagnosis of the disease was demonstrated in this study.

Direct DNA Modified CTAB Preparation from Nasal Exudate in Live M. bovis Infected Cattle in Mexico Provide with a Valuable Assay Extrapolated to Humans TB Diagnostic Test

“…Therefore, it is a urgent need for endemic regions to have a routine assay to boost field test (false positive and negative tests) in live cows [37]. Moreover, the development of an optimal PCR methods that can boost field tuberculin tests (false positive/false negative) of live cows while avoiding unnecessary sacrifice of animals a molecular method should fulfill some basic requirements such as the high quality DNA, the regions to be amplified and primers design [8,16,22,[24][25][26][27][28][29][30][31][37][38][39]. M. bovis detection either from cattle or humans samples have moderate sensitivity, mainly attributed to the difficult for DNA extraction (bacterial lysis, long manipulation steps) or quality of the sample collection [17,[25][26][27][28].…”

“…M. bovis detection either from cattle or humans samples have moderate sensitivity, mainly attributed to the difficult for DNA extraction (bacterial lysis, long manipulation steps) or quality of the sample collection [17,[25][26][27][28]. Nowadays, there are several molecular methods for the detection of M. bovis that goes from simple PCR to multiplex real time PCR using either milk, semen, urine or nasal exudate [16,23,[24][25][26][27][28][29][30][31], some of them fill one or two of the basic requirements mentioned above, but not all. In some of them, the results should be corroborated throughout histopathology and bacteriology, which would imply, time, and costs; and therefore, it can not be used extensively in epidemiological surveys [37,38,[39][40][41][42].…”

“…Furthermore, we observed complementation between the direct method for DNA preparation from exudate nasal/oral and PCR RD ' s amplification either from M. bovis or M. tuberculosis (in human MTb in preparation) with exudate seeding, colonies growth and RD's PCR amplification method [15][16][17]25] (Figures 2, 3III and 4B), To note is that tissues samples can be obtained only from slaughtered cattle, dampening more extensive screening studies. Thus, herein we are showing that through this improved and shortened M. bovis DNA preparation from nasal exudate, it is possible to avoid unnecessary sacrifice of animals, strenghtening tuberculin test, offering thus an advantage and a promising alternative that can be extrapolated on human molecular diagnostic and nasal/oral exudate sampling for TB epidemiological surveys and research.…”

“…From the annals of the literature toward the development of molecular detection methods in TBb, a test that relies in the rRNA determination was found but not further studies were made [9]. Instead, in the last decades, M. bovis molecular detection based on different types of PCR (nested, multiplex, real-time) have been developed with promising results [10,[11][12][13][14][15][16] For example, Liébana et al [10] performed a simple detection of M. bovis, directly from samples of bovine tissue by means of a PCR technique, but the test was not able to distinguish between the different members of the M. tuberculosis complex [10] In addition, PCR test was not as sensitive as the culture and it did not always detect those samples that contained a small number of organisms, which could be due to the difficulty of extracting DNA from the isolates (tissue) of infected animals [17]. Moreover, the sensitivity of PCR can be affected by inhibitors in clinical samples, inhibitors reagents derived from the extraction method or the yield of DNA [18] or procedures for bacteria lysis and DNA extraction involve time-consuming steps and costly which is not always available in developing countries [19], or a lack of specificity and sensitivity because the region to be amplified is not the optimal [18][19][20].…”

Detection of Mycobacterium bovis in cattle lungs from two abattoirs in Western and North Central provinces of Sri Lanka

“…An expected prevalence of 8 % was assumed for the calculation of sample size based on previous studies on BTB incidence in abattoirs in other endemic countries (Echeverría et al, 2014;Srinivasan et al, 2018).…”