Preliminary Observations on Mycobacterium Spp. In Dairy Cattle in Ecuador

Abstract

This study evaluated bovine tuberculosis in Mejia canton, a major dairy cattle production region in Ecuador. Randomly selected cattle (1,012 from 59 farms) classified according to herd size were tested by the single tuberculin test (STT). Sixty days later, positive reactors were tested again by the comparative tuberculin test (CTT). In addition, tissue samples from two STT-CTT-positive reactors detected on a farm were obtained in a local slaughterhouse and analyzed bacteriologically. A total of 4.24% of the cattle were positive in the STT and 3.85% were positive in the CTT, with the highest number (7.95%) in large herds versus 3.4% in medium herds and 0.3% in small herds. Mycobacterium bovis was isolated from mesenteric lymph nodes and lungs of one animal. A 16S ribosomal RNA-based polymerase chain reaction confirmed culture results and differentiated mycobacteria other than M. tuberculosis. This study confirms the zoonotic importance of tuberculosis in Ecuadorian dairy cattle with herd size likely to be a crucial parameter in the prevalence of the disease. The implementation of a national control program is necessary and should be based on the detection of positive cattle by STT in combination with CTT.

Comparative Intradermal Tuberculin Test in Dairy Cattle in the North of Ecuador and Risk Factors Associated with Bovine Tuberculosis

“…This prevalence is higher than the overall prevalence of 3.85% reported in a previous study in the same region in 2003. 7 This difference could be attributed to the fact that the study of 2003 involved a higher number of small farms, which are known to have a lower prevalence of BTB. 7 Our results might be an underestimate or overestimate of the true prevalence.…”

“…7 This difference could be attributed to the fact that the study of 2003 involved a higher number of small farms, which are known to have a lower prevalence of BTB. 7 Our results might be an underestimate or overestimate of the true prevalence. We observed a strong association between the avian and the bovine PPD response ( P < 0.01), with 3.73% and 4.74% of the PPD-B reactors also reacting to PPD-A.…”

“…6 A previous study in the same region estimated an overall prevalence of 3.85% in 1,012 cattle. 7 The Ecuadorian Service of Animal Health has no monitoring program, and economic losses caused by BTB have not been estimated.…”

Post-mortem examination and laboratory-based analysis for the diagnosis of bovine tuberculosis among dairy cattle in Ecuador

“…In Tanzania, Cleaveland and colleagues (2007) identified M. terrae, M. avium, M. chelonae, M. gordonae, M. fortuitum, M. flavescens and M. smegmatis in samples from slaughtered cattle with visible lesions; however, the clinical relevance of the isolation of these environmental mycobacteria needs to be confirmed. In Ecuador, the presence of M. aviumintracellulare-scrofulaceum, M. gordonae, M. szulgai and M. celatum was reported in slaughtered dairy cattle (Proaño-Perez et al, 2006). Therefore, the identification of the species plays a crucial role in the final diagnosis of the disease.…”

“…In Ecuador, there is no BTB control program in place. An apparent prevalence of 7.95% was observed among dairy cattle from large herds in 2004 (Proaño-Perez et al, 2006), and it increased to 8.63% three years later in the same region (Proaño-Pérez et al, 2009). Herd size was identified as an important risk factor in this husbandry system, and the number of skin-test-positive cases also increased significantly with cattle age (Proaño-Pérez et al, 2009).…”